Showing papers by "Nanyang Technological University published in 2004"

Extreme learning machine: a new learning scheme of feedforward neural networks

Abstract: It is clear that the learning speed of feedforward neural networks is in general far slower than required and it has been a major bottleneck in their applications for past decades. Two key reasons behind may be: 1) the slow gradient-based learning algorithms are extensively used to train neural networks, and 2) all the parameters of the networks are tuned iteratively by using such learning algorithms. Unlike these traditional implementations, this paper proposes a new learning algorithm called extreme learning machine (ELM) for single-hidden layer feedforward neural networks (SLFNs) which randomly chooses the input weights and analytically determines the output weights of SLFNs. In theory, this algorithm tends to provide the best generalization performance at extremely fast learning speed. The experimental results based on real-world benchmarking function approximation and classification problems including large complex applications show that the new algorithm can produce best generalization performance in some cases and can learn much faster than traditional popular learning algorithms for feedforward neural networks.

Customer Value, Satisfaction, Loyalty, and Switching Costs: An Illustration From a Business-to-Business Service Context:

Abstract: Although researchers and managers pay increasing attention to customer value, satisfaction, loyalty, and switching costs, not much is known about their interrelationships. Prior research has examined the relationships within subsets of these constructs, mainly in the business-to-consumer (B2C) environment. The authors extend prior research by developing a conceptual framework linking all of these constructs in a business-to-business (B2B) service setting. On the basis of the cognition-affect-behavior model, the authors hypothesize that customer satisfaction mediates the relationship between customer value and customer loyalty, and that customer satisfaction and loyalty have significant reciprocal effects on each other. Furthermore, the potential interaction effect of satisfaction and switching costs, and the quadratic effect of satisfaction, on loyalty are explored. The authors test the hypotheses on data obtained from a courier service provider in a B2B context. The results support most of the hypotheses and, in particular, confirm the mediating role of customer satisfaction.

How Ideas Spread: Whose Norms Matter? Norm Localization and Institutional Change in Asian Regionalism

Abstract: Questions about norm diffusion in world politics are not simply about whether and how ideas matter, but also which and whose ideas matter. Constructivist scholarship on norms tends to focus on “hard” cases of moral transformation in which “good” global norms prevail over the “bad” local beliefs and practices. But many local beliefs are themselves part of a legitimate normative order, which conditions the acceptance of foreign norms. Going beyond an existential notion of congruence, this article proposes a dynamic explanation of norm diffusion that describes how local agents reconstruct foreign norms to ensure the norms fit with the agents' cognitive priors and identities. Congruence building thus becomes key to acceptance. Localization, not wholesale acceptance or rejection, settles most cases of normative contestation. Comparing the impact of two transnational norms on the Association of Southeast Asian Nations (ASEAN), this article shows that the variation in the norms' acceptance, indicated by the changes they produced in the goals and institutional apparatuses of the regional group, could be explained by the differential ability of local agents to reconstruct the norms to ensure a better fit with prior local norms, and the potential of the localized norm to enhance the appeal of some of their prior beliefs and institutions.I thank Peter Katzenstein, Jack Snyder, Chris Reus-Smit, Brian Job, Paul Evans, Iain Johnston, David Capie, Helen Nesadurai, Jeffrey Checkel, Kwa Chong Guan, Khong Yuen Foong, Anthony Milner, John Hobson, Etel Solingen, Michael Barnett, Richard Price, Martha Finnemore, and Frank Schimmelfennig for their comments on various earlier drafts of the article. This article is a revised version of a draft prepared for the American Political Science Association annual convention, San Francisco, 29 August–2 September 2001. Seminars on the article were offered at the Belfer Center for Science and International Affairs, Harvard University, in April 2001; the Modern Asia Seminar Series at Harvard University's Asia Center, in May 2001; the Department of International Relations, Australian National University, in September 2001; and the Institute of International Relations, University of British Columbia, in April 2002. I thank these institutions for their lively seminars offering invaluable feedback. I gratefully acknowledge valuable research assistance provided by Tan Ban Seng, Deborah Lee, and Karyn Wang at the Institute of Defence and Strategic Studies. I am also grateful to Harvard University Asia Centre and the Kennedy School's Asia Pacific Policy Program for fellowships to facilitate my research during 2000–2001.

