Abolhasan, M & Wysocki, TA 2007, 'Dynamic zone topology routing protocol for MANETs', EUROPEAN TRANSACTIONS ON TELECOMMUNICATIONS, vol. 18, no. 4, pp. 351-368.
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The limited scalability of the proactive and reactive routing protocols have resulted in the introduction of new generation of routing in mobile ad hoc networks, called hybrid routing. These protocols aim to extend the scalability of such networks beyond several hundred to thousand of nodes by defining a virtual infrastructure in the network. However, many of the hybrid routing protocols proposed to date are designed to function using a common pre-programmed static zone map. Other hybrid protocols reduce flooding by grouping nodes into clusters, governed by a cluster-head, which may create performance bottlenecks or a single point of failures at each cluster-head node.We propose a new routing strategy in which zones are created dynamically, using a dynamic zone creation algorithm. Therefore, nodes are not restricted to a specific region. Additionally, nodes perform routing and data forwarding in a cooperative manner, which means that in the case failure, route recalculation is minimised. Routing overheads are also further reduced by introducing a number of GPS-based location tracking mechanisms, which reduces the route discovery area and the number of nodes queried to find the required destination.
Armand, S, Blumenstein, M & Muthukkumarasamy, V 2007, 'Off-line Signature Verification Using an Enhanced Modified Direction Feature with Single and Multi-classifier Approaches', IEEE Computational Intelligence Magazine, vol. 2, no. 2, pp. 18-25.
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A study was conducted to investigate the effectiveness of Modified Direction Feature (MDF) for performing off-line signature verification and dome modifications to the extracted features were proposed. The study was conducted by combining the 'Grupo de Procesado Digital de Senales' (GPDS) signature database and additional signatures collected by the researchers. A total of 2376 sample signatures were used to conduct the study. Reseahers used 44 sets of signatures, with 24 samples of genuine and 30 samples of forged signatures used. The binary image of each signature was processed, and edges extracted, providing the first step of reducing the amount of data that described each pattern. MDF and additional features were proposed to provide significant information for the signature verification problem.
Biswajeet, P & Saro, L 2007, 'Utilization of Optical Remote Sensing Data and GIS Tools for Regional Landslide Hazard Analysis Using an Artificial Neural Network Model', Earth Science Frontiers, vol. 14, no. 6, pp. 143-151.
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Blumenstein, M, Liu, XY & Verma, B 2007, 'An investigation of the modified direction feature for cursive character recognition', Pattern Recognition, vol. 40, no. 2, pp. 376-388.
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This paper describes and analyses the performance of a novel feature extraction technique for the recognition of segmented/cursive characters that may be used in the context of a segmentation-based handwritten word recognition system. The modified direction feature (MDF) extraction technique builds upon the direction feature (DF) technique proposed previously that extracts direction information from the structure of character contours. This principal was extended so that the direction information is integrated with a technique for detecting transitions between background and foreground pixels in the character image. In order to improve on the DF extraction technique, a number of modifications were undertaken. With a view to describe the character contour more effectively, a re-design of the direction number determination technique was performed. Also, an additional global feature was introduced to improve the recognition accuracy for those characters that were most frequently confused with patterns of similar appearance. MDF was tested using a neural network-based classifier and compared to the DF and transition feature (TF) extraction techniques. MDF outperformed both DF and TF techniques using a benchmark dataset and compared favourably with the top results in the literature. A recognition accuracy of above 89% is reported on characters from the CEDAR dataset. © 2006 Pattern Recognition Society.
Browne, M, Castelle, B, Strauss, D, Tomlinson, R, Blumenstein, M & Lane, C 2007, 'Near-shore swell estimation from a global wind-wave model: Spectral process, linear, and artificial neural network models', Coastal Engineering, vol. 54, no. 5, pp. 445-460.
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Estimation of swell conditions in coastal regions is important for a variety of public, government, and research applications. Driving a model of the near-shore wave transformation from an offshore global swell model such as NOAA WaveWatch3 is an economical means to arrive at swell size estimates at particular locations of interest. Recently, some work (e.g. Browne et al. [Browne, M., Strauss, D., Castelle, B., Blumenstein, M., Tomlinson, R., 2006. Local swell estimation and prediction from a global wind-wave model. IEEE Geoscience and Remote Sensing Letters 3 (4), 462-466.]) has examined an artificial neural network (ANN) based, empirical approach to wave estimation. Here, we provide a comprehensive evaluation of two data driven approaches to estimating waves near-shore (linear and ANN), and also contrast these with a more traditional spectral wave simulation model (SWAN). Performance was assessed on data gathered from a total of 17 near-shore locations, with heterogenous geography and bathymetry, around the continent of Australia over a 7 month period. It was found that the ANNs out-performed SWAN and the non-linear architecture consistently out-performed the linear method. Variability in performance and differential performance with regard to geographical location could largely be explained in terms of the underlying complexity of the local wave transformation. © 2006 Elsevier B.V. All rights reserved.
Choi, FC, Li, J, Samali, B & Crews, K 2007, 'An experimental study on damage detection of structures using a timber beam', Journal of Mechanical Science and Technology, vol. 21, no. 6, pp. 903-907.
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Using vibration methods for the damage detection and structural health monitoring in bridge structures is rapidly developing. However, very little work has so far been reported on timber bridges. This paper intends to address such shortcomings by experim
Choi, FC, Li, J, Samali, B & Crews, K 2007, 'Application of modal-based damage-detection method to locate and evaluate damage in timber beams', Journal of Wood Science, vol. 53, no. 5, pp. 394-400.
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Modal-based damage-detection algorithms were used to identify the location of defects commonly found in timber and to estimate their severities. In this study, the authors propose modifications to an existing damage-detection algorithm for locating and e
Choudhury, D & Nimbalkar, S 2007, 'Seismic rotational displacement of gravity walls by pseudo-dynamic method: Passive case', Soil Dynamics and Earthquake Engineering, vol. 27, no. 3, pp. 242-249.
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Prediction of the seismic rotational displacements of retaining wall under passive condition is an important aspect of design in earthquake prone region. In this paper, the pseudo-dynamic method is used to compute the rotational displacements of rigid retaining wall supporting cohesionless backfill under seismic loading for the passive earth pressure condition. The proposed method considers time, phase difference and effect of amplification in shear and primary waves propagating through both the backfill and the retaining wall. The influence of ground motion characteristics on rotational displacement of the wall is evaluated. Also the effects of variation of parameters like wall friction angle, soil friction angle, amplification factor, shear wave velocity, primary wave velocity, period of lateral shaking, horizontal and vertical seismic accelerations on the rotational displacements are studied. The rotational displacement of the wall increases substantially with increase in amplification of both shear and primary waves, time of input motion, period of lateral shaking and decreases with increase in soil friction angle, wall friction angle. The rotational displacements of the wall also increase when the effect of wall inertia is taken into account. Results are provided in graphical form. © 2006 Elsevier Ltd. All rights reserved.
Fatahi, B, Indraratna, B & Khabbaz, H 2007, 'Soft soil improvement induced by tree root suction', Australian Geomechanics Journal, vol. 42, no. 4, pp. 13-18.
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Bioengineering aspects of native vegetation are currently being evolved to improve soil stiffness, slope stabilisation, and erosion control. Tree roots provide three stabilising functions: (a) reinforcement of the soil, (b) dissipation of excess pore pressures and (c) establishing sufficient matric suction to increase the shear strength. The effects of vegetation on soil matric suction, shrinkage and ground settlement are discussed in this paper. A mathematical model for the rate of root water uptake that considers ground conditions, type of vegetation and climatic parameters has been developed. A conical shape is considered to represent the geometry of the tree root zone. Based on this proposed model, the distribution of the moisture and the matric suction profile adjacent to the tree are numerically analysed. Field measurements taken from literature published previously are compared with the authors' numerical model. The predicted results, calculated based on soil, plant, and atmospheric parameters contained in the numerical model, compared favourably with the measured results, justifying the assumptions upon which the model has been developed. The findings of this study indicate that due to significant changes in soil moisture content induced by tree roots, the shear strength of the soil will be enhanced. It is desirable to consider the influence zone of tree roots and the improved soil properties in modern geotechnical designs, benefiting from native vegetation.
