Showing papers by "University of Macau published in 2003"
01 Sep 2003
TL;DR: In this survey, the problem-solving paradigm of ACO is explicated and compared to traditional routing algorithms along the issues of routing information, routing overhead and adaptivity.
Abstract: Although an ant is a simple creature, collectively a colony of ants performs useful tasks such as finding the shortest path to a food source and sharing this information with other ants by depositing pheromone. In the field of ant colony optimization (ACO), models of collective intelligence of ants are transformed into useful optimization techniques that find applications in computer networking. In this survey, the problem-solving paradigm of ACO is explicated and compared to traditional routing algorithms along the issues of routing information, routing overhead and adaptivity. The contributions of this survey include 1) providing a comparison and critique of the state-of-the-art approaches for mitigating stagnation (a major problem in many ACO algorithms), 2) surveying and comparing three major research in applying ACO in routing and load-balancing, and 3) discussing new directions and identifying open problems. The approaches for mitigating stagnation discussed include: evaporation, aging, pheromone smoothing and limiting, privileged pheromone laying and pheromone-heuristic control. The survey on ACO in routing/load-balancing includes comparison and critique of ant-based control and its ramifications, AntNet and its extensions, as well as ASGA and SynthECA. Discussions on new directions include an ongoing work of the authors in applying multiple ant colony optimization in load-balancing.
503 citations
TL;DR: The data preliminarily reveal the state of contamination in this region and give insight into the fate of POPs in this sub-tropical area.
403 citations
TL;DR: The proposed classification scheme using log-polar wavelet signatures outperforms two other texture classification methods, its overall accuracy rate for joint rotation and scale invariance being 90.8 percent, and its robustness to noise also performs better than the other methods.
Abstract: Classification of texture images is important in image analysis and classification This paper proposes an effective scheme for rotation and scale invariant texture classification using log-polar wavelet signatures The rotation and scale invariant feature extraction for a given image involves applying a log-polar transform to eliminate the rotation and scale effects, but at same time produce a row shifted log-polar image, which is then passed to an adaptive row shift invariant wavelet packet transform to eliminate the row shift effects So, the output wavelet coefficients are rotation and scale invariant The adaptive row shift invariant wavelet packet transform is quite efficient with only O(n /spl middot/ log n) complexity A feature vector of the most dominant log-polar wavelet energy signatures extracted from each subband of wavelet coefficients is constructed for rotation and scale invariant texture classification In the experiments, we employed a Mahalanobis classifier to classify a set of 25 distinct natural textures selected from the Brodatz album The experimental results, based on different testing data sets for images with different orientations and scales, show that the proposed classification scheme using log-polar wavelet signatures outperforms two other texture classification methods, its overall accuracy rate for joint rotation and scale invariance being 908 percent, demonstrating that the extracted energy signatures are effective rotation and scale invariant features Concerning its robustness to noise, the classification scheme also performs better than the other methods
278 citations
TL;DR: This is the first report in identifying a polysaccharide from Cordyceps, which protects against the free radical-induced neuronal cell toxicity, and significantly attenuated the changes of glutathione peroxidase and superoxide dismutase activities in H(2)O(2)-treated cells in a dose-dependent manner.
224 citations
TL;DR: A Bayesian Fast Fourier Transform approach (BFFTA) for modal updating is presented which uses the statistical properties of the Fast Fouriers transform to obtain not only the optimal values of the updated modal parameters but also their associated uncertainties, calculated from their joint probability distribution.
Abstract: The problem of identification of the modal parameters of a structural model using measured ambient response time histories is addressed. A Bayesian Fast Fourier Transform approach (BFFTA) for modal updating is presented which uses the statistical properties of the Fast Fourier transform (FFT) to obtain not only the optimal values of the updated modal parameters but also their associated uncertainties, calculated from their joint probability distribution. Calculation of the uncertainties of the identified modal parameters is very important when one plans to proceed with the updating of a theoretical finite element model based on modal estimates. The proposed approach requires only one set of response data in contrast to many of the existing frequency-based approaches which require averaging. It is found that the updated PDF can be well approximated by a Gaussian distribution centred at the optimal parameters at which the posterior PDF is maximized. Examples using simulated data are presented to illustrate ...
152 citations
TL;DR: In this article, the influence of the pulse frequency of the laser beam on the mark depth, width and mark contrast have been studied in the laser marking process of stainless steel and the results showed that the effect of pulse frequency has a significant effect on mark quality.
107 citations
TL;DR: In this article, the pitting corrosion behavior of laser surface-melted specimens processed under different processing conditions in 3.5% NaCl solution at 23 °C was studied by potentiodynamic polarization technique.
