The Hong Kong Polytechnic University Pao Yue-kong Library

    An improved Tabu search for the global optimizations of electromagnetic devices

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    An extended Tabu algorithm with an aspiration factor is proposed. The algorithm is based on the success of techniques such as the memorization of the previously visited subspaces, the systematic diversification as well as the intensification process for neighborhood creations. The numerical results obtained by solving a mathematical test function and the benchmark problem 22 of the TEAM Workshop reported in this paper will demonstrate the usefulness of the proposed method.Department of Electrical EngineeringIndustrial CentreAuthor name used in this publication: S. L. HoAuthor name used in this publication: H. C. Won

    A pulse-width-modulation based sliding mode controller for buck converters

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    This paper presents the design and analysis of a pulse-width-modulation based sliding mode voltage controller for buck converters from a circuit design perspective. A practical design approach which aims at systematizing the procedure for the selection of the control parameters is introduced. Additionally, a simple analog form of the controller for practical realization is provided. It is found that this controller adopts a structure similar to the conventional pulse-width-modulated voltage mode controller. Simulation and experimental results show that the response of the converter agrees with the theoretical design.Department of Electronic and Information EngineeringAuthor name used in this publication: Martin K. H. CheungAuthor name used in this publication: Chi K. TseRefereed conference pape

    An adaptive sliding mode controller for buck converter in continuous conduction mode

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    This paper proposes a new adaptive sliding mode controller for buck converter operating in the continuous conduction mode. Through gain scheduling, the controller is designed to monitor the output loading condition, and adaptively changes its control parameters to give optimal dynamic performances corresponding to any loading variations. Simulations have been carried out to verify the idea. The results show faster transient response and reduced steady state error during over-loaded operation, and improved controller's reliability during under-loaded operation, under the adaptive controller.Department of Electronic and Information EngineeringAuthor name used in this publication: Chi K. TseAuthor name used in this publication: Martin K. H. CheungRefereed conference pape

    A new implementation of population based incremental learning method for optimizations in electromagnetics

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    To enhance the global search ability of population based incremental learning (PBIL) methods, it is proposed that multiple probability vectors are to be included on available PBIL algorithms. The strategy for updating those probability vectors and the negative learning and mutation operators are thus re-defined correspondingly. Moreover, to strike the best tradeoff between exploration and exploitation searches, an adaptive updating strategy for the learning rate is designed. Numerical examples are reported to demonstrate the pros and cons of the newly implemented algorithm.Department of Electrical EngineeringAuthor name used in this publication: S. L. H

    Reactive Web policing based on self-organizing maps

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    Almost without any doubt, the Internet and Web in particular, have brought about radical changes in information retrieval with unparallel benefits to organizations and individuals to gain access to vast amount of articles and documents. The focus on restricting inappropriate materials at their source is not well suited to the nature and open architecture of Internet, where information source maybe in a different legal jurisdiction than the recipient. This paper proposes a reactive approach based on SOM (Self-Organising Maps) neural network to deal with dynamic blocking and filtering of Internet contents. We describe the design and implementation of a web policing proxy (WebPolice) based on a Kohonen's neural network model that attempts to classify the web contents dynamically using competitive learning. The parameter setting of the network has been experimented to obtain the optimal classification rate and performance for the model.Department of ComputingElectronic Commerce and Internet Computing Lab, Department of ComputingRefereed conference pape

    Fabrication and characterization of ferroelectric field effect transistor

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    v, 103 leaves : ill. ; 30 cm.PolyU Library Call No.: [THS] LG51 .H577M AP 2001 SoManganese oxide La0.7Sr0.3MnO3 (LSMO) films and all-perovskite epitaxial Pb(Zr0.52Ti0.48)O3 (PZT)/La0.7Sr0.3MnO3 heterostructure on single crystal LaAlO3 (LAO) substrates have been fabricated by Pulsed Laser Deposition (PLD) method. It is found that the electrical transport properties of LSMO is very sensitive to the film's oxygen content, which can be tuned easily during deposition by controlling the ambient oxygen pressure. They are, however, very stable and remain unchanged in further thermal treatments. Epitaxial LSMO films are obtained at processing temperature as low as 500oC. Excellent crystalline quality of PZT(500 nm)/LSMO(40 nm) heterostructures have been realized. High remnant polarization (48 uC/cm2), low coercive field (57 kV/cm), low polarization loss (~8% up to 2x109 switching cycles) and long retention (>105s) are demonstrated for the ferroelectric PZT films. The leakage current in the Au/PZT/LSMO structure is about 5X10-7 A/cm2. The results of both structural and electrical properties of PZT/LSMO heterostructures show that this material system is a suitable candidate for use in non-volatile ferroelectric field effect transistor (FeFET). A small remnant field effect modulation (5.6%) has been obtained and further optimizations in developing FeFET are using PZT/LSMO heterostructures suggested.Department of Applied PhysicsM.Phil., Dept. of Applied Physics, The Hong Kong Polytechnic University, 2001

