Abolhasan, M & Lipman, J 2006, 'Load-balanced route discovery for mobile ad hoc networks', Journal of Telecommunications and Information Technology, vol. 1, no. 1, pp. 38-45.
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This paper presents flow-aware routing protocol (FARP), a new routing strategy designed to improve load balancing and scalability in mobile ad hoc networks. FARP is a hop-by-hop routing protocol, which introduces a flow-aware route discovery strategy to reduce the number of control overheads propagating through the network and distributes the flow of data through least congested nodes to balance the network traffic. FARP was implemented in GloMoSim and compared with AODV. To investigate the load distribution capability of FARP new performance metrics were introduced to measure the data packet flow distribution capability of the each routing protocol. The simulation results obtained illustrate that FARP achieves high levels of throughput, reduces the level of control overheads during route discovery and distributes the network load more evenly between nodes when compared to AODV. This paper also describes a number of alternative strategies and improvements for the FARP.
Al-Dawod, M, Samali, B & Li, J 2006, 'Experimental verification of an active mass driver system on a five-storey model using a fuzzy controller', STRUCTURAL CONTROL & HEALTH MONITORING, vol. 13, no. 5, pp. 917-943.
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This paper reports experimental tests conducted on a five-storey model using an active mass driver (AMD) system, where the control action was achieved by using a fuzzy logic controller (FLC) and the UTS state-of-the-art shake table facility. The performance of the fuzzy controller was checked against El Centro 1940, Hachinohe 1968, Northridge 1994, and Kobe 1995 earthquakes to verify the potential of using the fuzzy controller in real applications for active control of structures. Fuzzy logic is one of few mathematical model-free approaches to system identification and control. Other advantages of fuzzy logic controllers are that they can be nonlinear, adaptive, admit a high degree of parallel implementation, and tolerate uncertainty in the system. The building model under consideration is a large-scale five-storey, 3.6-m-tall, steel frame designed and manufactured at the University of Technology, Sydney. The paper details the experimental set up of the five-storey model with AMD system and the instrumentation used to measure the response, the design process of the Fuzzy Controller, and the earthquake excitations used in the experimental tests. The results of the experimental tests confirm the potential of using the adopted fuzzy controller for the active structural control using, an active mass driver (AMD) system
Browne, M, Strauss, D, Castelle, B, Blumenstein, M, Tomlinson, R & Lane, C 2006, 'Empirical Estimation of Nearshore Waves From a Global Deep-Water Wave Model', IEEE Geoscience and Remote Sensing Letters, vol. 3, no. 4, pp. 462-466.
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Global wind-wave models such as the National Oceanic and Atmospheric Administration WaveWatch 3 (NWW3) play an important role in monitoring the world's oceans. However, untransformed data at grid points in deep water provide a poor estimate of swell characteristics at nearshore locations, which are often of significant scientific, engineering, and public interest. Explicit wave modeling, such as the Simulating Waves Nearshore (SWAN), is one method for resolving the complex wave transformations affected by bathymetry, winds, and other local factors. However, obtaining accurate bathymetry and determining parameters for such models is often difficult. When target data is available (i.e., from in situ buoys or human observers, empirical alternatives such artificial neural networks (ANNs) and linear regression may be considered for inferring nearshore conditions from offshore model output. Using a sixfold cross-validation scheme, significant wave height Hs and period were estimated at one onshore and two nearshore locations. In estimating H s at the shoreline, the validation performance of the best ANN was r = 0.91, as compared to those of linear regression (0.82), SWAN (0.78), and the NWW3 Hs baseline (0.54). © 2006 IEEE.
Browne, M, Strauss, D, Tomlinson, R & Blumenstein, M 2006, 'Objective Beach-State Classification From Optical Sensing of Cross-Shore Dissipation Profiles', IEEE Transactions on Geoscience and Remote Sensing, vol. 44, no. 11, pp. 3418-3426.
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Remote sensing using terrestrial optical charge-coupled device cameras is a useful data collection method for geophysical measurement in the nearshore zone, where in situ measurement is difficult and time consuming. In particular, optical video sensing of the variability in human-visible surface refraction due to the nearshore incident wave field is becoming an established method for distal measurement of nearshore subtidal morphology. We report on the use of a low-mounted shore-normal camera for gathering data on cross-shore dissipative characteristics of a dynamic open beach. Data are analyzed for the purposes of classifying three of Wright and Shorts' intermediate classes of morphological beach state as determined by expert raters. Although these beach states are usually thought of as being distinctive in terms of their longshore bar variability, theory predicts that differences should also be observed in cross-shore dissipative characteristics. Three methods of generating features from statistical features from the archived optical data are described and compared in terms of their ability to discriminate between the beach states. Principal component scores of the percentile distributions were found to provide slightly better classification performance (i.e., 85%, while approximating the data using relatively fewer features), whereas classification using intensity distributions alone resulted in the worst performance, classifying 78% of beach states correctly. Class center moment profiles for each beach state were constructed, and results indicate that cross-shore wave dissipation becomes more disorganized as linear bars devolve into more complex transverse structures. © 2006 IEEE.
Choudhury, D & Nimbalkar, SS 2006, 'Pseudo-dynamic approach of seismic active earth pressure behind retaining wall', Geotechnical and Geological Engineering, vol. 24, no. 5, pp. 1103-1113.
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Knowledge of seismic active earth pressure behind rigid retaining wall is very important in the design of retaining wall in earthquake prone region. Commonly used Mononobe-Okabe method considers pseudo-static approach, which gives the linear distribution of seismic earth pressure in an approximate way. In this paper, the pseudo-dynamic method is used to compute the distribution of seismic active earth pressure on a rigid retaining wall supporting cohesionless backfill in more realistic manner by considering time and phase difference within the backfill. Planar rupture surface is considered in the analysis. Effects of a wide range of parameters like wall friction angle, soil friction angle, shear wave velocity, primary wave velocity and horizontal and vertical seismic accelerations on seismic active earth pressure have been studied. Results are provided in tabular and graphical non-dimensional form with a comparison to pseudo-static method to highlight the realistic non-linearity of seismic active earth pressures distribution. © Springer 2006.
Choudhury, D, Nimbalkar, SS & Mandal, JN 2006, 'Comparison of Pseudo-Static and Pseudo-Dynamic Methods for Seismic Earth Pressure on Retaining Wall', JOURNAL OF INDIAN GEOPHYSICAL UNION, vol. 10, no. 4, pp. 263-271.
Fogelman, S, Blumenstein, M & Zhao, H 2006, 'Estimation of chemical oxygen demand by ultraviolet spectroscopic profiling and artificial neural networks', Neural Computing and Applications, vol. 15, no. 3-4, pp. 197-203.
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A simple method based on the mathematical treatment of spectral absorbance profiles in conjunction with artificial neural networks (ANNs) is demonstrated for rapidly estimating chemical oxygen demand (COD) values of wastewater samples. In order to improve spectroscopic analysis and ANN training time as well as to reduce the storage space of the trained ANN algorithm, it is necessary to decrease the ANN input vector size by extracting unique characteristics from the raw input pattern. Key features from the spectral absorbance pattern were therefore selected to obtain the spectral absorbance profile, reducing the ANN input vector from 160 to 10 selected inputs. The results indicate that the COD values obtained from the selected absorbance profiles agreed well with those obtained from the entire absorbance pattern. The spectral absorbance profile technique was also compared to COD values estimated by a multiple linear regression (MLR) model to validate whether ANNs were better and more robust models for rapid COD analysis. It was found that the ANN model predicted COD values closer to standard COD values than the MLR model.
Fogelman, S, Zhao, H & Blumenstein, M 2006, 'A rapid analytical method for predicting the oxygen demand of wastewater', Analytical and Bioanalytical Chemistry, vol. 386, no. 6, pp. 1773-1779.
