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Hong Kong, China

City University of Hong Kong is a public research university located in Kowloon Tong, Hong Kong. It was founded in 1984 as City Polytechnic of Hong Kong and became a fully accredited university in 1994. CityU offers over 50 bachelor's degree programmes through its constituent colleges and schools. Postgraduate degree programmes are offered by the Chow Yei Ching School of Graduate Studies. Wikipedia.


Wang Y.-M.,Fuzhou University | Chin K.-S.,City University of Hong Kong
Information Sciences | Year: 2011

Eigenvector method (EM) is a well-known approach to deriving priorities from pairwise comparison matrices in the analytic hierarchy process (AHP), which requires the solution of a set of nonlinear eigenvalue equations. This paper proposes an approximate solution approach to the EM to facilitate its computation. We refer to the approach as a linear programming approximation to the EM, or LPAEM for short. As the name implies, the LPAEM simplifies the nonlinear eigenvalue equations as a linear programming for solution. It produces true weights for perfectly consistent pairwise comparison matrices. Numerical examples are examined to show the validity and effectiveness of the proposed LPAEM and its significant advantages over a recently developed linear programming method entitled LP-GW-AHP in rank preservation. © 2011 Elsevier Inc. All rights reserved. Source


Chung W.,City University of Hong Kong
Applied Energy | Year: 2011

Energy end-use for all sectors (commercial, residential, transport, industrial) in Hong Kong shows that the residential share increased from 14.2% in 1990 to 18.1% in 2007, such share increase has prompted the authors to analyze the issue. The Divisia decomposition analysis is used to evaluate the respective contributions of changes in (1) the number of households, (2) share of different types of residential households, (3) efficiency gains, and (4) climate condition to the energy use increase. The analysis reveals that the major contributor was the increase of the number of households, and the second major contributor was the intensity effect. As expected, the segment of the private housing (apartments) was becoming less energy efficient. In addition, it is interesting to note that the energy end-use per household in the segment of government rental subsidized housing (apartments) was decreasing. The decrease of the household income in this segment may be one of the reasons while statistics showing that the number of low-income household was increasing and leaning towards the lowest income classes. On the other hand, it is believed that people tend to consume more energy to obtain a quality life characterized with comfortable living with the growth of economy and improvement of living standard. However, Hong Kong becomes a counterexample since 2004. Therefore, changing the residents' behavior may not be an effective tactic for reducing energy consumption. © 2011 Elsevier Ltd. Source


Fuchs C.,City University of Hong Kong
Computer Assisted Language Learning | Year: 2016

This exploratory study contributes to the underexplored area of collaborative task formats in telecollaboration. The study investigates how English as a second language (ESL) student teachers in the US and English as a foreign language (EFL) student teachers in Turkey negotiated the design, implementation, and evaluation of technology-based English language learning tasks. The overall pedagogical goal of this spring 2014 project was to provide participants in different educational and institutional settings an opportunity to collaboratively explore and evaluate the affordances of technology tools in the design of joint learning tasks. This ethnographic case study triangulates questionnaires, telecollaboration logs, and computer-mediated communication data (blogs, emails) to examine the types of negotiation (personal, interactive, procedural) telecollaborative teams displayed at the project's micro levels (self, situated telecollaborative activity) and macro levels (institutional setting, political context). Findings indicate that one telecollaborative team, Global Team 2, effectively managed their learning as a group by making key decisions collectively about their work processes. The team's high number of procedural negotiation instances suggests a high degree of task-orientation, which may have aided their task completion. In contrast, the number of personal and interactive negotiation types was low. The latter, however, may have been called for midway through the project, when unexpected political developments in Turkey unfolded. Repercussions disturbed Turkish participants and affected social media, which were at the core of this telecollaboration. Implications focus on foregrounding personal and interactive negotiation via virtual Global Team check-ins, as well as on expanding collaborative tasks by incorporating perspectives on the wider institutional and sociopolitical contexts of participating institutions. © 2016 Informa UK Limited, trading as Taylor & Francis Group Source


Leung S.C.H.,City University of Hong Kong | Zhang D.,Xiamen University
Expert Systems with Applications | Year: 2011

In this paper, an orthogonal strip packing problem with rotation of items and without the guillotine packing constraint is considered. A fast heuristic algorithm for the large-scale problems is presented. This heuristic algorithm is mainly based on heuristic strategies inspired by the wall-building rule of bricklayers in daily life. The heuristics is simple and the setting of parameter is not required. Each layer is initialized with either a single item or a bunch of equal-width items. The remaining part of the layer is filled by a bottom-left strategy preferring items which eliminate corners of the current layout. Items can also be placed across several layers. Then, the evaluation rule, which is based on the fitness value for different rectangles to a given position, is able to select an appropriate rectangle to pack. The computational results on a broad range of benchmark problems show that the fast layer-based heuristic algorithm can compete with other latest heuristics and meta-heuristics from the literature in terms of both solution quality and computational time. The fast layer-based heuristic algorithm can compete with the latest published algorithms. In particular, it performs better for large-scale problem instances. © 2010 Elsevier Ltd. All rights reserved. Source


Yip N.M.,City University of Hong Kong | Tran H.A.,Malmo University
Urban Studies | Year: 2016

Despite the rapid transformation in the urban landscape of Vietnam, a simple and uncritical application of the ‘gentrification’ concept out of the specific spatial and temporal context of the country is problematic. Not only does the phenomenon progress in a highly compressed temporal scale compared with similar processes in cities in the Global North, it is also embedded within a paradigmatic shift of the entire socio-economic system. This paper attempts to explore the process of urban redevelopment in Vietnam and critically examines whether this concept, with its origin from the Global North, is capable of offering a conceptually robust lens through which the processes and outcomes of redevelopment can be consistently analysed. This helps to shed light on our understanding of the usefulness of the concept of gentrification in Vietnam and in transitional economies in Asia in general. © 2015, © Urban Studies Journal Limited 2015. Source


Wang F.,East China Normal University | Ngo C.-W.,City University of Hong Kong
IEEE Transactions on Multimedia | Year: 2012

