http://espace.library.uq.edu.au/ The University of Queensland en Fez http://blogs.law.harvard.edu/tech/rss http://espace.library.uq.edu.au/view/UQ:263476 In this study, an electromagnetics-based inverse sensitivity mapping method is introduced for applications in high field MRI. Instead of using simplistic numerical approximations, the sensitivity of the radio-frequency coil was determined through a field approach by using iterative optimization. The current study is an extension to previous studies on the inverse method, which has restricted itself to low-field applications due to the use of the Biot-Savart integration to account for the H field calculations. In the current study, full-wave solutions to the Maxwell's equations based MOM/FEM hybrid algorithm were employed to provide H field evaluation. It is demonstrated that the proposed method is able to produce high-fidelity sensitivity estimation which result in images with significantly less artefact power. 2011-12-14T00:00:00Z Jin, Jin og Liu, Feng og Li, Yu og Weber, Ewald og Xu, Wenlong og Crozier, Stuart http://espace.library.uq.edu.au/view/UQ:99227 2007-08-24T00:00:00Z Xin, Y. og Abeyratne, U. R. http://espace.library.uq.edu.au/view/UQ:262751 2011-12-02T00:00:00Z Antoniades, Marco A. og Eleftheriades, George V. http://espace.library.uq.edu.au/view/UQ:262774 2011-12-02T00:00:00Z Antoniades, Marco A. og Eleftheriades, George V. http://espace.library.uq.edu.au/view/UQ:103112 2007-08-23T00:00:00Z D'Souza, M. J. og Postula, A. J. og Bergmann, N. W. og Ros, M. http://espace.library.uq.edu.au/view/UQ:11270 This paper propses a multi-resolution method for cell segmentation, and outlines some of the advantages it has over other techniques. The research is based on approach developed by Wilson and Spann, and the other paper details some improvements on this algorithm for this particular problem. 2004-02-04T00:00:00Z Jeacocke, Mark B. og Lovell, Brian C. http://espace.library.uq.edu.au/view/UQ:96898 2007-08-24T00:00:00Z Xu, Z. og Dong, Z. Y. http://espace.library.uq.edu.au/view/UQ:182699 A spatial k-NN query returns k nearest points in a point dataset to a given query point. To measure the distance between two points, most of the literature focuses on the Euclidean distance or the network distance. For many applications, such as wildlife movement, it is necessary to consider the surface distance, which is computed from the shortest path along a terrain surface. In this paper, we investigate the problem of efficient surface k-NN (sk-NN) query processing. This is an important yet highly challenging problem because the underlying environment data can be very large and the computational cost of finding the shortest path on a surface can be very high. To minimize the amount of surface data to be used and the cost of surface distance computation, a multi-resolution surface distance model is proposed in this paper to take advantage of monotonic distance changes when the distances are computed at different resolution levels. Based on this innovative model, sk-NN queries can be processed efficiently by accessing and processing surface data at a just-enough resolution level within a just-enough search region. Our extensive performance evaluations using real world datasets confirm the efficiency of our proposed model. 2009-09-03T09:50:34Z Deng, Ke og Zhou, Xiaofang og Shen, Heng Tao og Liu, Qing og Xu, Kai og Lin, Xuemin http://espace.library.uq.edu.au/view/UQ:79401 Multiresolution Triangular Mesh (MTM) models are widely used to improve the performance of large terrain visualization by replacing the original model with a simplified one. MTM models, which consist of both original and simplified data, are commonly stored in spatial database systems due to their size. The relatively slow access speed of disks makes data retrieval the bottleneck of such terrain visualization systems. Existing spatial access methods proposed to address this problem rely on main-memory MTM models, which leads to significant overhead during query processing. In this paper, we approach the problem from a new perspective and propose a novel MTM called direct mesh that is designed specifically for secondary storage. It supports available indexing methods natively and requires no modification to MTM structure. Experiment results, which are based on two real-world data sets, show an average performance improvement of 5-10 times over the existing methods. 