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In this study, an investigation was undertaken to determine whether the predictive accuracy of an indirect, multiwavelength spectroscopic technique for rapidly determining oxygen demand (OD) values is affected by the use of unfiltered and turbid samples, as well as by the use of absorbance values measured below 200 nm. The rapid OD technique was developed that uses UV-Vis spectroscopy and artificial neural networks (ANNs) to indirectly determine chemical oxygen demand (COD) levels. It was found that the most accurate results were obtained when a spectral range of 190-350 nm was provided as data input to the ANN, and when using unfiltered samples below a turbidity range of 150 NTU. This is because high correlations of above 0.90 were obtained with the data using the standard COD method. This indicates that samples can be measured directly without the additional need for preprocessing by filtering. Samples with turbidity values higher than 150 NTU were found to produce poor correlations with the standard COD method, which made them unsuitable for accurate, real-time, on-line monitoring of OD levels. © Springer-Verlag 2006.
Gens, A, Sánchez, M & Sheng, D 2006, 'On constitutive modelling of unsaturated soils', Acta Geotechnica, vol. 1, no. 3, pp. 137-147.
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Golab, AN, Indraratna, B & Peterson, MA 2006, 'Performance of alkaline reactive materials in the remediation of acidic groundwater', Chinese Journal of Geochemistry, vol. 25, no. S1, pp. 88-89.
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Golab, AN, Indraratna, B, Peterson, MA & Hay, S 2006, 'Design of a Permeable Reactive Barrier to Remediate Acidic Groundwater', ASEG Extended Abstracts, vol. 2006, no. 1, pp. 1-3.
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Golab, AN, Peterson, MA & Indraratna, B 2006, 'Selection of potential reactive materials for a permeable reactive barrier for remediating acidic groundwater in acid sulphate soil terrains', Quarterly Journal of Engineering Geology and Hydrogeology, vol. 39, no. 2, pp. 209-223.
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A permeable reactive barrier is being designed to remediate leachate from acid sulphate soils. The current research relates to testing of alkaline materials for use in the barrier, with an emphasis on waste materials. Thirteen alkaline materials including recycled concrete, limestone, calcite-bearing zeolitic breccia, blast furnace slag, lime and fly ash were tested. The batch tests involved several phases, such as leaching in deionized water to characterize the soluble components of the materials and the pH that each material could achieve. Another phase involved testing with acidic water (pH 3) to determine the acid leachable components of the materials and the pH after neutralization. The pH achieved by each reactive material was controlled by the reaction kinetics of the dominant alkaline mineral. The concretes, fly ash, and air-cooled blast furnace slag (ACBFS) all achieved a pH that is consistent with the dissolution of lime (pH 11 to 12). The limestone and zeolitic breccias all achieved a pH consistent with the dissolution of calcite (pH c. 7.4). Based on the results of the batch tests, a short-list of materials was selected that included a recycled concrete, ACBFS, three zeolitic breccias and limestone. The short-listed materials were examined for exhaustion of neutralizing ability by repeatedly replacing the acidic water and monitoring the resultant pH. The precipitates that formed during this process were analysed to characterize the chemical reactions that occurred during the tests. Based on the results, the recycled concrete was selected for testing in columns that will simulate flow conditions through the barrier. © 2006 Geological Society of London.
GREEN, S, BLUMENSTEIN, M, BROWNE, M & TOMLINSON, R 2006, 'THE DETECTION OF PERSONS IN CLUTTERED BEACH SCENES USING DIGITAL VIDEO IMAGERY AND NEURAL NETWORK-BASED CLASSIFICATION', International Journal of Computational Intelligence and Applications, vol. 06, no. 02, pp. 149-160.
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This paper presents an investigation into the detection and quantification of persons in real-world beach scenes for the automated monitoring of public recreation areas. Aside from the obvious use of video and digital imagery for surveillance applications, this research focuses on the analysis of images for the purpose of predicting trends in the intensity of public usage at beach sites in Australia. The proposed system uses image enhancement and segmentation techniques to detect objects in cluttered scenes. Following these steps, a newly proposed feature extraction technique is used to represent salient information in the extracted objects for training of a neural network. The neural classifier is used to distinguish the extracted objects between 'person' and 'non-person' categories to facilitate analysis of tourist activity. Encouraging results are presented for person classification on a database of real-word beach scene images.
Halkon, BJ & Rothberg, SJ 2006, 'Rotor Vibration Measurements Using Laser Doppler Vibrometry: Essential Post-Processing for Resolution of Radial and Pitch/Yaw Vibrations', Journal of Vibration and Acoustics, vol. 128, no. 1, pp. 8-20.
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Laser Doppler vibrometry is now a well established technique enabling noncontact vibration measurements in the most challenging of environments. Rotor vibration measurements are often highlighted as a major application of laser vibrometers due to their noncontact operation and inherent immunity to shaft runout. In such measurements, resolution of the individual axial and torsional vibration components is possible via particular arrangement of the laser beam(s). Resolution of the radial or pitch/yaw vibration components, however, can only be achieved by essential post-processing of the data from simultaneous orthogonal measurements. This paper describes the principle and rigorous examination of a novel, dedicated resolution algorithm enabling, for the first time, real-time post-processing of the outputs from standard commercial instruments. The system performed well, even in the presence of noise and other typical measurement errors, and was implemented successfully in an engine vibration study.
Halkon, BJ & Rothberg, SJ 2006, 'Vibration measurements using continuous scanning laser vibrometry: Advanced aspects in rotor applications', Mechanical Systems and Signal Processing, vol. 20, no. 6, pp. 1286-1299.
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This paper builds on previous work concerned with the development of a comprehensive velocity sensitivity model for continuous scanning Laser Vibrometry. This versatile model predicts the measured velocity for arbitrary mirror scan angles and arbitrary target motion and it has been especially valuable in revealing the sources of additional components seen in continuous scanning and tracking measurements on rotors. The application to vibration measurements on rotors is the particular focus of this paper which includes, for the first time, a three-dimensional consideration of the incident point on the target and validation of the DC component of measured velocity leading to evaluation of the individual components of the small but inevitable misalignments between the rotor and optical axes. This has not previously been possible. Misalignments in the region 0.5 mm and 0.5° were found and the model shows how additional components of the order 10-20 mm/s result for typical measurements. Such levels are significant as they are comparable with vibration levels likely in real applications and, if unexpected, may lead to data misinterpretation. The first thorough analysis of laser speckle effects in scanning Laser Vibrometer measurements on rotors is presented in the form of a speckle repeat map, together with experimental data quantifying the dramatic reduction in speckle noise found in tracking measurements. Finally, the velocity sensitivity model and the description of laser speckle effects are used to enable confident interpretation of data from a series of measurements on a rotating bladed disc. © 2005 Elsevier Ltd. All rights reserved.
Huang, W, Fityus, S, Bishop, D, Smith, D & Sheng, D 2006, 'Finite-Element Parametric Study of the Consolidation Behavior of a Trial Embankment on Soft Clay', International Journal of Geomechanics, vol. 6, no. 5, pp. 328-341.
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The paper presents a case study for numerical analysis of the consolidation behavior of an instrumented trial embankment constructed on a soft soil foundation. Details are given to the geological profile, field instrumentation, laboratory test results, and determination of soil parameters for numerical modeling. Embankment settlement is estimated based on one-dimensional consolidation analysis and nonlinear finite-element analysis following Biot's consolidation theory. Finite-element results are calibrated against the measured field data for a period of more than 3years. Development and dissipation of excess pore pressure, long-term settlement, and horizontal displacement are predicted and discussed in light of sensitivity of embankment performance to some critical factors through a parametric study. © 2006 ASCE.
Indraratna, B & Raut, AK 2006, 'Enhanced Criterion for Base Soil Retention in Embankment Dam Filters', Journal of Geotechnical and Geoenvironmental Engineering, vol. 132, no. 12, pp. 1621-1627.
