Abas, AEP & Mahlia, TMI 2018, 'Development of energy labels based on consumer perspective: Room air conditioners as a case study in Brunei Darussalam', Energy Reports, vol. 4, pp. 671-681.
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© 2018 The Authors For the past years, Brunei Darussalam has seen an increase in its electricity consumption with an average annual rate of increase of 3% per annum from the year 2011 to 2015. Like other developing countries with tropical climates, electricity consumption from air conditioning systems contributes a big part to this electricity consumption. The Energy Department of the Prime Minister's Office is considering the implementation of energy label for air-conditioning system; to provide guideline for consumers to compare efficiencies of their systems, encourage manufacturers to improve the energy efficiency of their systems and ultimately, to reduce the overall energy consumption of the country. This paper proposes a suitable energy label for air conditioning system in this country based on an online survey. Data from the survey shall be analysed to come up with consumers’ preferred energy label with suggestions used for its improvement. This label is also suitable for other electrical systems without major modification.
Abdulkareem, JH, Pradhan, B, Sulaiman, WNA & Jamil, NR 2018, 'Review of studies on hydrological modelling in Malaysia', Modeling Earth Systems and Environment, vol. 4, no. 4, pp. 1577-1605.
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Hydrological models are vital component and essential tools for water resources and environmental planning and management. In recent times, several studies have been conducted with a view of examining the compatibility of model results with streamflow measurements. Some modelers are of the view that even the use of complex modeling techniques does not give better assessment due to soil heterogeneity and climatic changes that plays vital roles in the behavior of streamflow. In Malaysia, several public domain hydrologic models that range from physically-based models, empirical models and conceptual models are in use. These include hydrologic modeling system (HEC-HMS), soil water assessment tool (SWAT), MIKE-SHE, artificial neural network (ANN). In view of this, a study was conducted to evaluate the hydrological models used in Malaysia, determine the coverage of the hydrological models in major river basins and to identify the methodologies used (specifically model performance and evaluation). The results of the review showed that 65% of the studies conducted used physical-based models, 37% used empirical models while 6% used conceptual models. Of the 65% of physical-based modelling studies, 60% utilized HEC-HMS an open source models, 20% used SWAT (public domain model), 9% used MIKE-SHE, MIKE 11 and MIKE 22, Infoworks RS occupied 7% while TREX and IFAS occupy 2% each. Thus, indicating preference for open access models in Malaysia. In the case of empirical models, 46% from the total of empirical researches in Malaysia used ANN, 13% used Logistic Regression (LR), while Fuzzy logic, Unit Hydrograph, Auto-regressive integrated moving average (ARIMA) model and support vector machine (SVM) contributed 8% each. Whereas the remaining proportion is occupied by Numerical weather prediction (NWP), land surface model (LSM), frequency ratio (FR), decision tree (DT) and weight of evidence (WoE). Majority of the hydrological modelling studies utilized one or more statis...
Abdullahi, S, Pradhan, B & Mojaddadi, H 2018, 'City Compactness: Assessing the Influence of the Growth of Residential Land Use', Journal of Urban Technology, vol. 25, no. 1, pp. 21-46.
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© 2017 The Society of Urban Technology. In the urban sprawl paradigm, residential land use exhibits a more significant growth than other categories. Consequently, large proportions of the natural environment are converted to residential areas, particularly in tropical countries. Compact urban development is one of the most sustainable urban forms with environmental perspectives, such as rural development containment and natural environment preservation. However, no proper investigation of the relationship and influence of residential growth and city compactness is available. This study evaluated and forecasted the residential development of Kajang City in Malaysia based on compact development. First, the relationship between residential land use change and city compactness was evaluated. Second, residential growth was projected by utilizing the land transformation model (LTM) and the statistical-based weight of evidence (WoE) using various spatial parameters. Both models were evaluated with respect to observed land use and compactness maps. Results indicated that most of the newly developed residential areas were in zones where the degrees of compactness increase during certain periods. In addition, LTM performed better and provided a more accurate modeling of residential growth than the WoE. However, WoE provided clearer and more informative results than LTM in terms of functional relationships between dependent and independent variables related to city compactness.
Ahmed, A, Abu Bakar, MS, Azad, AK, Sukri, RS & Mahlia, TMI 2018, 'Potential thermochemical conversion of bioenergy from Acacia species in Brunei Darussalam: A review', Renewable and Sustainable Energy Reviews, vol. 82, pp. 3060-3076.
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© 2017 Elsevier Ltd As the demand for energy increases and fossil fuel resources are depleted, the search for clean sources of energy has intensified worldwide. This is coupled with a strong global desire to reduce CO2 emissions to curb global warming. Brunei Darussalam is committed to reduce its CO2 emissions but currently utilizes fossil fuels to meet almost all of its energy requirements. This situation provides good incentives to search for renewable and sustainable resources to produce energy in the country. Acacia species are exotic species that have invaded and spread to natural habitats in Brunei Darussalam. Acacia species are a sustainable source of high quality biomass feedstock to produce bioenergy in the country. Hot tropical weather of the country is highly suitable for the rapid growth of Acacias without requiring any major agricultural input. This study reviews the thermochemical conversion of Acacia species especially; Acacia mangium and Acacia auriculiformis to produce biofuels and bio-products. The prospective of using Acacia biomass as feedstock in pyrolysis, gasification, liquefaction and combustion is also discussed. Acacia biomass is a sustainable and renewable energy resource for Brunei Darussalam to be exploited for energy requirements and can be beneficial for the economy of the country by providing new investment and employment opportunities.
Ahmed, MB, Johir, MAH, Khourshed, C, Zhou, JL, Ngo, HH, Nghiem, DL, Moni, M & Sun, L 2018, 'Sorptive removal of dissolved organic matter in biologically-treated effluent by functionalized biochar and carbon nanotubes: Importance of sorbent functionality', Bioresource Technology, vol. 269, pp. 9-17.
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© 2018 Elsevier Ltd The sorptive removal of dissolved organic matter (DOM) in biologically-treated effluent was studied by using multi-walled carbon nanotube (MWCNT), carboxylic functionalised MWCNT (MWCNT-COOH), hydroxyl functionalized MWCNT (MWCNT-OH) and functionalized biochar (fBC). DOM was dominated by hydrophilic fraction (79.6%) with a significantly lower hydrophobic fraction (20.4%). The sorption of hydrophobic DOM was not significantly affected by the sorbent functionality (∼10.4% variation) and sorption capacity followed the order of MWCNT > MWCNT-COOH > MWCNT-OH > fBC. In comparison, the sorption of hydrophilic fraction of DOM changed significantly (∼37.35% variation) with the change of sorbent functionality with adsorption capacity decreasing as MWCNT-OH > MWCNT-COOH > MWCNT > fBC. Furthermore, the affinity of adsorbents toward a hydrophilic compound (dinitrobenzene), a hydrophobic compound (pyrene) and humic acid was also evaluated to validate the proposed mechanisms. The results provided important insights on the type of sorbents which are most effective to remove different DOM fractions.
Ahmed, MB, Zhou, JL, Ngo, HH, Johir, MAH & Sornalingam, K 2018, 'Sorptive removal of phenolic endocrine disruptors by functionalized biochar: Competitive interaction mechanism, removal efficacy and application in wastewater', Chemical Engineering Journal, vol. 335, pp. 801-811.
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© 2017 Elsevier B.V. Sorptive removal of six phenolic endocrine disrupting chemicals (EDCs) estrone (E1), 17β-estradiol (E2), estriol (E3), 17α-ethynylestradiol (EE2), bisphenol A (BPA) and 4-tert-butylphenol (4tBP) by functionalized biochar (fBC) through competitive interactions was investigated. EDC sorption was pH dependent with the maximum sorption at pH 3.0–3.5 due to hydrogen bonds and π-π interactions as the principal sorptive mechanism. Sorption isotherm of the EDCs was fitted to the Langmuir model. Sorption capacities and distribution coefficient values followed the order E1 > E2 ≥ EE2 > BPA > 4tBP > E3. The findings suggested that EDC sorption occurred mainly through pseudo-second order and external mass transfer diffusion processes, by forming H-bonds along with π-π electron-donor–acceptor (EDA) interactions at different pH. The complete removal of ∼500 μg L−1 of each EDC from different water decreased in the order: deionised water > membrane bioreactor (MBR) sewage effluent > synthetic wastewater. The presence of sodium lauryl sulphonate and acacia gum in synthetic wastewater significantly suppressed sorption affinity of EDCs by 38–50%, hence requiring more fBC to maintain removal efficacy.
Ahmed, MB, Zhou, JL, Ngo, HH, Johir, MAH, Sun, L, Asadullah, M & Belhaj, D 2018, 'Sorption of hydrophobic organic contaminants on functionalized biochar: Protagonist role of π-π electron-donor-acceptor interactions and hydrogen bonds', Journal of Hazardous Materials, vol. 360, pp. 270-278.
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© 2018 Elsevier B.V. The sorption of five potent endocrine disruptors as representative hydrophobic organic contaminants (HOCs) namely estrone (E1), 17β-estradiol (E2), estriol (E3), 17α-ethynylestradiol (EE2) and bisphenol A (BPA) on functionalized biochar (fBC) was systematically examined, with a particular focus on the importance of π-electron-donor (phenanthrene: PHEN) and π-electron-acceptors (1,3-dinitrobenzene: DNB, p-amino benzoic acid: PABA) on sorption. Experimental results suggested that hydrogen-bond formation and π-π-electron-donor-acceptor (EDA) interactions were the dominant sorption mechanisms. The sorption of HOCs decreased as E1 > E2 > EE2 > E3 > BPA based on the Freundlich and Polanyi-Mane-models. The comparison of adsorption coefficient (Kd) normalized against hexadecane-water partition coefficient (KHW) between HOCs and PHEN indicated strong π-π-EDA interactions. π-π interactions among DNB, PHEN and HOCs were verified by the observed upfield frequency (Hz) shifts using proton nuclear magnetic resonance (1H NMR) which identified the specific direction of π-π interactions. UV–vis spectra showed charge-transfer bands for π-donors (PHEN and HOCs) with the model π-acceptor (DNB) also demonstrating the role of π-π EDA interactions. The role of π-electron-donor and π-electron-acceptor domains in fBC was identified at different solution pH.
Ahmmad, MS, Haji Hassan, MB & Kalam, MA 2018, 'Comparative corrosion characteristics of automotive materials in Jatropha biodiesel', International Journal of Green Energy, vol. 15, no. 6, pp. 393-399.
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Ait Lamqadem, A, Pradhan, B, Saber, H & Rahimi, A 2018, 'Desertification Sensitivity Analysis Using MEDALUS Model and GIS: A Case Study of the Oases of Middle Draa Valley, Morocco', Sensors, vol. 18, no. 7, pp. 2230-2230.
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Oases can play a significant role in the sustainable economic development of arid and Saharan regions. The aim of this study was to map the desertification-sensitive areas in the Middle Draa Valley (MDV), which is in the southeast of Morocco. A total of 13 indices that affect desertification processes were identified and analyzed using a geographic information system. The Mediterranean desertification and land use approach; which has been widely used in the Mediterranean regions due to its simplicity; flexibility and rapid implementation strategy; was applied. All the indices were grouped into four main quality indices; i.e., soil quality; climate quality; vegetation quality and management quality indices. Each quality index was constructed by the combination of several sub-indicators. In turn; the geometric mean of the four quality index maps was used to construct a map of desertification-sensitive areas; which were classified into four classes (i.e., low; moderate; high and very high sensitivity). Results indicated that only 16.63% of the sites in the study were classified as least sensitive to desertification; and 50.34% were classified as highly and very highly sensitive areas. Findings also showed that climate and human pressure factors are the most important indicators affecting desertification sensitivity in the MDV. The framework used in this research provides suitable results and can be easily implemented in similar oasis arid areas.
Alazigha, DP, Indraratna, B, Vinod, JS & Heitor, A 2018, 'Mechanisms of stabilization of expansive soil with lignosulfonate admixture', Transportation Geotechnics, vol. 14, pp. 81-92.
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Ali, SM, Kim, JE, Phuntsho, S, Jang, A, Choi, JY & Shon, HK 2018, 'Forward osmosis system analysis for optimum design and operating conditions', Water Research, vol. 145, pp. 429-441.
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© 2018 Elsevier Ltd Low energy consumption and less fouling propensity of forward osmosis (FO) processes have been attractive as a promising water filtration technology. The performance of this process is however significantly influenced by its operating conditions. Moreover, these operating parameters have both favourable and adverse effects on its performance. Therefore, it is very important to optimize its performance for efficient and economic operation. This study aims to develop a software to analyze a full-scale FO system for optimum performance. A comprehensive theoretical framework was developed to estimate the performance of FO system. Analysis results were compared with the experimental results to validate the models. About 5% deviation of simulation results and the experimental findings shows a very good agreement between them. A novel optimization algorithm was then developed to estimate the minimum required draw solution (DS) inlet flowrate and the number of elements in a pressure vessel to attain the design objectives (i.e. desired final DS concentration and recovery rate at a specific feed solution (FS) flowrate). A detailed parametric study was also conducted to determine the optimum operating conditions for different objectives. It showed that for a specific design objective, higher recovery rate can be achieved by increasing the DS flowrate and number of elements in a pressure vessel. In contrast, lower final concentration can be obtained by lowering the DS flowrate and increasing the number of elements. Finally, a MATLAB based software with graphical user interface was developed to make the analysis process easier and efficient.
Alizadeh, M, Hashim, M, Alizadeh, E, Shahabi, H, Karami, M, Beiranvand Pour, A, Pradhan, B & Zabihi, H 2018, 'Multi-Criteria Decision Making (MCDM) Model for Seismic Vulnerability Assessment (SVA) of Urban Residential Buildings', ISPRS International Journal of Geo-Information, vol. 7, no. 11, pp. 444-444.
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Earthquakes are among the most catastrophic natural geo-hazards worldwide and endanger numerous lives annually. Therefore, it is vital to evaluate seismic vulnerability beforehand to decrease future fatalities. The aim of this research is to assess the seismic vulnerability of residential houses in an urban region on the basis of the Multi-Criteria Decision Making (MCDM) model, including the analytic hierarchy process (AHP) and geographical information system (GIS). Tabriz city located adjacent to the North Tabriz Fault (NTF) in North-West Iran was selected as a case study. The NTF is one of the major seismogenic faults in the north-western part of Iran. First, several parameters such as distance to fault, percent of slope, and geology layers were used to develop a geotechnical map. In addition, the structural construction materials, building materials, size of building blocks, quality of buildings and buildings-floors were used as key factors impacting on the building’s structural vulnerability in residential areas. Subsequently, the AHP technique was adopted to measure the priority ranking, criteria weight (layers), and alternatives (classes) of every criterion through pair-wise comparison at all levels. Lastly, the layers of geotechnical and spatial structures were superimposed to design the seismic vulnerability map of buildings in the residential area of Tabriz city. The results showed that South and Southeast areas of Tabriz city exhibit low to moderate vulnerability, while some regions of the north-eastern area are under severe vulnerability conditions. In conclusion, the suggested approach offers a practical and effective evaluation of Seismic Vulnerability Assessment (SVA) and provides valuable information that could assist urban planners during mitigation and preparatory phases of less examined areas in many other regions around the world.
Allioux, F-M, David, O, Merenda, A, Maina, JW, Benavides, ME, Tanaka, AP & Dumée, LF 2018, 'Catalytic nickel and nickel–copper alloy hollow-fiber membranes for the remediation of organic pollutants by electrocatalysis', Journal of Materials Chemistry A, vol. 6, no. 16, pp. 6904-6915.
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Electrocatalytic membrane reactors are becoming a viable solution for the treatment of wastewater contaminated with persistent organic pollutants and compounds.
Altaee, A 2018, 'Osmotic Power Plant: Process Innovation and Future Potential', Recent Advances in Petrochemical Science, vol. 4, no. 3, pp. 1-1.
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Osmotic power plant operating by Pressure Retarded Osmosis (PRO) is a promising technology for power generation from renewable resources. A wealth of literature has been published in PRO feasibility to replace conventional fossil fuel power plants. In this paper the PRO and the new innovative Dual Stage PRO process are briefly reviewed with the authors’ insight on the future development and application of the PRO power plants.
Altaee, A, Zaragoza, G, Millar, GJ, Sharif, AO & Alanezi, AA 2018, 'Limitations of osmotic gradient resource and hydraulic pressure on the efficiency of dual stage PRO process', DESALINATION AND WATER TREATMENT, vol. 105, pp. 11-22.
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© 2018 Desalination Publications. All rights reserved. A dual stage PRO process has been proposed for power generation from a salinity gradient across a semi-permeable membrane. Both closed-loop and open-loop dual stage PRO system were evaluated using 2 M NaCl and Dead Sea as draw solutions, whereas the feed solution was either fresh water or seawater. The impact of feed salinity gradient resource and feed pressure on the net power generation and water flux were evaluated. The results showed that power density in stage one reached a maximum amount at ΔP = p/2, but the maximum net power generation occurred at ΔP = p/2. This result was mainly attributed to the variation of net driving pressure in stage one and two of the PRO process. The dual stage PRO process was found to perform better at high osmotic pressure gradient across the PRO membrane, for example when Dead Sea brine or highly concentrated NaCl was the draw solution. Total power generation in the dual stage PRO process was up to 40% higher than that in the conventional PRO process. This outcome was achieved through harvesting the rest of the energy remaining in the diluted draw solution. Therefore, a dual stage PRO process has the potential of maximizing power generation from a salinity gradient resource.
Ansari, AJ, Hai, FI, He, T, Price, WE & Nghiem, LD 2018, 'Physical cleaning techniques to control fouling during the pre-concentration of high suspended-solid content solutions for resource recovery by forward osmosis', Desalination, vol. 429, pp. 134-141.
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Ansari, AJ, Hai, FI, Price, WE, Ngo, HH, Guo, W & Nghiem, LD 2018, 'Assessing the integration of forward osmosis and anaerobic digestion for simultaneous wastewater treatment and resource recovery', Bioresource Technology, vol. 260, pp. 221-226.
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© 2018 This study assessed the performance and key challenges associated with the integration of forward osmosis (FO) and anaerobic digestion for wastewater treatment and resource recovery. Using a thin film composite polyamide FO membrane, maximising the pre-concentration factor (i.e. system water recovery) resulted in the enrichment of organics and salinity in wastewater. Biomethane potential evaluation indicated that methane production increased correspondingly with the FO pre-concentration factor due to the organic retention in the feed solution. At 90% water recovery, about 10% more methane was produced when using NaOAc compared with NaCl because of the contribution of biodegradable reverse NaOAc flux. No negative impact on anaerobic digestion was observed when wastewater was pre-concentrated ten-fold (90% water recovery) for both draw solutes. Interestingly, the unit cost of methane production using NaOAc was slightly lower than NaCl due to the lower reverse solute flux of NaOAc, although NaCl is a much cheaper chemical.
Anwar, M, Rasul, M, Ashwath, N & Rahman, M 2018, 'Optimisation of Second-Generation Biodiesel Production from Australian Native Stone Fruit Oil Using Response Surface Method', Energies, vol. 11, no. 10, pp. 2566-2566.
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In this study, the production process of second-generation biodiesel from Australian native stone fruit have been optimised using response surface methodology via an alkali catalysed transesterification process. This process optimisation was performed varying three factors, each at three different levels. Methanol: oil molar ratio, catalyst concentration (wt %) and reaction temperature were the input factors in the optimisation process, while biodiesel yield was the key model output. Both 3D surface plots and 2D contour plots were developed using MINITAB 18 to predict optimum biodiesel yield. Gas chromatography (GC) and Fourier transform infrared (FTIR) analysis of the resulting biodiesel was also done for biodiesel characterisation. To predict biodiesel yield a quadratic model was created and it showed an R2 of 0.98 indicating the satisfactory performance of the model. Maximum biodiesel yield of 95.8% was obtained at a methanol: oil molar ratio of 6:1, KOH catalyst concentration of 0.5 wt % and a reaction temperature of 55 °C. At these reaction conditions, the predicted biodiesel yield was 95.9%. These results demonstrate reliable prediction of the transesterification process by Response surface methodology (RSM). The results also show that the properties of the synthesised Australian native stone fruit biodiesel satisfactorily meet the ASTM D6751 and EN14214 standards. In addition, the fuel properties of Australian native stone fruit biodiesel were found to be similar to those of conventional diesel fuel. Thus, it can be said that Australian native stone fruit seed oil could be used as a potential second-generation biodiesel source as well as an alternative fuel in diesel engines.
Arabameri, A, Pradhan, B, Pourghasemi, HR & Rezaei, K 2018, 'Identification of erosion-prone areas using different multi-criteria decision-making techniques and GIS', Geomatics, Natural Hazards and Risk, vol. 9, no. 1, pp. 1129-1155.
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Asif, MB, Hai, FI, Dhar, BR, Ngo, HH, Guo, W, Jegatheesan, V, Price, WE, Nghiem, LD & Yamamoto, K 2018, 'Impact of simultaneous retention of micropollutants and laccase on micropollutant degradation in enzymatic membrane bioreactor', Bioresource Technology, vol. 267, pp. 473-480.
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Asif, MB, Hai, FI, Kang, J, van de Merwe, JP, Leusch, FDL, Price, WE & Nghiem, LD 2018, 'Biocatalytic degradation of pharmaceuticals, personal care products, industrial chemicals, steroid hormones and pesticides in a membrane distillation-enzymatic bioreactor', Bioresource Technology, vol. 247, pp. 528-536.
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© 2017 Elsevier Ltd Laccase-catalyzed degradation of a broad spectrum of trace organic contaminants (TrOCs) by a membrane distillation (MD)-enzymatic membrane bioreactor (EMBR) was investigated. The MD component effectively retained TrOCs (94–99%) in the EMBR, facilitating their continuous biocatalytic degradation. Notably, the extent of TrOC degradation was strongly influenced by their molecular properties. A significant degradation (above 90%) of TrOCs containing strong electron donating functional groups (e.g., hydroxyl and amine groups) was achieved, while a moderate removal was observed for TrOCs containing electron withdrawing functional groups (e.g., amide and halogen groups). Separate addition of two redox-mediators, namely syringaldehyde and violuric acid, further improved TrOC degradation by laccase. However, a mixture of both showed a reduced performance for a few pharmaceuticals such as primidone, carbamazepine and ibuprofen. Mediator addition increased the toxicity of the media in the enzymatic bioreactor, but the membrane permeate (i.e., final effluent) was non-toxic, suggesting an added advantage of coupling MD with EMBR.
Asikin-Mijan, N, Lee, HV, Juan, JC, Noorsaadah, AR, Ong, HC, Razali, SM & Taufiq-Yap, YH 2018, 'Promoting deoxygenation of triglycerides via Co-Ca loaded SiO 2 -Al 2 O 3 catalyst', Applied Catalysis A: General, vol. 552, pp. 38-48.
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Atiquzzaman, M & Kandasamy, J 2018, 'Robustness of Extreme Learning Machine in the prediction of hydrological flow series', Computers & Geosciences, vol. 120, pp. 105-114.
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Awadallah, M, Tawadros, P, Walker, P & Zhang, N 2018, 'Comparative fuel economy, cost and emissions analysis of a novel mild hybrid and conventional vehicles', Proceedings of the Institution of Mechanical Engineers, Part D: Journal of Automobile Engineering, vol. 232, no. 13, pp. 1846-1862.
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Mild hybrid vehicles have been explored as a potential pathway to reduce vehicle emissions cost-effectively. The use of manual transmissions to develop novel hybrid vehicles provides an alternate route to producing low cost electrified powertrains. In this paper, a comparative analysis examining a conventional vehicle and a mild hybrid electric vehicle is presented. The analysis considers fuel economy, capital and ongoing costs and environmental emissions, and includes developmental analysis and simulation using mathematical models. Vehicle emissions (nitrogen oxides, carbon monoxide and hydrocarbons) and fuel economy are computed, analysed and compared using a number of alternative driving cycles and their weighted combination. Different driver styles are also evaluated. Studying the relationship between the fuel economy and driveability, where driveability is addressed using fuel-economical gear shift strategies. Our simulation suggests the hybrid concept presented can deliver fuel economy gains of between 5 and 10%, as compared to the conventional powertrain.
Aziz, N, Rasekh, H, Mirzaghorbanali, A, Yang, G, Khaleghparast, S & Nemcik, J 2018, 'An Experimental Study on the Shear Performance of Fully Encapsulated Cable Bolts in Single Shear Test', Rock Mechanics and Rock Engineering, vol. 51, no. 7, pp. 2207-2221.
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A set of single shear tests on fully encapsulated cable bolts was carried out using a newly developed and integrated Megabolt single shear apparatus. The instrument is designed to determine the pure shear strength of cable bolts where there is no contact between the host body faces during the shearing process. Eight different types of cable bolt were encapsulated in 40 MPa concrete cylinders, using Stratabinder HS grout. Prior to encapsulation, cable bolts were pretensioned at the desired value using a manual pretensioner. Effects of surface profile, pretension value and debonding on shear strength of cable bolts were investigated. It was found that the shear strength of spiral/indented cable bolts was lower than that of plain cable bolts. Increasing the pretension load decreased the peak shear load of cable bolts. In general, no debonding was observed for spiral/indented cable bolts during shear testing; however, all tested plain cable bolts were debonded.
Azuma, K, Sun, J, Choo, Y, Rokhlenko, Y, Dwyer, JH, Schweitzer, B, Hayakawa, T, Osuji, CO & Gopalan, P 2018, 'Self-Assembly of an Ultrahigh-χ Block Copolymer with Versatile Etch Selectivity', Macromolecules, vol. 51, no. 16, pp. 6460-6467.
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We report the successful synthesis of previously inaccessible poly(3-hydroxystyrene)-block-poly(dimethylsiloxane) (P3HS-b-PDMS) block copolymers (BCPs) with varying volume fractions, molecular weights, and narrow dispersities by sequential living anionic polymerization. The chemical structure and molecular weight were fully characterized by 1H NMR and gel permeation chromatography. The BCP phase behavior was investigated using small-angle X-ray scattering (SAXS) and transmission electron microscopy. Temperature-resolved SAXS measurements from symmetric disordered sample were used to determine the interaction parameter (χ) using mean-field theory. The results provide an estimate for interaction parameter, χHS/DMS(T) = 33.491/T + 0.3126, with an upper bound value of 0.39 at 150 °C. The calculated χ for P3HS-b-PDMS is approximately 4 times higher than that observed in a commonly studied high-χ system, PS-b-PDMS. The ultrahigh interaction parameter observed here affords the formation of well-ordered materials at remarkably low molecular weight. The presence of both PDMS and P3HS provides significant versatility in terms of etch selectivity, while the hydroxystyrene domain offers additional functionality as it can be exploited for immobilizing functional organic moieties.
Babaee, M & Castel, A 2018, 'Chloride diffusivity, chloride threshold, and corrosion initiation in reinforced alkali-activated mortars: Role of calcium, alkali, and silicate content', Cement and Concrete Research, vol. 111, pp. 56-71.
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The aim of this study is to investigate systematically the chloride diffusivity and chloride threshold of a wide range of calcium-rich and fly ash-dominated alkali-activated samples in light of their compositional differences. To this end, the effects of various fly ash (FA)-to-slag ratios, of alkali concentrations and of silicate content in the activator were investigated. The electrochemical aspects of the passive samples were also assessed. Results show the prominent role of calcium in the matrix to reduce the chloride diffusivity. While higher alkali concentration increased the porosity and chloride diffusivities in general, lower modulus ratios provided considerably better performance in the FA-dominated samples. Chloride threshold values range between 0.19 (wt% binder mass) for calcium-rich mortars fabricated at low levels of alkalinities and 0.69 for FA-dominated mortars fabricated with highly alkaline activators. Half-cell potential and polarization resistance of alkali-activated samples were in general lower than their Portland cement counterparts.
Babaee, M & Castel, A 2018, 'Water vapor sorption isotherms, pore structure, and moisture transport characteristics of alkali-activated and Portland cement-based binders', Cement and Concrete Research, vol. 113, pp. 99-120.
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Babaee, M, Khan, MSH & Castel, A 2018, 'Passivity of embedded reinforcement in carbonated low-calcium fly ash-based geopolymer concrete', Cement and Concrete Composites, vol. 85, pp. 32-43.
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Bach, Q-V, Le, VT, Yoon, YS, Bui, XT, Chung, W, Chang, SW, Ngo, HH, Guo, W & Nguyen, DD 2018, 'A new hybrid sewage treatment system combining a rolled pipe system and membrane bioreactor to improve the biological nitrogen removal efficiency: A pilot study', Journal of Cleaner Production, vol. 178, pp. 937-946.
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© 2018 Elsevier Ltd A new hybrid pilot plant configuration based on a modularized rolled pipe system (RPS) combined with a submerged flat sheet membrane bioreactor (MBR) was investigated to enhance the sewage treatment and membrane performance. The system was operated under actual conditions for more than four months, that is, at a constant flow rate of 30 m³/d and with two internal recycling ratios. The results indicate that the hybrid system produces an excellent effluent quality and considerably mitigated membrane fouling. The average concentrations of SS, COD, TN, NH4+-N, NO3−-N, and PO43--P remained below 2.81, 8.29, 8.77, 0.15, 8.17, and 1.49 mg/L, respectively. It was estimated that the periodic chemical cleaning of the membrane could be extended to approximately six months. The MBR and RPS can virtually complete nitrification and denitrification, respectively. The highest average denitrification rate of the RPS is 116.95 mg NO3-N/(g MLVSS d), with a hydraulic retention time of 1.05 h. Therefore, the RPS–MBR hybrid system has potential to improve the sewage treatability. The emerging RPS technique can obtain high rates of denitrification coupled with a compact design, ease of installation, and small footprint.
Baral, P, Rujikiatkamjorn, C, Indraratna, B & Kelly, R 2018, 'Radial consolidation characteristics of soft undisturbed clay based on large specimens', Journal of Rock Mechanics and Geotechnical Engineering, vol. 10, no. 6, pp. 1037-1045.
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Basack, S & Nimbalkar, S 2018, 'Measured and Predicted Response of Pile Groups in Soft Clay Subjected to Cyclic Lateral Loading', International Journal of Geomechanics, vol. 18, no. 7, pp. 04018073-04018073.
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© 2018 American Society of Civil Engineers. Major offshore and onshore structures, including transport corridors and high-rise buildings, resting on soft compressible clays are often supported by pile foundations. Apart from the usual vertical loading from the superstructures, these piles are usually subjected to large cyclic loads arising from the actions of waves, ship impacts, or moving vehicles. Under such circumstances, vertical and lateral modes of cyclic loading are predominant and affect overall stability. Such repetitive loading on piles leads to reversal of axial stresses in the adjacent soft clay, initiating progressive degradation in soil strength and stiffness that deteriorates the pile capacity with unacceptable displacements. Although several studies have been carried out to investigate the response of a single pile, a detailed investigation on a pile group in soft soil subjected to cyclic lateral loading, which is of immense practical interest to field engineers, had yet to be conducted. In this paper, extensive laboratory model tests with steel-pipe-pile groups in soft cohesive soil were conducted followed by the development of a numerical model that was based on a two-dimensional (2D) dynamic finite-element (FE) approach. The degradation of both axial and lateral capacities of the pile group and the pattern of the degradation with variations in the cyclic-loading parameters were studied. Comparisons of the experimental data with the computed results validated the numerical analysis. The study indicates that both the axial and lateral pile capacities and displacements were significantly influenced by the cyclic-loading parameters (number of cycles, frequency, and amplitude). Relevant design recommendations are presented.
Basack, S, Indraratna, B & Rujikiatkamjorn, C 2018, 'Effectiveness of stone column reinforcement for stabilizing soft ground with reference to transport infrastructure', Geotechnical Engineering, vol. 49, no. 1, pp. 8-14.
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The use of stone columns for soft soil stabilization has numerous advantages compared to other methods. There are many factors controlling performance of stone columns including column geometry and particle morphology. The reinforced soft ground supporting transport infrastructure like the railways and highways is subjected to cyclic loading, usually initiating a partially drained condition. The study reveals that the stone columns are more effective in mitigating the built up of cyclic excess pore water pressure compared to conventional vertical drains. This paper presents a brief overview on the rigorous theoretical and experimental studies carried out by the Authors to investigate the effectiveness of stone column reinforcement for stabilizing soft ground with particular reference to transport infrastructure.
Basack, S, Indraratna, B, Rujikiatkamjorn, C & Siahaan, F 2018, 'Closure to “Modeling the Stone Column Behavior in Soft Ground with Special Emphasis on Lateral Deformation” by Sudip Basack, Buddhima Indraratna, Cholachat Rujikiatkamjorn, and Firman Siahaan', Journal of Geotechnical and Geoenvironmental Engineering, vol. 144, no. 5, pp. 07018008-07018008.
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Basack, S, Siahaan, F, Indraratna, B & Rujikiatkamjorn, C 2018, 'Stone Column–Stabilized Soft-Soil Performance Influenced by Clogging and Lateral Deformation: Laboratory and Numerical Evaluation', International Journal of Geomechanics, vol. 18, no. 6, pp. 04018058-04018058.
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Bayuaji, R, Sigit Darmawan, M, Husin, NA, Anugraha, RB, Budipriyanto, A & Stewart, MG 2018, 'Corrosion damage assessment of a reinforced concrete canal structure of power plant after 20 years of exposure in a marine environment: A case study', Engineering Failure Analysis, vol. 84, pp. 287-299.
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Chloride attack is the primary cause of corrosion problem of concrete structures operate in marine environment. Therefore, concrete structures operate in such environment cannot escape from this corrosion related problem. This paper describes assessment of a reinforced concrete canal structure of power plant after 20 years of exposure in a marine environment. The work covers visual inspection of the structure, on-site and laboratory tests of the structure, analyses the current structural strength based on the tests, and proposing repair and/or strengthening for weak elements. Strength prediction is carried out using average and worst case scenarios. The strength calculations assuming average case scenario shows that by 2025 all the canal have no strength reduction due to corrosion. Calculation using the worst case scenario shows that all the canal by 2025 still comply with the limits specified in Indonesian Concrete Code, even though their strength has been reduced due to corrosion of the reinforcement.
Belhaj, D, Athmouni, K, Ahmed, MB, Aoiadni, N, El Feki, A, Zhou, JL & Ayadi, H 2018, 'Polysaccharides from Phormidium versicolor (NCC466) protecting HepG2 human hepatocellular carcinoma cells and rat liver tissues from cadmium toxicity: Evidence from in vitro and in vivo tests', International Journal of Biological Macromolecules, vol. 113, pp. 813-820.
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© 2018 Elsevier B.V. The in vitro antioxidant, cytotoxic and cytoprotective properties and in vivo hepatoprotective activities of crude polysaccharides extracted from cyanobacteria Phormidim versicolor NCC466 (CFv-PS) were investigated. The CFv-PS, identified as heteropolysaccharides with molecular weight of 63.79 kDa, exhibited relatively strong antioxidant activity, in a concentration-depended manner, in vitro assays. Additionally, CFv-PS did not induce cytotoxic effect on HepG2 human hepatocellular carcinoma cells within the range of tested concentrations (25–150 μg·mL−1) while preventing them against Cd. Moreover, in rats subjected to Cd-induced hepatotoxicity, CFv-PS pretreatment significantly (P < 0.05) reduced the level of ALAT, ASAT, biliburin, MDA, protein carbonyl and DNA damage, and markedly increased enzyme activities in liver tissues. These findings suggest that the cyanobacteria Phormidium versicolor is a potential source of natural products possessing antioxidant, cytoprotective and hepatoprotective properties.
Bian, X, Jin, W, Gu, Q, Zhou, X, Xi, Y, Tu, R, Han, S-F, Xie, G-J, Gao, S-H & Wang, Q 2018, 'Subcritical n-hexane/isopropanol extraction of lipid from wet microalgal pastes of Scenedesmus obliquus', World Journal of Microbiology and Biotechnology, vol. 34, no. 3, pp. 39-39.
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© 2018, Springer Science+Business Media B.V., part of Springer Nature. Abstract: Subcritical co-solvents of n-hexane/isopropanol were primarily utilized to extract lipid from wet microalgal pastes of Scenedesmus obliquus. The effects of key operational parameters were investigated, and the optimal parameters were obtained: solvent ratio of n-hexane to isopropanol was 3:2 (V:V), phase ratio of co-solvents to microalgal biomass was 35:1 (mL:g), reactor stirring speed was 900 rpm, extraction time was 60 min. Additional pretreatment with acid, ultrasonic and microwave as well as enhanced subcritical pressure/heating treatments were also applied to further study their effects on lipid extraction. The results showed that the lipid recovery rate with acid pretreatment was 8.6 and 6.2% higher than ultrasonic and microwave pretreatment; the optimum enhanced subcritical condition was 55 °C with atmospheric pressure. Under optimal operating conditions, the lipid and FAME yield were 13.5 and 7.2%, which was 82.6 and 135.1% higher than the traditional method. The results indicated that the subcritical n-hexane/isopropanol extraction process had promising application potential. Graphical Abstract: [Figure not available: see fulltext.].
Bjarnadottir, S, Li, Y, Reynisson, O & Stewart, MG 2018, 'Reliability-based assessment of climatic adaptation for the increased resiliency of power distribution systems subjected to hurricanes', Sustainable and Resilient Infrastructure, vol. 3, no. 1, pp. 36-48.
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Power distribution systems are vulnerable to hurricanes as has been documented in recent years. Hurricane intensity or/and frequency may change as a result of increased CO2 emissions. This paper proposes six climatic adaptation strategies for timber distribution poles that may aid in mitigating the hurricane damage costs that may be expected to increase because of global climate change. The effectiveness of adaptation is assessed through a life-cycle cost analysis, which includes direct cost (e.g. cost of pole replacement, maintenance, and adaptation) and indirect cost (e.g. cost of power outage to customers). The viability of the adaptation strategies is examined considering three CO2 emission scenarios. Furthermore, the scenario of no climate change is considered in this paper to show the applicability the proposed framework for hurricane risk mitigation under current conditions (i.e. wind speeds remain stationary). This paper finds that certain adaptation measures can effectively reduce costs, resulting in more resilient power distribution systems.
Boo, C, Wang, Y, Zucker, I, Choo, Y, Osuji, CO & Elimelech, M 2018, 'High Performance Nanofiltration Membrane for Effective Removal of Perfluoroalkyl Substances at High Water Recovery', Environmental Science & Technology, vol. 52, no. 13, pp. 7279-7288.
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We demonstrate the fabrication of a loose, negatively charged nanofiltration (NF) membrane with tailored selectivity for the removal of perfluoroalkyl substances with reduced scaling potential. A selective polyamide layer was fabricated on top of a poly(ether sulfone) support via interfacial polymerization of trimesoyl chloride and a mixture of piperazine and bipiperidine. Incorporating high molecular weight bipiperidine during the interfacial polymerization enables the formation of a loose, nanoporous selective layer structure. The fabricated NF membrane possessed a negative surface charge and had a pore diameter of ∼1.2 nm, much larger than a widely used commercial NF membrane (i.e., NF270 with pore diameter of ∼0.8 nm). We evaluated the performance of the fabricated NF membrane for the rejection of different salts (i.e., NaCl, CaCl2, and Na2SO4) and perfluorooctanoic acid (PFOA). The fabricated NF membrane exhibited a high retention of PFOA (∼90%) while allowing high passage of scale-forming cations (i.e., calcium). We further performed gypsum scaling experiments to demonstrate lower scaling potential of the fabricated loose porous NF membrane compared to NF membranes having a dense selective layer under solution conditions simulating high water recovery. Our results demonstrate that properly designed NF membranes are a critical component of a high recovery NF system, which provide an efficient and sustainable solution for remediation of groundwater contaminated with perfluoroalkyl substances.
Boton, C, Rivest, L, Forgues, D & Jupp, JR 2018, 'Comparison of shipbuilding and construction industries from the product structure standpoint', International Journal of Product Lifecycle Management, vol. 11, no. 3, pp. 191-191.
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The use of building information modelling (BIM) in construction compares to the use of product lifecycle management (PLM) in manufacturing. Previous research has shown that it is possible to improve BIM with the features and the best practices from the PLM approach. This article provides a comparison from the standpoint of the bill of materials (BOM) and product structures. It compares the product beginning of life in both construction and shipbuilding industries. The research then tries to understand the use, form and evolution of product structures and BOM concepts in shipbuilding with the aim of identifying equivalent notions in construction. Research findings demonstrate that similar concepts for structuring information exist in construction; however, the relationship between them is unclear. Further research is therefore required to detail the links identified by the authors and develop an equivalent central structuring backbone as found in PLM platforms.
Cai, C, Hu, S, Chen, X, Ni, B-J, Pu, J & Yuan, Z 2018, 'Effect of methane partial pressure on the performance of a membrane biofilm reactor coupling methane-dependent denitrification and anammox', Science of The Total Environment, vol. 639, pp. 278-285.
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© 2018 Complete nitrogen removal has recently been demonstrated by integrating anaerobic ammonium oxidation (anammox) and denitrifying anaerobic methane oxidation (DAMO) processes. In this work, the effect of methane partial pressure on the performance of a membrane biofilm reactor (MBfR) consisting of DAMO and anammox microorganisms was evaluated. The activities of DAMO archaea and DAMO bacteria in the biofilm increased significantly with increased methane partial pressure, from 367 ± 9 and 58 ± 22 mg-N L−1d−1 to 580 ± 12 and 222 ± 22 mg-N L−1d−1, respectively, while the activity of anammox bacteria only increased slightly, when the methane partial pressure was elevated from 0.24 to 1.39 atm in the short-term batch tests. The results were supported by a long-term (seven weeks) continuous test, when the methane partial pressure was dropped from 1.39 to 0.78 atm. The methane utilization efficiency was always above 96% during both short-term and long-term tests. Taken together, nitrogen removal rate (especially the nitrate reduction rate by DAMO archaea) and methane utilization efficiency could be maintained at high levels in a broad range of methane partial pressure (0.24–1.39 atm in this study). In addition, a previously established DAMO/anammox biofilm model was used to analyze the experimental data. The observed impacts of methane partial pressure on biofilm activity were well explained by the modeling results. These results suggest that methane partial pressure can potentially be used as a manipulated variable to control reaction rates, ultimately to maintain high nitrogen removal efficiency, according to nitrogen loading rate.
Cai, Q, Turner, BD, Sheng, D & Sloan, S 2018, 'Application of kinetic models to the design of a calcite permeable reactive barrier (PRB) for fluoride remediation', Water Research, vol. 130, pp. 300-311.
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Cao, DL, Hong, G & Wang, J 2018, 'Chemical Heat Storage for Saving the Exhaust Gas Energy in a Spark Ignition Engine', Journal of Clean Energy Technologie, vol. 6, no. 1, pp. 41-46.
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This study was aimed to develop a chemical heat storage system using magnesium hydroxide (Mg(OH)2) and its dehydration and hydration reactions to recover the energy wasted in internal combustion engines (IC engine). The thermal energy of exhaust gas will be stored in the dehydration of Mg(OH)2 to become MgO and H2O, and to release in the hydration of MgO. Experiments were conducted on a 6-cylinder spark ignition engine to estimate the amount of energy loss in the exhaust gas and the reactor efficiency in the dehydration process. The stored heat used to heat fresh air from the ambient temperature to more convenient temperature. Results of the preliminary investigation show that the proposed chemical heat storage system is feasible to recover approximately 5.8 % of the heat loss and the temperature of the air is from 275.5 K to 305.4 K (with the ambient temperature is from 253 K to 283 K and the water vapor pressure is 47kPa).
Chaei, MG, Akbarnezhad, A, Castel, A, Lloyd, R, Keyte, L & Foster, S 2018, 'Precision of cement hydration heat models in capturing the effects of SCMs and retarders', Magazine of Concrete Research, vol. 70, no. 23, pp. 1217-1231.
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A major input to numerical simulation models used to predict the risk of early-age thermal cracking in concrete is the hydration heat estimation. The precision of hydration heat estimation models has been extensively verified for different cement compositions in previous studies. However, little has been done to investigate the accuracy of such models for concrete mixes containing supplementary cementitious materials and retarders. This paper presents the results of a series of isothermal calorimetry tests conducted first to investigate the effects of Class F fly ash, ground-granulated blast-furnace slag (GGBFS) and three commonly used retarders (namely, retarder N, sucrose and citrate) on the heat of hydration profile of Australian general-purpose cement under different curing temperatures of 10, 23 and 30°C, and second to evaluate the precision of the two most commonly used hydration heat models in capturing the effects of fly ash, GGBFS, retarders and curing temperature on the hydration profile. The results reveal the possibility of considerable errors in estimating the hydration heat of concrete mixes containing supplementary cementitious materials and retarders under different curing temperatures, highlighting the need for re-calibration of the existing models for locally used materials to avoid misleading errors in numerical simulation of early-age thermal cracking.
Chekli, L, Pathak, N, Kim, Y, Phuntsho, S, Li, S, Ghaffour, N, Leiknes, T & Shon, HK 2018, 'Combining high performance fertiliser with surfactants to reduce the reverse solute flux in the fertiliser drawn forward osmosis process', Journal of Environmental Management, vol. 226, pp. 217-225.
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© 2018 Elsevier Ltd Solutions to mitigate the reverse diffusion of solutes are critical to the successful commercialisation of the fertiliser drawn forward osmosis process. In this study, we proposed to combine a high performance fertiliser (i.e., ammonium sulfate or SOA) with surfactants as additives as an approach to reduce the reverse diffusion of ammonium ions. Results showed that combining SOA with both anionic and non-ionic surfactants can help in reducing the reverse salt diffusion by up to 67%. We hypothesised that, hydrophobic interactions between the surfactant tails and the membrane surface likely constricted membrane pores resulting in increased rejection of ions with large hydrated radii such as SO42−. By electroneutrality, the rejection of the counter ions (i.e., NH4+) also therefore subsequently improved. Anionic surfactant was found to further decrease the reverse salt diffusion due to electrostatic repulsions between the surfactant negatively-charged heads and SO42−. However, when the feed solution contains cations with small hydrated radii (e.g., Na+); it was found that NH4+ ions can be substituted in the DS to maintain its electroneutrality and thus the diffusion of NH4+ to the feed solution was increased.
Chen, C, Guo, WS, Ngo, HH, Chang, SW, Nguyen, DD, Zhang, J, Liang, S, Guo, JB & Zhang, XB 2018, 'Effects of C/N ratio on the performance of a hybrid sponge-assisted aerobic moving bed-anaerobic granular membrane bioreactor for municipal wastewater treatment', Bioresource Technology, vol. 247, pp. 340-346.
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This study aimed to evaluate the impact of C/N ratio on the performance of a hybrid sponge-assisted aerobic moving bed-anaerobic granular membrane bioreactor (SAAMB-AnGMBR) in municipal wastewater treatment. The results showed that organic removal efficiencies were above 94% at all C/N conditions. Nutrient removal was over 91% at C/N ratio of 100/5 but was negatively affected when decreasing C/N ratio to 100/10. At lower C/N ratio (100/10), more noticeable membrane fouling was caused by aggravated cake formation and pore clogging, and accumulation of extracellular polymeric substances (EPS) in the mixed liquor and sludge cake as a result of deteriorated granular quality. Foulant analysis suggested significant difference existed in the foulant organic compositions under different C/N ratios, and humic substances were dominant when the fastest fouling rate was observed. The performance of the hybrid system was found to recover when gradually increasing C/N ratio from 100/10 to 100/5.
Chen, Q, Zhou, Y & Nimbalkar, S 2018, 'Closure to “Estimation of Passive Earth Pressure against Rigid Retaining Wall Considering Arching Effect in Cohesive-Frictional Backfill under Translation Mode” by Yanyan Cai, Qingsheng Chen, Yitao Zhou, Sanjay Nimbalkar, and Jin Yu', International Journal of Geomechanics, vol. 18, no. 7, pp. 07018012-07018012.
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Chen, Q, Zhou, Y & Nimbalkar, S 2018, 'Closure to 'Estimation of passive earth pressure against rigid retaining wall considering arching effect in cohesive- frictional backfill under translation mode' by Yanyan Cai, Qingsheng Chen, Yitao Zhou, Sanjay Nimbalkar, and Jin Yu', International Journal of Geomechanics, vol. 18, no. 7.
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Chen, S, Yu, H & Fang, J 2018, 'A novel multi-cell tubal structure with circular corners for crashworthiness', Thin-Walled Structures, vol. 122, pp. 329-343.
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© 2017 Elsevier Ltd Multi-cell structures have proven to own excellent energy absorbing capability and lightweight effect in the automotive and aerospace industries. The cross-sectional configuration of the multi-cell structure has a significant effect on crashworthiness. Unlike existing multi-cell tubes, a new type of five-cell profile with four circular elements at the corners (C5C) was proposed in this study. To investigate the crashworthiness of the new C5C tube, finite element (FE) models were first established by using the nonlinear finite element code LS-DYNA and validated with experimental results. Following that, the comparison of the C5C tube and other multi-cell tubes with the same mass was conducted to quantify the relative merits of the C5C tube. Then, a detailed study was performed to analyze the effect of the corner-cell size and wall thickness. Finally, the optimization design was carried out to seek the optimal structure. The results showed that the new multi-cell structure can absorb much more crash energy than other four types of tubes. Moreover, the energy absorption of this new multi-cell tube C5C was affected by the corner-cell size and wall thickness significantly. A proper corner-cell size and slightly thicker internal ribs were recommended. In addition, the multi-objective particle swarm optimization (MOPSO) algorithm and radial basis function (RBF) surrogate model can optimize the structure effectively. The outcomes of the present study will facilitate the design of multi-cell structures with better crashworthiness.
Chen, X, Li, Y, Li, J & Gu, X 2018, 'A dual-loop adaptive control for minimizing time response delay in real-time structural vibration control with magnetorheological (MR) devices', Smart Materials and Structures, vol. 27, no. 1, pp. 015005-015005.
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© 2017 IOP Publishing Ltd. Time delay is a challenge issue faced by the real-time control application of the magnetorheological (MR) devices. Not to deal with it properly may jeopardize the effectiveness of the control, even lead to instability of the control system or catastrophic failure. This paper proposes a dual-loop adaptive control to address the response time delay associated with MR devices. In the proposed dual-loop control, the inner loop is designed to compensate the time delay of MR device induced by the PWM current driver. While the outer loop control can be any structural control algorithm with aims to reducing structural responses of a building during extreme loadings. Here an adaptive control strategy is adopted. To verify the proposed dual-loop control, a smart base isolation system employing magnetorheological elastomer base isolators is used as an example to illustrate the control effect. Numerical study is then conducted using a 5 -storey shear building model equipped with smart base isolation system. The result shows that with the implementation of the inner loop, the control current can instantly follow the control command which reduce the possibility of instability caused by the time delay. Comparative studies are conducted between three control strategies, i.e. dual-loop control, Lyapunov's direct method based control and optimal passive base isolation control. The results of the study have demonstrated that the proposed dual-loop control strategy can achieve much better performance than the other two control strategies.
Chen, X, Porto, CL, Chen, Z, Merenda, A, Allioux, F-M, d'Agostino, R, Magniez, K, Dai, XJ, Palumbo, F & Dumée, LF 2018, 'Single step synthesis of Janus nano-composite membranes by atmospheric aerosol plasma polymerization for solvents separation', Science of The Total Environment, vol. 645, pp. 22-33.
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Solvent permeation across membranes is limited due to physical resistance to diffusion from the selective layer within the membrane and to plasticizing effects generated by the solvent molecules onto the polymeric macromolecular matrix. Nano-composite thin film membranes provide promising routes to generate controlled microstructural separation materials with higher selectivities and permeabilities. Here, the fabrication of nano-composite based on octamethyl-polyhedral oligomeric silsesquioxane - hexamethyldisiloxane thin film membranes is demonstrated by aerosol assisted atmospheric plasma deposition onto pre-formed nano-porous membrane supports for the first time. Stable, atomically smooth and continuous solid films with controllable thickness down to 50 nm were achieved. The deposition process allowed for the control of the wettability of the surfaces to water and organic solvents, leading to the generation of hydrophobic but alcohol-philic surfaces. The liquid entry pressure of the films to water was found to be 8 bar from plasma polymerization as oppose to 3 bar for the bare nano-porous support only. In addition, the ideal separation selectivity for ethanol to water, up to 6.5, highlight the impact of both the surface energy and level of cross-linking of the hexamethyldisiloxane nanostructures on the diffusion mechanisms. This new atmospheric plasma deposition strategy opens-up cost-effective and environmentally friendly routes for the design of the smart Janus membrane with customizable properties and performance.
Chen, X, Yuan, Z & Ni, B-J 2018, 'Nitrite accumulation inside sludge flocs significantly influencing nitrous oxide production by ammonium-oxidizing bacteria', Water Research, vol. 143, pp. 99-108.
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© 2018 Elsevier Ltd This work aims to clarify the role of potential nitrite (NO2−) accumulation inside sludge flocs in N2O production by ammonium-oxidizing bacteria (AOB) at different dissolved oxygen (DO) levels with focus on the conditions of no significant bulk NO2− accumulation (<0.2 mg N/L). To this end, an augmented nitrifying sludge with much higher abundance of nitrite-oxidizing bacteria (NOB) than AOB was enriched and then used for systematically designed batch tests, which targeted a range of DO levels from 0 to 3.0 mg O2/L at a fixed ammonium concentration of 10 mg N/L. A two-pathway N2O model was applied to facilitate the interpretation of batch experimental data, thus shedding light on the relationships between N2O production pathways and key process parameters (i.e., DO and NO2− accumulation inside sludge flocs). The results demonstrated (i) the biomass specific N2O production rate firstly increased and then decreased with DO, with the maximum value of 3.03 ± 0.05 mg N/h/g VSS obtained at DO level of 0.75 mg O2/L, (ii) the AOB denitrification pathway for N2O production was dominant (98.0%) at all DO levels tested even without significant bulk NO2− accumulation (<0.2 mg N/L) observed in the system, but its contribution decreased with DO, (iii) DO had a positive impact on the hydroxylamine pathway for N2O production which therefore increased with DO, and (iv) the nitrite accumulation existed inside the sludge flocs and induced significant N2O production from the AOB denitrification pathway.
Chen, Y, Wu, Y, Wang, D, Li, H, Wang, Q, Liu, Y, Peng, L, Yang, Q, Li, X, Zeng, G & Chen, Y 2018, 'Understanding the mechanisms of how poly aluminium chloride inhibits short-chain fatty acids production from anaerobic fermentation of waste activated sludge', Chemical Engineering Journal, vol. 334, pp. 1351-1360.
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© 2017 Elsevier B.V. Poly aluminum chloride (PAC) is accumulated in waste activated sludge at high levels. However, details of how PAC affects short-chain fatty acids (SCFA) production from anaerobic sludge fermentation has not been documented. This work therefore aims to fill this knowledge gap by analyzing the impact of PAC on the aggregate of sludge flocs, disruption of extracellular polymeric substances (EPS), and the bio-processes of hydrolysis, acidogenesis, and methanogenesis. The relationship between SCFA production and different aluminum species (i.e., Ala, Alb, and Alc) was also identified by controlling different OH/Al ratio and pH in different fermentation systems. Experimental results showed that with the increase of PAC addition from 0 to 40 mg Al per gram of total suspended solids, SCFA yield decreased from 212.2 to 138.4 mg COD/g volatile suspended solids. Mechanism exploration revealed that PAC benefited the aggregates of sludge flocs and caused more loosely- and tightly-bound extracellular polymeric substances remained in sludge cells. Besides, it was found that the hydrolysis, acidiogenesis, and methanogenesis processes were all inhibited by PAC. Although three types of Al species, i.e., Ala (Al monomers, dimer, and trimer), Alb (Al13(AlO4Al12(OH)24(H2O)7 + 12), and Alc (Al polymer molecular weight normally larger than 3000 Da), were co-existed in fermentation systems, their impacts on SCFA production were different. No correlation was found between SCFA and Ala, whereas SCFA production decreased with the contents of Alb and Alc. Compared with Alb, Alc was the major contributor to the decreased SCFA production (R2 = 0.5132 vs R2 = 0.98). This is the first report revealing the underlying mechanism of how PAC affects SCFA production and identifying the contribution of different Al species to SCFA inhibition.
Chen, Z, Wang, D, Sun, M, Hao Ngo, H, Guo, W, Wu, G, Jia, W, Shi, L, Wu, Q, Guo, F & Hu, H-Y 2018, 'Sustainability evaluation and implication of a large scale membrane bioreactor plant', Bioresource Technology, vol. 269, pp. 246-254.
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Membrane bioreactor (MBR) technology is receiving increasing attention in wastewater treatment and reuse. This study presents an integral sustainability evaluation of a full scale MBR plant. The plant is capable of achieving prominent technical performance in terms of high compliance rate, low variation in effluent quality and high removal efficiency during long term operation. It is also more responsive to the new local standard with rigorous limits. However, electricity consumption is found to be the dominant process resulting in elevated life cycle environmental impacts and costs, accounting for 51.6% of the costs. As such, it is suggested to optimize energy use in MBR unit and implement sludge treatment and management. The prolonged membrane life span could also contribute largely to reduced life cycle environmental concerns and expenses. This study is of great theoretical significance and applicable value in guaranteeing the performance and sustainability of large scale MBR schemes.
Chen, Z, Yu, T, Ngo, HH, Lu, Y, Li, G, Wu, Q, Li, K, Bai, Y, Liu, S & Hu, H-Y 2018, 'Assimilable organic carbon (AOC) variation in reclaimed water: Insight on biological stability evaluation and control for sustainable water reuse', Bioresource Technology, vol. 254, pp. 290-299.
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This review highlights the importance of conducting biological stability evaluation due to water reuse progression. Specifically, assimilable organic carbon (AOC) has been identified as a practical indicator for microbial occurrence and regrowth which ultimately influence biological stability. Newly modified AOC bioassays aimed for reclaimed water are introduced. Since elevated AOC levels are often detected after tertiary treatment, the review emphasizes that actions can be taken to either limit AOC levels prior to disinfection or conduct post-treatment (e.g. biological filtration) as a supplement to chemical oxidation based approaches (e.g. ozonation and chlorine disinfection). During subsequent distribution and storage, microbial community and possible microbial regrowth caused by complex interactions are discussed. It is suggested that microbial surveillance, AOC threshold values, real-time field applications and surrogate parameters could provide additional information. This review can be used to formulate regulatory plans and strategies, and to aid in deriving relevant control, management and operational guidance.
Chenari, RJ, Fatahi, B, Ghorbani, A & Alamoti, MN 2018, 'Evaluation of strength properties of cement stabilized sand mixed with EPS beads and fly ash', Geomechanics and Engineering, vol. 14, no. 6, pp. 533-544.
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The importance of using materials cost effectively to enhance the strength and reduce the cost, and weight of earth fill materials in geotechnical engineering led researchers to seek for modifying the soil properties by adding proper additives. Lightweight fill materials made of soil, binder, water, and Expanded polystyrene (EPS) beads are increasingly being used in geotechnical practices. This paper primarily investigates the behavior of sandy soil, modified by EPS particles. Besides, the mechanical properties of blending sand, EPS and the binder material such as fly ash and cement were examined in different mixing ratios using a number of various laboratory studies including the Modified Standard Proctor (MSP) test, the Unconfined Compressive Strength (UCS) test, the California Bearing Ratio (CBR) test and the Direct Shear test (DST). According to the results, an increase of 0.1% of EPS results in a reduction of the density of the mixture for 10%, as well as making the mixture more ductile rather than brittle. Moreover, the compressive strength, CBR value and shear strength parameters of the mixture decreases by an increase of the EPS beads, a trend on the contrary to the increase of cement and fly ash content.
Cheng, D, Ngo, HH, Guo, W, Liu, Y, Chang, SW, Nguyen, DD, Nghiem, LD, Zhou, J & Ni, B 2018, 'Anaerobic membrane bioreactors for antibiotic wastewater treatment: Performance and membrane fouling issues', Bioresource Technology, vol. 267, pp. 714-724.
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© 2018 Elsevier Ltd Antibiotic wastewater has become a major concern due to the toxicity and recalcitrance of antibiotics. Anaerobic membrane bioreactors (AnMBRs) are considered alternative technology for treating antibiotic wastewater because of their advantages over the conventional anaerobic processes and aerobic MBRs. However, membrane fouling remains the most challenging issue in the AnMBRs’ operation and this limits their application. This review critically discusses: (i) antibiotics removal and antibiotic resistance genes (ARGs) in different types of AnMBRs and the impact of antibiotics on membrane fouling and (ii) the integrated AnMBRs systems for fouling control and removal of antibiotics. The presence of antibiotics in AnMBRs could aggravate membrane fouling by influencing fouling-related factors (i.e., sludge particle size, extracellular polymeric substances (EPS), soluble microbial products (SMP), and fouling-related microbial communities). Conclusively, integrated AnMBR systems can be a practical technology for antibiotic wastewater treatment.
Cheng, DL, Ngo, HH, Guo, WS, Chang, SW, Nguyen, DD, Kumar, SM, Du, B, Wei, Q & Wei, D 2018, 'Problematic effects of antibiotics on anaerobic treatment of swine wastewater', Bioresource Technology, vol. 263, pp. 642-653.
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Swine wastewaters with high levels of organic pollutants and antibiotics have become serious environmental concerns. Anaerobic technology is a feasible option for swine wastewater treatment due to its advantage in low costs and bioenergy production. However, antibiotics in swine wastewater have problematic effects on micro-organisms, and the stability and performance of anaerobic processes. Thus, this paper critically reviews impacts of antibiotics on pH, COD removal efficiencies, biogas and methane productions as well as the accumulation of volatile fatty acids (VFAs) in the anaerobic processes. Meanwhile, impacts on the structure of bacteria and methanogens in anaerobic processes are also discussed comprehensively. Furthermore, to better understand the effect of antibiotics on anaerobic processes, detailed information about antimicrobial mechanisms of antibiotics and microbial functions in anaerobic processes is also summarized. Future research on deeper knowledge of the effect of antibiotics on anaerobic processes are suggested to reduce their adverse environmental impacts.