2007-08-15T00:00:00Z Xu, K og Zhou, XF og Lin, XM og Shen, HT og Deng, K http://espace.library.uq.edu.au/view/UQ:246052 2011-08-22T00:00:00Z Rowe, Christopher C. og Ellis, Kathryn A. og Rimajova, Miroslava og Bourgeat, Pierrick og Pike, Kerryn E. og Jones, Gareth og Fripp, Jurgen og Tochon-Danguy, Henri og Morandeau, Laurence og O'Keefe, Graeme og Price, Roger og Raniga, Parnesh og Robins, Peter og Acosta, Oscar og Lenzo, Nat og Szoeke, Cassandra og Salvado, Olivier og Head, Richard og Martins, Ralph og Masters, Colin L. og Ames, David og Villemagne, Victor L. http://espace.library.uq.edu.au/view/UQ:220337 2010-11-15T00:00:00Z Singh, A. og Sawan, S. og Hanmandlu, M. og Madasu, V. K. og Lovell, B. C. http://espace.library.uq.edu.au/view/UQ:231005 Classic argumentative discussions can be found in a variety of domains from traditional scientific publishing to today’s modern social software. An interactive argumentative discussion usually consists of an initial proposition stated by a single creator, followed by supporting propositions or counter-propositions from other contributors, usually part of the same virtual community. Thus, the actual argumentation semantics is hidden in the content created by the contributors. Although there are approaches that try to deal with this challenge, most of them focus on a particular domain, limiting the scope of the argumentation to that domain only. In this article, the authors describe an abstract model for argumentation which captures the semantics independently of the domain. Following a modularized approach, the authors also take into account additional important aspects of the argumentation, like the provenance information or its evolution (the temporal side). Consequently, they present a possible usage of the framework in the context of virtual communities. 2011-03-03T00:00:00Z Groza, Tudor og Handschuh, Siegfried og Breslin, John G. og Decker, Stefan http://espace.library.uq.edu.au/view/UQ:9858 The failure of medium voltage (MV) cables in North Queensland has led Ergon Energy to consider the relative economics of refurbishment or replacement. In order to provide data to inform decision making, an accelerated ageing program has been designed to investigate the ageing of new, field aged, and refurbished cables. This paper describes the considerations affecting the design of the ageing experiment and reviews the features of the test rig in which ageing is accelerated by a combination of high voltage stress, load-cycling to high temperatures and water immersion. Research into cable condition diagnostics will also be discussed. 2005-02-21T00:00:00Z Birtwhistle, D. og Lyall, J. S. og Foottit, F. og Wickramasuriya, P. og Gilbert, R. og Powell, L. og Saha, Tapan K. http://espace.library.uq.edu.au/view/UQ:261790 Small animal image registration is challenging because of its joint structure, and posture and position difference in each acquisition without a standard scan protocol. In this paper, we face the issue of mouse whole-body skeleton registration from CT images. A novel method is developed for analyzing mouse hind-limb and fore-limb postures based on geodesic path descriptor and then registering the major skeletons and fore limb skeletons initially by thin-plate spline (TPS) transform based on the obtained geodesic paths and their enhanced correspondence fields. A target landmark correction method is proposed for improving the registration accuracy of the improved 3D shape context non-rigid registration method we previously proposed. A novel non-rigid registration framework, combining the skeleton posture analysis, geodesic path based initial alignment and 3D shape context model, is proposed for mouse whole-body skeleton registration. The performance of the proposed methods and framework was tested on 12 pairs of mouse whole-body skeletons. The experimental results demonstrated the flexibility, stability and accuracy of the proposed framework for automatic mouse whole body skeleton registration. 2011-11-19T00:00:00Z Xiao, Di og Zahra, Pierrick og Bourgeat, Pierrick og Berghofer, Paula og Acasto Tamayo, Oscar og Wimberley, Catriona og Gregoire, Marie Claude og Salvado, Olivier http://espace.library.uq.edu.au/view/UQ:77845 The notorious "dimensionality curse" is a well-known phenomenon for any multi-dimensional indexes attempting to scale up to high dimensions. One well-known approach to overcome degradation in performance with respect to increasing dimensions is to reduce the dimensionality of the original dataset before constructing the index. However, identifying the correlation among the dimensions and effectively reducing them are challenging tasks. In this paper, we present an adaptive Multi-level Mahalanobis-based Dimensionality Reduction (MMDR) technique for high-dimensional indexing. Our MMDR technique has four notable features compared to existing methods. First, it discovers elliptical clusters for more effective dimensionality