Abstract: Laser surface melting of AISI 440C martensitic stainless steel was achieved using a 2.5-kW continuous wave Nd:YAG laser. The pitting corrosion behavior of laser surface-melted specimens processed under different processing conditions in 3.5% NaCl solution at 23 °C was studied by potentiodynamic polarization technique. The corrosion resistance of all laser surface-melted specimens was significantly improved, as evidenced by a shift from active corrosion to passivity, a wide passive range and a low passive current density. The pitting potential of the laser surface-melted specimens P08-440C-25 (laser power=0.8 kW, scanning speed=25 mm/s) and P12-440C-25 (laser power=1.2 kW, scanning speed=25 mm/s) was increased to 260 and 200 mV (SCE), respectively, and was much higher than that of the conventionally heat-treated AISI 440C. The pitting corrosion characteristics of the laser surface-melted specimens were strongly dependent on the processing conditions which resulted in different microstructures. The enhanced corrosion resistance was attributed to the dissolution or refinement of carbide particles and the presence of retained austenite. The amount of carbides in the melt layer, which indirectly determine the Cr content in solid solution and hence, the corrosion resistance, was related to the amount of C remaining in solid solution and to decarburization. The pit morphology of the laser surface-melted specimen was also studied.
86 citations
TL;DR: In this paper, fine WC powder was used as a convenient source of tungsten and carbon in the laser surface alloying of AISI 316 stainless steel for improving the cavitation erosion resistance.
Abstract: Fine WC powder of approximately 1 μm size was employed as a convenient source of tungsten and carbon in the laser surface alloying of AISI 316 stainless steel for improving the cavitation erosion resistance. A slurry containing WC powder was preplaced on the substrate by pasting and processed with a high-power CW Nd:YAG laser to achieve surface alloying. The composition and microstructure of the alloyed layer and the phases formed were investigated by energy-dispersive X-ray spectroscopy, optical microscopy, scanning electron microscopy, and X-ray diffractometry, respectively. The cavitation erosion behavior of the laser surface-alloyed samples in 3.5% NaCl solution was studied with a vibratory cavitation erosion tester. The microhardness of the alloyed layer increases with the total W content in the layer. By employing proper processing parameters, an alloyed layer that is hard but not too brittle can be formed, with a cavitation erosion resistance that may reach more than 30 times that of the as-received 316. The improvement in cavitation erosion resistance may be attributed to the increase of W in solid solution and to the precipitation of dendritic carbides, both resulting from the dissociation of the fine WC powder during laser processing.
84 citations
77 citations
TL;DR: In this article, a three-leg center split inverter is proposed to compensate the power quality issues including the zero-sequence compensation by the 3D voltage space vector PWM technique.
Abstract: In past decades, almost all the studies are focused in two-dimensional (2-D) PWM techniques on /spl alpha/-/spl beta/ frame. A four-legs inverter is proposed to compensate the three-phase four-wired system issues. However, three-legs center-split inverter can be applied to compensate the power quality issues including the zero-sequence compensation by the novel PWM technique: three-dimensional (3-D) PWM. In this paper, the mathematical model of shunt-connected three-level power inverter in three-phase four-wired system is studied in a-b-c-0 frame. The study of 3-D voltage space vector PWM technique in two-level and three-level inverters is performed in rectangular, cylindrical, and spherical coordinates, respectively. The 3DPWM performance indices are proposed. Comparative study of fixed switching sign cubical hysteresis control with this novel proposed technique "cylindrical coordinate control strategy" is accomplished. The results show that the performance of the proposed novel control strategy can overcome the drawbacks of fixed switching sign cubical hysteresis 3DPWM control strategy.
75 citations
TL;DR: The chemical analysis of these particles indicated the presence of 36 elements, water-soluble ions and carbonaceous species, including OC, sulfate, nitrate, ammonium, EC, Na, Cl and crustal elements including Si, Ca, Al, Fe, K and Mg.
25 Sep 2003-Materials Science and Engineering A-structural Materials Properties Microstructure and Processing
TL;DR: In this paper, the microstructure and the phases present in the laser surface-melted specimens were analyzed by optical microscopy, scanning electron microscopy and X-ray diffractometry, respectively.