Cheng, DL, Ngo, HH, Guo, WS, Liu, YW, Zhou, JL, Chang, SW, Nguyen, DD, Bui, XT & Zhang, XB 2018, 'Bioprocessing for elimination antibiotics and hormones from swine wastewater', Science of The Total Environment, vol. 621, pp. 1664-1682.
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© 2017 Elsevier B.V. Antibiotics and hormones in swine wastewater have become a critical concern worldwide due to the severe threats to human health and the eco-environment. Removal of most detectable antibiotics and hormones, such as sulfonamides (SAs), SMs, tetracyclines (TCs), macrolides, and estrogenic hormones from swine wastewater utilizing various biological processes were summarized and compared. In biological processes, biosorption and biodegradation are the two major removal mechanisms for antibiotics and hormones. The residuals in treated effluents and sludge of conventional activated sludge and anaerobic digestion processes can still pose risks to the surrounding environment, and the anaerobic processes’ removal efficiencies were inferior to those of aerobic processes. In contrast, membrane bioreactors (MBRs), constructed wetlands (CWs) and modified processes performed better because of their higher biodegradation of toxicants. Process modification on activated sludge, anaerobic digestion and conventional MBRs could also enhance the performance (e.g. removing up to 98% SMs, 88.9% TCs, and 99.6% hormones from wastewater). The hybrid process combining MBRs with biological or physical technology also led to better removal efficiency. As such, modified conventional biological processes, advanced biological technologies and MBR hybrid systems are considered as a promising technology for removing toxicants from swine wastewater.
Chia, SR, Chew, KW, Show, PL, Yap, YJ, Ong, HC, Ling, TC & Chang, J-S 2018, 'Analysis of Economic and Environmental Aspects of Microalgae Biorefinery for Biofuels Production: A Review', Biotechnology Journal, vol. 13, no. 6, pp. 1700618-1700618.
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Chia, SR, Ong, HC, Chew, KW, Show, PL, Phang, S-M, Ling, TC, Nagarajan, D, Lee, D-J & Chang, J-S 2018, 'Sustainable approaches for algae utilisation in bioenergy production', Renewable Energy, vol. 129, pp. 838-852.
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Chia, SR, Show, PL, Phang, S-M, Ling, TC & Ong, HC 2018, 'Sustainable approach in phlorotannin recovery from macroalgae', Journal of Bioscience and Bioengineering, vol. 126, no. 2, pp. 220-225.
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Chu Van, T, Ristovski, Z, Surawski, N, Bodisco, TA, Rahman, SMA, Alroe, J, Miljevic, B, Hossain, FM, Suara, K, Rainey, T & Brown, RJ 2018, 'Effect of sulphur and vanadium spiked fuels on particle characteristics and engine performance of auxiliary diesel engines', Environmental Pollution, vol. 243, no. Pt B, pp. 1943-1951.
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© 2018 Elsevier Ltd Particle emission characteristics and engine performance were investigated from an auxiliary, heavy duty, six-cylinder, turbocharged and after-cooled diesel engine with a common rail injection system using spiked fuels with different combinations of sulphur (S) and vanadium (V) spiking. The effect of fuel S content on both particle number (PN) and mass (PM) was clearly observed in this study. Higher PN and PM were observed for fuels with higher S contents at all engine load conditions. This study also found a correlation between fuel S content and nucleation mode particle number concentration which have more harmful impact on human health than larger particles. The highest PN and PM were observed at partial load conditions. In addition, S in fuel resulted in higher viscosity of spiked fuels, which led to lower engine blow-by. Fuel V content was observed in this study, evidencing that it had no clear effect on engine performance and emissions. Increased engine load also resulted in higher engine blow-by. The lower peak of in-cylinder pressure observed at both pre-mixed and diffusion combustion phases with the spiked fuels may be associated with the lower energy content in the fuel blends compared to diesel fuel.
Chuah, S, Li, W, Chen, SJ, Sanjayan, JG & Duan, WH 2018, 'Investigation on dispersion of graphene oxide in cement composite using different surfactant treatments', Construction and Building Materials, vol. 161, pp. 519-527.
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© 2017 Elsevier Ltd Graphene oxide (GO) is a novel class of two-dimensional nanoscale sheet material due to its excellent dispersibility in water, high aspect ratio and good intrinsic strengths. In order to obtain a well-distributed GO-reinforced cement composites, the dispersion of GO in water, alkali and several ionic species are investigated with the aid of UV–vis spectroscopy. High alkalinity and calcium ions are key factors inducing the agglomeration of GO in cement system. Dispersion of GO in simulated pore solution is the culmination of the alkali and salt experiments. Agglomeration of GO occurred when GO contacted with the simulated pore solution, highlighting the necessity to protect GO against such aggressive media. The test on surfactant compatibility was then carried out to ensure GO was effectively dispersed in polycarboxylate, air-entrainment and Gum Arabic admixtures within the pore solution. Polycarboxylate-based superplasticisers gave the most promising results to disperse GO in cement alkaline environment. Flexural experiments was performed to highlight the importance of fabrication protocol on the mechanical properties of GO-cement composites. The result shows that the amount of 0.03% GO by weight of cement can increase the flexural strength of GO-cement composite up to 67%.
Cu Thi, P, Ball, J & Dao, N 2018, 'Uncertainty Estimation Using the Glue and Bayesian Approaches in Flood Estimation: A case Study—Ba River, Vietnam', Water, vol. 10, no. 11, pp. 1641-1641.
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In the last few decades tremendous progress has been made in the use of catchment models for the analysis and understanding of hydrologic systems. A common application involves the use of these models to predict flows at catchment outputs. However, the outputs predicted by these models are often deterministic because they focused only on the most probable forecast without an explicit estimate of the associated uncertainty. This paper uses Bayesian and Generalized Likelihood Uncertainty Estimation (GLUE) approaches to estimate uncertainty in catchment modelling parameter values and uncertainty in design flow estimates. Testing of join probability of both these estimates has been conducted for a monsoon catchment in Vietnam. The paper focuses on computational efficiency and the differences in results, regardless of the philosophies and mathematical rigor of both methods. It was found that the application of GLUE and Bayesian techniques resulted in parameter values that were statistically different. The design flood quantiles estimated by the GLUE method were less scattered than those resulting from the Bayesian approach when using a closer threshold value (1 standard deviation departed from the mean). More studies are required to evaluate the impact of threshold in GLUE on design flood estimation.
Cui, Z, Wang, J, Zhang, H, Ngo, HH, Jia, H, Guo, W, Gao, F, Yang, G & Kang, D 2018, 'Investigation of backwashing effectiveness in membrane bioreactor (MBR) based on different membrane fouling stages', Bioresource Technology, vol. 269, pp. 355-362.
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In this study the effect of different fouling stages of hollow fiber membranes on effective backwashing length in MBR has been investigated. Computational fluid dynamics (CFD) is imported to simulate backwashing process. A multi-physics coupling model for free porous media flow, convective mass transfer and diluted species transport was established. The laser bijection sensors (LBS) were imported to monitor the backwashing solution position inside fiber lumen. Simulation results indicated that membrane fouling degree could change the velocity of backwash solution inside fiber lumen and make a further effect on effective backwash length. The signal variations of LBS are in accordance with the simulation results. The backwashing process can only play an active role when the filtration pressure is below the critical TMP. It can be concluded that backwash duration in industrial applications need to be set based on changes in TMP.
da Rocha, CG & Kemmer, S 2018, 'Integrating product and process design in construction', Construction Management and Economics, vol. 36, no. 9, pp. 535-543.
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© 2018, © 2018 Informa UK Limited, trading as Taylor & Francis Group. Product modularity namely the notion that products can be decomposed into parts (or modules) has been widely applied in manufacturing but not in construction, precluding this industry to also benefit from it. The narrow definition of a module, which is often simplistically equated to a sub-assembly produced off-site, and the lack of integration between product and process design, which is typical in construction, are argued to be two root causes of such problem. This paper starts by discussing the operational implications of misaligned decisions in these two domains in an empirical study addressing a high-rise apartments building project. Seven guidelines are then devised using a Design Science Research (DSR) approach for integrating product (product modularity and modules) and process (work structure and work packages) design. The results indicate that product modularity can be applied for improving operations regardless of the construction method(s) used. Yet, a revised understanding of modules (as a material, a component, a non-volumetric or a volumetric sub-assembly) is needed in addition to a coordinated product and process design, particularly for traditional construction.
da Rocha, CG & Miron, LIG 2018, 'The House Factory: A Simulation Game for Understanding Mass Customization in House Building', Journal of Professional Issues in Engineering Education and Practice, vol. 144, no. 1, pp. 05017007-05017007.
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Dadzie, J, Runeson, G & Ding, G 2018, 'Determinants of sustainable upgrade for energy efficiency – the case of existing buildings in Australia', Energy Procedia, vol. 153, pp. 284-289.
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© 2018 The Authors. Published by Elsevier Ltd. The impact of existing buildings on the environment is on the rise; thus to achieve environmental sustainability requires sustainable upgrade (SU) of existing built facilities. Over the years, SU has focused on technologies with little attention given to the nature and conditions of existing buildings. The purpose of this paper is to identify existing building characteristics that impact SU. A detailed literature review on the nature and characteristics of existing buildings, as well as energy and environmental performance was undertaken. A survey questionnaire with all the determinants of existing buildings was administered to sustainability and construction professionals in Australia. The results show that size of building, age of building, U-value of wall, U-value of ceiling, area of external wall, thickness of insulation materials, occupancy, size of window opening, life span of sustainable technologies, and the type of building impact sustainable upgrade of existing buildings for energy efficiency.
Dadzie, J, Runeson, G, Ding, G & Bondinuba, F 2018, 'Barriers to Adoption of Sustainable Technologies for Energy-Efficient Building Upgrade—Semi-Structured Interviews', Buildings, vol. 8, no. 4, pp. 57-57.
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© 2018 by the authors. Globally, only 2% of existing building stock is built yearly; the remaining 98% already exist. Energy consumption and indoor thermal comfort of the existing building stock are not encouraging. This is due to many challenges associated with existing buildings; the challenges range from cracks, leakages, poor insulation, heat losses and high rate of unsustainable technologies. This paper investigates possible barriers facing the adoption and application of sustainable technologies (STs) for sustainable or energy-efficient upgrade of existing buildings. New STs are manufactured on a regular basis to meet improved energy efficiency standards, yet there are minimal actions/attempts to adopt and apply improved technologies in existing buildings for energy efficiency. Indeed, there are limited studies focused on the use of qualitative approaches to identify barriers to adoption and use of STs. Thus, a semi-structured interview approach was adopted and applied using sustainability/energy efficiency professionals, building services engineers, project managers, architects, and facility managers in Australia. The results indicate that barriers to the adoption and application of sustainable technologies are perceived benefits in demolish-and-build, age of building, cost of STs, perceived poor payback time, unreliable energy-savings projections, existing design, hidden and overall cost of renovation, and cost of STs.
Damanik, N, Ong, HC, Tong, CW, Mahlia, TMI & Silitonga, AS 2018, 'A review on the engine performance and exhaust emission characteristics of diesel engines fueled with biodiesel blends', Environmental Science and Pollution Research, vol. 25, no. 16, pp. 15307-15325.
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© 2018, Springer-Verlag GmbH Germany, part of Springer Nature. Biodiesels have gained much popularity because they are cleaner alternative fuels and they can be used directly in diesel engines without modifications. In this paper, a brief review of the key studies pertaining to the engine performance and exhaust emission characteristics of diesel engines fueled with biodiesel blends, exhaust aftertreatment systems, and low-temperature combustion technology is presented. In general, most biodiesel blends result in a significant decrease in carbon monoxide and total unburned hydrocarbon emissions. There is also a decrease in carbon monoxide, nitrogen oxide, and total unburned hydrocarbon emissions while the engine performance increases for diesel engines fueled with biodiesels blended with nano-additives. The development of automotive technologies, such as exhaust gas recirculation systems and low-temperature combustion technology, also improves the thermal efficiency of diesel engines and reduces nitrogen oxide and particulate matter emissions.
De Medeiros, JF, Da Rocha, CG & Ribeiro, JLD 2018, 'Design for sustainable behavior (DfSB): Analysis of existing frameworks of behavior change strategies, experts' assessment and proposal for a decision support diagram', Journal of Cleaner Production, vol. 188, pp. 402-415.
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Deng, L, Ngo, H-H, Guo, W, Wang, J & Zhang, H 2018, 'Evaluation of a new sponge addition-microbial fuel cell system for removing nutrient from low C/N ratio wastewater', Chemical Engineering Journal, vol. 338, pp. 166-175.
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© 2018 This study developed a new microbial fuel cell (MFC) system (Sponge-MFC), which consisted of a cathodic chamber with an added sponge and two anodic chambers, for low carbon/nitrogen (C/N) wastewater treatment. When operating in the closed-circuit state, the Sponge-MFC(C) demonstrated its superior electrochemical performance compared to the closed-circuit MFC. This superiority took the form of higher coulombic efficiencies, voltage outputs, current densities and power densities. Adding a sponge could reduce the cathode's charge transfer resistance and solution resistance, and improve its capacitance, thus increasing cathodic reaction rate and power outputs. Simultaneous nitrification denitrification (SND) and bioelectrochemical denitrification processes on the cathode coupled with the sponge's SND process were responsible for efficient removal of nitrogen from the Sponge-MFC(C). Fluorescent in situ hybridization (FISH) analysis revealed that nitrifying bacteria and highly diversified denitrifying bacteria were distributed at the cathode's outer layer and inner layer, respectively. Higher phosphorus removal efficiencies (82.06 ± 1.21%) in the Sponge-MFC(C) than that in the MFC(C) (53.97 ± 2.32%) could be ascribed to biological phosphorus removal and precipitation of phosphate salts on the cathode. These results suggested the Sponge-MFC(C) could accomplish better electrochemical behaviors and nutrient removal due to sponge addition when treating wastewater with low C/N ratio.
Do, MH, Ngo, HH, Guo, WS, Liu, Y, Chang, SW, Nguyen, DD, Nghiem, LD & Ni, BJ 2018, 'Challenges in the application of microbial fuel cells to wastewater treatment and energy production: A mini review', Science of The Total Environment, vol. 639, pp. 910-920.
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© 2018 Wastewater is now considered to be a vital reusable source of water reuse and saving energy. However, current wastewater has multiple limitations such as high energy costs, large quantities of residuals being generated and lacking in potential resources. Recently, great attention has been paid to microbial fuel cells (MFCs) due to their mild operating conditions where a variety of biodegradable substrates can serve as fuel. MFCs can be used in wastewater treatment facilities to break down organic matter, and they have also been analysed for application as a biosensor such as a sensor for biological oxygen which demands monitoring. MFCs represent an innovation technology solution that is simple and rapid. Despite the advantages of this technology, there are still practical barriers to consider including low electricity production, current instability, high internal resistance and costly materials used. Thus, many problems must be overcome and doing this requires a more detailed analysis of energy production, consumption, and application. Currently, real-world applications of MFCs are limited due to their low power density level of only several thousand mW/m2. Efforts are being made to improve the performance and reduce the construction and operating costs of MFCs. This paper explores several aspects of MFCs such as anode, cathode and membrane, and in an effort to overcome the practical challenges of this system.
Dong, Y, Fatahi, B, Khabbaz, H & Zhang, H 2018, 'Influence of particle contact models on soil response of poorly graded sand during cavity expansion in discrete element simulation', Journal of Rock Mechanics and Geotechnical Engineering, vol. 10, no. 6, pp. 1154-1170.
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© 2018 Institute of Rock and Soil Mechanics, Chinese Academy of Sciences The discrete element method (DEM) has been extensively adopted to investigate many complex geotechnical related problems due to its capability to incorporate the discontinuous nature of granular materials. In particular, when simulating large deformations or distortion of soil (e.g. cavity expansion), DEM can be very effective as other numerical solutions may experience convergence problems. Cavity expansion theory has widespread applications in geotechnical engineering, particularly to the problems concerning in situ testing, pile installation and so forth. In addition, the behaviour of geomaterials in a macro-level is utterly determined by microscopic properties, highlighting the importance of contact models. Despite the fact that there are numerous contact models proposed to mimic the realistic behaviour of granular materials, there are lack of studies on the effects of these contact models on the soil response. Hence, in this study, a series of three-dimensional numerical simulations with different contact constitutive models was conducted to simulate the response of sandy soils during cylindrical cavity expansion. In this numerical investigation, three contact models, i.e. linear contact model, rolling resistance contact model, and Hertz contact model, are considered. It should be noted that the former two models are linear based models, providing linearly elastic and frictional plasticity behaviours, whereas the latter one consists of nonlinear formulation based on an approximation of the theory of Mindlin and Deresiewicz. To examine the effects of these contact models, several cylindrical cavities were created and expanded gradually from an initial radius of 0.055 m to a final radius of 0.1 m. The numerical predictions confirm that the calibrated contact models produced similar results regarding the variations of cavity pressure, radial stress, deviatoric stress, volumetric ...
Dorji, P, Choi, J, Kim, DI, Phuntsho, S, Hong, S & Shon, HK 2018, 'Membrane capacitive deionisation as an alternative to the 2nd pass for seawater reverse osmosis desalination plant for bromide removal', Desalination, vol. 433, pp. 113-119.
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© 2018 Elsevier B.V. Most Australian surface and ground waters have relatively high concentration of bromide between 400 and 8000 μg/L and even higher concentration in seawater between 60,000–78,000 μg/L. Although bromide is not regulated, even at low concentrations of 50–100 μg/L, it can lead to the formation of several types of harmful disinfection by-products (DBPs) during the disinfection process. One of the major concerns with brominated DBPs is the formation of bromate (BrO3−), a serious carcinogen that is formed when water containing a high concentration of bromide is disinfected. As a result, bromate is highly regulated in Australian water standards with the maximum concentration of 20 μg/L in the drinking water. Since seawater reverse osmosis (SWRO) desalination plays an important role in augmenting fresh water supplies in Australia, SWRO plants in Australia usually adopt 2nd pass brackish water reverse osmosis (BWRO) for effective bromide removal, which is not only energy-intensive to operate but also has higher capital cost. In this study, we evaluated the feasibility of membrane capacitive deionisation (MCDI) as one of the alternatives to the 2nd pass BWRO for effective bromide removal in a more energy efficient way.
Douglas, A, Torpy, F, Surawski, N & Irga, P 2018, 'Mapping Urban Aerosolized Fungi: Predicting Spatial and Temporal Indoor Concentrations', Human Ecology Review, vol. 24, no. 2, pp. 81-103.
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Duan, H, Wang, Q, Erler, DV, Ye, L & Yuan, Z 2018, 'Effects of free nitrous acid treatment conditions on the nitrite pathway performance in mainstream wastewater treatment', Science of The Total Environment, vol. 644, pp. 360-370.
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© 2018 Elsevier B.V. Inline sludge treatment using free nitrous acid (FNA) was recently shown to be effective in establishing the nitrite pathway in a biological nitrogen removal system. However, the effects of FNA treatment conditions on the nitrite pathway performance remained to be investigated. In this study, three different FNA treatment frequencies (daily sludge treatment ratios of 0.22, 0.31 and 0.38, respectively), two FNA concentrations (1.35 mgN/L and 4.23 mgN/L, respectively) and two influent feeding regimes (one- and two-step feeding) were investigated in four laboratory-scale sequencing batch reactors. The nitrite accumulation ratio was positively correlated to the FNA treatment frequency. However, when a high treatment frequency was used e.g., daily sludge treatment ratio of 0.38, a significant reduction in ammonia oxidizing bacteria (AOB) activity occurred, leading to poor ammonium oxidation. AOB were able to acclimatise to FNA concentrations up to of 4.23 mgN/L, whereas nitrite oxidizing bacteria (NOB) were limited by an FNA concentration of 1.35 mgN/L over the duration of the study (up to 120 days). This difference in sensitivity to FNA could be used to further enhance nitrite accumulation, with 90% accumulation achieved at an FNA concentration of 4.23 mgN/L and a daily sludge treatment ratio of 0.31 in this study. However, this high level of nitrite accumulation led to increased N2O emission, with emission factors of up to 3.9% observed. The N2O emission was mitigated (reduced to 1.3%) by applying two-step feeding resulting in a nitrite accumulation ratio of 45.1%. Economic analysis showed that choosing the optimal FNA treatment conditions depends on a combination of the wastewater characteristics, the nitrogen discharge standards, and the operational costs. This study provides important information for the optimisation and practical application of FNA-based sludge treatment technology for achieving the mainstream stable nitrite pathway.
Duong, HC, Ansari, AJ, Nghiem, LD, Pham, TM & Pham, TD 2018, 'Low Carbon Desalination by Innovative Membrane Materials and Processes', Current Pollution Reports, vol. 4, no. 4, pp. 251-264.
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Duong, HC, Chuai, D, Woo, YC, Shon, HK, Nghiem, LD & Sencadas, V 2018, 'A novel electrospun, hydrophobic, and elastomeric styrene-butadiene-styrene membrane for membrane distillation applications', Journal of Membrane Science, vol. 549, pp. 420-427.
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© 2017 In this study, a novel hydrophobic, microporous membrane was fabricated from styrene-butadiene-styrene (SBS) polymer using electrospinning and evaluated for membrane distillation applications. Compared to a commercially available polytetrafluoroethylene (PTFE) membrane, the SBS membrane had larger membrane pore size and fiber diameter and comparable membrane porosity. The fabricated SBS showed slightly lower water flux than the PTFE membrane because it was two times thicker. However, the SBS membrane had better salt rejection and most importantly could be fabricated via a simple process. The SBS membrane was also more hydrophobic than the reference PTFE membrane. In particular, as temperature of the reference water liquid increased to 60 °C, the SBS membrane remained hydrophobic with a contact angle of 100° whereas the PTFE became hydrophilic with a contact angle of less than 90°. The hydrophobic membrane surface prevented the intrusion of liquid into the membrane pores, thus improving the salt rejection of the SBS membrane. In addition, the SBS membrane had superior mechanical strength over the PTFE membrane. Using the SBS membrane, stable water flux was achieved throughout an extended MD operation period of 120 h to produce excellent quality distillate (over 99.7% salt rejection) from seawater.
Eeshwarasinghe, D, Loganathan, P, Kalaruban, M, Sounthararajah, DP, Kandasamy, J & Vigneswaran, S 2018, 'Removing polycyclic aromatic hydrocarbons from water using granular activated carbon: kinetic and equilibrium adsorption studies', Environmental Science and Pollution Research, vol. 25, no. 14, pp. 13511-13524.
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© 2018, Springer-Verlag GmbH Germany, part of Springer Nature. Polycyclic aromatic hydrocarbons (PAHs) constitute a group of highly persistent, toxic and widespread environmental micropollutants that are increasingly found in water. A study was conducted in removing five PAHs, specifically naphthalene, acenaphthylene, acenaphthene, fluorene and phenanthrene, from water by adsorption onto granular activated carbon (GAC). The pseudo-first-order (PFO) model satisfactorily described the kinetics of adsorption of the PAHs. The Weber and Morris diffusion model’s fit to the data showed that there were faster and slower rates of intra-particle diffusion probably into the mesopores and micropores of the GAC, respectively. These rates were negatively related to the molar volumes of the PAHs. Batch equilibrium adsorption data fitted well to the Langmuir, Freundlich and Dubinin–Radushkevich models, of which the Freundlich model exhibited the best fit. The adsorption affinities were related to the hydrophobicity of the PAHs as determined by the log Kow values. Free energies of adsorption calculated from the Dubinin–Radushkevich model and the satisfactory kinetic data fitting to the PFO model suggested physical adsorption of the PAHs. Adsorption of naphthalene, acenaphthylene and acenaphthene in fixed-bed columns containing a mixture of GAC (0.5 g) + sand (24.5 g) was satisfactorily simulated by the Thomas model.
Fang, J, Sun, G, Qiu, N, Pang, T, Li, S & Li, Q 2018, 'On hierarchical honeycombs under out-of-plane crushing', International Journal of Solids and Structures, vol. 135, pp. 1-13.
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© 2017 Hierarchy has been introduced to honeycomb structures in pursuing ultralight materials with outstanding mechanical properties. Nevertheless, the hierarchical honeycombs under the out-of-plane loads have not been well studied experimentally and analytically for energy absorption to date. This study aimed to apply a special structural hierarchy to the honeycomb by replacing the sides of hexagons with smaller hexagons. The quasi-static test of the hierarchical honeycomb specimen was first conducted experimentally to investigate the crushing behaviours; and then the corresponding finite element (FE) analyses were performed. Finally, the analytical solutions to the mean crushing force and plateau stress were derived based on the simplified super folding element (SSFE) method. It was shown that the experimental data and numerical results agreed well in terms of crushing force versus displacement relation and energy absorption characteristics; and the analytical results were validated by the experimental test. Importantly, the hierarchy could improve the energy absorption; and the increase in the order and number of replacement hexagons could excavate the advantage even further. Specifically, the second order honeycomb characterized by five smaller replacement hexagons at each order can yield a plateau stress 2.63 and 4.16 times higher than the regular honeycomb and the aluminium foam, respectively. While it might lead to global bending, structural hierarchy provides new architectural configurations for developing novel ultralight materials with exceptional energy absorption capacity under out-of-plane loads.
Fatahi, B, Van Nguyen, Q, Xu, R & Sun, W-J 2018, 'Three-Dimensional Response of Neighboring Buildings Sitting on Pile Foundations to Seismic Pounding', International Journal of Geomechanics, vol. 18, no. 4, pp. 04018007-04018007.
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© 2018 American Society of Civil Engineers. Seismic pounding occurs when the separation gap between buildings and structures is not wide enough, particularly during major earthquake events; this can cause them to collide, causing local damage or, in extreme cases, collapse. This study investigated the impact that this separation gap has on the seismic response of midrise buildings supported on piles while considering seismic soil-pile-structure interaction (SSPSI). To achieve this aim, three 15-story reinforced concrete buildings sitting on pile foundations and with five different separation gaps under excitations from the 1994 Northridge and 1995 Kobe earthquakes were numerically simulated. This study used three-dimensional numerical modeling to simultaneously capture the effects of seismic pounding and SSPSI. Because the considered structure, pile foundation, and soil deposit are three-dimensional in nature, the adopted three-dimensional numerical modeling can provide a more realistic simulation to capture the seismic behavior of the system. The nonlinear behavior of structural elements was included, and the dynamic soil properties were obtained from field data and backbone curves. A contact pair interface with small-sliding surface-to-surface formulation between buildings was used to capture possible seismic pounding, and contact interfaces with a finite-sliding formulation were used to simulate the interaction between the piles and the soil. The results, including lateral building deflections, interstory drifts, structural shear forces, foundation rocking, lateral pile deflections, and the distributions of bending moments and shear forces of the piles, are presented and discussed. The findings of this study will give engineers a better insight into the possible effects of seismic pounding on the seismic performance of buildings, and the response of endbearing piles in soft soils.
Fattah, IMR, Ming, C, Chan, QN, Wehrfritz, A, Pham, PX, Yang, W, Kook, S, Medwell, PR, Yeoh, GH, Hawkes, ER & Masri, AR 2018, 'Spray and Combustion Investigation of Post Injections under Low-Temperature Combustion Conditions with Biodiesel', Energy & Fuels, vol. 32, no. 8, pp. 8727-8742.
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Post injection is a multiple-injection strategy that is commonly used as a particulate matter control measure to reduce soot emissions, yet the mechanisms and the interactions between the main and post injections are only vaguely understood. For this work, experiments were performed to assess the effects of varying dwell time between the main and post injections in a compression-ignition (CI) engine environment simulated using a constant-volume combustion chamber. The ambient density, bulk temperature, and oxygen concentration used for this work were controlled at 19.4 kg/m3, 900 K, and 15 vol % O2, respectively. A canola oil-based biodiesel was tested and injected at a fixed injection pressure of 100 MPa into the simulated CI engine environment. A mass ratio of 80%-20% was maintained between the main and post injections, with the dwell time between the injections varied from 1.5 to 2.5 ms. Comparative measurements were performed using the same fuel and injection schedules, but at a higher ambient gas temperature condition of 1100 K. Optical diagnostics methods, including diffused-back illumination and high-speed flame luminosity imaging, were used to assess the spray and combustion processes of the post injection test case. Under the conditions of this work, it was found that the ignition delays, ignition locations, and flame lift-off lengths of the post injection flames are consistently shorter than those of the main injections, with the variations influenced by the extent of the interaction of the post injection with the combustion products from the main injection. A two-color pyrometry technique was also used to measure the soot temperature and soot concentration factor information on the main-post injection cases. The data revealed a greater interaction between the main and post injections resulted in a more rapid development of the soot zone of the post injection with higher temperature after ignition. The distribution of the most probable soot co...
Feng, J, Wu, D, Gao, W & Li, G 2018, 'Hybrid uncertain natural frequency analysis for structures with random and interval fields', Computer Methods in Applied Mechanics and Engineering, vol. 328, pp. 365-389.
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This paper presents a robust non-deterministic free vibration analysis for engineering structures involving hybrid, yet spatially dependent, uncertain system parameters. Distinguished from the conventional hybrid uncertain eigenvalue problem, the concept of interval field is enclosed with random field model such that, both the stochastic and non-stochastic representations of the spatial dependency of the uncertainties are simultaneously incorporated within a unified non-deterministic free vibration analysis. In order to determine the probabilistic characteristics (i.e., means and standard deviations) of the extremities of structural natural frequencies, an extended unified interval stochastic sampling (X-UISS) method is implemented for the purpose of effective hybrid uncertain free vibration analysis. By meticulously blending sharpness-promised interval eigenvalue analysis with stochastic sampling techniques, the stochastic profiles (i.e., probability density functions (PDFs) and the cumulative distribution functions (CDFs)) of the extreme bounds of the structural natural frequencies can be rigorously established by utilizing the adequate statistical inference methods. The applicability and effectiveness of the proposed computational framework are evidently demonstrated through the numerical investigations on various practically motivated engineering structures.
Fu, Q, Ranji-Burachaloo, H, Liu, M, McKenzie, TG, Tan, S, Reyhani, A, Nothling, MD, Dunstan, DE & Qiao, GG 2018, 'Controlled RAFT polymerization facilitated by a nanostructured enzyme mimic', Polymer Chemistry, vol. 9, no. 35, pp. 4448-4454.
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A nanostructured MOF composite was utilized as an enzyme mimic for the generation of hydroxyl radicals from hydrogen peroxide, which can subsequently initiate RAFT polymerizations in aqueous or organic media.
Fujioka, T, Nguyen, K, Hoang, A, Ueyama, T, Yasui, H, Terashima, M & Nghiem, L 2018, 'Biofouling Mitigation by Chloramination during Forward Osmosis Filtration of Wastewater', International Journal of Environmental Research and Public Health, vol. 15, no. 10, pp. 2124-2124.
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Pre-concentration is essential for energy and resource recovery from municipal wastewater. The potential of forward osmosis (FO) membranes to pre-concentrate wastewater for subsequent biogas production has been demonstrated, although biofouling has also emerged as a prominent challenge. This study, using a cellulose triacetate FO membrane, shows that chloramination of wastewater in the feed solution at 3–8 mg/L residual monochloramine significantly reduces membrane biofouling. During a 96-h pre-concentration, flux in the chloraminated FO system decreased by only 6% and this flux decline is mostly attributed to the increase in salinity (or osmotic pressure) of the feed due to pre-concentration. In contrast, flux in the non-chloraminated FO system dropped by 35% under the same experimental conditions. When the feed was chloraminated, the number of bacterial particles deposited on the membrane surface was significantly lower compared to a non-chloraminated wastewater feed. This study demonstrated, for the first time, the potential of chloramination to inhibit bacteria growth and consequently biofouling during pre-concentration of wastewater using a FO membrane.
Fujioka, T, O'Rourke, BE, Michishio, K, Kobayashi, Y, Oshima, N, Kodamatani, H, Shintani, T & Nghiem, LD 2018, 'Transport of small and neutral solutes through reverse osmosis membranes: Role of skin layer conformation of the polyamide film', Journal of Membrane Science, vol. 554, pp. 301-308.
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© 2018 Elsevier B.V. The polyamide skin layer of reverse osmosis (RO) membranes was characterised using advanced and complementary analytical techniques to investigate the mechanisms underlying the permeation of contaminants of emerging concern in potable water reuse – N-nitrosodimethylamine (NDMA) and N-nitrosomethylethylamine (NMEA). This study used five RO membrane samples with similar membrane properties. The five RO membrane samples spanned over a large range of water permeance (0.9–5.8 L/m2 h bar) as well as permeation of NDMA (9–66%) and NMEA (3–29%). Despite these differences among the five RO membranes, characterisations of the skin layer using positron annihilation lifetime spectroscopy, atomic force microscopy and field emission scanning electron microscopy revealed almost no variation in their free-volume hole-radius (0.270–0.275 nm), effective surface area (198–212%) and thickness (30–35 nm) of the skin layer. The results suggest that there could be other RO skin layer properties, such as the interconnectivity of the protuberances within the polyamide skin layer additional to the free-volume hole-size and thickness of the skin layer, which can also govern water and solute permeation.
Gan, YY, Ong, HC, Ling, TC, Zulkifli, NWM, Wang, C-T & Yang, Y-C 2018, 'Thermal conductivity optimization and entropy generation analysis of titanium dioxide nanofluid in evacuated tube solar collector', Applied Thermal Engineering, vol. 145, pp. 155-164.
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Gan, YY, Ong, HC, Show, PL, Ling, TC, Chen, W-H, Yu, KL & Abdullah, R 2018, 'Torrefaction of microalgal biochar as potential coal fuel and application as bio-adsorbent', Energy Conversion and Management, vol. 165, pp. 152-162.
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Gao, K, Gao, W, Wu, B, Wu, D & Song, C 2018, 'Nonlinear primary resonance of functionally graded porous cylindrical shells using the method of multiple scales', Thin-Walled Structures, vol. 125, pp. 281-293.
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An analytical method is proposed for the nonlinear primary resonance analysis of cylindrical shells made of functionally graded (FG) porous materials subjected to a uniformly distributed harmonic load including the damping effect. The Young's modulus, shear modulus and density of porous materials are assumed to vary through the thickness direction based on the assumption of a common mechanical feature of the open-cell foam. Three types of FG porous distributions, namely symmetric porosity distribution, non-symmetric porosity stiff or soft distribution and uniform porosity distribution are considered in this paper. Theoretical formulations are derived based on Donnell shell theory (DST) and accounting for von-Kármán strain-displacement relation and damping effect. The first mode of deflection function that satisfies the boundary conditions is introduced into this nonlinear governing partial differential equation and then a Galerkin-based procedure is utilized to obtain a Duffing-type nonlinear ordinary differential equation with a cubic nonlinear term. Finally, the governing equation is solved analytically by conducting the method of multiple scales (MMS) which results in frequency-response curves of FG porous cylindrical shells in the presence of damping effect. The detailed parametric studies on porosity distribution, porosity coefficient, damping ratio, amplitude and frequency of the external harmonic excitation, aspect ratio and thickness ratio, shown that the distribution type of FG porous cylindrical shells significantly affects primary resonance behavior and the response presents a hardening-type nonlinearity, which provides a useful help for the design and optimize of FG porous shell-type devices working under external harmonic excitation.
Gao, K, Gao, W, Wu, D & Song, C 2018, 'Nonlinear dynamic buckling of the imperfect orthotropic E-FGM circular cylindrical shells subjected to the longitudinal constant velocity', International Journal of Mechanical Sciences, vol. 138-139, pp. 199-209.
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In this study, an analytical approach on the nonlinear dynamic buckling of the orthotropic circular cylindrical shells made of exponential law functionally graded material (E-FGM) subjected to the longitudinal constant velocity is investigated with the incorporation of mercurial damping effect. The material properties are assumed to vary gradually in the thickness direction according to an exponential distribution function of the volume fraction of constituent materials. Theoretical formulations are derived based on improved Donnell shell theory (DST) and accounting for von-Kármán strain–displacement relation, initial imperfection and damping effect. By applying Galerkin method and Airy's stress function, the obtained nonlinear differential equations are solved numerically by the fourth-order Runge–Kutta method. The nonlinear dynamic stability of the orthotropic FG cylindrical shell is assessed based on Budiansky–Roth criterion. Additionally, a parametric study is conducted to demonstrate the effects of various velocities, initial imperfections, damping ratios, inhomogeneous parameters on nonlinear dynamic buckling behavior of an imperfect orthotropic FG cylindrical shell. Comparing results with those in other publications validates the proposed method.
Gao, K, Gao, W, Wu, D & Song, C 2018, 'Nonlinear dynamic stability of the orthotropic functionally graded cylindrical shell surrounded by Winkler-Pasternak elastic foundation subjected to a linearly increasing load', Journal of Sound and Vibration, vol. 415, pp. 147-168.
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This paper focuses on the dynamic stability behaviors of the functionally graded (FG) orthotropic circular cylindrical shell surrounded by the two-parameter (Winkler-Pasternak) elastic foundation subjected to a linearly increasing load with the consideration of damping effect. The material properties are assumed to vary gradually in the thickness direction based on an exponential distribution function of the volume fraction of constituent materials. Equations of motion are derived from Hamilton's principle and the nonlinear compatibility equation is considered by the means of modified Donnell shell theory including large deflection. Then the nonlinear dynamic buckling equation is solved by a hybrid analytical-numerical method (combined Galerkin method and fourth-order Runge-Kutta method). The nonlinear dynamic stability of the FG orthotropic cylindrical shell is assessed based on Budiansky-Roth criterion. Additionally, effects of different parameters such as various inhomogeneous parameters, loading speeds, damping ratios and aspect ratios and thickness ratios of the structure on dynamic buckling are discussed in details. Finally, the proposed method is validated with published literature.
Gao, L, Chen, J, Liu, Y, Yamauchi, Y, Huang, Z & Kong, X 2018, 'Revealing the chemistry of an anode-passivating electrolyte salt for high rate and stable sodium metal batteries', Journal of Materials Chemistry A, vol. 6, no. 25, pp. 12012-12017.
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A compact and conductive solid-electrolyte interphase formed by NaDFOB enables high performance of sodium metal batteries.
Gao, W, Wu, D, Gao, K, Chen, X & Tin-Loi, F 2018, 'Structural reliability analysis with imprecise random and interval fields', Applied Mathematical Modelling, vol. 55, pp. 49-67.
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This paper investigates the issue of reliability assessment for engineering structures involving mixture of stochastic and non-stochastic uncertain parameters through the Finite Element Method (FEM). Non-deterministic system inputs modelled by both imprecise random and interval fields have been incorporated, so the applicability of the structural reliability analysis scheme can be further promoted to satisfy the intricate demand of modern engineering application. The concept of robust structural reliability profile for systems involving hybrid uncertainties is discussed, and then a new computational scheme, namely the unified interval stochastic reliability sampling (UISRS) approach, is proposed for assessing the safety of engineering structures. The proposed method provides a robust semi-sampling scheme for assessing the safety of engineering structures involving multiple imprecise random fields with various distribution types and interval fields simultaneously. Various aspects of structural reliability analysis with multiple imprecise random and interval fields are explored, and some theoretically instructive remarks are also reported herein.
Gong, B, Wang, S, Sloan, SW, Sheng, D & Tang, C 2018, 'Modelling Coastal Cliff Recession Based on the GIM–DDD Method', Rock Mechanics and Rock Engineering, vol. 51, no. 4, pp. 1077-1095.
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Gong, L, Heitor, A & Indraratna, B 2018, 'An approach to measure infill matric suction of irregular infilled rock joints under constant normal stiffness shearing', Journal of Rock Mechanics and Geotechnical Engineering, vol. 10, no. 4, pp. 653-660.
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Gong, Y, Zhao, D & Wang, Q 2018, 'An overview of field-scale studies on remediation of soil contaminated with heavy metals and metalloids: Technical progress over the last decade', Water Research, vol. 147, pp. 440-460.
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© 2018 Elsevier Ltd Soil contamination by heavy metals and metalloids has been a major concern to human health and environmental quality. While many remediation technologies have been tested at the bench scale, there have been only limited reports at the field scale. This paper aimed to provide a comprehensive overview on the field applications of various soil remediation technologies performed over the last decade or so. Under the general categories of physical, chemical, and biological approaches, ten remediation techniques were critically reviewed. The technical feasibility and economic effectiveness were evaluated, and the pros and cons were appraised. In addition, attention was placed to the environmental impacts of the remediation practices and long-term stability of the contaminants, which should be taken into account in the establishment of remediation goals and environmental criteria. Moreover, key knowledge gaps and practical challenges are identified.
Gonzales, R, Park, M, Tijing, L, Han, D, Phuntsho, S & Shon, H 2018, 'Modification of Nanofiber Support Layer for Thin Film Composite forward Osmosis Membranes via Layer-by-Layer Polyelectrolyte Deposition', Membranes, vol. 8, no. 3, pp. 70-70.
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Electrospun nanofiber-supported thin film composite membranes are among the most promising membranes for seawater desalination via forward osmosis. In this study, a high-performance electrospun polyvinylidenefluoride (PVDF) nanofiber-supported thin film composite (TFC) membrane was successfully fabricated after molecular layer-by-layer polyelectrolyte deposition. Negatively-charged electrospun polyacrylic acid (PAA) nanofibers were deposited on electrospun PVDF nanofibers to form a support layer consisted of PVDF and PAA nanofibers. This resulted to a more hydrophilic support compared to the plain PVDF nanofiber support. The PVDF-PAA nanofiber support then underwent a layer-by-layer deposition of polyethylenimine (PEI) and PAA to form a polyelectrolyte layer on the nanofiber surface prior to interfacial polymerization, which forms the selective polyamide layer of TFC membranes. The resultant PVDF-LbL TFC membrane exhibited enhanced hydrophilicity and porosity, without sacrificing mechanical strength. As a result, it showed high pure water permeability and low structural parameter values of 4.12 L m−2 h−1 bar−1 and 221 µm, respectively, significantly better compared to commercial FO membrane. Layer-by-layer deposition of polyelectrolyte is therefore a useful and practical modification method for fabrication of high performance nanofiber-supported TFC membrane.
Gulzar, M, Mahmood, K, Zahid, R, Alabdulkarem, A, Masjuki, HH, Kalam, MA, Varman, M, Zulkifli, NWM, Ahmad, P & Malik, MSS 2018, 'The effect of particle size on the dispersion and wear protection ability of MoS2 particles in polyalphaolefin and trimethylolpropane ester', Proceedings of the Institution of Mechanical Engineers, Part J: Journal of Engineering Tribology, vol. 232, no. 8, pp. 987-998.
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The effect of particle size and surfactant on dispersion stability and wear protection ability was experimentally evaluated for polyalphaolefin (PAO 10) and bio-based base oil (palm trimethylolpropane ester) added with molybdenum disulfide (MoS2) particles. Nanolubricants were developed by adding 1 wt% of MoS2 particles that varied in size. In addition to the variation in particle size, an anionic surfactant was also used to analyze its interaction with both types of nanoparticles for stable suspensions and for the related effects on the antiwear characteristics. The wear protection characteristics of the formulations were evaluated by four-ball extreme pressure tests and piston ring on cylinder sliding wear tests. The wear surfaces were analyzed by scanning electron microscopy along with an energy-dispersive X-ray and an atomic force microscopy. The MoS2 nanoparticles with a nominal size of 20 nm exhibited a better load-carrying capacity, while better sliding wear protection was provided by nanoparticles with a nominal size of 50 nm.
Guo, Y, Xie, H, Zhang, J, Wang, W, Ngo, HH, Guo, W, Kang, Y & Zhang, B 2018, 'Improving nutrient removal performance of surface flow constructed wetlands in winter using hardy submerged plant-benthic fauna systems', RSC Advances, vol. 8, no. 73, pp. 42179-42188.
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A novel hardy submerged plant-benthic fauna systems to enhance the performance of surface flow constructed wetlands in winter.
Guo, Z, Le, AN, Feng, X, Choo, Y, Liu, B, Wang, D, Wan, Z, Gu, Y, Zhao, J, Li, V, Osuji, CO, Johnson, JA & Zhong, M 2018, 'Janus Graft Block Copolymers: Design of a Polymer Architecture for Independently Tuned Nanostructures and Polymer Properties', Angewandte Chemie, vol. 130, no. 28, pp. 8629-8633.
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AbstractThe graft‐through synthesis of Janus graft block copolymers (GBCPs) from branched macromonomers composed of various combinations of homopolymers is presented. Self‐assembly of GBCPs resulted in ordered nanostructures with ultra‐small domain sizes down to 2.8 nm (half‐pitch). The grafted architecture introduces an additional parameter, the backbone length, which enables control over the thermomechanical properties and processability of the GBCPs independently of their self‐assembled nanostructures. The simple synthetic route to GBCPs and the possibility of using a variety of polymer combinations contribute to the universality of this technique.
Guo, Z, Le, AN, Feng, X, Choo, Y, Liu, B, Wang, D, Wan, Z, Gu, Y, Zhao, J, Li, V, Osuji, CO, Johnson, JA & Zhong, M 2018, 'Janus Graft Block Copolymers: Design of a Polymer Architecture for Independently Tuned Nanostructures and Polymer Properties', Angewandte Chemie International Edition, vol. 57, no. 28, pp. 8493-8497.
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AbstractThe graft‐through synthesis of Janus graft block copolymers (GBCPs) from branched macromonomers composed of various combinations of homopolymers is presented. Self‐assembly of GBCPs resulted in ordered nanostructures with ultra‐small domain sizes down to 2.8 nm (half‐pitch). The grafted architecture introduces an additional parameter, the backbone length, which enables control over the thermomechanical properties and processability of the GBCPs independently of their self‐assembled nanostructures. The simple synthetic route to GBCPs and the possibility of using a variety of polymer combinations contribute to the universality of this technique.
Hamdani, Rizal, S, Riza, M & Mahlia, TMI 2018, 'Mechanical properties of concrete containing beeswax/dammar gum as phase change material for thermal energy storage', AIMS Energy, vol. 6, no. 3, pp. 521-529.
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© 2018 the Author(s). This study aims to investigate the mechanical properties of concrete containing phase change materials (PCM). This research begins with the investigation of melting temperature, enthalpy, the thermal conductivity of the phase change materials using the T-history method, followed by preparation of concrete containing PCM, and finally testing of mechanical properties of concrete through compressive strength test. This study used beeswax, tallow, and dammar gum as PCM mixture. From the results of the PCM properties test, shows that the latent heat energy content from beeswax and tallow exhibit an excellent potential to be used as PCM, while dammar gum is benefited in increasing the thermal conductivity of concrete containing PCM. From concrete specimen test containing 10%, 20% and 30% PCM with 7 days and 28 days aged, the results exhibit that the mechanical properties of the concrete decreased along with the increasing of PCM content. The same test also conducted at the PCM melting temperature. Therefore, the concrete compressive strength test conducted at 45 °C. From the test results, the concrete compressive strength decreased about 3-24% of PCM-0% concrete compressive strength. Drastic compressive strength reduction tends to occur in PCM-Tallow concrete mixture. This study concluded that the PCM is potentially useful as a heat energy absorber material in buildings and lightweight concrete rather than construction structures.
Han, F, Wei, D, Ngo, HH, Guo, W, Xu, W, Du, B & Wei, Q 2018, 'Performance, microbial community and fluorescent characteristic of microbial products in a solid-phase denitrification biofilm reactor for WWTP effluent treatment', Journal of Environmental Management, vol. 227, pp. 375-385.
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Microbial products, i.e. extracellular polymeric substance (EPS) and soluble microbial product (SMP), have a significant correlation with microbial activity of biologically based systems. In present study, the spectral characteristics of two kinds of microbial products were comprehensively evaluated in a solid-phase denitrification biofilm reactor for WWTP effluent treatment by using poly (butylene succinate) (PBS) as carbon source. After the achievement of PBS-biofilm, nitrate and total nitrogen removal efficiencies were high of 97.39 ± 1.24% and 96.38 ± 1.1%, respectively. The contents of protein and polysaccharide were changed different degrees in both LB-EPS and TB-EPS. Excitation-emission matrix (EEM) implied that protein-like substances played a significant role in the formation of PBS-biofilm. High-throughput sequencing result implied that the proportion of denitrifying bacteria, including Simplicispira, Dechloromonas, Diaphorobacter, Desulfovibrio, increased to 9.2%, 7.4%, 4.8% and 3.6% in PBS-biofilm system, respectively. According to EEM-PARAFAC, two components were identified from SMP samples, including protein-like substances for component 1 and humic-like and fulvic acid-like substances for component 2, respectively. Moreover, the fluorescent scores of two components expressed significant different trends to reaction time. Gas chromatography-mass spectrometer (GC-MS) implied that some new organic matters were produced in the effluent of SP-DBR due to biopolymer degradation and denitrification processes. The results could provide a new insight about the formation and stability of solid-phase denitrification PBS-biofilm via the point of microbial products.
Handique, L & Chakraborty, S 2018, 'A new four-parameter extension of Burr-XII distribution: its properties and applications', Japanese Journal of Statistics and Data Science, vol. 1, no. 2, pp. 271-296.
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Hannan, MA, Faisal, M, Ker, PJ, Mun, LH, Parvin, K, Mahlia, TMI & Blaabjerg, F 2018, 'A Review of Internet of Energy Based Building Energy Management Systems: Issues and Recommendations', IEEE Access, vol. 6, pp. 38997-39014.
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© 2013 IEEE. A building energy management system (BEMS) is a sophisticated method used for monitoring and controlling a building's energy requirements. A number of potential studies were conducted in nearly or net zero energy buildings (nZEBs) for the optimization of building energy consumption through efficient and sustainable ways. Moreover, policy makers are approving measures to improve building energy efficiency in order to foster sustainable energy usages. However, the intelligence of existing BEMSs or nZEBs is inadequate, because of the static set points for heating, cooling, and lighting, the complexity of large amounts of BEMS data, data loss, and network problems. To solve these issues, a BEMS or nZEB solution based on the Internet of energy (IoE) provides disruptive opportunities for revolutionizing sustainable building energy management. This paper presents a critical review of the potential of an IoE-based BEMS for enhancing the performance of future generation building energy utilization. The detailed studies of the IoE architecture, typical nZEB configuration, different generations of nZEB, and smart building energy systems for future BEMS are investigated. The operations, advantages, and limitations of the existing BEMSs or nZEBs are illustrated. A comprehensive review of the different types of IoE-based BEMS technologies, such as energy routers, storage systems and materials, renewable sources, and plug-and-play interfaces, is then presented. The rigorous review indicates that existing BEMSs require advanced controllers integrated with IoE-based technologies for sustainable building energy usage. The main objective of this review is to highlight several issues and challenges of the conventional controllers and IoE applications of BEMSs or nZEBs. Accordingly, the review provides several suggestions for the research and development of the advanced optimized controller and IoE of future BEMSs. All the highlighted insights and recommendatio...
Hawari, AH, Al-Qahoumi, A, Ltaief, A, Zaidi, S & Altaee, A 2018, 'Dilution of seawater using dewatered construction water in a hybrid forward osmosis system', Journal of Cleaner Production, vol. 195, pp. 365-373.
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© 2018 Elsevier Ltd In this study, dewatered construction water was used for the first time as the feed solution in a combined pretreatment-forward osmosis process to dilute seawater (i.e. draw solution) for further desalination. It was found that at a feed solution and a draw solution flow rate of 2.2 L min−1 gave the optimum membrane flux with minimal fouling effects. The addition of a spacer in the membrane feed side was effective at low flow rates (0.8 and 1.5 L min−1). The feed solution was then pretreated using two methods: settling and multimedia filtration and used in the forward osmosis unit at a low flow rate of 0.8 L min−1 using a spacer at the feed side. Results revealed a significant increase in the forward osmosis membrane flux by 64.3% when multimedia filtration was carried out with a flux reduction of 7.7%. While the settling method achieved only 13.5% increase in the permeate flux and 12.5% flux reduction. The multimedia filtration process removed most of the particles that would cause fouling which resulted in an elevated and more consistent membrane flux. Results also showed that the water flux was 1.3 times higher when the membrane's active layer was facing the draw solution than when it was facing the feed solution. Cost analysis showed that forward osmosis treatment of dewatered construction water was 7.88 $.day−1 and it was slightly cheaper when the forward osmosis operates in the pressure retarded osmosis mode.
He, X, Liang, D & Bolton, MD 2018, 'Run-out of cut-slope landslides: mesh-free simulations', Géotechnique, vol. 68, no. 1, pp. 50-63.
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This study uses an incompressible smoothed-particle hydrodynamics (ISPH) model to investigate the run-out and deposit morphology of granular materials flowing down cut slopes. The primary aim is to study the influence of various factors on the run-out and to summarise a quantitative relationship for direct use in landslide hazard management. In the model, the granular materials are modelled as a rigid perfectly plastic material with a Coulomb yield surface. The coupled continuity equation and momentum equation are solved by a semi-implicit algorithm. The model is first validated and its results are carefully compared with various controlled experiments regarding granular flows. The model reproduces the flows and correctly predicts the deposition profiles under various conditions. Then, the computational results are used to study the run-out and mobility of landslides. For granular columns collapsing onto a flat surface, a normalised run-out and a new scaling relationship are proposed, which are supported by numerous measured and numerical results. A similar relationship for the run-out of granular rectangles on steep slopes has also been explored. It is found that the normalised run-out is mainly determined by the slope angle and the normalised drop height. Furthermore, three types of idealised cut-slope landslides are simulated to study the influence of the initial landslide shape on the run-out. It is found that the normalised run-out of these idealised cut-slope landslides is smaller than that of granular rectangles on slopes of the same angles and drop heights. The difference between the run-outs is found to be mainly determined by the proportion of the whole mass that initially lies above a predictable discontinuity plane.
He, X, Liang, D, Wu, W, Cai, G, Zhao, C & Wang, S 2018, 'Study of the interaction between dry granular flows and rigid barriers with an SPH model', International Journal for Numerical and Analytical Methods in Geomechanics, vol. 42, no. 11, pp. 1217-1234.
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SummaryThis study uses an incompressible smoothed‐particle hydrodynamics model to investigate the interaction between dry granular material flows and rigid barriers. The primary aim is to summarise some practical guidelines for the design of debris‐resisting barriers. The granular materials are modelled as a rigid‐perfectly plastic material where the plastic flow corresponds to the critical state. The coupled continuity equation and momentum equation are solved by a semi‐implicit algorithm. Compared with flows in controlled flume experiments, the model adequately reproduces both the kinetic of the flows and the impact force under various conditions. Then the numerical simulations are used to study the detailed interaction process. It is illustrated quantitatively that the interaction force consists of two parts, ie, the earth pressure force caused by the weight of the soil and a dynamic force caused by the internal deformation (flowing mass on top of a dead zone). For the estimation of impact load, this study suggests that an increased earth pressure coefficient depending on the Froude number should be incorporated into the hydrostatic model.
He, Z, Zhang, S, Teng, J, Yao, Y & Sheng, D 2018, 'A coupled model for liquid water-vapor-heat migration in freezing soils', Cold Regions Science and Technology, vol. 148, pp. 22-28.
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Ho, L & Fatahi, B 2018, 'Analytical solution to axisymmetric consolidation of unsaturated soil stratum under equal strain condition incorporating smear effects', International Journal for Numerical and Analytical Methods in Geomechanics, vol. 42, no. 15, pp. 1890-1913.
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SummaryThis paper proposes closed‐form analytical solutions to the axisymmetric consolidation of an unsaturated soil stratum using the equal strain hypothesis. Following the 1‐dimensional (1D) consolidation theory for unsaturated soil mechanics, polar governing equations describing the air and water flows are first presented on the basis of Fick's law and Darcy's law, respectively. The current study takes into account the peripheral smear caused by an installation of vertical drain. Separation of variables and Laplace transformation are mainly adopted in the analytical derivation to obtain final solutions. Then, the hydraulic conductivity ratio, the radius of influence zone and smear parameters influencing time‐dependent excess pore pressures, and the average degree of consolidation are graphically interpreted. In this study, a comparison made between the proposed equal strain results and the existing free strain results suggests that both hypotheses would deliver similar predictions. Moreover, it is found that the smear zone resulting from vertical drain installations would hinder the consolidation rate considerably.
Ho, L, Fatahi, B & Khabbaz, H 2018, 'Analytical Solution to One-Dimensional Consolidation in Unsaturated Soil Deposit Incorporating Time-Dependent Diurnal Temperature Variation', International Journal of Geomechanics, vol. 18, no. 5, pp. 04018029-04018029.
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© 2018 American Society of Civil Engineers. Several experimental studies have demonstrated that temperature changes may significantly influence the deformation of unsaturated soils. Thus, there is an essential need to develop a predictive framework for unsaturated consolidation capturing the nonisothermal effect. This paper presents an analytical solution to the one-dimensional (1D) consolidation of unsaturated soil deposit in response to temperature variation. A set of governing equations of flow incorporating the nonisothermal condition were first obtained. Then, Fourier sine series and the Laplace transformation were used to derive solutions based on these governing equations. This study highlighted the effect of diurnal temperature variation on pore pressures and soil deformation at different depths while considering two conditions of interest: (1) no external applied load, and (2) application of step loading to the ground surface. In addition, the thermal diffusivity characterizing the consolidation behavior of unsaturated soils was also investigated and is discussed in this paper. It is predicted that a decrease in thermal diffusivity would attenuate the effects of diurnal temperature on the unsaturated consolidation.
Hoque, MA-A, Phinn, S, Roelfsema, C & Childs, I 2018, 'Assessing tropical cyclone risks using geospatial techniques', Applied Geography, vol. 98, pp. 22-33.
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Hoque, MA-A, Phinn, S, Roelfsema, C & Childs, I 2018, 'Modelling tropical cyclone risks for present and future climate change scenarios using geospatial techniques', International Journal of Digital Earth, vol. 11, no. 3, pp. 246-263.
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How, HG, Masjuki, HH, Kalam, MA & Teoh, YH 2018, 'Influence of injection timing and split injection strategies on performance, emissions, and combustion characteristics of diesel engine fueled with biodiesel blended fuels', Fuel, vol. 213, pp. 106-114.
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How, HG, Masjuki, HH, Kalam, MA, Teoh, YH & Chuah, HG 2018, 'Effect of Calophyllum Inophyllum biodiesel-diesel blends on combustion, performance, exhaust particulate matter and gaseous emissions in a multi-cylinder diesel engine', Fuel, vol. 227, pp. 154-164.
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Hu, J, Zhang, Q, Lee, D-J & Ngo, HH 2018, 'Feasible use of microbial fuel cells for pollution treatment', Renewable Energy, vol. 129, pp. 824-829.
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© 2017 Elsevier Ltd. The microbial fuel cells (MFC) can directly transform chemical energy in feed substance to electricity by anodic aspiration pathways. This mini review provides an order-of-magnitude argument that MFC has much lower catalyst density at electrode surface and much higher diffusional resistance for substrates than the chemical fuel cell, the former should not be used as an energy generation unit; rather, it should be applied in low power density level applications such as biofilm wastewater treatment. The literature studies using MFC for pollution treatment are discussed.
Hu, Y, Wang, XC, Ngo, HH, Sun, Q & Yang, Y 2018, 'Anaerobic dynamic membrane bioreactor (AnDMBR) for wastewater treatment: A review', Bioresource Technology, vol. 247, pp. 1107-1118.
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© 2017 Elsevier Ltd Recently, an increasing level of attention has focused on the emerging technology of anaerobic dynamic membrane bioreactors (AnDMBRs), owing to its merits such as low membrane module cost, easy control of membrane fouling, low energy consumption and sludge production, as well as biogas production. As research on AnDMBRs is still in the nascent stage, an introduction of bioreactor configurations, dynamic membrane (DM) module, and DM layer formation and cleaning is firstly presented. The process performance of the AnDMBR for wastewater treatment is then reviewed with regard to pollutant removal, DM filterability, biogas production, and potential advantages over the conventional anaerobic membrane bioreactor (AnMBR). In addition, the important parameters affecting process performance are briefly discussed. Lastly, the challenges encountered and perspectives regarding the future development of the AnDMBR process to promote its practical applications are presented.
Huang, L, Li, M, Ngo, HH, Guo, W, Xu, W, Du, B, Wei, Q & Wei, D 2018, 'Spectroscopic characteristics of dissolved organic matter from aquaculture wastewater and its interaction mechanism to chlorinated phenol compound', Journal of Molecular Liquids, vol. 263, pp. 422-427.
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© 2017 In present study, the characteristics of dissolved organic matter (DOM) from aquaculture wastewater and its interaction to 4-chlorophenol (4-CP) was evaluated via a spectroscopic approach. According to EEM-PARAFAC analysis, two components were derived from the interaction samples between DOM and 4-CP, including humic-like and fulvic-like substances for component 1 and protein-like substances for component 2, respectively. The fluorescence intensity scores of two PARAFAC-derived components decreased with increasing 4-CP concentration. Synchronous fluorescence coupled to two-dimensional correlation spectroscopy (2D-COS) implied that DOM fractions quenched different degrees and occurred in the order of fulvic-like and humic-like fractions > protein-like fraction. Moreover, the quenching mechanisms were mainly caused by static quenching process. It was also found from Fourier transform infrared spectroscopy that the main functional groups for interaction between 4-CP and DOM were O–H stretching and C[dbnd]O stretching vibration. The obtained results provided a spectroscopic approach for characterizing the interaction between organic pollutant and DOM from aquaculture wastewater.