reduction by using only the low-dimensional subspaces. Second, data points in the different axis systems are indexed using a single B+-tree. Third, our technique is highly scalable in terms of data size and dimension. Finally, it is also dynamic and adaptive to insertions. An extensive performance study was conducted using both real and synthetic datasets, and the results show that our technique not only achieves higher precision, but also enables queries to be processed efficiently. Copyright Springer-Verlag 2005 2007-08-15T00:00:00Z Shen, H. T. og Zhou, X. og Zhou, A. http://espace.library.uq.edu.au/view/UQ:165067 The notorious iodimensionality curseln is a well-known phenomenon for any multi-dimensional indexes attempting to scale up to high dimensions. One well known approach to overcoming degradation in performance with respect to increasing dimensions is to reduce the dimensionality of the original dataset before constructing the index. However, identifying the correlation among the dimensions and effectively reducing them is a challenging task. In this paper, we present an adaptive Multi-level Mahalanobis-based Dimensionality Reduction (MMDR) technique for high-dimensional indexing. Our MMDR technique has three notable features compared to existing methods. First, it discovers elliptical clusters using only the low-dimensional subspaces. Second, data points in the different axis systems are indexed using a single B+-tree. Third, our technique is highly scalable in terms of data size and dimensionality. An extensive performance study using both real and synthetic datasets was conducted, and the results show that our technique not only achieves higher precision, but also enables queries to be processed efficiently. 2009-02-25T00:00:00Z Jin, Hui og Ooi, Beng Chin og Shen, Heng Tao og Yu, Cui og Zhou, Ao Ying http://espace.library.uq.edu.au/view/UQ:172826 Due to its tremendous commercial potential, sports video has become a popular research topic nowadays. As the bridge of low-level features and high-level semantic contents, automatic shot clustering is an important issue in the field of sports video content analysis. In previous work, many clustering approaches need some professional knowledge of videos, some experimental parameters, or some thresholds to obtain good clustering results. In this article, we present a new efficient shot clustering algorithm for sports video which is generic and does not need any prior domain knowledge. The novel algorithm, which is called Valid Dimension Clustering(VDC), performs in an unsupervised manner. For the high-dimensional feature vectors of video shots, a new dimensionality reduction approach is proposed first, which takes advantage of the available dimension histogram to get ”valid dimensions” as a good approximation of the intrinsic characteristics of data. Then the clustering algorithm performs on valid dimensions one by one to furthest utilize the intrinsic characteristics of each valid dimension. The iterations of merging and splitting of similar shots on each valid dimension are repeated until the novel stop criterion which is designed inheriting the theory of Fisher Discriminant Analysis is satisfied. At last, we apply our algorithm on real video data in our extensive experiments, the results show that VDC has excellent performance and outperforms other clustering algorithms. 2009-03-31T11:56:53Z Liao, Jia og Wang, Guoren og Zhang, Bo og Zhou, Xiaofang og Yu, Ge http://espace.library.uq.edu.au/view/UQ:234840 An adaptive control strategy is described which was used for closed-loop computer control of blood pressure in patients in the Intensive Care and Cardiac Surgical Units of the Royal Melbourne Hospital in Australia. The initial development and testing of the control algorithm was done by simulation using computer facilities in the intensive care unit. Adaptation to patient variability utilizes a model reference strategy. Control is based on readings of mean arterial pressure obtained from a standard patient monitor unit and implemented by controlling the infusion rate of a volumetric infusion pump. Patient data are displayed graphically on a video display unit during control and stored on disk for subsequent postcontrol display and analysis by the medical staff. Clinical trials indicated that the system is robust and can maintain effective control following sudden large variations in the patient's blood pressure. 