Rushes footages are considered as cheap gold mine with the potential for reuse in broadcasting and filmmaking industries. However, mining gold from unedited videos such as rushes is challenging as the reusable segments are buried in a large set of redundant information. In this paper, we propose a unified framework for stock footage classification and summarization to support video editors in navigating and organizing rushes videos. Our approach is composed of two steps. First, we employ motion features to filter the undesired camera motion and locate the stock footage. A hierarchical hidden Markov model (HHMM) is proposed to model the motion feature distribution and classify video segments into different categories to decide their potential for reuse. Second, we generate a short video summary to facilitate quick browsing of the stock footages by including the objects and events that are important for storytelling. For objects, we detect the presence of persons and moving objects. For events, we extract a set of features to detect and describe visual (motion activities and scene changes) and audio events (speech clips). A representability measure is then proposed to select the most representative video clips for video summarization. Our experiments show that the proposed HHMM significantly outperforms other methods based on SVM, FSM, and HMM. The automatically generated rushes summaries are also demonstrated to be easy-to-understand, containing little redundancy, and capable of including ground-truth objects and events with shorter durations and relatively pleasant rhythm based on the TRECVID 2007, 2008, and our subjective evaluations. © 2006 IEEE. Source


Cai D.W.H.,California Institute of Technology | Quek T.Q.S.,Institute for Infocomm Research | Tan C.W.,City University of Hong Kong
IEEE Transactions on Signal Processing | Year: 2011

This paper studies the max-min weighted signal-to-interference-plus-noise ratio (SINR) problem in the multiple- input-multiple-output (MIMO) downlink, where multiple users are weighted according to priority and are subject to a weighted-sum-power constraint. First, we study the multiple-input-single-output (MISO) and single-input-multiple- output (SIMO) problems using nonlinear Perron-Frobenius theory. As a by-product, we solve the open problem of convergence for a previously proposed MISO algorithm by Wiesel, Eldar, and Shamai in 2006. Furthermore, we unify our analysis with respect to the previous alternate optimization algorithm proposed by Tan, Chiang, and Srikant in 2009, by showing that our MISO result can, in fact, be derived from their algorithm. Next, we combine our MISO and SIMO results into an algorithm for the MIMO problem. We show that our proposed algorithm is optimal when the channels are rank-one, or when the network is operating in the low signal-to-noise ratio (SNR) region. Finally, we prove the parametric continuity of the MIMO problem in the power constraint, and we use this insight to propose a heuristic initialization strategy for improving the performance of our (generally) suboptimal MIMO algorithm. The proposed initialization strategy exhibits improved performance over random initialization. © 2011 IEEE. Source


Arash B.,University of Manitoba | Wang Q.,University of Manitoba | Liew K.M.,City University of Hong Kong
Computer Methods in Applied Mechanics and Engineering | Year: 2012

A nonlocal elastic plate model that accounts for the scale effects is first developed for wave propagations in graphene sheets. Moreover, a finite element model developed from the weak-form of the elastic plate model is reported to fulfill a comprehensive wave study in the sheets and realize an application of the sheets as gas sensors. The applicability of the finite element model is verified by molecular dynamics simulations. The studies show that the nonlocal finite element plate model is indispensable in predicting graphene phonon dispersion relations, especially at wavelengths less than 1nm, when the small-scale effect becomes dominant. Moreover, the nonlocal parameter e 0a, a key parameter in the nonlocal model, is calibrated through the verification process. The dependence of the small-scale effect and the width of sheets on the dispersion relation is also investigated, and simulation results show that the phase velocity decreases to an asymptotic value with the width of sheets reaches a sufficiently large size. As an application of the investigation, the potential of graphene sheets as nano-sensors for noble gas atoms is explored by defining and examining an index based on the phase velocity shifts in a graphene sheet attached by gas atoms. © 2012 Elsevier B.V. Source


The P.-L.,Multimedia University | Sun H.,City University of Hong Kong
Industrial Management and Data Systems | Year: 2012

Purpose - There are very few studies on the impact of job attitude on knowledge sharing. The purpose of this paper is to examine the effects of job involvement, job satisfaction, organisational commitment, and organisational citizenship behaviour (OCB) on employees' knowledge sharing behaviour. Design/methodology/approach - This research is based on a survey of 116 Information Systems personnel in Malaysia. Structural equation modelling is used to test the hypothesis. Findings - The results show that job involvement, job satisfaction and OCB are independent and positively related to employees' knowledge sharing behaviour. However, organisational commitment has a negative relationship with knowledge sharing behaviour. It is found that OCB is not a significant mediator between job involvement, job satisfaction organisational commitment and knowledge sharing behaviour. Research limitations/implications - It is widely reported that knowledge workers may not be willing to share with others since they can always argue that it is not their job to share. Therefore, knowledge sharing can be regarded as an extra job. OCB is an extra-role behaviour which is especially relevant to research on knowledge sharing. Theories and research methods in OCB may be used in future research on knowledge sharing. Practical implications - Given the importance of knowledge sharing in today's competitive business world, this study provides a broader understanding of different dimensions of job attitudes in relation to employees' knowledge sharing behaviours. Our findings suggest that organisational administrators and managers should look into ways of improving the levels of job satisfaction, job involvement, and OCB in order to facilitate knowledge sharing behaviour. Originality/value - This study makes two distinct additions to the organisational behaviour and knowledge sharing literature. First, job attitudes appear to be significantly related to knowledge sharing behaviour, addressing a research gap in the literature of knowledge sharing and employee attitudes. Second, this study reveals that OCB directly affects knowledge sharing but it does not mediate employees' job attitudes to promote knowledge sharing behaviours. © Emerald Group Publishing Limited. Source


Liu Z.-W.,Huazhong University of Science and Technology | Guan Z.-H.,Huazhong University of Science and Technology | Shen X.,University of Waterloo | Feng G.,City University of Hong Kong
IEEE Transactions on Automatic Control | Year: 2012

In this technical note, an impulsive consensus algorithm is proposed for second-order continuous-time multi-agent networks with switching topology. The communication among agents occurs at sampling instants based on position only measurements. By using the property of stochastic matrices and algebraic graph theory, some sufficient conditions are obtained to ensure the consensus of the controlled multi-agent network if the communication graph has a spanning tree jointly. A numerical example is given to illustrate the effectiveness of the proposed algorithm. © 2012 IEEE. Source