Huang, L, Li, M, Si, G, Wei, J, Ngo, HH, Guo, W, Xu, W, Du, B, Wei, Q & Wei, D 2018, 'Assessment of microbial products in the biosorption process of Cu(II) onto aerobic granular sludge: Extracellular polymeric substances contribution and soluble microbial products release', Journal of Colloid and Interface Science, vol. 527, pp. 87-94.
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© 2018 In the present study, the responses of microbial products in the biosorption process of Cu(II) onto aerobic granular sludge were evaluated by using batch and spectroscopic approaches. Batch experimental data showed that extracellular polymeric substances (EPSs) contributed to Cu(II) removal from an aqueous solution, especially when treating low metal concentrations, whereas soluble microbial products (SMPs) were released under the metal stress during biosorption process. A three-dimensional excitation-emission matrix (3D-EEM) identified four main fluorescence peaks in the EPS, i.e., tryptophan protein-like, aromatic protein-like, humic-like and fulvic acid-like substances, and their fluorescence intensities decreased gradually in the presence of Cu(II) during the sorption process. Particularly, tryptophan protein-like substances quenched the Cu(II) binding to a much higher extent through a static quenching process with less than one class of binding sites. According to the synchronous fluorescence spectra, the whole fluorescence intensity of released SMP samples expressed an increased trend with different degrees along with contact time. Two-dimensional correlation spectroscopy (2D-COS) suggested that the fulvic-like fluorescence fraction might be more susceptible to metal exposure than other fractions. The result of molecular weight distribution demonstrated that the SMPs released from the biosorption process differed significantly according to contact time. The result obtained could provide new insights into the responses of microbial products from aerobic granular sludge with heavy metal treatment.
Huang, Y, Ng, ECY, Zhou, JL, Surawski, NC, Chan, EFC & Hong, G 2018, 'Eco-driving technology for sustainable road transport: A review', Renewable and Sustainable Energy Reviews, vol. 93, pp. 596-609.
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© 2018 Elsevier Ltd Road transport consumes significant quantities of fossil fuel and accounts for a significant proportion of CO2 and pollutant emissions worldwide. The driver is a major and often overlooked factor that determines vehicle performance. Eco-driving is a relatively low-cost and immediate measure to reduce fuel consumption and emissions significantly. This paper reviews the major factors, research methods and implementation of eco-driving technology. The major factors of eco-driving are acceleration/deceleration, driving speed, route choice and idling. Eco-driving training programs and in-vehicle feedback devices are commonly used to implement eco-driving skills. After training or using in-vehicle devices, immediate and significant reductions in fuel consumption and CO2 emissions have been observed with slightly increased travel time. However, the impacts of both methods attenuate over time due to the ingrained driving habits developed over the years. These findings imply the necessity of developing quantitative eco-driving patterns that could be integrated into vehicle hardware so as to generate more constant and uniform improvements, as well as developing more effective and lasting training programs and in-vehicle devices. Current eco-driving studies mainly focus on the fuel savings and CO2 reduction of individual vehicles, but ignore the pollutant emissions and the impacts at network levels. Finally, the challenges and future research directions of eco-driving technology are elaborated.
Huang, Y, Organ, B, Zhou, JL, Surawski, NC, Hong, G, Chan, EFC & Yam, YS 2018, 'Emission measurement of diesel vehicles in Hong Kong through on-road remote sensing: Performance review and identification of high-emitters', Environmental Pollution, vol. 237, pp. 133-142.
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© 2018 Elsevier Ltd A two-year remote sensing measurement program was carried out in Hong Kong to obtain a large dataset of on-road diesel vehicle emissions. Analysis was performed to evaluate the effect of vehicle manufacture year (1949–2015) and engine size (0.4–20 L) on the emission rates and high-emitters. The results showed that CO emission rates of larger engine size vehicles were higher than those of small vehicles during the study period, while HC and NO were higher before manufacture year 2006 and then became similar levels between manufacture years 2006 and 2015. CO, HC and NO of all vehicles showed an unexpectedly increasing trend during 1998–2004, in particular ≥6001 cc vehicles. However, they all decreased steadily in the last decade (2005–2015), except for NO of ≥6001 cc vehicles during 2013–2015. The distributions of CO and HC emission rates were highly skewed as the dirtiest 10% vehicles emitted much higher emissions than all the other vehicles. Moreover, this skewness became more significant for larger engine size or newer vehicles. The results indicated that remote sensing technology would be very effective to screen the CO and HC high-emitters and thus control the on-road vehicle emissions, but less effective for controlling NO emissions. No clear correlation was observed between the manufacture year and percentage of high-emitters for ≤3000 cc vehicles. However, the percentage of high-emitters decreased with newer manufacture year for larger vehicles. In addition, high-emitters of different pollutants were relatively independent, in particular NO emissions, indicating that high-emitter screening criteria should be defined on a CO-or-HC-or-NO basis, rather than a CO-and-HC-and-NO basis.
Huang, Y, Organ, B, Zhou, JL, Surawski, NC, Hong, G, Chan, EFC & Yam, YS 2018, 'Remote sensing of on-road vehicle emissions: Mechanism, applications and a case study from Hong Kong', Atmospheric Environment, vol. 182, pp. 58-74.
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© 2018 Elsevier Ltd Vehicle emissions are a major contributor to air pollution in cities and have serious health impacts to their inhabitants. On-road remote sensing is an effective and economic tool to monitor and control vehicle emissions. In this review, the mechanism, accuracy, advantages and limitations of remote sensing were introduced. Then the applications and major findings of remote sensing were critically reviewed. It was revealed that the emission distribution of on-road vehicles was highly skewed so that the dirtiest 10% vehicles accounted for over half of the total fleet emissions. Such findings highlighted the importance and effectiveness of using remote sensing for in situ identification of high-emitting vehicles for further inspection and maintenance programs. However, the accuracy and number of vehicles affected by screening programs were greatly dependent on the screening criteria. Remote sensing studies showed that the emissions of gasoline and diesel vehicles were significantly reduced in recent years, with the exception of NOx emissions of diesel vehicles in spite of greatly tightened automotive emission regulations. Thirdly, the experience and issues of using remote sensing for identifying high-emitting vehicles in Hong Kong (where remote sensing is a legislative instrument for enforcement purposes) were reported. That was followed by the first time ever identification and discussion of the issue of frequent false detection of diesel high-emitters using remote sensing. Finally, the challenges and future research directions of on-road remote sensing were elaborated.
Huang, Y, Yam, YS, Lee, CKC, Organ, B, Zhou, JL, Surawski, NC, Chan, EFC & Hong, G 2018, 'Tackling nitric oxide emissions from dominant diesel vehicle models using on-road remote sensing technology', Environmental Pollution, vol. 243, no. Pt B, pp. 1177-1185.
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© 2018 Elsevier Ltd Remote sensing provides a rapid detection of vehicle emissions under real driving condition. Remote sensing studies showed that diesel nitrogen oxides emissions changed little or were even increasing in recent years despite the tightened emission standards. To more accurately and fairly evaluate the emission trends, it is hypothesized that analysis should be detailed for individual vehicle models as each model adopted different emissions control technologies and retrofitted the engine/vehicle at different time. Therefore, this study was aimed to investigate the recent nitric oxide (NO) emission trends of the dominant diesel vehicle models using a large remote sensing dataset collected in Hong Kong. The results showed that the diesel vehicle fleet was dominated by only seven models, accounting for 78% of the total remote sensing records. Although each model had different emission levels and trends, generally all the dominant models showed a steady decrease or stable level in the fuel based NO emission factors (g/kg fuel) over the period studied except for BaM1 and BdM2. A significant increase was observed for the BaM1 2.49 L and early 2.98 L models during 2005–2011, which we attribute to the change in the diesel fuel injection technology. However, the overall mean NO emission factor of all the vehicles was stable during 1991–2006 and then decreased steadily during 2006–2016, in which the emission trends of individual models were averaged out and thus masked. Nevertheless, the latest small, medium and heavy diesel vehicles achieved similar NO emission factors due to the converging of operation windows of the engine and emission control devices. The findings suggested that the increasingly stringent European emission standards were not very effective in reducing the NO emissions of some diesel vehicle models in the real world. The European emission regulations were not very effective in reducing the NO emissions from some diesel vehicle...
Husin, H, Solo, BB, Ibrahim, IM, Chyuan, OH & Roslan, A 2018, 'Weight loss effect and potentiodynamic polarization response of 1-butyl-3-methylimidazolium chloride ionic liquid in highly acidic medium', Journal of Engineering Science and Technology, vol. 13, no. 4, pp. 1005-1015.
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Ionic liquids are increasingly being used as corrosion inhibitors when oil and gas industries started to give focus on sustainability and green impact in their operations. In this study, 1-butyl-3-methylimidazolium chloride ionic liquid in 2M HCl medium has been investigated on mild steel, stainless steel and aluminium bars by using weight loss technique and potentiodynamic polarization measurement. Results showed that 1-butyl-3-methylimidazolium chloride is able to reduce the weight loss of aluminium metal under acidic corrosive surrounding up to 11% compared to that of without the presence of 1-butyl-3-methylimidazolium chloride. Based on potentiodynamic polarization response, percentage of corrosion inhibition efficiency is found to be up to 99.3%. In summary, 1-butyl-3-methylimidazolium chloride is highly potential to act as an anti-corrosion agent, even in a very low concentration.
Hussaini, SKK, Indraratna, B & Vinod, JS 2018, 'A critical review of the performance of geosynthetic-reinforced railroad ballast', Geotechnical Engineering, vol. 49, no. 4, pp. 31-41.
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In the recent times, railway organizations across the world have resorted to the use of geosynthetics as a low-cost solution to stabilize ballast. In this view, extensive studies have been conducted worldwide to assess the performance of geosynthetic-reinforced ballast under various loading conditions. This paper evaluates the various benefits the rail industry could attain because of the geosynthetic reinforcement. A review of literature reveals that geogrid arrests the lateral spreading of ballast, reduces the extent of permanent vertical settlement and minimizes the particle breakage. The geogrid was also found to reduce the extent of volumetric compressions in ballast. The overall performance improvement due to geogrid was observed to be a function of the interface efficiency factor (φ). Moreover, studies also established the additional role of geogrids in reducing the differential track settlements and diminishing the stresses at the subgrade level. The geosynthetics were found to be more beneficial in case of tracks resting on soft subgrades. Furthermore, the benefits of geosynthetics in stabilizing ballast were found to be significantly higher when placed within the ballast. The optimum placement location of geosynthetics has been reported by several researchers to be about 200-250 mm below the sleeper soffit for a conventional ballast depth of 300-350 mm. A number of field investigations and track rehabilitation schemes also confirmed the role of geosynthetics/geogrids in stabilizing the tracks thereby helping in removing the stringent speed restrictions that were imposed earlier, and enhancing the time interval between maintenance operations.
Indraratna, B, Baral, P, Rujikiatkamjorn, C & Perera, D 2018, 'Class A and C predictions for Ballina trial embankment with vertical drains using standard test data from industry and large diameter test specimens', Computers and Geotechnics, vol. 93, pp. 232-246.
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Indraratna, B, Ferreira, FB, Qi, Y & Ngo, TN 2018, 'Application of geoinclusions for sustainable rail infrastructure under increased axle loads and higher speeds', Innovative Infrastructure Solutions, vol. 3, no. 1, p. 69.
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Given the ongoing demand for faster trains for carrying heavier loads, conventional ballasted railroads require considerable upgrading in order to cope with the increasing traffic-induced stresses. During train operations, ballast deteriorates due to progressive breakage and fouling caused by the infiltration of fine particles from the surface or mud-pumping from the underneath layers (e.g. sub-ballast, sub-grade), which decreases the load bearing capacity, impedes drainage and increases the deformation of ballasted tracks. Suitable ground improvement techniques involving geosynthetics and resilient rubber sheets are commonly employed to enhance the stability and longevity of rail tracks. This keynote paper focuses mainly on research projects undertaken at the University of Wollongong to improve track performance by emphasising the main research outcomes and their practical implications. Results from laboratory tests, computational modelling and field trials have shown that track behaviour can be significantly improved by the use of geosynthetics, energy-absorbing rubber mats, rubber crumbs and infilled-recycled tyres. Full-scale monitoring of instrumented track sections supported by rail industry (ARTC) has been performed, and the obtained field data for in situ stresses and deformations could verify the track performance, apart from validating the numerical simulations. The research outcomes provide promising approaches that can be incorporated into current track design practices to cater for high-speed freight trains carrying heavier loads.
Indraratna, B, Israr, J & Li, M 2018, 'Inception of geohydraulic failures in granular soils – an experimental and theoretical treatment', Géotechnique, vol. 68, no. 3, pp. 233-248.
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This paper outlines an experimental investigation into seepage-induced failures in soils subjected to static and cyclic loading. Internally stable, marginal and unstable soils are characterised by heave, composite heave–piping and suffusion that develops immediately upon instability. In this study, the stable specimens exhibited heave at larger hydraulic gradients than the unstable specimens failing by suffusion at relatively smaller hydraulic gradients. Under no external load (i.e. self-weight only), the relative density (Rd) and particle size distribution (PSD) in tandem controlled the internal stability of soils, although the effective stress magnitude (σ′vt) also had a role to play under both static and cyclic loading conditions. Instability in soils was governed by specific combinations of their geo-hydro-mechanical characteristics such as PSD, Rd, stress reduction factor, critical hydraulic gradients and associated effective stress levels. These factors are combined to model the development and inception of instability, and the paper offers visual guides as a practical tool for practitioners. Each soil has a unique critical envelope related to its PSD and Rd, and a critical path with its inclination that depends on the hydro-mechanical conditions. The current results of internal erosion tests conducted by the authors plus those adopted from published literature are used to verify the proposed model.
Indraratna, B, Qi, Y & Heitor, A 2018, 'Evaluating the Properties of Mixtures of Steel Furnace Slag, Coal Wash, and Rubber Crumbs Used as Subballast', Journal of Materials in Civil Engineering, vol. 30, no. 1, pp. 04017251-04017251.
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Indraratna, B, Sun, Q, Heitor, A & Grant, J 2018, 'Performance of Rubber Tire-Confined Capping Layer under Cyclic Loading for Railroad Conditions', Journal of Materials in Civil Engineering, vol. 30, no. 3, pp. 06017021-06017021.
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Israr, J & Indraratna, B 2018, 'Assessment of internal stability of filters under static and cyclic loading: An experimental and theoretical treatment', Australian Geomechanics Journal, vol. 53, no. 4, pp. 103-116.
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The occurrence of internal instability may significantly affect geo-mechanical characteristics of granular filters such as permeability and particle size distribution, consequently rendering them ineffective in retaining the protected base soils and thereby endangering the structural stability. This paper presents the results of 65 hydraulic tests performed on ten different granular soils compacted at varying relative densities between 0 and 100% and subjected to an upward hydraulic flow under both static and cyclic conditions. It was observed that the internal stability is a function of particle gradation and relative density in tandem, i.e. constriction size distribution, under static conditions. However, the agitation and pore pressure development under cyclic loading triggered excessively premature internal erosion in filters. Based on the analysis, new constriction-based criteria proposed for both static and cyclic conditions that showed remarkable accuracy in correctly assessing the potential of instability of filters compared to many existing criteria. Moreover, a new hydromechanical model is presented that could accurately capture the correct potential of instability of filters, thereby contributing toward increased confidence level for practical design of filters. Two practical design examples presented to demonstrate the implications of this research study in practice to conclude this paper.
Israr, J & Indraratna, B 2018, 'Closure to “Internal Stability of Granular Filters under Static and Cyclic Loading” by Jahanzaib Israr and Buddhima Indraratna', Journal of Geotechnical and Geoenvironmental Engineering, vol. 144, no. 12, pp. 07018033-07018033.
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Israr, J & Indraratna, B 2018, 'Mechanical response and pore pressure generation in granular filters subjected to uniaxial cyclic loading', Canadian Geotechnical Journal, vol. 55, no. 12, pp. 1756-1768.
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This paper presents results from a series of piping tests carried out on a selected range of granular filters under static and cyclic loading conditions. The mechanical response of filters subjected to cyclic loading could be characterized in three distinct phases; namely, (I) pre-shakedown, (II) post-shakedown, and (III) post-critical (i.e., the occurrence of internal erosion). All the permanent geomechanical changes such, as erosion, permeability variations, and axial strain developments, took place during phases I and III, while the specimen response remained purely elastic during phase II. The post-critical occurrence of erosion incurred significant settlement that may not be tolerable for high-speed railway substructures. The analysis revealed that a cyclic load would induce excess pore-water pressure, which, in corroboration with steady seepage forces and agitation due to dynamic loading, could then cause internal erosion of fines from the specimens. The resulting excess pore pressure is a direct function of the axial strain due to cyclic densification, as well as the loading frequency and reduction in permeability. A model based on strain energy is proposed to quantify the excess pore-water pressure, and subsequently validated using current and existing test results from published studies.
Jakowiecki, J, Sztyler, A, Filipek, S, Li, P, Raman, K, Barathiraja, N, Ramakrishna, S, Eswara, JR, Altaee, A, Sharif, AO, Ajayan, PM & Renugopalakrishnan, V 2018, 'Aquaporin–graphene interface: relevance to point-of-care device for renal cell carcinoma and desalination', Interface Focus, vol. 8, no. 3, pp. 20170066-20170066.
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The aquaporin superfamily of hydrophobic integral membrane proteins constitutes water channels essential to the movement of water across the cell membrane, maintaining homeostatic equilibrium. During the passage of water between the extracellular and intracellular sides of the cell, aquaporins act as ultra-sensitive filters. Owing to their hydrophobic nature, aquaporins self-assemble in phospholipids. If a proper choice of lipids is made then the aquaporin biomimetic membrane can be used in the design of an artificial kidney. In combination with graphene, the aquaporin biomimetic membrane finds practical application in desalination and water recycling using mostly Escherichia coli AqpZ. Recently, human aquaporin 1 has emerged as an important biomarker in renal cell carcinoma. At present, the ultra-sensitive sensing of renal cell carcinoma is cumbersome. Hence, we discuss the use of epitopes from monoclonal antibodies as a probe for a point-of-care device for sensing renal cell carcinoma. This device works by immobilizing the antibody on the surface of a single-layer graphene, that is, as a microfluidic device for sensing renal cell carcinoma.
Jayamali, KVSD, Nawagamuwa, UP & Indraratna, B 2018, 'Estimation of four-day soaked CBR using index properties', Australian Geomechanics Journal, vol. 53, no. 4, pp. 149-158.
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California Bearing Ratio (CBR) is an important parameter used to evaluate the strength of subgrade and sub-base soils for design of flexible pavements and hence it plays a significant role in road and highway constructions. Obtaining CBR is heavily time consuming and it is difficult to acquire a representative CBR value. Therefore, many correlations have been developed by various researchers worldwide to predict the CBR. Due to differences in soil formations in the tropical environment, these existing global correlations found to be not satisfactory with local soils in Sri Lanka. Hence, this study was carried out to develop empirical correlations between CBR and index properties those best suit for local soils, using the data obtained from Atterberg limits and sieve analysis tests together with compaction tests. The new correlations were established using the method of regression analysis in the form of empirical equations representing the role of index properties. Robust regression by the method of least absolute residuals using MATLAB was considered in the analysis to reduce the impact of outliers along with traditional multiple regression using Microsoft Excel. As a final verification, several laboratory tests were conducted to compare the results with proposed regression equations.
Jia, H, Liu, W, Wang, J, Ngo, H-H, Guo, W & Zhang, H 2018, 'Optimization of sensing performance in an integrated dual sensors system combining microbial fuel cells and upflow anaerobic sludge bed reactor', Chemosphere, vol. 210, pp. 931-940.
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Jiang, Q, Ngo, HH, Nghiem, LD, Hai, FI, Price, WE, Zhang, J, Liang, S, Deng, L & Guo, W 2018, 'Effect of hydraulic retention time on the performance of a hybrid moving bed biofilm reactor-membrane bioreactor system for micropollutants removal from municipal wastewater', Bioresource Technology, vol. 247, pp. 1228-1232.
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© 2017 Elsevier Ltd This study evaluated micropollutants removal and membrane fouling behaviour of a hybrid moving bed biofilm reactor-membrane bioreactor (MBBR-MBR) system at four different hydraulic retention times (HRTs) (24, 18, 12 and 6 h). The results revealed that HRT of 18 h was the optimal condition regarding the removal of most selected micropollutants. As the primary removal mechanism in the hybrid system was biodegradation, the attached growth pattern was desirable for enriching slow growing bacteria and developing a diversity of biocoenosis. Thus, the efficient removal of micropollutants was obtained. In terms of membrane fouling propensity analysis, a longer HRT (e.g. HRTs of 24 and 18 h) could significantly mitigate membrane fouling when compared with the shortest HRT of 6 h. Hence, enhanced system performance could be achieved when the MBBR-MBR system was operated at HRT of 18 h.
Jonasson, OJ & Kandasamy, J 2018, 'Decentralised water reuse in Sydney, Australia: drivers for implementation and energy consumption', Journal of Environmental Engineering and Science, vol. 13, no. 1, pp. 2-7.
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Water recycling and reuse is becoming increasingly common throughout the world. The objective of this study was to compare five decentralised water recycling and reuse systems in Sydney, Australia, in terms of the drivers for their implementation and their ongoing energy consumption, allowing comparison to conventional water sources. The security of supply was found to be the main driver for four out of the five schemes. For the fifth scheme, the driver was to obtain a high environmental rating for the building it is located in. The analysis shows that water reuse can provide water at the same or less energy consumption compared to water supplied through the mains network. However, where the water recycling ethos of ‘fit for purpose’ is not considered, this can often lead to a significant overall increase in power consumption. This study highlights the need for regulatory bodies to consider a wider range of impacts when preparing guidelines and incentive schemes for water reuse. When the focus is too narrow, there is a risk that unintentional negative impacts such as increased power consumption and potential carbon dioxide emissions are the outcomes.
Jupp, JR, Rivest, L, Forgues, D & Boton, C 2018, 'Comparison of shipbuilding and construction industries from the product structure standpoint', International Journal of Product Lifecycle Management, vol. 11, no. 3, pp. 191-191.
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Kalantar, B, Pradhan, B, Naghibi, SA, Motevalli, A & Mansor, S 2018, 'Assessment of the effects of training data selection on the landslide susceptibility mapping: a comparison between support vector machine (SVM), logistic regression (LR) and artificial neural networks (ANN)', Geomatics, Natural Hazards and Risk, vol. 9, no. 1, pp. 49-69.
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© 2017 The Author(s). Published by Informa UK Limited, trading as Taylor & Francis Group. All rights reserved. Landslide is a natural hazard that results in many economic damages and human losses every year. Numerous researchers have studied landslide susceptibility mapping (LSM), each attempting to improve the accuracy of the final outputs. However, few studies have been published on the training data selection effects on the LSM. Thus, this study assesses the training landslides random selection effects on support vector machine (SVM) accuracy, logistic regression (LR) and artificial neural networks (ANN) models for LSM in a catchment at the Dodangeh watershed, Mazandaran province, Iran. A 160 landslide locations inventory was collected by Geological Survey of Iran for this investigation. Different methods were implemented to define the landslide locations, such as inventory reports, satellite images and field survey. Moreover, 14 landslide conditioning factors were considered in the analysis of landslide susceptibility. These factors include curvature, plan curvature, profile curvature, altitude, slope angle, slope aspect, distance to faults, distance to stream, topographic wetness index, stream power index, terrain roughness index, sediment transport index, lithology and land use. The results show that the random landslide training data selection affected the parameter estimations of the SVM, LR and ANN algorithms. The results also show that the training samples selection had an effect on the accuracy of the susceptibility model because landslide conditioning factors vary according to the geographic locations in the study area. The LR model was found to be less sensitive than the SVM and ANN models to the training samples selection. Validation results showed that SVM and LR models outperformed the ANN model for all scenarios. The average overall accuracy of LR, SVM and ANN models are 81.42%, 79.82% and 70.2%, respectively.
Kalaruban, M, Loganathan, P, Kandasamy, J & Vigneswaran, S 2018, 'Submerged membrane adsorption hybrid system using four adsorbents to remove nitrate from water', Environmental Science and Pollution Research, vol. 25, no. 21, pp. 20328-20335.
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© 2017, Springer-Verlag Berlin Heidelberg. Nitrate contamination of ground and surface waters causes environmental pollution and human health problems in many parts of the world. This study tests the nitrate removal efficiencies of two ion exchange resins (Dowex 21K XLT and iron-modified Dowex 21K XLT (Dowex-Fe)) and two chemically modified bio-adsorbents (amine-grafted corn cob (AG corn cob) and amine-grafted coconut copra (AG coconut copra)) using a dynamic adsorption treatment system. A submerged membrane (microfiltration) adsorption hybrid system (SMAHS) was used for the continuous removal of nitrate with a minimal amount of adsorbents. The efficiency of membrane filtration flux and replacement rate of adsorbent were studied to determine suitable operating conditions to maintain the effluent nitrate concentration below the WHO drinking standard limit of 11.3 mg N/L. The volume of water treated and the amount of nitrate adsorbed per gramme of adsorbent for all four flux tested were in the order Dowex-Fe > Dowex > AG coconut copra > AG corn cob. The volumes of water treated (L/g adsorbent) were 0.91 and 1.85, and the amount of nitrate removed (mg N/g adsorbent) were 9.8 and 22.2 for AG corn cob and Dowex-Fe, respectively, at a flux of 15 L/(m2/h).
Kalaruban, M, Loganathan, P, Shim, W, Kandasamy, J & Vigneswaran, S 2018, 'Mathematical Modelling of Nitrate Removal from Water Using a Submerged Membrane Adsorption Hybrid System with Four Adsorbents', Applied Sciences, vol. 8, no. 2, pp. 194-194.
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© 2018 by the authors. Excessive concentrations of nitrate in ground water are known to cause human health hazards. A submerged membrane adsorption hybrid system that includes a microfilter membrane and four different adsorbents (Dowex 21K XLT ion exchange resin (Dowex), Fe-coated Dowex, amine-grafted (AG) corn cob and AG coconut copra) operated at four different fluxes was used to continuously remove nitrate. The experimental data obtained in this study was simulated mathematically with a homogeneous surface diffusion model that incorporated membrane packing density and membrane correlation coefficient, and applied the concept of continuous flow stirred tank reactor. The model fit with experimental data was good. The surface diffusion coefficient was constant for all adsorbents and for all fluxes. The mass transfer coefficient increased with flux for all adsorbents and generally increased with the adsorption capacity of the adsorbents.
Kalhori, H, Makki Alamdari, M, Zhu, X & Samali, B 2018, 'Nothing-on-Road Axle Detection Strategies in Bridge-Weigh-in-Motion for a Cable-Stayed Bridge: Case Study', Journal of Bridge Engineering, vol. 23, no. 8, pp. 05018006-05018006.
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© 2018 American Society of Civil Engineers. This case-study article aims to share the field-test observations of a real-world cable-stayed bridge with the research community of bridge-weigh-in-motion to address the challenges of axle identification. Various structural members of the bridge, including cables, girders, and the deck, were instrumented with strain gauges at different locations to measure the axial, bending, or shear strain responses. Numerous field tests were conducted by running light and heavy vehicles traveling at different speeds, in different traffic directions, and in different lateral locations on the bridge. Because the identification of closely spaced axles is important to ensuring true classification of the vehicles, vehicles with tandem- and tridem-axle configurations were adopted in the field test. The study aimed to identify the sensor arrangement through which the closely spaced axles can be reliably detected regardless of the speed, traveling direction, and lateral location of the vehicle on the bridge. It was found that the axial strains on the cables and bending strains in the girders provided the global response of the structure; hence, they were unable to identify the closely spaced axles. In contrast, it was observed that the longitudinal strains under the deck were able to identify the closely spaced axles, provided they were positioned as closely as possible to the wheel path. Finally, the shear responses at the end of the span were able to identify the closely spaced axles irrespective of the traveling direction and lateral location of the vehicle. In this study, due to the testing limitations, including the short span of the bridge and the presence of a roundabout at one end of the bridge, it was not feasible to maintain a constant speed; therefore, identification of axle weight and axle spacing, which requires a constant-speed assumption, is not discussed.
Kang, Y, Zhang, J, Li, B, Zhang, Y, Sun, H, Hao Ngo, H, Guo, W, Xie, H, Hu, Z & Zhao, C 2018, 'Improvement of bioavailable carbon source and microbial structure toward enhanced nitrate removal by Tubifex tubifex', Chemical Engineering Journal, vol. 353, pp. 699-707.
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Kani, K, Malgras, V, Jiang, B, Hossain, MSA, Alshehri, SM, Ahamad, T, Salunkhe, RR, Huang, Z & Yamauchi, Y 2018, 'Periodically Arranged Arrays of Dendritic Pt Nanospheres Using Cage‐Type Mesoporous Silica as a Hard Template', Chemistry – An Asian Journal, vol. 13, no. 1, pp. 106-110.
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AbstractDendritic Pt nanospheres of 20 nm diameter are synthesized by using a highly concentrated surfactant assembly within the large‐sized cage‐type mesopores of mesoporous silica (LP‐FDU‐12). After diluting the surfactant solution with ethanol, the lower viscosity leads to an improved penetration inside the mesopores. After Pt deposition followed by template removal, the arrangement of the Pt nanospheres is a replication from that of the mesopores in the original LP‐FDU‐12 template. Although it is well known that ordered LLCs can form on flat substrates, the confined space inside the mesopores hinders surfactant self‐organization. Therefore, the Pt nanospheres possess a dendritic porous structure over the entire area. The distortion observed in some nanospheres is attributed to the close proximity existing between neighboring cage‐type mesopores. This new type of nanoporous metal with a hierarchical architecture holds potential to enhance substance diffusivity/accessibility for further improvement of catalytic activity.
Katalo, R, Okuda, T, Nghiem, LD & Fujioka, T 2018, 'Moringa oleifera coagulation as pretreatment prior to microfiltration for membrane fouling mitigation', Environmental Science: Water Research & Technology, vol. 4, no. 10, pp. 1604-1611.
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Coagulation pretreatment using Moringa oleifera in the microfiltration of river water achieved membrane fouling mitigation and filtered water quality improvement.
Ke, G, Li, W, Li, R, Li, Y & Wang, G 2018, 'Mitigation Effect of Waste Glass Powders on Alkali–Silica Reaction (ASR) Expansion in Cementitious Composite', International Journal of Concrete Structures and Materials, vol. 12, no. 1.
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© 2018, The Author(s). The effects of different contents and particle sizes of waste glass powder on alkali–silica reaction (ASR) expansion of cementitious composite bar were investigated in this study. Waste glass powder with particle size less than 300 μm exhibits an excellent mitigation effect on ASR expansion. With larger content and smaller particle size, the mitigation effect of waste glass powder on ASR expansion gradually increases. The mitigation effect of waste glass powder with particle size ranging from 38 to 53 μm and 20% by weight of cement seems relatively better than that of fly ash. When the waste glass powder content reaches 30%, the mitigation effect is still effective and almost the same as that of fly ash. However, the waste glass powder with particle size larger than 300 μm presents negative mitigation effect on ASR expansion when the replacement rate is larger than 30%. On the other hand, the waste glass powder and calcium hydroxide (CH) further react, and produce more calcium–silicate–hydrate gels, which apparently reduce the amount of CH. Moreover, the increasing content of waste glass powder results in a lower pH value in the pore solution of cementitious composite.
Keshavarzi, A, Shrestha, CK, Melville, B, Khabbaz, H, Ranjbar-Zahedani, M & Ball, J 2018, 'Estimation of maximum scour depths at upstream of front and rear piers for two in-line circular columns', Environmental Fluid Mechanics, vol. 18, no. 2, pp. 537-550.
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© 2018, Springer Science+Business Media B.V., part of Springer Nature. Previous investigations indicate that scour around bridge piers is one of the most important factors for the failure of waterway bridges. Hence, it is essential to determine the accurate scour depth around the bridge piers. Most of the previous studies were based on scour around a single pier; however, in practice, new bridges are usually wide and then piers comprise two circular piers aligned in the flow direction that together support the loading of the structure. In this study, the effect on maximum scour depth of the spacing between two piers aligned in the flow direction was investigated experimentally under clear water scour conditions. The results show that the maximum scour depth at upstream of the front pier occurs when the spacing between the two piers is 2.5 times the diameter of the pier. Two semi empirical equations have been developed to predict the maximum scour depth at upstream of both front and rear piers as a function of the spacing between the piers, in terms of a pier-spacing factor. If the new equations for the pier-spacing factor are used with some of the existing equations for scour at a single pier, the predicted scouring depths are in good agreement with observed results. The S/M equation exhibited the best performance among the various equations tested and was recommended for use in prediction of the equilibrium scour depth. The findings of this study can be used to facilitate the positioning of piers when scouring is a design concern.
Keshavarzi, A, Shrestha, CK, Zahedani, MR, Ball, J & Khabbaz, H 2018, 'Experimental study of flow structure around two in-line bridge piers', Proceedings of the Institution of Civil Engineers - Water Management, vol. 171, no. 6, pp. 311-327.
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Previous investigations indicate that local scouring is one of the most common causes of waterway bridge failure. The scour mechanism around bridge piers is complicated by the interaction of flow and structure. To explore the local scouring process, it is therefore essential to study the flow–structure interaction around bridge piers. Most previous studies have been based on this interaction around a single pier; however, in practice, many bridges are wide and comprise a number of piers aligned in the flow direction that together support the loading. In this study, a particle image velocimetry technique was used to investigate two-dimensional flow–structure interaction around two in-line bridge piers with different spacings. Various influencing flow characteristics including turbulence intensity, turbulent kinetic energy and Reynolds stresses were calculated in different vertical planes around the bridge piers. Results indicated that the flow characteristics around two in-line bridge piers are very different than for a single pier and the spacing between two in-line piers significantly influences the flow characteristics, particularly in the rear of the piers. Furthermore, for spacing in the range of 2 ≤ L/D ≤ 3, stronger turbulence structures occurred behind pier 1 and, as a result, a higher scour depth can be expected around pier 1.
Khan, HA, Khan, MSH, Castel, A & Sunarho, J 2018, 'Deterioration of alkali-activated mortars exposed to natural aggressive sewer environment', Construction and Building Materials, vol. 186, pp. 577-597.
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Khan, MA, Ngo, HH, Guo, W, Liu, Y, Chang, SW, Nguyen, DD, Nghiem, LD & Liang, H 2018, 'Can membrane bioreactor be a smart option for water treatment?', Bioresource Technology Reports, vol. 4, pp. 80-87.
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The gradual increase of organic and inorganic micropollutants in natural and drinking watercourses has posed a greater challenge for current water treatment technologies. Currently established water treatment processes such as activated sludge, microfiltration, reverse osmosis, adsorption, carbon nanotube etc. have a limited range of application, low energy recovery, and cost-intensive operation. Membrane bioreactor has already been utilized as a useful option to remove soluble organics, nutrients, and micropollutants from wastewater. Although currently established Membrane Bioreactors have few limitations, recent developments on this technology have improved its energy efficiency and reduced the operating and maintenance cost. Implementing these research findings in full-scale operation can make this process a favorable option in industrial wastewater treatment.
Khan, MA, Ngo, HH, Guo, W, Liu, Y, Zhang, X, Guo, J, Chang, SW, Nguyen, DD & Wang, J 2018, 'Biohydrogen production from anaerobic digestion and its potential as renewable energy', Renewable Energy, vol. 129, pp. 754-768.
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© 2017. The current demand-supply scenario for fossil fuels requires an alternative energy source with cleaner combustion products whilst production of hydrogen from anaerobic digestion involves the utilization of waste materials and zero emission of greenhouse gasses. However, large scale industrial application has yet not been implemented due to numerous challenges in its production, storage, and transportation. This review study demonstrates that production of hydrogen from anaerobic digestion is potentially a worthy alternative regarding energy density, environmental impact, and cost. Moreover, dependence on fossil fuel systems in the future could be minimized when biohydrogen production is feasible from renewable energy sources.
Khan, MSH & Castel, A 2018, 'Effect of MgO and Na2SiO3 on the carbonation resistance of alkali activated slag concrete', Magazine of Concrete Research, vol. 70, no. 13, pp. 685-692.
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This paper investigates the effect of magnesium oxide (MgO) on the carbonation resistance of alkali-activated slag–fly ash blend containing 75% ground granulated blast furnace slag (GGBS) and 25% low-calcium fly ash. Two types of GGBS were used with different magnesium oxide content. Phenolphthalein indicator and pH profiles showed that the GGBS with higher levels of magnesium oxide offered no significant improvement in resistance against natural and 1% accelerated carbonation. X-ray diffraction confirmed no hydrotalcite formation, although the magnesium oxide content was 9·1%. A very small amount of free magnesium ions (Mg2+) was available in the pore solution, which was deemed insufficient to form hydrotalcite. Lack of its formation was the major reason for the lower carbonation resistance. Excessive silicate in the system reduces the calcium oxide/silicon dioxide ratio, which leads to the incorporation of magnesium ions in the calcium silicate hydrate structure. Hydrotalcite was observed when the activator concentration was reduced. The results suggest that in addition to magnesium and aluminium ion (Al3+) availability, silicate concentration also plays a strong role in deciding the hydrotalcite formation in alkali-activated GGBS concrete.
Kim, DI, Gwak, G, Dorji, P, He, D, Phuntsho, S, Hong, S & Shon, H 2018, 'Palladium Recovery through Membrane Capacitive Deionization from Metal Plating Wastewater', ACS Sustainable Chemistry & Engineering, vol. 6, no. 2, pp. 1692-1701.
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© 2017 American Chemical Society. The potential application of membrane capacitive deionization (MCDI) for recovery of palladium (Pd) ions from catalyst solution wastewater generated from the plating industry was investigated in this study. Several major issues were explored in this work to verify the suitability of MCDI for Pd recovery from a practical perspective: adsorption and desorption efficiencies, desorption mechanisms into high concentration of Pd concentrate, and its sustainability in long-term operation. The lab-scale MCDI operation achieved satisfactory and highly competitive Pd removal (99.07-99.94% removal with 1.42-1.52 of Pd selectivity over ammonium ions) showing that Pd can be effectively collected from plating industry wastewater. A high concentration of Pd concentrate (64.77 and 919.44 mg/L of Pd from the 10 and 100 mg/L Pd containing catalyst solution, respectively) was obtained through successive five operation cycles of adsorption/desorption phases. However, it is significant to note that the desorption efficiency was inversely proportional to the concentration of Pd concentrate which is likely due to the Pd ions discharged from carbon electrode toward Pd solution against the enhanced concentration gradient. The long-term operation results suggest that scaling could reduce the MCDI efficiency during Pd recovery (0.17% decrease in Pd removal for every cycle on average) and hence may require an adequate electrode cleaning regime.
Kim, JE, Phuntsho, S, Ali, SM, Choi, JY & Shon, HK 2018, 'Forward osmosis membrane modular configurations for osmotic dilution of seawater by forward osmosis and reverse osmosis hybrid system', Water Research, vol. 128, pp. 183-192.
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© 2017 Elsevier Ltd This study evaluates various options for full-scale modular configuration of forward osmosis (FO) process for osmotic dilution of seawater using wastewater for simultaneous desalination and water reuse through FO-reverse osmosis (RO) hybrid system. Empirical relationship obtained from one FO membrane element operation was used to simulate the operational performances of different FO module configurations. The main limiting criteria for module operation is to always maintain the feed pressure higher than the draw pressure throughout the housing module for safe operation without affecting membrane integrity. Experimental studies under the conditions tested in this study show that a single membrane housing cannot accommodate more than four elements as the draw pressure exceeds the feed pressure. This then indicates that a single stage housing with eight elements is not likely to be practical for safe FO operation. Hence, six different FO modular configurations were proposed and simulated. A two-stage FO configuration with multiple housings (in parallel) in the second stage using same or larger spacer thickness reduces draw pressure build-up as the draw flow rates are reduced to half in the second stage thereby allowing more than four elements in the second stage housing. The loss of feed pressure (pressure drop) and osmotic driving force in the second stage are compensated by operating under the pressure assisted osmosis (PAO) mode, which helps enhance permeate flux and maintains positive pressure differences between the feed and draw chamber. The PAO energy penalty is compensated by enhanced permeate throughput, reduced membrane area, and plant footprint. The contribution of FO/PAO to total energy consumption was not significant compared to post RO desalination (90%) indicating that the proposed two-stage FO modular configuration is one way of making the FO full-scale operation practical for FO-RO hybrid system.
Kim, JE, Phuntsho, S, Chekli, L, Choi, JY & Shon, HK 2018, 'Environmental and economic assessment of hybrid FO-RO/NF system with selected inorganic draw solutes for the treatment of mine impaired water', Desalination, vol. 429, pp. 96-104.
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© 2017 Elsevier B.V. A hybrid forward osmosis (FO) and reverse osmosis (RO)/nanofiltration (NF) system in a closed-loop operation with selected draw solutes was evaluated to treat coal mine impaired water. This study provides an insight of selecting the most suitable draw solution (DS) by conducting environmental and economic life cycle assessment (LCA). Baseline environmental LCA showed that the dominant components to energy use and global warming are the DS recovery processes (i.e. RO or NF processes) and FO membrane materials, respectively. When considering the DS replenishment in FO, the contribution of chemical use to the overall global warming impact was significant for all hybrid systems. Furthermore, from an environmental perspective, the FO-NF hybrid system with Na2SO4 shows the lowest energy consumption and global warming with additional considerations of final product water quality and FO brine disposal. From an economic perspective, the FO-NF with Na2SO4 showed the lowest total operating cost due to its lower DS loss and relatively low solute cost. In a closed-loop system, FO-NF with NaCl and Na2SO4 had the lowest total water cost at optimum NF recovery rates of 90 and 95%, respectively. FO-NF with Na2SO4 had the lowest environmental and economic impacts. Overall, draw solute performances and cost in FO and recovery rate in RO/NF play a crucial role in determining the total water cost and environmental impact of FO hybrid systems in a closed-loop operation.
Kim, S, Piao, G, Han, DS, Shon, HK & Park, H 2018, 'Solar desalination coupled with water remediation and molecular hydrogen production: a novel solar water-energy nexus', Energy & Environmental Science, vol. 11, no. 2, pp. 344-353.
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A novel solar water-energy nexus technology is presented that combines the solar desalination of saline water and desalination-driven wastewater remediation coupled with the production of H2.
Kook, S, Lee, C, Nguyen, TT, Lee, J, Shon, HK & Kim, IS 2018, 'Serially connected forward osmosis membrane elements of pressure-assisted forward osmosis-reverse osmosis hybrid system: Process performance and economic analysis', Desalination, vol. 448, pp. 1-12.
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© 2018 Elsevier B.V. Due to the improved dilution of draw streams, employing pressure-assisted forward osmosis (PAFO) to the hybrid system of forward osmosis (FO) followed by reverse osmosis (RO) for seawater desalination has been expected to reduce the overall economics. However, replacing FO with PAFO causes an additional energy cost in the seawater dilution step which inevitably leads to a question that PAFO-RO hybrid is truly an economically beneficial option. More importantly, though serial connection of FO elements improves the dilution of initial draw water, this economic benefit is also compensated with the additional membrane. To rationalize its overall performance and economic benefit, thorough performance and economic evaluations were conducted based on actual pilot-scale PAFO operations for serial connection of up to three 8040 FO elements. The results showed the FO-RO hybrid is not an economically feasible option unless a significant unit FO element cost cut-down is guaranteed. Meanwhile, PAFO-RO showed benefits with regards to target RO recovery and unit FO element cost, particularly when two FO elements are serially connected (SE2). It was found that PAFO-RO, indeed, has higher economic potential than FO-RO. A graphical overlapping method suggested in this work can help determine optimal serial configuration and operating conditions of PAFO-RO.
Lake, C & Sheng, D 2018, 'Note of appreciation / Note de reconnaissance', Canadian Geotechnical Journal, vol. 55, no. 12, pp. v-vii.
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Laloo, AE, Wei, J, Wang, D, Narayanasamy, S, Vanwonterghem, I, Waite, D, Steen, J, Kaysen, A, Heintz-Buschart, A, Wang, Q, Schulz, B, Nouwens, A, Wilmes, P, Hugenholtz, P, Yuan, Z & Bond, PL 2018, 'Mechanisms of Persistence of the Ammonia-Oxidizing Bacteria Nitrosomonas to the Biocide Free Nitrous Acid', Environmental Science & Technology, vol. 52, no. 9, pp. 5386-5397.
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© 2018 American Chemical Society. Free nitrous acid (FNA) exerts a broad range of antimicrobial effects on bacteria, although susceptibility varies considerably among microorganisms. Among nitrifiers found in activated sludge of wastewater treatment processes (WWTPs), nitrite-oxidizing bacteria (NOB) are more susceptible to FNA compared to ammonia-oxidizing bacteria (AOB). This selective inhibition of NOB over AOB in WWTPs bypasses nitrate production and improves the efficiency and costs of the nitrogen removal process in both the activated sludge and anaerobic ammonium oxidation (Anammox) system. However, the molecular mechanisms governing this atypical tolerance of AOB to FNA have yet to be understood. Herein we investigate the varying effects of the antimicrobial FNA on activated sludge containing AOB and NOB using an integrated metagenomics and label-free quantitative sequential windowed acquisition of all theoretical fragment ion mass spectra (SWATH-MS) metaproteomic approach. The Nitrosomonas genus of AOB, on exposure to FNA, maintains internal homeostasis by upregulating a number of known oxidative stress enzymes, such as pteridine reductase and dihydrolipoyl dehydrogenase. Denitrifying enzymes were upregulated on exposure to FNA, suggesting the detoxification of nitrite to nitric oxide. Interestingly, proteins involved in stress response mechanisms, such as DNA and protein repair enzymes, phage prevention proteins, and iron transport proteins, were upregulated on exposure to FNA. In addition enzymes involved in energy generation were also upregulated on exposure to FNA. The total proteins specifically derived from the NOB genus Nitrobacter was low and, as such, did not allow for the elucidation of the response mechanism to FNA exposure. These findings give us an understanding of the adaptive mechanisms of tolerance within the AOB Nitrosomonas to the biocidal agent FNA.
Lamqadem, A, Saber, H & Pradhan, B 2018, 'Quantitative Assessment of Desertification in an Arid Oasis Using Remote Sensing Data and Spectral Index Techniques', Remote Sensing, vol. 10, no. 12, pp. 1862-1862.
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Desertification is an environmental problem worldwide. Remote sensing data and technique offer substantial information for mapping and assessment of desertification. Desertification is one of the most serious forms of environmental threat in Morocco, especially in the oases in the south-eastern part of the country. This study aims to map the degree of desertification in middle Draa Valley in 2017 using a Sentinel-2 MSI (multispectral instrument) image. Firstly, three indices, namely, tasselled cap brightness (TCB), greenness (TCG) and wetness (TCW) were extracted using the tasselled cap transformation method. Secondly, other indices, such as normalized difference vegetation index (NDVI) and albedo, were retrieved. Thirdly, a linear regression analysis was performed on NDVI–albedo, TCG–TCB and TCW–TCB combinations. Results showed a higher correlation between TCW and TCB (r = −0.812) than with that of the NDVI–albedo (r = −0.50). On the basis of this analysis, a desertification degree index was developed using the TCW–TCB feature space classification. A map of desertification grades was elaborated and divided into five classes, namely, nondesertification, low, moderate, severe and extreme levels. Results indicated that only 6.20% of the study area falls under the nondesertification grade, whereas 26.92% and 32.85% fall under the severe and extreme grades, respectively. The employed method was useful for the quantitative assessment of desertification with an overall accuracy of 93.07%. This method is simple, robust, powerful, and easy to use for the management and protection of the fragile arid and semiarid lands.
Lee, J-H, Sameen, MI, Pradhan, B & Park, H-J 2018, 'Modeling landslide susceptibility in data-scarce environments using optimized data mining and statistical methods', Geomorphology, vol. 303, pp. 284-298.
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Lei, B, Li, W, Li, Z, Wang, G & Sun, Z 2018, 'Effect of Cyclic Loading Deterioration on Concrete Durability: Water Absorption, Freeze-Thaw, and Carbonation', Journal of Materials in Civil Engineering, vol. 30, no. 9, pp. 04018220-04018220.
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© 2018 American Society of Civil Engineers. The effect of cyclic loading deterioration on freeze-thaw and carbonation resistances of concrete were experimentally investigated in this study. A novel loading method was designed, which simultaneously considers both mechanical loading and environmental actions for concrete. It shows that with the increase of cyclic compressive loading, the porosity and water absorption of concrete initially decrease but then increase when the stress is above a threshold level because of the cracking initiation caused by cyclic compression. With the increase of concrete porosity, both dynamic elastic modulus loss and carbonation depth obviously exhibit an increasing trend. On the other hand, under the same stress level, the freeze-thaw and carbonation resistances of high-strength concrete are relatively superior to those of low-strength concrete. Compared with the unloaded concrete, the carbonation depth and dynamic elastic modulus loss after mechanical loading below the stress level threshold are lower. This is probably due to the denser microstructure compacted by the compression. However, if the loading level becomes above the threshold level, both the carbonation depth and dynamic elastic modulus loss dramatically increase, which is due to the cracks initiation and propagation after cyclic loading deterioration. Therefore, the combination of mechanical and environmental actions is more severe than a single environmental action without considering the mechanical loading.
Lei, B, Li, W, Tang, Z, Tam, VWY & Sun, Z 2018, 'Durability of recycled aggregate concrete under coupling mechanical loading and freeze-thaw cycle in salt-solution', Construction and Building Materials, vol. 163, pp. 840-849.
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© 2017 Elsevier Ltd In this study, a novel coupling testing protocol with separated repetitive loading and freezing-thaw cycles in salt-solution is designed to simulate coupling mechanical loading and complex environmental effects on durability and deterioration of recycled aggregate concrete (RAC). The Micromechanical properties and porosity of RAC were also characterized by scanning electron microscopy (SEM) and microhardness. The results show that the number and width of cracks of RAC and NAC under freeze-thaw cycles obviously increased with the increase of alternating times of repetitive load and the compressive stress level. The compressive strength losses for both RAC and NAC increase with the increase of compressive stress level and alternative times of repetitive load. However, the compressive strength of natural aggregate concrete (NAC) became lower than that of RAC after freeze-thaw cycles. It was found that the freeze-thaw resistance of RAC seems even better than that of NAC under the same freeze-thaw attacks and cyclic mechanical loading. It indicates that after freeze-thaw cycles in salt-solution, the durability of RAC is better than that of NAC. On the other hand, the microhardness and SEM characterization results indicate that the interface transition zone (ITZ) was a weak part in both RAC and NAC, and the ITZ in NAC obviously deteriorated faster than that of RAC.
Leong, KY, Razali, I, Ku Ahmad, KZ, Ong, HC, Ghazali, MJ & Abdul Rahman, MR 2018, 'Thermal conductivity of an ethylene glycol/water-based nanofluid with copper-titanium dioxide nanoparticles: An experimental approach', International Communications in Heat and Mass Transfer, vol. 90, pp. 23-28.
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Li, J & Wu, C 2018, 'Damage evaluation of ultra-high performance concrete columns after blast loads', International Journal of Protective Structures, vol. 9, no. 1, pp. 44-64.
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As emerging advanced construction material, ultra-high performance concretes have seen increasing field applications over the past two decades to take advantages of their ultra-high mechanical strength and durability; yet the systematic study on its dynamic behaviour under impact and blast loads is not commonly seen. This article presents an experimental and numerical study on the static and dynamic behaviour of an existing ultra-high performance concrete material. Experimental study on its flexural behaviour under static loads is conducted and an inverse study is carried out to derive its uniaxial tensile constitutive law. The derived relationship is used in the material model in hydro-code LS-DYNA together with dynamic material properties to study ultra-high performance concrete columns under blast loads. The residual loading capacity of the column is studied and pressure–impulse diagrams for assessing the ultra-high performance concrete column damage under blast loads are proposed. Parametric study on effects of ultra-high performance concrete strength, column height, cross-section size and reinforcement ratio is performed and analytical equations are proposed for generating pressure–impulse diagrams for generic ultra-high performance concrete columns.
Li, J, Wei, J, Ngo, HH, Guo, W, Liu, H, Du, B, Wei, Q & Wei, D 2018, 'Characterization of soluble microbial products in a partial nitrification sequencing batch biofilm reactor treating high ammonia nitrogen wastewater', Bioresource Technology, vol. 249, pp. 241-246.
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In present study, the characterization of soluble microbial products (SMP) was evaluated in a partial nitrification sequencing batch biofilm reactor (SBBR). During the stable operation of SBBR, the NH4+-N removal efficiency and nitrite accumulation ratio were 96.70±0.41% and 93.77±1.04%, respectively. According to excitation-emission matrix (EEM), the intensities of protein-like substances were reduced under anoxic and aerobic phases, whereas humic-like substances had little change during the whole cycle. Parallel factor analysis (PARAFAC) further indentified two components and their fluorescence intensity scores were both reduced. Synchronous fluorescence spectra revealed that the fluorescence intensity of protein-like fraction decreased with reaction time. Two-dimensional correlation spectroscopy (2D-COS) further demonstrated that protein-like fraction might decrease earlier than the other fractions. The information obtained in present study is of fundamental significance for understanding the key components in SMP and their changes in partial nitrification system by using a spectral approach.
Li, J, Wu, C & Liu, Z-X 2018, 'Comparative evaluation of steel wire mesh, steel fibre and high performance polyethylene fibre reinforced concrete slabs in blast tests', Thin-Walled Structures, vol. 126, pp. 117-126.
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© 2017 Elsevier Ltd Concrete is the most widely used construction material in the modern construction practice. Due to its relatively low tensile resistance, concrete tends to experience tensile failure and cracking under external loads. To enhance the tensile performance and ductility of concrete material, possible solutions including fibre reinforcement and steel mesh reinforcement are investigated in the present study. Steel fibre, ultra-high molecular weight polyethylene (UHMWPE) fibre and steel wire meshes were mixed with varying volume fraction in the concrete matrix. Static material tests including uniaxial compression and flexural bending tests showed that the steel fibre addition yielded better strength enhancement while UHMWPE fibre provided better material ductility. Concrete samples with hybrid steel fibre-steel mesh reinforcement showed high strength and ductility. Field blast tests are designed to study the behaviour of reinforced concrete slabs under close-in detonations. Different damage profiles are observed from the blast tests. The advantages and disadvantages of using different reinforcing materials are discussed. From the results, the advantages of replacing steel fibre with UHMWPE fibre or steel wire mesh were demonstrated.
Li, J, Wu, C, Hao, H, Liu, Z & Yang, Y 2018, 'Basalt scale-reinforced aluminium foam under static and dynamic loads', Composite Structures, vol. 203, pp. 599-613.
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© 2018 Elsevier Ltd In this paper, mechanical performance and deformation behaviour of basalt scale-reinforced closed-cell aluminium foams are investigated. Quasi-static uniaxial compressive tests on the constitutive alloy material reveal that after basalt scale reinforcement, the alloy elasticity modulus and yield strength show noticeable enhancement. Quasi-static compression tests on the foam material show that while basalt scale-reinforced aluminium foam has higher plastic crush stress and plateau stress, the densification strain is lower than non-reinforced foam. A method based on energy absorption efficiency is adopted to accurately measure the densification strain for both foam materials. In the subsequent split-Hopkinson pressure bar tests, dynamic compressive behaviour of basalt scale-reinforced aluminium foams with relative densities ranged from 14% to 33% is studied experimentally under strain rate ranging from 480/s to 1720/s. Clear material rate sensitivity is noted from the dynamic tests. The results indicate that the plateau stress of aluminium foam increases with relative density and strain rate. In addition, with the increase in strain rates, an increase in the energy absorption capacity is observed and this characteristic is beneficial when the foam material is used to absorb impact energy. A mesoscopic model based on the X-ray CT for the aluminium foam material is developed. The simulations and the test data agreed well for the quasi-static loading case. However, it is noted that the mesoscale model without consideration of the base material rate sensitivity and the entrapped gas underestimated the strength enhancement under dynamic loading scenario.
Li, J, Ye, W, Wei, D, Ngo, HH, Guo, W, Qiao, Y, Xu, W, Du, B & Wei, Q 2018, 'System performance and microbial community succession in a partial nitrification biofilm reactor in response to salinity stress', Bioresource Technology, vol. 270, pp. 512-518.
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© 2018 Elsevier Ltd The system performance and microbial community succession in a partial nitrification biofilm reactor in response to salinity stress was conducted. It was found that the NH 4+ -N removal efficiency decreased from 98.4% to 42.0% after salinity stress increased to 20 g/L. Specific oxygen uptake rates suggested that AOB activity was more sensitive to the stress of salinity than that of NOB. Protein and polysaccharides contents showed an increasing tendency in both LB-EPS and TB-EPS after the salinity exposure. Moreover, EEM results indicated that protein-like substances were the main component in LB-EPS and TB-EPS as self-protection in response to salinity stress. Additionally, humic acid-like substances were identified as the main component in the effluent organic matter (EfOM) of partial nitrification biofilm, whereas fulvic acid-like substances were detected at 20 g/L salinity stress. Microbial community analysis found that Nitrosomonas as representative species of AOB were significantly inhibited under high salinity condition.
Li, K, Gao, W, Wu, D, Song, C & Chen, T 2018, 'Spectral stochastic isogeometric analysis of linear elasticity', Computer Methods in Applied Mechanics and Engineering, vol. 332, pp. 157-190.
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© 2017 Elsevier B.V. The stochastic isogeometric analysis of linear elasticity problem is investigated in this study. The spectral stochastic analysis is introduced into isogeometric analysis (IGA), and a novel, yet robust, stochastic analysis framework, namely the spectral stochastic isogeometric analysis (SSIGA), is freshly proposed. Unlike traditional numerical solutions of the Karhunen–Loève (K-L) expansion, the non-uniform rational B-spline (NURBS) and T-spline basis functions are employed within the proposed framework of SSIGA, so the random fields acting on a continuous physical medium with complex geometry can be handled in an appropriate, physically feasible and efficient fashion. The polynomials chaos expansion (PCE) is implemented to represent the stochastic structural response (e.g., displacement, strain and stress), such that all corresponding statistical characteristics (e.g., mean and standard deviation) can be robustly acquired. Furthermore, by utilizing the nonparametric statistical analysis, both probability density functions (PDFs) and cumulative distribution functions (CDFs) of concerned structural displacements and stresses can be effectively established. Within the framework of IGA, by meticulously implementing the concept of the higher-order k-refinement, the proposed SSIGA provides a more legitimate and efficient stochastic computational approach for modern engineering structures which are complicated by both spatially dependent uncertainties and complex geometries.
Li, K, Wu, D & Gao, W 2018, 'Spectral stochastic isogeometric analysis for static response of FGM plate with material uncertainty', Thin-Walled Structures, vol. 132, pp. 504-521.
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In this study, the nondeterministic structural responses of functionally graded material (FGM) plates under static loads with uncertain material property is investigated. The considered spatially dependent uncertainties are modelled as random fields with Gaussian distribution. A novel spectral stochastic isogeometric analysis (SSIGA) framework is proposed for such uncertainty quantification through the first-order shear deformation theory. Within the SSIGA framework, the non-uniform rational B-spline (NURBS) is adopted for both the geometry modelling of the random fields of the uncertain material properties and random field discretization through the Karhunen-Loève (K-L) expansion. Such new feature provides an effective and practically applicable random field modelling technique, especially for uncertain parameters over complex physical domains. The polynomial chaos expansion (PCE) is employed for estimating the statistical characteristics (e.g., mean and standard deviation) of any concerned structural responses (e.g., displacement and stress). By further implementing various statistical inference techniques, the probability density functions (PDF) and cumulative distribution functions (CDF) of structural responses can be established to determine both serviceability and strength limits of FGM plate. Two numerical examples are thoroughly investigated to illustrate the applicability, effectiveness and efficiency of the proposed computational approach.
Li, K, Wu, D, Chen, X, Cheng, J, Liu, Z, Gao, W & Liu, M 2018, 'Isogeometric Analysis of functionally graded porous plates reinforced by graphene platelets', Composite Structures, vol. 204, pp. 114-130.
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This paper investigates the static linear elasticity, natural frequency, and buckling behaviour of functionally graded porous plates reinforced by graphene platelets (GPLs). Both first- and third-order shear deformation plate theories are incorporated within the Isogeometric Analysis (IGA) framework. The pores and the GPLs within the plates are distributed in the metal matrix either uniformly or non-uniformly according to different patterns. The graded distributions of porosity and nanocomposite are achieved by material parameters varying across the thickness direction of plate. The Halpin-Tsai micromechanics model is implemented to establish the relationship between porosity coefficient and Young's modulus, as well as to obtain the mass density of the nanocomposite. The variation of Poisson's ratio is determined by the mechanical properties of closed-cell cellular solids under Gaussian Random Field scheme. A comprehensive parametric study is accomplished to investigate the effects of weight fraction, distribution pattern, geometry, and size of the GPLs reinforcement on the static linear elasticity, natural frequency, and buckling behaviour of the nanocomposite plates with diverse metal matrices and porosity coefficients. The outcome of numerical investigation shows that the inclusion of the GPLs can effectively improve the stiffness of functionally graded porous plate.
Li, L, Nimbalkar, S & Zhong, R 2018, 'Finite element model of ballasted railway with infinite boundaries considering effects of moving train loads and Rayleigh waves', Soil Dynamics and Earthquake Engineering, vol. 114, pp. 147-153.