2011-03-11T00:00:00Z Packer, John S. og Mason, D. G. og Cade, John F. og McKinley, Sharon M. http://espace.library.uq.edu.au/view/UQ:58887 This paper proposed a novel model for short term load forecast in the competitive electricity market. The prior electricity demand data are treated as time series. The forecast model is based on wavelet multi-resolution decomposition by autocorrelation shell representation and neural networks (multilayer perceptrons, or MLPs) modeling of wavelet coefficients. To minimize the influence of noisy low level coefficients, we applied the practical Bayesian method Automatic Relevance Determination (ARD) model to choose the size of MLPs, which are then trained to provide forecasts. The individual wavelet domain forecasts are recombined to form the accurate overall forecast. The proposed method is tested using Queensland electricity demand data from the Australian National Electricity Market. (C) 2001 Elsevier Science B.V. All rights reserved. 2007-08-14T00:00:00Z Zhang, B. L. og Dong, Z. Y. http://espace.library.uq.edu.au/view/UQ:81743 2007-08-15T00:00:00Z Uthansakul, P. og Bialkowski, M E http://espace.library.uq.edu.au/view/UQ:103817 2007-08-23T00:00:00Z Uthansakul, P. og Bialkowski, M E http://espace.library.uq.edu.au/view/UQ:65512 Frequency deviation is a common problem for power system signal processing. Many power system measurements are carried out in a fixed sampling rate assuming the system operates in its nominal frequency (50 or 60 Hz). However, the actual frequency may deviate from the normal value from time to time due to various reasons such as disturbances and subsequent system transients. Measurement of signals based on a fixed sampling rate may introduce errors under such situations. In order to achieve high precision signal measurement appropriate algorithms need to be employed to reduce the impact from frequency deviation in the power system data acquisition process. This paper proposes an advanced algorithm to enhance Fourier transform for power system signal processing. The algorithm is able to effectively correct frequency deviation under fixed sampling rate. Accurate measurement of power system signals is essential for the secure and reliable operation of power systems. The algorithm is readily applicable to such occasions where signal processing is affected by frequency deviation. Both mathematical proof and numerical simulation are given in this paper to illustrate robustness and effectiveness of the proposed algorithm. Crown Copyright (C) 2003 Published by Elsevier Science B.V. All rights reserved. 2007-08-15T00:00:00Z Jiang, H. L. og Tang, X. J. og Dong, Z. Y. og Saha, T. K. http://espace.library.uq.edu.au/view/UQ:233630 As one of the electricity infrastructure, a robust power network is needed to support the sustainability of energy supply. Compared to other common customer goods, electric energy has some unique features that require specific consideration. Unlike most products, electricity cannot be stored in large amounts in an economical manner. Accordingly, electricity has to be simultaneously produced and distributed on demand. Transmission and distribution network systems are then used to deliver the power. The operating capability of generation, transmission and distribution systems must be adequate to meet the fluctuating demands of the customers. As illustrated in Figure 1, a simple configuration of an interconnected power system has basically three important parts, namely: generator as source of the electrical energy, transmission line for transmitting power to remote areas and the load which consumes the power. 2011-03-09T00:00:00Z Nappu, Muhammad Bachtiar og Saha, Tapan Kumar http://espace.library.uq.edu.au/view/UQ:136033 With the increased interest in multi-user systems with distributed decision making tasks, such as network centric warfare and free-flight air traffic control, the concept of shared situation awareness (SSA) has become more important. SSA relates to the awareness that different operators have of the system state and the information needs of their team-mates, in order to coordinate their actions effectively. However, there are many different definitions of SSA in the literature and no generally agreed methodology for measuring it. Investigation to date has primarily been conducted through human-in-the-loop (HIL) experiments, which typically are costly and return only subjective results. Agent based modelling has been proposed as a partial solution, using software agents to take the place of humans in experiments. This paper describes the application of agent based modelling to a multi-user system: namely, the SCUDhunt game. The paper examines different ways of sharing information between operators, and their effect on team performance in cases with less than perfect information. Agent based modelling enables performance to be tested on a wide range of scenarios quickly and repeatedly and yields insights that would be difficult to achieve through HIL experiments alone. 