Qiu J.,Harbin Institute of Technology | Feng G.,City University of Hong Kong | Feng G.,Nanjing University of Science and Technology | Gao H.,Harbin Institute of Technology
IEEE Transactions on Fuzzy Systems | Year: 2012

This paper is concerned with the problem of robust ${\mathscr H}infty output feedback control for a class of continuous-time Takagi-Sugeno (T-S) fuzzy affine dynamic systems using quantized measurements. The objective is to design a suitable observer-based dynamic output feedback controller that guarantees the global stability of the resulting closed-loop fuzzy system with a prescribed ${\mathscr H}\infty disturbance attenuation level. Based on common/piecewise quadratic Lyapunov functions combined with S-procedure and some matrix inequality convexification techniques, some new results are developed to the controller synthesis for the underlying continuous-time T-S fuzzy affine systems with unmeasurable premise variables. All the solutions to the problem are formulated in the form of linear matrix inequalities (LMIs). Finally, two simulation examples are provided to illustrate the advantages of the proposed approaches. © 1993-2012 IEEE. Source


Dai L.,City University of Hong Kong
IEEE Transactions on Wireless Communications | Year: 2012

In this paper, a unified analytical approach is developed to characterize the stability and delay performance of buffered Aloha networks. It is demonstrated that a buffered Aloha network can be stabilized if backoff parameters are properly selected. The stable region of backoff factor q is derived and shown to be enlarged by increasing the cutoff phase K. With Geometric Retransmission (K{=}1), for instance, the stable region rapidly diminishes as the number of nodes n increases, implying that a slight change of network size may lead to instability if the backoff factor q is not updated accordingly. In contrast, a buffered Aloha network with Exponential Backoff (K{=}) is much more robust as the stable region becomes insensitive to the number of nodes n. The improvement on stability performance is, nevertheless, achieved at the cost of severe delay jitter. The delay analysis further reveals that the second moment of access delay of Head-of-Line (HOL) packets rapidly grows with the cutoff phase K when the network is saturated. In spite of an improved stable region, an excessively large K will lead to significant degradation of queueing performance. © 2012 IEEE. Source


Tjong S.C.,City University of Hong Kong
Energy and Environmental Science | Year: 2011

The demand for lightweight, good performance and high efficiency for proton exchange membrane fuel cells (PEMFCs) is ever increasing in both industrial and transportation sectors. High performance PEMFCs require the use of advanced bipolar plates with high electrical conductivity and good mechanical strength. This can be achieved by using high performance polymer composites reinforced with carbon nanotubes, expanded graphite and graphite nanoplatelets having high electrical conductivity and large aspect ratio. This article provides a state-of-the-art review for the current development, manufacturing and structure-property relationship of polymer nanocomposites designed for bipolar plate applications. © 2011 The Royal Society of Chemistry. Source


Cai D.W.H.,California Institute of Technology | Quek T.Q.S.,Singapore University of Technology and Design | Tan C.W.,City University of Hong Kong | Low S.H.,California Institute of Technology
IEEE Transactions on Signal Processing | Year: 2012

This paper considers the max-min weighted signal-to-interference-plus-noise ratio (SINR) problem subject to multiple weighted-sum power constraints, where the weights can represent relative power costs of serving different users. First, we study the power control problem. We apply nonlinear Perron-Frobenius theory to derive closed-form expressions for the optimal value and solution and an iterative algorithm which converges geometrically fast to the optimal solution. Then, we use the structure of the closed-form solution to show that the problem can be decoupled into subproblems each involving only one power constraint. Next, we study the multiple-input-single-output (MISO) transmit beamforming and power control problem. We use uplink-downlink duality to show that this problem can be decoupled into subproblems each involving only one power constraint. We apply this decoupling result to derive an iterative subgradient projection algorithm for the problem. © 1991-2012 IEEE. Source


Yuan X.,Chinese University of Hong Kong | Ping L.,City University of Hong Kong
IEEE Transactions on Signal Processing | Year: 2012

We propose a low-complexity dual-diagonal (DD-) linear-minimum-mean-square- error (LMMSE) channel estimation algorithm for orthogonal frequency-division multiplexing (OFDM) systems involving iterative channel estimation and signal detection. Computational complexity and mean-square-error (MSE) analysis are presented to evaluate the efficiency of the proposed algorithm. A closed-form expression is derived for the asymptotic MSE of the DD-LMMSE channel estimator. Both analysis and numerical results show that DD-LMMSE performs close to the well-known LMMSE estimator with much lower complexity. © 1991-2012 IEEE. Source


Sorooshyari S.,Bell LaboratoriesAlcatel Lucent | Tan C.W.,City University of Hong Kong | Chiang M.,Princeton University
IEEE/ACM Transactions on Networking | Year: 2012

The deployment of cognitive radio networks enables efficient spectrum sharing and opportunistic spectrum access. It also presents new challenges to the classical problem of interference management in wireless networks. This paper develops an axiomatic framework for power allocation in cognitive radio networks based on four goals: QoS protection to primary users, opportunism to secondary users, admissibility to secondary users, and autonomous operation by individual users. Two additional goals, licensing and versatility, which are desirable rather than essential, are also presented. A general class of Duo Priority Class Power Control (DPCPC) policies that satisfy such goals is introduced. Through theoretical analysis and simulation, it is shown that a specific interference-aware power-control algorithm reaches such goals. © 2012 IEEE. Source


Tao X.,City University of Hong Kong | Hui S.Y.R.,University of Hong Kong | Hui S.Y.R.,Imperial College London
IEEE Transactions on Industrial Electronics | Year: 2012

This paper presents a dynamic photoelectrothermal theory for light-emitting diode (LED) systems. In addition to photometric, electrical, and thermal aspects, this theory incorporates the time domain into the generalized equations. A dynamic model for a general LED system is developed for system analysis. This theory highlights the fact that the luminous output of an LED system will decrease with time from the initial operation to the steady state due to the rising temperature of the heat sink and the LED devices. The essential thermal time constants involved in the LED systems are explained. The time factor is critical in understanding how much the luminous output will decrease with time and is essential to the optimal designs of the LED systems that are operated continuously (e.g., general lighting) or momentarily (e.g., traffic lights). Experiments on several LED systems at different time frames have been conducted, and the practical measurements confirm the validity of this theory. © 2011 IEEE. Source