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Indraratna, B, Fatahi, B & Khabbaz, H 2006, 'Numerical analysis of matric suction effects of tree roots', PROCEEDINGS OF THE INSTITUTION OF CIVIL ENGINEERS-GEOTECHNICAL ENGINEERING, vol. 159, no. 2, pp. 77-90.
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The use of native vegetation in the coastal regions of Australia has become increasingly popular for stabilising railway corridors built over expansive clays and compressive soft soils. The tree roots provide three stabilising functions: (a) they reinforce the soil; (b) they dissipate excess pore pressures; and (c) they establish sufficient matric suction to increase the shear strength. The matric suction generated within the tree root zone propagates radially into the soil matrix, as a function of the moisture content change. Considering soil conditions, the type of vegetation and atmospheric conditions, a mathematical model for the rate of root water uptake is developed. A conical shape is considered to represent the geometry of the tree root zone. Based on this model for the rate of root water uptake, the pore water pressure distribution and the movement of the ground adjacent to the tree are numerically analysed. Field measurements taken from the previously published literature are compared with the authors' numerical predictions. It is found that, given the approximation of the assumed model parameters, the agreement between the predicted results and field data is still promising. The study indicates that native vegetation improves the shear strength of the soil by increasing the matric suction, and also curtails soil movements.
Indraratna, B, Golab, AN & Banasiak, LJ 2006, 'Installation of a lime injection barrier for the remediation of acid sulphate soil problems', Quarterly Journal of Engineering Geology and Hydrogeology, vol. 39, no. 4, pp. 391-401.
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Indraratna, B, Khabbaz, H, Salim, W & Christie, D 2006, 'Geotechnical Properties of Ballast and the Role of Geosynthetics', Institution of Civil Engineers. Proceedings. Ground..., vol. 10, no. 3, pp. 91-102.
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The ballast and its engineering behaviour have a key role in governing the stability and performance of railway tracks. The deformation and degradation behaviour of ballast under static and dynamic loads was studied based on large-scale triaxial testing. The possible use of different types of geosynthetics to improve the performance of fresh and recycled ballast was also investigated. The research findings showed that the inclusion of geosynthetics improves the performance of ballasted tracks.
Indraratna, B, Khabbaz, H, Salim, W & Christie, D 2006, 'Geotechnical properties of ballast and the role of geosynthetics in rail track stabilisation', Proceedings of the Institution of Civil Engineers - Ground Improvement, vol. 10, no. 3, pp. 91-101.
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The ballast and its engineering behaviour have a key role in governing the stability and performance of railway tracks. The deformation and degradation behaviour of ballast under static and dynamic loads was studied based on large-scale triaxial testing. The possible use of different types of geosynthetics to improve the performance of fresh and recycled ballast was also investigated. The research findings showed that the inclusion of geosynthetics improves the performance of ballasted tracks.Le ballast et son comportement mécanique ont une influence importante sur la stabilité et la performance des voies ferrées. Nous avons étudié le comportement de détérioration et de déformation du ballast sous charge statiques et dynamiques en nous basant sur des essais triaxiaux à grande échelle. Nous avons également étudié la possibilité d'utiliser divers types de géosynthétiques pour améliorer la performance du ballast neuf et recyclé. Les résultats de cette recherche ont montré que l'adjonction de géosynthétiques améliorait la performance des voies ballastées.
Indraratna, B, Rujikiatkamjorn, C & Sathananthan, I 2006, 'Reply to the discussion by T.A. Tran and T. Mitachi on 'Analytical and numerical solutions for a single vertical drain including the effects of vacuum preloading'', Canadian Geotechnical Journal, vol. 43, no. 12, pp. 1404-1405.
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Ji, JC 2006, 'Nonresonant Hopf bifurcations of a controlled van der Pol-Duffing oscillator', JOURNAL OF SOUND AND VIBRATION, vol. 297, no. 1-2, pp. 183-199.
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The trivial equilibrium of a van der Pol-Duffing oscillator with a nonlinear feedback control may lose its stability via Hopf bifurcations, when the time delay involved in the feedback control reaches certain values. Nonresonant Hopf-Hopf interactions may occur in the controlled van der Pol-Duffing oscillator when the corresponding characteristic equation has two pairs of purely imaginary roots. With the aid of normal form theory and centre manifold theorem as well as a perturbation method, the dynamic behaviour of the nonresonant co-dimension two bifurcation is investigated by studying the possible solutions and their stability of the four-dimensional ordinary differential equations on the centre manifold. In the vicinity of the nonresonant Hopf bifurcation, the oscillator may exhibit the initial equilibrium solution, two periodic solutions as well as a quasi-periodic solution on a two-dimensional torus, depending on the dummy unfolding parameters and nonlinear terms. The analytical predictions are found to be in good agreement with the results of numerical integration of the original delay differential equation. © 2006 Elsevier Ltd. All rights reserved.
Ji, JC & Hansen, CH 2006, 'Stability and dynamics of a controlled van der Pol-Duffing oscillator', CHAOS SOLITONS & FRACTALS, vol. 28, no. 2, pp. 555-570.
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The trivial equilibrium of a van der Pol-Duffing oscillator under a linear-plus-nonlinear feedback control may change its stability either via a single or via a double Hopf bifurcation if the time delay involved in the feedback reaches certain values. It is found that the trivial equilibrium may lose its stability via a subcritical or supercritical Hopf bifurcation and regain its stability via a reverse subcritical or supercritical Hopf bifurcation as the time delay increases. A stable limit cycle appears after a supercritical Hopf bifurcation occurs and disappears through a reverse supercritical Hopf bifurcation. The interaction of the weakly periodic excitation and the stable bifurcating solution is investigated for the forced system under primary resonance conditions. It is shown that the forced periodic response may lose its stability via a Neimark-Sacker bifurcation. Analytical results are validated by a comparison with those of direct numerical integration. © 2005 Elsevier Ltd. All rights reserved.
Kwok, NM, Ha, QP, Nguyen, TH, Li, J & Samali, B 2006, 'A novel hysteretic model for magnetorheological fluid dampers and parameter identification using particle swarm optimization', SENSORS AND ACTUATORS A-PHYSICAL, vol. 132, no. 2, pp. 441-451.
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Non-linear hysteresis is a complicated phenomenon associated with magnetorheological (MR) fluid dampers. A new model for MR dampers is proposed in this paper. For this, computationally-tractable algebraic expressions are suggested here in contrast to the commonly-used Bouc-Wen model, which involves internal dynamics represented by a non-linear differential equation. In addition, the model parameters can be explicitly related to the hysteretic phenomenon. To identify the model parameters, a particle swarm optimization (PSO) algorithm is employed using experimental force-velocity data obtained from various operating conditions. In our algorithm, it is possible to relax the need for a priori knowledge on the parameters and to reduce the algorithmic complexity. Here, the PSO algorithm is enhanced by introducing a termination criterion, based on the statistical hypothesis testing to guarantee a user-specified confidence level in stopping the algorithm. Parameter identification results are included to demonstrate the accuracy of the model and the effectiveness of the identification process. © 2006 Elsevier B.V. All rights reserved.
Lee, S & Pradhan, B 2006, 'Probabilistic landslide hazards and risk mapping on Penang Island, Malaysia', Journal of Earth System Science, vol. 115, no. 6, pp. 661-672.
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Li, C & Dai, W 2006, 'The Application of Grey Relation Close Degree Model in the Fault Diagnosis', Mechanics Research Communications, vol. 33, no. 5, pp. 614-619.
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In this paper, the dynamics of a system of two van der Pol oscillators with delayed position and velocity coupling is studied by the method of averaging together with truncation of Taylor expansions. According to the slow-flow equations, the dynamics of 1:1 internal resonance is more complex than that of non-1:1 internal resonance. For 1:1 internal resonance, the stability and the number of periodic solutions vary with different time delay for given coupling coefficients. The condition necessary for saddle-node and Hopf bifurcations for symmetric modes, namely in-phase and out-of-phase modes, are determined. The numerical results, obtained from direct integration of the original equation, are found to be in good agreement with analytical predictions. © 2005 Elsevier Ltd. All rights reserved.
