Showing papers by "Nanyang Technological University published in 1994"

Robust Kalman filtering for uncertain discrete-time systems

Abstract: This paper is concerned with the problem of a Kalman filter design for uncertain discrete-time systems. The system under consideration is subjected to time-varying norm-bounded parameter uncertainty in both the state and output matrices. The problem addressed is the design of a linear filter such that the variance of the filtering error is guaranteed to be within a certain bound for all admissible uncertainties. Furthermore, the guaranteed cost can be optimized by appropriately searching a scaling design parameter. >

How Different is Japanese Corporate Finance? An Investigation of the Information Content of New Security Issues

Abstract: This paper studies the shareholder wealth effects associated with 875 new security issues in Japan from January 1, 1985 to May 31, 1991. The sample includes public equity, private equity, rights offerings, straight debt, warrant debt and convertible debt issues. Contrary to the U.S., the announcement of convertible debt issues is accompanied by a significant positive abnormal return of 1.05%. The announcement of equity issues has a positive abnormal return of 0.45%, significant at the 0.10 level, but this positive abnormal return can be attributed to one year in our sample and is offset by a negative issue date abnormal return of -1.01%. The abnormal returns are negatively related to firm size, so that for equity issues (but not for convertible debt issues), large Japanese firms have significant negative announcement abnormal returns. Our evidence is consistent with the view that Japanese managers decide to issue shares based on different considerations than American managers.

Markov random field models in computer vision

Abstract: A variety of computer vision problems can be optimally posed as Bayesian labeling in which the solution of a problem is defined as the maximum a posteriori (MAP) probability estimate of the true labeling. The posterior probability is usually derived from a prior model and a likelihood model. The latter relates to how data is observed and is problem domain dependent. The former depends on how various prior constraints are expressed. Markov Random Field Models (MRF) theory is a tool to encode contextual constraints into the prior probability. This paper presents a unified approach for MRF modeling in low and high level computer vision. The unification is made possible due to a recent advance in MRF modeling for high level object recognition. Such unification provides a systematic approach for vision modeling based on sound mathematical principles.

Reverse engineering of relational databases: extraction of an EER model from a relational database

Abstract: A methodology for extracting an extended Entity-Relationship (EER) model from a relational database is presented. Through a combination of data schema and data instance analysis, an EER model is derived which is semantically richer and more comprehensible for maintenance and design purposes than the original database. Classification schemes for relations and attributes necessary for the EER model extraction are derived and justified. These have been demonstrated to be implementable in a knowledge-based system; a working prototype system which does so is briefly discussed. In addition, cases in which human input is required are also clearly identified. This research also illustrates that the database reverse engineering process can be implemented at a high level of automation.

Automatic parsing of news video

Abstract: Video content parsing is possible when one has an a priori model of a video's structure based on domain knowledge. This paper presents work on using domain knowledge to parse content of news video programs. Approaches to locating and identifying frame structure models based on temporal and spatial structure of news video data, along with algorithms to apply these models in parsing news video, have been developed and are presented in detail in this paper. Experimental results are also discussed in detail to evaluate the approaches and algorithms. Finally, proposals for future work are summarized. >

Modeling the determinants of audit expertise

Abstract: Libby & Luft [ Accounting, Organizations and Society (1993) pp. 425–450] presented a model of the relations between experience, ability, knowledge, and performance in audit judgment. This paper extends the model by developing a framework for predicting the structure of these relations in different judgment in different judgment settings and provides an initial test of the predictions by analyzing data from Bonner & Lewis's [ Journal of Accounting Research (Supplement 1990) pp. 1–20] four tasks using LISREL. Key predictions were that problem-solving ability would directly affect performance only in unstructured tasks and would indirectly affect performance through its effect on knowledge acquisition where the learning environment was impoverished. The predictions were supported in most cases. In addition, the paper provides and tests a basis for predicting the associations between performance on different audit tasks. Construct measurement problems that need to be addressed in future research are also indicated.