Fischer, KA, Sheng, D & Abbo, AJ 2007, 'Modeling of pile installation using contact mechanics and quadratic elements', Computers and Geotechnics, vol. 34, no. 6, pp. 449-461.
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Hossain, Z, Indraratna, B, Darve, F & Thakur, PK 2007, 'DEM analysis of angular ballast breakage under cyclic loading', Geomechanics and Geoengineering, vol. 2, no. 3, pp. 175-181.
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Railway ballast particles undergo significant amount of breakage under repeated train load. Breakage of ballast particles, especially highly angular fresh ones, causes an increase in settlement, contributing to track degradation. The quantitative analysis of the influence of breakage on the stress-strain properties of ballast can be performed either experimentally or numerically. Numerical modeling has the advantage of simulating ballast breakage subject to various types of loading and different boundary conditions for a range of material properties. In this paper, ballast breakage under cyclic loading is simulated using a 2D discrete element method (DEM) utilizing the software PFC2D. A new subroutine is developed and incorporated in the PFC2D analysis to study ballast breakage and to quantify breakage in relation to particle size distribution. The influence of confining pressure on both breakage and permanent deformation is also studied and compared with laboratory observations. The findings of this paper provide an insight into the true ballast behavior under cyclic loading and are expected to assist railway practitioners in developing suitable design criteria for track stability.
Indraratna, B, Raut, AK & Khabbaz, H 2007, 'Constriction-based retention criterion for granular filter design', JOURNAL OF GEOTECHNICAL AND GEOENVIRONMENTAL ENGINEERING, vol. 133, no. 3, pp. 266-276.
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The filter design criteria in practice are currently based on laboratory tests that were carried out on uniform base soil and filter materials. These criteria mostly involve specific particle size ratios, where the system of base soil and filter is represented by some characteristic particle sizes. Consequently, these criteria have limitations when applied to nonuniform materials. In filters, it is the constriction size rather than the particle size that affects filtration. In this paper, a mathematical procedure to determine the controlling constriction size is introduced, and subsequently, a constriction-based retention criterion for granular filters is presented. The model also incorporates the effect of nonuniformity of base soil in terms of its particle size distribution, considering the surface area of the particles. The proposed retention criterion is verified based on experimental data taken from past studies plus large-scale filtration tests carried out by the authors. The model successfully and distinctly demarcates the boundary between effective and ineffective filters in the case of cohensionless base soils. © 2007 ASCE.
Indraratna, B, Shahin, MA & Salim, W 2007, 'Stabilisation of granular media and formation soil using geosynthetics with special reference to railway engineering', Proceedings of the Institution of Civil Engineers - Ground Improvement, vol. 11, no. 1, pp. 27-43.
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Railway ballast breaks down and deteriorates progressively under train cyclic loading, and soft formation soil fails due to repetitive stress, leading to costly rail track maintenance. Using geosynthetics, track conditions can be improved and maintenance costs can be reduced. This paper addresses the potential use of geosynthetics for improving the deformation characteristics of rail ballast and formation soil. The prospective use of different types of geosynthetics was investigated using a large-scale prismoidal triaxial rig, and a plane strain finite element analysis (PLAXIS) of the rig was carried out to obtain the optimum location of geosynthetics in rail track substructure. A large-scale consolidometer was also employed to determine the effect of prefabricated vertical drains (PVDs) in optimising the accelerated primary consolidation of track soft formation. This paper also includes a section where recommendations are made on how to prepare the stability of rail tracks on surface formation soils considerably disturbed/remoulded by the Asian tsunami in Sri Lanka. The research findings reveal that geosynthetics have a good potential for resilient track construction and for reducing the cost of track maintenance. Le ballast d'infrastructure ferroviaire se fracture et se détériore progressivement sous le chargement cyclique des trains et le sol de formation molle se fracture en raison de la charge répétée. Ces dégradations sont à l'origine d'une maintenance coûteuse des voies ferrées. Les conditions de ces infrastructures peuvent s'améliorer et le coût de leur maintenance diminuer grâce à l'utilisation de la géosynthétique. Cet article illustre l'application potentielle de la géosynthétique pour l'amélioration des caractéristiques de déformation du ballast des voies ferroviaires et du sol de formation. L'utilisation prospective de différents types de géosynthétique est étudiée au moyen d'un montage triaxial prismoïde et une a...
Joorabchi, A, Zhang, H & Blumenstein, M 2007, 'Application of artificial neural networks in flow discharge prediction for the Fitzroy River, Australia', Journal of Coastal Research, no. SPEC. ISSUE 50, pp. 287-291.
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Prediction of flow discharge, and in particular floods, in rivers is one of the basic and key information in regards to operation and management of the river systems. The Fitzroy River, one of the largest Australian river systems, has a historical recording of heavy floods and there is a concern for the people of that area to have a clear prediction of the stream discharge to avoid damages. In this paper a feed-forward artificial neural network (ANN) model has been used to forecast the daily flow discharge of the Fitzroy River up to four days ahead. The feed-forward neural network uses error Back-propagation learning algorithm. A cross validation method is applied to prevent the over-fitting problem. The network uses multiple inputs including the daily values of discharge. The network output consists of four neurons in respect to the number of forecasted days. A suitable number of inputs for time-series data were selected by trial and error. Two different multi-layer networks were compared to find the optimised network. The results show an accurate forecasting of flow discharge during flood events. However, the neural network overestimates during low discharge with a mean value of 80 (m3/s).
Kumar, S, Nageswara Rao, B & Pradhan, B 2007, 'Effect of Impactor Parameters and Laminate Characteristics on Impact Response and Damage in Curved Composite Laminates', Journal of Reinforced Plastics and Composites, vol. 26, no. 13, pp. 1273-1290.
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The impact response and the impact-induced damage in a curved composite laminate subjected to transverse impact by a metallic impactor are studied using a three-dimensional finite element method. Several example problems of a graphite/epoxy cylindrical shell are considered and effects of impactor parameter (impactor velocity and impactor mass) and laminate characteristics (shell curvature and fiber orientation of plies) are established. Impact-induced damages (matrix cracking and delamination) are predicted using appropriate three-dimensional stress-based failure criteria. In order to take account of degradation of material due to damage during the impact, the stiffness matrix of the failed region of the laminate is reduced as the solution progresses.
Kwok, NM, Ha, QP, Nguyen, MT, Li, J & Samali, B 2007, 'Bouc-Wen model parameter identification for a MR fluid damper using computationally efficient GA', ISA TRANSACTIONS, vol. 46, no. 2, pp. 167-179.
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A non-symmetrical Bouc-Wen model is proposed in this paper for magnetorheological (MR) fluid dampers. The model considers the effect of non-symmetrical hysteresis which has not been taken into account in the original Bouc-Wen model. The model parameters are identified with a Genetic Algorithm (GA) using its flexibility in identification of complex dynamics. The computational efficiency of the proposed GA is improved with the absorption of the selection stage into the crossover and mutation operations. Crossover and mutation are also made adaptive to the fitness values such that their probabilities need not be user-specified. Instead of using a sufficiently number of generations or a pre-determined fitness value, the algorithm termination criterion is formulated on the basis of a statistical hypothesis test, thus enhancing the performance of the parameter identification. Experimental test data of the damper displacement and force are used to verify the proposed approach with satisfactory parameter identification results. © 2007 ISA.
Lackenby, J, Indraratna, B, McDowell, G & Christie, D 2007, 'Effect of confining pressure on ballast degradation and deformation under cyclic triaxial loading', Géotechnique, vol. 57, no. 6, pp. 527-536.