2008-04-22T00:00:00Z Connelly, S. og Lindsay, P. A. og Gallagher, M. http://espace.library.uq.edu.au/view/UQ:123424 In this work we study a dynamical system with a complicated nonlinearity, which describes oscillation of a turbine rotor, and give an algorithm to compute Melnikov functions for analysis of its chaotic behavior. We first derive the rotor model whose nonlinear term brings difficulties to investigating the distribution and qualitative properties of its equilibria. This nonlinear model provides a typical example of a system for which the homoclinic and heteroclinic orbits cannot be analytically determined. In order to apply Melnikov's method to make clear the underlying conditions for chaotic motion, we present a generic algorithm that provides a systematic procedure to compute Melnikov functions numerically. Substantial analysis is done so that the numerical approximation precision at each phase of the computation can be guaranteed. Using the algorithm developed in this paper, it is straightforward to obtain a sufficient condition for chaotic motion under damping and periodic external excitation, whenever the rotor parameters are given. 2008-01-25T00:00:00Z Xu, JX og Yan, R og Zhang, WN http://espace.library.uq.edu.au/view/UQ:268633 2012-02-28T13:51:18Z Zhang, Chenyi og Pang, Jun http://espace.library.uq.edu.au/view/UQ:9706 Defeasible logic is a non-monotonic logic with applications in rule-based domains such as law. To ease the development and improve the accuracy of expert systems based on defeasible logic, it is desirable to automatically induce a theory of the logic from a training set of precedent data. Empirical evidence suggests that minimal theories that describe the training set tend to be more faithful representations of reality. We show via transformation from the hitting set problem that this global minimization problem is intractable, belonging to the class of NP optimisation problems. Given the inherent difficulty of finding the optimal solution, we instead use heuristics and demonstrate that a best-first, greedy, branch and bound algorithm can be used to find good theories in short time. This approach displays significant improvements in both accuracy and theory size as compared to recent work in the area that post-processed the output of an Aprori association rule-mining algorithm, with comparable execution times. 2005-03-21T00:00:00Z Johnston, Benjamin og Governatori, Guido http://espace.library.uq.edu.au/view/UQ:175092 2009-04-10T00:00:00Z McKilliam, R. og Clarkson, I. V. L. og Quinn, B. G. http://espace.library.uq.edu.au/view/UQ:99473 2007-08-24T00:00:00Z Miller, A. M. og Sanderson, P. M. http://espace.library.uq.edu.au/view/UQ:173854 2009-04-05T00:00:00Z Nappu, M.B. og Saha, T. K. og Fonseka, J. http://espace.library.uq.edu.au/view/UQ:8299 Over the last twenty five years we have had repeated evaluations of the history of stone artefact analysis in Australia (e.g. Mulvaney 1977; Hiscock 1983, 1998; Fullagar 1994; Holdaway 1995). Each of these reviews brought a different emphasis to the quest for an understanding of the trends, motive factors and constraints in archaeological investigations of bygone years. Although it is pleasing to observe the progress of analytical practice it is equally clear that the major benefit of these historical reviews is their ability to identify those subject areas requiring remedial attention and warranting emphasis in future investigations. With this point in mind it is not our intention to revisit the intellectual history of artefact analysis, but to concentrate on developing a summary of issues that might be the focus of our research efforts over coming decades. Our purpose is to define elements of a research agenda for the study of archaeological stone artefacts, and to this end we do not offer solutions to those problems that remain but seek to identify components of research design deserving attention. 2006-06-01T00:00:00Z Clarkson, Chris og Hiscock, Peter http://espace.library.uq.edu.au/view/UQ:279297 Since the ‘empirical turn’ in design studies, many methods drawn from the social and human sciences have been applied to the study of designers' activities. Recently, conversation analysis (CA) has been gaining some attention as one of these approaches that may offer promise for design studies. In this paper, we present an analysis of design work informed by CA. Our analysis is intended both as a means of exemplifying how the approach can be applied to design, and as empirical groundwork for sketching out what a CA program of research in design studies could offer the field. We argue that CA can provide an empirical respecification of central conceptual and theoretical topics in design research. 