Zhang H.,City University of Hong Kong | Lewis F.L.,University of Texas at Arlington | Qu Z.,University of Central Florida
IEEE Transactions on Industrial Electronics | Year: 2012

This paper presents three design techniques for cooperative control of multiagent systems on directed graphs, namely, Lyapunov design, neural adaptive design, and linear quadratic regulator (LQR)-based optimal design. Using a carefully constructed Lyapunov equation for digraphs, it is shown that many results of cooperative control on undirected graphs or balanced digraphs can be extended to strongly connected digraphs. Neural adaptive control technique is adopted to solve the cooperative tracking problems of networked nonlinear systems with unknown dynamics and disturbances. Results for both first-order and high-order nonlinear systems are given. Two examples, i.e., cooperative tracking control of coupled Lagrangian systems and modified FitzHugh-Nagumo models, justify the feasibility of the proposed neural adaptive control technique. For cooperative tracking control of the general linear systems, which include integrator dynamics as special cases, it is shown that the control gain design can be decoupled from the topology of the graphs, by using the LQR-based optimal control technique. Moreover, the synchronization region is unbounded, which is a desired property of the controller. The proposed optimal control method is applied to cooperative tracking control of two-mass-spring systems, which are well-known models for vibration in many mechanical systems. © 2012 IEEE. Source


Kim J.-S.,City University of Hong Kong | Jain S.,University of Maine, United States
Environmental Research Letters | Year: 2011

Typhoons originating in the west Pacific are major contributors to climate-related risk over the Korean peninsula. The current perspective regarding improved characterization of climatic risk and the projected increases in the intensity, frequency, duration, and power dissipation of typhoons during the 21st century in the western North Pacific region motivated a reappraisal of historical trends in precipitation. In this study, trends in the magnitude and frequency of seasonal precipitation in the five major river basins in Korea are analyzed on the basis of a separation analysis, with recognition of moisture sources (typhoon and non-typhoon). Over the 1966-2007 period, typhoons accounted for 21-26% of seasonal precipitation, with the largest values in the Nakdong River Basin. Typhoon-related precipitation events have increased significantly over portions of Han, Nakdong, and Geum River Basins. Alongside broad patterns toward increases in the magnitude and frequency of precipitation, distinct patterns of trends in the upper and lower quartiles (corresponding to changes in extreme events) are evident. A trend typology - spatially resolved characterization of the combination of shifts in the upper and lower tails of the precipitation distribution - shows that a number of sub-basins have undergone significant changes in one or both of the tails of the precipitation distribution. This broader characterization of trends illuminates the relative role of causal climatic factors and an identification of 'hot spots' likely to experience high exposure to typhoon-related climatic extremes in the future. © 2011 IOP Publishing Ltd. Source


Tjong S.C.,City University of Hong Kong | Tjong S.C.,King Abdulaziz University
Journal of Nanoscience and Nanotechnology | Year: 2014

Graphene with extraordinary high elastic modulus and excellent electrical conductivity has good prospects for use as the filler material for fabricating novel polymer composites designed for electrostatic discharge and EMI shielding protection, field emission, gas sensor, and fuel cell applications. Large amounts of graphene oxide (GO) can be obtained by wet chemical oxidation of graphite into a mixture of concentrated sulfuric acid, sodium nitrate and potassium permanganate. Accordingly, carbon atoms in the basal plane and edges of GO are decorated with oxygenated functional groups, forming an electrical insulator. To restore electrical conductivity, chemical reduction or thermal annealing is needed to eliminate oxygenated groups of GO. However, such treatments induce internal defects and remove oxygenated atoms of GO partially. The remnant-oxygenated groups affect electrical conductivity of graphene greatly. Nevertheless, reduced graphene oxide and thermally reduced graphene oxide are sufficiently conductive to form polymer nanocomposites at very low percolation threshold. This review provides the fundamentals and state-of-the-art developments in the fabrication methods and electrical property characterizations as well as the applications of novel graphene/polymer nanocomposites. Particular attention is paid to their processing- structuralelectrical property relationships. © 2014 American Scientific Publishers. Source


Gao L.,Chinese University of Hong Kong | Huang J.,Chinese University of Hong Kong | Chen Y.-J.,University of California at Berkeley | Shou B.,City University of Hong Kong
IEEE Journal on Selected Areas in Communications | Year: 2013

Providing proper economic incentives to all parties involved is essential for the success of dynamic spectrum access. Market-driven secondary spectrum trading is an effective way to achieve this goal, where primary spectrum owners (POs) temporarily lease their licensed spectrum bands to unlicensed secondary users (SUs). In this paper, we consider the short-term secondary spectrum trading between one PO (seller) and multiple SUs (buyers) in a hybrid spectrum market with both guaranteed contracts (futures market) and spot transactions (spot market). In particular, we focus on the PO's expected profit maximization under revvstochastic network information. The optimal solution consists of (i) a policy that maximizes the ex-ante expected profit based on the distribution of network information, and (ii) a selling mechanism that determines the real-time allocation and charging based on the realized network information and the derived policy. We study the optimal solution systematically under both information symmetry and asymmetry, depending on whether the PO can observe the SUs' realized private information. Under information symmetry, we show that the optimal solution can be achieved by a perfect price discrimination mechanism, which maximizes both the PO's expected profit (optimality) and the social welfare (efficiency). Under information asymmetry, we propose an integrated contract and auction design-ContrAuction-to elicit SUs' private information effectively. We derive analytically the optimal ContrAuction mechanisms that maximize the PO's expected profit with and without the constraint of efficiency, and characterize systematically the tradeoff between the PO's profit and the social welfare. keywords Contract, Auction, Secondary Spectrum Market © 1983-2012 IEEE. Source


Chui W.H.,University of Hong Kong | Chan H.C.,City University of Hong Kong
Child Abuse and Neglect | Year: 2013