An image database system with content capturing and fast image indexing abilities

Abstract: While general object recognition is difficult, it is relatively easy to capture some primitive image properties such as color distribution, prominent regions and their geometrical properties from an image and use these features to narrow down the search space when attempts to retrieving images by contents from an image database are made. The authors are building an image database in which images are indexed by both the numerical index keys generated automatically from the captured primitive image features using a set of rules, and traditional descriptive keywords entered by users when images are loaded. Users can either use the descriptive keywords or provide information regarding these image properties to query and retrieve images from the database. With this approach, the authors turn the difficult problem of image matching into image retrieval by index keys, which can be performed easily and rapidly using current database techniques. Initial experiments on the image database system show promising performance. >

Incipient sediment motion on non-horizontal slopes

Abstract: The study investigates the threshold condition for the initiation of cohesionless sediment transport on a nonhorizontal streamwise slope. Theoretical study of the stability of a sediment particle lying on a non-horizontal bed slope shows that the critical shear stress is a function of the streamwise bed slope. Experiments conducted with a closed-conduit flow show that the equation derived from force analysis adequately evaluates the critical shear stress of sediments lying on slopes ranging from steep positive to negative (adverse). Tests conducted with a closed-conduit flow avoid the problems associated with those conducted with an open channel flow. In the latter flow condition, uniform flow is often difficult to achieve in a steep channel, and impossible to achieve when the streamwise bed slope is adverse.

Application of generalized differential quadrature method to structural problems

Abstract: SUMMARY This paper presents the first endeavour to exploit a generalized differential quadrature method as an accurate, efficient and simple numerical technique for structural analysis. Firstly, drawbacks existing in the method of differential quadrature (DQ) are evaluated and discussed. Then, an improved and simpler generalized differential quadrature method (GDQ) is introduced to overcome the existing drawback and to simplify the procedure for determining the weighting coefficients. Subsequently, the generalized differential quadrature is systematically employed to solve problems in structural analysis. Numerical examples have shown the superb accuracy, efficiency, convenience and the great potential of this method. Numerical approximation methods for solving partial differential equations have been widely used in various engineering fields. Classical techniques such as finite element and finite difference methods are well developed and well known. These methods can provide very accurate results by using a large number of grid points. However, in a large number of cases, reasonably approximate solutions are desired at only a few specific points in the physical domain. In order to get results even at or around a point of interest with acceptable accuracy, conventional finite element and finite difference methods still require the use of a large number of grid points. Consequently, the requirement for computer capacity is often unnecessarily large in such cases. In seeking an alternate numerical method using fewer grid points to find results with acceptable accuracy, the method of differential quadrature (DQ) was introduced by Bellman et a!.'. The method of DQ is a global approximate method. This method is based on the ideas that the derivative of a function with respect to a co-ordinate direction can be expressed as a weighted linear sum of all the function values at all mesh points along that direction and that a continuous function can be approximated by a higher-order polynomial in the overall domain. The DQ method differs from the finite element method (FEM) in two aspects. Firstly, the FEM uses lower-order polynomials to approximate a function on a local element level, while the DQ method approximates a function on the global area using higher-order polynomials. Secondly, the DQ method directly approximates the derivatives of a function at a point, while the FEM approximates a function over a local element and the derivatives can then be derived from the approximate function. In this aspect, the DQ method is more similar to the finite difference method (FDM). However, the FDM is also a local approximation method based on lower-order polynomial approximation. In fact, it can be shown that the FDM is just a special case of the DQ method where it is applied locally on the range [.xi- xi + l]. Owing to the higher-order

Factors Affecting Income Smoothing Among Listed Companies in Singapore

Abstract: The objective of this study is to identify the factors associated with the incidence of income smoothing. The sample comprises 153 companies listed in the Singapore stock exchange during the period 1980 to 1990. Descriptive statistics indicate that income smoothing is practised and that operational income is the most common income smoothing objective. Four hypotheses relating income smoothing to company size (total assets), profitability (net income after tax to total assets), industry (industrial and commercial, hotels and properties, and others), and nationality (Singaporean and Malaysian companies) are tested in the study. Results from t-tests of differences, chi-square tests of independence, and logit analyses largely support the alternative hypotheses put forward except for company size. The primary findings are that income smoothers tend to be less profitable companies, companies in more ‘risky’ industries, and Malaysian companies. It is hoped that this study, which is conducted in an econo...

