Showing papers by "City University of Hong Kong published in 2003"

Complex networks: small-world, scale-free and beyond

Abstract: In the past few years, the discovery of small-world and scale-free properties of many natural and artificial complex networks has stimulated a great deal of interest in studying the underlying organizing principles of various complex networks, which has led to dramatic advances in this emerging and active field of research. The present article reviews some basic concepts, important progress, and significant results in the current studies of various complex networks, with emphasis on the relationship between the topology and the dynamics of such complex networks. Some fundamental properties and typical complex network models are described; and, as an example, epidemic dynamics are analyzed and discussed in some detail. Finally, the important issue of robustness versus fragility of dynamical synchronization in complex networks is introduced and discussed.

Small-Diameter Silicon Nanowire Surfaces

Abstract: Small-diameter (1 to 7 nanometers) silicon nanowires (SiNWs) were prepared, and their surfaces were removed of oxide and terminated with hydrogen by a hydrofluoric acid dip. Scanning tunneling microscopy (STM) of these SiNWs, performed both in air and in ultrahigh vacuum, revealed atomically resolved images that can be interpreted as hydrogen-terminated Si (111)-(1 × 1) and Si (001)-(1 × 1) surfaces corresponding to SiH 3 on Si (111) and SiH 2 on Si (001), respectively. These hydrogen-terminated SiNW surfaces seem to be more oxidation-resistant than regular silicon wafer surfaces, because atomically resolved STM images of SiNWs were obtained in air after several days9 exposure to the ambient environment. Scanning tunneling spectroscopy measurements were performed on the oxide-removed SiNWs and were used to evaluate the electronic energy gaps. The energy gaps were found to increase with decreasing SiNW diameter from 1.1 electron volts for 7 nanometers to 3.5 electron volts for 1.3 nanometers, in agreement with previous theoretical predictions.

Query processing in spatial network databases

Abstract: Despite the importance of spatial networks in real-life applications, most of the spatial database literature focuses on Euclidean spaces. In this paper we propose an architecture that integrates network and Euclidean information, capturing pragmatic constraints. Based on this architecture, we develop a Euclidean restriction and a network expansion framework that take advantage of location and connectivity to efficiently prune the search space. These frameworks are successfully applied to the most popular spatial queries, namely nearest neighbors, range search, closest pairs and e-distance joins, in the context of spatial network databases.

Oxide-Assisted Growth of Semiconducting Nanowires†

Abstract: In this contribution, we outline oxide-assisted growth (OAG) (distinct from the conventional metal-catalytic vapor-liquid-solid (VLS) process) for the growth of nanostructured materials. This synthesis technique, in whichoxides instead of metals play an important role in inducing the nucleation and growth of nanowires, is capable of producing large quantities of high-purity silicon nanowires with a preferential growth direction, uniform size, and long length, without the need for a metal catalyst. The OAG 1D nanomaterials synthesis is complementary to, and coexistent with, the conventional metal-catalyst VLS approach, and can be utilized to produce nanowires from a host of materials other than Si including Ge nanowires, carbon nanowires, silicon and SnO 2 nanoribbons, and Group III-V and II-VI compound semiconductor nanowires.

The TPR*-tree: an optimized spatio-temporal access method for predictive queries

Abstract: A predictive spatio-temporal query retrieves the set of moving objects that will intersect a query window during a future time interval. Currently, the only access method for processing such queries in practice is the TPR-tree. In this paper we first perform an analysis to determine the factors that affect the performance of predictive queries and show that several of these factors are not considered by the TPR-tree, which uses the insertion/deletion algorithms of the R*-tree designed for static data. Motivated by this, we propose a new index structure called the TPR*- tree, which takes into account the unique features of dynamic objects through a set of improved construction algorithms. In addition, we provide cost models that determine the optimal performance achievable by any data-partition spatio-temporal access method. Using experimental comparison, we illustrate that the TPR*-tree is nearly-optimal and significantly outperforms the TPR-tree under all conditions.

Challenges in the migration to 4G mobile systems

Abstract: With the rapid development of wireless communication networks, it is expected that fourth-generation mobile systems will be launched within decades. 4G mobile systems focus on seamlessly integrating the existing wireless technologies including GSM, wireless LAN, and Bluetooth. This contrasts with 3G, which merely focuses on developing new standards and hardware. 4G systems supports comprehensive and personalized services, providing stable system performance and quality service. However, migrating current systems to 4G presents enormous challenges. In this article, these challenges are discussed under the headings of mobile station system, and service aspects. Proposed solutions to the research problems in each aspect are also examined.