Emergency Logistics Planning in Natural Disasters

Abstract: Logistics planning in emergency situations involves dispatching commodities (e.g., medical materials and personnel, specialised rescue equipment and rescue teams, food, etc.) to distribution centres in affected areas as soon as possible so that relief operations are accelerated. In this study, a planning model that is to be integrated into a natural disaster logistics Decision Support System is developed. The model addresses the dynamic time-dependent transportation problem that needs to be solved repetitively at given time intervals during ongoing aid delivery. The model regenerates plans incorporating new requests for aid materials, new supplies and transportation means that become available during the current planning time horizon. The plan indicates the optimal mixed pick up and delivery schedules for vehicles within the considered planning time horizon as well as the optimal quantities and types of loads picked up and delivered on these routes. In emergency logistics context, supply is available in limited quantities at the current time period and on specified future dates. Commodity demand is known with certainty at the current date, but can be forecasted for future dates. Unlike commercial environments, vehicles do not have to return to depots, because the next time the plan is re-generated, a node receiving commodities may become a depot or a former depot may have no supplies at all. As a result, there are no closed loop tours, and vehicles wait at their last stop until they receive the next order from the logistics coordination centre. Hence, dispatch orders for vehicles consist of sets of “broken” routes that are generated in response to time-dependent supply/demand. The mathematical model describes a setting that is considerably different than the conventional vehicle routing problem. In fact, the problem is a hybrid that integrates the multi-commodity network flow problem and the vehicle routing problem. In this setting, vehicles are also treated as commodities. The model is readily decomposed into two multi-commodity network flow problems, the first one being linear (for conventional commodities) and the second integer (for vehicle flows). In the solution approach, these sub-models are coupled with relaxed arc capacity constraints using Lagrangean relaxation. The convergence of the proposed algorithm is tested on small test instances as well as on an earthquake scenario of realistic size.

TiNi-based thin films in MEMS applications: a review

Abstract: TiNi thin films have attracted much attention in recent years as intelligent and functional materials because of their unique properties. TiNi thin film based micro-actuators will become the actuator of choice in many aspects in the rapidly growing field of micro-electro-mechanical systems (MEMSs). In this review paper, some critical issues and problems in the development of TiNi thin films are discussed, including preparation and characterization considerations, residual stress and adhesion, frequency improvement, fatigue and stability, modeling of behavior as well as functionally graded or composite thin films. Comparison is made of TiNi SMA micro-actuation with other micro-actuation methods. Different types of TiNi thin film based microdevices, such as microgrippers, microswitches, microvalves and pumps, microsensors, etc. are also described and discussed.

Design, analysis, and real-time testing of a controller for multibus microgrid system

Abstract: This paper concentrates on the design and analysis of a controller for multibus microgrid system. The controller proposed for use with each distributed generation (DG) system in the microgrid contains inner voltage and current loops for regulating the three-phase grid-interfacing inverter, and external power control loops for controlling real and reactive power flow and for facilitating power sharing between the paralleled DG systems when a utility fault occurs and the microgrid islands. The controller also incorporates synchronization algorithms for ensuring smooth and safe reconnection of the micro and utility grids when the fault is cleared. With the implementation of the unified controller, the multibus microgrid system is able to switch between islanding and grid-connected modes without disrupting the critical loads connected to it. The performance of this unified controller has been verified in simulation using a real-time digital simulator and experimentally using a scaled laboratory prototype.

Meta-Lamarckian learning in memetic algorithms

Abstract: Over the last decade, memetic algorithms (MAs) have relied on the use of a variety of different methods as the local improvement procedure. Some recent studies on the choice of local search method employed have shown that this choice significantly affects the efficiency of problem searches. Given the restricted theoretical knowledge available in this area and the limited progress made on mitigating the effects of incorrect local search method choice, we present strategies for MA control that decide, at runtime, which local method is chosen to locally improve the next chromosome. The use of multiple local methods during a MA search in the spirit of Lamarckian learning is here termed Meta-Lamarckian learning. Two adaptive strategies for Meta-Lamarckian learning are proposed in this paper. Experimental studies with Meta-Lamarckian learning strategies on continuous parametric benchmark problems are also presented. Further, the best strategy proposed is applied to a real-world aerodynamic wing design problem and encouraging results are obtained. It is shown that the proposed approaches aid designers working on complex engineering problems by reducing the probability of employing inappropriate local search methods in a MA, while at the same time, yielding robust and improved design search performance.