Li, X, Ji, JC & Hansen, CH 2006, 'Dynamics of two delay coupled van der Pol oscillators', MECHANICS RESEARCH COMMUNICATIONS, vol. 33, no. 5, pp. 614-627.
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In this paper, the dynamics of a system of two van der Pol oscillators with delayed position and velocity coupling is studied by the method of averaging together with truncation of Taylor expansions. According to the slow-flow equations, the dynamics of 1: 1 internal resonance is more complex than that of non-1: 1 internal resonance. For 1: 1 internal resonance, the stability and the number of periodic solutions vary with different time delay for given coupling coefficients. The condition necessary for saddle-node and Hopf bifurcations for symmetric modes, namely in-phase and out-of-phase modes, are determined. The numerical results, obtained from direct integration of the original equation, are found to be in good agreement with analytical predictions.
Li, X, Ji, JC & Hansen, CH 2006, 'Non-linear normal modes and their bifurcation of a two DOF system with quadratic and cubic non-linearity', INTERNATIONAL JOURNAL OF NON-LINEAR MECHANICS, vol. 41, no. 9, pp. 1028-1038.
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The non-linear normal modes (NNMs) and their bifurcation of a complex two DOF system are investigated systematically in this paper. The coupling and ground springs have both quadratic and cubic non-linearity simultaneously. The cases of ω1:ω2 = 1:1, 1:2 and 1:3 are discussed, respectively, as well as the case of no internal resonance. Approximate solutions for NNMs are computed by applying the method of multiple scales, which ensures that NNM solutions can asymtote to linear normal modes as the non-linearity disappears. According to the procedure, NNMs can be classified into coupled and uncoupled modes. It is found that coupled NNMs exist for systems with any kind of internal resonance, but uncoupled modes may appear or not appear, depending on the type of internal resonance. For systems with 1:1 internal resonance, uncoupled NNMs exist only when coefficients of cubic non-linear terms describing the ground springs are identical. For systems with 1:2 or 1:3 internal resonance, in additional to one uncoupled NNM, there exists one more uncoupled NNM when the coefficients of quadratic or cubic non-linear terms describing the ground springs are identical. The results for the case of internal resonance are consistent with ones for no internal resonance. For the case of 1:2 internal resonance, the bifurcation of the coupled NNM is not only affected by cubic but also by quadratic non-linearity besides detuning parameter although for the cases of 1:1 and 1:3 internal resonance, only cubic non-linearity operate. As a check of the analytical results, direct numerical integrations of the equations of motion are carried out. © 2006 Elsevier Ltd. All rights reserved.
Li, XY, Ji, JC, Hansen, CH & Tan, CX 2006, 'The response of a Duffing-van der Pol oscillator under delayed feedback control', JOURNAL OF SOUND AND VIBRATION, vol. 291, no. 3-5, pp. 644-655.
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The nonlinear dynamics of a Duffing-van der Pol oscillator under linear-plus-nonlinear state feedback control with a time delay are investigated. By means of the averaging method and Taylor expansion, two slow-flow equations for the amplitude and phase of the primary resonance response are derived, from which the relations between the amplitude and phase of the primary resonance response and all other parameters are obtained, respectively. The singularity analysis of the equation governing the amplitude of the primary resonance response shows that the bifurcation modes are perturbations of the pitchfork bifurcation. Conditions preventing multiple solutions, corresponding to two different kinds of bifurcation modes, are given, since cases for which multiple solutions are available should be avoided. The stable condition for steady-state response is also given by the Routh-Hurwitz criterion. It is also shown that coupled nonlinear state feedback control can be replaced by uncoupled nonlinear state feedback control.
Liu, Z, Shi, B & Sheng, D 2006, 'A Micropenetrometer for Detecting Structural Strength Inside Soft Soils', Geotechnical Testing Journal, vol. 29, no. 6, pp. 443-450.
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Abstract A micropenetrometer is developed to measure structural strength inside soft soils. Different from the traditional detective technology for soil structure, the micropenetrometer is an intrusion technology to estimate the characteristics of soft soils. The work principle and main configuration of the micropenetrometer are introduced, followed by its calibration and some operation techniques. Finally, two application tests are carried out. Different soil textures such as sandy soil or clayey soil have different types of penetration curves. Through the end resistance variation, detailed description of the structural strength along penetration depth can be obtained. In addition, three-dimensional strength distribution on the vertical or transverse sections can be achieved from the penetration data evenly arranged on the grid nodes of the same surface through interpolation method. Such a technique is of significance for checking the effectiveness of soil improvement or monitoring the moisture movement in soil.
Nazem, M, Sheng, D & Carter, JP 2006, 'Stress integration and mesh refinement for large deformation in geomechanics', International Journal for Numerical Methods in Engineering, vol. 65, no. 7, pp. 1002-1027.
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AbstractThis paper first discusses alternative stress integration schemes in numerical solutions to large‐ deformation problems in hardening materials. Three common numerical methods, i.e. the total‐Lagrangian (TL), the updated‐Lagrangian (UL) and the arbitrary Lagrangian–Eulerian (ALE) methods, are discussed. The UL and the ALE methods are further complicated with three different stress integration schemes. The objectivity of these schemes is discussed. The ALE method presented in this paper is based on the operator‐split technique where the analysis is carried out in two steps; an UL step followed by an Eulerian step. This paper also introduces a new method for mesh refinement in the ALE method. Using the known displacements at domain boundaries and material interfaces as prescribed displacements, the problem is re‐analysed by assuming linear elasticity and the deformed mesh resulting from such an analysis is then used as the new mesh in the second step of the ALE method. It is shown that this repeated elastic analysis is actually more efficient than mesh generation and it can be used for general cases regardless of problem dimension and problem topology. The relative performance of the TL, UL and ALE methods is investigated through the analyses of some classic geotechnical problems. Copyright © 2005 John Wiley & Sons, Ltd.
Nimbalkar, SS, Choudhury, D & Mandal, JN 2006, 'Seismic stability of reinforced-soil wall by pseudo-dynamic method', Geosynthetics International, vol. 13, no. 3, pp. 111-119.
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Determination of the internal stability of reinforced soil walls under earthquake conditions is an important part of seismic design. The horizontal method of slices is used for determining internal stability or for tieback analysis of the reinforced soil wall. A pseudo-dynamic method is adopted in the present analysis, which considers the effect of phase difference in both the shear and primary waves travelling through the backfill due to seismic excitation. Reinforced soil walls with cohesionless backfill material have been considered in the analysis. Results are presented in graphical and tabular form to show the required tensile force and length of geosynthetic reinforcement to maintain the stability of the reinforced soil wall under seismic conditions. The effects of variation of parameters such as soil friction angle and horizontal and vertical seismic accelerations on the stability of the reinforced soil wall have been studied. With an increase of seismic accelerations in both the horizontal and vertical directions the stability of the reinforced soil wall decreases significantly, and thus greater strength and length of the geosynthetic reinforcement are required to maintain stability of the wall. The seismic vertical acceleration in an upward direction gives higher values of the required geosynthetic tensile strength, and the seismic vertical acceleration in the downward direction yields higher values of the length of geosynthetic reinforcement. Comparisons of the present results with available pseudo-static results are shown, and the limitations of the pseudo-static results are highlighted.
Pradhan, B, Kumar, S, Mansor, S, Ramli, AR & Sharif, ARBM 2006, 'Spatial data compression and denoising via wavelet transformation', Applied GIS, vol. 2, no. 1, pp. 6.1-6.16.
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Pradhan, B, Sandeep, K, Mansor, S, Ramli, AR & Sharif, ARBM 2006, 'A Fast Processing Algorithm for Lidar Data Compression Using Second Generation Wavelets', KOREAN JOURNAL OF REMOTE SENSING, vol. 22, no. 1, pp. 49-61.