Force of Habit and Information Systems Usage: Theory and Initial Validation

Abstract: Over the last two decades, information systems (IS) research has primarily focused on people’s conscious (intentional) behavior when trying to explain and predict IS usage. Consequently, almost no research has investigated the potential importance of subconscious (automatic) behaviors, also known as habits. This study represents a first step toward validating the idea that one can add explanatory power to a behavioral model such as Ajzen’s [1985] theory of planned behavior (TPB) by including the habit construct. We conducted a two-stage questionnaire-based survey involving two different groups of students who had access to a sophisticated internet-based communication tool (IBCT). These data were used to test a behavioral model integrating theoretical constructs of TPB and a relevant subset of Triandis’ [1980] behavioral framework. Our findings highlight the importance of considering both conscious (intentions) and subconscious (habits) factors in explaining usage behavior. Furthermore, we share our observations about antecedents of IBCT usage in the educational context. Implications for practice and research are discussed.

An empirical study of the effects of interactivity on web user attitude

Abstract: Despite the growing attention given to Web usability, little is understood as to what Web design features contribute to Web users' attitude, a major component of the usability of a Web site. This research investigates the effects of interactivity level on Web user's attitude towards commercial Web sites. It extends existing Web interface design and usability literature by empirically examining the critical roles of interactivity. Three Web sites with different levels of interactivity were compared in a controlled laboratory experiment. Three eighteen-person groups completed each treatment. The independent variable is the incremental levels of interactivity. The dependent variables are satisfaction, effectiveness, efficiency, value, and attitude towards the Web site. Results suggest that increased level of interactivity on a Web site have positive effects on user's perceived satisfaction, effectiveness, efficiency, value, and overall attitude towards a Web site. Implications for Web site designers and researchers are discussed.

A local-world evolving network model

Abstract: We propose and study a novel evolving network model with the new concept of local-world connectivity, which exists in many physical complex networks. The local-world evolving network model represents a transition between power-law and exponential scaling, while the Barabasi–Albert scale-free model is only one of its special (limiting) cases. We found that this local-world evolving network model can maintain the robustness of scale-free networks and can improve the network reliance against intentional attacks, which is the inherent fragility of most scale-free networks.

Critical success factors of enterprise resource planning systems implementation success in China

Abstract: ERP implementation issues have been given much attention since two decades ago due to its low implementation success. Nearly 90 percent of ERP implementations are late or over budget (Martin, 1998) and the success rate with ERP implementation is about 33%. In China, the success rate of implementing ERP systems is extremely low at 10% (Zhu and Ma, 1999) which is much lower than that in West countries. This study attempts to study critical success factors affecting enterprise resource planning (ERP) systems implementation success in China with focus on both generic and unique factors. User satisfaction and White's ABCD classification method are used to judge whether an ERP system implementation is a success or a failure. Survey methodology and structural equation modeling technique of PLS-graph are used to collect and analyze data. Discussions on the results of data analysis are made.

The antecedents of service quality and product quality and their influences on bank reputation: evidence from the banking industry in China

Abstract: Although an increasing number of studies is being performed in the field of service management, less work is being done on an integrated framework of service quality and product quality, especially that supported with evidence from developing countries. As a result, little is known about the distinction between service quality and product quality, their respective antecedents, and their distinctive contributions to performance in service industries in the developing world. Generalization of related findings from developed countries is not necessarily appropriate. Unlike most related studies that are based on evidence from developed countries, focuses attention on the distinction between, and respective antecedents of, service quality and product quality in the Chinese context. Gives much emphasis to the importance of a positive bank reputation. The findings are based on structural equation models developed by AMOS.

Fuzzy adaptive sliding-mode control for MIMO nonlinear systems

Abstract: A stable adaptive fuzzy sliding-mode controller is developed for nonlinear multivariable systems with unavailable states. When the system states are not available, the estimated states from a semi-high gain observer are used to construct the output feedback fuzzy controller by incorporating the dynamic sliding mode. It is proved that uniformly asymptotic output feedback stabilization can be achieved with the tracking error approaching to zero. A nonlinear system simulation example is presented to verify the effectiveness of the proposed controller.