Objective: Macau is a Special Administrative Region (SAR) of China with over 95% of the population is of Chinese descent. Research on school bullying using Macanese samples is virtually nonexistent. Thus, this study is among the first to sample this population by exploring the association between bullying perpetration and victimization, and the level of self-control among a group of school-aged Macanese adolescents. Methods: A total of 365 participants, aged between 10 and 17 years, from two male-only schools (a boarding and a non-boarding schools) in Macau are surveyed. The Illinois Bully Scale (Espelage & Holt, 2001) and Self-Control Scale (Grasmick, Tittle, Bursik, & Arneklev, 1993) are used to measure the participants bullying behaviors and self-control level, respectively. Results: Overall finding indicates that bullying perpetration is negatively associated with the participants' level of self-control. Conclusion: These findings provide further support for the importance of self-control in bullying perpetration. Implications of the findings are offered by way to increase the youngsters' level of self-control in order to reduce their propensity to engage in bullying perpetration at school. © 2012 Elsevier Ltd. Source


Zhang H.,University of Electronic Science and Technology of China | Zhong H.,University of Electronic Science and Technology of China | Dang C.,City University of Hong Kong
IEEE Transactions on Fuzzy Systems | Year: 2012

This paper is concerned with the problem of delay-dependent H∞ filter design for a class of discrete-time nonlinear interconnected system with time-varying delays via the Takagi-Sugeno (T-S) fuzzy model. The T-S fuzzy model consists of N time-delay T-S fuzzy subsystems, and a decentralized H∞ filter is designed for each subsystem. Based on the delay-dependent piecewise Lyapunov-Krasovskii functional (DDPLKF) and with an improved free-weighting matrix technique, the delay-dependent stability and a prescribed H∞ performance index are guaranteed for the overall filtering error system. A sufficient condition for the existence of such a filter is established by using linear matrix inequalities (LMIs) that are numerically feasible. Two numerical examples are given to demonstrate the effectiveness and advantage of the proposed approach. © 2012 IEEE. Source


Zhang G.,Central South University | Li H.-X.,City University of Hong Kong
IEEE Transactions on Fuzzy Systems | Year: 2012

A novel inference configuration is proposed to improve the computational efficiency and information loss in the probabilistic fuzzy inference process. The probabilistic inference and the fuzzy inference are unified in one operation based on the continuous form of the probabilistic fuzzy set. Besides the faster inference operation, it is able to produce fuzzy outputs in a complete probabilistic distribution that in turn will provide information about the approximation bound. The computational analyses of six different fuzzy systems demonstrate the inference efficiency of the proposed method. Its effectiveness can be further demonstrated on the application to modeling of an industrial curing process. The robust modeling performance discloses its potential in process modeling under complex environment. © 2012 IEEE. Source


Wu H.-N.,Beihang University | Wang J.-W.,Beihang University | Li H.-X.,City University of Hong Kong
IEEE Transactions on Fuzzy Systems | Year: 2012

This paper deals with the exponential stabilization problem for a class of nonlinear spatially distributed processes that are modeled by semilinear parabolic partial differential equations (PDEs), for which a finite number of actuators are used. A fuzzy control design methodology is developed for these systems by combining the PDE theory and the Takagi-Sugeno (T-S) fuzzy-model-based control technique. Initially, a T-S fuzzy parabolic PDE model is proposed to accurately represent a semilinear parabolic PDE system. Then, based on the T-S fuzzy model, a Lyapunov technique is used to design a continuous fuzzy state feedback controller such that the closed-loop PDE system is exponentially stable with a given decay rate. The stabilization condition is presented in terms of a set of spatial differential linear matrix inequalities (SDLMIs). Furthermore, a recursive algorithm is presented to solve the SDLMIs via the existing linear matrix inequality optimization techniques. Finally, numerical simulations on the temperature profile control of a catalytic rod are given to verify the effectiveness of the proposed design method. © 2012 IEEE. Source


Chen H.,Harbin Institute of Technology | Sun D.,City University of Hong Kong
IEEE Transactions on Robotics | Year: 2012

Significant demand for both accuracy and productivity in batch manipulation of microparticles highlights the need to develop an automatic arraying approach to placing groups of particles into a predefined array with right pairs. This paper presents our latest effort to achieve this objective using integrated robotics and holographic optical tweezers technologies, where holographic optical tweezers function as special robot end-effectors to manipulate the microparticles. Based on the physical dynamics of trapping, a potential-field-based controller is developed to drive every pair of particles to the assigned array, while preventing collisions between particles. The significance of the proposed controller lies in the capability of driving two groups of particles into a common array in right pair and controlling the interdistances between the particles in pairs. Experiments are performed to demonstrate the effectiveness of the proposed approach. © 2012 IEEE. Source


Shen G.,Soochow University of China | Zukerman M.,City University of Hong Kong
IEEE Communications Magazine | Year: 2012

Traditional ITU-T fixed frequency grid-based optical transport networks suffer several drawbacks such as low fiber spectral efficiency, difficulty in supporting large-bandwidth super-channels, and inflexibility in network bandwidth reconfiguration and modification. To overcome these drawbacks, a new-generation optical transport network based on the concepts of agile spectrum operation and elastic bandwidth allocation has been recently proposed and is receiving increasing attention. This new-generation network is called coherent optical orthogonal frequency-division multiplexing (CO-OFDM) optical transport network. It employs the promising CO-OFDM transmission technique and the new-generation bandwidth-variable ROADMs that use the coherent detection capability of the CO-OFDM transmission for optical channel filtering. The CO-OFDM optical transport network is characterized by arbitrarily assigning center frequency and bandwidth of an optical channel, thereby providing flexibility in network design and operation and achieving efficient fiber spectrum utilization. Despite the increasing attention and considerable progress, there are still many outstanding issues regarding the implementation of CO-OFDM optical transport networks. This article reviews the literature on the architectures of the CO-OFDM optical transport network and discusses key issues, particularly involving network control plane, lightpath routing and spectrum assignment, impact of channel modulation format and optical reach, subwavelength traffic grooming, network survivability, and network reconfiguration. © 1979-2012 IEEE. Source


Wang J.,City University of Hong Kong | Gutierrez M.,Colorado School of Mines
Geotechnique | Year: 2010