    Manipulation of numerical coastal flow and water quality models

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    Nowadays, numerical flow and water quality models are widely applied to solve coastal engineering problems. The outcomes of the algorithmic execution often deviate from those anticipated, particularly when the model is set up initially. This necessitates the modeler to perform the manipulation procedure, which comprises feed back and modification. As such, it is desirable that expert system technology be integrated into the modeling system to furnish assistance for the novice user who lacks the requisite knowledge to establish the model and assess the results. In this paper, a prototype expert system on manipulation of numerical coastal flow and water quality models is developed and implemented by employing an expert system shell, Visual Rule Studio, as an Active Designer under Microsoft Visual Basic environment. Through the successful development of this prototype system, it is shown that the expert system technology can be coupled into numerical modeling for mimicking the manipulation process. It assists the user to formulate a suitable strategy for striking a balance between accuracy and effectiveness and to tune the model to accomplish satisfactory modeling of real phenomena. It is able to bridge the existing gap between numerical modelers and practitioners in this field.Department of Civil and Environmental EngineeringAuthor name used in this publication: K. W. Cha

    Effects of step loadings on stability of anaerobic hybrid reactor

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    xi, 89 leaves : ill. ; 30 cm.PolyU Library Call No.: [THS] LG51 .H577M CSE 2000 NgPlastic rings were packed in the separator zone of a conventional upflow anaerobic sludge blanket reactor (UASB) to form an additional biofilter (BF) section. The resulting anaerobic hybrid reactor (AHR) was used to treat food - processing wastewater. The treatment performance at different step loadings was studied. The hydraulic retention time (HRT) decreased stepwise from 1.50 to 1.00, 0.75, 0.60, 0.50 and 0.40, and corresponding steady state COD removal efficiencies were 72.9, 65.9, 61.5, 56.0, 48.7 and 33.2 % respectively. In the UASB section, the COD removal accounted for between 78.2 and 64.2 % of overall removal in the AHR. In the BF section, the COD removal accounted for between 21.8 and 35.8 % of overall removal in the AHR. On the other hand, during the transient state when each step loading was introduced, the COD removal in the BF section accounted for significantly high percentage, between 66.9 % and 98.6 % of the overall removal in the AHR, because of the better stability of the immobilised microorganisms in this section. Immobilised microorganisms in the BF remained in a normal population distribution during the transient state operation, which rendered a swift recovery when favourable operation conditions were restored.Department of Civil and Environmental EngineeringM.Phil., Dept. of Civil and Structural Engineering, The Hong Kong Polytechnic University, 2000

    New forecasting models

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    Tourism forecasting plays an important role in tourism planning and management. Various forecasting techniques have been developed and applied to the tourism context, amongst which econometric forecasting has been winning an increasing popularity in tourism research. This paper therefore aims to introduce the latest developments of econometric forecasting approaches and their applications to tourism demand analysis. Particular emphases are placed on the time varying parameter (TVP) forecasting technique and its application to the almost ideal demand system (AIDS). The discussions in this paper fall into two main parts, in line with the two broad categories of econometric forecasting approaches: the first part refers to the single-equation forecasting techniques, focusing particularly on both long-run and short-term TVP models. The second part introduces the system-of-equations forecasting models, represented by the AIDS and its dynamic versions including the combination with the TVP technique, will be discussed one by one following the order of methodological developments.School of Hotel and Tourism Managemen

    On interpretation of graffiti digits and characters for eBooks : neural-fuzzy network and genetic algorithm approach

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    This paper presents the rule optimization, tuning of the membership functions, and optimization of the number of fuzzy rules, of a neural-fuzzy network (NFN) using a genetic algorithm (GA). The objectives are achieved by training a proposed NFN with rule switches. The proposed NFN and GA are employed to interpret graffiti number inputs and commands for electronic books (eBooks).Department of Electronic and Information EngineeringAuthor name used in this publication: K. F. LeungCentre for Multimedia Signal Processing, Department of Electronic and Information Engineerin
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