Audit Quality and the Pricing of Discretionary Accruals

Abstract: Accrual‐based earnings is considered superior to cash flows Accruals allow managers to communicate their private and inside information and thereby improve the ability of earnings to reflect underlying economic value However, managers could engage in aggressive reporting of accruals that would seriously undermine the informativeness of reported earnings Since outsiders cannot directly observe earnings, high‐accrual firms face greater agency costs relative to low‐accrual firms Auditing plays an important role in mitigating these agency costs by constraining opportunistic management of accruals This study examines whether there is a linkage between audit quality and pricing of discretionary accruals The findings indicate that the association between stock returns and discretionary accruals is greater for firms audited by Big 6 auditors than for firms audited by non‐Big 6 auditors Further, discretionary accruals of clients of Big 6 auditors have a greater association with future profitability than dis

An adaptive spatial fuzzy clustering algorithm for 3-D MR image segmentation

Abstract: An adaptive spatial fuzzy c-means clustering algorithm is presented in this paper for the segmentation of three-dimensional (3-D) magnetic resonance (MR) images. The input images may be corrupted by noise and intensity nonuniformity (INU) artifact. The proposed algorithm takes into account the spatial continuity constraints by using a dissimilarity index that allows spatial interactions between image voxels. The local spatial continuity constraint reduces the noise effect and the classification ambiguity. The INU artifact is formulated as a multiplicative bias field affecting the true MR imaging signal. By modeling the log bias field as a stack of smoothing B-spline surfaces, with continuity enforced across slices, the computation of the 3-D bias field reduces to that of finding the B-spline coefficients, which can be obtained using a computationally efficient two-stage algorithm. The efficacy of the proposed algorithm is demonstrated by extensive segmentation experiments using both simulated and real MR images and by comparison with other published algorithms.

IT outsourcing evolution---: past, present, and future

Abstract: To achieve complex solutions in the rapidly changing world of e-commerce, it is impossible to go it alone. This explains the latest trend in IT outsourcing---global and partner-based alliances. But where do we go from here?

Face consciousness and risk aversion: Do they affect consumer decision‐making?

Abstract: This article explores the effects of two cultural dimensions, face consciousness and risk aversion, on consumers' decision-making styles. Data from China and the United States show that consumers in the United States differ from their counterparts in China in decision-making styles. Face consciousness and risk aversion appear to contribute to such divergence. Implications for future research are discussed. © 2003 Wiley Periodicals, Inc.

Raman spectroscopy of silicon nanowires

Abstract: We measure the effects of phonon confinement on the Raman spectra of silicon nanowires. We show how previous spectra were inconsistent with phonon confinement, but were due to intense local heating caused by the laser. This is peculiar to nanostructures, and would require orders of magnitude more power in bulk Si. By working at very low laser powers, we identify the contribution of pure confinement typical of quantum wires.

Aquatic Hypoxia Is an Endocrine Disruptor and Impairs Fish Reproduction

Abstract: There is increasing concern that certain chemicals in the aquatic environment can disrupt endocrine systems, leading to reproductive impairment and threatening survival of wild populations of invertebrates, fish, bird, reptiles, and wildlife. For the first time, we report that hypoxia is also an endocrine disruptor and poses a significant threat to the reproduction and hence sustainability of fish populations. Serum levels of testosterone, estradiol, and triiodothyronine significantly decreased in carp (Cyprinus carpio) upon chronic exposure to hypoxia. These hormonal changes were associated with retarded gonadal development in both male and female carp, reduced spawning success, sperm motility, fertilization success, hatching rate, and larval survival, indicating that adverse effects of hypoxia on reproductive performance resulted from endocrine disruption. Since aquatic hypoxia commonly occurs over thousands of square kilometers in aquatic systems worldwide, our results imply that endocrine disruption and reproductive impairment in fish may be a widespread environmental problem.

Variance-constrained filtering for uncertain stochastic systems with missing measurements

Abstract: In this note, we consider a new filtering problem for linear uncertain discrete-time stochastic systems with missing measurements. The parameter uncertainties are allowed to be norm-bounded and enter into the state matrix. The system measurements may be unavailable (i.e., missing data) at any sample time, and the probability of the occurrence of missing data is assumed to be known. The purpose of this problem is to design a linear filter such that, for all admissible parameter uncertainties and all possible incomplete observations, the error state of the filtering process is mean square bounded, and the steady-state variance of the estimation error of each state is not more than the individual prescribed upper bound. It is shown that, the addressed filtering problem can effectively be solved in terms of the solutions of a couple of algebraic Riccati-like inequalities or linear matrix inequalities. The explicit expression of the desired robust filters is parameterized, and an illustrative numerical example is provided to demonstrate the usefulness and flexibility of the proposed design approach.