Pradhan, B, Tham, LG, Yue, ZQ, Junaideen, SM & Lee, CF 2006, 'Soil–Nail Pullout Interaction in Loose Fill Materials', International Journal of Geomechanics, vol. 6, no. 4, pp. 238-247.
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A laboratory study was conducted to investigate the behavior of soil nails embedded in loosely compacted sandy fills. By varying the overburden pressure, the peak pullout force and the load-displacement behavior were determined by carrying out pullout tests in a displacement-rate controlled manner. The test results were compared to other published ones. The present results show that the pullout resistance can be interpreted with conventional soil parameters. The effect of retrained dilatancy, which is considered to be the reason for high pullout resistance in dense materials, is negligible in loose fill materials except under very low stress level. Furthermore, pullout resistance increases with overburden pressure opposed to some field test results reported in the literature which show no systematic trend in pullout resistance with overburden pressure. A numerical model was developed to simulate the mobilization of pullout force in soil nails. It has been shown that a simple one-dimensional spring model can be used to simulate the pullout load-displacement relationship. © 2006 ASCE.
Sathananthan, I & Indraratna, B 2006, 'Laboratory Evaluation of Smear Zone and Correlation between Permeability and Moisture Content', Journal of Geotechnical and Geoenvironmental Engineering, vol. 132, no. 7, pp. 942-945.
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Sathananthan, I & Indraratna, B 2006, 'Plane-strain lateral consolidation with non-Darcian flow', Canadian Geotechnical Journal, vol. 43, no. 2, pp. 119-133.
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New plane-strain lateral consolidation equations are formulated that neglect the well resistance of vertical drains but are applicable for both Darcian and non-Darcian flow. The results of consolidation analyses using conventional Darcian (linear) flow and the new solution based on non-Darcian (exponential) flow are compared. A good match has been obtained between equivalent plane-strain and axisymmetric solutions. The advantage of the equivalent plane-strain procedure is that it not only matches the average degree of radial (axisymmetric) consolidation but also yields a more realistic excess pore pressure distribution in the lateral direction than the Darcian flow condition. The relevant parameters are illustrated graphically for convenience. Good agreement was obtained between the prediction of the new equivalent plane-strain solution and field data from a test area in Ska-Edeby, Sweden.Key words: plane strain, consolidation, soft clay, vertical drains.
Shahin, MA & Indraratna, B 2006, 'Modeling the mechanical behavior of railway ballast using artificial neural networks', Canadian Geotechnical Journal, vol. 43, no. 11, pp. 1144-1152.
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Ballast is one of the most commonly used construction materials in railway tracks. Under heavy train loads, ballast is subjected to a high stress level that is always associated with significant track deformation. Consequently, an accurate prediction of the mechanical behavior of ballast under static and dynamic loading conditions is important for the stability of railway tracks. In this paper, the feasibility of using artificial neural networks (ANNs) for modeling the mechanical behavior of railway ballast under static loading is investigated. The database used for the development of the ANN model is obtained from selected literature and comprises a series of 29 large-scale drained triaxial compression tests conducted on three types of commonly used ballast (i.e., basalt, dolomite, and granite). Predictions from the ANN model are compared with the results of experimental tests and with those obtained from the hardening-soil constitutive model in PLAXIS finite-element code. The results indicate that the ANN model is able to accurately predict the stress–strain and volume change behavior of ballast. The plastic dilation and contraction of ballast at various confining pressures and the strain-hardening and postpeak strain-softening behavior of ballast are also well simulated.Key words: ballast, modeling, neural networks, prediction, railway, triaxial tests.
Sheng, D, Sun, D-A & Matsuoka, H 2006, 'Cantilever Sheet-Pile Wall Modelled by Frictional Contact', Soils and Foundations, vol. 46, no. 1, pp. 29-37.
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Sheng, D, Wriggers, P & Sloan, SW 2006, 'Improved numerical algorithms for frictional contact in pile penetration analysis', Computers and Geotechnics, vol. 33, no. 6-7, pp. 341-354.
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Walker, R & Indraratna, B 2006, 'Vertical Drain Consolidation with Parabolic Distribution of Permeability in Smear Zone', Journal of Geotechnical and Geoenvironmental Engineering, vol. 132, no. 7, pp. 937-941.
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Yang Wang & Rajapakse, JC 2006, 'Contextual modeling of functional MR images with conditional random fields', IEEE Transactions on Medical Imaging, vol. 25, no. 6, pp. 804-812.
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Yang Wang, Kia-Fock Loe & Jian-Kang Wu 2006, 'A dynamic conditional random field model for foreground and shadow segmentation', IEEE Transactions on Pattern Analysis and Machine Intelligence, vol. 28, no. 2, pp. 279-289.
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Zhao, J & Sheng, D 2006, 'Strain gradient plasticity by internal-variable approach with normality structure', International Journal of Solids and Structures, vol. 43, no. 18-19, pp. 5836-5850.
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Zhao, J, Sheng, D & Collins, I 2006, 'Thermomechanical formulation of strain gradient plasticity for geomaterials', Journal of Mechanics of Materials and Structures, vol. 1, no. 5, pp. 837-863.
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Abolhasan, M & Lipman, J 1970, 'Self-selection route discovery strategies for reactive routing in ad hoc networks', Proceedings of the first international conference on Integrated internet ad hoc and sensor networks - InterSense '06, the first international conference, ACM Press, Nice, France.
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Routing in Ad hoc Networks has received a significant amount of attention. In recent years, the focus of research has been in on-demand (or reactive) routing protocols due to the recognition that these protocols have the potential to achieve higher levels of scalability than proactive routing strategies. However, most on-demand routing protocols proposed to date attempt to increase routing efficiency by using existing knowledge about the destination or by increasing the stability of the routes. Little research has been done to reduce route discovery overhead when no previous destination information is available. We present a number of different strategies, which encourage a more distributed and localised approach to route discovery by allowing each intermediate node during route discovery to make forwarding decisions using localised knowledge and self-selection. The use of self-selection for route discovery enables nodes to independently make route request (RREQ) forwarding decisions based upon a selection criterion or by satisfying certain conditions. The nodes which do not satisfy the selection criterion do not rebroadcast the RREQs. This provides a more effective and efficient search strategy than the use of traditional brute force blind flooding. We implemented our self-selecting route discovery strategies over AODV using the GloMoSim network simulation package, and compared the performance with existing routing protocols. Our simulation results show that a significant drop in the number of control packets can be achieved by giving each intermediate node more authority for self-selection during route discovery. Furthermore, a significant increase in routing performance is achieved as the number of nodes in the network is increased. © 2006 ACM.
Abolhasan, M, Wysocki, T, Franklin, DR & Lipman, J 1970, 'Capacity of Single-Radio Ad-hoc Networks for Handling High Bit Rate Real-time Internet Applications', Proceedings of the 5th Workshop on the Internet, Telecommunications and Signal Processing, WITSP '06, University of Nebraska - Lincoln, Hobart, Tasmania, pp. 1-6.
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Until now, the main focus in ad hoc networking has been improving Routing and Medium Access Control (MAC) Strategies. As a result, a diverse range of routing and MAC protocols have been proposed. To evaluate these protocols, much of the existing research has been based on simulation scenarios which assume ideal channel conditions and low node and traffic densities. Therefore, despite a few studies which have shown the performance limitations of ad hoc networks theoretically, there has not been many simulation studies performed which investigate the performance of ad hoc networks under a high node and traffic density. This paper investigates the performance of ad hoc networks under a high node density and high-bit rate real-time traffic such as VoIP. Our results show that the performane of single radio ad hoc networks drops significantly as traffic density is increased. To improve the performance of ad hoc networks, a number of different strategies and research areas are described.
