Digital Commons Network^™

Pickup And Delivery Problem With Time Windows: Algorithms And Test Case Generation, Hoong Chuin Lau, Zhe Liang

Research Collection School Of Computing and Information Systems

In the pickup and delivery problem with time windows (PDPTW), vehicles have to transport loads from origins to destinations respecting capacity and time constraints. In this paper, we present a two-phase method to solve the PDPTW. In the first phase, we apply a novel construction heuristics to generate an initial solution. In the second phase, a tabu search method is proposed to improve the solution. Another contribution of this paper is a strategy to generate good problem instances and benchmarking solutions for PDPTW, based on Solomon' s benchmark test cases for VRPTW. Experimental results show that our approach yields very …

Personalized Classification For Keyword-Based Category Profiles, Aixin Sun, Ee Peng Lim, Wee-Keong Ng

Research Collection School Of Computing and Information Systems

Personalized classification refers to allowing users to define their own categories and automating the assignment of documents to these categories. In this paper, we examine the use of keywords to define personalized categories and propose the use of Support Vector Machine (SVM) to perform personalized classification. Two scenarios have been investigated. The first assumes that the personalized categories are defined in a flat category space. The second assumes that each personalized category is defined within a pre-defined general category that provides a more specific context for the personalized category. The training documents for personalized categories are obtained from a training …

The General Dominance Of Lottery Over Waiting-Line Auction, Winston T. H. Koh, Zhenlin Yang, Lijing Zhu

Research Collection School Of Economics

This paper examines the allocative efficiency of two popular non-price allocation mechanisms — the lottery (random allocation) and the waiting-line auction (queue system) — for the cases where consumers possess identical time costs (the homogeneous case), and where time costs are correlated with time valuations (the heterogeneous case). We show that the relative efficiency of the two mechanisms depends critically on the scarcity factor (measured by the ratio of the number of objects available for allocation over the number of participants) and on the shape of the distribution of valuations. We obtain a set of analytical results showing that the …

Cryptanalysis Of Some Hash Functions Based On Block Ciphers And Codes, Hongjun Wu, Feng Bao, Robert Huijie Deng

Research Collection School Of Computing and Information Systems

At PKC 2000, Inoue and Sakurai proposed some methods to design hash functions from block ciphers and codes (block codes and convolutional codes). They claimed that their hash functions are secure: 2(d-1)m/2 encryptions are necessary to find a collision, where d and m are the minimal distance of the code and the block size of block cipher, respectively. However, we show in this paper that a collision could be found with about a.2m encryptions, where a is a small number.

A Label-Switching Packet Forwarding Architecture For Multi-Hop Wireless Lans, Arup Acharya, Archan Misra, Sorav Bansal

Research Collection School Of Computing and Information Systems

A router in wired network typically requires multiple network interfaces to act as a router or a forwarding node. In an ad-hoc multi-hop wireless network on the other hand, any node with a wireless network interface card can operate as a router or a forwarding node, since it can receive a packet from a neighboring node, do a route lookup based on the packet's destination IP address, and then transmit the packet to another neighboring node using the same wireless interface. This paper investigates a combined medium access and next-hop address lookup based on fixed length labels (instead of IP …

In Search Of Permanent Homes: Singapore's House Churches And The Politics Of Space, Lily Kong

Research Collection School of Social Sciences

This paper focuses on one category of the 'unofficially sacred'-namely, those secular spaces which are used for worship and, in particular, residential spaces which are turned into 'house churches'. Using the case study of a house church in Singapore, the paper examines issues about the politics of religion in urban landscapes in a secular and simultaneously multireligious state. Contrary and in addition to current wisdoms about the politics of religious space, it is argued that various politics are observed: a politics of inclusion; a politics of hybridisation and in-betweenness; a politics of appropriation and nationalisation; and a politics of impermanence …

On Uncertainty, Ambiguity, And Complexity In Project Management, Michael T. Pich, Christoph H. Loch, Arnoud De Meyer

Research Collection Lee Kong Chian School Of Business

This article develops a model of a project as a payoff function that depends on the state of the world and the choice of a sequence of actions. A causal mapping, which may be incompletely known by the project team, represents the impact of possible actions on the states of the world. An underlying probability space represents available information about the state of the world. Interactions among actions and states of the world determine the complexity of the payoff function. Activities are endogenous, in that they are the result of a policy that maximizes the expected project payoff.