2012-08-24T11:26:03Z Matthews, Ben og Heinemann, Trine http://espace.library.uq.edu.au/view/UQ:7779 In stream authentication protocols used for large-scale data dissemination in autonomuous systems, authentication is based on the timing of the publication of keys, and depends on trust of the receiver in the sender and belief on whether an intruder can have prior knowledge of a key before it is published by a protocol. Many existing logics and approaches have successfully been applied to specify other types of authentication protocols, but most of them are not appropriate for analysing stream authentication protocols. We therefore consider a fibred modal logic that combines a belief logic with a linear-time temporal logic which can be used to analyse time-varying aspects of certain problems. With this logical system one is able to build theories of trust for analysing stream authentication protocols, which can deal with not only agent beliefs but also the timing properties of an autonomous agent-based system. 2006-11-03T00:00:00Z Orgun, M. A. og Ma, J. og Liu, C. og Governatori, G. http://espace.library.uq.edu.au/view/UQ:9811 This paper presents a novel voltage stability analysis and assessment method based on an observation of the sensitivity of generator reactive power outputs to changes in loading at buses in a power system. This information can be used to assess the relative stability of a power system and to determine the sets of generators that cause voltage instability when they lose voltage control and the associated buses that provide the mechanisms for collapse. This method has been tested on a modified Cigre ‘Nordic’ test system and on the large scale Queensland Transmission system and the results of these tests are provided in this paper. This method is compared to another widely excepted voltage stability assessment method. 2005-02-24T00:00:00Z Aumuller, Craig og Saha, Tapan K. http://espace.library.uq.edu.au/view/UQ:189089 2009-12-04T00:00:00Z Boonchiam, P. og Mithulananthan, Nadarajah http://espace.library.uq.edu.au/view/UQ:188039 2009-11-26T00:00:00Z Srisongkram, W. og Phanthuna, N. og Boonchiam, P. og Subsingha, W. og Mithulananthan, N. http://espace.library.uq.edu.au/view/UQ:293936 2013-03-17T00:24:16Z Zhang, Z. J. og Bergmann, N. W. og Li, H. M. http://espace.library.uq.edu.au/view/UQ:283127 An ultra-wideband unequal-split Wilkinson power divider with a 2:1 split ratio is presented. To achieve the ultra-wideband characteristics, the conventional quarter-wave arms of the divider are replaced by tapered lines. Moreover, two extra tapered transformers are incorporated at the output ports for matching purposes as the designed divider is of an unequal-split type. To obtain good isolation between the output ports, five isolation resistors are used, the values of which are determined using the simple odd-mode analysis of the Wilkinson power divider. For verification purposes, an ultra-wideband Wilkinson power divider that operates over a frequency range extending from 2 to 12 GHz is designed, simulated, fabricated, and measured. The results of the full-wave simulation and measurements verify the validity of the design procedure. 2012-10-12T10:25:47Z Al Shamaileh, Khair A. og Dib, Nihad I. og Abbosh, Amin http://espace.library.uq.edu.au/view/UQ:175261 There are concerns about workers repeatedly exposed to magnetic fields exceeding regulatory limits with respect to modern magnetic resonance imaging (MRI). As a result, there is need for an ambulatory magnetic field dosimeter capable of measuring these fields in and around an MRI scanner in order to evaluate the regulatory guidelines and determine any underlying exposure risks. This study presents results of tri-axial measurements using an ambulatory magnetic field dosimeter worn by workers during normal working shifts. We recorded and analyzed magnetic field exposures in and around 1.5 T, 2 T, and 4 T magnets during routine patient procedures. The data was integrated and averaged over time and evaluated against the latest exposure standards. Time-varying magnetic fields occur when individuals move through spatially non-uniform static magnetic fields or during gradient-pulsed magnetic fields or a combination of both. Our previous numerical analysis shows that at certain positions surrounding the MRI scanner ends, such fields may induce current densities and electric fields that may exceed the relevant EU, ICNIRP, and IEEE standards. A high-speed acquisition version of the dosimeter measured gradient-pulsed fields at positions accessible by MRI