Armand, S, Blumenstein, M & Muthukkumarasamy, V 1970, 'Off-line Signature Verification based on the Modified Direction Feature', 18th International Conference on Pattern Recognition (ICPR'06), 18th International Conference on Pattern Recognition (ICPR'06), IEEE, pp. 509-512.
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Signature identification and verification has been a topic of interest and importance for many years in the area of biometrics. In this paper we present an effective method to perform off-line signature verification and identification. To commence the process, the signature's contour is first determined from its binary representation. Unique structural features are subsequently extracted from the signature's contour through the use of a novel combination of the Modified Direction Feature (MDF) in conjunction with additional distinguishing features to train and test two Neural Network-based classifiers. A Resilient Back Propagation neural network and a Radial Basis Function neural network were compared. Using a publicly available database of 2106 signatures containing 936 genuine and 1170 forgeries, we obtained a verification rate of 91.12%. © 2006 IEEE.
Armand, S, Blumenstein, M & Muthukkumarasamy, V 1970, 'Off-line Signature Verification using the Enhanced Modified Direction Feature and Neural-based Classification', The 2006 IEEE International Joint Conference on Neural Network Proceedings, The 2006 IEEE International Joint Conference on Neural Network Proceedings, IEEE, pp. 684-691.
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Signatures continue to be an important biometric for authenticating the identity of human beings. This paper presents an effective method to perform off-line signature verification using unique structural features extracted from the signature's contour. A novel combination of the Modified Direction Feature (MDF) and additional distinguishing features such as the centroid, surface area, length and skew are used for classification. A Resilient Backpropagation (RBP) neural network and a Radial Basis Function (RBF) network were compared in terms of verification accuracy. Using a publicly available database of 2106 signatures (936 genuine and 1170 forgeries), verification rates of 91.21% and 88.0% were obtained using RBF and RBP respectively. © 2006 IEEE.
Cha, D, Jeng, DS, Blumenstein, M & Zhang, H 1970, 'Evaluation of wave-induced liquefaction in a porous seabed: Using an artificial neural network and a genetic algorithm -based model', Proceedings of the International Offshore and Polar Engineering Conference, pp. 302-308.
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The evaluation of wave-induced liquefaction is one of the key factors for analysing seabed characteristics and the design of marine structures. Numerous investigations of wave-induced liquefaction have been proposed. However, most previous research has focused on complicated mathematical theories and laboratory work. In this study, we contribute an alternative approach for the prediction of the waveinduced liquefaction using an Artificial Neural Network (ANN) and a Genetic Algorithm (GA)-based model. Combined ANN and GA-based models are still a newly developed area in coastal engineering. In this study, a Genetic Algorithm-based approach is proposed to find optimal weights for the ANN model. It reduces the training time, and improves the forecasting accuracy for wave-induced maximum liquefaction depth, compared to using the normal ANN training procedure. Simulation results demonstrate the capacity of the proposed ANN model for the prediction of wave induced maximum liquefaction depth in addition to the proposal of GAs for training the ANN model. Copyright ©2006 by The International Society of Offshore and Polar Engineers.
Choi, FC, Crews, K, Samali, B & Li, J 1970, 'Calibration of a laboratory timber bridge finite element model using the experimental modal data', 9th World Conference on Timber Engineering 2006, WCTE 2006, pp. 879-886.
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In recent years, a great deal of attention has been focused on the condition and safety of aging timber bridges in Australia. Vibration-based damage identification techniques to detect structural deterioration at an early stage have significant potential to reduce the costs and down-time associated with repair of damaged members as well as enhancing the safety and reliability of timber bridges. In this paper, the process of developing and calibrating a scale timber bridge, which accurately simulates the behaviour of a 'real' bridge under laboratory conditions, is presented. A finite element (FE) model has been developed and calibrated with experimental modal data. The FE model shows acceptable correlations when compared to the experimental data, with minor adjustment of the actual material properties. It forms a tool for predicting the behaviour of the damaged laboratory bridge, as well as potential identification of damage in real timber bridges.
Choudhury, D, Nimbalkar, SS & Mandal, JN 1970, 'Influence of soil-wall interface friction on pseudo-dynamic earth pressure', 8th US National Conference on Earthquake Engineering 2006, pp. 6466-6475.
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Knowledge of the dynamic earth pressure is essential for the safe design of retaining wall in the seismic zone due to the devastating effect of earthquake. In this paper the seismic earth pressure on a rigid retaining structure for both active and passive conditions are determined by pseudo-dynamic method. Conventional pseudo-static approach gives the linear distribution of seismic earth pressure behind retaining wall in an approximate way. However, the proposed pseudodynamic method gives the non-linear distribution of seismic earth pressure in more realistic manner by considering the variation of shear and primary wave velocities along the depth of the wall combined with the horizontal and vertical seismic accelerations. Movement of the wall with respect to soil guides the formation of active or passive earth pressure along with the frictional force at soil-wall. Results are presented in graphical form for non-dimensional seismic earth pressure distribution for different cases of wall friction angle under both active and passive conditions. Design values of the seismic earth pressure coefficients are found to change significantly under seismic conditions. Comparison of present results with pseudo-static approach describes the necessity and merits of the present solution. Copyright © (2006) by Earthquake Engineering Research Institute All rights reserved.
CHUA, HC, LEONG, EC, JAYANATHAN, M, INDRARATNA, B, WELIDENIYA, HS, KAWAKITA, M, OHTSUKA, I, IWANO, M, SHIMAYA, S, MATSUBARA, M, VALUER, F, BOULON, M, MITANI, Y, ESAKI, T, ZHANG, FM, CHEN, ZY, WANG, XG, JIA, ZX, DONG, YF, ZHANG, FM, LI, J, WU, L, WANG, XG & CHEN, ZY 1970, 'EXTENDED ABSTRACTS: 8. DISCONTINUITIES – 8.1. General', Rock Mechanics in Underground Construction, Proceedings of the ISRM International Symposium 2006 and the 4th Asian Rock Mechanics Symposium, WORLD SCIENTIFIC.
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Deaho Cha, Blumenstein, M, Hong Zhang & Dong-Sheng Jeng 1970, 'Improvement of an Artificial Neural Network Model using Min-Max Preprocessing for the Prediction of Wave-induced Seabed Liquefaction', The 2006 IEEE International Joint Conference on Neural Network Proceedings, The 2006 IEEE International Joint Conference on Neural Network Proceedings, IEEE, pp. 4577-4581.
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In the past decade, artificial neural networks (ANNs) have been widely applied to the engineering problems with a complicated system. ANNs are becoming an important alternative option for solving problems in comparison to traditional engineering solutions, which are usually involved in complicated mathematical theories. In this study, we apply an ANN model to the wave-induced seabed liquefaction problem, which is a key issue in the area of coastal and ocean engineering. Furthermore, we adopted an ANN model with preprocessing (MIN-MAX) on difficult training data. This paper demonstrates the capacity of the proposed ANN model using MIN-MAX pre-processing to provide coastal engineers with another effective tool to analyse the stability of seabed sediment. © 2006 IEEE.
Fatahi, B, Indraratna, B & Khabbaz, H 1970, 'Modelling of soil improvement induced by tree root suction', Soft Ground Engineering: Proceedings of the Sydney Chapter 2006 Symposium, Sydney Chapter Symposium, Engineers Australia, Sydney, Australia, pp. 155-166.
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Fischer, K & Sheng, D 1970, 'Different aspects of large deformation contact formulations applied to pile-soil FE-analysis', Numerical Methods in Geotechnical Engineering, 6th European Conference on Numerical Methods in Geotechnical Engineering, Taylor & Francis, Graz, AUSTRIA, pp. 613-618.
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Green, S & Blumenstein, M 1970, 'An Exhaustive Search Strategy for Detecting Persons in Beach Scenes using Digital Video Imagery and Neural Network-based Classification', The 2006 IEEE International Joint Conference on Neural Network Proceedings, The 2006 IEEE International Joint Conference on Neural Network Proceedings, IEEE, pp. 2439-2444.