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Traditional railway foundations or substructures have become increasingly overloaded in recent years, owing to the introduction of faster and heavier trains. A lack of substructure re-engineering has resulted in maintenance cycles becoming more frequent and increasingly expensive. Two significant problems arising from increasing axle loads are differential track settlement and ballast degradation. One potential method of enhancing the substructure is to manipulate the level of ballast confinement. To investigate this possibility, a series of high-frequency cyclic triaxial tests has been conducted to examine the effects of confining pressure and deviator stress magnitude on ballast deformation (permanent and resilient) and degradation. Experimental results indicate that, for each deviator stress considered, an 'optimum' range of confining pressures exists such that degradation is minimised. This range was found to vary from 15–65 kPa for a maximum deviator stress of 230 kPa to 50–140 kPa when deviatoric stresses increase to 750 kPa. Ballast specimens tested at low confining pressures indicative of current in situ conditions were characterised by excessive axial deformations, volumetric dilation, and an unacceptable degree of degradation associated mainly with angular corner breakage. The results suggest that in situ lateral pressures should be increased to counteract the axle loads of heavier trains, and practical methods of achieving increased confinement are suggested.
Lee, S & Pradhan, B 2007, 'Landslide hazard mapping at Selangor, Malaysia using frequency ratio and logistic regression models', Landslides, vol. 4, no. 1, pp. 33-41.
Lee, S & Pradhan, B 2007, 'Landslide hazard mapping at Selangor, Malaysia using frequency ratio and logistic regression models', Landslides, vol. 4, no. 1, pp. 33-41.
Lee, S & Pradhan, B 2007, 'Landslide hazard mapping at Selangor, Malaysia using frequency ratio and logistic regression models', Landslides, vol. 4, no. 1, pp. 33-41.
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Lee, S & Pradhan, B 2007, 'Landslide hazard mapping at Selangor, Malaysia using frequency ratio and logistic regression models. Landslides 4: 3341Lee S, Sambath T (2006) Landslide susceptibility mapping in the Damrei Romel area, Cambodia using frequency ratio and logistic regression models', Environ Geol, vol. 50, no. 6, p. 847855Lee.
Li, J, Choi, FC, Samali, B & Crews, K 2007, 'Damage localisation and severity evaluation of a beam-like timber structure based on modal strain energy and flexibility approaches', Journal of Building Appraisal, vol. 2, no. 4, pp. 323-334.
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Li, X, Chu, X & Sheng, DC 2007, 'A saturated discrete particle model and characteristic‐based SPH method in granular materials', International Journal for Numerical Methods in Engineering, vol. 72, no. 7, pp. 858-882.
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AbstractBased on the discrete particle model for solid‐phase deformation of granular materials consisting of dry particulate assemblages, a discrete particle–continuum model for modelling the coupled hydro‐mechanical behaviour in saturated granular materials is developed. The motion of the interstitial fluid is described by two parallel continuum schemes governed by the averaged incompressible N–S equations and Darcy's law, respectively, where the latter one can be regarded as a degraded case of the former.Owing to the merits in both Lagrangian and mesh‐free characters, the characteristic‐based smoothed particle hydrodynamics (SPH) method is proposed in this paper for modelling pore fluid flows relative to the deformed solid phase that is modelled as packed assemblages of interacting discrete particles. It is assumed that the formulation is Lagrangian with the co‐ordinate system transferring with the movement of the solid particles. The assumed continuous fluid field is discretized into a finite set of Lagrangian (material) points with their number equal to that of solid particles situated in the computational domain. An explicit meshless scheme for granular materials with interstitial water is formulated. Numerical results illustrate the capability and performance of the present model in modelling the fluid–solid interaction and deformation in granular materials saturated with water. Copyright © 2007 John Wiley & Sons, Ltd.
Mansor, S, Pradhan, B, Daud, M, Khuzaimah, Z & Lee, S 2007, 'Utilization of optical remote sensing data and GIS tools for regional landslide hazard analysis in Malaysia', Journal of the Institution of Surveyors Malaysia, vol. 51, pp. 50-55.
Merz, S, Oberst, S, Dyleiko, PG, Kessissoglou, N, Tso, YK & Marburg, S 2007, 'Document Development of coupled FE/BE models to investigate the structural and acoustic responses of a submerged vessel', Journal of Computational Acoustics, vol. 15, no. 1, pp. 23-47.
Nimbalkar, S & Choudhury, D 2007, 'Sliding stability and seismic design of retaining wall by pseudo-dynamic method for passive case', Soil Dynamics and Earthquake Engineering, vol. 27, no. 6, pp. 497-505.
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Pradhan, B & Awang, MAB 2007, 'Application of Remote Sensing and GIS for forest fire susceptibility mapping using likelihood ratio model'.
Pradhan, B & Lee, S 2007, '利用光学遥感数据, GIS 及人工神经网络模型分析区域滑坡灾害', 地学前缘, vol. 14, no. 6, pp. 143-152.
Pradhan, B & Mansor, S 2007, 'Application of remote sensing data and gis tools for regional landslide hazard analysis at Cameron Highland, Malaysia by using logistic regression model', Proceedings of IEEE International Geoscience and Remote Sensing, pp. 23-27.
Pradhan, B, Dini Hairi Bin Suliman, M & Arshad Bin Awang, M 2007, 'Forest fire susceptibility and risk mapping using remote sensing and geographical information systems (GIS)', Disaster Prevention and Management: An International Journal, vol. 16, no. 3, pp. 344-352.
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PurposeIn a tropical country like Malaysia, forest fire is a very common natural and man‐made disaster that prevails in the whole South East Asian region throughout the year. Recently, the haze problem in Malaysia has created a lot of awareness among the government and eco‐tourism sectors. Therefore, detection of the hotspot is very important to delineate the forest fire susceptibility mapping. In this study, remote sensing and geographical information systems (GIS) have been used to evaluate forest fire susceptibility at Sungai Karang and Raja Muda Musa Forest Reserve, Selangor, Malaysia. Frequency ratio model has been applied for the delineation of forest fire mapping for the study area.Design/methodology/approachForest fire locations were identified in the study area from historical hotspots data from year 2000 to 2005 using AVHRR NOAA 12 and NOAA 16 satellite images. Various other supported data such as soil map, topographic data, and agro climate were collected and created using GIS. These data were constructed into a spatial database using GIS. The factors that influence fire occurrence, such as fuel type and Normalized Differential Vegetation Index (NDVI), were extracted from classified Landsat‐7 ETM imagery. Slope and aspect of topography were calculated from topographic database. Soil type was extracted from soil database and dry month code from agroclimate data. Forest fire susceptibility was analyzed using the forest fire occurrence factors by likelihood ratio method.FindingsA new statistical method has been applied for the forest fire susceptibility mapping. The results of the analysis were verified using forest fire location data with the help of a newly written programming code. ...
Pradhan, B, Sandeep, K, Mansor, S, Rahman Ramli, A & Sharif, ARBM 2007, 'Second generation wavelets based GIS terrain data compression using Delaunay triangulation', Engineering Computations, vol. 24, no. 2, pp. 200-213.
Pradhan, B, Sandeep, K, Mansor, S, Rahman Ramli, A & Sharif, ARBM 2007, 'Second generation wavelets based GIS terrain data compression using Delaunay triangulation', Engineering Computations, vol. 24, no. 2, pp. 200-213.
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PurposeIn GIS applications for a realistic representation of a terrain a great number of triangles are needed that ultimately increases the data size. For online GIS interactive programs it has become highly essential to reduce the number of triangles in order to save more storing space. Therefore, there is need to visualize terrains at different levels of detail, for example, a region of high interest should be in higher resolution than a region of low or no interest. Wavelet technology provides an efficient approach to achieve this. Using this technology, one can decompose a terrain data into hierarchy. On the other hand, the reduction of the number of triangles in subsequent levels should not be too small; otherwise leading to poor representation of terrain.Design/methodology/approachThis paper proposes a new computational code (please see Appendix for the flow chart and pseudo code) for triangulated irregular network (TIN) using Delaunay triangulation methods. The algorithms have proved to be efficient tools in numerical methods such as finite element method and image processing. Further, second generation wavelet techniques popularly known as “lifting schemes” have been applied to compress the TIN data.FindingsA new interpolation wavelet filter for TIN has been applied in two steps, namely splitting and elevation. In the splitting step, a triangle has been divided into several sub‐triangles and the elevation step has been used to “modify” the point values (point coordinates for geometry) after the splitting. Then, this data set is compressed at the desired locations by using second generation wavelets.Originality/va...
