Showing papers by "Nanyang Technological University published in 1996"

Output feedback H∞ control of systems with parameter uncertainty

Abstract: This paper deals with H ∞ control problem for systems with parametric uncertainty in all matrices of the system and output equations. The parametric uncertainty under consideration is of a linear fractional form. Both the continuous and the discrete-time cases are considered. Necessary and sufficient conditions for quadratic stability with H ∞ disturbance attenuation are obtained.

Testing hypotheses of entrepreneurial characteristics: A study of Hong Kong MBA students

Abstract: Investigates if entrepreneurial inclination is significantly associated with the following psychological characteristics: need for achievement, locus of control, propensity to take risk, tolerance of ambiguity, self‐confidence and innovativeness. A self‐administered, fixed‐alternative questionnaire is administered to 100 MBA students in Hong Kong, yielding a usable response rate of 54 per cent. χ2 tests of independence show that those who are entrepreneurially inclined and those who are not are homogeneous with respect to demographic and family characteristics. T‐test results and logit analysis indicate that those who are entrepreneurially inclined have greater innovativeness, more tolerance of ambiguity and higher propensity to take risk as compared with those who are not entrepreneurially inclined. The logit model has an overall holdout accuracy rate of 87.4 per cent. Although not statistically significant, descriptive statistics suggest that the entrepreneurially inclined also possess a higher need for achievement, greater (internal) locus of control and more self‐confidence.

Nationality and Subsidiary Ownership Patterns in Multinational Corporations

Abstract: This paper examines the notion that the multinational's nationality influences its foreign subsidiary ownership decisions. It identifies theoretically meaningful constructs to represent nationality and examines, under carefully controlled conditions, their influence on subsidiary ownership preferences in American and European multinationals. The paper concludes that there are indeed significant differences in ownership preferences among various nationalities that can be explained using cultural as well as economic variables, but that these differences may become weaker in larger multinationals.

Properties of carbon ion deposited tetrahedral amorphous carbon films as a function of ion energy

Abstract: Ion energy, controlled by the substrate bias, is an important parameter in determining properties of films deposited by the filtered cathodic vacuum arc technique. The substrate bias determines the ion energy distribution of the growth species. The ion energy is varied, while keeping the other deposition conditions constant, in order to study the effect of ion energy on the film properties. The films were characterized by their optical and mechanical parameters using an ellipsometer, surface profilometer, optical spectrometer, and nanoindenter. Electron energy‐loss spectroscopy and Raman spectroscopy were used for structural analysis of the films.

Employment outsourcing in information systems

Abstract: growing trend. I N recent years, information systems (IS) outsourcing has become so pervasive it can no longer be ignored. An important question is why firms choose to outsource IS work. This question has been considered from a number of perspectives. Lacity and Hirschheim [14], for example, showed how the dynamics of internal politics led to IS outsourcing. Loh and Venkatraman [15] suggested that the outsourcing behavior of a prominent blue-chip company, such as Eastman Kodak, can lead to imitative behavior throughout the IS community. In contrast, our study examines the reasons for IS outsourcing from a somewhat different perspective----that of labor market economics. From this perspective, outsourcing is a result of how firms respond to the costs and benefits of employment arrangements with their IS workers. In the classic economic view of labor markets, workers move freely and frequently between jobs to take advantage of better employment opportunities. According to Doeringer and Piore [8], the traditional long-term employment arrangement replaced the open labor market because it afforded principals (employers) greater control and influence over agents (their employees). More recently, however, firms have been moving away from the traditional, long-term employment arrangement (insourcing) to relatively shorter-term, market-mediated arrangements (outsourcing). Outsourcing reflects the increasing trend toward “taking the workers back out” [19], in which organizations alter the work relationship with their employees by reducing the duration of employment and their degree of administrative control over workers. In IS outsourcing, taking the workers back out can occur in many ways. A firm can either contract directly with an IS professional for his or her services or contract indirectly with an employee leasing company, a consulting firm, or an IS service provider. Such practices can benefit both the firm and the IS worker. Although the Eastman Kodak outsourcing arrangement represents total IS outsourcing and has become a popular practice in industry, firms can also choose to selectively outsource for particular IS skills or jobs. But why do firms choose to selectively or completely outsource IS? From a labor market perspective, outsourcing is the response of firms to the costs and disadvantages of the traditional permanent work arrangement that arise from dynamic changes in technology and the environment. Due to the increasingly rapid evolution of information technology (IT), IS work is characterized by skills deterioration and specific skills shortages [16, 25]. Thus, a firm’s ability to find and acquire the necessary IS skills is paramount. Under these circumstances, relying on retraining a permanent work force may be cost prohibitive. In addition, because IT evolves so rapidly, by the time a firm invests in and trains its IS staff on a certain technology, that technology may be obsolete. There are indications that firms face increasing turbulence in the environment. As firms become inteEmployment Outsourcing

High-Resolution Surface Temperature Patterns Related to Urban Morphology in a Tropical City: A Satellite-Based Study.