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This paper presents an investigation of a neural-based technique for detecting and quantifying persons in beach imagery for the purpose of predicting trends of tourist activities at beach sites. The proposed system uses various pre-processing and segmentation techniques to initially isolate potential objects in cluttered scenes. A structural feature extraction technique is then used to represent objects of interest for training a neural classifier. An exhaustive search strategy, incorporating a neural network, is proposed to effectively scan beach images to determine whether objects are "person" or "non-person". Encouraging results are presented for person detection using video imagery collected from a beach site on the coast of Australia. ©2006 IEEE.
Indraratna, B & Fatahi, B 1970, 'Sensitivity analysis to examine tree root effectiveness in soft ground stabilisation', Numerical Methods in Geotechnical Engineering, European Conference on Numerical Methods in Geotechnical Engineering, Balkema, Taylor & Francis Group, Austria, pp. 735-741.
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ABSTRACT: Native vegetation in Australia is becoming increasingly popular for stabilising railway corridors built over soft soils. A model previously developed to measure the rate of tree root water uptake and a computer model are used to investigate the effect of a wide range of soil, tree, and atmospheric parameters on partially saturated ground. First, sensitivity analysis is used to investigate the affect of different parameters on the maximum initial rate of root water uptake, and then a reference example is simulated using finite element analysis. The influence of parameters such as time, potential transpiration rate and its distribution factor, wilting point suction, the coefficient of permeability, and the distribution of root length density are studied. Soil suction and settlement was found to increase over time, with the effect being more significant in the first stages of transpiration. The most sensitive parameters are wilting point suction, the coefficient of saturation permeability at higher values, the rate of potential transpiration at lower values, and vertical root distribution when the coefficient is high.
Indraratna, B, Fatahi, B & Khabbaz, H 1970, 'Numerical Prediction of Vadose Zone Behaviour Influenced by Vegetation', Unsaturated Soils 2006, Fourth International Conference on Unsaturated Soils, American Society of Civil Engineers, Arizona, USA, pp. 2256-2267.
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Bioengineering aspects of native vegetation are currently, and rapidly, being evolved to improve soil stiffness, slope stabilisation, and erosion control. Apart from the reinforcement effect, tree roots establish sufficient matric suction to increase the shear strength and stiffness of the soil. This paper looks at the way, vegetation influences soil matric suction, shrinkage, and ground settlement. A mathematical model for the rate of root water uptake that considers ground conditions, type of vegetation and climatic parameters, has been developed. Based on this proposed model, the distribution of moisture and the matric suction profile adjacent to the tree are numerically analysed. The model formulation is based on the general effective stress theory of unsaturated soils. Field measurements taken from literature published previously are compared with the authors' numerical model. The predicted results calculated using the soil, plant, and atmospheric parameters contained in the numerical model, compared favourably with the measured results, justifying the assumptions upon which the model was developed. Copyright ASCE 2006.
Indraratna, B, Fatahi, B & Khabbaz, H 1970, 'Parametric Study on Suction Effects Induced by Tree Roots on Ground Conditions', GeoCongress 2006, GeoCongress 2006, American Society of Civil Engineers, Atlanta, Georgia, USA, pp. 158-163.
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A model developed for the rate of tree root water uptake is applied numerically based on finite element analysis, to investigate the effects of the soil, tree and atmospheric parameters on the ground behaviour. The influences of potential transpiration rate, permeability coefficient, and the maximum root length density are studied and quantified. Although the rate of transpiration increases the soil matric suction and the ground settlement, permeability (saturated) decreases the matric suction generated and the corresponding settlement. The maximum root density also affects the change in peak matric suction as demonstrated in the paper. Copyright ASCE 2006.
Indraratna, B, Shahin, MA, Rujikiatkamjiorn, C & Christie, D 1970, 'Stabilization of Ballasted Rail Tracks and Underlying Soft Formation Soils with Geosynthetic Grids and Drains', Ground Modification and Seismic Mitigation, GeoShanghai International Conference 2006, American Society of Civil Engineers, pp. 143-152.
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Railway ballast deforms and degrades progressively under heavy cyclic loading. Ballast degradation is influenced by several factors including the amplitude and number of load cycles, gradation of aggregates, track confining pressure, angularity and fracture strength of individual grains. The degraded ballast is usually cleaned on track, otherwise, fully or partially replaced by fresh ballast, depending on the track settlement and current density. The use of composite geosynthetics at the bottom of recycled ballast layer is highly desirable to serve the functions of both drainage and separation of ballast from subballast. Construction of the rail track also requires appropriate improvement of the subgrade soils to achieve an adequately stiff surface layer prior to placing the ballast and subballast. Based on extensive research at University of Wollongong, it is found that the gradation of ballast plays a significant role in the strength, deformation, degradation, stability and drainage of rail tracks. Results from large-scale triaxial testing indicate that a small increase in confining pressure improves track stability with less ballast degradation. Bonded geogrids-geotextiles also decrease differential settlements of tracks, ballast degradation and lateral movement, and the risk of subgrade pumping. Stabilization of soft subgrade soils is also essential for improving the overall stability of track and to reduce the differential settlement during the operation of trains. This paper also highlights the effectiveness of using prefabricated vertical drains (PVDs) for improving the behavior of soft formations underlying rail tracks. Copyright ASCE 2006.
Kwok, N, Nguyen, T, Ha, QP, Li, J & Samali, B 1970, 'Parameter Identification for a simple MR Damper model using Particle Swarm Optimisation', Disgest Book of the Asia Pacific Symposium on Applied Electromagnetic and Mechanics, Asia Pacific Symposium on Applied Electromagnetics and Mechanics, UTS, Sydney, Australia, p. 11.
Nguyen, T, Kwok, N, Ha, QP, Li, J & Samali, B 1970, 'Symmetric Quantized Sliding Model Control for Civil Structures Using Magnetorcheological Dampers', Digest Book of the Asia-Pacific Symposium on Applied Electromagnetics and Mechanics, Asia Pacific Symposium on Applied Electromagnetics and Mechanics, UTS, Sydney, Australia, p. 47.
Nguyen, TH, Kwok, NM, Ha, QP, Li, J & Samali, B 1970, 'Adaptive Sliding Mode Control for Civil Structures Using Magnetorheological Dampers', Proceedings of the International Symposium on Automation and Robotics in Construction (IAARC), 23rd International Symposium on Automation and Robotics in Construction, International Association for Automation and Robotics in Construction (IAARC), Tokyo, Japan, pp. 636-641.
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An adaptive sliding mode controller for vibration control is proposed in this paper for structures embedded with magnetorheological (MR) dampers. Civil structures and buildings are liable to damages during earthquake periods. The application of structural control methodologies is important in order to suppress vibrations due to seismic phenomena and dynamic loading. The use of sliding mode control is accounted for by its robustness to system uncertainties and external disturbances while a MR damper is technologically-efficient for its vibration control and also fail-safe for an ideal semiactive device. The control performance is enhanced by implementing an adaptive control law in estimating the system parameters. Simulation results are included to demonstrate the effectiveness of the proposed controller in a building model under earthquake-like excitations.
Pradhan, B, Mansor, S, Rahman Ramli, A, Rashid Mohd Sharrif, A & Kumar, S 1970, 'Compression of LIDAR Data for Web Based Visualization Using Second Generation Wavelets', 36th COSPAR Scientific Assembly.
Pradhan, B, Mansor, S, Ramli, AR, Sharif, ARBM & Sandeep, K 1970, 'A new robust data comprssor for lidar data', Asian Association on Remote Sensing - 27th Asian Conference on Remote Sensing, ACRS 2006, pp. 527-533.