Rujikiatkamjorn, C & Indraratna, B 2007, 'Analytical solutions and design curves for vacuum-assisted consolidation with both vertical and horizontal drainage', Canadian Geotechnical Journal, vol. 44, no. 2, pp. 188-200.
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A system of vertical drains combined with vacuum preloading is an effective method for promoting radial flow to accelerate soil consolidation. This study presents the analytical modeling of the consolidation of vertical drains incorporating vacuum preloading considering both vertical and horizontal drainage. The effects of a number of dimensionless parameters involving the drain length, soil permeability, and vacuum pressure are examined through average excess pore pressure, degree of consolidation, associated settlement, and time factor analyses. An analysis of selected case histories compliments the use of the proposed solutions. Design charts are also presented for practical use.Key words: analytical solution, consolidation, design charts, vertical drains.
Rujikiatkamjorn, C & Indraratna, B 2007, 'Soft ground improvement by vacuum-assisted preloading', Australian Geomechanics Journal, vol. 42, no. 4, pp. 19-29.
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This paper describes the behaviour of soft soil foundation stabilized with vacuum-assisted preloading at the New Bangkok International Airport, Thailand. An analytical solution considering the variation of soil permeability and compressibility and a finite element analysis based on an equivalent plane strain model developed by the authors are employed to investigate the performance of the test embankment. The converted equivalent plane strain parameters are incorporated in the finite element code ABAQUS. The associated settlement, excess pore pressure and lateral movement are predicted and compared with the available field measurements. The data indicate that the efficiency of the prefabricated vertical drains depends on the magnitude and distribution of vacuum pressure as well as on the extent of air leak protection provided in practice. The height of sand surcharge and consolidation time are significantly reduced in comparison with the conventional method of surcharge alone. The effectiveness of this method, its economies and its merit potential are also discussed.
Rujikiatkamjorn, C, Indraratna, B & Chu, J 2007, 'Numerical modelling of soft soil stabilized by vertical drains, combining surcharge and vacuum preloading for a storage yard', Canadian Geotechnical Journal, vol. 44, no. 3, pp. 326-342.
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This paper presents a finite element analysis of a case study of a combined vacuum and surcharge load through prefabricated vertical drains (PVD) at a storage yard at Port of Tianjin, China. The top 15 m of soil at this site was very soft to soft and needed to be improved using preloading surcharges of more than 140 kPa. To avoid any stability problems associated with a high surcharge embankment, 80 kPa vacuum pressure combined with fill surcharge was applied (40 and 58 kPa for sections I and II, respectively). A plane strain analysis was performed using equivalent permeability and transformed unit-cell geometry. The converted (equivalent) parameters were incorporated in the finite element code ABAQUS, using the modified Cam-Clay theory. The performance of a trial embankment at the site of the storage yard is predicted on the basis of a constant vacuum pressure applied on the soil surface and distributed along the length of the drain. The predictions of settlement, pore-water pressure, and lateral displacement were compared with the available field data, and an acceptable agreement was found based on this numerical approach. The combination of vacuum and surcharge load can effectively shorten the preloading period, reduce the height of the embankment, and counterbalance excessive lateral displacements.Key words: consolidation, finite element analysis, plane strain method, soil improvement, vertical drains.
Samali, B, Li, J, Crews, KI & Al-dawod, M 2007, 'Load rating of impaired bridges using a dynamic method', Electronic Journal of Structural Engineering, vol. 7, pp. 66-75.
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Local Government in Australia is responsible for the operational management and maintenance of over 20,000 bridges. More than 70% of these bridges comprise aging timber bridges, the load capacity and structural adequacy of many of which have been impaired over time. This is partly due to increased vehicular loads with little attention to consequence of such increases. It is now necessary to determine the load carrying capacity of these bridges using simple yet reliable methods to allow local authorities to upgrade, replace or sign post at-risk bridges. In this paper a novel dynamic based method is presented by which the in-service stiffness of the bridge is estimated first. From this stiffness the load carrying capacity of the bridge is estimated following a statistically based analysis.
Sheng, D, Wriggers, P & Sloan, SW 2007, 'Application of Frictional Contact in Geotechnical Engineering', International Journal of Geomechanics, vol. 7, no. 3, pp. 176-185.
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Soil-structure interaction is traditionally simplified to prescribed boundary conditions or modeled by joint elements. Both of these approaches are limited to small and continuous relative displacements at the interface. The use of contact constraints opens up a fresh range of possibilities for geotechnical analysis, especially for cases involving large interfacial deformation. This paper demonstrates the application of computational contact mechanics in geotechnical engineering. It first outlines a general description of kinematic constraints for frictional contact and the associated numerical algorithms. A number of classical geotechnical problems are then analyzed using finite-element contact methods. These problems include a strip footing under eccentric and inclined loads and a cone penetration test. It is shown that the finite-element method with frictional contact is indeed very useful in geotechnical analysis, and can provide solutions to problems that are otherwise very difficult to analyze. © 2007 ASCE.
Sun, D, Sheng, D & Sloan, SW 2007, 'Elastoplastic modelling of hydraulic and stress–strain behaviour of unsaturated soils', Mechanics of Materials, vol. 39, no. 3, pp. 212-221.
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Sun, D, Sheng, D & Xu, Y 2007, 'Collapse behaviour of unsaturated compacted soil with different initial densities', Canadian Geotechnical Journal, vol. 44, no. 6, pp. 673-686.
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Very few experimental data on the mechanical behaviour of unsaturated soils exists, particularly on the collapse behaviour under general stress states, because of the technical difficulties and time-consuming nature of measuring suction and deformation. This paper presents the results of a series of controlled-suction triaxial tests on the collapse behaviour of an unsaturated compacted clay with different initial dry densities and suctions. The collapse behaviour here includes deformation characteristics, such as volume changes, and hydraulic characteristics, such as saturation changes. It is found that the wetting-caused collapse mainly depends on the mean net stress and the initial density, and that the volume decrease reaches a maximum when the specimen is under the initial yielding mean net stress. It is also found that the soil-water characteristic curve in terms of suction and degree of saturation shifts upwards with increasing specimen density. The soil-water characteristic curve of a compacted soil mainly depends upon the current density, not directly upon the stress state. In addition, experimental data show that the collapse occurs mainly in an intermediate range of suction levels, which are neither very high nor very low, and that the wetting-caused volume decrease is accompanied by an increase in the degree of saturation.Key words: unsaturated soil, density, triaxial test, suction, collapse, degree of saturation.
Sun, DA, Cui, HB, Matsuoka, H & Sheng, DC 2007, 'A Three-Dimensional Elastoplastic Model for Unsaturated Compacted Soils with Hydraulic Hysteresis', Soils and Foundations, vol. 47, no. 2, pp. 253-264.
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Sun, DA, Sheng, DC, Cui, HB & Sloan, SW 2007, 'A density‐dependent elastoplastic hydro‐mechanical model for unsaturated compacted soils', International Journal for Numerical and Analytical Methods in Geomechanics, vol. 31, no. 11, pp. 1257-1279.