This paper presents a study of the micromechanics of granular materials as affected by the direct shear test scale using the discrete element method (DEM). Parametric studies were conducted to investigate the effects of specimen length and height scales (in relation to the particle size) on the bulk material shear strength and shear banding behaviour in the direct shear test. A mesh-free strain calculation method previously developed by the authors was used to capture and visualise the evolution of strain localisation inside the direct shear box. Simulation results show that the maximum shear strength measured at the model boundaries increases with decreasing specimen length scale and increasing specimen height scale. Micromechanics-based analysis indicates that the local and global aspects of fabric change and failure are the major mechanisms responsible for the specimen scale effect. Global failure along the primary shear band prevails when the specimen length scale and length to height aspect ratio are small, while progressive failure becomes more likely when the specimen length scale and aspect ratio become larger. Further quantifications of the specimen scale effects on the macroscopic behaviour of granular materials rely on the fundamental understanding of quantitative relationships between material fabric, anisotropy and bulk strength. Source


Liu X.,Southwest University for Nationalities | Dang C.,City University of Hong Kong
IEEE Transactions on Automatic Control | Year: 2011

This technical note addresses the stability problem of delayed positive switched linear systems whose subsystems are all positive. Both discrete-time systems and continuous-time systems are studied. In our analysis, the delays in systems can be unbounded. Under certain conditions, several stability results are established by constructing a sequence of functions that are positive, monotonically decreasing, and convergent to zero as time tends to infinity (additionally continuous for continuous-time systems). It turns out that these functions can serve as an upper bound of the systems' trajectories starting from a particular region. Finally, a numerical example is presented to illustrate the obtained results. © 2011 IEEE. Source


Wang Y.-M.,Fuzhou University | Chin K.-S.,City University of Hong Kong
Information Sciences | Year: 2011

Quality function deployment (QFD) is a planning tool used in new product development and quality management. It aims at achieving maximum customer satisfaction by listening to the voice of customers. To implement QFD, customer requirements (CRs) should be identified and assessed first. The current paper proposes a linear goal programming (LGP) approach to assess the relative importance weights of CRs. The LGP approach enables customers to express their preferences on the relative importance weights of CRs in their preferred or familiar formats, which may differ from one customer to another but have no need to be transformed into the same format, thus avoiding information loss or distortion. A numerical example is tested with the LGP approach to demonstrate its validity, effectiveness and potential applications in QFD practice. © 2011 Elsevier Inc. All rights reserved. Source


Dai L.,City University of Hong Kong
IEEE Journal on Selected Areas in Communications | Year: 2011

It has been long believed that the distributed antenna system (DAS) has great potentials for capacity improvement compared to the traditional cellular system with co-located base-station antennas. Intuitively, the distributed characteristic of antennas provides a much more efficient utilization of spatial resources. It, however, also significantly complicates the channel modeling and system analysis. Despite an increasing amount of academic attention and industrial interest, how to characterize the capacity advantages of the DAS in the multiuser scenario remains largely unknown. In this paper, we present a comparative study on the uplink ergodic sum capacity with multiple base-station antennas either co-located or uniformly distributed within a given area. We demonstrate that under the same consumption of transmission power, enormous gains can be achieved by the distributed antenna layout thanks to 1) reduced minimum access distance of each user; and 2) enhanced channel fluctuations which provide a significant boost to the sum capacity when the channel state information is available at both the transmitter and the receiver sides. We further apply the analysis to a cellular system with full cooperation among base stations. The comparison verifies that the DAS yields a much higher sum capacity, and capacity gains increase with the number of base-station antennas per cell. © 2011 IEEE. Source


Yu W.,Nanjing Southeast University | Yu W.,University of Western Sydney | Zheng W.X.,University of Western Sydney | Chen G.,City University of Hong Kong | And 2 more authors.
Automatica | Year: 2011

This paper studies second-order consensus in multi-agent dynamical systems with sampled position data. A distributed linear consensus protocol with second-order dynamics is designed, where both the current and some sampled past position data are utilized. It is found that second-order consensus in such a multi-agent system cannot be reached without any sampled position data under the given protocol while it can be achieved by appropriately choosing the sampling period. A necessary and sufficient condition for reaching consensus of the system in this setting is established, based on which consensus regions are then characterized. It is shown that if all the eigenvalues of the Laplacian matrix are real, then second-order consensus in the multi-agent system can be reached for any sampling period except at some critical points depending on the spectrum of the Laplacian matrix. However, if there exists at least one eigenvalue of the Laplacian matrix with a nonzero imaginary part, second-order consensus cannot be reached for sufficiently small or sufficiently large sampling periods. In such cases, one nevertheless may be able to find some disconnected stable consensus regions determined by choosing appropriate sampling periods. Finally, simulation examples are given to verify and illustrate the theoretical analysis. © 2011 Elsevier Ltd. All rights reserved. Source


Qian Y.,Shanxi University | Liang J.,Shanxi University | Wu W.-Z.Z.,Zhejiang Ocean University | Dang C.,City University of Hong Kong
IEEE Transactions on Fuzzy Systems | Year: 2011

Zadehs seminal work in theory of fuzzy-information granulation in human reasoning is inspired by the ways in which humans granulate information and reason with it. This has led to an interesting research topic: granular computing (GrC). Although many excellent research contributions have been made, there remains an important issue to be addressed: What is the essence of measuring a fuzzy-information granularity of a fuzzy-granular structure? What is needed to answer this question is an axiomatic constraint with a partial-order relation that is defined in terms of the size of each fuzzy-information granule from a fuzzy-binary granular structure. This viewpoint is demonstrated for fuzzy-binary granular structure, which is called the binary GrC model by Lin. We study this viewpoint from from five aspects in this study, which are fuzzy BINARY-granular-structure operators, partial-order relations, measures for fuzzy-information granularity, an axiomatic approach to fuzzy-information granularity, and fuzzy-information entropies. © 2010 IEEE. Source


Niu Y.,East China University of Science and Technology | Ho D.W.C.,City University of Hong Kong | Ho D.W.C.,Nanjing University of Science and Technology
Automatica | Year: 2014