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For a realistic representation of a terrain Light Detection and Ranging data (LiDAR) requires trillion numbers of points. These points connected in triangles that represent the surface of the terrain ultimately increase 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. In this paper, it is extended to the LiDAR data compression. A newly developed data compression approach to approximate the LiDAR surface with a series of non-overlapping triangles has been presented. Generally a Triangulated Irregular Networks (TIN) are the most common form of digital surface model that consists of elevation values with x, y coordinates that make up triangles. Compression of TIN is needed for efficient management of large data and good surface visualization. This approach covers following steps: First, by using a Delaunay triangulation, an efficient algorithm is developed to generate TIN, which forms the terrain from an arbitrary set of data. A 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. The quality of geographical surface representation after using proposed technique is compared with the original LIDAR data. The results show that this method can be used for significant reduction of data set.
Pradhan, B, Singh, RP & Buchroithner, MF 1970, 'Estimation of stress and its use in evaluation of landslide prone regions using remote sensing data', Advances in Space Research, Elsevier BV, pp. 698-709.
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Pradhan, B, Talib, JA & Lee, S 1970, 'Application of remote sensing data in determining regional landslide hazard analysis by using logistic regression model and GIS', Asian Association on Remote Sensing - 27th Asian Conference on Remote Sensing, ACRS 2006, pp. 1053-1059.
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This paper presents the use of remote sensing data for landslide hazard analysis around Penang Island area, Malaysia. The study area consider as one of the frequent occurrence landslide zone in Malaysia. Efforts have been made to use a linear logistic regression model for landslide hazard delineation by using remote sensing and GIS data. Landslide locations were identified in the study area from interpretation of aerial photographs, high resolution satellite imageries and from field surveys. Terrain information such as land cover, topographic slope, topographic aspect and topographic curvature has been derived from the satellite imageries; and the existing thematic information has been updated to enable the quantification of landslide causative parameters. The other factors chosen that influence landslide occurrence were: lithology, soil, distance from lineament, and distance from drainage and the vegetation index value from SPOT 5 image. Spatial and temporal multi-layered information have been used for landslide hazard analysis. The qualitative hazard analysis has been carried out using the map overlying techniques using the logistic regression model in GIS environment. Landslide locations were used to verify results of the landslide hazard map and the verification results showed 86.62% accuracy. The verification results showed sufficient agreement between the presumptive hazard map and the existing data on landslide areas.
Rujikaitkamjorn, C & Indraratna, B 1970, 'Improvement of Soft Clays Using Vacuum-Assisted Consolidation Method', GeoCongress 2006, GeoCongress 2006, American Society of Civil Engineers, p. 264.
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In this study, the analytical modeling of one-dimensional consolidation by vertical drains with vacuum preloading considering both vertical and horizontal drainage is presented. In this method, the total degree of consolidation based on excess pore water pressure dissipation is related to the time factor (T h), drain configuration and anisotropic soil permeability. The analytical predictions are compared with the observed data from consolidation testing. Three different test series were conducted in a large-scale consolidation apparatus designed and installed at the University of Wollongong. It is shown that the authors' analytical model can accurately predict the laboratory behavior. Finally, the analysis of a selected case history employing the authors' model demonstrates the applicability of this approach for typical field conditions. Copyright ASCE 2006.
Rujikiatkamjorn, C & Indraratna, B 1970, 'Elastic visco-plastic consolidation modelling of soft clays improved by geosynthetic vertical drains', GEOSYNTHETICS, VOLS 1-4, 8th International Conference on Geosynthetics (8ICG), MILLPRESS SCIENCE PUBLISHERS, Yokohama, JAPAN, pp. 439-+.
Rujikiatkamjorn, C & Indraratna, B 1970, 'Three-Dimensional Numerical Modeling of Soft Soil Consolidation Improved by Prefabricated Vertical Drains', Ground Modification and Seismic Mitigation, GeoShanghai International Conference 2006, American Society of Civil Engineers, pp. 161-168.
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A system of prefabricated vertical drains (PVDs) with a surcharge load is an effective method for accelerating soil consolidation by promoting radial flow. This study presents a three-dimensional (3D) finite element model for soft soil improved by a single drain. In the finite element analysis, the actual rectangular PVD cross-section is considered, and the equivalent drain diameter is then back calculated based on the consolidation curves. The numerical predictions are then compared to previous studies. The settlements observed in the laboratory are subsequently compared with the three-dimensional finite element analysis incorporating the modified Cam-Clay model and Hansbo's theory. Copyright ASCE 2006.
Shahin, MA & Indraratna, B 1970, 'Parametric Study on the Resilient Response of Ballasted Railway Track Substructure Using Numerical Modeling', GeoCongress 2006, GeoCongress 2006, American Society of Civil Engineers, p. 85.
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Ballasted rail track substructure usually consists of graded layers of granular media of ballast and subballast (capping) placed above a compacted subgrade (formation soil). The optimum design of railway track substructure relies on many factors that affect the performance of the track. In this paper, the response of railway track to various factors affecting track performance is investigated by carrying out a parametric study using the finite element analysis (PLAXIS). A plane strain finite element model of railway track section is developed and used for the parametric study. The feasibility of the developed finite element model is examined by comparing its results with measured field test data. The various track factors investigated include the thickness and stiffness of different track layers, shoulder width, and track modulus. The results demonstrate that the subgrade stiffness seems to be the most significant factor affecting track response, thus, the numerical model and experimental data are used to investigate the capability of different stabilization techniques, such as geosynthetics and grout columns, for improving track subgrade behavior. Copyright ASCE 2006.
Sun, DA & Sheng, DC 1970, 'Collapse Behavior of Unsaturated Compacted Soils', Advances in Unsaturated Soil, Seepage, and Environmental Geotechnics, GeoShanghai International Conference 2006, American Society of Civil Engineers, pp. 102-110.
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This paper presents comprehensive results of a series of collapse tests on unsaturated compacted clay using a suction-controllable triaxial apparatus for identifying the collapse behaviour, which includes deformation characteristics such as volume changes and hydraulic characteristics such as degree of saturation changes. The collapse tests were conducted by decreasing the imposed matric suction from 147 to 0kPa step by step under constant isotropic net stresses. Experimental data show that the wetting-induced collapse deformation mainly depends on the initial density and mean net stress at which the collapse occurs, i.e., the denser the specimen or the larger the mean net stress, the smaller the collapse deformation. In addition, the soil-water characteristic curve obtained for an initial denser specimen tends to shift upwards in the Sr - lns plane, compared to an initially looser specimen. It is shown that the collapse mainly occurs in the suction range from 20 to 80 kPa for the tested soil. Copyright ASCE 2006.
Sun, DA, Sheng, DC, Cui, HB & Li, J 1970, 'Effect of Density on the Soil-Water-Retention Behaviour of Compacted Soil', Unsaturated Soils 2006, Fourth International Conference on Unsaturated Soils, American Society of Civil Engineers, pp. 1338-1347.
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This paper presents a series of experimental results obtained from wetting and/or drying cyclic tests and constant suction triaxial tests on unsaturated compacted clay with different initial densities using two suction-controllable triaxial apparatus. The primary objective of this research is to investigate the influence of the soil density on the soil-water-retention behaviour. The initial density and initial degree of saturation were controlled by changing the compaction energy using clay powders with almost the same water content. The test results contain the water-retention curves and deformation behavior at different initial densities using different specimens and one specimen before and after collapse. The test data indicate that the measured water-retention curves vary with the current specimen density. A denser specimen results in a higher degree of saturation at the same imposed suction, which implies that the water-retention curve shifts to the right in the ln s-Sr plane. Copyright ASCE 2006.
Yan Tong, Yang Wang, Zhiwei Zhu & Qiang Ji 1970, 'Facial Feature Tracking using a Multi-State Hierarchical Shape Model under Varying Face Pose and Facial Expression', 18th International Conference on Pattern Recognition (ICPR'06), 18th International Conference on Pattern Recognition (ICPR'06), IEEE.
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