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© 2018 Elsevier Ltd This paper proposes a three-dimensional model incorporating finite element (FE) meshes with infinite element (IE) boundaries for ballasted railways. Moving train loads are simulated with sliding motions of moving elements which have hard contact feature at the interface with supporting rails. Dynamic responses of ballasted railway under different train speeds are investigated in time domain and frequency domain to identify the predominant frequency and critical speed. Rayleigh wave (R-Wave) propagation is simulated using the combined FE-IE model to determine the velocity of R-Wave in the layered embankment model and its relationship with the critical speed of the ballasted railway. The proposed model is successfully validated against the results of Euler-Bernoulli Elastic Beam (E-BEB) model.
Li, Q, Wu, D, Chen, X, Liu, L, Yu, Y & Gao, W 2018, 'Nonlinear vibration and dynamic buckling analyses of sandwich functionally graded porous plate with graphene platelet reinforcement resting on Winkler–Pasternak elastic foundation', International Journal of Mechanical Sciences, vol. 148, pp. 596-610.
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The nonlinear vibration and the dynamic buckling of a graphene platelet reinforced sandwich functionally graded porous (GPL-SFGP) plate are thoroughly investigated in this paper. The investigated GPL-SFGP plate consists of two metal face layers and a functionally graded porous core with graphene platelet reinforcement. The effects of the Winkler–Pasternak elastic foundation, thermal environment and damping are incorporated. The open-cell metal foam model is implemented to model the mechanical properties of the porous core. Axial compressive stress is applied on the GPL-SFGP plate by exerting various compressive loading speeds at one edge of the plate. Grounded on the classical plate theory, both motion and geometric compatibility equations of the plate are deduced by introducing the Von Kármán strain-displacement relationship and stress function. Both the Galerkin and the fourth-order Runge–Kutta methods are implemented to solve the governing equation of the dynamic system. Meticulously designed numerical experiments are conducted to identify the critical influential factors of the dynamic stability of the GPL-SFGP plate. The influences of loading speed, damping ratio, temperature variation, initial imperfection, elastic foundation parameters, porosity, GPL weight fraction and the dimensions of the GPL on the overall dynamic stability of the GPL-SFGP plate are evidently demonstrated.
Li, W, Luo, Z, Long, C, Huang, Z, Huang, L, Yu, Q & Sun, Z 2018, 'Mechanical Strengths and Microstructures of Recycled Aggregate Concrete Incorporating Nanoparticles', Advances in Civil Engineering Materials, vol. 7, no. 1, pp. 188-205.
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Abstract The influences of nanoparticles on the mechanical properties and microstructures of recycled aggregate concrete (RAC) were investigated in this study. The compressive and flexural strengths of RAC with different dosages of nanoSiO2 (NS) and nanoCaCO3 (NC) were tested. Both the scanning electron microscopy (SEM) and mercury intrusion porosimetry (MIP) techniques were applied to analyze the microstructures and porosity of interfacial transition zones (ITZs) in RAC. Based on the comparison on compressive strength and flexural strength, the NS is more effective than the NC for improving the mechanical properties of RAC. Dispersion of NC particles by a superplasticizer can somewhat improve the early-age strength of RAC but is unlikely to enhance the 28-day mechanical strengths. This may be attributed to the better dispersion and pozzolanic activity of NS compared to NC. The results show that a denser microstructure and a reduction of porosity within ITZs were observed by incorporating NS, which occurred along with the improvement of the mechanical strengths of RAC. Moreover, the NS-modified RAC exhibits less total porosity than the NC-modified RAC. The NS-modified RAC mainly contains small size pores, but the NC-modified RAC has more large pores than the NS-modified RAC, which has negative effects on the mechanical properties of RAC.
Li, W, Luo, Z, Sun, Z, Hu, Y & Duan, WH 2018, 'Numerical modelling of plastic–damage response and crack propagation in RAC under uniaxial loading', Magazine of Concrete Research, vol. 70, no. 9, pp. 459-472.
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In order to better understand the failure mechanism of recycled aggregate concrete (RAC), a numerical study on modelled recycled aggregate concrete (MRAC) was conducted to investigate the plastic–damage response and crack propagation under uniaxial loading. In the numerical model, the nanoscale mechanical properties and the thickness of the interfacial transition zones (ITZs) were obtained based on advanced nanoindentation. The constitutive relationships of new and old cement mortars and corresponding ITZs were developed using plastic–damage constitutive relationships. The effects of the relative mechanical properties between new and old cement mortars on the failure pattern and stress–strain response of MRAC were investigated. After calibration and verification with the uniaxial compression test, the numerical model was found to be able to reveal the failure pattern and stress–strain curves of MRAC under uniaxial tension. The results showed that microcracks usually first appear around the weak new and old ITZs, and then propagate into the new and old cement mortars. With an increase in the relative strength between new and old cement mortars, the microcrack initiation locations gradually shifted from the new ITZs to the old ITZs. Therefore, the numerical results can provide insight into the modification of RAC using mix design optimisation and ITZ enhancement.
Li, W, Luo, Z, Wu, C & Duan, WH 2018, 'Impact performances of steel tube-confined recycled aggregate concrete (STCRAC) after exposure to elevated temperatures', Cement and Concrete Composites, vol. 86, pp. 87-97.
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© 2017 Elsevier Ltd The impact behaviours of steel tube-confined recycled aggregate concrete (STCRAC) following exposure to elevated temperatures of 20 °C, 200 °C, 500 °C and 700 °C were experimentally investigated using a 100 mm-diameter split Hopkinson pressure bar (SHPB). The recycled coarse aggregate (RCA) replacement ratios were set as 0, 50% and 100%. The effect of RCA replacement ratio and exposure temperature on the impact properties of STCRAC were analysed in terms of failure modes, stress-strain time history curve and dynamic increase factor (DIF). The results show that the fire-damaged STCRAC can maintain its integrity during impact load. However, there were evident degradations in the dynamic behaviour of STCRAC after exposure to high temperatures of 500 °C and 700 °C. The ultimate impact strength, impact secant modulus and residual impact strength of STCRAC obviously decreased because of the damage due to high temperature exposure. But the degradations of both the ultimate impact strength and impact secant modulus of STCRAC under impact loading were less severe than those under quasi-static loading. The remaining strength factor and the DIF tended to increase with the raise of the elevated temperatures. Overall, during the impact loading, the fire-deteriorated STCRAC exhibited excellent impact behaviour.
Li, X, Liu, YM, Li, WG, Li, CY, Sanjayan, JG, Duan, WH & Li, Z 2018, 'Corrigendum to “Effects of graphene oxide agglomerates on workability, hydration, microstructure and compressive strength of cement paste” [Constr. Build. Mater. 145 (2017) 402–410]', Construction and Building Materials, vol. 179, pp. 537-538.
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Li, X, Mei, Q, Yan, X, Dong, B, Dai, X, Yu, L, Wang, Y, Ding, G, Yu, F & Zhou, J 2018, 'Molecular characteristics of the refractory organic matter in the anaerobic and aerobic digestates of sewage sludge', RSC Advances, vol. 8, no. 58, pp. 33138-33148.
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The chemical characteristics of the refractory organic matter in anaerobic and aerobic digestates are hardly known although they are significant for further improving the degradation of organic matter during sludge digestion.
Li, X, Wang, L, Liu, Y, Li, W, Dong, B & Duan, WH 2018, 'Dispersion of graphene oxide agglomerates in cement paste and its effects on electrical resistivity and flexural strength', Cement and Concrete Composites, vol. 92, pp. 145-154.
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© 2018 Elsevier Ltd Actual dispersion of graphene oxide (GO) in cement paste was investigated by using both X-ray computed tomography and X-ray photoelectron spectroscopy. It was found that GO nanosheets are mainly agglomerated, as an individual phase, with platelet-like morphology and little GO being absorbed onto surfaces of cement particles and hydration products. By performing an electrical resistivity test, GO agglomerates are found to be more electrically insulative than cement paste. Therefore, it is not possible to develop self-sensing cement composites by incorporating GO directly without resolving its dispersion issue. However, GO agglomerates enhance the flexural strength of cement paste because of their special morphology and intrinsic strength. Results showed that the flexural strength of cement paste was increased by 83% with incorporation of 0.04% GO by weight of cement.
Li, XP, Ji, G, Eder, K, Yang, LM, Addad, A, Vleugels, J, Van Humbeeck, J, Cairney, JM & Kruth, JP 2018, 'Additive manufacturing of a novel alpha titanium alloy from commercially pure titanium with minor addition of Mo2C', Materialia, vol. 4, pp. 227-236.
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Li, Y, Li, W, Deng, D, Wang, K & Duan, WH 2018, 'Reinforcement effects of polyvinyl alcohol and polypropylene fibers on flexural behaviors of sulfoaluminate cement matrices', Cement and Concrete Composites, vol. 88, pp. 139-149.
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© 2018 Elsevier Ltd The fracture behavior of unoiled/uncoated polyvinyl alcohol (PVA) fiber reinforced sulphoaluminate cement (SAC) matrices was experimentally investigated and compared with those of polypropylene (PP) fiber reinforced SAC and PVA fiber reinforced Portland cement (PC) matrices in this study. In the experimental investigation, three-point bending tests were carried out for notched fiber reinforced cement beams. Special attentions were paid on their deflection-hardening and multiple crack patterns. The different flexural behaviors between the plain SAC and PC matrices were evaluated using the double-K fracture model. The results indicate that the PVA fiber reinforced SAC matrices exhibited better flexural behaviors when compared with the PVA fiber reinforced PC matrix having comparable matrix strength. The bond strength between SAC matrix and PVA fiber are relatively better than that between the counterpart PC matrix and PVA fiber, while the bond strength between SAC matrix and PVA fiber is obviously stronger than that between the SAC and PP fibers.
Liang, X & Wu, C 2018, 'Investigation on Thermal Conductivity of Steel Fiber Reinforced Concrete Using Mesoscale Modeling', International Journal of Thermophysics, vol. 39, no. 12.
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© 2018, Springer Science+Business Media, LLC, part of Springer Nature. A mesoscale model was developed to investigate the effect of steel fiber on the thermal conductivity of steel fiber-reinforced concrete (SFRC). Delaunay triangulation was employed to generate the unstructured mesh for SFRC materials. The model was validated using the existing experimental data. Then, it was used to study how model thickness affected simulation outcomes of thermal conductivity of models with different fiber lengths, by which an appropriate thickness was determined for the later analyses. The validated and optimized model was applied to the study of relationships between thermal conductivity and factors such as fiber content, fiber aspect ratio and different parts of an SFRC block by conducting steady-state heat analyses with the finite element analysis software ANSYS. The simulation results reveal that adding steel fiber increases thermal conductivity considerably, while fiber aspect ratio only has an insignificant effect. Besides, the presence of steel fibers has an obvious impact on the distribution of temperature and heat flux vector of the SFRC blocks.
Liang, X & Wu, C 2018, 'Meso-scale modelling of steel fibre reinforced concrete with high strength', Construction and Building Materials, vol. 165, pp. 187-198.
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© 2018 Based on Delaunay triangulation, a 3D meso-scale model is successfully developed and verified. This approach modelling fibre and concrete separately and linking them with slide line contact has the capability to truly reflect the interfacial behaviour of fibre and mortar, and thus achieve high fidelity of numerical simulations. However, meso-scale modelling usually means tremendous complexity and long computational time. This paper proposes a model to achieve relatively high computation efficiency, as well as accuracy. Besides, the model has the potential to deal with small specimens cut from steel fibre reinforced concrete (SFRC) blocks.
Liang, X, Wu, C, Su, Y, Chen, Z & Li, Z 2018, 'Development of ultra-high performance concrete with high fire resistance', Construction and Building Materials, vol. 179, pp. 400-412.
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© 2018 Elsevier Ltd Fire or high temperature is a big challenge to ultra-high performance concrete (UHPC). Strength loss of UHPCs can reach up to 80% after exposure to 800 °C. In this study, a total of six UHPC mixtures were designed and tested after subjected to elevated temperatures up to 1000 °C. The effects of aggregate type, fibre type and heating rate were investigated. Residual compressive strengths and stress-strain relationships were studied. Besides, attention was paid to explosive spalling since UHPCs are usually of compact structure and thus more vulnerable to explosive spalling than other concretes. Scanning electron microscope (SEM) analysis was conducted to help understand the mechanism of variation of internal structure under different temperatures. It was found the mixture containing steel slag and hybrid fibre had excellent fire resistance. After being subjected to 1000 °C, this mixture retained a residual compressive strength of 112.8 MPa or a relative value of 69%.
Lim, S, Park, MJ, Phuntsho, S, Mai-Prochnow, A, Murphy, AB, Seo, D & Shon, H 2018, 'Dual-layered nanocomposite membrane incorporating graphene oxide and halloysite nanotube for high osmotic power density and fouling resistance', Journal of Membrane Science, vol. 564, pp. 382-393.
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© 2018 Elsevier B.V. This study introduces a thin-film composite (TFC) membrane with a dual-layered nanocomposite substrate synthesized using a dual-blade casting approach for application in osmotic power generation by the pressure-retarded osmosis (PRO) process. The approach incorporates halloysite nanotubes (HNTs) into the bottom polymer substrate layer and graphene oxide (GO) on the top layer substrate, on which a thin polyamide active layer is formed. The fabricated membrane substrate showed highly desirable membrane substrate properties such as a high porosity, opened-bottom surface, suitable top-skin surface morphology for subsequent active layer formation and high mechanical strength, which are essential for high-performance PRO processes. At a GO loading of 0.25 wt% and HNT loading of 4 wt%, the power density (PD) of the nanocomposite membrane was 16.7 W/m2 and the specific reverse solute flux (SRSF) was 2.4 g/L operated at 21 bar applied pressure using 1 M NaCl as draw solution and deionized water as feed, which is significantly higher than the those for a single-layered or commercial PRO membrane. This membrane performance was observed to be stable in the pressure cycle test and under long-term operation. The membrane substrate with HNTs incorporated exhibited high fouling resistance to sodium alginate and colloidal silica foulants, with the PD decreasing by 17% after 3 h of operation, compared to a membrane substrate without HNTs and commercial PRO membranes, which decreased by 26% and 57%, respectively. A fluorescence microscope study of the membranes subjected to feed water containing Escherichia coli confirmed the good antibacterial properties of the dual-layered TFC membrane. The study provides an attractive alternative approach for developing PRO membranes with high PD and fouling resistance.
Lin, M, Shan, S, Liu, P, Ma, L, Huang, L, Yang, M, Lawson, T, Wang, Z, Huang, Z, Shi, B, Yan, L & Liu, Y 2018, 'Hydroxyl-Functional Groups on Graphene Trigger the Targeted Delivery of Antitumor Drugs', Journal of Biomedical Nanotechnology, vol. 14, no. 8, pp. 1420-1429.
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© 2018 American Scientific Publishers. An efficient and targeted treatment for tumor cells is demonstrated. This targeting is based upon the strong affinity between hydroxyl-functional groups on graphene and acidic tumors. The hydroxylated graphene (GOH) with a unique 2D architecture further improve the targeting capacity of the system via an enhanced permeability and retention (EPR) process. Polyethylene glycol (PEG) was employed for better biocompatibility and the antitumor drug doxorubicin (DOX) was then incorporated. These additions created a biocompatible system with a superior pH-dependent drug release property. Its proficiency was due to its ability to pass through cell membranes via a process of endocytosis and exocytosis. The results from a Transwell co-culture system discovered that the PEG-GOH-DOX system had a large impact on tumor cell viability (less than 10% survived after treatment) and little influence on normal cells (more than 80% survived). An in vitro 3D tumor model study demonstrated that the size of the PEG-GOH-DOX treated tumor was 50% less than that of the pristine DOX treated tumor. In vivo data indicated that the PEG-GOH-DOX system was able to inhibit the size of tumors by a factor of 6.5 when compared to the untreated tumors.
Liu, J, Wu, C, Li, J, Su, Y & Chen, X 2018, 'Numerical investigation of reactive powder concrete reinforced with steel wire mesh against high-velocity projectile penetration', Construction and Building Materials, vol. 166, pp. 855-872.
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© 2018 Elsevier Ltd This paper numerically investigates the effects of steel wire mesh reinforcement on reactive powder concrete (RPC) targets subjected to high-velocity projectile penetration. A numerical model based on a computer program called LS-DYNA was validated with experimental data concerning the depth of penetration (DOP) and crater diameter of reinforced RPC targets. With the validated numerical model, a series of parametric studies are conducted to investigate how the variables of steel wire mesh reinforcement such as the configuration of steel wire meshes, number of layers, space between layers, space between steel wires per layer, as well as the diameter and tensile strength of steel wires affect DOP and crater diameter of reinforced RPC targets. Moreover, the energy evolution of projectile and steel wire meshes during the projectile penetration is discussed. Based on the results of parametric studies, an empirical equation derived from the simulation data is proposed to predict DOP of reinforced RPC targets.
Liu, J, Wu, C, Su, Y, Li, J, Shao, R, Chen, G & Liu, Z 2018, 'Experimental and numerical studies of ultra-high performance concrete targets against high-velocity projectile impacts', Engineering Structures, vol. 173, pp. 166-179.
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© 2018 Elsevier Ltd Ultra-high performance concrete (UHPC) which is known for high strength, high toughness, excellent ductility and good energy absorption capacity can be adopted as an ideal material in the impact resistant design of structures. In the present study, impact responses of UHPC targets with 3 vol-% ultra-high molecular weight polyethylene (UHMWPE) fibres and UHPC targets with 3 vol-% steel fibres are experimentally investigated subjected to high-velocity projectile penetration, and plain concrete targets under the same loading scenarios are also tested as control specimens for comparative purpose. In addition, numerical studies are conducted to simulate the projectile penetration process into UHPC targets with the assistance of a computer program LS-DYNA. The numerical results in terms of the depth of penetration (DOP) and crater diameter as well as projectile abrasions and damages are compared with the experimental results. Moreover, DOPs of these two types of UHPC targets obtained from tests are compared with the previously proposed empirical model.
Liu, K, Law, SS & Zhu, XQ 2018, 'A layered beam element for modeling de-bonding of steel bars in concrete and its detection using static measurements', Structural Control and Health Monitoring, vol. 25, no. 4, pp. e2142-e2142.
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Copyright © 2018 John Wiley & Sons, Ltd. In the formulation of finite elements, the variation of elemental internal forces and displacements are interpolated. The force interpolation functions are known to reproduce the variations of forces better than the interpolation functions on the displacements. Layered section beam model is not as complicated as the fiber model, and yet, it is much more accurate than ordinary beam model. The force-based finite element is revisited in this paper with its application in the numerical studies of a damage detection strategy for a reinforced concrete beam under static load. Two kinds of damages are studied including the cracking or other local damage of the concrete and the bonding between the concrete and the steel bar. Both kinds of damages in an element can be detected separately or in combinations with the proposed strategy. The force-based layered finite element is shown to be a practical, accurate, and efficient representation of the bonding damage of steel bars in concrete structures.
Liu, K, Li, Q, Wu, C, Li, X & Li, J 2018, 'A study of cut blasting for one-step raise excavation based on numerical simulation and field blast tests', International Journal of Rock Mechanics and Mining Sciences, vol. 109, pp. 91-104.
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© 2018 Elsevier Ltd Over the past several decades, raise excavation has been widely employed in underground mining, civil engineering and military engineering. One-step raise excavation with burn cuts, where all the boreholes are pre-drilled and detonated at one time and no workers need to be underneath the freshly blasted and dangerous ground, is an important and promising method in raise excavation. Cut parameters, especially the parameters of prime cut which used empty hole as a free surface and swelling space, have significant influence on the effect of raise formed. In this study, two small-scale experimental methods, spiral hole spacing method and observation hole method, are designed to determine the prime cut parameters such as hole spacing (L), stemming length (Ls1, Ls2) and air deck length (La) which are normally determined by empirical formula. In order to study the feasibility of the two methods, numerical analysis and experimental tests are conducted in V zone of Sandaozhuang molybdenum mine (SMM), in which there are large numbers of underground goafs need to be controlled by filled raise. The Riedel–Hiermaier–Thoma (RHT) material model, which considers compression damage and tension damage effect under blasting loading, is employed in the LS-DYNA software to study the rock damage zone. Meanwhile, the field tests are carried out according to the two small-scale experimental methods. The comparison results show that the damage zone of numerical simulation has a good agreement with the experimental data. Further, the optimal prime cut parameters obtained from experimental tests are applied in one-step filled-raise excavation, and a 23 m raise that meets the design requirements is formed through the proposed technology. The results indicate that these cut parameters determined by the small-scale experiments are suited for one-step raise excavation. This study can provide two simple field experiments to determine the important prime cut paramet...
Liu, M, Gurr, PA, Fu, Q, Webley, PA & Qiao, GG 2018, 'Two-dimensional nanosheet-based gas separation membranes', Journal of Materials Chemistry A, vol. 6, no. 46, pp. 23169-23196.
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Two-dimensional nanosheets as building blocks for the preparation of high-performance gas separation membranes.
Liu, Q, Gao, R, Tam, VWY, Li, W & Xiao, J 2018, 'Strain monitoring for a bending concrete beam by using piezoresistive cement-based sensors', Construction and Building Materials, vol. 167, pp. 338-347.
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© 2018 Elsevier Ltd Graphite nanoplatelets (GNPs), promising in improving electrical properties of cement-based materials and its smartness, were used to prepare piezoresistive cement-based strain sensors (PCSSs) in this study. Their piezoresistive responses along vertical, horizontal and inclined directions were measured during applying a vertical cyclic compression. After calibrating free PCSSs by analyzing their gauge factors, three PCSSs are embedded in a four-point bending beam at different stress zones, i.e. uniaxial compression, uniaxial tension and combined shear and compression. In addition to investigating piezoresistive responses of PCSSs embedded in the beam, traditional strain gauges and finite element method (FEM) were also used to grasp the strains at relevant positions for comparison. For free PCSSs, It was found that the electrical resistances along vertical, horizontal and diagonal directions drop by amplitudes of 5.5%, 1.8% and 6.7% respectively, as the increasing of vertical compression. The gauge factor along loading direction was calculated to be −160.8, which illustrated a better sensitivity. In the four-point bending beam, the PCSSs in compressive zone and tensile zone can be used to presume the strain variation by considering the gauge factor obtained from the free PCSS. The reaction of the PCSS in shear zone can illustrate its strain features because a slight volume variation happened in this area, which can also be testified to be only 0.012‰with FEM analysis.
Liu, Q, Shen, H, Wu, Y, Xia, Z, Fang, J & Li, Q 2018, 'Crash responses under multiple impacts and residual properties of CFRP and aluminum tubes', Composite Structures, vol. 194, pp. 87-103.
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© 2018 Elsevier Ltd This study aimed to explore the impact responses and residual properties of thin-walled carbon fiber reinforced plastics (CFRP) tubes and aluminum (Al) tubes subjected to multiple axial impacts. Five repeated impacts with the same impact energy were first conducted to evaluate the effect of repeated impact number, and then the crushing tests were performed to explore the post-impact residual behavior. Regardless of number of repeated impacts, the progressive end crushing modes for the CFRP tubes and stable progressive folding mode for aluminum tubes were identified under repeated dynamic impacts. The CFRP tubes exhibited the highest specific energy absorption (SEA) under the 1st impact, then the similar SEA values in the other four subsequent impacts; whereas the SEA of aluminum tubes fluctuated with the repeated impact numbers which were related to formation of different folds. The quasi-static crushing tests revealed that the residual SEAs of the CFRP tubes and aluminum tubes were not much influenced by the impact number, only within a difference of 5% under the 5 repetitive impacts conducted. It was demonstrated that the CFRP tubes had much better performance in energy absorption capability in comparison with the aluminum tubes in terms of repeated impacts and residual crushing tests.
Liu, X, Ni, S-Q, Guo, W, Wang, Z, Ahmad, HA, Gao, B & Fang, X 2018, 'N2O emission and bacterial community dynamics during realization of the partial nitrification process', RSC Advances, vol. 8, no. 43, pp. 24305-24311.
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In this study, greenhouse gas emissions and microbial community succession during the realization of the partial nitrification (PN) process were studied.
Liu, X, Xu, Q, Wang, D, Yang, Q, Wu, Y, Yang, J, Gong, J, Ye, J, Li, Y, Wang, Q, Liu, Y, Ni, B-J, Zeng, G & Li, X 2018, 'Revealing the Underlying Mechanisms of How Initial pH Affects Waste Activated Sludge Solubilization and Dewaterability in Freezing and Thawing Process', ACS Sustainable Chemistry & Engineering, vol. 6, no. 11, pp. 15822-15831.
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Copyright © 2018 American Chemical Society. In this study, the effect of initial pH ranging from 3 to 11 on waste activated sludge solubilization and dewaterability in the freezing and thawing (F/T) process was investigated. Experimental results showed that alkaline conditions enhanced the solubilization of sludge in F/T treatment, whereas acidic conditions improved the dewaterability of sludge. Optimum solubilization with organic substances being 189.7 mg COD/g VSS occurred at initial pH 10, which was 12.9 times higher and more biodegradable than the control. Optimal dewaterability performance was achieved at initial pH 4, with capillary suction time and specific resistance to filterability reduction being reached to 85.4% and 87.8%, respectively. It was found that F/T treatment at initial alkaline condition also obtained good dewatering performance, and F/T treatment at initial acidic condition acquired fine solubilization too. Mechanism explorations exhibited that the OH- and freezing had synergetic effects on the degradation of extracellular polymeric substances (EPS) to enhance sludge solubilization, and OH- can be concentrated to a much higher level in the liquid-like boundary region upon freezing, which further strengthened this effects. The H+ and freezing also showed synergetic effects on the protonation of functional groups of EPS and flocculation of the colloidal sludge to improve sludge dewaterability. This study clearly reveals the role and mechanisms of initial pH on the F/T process aiming at solubilization and dewaterability of sludge, and might provide supports for the application of F/T-based strategy in field situations in the future.
Liu, X, Xu, Q, Wang, D, Zhao, J, Wu, Y, Liu, Y, Ni, B-J, Wang, Q, Zeng, G, Li, X & Yang, Q 2018, 'Improved methane production from waste activated sludge by combining free ammonia with heat pretreatment: Performance, mechanisms and applications', Bioresource Technology, vol. 268, pp. 230-236.
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© 2018 Elsevier Ltd Anaerobic digestion of waste activated sludge (WAS) is often limited by low hydrolysis efficiencies and poor methane potentials. This work presents a novel pretreatment technology for WAS anaerobic digestion, i.e., combining free ammonia with heat pretreatment (CFHP). Experimental results showed that compared with control, solo free ammonia (135.4 mg NH3-N/L) and solo heat (70 °C) pretreatment, the combined free ammonia and heat (135.4 mg NH3-N/L with 70 °C) obtained 52.2%, 25.5% and 30.2% faster in hydrolysis rate and 25.2%, 17.9% and 16.5% higher in biochemical methane potential, respectively. Mechanism investigations showed that the combined pretreatment not only largely facilitated the disintegration of WAS but also increased the proportion of biodegradable organic matters, thereby providing better contract between biodegradable organics and the anaerobic microbes for methane production. Considering its effectiveness and renewability, the combined pretreatment is an attractive technology for the application in real-world situations.
Liu, Y, Li, J, Guo, W, Ngo, HH, Hu, J & Gao, M-T 2018, 'Use of magnetic powder to effectively improve the performance of sequencing batch reactors (SBRs) in municipal wastewater treatment', Bioresource Technology, vol. 248, no. Part B, pp. 135-139.
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This study aims to investigate the effect of adding magnetic powder in the sequencing batch reactor (SBR) on the reactor performance and microbial community. Results indicated that, the magnetic activated sludge sequencing batch reactor (MAS-SBR) had 7.76% and 4.76% higher ammonia nitrogen (NH4(+)-N) and chemical oxygen demand (COD) removal efficiencies than that of the conventional SBR (C-SBR). The MAS-SBR also achieved 6.86% sludge reduction compared with the C-SBR. High-throughput sequencing demonstrated that the dominant phyla of both SBRs (present as ≥1% of the sequence reads) were Protebacteria, Bacteroidetes, Chloroflexi, Saccharibacteria, Chlorobi, Firmicutes, Actinobactoria, Acidobacteria, Planctomycetes and unclassified_Bacteria. The relative abundance of Protebacteria and Bacteroidetes simultaneously declined whereas the other 8 phyla increased following the addition of magnetic powder. Adding magnetic powder in the SBR significantly affected the microbial diversity and richness of activated sludge, consequently affecting the reactor performance.
Liu, Y, Liu, Q, Li, J, Ngo, HH, Guo, W, Hu, J, Gao, M-T, Wang, Q & Hou, Y 2018, 'Effect of magnetic powder on membrane fouling mitigation and microbial community/composition in membrane bioreactors (MBRs) for municipal wastewater treatment', Bioresource Technology, vol. 249, pp. 377-385.
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This study aims to investigate the usefulness of magnetic powder addition in membrane bioreactors (MBRs) for membrane fouling mitigation and its effect on microbial community and composition. The comparison between the two MBRs (one with magnetic powder (MAS-MBR) and one without magnetic powder (C-MBR)) was carried out to treat synthetic municipal wastewater. Results showed that bioflocculation and adsorption of magnetic powder contributed only minimally to membrane fouling mitigation while the slower fouling rate might be ascribed to magnetic bio-effect. The macromolecules (larger than 500 kDa and 300-500 kDa) of soluble microbial product from the MAS-MBR were reduced by 24.06% and 11.11%, respectively. High-throughput sequencing demonstrated the most abundant genera of biofilm sludge indicated lower abundance in bulk sludge from the MAS-MBR compared to the C-MBR. It is possible that less membrane fouling is connected to reductions in large molecules and pioneer bacteria from bulk sludge.
Liu, Y, Ngo, HH, Guo, W, Peng, L, Chen, X, Wang, D, Pan, Y & Ni, B 2018, 'Modeling electron competition among nitrogen oxides reduction and N2O accumulation in hydrogenotrophic denitrification', Biotechnology and Bioengineering, vol. 115, no. 4, pp. 978-988.
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AbstractHydrogenotrophic denitrification is a novel and sustainable process for nitrogen removal, which utilizes hydrogen as electron donor, and carbon dioxide as carbon source. Recent studies have shown that nitrous oxide (N2O), a highly undesirable intermediate and potent greenhouse gas, can accumulate during this process. In this work, a new mathematical model is developed to describe nitrogen oxides dynamics, especially N2O, during hydrogenotrophic denitrification for the first time. The model describes electron competition among the four steps of hydrogenotrophic denitrification through decoupling hydrogen oxidation and nitrogen reduction processes using electron carriers, in contrast to the existing models that couple these two processes and also do not consider N2O accumulation. The developed model satisfactorily describes experimental data on nitrogen oxides dynamics obtained from two independent hydrogenotrophic denitrifying cultures under various hydrogen and nitrogen oxides supplying conditions, suggesting the validity and applicability of the model. The results indicated that N2O accumulation would not be intensified under hydrogen limiting conditions, due to the higher electron competition capacity of N2O reduction in comparison to nitrate and nitrite reduction during hydrogenotrophic denitrification. The model is expected to enhance our understanding of the process during hydrogenotrophic denitrification and the ability to predict N2O accumulation.
Liu, Y, Zhang, X, Hao Ngo, H, Guo, W, Wen, H, Deng, L, Li, Y & Guo, J 2018, 'Specific approach for membrane fouling control and better treatment performance of an anaerobic submerged membrane bioreactor', Bioresource Technology, vol. 268, pp. 658-664.
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This paper investigated a strategy to minimize membrane fouling and increase treatment efficiency through an investigation of a specific approach by adding sponges into a conventional submerged anaerobic membrane bioreactor (CAnSMBR). During the operation, the protein-based soluble microbial products as the main factor affecting the membrane fouling could be reduced by sponge addition in the CAnSMBR (SAnSMBR). Furthermore, reducing HRT from 18 h to 12 h could shorten the membrane fouling cycle to 62% and 87% in CAnSMBR and SAnSMBR, respectively. At the initial of COD/NO3 ratio ranges from 5 to 4, only 88% of nitrogen in CAnSMBR was removed, while the SAnSMBR could remove more than 90%. TOC removal efficiency could reach more than 95% under a good stirring scenario. It is evident that the SAnSMBR is a promising solution for improving overall CAnSMBR performance and substantially mitigating membrane fouling.
Liu, Z, Wang, D, Liang, J, Wu, F & Wu, C 2018, 'The fast multi-pole indirect BEM for solving high-frequency seismic wave scattering by three-dimensional superficial irregularities', Engineering Analysis with Boundary Elements, vol. 90, pp. 86-99.
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© 2018 Elsevier Ltd Taking full advantage of the indirect boundary element method (IBEM) and fast multi-pole expansion algorithm, this paper proposes a fast multi-pole indirect boundary element method (FM-IBEM) to solve the scattering of high-frequency seismic waves by three-dimensional (3-D) superficial irregularities or heterogeneity in a solid half-space. First, IBEM utilizes an exact dynamic Green's function for a full-space to construct the scattered wave field. Subsequently, by employing plane waves expansion of 3-D potential functions of compressional and shear waves, the multi-pole expansion and local expansion coefficients were derived. Implementation of FM-IBEM is presented in detail for wave-scattering problems. Numerical examples illustrate that the proposed FM-IBEM can reduce the memory required by more than an order of magnitude and also greatly improve the computing efficiency, retaining excellent accuracy as well. Ultimately, several high-frequency plane wave scattering problems of 3-D superficial irregularities in a solid half-space are illustrated, and several important scattering characteristics are described based on the high-precision numerical results.
Llano-Serna, MA, Farias, MM, Pedroso, DM, Williams, DJ & Sheng, D 2018, 'An assessment of statistically based relationships between critical state parameters', Géotechnique, vol. 68, no. 6, pp. 556-560.
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Reliability-based design (RBD) has been proved effective in the application of probability theory to research and practice in geotechnical engineering. However, the limited field and laboratory information makes it difficult to build robust predictions. This note shows some statistical relationships that may help with additional information in this area. Descriptive statistics are performed in the note followed by demonstrations of the close relationship between deformabilty parameters. The strong correlation between the slope of the critical state line and the earth pressure coefficient at rest is found. The applicability of the statistical relationships is also examined using RBD. Numerical analysis of oedometer tests demonstrates how RBD can consider the influence of the uncertainty of the critical state parameters.
Llano-Serna, MA, Farias, MM, Pedroso, DM, Williams, DJ & Sheng, D 2018, 'Considerations on the Experimental Calibration of the Fall Cone Test', Geotechnical Testing Journal, vol. 41, no. 6, pp. 1131-1138.
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Abstract The fall cone test is widely used in soil mechanics to determine the liquid limit of fine-grained soils as an aid to soil classification. The test can also be used to obtain the undrained shear strength of a fine-grained soil, based on the “cone factor,” K. Reports from different authors show K values ranging from 0.4–1.33. Differences are mostly attributed to the cone surface roughness. This article presents a reinterpretation of several experimental observations available in the literature. It is observed that besides the cone roughness, testing methods have a clear influence when calibrating the fall cone for determining the undrained shear strength of materials with low and very low consistency. The results show that existing K reports should be extrapolated with care. Finally, we propose a series of recommendations and good practices for future calibrations.
Lloret-Cabot, M, Wheeler, SJ, Pineda, JA, Romero, E & Sheng, D 2018, 'From saturated to unsaturated conditions and vice versa', Acta Geotechnica, vol. 13, no. 1, pp. 15-37.
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Lloret-Cabot, M, Wheeler, SJ, Pineda, JA, Romero, E & Sheng, D 2018, 'Reply to “Discussion of “From saturated to unsaturated conditions and vice versa” by M. Lloret-Cabot et al. (DOI 10.1007/s11440-017-0577-6)” by S. Qi et al. (DOI 10.1007/s11440-017-0625-2)', Acta Geotechnica, vol. 13, no. 2, pp. 493-495.
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Loganathan, P, Shim, WG, Sounthararajah, DP, Kalaruban, M, Nur, T & Vigneswaran, S 2018, 'Modelling equilibrium adsorption of single, binary, and ternary combinations of Cu, Pb, and Zn onto granular activated carbon', Environmental Science and Pollution Research, vol. 25, no. 17, pp. 16664-16675.
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© 2018, Springer-Verlag GmbH Germany, part of Springer Nature. Elevated concentrations of heavy metals in water can be toxic to humans, animals, and aquatic organisms. A study was conducted on the removal of Cu, Pb, and Zn by a commonly used water treatment adsorbent, granular activated carbon (GAC), from three single, three binary (Cu-Pb, Cu-Zn, Pb-Zn), and one ternary (Cu-Pb-Zn) combination of metals. It also investigated seven mathematical models on their suitability to predict the metals adsorption capacities. Adsorption of Cu, Pb, and Zn increased with pH with an abrupt increase in adsorption at around pH 5.5, 4.5, and 6.0, respectively. At all pHs tested (2.5–7.0), the adsorption capacity followed the order Pb > Cu > Zn. The Langmuir and Sips models fitted better than the Freundlich model to the data in the single-metal system at pH 5. The Langmuir maximum adsorption capacities of Pb, Cu, and Zn (mmol/g) obtained from the model’s fits were 0.142, 0.094, and 0.058, respectively. The adsorption capacities (mmol/g) for these metals at 0.01 mmol/L equilibrium liquid concentration were 0.130, 0.085, and 0.040, respectively. Ideal Adsorbed Solution (IAS)-Langmuir and IAS-Sips models fitted well to the binary and ternary metals adsorption data, whereas the Extended Langmuir and Extended Sips models’ fits to the data were poor. The selectivity of adsorption followed the same order as the metals’ capacities and affinities of adsorption in the single-metal systems.
Long, G, Liu, H, Ma, K, Xie, Y & Li, W 2018, 'Development of High-Performance Self-Compacting Concrete Applied as the Filling Layer of High-Speed Railway', Journal of Materials in Civil Engineering, vol. 30, no. 2, pp. 04017268-04017268.
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© 2017 American Society of Civil Engineers. The filling layer of a China rail track system III (CRTS III) type ballastless track structure of a high-speed railway is a complicated structure typically constructed from self-compacting concrete (SCC). Excellent properties of SCC are of great importance to ensure the quality of construction technology and long-term service performance of the filling layer. In this study, preparation methodologies and properties of SCC applied as a filling layer are systematically investigated by series of experiments. The results indicate that high-performance SCC with high stability in a fresh state and low deformation in a hardened state was successfully achieved by optimizing aggregates and binder components. Use of viscosity-enhancing compounds can not only effectively improve the workability of fresh SCC, but also significantly enhance mechanical properties and decrease drying shrinkage and creep of hardened concrete.
Lu, C, Yang, D, Guo, J, Xie, Z, Song, Y, Xing, Y, Ngo, HH, Han, Y & Li, H 2018, 'The catalysis biodecolorization characteristics of novel recyclable insoluble redox mediators onto magnetic nanoparticles', DESALINATION AND WATER TREATMENT, vol. 107, pp. 62-71.
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© 2018 Desalination Publications. All rights reserved. The insoluble redox mediators (RMs) were prepared to overcome limitations of soluble RMs that are eluted with water flow in wastewater treatment process. Magnetic nanoparticles possess good performance, due to their high specific surface area, the absence of internal diffusion resistance and easy separation in presence of an external magnetic field. In this study, insoluble RMs were prepared by immobilizing anthraquinone-2-sulfate (AQS) onto magnetic nanoparticles. AQS modified magnetic nanoparticles (FeSi@AQS) were formed by chemical reaction between the sulfochlorides group of anthraquinone-2-sulfonyl choride and amino-modified magnetic nanoparticles, with formation confirmed by Fourier transform infrared spectra. Results of energy dispersive X-ray and thermal grav-imetric analysis showed that AQS occupied a 21.47 wt.% proportion of the FeSi@AQS complex. FeSi@ AQS was used as insoluble RMs to catalyze biodecolorization of several kinds of azo dyes. When the concentration of FeSi@AQS was as low as 40 mg/L, biodecolorization rate of reactivered K-2BP was increased by 2.18-fold. FeSi@AQ Scan then be separated and gathered from wastewater by magnetic attraction and reused for further catalysis of azo dye decolorization in a modified SBR system. These findings show that the immobilization of RMs on magnetic nanoparticle surfaces, benefits potential industrial applications of RMs.
Lu, Z-H, Li, H, Li, W, Zhao, Y-G & Dong, W 2018, 'An empirical model for the shear strength of corroded reinforced concrete beam', Construction and Building Materials, vol. 188, pp. 1234-1248.
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© 2018 Elsevier Ltd A total of 158 experimental tests of shear behavior of corroded reinforced concrete (CRC) beams under action of concentrated load, published in the literature were collected and compiled into a shear strength database. This database was firstly used to discuss important parameters which affect the shear strength of CRC beams. The results show that the effect of stirrups’ corrosion on shear capacity of CRC beams is greater than that of longitudinal reinforcement corrosion. The shear span-to-depth ratio is also an important factor on shear strength of CRC beams. Total 9 available empirical models for predicting the residual shear strength are evaluated and compared based on the test database. It is found that eight of the nine models underestimate the shear strength of CRC beams while the other model gives the overestimated results. It is in this regard that a new empirical model for predicting the residual shear strength of CRC beams is proposed, in which a reduction coefficient is incorporated with the consideration of the effect of stirrups’ corrosion as well as shear span-to-depth ratio. The comparison studies demonstrate that the new proposal can provide an effective and accurate prediction of the shear capacity of CRC beams with a wide range of reinforcement corrosion damages.
Luo, W, Xie, M, Song, X, Guo, W, Ngo, HH, Zhou, JL & Nghiem, LD 2018, 'Biomimetic aquaporin membranes for osmotic membrane bioreactors: Membrane performance and contaminant removal', Bioresource Technology, vol. 249, pp. 62-68.
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© 2017 Elsevier Ltd In this study, we investigated the performance of an osmotic membrane bioreactor (OMBR) enabled by a novel biomimetic aquaporin forward osmosis (FO) membrane. Membrane performance and removal of 30 trace organic contaminants (TrOCs) were examined. Results show that the aquaporin FO membrane had better transport properties in comparison with conventional cellulose triacetate and polyamide thin-film composite FO membranes. In particular, the aquaporin FO membrane exhibited much lower salt permeability and thus smaller reverse salt flux, resulting in a less severe salinity build-up in the bioreactor during OMBR operation. During OMBR operation, the aquaporin FO membrane well complemented biological treatment for stable and excellent contaminant removal. All 30 TrOCs selected here were removed by over 85% regardless of their diverse properties. Such high and stable contaminant removal over OMBR operation also indicates the stability and compatibility of the aquaporin FO membrane in combination with activated sludge treatment.
Luo, Z, Li, W, Wang, K & Shah, SP 2018, 'Research progress in advanced nanomechanical characterization of cement-based materials', Cement and Concrete Composites, vol. 94, pp. 277-295.
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© 2018 Elsevier Ltd Advanced characterization techniques have provided powerful tools for characterizations of materials at micro- and nano-scales worldwide. Although some overviews on nanomechanical characterizations of cement-based materials have been published, they have often focused on nanoindentation. Very limited reviews have been reported on the applications of modulus mapping, PeakForce quantitative nanomechanical mapping, and nanoscratch for researches on the micro and nanoscale compositions, structures and mechanical properties of modern cement-based materials. This paper is aimed at filling this blank. Based on an extensive literature review and authors’ own experience, the basic knowledge (e.g., general concepts, developments, and progresses) involved in the state-of-the-art nanomechanical characterization techniques have been systematically summarized in this paper. The critical issues (e.g., sample preparation procedures and requirements, measurements, and data analysis methods) of these techniques have been discussed in details. The applications of these techniques, especially their suitability for critical characterization of different scales of interfaces of cement-based materials are compared. Finally, the future perspectives of these nanomechanical characterization techniques are highlighted. It is expected that the outlook of this paper can help future researchers make scientific justification on selection of nanomechanical characterization methods and steer inquisitive readers into substantial details that may lead them to successful applications of these advanced techniques.
Ly, QV, Nghiem, LD, Cho, J & Hur, J 2018, 'Insights into the roles of recently developed coagulants as pretreatment to remove effluent organic matter for membrane fouling mitigation', Journal of Membrane Science, vol. 564, pp. 643-652.
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Ly, QV, Nghiem, LD, Sibag, M, Maqbool, T & Hur, J 2018, 'Effects of COD/N ratio on soluble microbial products in effluent from sequencing batch reactors and subsequent membrane fouling', Water Research, vol. 134, pp. 13-21.
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The relative ratios of chemical oxygen demand (COD) to nitrogen (N) in wastewater are known to have profound effects on the characteristics of soluble microbial products (SMP) from activated sludge. In this study, the changes in the SMP characteristics upon different COD/N ratios and the subsequent effects on ultrafiltration (UF) membrane fouling potentials were examined in sequencing batch reactors (SBR) using excitation emission matrix-parallel factor analysis (EEM-PARAFAC) and size exclusion chromatography (SEC). Three unique fluorescent components were identified from the SMP samples in the bioreactors operated at the COD/N ratios of 100/10 (N rich), 100/5 (N medium), and 100/2 (N deficient). The tryptophan-like component (C1) was the most depleted at the N medium condition. Fulvic-like (C2) and humic-like (C3) components were more abundant with N rich wastewater. Greater abundances of large size biopolymer (BP) and low molecular weight neutrals (LMWN) were found under the N deficient and N rich conditions, respectively. SMPs from various COD/N exhibited a greater degree on membrane fouling following the order of 100/2 > 100/10 > 100/5. C1 and C2 had close associations with reversible and irreversible fouling, respectively, while the reversible fouling potential of C3 depended on the COD/N ratios. No significant impact of COD/N ratio was observed on the relative contributions of SMP size fractions to either reversible or irreversible fouling potential. However, the COD/N ratios likely altered the BP foulants' composition with greater contribution of proteinaceous substances to reversible fouling under the N deficient condition than at other N richer conditions. The opposite trend was observed for irreversible fouling. Our results provided further insight into changes in different SMP constitutes and their membrane fouling in response to microbial activities under different COD/N ratios.
Ma, C, Chen, C, Li, Q, Gao, H, Kang, Q, Fang, J, Cui, H, Teng, K & Lv, X 2018, 'Analytical Calculation of No-Load Magnetic Field of External Rotor Permanent Magnet Brushless Direct Current Motor Used as In-Wheel Motor of Electric Vehicle', IEEE Transactions on Magnetics, vol. 54, no. 4, pp. 1-6.
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© 1965-2012 IEEE. An analytical method for calculating the no-load magnetic field of external rotor permanent magnet brushless direct current motor (PMBLDCM) used as in-wheel motor of electric vehicle in the stator static coordinate and the rotor motion coordinate is presented in this paper. First, the analytic formulas of slotless permanent magnetic field in both coordinate systems are derived, respectively. Then, the complex relative permeance of external rotor PMBLDCM in both coordinate systems is calculated. Finally, the analytical solution of the no-load magnetic field in both coordinate systems is derived by applying the magnetic potential multiplied by the complex relative permeance. In this paper, a 46-pole-51-slot external rotor PMBLDCM is taken as an example, and the accuracy of the proposed analytical model is verified by the finite-element results. Based on the analytical model, the influences of the stator slotting effect on the no-load magnetic field of the external rotor and the inner stator are analyzed. The spatial order characteristics and frequency characteristics of the no-load magnetic field of the external rotor PMBLDCM in both coordinate systems are revealed, respectively.
Ma, J, Fan, F, Zhang, L, Wu, C & Zhi, X 2018, 'Failure modes and failure mechanisms of single-layer reticulated domes subjected to interior blasts', Thin-Walled Structures, vol. 132, pp. 208-216.
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© 2018 Single-layer reticulated domes are very common spatial structures. As landmarks, these types of structures can more easily be the targets of terrorist attacks than other buildings. However, blast resistance is not taken into consideration in the design of most civil structures. Therefore, it is important to know the damage level that may be imparted to single-layer reticulated domes after a blast attack. In this study, the dynamic response of reticulated domes subjected to an interior blast was investigated with numerical simulations, and five typical failure modes were identified from the results. In addition, the effects of some important parameters were investigated with a case study. Relationships between failure modes and interior blast impulses were summarised. Finally, the failure mechanisms were analysed, which could provide some design suggestions to decrease the probability of severe damage in spatial structures subjected to extreme dynamic loads.
Ma, XY, Li, Q, Wang, XC, Wang, Y, Wang, D & Ngo, HH 2018, 'Micropollutants removal and health risk reduction in a water reclamation and ecological reuse system', Water Research, vol. 138, pp. 272-281.
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Mahlia, TMI, Lim, JY, Aditya, L, Riayatsyah, TMI, Pg Abas, AE & Nasruddin 2018, 'Methodology for implementing power plant efficiency standards for power generation: potential emission reduction', Clean Technologies and Environmental Policy, vol. 20, no. 2, pp. 309-327.
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© 2017, The Author(s). Some methods of generating power such as power generation through coal, natural gas, oil result in inevitable emissions of greenhouse gases. While power generation is necessary due to its increasing demand, it is important for power companies to generate their power in an efficient manner to reduce its effect on the environment. One of the most effective ways of tackling inefficiency issues is through the implementation of efficiency standard. While there exist a lot of studies addressing the topic of energy efficiency standards, there are very few papers that deal specifically with efficiency standard for power generation plant. This paper presents methodology for the implementation of power plant efficiency standard; as mandatory or voluntary regulatory instrument, that may be implemented by the government to control greenhouse emissions from power plants. It is hoped that through its implementation, power companies shall become more conscious of their efficiency and emission quality, hereby encouraging the adoption of more efficient energy sources and latest available technologies. In this paper, methods of calculating greenhouse intensity value and its corresponding allowable ranges have been demonstrated. Case study on a 10-year-old base-load multi-fuel-fired power plant in Malaysia has shown that the power plant is in conformance to the power plant efficiency standard, with an actual greenhouse intensity of 859.4461 kgCO2/MWh sent-out, well within the allowable range of greenhouse intensities for that power plant which is between 760 and 890 kgCO2/MWh sent-out. It has also been demonstrated that older power plants are allowed to have higher values of greenhouse intensity. Benefits of utilising natural gas and operating the power plant at full load have also been shown.
Mannan, A, Sabri, MFM, Kalam, MA & Hassan, MH 2018, 'Tribological performance of DLC/DLC and steel/DLC contacts in the presence of additivated oil', International Journal of Surface Science and Engineering, vol. 12, no. 1, pp. 60-60.
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Mazaheri, H, Ong, HC, Masjuki, HH, Amini, Z, Harrison, MD, Wang, C-T, Kusumo, F & Alwi, A 2018, 'Rice bran oil based biodiesel production using calcium oxide catalyst derived from Chicoreus brunneus shell', Energy, vol. 144, pp. 10-19.
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Meng, J, Huang, J, Sheng, D & Sloan, SW 2018, 'Closure to “Quasi-Static Rheology of Granular Media Using the Static DEM” by J. Meng, J. Huang, D. Sheng, and S. W. Sloan', International Journal of Geomechanics, vol. 18, no. 12, pp. 07018016-07018016.
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Meng, J, Huang, J, Sloan, SW & Sheng, D 2018, 'Discrete modelling jointed rock slopes using mathematical programming methods', Computers and Geotechnics, vol. 96, pp. 189-202.
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Meng, J, Huang, J, Yao, C & Sheng, D 2018, 'A discrete numerical method for brittle rocks using mathematical programming', Acta Geotechnica, vol. 13, no. 2, pp. 283-302.
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Milano, J, Ong, HC, Masjuki, HH, Silitonga, AS, Chen, W-H, Kusumo, F, Dharma, S & Sebayang, AH 2018, 'Optimization of biodiesel production by microwave irradiation-assisted transesterification for waste cooking oil-Calophyllum inophyllum oil via response surface methodology', Energy Conversion and Management, vol. 158, pp. 400-415.
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In this study, microwave irradiation-assisted alkaline-catalysed transesterification was used to produce W70CI30 biodiesel from a mixture of waste cooking oil and Calophyllum inophyllum oil. The methanol/oil ratio, catalyst concentration, stirring speed, and reaction time were optimized using response surface methodology based on the Box-Behnken experimental design in order to maximize the biodiesel yield. The quadratic response surface regression model was used to predict the biodiesel yield. It is found that the optimum methanol/oil ratio, catalyst concentration, stirring speed, and reaction time are 59.60 (v/v)%, 0.774 (w/w)%, 600 rpm, and 7.15 min, respectively, and the predicted biodiesel yield is 97.40%. Experiments were conducted using the optimum process parameters and the average biodiesel yield is 97.65%, which is in excellent agreement with the predicted value. The physicochemical properties of the W70CI30 biodiesel produced using the optimum process parameters were measured and it is found that the biodiesel has significantly higher oxidation stability (18.03 h) compared with the waste cooking oil biodiesel (4.61 h). In addition, the physicochemical properties and cold flow properties of the biodiesel fulfil the fuel specifications stipulated in the ASTM D6751 and EN 14214 standards. It can be concluded that microwave irradiation-assisted transesterification is effective to boost the biodiesel yield and produce biodiesel of superior quality. In addition, this method significantly reduces the reaction time of the transesterification process to 9.15 min and the process is energy-efficient. It is believed that the findings of this study will be beneficial for microwave irradiation-assisted biodiesel synthesis on the industrial scale.
Milano, J, Ong, HC, Masjuki, HH, Silitonga, AS, Kusumo, F, Dharma, S, Sebayang, AH, Cheah, MY & Wang, C-T 2018, 'Physicochemical property enhancement of biodiesel synthesis from hybrid feedstocks of waste cooking vegetable oil and Beauty leaf oil through optimized alkaline-catalysed transesterification', Waste Management, vol. 80, pp. 435-449.
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Recycling waste cooking vegetable oils by reclaiming and using these oils as biodiesel feedstocks is one of the promising solutions to address global energy demands. However, producing these biodiesels poses a significant challenge because of their poor physicochemical properties due the high free fatty acid content and impurities present in the feedstock, which will reduce the biodiesel yields. Hence, this study implemented the following strategy in order to address this issue: (1) 70 vol% of waste cooking vegetable oil blended with 30 vol% of Calophyllum inophyllum oil named as WC70CI30 used to alter its properties, (2) a three-stage process (degumming, esterification, and transesterification) was conducted which reduces the free fatty acid content and presence of impurities, and (3) the transesterification process parameters (methanol/oil ratio, reaction temperature, reaction time, and catalyst concentration) were optimized using response surface methodology in order to increase the biodiesel conversion yield. The results show that the WC70CI30 biodiesel has favourable physicochemical properties, good cold flow properties, and high oxidation stability (22.4 h), which fulfil the fuel specifications stated in the ASTM D6751 and EN 14214 standards. It found that the WC70CI30 biodiesel has great potential as a diesel substitute without the need for antioxidants and pour point depressants.
Ming, C, Rizwanul Fattah, IM, Chan, QN, Pham, PX, Medwell, PR, Kook, S, Yeoh, GH, Hawkes, ER & Masri, AR 2018, 'Combustion characterization of waste cooking oil and canola oil based biodiesels under simulated engine conditions', Fuel, vol. 224, pp. 167-177.
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Alternative fuels will come from a variety of feed stocks and refinement processes. Understanding the fundamentals of combustion and pollutants formation processes of these fuels will be useful for their implementation in different combustion systems. In this work, optical diagnostics were performed to waste cooking oil (WCO) and canola oil (CAO) based biodiesel sprays to assess their combustion and soot formation processes. Conventional diesel was used as a reference fuel for comparison with the biodiesels. The experiments were conducted in an optically-accessible constant-volume combustion chamber (CVCC) with simulated compression-ignition engine conditions, with different degree of exhaust gas recirculation. The liquid length and lift-off length results indicate that there was no significant interaction between the liquid phases of the fuels and their combustion regions. The flame lift-off lengths were found to be affected by both the chemical and physical properties of the fuels. It was observed that a larger difference between the lift-off length and the first-luminosity distance was correlated with lesser downstream soot formation, although the molecular structure of the fuel was found to affect the process too. Assessing the sooting and combustion characteristics of the biodiesel and diesel flames across the varied ambient O atmospheres revealed that the estimated soot contents of the biodiesel and diesel flames peaked at 15 and 21 vol.% O concentration, respectively. The peak soot contents of the WCO and CAO biodiesel flames were found be comparable, but lower than that of diesel, across the various O environment. The results also demonstrated that the biodiesels have higher normalized peak pressure values than diesel at all O conditions. Two-color pyrometry data demonstrated that the measured soot temperature and soot KL factors of the flames were similar at 15 and 21 vol.% O , but varied with further reduction of ambient O concentration. ...
Mirzababaei, M, Arulrajah, A, Haque, A, Nimbalkar, S & Mohajerani, A 2018, 'Effect of fiber reinforcement on shear strength and void ratio of soft clay', Geosynthetics International, vol. 25, no. 4, pp. 471-480.
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In this study, a series of multi-stage drained reverse direct shear tests were carried out on soft clay samples reinforced with 0.25% and 0.50% polypropylene fibers of 6 mm, 10 mm and 19 mm in length. Tests were carried out at different normal effective stresses and cumulative horizontal shear displacement of 1.17 times of the sample width. Results showed an increase of the shear strength with the increase of fiber content and length. However, the rate of improvement was capped with the normal effective stress applied during the shearing stage. At a high normal effective stress, the shear strength of the fiber-reinforced soft clay approached that of the unreinforced clay regardless of the amount of fiber inclusion. The rate of shear strength improvement decayed with the number of shear cycles. Fiber reinforcement also resulted in a reduction of the compressibility of the soft clay at consecutive consolidation and shear stages. Although the effective internal friction angle of the soft clay was not altered significantly with the fiber reinforcement, the effective cohesion of the soft clay improved significantly as much as 6.4 and 8.5 times with the inclusion of 0.25% and 0.50% of 10 mm long fibers, respectively.
Mohsen, M, Ahmed, MB & Zhou, JL 2018, 'Particulate matter concentrations and heavy metal contamination levels in the railway transport system of Sydney, Australia', Transportation Research Part D: Transport and Environment, vol. 62, pp. 112-124.
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© 2018 Elsevier Ltd Sampling campaign was conducted over six weeks to determine particulate matter (PM) concentrations from Sydney Trains airport line (T2) at both underground and ground levels using DustTrak. Dust samples were collected and analysed for 12 metals (Fe, Ca, Mn, Cr, Zn, Cu, Pb, Al, Co, Ni, Ba and Na) by atomic emission spectroscopy. Average underground PM10 and PM2.5 concentrations from inside the trains were 2.8 and 2.5 times greater than at ground level. Similarly, PM10 and PM2.5 concentrations on underground platforms were 2.7 and 2.5 times greater than ground level platforms. Average underground PM concentrations exceeded the national air quality standards for both PM10 (50 µg/m3) and PM2.5 (25 µg/m3). Correlation analysis showed a strong to moderate association between PM concentrations at ground level and background PM concentrations (r2 from 0.952 to 0.500). The findings suggested that underground PM concentrations were less influenced by the ambient background than at ground level. The metal concentrations decreased in the order of Fe, Cr, Ca, Al, Na, Ba, Mn, Zn, Cu, Ni, Co and Pb. The pollution index (PI) and enrichment factor (EF) values were calculated to identify the levels and sources of contamination in the underground railway microenvironments. PM was remarkably rich in Fe with a mean concentration of 73.51 mg/g and EF of 61.31, followed by Ni and Cr. These results noticeably indicated a high level of metal contamination in the underground environments, with the principal contribution from track abrasion and wear processes.
Mokhtar, ES, Pradhan, B, Ghazali, AH & Shafri, HZM 2018, 'Assessing flood inundation mapping through estimated discharge using GIS and HEC-RAS model', Arabian Journal of Geosciences, vol. 11, no. 21.
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© 2018, Saudi Society for Geosciences. Water discharge is the main parameter in hydraulic modeling for flood hazard assessment. However, the unavailability of data on discharge and observed river morphologies resulted in erroneous calculations and irregularities in flood inundation mapping. The objectives of this study are (i) to investigate uncertainties of hydraulic parameters (width, cross-sectional depth, and channel slope) used in discharge equation and (ii) to examine the influence of estimate discharge on water extent and flood depth with different boundary conditions on interferometric synthetic aperture radar (IFSAR) and modified IFSAR DEMs. Sensitivity analysis was conducted with the Monte Carlo simulation method to generate random data combinations. Bjerklie’s equation was used to calculate discharge based on the three variables, and Manning’s n was substituted into the Hydrologic Engineering Center River Analysis System (HEC-RAS) model. TerraSAR-X was used to distinguish existing flood water bodies and normal water extent. The uncertainty of the combined variables was assessed with the likelihood measures such as F-statistic, mean absolute error, root mean square error, and Nash–Sutcliffe efficiency which compares observed and predicted inundated area as well as flood water depth simulated using the HEC-RAS model.
Mortazavi, M, Sharafi, P, Ronagh, H, Samali, B & Kildashti, K 2018, 'Lateral behaviour of hybrid cold-formed and hot-rolled steel wall systems: Experimental investigation', Journal of Constructional Steel Research, vol. 147, pp. 422-432.