Robust stabilization for a class of discrete-time non-linear systems via output feedback: The unified LMI approach

Abstract: This paper discusses a robust stabilization problem for a class of multi-input and multi-output (MIMO) discrete-time non-linear systems with both state and control inputs containing non-linear perturbations. The problem is solved via static output feedback and dynamic output feedback, respectively. A unified approach is used to cast the problem into a convex optimization involving linear matrix inequalities (LMI), all the controllers can robustly stabilize the systems and maximize the bound on the non-linear perturbations. This paper also extends the output feedback centralized design approach to a class of discrete-time MIMO non-linear decentralized systems, both robust static and dynamic output feedback controllers are obtained.

A Polynomial-Time Approximation Scheme for the Minimum-Connected Dominating Set in Ad Hoc Wireless Networks

Abstract: A connected dominating set in a graph is a subset of vertices such that every vertex is either in the subset or adjacent to a vertex in the subset and the subgraph induced by the subset is connected. A minimum-connected dominating set is such a vertex subset with minimum cardinality. An application in ad hoc wireless networks requires the study of the minimum-connected dominating set in unit-disk graphs. In this paper, we design a (1 + 1/s)-approximation for the minimum-connected dominating set in unit-disk graphs, running in time nO((s log s)2). © 2003 Wiley Periodicals, Inc.

Discretionary Accounting Accruals, Managers' Incentives, and Audit Fees*

Abstract: This paper examines the linkages between discretionary accruals (DAs), managerial share ownership, management compensation, and audit fees. It draws on the theory that managers of firms with high management ownership are likely to use DAs to communicate value-relevant information, while managers of firms with high accounting-based compensation are likely to use DAs opportunistically to manage earnings to improve their compensation. OLS regression results of 648 Australian firms show that (1) there is a positive association between DAs and audit fees; (2) managerial ownership negatively affects the positive relationship between DAs and audit fees; and (3) this negative impact is further found to be weaker for firms with high accounting-based management compensation.

Radiochromic film for medical radiation dosimetry

Abstract: Photon, electron and proton radiations are used extensively for medical purposes in diagnostic and therapeutic procedures. Dosimetry of these radiation sources can be performed with radiochromic films, devices that have the ability to produce a permanent visible colour change upon irradiation. Within the last 10 years, the use of radiochromic films has expanded rapidly in the medical world due to commercial products becoming more readily available, higher sensitivity films and technology advances in imaging which have allowed scientists to use two-dimensional (2D) dosimetry more accurately and inexpensively. Radiochromic film dosimeters are now available in formats, which have accurate dose measurement ranges from less than 1 Gy up to many kGy. A relatively energy independent dose response combined with automatic development of radiochromic film products has made these detectors most useful in medical radiation dosimetry.

Thermal Reduction Route to the Fabrication of Coaxial Zn/ZnO Nanocables and ZnO Nanotubes

Abstract: Coaxial Zn/ZnO nanocables and ZnO nanotubes have been fabricated via a thermal reduction route using ZnS powder as the source material. The samples were characterized using X-ray powder diffraction, scanning electron microscopy, transmission electron microscopy, and energy-dispersive X-ray spectrometry. The as-synthesized Zn/ZnO nanocables consisted of a metallic core (Zn) ≈50 nm in diameter and a semiconductor outer shell (ZnO) ≈5 nm in thickness and several micrometers in length. A good epitaxial relationship between the Zn core and ZnO shell was observed, and misfit dislocations were observed at the Zn/ZnO interface, which accommodated the relatively large lattice mismatch. The outer diameter and wall thickness of the ZnO nanotubes are ≈60 and ≈10 nm, respectively. The possible formation mechanisms for the Zn/ZnO nanocables and ZnO nanotubes are discussed.

The Effects of Centrifugal and Centripetal Forces on Product Development Speed and Quality: How Does Problem Solving Matter?

Abstract: Data from high-technology firms in Hong Kong were used to investigate whether the outcomes of problem-solving processes (solutions found, problem-solving speed, and solution quality) mediated the e...