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AbstractThis paper presents a three‐dimensional elastoplastic constitutive model for predicting the hydraulic and mechanical behaviour of unsaturated soils. It is based on experimental results obtained from a series of controlled‐suction triaxial tests on unsaturated compacted clay with different initial densities. Hydraulic hysteresis in the water‐retention behaviour is modelled as an elastoplastic process, with the elastic part modelled by a series of scanning curves and the elastoplastic part modelled by the main drying and wetting curves. The effect of void ratio on the water‐retention behaviour is studied using data obtained from controlled‐suction wetting–drying cyclic tests on unsaturated compacted clay with different initial densities. The effect of the degree of saturation on the stress–strain‐strength behaviour and the effect of void ratio on the water‐retention behaviour are considered in the model, as is the effect of suction on the hydraulic and mechanical behaviour. The initial density dependency of the compacted soil behaviour is modelled by experimental relationships between the initial density and the corresponding yield stress and, thereby, between the initial density and the normal compression line. The model is generalized to three‐dimensional stress states by assuming that the shapes of the failure and yield surfaces in the deviatoric stress plane are given by the Matsuoka–Nakai criterion. Model predictions of the stress–strain and water‐retention behaviour are compared with those obtained from triaxial tests with different initial densities under isotropic compression, triaxial compression and triaxial extension, with or without variation in suction. The comparisons indicate that the model accurately predicts the hydraulic and mechanical behaviour of unsaturated compacted soils with different initial densities using the same material constant. Copyright © 2006 John Wiley & Sons, Ltd.
Tong, Y, Wang, Y, Zhu, Z & Ji, Q 2007, 'Robust facial feature tracking under varying face pose and facial expression', Pattern Recognition, vol. 40, no. 11, pp. 3195-3208.
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Walker, R & Indraratna, B 2007, 'Vertical drain consolidation with overlapping smear zones', Géotechnique, vol. 57, no. 5, pp. 463-467.
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Widjaja, J, Samali, B & Li, J 2007, 'Erratum: The use of displacement threshold for switching frequency strategy for structural vibration mitigation (Journal of Mechanical Science and Technology (2007) 21 (865-869))', Journal of Mechanical Science and Technology, vol. 21, no. 10, p. 1756.
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Widjaja, J, Samali, B & Li, J 2007, 'The use of displacement threshold for switching frequency strategy for structural vibration mitigation', Journal of Mechanical Science and Technology, vol. 21, no. 6, pp. 865-869.
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Zhang, H, Jeng, DS, Cha, D & Blumenstein, M 2007, 'Parametric study on the prediction of wave-induced liquefaction using an artificial neural network model', Journal of Coastal Research, no. SPEC. ISSUE 50, pp. 374-378.
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The prediction of the wave-induced liquefaction potential is particularly important for coastal engineers involved in the design of marine structures. An artificial neural network (ANN) model is used to estimate the waveinduced liquefaction in terms of wave and seabed sediment conditions. The sensitivity of wave and seabed sediment parameters is extensively investigated to get the most accurate results. The deterministic wave and liquefaction models are used to explain the parameter features physically. Numerical examples demonstrate the capacity of the ANN modelling approach in simulating complex mechanisms such as wave-induced liquefaction with adequate information.
Zhao, J, Sheng, D & Sloan, SW 2007, 'Cavity expansion of a gradient-dependent solid cylinder', International Journal of Solids and Structures, vol. 44, no. 13, pp. 4342-4368.
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Zhao, J, Sheng, D, Sloan, SW & Krabbenhoft, K 2007, 'Limit theorems for gradient-dependent elastoplastic geomaterials', International Journal of Solids and Structures, vol. 44, no. 2, pp. 480-506.
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Abolhasan, M, Wang, JC-P & Franklin, DR 1970, 'On Indoor Multi-hopping capacity of Wireless Ad-Hoc Mesh Networks.', MASS, MASS 2007, IEEE Computer Society, Pisa, Italy, pp. 1-6.
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The capacity and multi-hopping performance of ad hoc mesh networks in dynamic environment still remains an open research issue. Previous theoretical studies suggest that they do not scale in densely distributed networks. However, a study has shown that scalability and hence the multi- hopping capacity of mesh network is not only bound by the number of nodes in the network but also the number of hops [3]. In this paper we investigate the performance of multi- hop ad hoc mesh networks, using both simulation studies and an experimental test-bed, and monitor the performance of the network as the number of hops in the network increases. Our results show that the drop in performance in multi-hopping is much more significant when the traffic levels are high. Furthermore our test-bed study shows that ad hoc mesh networks can maintain high levels of packet delivery and throughput when traffic levels are low, however, the delay experienced continues to increase after each hop.
Abolhasan, M, Wang, JC-P, Franklin, DR & IEEE 1970, 'On indoor multi-hopping capacity of wireless ad-hoc mesh networks', 2007 IEEE INTERNATIONAL CONFERENCE ON MOBILE AD-HOC AND SENSOR SYSTEMS, VOLS 1-3, IEEE International Conference on Mobile Adhoc and Sensor Systems, IEEE, Pisa, ITALY, pp. 917-922.
Choi, FC, Li, J, Samali, B & Crews, K 1970, 'Damage evaluation of a timber beam using a modal-based method', Progress in Mechanics of Structures and Materials - Proceedings of the 19th Australasian Conference on the Mechanics of Structures and Materials, ACMSM19, Australasian Conference on the Mechanics of Structures and Materials, Taylor and Francis, Christchurch, New Zealand, pp. 1005-1010.
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In Australia, many timber bridges are old and increasingly experience deterioration, aging and traffic overloading problems. These have attracted attention of researchers to evaluate the current state of such bridges. Whilst proof-load testing and traditional nondestructive evaluation (NDE) provide valuable tools, such procedures are often time consuming and costly. For bridge structures, to develop effective NDE at global level viz damage identification and structural health monitoring using modal-based damage identification methods have engrossed recent worldwide research efforts. However, to date there are few works reported on timber bridges using modal-based damage identification methods to evaluate their state of health. In this paper, modal-based damage identification methods for localization of damage in timber bridges are presented based on finite element analysis (FEA) and test results of a timber beam. Two algorithms of global NDE for identifying local damage and decay in timber structures are investigated. The methods employ modal parameters that monitor changes in modal strain energy (MSE) based on curvature mode shapes of a damaged beam with respect to the undamaged one. The aim of the study is to investigate the capability and limitations of the proposed algorithms for detecting damage with multiple damage scenarios in timber structures. Between the two proposed modal based damage identification algorithms, the modified method has shown better results in solving multiple damage problems. © 2007 Taylor & Francis Group, London.
Conder, P, Gao, J, Abolhasan, M & IEEE 1970, 'Distributed MIMO systems using Asterism decoding', 2007 INTERNATIONAL SYMPOSIUM ON COMMUNICATIONS AND INFORMATION TECHNOLOGIES, VOLS 1-3, International Symposium on Communications and Information Technologies, IEEE, Sydney, Australia, pp. 269-272.
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Multiple Input Multiple Output (MIMO) systems have received enormous attention by researchers as they can provide a roughly linear increase in capacity of wireless communications systems by using multiple transmit and receive antennas. Even with the larger raw data rates provided by MIMO, the throughput of these systems can be limited by the number of users (or networks) sharing the medium. This paper shows how multiple users (or networks) transmitting simultaneously can be represented as a MIMO system with a lager number of transmit than receive antennas. After reviewing existing decoders for such a MIMO system, this paper then proposes applying an Asterism based decoder to distinguish between multiple users transmitting simultaneously. This produces a new multi-user access scheme that can be applied in addition to a primary access method, such as CSMA-CA.
Fatahi, B, Indraratna, B & Khabbaz, H 1970, 'Analysing Soft Ground Improvement Caused by Tree Root Suction', Advances in Measurement and Modeling of Soil Behavior, Geo-Denver 2007, American Society of Civil Engineers, Denver, Colorado, USA, pp. 6-10.
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Bioengineering aspects of native vegetation are currently being evolved to improve soil stiffness, slope stabilisation, and erosion control. Vegetation contributes to weak soil stabilisation through reinforcement of the soil, dissipation of excess pore pressures, and increasing the shear strength by induced matric suction. This paper looks at the way that vegetation influences soil matric suction, shrinkage, and ground settlement. A theoretical model previously developed by the authors for the rate of tree root water uptake together with an associated numerical simulation is used in this study. A conical shape is considered to represent the geometry of the tree root zone. Based on this proposed model, the distribution of moisture and the matric suction profile adjacent to the tree are numerically analysed. Field measurements taken from previously published literature are compared with numerical predictions for further validation. The predicted results compared favourably with the measured results, justifying the assumptions upon which the model was developed. It is desirable to consider the influence zone of tree roots and the improved soil properties in modern geotechnical designs, benefiting from native vegetation. Copyright ASCE 2007.