workers near the scanner ends, and the results were evaluated and compared against the numerical simulations and the standards. Our measurements confirm that workers can be exposed to magnetic fields exceeding the guidelines at positions near the gradient coil ends during clinical imaging and a high degree of correlation exists with the numerical results. While the time-weighted average magnetic field exposures in 1.5 T, 2 T, and 4 T were all within the regulatory limits during static magnetic field measurements, the peak limits for the head can be exceeded in some circumstances. This study presents a small number of routine shifts of data that provide indicative results of magnetic field exposure in real situations. 2009-04-13T00:00:00Z Fuentes, M. A. og Trakic, A. og Wilson, S.J. og Crozier, S. http://espace.library.uq.edu.au/view/UQ:279490 As the amount of non-scheduled small scale distributed generation (DG) units are increasing, lack of fault ride through (FRT) capability of these generators may have an adverse affect on the overall power system. This study focuses on the basics of transient overvoltage issue arising under faulty condition with integration of power-electronic (PE) interface based DG units in a system. Reasons behind this overvoltage issue and its impact on DG integration with present grid standard have been investigated. A methodology has been utilized to overcome this overvoltage issue in a system, which has conventional generator as well as wide penetration of fullconverter based solar and wind generation. An IEEE industrial test system with varieties of motor loads has been used to carry out the analysis and to verify the methodology. 2012-08-30T14:46:30Z Aziz, Tareq og Saha, Tapan K. og Nadarajah, Mithulananthan http://espace.library.uq.edu.au/view/UQ:9813 This paper reports the modeling on dielectric response for power transformer condition assessment. A model (a numerical tool) is implemented by C++ code based on dielectric theory. The model can calculate return voltage and polarization/depolarization currents. It can also calculate the maximum return voltage to generate spectrum data. Through the modeling, the parameters which contribute to the dielectric response in the real measurement can be seen much more clearly. A good numerical model is indispensable to remove the uncertainty and to accurately interpret the measurement results. The model can help us quantitatively analyze the measurement results from dielectric responses of oil paper insulation. 2005-02-24T00:00:00Z Yao, Zang Tong og Saha, Tapan Kumar http://espace.library.uq.edu.au/view/UQ:97017 2007-08-24T00:00:00Z Bialkowski, M. E. og Janapsatya, J. og Song, H.J. http://espace.library.uq.edu.au/view/UQ:61644 A field matching method is described to analyze a recessed circular cavity radiating into a radial waveguide. Using the wall impedance approach, the analysis is divided into two separate problems of the cavity and its external environment. Based on this analysis, a computer algorithm is developed for determining wall admittances as seen at the edge of the patch in the cavity, the radial admittance matrix for the two-probe feed arrangement, and the input impedance as observed from the coaxial line feeding the cavity. This algorithm is tested against the general-purpose Hewlett-Packard finite-element High Frequency Structure Simulator as well as against measured results. Good agreement in all considered cases is noted. 2007-08-14T00:00:00Z Bialkowski, M. E. og Davis, P. W. http://espace.library.uq.edu.au/view/UQ:61641 A radial guide field matching method (RGFMM) is used to analyze a circular array antenna consisting of one active monopole surrounded by a concentric array of passive monopoles terminated in arbarary loads. An equivalent admittance matrix for this antenna system is determined to study the input admittance of the active monopole when the peripheral elements are terminated in open or short circuits. RGFMM results are compared with free-space method of moments (FS-MoM) results for a small switched-beam array a seven monopoles. Good agreement is noted. (C) 2002 Wiley Periodicals, Inc. 2007-08-14T00:00:00Z Janapsatya, J. og Bialkowski, M. E. http://espace.library.uq.edu.au/view/UQ:77899 This paper describes a biventricular model, which couples the electrical and mechanical properties of the heart, and computer simulations of ventricular wall motion and deformation by means of a biventricular model. In the constructed electromechanical model, the mechanical analysis was based on composite material theory and the finite-element method; the propagation of electrical excitation was simulated using an electrical heart model, and