Abstract: Laser surface melting of plastics mold steels P21 (Fe–3% Ni–1.5% Mn–1% Al–0.3% Si–0.15% C) and 440C (Fe–17% Cr–1.1% C) was achieved by a 500 W CW Nd:YAG laser using different scanning speeds. The microstructure and the phases present in the laser surface-melted specimens were analysed by optical microscopy, scanning electron microscopy and X-ray diffractometry, respectively. The corrosion characteristics of the laser surface-melted specimens in 3.5% NaCl solution and in 1 M sulphuric acid at 23 °C were studied by potentiodynamic polarisation technique. X-ray diffraction spectra showed that laser surface-melted P21 and 440C contain martensite and austenite as the major phase, respectively. Laser surface-melted 440C exhibits passivity whereas laser surface-melted P21 does not. The corrosion resistance of laser surface-melted P21 in both corrosive media is improved as evidenced by a lower corrosion current density compared with that of the untreated specimens. The increase in corrosion resistance of laser surface-melted P21 is due to the dissolution of the intermetallic phase Ni3Al to form a homogeneous solid solution by rapid solidification. The corrosion resistance of laser surface-melted 440C in NaCl solution is also increased significantly, with the exhibition of a wide passive range and a low passive current density, but the improvement in sulphuric acid is less pronounced. The enhanced corrosion resistance of laser surface-melted 440C results from the combined effect of the refinement of carbide particles with increased C and Cr in solid solution, and the presence of retained austenite. The corrosion characteristics of all the laser surface-melted specimens are strongly dependent on the laser scanning speed, which in turn results in different microstructures.
Posted Content•
TL;DR: The results imply that some sub-regions are potential candidates for forming OCAs, as their shocks are correlated and small, and the economies adjust rapidly to such shocks.
Abstract: This paper examines whether forming an optimum currency area (OCA) is viable for the East Asian region by testing the symmetry of underlying structural shocks. A structural vector autoregression (VAR) method is used to identify the underlying shocks and to examine the correlation in shocks for specified sample periods. Decomposition of the variance of shocks and impulse response analysis are used to examine the size and the speed of adjustments to shocks. The results imply that some sub-regions are potential candidates for forming OCAs, as their shocks are correlated and small, and the economies adjust rapidly to such shocks.
05 Nov 2003
TL;DR: The focus of this paper is the development of a semantic model to consistently combine a use-case model and a conceptual class diagram to form a system specification.
Abstract: This paper is towards the development of a methodology for object-oriented software development. The intention is to support effective use of a formal model for specifying and reasoning during the requirements analysis and design of a software development process. The overall purpose is to enhance the application of the Unified Modelling Language (UML) with a formal semantics in the Rational Unified Software Development Process (RUP). The semantic framework defines the meaning of some UML submodels. It identifies both the static and dynamic relationships among these submodels. Thus, the focus of this paper is the development of a semantic model to consistently combine a use-case model and a conceptual class diagram to form a system specification.
TL;DR: In this article, a structural equation model explaining the influence of Chinese cultural values on total quality management (TQM) was tested using a sample of TQM companies operating in mainland China, Hong Kong, and Taiwan.
Abstract: Using a sample of total quality management (TQM) companies operating in mainland China, Hong Kong, and Taiwan, a structural equation model explaining the influence of Chinese cultural values on TQM was tested. Results indicated that the proposed model demonstrated satisfactory goodness of fit. The underlying Chinese values of abasement, adaptiveness, harmony with people, harmony with the universe, interdependence, and respect for authority were found to have important influences on four quality dimensions, namely climate, processes, methods, and results.
TL;DR: For a harmonic function, by replacing its variables with norms of vectors in some multi-dimensional spaces, this paper showed that after applying to it a certain power of the Laplacian, they obtained a new harmonic function in the higher dimensional space.
Abstract: For a harmonic function, by replacing its variables with norms of vectors in some multi-dimensional spaces we may induce a new function in a higher dimensional space. We show that after applying to it a certain power of the Laplacian we obtain a new harmonic function in the higher dimensional space. We show that Poisson and Cauchy kernels and Newton potentials, as well as heat kernels are all deducible using this method based on their forms in the lowest dimensional spaces. Fueter’s Theorem and its generalizations are deducible as well from our results. The latter has been used to singular integral and Fourier multiplier theory on the unit spheres and their Lipschitz perturbations of higher dimensional Euclidean spaces.
TL;DR: The photochromic diarylethene, 1,2-bis(2-methyl-5-(2,2′-dicyanovinyl)-thien-3-yl)perfluorocyclopentene ( 1a ), was synthesized by a novel method as mentioned in this paper.
Posted Content•
TL;DR: According to 19 experts, many predictions found in the prior literature will materialise (such as the Internet will become increasingly important in disseminating corporate information), however, the experts also rejected some prior forecasts.