Fatahi, B, Indraratna, B & Khabbaz, H 1970, 'Enhanced numerical analysis of ground behaviour influenced by tree root suction', Common Ground: Proceedings of the 10th Australia and New Zealand Conference on Geomechanics, Australia New Zealand Geomechanics conference, Coffey Geotechnics, Brisbane, Australia, pp. 142-147.
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Tree roots provide three stabilising functions: (a) reinforcement of the soil, (b) dissipation of excess pore pressures, (c) establishing sufficient matric suction to increase the shear strength. This paper looks at the way that vegetation influences soil moisture content distribution, and ground settlement. A theoretical model previously developed by the authors for the rate of tree root water uptake together with an associated numerical simulation is used in this study. Field measurements taken from literature published previously are compared with the authors' numerical model. The predicted results obtained from the numerical analysis, compared favourably with the field measurements, justifying the assumptions upon which the model was developed.
Green, S & Blumenstein, M 1970, 'A Comparison of Neural-Based Techniques Investigating Rotational Invariance for Upright People Detection in Low Resolution Imagery', Lecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics), Springer Berlin Heidelberg, pp. 647-653.
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This paper describes a neural-based technique for detecting upright persons in low-resolution beach imagery in order to predict trends of tourist activities at beach sites. The proposed system uses a structural feature extraction technique to represent objects of interest for training a selection of neural classifiers. A number of neural-based classifiers are compared in this study and a direction-based feature extraction technique is investigated in conjunction with a rotationally invariant procedure for the purpose of beach object classification. Encouraging results are presented for person detection using video imagery collected from a beach site on the coast of Australia. © Springer-Verlag Berlin Heidelberg 2007.
Indraratna, B, Golab, A, Glamore, W & Blunden, B 1970, 'Acid sulphate soil remediation techniques on the Broughton Creek Floodplain, New South Wales, Australia', Geotechnical and Environmental Aspects of Waste Disposal Sites - Proceedings of Green4 International Symposium on Geotechnics Related to the Environment, pp. 349-357.
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One-way floodgates were commonly installed on flood mitigation drains in coastal areas of Australia during the late 1960s. In acid sulphate soil affected regions, the floodgates create reservoirs of acidic water that discharge at low tide. Several successful remediation techniques have been used in south-eastern NSW, Australia. Groundwater elevation and quality were monitored and modelled using finite element software and fixed level v-notch weirs were installed at three elevations in a drain. The weirs successfully maintained the groundwater elevation above the acid sulphate soil layer and reduced the acid discharge rate to the drain. Following geochemi-cal modelling, modified two-way floodgates that allow tidal ingress were installed. The modified floodgates buffer the drain water pH before discharging into adjacent waterways. Monitoring proved that saline intrusion into the surrounding soil from the drains was not a major concern for the pastureland or other agricultural activities. © 2007 Taylor & Francis Group, London.
Indraratna, B, Rujikiatkamjorn, C & Chu, J 1970, 'Soft Clay Stabilization with Geosynthetic Vertical Drains beneath Road and Railway Embankments: A Critical Review of Analytical Solutions and Numerical Analysis', Advances in Measurement and Modeling of Soil Behavior, Geo-Denver 2007, American Society of Civil Engineers, p. 7.
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In the wide array of existing ground improvement schemes, the use of vertical drains with vacuum preloading is considered as the most effective and economical method for improving soft clays (normally consolidated to lightly over-consolidated) prior to construction of infrastructure. Vertical drains installed to significant depths promote radial flow inducing consolidation rapidly enhancing the shear strength of the compressed ground. In this paper, the analytical solutions based on lateral soil permeability (parabolic variation) are discussed considering the variation of vacuum pressure with depth along the prefabricated vertical drains (PVD). Using the Cavity Expansion Theory (CET), the smear zone caused by the installation of PVD by steal mandrel was predicted and compared with laboratory measurements obtained from large-scale radial consolidation tests. The effects of drain unsaturation and vacuum pressure along the drain length are also discussed. The numerical analyses incorporating equivalent plane strain solutions were performed to predict the soil responses based on two selected case histories in Thailand. The research findings provided insight as to which of the above aspects needed to be simulated accurately in numerical modelling. The application of cyclic loading on PVD stabilized ground was also examined using a finite element approach under railway embankment. It is demonstrated that short drains less than 8 m installed beneath tracks are still useful for effective dissipation of cyclic pore pressures and curtailing unacceptable lateral movement immediately below the track level, at the same time avoiding excessive settlement of the track in the short-term. Copyright ASCE 2007.
Indraratna, B, Rujikiatkamjorn, C, Wijeyakulasuriya, V, Shahin, MA & Christie, D 1970, 'Soft soil stabilisation with special reference to road and railway embankments', Proceedings of the 4th International Conference on Soft Soil Engineering - Soft Soil Engineering, 4th International Conference on Soft Soil Engineering, TAYLOR & FRANCIS LTD, Vancouver, CANADA, pp. 35-55.
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Much of Australian railway tracks traverse coastal areas containing soft soils and marine deposits. Pre-construction stabilization of soft formation soils by applying a surcharge load alone often takes too long. The installation of prefabricated vertical drains (PVDs) can reduce the preloading period significantly by decreasing the drainage path length, sometimes by a factor of 10 or more. The analytical solution based on actual radial soil permeability is proposed considering the variation of vacuum pressure, and the Cavity Expansion Theory is employed to predict the smear zone caused by the installation of mandrel driven vertical drains. The predicted smear zone and the effect of drain unsaturation are compared with data obtained from a large-scale radial consolidation tests and the results are explained. When a higher load is required to meet the desired rate of settlement and the cost of surcharge is also significant, the application of vacuum pressure with reduced surcharge loading can be used. In this method, an external negative load is applied to the soil surface in the form of vacuum pressure through a sealed membrane system. The applied vacuum pressure generates negative pore water pressure, resulting in an increase in effective stress and accelerated consolidation, also avoiding the need for a high surcharge embankment. The analytical and numerical analyses incorporating the authors' equivalent plane strain solution for both Darcian and non-Dracian flow are conducted to predict the excess pore pressures, lateral and vertical displacements and several selected case histories are analysed and presented. Cyclic loading of PVDs is also examined in the laboratory in a manner appropriate for railway environments. It is shown that short PVDs can dissipate excess pore pressure as fast as they are built up under repeated loading conditions. The research findings verify that the impact of smear and vacuum pressure can significantly affect soil consolid...
Li, J, Choi, FC & Samali, B 1970, 'Modal-based damage identification methods for plate-like structures', Progress in Mechanics of Structures and Materials - Proceedings of the 19th Australasian Conference on the Mechanics of Structures and Materials, ACMSM19, Australasian Conference on the Mechanics of Structures and Materials, Taylor and Francis, Christchurch, New Zealand, pp. 909-914.
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A great deal of work has been done in the area of damage identification in structures using changes of modal parameters before and after damage. Most of the developments have been based on beam theory and application to beam-like or truss structures. Few researchers have contributed to in-depth study of damage identification of plate-like structures employing modal-based methods. In this paper, two modal strain energy based damage identification methods have been expanded for detecting damage and evaluation of damage severity in plate-like structures. The study is based on finite element analysis (FEA) results of a plate model. The purpose of the study is to explore feasibility of using modal strain energy based methods for damage identification of plate-like structures. The results show that one modified method based on a two-dimensional mode shape curvature in computing the damage index provides very good damage localisation and severity estimation. © 2007 Taylor & Francis Group, London.
Li, J, Samali, B & Crews, K 1970, 'A cost effective approach for integrity assessment of timber bridges', Progress in Mechanics of Structures and Materials - Proceedings of the 19th Australasian Conference on the Mechanics of Structures and Materials, ACMSM19, Australasian Conference on the Mechanics of Structures and Materials, Taylor and Francis, Christchurch, New Zealand, pp. 1037-1042.