Automated feature extraction in color retinal images by a model based approach

Abstract: Color retinal photography is an important tool to detect the evidence of various eye diseases. Novel methods to extract the main features in color retinal images have been developed in this paper. Principal component analysis is employed to locate optic disk; A modified active shape model is proposed in the shape detection of optic disk; A fundus coordinate system is established to provide a better description of the features in the retinal images; An approach to detect exudates by the combined region growing and edge detection is proposed. The success rates of disk localization, disk boundary detection, and fovea localization are 99%, 94%, and 100%, respectively. The sensitivity and specificity of exudate detection are 100 % and 71 %, correspondingly. The success of the proposed algorithms can be attributed to the utilization of the model-based methods. The detection and analysis could be applied to automatic mass screening and diagnosis of the retinal diseases.

A review of anode materials development in solid oxide fuel cells

Abstract: High temperature solid oxide fuel cell (SOFC) has prospect and potential to generate electricity from fossil fuels with high efficiency and very low greenhouse gas emissions as compared to traditional thermal power plants. In the last 10 years, there has been significant progress in the materials development and stack technologies in SOFC. The objective of this paper is to review the development of anode materials in SOFC from the viewpoint of materials microstructure and performance associated with the fabrication and optimization processes. Latest development and achievement in the Ni/Y2O3-ZrO2 (Ni/YSZ) cermet anodes, alternative and conducting oxide anodes and anode-supported substrate materials are presented. Challenges and research trends based on the fundamental understanding of the materials science and engineering for the anode development for the commercially viable SOFC technologies are discussed.

Windowed Fourier transform for fringe pattern analysis

Abstract: Fringe patterns in optical metrology systems need to be demodulated to yield the desired parameters. Time-frequency analysis is a useful concept for fringe demodulation, and a windowed Fourier transform is chosen for the determination of phase and phase derivative. Two approaches are developed: the first is based on the concept of filtering the fringe patterns, and the second is based on the best match between the fringe pattern and computer-generated windowed exponential elements. I focus on the extraction of phase and phase derivatives from either phase-shifted fringe patterns or a single carrier fringe pattern. Principles as well as examples are given to show the effectiveness of the proposed methods.

T-spline simplification and local refinement

Abstract: A typical NURBS surface model has a large percentage of superfluous control points that significantly interfere with the design process. This paper presents an algorithm for eliminating such superfluous control points, producing a T-spline. The algorithm can remove substantially more control points than competing methods such as B-spline wavelet decomposition. The paper also presents a new T-spline local refinement algorithm and answers two fundamental open questions on T-spline theory.

Adaptive backstepping control of a class of uncertain nonlinear systems with unknown backlash-like hysteresis

Abstract: In this note, we consider the same class of systems as in a previous paper, i.e., a class of uncertain dynamic nonlinear systems preceded by unknown backlash-like hysteresis nonlinearities, where the hysteresis is modeled by a differential equation, in the presence of bounded external disturbances. By using backstepping technique, robust adaptive backstepping control algorithms are developed. Unlike some existing control schemes for systems with hysteresis, the developed backstepping controllers do not require the uncertain parameters within known intervals. Also, no knowledge is assumed on the bound of the "disturbance-like" term, a combination of the external disturbances and a term separated from the hysteresis model. It is shown that the proposed controllers not only can guarantee global stability, but also transient performance.

IT Outsourcing Success: A Psychological Contract Perspective

Abstract: Information technology (IT) outsourcing success requires careful management of customer-supplier relationships. However, there are few published studies on the ongoing relationships, and most of these adopt a customer perspective, de-emphasizing suppliers. In this study, we look at both customer and supplier perspectives, by means of the psychological contract of customer and supplier project managers. We apply the concept of psychological contract to perceived mutual obligations, and to how such fulfillment of obligations can predict success. Our research questions are (1) What are the critical customer-supplier obligations in an IT outsourcing relationship? and (2) What is the impact of fulfilling these obligations on success?We use a sequential, qualitative-quantitative approach to develop and test our model. In the qualitative study, we probe the nature of customer-supplier obligations using in-depth interviews. Content analysis of interview transcripts show that both customers and suppliers identify six obligations that are critical to success. Customers perceive supplier obligations to be accurate project scoping, clear authority structures, taking charge, effective human capital management, effective knowledge transfer, and effective interorganizational teams. Suppliers perceive customer obligations as clear specifications, prompt payment, close project monitoring, dedicated project staffing, knowledge sharing, and project ownership. In the second quantitative study, we assess the impact of fulfilling these obligations on success through a field study of 370 managers. Results show that fulfilled obligations predict success over and above the effects of contract type, duration, and size.