Abstract: This paper reports the views of the immediate trends and trends by 2010 in Internet-based financial reporting provided by 19 experts in accounting and/or the Internet. Specifically, this paper reports these expert's predictions on what will and will not happen, when it will happen and what will be different between these two time periods. The predictions were obtained through two stages: an open ended questionnaire and a structured Likert scale questionnaire which was subsequently constructed. According to our experts, many predictions found in the prior literature will materialise (such as the Internet will become increasingly important in disseminating corporate information). However, the experts also rejected some prior forecasts (such as free access to disaggregated corporate data and real-time reporting). Many aspects of financial reporting will remain the same between the two time periods although there will be significant differences. Our experts portrayal of the future of Internet reporting can be seen as a ladder. Issues of importance at the lower rungs of the ladder are more basic (such as the survival of the hardcopy reports); while at the higher rungs of the ladder issues are more complex (for instance, the possibility of real-time reporting and continuous auditing).
TL;DR: Experimental results show that this rotation-invariant texture feature is effective and outperforms the other image retrieval algorithms.
TL;DR: In this article, a modified plate buckling formula, which considers the shear buckling phenomenon at the coped region, is proposed to give a better prediction of the local web buckling strength of a coped I beam.
Abstract: When a beam flange is coped to allow clearance at the connection, the strength of the coped region will be reduced. Local web buckling at the coped region may occur when the cope length is long and/or the compression flange is braced. Experimental and analytical investigation of the strength of coped steel I beams were conducted by a number of researchers and design formula was also proposed. However, the proposed formula underestimates the local web buckling capacity of a coped I beam, especially when the cope-depth to beam-depth ratio is small. To improve this discrepancy, full-scale tests of the web buckling strength of coped steel I beams and a series of analytical studies were carried out. A modified plate buckling formula, which considers the shear buckling phenomenon at the coped region, is proposed. The modified formula gives a better prediction of the local web buckling strength of a coped I beam. The test-to-predicted ratios varies from 0.92 to 1.06.
10 Nov 2003
TL;DR: The joint parameters of redundant manipulators are prerequisite data for effective dynamics control and an identification method via fuzzy theory and Genetic Algorithm has been presented to study modular redundant robots.
Abstract: The joint parameters of redundant manipulators are prerequisite data for effective dynamics control. An identification method via fuzzy theory and Genetic Algorithm has been presented to study modular redundant robots. The Genetic Algorithm is used in the fuzzy optimization expecting to obtain global optimal solutions. Experimental modal analysis and Finite Element Method have been exploited in dynamics modeling. The joint parameters of a 9-DOF modular redundant robot have been identified. Active vibration control has been approached to a simplified 4-DOF modular manipulator by DOF reduction to the 9-DOF modular manipulator.
13 Jul 2003
TL;DR: In this article, a novel technique for current differential pilot relay protection (CDPR) by using wavelet analysis is described, which is used to generate current signals at both ends of a transmission line in a typical system with fault at various locations.
Abstract: Summary form only given. This paper describes a novel technique for current differential pilot relay protection (CDPR) by using wavelet analysis. PSCAD is used to generate current signals at both ends of a transmission line in a typical system with fault at various locations. In this paper, discriminating between internal fault and external fault/change, identifying of faulted phase and classifying fault type are achieved by using wavelet analysis. The simulation results show that this approach provides a high operating sensitivity for internal fault and remains stable for external fault/change.
21 Mar 2003
TL;DR: Experimental results show that MACO is effective in balancing the load, and more effective than traditional ACO for load balancing in circuit-switched networks.
Abstract: This paper presents a Multiple Ant Colony Optimization (MACO) approach for load balancing in circuit-switched networks. Based on the problem-solving approach of ants in nature, Ant Colony Optimization (ACO) has been applied to solve problems in optimization, network routing and load balancing by modeling ants as a society of mobile agents. While traditional ACO approaches employed one ant colony for routing, MACO uses multiple ant colonies to search for alternatives to an optimal path. One of the impetuses of MACO is to optimize the performance of a congested network by routing calls via several alternatives paths to prevent possible congestion along an optimal path. Ideas of applying MACO for load-balancing in circuit-switched networks have been implemented in a testbed. Using fairness ratio as a performance measure, experimental results show that MACO is (1) effective in balancing the load, and (2) more effective than traditional ACO for load balancing.
TL;DR: Experimental results show that this rotation and scale invariant log-polar wavelet texture feature is quite effective for image retrieval and outperforms the traditional wavelet packet signatures.