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To develop a reliable and cost effective tool to assess the structural integrity of aged timber bridges is currently a challenge facing structural engineers. Whilst proof-load testing and Non-destructive Evaluation (NDE) techniques provide valuable assessment, such procedures are generally too complex, costly and time consuming to be applied across the entire inventory of timber bridges. A simple dynamic based testing method was developed by authors to lower the cost and shorten the testing time. The method has recently been used successfully to undertake field-testing of more than 180 timber bridges across NSW. This paper summarises the analytical development of this new approach together with some experimental examples. In the analytical studies, a closed form solution was obtained to provide an explicit relationship between the flexural stiffness and measured modal parameters. A beam with spring and masses attached was used to model a bridge with added mass or alternative added mass such as a trailer and/or a water tank for bridge testing. After obtaining the in-service stiffness of the tested bridge, a probabilistic modelling based on bending strength and gross stiffness (EI) of timber girders, is developed to provide an assessment of bridge load carrying capacity by using predicted in-service stiffness. Results of experimental studies and field testing using this approach are given in the references. © 2007 Taylor & Francis Group, London.
Mansor, S, Pradhan, B, Daud, M, Jamaludin, N & Khuzaimah, Z 1970, 'Landslide susceptibility analysis using an artificial neural network model', SPIE Proceedings, Remote Sensing, SPIE, Florence, ITALY.
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Mansor, S, Pradhan, B, Daud, M, Jamaludin, N & Khuzaimah, Z 1970, 'Landslide susceptibility analysis using an artificial neural network model', Remote Sensing, International Society for Optics and Photonics, pp. 67490J-67490J.
Mansor, S, Pradhan, B, Daud, M, Jamaludin, N & Khuzaimah, Z 1970, 'Landslide susceptibility analysis using an artificial neural network model [6749-18]', PROCEEDINGS-SPIE THE INTERNATIONAL SOCIETY FOR OPTICAL ENGINEERING, International Society for Optical Engineering; 1999, p. 6749.
MERZ, S, OBERST, S, DYLEJKO, PG, KESSISSOGLOU, NJ, TSO, YK & MARBURG, S 1970, 'DEVELOPMENT OF COUPLED FE/BE MODELS TO INVESTIGATE THE STRUCTURAL AND ACOUSTIC RESPONSES OF A SUBMERGED VESSEL', Journal of Computational Acoustics, 7th International Conference on Theoretical and Computational Acoustics, World Scientific Pub Co Pte Lt, Hangzhou, PEOPLES R CHINA, pp. 23-47.
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An analytical model and a fully coupled finite element/boundary element model are developed for a simplified physical model of a submarine. The submerged body is modeled as a ring-stiffened cylindrical shell with finite rigid end closures, separated by bulkheads into a number of compartments and under axial excitation from the propeller-shafting system. Lumped masses are located at each end to maintain a condition of neutral buoyancy. Excitation of the hull axial modes from the propeller-shafting system causes both axial motion of the end closures and radial motion of the shell, resulting in a high level of radiated noise. In the low frequency range, only the axial modes in breathing motion are examined, which gives rise to an axisymmetric case, since these modes are efficient radiators. An expression for the structurally radiated sound pressure contributed by axial movement of the end plates and radial motion of the shell was obtained using the Helmholtz integral equation. In the computational model, the effects of the various influencing factors (ring stiffeners, bulkheads, realistic end closures, and fluid loading) on the free vibrational characteristics of the thin walled cylinder are examined. For both the analytical and computational models, the frequency responses, axial and radial responses of the cylinder, and the radiated sound pressure are compared.
Nazem, M, Sheng, D & Abbo, AJ 1970, 'Alternative stress integration schemes in large deformation problems of geomechanics', NUMERICAL MODELS IN GEOMECHANICS: NUMOG X, 10th International Symposium on Numerical Models in Geomechanics (NUMOG X), TAYLOR & FRANCIS LTD, Rhodes, GREECE, pp. 219-224.
Nazem, M, Sheng, D & Abbo, AJ 1970, 'Alternative stress integration schemes in large deformation problems of geomechanics', Proceedings of the 10th International Symposium on Numerical Models in Geomechanics NUMOG 10 - Numerical Models in Geomechanics NUMOG 10, pp. 219-224.
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In nonlinear finite element analysis, loads are usually applied in increments and the corresponding incremental displacements are obtained by solving the global equilibrium equations. The incremental strains can be computed from the incremental displacements. These strain increments are then used to determine the stresses at integration points by integrating the nonlinear constitutive equations. In a large deformation analysis, the stress-strain relationships must be objective. The objectivity requires that the constitutive equations be frame-independent such that any rigid body motion does not induce strain within the material. This principle is generally satisfied by introducing an objective stress-rate, such as Jaumann or Truesdell stress rates, into the stress-strain relationships. This study investigates alternative schemes for integrating stress-strain relationships in the large deformation analysis of geotechnical problems. It is shown that the effect of rigid body motion is equivalent to a stress transformation and this transformation can be introduced before, after or during integration of the stress-strain constitutive equations. However there is no theoretical advantage for selecting one of these strategies over the others, except the objectivity consideration. In this paper, three methods for the integration of stress-strain relationships in large deformation analysis are presented. The performance of proposed algorithms are studied and compared by means of numerical examples. The results of this study can be used in development of fast and robust algorithms for stress-integration of constitutive equations in nonlinear finite element analysis. © 2007 Taylor & Francis Group.
Nguyen, MT, Kwok, NM, Ha, QP, Li, J & Samali, B 1970, 'Semi-active direct control of civil structure seismic responses using magneto-rheological dampers', Automation and Robotics in Construction - Proceedings of the 24th International Symposium on Automation and Robotics in Construction, International Symposium on Automation and Robotics in Construction, Lokavani Southern Printers, Kochi, India, pp. 157-162.
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As building structures frequently collapse and cause losses of lives and properties, due to excessive vibrations induced during earthquake periods, it is crucial to reduce the structural vibrations. This paper develops a Lyapunov-based controller for Magnetorheological (MR) dampers embedded in building structures to mitigate quake-induced vibrations. In this work, MR dampers are used as semi-active devices, taking the advantages of the fail-safe operation and low power requirement. To enhance the system performance, a Lyapunov-based controller is proposed here for direct control of the supply currents of the MR dampers placed in a multi-storey building. The effectiveness of the proposed technique is verified in simulation by using a ten-storey building model subject to quake-like excitations.
Nguyen, V, Blumenstein, M, Muthukkumarasamy, V & Leedharn, G 1970, 'Off-line signature verification using enhanced modified direction features in conjunction with neural classifiers and support vector machines', ICDAR 2007: NINTH INTERNATIONAL CONFERENCE ON DOCUMENT ANALYSIS AND RECOGNITION, VOLS I AND II, PROCEEDINGS, 9th International Conference on Document Analysis and Recognition, IEEE COMPUTER SOC, Curitiba, BRAZIL, pp. 734-738.
Pradhan, B & Mansor, S 1970, 'Three dimensional terrain data compression using second generation wavelets', WIT Transactions on Information and Communication Technologies, Vol 38, DATA MINING & INFORMATION ENGINEERING 2007, WIT Press, p. 35.
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Rujikiatkamjorn, C & Indraratna, B 1970, 'Analysis of Radial Vacuum-Assisted Consolidation Using 3D Finite Element Method', Advances in Measurement and Modeling of Soil Behavior, Geo-Denver 2007, American Society of Civil Engineers, p. 12.
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In this study, a 3D numerical modelling of a single vertical drains consolidation incorporating vacuum preloading considering both vertical and horizontal drainage is presented. The effects of nonlinear soil compressibility, varying permeability and vacuum pressure distribution along the drain are examined through the dissipation of average excess pore pressure and associated settlement. A selected case history, using 3D finite element method, is employed to analyse two embankments constructed at the Second Bangkok International Airport, Thailand stabilised with prefabricated vertical drains and vacuum preloading. The behaviour of this embankment including settlements and excess pore pressures is then compared with the numerical predictions. This study reveals a close agreement between the predictions results obtained from the numerical model and the field measurements. Copyright ASCE 2007.