Aerodynamic Data Reconstruction and Inverse Design Using Proper Orthogonal Decomposition

Abstract: The application of proper orthogonal decomposition for incomplete (gappy) data for compressible external aerodynamic problems has been demonstrated successfully in this paper for the first time. Using this approach, it is possible to construct entire aerodynamic flowfields from the knowledge of computed aerodynamic flow data or measured flow data specified on the aerodynamic surface, thereby demonstrating a means to effectively combine experimental and computational data. The sensitivity of flow reconstruction results to available measurements and to experimental error is analyzed. Another new extension of this approach allows one to cast the problem of inverse airfoil design as a gappy data problem. The gappy methodology demonstrates a great simplification for the inverse airfoil design problem and is found to work well on a range of examples, including both subsonic and transonic cases.

The effects of extracellular polymeric substances on the formation and stability of biogranules

Abstract: Biogranulation is a promising biotechnology developed for wastewater treatment. Biogranules exhibit a matrix microbial structure, and intensive research has shown that extracellular polymeric substances (EPS) are a major component of the biogranule matrix material in both anaerobic and aerobic granules. This paper aims to review the role of EPS in biogranulation, factors influencing EPS production, the effect of EPS on cell surface properties of biogranules, and the relationship of EPS to the structural stability of biogranules. EPS production is substantially enhanced when the microbial community is subject to stressful culture conditions, and the stimulated EPS production in the microbial matrix in turn favours the formation of anaerobic and aerobic granules. EPS can also play an essential role in maintaining the integrity and stability of spatial structure in mature biogranules. It is expected that this paper can provide deep insights into the functions of EPS in the biogranulation process.

The Impact of Online Recommendations and Consumer Feedback on Sales

Abstract: Quality uncertainty and high search costs for identifying relevant information from an ocean of information may prevent customers from making purchases. Recognizing potential negative impacts of this search cost for quality information and relevant information, firms began to invest in creating a virtual community that enables consumers to share their opinions and experiences to reduce quality uncertainty, and in developing recommendation systems that help customers identify goods in which they might have an interest. However, not much is known regarding the effectiveness of these efforts. In this paper, we empirically investigate the impacts of recommendations and consumer feedbacks on sales based on data gathered from Amazon.com. Our results indicate that more recommendations indeed improve sales at Amazon.com; however, consumer ratings are not found to be related to sales. On the other hand, number of consumer reviews is positively associated with sales. We also find that recommendations work better for less-popular books than for more-popular books. This is consistent with the search cost argument: a consumer’s search cost for less-popular books may be higher, and thus they may rely more on recommendations to locate a product of interest.

A-STAR: A Mobile Ad Hoc Routing Strategy for Metropolis Vehicular Communications

Abstract: One of the major issues that affect the performance of Mobile Ad hoc NETworks (MANET) is routing. Recently, position-based routing for MANET is found to be a very promising routing strategy for inter-vehicular communication systems (IVCS). However, position-based routing for IVCS in a built-up city environment faces greater challenges because of potentially more uneven distribution of vehicular nodes, constrained mobility, and difficult signal reception due to radio obstacles such as high-rise buildings. This paper proposes a new position-based routing scheme called Anchor-based Street and Traffic Aware Routing (A-STAR), designed specifically for IVCS in a city environment. Unique to A-STAR is the usage of information on city bus routes to identify an anchor path with high connectivity for packet delivery. Along with a new recovery strategy for packets routed to a local maximum, the proposed protocol shows significant performance improvement in a comparative simulation study with other similar routing approaches.

Analyst Coverage and Financing Decisions

Abstract: We provide evidence that analyst coverage affects the pattern of security issuance. First, firms covered by fewer analysts are less likely to issue equity as opposed to debt. They issue equity less frequently, but when they do so, it is in larger amounts. Moreover, these firms depend more on favorable market conditions for their equity issuance decisions. Although all firms issue larger amounts of equity after favorable stock returns, this tendency is more pronounced for less covered firms. Finally, debt ratios of firms followed by fewer analysts are more affected by Baker and Wurgler's (2002) external finance-weighted average market-to-book ratio than those of firms followed by more analysts. These results are consistent with market timing behavior in the presence of information asymmetry, as well as behavior implied by dynamic adverse selection models of equity issuance.