Abstract: High-resolution thermal data derived from Landsat`s thematic mapper are evaluated for their correspondence to building geometry and landscape features in Singapore`s high-rise housing estates. The image data are sufficiently detailed to reveal that differences in solar azimuth on images taken at different times of year create different thermal patterns due to building geometry and surface materials. Field measurements of surface and adjacent air temperatures in urban canyons at different orientations and at different elevations above ground demonstrate that for Singapore conditions satellite-derived surface temperature patterns are a good indicator of the daytime urban heat island. 18 refs., 11 figs., 2 tabs.

Mixed Poisson regression models with covariate dependent rates.

Abstract: This paper studies a class of Poisson mixture models that includes covariates in rates. This model contains Poisson regression and independent Poisson mixtures as special cases. Estimation methods based on the EM and quasi-Newton algorithms, properties of these estimates, a model selection procedure, residual analysis, and goodness-of-fit test are discussed. A Monte Carlo study investigates implementation and model choice issues. This methodology is used to analyze seizure frequency and Ames salmonella assay data.

A microcellular communications propagation model based on the uniform theory of diffraction and multiple image theory

Abstract: Presents a comprehensive uniform theory of diffraction (UTD) propagation model for a city street grid, using the multiple image concept and the generalized Fermat's principle to describe the multiple reflections and diffractions. The model is a quasi 3D one in the sense that the building walls are assumed to be much higher than the transmitter height so that the diffractions from the rooftops can be neglected. The model includes all possible specular wall and ground reflections and corner diffractions in the main street, side streets, and parallel streets of a microcell. This enables the signal propagation through all the possible paths to be tracked to the receiver at various line-of-sight (LOS) or out-of-sight (OOS) positions. Previous papers on such propagation models have included only a limited number of specular reflections and diffractions or they are restricted to a rectilinear grid where all the building walls on each side of the street are coplanar. Our model includes contributions to the received signal from all possible propagation paths, including ground and wall reflections from diffracted and specularly reflected signals both in the LOS and OOS regions. Within the scope of the UTD model, the accuracy of our model is limited mainly by the assumptions of characterizing the building walls as "smoothed-out" flat surfaces with average relative permittivity /spl epsiv//sub r/ and conductivity /spl sigma/. Our theoretical results of the signal path loss along the streets are compared with measurements which have been reported for city streets in Tokyo and New York City.

Electromagnetic dyadic Green's function in cylindrically multilayered media

Abstract: A spectral-domain dyadic Green's function for electromagnetic fields in cylindrically multilayered media with circular cross section is derived in terms of matrices of the cylindrical vector wave functions. Some useful concepts, such as the effective plane wave reflection and transmission coefficients, are extended in the present spectral domain eigenfunction expansion. The coupling coefficient matrices of the scattering dyadic Green's functions are given by applying the principle of scattering superposition. The general solution has been applied to the case of axial symmetry (n=0, n is eigenvalue parameter in /spl phi/ direction) where the scattering coefficients are decoupled between TM and TE waves. Two specific geometries, i.e., two- and three-layered media that are frequently employed to model the practical problems are considered in detail, and the coupling coefficient matrices of their dyadic Green's functions are given, respectively.

In Search of Legitimacy: The Private Entrepreneur in China:

Abstract: Private business is booming in China and the entrepreneurial spirit sweeps through the country. However, the apparent contradiction between Marxist ideology and private ownership has not been satis...

Tutor Versus Peer Group Assessment of Student Performance in a Simulation Training Exercise

Abstract: The performance of a group of third‐year higher diploma students from the Department of Hotel & Tourism in a simulation training exercise was assessed separately by the tutor and peer group, using an identical checklist. Ninety‐six pairs of tutor and peer group assessment marks were obtained and compared. Results showed that there was some degree of agreement between tutor and peer group markings, although the level of congruence was somewhat less than reported in earlier studies. However, when the tutor and peer group average marks were converted to grades, agreement was found in only 46.9% of the cases and the level of agreement between the two gradings was not statistically significant. Significant differences were also found in the variability of tutor and peer group markings. Furthermore, there were indications that peer group markings tended to be more stringent than tutor markings in the higher mark range, but relatively more lenient in the lower mark range. This trend was particularly obv...