A key …

Trying To Understand The Different Pieces Of The Construct Validity Puzzle Of Assessment Centers: An Examination Of Assessor And Assessee Effects, Filip Lievens

Research Collection Lee Kong Chian School Of Business

This study examined the effects of assessor-related factors (i.e., type of assessor) and assessee-related factors (i.e., type of assessee profile) on the construct validity of assessment center ratings. In particular, 3 types of assessors (26 industrial/organizational [I/O] psychologists, 20 managers, and 27 students), rated assessee performances that varied according to cross-exercise consistency (i.e., relatively inconsistent vs. relatively consistent) and dimension differentiation (relatively undifferentiated vs. relatively differentiated). Construct validity evidence was established for only one assessee profile and only in the I/O psychologist and managerial samples. More generally, these results indicate that 3 factors (poor design, assessor unreliability, and especially cross-situational …

Trust In Leadership: Meta-Analytic Findings And Implications For Research And Practice, Kurt T. Dirks, Donald L. Ferrin

Research Collection Lee Kong Chian School Of Business

In this study, the authors examined the findings and implications of the research on trust in leadership that has been conducted during the past 4 decades. First, the study provides estimates of the primary relationships between trust in leadership and key outcomes, antecedents, and correlates (k = 106). Second, the study explores how specifying the construct with alternative leadership referents (direct leaders vs. organizational leadership) and definitions (types of trust) results in systematically different relationships between trust in leadership and outcomes and antecedents. Direct leaders (e.g., supervisors) appear to be a particularly important referent of trust. Last, a theoretical framework …

A Misspecification-Robust Impulse Response Estimator, Pao Li Chang, Shinichi Sakata

Research Collection School Of Economics

Impulse response analysis is typically conducted by fitting an autoregression model to a time series and calculating the moving average coefficients implied by the estimated autoregression model. The possible shape and persistence of the impulse response function implied by a parsimonious autoregression specification are very limited. This paper proposes an alternative approach to estimating impulse response function, which is asymptotically valid yet is less sensitive to model misspecifications in small samples. The small sample advantages of the proposed impulse response estimator over the conventional approach is demonstrated by Monte Carlo studies. The large sample validity of the proposed estimator is …

Detection Of Slide Transition For Topic Indexing, Chong-Wah Ngo, Ting-Chuen Pong, Thomas S. Huang

Research Collection School Of Computing and Information Systems

This paper presents an automatic and novel approach in detecting the transitions of slides for video sequences of technical lectures. Our approach adopts a foreground vs background segmentation algorithm to separate a presenter from the projected electronic slides. Once a background template is generated, text captions are detected and analyzed. The segmented caption regions as well as background templates together provide salient visual cues to decide whether a slide is flipped and replaced. The partitioning of videos according to slide changes not only structure the content of video according to topics, but also facilitate the synchronization of video, audio and …

Hci Research Issues In Electronic Commerce, Fiona Fui-Hoon Nah, Sid Davis

Research Collection School Of Computing and Information Systems

This article outlines a number of important research issues in human-computer interaction in the e-commerce environment. It highlights some of the challenges faced by users in browsing Web sites and conducting searches for information, and suggests several areas of research for promoting ease of navigation and search. Also, it discusses the importance of trust in the online environment, describing some of the antecedents and consequences of trust, and provides guidelines for integrating trust into Web site design. The issues discussed in this article are presented under three broad categories of human-computer interaction – Web usability, interface design, and trust – …

G-Portal : A Map-Based Digital Library For Distributed Geospatial And Georeferenced Resources, Ee Peng Lim, Dion Hoe-Lian Goh

Research Collection School Of Computing and Information Systems

As the World Wide Web evolves into an immense information network, it is tempting to build new digital library services and expand existing digital library services to make use of web content. In this paper, we present the design and implementation of G-Portal, a web portal that aims to provide digital library services over geospatial and georeferenced content found on the World Wide Web. G-Portal adopts a map-based user interface to visualize and manipulate the distributed geospatial and georeferenced content. Annotation capabilities are supported, allowing users to contribute geospatial and georeferenced objects as well as their associated metadata. The other …

A Digital Library For Geography Examination Resources, Lian-Heong Chua, Dion Hoe-Lian Goh, Zehua Liu, Ee Peng Lim, Rebecca Pei-Hui Ang

Research Collection School Of Computing and Information Systems

We describe a Web-based application developed above a digital library of geographical resources for Singapore students preparing to take a national examination in geography. The application provides an interactive, non-sequential approach to learning that supplements textbooks.