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The seismic design of light steel frames (LSF) can not only rely on the application of cold-formed steel (CFS). Some mixed systems and integrated solutions such as hybrid systems can offer new possibilities, in particular with regard to applications in mid-rise construction. A hybrid solution is to replace some CFS chord studs with hot-rolled square hollow section SHS, in order to achieve higher capacity. This paper provides the results of experimental studies on the lateral behaviour of a hybrid light-weight steel panel and investigates the implication of any further system improvements for mid-rise construction. Each hybrid wall panel (HWP) consists of a hot-rolled SHS frame, laterally incorporated in a cold-formed panel. The study includes investigating the lateral performance of HWP, while a CFS top chord acting as a load collector, and a hot-rolled steel frame acting as a lateral load resisting system. The behaviour of specimens is investigated under monotonic and cyclic loads, and the step-by-step enhancement is implemented according to the results. The outcomes revealed that although the hysteretic behaviour of the HWP represents pinching effect, mainly due to poor performance of the cold-formed steel collector, by strengthening the top chord design the behaviour is improved. Relying on the cold-formed part to resist the major portion of gravity loads, while the hot-rolled collector transfers the entire lateral load to the hot-rolled frame, results in significantly improved hysteretic behaviour.
Murray, A, Gilbert, RI & Castel, A 2018, 'Spacing of Cracks in Reinforced Concrete Based on a Variable Transfer Length Model', Journal of Structural Engineering, vol. 144, no. 7, pp. 04018090-04018090.
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Musa, IA, Mashiri, FR & Zhu, X 2018, 'Parametric study and equation of the maximum SCF for concrete filled steel tubular T-joints under axial tension', Thin-Walled Structures, vol. 129, pp. 145-156.
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© 2018 Concrete-filled steel tubular joints are increasingly being used for built infrastructure such as bridges and towers. In this study, the variation of the maximum Stress Concentration Factor (SCFmax) with non-dimensional geometric parameters in concrete-filled steel tubular (CFST) T-joints under axial tension has been investigated. A database of the maximum SCFs in CFST T-joints under axial tension is developed based on three-dimensional (3D) finite element (FE) models. The 3D FE models developed using ABAQUS software have been verified using experimental results. Graphs showing variation of the maximum SCF, in CFST T-joints, with non-dimensional geometric parameters have been produced and compared with those for non-filled empty T-joints. A parametric equation for predicting the maximum SCFs in CFST T-joints, a useful parameter for design, has been developed in a multiple nonlinear regression analysis. There is a good agreement between the maximum SCFs predicted by the parametric equation and those determined from the experiments.
Musa, IA, Mashiri, FR, Zhu, X & Tong, L 2018, 'EXPERIMENTAL STRESS CONCENTRATION FACTOR IN CONCRETE-FILLED STEEL TUBULAR T-JOINTS', Journal of Constructional Steel Research, vol. 150, pp. 442-451.
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© 2018 Elsevier Ltd An experimental investigation of stress concentration factor (SCF) in Steel circular hollow section brace welded to concrete-filled circular hollow section chord (CHS-to-CFCHS) T-joints has been performed under axial tension, axial compression, in-plane bending and out-of-plane bending. The distribution of SCF around the welded brace-to-chord intersection on both the brace and chord has been investigated using three CHS-to-CFCHS T-joint specimens. The experimental SCF results have been compared with the predicted SCF in empty T-joints. The relationship between the maximum SCF in relation to parameter β, with fixed other geometrical parameters, has been investigated for the basic load conditions. The experimental maximum SCF under axial tension has been compared with the predicted maximum SCF from parametric equations for CHS-to-CFCHS T-joints previously developed by the authors. The results show that the concrete has a significant effect in reducing the SCF, mostly under axial tension and the parametric equations for predicting SCFs in empty T-joints are not suitable for CHS-to-CFCHS T-joints. The effect of parameter β on the maximum SCF in CHS-to-CFCHS T-joints is significant under axial tension and out-of-plane bending moment.
Nahhas, FH, Shafri, HZM, Sameen, MI, Pradhan, B & Mansor, S 2018, 'Deep Learning Approach for Building Detection Using LiDAR–Orthophoto Fusion', Journal of Sensors, vol. 2018, pp. 1-12.
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This paper reports on a building detection approach based on deep learning (DL) using the fusion of Light Detection and Ranging (LiDAR) data and orthophotos. The proposed method utilized object-based analysis to create objects, a feature-level fusion, an autoencoder-based dimensionality reduction to transform low-level features into compressed features, and a convolutional neural network (CNN) to transform compressed features into high-level features, which were used to classify objects into buildings and background. The proposed architecture was optimized for the grid search method, and its sensitivity to hyperparameters was analyzed and discussed. The proposed model was evaluated on two datasets selected from an urban area with different building types. Results show that the dimensionality reduction by the autoencoder approach from 21 features to 10 features can improve detection accuracy from 86.06% to 86.19% in the working area and from 77.92% to 78.26% in the testing area. The sensitivity analysis also shows that the selection of the hyperparameter values of the model significantly affects detection accuracy. The best hyperparameters of the model are 128 filters in the CNN model, the Adamax optimizer, 10 units in the fully connected layer of the CNN model, a batch size of 8, and a dropout of 0.2. These hyperparameters are critical to improving the generalization capacity of the model. Furthermore, comparison experiments with the support vector machine (SVM) show that the proposed model with or without dimensionality reduction outperforms the SVM models in the working area. However, the SVM model achieves better accuracy in the testing area than the proposed model without dimensionality reduction. This study generally shows that the use of an autoencoder in DL models can improve the accuracy of building recognition in fused LiDAR–orthophoto data.
Navaratnarajah, SK & Indraratna, B 2018, 'Closure to “Use of Rubber Mats to Improve the Deformation and Degradation Behavior of Rail Ballast under Cyclic Loading” by Sinniah K. Navaratnarajah and Buddhima Indraratna', Journal of Geotechnical and Geoenvironmental Engineering, vol. 144, no. 7, pp. 07018014-07018014.
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Navaratnarajah, SK, Indraratna, B & Ngo, NT 2018, 'Influence of Under Sleeper Pads on Ballast Behavior Under Cyclic Loading: Experimental and Numerical Studies', Journal of Geotechnical and Geoenvironmental Engineering, vol. 144, no. 9, pp. 04018068-04018068.
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Railway industries are placing greater emphasis on implementing fast and heavy haul corridors for bulk freight and commuter transport in order to deliver more efficient and cost-effective services. However, increasing dynamic stresses from the passage of trains progressively degrades and fouls the primary load-bearing ballast layer, which inevitably leads to excessive settlement and instability, damage to track elements, and more frequent maintenance. Ballasted tracks are subjected to even greater stresses and faster deterioration in sections where a reduced ballast thickness is used (e.g., bridge decks) or at locations where heavier concrete sleepers are used instead of lightweight timber sleepers. The inclusion of under sleeper pads (USPs) at the base of a concrete sleeper is one measure used to minimize dynamic stresses and subsequent track deterioration. In this study, cyclic loads from fast and heavy haul trains were simulated using a large-scale process simulation prismoidal triaxial apparatus (PSPTA) to investigate the performance of ballast improved by USPs. The laboratory results indicate that the inclusion of an elastic element at the harder interface of the concrete sleeper-ballast reduces the stresses transmitted to the ballast and the underlying layers and minimizes the amount of deformation and degradation of the ballast. A three-dimensional finite-element model was used to predict the behavior of ballast, and the influence of USPs on the stress-strain responses of ballast generally agree with the experimental findings.
Ngo, NT, Indraratna, B, Ferreira, FB & Rujikiatkamjorn, C 2018, 'Improved performance of geosynthetics enhanced ballast: laboratory and numerical studies', Proceedings of the Institution of Civil Engineers - Ground Improvement, vol. 171, no. 4, pp. 202-222.
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Ballasted rail tracks form one of the most important worldwide transportation modes in terms of traffic tonnage, serving the needs of bulk freight and passenger movement. High impact and cyclic loads can cause a significant deformation leading to poor track geometry. In order to mitigate these problems, the concept of the inclusion of geosynthetics in rail tracks is introduced. This paper presents the current state-of-the-art knowledge of rail track geomechanics, including results obtained from laboratory testing, field investigations and numerical modelling to study the load–deformation behaviour of ballast improved by geosynthetics. The shear stress–strain and deformation behaviour of geosynthetic-reinforced ballast are investigated in the laboratory using a large-scale direct shear test device, a track process simulation apparatus and a drop-weight impact testing equipment. Computational modelling using the discrete-element method is employed to simulate geosynthetic-reinforced ballasted tracks, capturing the discrete nature of ballast aggregates when subjected to various types of loading and boundary conditions. Discrete-element modelling is also used to conduct micromechanical analysis at the interface between ballast and geogrid, providing further insight into the behaviour of ballast subjected to cyclic loadings. These results provide promising approaches to incorporate into existing track design routines catering for future high-speed trains and heavier heavy hauls.
Nguyen, LN, Nghiem, LD & Oh, S 2018, 'Aerobic biotransformation of the antibiotic ciprofloxacin by Bradyrhizobium sp. isolated from activated sludge', Chemosphere, vol. 211, pp. 600-607.
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Nguyen, NC, Chen, S-S, Jain, S, Nguyen, HT, Ray, SS, Ngo, HH, Guo, W, Lam, NT & Duong, HC 2018, 'Exploration of an innovative draw solution for a forward osmosis-membrane distillation desalination process', Environmental Science and Pollution Research, vol. 25, no. 6, pp. 5203-5211.
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Forward osmosis (FO) has emerged as a viable technology to alleviate the global water crisis. The greatest challenge facing the application of FO technology is the lack of an ideal draw solution with high water flux and low reverse salt flux. Hence, the objective of this study was to enhance FO by lowering reverse salt flux and maintaining high water flux; the method involved adding small concentrations of Al2(SO4)3 to a MgCl2 draw solution. Results showed that 0.5 M MgCl2 mixed with 0.05 M of Al2(SO4)3 at pH 6.5 achieved a lower reverse salt flux (0.53 gMH) than that of pure MgCl2 (1.55 gMH) using an FO cellulose triacetate nonwoven (CTA-NW) membrane. This was due possibly to the flocculation of aluminum hydroxide in the mixed draw solution that constricted membrane pores, resulting in reduced salt diffusion. Moreover, average water fluxes of 4.09 and 1.74 L/m(2)-h (LMH) were achieved over 180 min, respectively, when brackish water (5 g/L) and sea water (35 g/L) were used as feed solutions. Furthermore, three types of membrane distillation (MD) membranes were selected for draw solution recovery; of these, a polytetrafluoroethylene membrane with a pore size of 0.45 μm proved to be the most effective in achieving a high salt rejection (99.90%) and high water flux (5.41 LMH) in a diluted draw solution.
Nguyen, NC, Chen, S-S, Nguyen, HT, Chen, Y-H, Ngo, HH, Guo, W, Ray, SS, Chang, H-M & Le, QH 2018, 'Applicability of an integrated moving sponge biocarrier-osmotic membrane bioreactor MD system for saline wastewater treatment using highly salt-tolerant microorganisms', Separation and Purification Technology, vol. 198, pp. 93-99.
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© 2017 Elsevier B.V.Osmotic membrane bioreactors (OsMBRs) are a recent breakthrough technology designed to treat wastewater. Nevertheless, their application in high-salinity wastewater treatment is not widespread because of the effects of saline conditions on microbial community activity. In response, this study developed an integrated sponge biocarrier-OsMBR system using highly salt-tolerant microorganisms for treating saline wastewater. Results showed that the sponge biocarrier-OsMBR obtained an average water flux of 2L/m2 h during a 92-day operation when 1M MgCl2 was used as the draw solution. The efficiency in removing dissolved organic compounds from the proposed system was more than 99%, and nutrient rejection was close to 100%, indicating excellent performance in simultaneous nitrification and denitrification processes in the biofilm layer on the carriers. Moreover, salt-tolerant microorganisms in the sponge biocarrier-OsMBR system worked efficiently in salt concentrations of 2.4%. A polytetrafluoroethylene MD membrane (pores=0.45μm) served to regenerate the diluted draw solution in the closed-loop system and produce high-quality water. The moving sponge biocarrier-OsMBR/MD hybrid system demonstrated its potential to treat salinity wastewater treatment, with 100% nutrient removal and 99.9% conductivity rejection.
Nguyen, QD, Khan, MSH & Castel, A 2018, 'Engineering Properties of Limestone Calcined Clay Concrete', Journal of Advanced Concrete Technology, vol. 16, no. 8, pp. 343-357.
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In this paper, various engineering properties of both fresh and hardened concrete with various limestone and calcined clay contents are investigated. Two concrete grades were considered: 50 MPa or 30 MPa average 28 days compressive strength. A low grade calcined clay was used with about 50% amorphous phase. A reduction in concrete workability was observed with the increase in General Purpose (GP) cement substitution. Superplasticiser was required to obtain a slump equivalent to that of reference GP cement concrete. With 15% GP cement replacement rate, the 28 days compressive strength achieved was superior to that of reference grade 50 MPa concrete, reaching 58 MPa. However, the average 28 days compressive strength reduced significantly with 30% and 45% GP cement replacement, reaching about 35 MPa. Considering concretes with similar 28-day compressive strength, results showed that the 7-day compressive strength was only marginally affected by the limestone and calcined clay substitution. Mercury intrusion porosimetry results revealed that incorporating calcined clay and limestone led to significant refinement of the porosity: increase in the quantity of pores inferior to 0.01µm and reduction in the quantity of coarse pores (with size > 0.1 µm).
Nguyen, TC, Loganathan, P, Nguyen, TV, Kandasamy, J, Naidu, R & Vigneswaran, S 2018, 'Adsorptive removal of five heavy metals from water using blast furnace slag and fly ash', Environmental Science and Pollution Research, vol. 25, no. 21, pp. 20430-20438.
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© 2017, Springer-Verlag GmbH Germany. Heavy metals can be serious pollutants of natural water bodies causing health risks to humans and aquatic organisms. The purpose of this study was to investigate the removal of five heavy metals from water by adsorption onto an iron industry blast furnace slag waste (point of zero charge (PZC) pH 6.0; main constituents, Ca and Fe) and a coal industry fly ash waste (PZC 3.0; main constituents, Si and Al). Batch study revealed that rising pH increased the adsorption of all metals with an abrupt increase at pH 4.0–7.0. The Langmuir adsorption maximum for fly ash at pH 6.5 was 3.4–5.1 mg/g with the adsorption capacity for the metals being in the order Pb > Cu > Cd, Zn, Cr. The corresponding values for furnace slag were 4.3 to 5.2 mg/g, and the order of adsorption capacities was Pb, Cu, Cd > Cr > Zn. Fixed-bed column study on furnace slag/sand mixture (1:1 w/w) revealed that the adsorption capacities were generally less in the mixed metal system (1.1–2.1 mg/g) than in the single metal system (3.4–3.5 mg/g). The data for both systems fitted well to the Thomas model, with the adsorption capacity being the highest for Pb and Cu in the single metal system and Pb and Cd in the mixed metal system. Our study showed that fly ash and blast furnace slag are effective low-cost adsorbents for the simultaneous removal of Pb, Cu, Cd, Cr and Zn from water.
Nguyen, TD, La Fontaine, A, Yang, L, Cairney, JM, Zhang, J & Young, DJ 2018, 'Atom probe study of impurity segregation at grain boundaries in chromia scales grown in CO2 gas', Corrosion Science, vol. 132, pp. 125-135.
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Nguyen, TT, Indraratna, B & Carter, J 2018, 'Laboratory Investigation into Biodegradation of Jute Drains with Implications for Field Behavior', Journal of Geotechnical and Geoenvironmental Engineering, vol. 144, no. 6, pp. 04018026-04018026.
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Naturally occurring materials such as jute and coir have some favorable engineering characteristics and also degrade over time, so they have increasingly been used in engineering applications in recent years. The efficient way that naturally prefabricated vertical drains made from those materials help accelerate soil consolidation has been shown in previous studies, but they also tend to decompose rapidly in adverse environments, where cellulose-degrading bacteria cause a serious deterioration of their favorable drainage properties. This study presents a laboratory investigation into the biodegradation of prefabricated vertical jute drains in saturated soft soils, where the tensile strength of jute and coir fibers and the discharge capacity of drains decrease in response to different environments. Micro-observation also shows a transformation of the jute fibers and destruction of the drain structure due to biodegradation. DNA extraction and sequencing techniques to determine the microbial properties of these decayed fibers indicate that bacteria such as species of the genera Clostridium and Bacillus can cause rapid decomposition of cellulose-based material (i.e., jute), whereas other organic matter-consuming microbes such as sulfate-reducing bacteria do not directly contribute to the biodegradation of jute. In response, an analytical approach that incorporates various forms of drain discharge capacity over time is proposed to predict soil consolidation. The results indicate there is considerable deviation in dissipating the excess pore pressure when the drain degrades in different ways.
Nguyen, TT, Indraratna, B & Rujikiatkamjorn, C 2018, 'Challenges and solutions towards natural prefabricated vertical drains', Australian Geomechanics Journal, vol. 53, no. 4, pp. 89-100.
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In recent years, natural fibres such as jute and coir are emerging as a reasonable alternative to synthetic materials because they do not only have favourable engineering characteristics but also degrade biologically over time. Of promising applications of those environmentally friendly materials, natural prefabricated vertical drains (NPVDs) have received considerable attention, however their application is still limited. This paper summarises existing issues which are hampering these novel drains from a wider application, followed by studies carried out by the authors to overcome those limitations. Particularly this includes: (1) hydraulic properties of NPVDs considering macro and micro features; (2) modelling NPVDS including analytical method and a novel numerical approach to capture micro-hydraulic behavior of fibre drains considering fluid-fibre interaction; (3) bioderadable characteristics of NPVDs exposed to saturated soft soils; (4) analytical and numerical solutions to incorporate biodegradation of NPVDs into consolidation of soil.
Nguyen, VV, Li, J, Erkmen, E, Alamdari, MM & Dackermann, U 2018, 'FRF Sensitivity-Based Damage Identification Using Linkage Modeling for Limited Sensor Arrays', International Journal of Structural Stability and Dynamics, vol. 18, no. 08, pp. 1840002-1840002.
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This paper presents a novel method to localize and quantify damage in a jack arch structure by introducing a linkage modeling technique to overcome issues caused by having limited sensors. The main strategy in the proposed Frequency Response Function (FRF)-based sensitivity model updating approach is to divide the specimen into partitions. The Young’s modulus of each partition is then updated to detect stiffness reduction caused by damage. System Equivalent Reduction Expansion Process (SEREP) is used to reduce the full finite element (FE) model to a linkage model. The number of measured degrees of freedom (DOFs) is then expanded to the linkage model using the mass and stiffness matrices of the linkage model for the synthesis of interpolated FRFs. The FRF sensitivities are then formulated using the linkage model along with the interpolated FRFs to iteratively calculate the values of the updating parameters until convergence is achieved. The methodology and theory behind this procedure are discussed and verified using a numerical and experimental study. The successful implementation of this method has the potential to detect the location and severity of damage where sensor placement is limited.
Nguyen, XC, Chang, SW, Nguyen, TL, Ngo, HH, Kumar, G, Banu, JR, Vu, MC, Le, HS & Nguyen, DD 2018, 'A hybrid constructed wetland for organic-material and nutrient removal from sewage: Process performance and multi-kinetic models', Journal of Environmental Management, vol. 222, pp. 378-384.
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© 2018 Elsevier Ltd A pilot-scale hybrid constructed wetland with vertical flow and horizontal flow in series was constructed and used to investigate organic material and nutrient removal rate constants for wastewater treatment and establish a practical predictive model for use. For this purpose, the performance of multiple parameters was statistically evaluated during the process and predictive models were suggested. The measurement of the kinetic rate constant was based on the use of the first-order derivation and Monod kinetic derivation (Monod) paired with a plug flow reactor (PFR) and a continuously stirred tank reactor (CSTR). Both the Lindeman, Merenda, and Gold (LMG) analysis and Bayesian model averaging (BMA) method were employed for identifying the relative importance of variables and their optimal multiple regression (MR). The results showed that the first-order–PFR (M2) model did not fit the data (P > 0.05, and R2 < 0.5), whereas the first-order–CSTR (M1) model for the chemical oxygen demand (CODCr) and Monod–CSTR (M3) model for the CODCr and ammonium nitrogen (NH4−N) showed a high correlation with the experimental data (R2 > 0.5). The pollutant removal rates in the case of M1 were 0.19 m/d (CODCr) and those for M3 were 25.2 g/m2∙d for CODCr and 2.63 g/m2∙d for NH4-N. By applying a multi-variable linear regression method, the optimal empirical models were established for predicting the final effluent concentration of five days' biochemical oxygen demand (BOD5) and NH4-N. In general, the hydraulic loading rate was considered an important variable having a high value of relative importance, which appeared in all the optimal predictive models.
Nimbalkar, S, Annapareddy, VSR & Pain, A 2018, 'A simplified approach to assess seismic stability of tailings dams', Journal of Rock Mechanics and Geotechnical Engineering, vol. 10, no. 6, pp. 1082-1090.
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© 2018 Institute of Rock and Soil Mechanics, Chinese Academy of Sciences In the zones of high seismic activity, tailings dam should be assessed for the stability against earthquake forces. In the present paper, a simplified method is proposed to compute the factor of safety of tailings dams. The strain-dependent dynamic properties are used to assess the stability of tailings dams under seismic conditions. The effect of foundation soil properties on the seismic stability of tailings dams is studied using the proposed method. For the given input parameters, the factor of safety for low-frequency input motions is nearly 26% lower than that for high-frequency input excitations. The impedance ratio and the depth of foundation have significant effect on the seismic factor of safety of tailings dams. The results from the proposed method are well compared with the existing pseudo-static method of analysis. Tailings dams are vulnerable to damage for low-frequency input motions.
Nimbalkar, S, Dash, SK & Indraratna, B 2018, 'Performance of ballasted track under impact loading and applications of recycled rubber inclusion', Geotechnical Engineering, vol. 49, no. 4, pp. 79-91.
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In this paper a review of the sources of impact loads and their effect on the performance of ballasted track is presented. The typical characteristics and implications of impact loading on track deterioration, particularly ballast degradation, are discussed. None of the procedures so far developed to design rail track incorporate the impact that dynamic loading has on the breakage of ballast and therefore it can be said to be incomplete. An intensive study on the impact of induced ballast breakage is needed in order to understand this phenomenon and then use the knowledge gained to further advance the design methodology. A stiff track structure can create severe dynamic loading under operating conditions which causes large scale component failure and increases maintenance requirements. Installing resilient mats such as rubber pads (ballast mat, soffit pad) in rail tracks can attenuate the dynamic force and improve overall performance. The efficacy of ballast mats to reduce structural noise and ground vibration has been studied extensively, but a few recent studies has reported how ballast mats and soffit pads reduce ballast degradation, thus obviating the necessity of a comprehensive study in this direction.
Niu, W, Guo, J, Lian, J, Ngo, HH, Li, H, Song, Y, Li, H & Yin, P 2018, 'Effect of fluctuating hydraulic retention time (HRT) on denitrification in the UASB reactors', Biochemical Engineering Journal, vol. 132, pp. 29-37.
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© 2017 Elsevier B.V. This study cultivated denitrifying granular sludge in three up-flow anaerobic sludge blanket (UASB) reactors using different fluctuation hydraulic retention time (HRT) strategies (reactor 1 (RC): constant HRT (C-HRT); reactor 2 (RDF): downward fluctuation HRT (DF-HRT); and reactor 3 (RUF): upward fluctuation HRT (UF-HRT)). The results verified that these fluctuation HRT strategies could enhance microbial diversity, while robust against fluctuations in nutrient load of the denitrifying granular sludge. Microbial aggregates appeared in RC, RUF and RDF on days 22, 12 and 7, respectively. The sludge in RUF and RDF achieved complete granulation on days 22 and 14, respectively. Compared to the results of RC and RUF, the acyl homoserine lactones (AHLs) concentration rapidly increased, and changed the components of extracellular polymeric substances (EPS) resulted in the rapid formation of denitrifying granular sludge in RDF. These results demonstrate that microbial community, AHLs, EPS, and the denitrifying sludge granulation process were associated with each other. Informed from quorum sensing system, a mechanism for the granulation of denitrifying sludge using the DF-HRT strategy was proposed. The DF-HRT strategy is an economical and fast method to cultivate denitrifying granular sludge. We hope that the results of our research would provide some theoretical support for wastewater producing unstable plants.
Norhasyima, RS & Mahlia, TMI 2018, 'Advances in CO₂ utilization technology: A patent landscape review', Journal of CO2 Utilization, vol. 26, pp. 323-335.
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© 2018 Elsevier Ltd. All rights reserved. There is rising concern on the increasing trend of global warming due to anthropogenic CO2 emission which steers progress of carbon capture and storage (CCS) projects worldwide. However, due to high cost and uncertainties in long term geological storage, there is a growing inclination to include utilization, which re-use the CO2, hence carbon capture utilization and storage (CCUS). Additionally, it is expected to generate income to offset the initial costs. This study methodically review patents on CO2 utilization technologies for CCUS application published between year 1980-2017. It was conducted using the Derwent Innovation patent database and more than 3000 number of patents was identified. The patents identified are in the field of enhanced oil recovery (EOR) and enhanced coal-bed methane (ECBM), chemical and fuel, mineral carbonation, biological algae cultivation and enhanced geothermal system (EGS). Over 60% of these patents were published since the last 10 years, and a sharp increase in patents were seen in the last 5 years (∼38%). The top major patent types are patents granted in the United States (US), China (CN) and Canada (CA) which makes of 3/5 of the overall patent type found. Recent patents published include enhancements to the state-of-the-art technologies and hybrid concepts such as in photo-bioreactor in algae cultivation, chemical reaction and EGS. From this study, it was found that further research for the best CO2 utilization method which fulfil the need of an economic, safe, non-location dependent and environmentally friendly whilst efficiently mitigate the worldwide global warming issue is much needed.
Noushini, A & Castel, A 2018, 'Performance-based criteria to assess the suitability of geopolymer concrete in marine environments using modified ASTM C1202 and ASTM C1556 methods', Materials and Structures, vol. 51, no. 6.
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© 2018, RILEM. In marine or coastal zones, the most harmful exposure for reinforced concrete structures to chloride ions. The ASTM C1556 chloride diffusion test (or its European equivalent NT BUILD 443) has been widely used as the most reliable testing method to assess the performance of concrete against chloride penetration. However, this test is time demanding and labour intensive. As a result, accelerated test ASTM C1202 (RCPT) is often preferred, providing fast and acceptable assessment of chloride penetrability of Ordinary Portland Cement Concrete. This study aimed to investigate the suitability of RCPT to assess the performance of Geopolymer Concrete (GPC) in chloride environment. The correlation between several GPC properties [i.e. compressive strength, volume of permeable voids (VPV) and sorptivity] and the chloride diffusion coefficient are examined. Results indicate that the compressive strength, the VPV and the sorptivity coefficient are not suitable indicators of the GPC performance. The ASTM C1202 standard RCPT failed to measure the charges passed through most of the GPCs tested. A modified version of RCPT using 10 V (as opposed to 60 V specified by standard ASTM C1202) is proposed in this paper, allowing to successfully measure the charges passed through all GPC samples using a wide range of binders. A good correlation was observed between modified ASTM C1202 and Standard ASTM C1556 test results. Performance-based recommendations are proposed in this paper. Both experimental results from this study and appropriate reference concretes from the literature were used to calibrate the modified ASTM C1202 and ASTM C1556 performance-based requirements for GPCs.
Noushini, A, Hastings, M, Castel, A & Aslani, F 2018, 'Mechanical and flexural performance of synthetic fibre reinforced geopolymer concrete', Construction and Building Materials, vol. 186, pp. 454-475.
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© 2018 A comprehensive experimental program was undertaken to analyse the structural and material characteristics of synthetic fibre reinforced geopolymer concrete. This study focused on the effect of monofilament and fibrillated polypropylene fibres and monofilament structural polyolefin fibres on mechanical and flexural performance of fly ash based geopolymer concrete. Five types of synthetic fibres at a 0.5% volume fraction were added to geopolymer concretes. The specimens’ compressive strength, indirect tensile strength, modulus of elasticity, modulus of rupture, flexural toughness and fracture energy were determined. Where possible, comparative analyses where conducted to assess the performance of fibre reinforced geopolymer concrete against conventional Portland cement based systems. The flexural toughness parameters were obtained using procedure laid down in ASTM C1018, JCI-SF4 and ASTM C1609. The results indicated that the macro polyolefin fibres exhibited the largest fracture energy which is likely due to high mechanical bonding and low fibre aspect ratio. Relationships are established to predict the compressive and tensile strengths, modulus of elasticity, compressive stress–strain curve and relation between the deflection and CMOD of synthetic fibre reinforced geopolymer concrete.
Nur, T, Loganathan, P, Ahmed, MB, Johir, M, Kandasamy, J & Vigneswaran, S 2018, 'Struvite production using membrane-bioreactor wastewater effluent and seawater', Desalination, vol. 444, pp. 1-5.
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© 2018 Elsevier B.V. Wastewater phosphorus (P) released into natural water bodies such as lakes and rivers, can cause water pollution as a result of eutrophication. If this P is effectively removed from wastewaters and economically recovered for use as fertilisers, not only can the water pollution be controlled, but also reduce the anticipated global shortage of P. This scarcity will result from the natural phosphate rock reserve being exhausted. Three experiments were conducted using membrane-bioreactor effluent (MBR, 35 mg PO 4 /L) and reverse osmosis concentrate (ROC, 10 mg PO 4 /L) waters to supply phosphate, and sea water (1530 mg Mg/L) to supply Mg for the production of struvite. The phosphate in the MBR and ROC was concentrated approximately 15 times by adsorption onto an ion exchange resin column followed by desorption. Struvite was precipitated by mixing the desorbed solution with seawater and NH 4 Cl. The chemical composition and mineral structure of the precipitates agreed with those of the reference struvite. When Ca in seawater (300 mg Ca/L) was removed before mixing the water with MBR or ROC, the purity of the struvite improved.
Nur, T, Loganathan, P, Johir, MAH, Kandasamy, J & Vigneswaran, S 2018, 'Removing rubidium using potassium cobalt hexacyanoferrate in the membrane adsorption hybrid system', Separation and Purification Technology, vol. 191, pp. 286-294.
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© 2017 Elsevier B.V. Highly-priced rubidium (Rb) can be effectively extracted from seawater using potassium cobalt hexacyanoferrate (KCoFC) and ammonium molybdophosphate (AMP) adsorbents in the membrane adsorption hybrid system (MAHS). KCoFC (<0.075 mm), KCoFC (0.075–0.15 mm), and AMP (<0.075 mm) had Langmuir adsorption capacities of 145, 113, and 77 mg/g at pH 6.5–7.5, respectively. When KCoFC (<0.075 mm) at a dose of 0.2 g/L was initially added to 4 L of a solution containing 5 mg Rb/L in the MAHS and 25% of the initial dose was repeatedly added every hour, the amount of Rb removed remained steady at 90–96% for the experiment's 26 h duration. The removal of Rb by AMP under similar conditions was 80–82%. The cumulative Rb removed by KCoFC (<0.075 mm) in MAHS was only 33% reduced in the presence of high concentrations of other cations in synthetic seawater compared to that in solution containing only Rb. Approximately 30% of the adsorbed Rb was desorbed using 1 M KCl. When the desorbed solution was passed through a column containing resorcinol formaldehyde (RF), 35% of the Rb in the desorbed solution was adsorbed on RF. Furthermore 50% of the Rb adsorbed on RF was recovered by 1 M HCl leaching of the column. This sequence of concentration and separation of Rb in the presence of other cations in synthetic seawater is an efficient method for recovering pure Rb from real seawater and seawater reverse osmosis brine.
Nuruzzaman, M, Liu, Y, Rahman, MM, Naidu, R, Dharmarajan, R, Shon, HK & Woo, YC 2018, 'Core–Shell Interface-Oriented Synthesis of Bowl-Structured Hollow Silica Nanospheres Using Self-Assembled ABC Triblock Copolymeric Micelles', Langmuir, vol. 34, no. 45, pp. 13584-13596.
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© 2018 American Chemical Society. Hollow porous silica nanospheres (HSNs) are emerging classes of cutting-edge nanostructured materials. They have elicited much interest as carriers of active molecule delivery due to their amorphous chemical structure, nontoxic nature, and biocompatibility. Structural development with hierarchical morphology is mostly required to obtain the desired performance. In this context, large through-holes or pore openings on shells are desired so that the postsynthesis loading of active-molecule onto HSNs via a simple immersion method can be facilitated. This study reports the synthesis of HSNs with large through-holes or pore openings on shells, which are subsequently termed bowl-structured hollow porous silica nanospheres (BHSNs). The synthesis of BHSNs was mediated by the core-shell interfaces of the core-shell corona-structured micelles obtained from a commercially available ABC triblock copolymer (polystyrene-b-poly(2-vinylpyridine)-b-poly(ethylene oxide) (PS-P2VP-PEO)). In this synthesis process, polymer@SiO2 composite structure was formed because of the deposition of silica (SiO2) on the micelles' core. The P2VP block played a significant role in the hydrolysis and condensation of the silica precursor, i.e., tetraethylorthosilicate (TEOS) and then maintaining the shell's growth. The PS core of the micelles built the void spaces. Transmission electron microscopy (TEM) images revealed a spherical hollow structure with an average particle size of 41.87 ± 3.28 nm. The average diameter of void spaces was 21.71 ± 1.22 nm, and the shell thickness was 10.17 ± 1.68 nm. According to the TEM image analysis, the average large pore was determined to be 15.95 nm. Scanning electron microscopy (SEM) images further confirmed the presence of large single pores or openings in shells. These were formed as a result of the accumulated ethanol on the PS core acting to prevent the growth of silica.
Oweis, IS 2018, 'Discussion of “Modeling the Stone Column Behavior in Soft Ground with Special Emphasis on Lateral Deformation” by Sudip Basack, Buddhima Indraratna, Cholachat Rujikiatkamjorn, and Firman Siahaan', Journal of Geotechnical and Geoenvironmental Engineering, vol. 144, no. 5, pp. 07018007-07018007.
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Pace, B, Munroe, P, Marjo, CE, Thomas, P, Gong, B, Shepherd, J, Buss, W & Joseph, S 2018, 'The mechanisms and consequences of inorganic reactions during the production of ferrous sulphate enriched bamboo biochars', Journal of Analytical and Applied Pyrolysis, vol. 131, pp. 101-112.
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Pain, A, Ramakrishna Annapareddy, VS & Nimbalkar, S 2018, 'Seismic Active Thrust on Rigid Retaining Wall Using Strain Dependent Dynamic Properties', International Journal of Geomechanics, vol. 18, no. 12, pp. 06018034-06018034.
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Pang, YL, Tee, SF, Lim, S, Abdullah, AZ, Ong, HC, Wu, C-H, Chong, WC, Mohammadu, AW & Mahmoudi, E 2018, 'Enhancement of photocatalytic degradation of organic dyes using ZnO decorated on reduced graphene oxide (rGO)', DESALINATION AND WATER TREATMENT, vol. 108, pp. 311-321.
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Park, MJ, Gonzales, RR, Abdel-Wahab, A, Phuntsho, S & Shon, HK 2018, 'Hydrophilic polyvinyl alcohol coating on hydrophobic electrospun nanofiber membrane for high performance thin film composite forward osmosis membrane', Desalination, vol. 426, pp. 50-59.
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© 2017 Elsevier B.V. In this study, the hydrophilic property of polyvinyl alcohol (PVA) was utilized to improve the hydrophilicity and mechanical strength of electrospun polyvinylidene fluoride (PVDF)-supported thin film composite (TFC) forward osmosis (FO) membranes. The PVDF nanofiber support was modified with PVA via dip coating and acid-catalyzed crosslinking with glutaraldehyde prior to formation of polyamide active layer on the support via interfacial polymerization. The influence of PVA modification on the morphology and physical properties of PVDF support was evaluated through several characterization techniques while the flux performance was assessed using lab-scale FO membrane unit. The fabricated PVA-modified TFC FO membranes exhibited high hydrophilicity, porosity, and mechanical strength. FO performance tests reveal excellent flux performance (34.2 LMH using 1 M NaCl and DI water as draw and feed solution, respectively) and low structural parameters (154 μm) of the PVA-modified TFC FO membrane. Dip coating of the nanofiber support in PVA is therefore a simple and effective method for the improvement of PVDF support hydrophilicity to fabricate high performance TFC FO membranes.
Pathak, N, Fortunato, L, Li, S, Chekli, L, Phuntsho, S, Ghaffour, N, Leiknes, T & Shon, HK 2018, 'Evaluating the effect of different draw solutes in a baffled osmotic membrane bioreactor-microfiltration using optical coherence tomography with real wastewater', Bioresource Technology, vol. 263, pp. 306-316.
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© 2018 Elsevier Ltd This study investigated the performance of an integrated osmotic and microfiltration membrane bioreactor for real sewage employing baffles in the reactor. To study the biofouling development on forward osmosis membranes optical coherence tomography (OCT) technique was employed. On-line monitoring of biofilm growth on a flat sheet cellulose triacetate forward osmosis (CTA-FO) membrane was conducted for 21 days. Further, the process performance was evaluated in terms of water flux, organic and nutrient removal, microbial activity in terms of soluble microbial products (SMP) and extracellular polymeric substance (EPS), and floc size. The measured biofouling layer thickness was in the order sodium chloride (NaCl) > ammonium sulfate (SOA) > potassium dihydrogen phosphate (KH2PO4). Very high organic removal (96.9 ± 0.8%) and reasonably good nutrient removal efficiency (85.2 ± 1.6% TN) was achieved. The sludge characteristics and biofouling layer thickness suggest that less EPS and higher floc size were the governing factors for less fouling.
Pathak, N, Li, S, Kim, Y, Chekli, L, Phuntsho, S, Jang, A, Ghaffour, N, Leiknes, T & Shon, HK 2018, 'Assessing the removal of organic micropollutants by a novel baffled osmotic membrane bioreactor-microfiltration hybrid system', Bioresource Technology, vol. 262, pp. 98-106.
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© 2018 Elsevier Ltd A novel approach was employed to study removal of organic micropollutants (OMPs) in a baffled osmotic membrane bioreactor-microfiltration (OMBR-MF) hybrid system under oxicanoxic conditions. The performance of OMBR-MF system was examined employing three different draw solutes (DS), and three model OMPs. The highest forward osmosis (FO) membrane rejection was attained with atenolol (100%) due to its higher molar mass and positive charge. With inorganic DS caffeine (94–100%) revealed highest removal followed by atenolol (89–96%) and atrazine (16–40%) respectively. All three OMPs exhibited higher removal with organic DS as compared to inorganic DS. Significant anoxic removal was observed for atrazine under very different redox conditions with extended anoxic cycle time. This can be linked with possible development of different microbial consortia responsible for diverse enzymes secretion. Overall, the OMBR-MF process showed effective removal of total organic carbon (98%) and nutrients (phosphate 97% and total nitrogen 85%), respectively.
Peng, L, Dai, X, Liu, Y, Sun, J, Song, S & Ni, B-J 2018, 'Model-based assessment of estrogen removal by nitrifying activated sludge', Chemosphere, vol. 197, pp. 430-437.
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© 2018 Elsevier Ltd Complete removal of estrogens such as estrone (E1), estradiol (E2), estriol (E3) and ethinylestradiol (EE2) in wastewater treatment is essential since their release and accumulation in natural water bodies are giving rise to environment and health issues. To improve our understanding towards the estrogen bioremediation process, a mathematical model was proposed for describing estrogen removal by nitrifying activated sludge. Four pathways were involved in the developed model: i) biosorption by activated sludge flocs; ii) cometabolic biodegradation linked to ammonia oxidizing bacteria (AOB) growth; iii) non-growth biodegradation by AOB; and iv) biodegradation by heterotrophic bacteria (HB). The degradation kinetics was implemented into activated sludge model (ASM) framework with consideration of interactions between substrate update and microorganism growth as well as endogenous respiration. The model was calibrated and validated by fitting model predictions against two sets of batch experimental data under different conditions. The model could satisfactorily capture all the dynamics of nitrogen, organic matters (COD), and estrogens. Modeling results suggest that for E1, E2 and EE2, AOB-linked biodegradation is dominant over biodegradation by HB at all investigated COD dosing levels. However, for E3, the increase of COD dosage triggers a shift of dominant pathway from AOB biodegradation to HB biodegradation. Adsorption becomes the main contributor to estrogen removal at high biomass concentrations.
Peng, L, Dai, X, Liu, Y, Wei, W, Sun, J, Xie, G-J, Wang, D, Song, S & Ni, B-J 2018, 'Kinetic assessment of simultaneous removal of arsenite, chlorate and nitrate under autotrophic and mixotrophic conditions', Science of The Total Environment, vol. 628-629, pp. 85-93.
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© 2018 In this work, a kinetic model was proposed to evaluate the simultaneous removal of arsenite (As (III)), chlorate (ClO3−) and nitrate (NO3−) in a granule-based mixotrophic As (III) oxidizing bioreactor for the first time. The autotrophic kinetics related to growth-linked As (III) oxidation and ClO3− reduction by As (III) oxidizing bacteria (AsOB) were calibrated and validated based on experimental data from batch test and long-term reactor operation under autotrophic conditions. The heterotrophic kinetics related to non-growth linked As (III) oxidation and ClO3− reduction by heterotrophic bacteria (HB) were evaluated based on the batch experimental data under heterotrophic conditions. The existing kinetics related to As (III) oxidation with NO3− as the electron acceptor together with heterotrophic denitrification were incorporated into the model framework to assess the bioreactor performance in treatment of the three co-occurring contaminants. The results revealed that under autotrophic conditions As (III) was completely oxidized by AsOB (over 99%), while ClO3− and NO3− were poorly removed. Under mixotrophic conditions, the simultaneous removal of the three contaminants was achieved with As (III) oxidized mostly by AsOB and ClO3− and NO3− removed mostly by HB. Both hydraulic retention time (HRT) and influent organic matter (COD) concentration significantly affected the removal efficiency. Above 90% of As (III), ClO3− and NO3− were removed in the mixotrophic bioreactor under optimal operational conditions of HRT and influent COD.
Peng, L, Ngo, HH, Guo, WS, Liu, Y, Wang, D, Song, S, Wei, W, Nghiem, LD & Ni, BJ 2018, 'A novel mechanistic model for nitrogen removal in algal-bacterial photo sequencing batch reactors', Bioresource Technology, vol. 267, pp. 502-509.
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© 2018 Elsevier Ltd A comprehensive mathematical model was constructed to evaluate the complex substrate and microbial interaction in algal-bacterial photo sequencing batch reactors (PSBR). The kinetics of metabolite, growth and endogenous respiration of ammonia oxidizing bacteria, nitrite oxidizing bacteria and heterotrophic bacteria were coupled to those of microalgae and then embedded into widely-used activated sludge model series. The impact of light intensity was considered for microalgae growth, while the effect of inorganic carbon was considered for each microorganism. The integrated model framework was assessed using experimental data from algal-bacterial consortia performing sidestream nitritation/denitritation. The validity of the model was further evaluated based on dataset from PSBR performing mainstream nitrification. The developed model could satisfactorily capture the dynamics of microbial populations and substrates under different operational conditions (i.e. feeding, carbon dosing and illuminating mode, light intensity, influent ammonium concentration), which might serve as a powerful tool for optimizing the novel algal-bacterial nitrogen removal processes.
Phan, HV, Wickham, R, Xie, S, McDonald, JA, Khan, SJ, Ngo, HH, Guo, W & Nghiem, LD 2018, 'The fate of trace organic contaminants during anaerobic digestion of primary sludge: A pilot scale study', Bioresource Technology, vol. 256, pp. 384-390.
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© 2018 A pilot-scale study was conducted to investigate the fate of trace organic contaminants (TrOCs) during anaerobic digestion of primary sludge. Of the 44 TrOCs monitored, 24 were detected in all primary sludge samples. Phase distribution of TrOCs was correlated well with their hydrophobicity (>67% mass in the solid phase when LogD > 1.5). The pilot-scale anaerobic digester achieved a steady performance with a specific methane yield of 0.39–0.92 L/gVSremoved and methane composition of 63–65% despite considerable variation in the primary sludge. The fate of TrOCs in the aqueous and solid phases was governed by their physicochemical properties. Biotransformation was significant (>83%) for five TrOCs with logD < 1.5 and electron donating functional groups in molecular structure. The remaining TrOCs with logD < 1.5 were persistent and thus accumulated in the aqueous phase. Most TrOCs with logD > 1.5 were poorly removed under anaerobic conditions. Sorption onto the solid phase appears to impede the biodegradation of these TrOCs.
Phwan, CK, Ong, HC, Chen, W-H, Ling, TC, Ng, EP & Show, PL 2018, 'Overview: Comparison of pretreatment technologies and fermentation processes of bioethanol from microalgae', Energy Conversion and Management, vol. 173, pp. 81-94.
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Plattner, J, Kazner, C, Naidu, G, Wintgens, T & Vigneswaran, S 2018, 'Removal of selected pesticides from groundwater by membrane distillation', Environmental Science and Pollution Research, vol. 25, no. 21, pp. 20336-20347.
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© 2017, Springer-Verlag Berlin Heidelberg. The removal of five selected pesticide compounds in a brackish model groundwater solution was examined using a bench scale direct contact membrane distillation (DCMD) system. It was found that the rejection rate of the pesticides in DCMD is mainly influenced by its properties. Compounds with low hydrophobic characteristics and low vapour pressure showed a high rejection rate (70–99%), whereas compounds with a high vapour pressure or high hydrophobicity (LogD) showed a reduced rejection (30–50%) at a water recovery of 75%. The influence of groundwater feed solution contents such as the presence of organics (humic acid) and inorganic ions (Na+, Ca2+, Mg2+, Cl− and SO42−) as well as feed temperature (40, 55 and 70 °C) on the rejection of the pesticides in DCMD operation was also evaluated. The results showed that the presence of inorganic ions and organics in the feed solution influences the pesticides rejection in DCMD operation to a minor degree. In contrast, reduced rejection of pesticides with high vapour pressure was observed. A rapid small-scale column test (RSSCT) was carried out to study the removal of any remaining substances in the permeate by adsorption onto granular activated carbon (GAC). RSSCT showed promising performance of GAC as a post-treatment option.
Pradhan, B, Moneir, AAA & Jena, R 2018, 'Sand dune risk assessment in Sabha region, Libya using Landsat 8, MODIS, and Google Earth Engine images', Geomatics, Natural Hazards and Risk, vol. 9, no. 1, pp. 1280-1305.
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Globally, sand dunes are a major environmental problem that causes damage to urban areas, transportation, and population. The current study proposes a comprehensive investigation on sand dune risk modeling in Sabha located in the southwestern part of Libya. Data from various sources were collected and prepared in a GIS database. Data from 2016 were used to derive several controlling factors, such as altitude, rainfall, soil texture, wind direction and speed, land cover, and population density. Next, sand dune susceptibility, hazard and vulnerability assessments were performed. Finally, a risk map was produced. Results indicate that land use and soil are the most influential factors affecting the sand dunes in the study area, whereas rainfall is the least significant factor. Results indicate that, southern part has a higher chance of sand dune occurrence than the northern part, whereas the highest risk zone is located in the middle part, where the urban and agricultural lands are present. More than 200 km2 of the study area are under high and very high risk zones. Overall, this study provides an effective tool for assessing sand dune risk in Sabha, which can be useful for land management.
Qi, Y, Indraratna, B & Vinod, JS 2018, 'Behavior of Steel Furnace Slag, Coal Wash, and Rubber Crumb Mixtures with Special Relevance to Stress–Dilatancy Relation', Journal of Materials in Civil Engineering, vol. 30, no. 11, pp. 04018276-04018276.
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Qi, Y, Indraratna, B, Heitor, A & Vinod, J 2018, 'Effect of Rubber Crumbs on the Cyclic Behaviour of Steel Furnace Slag and Coal Wash Mixtures', Journal of Geotechnical and Geoenvironmental Engineering, vol. 144, no. 2.
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Qi, Y, Indraratna, B, Heitor, A & Vinod, JS 2018, 'Effect of Rubber Crumbs on the Cyclic Behavior of Steel Furnace Slag and Coal Wash Mixtures', Journal of Geotechnical and Geoenvironmental Engineering, vol. 144, no. 2, pp. 04017107-04017107.
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The practical application of waste materials such as steel furnace slag (SFS) and coal wash (CW) is becoming more prevalent in many geotechnical projects. While adding rubber crumbs (RCs) from recycled tires into mixtures of SFS and CW not only solves the problem of large stockpiles of waste tires, it also can provide an energy-absorbing medium that will reduce vibration and prevent track degradation. Thus, the engineering insight into the effect that rubber crumbs have on the dynamic behavior of SFS + CW + RC mixtures is in urgent demand. In this study the influence that RC contents and confining pressures have on the deformation, resilient modulus, damping ratio, and shear modulus was investigated by cyclic triaxial tests. Test results reveal that with the inclusion of RC, the axial strain, volumetric strain, damping ratio, and energy-absorbing capacity of the SFS + CW + RC mixture increase, while its resilient modulus and shear modulus decrease. Based on these properties, an amount of 10% RC is recommended as an optimal blended mix to be used as railway subballast. A three-dimensional (3D) empirical model of the relationship between the maximum axial strain, volumetric strain, and resilient modulus with RC contents and the effective confining pressure was developed, and the energy-absorbing capacity of these waste mixtures has also been analyzed for practical purposes based on their comprehensive parameters.
Qin, L, Gao, X, Li, W & Ye, H 2018, 'Modification of Magnesium Oxysulfate Cement by Incorporating Weak Acids', Journal of Materials in Civil Engineering, vol. 30, no. 9, pp. 04018209-04018209.
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© 2018 American Society of Civil Engineers. This paper investigates the effects of weak acids (citric acid, boric acid, and trisodium citrate) with dosages of 0.5, 1.5, and 2.5% of MgO weight on compressive strength, water resistance, and drying shrinkage of magnesium oxysulfate (MOS) cement. Hydration products and microstructure of typical samples are studied by using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), differential thermal analysis-thermogravimetry (DTA-TG), and scanning electron microscope (SEM) facilities. The results show that compressive strength of MOS cement increases with an increasing MgO/MgSO4 molar ratio and decreasing H2O/MgSO4 molar ratio. The addition of citric acid, boric acid, or trisodium citrate significantly enhances compressive strength and water resistance and alleviates drying shrinkage of MOS cement paste. With the incorporation of weak acid, 5 · 1 · 7 [5Mg(OH)2 · MgSO4 · 7H2O] phase, which is a new magnesium subsulfate crystalline product with a needlelike crystal whisker shape, forms in cement paste. This substance behaves in a criss-crossing manner and fills in pores and microcracks, inducing the improved performance of MOS cement paste. With optimum dosages of 0.5, 2.5, and 0.5%, respectively, citric acid, trisodium citrate, and boric acid exhibit decreasing improvement effect.
Qiu, N, Gao, Y, Fang, J, Sun, G & Kim, NH 2018, 'Topological design of multi-cell hexagonal tubes under axial and lateral loading cases using a modified particle swarm algorithm', Applied Mathematical Modelling, vol. 53, pp. 567-583.
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© 2017 Elsevier Inc. Multi-cell structures have widely been studied due to their excellent energy absorption ability. However, few systematic studies have been conducted on the topological design of cross-sectional configurations of thin-walled tubes. To make full use of the material, topology optimization of multi-cell hexagonal tubes was conducted under both axial compression and lateral bending loadings. A binary particle swarm optimization (PSO) was enhanced by introducing the mass constraint factor to guide the movement of particles, which could improve the success rate of obtaining the global optimum. It was found that the optimum designs under the axial load placed the material outward to strengthen the interaction between the outer and inner walls and created more partitions between the inside rib walls. While under the lateral load, all the optimum designs have diagonally-connected elements to resist local deformation, and the material was also placed outward to increase the moment of inertia and thus to resist the global deformation. For the multiple loading cases, the final optimal designs are similar to the compression designs or combined designs from the two loading cases.
Qiu, N, Gao, Y, Fang, J, Sun, G, Li, Q & Kim, NH 2018, 'Crashworthiness optimization with uncertainty from surrogate model and numerical error', Thin-Walled Structures, vol. 129, pp. 457-472.
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© 2018 Elsevier Ltd Due to the expensive cost of full-scale tests, more and more designs rely on simulation. For highly nonlinear crash simulation, numerical uncertainty is an inherent by-product, which refers to the oscillation of results when the simulation is repeated at the same design or the design variables are slightly changed. This oscillation directly influences the quality and reliability of the optimal design. This paper shows how these issues can be addressed by proposing a simple uncertainty quantification method for numerical uncertainty (noise) and surrogate model uncertainty (error) in the optimization process. Three engineering problems, a tube crush example, an automotive front-rail crush example and a multi-cell structure crush example, are used to illustrate this method. Firstly, the level of numerical uncertainty is quantified in terms of noise frequency and amplitude, and the convergence study of these two criteria is employed to determine an appropriate data size to describe numerical noise. Secondly, an estimation method considering both numerical noise and surrogate model error is proposed based on the prediction variance of the polynomial response surface. Finally, the tube and front rail structures are optimized according to the proposed uncertainty quantification method. It was found that by considering the two sources of uncertainty, the optimal designs are more reliable than the deterministic solutions.
Qiu, N, Park, C, Gao, Y, Fang, J, Sun, G & Kim, NH 2018, 'Sensitivity-Based Parameter Calibration and Model Validation Under Model Error', Journal of Mechanical Design, vol. 140, no. 1, pp. 1-9.
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In calibrating model parameters, it is important to include the model discrepancy term in order to capture missing physics in simulation, which can result from numerical, measurement, and modeling errors. Ignoring the discrepancy may lead to biased calibration parameters and predictions, even with an increasing number of observations. In this paper, a simple yet efficient calibration method is proposed based on sensitivity information when the simulation model has a model error and/or numerical error but only a small number of observations are available. The sensitivity-based calibration method captures the trend of observation data by matching the slope of simulation predictions and observations at different designs and then utilizing a constant value to compensate for the model discrepancy. The sensitivity-based calibration is compared with the conventional least squares calibration method and Bayesian calibration method in terms of parameter estimation and model prediction accuracies. A cantilever beam example, as well as a honeycomb tube crush example, is used to illustrate the calibration process of these three methods. It turned out that the sensitivity-based method has a similar performance with the Bayesian calibration method and performs much better than the conventional method in parameter estimation and prediction accuracy.
Rahnema, H, Hashemi Jokar, M & Khabbaz, H 2018, 'Predicting the Effective Stress Parameter of Unsaturated Soils Using Adaptive Neuro-Fuzzy Inference System', Scientia Iranica, vol. 0, no. 0, pp. 0-0.
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Rajput, A, Iqbal, MA & Wu, C 2018, 'Prestressed concrete targets under high rate of loading', International Journal of Protective Structures, vol. 9, no. 3, pp. 362-376.
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Prestressed concrete is highly being preferred as material for construction in the case of strategic and relevant structures such as, for instance, nuclear containments, armor deposits, shelters, bridges, and military bunkers. It is highly durable, fire and corrosion resistant, and non-porous. In order to study the influence of prestressing on the mechanics of deformation, energy absorption capacity, and failure modes of concrete targets, finite element simulations have been carried out using hard steel bullets and compared with the experiments carried out by the authors earlier. Prestressed concrete targets of plan size 450 mm × 450 mm and thickness of 80 mm were impacted by 0.5-kg hard steel projectiles. The concrete was designed to obtain an unconfined compressive strength of 48 MPa. An initial stress of 10% magnitude of compressive strength was induced by 4-mm-diameter high-tensile-strength (1700 MPa) steel wires in prestressed concrete targets. A grid of 8-mm-diameter steel bars was inserted in the reinforced and prestressed concrete targets to enable the straight comparison between these concretes. The prestressing in concrete has been found to be effective in reducing the volume of scabbed material as well as the ballistic resistance of prestressed concrete targets. The ballistic limit of prestressed concrete with 10% induced stress was found to be, respectively, 14% higher than that of the plain concrete target and 10.2% higher than the reinforced concrete. Failure modes predicted through finite element simulations were found in agreement with that of the actual results.
Ranjbar-Zahedani, M, Keshavarzi, A, Khabbaz, H & Ball, J 2018, 'Protecting bridge piers against local scour using a flow-diversion structure', Proceedings of the Institution of Civil Engineers - Water Management, vol. 171, no. 5, pp. 271-280.
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Previous studies indicate that local scour is a leading cause of most waterway bridge failures during flood events. Using armouring countermeasures such as riprap and gabions is a conventional way of reducing scour around bridge piers, but is very costly and time consuming. As an alternative, a flow-diversion structure is proposed that has a triangular prismatic shape with dimensions much smaller than the actual pier and should be installed upstream of the pier. To assess its performance, experiments were conducted under clear-water scour conditions. After achieving equilibrium bed conditions, the bed profile was measured and the maximum scour depth and volume of the scour hole were determined for each experimental test. The results indicated that the clear distance between the pier and the countermeasure to achieve the maximum reduction in local scour was 1·5 times the pier diameter. For this condition, the proposed countermeasure reduced the maximum scour depth by 38% and the volume of the scour hole was decreased by around 61%. To determine the influence of the countermeasure on flow field around the pier, three-dimensional velocity components were measured at grid points using a micro-acoustic Doppler velocity meter. Analysis of the results indicated that the proposed structure could change both the magnitude and direction of the velocity components upstream of the pier and consequently induce a significant reduction in local scour depth and volume around the pier.
Ranji-Burachaloo, H, Fu, Q, Gurr, PA, Dunstan, DE & Qiao, GG 2018, 'Improved Fenton Therapy Using Cancer Cell Hydrogen Peroxide', Australian Journal of Chemistry, vol. 71, no. 10, pp. 826-826.
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Fenton cancer therapy as a new methodology for the treatment of tumour cells is largely restricted owing to the low stability, high aggregation, and poor selectivity of reported nanoparticles. In this study, an improved approach for the selective destruction of cancer cells is reported. Metal–organic framework (MOF) nanoparticles were synthesized and reduced via a hydrothermal method, and then PEGylated through the surface-initiated atom transfer radical polymerization (SI-ATRP) reaction to produce a PEGylated reduced MOF (P@rMOF). The ratio of PEG to nanoparticles was used to optimize the size and aggregation of the nanoparticles, with 2P@rMOF (2 : 1 mass ratio) having the smallest hydrodynamic diameter. The nanoparticles were further conjugated with folic acid for cell targeting. In vitro cell uptake experiments demonstrated that the internalization of 2P@rMOF-FA nanoparticles into cancer cells (HeLa) was almost 3-fold that of normal cells (NIH-3T3). In the presence of 2P@rMOF-FA, the HeLa cell viability decreased dramatically to 22 %, whereas the NIH-3T3 cell viability remained higher than 80 % after 24 h incubation. The selectivity index for 2P@rMOF-FA is 4.48, which is significantly higher than those reported in the literature for similar strategies. This work thus demonstrates the most stable and selective nanoparticle system for the treatment of cancer cells using the cell’s own H2O2.
Rao, P, Chen, Q, Nimbalkar, S & Liu, Y 2018, 'Effect of water and salinity on soil behaviour under lightning', Environmental Geotechnics, vol. 5, no. 1, pp. 56-62.
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The east coast of China, in particular Shanghai, is frequently exposed to lightning, and the resulting annual loss approaches US$30 million. All kinds of protection devices transfer the lightning current and the energy into the ground. In this study, the characteristics of the typical soft soil in Shanghai with different values of water content and salinity under the action of lightning shock have been analysed by an impulse current generator and a self-designed test equipment. The test results show that the current waveform from the impact of lightning in soils has a steep rise and a slow fall. At the same lightning intensity, higher water content or salinity leads to (a) shorter peak time, (b) larger peak current waveform, (c) quicker release speed and (d) larger lightning impulse response. The test results are valuable in guiding the design and the reformation of lightning protection and grounding systems.
Ratiko, R, Samudera, SA, Hindami, R, Siahaan, AT, Naldi, L, Safitri, DH, Mahlia, DTMI & Nasruddin, IN 2018, 'Optimization of Dry Storage for Spent Fuel from G.A. Siwabessy Nuclear Research Reactor', International Journal of Technology, vol. 9, no. 1, pp. 55-55.
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© IJTech 2018. This study proposes a method of optimizing the dry storage design for nuclear-spent fuel from the G.A. Siwabessy research reactor at National Nuclear Energy Agency of Indonesia (BATAN). After several years in a spent fuel pool storage (wet storage), nuclear spent fuel is often moved to dry storage. Some advantages of dry storage compared with wet storage are that there is no generation of liquid waste, no need for a complex and expensive purification system, less corrosion concerns and that dry storage is easier to transport if in the future the storage needs to be sent to the another repository or to the final disposal. In both wet and dry storage, the decay heat of spent fuel must be cooled to a safe temperature to prevent cracking of the spent fuel cladding from where hazardous radioactive nuclides could be released and harm humans and the environment. Three optimization scenarios including the thermal safety single-objective, the economic single-objective and the multi-objective optimizations are obtained. The optimum values of temperature and cost for three optimization scenarios are 317.8K (44.7°C) and 11638.1 US$ for the optimized single-objective thermal safety method, 337.1K (64.0°C) and 6345.2 US$ for the optimized single-objective cost method and 325.1K (52.0°C) and 8037.4 US$ for the optimized multi-objective method, respectively.
Reyhani, A, Nothling, MD, Ranji‐Burachaloo, H, McKenzie, TG, Fu, Q, Tan, S, Bryant, G & Qiao, GG 2018, 'Blood‐Catalyzed RAFT Polymerization', Angewandte Chemie International Edition, vol. 57, no. 32, pp. 10288-10292.
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AbstractThe use of hemoglobin (Hb) contained within red blood cells to drive a controlled radical polymerization via a reversible addition‐fragmentation chain transfer (RAFT) process is reported for the first time. No pre‐treatment of the Hb or cells was required prior to their use as polymerization catalysts, indicating the potential for synthetic engineering in complex biological microenvironments without the need for ex vivo techniques. Owing to the naturally occurring prevalence of the reagents employed in the catalytic system (Hb and hydrogen peroxide), this approach may facilitate the development of new strategies for in vivo cell engineering with synthetic macromolecules.