An efficient sequential learning algorithm for growing and pruning RBF (GAP-RBF) networks

Abstract: This work presents a simple sequential growing and pruning algorithm for radial basis function (RBF) networks. The algorithm referred to as growing and pruning (GAP)-RBF uses the concept of "Significance" of a neuron and links it to the learning accuracy. "Significance" of a neuron is defined as its contribution to the network output averaged over all the input data received so far. Using a piecewise-linear approximation for the Gaussian function, a simple and efficient way of computing this significance has been derived for uniformly distributed input data. In the GAP-RBF algorithm, the growing and pruning are based on the significance of the "nearest" neuron. In this paper, the performance of the GAP-RBF learning algorithm is compared with other well-known sequential learning algorithms like RAN, RANEKF, and MRAN on an artificial problem with uniform input distribution and three real-world nonuniform, higher dimensional benchmark problems. The results indicate that the GAP-RBF algorithm can provide comparable generalization performance with a considerably reduced network size and training time.

Performance analysis of IEEE 802.11e contention-based channel access

Abstract: The new standard IEEE 802.11e is specified to support quality-of-service in wireless local area networks. A comprehensive study of the performance of enhanced distributed channel access (EDCA), the fundamental medium access control mechanism in IEEE 802.11e, is reported in this paper. We present our development of an analytical model, in which most new features of the EDCA such as virtual collision, different arbitration interframe space (AIFS), and different contention window are taken into account. Based on the model, we analyze the throughput performance of differentiated service traffic and propose a recursive method capable of calculating the mean access delay. Service differentiation functionality and effectiveness of the EDCA are investigated through extensive numerical and simulation results. The model and the analysis provide an in-depth understanding and insights into the protocol and the effects of different parameters on the performance.

Microgrid power quality enhancement using a three-phase four-wire grid-interfacing compensator

Abstract: This paper presents a three-phase four-wire grid-interfacing power quality compensator for microgrid applications. The compensator is proposed for use with each individual distributed generation (DG) system in the microgrid and consists of two four-phase-leg inverters (a shunt and a series), optimally controlled to achieve an enhancement of both the quality of power within the microgrid and the quality of currents flowing between the microgrid and the utility system. During utility grid voltage unbalance, the four-phase-leg compensator can compensate for all the unwanted positive-, negative-, and zero-sequence voltage-current components found within the unbalanced utility. Specifically, the shunt four-leg inverter is controlled to ensure balanced voltages within the microgrid and to regulate power sharing among the parallel-connected DG systems. The series inverter is controlled complementarily to inject negative- and zero-sequence voltages in series to balance the line currents, while generating zero real and reactive power. During utility voltage sags, the series inverter can also be controlled using a newly proposed flux-charge current-limiting algorithm to limit the flow of large fault currents between the micro- and utility grids. The performance of the proposed compensator has been verified in simulations and experimentally using a laboratory prototype.

Ultra low-voltage low-power CMOS 4-2 and 5-2 compressors for fast arithmetic circuits

Abstract: This paper presents several architectures and designs of low-power 4-2 and 5-2 compressors capable of operating at ultra low supply voltages. These compressor architectures are anatomized into their constituent modules and different static logic styles based on the same deep submicrometer CMOS process model are used to realize them. Different configurations of each architecture, which include a number of novel 4-2 and 5-2 compressor designs, are prototyped and simulated to evaluate their performance in speed, power dissipation and power-delay product. The newly developed circuits are based on various configurations of the novel 5-2 compressor architecture with the new carry generator circuit, or existing architectures configured with the proposed circuit for the exclusive OR (XOR) and exclusive NOR ( XNOR) [XOR-XNOR] module. The proposed new circuit for the XOR-XNOR module eliminates the weak logic on the internal nodes of pass transistors with a pair of feedback PMOS-NMOS transistors. Driving capability has been considered in the design as well as in the simulation setup so that these 4-2 and 5-2 compressor cells can operate reliably in any tree structured parallel multiplier at very low supply voltages. Two new simulation environments are created to ensure that the performances reflect the realistic circuit operation in the system to which these cells are integrated. Simulation results show that the 4-2 compressor with the proposed XOR-XNOR module and the new fast 5-2 compressor architecture are able to function at supply voltage as low as 0.6 V, and outperform many other architectures including the classical CMOS logic compressors and variants of compressors constructed with various combinations of recently reported superior low-power logic cells.

Modeling of transfer Characteristics for the broadband power line communication channel

Abstract: This paper presents a novel approach to model the transfer function of electrical power lines for broadband power line communication. In this approach, the power line is approximated as a transmission line and the two intrinsic parameters, the characteristic impedance and the propagation constants, are derived based on the lumped-element circuit model. Using these intrinsic parameters, the transfer characteristics for a N-branch power distribution network are derived based on the scattering matrix method. Detail derivation of this line model is given in this paper. The model has been verified with practical measurements conducted on actual power networks. It is demonstrated that the model accurately determine the line characteristics under different network configuration and when different household appliances are connected.