Exchange-Rate Systems And Interest-Rate Behavior: The Experience Of Hong Kong And Singapore, Yiu Kuen Tse, Paul S. L. Yip

Research Collection School Of Economics

In this paper we consider the implications of the two different exchange-rate systems in Hong Kong (HK) and Singapore (SP) on the economic performance of these two economies. While HK has a pegged exchange-rate regime under a currency board system (CBS), SP has a managed-float system with monitoring band. We examine whether the managed-float system of SP provides an advantage over the rigid CBS of HK in mitigating the recession caused by the Asian Financial Crisis (AFC), and the implications of the differences in the exchange-rate systems on interest-rate behaviour. Our empirical results show that the monitoring band system in …

A Modified Family Of Power Transformations, Zhenlin Yang

Research Collection School Of Economics

A modified family of power transformation, called the Dual Power Transformation, is proposed, which overcomes the truncation problem of the Box-Cox power transformation. The new transformation possesses properties similar to those of the Box-Cox power transformation. It generates a rich family of distributions that is seen to be very useful in modeling and analysis of economic durations and medical/engineering event-times. Further, it gives rise to transformed (regression) models such that all the standard asymptotic results of the maximum likelihood theory apply. Empirical results presented are more favorable to the new transformation than to the Box-Cox power transformation in terms of …

Optimal Organizational Design In A Dichotomous-Choice Project Selection Model, Winston T. H. Koh

Research Collection School Of Economics

This paper studies collective decision making in the context of a project selection model. We derive the optimal decision architecture when marginal decision costs are present, and investigate the circumstances under which the hierarchy and polyarchy exist as optimal sequential architectures. Our analysis extends previous results on optimal committee decision-making to a sequential setting, and further demonstrates the fragility of the hierarchy and polyarchy as optimal architectures.

Data Management In Location-Dependent Information Services: Challenges And Issues, Dik Lun Lee, Jianliang Xu, Baihua Zheng, Wang-Chien Lee

Research Collection School Of Computing and Information Systems

Location-dependent information services have great promise for mobile and pervasive computing environments. They can provide local and nonlocal news, weather, and traffic reports as well as directory services. Before they can be implemented on a large scale, however, several research issues must be addressed.

Fast Filter-And-Refine Algorithms For Subsequence Selection, Beng-Chin Ooi, Hwee Hwa Pang, Hao Wang, Limsoon Wong, Cui Yu

Research Collection School Of Computing and Information Systems

Large sequence databases, such as protein, DNA and gene sequences in biology, are becoming increasingly common. An important operation on a sequence database is approximate subsequence matching, where all subsequences that are within some distance from a given query string are retrieved. This paper proposes a filter-and-refine algorithm that enables efficient approximate subsequence matching in large DNA sequence databases. It employs a bitmap indexing structure to condense and encode each data sequence into a shorter index sequence. During query processing, the bitmap index is used to filter out most of the irrelevant subsequences, and false positives are removed in the …

Untimely Punishment And Dubious Desert, John N. Williams

Research Collection School of Social Sciences

Discussions of punishment have always assumed (e.g.[4, pp. 80-5]) that there are no circumstances in which someone can be justifiably punished for a crime that he will commit. This assumption has been directly challenged by Christopher New’s apparent example of morally justified ‘prepunishment’ [7]. In a recent paper, Fred Feldman rejects the ‘received wisdom’1 that desert cannot precede its basis by giving apparent examples of ‘predeserved’ charity, reward and apology [3, pp. 71-75]. If there can be cases of predeserved punishment as well, then anyone who holds that it is morally justifiable to punish an offender if and only if …

Orwell And Huxley: Making Dissent Unthinkable, John N. Williams

Research Collection School of Social Sciences

In this paper I compare the fictional world depicted by Orwell’s 1984 with that of Huxley’s Brave New World from the point of view of an analytic philosopher. Neither novel should be read as predictions, the accuracy of which can be used to judge them. Rather, both attempt to portray what humanity could conceivably become. The authenticity of this conceivability is a necessary condition of the power of both works to raise central philosophical questions about the human condition. What is ethically wrong with control? How far can Man go in recreating himself? In what sense are these worlds anti-utopian? …

Moorean Absurdities And Higher Order Beliefs, John N. Williams

Research Collection School of Social Sciences

No abstract provided.

Superman, Wittgenstein And The Disappearance Of Moorean Absurdity, John N. Williams

Research Collection School of Social Sciences

'You have known me for years, Lois' explains Superman, as I lay aside my copy of Crimmins’s example (1992). 'But there is something you have not yet discovered. You also know me under a disguise. You have not yet realized that this person is I in disguise. On that way of thinking about me, you have different opinions of me. In fact you think me an idiot.' I've just informed Superman that I accept his testimony on the strength of his intelligence. But I confess I don’t quite know how to acknowledge my acceptance of his final remark.