Robson, EN, Wijayaratna, KP & Dixit, VV 2018, 'A review of computable general equilibrium models for transport and their applications in appraisal', Transportation Research Part A: Policy and Practice, vol. 116, pp. 31-53.
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© 2018 Elsevier Ltd In the transport planning process, decision makers require reliable and informative appraisals to facilitate comparisons and determine if a proposal is worthwhile to society. The cost–benefit analysis is the most common form of appraisal, where benefits are primarily measured from the change in consumer surplus in the transport market. However, these benefits will only reflect maximum social welfare if markets operate perfectly competitively and without any market failures. There may be significant uncaptured impacts, known as wider economic impacts, which agencies are beginning to incorporate in appraisals using ad-hoc methods. Computable general equilibrium (CGE) models are an increasingly popular method for assessing the economic impact of transport, including both direct and wider economic impacts, as they can determine the distribution of impacts among every market and agent in the economy by simulating the behaviour of households, firms and others from microeconomic first principles. Aside from their traditional role estimating changes in macroeconomic variables, CGE models can provide a measure of welfare that guarantees no double counting and accounts for nth order effects. This paper reviews the full range of CGE models that have been applied to transport issues and discusses their role in transport appraisal. CGE models for transport have been developed in urban, regional and environmental economics as well as other fields, and each field has applied its own theory, assumptions and practices to represent the relationships between transport and the economy relevant to the field. This paper also discusses the general role of CGE modelling in transport appraisal, as well as theoretical and practical concerns regarding CGE modelling practice.
Rocha, CGD, Anzanello, MJ & Gerchman, M 2018, 'Method to Assess the Match between Clients’ Input and Decoupling Points in Customized Building Projects', Journal of Construction Engineering and Management, vol. 144, no. 5, pp. 04018018-04018018.
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Roobavannan, M, van Emmerik, THM, Elshafei, Y, Kandasamy, J, Sanderson, MR, Vigneswaran, S, Pande, S & Sivapalan, M 2018, 'Norms and values in sociohydrological models', Hydrology and Earth System Sciences, vol. 22, no. 2, pp. 1337-1349.
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Abstract. Sustainable water resources management relies on understanding how societiesand water systems coevolve. Many place-based sociohydrology (SH) modelingstudies use proxies, such as environmental degradation, to capture keyelements of the social component of system dynamics. Parameters of assumedrelationships between environmental degradation and the human response to itare usually obtained through calibration. Since these relationships are notyet underpinned by social-science theories, confidence in the predictivepower of such place-based sociohydrologic models remains low. Thegeneralizability of SH models therefore requires major advances inincorporating more realistic relationships, underpinned by appropriatehydrological and social-science data and theories. The latter is a criticalinput, since human culture – especially values and norms arising from it –influences behavior and the consequences of behaviors. This paper reviews akey social-science theory that links cultural factors to environmentaldecision-making, assesses how to better incorporate social-science insightsto enhance SH models, and raises important questions to be addressed inmoving forward. This is done in the context of recent progress insociohydrological studies and the gaps that remain to be filled. The paperconcludes with a discussion of challenges and opportunities in terms ofgeneralization of SH models and the use of available data to allow futureprediction and model transfer to ungauged basins.
Rossi, MJ, Ares, JO, Jobbágy, EG, Vivoni, ER, Vervoort, RW, Schreiner-McGraw, AP & Saco, PM 2018, 'Vegetation and terrain drivers of infiltration depth along a semiarid hillslope', Science of The Total Environment, vol. 644, pp. 1399-1408.
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Saco, PM, Moreno-de las Heras, M, Keesstra, S, Baartman, J, Yetemen, O & Rodríguez, JF 2018, 'Vegetation and soil degradation in drylands: Non linear feedbacks and early warning signals', Current Opinion in Environmental Science & Health, vol. 5, pp. 67-72.
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Sahebi, S, Shon, HK, Phuntsho, S & Ramavandi, B 2018, 'Fabricating robust thin film composite membranes reinforced on woven mesh backing fabric support for pressure assisted and forward osmosis: A dataset', Data in Brief, vol. 21, pp. 364-370.
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© 2018 The Authors The data presented in this paper are produced as part of the original research article entitled “Thin-film composite membrane on a compacted woven backing fabric for pressure assisted osmosis” (Sahebi et al., 2017). This article describes how to fabricate a defect free membrane for forward osmosis (FO) and pressure assisted osmosis (PAO) on the woven mesh backing fabric support. Casting polymer on backing fabric support may limit the interfacial polyemirization due to wrinkled membrane surface. This paper presents data obtained from two different backing fabrics used as support for fabrication of thin film composite FO membrane. Backing fabric support were woven polyester mesh with different opening size. The data include the characterization of the intrinsic properties of the membrane samples, SEM and their performance under FO process. The structural parameters (S value) of the substrate were computed from thickness and porosity of the substrates. Thin film composite (TFC) membrane achieved a water flux of 8.1 L m2 h−1 in FO process and 37 L m2 h−1 using 0.5 M NaCl as draw solution (DS) and deionised (DI) water as the feed solution (FS) when applied hydraulic pressure was 10 bar.
Sakal, A, Ball, J & van Kalken, T 2018, 'Concept of the Integrated Hydrological Ensemble Prediction System applied for the Nattai River Catchment, Australia', Journal of Applied Water Engineering and Research, vol. 6, no. 2, pp. 162-169.
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© 2016 IAHR and WCCE. Reservoir inflow predictions are essential to ensure effective operations of Sydney’s main drinking water reservoir. The reservoir’s forecast system is based on empirical rainfall forecast scenarios. Those scenarios are only indicators of possible significant future rainfall events. Recently, the Short-Term Ensemble Prediction System (STEPS) has become available in real time, which provides high-resolution rainfall forecast predictions over the catchment. The availability of STEPS rainfall forecast made it possible to develop the Integrated Hydrological Ensemble Prediction System that integrates the STEPS ensemble rainfall forecast with the fully distributed MIKE Système Hydrologique Européen model, which captures the rainfall spatial variability over the catchment and provides ensemble reservoir inflow predictions. The newly developed forecast system is embedded into the existing forecast system. This article describes the development of the forecast system and its implementation to the Nattai River catchment, one of the major inflow sources to Sydney’s main drinking water reservoir.
Salari, Z, Vakhshouri, B & Nejadi, S 2018, 'Analytical review of the mix design of fiber reinforced high strength self-compacting concrete', Journal of Building Engineering, vol. 20, pp. 264-276.
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© 2018 Elsevier Ltd Despite application of fiber reinforced concrete, high strength concrete and self-compacting concrete in the construction industry in the last decades, the investigations about combination of these types of concrete in Fiber Reinforced High-Strength Self-Compacting Concrete (FRHSSCC) is very rare in the literature. This study reviews a wide range of experimental data of the mix design in terms of the components and their proportions and the compressive strength of FRHSSCC in the last 12 years. The applied coarse and fine aggregates, chemical and mineral admixtures, fibers, cement, water, powder components and the ratios of water to cement and water to binder are broadly analyzed and evaluated. In addition, the compressive strength of the FRHSSCC mixtures are evaluated. The relationship between the compressive strength with water to cement and water to binder ratios in the mixture, water content, fine and coarse aggregates and the powder content is also discussed and compared in the case studies. Considerable variety of the mix designs with different components and proportions to achieve FRHSSCC without the mixing problems is evident in the collected case studies.
Samaei, SM, Gato-Trinidad, S & Altaee, A 2018, 'The application of pressure-driven ceramic membrane technology for the treatment of industrial wastewaters – A review', Separation and Purification Technology, vol. 200, pp. 198-220.
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© 2018 Elsevier B.V. This paper presents a review of the previous laboratory analysis and case studies on the application of the pressure-driven ceramic membrane technology for treatment of industrial wastewaters. Ceramic membranes has attracted remarkable interests in recent decades for industrial wastewater treatment because of their superior characteristic such as high fluxes, reliable working lifetime under aggressive operating conditions and ease of cleaning. The literature review revealed that the efficiency of this technology has been proven in a wide variety of wastewaters from different industries and activities including pulp and paper, textile, pharmaceutical, petrochemical, food and mining. However, there are still challenges and questions for this technology that need to be addressed in future researches such as investment cost optimisation by introducing new fabrication technologies, selectivity, permeability and packing densities improvement, fouling minimisation and proposing scale up based on experimental research results.
Samanta, M, Punetha, P & Sharma, M 2018, 'Effect of roughness on interface shear behavior of sand with steel and concrete surface', Geomechanics and Engineering, vol. 14, no. 4, pp. 387-398.
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The present study evaluates the interface shear strength between sand and different construction materials, namely steel and concrete, using direct shear test apparatus. The influence of surface roughness, mean size of sand particles, relative density of sand and size of the direct shear box on the interface shear behavior of sand with steel and concrete has been investigated. Test results show that the surface roughness of the construction materials significantly influences the interface shear strength. The peak and residual interface friction angles increase rapidly up to a particular value of surface roughness (critical surface roughness), beyond which the effect becomes negligible. At critical surface roughness, the peak and residual friction angles of the interfaces are 85-92% of the peak and residual internal friction angles of the sand. The particle size of sand (for morphologically identical sands) significantly influences the value of critical surface roughness. For the different roughness considered in the present study, both the peak and residual interaction coefficients lie in the range of 0.3-1. Moreover, the peak and residual interaction coefficients for all the interfaces considered are nearly identical, irrespective of the size of the direct shear box. The constitutive modeling of different interfaces followed the experimental investigation and it successfully predicted the pre-peak, peak and post peak interface shear response with reasonable accuracy. Moreover, the predicted stress-displacement relationship of different interfaces is in good agreement with the experimental results. The findings of the present study may also be applicable to other non-yielding interfaces having a similar range of roughness and sand properties.
Samanta, M, Punetha, P & Sharma, M 2018, 'Influence of surface texture on sand–steel interface strength response', Géotechnique Letters, vol. 8, no. 1, pp. 40-48.
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The surface texture of the interface material plays a significant role in the shear behaviour of soil–continuum interface. This study investigates the influence of surface texture of steel on the shear behaviour of sand–steel interface using different types of steel counterfaces with distinct texturing patterns. The patterns include concentric circular asperities, square-tiled surfaces with equally spaced individual asperities and ruled ribbed asperities oriented parallel, perpendicular and at an angle to the shear direction. The results show that the texturing pattern of the steel counterface significantly affects the shear strength of the sand–steel interface. The peak and residual interface friction angles for the sand–steel interfaces with different texturing patterns (with identical asperity height and spacing) varied from 26·6° to 37·5° and 14·2° to 28·7°, respectively. Moreover, the surface with ruled ribs/asperities inclined at right angle to the shear direction shows the maximum interface shear strength among all the texturing patterns tested. The findings presented herein are imperative for a realistic assessment of the performance of geotechnical structures involving soil–steel interaction.
Sandi, SG, Rodríguez, JF, Saintilan, N, Riccardi, G & Saco, PM 2018, 'Rising tides, rising gates: The complex ecogeomorphic response of coastal wetlands to sea-level rise and human interventions', Advances in Water Resources, vol. 114, pp. 135-148.
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Seo, DH, Pineda, S, Woo, YC, Xie, M, Murdock, AT, Ang, EYM, Jiao, Y, Park, MJ, Lim, SI, Lawn, M, Borghi, FF, Han, ZJ, Gray, S, Millar, G, Du, A, Shon, HK, Ng, TY & Ostrikov, K 2018, 'Anti-fouling graphene-based membranes for effective water desalination', Nature Communications, vol. 9, no. 1.
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AbstractThe inability of membranes to handle a wide spectrum of pollutants is an important unsolved problem for water treatment. Here we demonstrate water desalination via a membrane distillation process using a graphene membrane where water permeation is enabled by nanochannels of multilayer, mismatched, partially overlapping graphene grains. Graphene films derived from renewable oil exhibit significantly superior retention of water vapour flux and salt rejection rates, and a superior antifouling capability under a mixture of saline water containing contaminants such as oils and surfactants, compared to commercial distillation membranes. Moreover, real-world applicability of our membrane is demonstrated by processing sea water from Sydney Harbour over 72 h with macroscale membrane size of 4 cm2, processing ~0.5 L per day. Numerical simulations show that the channels between the mismatched grains serve as an effective water permeation route. Our research will pave the way for large-scale graphene-based antifouling membranes for diverse water treatment applications.
Shafaghat, A, Khabbaz, H, Moravej, S & Shafaghat, A 2018, 'Effect of footing shape on bearing capacity and settlement of closely spaced footings on sandy soil', International Journal of Geotechnical and Geological Engineering, vol. 12, no. 11.
Shao, R, Wu, C, Liu, Z, Su, Y, Liu, J, Chen, G & Xu, S 2018, 'Penetration resistance of ultra-high-strength concrete protected with layers of high-toughness and lightweight energy absorption materials', Composite Structures, vol. 185, pp. 807-820.
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© 2017 Elsevier Ltd Aluminium foam has advantages of excellent shock absorption, cyclic utilization, and lightweight. Ultra-high-molecular-weight polyethylene (UHMWPE) fibre has a low density, a high specific strength, a high modulus and a great capability in energy absorption. Steel wire mesh has high toughness and elongation properties and a good effect on energy absorption. In the present study, UHMWPE fibre, steel wire mesh and aluminium foam were used to protect ultra-high-strength concrete (UHSC) targets to resist DT300 high-strength alloy-steel projectile penetration with striking velocities from 550 m/s to 800 m/s. High-speed impact tests on normal-strength concrete (NSC) targets were also conducted for comparison. Testing results including the failure mode, depth of penetration (DOP), crater dimensions and damage area of protected concrete targets, indicate that the new composite material protective cover has an outstanding performance in the shock wave absorption, especially in reducing the crack propagation and debris spatter of protected UHSC targets, as well as increasing the deviation angles of projectile terminal ballistic trajectories. It is a successful demonstration of anti-penetration properties research for new concrete composite structures.
Sharafi, P, Mortazavi, M, Samali, B & Ronagh, H 2018, 'Interlocking system for enhancing the integrity of multi-storey modular buildings', Automation in Construction, vol. 85, pp. 263-272.
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Maintaining the structural integrity against severe loading conditions and accidental loads is one of the primary concerns when designing multi-storey modular buildings. Connections between the modular units play a central role in providing integrity in modular buildings. This paper describes the development of an innovative interlocking system for improving the integrity of multi-storey modular buildings. The concept of Modular Integrating System (MIS) and the procedure used to develop an efficient interlocking system, which can be widely used in the construction of modular buildings, is investigated. MIS is a patented joining system including a set of interlocking connections and the method of assembly of modular units that provides a high level of integrity that prevents accidental disassembly and stress concentrations at the points of attachments in case of extreme loading occurrence. The creative easy to install, self-fit and self-locking mechanism of this system can also considerably facilitate the automated assembly of modular buildings and provide an effective solution for controlling construction tolerance. The robustness provided by the proposed system is demonstrated through numerical and experimental analysis.
Sharafi, P, Mortazavi, M, Usefi, N, Kildashti, K, Ronagh, H & Samali, B 2018, 'Lateral force resisting systems in lightweight steel frames: Recent research advances', Thin-Walled Structures, vol. 130, pp. 231-253.
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Lightweight Steel Frames (LSF) made by framing thin gauge cold-formed steel (CFS) into different structural elements such as walls, trusses and joists are commonplace in Australia and many parts of the world. The great progress in the knowledge of CFS structures achieved in the past two decades, together with the modern design and fabrication methods supported by progressively improved specifications, have equipped the industry of the lightweight steel construction with tools and confidence to play an important part in the future of building construction. Despite the ever-increasing demand on the use of cold formed steel (CFS) framing into more complex and taller structures, the lateral load resistance capacity of lightweight steel frames has proven to be a major hindrance and a major concern. This paper reviews and summarises the research developments made in the area of lateral load resistance capacity of lightweight steel frames (LSF) as published in leading journals and codes’ provisions in the area. Research advances in conventional systems such as shear walls clad with face sheathings and LSF strap-braced wall systems in addition to other less conventional systems such as special bolted moment frames are reviewed here, and the solutions for improving the lateral performance of these systems are classified.
Sharafi, P, Rashidi, M, Samali, B, Ronagh, H & Mortazavi, M 2018, 'Identification of Factors and Decision Analysis of the Level of Modularization in Building Construction', Journal of Architectural Engineering, vol. 24, no. 2, pp. 04018010-04018010.
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In the majority of ordinary housing development projects, instead of using complex multicriteria decision-making systems, companies still rely on expert knowledge, checklists, or similar tools to decide on an appropriate level of modularization. Generally, in these types of projects the level of modularization is mainly driven by site constraints, such as accessibility and harsh weather conditions. Because of the lack of appropriate decision support tools, it is very hard for decision makers to include factors, such as lifecycle costs, quality, productivity, efficiency, and design complexity, into their decision, even if they are willing to do so. Simple decision support tools are required to provide practical assistance to the decision makers to adopt an appropriate level of modularization for such projects. This study, as a part of a broad ongoing research project on the optimum level of modularization in building construction, has compiled the expert knowledge for decision support that enables the decision makers to perform an easy initial feasibility study on the use of an appropriate level of modularization in their construction projects. First, a list of critical decision-making criteria is created. These criteria are obtained from an extensive literature review, qualitative survey questionnaires, and semistructured interviews with researchers and professionals in the construction industry as well as modular manufacturers. Then, using the results, a simple multicriteria decision analysis (MCDA) approach is developed as a practical decision support system to facilitate the decision-making process for selecting appropriate construction systems as well as determining the proper level of modularization for building construction projects. The validation of the study is demonstrated through a local actual case study.
Shi, X, Ngo, HH, Sang, L, Jin, P, Wang, XC & Wang, G 2018, 'Functional evaluation of pollutant transformation in sediment from combined sewer system', Environmental Pollution, vol. 238, pp. 85-93.
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© 2018 Elsevier Ltd In this study, a pilot combined sewer system was constructed to characterize the pollutant transformation in sewer sediment. The results showed that particulate contaminants deposited from sewage could be transformed into dissolved matter by distinct pollutant transformation pathways. Although the oxidation-reduction potential (ORP) was varied from −80 mV to −340 mV in different region of the sediment, the fermentation was the dominant process in all regions of the sediment, which induced hydrolysis and decomposition of particulate contaminants. As a result, the accumulation of dissolved organic matter and the variation of ORP values along the sediment depth led to the depth-dependent reproduction characteristics of methanogens and sulfate-reducing bacteria, which were existed in the middle and deep layer of the sediment respectively. However, the diversity of nitrifying and polyphosphate-accumulating bacteria was low in sewer sediment and those microbial communities showed a non-significant correlation with nitrogen and phosphorus contaminants, which indicated that the enrichment of nitrogen and phosphorus contaminants was mainly caused by physical deposition process. Thus, this study proposed a promising pathway to evaluate pollutant transformation and can help provide theoretical foundation for urban sewer improvement.
Shi, X, Zhu, S, Ni, YQ & Li, J 2018, 'Vibration suppression in high-speed trains with negative stiffness dampers', Smart Structures and Systems, vol. 21, no. 5, pp. 653-668.
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This work proposes and investigates re-centering negative stiffness dampers (NSDs) for vibration suppression in high-speed trains. The merit of the negative stiffness feature is demonstrated by active controllers on a high-speed train. This merit inspires the replacement of active controllers with re-centering NSDs, which are more reliable and robust than active controllers. The proposed damper design consists of a passive magnetic negative stiffness spring and a semi-active positioning shaft for re-centering function. The former produces negative stiffness control forces, and the latter prevents the amplification of quasi-static spring deflection. Numerical investigations verify that the proposed re-centering NSD can improve ride comfort significantly without amplifying spring deflection.
Shibuya, M, Park, MJ, Lim, S, Phuntsho, S, Matsuyama, H & Shon, HK 2018, 'Novel CA/PVDF nanofiber supports strategically designed via coaxial electrospinning for high performance thin-film composite forward osmosis membranes for desalination', Desalination, vol. 445, pp. 63-74.
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© 2018 Elsevier B.V. This study introduces a novel electrospun nanofiber mat fabricated via coaxial electrospinning as a support for high performance thin-film composite (TFC) forward osmosis (FO) membrane. This method produces a dual layer composite nanofiber support consisted of a polyvinylidene fluoride (PVDF) core layer and a cellulose acetate (CA) sheath layer, which provide mechanical stability and hydrophilicity, respectively. The CA sheath layer aims to cover the hydrophobic core layer and improve its hydrophilicity. The TFC FO membrane with coaxial electrospun CA/PVDF support layer not only showed high improvement in water flux due to improved hydrophilicity, but also exhibited comparable mechanical strength with pure PVDF nanofiber support. After FO operation using 0.5 M NaCl as draw solution and deionized water as feed solution, the coaxial electrospun CA/PVDF composite based TFC-FO membrane achieved the following: water flux of 31.2 L m−2 h−1, remarkably lower specific reverse salt flux of 0.03 g L−1, and low structural parameter of 190 μm. Coaxial electrospinning is therefore a promising approach to fabricate high performance FO membrane whose support exhibits high porosity, mechanical stability, and hydrophilicity.
Siahaan, F, Indraratna, B, Ngo, NT, Rujikiatkamjorn, C & Heitor, A 2018, 'Influence of Particle Gradation and Shape on the Performance of Stone Columns in Soft Clay', Geotechnical Testing Journal, vol. 41, no. 6, pp. 1076-1091.
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Abstract A stone column typically consists of particles whose influence has largely been overlooked in design practice in terms of stress transfer, pattern of deformation, and intrusion of fines (clogging). This article presents an experimental study on the load-deformation behavior of a model stone column installed in soft clay with a particular emphasis on the influence of particle gradation and shape under undrained loading. The results show that particle gradation and shape have a significant influence on the load-deformation behavior and the extent of fines intrusion into the stone columns. Relatively well-graded particle sizes favor the development of higher peak shear stresses accompanied by lateral bulging, whereas more uniform grading results in the development of distinct shear planes and smaller peak shear stresses. Deformed columns were also examined using computed tomography, and the porosity profiles at the end of the test were determined using micrographs. Maximum porosity typically occurred in the zone of extreme lateral deformation, with the results suggesting that the extent of fines intrusion was influenced by particle morphology.
Silitonga, AS, Masjuki, HH, Ong, HC, Sebayang, AH, Dharma, S, Kusumo, F, Siswantoro, J, Milano, J, Daud, K, Mahlia, TMI, Chen, W-H & Sugiyanto, B 2018, 'Evaluation of the engine performance and exhaust emissions of biodiesel-bioethanol-diesel blends using kernel-based extreme learning machine', Energy, vol. 159, pp. 1075-1087.
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© 2018 Elsevier Ltd It is known that biodiesel and bioethanol are viable alternative fuels to replace diesel for compression ignition engines. In this study, an experimental investigation is carried out to evaluate the performance and exhaust emissions of a single cylinder diesel engine fuelled with biodiesel-bioethanol-diesel blends. The engine performance parameters evaluated are the brake specific fuel consumption and brake thermal efficiency whereas the exhaust emission parameters evaluated are carbon monoxide, nitrogen oxide, and smoke opacity. Kernel-based extreme learning machine is used to predict the engine performance and exhaust emission parameters of the fuel blends at full throttle conditions. Based on the experimental results, the brake specific fuel consumption is lower while the brake thermal efficiency is higher for the biodiesel-bioethanol-diesel blends. The carbon monoxide emissions and smoke opacity are also lower for these fuel blends. The mean absolute percentage error of the brake specific fuel consumption, brake thermal efficiency, carbon monoxide, nitrogen oxide, and smoke opacity is 1.363, 1.482, 4.597, 2.224, and 2.090%, respectively. Thus, it can be concluded that K-ELM is a reliable method to estimate the engine performance and exhaust emission parameters of a single cylinder compression ignition engine fuelled with biodiesel-bioethanol-diesel blends to reduce fuel consumption and exhaust emissions.
Song, X, Luo, W, Hai, FI, Price, WE, Guo, W, Ngo, HH & Nghiem, LD 2018, 'Resource recovery from wastewater by anaerobic membrane bioreactors: Opportunities and challenges', Bioresource Technology, vol. 270, pp. 669-677.
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© 2018 This review examines the potential of anaerobic membrane bioreactor (AnMBR) to serve as the core technology for simultaneous recovery of clean water, energy, and nutrient from wastewater. The potential is significant as AnMBR treatment can remove a board range of trace organic contaminants relevant to water reuse, convert organics in wastewater to biogas for subsequent energy production, and liberate nutrients to soluble forms (e.g. ammonia and phosphorus) for subsequent recovery for fertilizer production. Yet, there remain several significant challenges to the further development of AnMBR. These challenges evolve around the dilute nature of municipal wastewater, which entails the need for pre-concentrating wastewater prior to AnMBR, and hence, issues related to salinity build-up, accumulation of substances, membrane fouling, and membrane stability. Strategies to address these challenges are proposed and discussed. A road map for further research is also provided to guide future AnMBR development toward resource recovery.
Song, X, Luo, W, McDonald, J, Khan, SJ, Hai, FI, Guo, W, Ngo, HH & Nghiem, LD 2018, 'Effects of sulphur on the performance of an anaerobic membrane bioreactor: Biological stability, trace organic contaminant removal, and membrane fouling', Bioresource Technology, vol. 250, pp. 171-177.
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© 2017 This study investigated the impact of sulphur content on the performance of an anaerobic membrane bioreactor (AnMBR) with an emphasis on the biological stability, contaminant removal, and membrane fouling. Removal of 38 trace organic contaminants (TrOCs) that are ubiquitously present in municipal wastewater by AnMBR was evaluated. Results show that basic biological performance of AnMBR regarding biomass growth and the removal of chemical oxygen demand (COD) was not affected by sulphur addition when the influent COD/SO42− ratio was maintained higher than 10. Nevertheless, the content of hydrogen sulphate in the produced biogas increased significantly and membrane fouling was exacerbated with sulphur addition. Moreover, the increase in sulphur content considerably affected the removal of some hydrophilic TrOCs and their residuals in the sludge phase during AnMBR operation. By contrast, no significant impact on the removal of hydrophobic TrOCs was noted with sulphur addition to AnMBR.
Song, X, Luo, W, McDonald, J, Khan, SJ, Hai, FI, Price, WE & Nghiem, LD 2018, 'An anaerobic membrane bioreactor – membrane distillation hybrid system for energy recovery and water reuse: Removal performance of organic carbon, nutrients, and trace organic contaminants', Science of The Total Environment, vol. 628-629, pp. 358-365.
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© 2018 In this study, a direct contact membrane distillation (MD) unit was integrated with an anaerobic membrane bioreactor (AnMBR) to simultaneously recover energy and produce high quality water for reuse from wastewater. Results show that AnMBR could produce 0.3–0.5 L/g CODadded biogas with a stable methane content of approximately 65%. By integrating MD with AnMBR, bulk organic matter and phosphate were almost completely removed. The removal of the 26 selected trace organic contaminants by AnMBR was compound specific, but the MD process could complement AnMBR removal, leading to an overall efficiency from 76% to complete removal by the integrated system. The results also show that, due to complete retention, organic matter (such as humic-like and protein-like substances) and inorganic salts accumulated in the MD feed solution and therefore resulted in significant fouling of the MD unit. As a result, the water flux of the MD process decreased continuously. Nevertheless, membrane pore wetting was not observed throughout the operation.
Song, Y-C, Kim, M, Shon, H, Jegatheesan, V & Kim, S 2018, 'Modeling methane production in anaerobic forward osmosis bioreactor using a modified anaerobic digestion model No. 1', Bioresource Technology, vol. 264, pp. 211-218.
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Sornalingam, K, McDonagh, A, Zhou, JL, Johir, MAH & Ahmed, MB 2018, 'Photocatalysis of estrone in water and wastewater: Comparison between Au-TiO2 nanocomposite and TiO2, and degradation by-products', Science of The Total Environment, vol. 610-611, pp. 521-530.
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© 2017 Elsevier B.V. Gold-modified TiO2 (Au-TiO2) photocatalysts were utilised for the degradation of estrone (E1), a major endocrine disrupting chemical in water and wastewater. Au-TiO2 catalysts were synthesised by a deposition-precipitation method with gold loadings of 0–8% (wt%). The Au-TiO2 nanocomposite exhibited superior activity compared to P25 TiO2 under UVA (λ = 365 nm), cool white (λ > 420 nm) and green (λ = 523 nm) light emitting diodes (LEDs), for treating 1 mg l− 1 of E1. The 4 wt% Au loading was found to produce the best photocatalytic activity with a rate constant of 2.44 ± 0.36 h− 1, compared to 0.06 ± 0.01 h− 1 for P25 TiO2, under visible light. In total 4 by-products were identified, one from negative ionization mode (m/z = 269) and three from positive ionization mode (m/z = 287) during photocatalysis, which were also degraded with time by Au-TiO2. For different water matrices, the photodegradation rate of E1 decreased in the order: ultrapure water > synthetic wastewater ≈ wastewater effluent from membrane bio-reactor. Overall, 4 wt% Au-TiO2 demonstrated superior performance compared to P25 TiO2 in water and wastewater.
Soudagar, MEM, Nik-Ghazali, N-N, Abul Kalam, M, Badruddin, IA, Banapurmath, NR & Akram, N 2018, 'The effect of nano-additives in diesel-biodiesel fuel blends: A comprehensive review on stability, engine performance and emission characteristics', Energy Conversion and Management, vol. 178, pp. 146-177.
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Stewart, MG & Mueller, J 2018, 'Risk and economic assessment of U.S. aviation security for passenger-borne bomb attacks', Journal of Transportation Security, vol. 11, no. 3-4, pp. 117-136.
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A systems reliability analysis is developed that includes 18 layers of security that might disrupt a terrorist organisation undeterred and intent on downing an airliner with a passenger-borne bomb. Overall, they reduce the risk that such an attack would be successful by 93%. The odds that a lone wolf will be successful in such an attack are considerably lower. This level of risk reduction is very robust: security remains high even when the disruption rates that make it up are varied considerably. The same model is used to explore the risk reduction of aviation security measures in other western countries and in Israel. The benefit-to-cost ratio is then calculated for most of the security measures. It considers the costs and the risk reduction of the layer, the losses from a successful terrorist attack, and the attack probability. It is found that the Joint Terrorism Task Force (JTTF) and police, PreCheck, Visible Intermodal Protection Response (VIPR) teams, and canines pass a cost-benefit assessment. However, it finds that air marshals and behavior detection officers, at a combined cost of nearly $1.3 billion per year, fail to be cost-effective. Accordingly, there are likely to be spending reductions that could be made with little or no consequent reduction in security.
Stewart, MG, Ginger, JD, Henderson, DJ & Ryan, PC 2018, 'Fragility and climate impact assessment of contemporary housing roof sheeting failure due to extreme wind', Engineering Structures, vol. 171, pp. 464-475.
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The paper describes a risk analysis of the economic impact of damage to metal roofing of a typical contemporary (new) Australian house subject to extreme wind loading. The failure modes considered are roof cladding and batten-to-truss connection failures, with the effect of defective construction also considered. Monte-Carlo simulation and structural reliability methods are used to stochastically model spatially varying pressure coefficients, roof component failure, and load re-distribution across the roof. This spatial reliability analysis enables fragility curves to be developed that relate likelihood and extent of roof cover loss to gust wind speed. The annual economic risk is up to 0.3% of house replacement value. A typical house with construction defects increases economic risk more than sixfold when compared to the defect-free house. There is a 10% chance that a changing climate will increase expected losses for houses in Brisbane and Melbourne by 6–18% over the next 50 years.
Sullivan, AL, Surawski, NC, Crawford, D, Hurley, RJ, Volkova, L, Weston, CJ & Meyer, CP 2018, 'Effect of woody debris on the rate of spread of surface fires in forest fuels in a combustion wind tunnel', Forest Ecology and Management, vol. 424, pp. 236-245.
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© 2018 The treatment of the contribution of woody debris (WD, such as branches or small logs >6–50 mm diameter) to the rate of forward spread of a fire in current operational forest fire spread models is inconsistent. Some models do not take into account this fuel at all (i.e. only consider the combustion of fine fuels (⩽6 mm diameter)), while others incorporate effects based on little or no data. An experimental programme utilising a large combustion wind tunnel investigated the effect of WD on the spread of fires burning through forest litter (surface fuel) beds of 1.0 kg m-2. Fires spreading with (heading) and against (backing) the wind were investigated. Three treatments of WD load (0.2, 0.6 and 1.2 kg m-2) and a control (0 kg m-2) were studied using a single constant wind speed (1.0 m s-1) and a narrow range of fine and woody fuel moisture contents (10.0–12.7% and 9.2–11.6% oven-dry weight, respectively) determined by ambient conditions. Presence of WD was found to approximately halve the overall rate of spread of heading fires relative to when no WD was present, regardless of the level of treatment. No effect of WD on rate of spread was found for backing fires. Potential explanations of these findings and implications for the use of operational forest fire spread models are explored, as are future research needs.
Sun, G, Liu, T, Fang, J, Steven, GP & Li, Q 2018, 'Configurational optimization of multi-cell topologies for multiple oblique loads', Structural and Multidisciplinary Optimization, vol. 57, no. 2, pp. 469-488.
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© 2017, Springer-Verlag GmbH Germany. Multi-cell thin-walled structures exhibit significant advantages in maximizing energy absorption and minimizing mass during vehicle crashes. Since the topological distribution of wall members has an appreciable effect on the crashworthiness, their design signifies an important area of research. As a major energy absorber, multi-cell tubes are more commonly encounter oblique loading in real life. Thus, this study aimed to optimize multi-cell cross-sectional configuration of tubal structures for multiple oblique loading cases. An integer coded genetic algorithm (ICGA) is introduced here to optimize topological distribution of multi-celled web members for single/multiple oblique impacting conditions. Specifically, material distribution in a form of allocating web wall thickness, starting from zero, is considered as design variables and maximization of energy absorption (EA) as the design objective under the predefined peak crushing force and structural mass constraints. The optimization allows generating uniform or non-uniform thickness distribution in different web wall configurations to maximize usage efficiency of material. Compared with the baseline structure, the optimized configurations largely improved the energy absorption in both single and multiple load cases. The examples demonstrate that the proposed ICGA-based design method not only provides a useful approach to searching for novel crashworthy structures in a systematic fashion, but also develops a series of novel multi-cell topologies for multiple oblique loading cases.
Sun, G, Zhang, H, Fang, J, Li, G & Li, Q 2018, 'A new multi-objective discrete robust optimization algorithm for engineering design', Applied Mathematical Modelling, vol. 53, pp. 602-621.
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© 2017 Elsevier Inc. This paper proposes a novel multi-objective discrete robust optimization (MODRO) algorithm for design of engineering structures involving uncertainties. In the present MODRO procedure, grey relational analysis (GRA), coupled with principal component analysis (PCA), was used as a multicriteria decision making model for converting multiple conflicting objectives into one unified cost function. The optimization process was iterated using the successive Taguchi approach to avoid the limitation that the conventional Taguchi method fails to deal with a large number of design variables and design levels. The proposed method was first verified by a mathematical benchmark example and a ten-bar truss design problem; and then it was applied to a more sophisticated design case of full scale vehicle structure for crashworthiness criteria. The results showed that the algorithm is able to achieve an optimal design in a fairly efficient manner attributable to its integration with the multicriteria decision making model. Note that the optimal design can be directly used in practical applications without further design selection. In addition, it was found that the optimum is close to the corresponding Pareto frontier generated from the other approaches, such as the non-dominated sorting genetic algorithm II (NSGA-II), but can be more robust as a result of introduction of the Taguchi method. Due to its independence on metamodeling techniques, the proposed algorithm could be fairly promising for engineering design problems of high dimensionality.
Sun, J, Ni, B-J, Sharma, KR, Wang, Q, Hu, S & Yuan, Z 2018, 'Modelling the long-term effect of wastewater compositions on maximum sulfide and methane production rates of sewer biofilm', Water Research, vol. 129, pp. 58-65.
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© 2017 Elsevier Ltd Reliable modelling of sulfide and methane production in sewer systems is required for efficient sewer emission management. Wastewater compositions affect sulfide and methane production kinetics through both its short-term variation influencing the substrate availability to sewer biofilms, and its long-term variation affecting the sewer biofilm structure. While the short-term effect is well considered in existing sewer models with the use of Monod or half-order equations, the long-term effect has not been explicitly considered in current sewer models suitable for network modelling. In this study, the long-term effect of wastewater compositions on sulfide and methane production activities in rising main sewers was investigated. A detailed biofilm model was firstly developed, and then calibrated and validated using experimental data measured during the entire biofilm development period of a laboratory sewer reactor. Based on scenario simulations using the detailed biofilm model, empirical equations describing the long-term effect of sulfate and sCOD (soluble chemical oxygen demand) concentrations on kH2S (the maximum sulfide production rate of sewer biofilm) and kCH4 (the maximum methane production rate of sewer biofilm) were proposed. These equations require further verification in future studies before their potential integration into network-wide sewer models.
Sun, Y, Nimbalkar, S & Chen, C 2018, 'Grading and frequency dependence of the resilient modulus of ballast', Géotechnique Letters, vol. 8, no. 4, pp. 305-309.
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The stress–strain and degradation response of railway ballast to imparted train loading is often largely dominated by intrinsic properties, including particle size and particle-size distribution (PSD). To investigate these aspects, a series of large-scale triaxial cyclic tests were conducted on railway ballast. To investigate the influence of grading and frequency on the resilient modulus of railroad ballast, laboratory data from previous work were analysed and discussed. It was observed that the resilient modulus of ballast decreased with an increase in the coefficient of uniformity and cyclic loading frequency. However, for samples with the constant coefficient of uniformity, the resilient modulus appeared to decrease as the particle size and the associated broadness increased. It was also found that the resilient modulus underwent substantial reduction with the evolution of particle breakage by shifting the initial PSD to a broader range.
Tai, P, Indraratna, B & Rujikiatkamjorn, C 2018, 'Experimental simulation and mathematical modelling of clogging in stone column', Canadian Geotechnical Journal, vol. 55, no. 3, pp. 427-436.
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In this paper, time-dependent clogging is studied considering a unit cell consisting of a single stone column interacting with the surrounding soft clay. Clogging is assessed quantitatively and the corresponding void space of the column is determined using computed tomography. It is observed that the extent of clogging is substantial in the upper part of the column, but diminishes rapidly with depth. The soil properties in the clogged zone are determined indirectly through additional tests of clay–aggregates mixtures with various clay fractions. An equal strain consolidation model based on the principle of unit cell analysis is developed to capture both the initial and time-dependent clogging. The model accounts for a reduction in permeability and an increase in compressibility of the column. This current model, as expected, offers identical results to some previous studies if clogging is ignored, while the comparison with other selected models demonstrates the influence that clogging of the stone column can have on the consolidation of the surrounding soil. Furthermore, load–settlement predictions from the proposed “equal strain” model are also compared with the consolidation response of a previously developed “free strain” model.
Tan, SX, Ong, HC, Lim, S & Pang, YL 2018, 'In situ reactive extraction of Jatropha curcas L. seeds assisted by ultrasound: Preliminary studies', Energy Sources, Part A: Recovery, Utilization, and Environmental Effects, vol. 40, no. 14, pp. 1772-1779.
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Tang, CY, Yang, Z, Guo, H, Wen, JJ, Nghiem, LD & Cornelissen, E 2018, 'Potable Water Reuse through Advanced Membrane Technology', Environmental Science & Technology, vol. 52, no. 18, pp. 10215-10223.
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© 2018 American Chemical Society. Recycling water from municipal wastewater offers a reliable and sustainable solution to cities and regions facing shortage of water supply. Places including California and Singapore have developed advanced water reuse programs as an integral part of their water management strategy. Membrane technology, particularly reverse osmosis, has been playing a key role in producing high quality recycled water. This feature paper highlights the current status and future perspectives of advanced membrane processes to meet potable water reuse. Recent advances in membrane materials and process configurations are presented and opportunities and challenges are identified in the context of water reuse.
Tang, G, Huang, J, Sheng, D & Sloan, SW 2018, 'Stability analysis of unsaturated soil slopes under random rainfall patterns', Engineering Geology, vol. 245, pp. 322-332.
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The significance of rainfall pattern in the assessment of rainfall-induced landslide is widely recognized. However, much work so far is limited to several simplified typical rainfall patterns. In this study, the random rainfall pattern (RRP) is introduced and generated using random cascade model based on the rainfall event characterized by average rainfall intensity and duration. The stability of unsaturated slope considering RRPs is studied from three perspectives: deterministic analysis by means of safety factor under different generated RRPs, probabilistic analysis through conditional failure probability considering the diversity of generated RRPs based on Monte Carlo method and risk assessment analysis by introducing annual failure probability (AFP) considering also the occurrence frequencies of rainfall events. Three typical rainfall patterns are introduced for comparison analysis. The results show that slope stability is sensitive to the RRP and is strongly depend on the temporal distribution of rainfall intensity in RRP. High likelihood of slope failure may occur considering the variety of RRPs even though the slope is in a stable state in terms of deterministic analysis. The AFP considering RRPs increases rapidly with increasing rainfall duration and is significantly different from those under typical rainfall patterns. The findings lead to the conclusion that RRPs should be considered in the estimation of unsaturated slope stability.
Tang, J, Wang, XC, Hu, Y, Pu, Y, Huang, J, Hao Ngo, H, Zeng, Y & Li, Y 2018, 'Nitrogen removal enhancement using lactic acid fermentation products from food waste as external carbon sources: Performance and microbial communities', Bioresource Technology, vol. 256, pp. 259-268.
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Tang, Z-E, Lim, S, Pang, Y-L, Ong, H-C & Lee, K-T 2018, 'Synthesis of biomass as heterogeneous catalyst for application in biodiesel production: State of the art and fundamental review', RENEWABLE & SUSTAINABLE ENERGY REVIEWS, vol. 92, no. C, pp. 235-253.
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Biodiesel is gaining attention as a remedy for the increasing demand of fossil fuels which is depleting rapidly. Commercial homogeneous catalysts in the biodiesel production industry are facing challenges such as separation difficulties and severe corrosion which will lead to the increment of production and maintenance cost. Herein, this paper focuses on the comprehensive review of literature reported on the usage of biomass as the precursor for the catalyst used in biodiesel production. Compared to other commercial catalysts, the usage of biomass as catalyst precursor possesses several advantages such as abundantly available, cheaper raw materials, reusable, non-toxic and biodegradable. Carbon material synthesized from biomass which acts as the efficient support for active sites due to its high porosity and surface area characteristic has been studied widely. The latest development of biomass derived basic, acidic and magnetic heterogeneous catalyst through several state of the art synthesis pathways starting from the synthesis of the supporting material (carbon) until the functionalization process to form the complete catalyst was reviewed. Apart from direct sulfonation using sulfuric acid, sulfonation by reduction and arylation were less hazardous and provided comparable active sites activity. Most biomass based catalysts exhibited good catalytic performance by providing high biodiesel yield of above 80% at optimum conditions. Besides that, various kinetic models developed from the reaction kinetic study catalyzed by biomass based catalyst were also reviewed as a preparatory stage for the scaled-up commercialization process of the studied catalyst in the biodiesel production sector. This catalyst could assist to lower the activation energy required for the reactions and thus enables higher reaction rate to reach equilibrium. Continuous research on producing high performing biomass based catalyst with minimum resources is needed in order to achieve th...
Tapas, M, Brenner, J, Vessalas, K, Thomas, P & Sirivivatnanon, V 2018, 'Effect of Limestone Content in Cement on Alkali-Silica Reaction Using Accelerated Mortar Bar Test', Concrete in Australia, vol. 44, no. 2, pp. 41-47.
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This paper reports the effect of interground limestone content on Alkali Silica Reaction (ASR) in binder systems with and without supplementary cementitious materials (SCMs) using commercial Portland cement (Type GP) with no limestone addition and a masonry cement with 17% limestone. The results show that increasing cement limestone content up to 17% has no adverse effect on expansion of mortar bars containing reactive greywacke aggregate tested using Australian Standard AS 1141.60.1. The high limestone content of 17% also appears to stabilise the Accelerated Mortar Bar Test (AMBT) expansion after 14 days of immersion in 1M NaOH 80 oC. This is possibly because of the formation of monocarboaluminate as detected by X-Ray Diffraction (XRD), resulting from the reaction of limestone with the aluminate phases in the cement, which may lead to reduced porosity in the mortar as well as the reduced amount of portlandite in the hydrated masonry cement as confirmed by Thermogravimetric Analysis (TGA). Moreover, it was found that the limestone content had no detrimental effect on the efficacy of SCMs to suppress ASR as shown in the expansion of the accelerated mortar bar tests.
Teoh, YH, Masjuki, HH, How, HG, Kalam, MA, Yu, KH & Alabdulkarem, A 2018, 'Effect of two-stage injection dwell angle on engine combustion and performance characteristics of a common-rail diesel engine fueled with coconut oil methyl esters-diesel fuel blends', Fuel, vol. 234, pp. 227-237.
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Thaib, R, Rizal, S, Hamdani, Mahlia, TMI & Pambudi, NA 2018, 'Experimental analysis of using beeswax as phase change materials for limiting temperature rise in building integrated photovoltaics', Case Studies in Thermal Engineering, vol. 12, pp. 223-227.
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© 2018 The Authors. Indonesia has the potential of saving from 10% to 30% of energy in the commercial sector which consists of trade, hotels, restaurants, finances, government agencies, schools, hospitals, and communications. By simultaneously serving as building envelope material and power generator, BIPV systems can represent savings in the cost of materials and electricity. It reduce the use of fossil fuels and emission of ozone depleting gases, and also add architectural interest to buildings. However, the temperature rise poses a challenge for BIPV, given that it manifests itself in electrical efficiency and overheating. The experiments present in this study aim at understanding the behavior of the PV-PCM systems in realistic outdoor uncontrolled conditions to determine how effective they are. In addition, the PV-PCM systems were tried in the low latitude and hot climate of Banda Aceh, Indonesia. Experiments were conducted outdoors at the Engineering Faculty in Syiah Kuala University, located in Banda Aceh, Indonesia (05:57 N, 95.37 E). In this study, both paraffin wax and beeswax were used as a phase change material. The final results showed that the electrical efficiency of PV panels without PCM is ranged between 6.1% and 6.5%. While for PV panels with PCM the efficiency is ranged at 7.0-7.8%. This proved that the process of water cooling is capable of increasing the efficiency of PV panels.
Thomas, D & Ding, G 2018, 'Comparing the performance of brick and timber in residential buildings – The case of Australia', Energy and Buildings, vol. 159, pp. 136-147.
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© 2017 Elsevier B.V. There is currently a limited use of timber products in residential development in Australia due to the dominance of heavy materials such as concrete, steel and brick. This dominant use of heavy materials is a reversal of the traditional material choice that was based predominantly on timber products. Technological advances and efficiencies drove the change to heavy materials to use in residential construction. The emerging issue with this reliance on heavy materials is the impact of their use on the environment. The carbon impact and problem of finite resource depletion associated with concrete, steel and bricks need to be addressed due to the increasing pressure from national and international requirements and legislations. The construction industry needs to reduce its negative impact on the environment and the renewable nature of timber presents a material solution to the problem. Timber from sustainably managed forests and plantations can be utilised as lumber or manufactured into engineered products for residential development. This paper examines the benefits of timber used in building envelopes when compared with conventional high-density materials such as brick and concrete when construction is designed with equivalent thermal performance. Multiple case studies were used to demonstrate the reduced life cycle energy and costs, and the time of construction benefits of timber when used as an alternative to heavy materials. Results revealed that Life cycle energy and time of construction showed noticeable differences between timber construction and heavy materials and cost showing marginal differences.
To, VHP, Nguyen, TV, Vigneswaran, S, Bustamante, H, Higgins, M & van Rys, D 2018, 'Novel methodologies for determining a suitable polymer for effective sludge dewatering', Journal of Environmental Chemical Engineering, vol. 6, no. 4, pp. 4206-4214.
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© 2018 Elsevier Ltd. All rights reserved. Understanding the interactions between sludge particles and polymers during sludge dewatering is necessary to: firstly, maximize dewatered cake solids content; and secondly, minimize polymer demand. In this study, two scientific methodologies, namely the 'y-intercept' concept and Higgins modified centrifugal technique (Higgins MCT) were used to identify the optimum polymer demand and type for effective conditioning and dewatering. Results from the 'y-intercept' concept show that a large amount of polymer required during conditioning of anaerobically digested sludge (ADS) is mainly due to neutralization of soluble biopolymers. In contrast, conditioning of aerobically digested sludge (AEDS) and waste activated sludge (WAS) is mostly controlled by a polymer bridging mechanism. The results indicated that, in order to achieve maximum dewatering performance with minimum conditioning polymer requirement, high charge density polymers are suitable for ADS while branched (or cross-linked) polymers can be used for AEDS and WAS. The new lab-scale technique, Higgins MCT, was successfully implemented for measuring cake solids content achievable by centrifuge and determining the optimum polymer demand (OPD). The Higgins MCT also helped to understand the relationship between digestion, conditioning and dewatering.
Tong, C-X, Burton, GJ, Zhang, S & Sheng, D 2018, 'A simple particle-size distribution model for granular materials', Canadian Geotechnical Journal, vol. 55, no. 2, pp. 246-257.
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Particle-size distribution (PSD) is a fundamental soil property that plays an important role in soil classification and soil hydromechanical behaviour. A continuous mathematical model representing the PSD curve facilitates the quantification of particle breakage, which often takes place when granular soils are compressed or sheared. This paper proposes a simple and continuous PSD model for granular soils involving particle breakage. The model has two parameters and is able to represent different types of continuous PSD curves. It is found that one model parameter is closely related to the coefficient of nonuniformity (Cu) and the coefficient of curvature (Cc), while the other represents a characteristic particle diameter. A database of 53 granular soils with 154 varying PSD curves is analyzed to evaluate the performance of the proposed PSD model, as well as that of three other PSD models in the literature. The results show that the proposed model has improved overall performance and captures the typical trends in PSD evolution during particle breakage. In addition, the proposed model is also used for assessing the internal stability of 27 widely graded soils.
Tran, HN, Lee, C-K, Nguyen, TV & Chao, H-P 2018, 'Saccharide-derived microporous spherical biochar prepared from hydrothermal carbonization and different pyrolysis temperatures: synthesis, characterization, and application in water treatment', Environmental Technology, vol. 39, no. 21, pp. 2747-2760.
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© 2017, © 2017 Informa UK Limited, trading as Taylor & Francis Group. Three saccharides (glucose, sucrose, and xylose) were used as pure precursors for synthesizing spherical biochars (GB, SB, and XB), respectively. The two-stage synthesis process comprised: (1) the hydrothermal carbonization of saccharides to produce spherical hydrochar’ and (2) pyrolysis of the hydrochar at different temperatures from 300°C to 1200°C. The results demonstrated that the pyrolysis temperatures insignificantly affected the spherical morphology and surface chemistry of biochar. The biochar’ isoelectric point ranged from 2.64 to 3.90 (abundant oxygen-containing functionalities). The Brunauer–Emmett–Teller (BET)-specific surface areas (SBET) and total pore volumes (Vtotal) of biochar increased with the increasing pyrolysis temperatures. The highest SBET and Vtotal were obtained at a pyrolysis temperature of 900°C for GB (775 m2/g and 0.392 cm3/g), 500°C for SB (410 m2/g and 0.212 cm3/g), and 600°C for XB (426 m2/g and 0.225 cm3/g), respectively. The spherical biochar was a microporous material with approximately 71–98% micropore volume. X-ray diffraction results indicated that the biochar’ structure was predominantly amorphous. The spherical biochar possessed the graphite structure when the pyrolysis temperature was higher than 600°C. The adsorption capacity of GB depended strongly on the pyrolysis temperature. The maximum Langmuir adsorption capacities ((Formula presented.)) of 900GB exhibited the following selective order: phenol (2.332 mmol/g) > Pb2+ (1.052 mmol/g) > Cu2+ (0.825 mmol/g) > methylene green 5 (0.426 mmol/g) > acid red 1 (0.076 mmol/g). This study provides a simple method to prepare spherical biochar–a new and potential adsorbent for adsorbing heavy metals and aromatic contaminants.
Uddin, MN, Techato, K, Taweekun, J, Mofijur, M, Rasul, MG, Mahlia, TMI & Ashrafur, SM 2018, 'An Overview of Recent Developments in Biomass Pyrolysis Technologies', Energies, vol. 11, no. 11, pp. 3115-3115.
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Biomass is a promising sustainable and renewable energy source, due to its high diversity of sources, and as it is profusely obtainable everywhere in the world. It is the third most important fuel source used to generate electricity and for thermal applications, as 50% of the global population depends on biomass. The increase in availability and technological developments of recent years allow the use of biomass as a renewable energy source with low levels of emissions and environmental impacts. Biomass energy can be in the forms of biogas, bio-liquid, and bio-solid fuels. It can be used to replace fossil fuels in the power and transportation sectors. This paper critically reviews the facts and prospects of biomass, the pyrolysis process to obtain bio-oil, the impact of different pyrolysis technology (for example, temperature and speed of pyrolysis process), and the impact of various reactors. The paper also discusses different pyrolysis products, their yields, and factors affecting biomass products, including the present status of the pyrolysis process and future challenges. This study concluded that the characteristics of pyrolysis products depend on the biomass used, and what the pyrolysis product, such as bio-oil, can contribute to the local economy. Finally, more research, along with government subsidies and technology transfer, is needed to tackle the future challenges of the development of pyrolysis technology.
Vahedian, A, Shrestha, R & Crews, K 2018, 'Analysis of externally bonded Carbon Fibre Reinforced Polymers sheet to timber interface', Composite Structures, vol. 191, pp. 239-250.
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Vahedian, A, Shrestha, R & Crews, K 2018, 'Bond strength model for externally bonded FRP-to-timber interface', Composite Structures, vol. 200, pp. 328-339.
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Vahedian, A, Shrestha, R & Crews, K 2018, 'Experimental Investigation on the Effect of Bond Thickness on the Interface Behaviour of Fibre Reinforced Polymer Sheet Bonded to Timber', International Journal of Structural and Construction Engineering, vol. 12, no. 12, pp. 1157-1163.
Vakhshouri, B & Nejadi, S 2018, 'Effect of fiber reinforcing on instantaneous deflection of self-compacting concrete one-way slabs under early-age loading', Structural Engineering and Mechanics, vol. 67, no. 2, pp. 155-163.
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The Early-age construction loading and changing properties of concrete, especially in the multi-story structures can affect the slab deflection, significantly. Based on previously conducted experiment on eight simply-supported one-way slabs this paper investigates the effect of concrete type, fiber type and content, loading value, cracking moment, ultimate moment and applied moment on the instantaneous deflection of Self-Compacting Concrete (SCC) slabs. Two distinct loading levels equal to 30% and 40% of the ultimate capacity of the slab section were applied on the slabs at the age of 14 days. A wide range of the existing models of the effective moment of inertia which are mainly developed for conventional concrete elements, were investigated. Comparison of the experimental deflection values with predictions of the existing models shows considerable differences between the recorded and estimated instantaneous deflection of SCC slabs. Calculated elastic deflection of slabs at the ages of 14 and 28 days were also compared with the experimental deflection of slabs. Based on sensitivity analysis of the effective parameters, a new model is proposed and verified to predict the effective moment of inertia in SCC slabs with and without fiber reinforcing under two different loading levels at the age of 14 days.
Vakhshouri, B & Nejadi, S 2018, 'Instantaneous deflection of self-compacting and lightweight concrete slabs at early-age', Engineering Solid Mechanics, vol. 6, no. 2, pp. 143-154.
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© 2018 Growing Science Ltd. All rights reserved. This paper describes laboratory tests on twelve simply-supported one-way slabs including four lightweight concrete slabs in this study and previously conducted experiments on eight self-compacting reinforced concrete slabs subjected to loading at the age of 14 days. All slab were identical by dimensions of 3.8 m long supported on 3.5 m span, 400 mm wide, and 161 mm deep with 4N12 bars at an effective depth of 136 mm providing a reinforcement ratio of 0.008. After seven days moist-curing, the specimens were removed from the formworks and subjected to different values of the uniformly distributed loading including the self-weight of slabs. The mid-span deflection of slabs was recorded immediately after putting the loading blocks on the slabs. Despite close values of the compressive strength of the mixtures, the obtained results validate the effect of the concrete type on the instantaneous deflection of slabs. A wide range of existing models of the effective stiffness of reinforced concrete section were investigated to predict the instantaneous deflection of slabs. Majority of the models are developed for conventional concrete. Comparing the predicted and experimental results of mid-span deflection confirmed that the existing models are inadequate for lightly reinforced specimens such as slabs. New models are proposed and verified to predict the effective moment of inertia in the slabs with and without fiber reinforcing concretes.
Vakhshouri, B & Nejadi, S 2018, 'Prediction of compressive strength of self-compacting concrete by ANFIS models', Neurocomputing, vol. 280, pp. 13-22.
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© 2017 Elsevier Ltd. Many studies predict the compressive strength of conventional concrete from hardened characteristics; however, in the case of self-compacting concrete, these investigations are very rare. There is no study to predict the compressive strength of self-compacting concrete from mixture proportions and slump flow. This paper designs ANFIS models to establish relationship between the compressive strength as output, and slump flow and mixture proportions as input in eighteen combinations of input parameters. The applied dada is taken from 55 previously conducted experimental studies. Effect of each parameter on the compressive strength and its importance level in the developed model has been investigated. Based on the error size in each combination analysis, weighting factor and importance level of each parameter is evaluated to apply the correction factors to get the most optimized relationship. Obtained results indicate that the model including all input data (slump flow and mixture proportions) gives the best prediction of the compressive strength. Excluding the slump flow from combinations affects the prediction of compressive strength, considerably. However it's not as much as the effect of the maximum aggregate size and aggregate volume in the mixture design. In addition, different values of powder volume, aggregate volume and paste content in the mixture reveal different ascending and descending effects on the compressive strength.
Vakhshouri, B & Nejadi, S 2018, 'Review on the mixture design and mechanical properties of the lightweight concrete containing expanded polystyrene beads', Australian Journal of Structural Engineering, vol. 19, no. 1, pp. 1-23.
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© 2017, © 2017 Engineers Australia. Lightweight concrete containing expanded polystyrene beads (EPS-LWC) is frequently used in different structural and non-structural applications, since it was first developed about 60 years ago. However, effect of new materials and admixtures to improve its performance and strength are not investigated properly. A wide range of investigations about EPS-LWC since 1976, including the experimental data are evaluated. The collected data contain the information of curing methods, type of fine and coarse aggregates, mineral fillers, chemical admixtures and fibres in each experiment. In addition, the mixture proportions including the size and volume of EPS beads, density and compressive strength of the concrete are presented. Mechanical properties of EPS-LWC from 154 mixture design in 55 experimental programmes are also assessed. Utilising the experimental data, new models are developed and verified by the existing models of the mechanical properties of concrete. The existing models of the mechanical properties of LWC are also compared with those of the convention concrete.
Vakhshouri, B & Nejadi, S 2018, 'Sensitivity of concrete properties to compressive strength', Proceedings of the Institution of Civil Engineers - Engineering and Computational Mechanics, vol. 171, no. 1, pp. 29-44.
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Concrete is generally classified by compressive strength (CS) grade, which signifies the characteristic strength required. Other mechanical parameters of concrete are expressed in terms of the CS. Depending on design objectives, economic issues and available materials, normal-strength concrete, high-strength concrete (HSC) or ultra-high-strength concrete (UHSC) might be used in design and construction. Due to the non-linear nature of concrete, there is no proportional relation between properties of concrete, even in corresponding characteristics in different types of concrete. Although design codes and experimental investigations define different limits for HSC and UHSC and present relations for properties of various concrete classes, predicted values are sometimes significantly imprecise. This study broadly presents equations to estimate modulus of elasticity, splitting tensile strength and modulus of rupture for different CS classifications and validates them by comparing with empirical relations and international design codes' formulae.
Vakhshouri, B & Nejadi, S 2018, 'Size effect and age factor in mechanical properties of BST Light Weight Concrete', Construction and Building Materials, vol. 177, pp. 63-71.
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© 2018 Elsevier Ltd Replacement of whole or part of normal aggregates with Expanded Polystyrene (EPS) beads in the concrete mix is a reliable method to produce Light Weight Concrete (LWC) with considerable advantages. Due to modification effect on mechanical properties of LWC, it is important to examine whether all the assumed hypotheses about conventional concrete also are applicable for LWC structures. Based on an experimental program, this study investigates the effects of specimen size and shape on the compressive and tensile strength of this type of LWC. In this regard, cylinder specimens with 75 × 150, 100 × 200 and 150 × 300 mm dimensions and cube specimens with 100 and 150 mm dimensions were cast and cured in laboratory conditions. Compressive and tensile strengths were tested after 3, 7, 14, 21, 28, 56 and 91 days. The correlation factor between the compressive strength, tensile strength and the shape and size of specimens is evaluated also.
Van, HT, Nguyen, TMP, Thao, VT, Vu, XH, Nguyen, TV & Nguyen, LH 2018, 'Applying Activated Carbon Derived from Coconut Shell Loaded by Silver Nanoparticles to Remove Methylene Blue in Aqueous Solution', Water, Air, & Soil Pollution, vol. 229, no. 12.