the resulting active forces were used to calculate ventricular wall motion. Regional deformation and Lagrangian strain tensors were calculated during the systole phase. Displacements, minimum principal strains and torsion angle were used to describe the motion of the two ventricles. The simulations showed that during the period of systole, (1) the right ventricular free wall moves towards the septum, and at the same time, the base and middle of the free wall move towards the apex, which reduces the volume of the right ventricle; the minimum principle strain (E3) is largest at the apex, then at the middle of the free wall and its direction is in the approximate direction of the epicardial muscle fibres; (2) the base and middle of the left ventricular free wall move towards the apex and the apex remains almost static; the torsion angle is largest at the apex; the minimum principle strain E3 is largest at the apex and its direction on the surface of the middle wall of the left ventricle is roughly in the fibre orientation. These results are in good accordance with results obtained from MR tagging images reported in the literature. This study suggests that such an electromechanical biventricular model has the potential to be used to assess the mechanical function of the two ventricles, and also could improve the accuracy ECG simulation when it is used in heart torso model-based body surface potential simulation studies. 2007-08-15T00:00:00Z Xia, Ling og Huo, Meimei M. og Wei, Qing og Liu, Feng og Crozier, Stuart http://espace.library.uq.edu.au/view/UQ:204981 Power system stabilizers (PSSs) have become very common in the operation of large electric power systems. The stability of electric power systems is increased by the use of power system stabilizers. It is a challenging task to design a stabilizer that delivers good performance in a wider range of operating conditions and under disturbances. This paper presents a fuzzy logic power system stabilizer (FLPSS) and demonstrates the good performance of this stabilizer under a wide range of operating conditions and disturbances. The performance of FLPSS is compared with that of a speed deviation (delta-omega) PSS in the variation of four different operating conditions, i.e., inertia constant (H), automatic voltage regulator (AVR) gain (Ka), internal reactance (Xe), and reactive power (Q). 2010-05-09T00:00:00Z Chopra, R. og Joshi, D. og Bansal, R. C. http://espace.library.uq.edu.au/view/UQ:100454 2007-08-23T00:00:00Z Petrovic, N. og O'Brien, C. J. og Rakic, A. http://espace.library.uq.edu.au/view/UQ:293278 This paper proposed a new entropy measure, Fuzzy Measure Entropy (FuzzyMEn), for the analysis of heart rate variability (HRV) signals. FuzzyMEn was calculated based on the fuzzy set theory and improved the poor statistical stability in the approximate entropy (ApEn) and sample entropy (SampEn). The simulation results also demonstrated that the FuzzyMEn had better algorithm discrimination ability when compared with the recently published fuzzy entropy (FuzzyEn), The validity of FuzzyMEn was tested for clinical HRV analysis on 120 subjects (60 heart failure and 60 healthy control subjects). It is concluded that FuzzyMEn could be considered as a valid and reliable method for a clinical HRV application. 2013-03-10T00:39:35Z Liu, Chengyu og Li, Ke og Zhao, Lina og Liu, Feng og Zheng, Dingchang og Liu, Changchun og Liu, Shutang http://espace.library.uq.edu.au/view/UQ:128619 The effect of transmitter and receiver array configurations on the performance of free-space optical interconnects (FSOIs) was investigated. Experimentally measured, spectrally resolved, near-field images of vertical-cavity surface-emitting laser (VCSEL) transverse modes were used as extended sources in our simulation model and combined with laser relative intensity noise and the receiver noise to determine the optimal array geometry. Our results demonstrate the importance of stray-light cross talk in both square and hexagonal configurations. By changing the array lattice geometry from square to hexagonal, we obtained an overall optical signal-to-noise ratio improvement of 3 dB. We demonstrated that the optical signal-to-noise ratio is optimal for the hexagonal channel arrangement regardless of the transverse mode structure of the VCSEL beam. We also determined the VCSEL drive current required for the best performance of the FSOI system. (c) 2007 Optical Society of America. 2008-02-18T00:00:00Z Tsai, Feng-Chuan F. og O'Brien, Christopher J. og Petrovic, Novak S. og Rakic, Aleksandar D. http://espace.library.uq.edu.au/view/UQ:147204 2008-06-06T00:00:00Z Hsu, C. T. og Lau, M. P. og Yeow, T. Y. T. og Yao, Z. Q.