Security Analysis And Improvement Of The Global Key Recovery System, Yanjiang Yang, Feng Bao, Robert H. Deng

Research Collection School Of Computing and Information Systems

Key recovery is a technology that allows the owner of encrypted data or a trusted third party to recover encrypted data, mostly by reconstructing lost decryption key. In [HLG99], Harn et al proposed a Global Key Recovery System (GKRS) that combines the functions of the key recovery authorities and the public key certification authorities (CAs). Among other features, user-dominance, i.e., a user is allowed to select his own public-private key pair and especially a public element for verifying the validity of the public-private key pair, is considered extremely important by [HLG99] for wide acceptance of GKRS. In this paper, we …

Digital Libraries To Knowledge Portals: Towards A Global Knowledge Portal For Secondary Schools In Singapore, Yin-Leng Theng, Dion Hoe-Lian Goh, Chu Keong Lee, Ee Peng Lim, Zehua Liu

Research Collection School Of Computing and Information Systems

For digital libraries to remain relevant in the new millennium where the ability to manage knowledge is critical, this paper explores how digital libraries could strategically be evolved into knowledge portals to encapsulate knowledge creation, management, sharing and reusability, features evidently lacking in most conventional digital libraries. Two digital library scenarios of use in education are described and implemented as knowledge portals using G-Portal and the Greenstone software. We hope that the initial work carried out on these two portal-like DLs will eventually form part of a Global Knowledge Portal for Secondary Schools in Singapore. Keywords Digital libraries, information portals, …

Beware Of The Dog: Assaults In Prison And Cultures Of Secrecy, Mark Findlay

Research Collection Yong Pung How School Of Law

In recent months I have been involved in a series of personal injury claims made by prisoners, against the State of NSW, arising out of incidents of inmate violence. The standard scenario occurs on a Sunday where the victim is stabbed with a shiv in a prison yard, barber-shop or gymnasium, out of sight from prison officers. Most victims have suffered a history of violence and intimidation in gaol, and the injuries forming the basis of the claims, are generally shocking. There are many reasons for inmate violence. A disturbing feature of such violence in NSW prisons today is its …

Structural Change And Lead-Lag Relationship Between The Nikkei Spot Index And Futures Price: A Genetic Programming Approach, Donald Lien, Yiu Kuen Tse, X. B. Chang

Research Collection School of Economics

In this paper we adopt a nonparametric genetic programming approach to identify the structural changes in the Nikkei spot index and futures price. Due to the dominance of the “normal” period in sample size, the lead-lag relationship identified in the spot-futures system based on conventional methods such as test for Granger causality pertains to the normal period and may not be applicable in the “extreme” period. Using genetic programming we identify the lead-lag relationship based on the chronological ordering of the structural changes in the spot and futures markets. Our results show that in recent periods, major market changes originated …

Cryptanalysis Of Some Hash Functions Based On Block Ciphers And Codes, Hongjun Wu, Feng Bao, Robert H. Deng

Research Collection School Of Computing and Information Systems

At PKC 2000, Inoue and Sakurai proposed some methods to design hash functions from block ciphers and codes (block codes and convolutional codes). They claimed that their hash functions are secure: 2^(d-1)m/2 encryptions are necessary to find a collision, where d and m are the minimal distance of the code and the block size of block cipher, respectively. However, we show in this paper that a collision could be found with about alpha*2^m encryptions, where alpha is a small number.

Levy Solutions For Vibration Of Multi-Span Rectangular Plates, Y. Xiang, Yibao Zhao, G. W. Wei

Research Collection Lee Kong Chian School Of Business

This paper presents the Levy method to investigate the vibration behaviour of multi-span rectangular plates. The Levy method is applicable and analytical for rectangular plates with at least two parallel simply supported edges. The continuity at an interface between two spans is maintained by imposing both the essential and natural boundary conditions along the interface. The impact of the internal line supports on the vibration behaviour of the plates is investigated by varying both the number of internal lines and the line positions. Results for the vibration of two- and three-span rectangular plates are presented, in which the first-known exact …

How Should We Interpret Evidence Of Time Varying Conditional Skewness?, Gamini Premaratne, Anthony S. Tay

Research Collection School Of Economics

Several recent articles report evidence of predictability in the skewness of equity returns, raising hopes that predictability in third moments will be useful for forecasting the probability of tail events. The evidence is unfortunately difficult to interpret, partly because they were obtained mainly from parametric models of time-varying conditional skewness, and because little is known about the behavior of such models, for instance, when there are outliers. We investigate a non-parametric approach to testing for predictability in skewness. Specifically, we explore the size and power of a Runs tests, and compare this approach with other tests. A re-examination of daily …