A stabilizing controller designed without considering quantization may not be effectively implemented for the systems with quantized information due to quantization errors. Hence, an interesting issue is how to design the quantizer such that the desired system performance can be still attained by the above controller. In this work, a new control strategy with on-line updating the quantizer's parameter is proposed. This scheme may ensure the controlled system to attain the same dynamic performance, H→ disturbance attenuation level, as the one without signal quantization. A practical adjusting rule on quantizer's parameter is proposed such that the state-dependent parameter is available on both sides of encoder/decoder. Finally, some numerical examples have been provided to illustrate the present control scheme. © 2014 Elsevier Ltd. Source


Dou F.F.,University of Electronic Science and Technology of China | Hon Y.C.,City University of Hong Kong
Engineering Analysis with Boundary Elements | Year: 2014

Based on kernel-based approximation technique, we devise in this paper an efficient and accurate numerical scheme for solving a backward problem of time-fractional diffusion equation (BTFDE). The kernels used in the approximation are the fundamental solutions of the time-fractional diffusion equation which can be expressed in terms of the M-Wright functions. To stably and accurately solve the resultant highly ill-conditioned system of equations, we successfully combine the standard Tikhonov regularization technique and the L-curve method to obtain an optimal choice of the regularization parameter and the location of source points. Several 1D and 2D numerical examples are constructed to demonstrate the superior accuracy and efficiency of the proposed method for solving both the classical backward heat conduction problem (BHCP) and the BTFDE. © 2013 Elsevier Ltd. All rights reserved. Source


Cheung R.,University of South Australia | Vogel D.,City University of Hong Kong
Computers and Education | Year: 2013

Collaborative technologies support group work in project-based environments. In this study, we enhance the technology acceptance model to explain the factors that influence the acceptance of Google Applications for collaborative learning. The enhanced model was empirically evaluated using survey data collected from 136 students enrolled in a full-time degree program that used Google Applications to support project work. According to the research results, determinants of the technology acceptance model are the major factors influencing the adoption of the technology. In addition, the subjective norm represented by peers is found to significantly moderate the relationship between attitude and intention toward the technology. However, our results do not show a significant effect of subjective norms represented by instructors and mass media on students' intentions to use the technology. The ability to share information in the collaborative learning environment is found to influence intention and behavior toward the Google Applications platform. © 2012 Elsevier Ltd. All rights reserved. Source


Niu Y.,East China University of Science and Technology | Ho D.W.C.,City University of Hong Kong
Journal of the Franklin Institute | Year: 2012

This paper considers the problem of sliding mode control for discrete-time stochastic systems with parameter uncertainties and state-dependent noise perturbation. An integral-like sliding surface is chosen and a discrete-time sliding mode controller is designed. The key feature in this work is that both the reachability of the quasi-sliding mode and the stability of system states are simultaneously analyzed, due to the existence of state-dependent noise perturbation. By utilizing an Lyapunov function involving system states and sliding mode variables, the sufficient condition for reachability is obtained. Finally, numerical simulation results are provided. © 2011 The Franklin Institute. Published by Elsevier Ltd. All rights reserved. Source


Yang K.,Soochow University of China | Zhang S.,Soochow University of China | Zhang G.,Beijing University of Chemical Technology | Sun X.,Beijing University of Chemical Technology | And 2 more authors.
Nano Letters | Year: 2010

Although biomedical applications of carbon nanotubes have been intensively studied in recent years, its sister, graphene, has been rarely explored in biomedicine. In this work, for the first time we study the in vivo behaviors of nanographene sheets (NGS) with polyethylene glycol (PEG) coating by a fluorescent labeling method. In vivo fluorescence imaging reveals surprisingly high tumor uptake of NGS in several xenograft tumor mouse models. Distinctive from PEGylated carbon nanotubes, PEGylated NGS shows several interesting in vivo behaviors including highly efficient tumor passive targeting and relatively low retention in reticuloendothelial systems. We then utilize the strong optical absorbance of NGS in the near-infrared (NIR) region for in vivo photothermal therapy, achieving ultraefficient tumor ablation after intravenous administration of NGS and low-power NIR laser irradiation on the tumor. Furthermore, no obvious side effect of PEGylated NGS is noted for the injected mice by histology, blood chemistry, and complete blood panel analysis in our pilot toxicity study. Although a lot more efforts are required to further understand the in vivo behaviors and the long-term toxicology of this new type of nanomaterials, our work is the first success of using carbon nanomaterials for efficient in vivo photothermal therapy by intravenous administration and suggests the great promise of graphene in biomedical applications, such as cancer treatment. © 2010 American Chemical Society. Source


Zhong W.,City University of Hong Kong | Lee C.K.,Hong Kong Polytechnic University | Ron Hui S.Y.,University of Hong Kong | Ron Hui S.Y.,Imperial College London
IEEE Transactions on Industrial Electronics | Year: 2013

In this paper, we present a brief overview of historical developments of wireless power and an analysis on the use of Tesla's resonators in domino forms for wireless power transfer. Relay resonators are spaced between the transmitter and receiver coils with the objectives of maximizing energy efficiency and increasing the overall transmission distance between the power source and the load. Analytical expressions for the optimal load and maximum efficiency at resonance frequency are derived. These equations are verified with practical measurements obtained from both coaxial and noncoaxial domino resonator systems. To avoid the use of high operating frequency for wireless power transfer in previous related research, the technique presented here can be used at submegahertz operation so as to minimize the power loss in both the power supply and the output stage. We demonstrated both theoretically and practically that unequal spacing for the coaxial straight domino systems has better efficiency performance than the equal-spacing method. Also, the flexibility of using resonators in various domino forms is demonstrated. © 2012 IEEE. Source


Cai S.,Carleton University | Jun M.,New Mexico State University | Yang Z.,City University of Hong Kong
Journal of Operations Management | Year: 2010

This study investigates the effects of Chinese companies' institutional environment on the development of trust and information integration between buyers and suppliers. Three aspects of China's institutional environment are salient: legal protection, government support, and the importance of guanxi (interpersonal relationships). This study uses structural equation modeling to analyze data collected from 398 Chinese manufacturing companies. Government support and importance of guanxi significantly affect trust, which subsequently influences two elements of information integration, namely, information sharing and collaborative planning. Furthermore, the importance of guanxi has a direct, positive impact on information sharing, and government support has a direct, positive effect on both information sharing and collaborative planning. © 2009 Elsevier B.V. Source