Image indexing and retrieval based on color histograms

Abstract: While general object recognition is difficult, it is relatively easy to capture various primitive properties such as color distributions, prominent regions and their topological features from an image and use them to narrow down the search space when attempts to retrieving images by contents from an image database are made. In this paper, we present an image database in which images are indexed and retrieved based on color histograms. We first address the problems inherent in color histograms created by the conventional method, and then propose a new method to create histograms which are compact in size and insensitive to minor illumination variations such as highlight, shape, and etc. A powerful indexing scheme where each histogram of an image is encoded into a numerical key, and stored in a two-layered tree structure is introduced. This approach turns the problem of histogram matching, which is computation intensive, into index key search, so as to realize quick data access in a large scale image database. Two types of user interfaces, Query by user provided sample images, and Query by combination of the system provided templates, are provided to meet various user requests. Various experimental evaluations exhibit the effectiveness of the image database system.

A New Optimal Algorithm for the Joint Replenishment Problem

Abstract: In this paper, we propose a new optimal algorithm for the Joint Replenishment Problem. The proposed algorithm can be used to determine the optimal strict-cyclic policy, as well as the optimal among all cyclic policies for the joint replenishment problem. Computational experiments on randomly generated problems reveal that the proposed algorithm performs better than existing optimal algorithms for the problem.

Robust decentralised load-frequency control of multi-area power systems

Abstract: A robust decentralised load-frequency controller, based on the Riccati-equation approach, is proposed for multi-area power systems with parametric uncertainties. It comprises N local robust load-frequency controllers for a N-area power system. N interlinked Riccati equations are produced initially which are separated via a decoupling technique. Bounds of system parametric uncertainties are included in these Riccati equations to improve the robustness of the intended controller. One local robust load-frequency relationship is obtained by solving the corresponding decoupled Riccati equation. It operates on its local measurements; feedback from other areas is not needed. The overall system is asymptotically stable, for all admissible system parametric uncertainties, when all the local load-frequency controllers are working together. Good performance is reported from the studied three-area power system even in the presence of the generation-rate constraint.

Foreign Direct Investment by Japanese Electronics Firms in the United States and Canada: Modelling the Timing of Entry

Abstract: This paper examines the relationship between attributes of Japanese electronics firms and the sequence of their investments in the U.S. and Canada. It is argued that a useful way to model foreign direct investment (FDI) decisions is to recognize explicitly the uncertainties involved in them. A probabilistic model of FDI is specified. The following hypotheses are incorporated in the model: 1) the higher the risk-adjusted expected net benefits from foreign direct investment, ceteris paribus, the higher the probability of making an investment at any particular moment and thus the probability of investing earlier; 2) risk-adjusted expected net benefits from FDI by a firm are a function of its possession of certain types of intangible, transportable assets; 3) the uncertainties involved with FDI may be reduced with the passage of time and with increased experience with foreign operations; 4) parent company attributes that facilitate market intelligence capabilities permit early recognition of investment opportunities; and 5) timing of entry may reflect strategic considerations such as responding to growing foreign market opportunities, the need to ensure market access and the presence of opportunities to obtain abnormal profits due to market concentration. The models are estimated using Cox's proportional hazards regression model. Results generally confirm the hypotheses that size and financial capabilities, as well as possession of some knowledge-based, firm-specific strategic assets, are significantly related to early FDI. They also confirm that timing of entry is affected by market opportunities and in some cases by the need to ensure market access. We did not find evidence in this sector that differences in market concentration significantly affected the timing of FDI. Analyses are also provided of inter-period changes in the importance of different types of intangible assets in explaining earlier FDI as well as changes that reflect differences in host country environments.

A study of stereolithography file errors and repair. Part 1. Generic solution

Abstract: The most commonly used input to a rapid prototyping (RP) system is thede facto stereolithography file (STL). Several problems plague these STL files owing to the very nature of STL files and the non-robustness of commercial CAD system model tessellators. The consequences of not correcting these errors are detrimental to the creation of the intended prototype. These are highlighted in the paper. In Part 1 of two papers, a description of all STL-files-related errors is given. The paper also proposed a generic solution to solve one of the major problems in the proper creation of a prototype, that is, the problem of missing facets. Part 2 deals with special cases of errors associated with the STL files. The performance evaluation of the proposed solution is also given.