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© 2018, Springer Nature Switzerland AG. This study developed a new adsorbent, specifically activated carbon-loaded silver nanoparticles (AgNPs-AC) by coating the silver nanoparticles (AgNPs) onto activated carbon (AC). The obtained AgNPs-AC were characterized by scanning electron microscopy (SEM), energy-dispersive spectrometry (EDS), Fourier transform infrared spectroscopy (FTIR), and Brunauer-Emmett-Teller (BET). The ability of AgNPs-AC to remove methylene blue (MB) was evaluated using different experimental factors, these being pH solution, contact time, adsorbent dose, and initial MB concentration. Results indicated that the highest adsorption capacity of MB onto AgNPs-AC was obtained when the AC was loaded onto AgNPs at the impregnation ratio of 0.5% w/w for AC and AgNPs. The best conditions in which AgNPs-AC could remove MB were as follows: pH 10, contact time lasting 120 min, and adsorbent dose being 250 mg/25 mL solution. In this scenario, the maximum adsorption capacity of MB onto AgNPs-AC was 172.22 mg/g. The adsorption isothermal equilibrium was well described by the Langmuir, Freundlich and Sips models. The Sips equations had the highest correlation coefficient value (R2 = 0.935). The pseudo-first-order and pseudo-second-order kinetic models agree well with the dynamic behavior of the adsorption of dye MB on AgNPs-AC.
Vo Hoang Nhat, P, Ngo, HH, Guo, WS, Chang, SW, Nguyen, DD, Nguyen, PD, Bui, XT, Zhang, XB & Guo, JB 2018, 'Can algae-based technologies be an affordable green process for biofuel production and wastewater remediation?', Bioresource Technology, vol. 256, pp. 491-501.
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© 2018 Elsevier Ltd Algae is a well-known organism that its characteristic is prominent for biofuel production and wastewater remediation. This critical review aims to present the applicability of algae with in-depth discussion regarding three key aspects: (i) characterization of algae for its applications; (ii) the technical approaches and their strengths and drawbacks; and (iii) future perspectives of algae-based technologies. The process optimization and combinations with other chemical and biological processes have generated efficiency, in which bio-oil yield is up to 41.1%. Through life cycle assessment, algae bio-energy achieves high energy return than fossil fuel. Thus, the algae-based technologies can reasonably be considered as green approaches. Although selling price of algae bio-oil is still high (about $2 L−1) compared to fossil fuel's price of $1 L−1, it is expected that the algae bio-oil's price will become acceptable in the next coming decades and potentially dominate 75% of the market.
Vo, T-D-H, Bui, X-T, Nguyen, D-D, Nguyen, V-T, Ngo, H-H, Guo, W, Nguyen, P-D, Nguyen, C-N & Lin, C 2018, 'Wastewater treatment and biomass growth of eight plants for shallow bed wetland roofs', Bioresource Technology, vol. 247, pp. 992-998.
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© 2017 Elsevier Ltd Wetland roof (WR) could bring many advantages for tropical cities such as thermal benefits, flood control, green coverage and domestic wastewater treatment. This study investigates wastewater treatment and biomass growth of eight local plants in shallow bed WRs. Results showed that removal rates of WRs were 21–28 kg COD ha−1 day−1, 9–13 kg TN ha−1 day−1 and 0.5–0.9 kg TP ha−1 day−1, respectively. The plants generated more biomass at lower hydraulic loading rate (HLR). Dry biomass growth was 0.4–28.1 g day−1 for average HLR of 247–403 m3 ha−1 day−1. Green leaf area of the plants was ranging as high as 67–99 m2 leaves per m2 of WR. In general, the descent order of Kyllinga brevifoliaRottb (WR8), Cyperus javanicus Houtt (WR5) and Imperata cylindrical (WR4) was suggested as effective vegetations in WR conditions in terms of wastewater treatment, dry biomass growth and green coverage ratio.
Volpin, F, Chekli, L, Phuntsho, S, Cho, J, Ghaffour, N, Vrouwenvelder, JS & Kyong Shon, H 2018, 'Simultaneous phosphorous and nitrogen recovery from source-separated urine: A novel application for fertiliser drawn forward osmosis', Chemosphere, vol. 203, pp. 482-489.
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© 2018 Elsevier Ltd Re-thinking our approach to dealing with waste is one of the major challenges in achieving a more sustainable society. However, it could also generate numerous opportunities. Specifically, in the context of wastewater, nutrients, energy and water could be mined from it. Because of its exceptionally high nitrogen (N) and phosphorous (P) concentration, human urine is particularly suitable to be processed for fertiliser production. In the present study, forward osmosis (FO) was employed to mine the P and N from human urine. Two Mg2+-fertilisers, i.e. MgSO4 and Mg(NO3)2 were selected as draw solution (DS) to dewater synthetic non-hydrolysed urine. In this process, the Mg2+ reverse salt flux (RSF) were used to recover P as struvite. Simultaneously, the urea was recovered in the DS as it is poorly rejected by the FO membrane. The results showed that, after concentrating the urine by 60%, about 40% of the P and 50% of the N were recovered. XRD and SEM – EDX analysis confirmed that P was precipitated as mineral struvite. If successfully tested on real urine, this process could be applied to treat the urine collected in urban areas e.g., high-rise building. After the filtration, the solid struvite could be sold for inland applications whereas the diluted fertiliser used for direct fertigation of green walls, parks or for urban farming. Finally, reduction in the load of N, P to the downstream wastewater treatment plant would also ensure a more sustainable urban water cycle.
Volpin, F, Gonzales, RR, Lim, S, Pathak, N, Phuntsho, S & Shon, HK 2018, 'GreenPRO: A novel fertiliser-driven osmotic power generation process for fertigation', Desalination, vol. 447, pp. 158-166.
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© 2018 This study introduces and describes GreenPRO, a novel concept involving fertiliser-driven osmotic energy generation via pressure retarded osmosis (PRO). The potential of GreenPRO was proposed for three objectives: (a) power generation, (b) water pressurisation for fertiliser-based irrigation, and (c) water treatment, as a holistic water-energy-food nexus process. Three pure agricultural fertilisers and two commercial blended fertiliser solutions were used as the draw solution and irrigation water as feed to test this concept for power generation. Theoretical thermodynamic simulation of the maximum extractable Gibbs energy, was first performed. After which, a series of bench-scale experiments were conducted to obtain realistic extractable energy data. The results showed that concentrated fertilisers potentially have 11 times higher energy than seawater. Even after accounting for the irreversibility losses due to constant pressure operation, the investigated pure fertilisers were found to have between 2.5 and 4.6 Wh/kg of energy. The outcomes from the flux and power density modelling were then validated with real experimental data. This study has successfully demonstrated that concentrated fertilisers can release a substantial amount of chemical potential energy when diluted for fertigation. This energy could be harnessed by transforming it into electric energy or pressure energy via PRO.
Vu, MT, Ansari, AJ, Hai, FI & Nghiem, LD 2018, 'Performance of a seawater-driven forward osmosis process for pre-concentrating digested sludge centrate: organic enrichment and membrane fouling', Environmental Science: Water Research & Technology, vol. 4, no. 7, pp. 1047-1056.
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This study demonstrated the potential of seawater-driven forward osmosis for enriching organic matter in digested sludge centrate.
Walker, RTR & Indraratna, B 2018, 'Moving Loads on a Viscoelastic Foundation with Special Reference to Railway Transition Zones', International Journal of Geomechanics, vol. 18, no. 11, pp. 04018145-04018145.
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Wang, C, Gao, B, Zhao, P, Yue, Q, Shon, HK & Yang, S 2018, 'The forward osmosis application: using the secondary effluent as makeup water for cooling water dilution', DESALINATION AND WATER TREATMENT, vol. 105, pp. 1-10.
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© 2018 Desalination Publications. All rights reserved. This study evaluated the feasibility of using the secondary effluent as makeup water for cooling water. The secondary effluent and the simulated cooling water were used as feed solution (FS) and draw solution (DS) in FO process. Ammonium bicarbonate was added into the simulated cooling water to promote the osmotic pressure. The tests were studied under different membrane orientations, temperatures and flow rates using both TFC-FO and CTA-FO membranes, and determined in terms of water flux, the permeate recovery and membrane fouling. The considerable permeate recovery (18.9% at 20 h) and reversible membrane fouling indicated that the feasibility of using FO for cooling water reuse. CTA- and TFC-PRO modes had higher initial water flux, but more significant flux decline compared to CTA- and TFC-FO modes. The optimal conditions were determined to be 25°C and 17.0 cm/s in which the water flux was highest. The results showed that water flux did not increase with the temperature when it was above than 30°C. The same situation occurred at the cross flow velocity above than 17 cm/s. The fouling of TFC membrane was serious after running 20 h, but it could be cleaned well by 1 h simple surface flushing and the water flux could restore nearly 93.8%.
Wang, C, Wang, Y, Zhou, J, Wang, M, Zhong, J & Duan, B 2018, 'Compensation method for distorted planar array antennas based on structural–electromagnetic coupling and fast Fourier transform', IET Microwaves, Antennas & Propagation, vol. 12, no. 6, pp. 954-962.
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© The Institution of Engineering and Technology 2017. Complex operating environment could introduce serious degradation to the electromagnetic performance of active phased array antenna in both the main lobe and sidelobe areas. The effective compensation techniques become the key for antenna to perform in reliable service condition. Therefore, a method combined coupled structural-electromagnetic model with two-dimensional fast Fourier transform for compensation is presented. A compensation calculation model of the excitation current for planar array is established accordingly, quantitatively expressing the relationship between the excitation current compensation and the structure error. The adjustment quantities of excitation amplitude and phase can be quickly obtained and implemented to recover a high-quality pattern from a distorted antenna in both the main lobe and sidelobe areas. Lastly, the simulation of the space-based array antenna is illustrated to compensate its property under the impact of space environment and heat power from its electric devices. Furthermore, an experiment platform of an X-band active phased array antenna with 32 × 24 elements is built and tested for the electromagnetic performance compensation. The simulation and experimental results show that the proposed method can guarantee the performance of the service antenna quickly and effectively in the whole observation area.
Wang, C-T, Huang, Y-S, Sangeetha, T, Chen, Y-M, Chong, W-T, Ong, H-C, Zhao, F & Yan, W-M 2018, 'Novel bufferless photosynthetic microbial fuel cell (PMFCs) for enhanced electrochemical performance', Bioresource Technology, vol. 255, pp. 83-87.
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Wang, D, Duan, Y, Yang, Q, Liu, Y, Ni, B-J, Wang, Q, Zeng, G, Li, X & Yuan, Z 2018, 'Free ammonia enhances dark fermentative hydrogen production from waste activated sludge', Water Research, vol. 133, pp. 272-281.
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© 2018 Elsevier Ltd Ammonium and/or free ammonia (the unionized form of ammonium) are generally thought to inhibit the activities of microbes involved in anaerobic digestion of waste activated sludge. It was found in this work, however, that the presence of ammonium (NH4+-N) largely enhanced dark fermentative hydrogen production from alkaline pretreated-sludge. With the increase of initial NH4+-N level from 36 to 266 mg/L, the maximal hydrogen production from alkaline (pH 9.5) pretreated-sludge increased from 7.3 to 15.6 mL per gram volatile suspended solids (VSS) under the standard condition. Further increase of NH4+-N to 308 mg/L caused a slight decrease of hydrogen yield (15.0 mL/g VSS). Experimental results demonstrated that free ammonia instead of NH4+-N was the true contributor to the enhancement of hydrogen production. It was found that the presence of free ammonia facilitated the releases of both extracellular and intracellular constituents, which thereby provided more substrates for subsequent hydrogen production. The free ammonia at the tested levels (i.e., 0–444 mg/L) did not affect acetogenesis significantly. Although free ammonia inhibited all other bio-processes, its inhibition to the hydrogen consumption processes (i.e., homoacetogenesis, methanogenesis, and sulfate-reducing process) was much severer than that to the hydrolysis and acidogenesis processes. Further investigations with enzyme analyses showed that free ammonia posed slight impacts on protease, butyrate kinase, acetate kinase, CoA-transferase, and [FeFe] hydrogenase activities but largely suppressed the activities of coenzyme F420, carbon monoxide dehydrogenase, and adenylyl sulfate reductase, which were consistent with the chemical analyses performed above.
Wang, D, He, C, Wu, C & Zhang, Y 2018, 'Mechanical behaviors of tension and relaxation of tongue and soft palate: Experimental and analytical modeling', Journal of Theoretical Biology, vol. 459, pp. 142-153.
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© 2018 This study is to characterize mechanical properties of uniaxial tension and stress relaxation responses of muscle tissues of tongue and soft palate. Uniaxial tension test and stress relaxation test on 39 fresh tissue samples from four five-month-old boars (65 ± 15 kg) are conducted. Firstly, the rationality of the samples’ dimension design and experimenal data measurement is validated by one-way ANOVA F-type test. Mechanical properties, including stress-strain relationship and stress relaxation characteristic, are then investigated in details to show the nonlinear behaviors of the tissue samples clearly. Finally, a constitutive model of representing the mechanical properties is formulated within the nonlinear integral representation framework proposed by Pinkin and Rogers, and corresponding material parameters are fitted to the experimental data based on the Levenberg-Marquardt minimization algorithm. The results of the fitting comparison prove that the formulated constitutive model can capture the observed nonlinear behaviors of the muscle tissue samples in both the axial tension and stress relaxation experiments.
Wang, D, Liu, B, Liu, X, Xu, Q, Yang, Q, Liu, Y, Zeng, G, Li, X & Ni, B-J 2018, 'How does free ammonia-based sludge pretreatment improve methane production from anaerobic digestion of waste activated sludge', Chemosphere, vol. 206, pp. 491-501.
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© 2018 Elsevier Ltd Previous studies reported that free ammonia (FA) pretreatment could improve methane production from anaerobic digestion of waste activated sludge (WAS) effectively. However, details of how FA pretreatment improves methane production are poorly understood. This study therefore aims to reveal the underlying mechanisms of FA pretreatment affecting anaerobic digestion of WAS through a series of batch tests using either real sludge or synthetic media as the digestion substrates at different pH values. At pH 8.5 level, with an increase of FA level from 18.5 to 92.5 mg/L (i.e., NH+ 4-N: 100–500 mg/L; pH 8.5) the maximum methane yield varied between 194.0 ± 3.9 and 196.9 ± 7.7 mL/g of VSS (25 °C, 1 atm). At pH 9.5 or 10 level, however, with an increase of initial FA level from 103.2 to 516.2 mg/L, the maximal methane yield increased linearly. The mechanism studies revealed that FA pretreatment at high levels not only accelerated the disintegration of WAS but also enhanced the biodegradability of WAS. Although pH in the digesters was adjusted to 7.0 ± 0.1, the high levels of NH+ 4-N added or released led to substantial levels of residual FA ranging from 4.4 to 11.6 mg/L. It was found that this level of FA inhibited homoacetogenesis and methanogenesis significantly, though hydrolysis, acidogenesis, and acetogenesis processes were unaffected largely. Further analyses showed that the inhibition constant of FA to substrate degradation was in the sequence of dextran > glucose > hydrogen > acetate, indicating the methanogenesis process was more sensitive to FA.
Wang, D, Liu, X, Zeng, G, Zhao, J, Liu, Y, Wang, Q, Chen, F, Li, X & Yang, Q 2018, 'Understanding the impact of cationic polyacrylamide on anaerobic digestion of waste activated sludge', Water Research, vol. 130, pp. 281-290.
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© 2017 Elsevier Ltd Previous investigations showed that cationic polyacrylamide (cPAM), a flocculant widely used in wastewater pretreatment and waste activated sludge dewatering, deteriorated methane production during anaerobic digestion of sludge. However, details of how cPAM affects methane production are poorly understood, hindering deep control of sludge anaerobic digestion systems. In this study, the mechanisms of cPAM affecting sludge anaerobic digestion were investigated in batch and long-term tests using either real sludge or synthetic wastewaters as the digestion substrates. Experimental results showed that the presence of cPAM not only slowed the process of anaerobic digestion but also decreased methane yield. The maximal methane yield decreased from 139.1 to 86.7 mL/g of volatile suspended solids (i.e., 1861.5 to 1187.0 mL/L) with the cPAM level increasing from 0 to 12 g/kg of total suspended solids (i.e., 0–236.7 mg/L), whereas the corresponding digestion time increased from 22 to 26 d. Mechanism explorations revealed that the addition of cPAM significantly restrained the sludge solubilization, hydrolysis, acidogenesis, and methanogenesis processes. It was found that ∼46% of cAPM was degraded in the anaerobic digestion, and the degradation products significantly affected methane production. Although the theoretically biochemical methane potential of cPAM is higher than that of protein and carbohydrate, only 6.7% of the degraded cPAM was transformed to the final product, methane. Acrylamide, acrylic acid, and polyacrylic acid were found to be the main degradation metabolites, and their amount accounted for ∼50% of the degraded cPAM. Further investigations showed that polyacrylic acid inhibited all the solubilization, hydrolysis, acidogenesis, and methanogenesis processes while acrylamide and acrylic acid inhibited the methanogenesis significantly.
Wang, D, Shuai, K, Xu, Q, Liu, X, Li, Y, Liu, Y, Wang, Q, Li, X, Zeng, G & Yang, Q 2018, 'Enhanced short-chain fatty acids production from waste activated sludge by combining calcium peroxide with free ammonia pretreatment', Bioresource Technology, vol. 262, pp. 114-123.
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© 2018 Elsevier Ltd This study reported a new low-cost and high-efficient combined method of CaO2 + free ammonia (FA) pretreatment for sludge anaerobic fermentation. Experimental results showed that the optimal short-chain fatty acids (SCFA) yield of 338.6 mg COD/g VSS was achieved when waste activated sludge (WAS) was pretreated with 0.05 g/g VSS of CaO2 + 180 mg/L of FA for 3 d, which was 2.5-fold of that from CaO2 pretreatment and 1.5-fold of that from FA pretreatment. The mechanism investigations exhibited that the CaO2 + FA could provided more biodegradable substrates, this combination accelerated the disintegration of sludge cells, which thereby providing more organics for subsequent SCFA production. It was also found that the combination of CaO2 and FA inhibited the specific activities of hydrolytic microbes, SCFA producers, and methanogens to some extents, but its inhibition to methanogens was much severer than that to the other two types of microbes.
Wang, Q, Song, K, Hao, X, Wei, J, Pijuan, M, van Loosdrecht, MCM & Zhao, H 2018, 'Evaluating death and activity decay of Anammox bacteria during anaerobic and aerobic starvation', Chemosphere, vol. 201, pp. 25-31.
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© 2018 Elsevier Ltd The decreased activity (i.e. decay) of anaerobic ammonium oxidation (Anammox) bacteria during starvation can be attributed to death (i.e. decrease in the amount of viable bacteria) and activity decay (i.e. decrease in the specific activity of viable bacteria). Although they are crucial for the operation of the Anammox process, they have never been comprehensively investigated. This study for the first time experimentally assessed death and activity decay of the Anammox bacteria during 84 days’ starvation stress based on ammonium removal rate, Live/Dead staining and fluorescence in-situ hybridization. The anaerobic and aerobic decay rates of Anammox bacteria were determined as 0.015 ± 0.001 d−1 and 0.028 ± 0.001 d−1, respectively, indicating Anammox bacteria would lose their activity more quickly in the aerobic starvation than in the anaerobic starvation. The anaerobic and aerobic death rates of Anammox bacteria were measured at 0.011 ± 0.001 d−1 and 0.025 ± 0.001 d−1, respectively, while their anaerobic and aerobic activity decay rates were determined at 0.004 ± 0.001 d−1 and 0.003 ± 0.001 d−1, respectively. Further analysis revealed that death accounted for 73 ± 4% and 89 ± 5% of the decreased activity of Anammox bacteria during anaerobic and aerobic starvations, and activity decay was only responsible for 27 ± 4% and 11 ± 5% of the decreased Anammox activity, respectively, over the same starvation periods. These deeply shed light on the response of Anammox bacteria to the starvation stress, which would facilitate operation and optimization of the Anammox process.
Wang, Q, Sun, J, Song, K, Zhou, X, Wei, W, Wang, D, Xie, G-J, Gong, Y & Zhou, B 2018, 'Combined zero valent iron and hydrogen peroxide conditioning significantly enhances the dewaterability of anaerobic digestate', Journal of Environmental Sciences, vol. 67, pp. 378-386.
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© 2017 The importance of enhancing sludge dewaterability is increasing due to the considerable impact of excess sludge volume on disposal costs and on overall sludge management. This study presents an innovative approach to enhance dewaterability of anaerobic digestate (AD) harvested from a wastewater treatment plant. The combination of zero valent iron (ZVI, 0–4.0 g/g total solids (TS)) and hydrogen peroxide (HP, 0–90 mg/g TS) under pH 3.0 significantly enhanced the AD dewaterability. The largest enhancement of AD dewaterability was achieved at 18 mg HP/g TS and 2.0 g ZVI/g TS, with the capillary suction time reduced by up to 90%. Economic analysis suggested that the proposed HP and ZVI treatment has more economic benefits in comparison with the classical Fenton reaction process. The destruction of extracellular polymeric substances and cells as well as the decrease of particle size were supposed to contribute to the enhanced AD dewaterability by HP + ZVI conditioning.
Wang, Q, Wei, W, Liu, S, Yan, M, Song, K, Mai, J, Sun, J, Ni, B-J & Gong, Y 2018, 'Free Ammonia Pretreatment Improves Degradation of Secondary Sludge During Aerobic Digestion', ACS Sustainable Chemistry & Engineering, vol. 6, no. 1, pp. 1105-1111.
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Aerobic digestion is commonly used to achieve secondary sludge reduction in the small-size wastewater treatment plants. Nevertheless, secondary sludge degradation is usually restricted by the slow hydrolysis rate and low degradable percentage of secondary sludge. Here, we present an innovative approach using pretreatment of free ammonia (FA, i.e. NH3), a renewable chemical from wastewater, to improve the degradation of secondary sludge during aerobic digestion. The secondary sludge was degraded by 36 ± 4% (volatile solids (VS) basis) within 15 days of aerobic digestion while being pretreated at 300 mg NH3-N/L (pH 9.0; total ammonia nitrogen = 800 mg N/L) for 24 h, whereas only 23 ± 3% (VS basis) of the secondary sludge without FA pretreatment was degraded over the same period. Similarly, the production of inorganic nitrogen also increased from 27 ± 2 to 38 ± 2 mg N/g VS after implementing FA pretreatment, corroborating the idea that degradation of secondary sludge was effectively improved by FA pretreatment. Further analysis by model revealed that the improved hydrolysis rate and increased degradable percentage of secondary sludge were responsible for the enhanced sludge degradation in aerobic digestion. It was also found that FA pretreatment would produce an aerobic digestate with a better stability and dewaterability, as indicated by the lower degradable percentage of digestate and the decrease of capillary suction time from 38 ± 1 to 34 ± 1 s, respectively. Economic analysis indicates that the FA pretreatment approach would be economically favorable when the sludge transport and disposal cost is higher than $40/wet tone.
Wang, Q, Ye, X, Wang, S, Sloan, SW & Sheng, D 2018, 'Use of photo-based 3D photogrammetry in analysing the results of laboratory pressure grouting tests', Acta Geotechnica, vol. 13, no. 5, pp. 1129-1140.
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This paper presents a non-destructive, low-cost, photo-based, 3D reconstruction technique for characterizing geo-materials with irregular shapes of a relatively large size. After being validated against two traditional volume measurement methods, namely the vernier caliper method and the fluid displacement method for regular and irregular shapes, respectively, 3D photogrammetry was used to analyse the grout bulbs formed in laboratory pressure grouting tests. The reconstructed 3D mesh model of the sample provides accurate and detailed 3D vertex data, which allowed the volume, densification efficiency and bleeding behaviour of the grout bulbs to be analysed. Comparing the bulb section views at different grouting pressures also offers an intuitive observation of the grout development and propagation process. Moreover, the 3D vertex data and surface area included in the model are of great importance in validating numerical predictions of the pressure grouting process and analysing the interface shear resistance of grouted soil nails or anchors. Compared to existing approaches, the new 3D photogrammetry method possesses several key advantages: (a) it does not require expensive, specialized equipment; (b) samples are not destroyed or modified during testing; (c) it allows to reconstruct objects of various scales and (d) the software is public domain. Therefore, the adoption of this 3D photogrammetry method will facilitate research in the pressure grouting process and can be extended to other problems in geotechnical engineering.
Wang, S, Wu, W, Peng, C, He, X & Cui, D 2018, 'Numerical integration and FE implementation of a hypoplastic constitutive model', Acta Geotechnica, vol. 13, no. 6, pp. 1265-1281.
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Wang, S, Wu, W, Yin, Z, Peng, C & He, X 2018, 'Modelling the time‐dependent behaviour of granular material with hypoplasticity', International Journal for Numerical and Analytical Methods in Geomechanics, vol. 42, no. 12, pp. 1331-1345.
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SummaryThis paper presents a constitutive model for time‐dependent behaviour of granular material. The model consists of 2 parts representing the inviscid and viscous behaviour of granular materials. The inviscid part is a rate‐independent hypoplastic constitutive model. The viscous part is represented by a rheological model, which contains a high‐order term denoting the strain acceleration. The proposed model is validated by simulating some element tests on granular soils. Our model is able to model not only the non‐isotach behaviour but also the 3 creep stages, namely, primary, secondary, and tertiary creep, in a unified way.
Wang, W, Wu, C & Li, J 2018, 'Numerical Simulation of Hybrid FRP-Concrete-Steel Double-Skin Tubular Columns under Close-Range Blast Loading', Journal of Composites for Construction, vol. 22, no. 5, pp. 04018036-04018036.
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© 2018 American Society of Civil Engineers. Hybrid fiber-reinforced polymer (FRP)-concrete-steel double-skin tubular columns (DSTCs) are a new form of composite columns that consist of an outer FRP tube and an inner steel tube, with the space between them filled with concrete. Although many studies have been conducted on the hybrid DSTCs, no studies have been conducted on their behavior under blast loading. This study presents the results of a numerical study on the behavior of hybrid DSTCs under close-in blast loading. Numerical models of hybrid DSTCs are developed using finite-element code LS-DYNA, and the reliability of the developed models are validated with available testing results. With the validated models, numerical simulations are carried out to investigate the structural responses of hybrid DSTCs under blast loading. The simulation results indicate that the hybrid DSTCs behave in a ductile manner under blast loading. The outer FRP tube can effectively provide confinement to the infilled concrete, and the inner steel tube plays a key role in resisting the blast loading. Detailed parametric analyses are conducted to investigate the influences of different parameters on the blast behavior of hybrid DSTCs. The blast resistance capacities of the hybrid DSTCs, concrete-filled steel tubes (CFSTs), and concrete-filled double-skin steel tubes (CFDSTs) are compared and discussed based on the simulation results.
Wang, W, Wu, C, Liu, Z & Si, H 2018, 'Compressive behavior of ultra-high performance fiber-reinforced concrete (UHPFRC) confined with FRP', Composite Structures, vol. 204, pp. 419-437.
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© 2018 Elsevier Ltd This study presents the results of an experimental program on the compressive behavior of fiber reinforced polymer (FRP) confined ultra-high performance fiber-reinforced concrete (UHPFRC). A total of 38 specimens were prepared and tested under axial compression. In addition to FRP confined UHPFRC, FRP confined ultra-high performance concrete without fiber addition (UHPC), high strength concrete (HSC), and normal strength concrete (NSC) were also tested to investigate their comparative performances. The test results indicate that the FRP confined UHPFRC can exhibit ductile behavior if sufficient FRP confinement is provided. However, due to their ultra-high strength as well as the unique microstructure, FRP confined UHPFRC is likely to exhibit more brittle behavior than FRP confined NSC and HSC. Compared to FRP confined NSC and HSC, the confinement efficiency is less for FRP confined UHPFRC. Sudden stress reduction or stress fluctuations are observed shortly after the initial peak stress (axial stress at the first peak point) for FRP confined UHPFRC. Based on the confinement level, the stress-strain behavior of FRP confined UHPFRC may experience a second ascending branch or a continuous descending branch after the sudden stress reduction or stress fluctuations. The influences of FRP layers, FRP types, and fiber addition on the compressive behavior of FRP confined UHPFRC are observed to be significant. Moreover, existing stress-strain models available for FRP confined UHPFRC are evaluated by using a database collected in this study.
Wang, Y, Fan, S, Wu, S, Wang, C, Huang, Z & Zhang, L 2018, 'In Situ Synthesis and Unprecedented Electrochemical Performance of Double Carbon Coated Cross-Linked Co3O4', ACS Applied Materials & Interfaces, vol. 10, no. 49, pp. 42372-42379.
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© 2018 American Chemical Society. Improving the structural stability and the electron/ion diffusion rate across whole electrode particles is crucial for transition metal oxides as next-generation anodic materials in lithium-ion batteries. Herein, we report a novel structure of double carbon-coated Co 3 O 4 cross-linked composite, where the Co 3 O 4 nanoparticle is in situ covered by nitrogen-doped carbon and further connected by carbon nanotubes (Co 3 O 4 NP@NC@CNTs). This double carbon-coated Co 3 O 4 NP@NC@CNTs framework not only endows a porous structure that can effectively accommodate the volume changes of Co 3 O 4, but also provides multidimensional pathways for electronic/ionic diffusion in and among the Co 3 O 4 NPs. Electrochemical kinetics investigation reveals a decreased energy barrier for electron/ion transport in the Co 3 O 4 NP@NC@CNTs, compared with the single carbon-coated Co 3 O 4 NP@NC. As expected, the Co 3 O 4 NP@NC@CNT electrode exhibits unprecedented lithium storage performance, with a high reversible capacity of 1017 mA h g -1 after 500 cycles at 1 A g -1 , and a very good capacity retention of 75%, even after 5000 cycles at 15 A g -1 . The lithiation/delithiation process of Co 3 O 4 NP@NC@CNTs is dominated by the pseudocapacitive behavior, resulting in excellent rate performance and durable cycle stability.
Wang, Y, Wang, R, Zhou, Y, Huang, Z, Wang, J & Jiang, L 2018, 'Directional Droplet Propulsion on Gradient Boron Nitride Nanosheet Grid Surface Lubricated with a Vapor Film below the Leidenfrost Temperature', ACS Nano, vol. 12, no. 12, pp. 11995-12003.
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© Copyright 2018 American Chemical Society. Controlled propulsion of liquid droplets on a solid surface offers important applications in various fields, including fog harvesting, heat transfer, microfluidics, and microdevice technologies. The propulsion of the liquid droplet is realized only if the driven force exceeds the resistance force. Sometimes the directional propulsion of droplets only takes place at the Leidenfrost state to achieve enough lubrication for a vapor cushion. The thick vapor cushions levitate liquid droplets to reduce resistance force. However, it is still challenging to reduce the vapor cushion thickness and simultaneously realize the directional droplet's motion, especially below the Leidenfrost temperature. Here, a structurally hydrophobic boron nitride nanosheet (BNNS) grid surface was constructed with a two-direction topographical gradient, i.e., the perpendicular altitude gradient and the horizontal density gradient. The polar nature of the B-N bonds results in intrinsic hydrophilicity of the boron nitride layer, which increases the Leidenfrost point and facilitates wetting even at high temperature. Much thinner vapor-lubricating layers are competent in the droplet's directional motion below the Leidenfrost temperature of the BNNS grid surface because the air gap trapped within boron nitride nanosheet grids acts as a part of the lubrication layer.
Wang, Y, Zhao, J, Wang, D, Liu, Y, Wang, Q, Ni, B-J, Chen, F, Yang, Q, Li, X, Zeng, G & Yuan, Z 2018, 'Free nitrous acid promotes hydrogen production from dark fermentation of waste activated sludge', Water Research, vol. 145, pp. 113-124.
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© 2018 Elsevier Ltd Simultaneous sludge fermentation and nitrite removal is an effective approach to enhance nutrient removal from low carbon-wastewater. It was found in this work that the presence of nitrite largely promoted hydrogen production from acidic fermentation of waste activated sludge (WAS). The results showed that with an increase of nitrite from 0 to 250 mg/L, the maximal hydrogen yield increased from 8.5 to 15.0 mL/g VSS at pH 5.5 fermentation and 8.1–13.0 mL/g VSS at pH 6 fermentation. However, the maximal hydrogen yield from WAS fermentation at pH 8 remained almost constant (2.9–3.7 mL/g VSS) when nitrite was in the range of 0–250 mg/L. Further analyses revealed that free nitrous acid (FNA) rather than nitrite was the major contributor to the promotion of hydrogen yield. The mechanism investigations showed that FNA not only accelerated the disruption of sludge cells but also promoted the biodegradability of organics released, thereby provided more biodegradable substrates for subsequent hydrogen production. Although FNA inhibited activities of all microbes involved in the anaerobic fermentation, its inhibitions to hydrogen consumers were much severer than those to hydrolytic microorganisms and hydrogen producers. Further investigations with microbial community showed that FNA increased the abundances of hydrogen producers (e.g., Citrobacter sp.) and denitrifiers (e.g., Dechloromonas sp.), but reduced the abundances of hydrogen consumers (e.g., Clostridium_aceticum). This work demonstrated for the first time that FNA in WAS fermentation systems enhanced hydrogen production. The findings obtained expand the application field of FNA and may provide supports for sustainable operation of wastewater treatment plants.
Wang, Z, Wu, S, Huang, Y, Huang, S, Shi, S, Cheng, X & Huang, R 2018, 'Experimental investigation on spray, evaporation and combustion characteristics of ethanol-diesel, water-emulsified diesel and neat diesel fuels', Fuel, vol. 231, pp. 438-448.
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© 2018 This paper explored the spray and combustion characteristics of ethanol-diesel (E10), water-emulsified diesel (W10) and neat diesel (D100), especially micro-explosion of E10 and W10. The experiments were conducted in a constant volume combustion chamber under cold (383 K, 0% O2), evaporating (900 K, 0% O2) and combustion (900 K, 21% O2) conditions. Results showed that the spray expansion capacities of E10 and W10 under cold condition were much weaker than that of D100 due to the larger viscosity of emulsified diesels. Under evaporating condition, the spray volume of E10, W10 and D100 increased by 59%, 34% and 21% respectively comparing with cold spray volume. The higher increasing rates of E10 and W10 were mainly due to the micro-explosion effects of ethanol and water contents. Under combustion condition, the integrated natural flame luminosity (INFL) demonstrated that the ethanol content could accelerate the oxidation of soot, while the water content could prohibit soot generation. Therefore, both ethanol- and water-emulsified diesels could inhibit the soot emission, causing lower final residual soot emission of E10 and W10 than that of D100 by 21% and 39% respectively. Moreover, the flame lift-off length (LOL) and flame spread velocity showed that the effects of micro-explosion in E10 and W10 are different. The micro-explosion in ethanol occurred earlier, which enhanced the reaction rate in upstream flame and reduced the LOL. However, the micro-explosion in W10 occurred later, which enhanced the combustion rate in downstream flame.
Wattanapornprom, R, Valerio, DNR, Pansuk, W, Nguyen, TN & Pheinsusom, P 2018, 'Fire Resistance Performance of Reactive Powder Concrete Columns', Engineering Journal, vol. 22, no. 4, pp. 67-82.
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© 2018, Chulalongkorn University. All rights reserved. This paper experimentally explores the fire resistance of reactive powder concrete (RPC) columns with varying steel and polypropylene (PP) fiber content. RPC is a concrete composition with the highest developed compressive strength and is incorporated with steel fibers that can improve the tensile strength and ductility of RPC structures. The fire resistance of RPC structures, however, has been disputed by engineers and researchers. Four columns with different weight contents of fiber were tested in fire for 30 and 60 minutes with a load applied afterwards. Then, the performance of RPC columns in elevated temperature was investigated, focusing on spalling depth, failure mechanism in fiber and residual strength. The results showed that increasing the volume fraction of steel fiber or the presence of PP fiber improves the fire resistance of the columns. However, the columns lost significant cross-sectional area and load capacity. With the knowledge that this research would provide, a better understanding for making decisions could be developed.
Wei, D, Ngo, HH, Guo, W, Xu, W, Du, B & Wei, Q 2018, 'Partial nitrification granular sludge reactor as a pretreatment for anaerobic ammonium oxidation (Anammox): Achievement, performance and microbial community', Bioresource Technology, vol. 269, pp. 25-31.
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Partial nitrification granular sludge was successfully cultivated in a sequencing batch reactor as a pretreatment for anaerobic ammonium oxidation (Anammox) through shortening settling time. After 250-days operation, the effluent NH4+-N and NO2--N concentrations were average at 277.5 and 280.5 mg/L with nitrite accumulation rate of 87.8%, making it as an ideal influent for Anammox. Simultaneous free ammonia (FA) and free nitrous acid (FNA) played major inhibitory roles on the activity of nitrite oxidizing bacteria (NOB). The MLSS and SVI30 of partial nitrification reactor were 14.6 g/L and 25.0 mL/g, respectively. Polysaccharide (PS) and protein (PN) amounts in extracellular polymeric substances (EPS) from granular sludge were about 1.3 and 2.8 times higher than from seed sludge. High-throughput pyrosequencing results indicated that Nitrosomonas affiliated to the ammonia oxidizing bacteria (AOB) was the predominant group with a proportion of 24.1% in the partial nitrification system.
Wei, D, Ngo, HH, Guo, W, Xu, W, Du, B, Khan, MS & Wei, Q 2018, 'Biosorption performance evaluation of heavy metal onto aerobic granular sludge-derived biochar in the presence of effluent organic matter via batch and fluorescence approaches', Bioresource Technology, vol. 249, pp. 410-416.
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In present study, the biosorption process of Cu(II) onto aerobic granular sludge-derived biochar was evaluated in the absence and presence of effluent organic matter (EfOM) by using batch and fluorescence approaches. It was found that EfOM gave rise to enhancement of Cu(II) removal efficiency onto biochar, and the sorption data were better fitted with pseudo-second order model and Freundlich equation, in despite of the absence and presence of EfOM. According to excitation-emission matrix (EEM), EfOM was mainly comprised by humic-like substances and fulvic-like substances and their intensities were reduced in the addition of biochar and Cu(II) from batch biosorption process. Synchronous fluorescence spectra coupled to two-dimensional correlation spectroscopy (2D-COS) further implied that a successive fluorescence quenching was observed in various EfOM fractions with the increasing Cu(II) concentration. Moreover, fulvic-like fraction was more susceptibility than other fractions for fluorescence quenching of EfOM.
Wei, W, Cai, Z, Fu, J, Xie, G-J, Li, A, Zhou, X, Ni, B-J, Wang, D & Wang, Q 2018, 'Zero valent iron enhances methane production from primary sludge in anaerobic digestion', Chemical Engineering Journal, vol. 351, pp. 1159-1165.
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© 2018 Elsevier B.V. This study proposed a novel zero valent iron (ZVI) technology to enhance anaerobic methane production from primary sludge in the anaerobic digester and to improve the dewaterability of digested sludge for the first time. Compared to the control test without ZVI, the anaerobic digester with ZVI at all levels (1, 4 and 20 g/L) played a driving role in anaerobic methane production from primary sludge. The maximal biochemical methane production of 439 ± 5 L CH4/kg VS was achieved at ZVI of 4 g/L, while only 345 ± 2 L CH4/kg VS (volatile solids) was produced in the case of no-ZVI dosage, representing a relative increase of 26.9 ± 0.1%. It was also found that ZVI addition would produce an anaerobically digested sludge with a better dewaterability, as indicated by the decrease of the normalized capillary suction time from 100 to 63 ∼ 89 s, respectively. Model based analysis revealed that the enhanced methane production from primary sludge was due to an increase in both hydrolysis rate and biochemical methane potential of primary sludge. Economic analysis demonstrated that ZVI technology was economically favorable.
Wei, W, Li, A, Ma, F, Pi, S, Yang, J, Wang, Q & Ni, B 2018, 'Simultaneous sorption and reduction of Cr(VI) in aquatic system by microbial extracellular polymeric substances from Klebsiella sp. J1', Journal of Chemical Technology & Biotechnology, vol. 93, no. 11, pp. 3152-3159.
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AbstractBACKGROUNDCr(VI) is being increasingly used in a variety of fields, including electroplating, metallurgy, pigment synthesis and leather tanning. The possible application of a microbial extracellular polymeric substance (EPS) from Klebsiella sp. J1 with abundant functional groups in remediating Cr(VI) pollution in water system was demonstrated.RESULTSThe maximum biosorption capacity of EPS for Cr(VI) was found to be 53.3 mg g−1 at an EPS dose of 1.5 g L−1, which was better than the majority of reported biosorbents. The adsorption of EPS for Cr(VI) was a spontaneous and endothermic process. The removal mechanism of Cr(VI) in aquatic environments was explored qualitatively and quantitatively by Zeta‐potential meter, X‐ray photoelectron spectrometer (XPS) as well as Fourier transform infrared spectrometer. The superior Cr(VI) removal performance was attributed mainly to Cr(VI) adsorption on EPS via chelation and ion‐exchange sorption, and the efficient reduction (82.3%) of Cr(VI) to Cr(III) by benzenoid amine (–NH–) on EPS, followed by generated Cr(III) immobilization on the surface of EPS via surface physical sorption and chelation, which might control the reaction rate of Cr(VI) removal process.CONCLUSIONThe removal of Cr(VI) by EPS from Klebsiella sp. J1 was attributed mainly to simultaneous sorption and reduction of Cr(VI) by EPS. The results demonstrated that EPS from Klebsiella sp. J1 has great potential in treating Cr(VI)‐contaminated water. © 2018 Society of Chemical Industry
Wei, W, Li, A, Pi, S, Wang, Q, Zhou, L, Yang, J, Ma, F & Ni, B-J 2018, 'Synthesis of Core–Shell Magnetic Nanocomposite Fe3O4@ Microbial Extracellular Polymeric Substances for Simultaneous Redox Sorption and Recovery of Silver Ions as Silver Nanoparticles', ACS Sustainable Chemistry & Engineering, vol. 6, no. 1, pp. 749-756.
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Microbial extracellular polymeric substance (EPS) is a complex high molecular weight compound secreted from many organisms. In this work, magnetic nanocomposite Fe3O4@EPS of Klebsiella sp. J1 were first synthesized for silver ions (Ag+) wastewater remediation, which synergistically combined the advantages of the easy separation property of magnetic Fe3O4 nanoparticles and the superior adsorption capacity of EPS of Klebsiella sp. J1. The physical and chemical properties of Fe3O4@EPS were analyzed comprehensively. Fe3O4@EPS exhibited the well-defined core-shell structure (size 50 nm) with high magnetic (79.01 emu g-1). Batch adsorption experiments revealed that Fe3O4@EPS achieved high Ag+ adsorption capacity (48 mg g-1), which was also much higher than many reported adsorbents. The optimal solution pH for Ag+ adsorption was around 6.0, with the sorption process followed pseudo-second-order kinetics. Ag+ adsorption on Fe3O4@EPS was mainly attributed to the reduction of Ag+ to silver nanoparticles (AgNPs) by benzenoid amine (-NH-), accompanied by the chelation between Ag+ and hydroxyl groups, ion exchange between Ag+ and Mg2+ and K+, and physical electrostatic sorption. The repeated adsorption-desorption experiments showed a good recycle performance of Fe3O4@EPS. This study has great importance for demonstrating magnetic Fe3O4@EPS as potential adsorbent to remove Ag+ from contaminated aquatic systems.
Wei, W, Wang, Q, Zhang, L, Laloo, A, Duan, H, Batstone, DJ & Yuan, Z 2018, 'Free nitrous acid pre-treatment of waste activated sludge enhances volatile solids destruction and improves sludge dewaterability in continuous anaerobic digestion', Water Research, vol. 130, pp. 13-19.
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© 2017 Elsevier Ltd Previous work has demonstrated that pre-treatment of waste activated sludge (WAS) with free nitrous acid (FNA i.e. HNO2) enhances the biodegradability of WAS, identified by a 20–50% increase in specific methane production in biochemical methane potential (BMP) tests. This suggests that FNA pre-treatment would enhance the destruction of volatile solids (VS) in an anaerobic sludge digester, and reduce overall sludge disposal costs, provided that the dewaterability of the digested sludge is not negatively affected. This study experimentally evaluates the impact of FNA pre-treatment on the VS destruction in anaerobic sludge digestion and on the dewaterability of digested sludge, using continuously operated bench-scale anaerobic digesters. Pre-treatment of full-scale WAS for 24 h at an FNA concentration of 1.8 mg NN/L enhanced VS destruction by 17 ± 1% (from 29.2 ± 0.9% to 34.2 ± 1.1%) and increased dewaterability (centrifuge test) from 12.4 ± 0.4% to 14.1 ± 0.4%. Supporting the VS destruction data, methane production increased by 16 ± 1%. Biochemical methane potential tests indicated that the final digestate stability was also improved with a lower potential from FNA treated digestate. Further, a 2.1 ± 0.2 log improvement in pathogen reduction was also achieved. With inorganic solids representing 15–22% of the full-scale WAS used, FNA pre-treatment resulted in a 16–17% reduction in the volume of dewatered sludge for final disposal. This results in significantly reduced costs as assessed by economic analysis.
Wei, W, Zhou, X, Wang, D, Sun, J, Nghiem, LD & Wang, Q 2018, 'Free Ammonia Pretreatment to Enhance Biodegradation of Anaerobically Digested Sludge in Post Aerobic Digestion', ACS Sustainable Chemistry & Engineering, vol. 6, no. 9, pp. 11836-11842.
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Copyright © 2018 American Chemical Society. In wastewater treatment plants (WWTPs), sludge reduction was implemented via sequential anaerobic-aerobic digestion. However, the performance of post aerobic digestion for anaerobically digested sludge (ADS) is limited. Free ammonia (FA)-based pretreatment technology is proposed in this study as an innovative method to enhance the degradation efficiency of post aerobic digestion for ADS. Pretreatment using FA at >440 mg NH3-N/L for 24 h significantly increased ADS solubilization. The highest solubilization was reached at 1030 mg NH3-N/L, which (0.12 mg COD/mg VS) is 6 times that (0.02 mg COD/mg VS) of no treatment. The batch experiments of post aerobic digestion demonstrated unpretreated ADS over the 8 days post aerobic digestion was degraded by 18.4%, whereas 31.3-33.6% of the pretreated ADS with FA at 440-1030 mg NH3-N/L was degraded, representing a relative increase of 70-83%. Accordingly, inorganic nitrogen production increased in a similar way. Model analysis results revealed the enhanced ADS degradation was because of the increase in both hydrolysis rate and degradable percentage of ADS. Capillary suction time (CST) tests demonstrated FA-based pretreatment was able to generate ADS with greater dewaterability, as revealed by the decline of normalized CST from 77 s for ADS without pretreatment to 63-74 s for ADS with FA pretreatment at 65-1030 NH3-N/L, with the best ADS dewaterability at 1030 mg NH3-N/L of FA. Economic assessment showed that this FA pretreatment technology could be economically favorable.
Wickham, R, Xie, S, Galway, B, Bustamante, H & Nghiem, LD 2018, 'Anaerobic digestion of soft drink beverage waste and sewage sludge', Bioresource Technology, vol. 262, pp. 141-147.
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© 2018 Soft drink beverage waste (BW) was evaluated as a potential substrate for anaerobic co-digestion with sewage sludge to increase biogas production. Results from this study show that the increase in biogas production is proportional to the increase in organic loading rate (OLR) rate due to BW addition. The OLR increase of 86 and 171% corresponding to 10 and 20% BW by volume in the feed resulted in 89 and 191% increase in biogas production, respectively. Under a stable condition, anaerobic co-digestion with BW did not lead to any significant impact on digestate quality (in terms of COD removal and biosolids odour) and biogas composition. The results suggest that existing nutrients in sewage sludge can support an increase in OLR by about 2 kg COD/m3/d from a carbon rich substrate such as soft drink BW without inhibition or excessive impact on subsequent handling of the digestate.
Woo, YC, Kim, Y, Yao, M, Tijing, LD, Choi, J-S, Lee, S, Kim, S-H & Shon, HK 2018, 'Hierarchical Composite Membranes with Robust Omniphobic Surface Using Layer-By-Layer Assembly Technique', Environmental Science & Technology, vol. 52, no. 4, pp. 2186-2196.
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© 2018 American Chemical Society. In this study, composite membranes were fabricated via layer-by-layer (LBL) assembly of negatively charged silica aerogel (SiA) and 1H,1H,2H,2H-perfluorodecyltriethoxysilane (FTCS) on a polyvinylidene fluoride phase inversion membrane and interconnecting them with positively charged poly(diallyldimethylammonium chloride) (PDDA) via electrostatic interaction. The results showed that the PDDA-SiA-FTCS coated membrane had significantly enhanced the membrane structure and properties. New trifluoromethyl and tetrafluoroethylene bonds appeared at the surface of the coated membrane, which led to lower surface free energy of the composite membrane. Additionally, the LBL membrane showed increased surface roughness. The improved structure and property gave the LBL membrane an omniphobic property, as indicated by its good wetting resistance. The membrane performed a stable air gap membrane distillation (AGMD) flux of 11.22 L/m2 h with very high salt rejection using reverse osmosis brine from coal seam gas produced water as feed with the addition of up to 0.5 mM SDS solution. This performance was much better compared to those of the neat membrane. The present study suggests that the enhanced membrane properties with good omniphobicity via LBL assembly make the porous membranes suitable for long-term AGMD operation with stable permeation flux when treating challenging saline wastewater containing low surface tension organic contaminants.
Wu, B, Wu, D, Gao, W & Song, C 2018, 'Time-variant random interval natural frequency analysis of structures', Journal of Sound and Vibration, vol. 414, pp. 284-298.
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© 2017 Elsevier Ltd This paper presents a new robust method namely, unified interval Chebyshev-based random perturbation method, to tackle hybrid random interval structural natural frequency problem. In the proposed approach, random perturbation method is implemented to furnish the statistical features (i.e., mean and standard deviation) and Chebyshev surrogate model strategy is incorporated to formulate the statistical information of natural frequency with regards to the interval inputs. The comprehensive analysis framework combines the superiority of both methods in a way that computational cost is dramatically reduced. This presented method is thus capable of investigating the day-to-day based time-variant natural frequency of structures accurately and efficiently under concrete intrinsic creep effect with probabilistic and interval uncertain variables. The extreme bounds of the mean and standard deviation of natural frequency are captured through the embedded optimization strategy within the analysis procedure. Three particularly motivated numerical examples with progressive relationship in perspective of both structure type and uncertainty variables are demonstrated to justify the computational applicability, accuracy and efficiency of the proposed method.
Wu, D, Gao, W, Hui, D, Gao, K & Li, K 2018, 'Stochastic static analysis of Euler-Bernoulli type functionally graded structures', Composites Part B: Engineering, vol. 134, pp. 69-80.
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In this study, the uncertain static analysis of Euler-Bernoulli type functionally graded structures with probabilistic parameters is investigated. An effective, yet efficient, computational method is proposed within the framework of the finite element analysis (FEA). Various uncertain systematic parameters, which are including the material properties, dimensions of structural elements, as well as applied forces, can be simultaneously incorporated within the unified analysis framework. By meticulously combining the matrix perturbation theory with Tayler's series expansion, both first and second order statistical characteristics (i.e., mean and variances) of the concerned structural responses can be robustly estimated for practically motivated functionally graded structures. In order to illustrate the applicability, accuracy, as well as efficiency of the proposed computational approach, three distinctive functionally graded engineering structures are thoroughly investigated by comparing the performance of the proposed approach with the simulation based reference method. Furthermore, complementary parametric investigations are also conducted to explore the sensitivity of the Euler-Bernoulli type functionally graded structures against various degrees of uncertainty of each considered uncertain system parameter.
Wu, D, Liu, A, Huang, Y, Huang, Y, Pi, Y & Gao, W 2018, 'Dynamic analysis of functionally graded porous structures through finite element analysis', Engineering Structures, vol. 165, pp. 287-301.
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A finite element method (FEM) analysis framework is introduced for the free and forced vibration analyses of functionally graded porous (FGP) beam type structures. Within the proposed computational scheme, both Euler-Bernoulli and Timoshenko beam theories have been adopted such that the explicit stiffness and mass matrices for 2-D FGP beam element through both beam theories are explicitly expressed. Both Young's modulus and material density of the FGP beam element are simultaneously considered as grading through the thickness of the beam. The material constitutive law of a FGP beam is governed by the typical open-cell metal foam. Furthermore, the damping effects of the FGP structures can be also incorporated within the proposed FEM analysis framework through the Rayleigh damping model. Consequently, the proposed approach establishes a more unified analysis framework which can investigate simple FGP beams as well as complex FGP structural systems involving mixture of different materials. In order to demonstrate the applicability, accuracy, as well as the efficiency of the proposed computational scheme, both FGP beams and frame structures with multiple porosities have been rigorously explored.
Wu, D, Liu, A, Huang, Y, Huang, Y, Pi, Y & Gao, W 2018, 'Mathematical programming approach for uncertain linear elastic analysis of functionally graded porous structures with interval parameters', Composites Part B: Engineering, vol. 152, pp. 282-291.
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© 2018 Elsevier Ltd This paper investigates the non-deterministic linear elastic problem of bar-type functionally graded porous (FGP) structures with uncertain-but-bounded system parameters. For achieving a robust uncertainty analysis framework, a non-stochastic structural analysis for FGP engineering structures, whose system inputs possess interval uncertainties, through the framework of Finite Element Method (FEM) is proposed. The Timoshenko beam theory is adopted to incorporate the shear effect, so a more generalized uncertain static analysis of FGP structures can be anticipated. Various uncertain system input parameters, for example, the Young's moduli, the dimensions of the cross-sections, the porosities, as well as the applied loads can be simultaneously incorporated within the proposed method. To demonstrate the capability of the proposed approach, two distinctive numerical examples have been thoroughly investigated. Additional numerical experiments have also been conducted to further explore various effects of uncertainties of different system inputs acting on the overall FGP structural responses.
Wu, H, Fan, J, Zhang, J, Ngo, HH & Guo, W 2018, 'Large-scale multi-stage constructed wetlands for secondary effluents treatment in northern China: Carbon dynamics', Environmental Pollution, vol. 233, pp. 933-942.
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Multi-stage constructed wetlands (CWs) have been proved to be a cost-effective alternative in the treatment of various wastewaters for improving the treatment performance as compared with the conventional single-stage CWs. However, few long-term full-scale multi-stage CWs have been performed and evaluated for polishing effluents from domestic wastewater treatment plants (WWTP). This study investigated the seasonal and spatial dynamics of carbon and the effects of the key factors (input loading and temperature) in the large-scale seven-stage Wu River CW polishing domestic WWTP effluents in northern China. The results indicated a significant improvement in water quality. Significant seasonal and spatial variations of organics removal were observed in the Wu River CW with a higher COD removal efficiency of 64-66% in summer and fall. Obvious seasonal and spatial variations of CH4 and CO2 emissions were also found with the average CH4 and CO2 emission rates of 3.78-35.54 mg m-2 d-1 and 610.78-8992.71 mg m-2 d-1, respectively, while the higher CH4 and CO2 emission flux was obtained in spring and summer. Seasonal air temperatures and inflow COD loading rates significantly affected organics removal and CH4 emission, but they appeared to have a weak influence on CO2 emission. Overall, this study suggested that large-scale Wu River CW might be a potential source of GHG, but considering the sustainability of the multi-stage CW, the inflow COD loading rate of 1.8-2.0 g m-2 d-1 and temperature of 15-20 °C may be the suitable condition for achieving the higher organics removal efficiency and lower greenhouse gases (GHG) emission in polishing the domestic WWTP effluent. The obtained knowledge of the carbon dynamics in large-scale Wu River CW will be helpful for understanding the carbon cycles, but also can provide useful field experience for the design, operation and management of multi-stage CW treatments.
Wu, H, Zhang, J, Guo, W, Liang, S & Fan, J 2018, 'Secondary effluent purification by a large-scale multi-stage surface-flow constructed wetland: A case study in northern China', Bioresource Technology, vol. 249, pp. 1092-1096.
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Assessment of treatment performance in the large-scale constructed wetland (CW) for secondary effluent purification remains limited. The aim of this case study was to therefore to investigate the long-term treatment capacity of organics and ammonium pollutants in a large-scale multi-stage surface-flow (SF) CW fed with secondary effluents from the wastewater treatment plants (WWTPs) in northern China. The results for two-and-half-year study period indicated that the water quality parameters including chemical oxygen demand (COD) and ammonium (NH4+-N) met the Chinese Grade III of Environmental Quality Standards. The mass reductions of COD and NH4+-N were 53% (4032 kg ha-1 y-1) and 72% (511 kg ha-1 y-1), respectively. However, there was a significant positive correlation between influent loads and treatment performance. The optimal loading of 2.5 g m-2 d-1 for COD and 0.3 g m-2 d-1 for NH4+-N could be recommended for designing the sustainable large-scale multi-stage SF CW wastewater treatments.
Wu, W-H, Thomas, P, Hume, P & Jin, J 2018, 'Effective Conversion of Amide to Carboxylic Acid on Polymers of Intrinsic Microporosity (PIM-1) with Nitrous Acid', Membranes, vol. 8, no. 2, pp. 20-20.
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Carboxylate-functionalised polymers of intrinsic microporosity (C-PIMs) are highly desirable materials for membrane separation applications. The recently reported method to afford C-PIMs was via an extensive base hydrolysis process requiring 360 h. Herein, a novel and effective method to convert PIM-CONH₂ to C-PIM using nitrous acid was studied. The chemical structure of C-PIM was characterised by ¹H NMR, 13C NMR, FTIR, elemental analysis, UV-Vis, TGA and TGA-MS. Complete conversion from amide to carboxylic acid groups was confirmed. Decarboxylation of C-PIM was also successfully studied by TGA-MS for the first time, with a loss of m/z 44 amu (CO₂) observed at the first degradation stage. TGA also revealed decreased thermal stability of C-PIM relative to PIM-CONH₂ under both N₂ and air atmosphere. Gel permeation chromatography (GPC) analysis showed continuous molecular weight degradation of C-PIM with extended reaction time. Aromatic nitration was also observed as a side reaction in some cases.
Wu, Y, Fang, J, He, Y & Li, W 2018, 'Crashworthiness of hierarchical circular-joint quadrangular honeycombs', Thin-Walled Structures, vol. 133, pp. 180-191.
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© 2018 Elsevier Ltd The new hierarchical circular-joint quadrangular honeycomb is proposed by iteratively replacing the edge-junctions of regular honeycomb with a circular joint. Firstly, the nonlinear finite element analysis is performed through LS-DYNA and the results are validated by experimental data. Then, analytical solutions to crushing resistance of the hierarchical honeycomb are obtained based on the Simplified Super Folding Element (SSFE) theory. The results between the numerical and analytical method are in good agreement, which indicates that the analytical solutions are reliable. Furthermore, parametric studies of the first and second hierarchical order structures are conducted numerically. The results show that the specific energy absorption of the first and second-order hierarchical honeycomb is improved by up to 81.8%, 115.3% respectively compared with the regular honeycomb. It is also found that the out-of-plane crashworthiness performance of the second-order hierarchical honeycomb can be enhanced by increasing relative density. However, the peak crushing force would also increase with the increase in relative density. The findings of this study show that the proposed hierarchical honeycomb is a structural configuration with high energy absorption capacity.
Wu, Y, Li, W, Fang, J & Lan, Q 2018, 'Multi-objective robust design optimization of fatigue life for a welded box girder', Engineering Optimization, vol. 50, no. 8, pp. 1252-1269.
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© 2017 Informa UK Limited, trading as Taylor & Francis Group. To reduce the scatter of fatigue life for welded structures, a robust optimization method is presented in this study based on a dual surrogate modelling and multi-objective particle swam optimization algorithm. Considering the perturbations of material parameters and environment variables, the mean and standard deviation of fatigue life are fitted using dual surrogate modelling and selected as the objective function to be minimized. As an example, a welded box girder is presented to reduce the standard deviation of fatigue life. A set of non-dominated solutions is produced through a multi-objective particle swam optimization algorithm. A cognitive approach is used to select the optimum solution from the Pareto sets. As a comparative study, traditional single objective optimizations are also presented in this study. The results reduced the standard deviation of the fatigue life by about 16.5%, which indicated that the procedure improved the robustness of the fatigue life.
Xie, K, Fu, Q, Webley, PA & Qiao, GG 2018, 'MOF Scaffold for a High‐Performance Mixed‐Matrix Membrane', Angewandte Chemie International Edition, vol. 57, no. 28, pp. 8597-8602.
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AbstractA novel composite membrane consisting of an interconnected MOF scaffold coated with cross‐linked poly(ethylene glycol) (PEG) has been developed. As a result of its unique structure, the membrane shows an exceptional 18‐fold permeability enhancement as compared to pristine PEG membranes, without compromising the selectivity. This performance is unattainable with current mixed‐matrix membranes (MMMs). Our optimized membrane has a permeability of 2700 Barrer with a CO2/N2 selectivity of 35, which surpasses the latest Robeson upper bound.
Xie, K, Fu, Q, Webley, PA & Qiao, GG 2018, 'MOF Scaffold for a High‐Performance Mixed‐Matrix Membrane', Angewandte Chemie, vol. 130, no. 28, pp. 8733-8738.
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AbstractA novel composite membrane consisting of an interconnected MOF scaffold coated with cross‐linked poly(ethylene glycol) (PEG) has been developed. As a result of its unique structure, the membrane shows an exceptional 18‐fold permeability enhancement as compared to pristine PEG membranes, without compromising the selectivity. This performance is unattainable with current mixed‐matrix membranes (MMMs). Our optimized membrane has a permeability of 2700 Barrer with a CO2/N2 selectivity of 35, which surpasses the latest Robeson upper bound.