Abstract: This article introduces an effective rotation and scale invariant log-polar wavelet texture feature for image retrieval. The proposed feature is an attempt to enhance the existing content-based image retrieval systems that largely present difficulty in coping with images with changes in orientations and scales. The underlying feature extraction process involves a log-polar transform followed by an adaptive row shift invariant wavelet packet transform. The log-polar transform converts a given image into a rotation and scale invariant but row-shifted image, which is then further processed through an adaptive row-shift invariant wavelet packet transform operation to generate adaptively selected subbands of rotation and scale invariant wavelet coefficients, based on an information cost function. An energy signature is computed for each subband of these wavelet coefficients. To reduce feature dimensionality, only the most dominant log-polar wavelet energy signatures are selected for the feature vector for image retrieval. The overall feature extraction process is quite efficient and involves only O(n . log n) complexity. Experimental results show that this rotation and scale invariant wavelet feature is quite effective for image retrieval and outperforms the traditional wavelet packet signatures.
TL;DR: In this article, the authors investigated the extent that the daily return data from the Shanghai Stock Exchange Index and the Shenzhen stock exchange index exhibit non-random, nonlinear and chaotic characteristics.
Abstract: After the stock market crash of October 19, 1987, interest in nonlinear dynamics and chaotic dynamics have increased in the field of financial analysis. The extent that the daily return data from the Shanghai Stock Exchange Index and the Shenzhen Stock Exchange Index exhibit non-random, nonlinear and chaotic characteristics are investigated by employing various tests from chaos theory. The Hurst exponent in R/S analysis rejects the hypothesis that the index return series are random, independent and identically distributed. The BDS test provides evidence for nonlinearity. The estimated correlation dimensions provide evidence for deterministic chaotic behaviors.
TL;DR: Hong Kong Chinese Everyday Competence Scale as mentioned in this paper was developed based on six major daily activities (shopping, transportation, symbols used in daily life, using electric appliances, consulting doctors, financial management) within Hong Kong context.
Abstract: The objective of this study was to validate a scale called the Hong Kong Chinese Everyday Competence Scale in Hong Kong Chinese elders. The Hong Kong Chinese Everyday Competence Scale is developed based on six major daily activities (shopping, transportation, symbols used in daily life, using electric appliances, consulting doctors, financial management) within Hong Kong context. There are six items for each aspect of these daily activities which are relevant to Hong Kong society. The Hong Kong Chinese Everyday Competence Scale was completed by 204 people aged 60 years or older who attend the social centers for the elderly in Hong Kong. Firstly, reliability (internal consistency) of the Hong Kong Chinese Everyday Competence Scale was found to be excellent. Concurrent validity was also established by strong correlations between the Hong Kong Chinese Everyday Competence Scale and two global measures of cognitive ability, namely the Mini-Mental State Examination and Short Portable Mental Status Ques...
TL;DR: Doak and Fu as mentioned in this paper, in their book "Constructing Nationhood in Modern East Asia: Kai-wing Chow and Poshek Fu, 2001", published by University of Michigan Press.
Abstract: Constructing Nationhood in Modern East Asia. Kai-wing Chow. Kevin M. Doak. and Poshek Fu, eds. Ann Arbor: University of Michigan Press, 2001. 404 pp., index.
TL;DR: If a Pk1,k2-stable BVM is used for solving an m-by-m system of DDEs, then the authors' preconditioner is invertible and all the eigenvalues of the preconditionsed system are clustered around 1.
Abstract: We consider the solution of delay differential equations (DDEs) by using boundary value methods (BVMs). These methods require the solution of one or more nonsymmetric, large and sparse linear systems. The GMRES method with the Strang-type block-circulant preconditioner is proposed for solving these linear systems. We show that if a P
k
1,k
2-stable BVM is used for solving an m-by-m system of DDEs, then our preconditioner is invertible and all the eigenvalues of the preconditioned system are clustered around 1. It follows that when the GMRES method is applied to solving the preconditioned systems, the method may converge fast. Numerical results are given to illustrate the effectiveness of our methods.
TL;DR: This paper aims to integrate several variants of Duration Calculus, and to provide a semantic framework for real-time programming languages and sequential hybrid programs.
Abstract: Duration Calculus was introduced as a logic to specify real-time requirements of computing systems. It has been used successfully in a number of case studies. Moreover, many variants were proposed to deal with various features of real time systems, including sequential communicating processes, sequential hybrid systems and imperative programming languages. This paper aims to integrate several variants of Duration Calculus, and to provide a semantic framework for real-time programming languages and sequential hybrid programs.