Valuation effects of international stock exchange listings

Abstract: A comprehensive data set consisting of 346 U.S. firm stock listings on ten different stock exchanges is examined in order to determine the valuation consequences of listing on a foreign stock exchange. For the sample of U.S. firms listing abroad, abnormal returns in U.S. trading were: (1) positive around the date of acceptance on the foreign exchange; (2) negative on the first trading day; and (3) negative in the post-listing period for firms listing on the Tokyo and Basel exchanges. Tests for the equality of stock return variances between event periods and market model estimation periods failed to reveal a definitive impact.

Video parsing using compressed data

Abstract: Parsing video content is an important first step in the video indexing process. This paper presents algorithms to automate the video parsing task, including video partitioning and video clip classification according to camera operations using compressed video data. We have studied and implemented two algorithms for partitioning video data compressed according to the MPEG standard. The first one is based on discrete cosine transform coefficients of video frames, and the other based on correlation of motion vectors. Algorithms to detect camera operations using motion vectors are presented.

Estimation of the spontaneous emission factor for microdisk lasers via the approximation of whispering gallery modes

Abstract: Microdisk structures have been used to achieve low‐threshold lasing. For these microcavity lasers, the spontaneous emission coupling factor β is an important parameter since it determines the threshold current of the laser. Theoretical calculation of β based on the exact solution of the modes in a microdisk is complicated. A simple, approximate method for solving the waveguide modes and the density of states is developed here, using conformal transformation and the Wentzel–Kramers–Brillouin approximation and taking into account the effect of the disk thickness. We find that the β value for a microdisk laser is smaller than that of an ideal laser that has a cylindrical waveguide structure with a strong index guiding. A considerably high value of β can still be achieved, however, in a microdisk laser.

Applying spatial representation techniques to the container packing problem

Abstract: This paper describes an efficient method of packing boxes into a container using a unique spatial representation technique. Unlike other algorithms, the packing algorithm in this paper is not constrained by the physical packing sequence, that is, back to front, or bottom to top. This extra flexibility allows the program to pack the boxes more efficiently. The packing plan can be generated to suit the actual packing sequence. The program is implemented on an IBM PC and a comparison has been made with a similar software. The results, in terms of packing efficiency and packing time, are promising.

An evaluation of computer‐assisted learning in terms of achievement, attitudes and classroom environment

Abstract: In contrast to considerable past research which has shown that computer‐assisted learning (CAL) typically is associated with a modest effect size of only 0.4 standard deviations of difference between an experimental and a control group, this evaluation of micro‐PROLOG‐based CAL revealed massive effect sizes of 3.5 for achievement and 1.4 for attitudes. Also this evaluation broke new ground in that it involved the development and use of an instrument which assesses student perceptions of the psychosocial environment of CAL classroom settings. Effect sizes for classroom environment scales ranged from 1.0 to 1.9, with CAL students perceiving their classes as having greater gender equity, investigation, innovation and resource adequacy.

Human Resource Management Problems in Sino‐foreign Joint Ventures

Abstract: Sino‐foreign joint ventures have been the major form of foreign direct investment in China since the economic reform in late 1978. Among the many problems faced by the foreign partner of a joint venture, human resource management (HRM) is one of the most often cited. Offers a comprehensive review of the major HRM problems, namely recruitment, dismissal, remuneration, labour discipline, managerial skills, training and trade unions. In order to understand the nature of the problems better, an effort is made to trace the origin of these problems back to the former centrally planned economy and the Chinese culture. The discussion covers the entire Chinese workforce consisting of both workers and managers. Cites survey results and real life cases for illustration. In addition to analysing the problems, offers some practical solutions.