Xie, K, Fu, Q, Xu, C, Lu, H, Zhao, Q, Curtain, R, Gu, D, Webley, PA & Qiao, GG 2018, 'Continuous assembly of a polymer on a metal–organic framework (CAP on MOF): a 30 nm thick polymeric gas separation membrane', Energy & Environmental Science, vol. 11, no. 3, pp. 544-550.
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A 30 nm thick polymeric membrane on a metal–organic framework substrate was fabricated via a bottom-up approach, exhibiting excellent CO2/N2 separation performance.
Xie, M, Luo, W, Guo, H, Nghiem, LD, Tang, CY & Gray, SR 2018, 'Trace organic contaminant rejection by aquaporin forward osmosis membrane: Transport mechanisms and membrane stability', Water Research, vol. 132, pp. 90-98.
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We investigated transport mechanisms of trace organic contaminants (TrOCs) through aquaporin thin-film composite forward osmosis (FO) membrane, and membrane stability under extreme conditions with respect to TrOC rejections. Morphology and surface chemistry of the aquaporin membrane were characterised to identify the incorporation of aquaporin vesicles into membrane active layer. Pore hindrance model was used to estimate aquaporin membrane pore size as well as to describe TrOC transport. TrOC transport mechanisms were revealed by varying concentration and type of draw solutions. Experimental results showed that mechanism of TrOC transport through aquaporin-embedded FO membrane was dominated by solution-diffusion mechanism. Non-ionic TrOC rejections were molecular-weight dependent, suggesting steric hindrance mechanisms. On the other hand, ionic TrOC rejections were less sensitive to molecular size, indicating electrostatic interaction. TrOC transport through aquaporin membrane was also subjected to retarded forward diffusion where reverse draw solute flux could hinder the forward diffusion of feed TrOC solutes, reducing their permeation through the FO membrane. Aquaporin membrane stability was demonstrated by either heat treatment or ethanol solvent challenges. Thermal stability of the aquaporin membrane was manifested as a relatively unchanged TrOC rejection before and after the heat treatment challenge test. By contrast, ethanol solvent challenge resulted in a decrease in TrOC rejection, which was evident by the disappearance of the lipid tail of the aquaporin vesicles from infrared spectrum and a notable decrease in the membrane pore size.
Xie, S, Higgins, MJ, Bustamante, H, Galway, B & Nghiem, LD 2018, 'Current status and perspectives on anaerobic co-digestion and associated downstream processes', Environmental Science: Water Research & Technology, vol. 4, no. 11, pp. 1759-1770.
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Anaerobic co-digestion (AcoD) has the potential to utilise spare digestion capacity at existing wastewater treatment plants to simultaneously enhance biogas production by digesting organic rich industrial waste and achieve sustainable organic waste management.
Xu, B, Ahmed, MB, Zhou, JL, Altaee, A, Xu, G & Wu, M 2018, 'Graphitic carbon nitride based nanocomposites for the photocatalysis of organic contaminants under visible irradiation: Progress, limitations and future directions', Science of The Total Environment, vol. 633, pp. 546-559.
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© 2018 Elsevier B.V. Graphitic carbon nitride (g-C3N4) has drawn great attention recently because of its visible light response, suitable energy band gap, good redox ability, and metal-free nature. g-C3N4 can absorb visible light directly, therefore has better photocatalytic ability under solar irradiation and is more energy-efficient than TiO2. However, pure g-C3N4 still has the drawbacks of insufficient light absorption, small surface area and fast recombination of photogenerated electron and hole pairs. This review summarizes the recent progress in the development of g-C3N4 nanocomposites to photodegrade organic contaminants in water. Element doping especially by potassium has been reported to be an efficient method to promote the degradation efficacy. In addition, compound doping improves photodegradation performance of g-C3N4, especially Ag3PO4-g-C3N4 which can completely degrade 10 mg L−1 of methyl orange under visible light irradiation in 5 min, with the rate constant (k) as high as 0.236 min−1. Moreover, co-doping enhances the photodegradation rate of multiple contaminants while immobilization significantly improves catalyst stability. Most of g-C3N4 composites possess high reusability enabling their practical applications in wastewater treatment. Furthermore, environmental conditions such as solution pH, reaction temperature, dissolved oxygen, and dissolved organic matter all have important effects on the photocatalytic ability of g-C3N4 photocatalyst. Future work should focus on the synthesis of innovative g-C3N4 nanocomposites for the efficient removal of organic contaminants in water and wastewater.
Xu, KJ, Liu, MD, Indraratna, B & Horpibulsuk, S 2018, 'Explicit stress–strain equations for modeling frictional materials', Marine Georesources & Geotechnology, vol. 36, no. 6, pp. 722-734.
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Xu, Q, Liu, X, Fu, Y, Li, Y, Wang, D, Wang, Q, Liu, Y, An, H, Zhao, J, Wu, Y, Li, X, Yang, Q & Zeng, G 2018, 'Feasibility of enhancing short-chain fatty acids production from waste activated sludge after free ammonia pretreatment: Role and significance of rhamnolipid', Bioresource Technology, vol. 267, pp. 141-148.
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© 2018 Elsevier Ltd This study reported a new, renewable and high-efficient strategy for anaerobic fermentation, i.e., using free ammonia (FA) to pretreat waste activated sludge (WAS) for 1 d and then combining with rhamnolipid (RL), by which the short-chain fatty acids (SCFA) production was remarkably improved. Experimental results showed the maximal SCFA production of 324.7 ± 13.9 mg COD/g VSS was achieved at 62.6 mg FA/L pretreatment combined with 0.04 g RL/g TSS, which was respectively 5.95-fold, 1.63-fold and 1.41-fold of that from control, FA pretreatment and RL pretreatment. Mechanism investigations revealed that FA + RL enhanced sludge solubilization and hydrolysis, providing more organics for subsequent SCFA production. It was also found that the combined method inhibited acidogenesis and methanogenesis, but the inhibition to methanogenesis was much severer than that to acidogenesis. Finally, the feasibility of NH4+-N and PO3−4-P, released in fermentation liquor, being recovered as magnesium ammonium phosphate (MAP) was confirmed.
Xu, Q, Liu, X, Wang, D, Wu, Y, Wang, Q, Liu, Y, Li, X, An, H, Zhao, J, Chen, F, Zhong, Y, Yang, Q & Zeng, G 2018, 'Free ammonia-based pretreatment enhances phosphorus release and recovery from waste activated sludge', Chemosphere, vol. 213, pp. 276-284.
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© 2018 Elsevier Ltd The recovery of phosphorus from waste activated sludge (WAS) was usually at low levels due to low phosphorus release. This study presents a novel, cost-effective and eco-friendly pretreatment method, e.g., using free ammonia (FA) to pretreat WAS, to enhance the phosphorus release from WAS. Experimental results showed that the phosphorus release from WAS was significantly increased after FA pretreatment at up to 189.4 mg NH3-N L−1 for 24 h, under which the released PO43--P (i.e. 101.6 ± 6.7 mg L−1) was higher than that pH 9 (i.e. 62.6 ± 4.54 mg L−1) and control (without pH and FA pretreatment) (i.e. 15.1 ± 1.86 mg L−1). More analysis revealed that the FA induced improvement in phosphorus release could be attributed to the disintegration of extracellular polymeric substances (EPS) and cell envelope of sludge cells. Moreover, the released phosphorus recovered as magnesium ammonium phosphate (MAP) was confirmed. The findings reported may guide engineers to develop an economic and practical strategy to enhance resources and energy recovery from WAS.
Xu, Q, Liu, X, Zhao, J, Wang, D, Wang, Q, Li, X, Yang, Q & Zeng, G 2018, 'Feasibility of enhancing short-chain fatty acids production from sludge anaerobic fermentation at free nitrous acid pretreatment: Role and significance of Tea saponin', Bioresource Technology, vol. 254, pp. 194-202.
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© 2018 Elsevier Ltd Short-chain fatty acids (SCFA), raw substrates for biodegradable plastic production and preferred carbon source for biological nutrients removal, can be produced from anaerobic fermentation of waste activated sludge (WAS). This paper reports a new, high-efficient and eco-friendly strategy, i.e., using free nitrous acid (FNA) pretreatment combined with Tea saponin (TS), to enhance SCFA production. Experimental results showed 0.90 mg/L FNA pretreatment and 0.05 g/g total suspended solids TS addition (FNA + TS) not only significantly increased SCFA production to 315.3 ± 8.8 mg COD/g VSS (5.52, 1.76 and 1.93 times higher than that from blank, solo FNA and solo TS, respectively) but also shortened fermentation time to 4 days. Mechanism investigations revealed that FNA pretreatment combined with TS cause a positive synergetic effect on sludge solubilization, resulting in more release of organics. It was also found that the combination benefited hydrolysis and acidogenesis processes but inhibited the methanogenesis.
Xu, R & Fatahi, B 2018, 'Geosynthetic-reinforced cushioned piles with controlled rocking for seismic safeguarding', Geosynthetics International, vol. 25, no. 6, pp. 561-581.
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In this study, a cushioned pile foundation reinforced with geosynthetics is proposed to protect buildings and foundations from seismic energy. This composite foundation utilises piles to control foundation settlement while the geosynthetic-reinforced cushion modifies the dynamic structural characteristics and the load transfer mechanism. The seismic performance of this proposed foundation system is evaluated numerically using FLAC3D software. A fully coupled nonlinear dynamic analysis was conducted in the time domain. The variation of shear modulus corresponding to shear strains in the soil is used to simulate the dynamic behaviour of the soil, while the influence of the plasticity index is also captured. The soil-geosynthetic interface utilises the Mohr-Coulomb failure criterion to capture possible sliding and pull-out of the reinforcement layers. 3D numerical predictions of the tensile forces mobilised in the geosynthetic layers, the shear forces, the lateral deformations and maximum and residual inter-storey drifts in the building are presented and discussed in this paper, as well as how the shear forces and bending moments develop in the piles, and the lateral pile displacements. The results indicate that the proposed geosynthetic-reinforced cushioned pile foundation can provide design engineers with an alternative solution for safeguarding buildings constructed on soft soils in earthquake-prone regions.
Xu, S, Wu, C, Liu, Z & Li, J 2018, 'Numerical study of ultra-high-performance steel fibre–reinforced concrete columns under monotonic push loading', Advances in Structural Engineering, vol. 21, no. 8, pp. 1234-1248.
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A finite element model is developed to investigate the behaviour of ultra-high-performance steel fibre–reinforced concrete columns under combined axial compression and horizontal monotonic push loading. The effects of steel fibre content, axial compression ratio, reinforcement ratio (or rebar ratio), stirrup ratio and shear span ratio on the structural behaviour of ultra-high-performance steel fibre–reinforced concrete columns are investigated in detail. The numerical model shows good agreement in bond–slip behaviour of specimens based on CEB model results and numerical results, and such behaviour should be taken into consideration in engineering practice. The results indicate that the developed finite element model could predict the structural behaviour and failure mode of ultra-high-performance steel fibre–reinforced concrete columns effectively. It is found that the reinforcement ratio, axial compression ratio, shear span ratio and volume fraction of steel fibre have a great influence on both the structural behaviour and failure modes of specimens.
Xu, T, Castel, A & Gilbert, RI 2018, 'On the Reliability of Serviceability Calculations for Flexural Cracked Reinforced Concrete Beams', Structures, vol. 13, pp. 201-212.
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Under in-service conditions, beams and slabs in reinforced concrete structures are almost always cracked, as the tensile strength of the concrete is low. Due to the irreversible reduction in overall stiffness resulting from cracking and the residual deflection after unloading, the structural response is load path dependent. In this paper, an existing average moment of inertia model and Monte Carlo simulation (MCS) are adopted to take into account the effect of historical cracking damage on the reliability of serviceability calculations for reinforced concrete (RC) members. The suitability of the average moment of inertia model for reliability analysis is verified by considering experimental tests on a total of eleven reinforced concrete beams. The errors associated with both the effective and average moment of inertia predicted by the model are calibrated using the experimental data. By using the proposed approach to account for the various sources of uncertainty in reinforced concrete beams, the quantitative loss in the short-term and long-term serviceability reliability of a cracked reinforced concrete beam was calculated. The results confirm that the effect of historical cracking damage on short-term serviceability reliability should be taken into account when the deflection induced by historical loading is larger than the deflection limitation. Light historical damage has no influence on the short-term serviceability reliability, although it affects the probability density distribution of the deflection. However, in the long-term serviceability reliability analysis, even when the historical damage is light, the long-term serviceability reliability index is decreased as the cracking damage to the stiffness affects the time-dependent deflection. Additionally, the later a damaging load is applied to a reinforced concrete beam, the less is the influence of cracking damage on the long-term serviceability reliability.
Xu, T, Huang, J, Castel, A, Zhao, R & Yang, C 2018, 'Influence of steel–concrete bond damage on the dynamic stiffness of cracked reinforced concrete beams', Advances in Structural Engineering, vol. 21, no. 13, pp. 1977-1989.
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In this article, experiments focusing at the influence of steel–concrete bond damage on the dynamic stiffness of cracked reinforced concrete beams are reported. In these experiments, the bond between concrete and reinforcing bar was damaged using appreciate flexural loads. The static stiffness of cracked reinforced concrete beam was assessed using the measured load–deflection response under cycles of loading and unloading, and the dynamic stiffness was analyzed using the measured natural frequencies with and without sustained loading. Average moment of inertia model (Castel et al. model) for cracked reinforced beams by taking into account the respective effect of bending cracks (primary cracks) and the steel–concrete bond damage (interfacial microcracks) was adopted to calculate the static load–deflection response and the natural frequencies of the tested beams. The experimental results and the comparison between measured and calculated natural frequencies show that localized steel–concrete bond damage does not influence remarkably the dynamic stiffness and the natural frequencies both with and without sustained loading applied. Castel et al. model can be used to calculate the dynamic stiffness of cracked reinforced concrete beam by neglecting the effect of interfacial microcracks.
Xu, T, Zhu, L, Castel, A & Gilbert, RI 2018, 'Assessing Immediate and Time-Dependent Instantaneous Stiffness of Cracked Reinforced Concrete Beams Using Residual Cracks', Journal of Structural Engineering, vol. 144, no. 4, pp. 04018022-04018022.
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Xu, Y, Chen, X, Yuan, Z & Ni, B-J 2018, 'Modeling of Pharmaceutical Biotransformation by Enriched Nitrifying Culture under Different Metabolic Conditions', Environmental Science & Technology, vol. 52, no. 5, pp. 2835-2843.
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© 2018 American Chemical Society. Pharmaceutical removal could be significantly enhanced through cometabolism during nitrification processes. To date, pharmaceutical biotransformation models have not considered the formation of transformation products associated with the metabolic type of microorganisms. Here we report a comprehensive model to describe and evaluate the biodegradation of pharmaceuticals and the formation of their biotransformation products by enriched nitrifying cultures. The biotransformation of parent compounds was linked to the microbial processes via cometabolism induced by ammonium-oxidizing bacteria (AOB) growth, metabolism by AOB, cometabolism by heterotrophs (HET) growth, and metabolism by HET in the model framework. The model was calibrated and validated using experimental data from pharmaceutical biodegradation experiments at realistic levels, taking two pharmaceuticals as examples, i.e., atenolol and acyclovir. Results demonstrated the good predictive performance of the established biotransformation model under different metabolic conditions, as well as the reliability of the established model in predicting different pharmaceutical biotransformations. The linear positive correlation between ammonia oxidation rate and pharmaceutical degradation rate confirmed the major role of cometabolism induced by AOB in the pharmaceutical removal. Dissolved oxygen was also revealed to be capable of regulating the pharmaceutical biotransformation cometabolically, and the substrate competition between ammonium and pharmaceuticals existed especially at high ammonium concentrations.
Yan, T, Ye, Y, Ma, H, Zhang, Y, Guo, W, Du, B, Wei, Q, Wei, D & Ngo, HH 2018, 'A critical review on membrane hybrid system for nutrient recovery from wastewater', Chemical Engineering Journal, vol. 348, pp. 143-156.
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© 2018 Wastewater has been investigated as a source for nutrient recovery for two reasons: firstly it contains a high concentration of nutrients; and secondly, it exists in large quantities. Recovering nutrient from wastewater can minimize the environmental footprint of wastewater treatment; simultaneously, the recovered nutrient can be added to fertilizer production to ensure food security. The membrane technique integrated with chemical and biological processes as a membrane hybrid system is a promising method to recover nutrient from wastewater since the membrane can enrich nutrient. It can subsequently increase the technical and economic feasibility of the nutrient recovery process. For this reason, this paper comprehensively and critically reviews the current state of the membrane hybrid system for nutrient recovery from wastewater. Membrane hybrid systems consisting of membrane-based hybrid systems and membrane bioreactor (MBR)-based hybrid systems are explained with reference to their general features, such as mechanisms and processes. Furthermore the advantages and challenges of the membrane hybrid systems are compared as well as their economic feasibility. Future research avenues into membrane hybrid systems are suggested and what can the system more accessible.
Yang, G, Wang, D, Yang, Q, Zhao, J, Liu, Y, Wang, Q, Zeng, G, Li, X & Li, H 2018, 'Effect of acetate to glycerol ratio on enhanced biological phosphorus removal', Chemosphere, vol. 196, pp. 78-86.
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© 2017 Elsevier Ltd Enhanced biological phosphorus removal (EBPR) is a sustainable and promising technology for phosphorus removal from wastewater. The efficiency of this technology, however, is often discounted due to the insufficient carbon sources in influent. In this work, the effect of acetate to glycerol ratio on the EBPR performance was evaluated. The experimental results showed when the ratio of acetate to glycerol decreased from 100/0% to 50/50%, the EBPR efficiency increased from 90.2% to 96.2%. Further decrease of acetate to glycerol ratio to 0/100% decreased the efficiency of EBPR to 30.5%. Fluorescence in situ hybridization analysis demonstrated appropriate increase of glycerol benefited to increase the relative abundance of phosphate accumulating organisms. Further investigation revealed the proper addition of glycerol increased the amount of polyhydroxyalkanoates synthesis, and then produced sufficient energy for oxic luxury phosphorus in the subsequent oxic phase.
Yang, Y-C, Wang, P-H, Tsai, Y-T & Ong, H-C 2018, 'Influences of feedstock and plasma spraying parameters on the fabrication of tubular solid oxide fuel cell anodes', Ceramics International, vol. 44, no. 7, pp. 7824-7830.
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Yao, J, Sun, Y, Wang, Y, Fu, Q, Xiong, Z & Liu, Y 2018, 'Magnet-induced aligning magnetorheological elastomer based on ultra-soft matrix', Composites Science and Technology, vol. 162, pp. 170-179.
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A novel magnet-induced aligning magnetorheological elastomer (MIMRE) based on ultra-soft polymeric matrix was prepared through an innovative synthetic approach, enables the magnetic particles to mobile and align in elastomer matrix under magnetic field at room temperature. The effect of polymeric matrix modulus on the formation of MIMRE was investigated in detail. It was found that the MIMRE showed excellent magnetorheological (MR) effect, and the absolute and relative MR effect was of 3.61 MPa and 17,286%, respectively. The relative MR effect of magnetorheological elastomer was almost 100 times higher than that of elastomers reported in previous literature. In addition, the application of MIMRE in actuators and self-healing materials was evaluated. The present MIMRE thus opens up a new avenue for the improvement of MR effect of magnetorheological elastomer, while avoiding the use of conventional plasticizer (e.g. silicon oil).
Yao, M, Woo, YC, Tijing, LD, Choi, J-S & Shon, HK 2018, 'Effects of volatile organic compounds on water recovery from produced water via vacuum membrane distillation', Desalination, vol. 440, pp. 146-155.
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© 2017 Elsevier B.V. Membrane distillation (MD) has great potentials to treat produced water in energy industries. However, volatile organic compounds (VOCs) existing in the produced water added in the fracking process can hinder the treatment process regarding two aspects: permeate quality and MD flux performance. To address this challenge, this study aims to systematically study the effects of the VOCs on the MD permeation performance and permeate quality, and the mechanism of its penetration. Acetic acid, ethylene glycol, isopropyl alcohol (IPA), and 2-Butoxyethanol (2-BE), which are commonly found in the produced water, were extensively investigated and their impacts were reviewed and compared. Among all the VOCs, 2-BE had the highest mass transfer despite its low vapour pressure and large molecule weight. Some of the VOCs had surfactant properties, which meant they could penetrate the membrane pores easily during MD process. In long-term operation, pore wetting started to appear as the salt rejection was dropping in the MD process, and flux was also decreasing. Based on the results, this study suggested that the strength of surfactant properties and intra-molecular hydrogen bonds between water molecules and VOCs are as significant as vapour pressure for the VOCs in terms of mass transfer efficiency in MD system.
Ye, Y, Liu, W, Jiang, W, Kang, J, Ngo, HH, Guo, W & Liu, Y 2018, 'Defluoridation by magnesia–pullulan: Surface complexation modeling and pH neutralization of treated fluoride water by aluminum', Journal of the Taiwan Institute of Chemical Engineers, vol. 93, pp. 625-631.
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Ye, Y, Ngo, HH, Guo, W, Liu, Y, Chang, SW, Nguyen, DD, Liang, H & Wang, J 2018, 'A critical review on ammonium recovery from wastewater for sustainable wastewater management', Bioresource Technology, vol. 268, pp. 749-758.
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© 2018 Elsevier Ltd The growing global population's demand for ammonium has triggered an increase in its supply, given that ammonium plays a crucial role in fertilizer production for the purpose of food security. Currently, ammonia used in fertilizer production is put through what is known as the industrial Haber Bosch process, but this approach is substantially expensive and requires much energy. For this reason, looking for effective methods to recover ammonium is important for environmental sustainability. One of the greatest opportunities for ammonium recovery occurs in wastewater treatment plants due to wastewater containing a large quantity of ammonium ions. The comprehensively and critically review studies on ammonium recovery conducted, have the potential to be applied in current wastewater treatment operations. Technologies and their ammonium recovery mechanisms are included in this review. Furthermore the economic feasibility of such processes is analysed. Possible future directions for ammonium recovery from wastewater are suggested.
Ye, Y, Yang, J, Jiang, W, Kang, J, Hu, Y, Ngo, HH, Guo, W & Liu, Y 2018, 'Fluoride removal from water using a magnesia-pullulan composite in a continuous fixed-bed column', Journal of Environmental Management, vol. 206, pp. 929-937.
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A magnesia-pullulan composite (MgOP) was previously shown to effectively remove fluoride from water. In the present study, a continuous fixed-bed column was used to examine the application of the composite at an industrial scale. The influencing parameters included bed mass (4.0, 6.0 and 8.0 g), influent flow rate (8, 16 and 32 mL/min), inlet fluoride concentration (5, 10 and 20 mg/L), reaction temperature (20, 30 and 40 °C), influent pH (4, 7 and 10) and other existing anions (HCO3-, SO42-, Cl- and NO3-), through which the breakthrough curves could be depicted for the experimental data analysis. The results indicated that MgOP is promising for fluoride removal with a defluoridation capacity of 16.6 mg/g at the bed mass of 6.0 g, influent flow rate of 16 mL/min and inlet fluoride concentration of 10 mg/L. The dynamics of the fluoride adsorption process were modeled using the Thomas and Yan models, in which the Yan model presented better predictions for the breakthrough curves than the Thomas model. Moreover, the concentration of magnesium in the effluent was monitored to determine Mg stability in the MgOP composite. Results indicated the effluent concentration of Mg2+ ions could be kept at a safe level. Calcination of fluoride-loaded MgOP effectively regenerated the material.
Yi, Z, Merenda, A, Kong, L, Radenovic, A, Majumder, M & Dumée, LF 2018, 'Single step synthesis of Schottky-like hybrid graphene - titania interfaces for efficient photocatalysis', Scientific Reports, vol. 8, no. 1, p. 8154.
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AbstractThe development of 2D nanomaterial coatings across metal surfaces is a challenge due to the mismatch between the metal microstructure and the nanoscale materials. The naturally occurring thin oxidative layer present across all metal surfaces, may lead to low adherence and connectivity. In this paper, graphene/titania/Titanium hybrid films were for the first time fabricated by a single step chemical vapour deposition process across Titanium foils. The presence of graphene as a dopant was found to enhance the photocatalytic performance of the final products, applied to the degradation of organic molecules and to lead to Schottky-like junction formation at the metal/oxide interface. These Schottky junctions, where vacancies are present across the titania material due to the graphene doping and where Ti3+ ions are predominantly located, yield enhanced catalytic performance. The highest degradation rate was found to be 9.66 × 10−6 min−1, achieved by the sample grown at 700 °C for 5 min, which was 62% higher than the sample just treated at that temperature without graphene growth. This work provides evidence that graphene may be grown across pure Titanium metal and opens new avenues in biomedical devices design, tribological or separation applications.
Ying, XY, Li, WZ, Kan, Q, Zhang, Z & Ding, G 2018, 'Numerical method for shape optimization of standard floor of the high-rise buildings in hot-summer and cold-winter areas under the low energy consumption target—taking the L-shape as an example', Lowland Technology International, vol. 20, no. 1, pp. 57-64.
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Shape is an important consideration in building design due to its significant impact on building performance in energy consumption. This paper presents a methodology to program planes using MATLAB language. Three side length factors were proposed as the design variables for L-shaped layouts, and eighteen kinds of L-shaped layouts were generated by changing those variables individually. An energy consumption simulation software (DesignBuilder) was developed to simulate the energy consumption of these layouts of high-rise buildings as experimental models. The correlativity between the width ratio and depth ratio of all experimental models and their energy consumption was examined when deriving the corresponding polynomial function. The main finding of the study suggested that there were certain critical points for both width ratio and depth ratio of the standard floor of high-rise buildings with L-shaped plane, which was 0.4 for width ratio and 0.67 for depth ratio. The energy consumption increased rapidly beyond the critical point, and there was a slight fluctuation at another interval. Further, this paper provided a range of side length ratio in contour plots which showed the variation of energy consumption of L-shape high-rise buildings with width ratio and depth ratio under the weather condition in Hangzhou, China.
Yu, KL, Show, PL, Ong, HC, Ling, TC, Chen, W-H & Salleh, MAM 2018, 'Biochar production from microalgae cultivation through pyrolysis as a sustainable carbon sequestration and biorefinery approach', Clean Technologies and Environmental Policy, vol. 20, no. 9, pp. 2047-2055.
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Yu, Y, Chen, X, Gao, W, Li, Q, Wu, D & Liu, M 2018, 'Stochastic leaching analysis on cementitious materials considering the influence of material uncertainty', Construction and Building Materials, vol. 184, pp. 186-202.
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© 2018 Elsevier Ltd Uncertainties significantly influence the durability-related experiments and field studies, which can hardly be addressed by deterministic approaches. This work aims at developing a stochastic numerical framework to disentangle the influence of material uncertainty on the case of leaching. To ensure the robustness of the numerical framework, a realistic stochastic reactive-transportation model is developed, which consists of a novel sampling algorithm and a comprehensive deterministic model. By using the proposed sampling algorithm, a more effective and efficient sampling process can be achieved without compromising the randomness of the uncertain properties. Besides, realistic mechanisms of leaching are considered by the deterministic model, including the simultaneous processes of ionic transportation, chemical reactions and material degradation. By performing the stochastic leaching analyses, numerical results suggest the overwhelming influence of the physical uncertainty on long-term leaching, while the impact of chemical uncertainty is more evident in terms of short-term leaching. It is also revealed that the root-time relation as determined from short-term experiments is inappropriate for long-term predictions. Thus, a modified relation is developed based on the stochastic leaching analysis, which generates accurate predictions for both the short-term and long-term leaching.
Yu, Y, Li, W, Li, J & Nguyen, TN 2018, 'A novel optimised self-learning method for compressive strength prediction of high performance concrete', Construction and Building Materials, vol. 184, pp. 229-247.
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© 2018 Elsevier Ltd Concrete strength (CS) is one of the most important performance parameters that are crucial in the design of concrete structure. The reliable prediction of strength can reduce the cost and time in design and avoid the waste of materials caused by a large number of mixture trials. In this study, a novel predictive model is put forward to predict the CS of high performance concrete (HPC) using support vector machine (SVM) approach, which has benefits of nonlinear mapping, high robustness and great generalisation capacity. In the proposed model, the input variables include the contents of water, cement, blast furnace slag, fly ash, super plasticiser, coarse and fine aggregates and curing age, which produces the CS of HPC as the output. In order to improve the model performance, a type of enhanced cat swarm optimisation (ECSO) is adopted to optimise the key parameters of SVM. Finally, the model is trained and evaluated using a total of 1761 data records, which are collected from existing literatures. The results indicate that the proposed SVM-based model exhibits better recognition ability and higher prediction accuracy than other commonly used models, and it can be considered as an effective method to predict the CS property of HPC in infrastructure practice.
Yu, Y, Li, Y, Li, J, Gu, X & Royel, S 2018, 'Nonlinear Characterization of the MRE Isolator Using Binary-Coded Discrete CSO and ELM', International Journal of Structural Stability and Dynamics, vol. 18, no. 08, pp. 1840007-1840007.
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Magnetorheological elastomer (MRE) isolator has been proved as a promising semi-active control device for structural vibration control. For its engineering application, developing an accurate and robust model is definitely necessary and also a challenging task. Most of the present models, belonging to parametric models, need to identify various model parameters and sometimes are not capable of perfectly capturing the unique characteristics of the device. In this work, a novel nonparametric model is proposed to characterize the inherent dynamics of the MRE isolator with the features of hysteresis and nonlinearity. Initially, dynamic tests are conducted to evaluate the performance of the isolator under various loading conditions, including harmonic, random, and seismic excitations. Then, on the basis of the captured experimental results, a hybrid learning method is designed to forecast the nonlinear responses of the device with known external inputs. In this method, a type of single hidden layer feed-forward network, called extreme learning machine (ELM), is developed to forecast the nonlinear responses (shear force) of the device with captured velocity, displacement, and current level. To obtain optimal performance of the developed model, an improved binary-coded discrete cat swarm optimization (BCDCSO) method is adopted to select optimal inputs and neuron number in the hidden layer for the network development. The performance of the proposed method is verified through the comparison between experimental results and model predictions. Due to the noise influence in the practical condition, the robustness of the proposed method is also validated via adding noise disturbance into the supplying currents. The results show that the proposed method outperforms the standard ELM in terms of characterization of the MRE isolator, even though the captured responses are polluted with external measurement noises.
Yu, Z, Zhang, X, Ngo, HH, Guo, W, Wen, H, Deng, L, Li, Y & Guo, J 2018, 'Removal and degradation mechanisms of sulfonamide antibiotics in a new integrated aerobic submerged membrane bioreactor system', Bioresource Technology, vol. 268, pp. 599-607.
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Zahid, R, Hj. Hassan, M, Alabdulkarem, A, Varman, M, Kalam, MA, Mufti, RA, Mohd Zulkifli, NW, Gulzar, M, Bhutta, MU, Ali, MA, Abdullah, U & Yunus, RH 2018, 'Tribological characteristics comparison of formulated palm trimethylolpropane ester and polyalphaolefin for cam/tappet interface of direct acting valve train system', Industrial Lubrication and Tribology, vol. 70, no. 5, pp. 888-901.
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PurposeThere is a continuous drive in automotive sector to shift from conventional lubricants to environmental friendly ones without adversely affecting critical tribological performance parameters. Because of their favorable tribological properties, chemically modified vegetable oils such as palm trimethylolpropane ester (TMP) are one of the potential candidates for the said role. To prove the suitability of TMP for applications involving boundary-lubrication regime such as cam/tappet interface of direct acting valve train system, a logical step forward is to investigate their compatibility with conventional lubricant additives.Design/methodology/approachIn this study, extreme pressure and tribological characteristics of TMP, formulated with glycerol mono-oleate (GMO), molybdenum dithiocarbamate (MoDTC) and zinc dialkyldithiophosphate (ZDDP), has been investigated using four-ball wear tester and valve train test rig. For comparison, additive-free and formulated versions of polyalphaolefin (PAO) were used as reference. Moreover, various surface characterization techniques were deployed to investigate mechanisms responsible for a particular tribological behavior.FindingsIn additive-free form, TMP demonstrated better extreme pressure characteristics compared to PAO and lubricant additives which are actually optimized for conventional base-oils such as PAO, are also proved to be compatible with TMP to some extent, especially ZDDP. During cylinder head tests, additive-free TMP proved to be more effective compared to PAO in reducing friction of cam/tappet interface, but opposite behavior was seen when formulated lubricants were used. Therefore, there is a need to synthesize speci...
Zahid, R, Mufti, RA, Gulzar, M, Bin Haji Hassan, M, Alabdulkarem, A, Varman, M, Kalam, MA, Binti Mohd Zulkifli, NW & Yunus, R 2018, 'Tribological compatibility analysis of conventional lubricant additives with palm trimethylolpropane ester (TMP) and tetrahedral amorphous diamond-like carbon coating (ta-C)', Proceedings of the Institution of Mechanical Engineers, Part J: Journal of Engineering Tribology, vol. 232, no. 8, pp. 999-1013.
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Modern industrial applications involve rigorous operating conditions due to which lubricant either slips out of the contact or its thin layer resides between the interacting surfaces. Deposition of diamond-like carbon coatings and using lubricants capable of physically adsorbing on the interacting surfaces can significantly improve tribological performance. In this study, tribological compatibility of glycerol mono-oleate, molybdenum dithiocarbamate and zinc dialkyldithiophosphate with palm trimethylolpropane ester and tetrahedral amorphous diamond-like carbon coating has been investigated using universal wear testing machine. For comparison, additive-free and formulated versions of polyalphaolefin were used. Moreover, spectroscopic techniques were used to investigate mechanisms responsible for a particular tribological behavior. Among base oils, trimethylolpropane ester proved to be more effective in enhancing friction performance and mitigating wear of contacts when one of the interacting surfaces was ferrous-based. Self-mated tetrahedral amorphous diamond-like carbon coating surfaces resulted in lowest values of friction and wear coefficient of balls.
Zainal, BS, Zinatizadeh, AA, Chyuan, OH, Mohd, NS & Ibrahim, S 2018, 'Effects of process, operational and environmental variables on biohydrogen production using palm oil mill effluent (POME)', International Journal of Hydrogen Energy, vol. 43, no. 23, pp. 10637-10644.
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Zeweldi, HG, Limjuco, LA, Bendoy, AP, Kim, H-S, Park, MJ, Shon, HK, Johnson, EM, Lee, H, Chung, W-J & Nisola, GM 2018, 'The potential of monocationic imidazolium-, phosphonium-, and ammonium-based hydrophilic ionic liquids as draw solutes for forward osmosis', Desalination, vol. 444, pp. 94-106.
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© 2018 The widespread implementation of forward osmosis (FO) is highly constrained by the limited availability of suitable draw solutes (DS). Herein, monocationic hydrophilic ionic liquids (ILs) were probed as FO DS. Water (Jv), reverse solute (Js), and specific reverse solute (Js/Jv) fluxes were determined and correlated with IL properties: Van't Hoff factor (i), ionic strength, hydrated ionic radius (rH), diffusivity and membrane affinity. Most of the ILs have comparable Jv with the benchmark draw solute NaCl but their Js were significantly lower, particularly under PRO mode. Their remarkably lower Js/Jv (i.e. <0.010 ± 7.45 × 10−4 mol L−1) than NaCl (0.021 ± 0.003 mol L−1) validates their potential use as FO DS. Tetraethylammonium bromide ([N2222]Br) is the most suitable IL DS due to its high π high ionic strength, small rH, least membrane permeability (B = 0.14 L m−2 h−1) and lowest Js/Jv = 0.004 ± 5.53 × 10−4 mol L−1. Moreover, [N2222]Br effectively desalinated seawater (0.6 M NaCl). It is thermally stable and can be effectively regenerated through direct contact membrane distillation. The final permeated water had only trace [N2222]Br, which is safe for consumption as confirmed by in vitro toxicity tests. These results demonstrate that certain ILs like [N2222]Br can be identified as suitable draw solutes for FO desalination process.
Zhang, C, Qin, Y, Xu, Q, Liu, X, Liu, Y, Ni, B-J, Yang, Q, Wang, D, Li, X & Wang, Q 2018, 'Free Ammonia-Based Pretreatment Promotes Short-Chain Fatty Acid Production from Waste Activated Sludge', ACS Sustainable Chemistry & Engineering, vol. 6, no. 7, pp. 9120-9129.
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© Copyright 2018 American Chemical Society. This work reports a new waste activated sludge (WAS) pretreatment method based on free ammonia (FA) for promoting the generation of short-chain fatty acids (SCFAs). Experimental results showed that pretreatment of WAS for 3 days with FA largely improved WAS disintegration, with the highest dissolution (soluble chemical oxygen demand (COD), 3400 ± 120 mg/L at initial FA level of 237.8 mg/L) being 4.5-fold that without FA pretreatment. The pretreatment method by FA facilitated the breakdown of extracellular polymeric substances and cell envelope of sludge cells and killed more live microbial cells, which thereby accelerated the dissolution of substances from WAS. It was also found that FA severely suppressed the SCFA consumption process, but the acetogenesis process was unaffected. Although FA also inhibited hydrolysis, acidogenesis, and homoacetogenesis to some extent, the inhibitions did not largely affect the biodegradation of the relevant substances at all the tested FA levels. Finally, using FA to pretreat WAS for SCFA enhancement was confirmed. When FA concentrations ranged from 53.5 to 176.5 mg/L, the maximum generation of SCFA was enhanced from 196.8 to 267.2 mg COD/g VSS, which was 2.3-3.2 times that of the blank. Further FA leveling (237.8 mg/L) caused a slight decline of maximum SCFA generation (226.9 mg COD/g VSS). The findings reported may instruct engineers to develop an economic and effective strategy to enhance SCFA production, which might support the operation of wastewater treatment plants in sustainable paradigms with low energy input in the future.
Zhang, C-C, Zhu, H-H, Shi, B & Fatahi, B 2018, 'A long term evaluation of circular mat foundations on clay deposits using fractional derivatives', Computers and Geotechnics, vol. 94, pp. 72-82.
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© 2017 Elsevier Ltd This study proposes to use fractional derivatives to evaluate the long term performance of circular mat foundations overlying clays and also predict the associated ground settlement. Closed form solutions for the deflection and bending moment of foundations and the subsequent reaction of subgrade are obtained with the Mittag–Leffler function. Numerical examples are used to determine how the fractional order affects the time dependent properties of the foundation and ground settlement, and to simulate the case history of a large standpipe constructed over Tertiary sediments. New insights into design and prediction of shallow foundations and ground settlement are also discussed.
Zhang, L, Chen, Q, Gao, G-Y, Nimbalkar, S & Chiaro, G 2018, 'A New Failure Load Criterion for Large-Diameter Under-Reamed Piles: Practical Perspective', International Journal of Geosynthetics and Ground Engineering, vol. 4, no. 1.
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© 2017, Springer International Publishing AG, part of Springer Nature. Sustainable performance of heavy structures such as tanks, storage yards and tall buildings often rely on an efficient transfer of vertical and lateral loads to underlying ground. If the foundation soil does not have sufficient strength, the piles may be belled out (under-reamed) at the base, often termed as large-diameter belled piles (LDBPs). In reality the deformation and failure mechanism of LDBPs are significantly different and are influenced by the nature of foundation soil. However, in the absence of appropriate design guidelines, LDBPs are simply treated as conventional straight piles, often ignoring enlarged base. To access effects of enlarged base on load-deformation behavior, full-scale load tests are conducted on several LDBPs. A novel interpreted failure load criterion is proposed for LDBPs. The general applicability of this criterion is verified using the data from nine independent pile load tests retrieved from four different projects across China. Adopting the proposed method, provision of a much effective and economic design for LDBPs is feasible in comparison with the criteria currently prevalent in practice.
Zhang, X, Hu, Z, Ngo, HH, Zhang, J, Guo, W, Liang, S & Xie, H 2018, 'Simultaneous improvement of waste gas purification and nitrogen removal using a novel aerated vertical flow constructed wetland', Water Research, vol. 130, pp. 79-87.
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Insufficient oxygen supply is identified as one of the major factors limiting organic pollutant and nitrogen (N) removal in constructed wetlands (CWs). This study designed a novel aerated vertical flow constructed wetland (VFCW) using waste gas from biological wastewater treatment systems to improve pollutant removal in CWs, its potential in purifying waste gas was also identified. Compared with unaerated VFCW, the introduction of waste gas significantly improved NH4+-N and TN removal efficiencies by 128.48 ± 3.13% and 59.09 ± 2.26%, respectively. Furthermore, the waste gas ingredients, including H2S, NH3, greenhouse gas (N2O) and microbial aerosols, were remarkably reduced after passing through the VFCW. The removal efficiencies of H2S, NH3 and N2O were 77.78 ± 3.46%, 52.17 ± 2.53%, and 87.40 ± 3.89%, respectively. In addition, the bacterial and fungal aerosols in waste gas were effectively removed with removal efficiencies of 42.72 ± 3.21% and 47.89 ± 2.82%, respectively. Microbial analysis results revealed that the high microbial community abundance in the VFCW, caused by the introduction of waste gas from the sequencing batch reactor (SBR), led to its optimized nitrogen transformation processes. These results suggested that the VFCW intermittently aerated with waste gas may have potential application for purifying wastewater treatment plant effluent and waste gas, simultaneously.
Zhang, X, Hu, Z, Zhang, J, Fan, J, Ngo, HH, Guo, W, Zeng, C, Wu, Y & Wang, S 2018, 'A novel aerated surface flow constructed wetland using exhaust gas from biological wastewater treatment: Performance and mechanisms', Bioresource Technology, vol. 250, pp. 94-101.
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© 2017 In this study, a novel aerated surface flow constructed wetland (SFCW) using exhaust gas from biological wastewater treatment was investigated. Compared with un-aerated SFCW, the introduction of exhaust gas into SFCW significantly improved NH4+-N, TN and COD removal efficiencies by 68.30 ± 2.06%, 24.92 ± 1.13% and 73.92 ± 2.36%, respectively. The pollutants removal mechanism was related to the microbial abundance and the highest microbial abundance was observed in the SFCW with exhaust gas because of the introduction of exhaust gas from sequencing batch reactor (SBR), and thereby optimizing nitrogen transformation processes. Moreover, SFCW would significantly mitigate the risk of exhaust gas pollution. SFCW removed 20.00 ± 1.23%, 34.78 ± 1.39%, and 59.50 ± 2.33% of H2S, NH3 and N2O in the exhaust gas, respectively. And 31.32 ± 2.23% and 32.02 ± 2.86% of bacterial and fungal aerosols in exhaust gas were also removed through passing SFCW, respectively.
Zhang, Y, Huang, R, Huang, Y, Huang, S, Ma, Y, Xu, S & Zhou, P 2018, 'Effect of ambient temperature on the puffing characteristics of single butanol-hexadecane droplet', Energy, vol. 145, pp. 430-441.
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© 2018 Elsevier Ltd Puffing characteristics of BUT50 (50% n-butanol and 50% n-hexadecane by mass) were investigated using the droplet suspension technology under 638, 688 and 738 K. Experimental results showed that BUT50 underwent transient heating, fluctuation evaporation and equilibrium evaporation phases under all ambient temperatures. In the fluctuation evaporation phase, the fluctuation frequency of 738 K was higher than that of 638 K. (Dmax/D0)2 of 738 K was lower than that of 638 K. Easy bubble rupture led to high fluctuation frequency and low (Dmax/D0)2 at 738 K. Three turning points were found in transient temperature growth rate at 638 and 738 K. Four characteristic droplet temperatures were analyzed, including droplet temperatures at the start (T1) and end (T2) of transient heating phase, at (Dmax/D0)2 (T3) and at the end of total lifetime (T4). T2 was slightly lower and T3 was slightly higher than the boiling point of n-butanol. T4 was lower than the boiling point of n-hexadecane. Furthermore, the transient heating duration (tTH), fluctuation evaporation duration (tFE) and total lifetime (tTL) decreased with increasing ambient temperature. The reduction of tFE played an important role in the decrease of tTL. The percentages of tTH/tTL and tFE/tTL were stable with increasing ambient temperature.
Zhang, Y, Huang, R, Huang, Y, Huang, S, Zhou, P, Chen, X & Qin, T 2018, 'Experimental study on combustion characteristics of an n-butanol-biodiesel droplet', Energy, vol. 160, pp. 490-499.
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© 2018 Elsevier Ltd This work was aimed to study droplet combustion which was a foundation of spray combustion. Combustion characteristics of BUT00 (pure biodiesel) and BUT50 (50% n-butanol and 50% biodiesel by mass) were investigated using droplet suspension technology under 1 bar and 900 K. One flame was observed for BUT00 while two flames were observed for BUT50. The flame of BUT00 underwent successively faint luminosity, bright luminosity, soot aggregate and soot spread. The first flame of BUT50 was faint and the second one was similar to that of BUT00 because they were caused by n-butanol and biodiesel combustion respectively. Before the auto-ignition of BUT00, (D/D0)2 was approximately unchanged at 1.0 and similarity degree (SD) was higher than 97%. Temperature growth rate (TGR) decreased first quickly and then slowly. After the auto-ignition of BUT00, (D/D0)2 sharply decreased and SD was in the range of 90–97%. The flame heating led to the increase of TGR. For BUT50, obvious fluctuations were found in (D/D0)2, SD and TGD. The SD of BUT50 was generally lower than 97%. The (D/D0)2 of BUT50 included transient heating, fluctuation evaporation and equilibrium evaporation phases. Some characteristic parameters were deterministic although (D/D0)2 in fluctuation evaporation phase was a non-deterministic process.
Zhang, Y, Huang, Y, Huang, R, Huang, S, Ma, Y, Xu, S & Wang, Z 2018, 'A new puffing model for a droplet of butanol-hexadecane blends', Applied Thermal Engineering, vol. 133, pp. 633-644.
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© 2018 Elsevier Ltd A new model was developed to investigate the puffing process of a butanol-hexadecane droplet. The puffing model took into account all the key processes, including the surface evaporation, bubble formation, bubble growth and bubble breakup. The Rayleigh equation was modified to simulate the bubble growth inside a small droplet. The sub-models for surface evaporation and bubble growth were firstly verified against the previous experimental data. Then the droplet puffing experiments of butanol-hexadecane blends were conducted under 1 bar and 750 K condition using the droplet suspension technique to further verify the puffing model. Results showed that the puffing model well simulated three phases of BUT50 (50% butanol and 50% hexadecane by mass). The three phases were the transient heating, fluctuation evaporation and equilibrium evaporation phases. An extremely strong fluctuation and several weak fluctuations were observed during the fluctuation evaporation phase from the experimental normalized squared diameter. Due to the model hypotheses, these weak fluctuations were ignored and only the strong fluctuation was simulated in the present model. Furthermore, a significant turning point was observed in the experimental temperature curve when the droplet diameter had the strong fluctuation. The occurrence of the strong fluctuation was caused by the obvious bubble expansion inside the droplet. The numerical results showed that the significant heat absorption for the bubble expansion led to the turning point in the temperature curve.
Zhang, Z, Dissanayake, D, Saputra, A, Wu, D & Song, C 2018, 'Three-dimensional damage analysis by the scaled boundary finite element method', Computers & Structures, vol. 206, pp. 1-17.
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© 2018 Elsevier Ltd A novel and effective approach within the framework of the scaled boundary finite element method (SBFEM) is proposed for the damage analysis of structures in three dimensions. The integral-type nonlocal model is extended to SBFEM to eliminate the mesh sensitivity concerning the strain localization. In order to reduce the number of degrees of freedoms (DOFs), an automatic mesh generation algorithm using octree decomposition is employed to refine the localized damage process zone (DPZ), but no extra effort is required to deal with hanging nodes existing between adjacent subdomains with different sizes. A double-notched tension beam is simulated with two different meshes to illustrate the mesh-independence. Three benchmarks are modelled to further verify the effectiveness and robustness of the proposed approach. It is shown that the proposed computational approach is capable of accurately capturing the damage evolution under complicated boundary conditions, and the results agree well with the experimental observations and prior numerical simulations reported in the literatures.
Zhao, J, Liu, Y, Wang, Y, Lian, Y, Wang, Q, Yang, Q, Wang, D, Xie, G-J, Zeng, G, Sun, Y, Li, X & Ni, B-J 2018, 'Clarifying the Role of Free Ammonia in the Production of Short-Chain Fatty Acids from Waste Activated Sludge Anaerobic Fermentation', ACS Sustainable Chemistry & Engineering, vol. 6, no. 11, pp. 14104-14113.
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Copyright © 2018 American Chemical Society. Free ammonia (FA) could accumulate at high levels in the sludge anaerobic fermentation, especially under alkaline fermentation conditions, which might significantly affect the anaerobic fermentation. However, its role in the sludge fermentation process has not been revealed fundamentally. This work therefore aims to fill the knowledge gap through the integration of experimental and mathematical approaches. Experimental results showed that when the initial ammonium concentration increased from 20 to 300 mg/L, the maximal short-chain fatty acid (SCFA) yield from fermentation systems with different pH values varied from 91.2 to 296.7 mg of chemical oxygen demand/g volatile suspended solids (VSS). The increasing SCFA production was observed to correlate with the FA level rather than the ammonium level, suggesting that FA, instead of ammonium, is likely the true contributor to enhance SCFA production. Batch tests confirmed that ammonium in the fermentation-strength range (e.g., 0-300 mg/L) did not affect any process of sludge fermentation, but all the processes were affected significantly by FA, pH, or combined FA-pH. It was found that FA facilitated sludge disintegration but inhibited the processes of hydrolysis, acidification, and methanogenesis. When FA and alkaline conditions were combined, synergistic effects on all these processes were observed. The significant contribution of FA to SCFA production was finally confirmed by a sludge fermentation mathematical model proposed recently. The findings reported here revealed the actually existing, yet previously unrecognized contributor to the sludge fermentation, which help engineers better understand the role of FA in sludge anaerobic fermentation.
Zhao, J, Wang, D, Liu, Y, Ngo, HH, Guo, W, Yang, Q & Li, X 2018, 'Novel stepwise pH control strategy to improve short chain fatty acid production from sludge anaerobic fermentation', Bioresource Technology, vol. 249, pp. 431-438.
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This study reports an innovative strategy known as stepwise pH fermentation, developed to enhance the production of short chain volatile fatty acids (SCFA) from waste activated sludge (WAS) anaerobic fermentation. Experimental results confirmed the optimal pH for WAS disruption and acidification was 11 and 9, respectively, and corresponding optimal time was, respectively, 5 d and 2 d. In this scenario, the optimal SCFA yield was 2356 mg chemical oxygen demand (COD)/L, which was much higher than that derived from alkaline fermentation system. Investigation of the mechanism indicated that pH 11 could accelerate the disruption of WAS and inhibit the activities of methanogens; furthermore, pH 9 was beneficial to the activity of acid-producing bacteria, resulting in more SCFA production. Stepwise pH fermentation integrated with sodium chloride (NaCl) present in WAS had synergistic impacts on WAS anaerobic fermentation.
Zhao, S, He, T, Li, X, Gao, C, Shon, HK, Nghiem, LD & Elimelech, M 2018, 'Highlights of international forward osmosis technology symposium (IFOS2016): is forward osmosis feasible?', Huagong Xuebao/CIESC Journal, vol. 69, no. 4, pp. 1255-1260.
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The research highlights on forward osmosis (FO) technology at the International Forward Osmosis Symposium (IFOS2016) in Sydney by the end of 2016 are summarized. For FO membrane materials, reduction in the structure parameter of the support layer, rather than the increase of the permeability of the active separation layer, is the key to improve the FO flux. Overall, the improvement in the rejection and antifouling properties is the key factor for high performance membrane. For draw solutes, inorganic salts appear to be the most promising candidates. Osmotic dilution and hybrid processes with other separation technologies for treating high salinity wastewater remain the main potential application. Unfortunately, in a short term, FO based salinity power generation is not competitive to other new energy alternatives.
Zhao, Z, Ball, J & Hazelton, P 2018, 'Application of Statistical Inference for Analysis of Heavy Metal Variability in Roadside Soil', Water, Air, & Soil Pollution, vol. 229, no. 1.
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© 2018, Springer International Publishing AG, part of Springer Nature. Previous studies have found there are a variety of factors that influence heavy metal concentrations and Pb isotope ratios in roadside soil. One issue in assessing these factors is the need to distinguish between the natural sample variability at a single site and the variability between different sites. Data constraint often results in the lack of an adequate number of samples and hence is often a constraint on statistical reliability. Presented herein is a regionalisation approach that can be used to overcome the data constraint. This approach was used to analyse data collected at Miranda Park, Sydney, for assessment of the influence of rainfall, distance, depth and soil types. Application of the regionalisation approach enabled discrimination between natural sample variability and that from changes in the factors being considered. The regionalisation approach mitigates the data constraint and may assist researchers in their analysis of constrained data sets enabling more efficient monitoring of potential environmental issues. Additionally, it was found that the primary factors for heavy metal concentrations were rainfall, distance and soil types while depth was a secondary factor. A similar result was determined for the anthropogenic Pb component but not for the natural Pb component.
Zheng, J, Li, Y, Hu, M, Wen, J, Wang, J & Kan, J 2018, 'Feasibility study of a miniaturized magnetorhological grease timing trigger as safety and arming device for spinning projectile', Smart Materials and Structures, vol. 27, no. 11, pp. 115030-115030.
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Safety and arming (S&A) device is to keep the fuze for projectile unarmed during shipping, handling and storage, while arming the firing section at a proper time via sensing external conditions such as pressure, position, etc. With the increasing need for smaller S&A devices, miniature design with a compact configuration and high reliability is on demand. This paper proposes a miniaturized timing trigger as S&A device for a spinning projectile by utilizing the "locking" and "unlocking" properties of magnetorheological (MR) grease with/without the presence of magnetic field. The design and arming mechanism of the timing trigger are firstly introduced in which the MR grease is locked by a magnetic field generated by two permanent magnets (PMs). Under sufficient firing acceleration, the PMs disengage to unlock the contraction flow of MR grease, which enables its triggering function. A theoretical analysis was conducted to interpolate the delayed time against the geometry of the device, shear/extensional characteristics of MR grease and the spinning rate of a projectile. A series of tests have been conducted to measure the delayed times by tuning the physical parameters, including particle concentration, spinning rate and orifice diameter, etc. The experimental results showed that this theoretical model is capable of well calculating the delayed time of MR grease timing trigger.
Zheng, J, Li, Y, Wang, J, Shiju, E & Li, X 2018, 'Accelerated thermal aging of grease-based magnetorheological fluids and their lifetime prediction', Materials Research Express, vol. 5, no. 8, pp. 085702-085702.
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© 2018 IOP Publishing Ltd. In this article, the effect of elevated temperature on the rheological properties of grease-based magnetorheological fluids (G-MRFs) with the focus on long-term storage lifetime has been investigated. These G-MRF samples were subjected to accelerated heat aging process for the estimation of thermal stability and useful lifetime prediction. The well-known Arrhenius-Weibull relationship with a modified Powell-Beal conjugate gradient (CGP) algorithm was employed to model the 'life in service' for the achievement of possible life distribution at different temperature conditions. By defining the failure criteria of G-MRF samples as a maximum reduction of either viscosity or shear stress by more than 10%, the underlying degradation mechanism was revealed through Fourier transform infrared (FTIR) spectroscopy and scanning electron microscopy (SEM) analysis. Based on the statistical inference from accelerated life test (ALT), the life expectancy of G-MRF under nominal operating temperature is estimated to be 15.2 years, which outpaces the capability of most industrial applications. Experimental results showed that the performance of shear stress is more likely to degrade under long-term treatment of high temperature in comparison with low temperature. Thus, it is suggested to store the G-MRF at relatively low temperatures for longevity extension and reliability improvement.
Zheng, Y, Dzakpasu, M, Wang, X, Zhang, L, Ngo, HH, Guo, W & Zhao, Y 2018, 'Molecular characterization of long-term impacts of macrophytes harvest management in constructed wetlands', Bioresource Technology, vol. 268, pp. 514-522.
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Zhou, A, Wu, S, Li, J & Sheng, D 2018, 'Including degree of capillary saturation into constitutive modelling of unsaturated soils', Computers and Geotechnics, vol. 95, pp. 82-98.
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The degree of saturation (S) of soil can be separated into two components: the degree of capillary saturation (S′) that is based on the capillary water and the degree of adsorptive saturation (S″) that is based on the adsorbed water. This paper discusses the role of the degree of capillary saturation (S′) in modelling the coupled hydro-mechanical behaviour of unsaturated soils and proposes a new constitutive model for unsaturated soils by using the degree of capillary saturation (S′) and the effective inter-particle stress (σij′). An enhanced hydraulic model is introduced to describe the hydraulic hysteresis and hydro-mechanical interaction in terms of the degree of capillary saturation (S′). In the proposed constitutive model, the shear strength, yield stress and deformation behaviour of unsaturated soils are governed directly by the above two constitutive variables, namely σij′ and S′. To be in line with the existing finite element frameworks for unsaturated soils, the proposed model is eventually generalised to constitutive functions consisting of only primary variables such as the net stress (σij), suction (s) and degree of saturation (S). The typical performance of the model for simulating the characteristic trends of unsaturated soil behaviour is discussed in several different scenarios. The model is then validated against a variety of experimental data in the literature, and the results show that a reasonable agreement can be obtained using this new constitutive model.
Zhu, B, Duke, M, Dumée, L, Merenda, A, des Ligneris, E, Kong, L, Hodgson, P & Gray, S 2018, 'Short Review on Porous Metal Membranes—Fabrication, Commercial Products, and Applications', Membranes, vol. 8, no. 3, pp. 83-83.
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Porous metal membranes have recently received increasing attention, and significant progress has been made in their preparation and characterisation. This progress has stimulated research in their applications in a number of key industries including wastewater treatment, dairy processing, wineries, and biofuel purification. This review examines recent significant progress in porous metal membranes including novel fabrication concepts and applications that have been reported in open literature or obtained in our laboratories. The advantages and disadvantages of the different membrane fabrication methods were presented in light of improving the properties of current membrane materials for targeted applications. Sintering of particles is one of the main approaches that has been used for the fabrication of commercial porous metal membranes, and it has great advantages for the fabrication of hollow fibre metal membranes. However, sintering processes usually result in large pores (e.g., >1 µm). So far, porous metal membranes have been mainly used for the filtration of liquids to remove the solid particles. For porous metal membranes to be more widely used across a number of separation applications, particularly for water applications, further work needs to focus on the development of smaller pore (e.g., sub-micron) metal membranes and the significant reduction of capital and maintenance costs.
Zhu, X, Mochiku, T, Fujii, H, Tang, K, Hu, Y, Huang, Z, Luo, B, Ozawa, K & Wang, L 2018, 'A new sodium iron phosphate as a stable high-rate cathode material for sodium ion batteries', Nano Research, vol. 11, no. 12, pp. 6197-6205.
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© 2018, Tsinghua University Press and Springer-Verlag GmbH Germany, part of Springer Nature. Low-cost room-temperature sodium-ion batteries (SIBs) are expected to promote the development of stationary energy storage applications. However, due to the large size of Na+, most Na+ host structures resembling their Li+ counterparts show sluggish ion mobility and destructive volume changes during Na ion (de)intercalation, resulting in unsatisfactory rate and cycling performances. Herein, we report a new type of sodium iron phosphate (Na0.71Fe1.07PO4), which exhibits an extremely small volume change (~ 1%) during desodiation. When applied as a cathode material for SIBs, this new phosphate delivers a capacity of 78 mA·h·g−1 even at a high rate of 50 C and maintains its capacity over 5,000 cycles at 20 C. In situ synchrotron characterization disclosed a highly reversible solid-solution mechanism during charging/discharging. The findings are believed to contribute to the development of high-performance batteries based on Earth-abundant elements. [Figure not available: see fulltext.].
Zhu, XQ, Law, SS & Huang, L 2018, 'Identification of Railway Ballasted Track Systems from Dynamic Responses of In-Service Trains', Journal of Aerospace Engineering, vol. 31, no. 5, pp. 04018060-04018060.
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© 2018 American Society of Civil Engineers. Railway track is one of the most important parts of the railway system, and monitoring its condition is essential to ensure the safety of trains and reduce maintenance cost. An adaptive regularization approach is adopted in this paper to identify the parameters of a railway ballasted track system (substructure) from dynamic measurements on in-service vehicles. The vehicle-track interaction system is modeled as a discrete spring-mass model on a Winkler elastic foundation. Damage is defined as the stiffness reduction of the track due to foundation settlement, loosening in the rail fastener, and lack of compaction of the ballast. Accelerometers are installed on the underframe of the train to capture the dynamic responses from which the interaction forces between the vehicle and the railway track are determined. The damage of the railway track can be detected via changes in the interaction force. Numerical results show that the proposed approach can identify all stiffness parameters successfully at a low moving speed and at a high sampling rate when measurement noise is involved.
Zhu, XQ, Law, SS, Huang, L & Zhu, SY 2018, 'Damage identification of supporting structures with a moving sensory system', Journal of Sound and Vibration, vol. 415, pp. 111-127.
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© 2017 Elsevier Ltd An innovative approach to identify local anomalies in a structural beam bridge with an instrumented vehicle moving as a sensory system across the bridge. Accelerations at both the axle and vehicle body are measured from which vehicle-bridge interaction force on the structure is determined. Local anomalies of the structure are estimated from this interaction force with the Newton's iterative method basing on the homotopy continuation method. Numerical results with the vehicle moving over simply supported or continuous beams show that the acceleration responses from the vehicle or the bridge structure are less sensitive to the local damages than the interaction force between the wheel and the structure. Effects of different movement patterns and moving speed of the vehicle are investigated, and the effect of measurement noise on the identified results is discussed. A heavier or slower vehicle has been shown to be less sensitive to measurement noise giving more accurate results.