Samali, B, Choi, F, Li, J & Crews, KI 1970, 'Experimental investigations on a laboratory timber bridge using Damage Index Method for plate-like structures', Proceedings of the 5th Australasian Congress on Applied Mechanics, ACAM 2007, Australasian Congress on Applied Mechanics, Engineers Australia, Brisbane, Australia, pp. 114-119.
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A great deal of work has been done in the area of damage identification in structures using changes of modal parameters before and after damage. Most of the developments have been based on beam theory and applied to beam-like or truss structures. Few researchers have made contributions to damage identification of plate-like structures employing a damage index method, especially for timber structures. In this paper, experimental investigations on a laboratory timber bridge using damage index method for plate-like structures are reported. Experimental modal analysis was performed to extract essential modal parameters from test data. Mode shape curvatures derived from the mode shapes were utilised in a damage index method for plate-like structures to detect single and two damage scenarios in a timber bridge. The purpose of the study is to explore feasibility of using modal strain energy based methods for damage identification of plate-like structures. The results show that the damage index method for plate-like structures using higher modes provides reasonable damage localisation for single and multiple damage cases.
Sheng, D 1970, 'Finite element modelling of penetration problems in geomechanics', Proceedings of the 10th International Symposium on Numerical Models in Geomechanics NUMOG 10 - Numerical Models in Geomechanics NUMOG 10, 10th International Symposium on Numerical Models in Geomechanics (NUMOG X), TAYLOR & FRANCIS LTD, Rhodes, GREECE, pp. 239-245.
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Penetration problems in geomechanics involve the insertion of solid bodies into the ground. The solid body can be a displacement pile used to support a structural load or a testing device used to measure soil properties. Such problems are extremely difficult to model, because they usually involve severe mesh distortion caused by large deformation and frictional contact. In this paper, an Arbitrary Lagrangian-Eulerian method is proposed to overcome the mesh distortion problem. The ALE method, incorporated with an automatic load stepping scheme and a smooth contact discretisation technique, is then used to analyse the penetration of axial displacement piles into the ground. © 2007 Taylor & Francis Group.
Sheng, D 1970, 'Frictional Contact for Pile Installation', IUTAM SYMPOSIUM ON COMPUTATIONAL METHODS IN CONTACT MECHANICS, IUTAM Symposium on Computational Methods in Contact Mechanics, Springer Netherlands, Hannover, GERMANY, pp. 239-255.
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Sun, DA, Huang, WX, Sheng, DC & Yamamoto, H 1970, 'An Elastoplastic Model for Granular Materials Exhibiting Particle Crushing', Key Engineering Materials, 8th Asia-Pacific Symposium on Engineering Plasticity and Its Applications (AEPA 2006), Trans Tech Publications, Ltd., Nagoya Univ, Nagoya, JAPAN, pp. 1273-1278.
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A practical elastoplastic constitutive model for granular materials is presented. And themodel is suitable for description of the material behaviour for a wide range of stresses, including thosesufficient to cause particle crushing. With a limited number of model parameters, the model canpredict the confining-pressure dependent stress-strain relation and shear strength of granular materialsin three-dimensional stresses, especially of variation of shear strength and dilatancy characteristicsdue to particle crushing under high confining pressure. The model parameters, which have clearphysical meanings, can be determined from the results of isotropic compression test and conventionaltriaxial compression tests. The model performance is demonstrated for triaxial compression tests of asand for a wide range of the confining-pressure from 0.2MPa to 8.0MPa.
Wang, JC-P, Abolhasan, M, Franklin, DR, Safaei, F & Lipman, J 1970, 'On Separating Route Control and Data Flows in Multi-radio Multi-hop Ad Hoc Network.', ICON, IEEE International Conference on Networks, IEEE, Adelaide, Australia, pp. 19-24.
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Ad hoc networks typically require a significant amount of routing and control information to be distributed in a timely and reliable manner throughout the network, particularly in dynamic environments. As traffic levels increase and the network becomes more heavily congested, there is an increased probability that these critical packets are lost, resulting in obsolete control information being used to make important decisions. This would further compound the problem of network congestion and lead to a very rapid loss of connectivity and throughput. Given this, we argue the solutions to these problems should not rely on putting extra bandwidth on a radio interface. Instead, we should exploit the use of multiple radios to ensure the route can be firmly established. In this paper, we propose a multi-radio solution which reserves one radio channel exclusively for routing. Our simulation results have demonstrated that using a separate radio for routing protocol would dramatically improve reliability in heavily loaded ad hoc wireless networks, thereby effectively alleviating the impact of network congestion. © 2007 IEEE.
Wang, JC-P, Abolhasan, M, Franklin, DR, Safaei, F, Lipman, J & IEEE 1970, 'On separating route control and data flows in multi-radio multi-hop ad hoc network', 2007 15TH IEEE INTERNATIONAL CONFERENCE ON NETWORKS, 15th IEEE International Conference on Networks, IEEE, Adelaide, AUSTRALIA, pp. 114-119.
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Wang, JC-P, Abolhasan, M, Safaei, F, Franklin, D & IEEE 1970, 'A survey on control separation techniques in multi-radio multi-channel MAC protocols', 2007 INTERNATIONAL SYMPOSIUM ON COMMUNICATIONS AND INFORMATION TECHNOLOGIES, VOLS 1-3, International Symposium on Communications and Information Technologies, IEEE, Sydney, Australia, pp. 854-859.
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The rapid diminishing in the cost of commodity wireless hardware in recent years has prompted the use of multiple radios to improve the capacity of wireless networks. However, the research has shown that the improvement obtained from using multiple radios does not solely depend on the number of radios, but primarily on how these radios can be integrated in a constructive manner. A common way of integration multiple radios is to use a dedicated radio for control. To date, a number of multi-radio MAC protocol are employing a dedicated radio to control and coordinate the other radios, though the approaches are varied from one to another. In this paper, the control separation techniques in the multi-radio multi-channel MAC have been surveyed, and a classification of control separation techniques is provided. Moreover, this study points out the open research issues and intends to spark new interests and developments in this field.
Widjaja, J, Samali, B & Li, J 1970, 'The use of displacement threshold for switching frequency strategy for structural vibration mitigation', JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY, 8th International Conference on Motion and Vibration Control, KOREAN SOC MECHANICAL ENGINEERS, Daejeon, SOUTH KOREA, pp. 865-869.
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Zhao, JD, Sheng, DC & Sloan, SW 1970, 'Microstructural effect on the cavity expansion in a soil cylinder', Proceedings of the 10th International Symposium on Numerical Models in Geomechanics NUMOG 10 - Numerical Models in Geomechanics NUMOG 10, 10th International Symposium on Numerical Models in Geomechanics (NUMOG X), TAYLOR & FRANCIS LTD, Rhodes, GREECE, pp. 715-720.
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This paper presents an elastoplastic analysis for cavity expansion in a soil cylinder. Emphasis here is laid on the influence of microstructures in the soil on the macroscopic behaviour of the cavity expansion. In doing so, a strain gradient plasticity model is employed to model the soil behaviour in the cylinder. A numerical shooting method is developed to solve the resulting fourth-order ordinary differential equation with two-point boundary conditions for the gradient-dependent problem. Fully elastic-plastic solutions to the cavity expansion are obtained and they are compared with the corresponding conventional results. It is demonstrated that, in consideration of microstructural effects, the deformation and stress distributions in the cylinder are highly inhomogeneous during both the initial loading and the subsequent elastic and plastic expansion stages. The overall elastic-plastic behaviour of the gradient-dependent cylinder depends on the material parameters as well as the cylinder thickness. Interesting scale effects are observed and interpreted by the gradient-dependent model whereas this would be impossible by the corresponding conventional modeling. The results in this paper can be useful for benchmarking further numerical investigations of the cavity expansion problem. © 2007 Taylor & Francis Group.