A phone-based remote controller for home and office automation

Abstract: In modern society, home and office automation become increasingly important and interesting. They not only provide better ways to transfer information within homes/offices and between homes/offices, they provide better time management too. These also improve the quality of our lives by automating some of the electrical home appliances such as light source, A/V equipment, computer, security device, etc. The paper describes a hardware-based remote controller for power point control. Users can input the control commands and their own passcodes by using local or external telephones. The paper also discusses the operational sequence of the remote controller. >

Three-dimensional rapid prototyping technologies and key development areas

Abstract: Since the 1970s, the prototyping of physical models used in the engineering world has passed through three distinct phases. In the third phase, a series of different revolutionary methodologies-collectively called the 3D rapid prototyping methodologies-is capable of producing a physical prototype from the computer model in a very short turnround time and without the fuss required by NC programming systems. This article covers the benefits rapid prototyping methodologies offer in contrast to conventional methods of prototyping. There are currently no less than five such commercialised methods: stereolithography apparatus, solid ground curing, selective laser sintering, laminated object manufacturing and fused deposition modelling. The working mechanism of each method as well as a comparison between the various methods is discussed. The article also looks at efforts to improve the performance and functionality of the mechanism and experiments with new materials for the prototype.

Determination of reliability worth for distribution system planning

Abstract: There is an ever growing demand to justify reliability projects on a more quantifiable basis, i.e. investments related to the provision of service reliability needs to be carefully evaluated in regard to their cost and benefit implications. In addition, utilities are recognizing the significant customer and community costs that are incurred when electric supply is abruptly curtailed. Consequently, the utility industry is under pressure to assess their reliability evaluation tools and formulate methods for incorporating the economics of reliability in the decision-making process. This paper is concerned with the evaluation of a reliability worth index that can be used to make decisions in distribution system planning and design. The reliability worth index is termed the interrupted energy assessment rate (IEAR) and is obtained by relating the reliability indices to the customer cost of interruption data. Three fundamentally different approaches for evaluating distribution system reliability worth indices are presented and compared using a small but comprehensive test system. The impact on the worth indices of distribution system operating policies and configurations is also illustrated using the three methods. The worth indices developed can be used to determine the monetary implications of customer supply interruptions thereby incorporating economics in the reliability cost-benefit equation. >

An Agency Theory and Probit Analytic Approach to Corporate Non-mandatory Disclosure Compliance

Abstract: Using the agency theory framework, this study examines the impact of corporate size, profitability, solvency, operational complexity, industry and auditor on the compliance with non-mandatory accounting pronouncements. Results of the probit analysis of 106 listed companies are generally consistent with agency theory hypotheses. In particular, companies that are large, profitable and highly geared are more likely to comply with non-mandatory accounting pronouncements. Also, companies in the industrial and commercial sector and companies audited by large public accounting firms are more likely to comply with nonmandatory pronouncements than do their counterparts. The hold-out accuracy rates of the probit model are 78.6% for non-compliance, 87.5% for compliance, and 84.0% overall.

New robust adaptive load-frequency control with system parametric uncertainties

Abstract: In the paper, based on a combination of the robust control approach and an adaptive control technique, a design procedure of a new robust adaptive controller is proposed for power system load-frequency control with system parametric uncertainties. The system parametric uncertainties are obtained by changing parameters by 30% to 50% simultaneously from their typical values. In the design of the proposed controller, only the bounds of system parameters are required. The motivation of combining the robust control with an adaptive control is to use the robust control approach to deal with the small parametric uncertainties and to use the adaptive control for large parametric uncertainties so that stability of the overall system and good performance can both be achieved for all admissible uncertainties. The simulation results demonstrate that for the example system the proposed load-frequency controller can achieve good performance even in the presence of the generation rate constraint (GRC).