Au S.-K.,City University of Hong Kong
Mechanical Systems and Signal Processing | Year: 2011

Assembling (or 'gluing') mode shapes identified from multiple setups is a problem frequently encountered in full-scale modal tests that cover a large number of locations with a limited number of sensors. Mode shapes identified in individual setups can have different sense and scaling. Depending on the number of reference degrees-of-freedom (dofs) and the quality of identified mode shapes, implementation issues can arise when determining the optimal mode shape that compromise among different setups. This paper presents a theory with an automated procedure for determining the optimal mode shape that fits the mode shapes identified from multiple setups in a least square sense. The measure-of-fit function is defined as the squared difference between the theoretical and identified mode shapes suitably oriented and scaled to the same norm. Due to the nonlinear nature of the objective function, the optimal mode shape cannot be determined analytically as in conventional least square problems. A fast iterative procedure is proposed, making use of partially optimal solutions that can be derived analytically. The proposed method can be implemented in an automated manner without the need to select the reference dof or setup for scaling purpose. It is applied to assembling mode shapes identified from ambient vibration tests of two full-scale structures. © 2010 Elsevier Ltd. All rights reserved. Source


Chen Z.-Z.,Tokyo Denki University | Wang L.,City University of Hong Kong
IEEE/ACM Transactions on Computational Biology and Bioinformatics | Year: 2011

We present two parameterized algorithms for the closest string problem. The first runs in O(nL + nd · 17.97 d) time for DNA strings and in O(nL + nd · 61.86 d) time for protein strings, where n is the number of input strings, L is the length of each input string, and d is the given upper bound on the number of mismatches between the center string and each input string. The second runs in O(nL + nd · 13.92 d) time for DNA strings and in O(nL + nd · 47.21 d) time for protein strings. We then extend the first algorithm to a new parameterized algorithm for the closest substring problem that runs in O((n-1)m 2(L + d · 17.97 d · m ⌊log2(d+1)⌋)) time for DNA strings and in O((n-1)m 2(L + d · 61.86 d · m ⌊log2(d+1)⌋)) time for protein strings, where n is the number of input strings, L is the length of the center substring, L - 1 + m is the maximum length of a single input string, and d is the given upper bound on the number of mismatches between the center substring and at least one substring of each input string. All the algorithms significantly improve the previous bests. To verify experimentally the theoretical improvements in the time complexity, we implement our algorithm in C and apply the resulting program to the planted (L, d)-motif problem proposed by Pevzner and Sze in 2000. We compare our program with the previously best exact program for the problem, namely PMSPrune (designed by Davila et al. in 2007). Our experimental data show that our program runs faster for practical cases and also for several challenging cases. Our algorithm uses less memory too. © 2006 IEEE. Source


Prasarnphanich P.,Chulalongkorn University | Wagner C.,City University of Hong Kong
IEEE Transactions on Industrial Electronics | Year: 2011

This paper investigates the sustainability of a type of digital ecosystem, namely, knowledge-sharing communities built on the wiki model. Sustainability is hypothesized to result from the participation of contributors with varying levels of resources and interests. The differences in resources and interests, according to the critical-mass theory, enable such communities to overcome typical start-up and growth problems. This paper describes a preliminary empirical test of the critical-mass theory in this context, with Wikipedia as a test case that demonstrates sustainability as well as resource and interest heterogeneity, based on a survey of 78 Wikipedians. The characteristic patterns of success exhibited in Wikipedia are expected to inform the management of other wiki-based information assets. © 2009 IEEE. Source


Liang J.,Shanxi University | Wang F.,Shanxi University | Dang C.,City University of Hong Kong | Qian Y.,Shanxi University
IEEE Transactions on Knowledge and Data Engineering | Year: 2014

Many real data increase dynamically in size. This phenomenon occurs in several fields including economics, population studies, and medical research. As an effective and efficient mechanism to deal with such data, incremental technique has been proposed in the literature and attracted much attention, which stimulates the result in this paper. When a group of objects are added to a decision table, we first introduce incremental mechanisms for three representative information entropies and then develop a group incremental rough feature selection algorithm based on information entropy. When multiple objects are added to a decision table, the algorithm aims to find the new feature subset in a much shorter time. Experiments have been carried out on eight UCI data sets and the experimental results show that the algorithm is effective and efficient. © 1989-2012 IEEE. Source


Chan C.T.W.,City University of Hong Kong
Construction Management and Economics | Year: 2012

Estimation is the first step in the project development process. Information technology provides an efficient platform for estimators to obtain quotations and specifications for their bid estimates. However, in practice, project overhead estimation relies heavily on the professional judgement and intuition of the estimators. This reduces the overall accuracy and reliability of the bid and a better understanding of the factors affecting project overheads is fundamental before any improved estimating methods can be devised. Unfortunately, the published literature on this topic is very limited. Using exploratory factor analysis, we aim to bridge the current knowledge gap by highlighting the principal factors affecting project overheads. Questionnaires detailing 27 variables were sent to quantity surveying managers of large contractors in Hong Kong. Seventy-nine valid responses were analysed by exploratory factor analysis. From the results, eight factors were extracted with their latent properties identified with reference to the expert opinions collected from telephone interviews. The findings clarify some misconceptions about the factors affecting project overheads and provide useful evidence for practitioners and researchers to understand project overheads. Estimators who address the identified factors when assessing future project overhead costs can improve the accuracy of their cost estimates and project budgets. © 2012 Copyright Taylor and Francis Group, LLC. Source


Yau Y.,City University of Hong Kong
Journal of Urban Planning and Development | Year: 2012

As the residential building stocks in most developed cities are getting older, there is an urgent call for the management of the stocks in a more sustainable manner. Although redevelopment can completely revamp the quality of housing, this approach is far from perfect because of its negative social and environmental effects. In fact, timely maintenance can achieve sustainable housing stock management in theory. However, in a high-rise setting, a large number of homeowners are involved in the maintenance of communal building elements. Conflicts occur because of the divergent interests of different stakeholders in deciding on the way forward for a maintenance project, eventually holding the work back. Against this background, this study explores the relative importance of different criteria for decision making in the maintenance of multiowned residential buildings in Hong Kong. Through a literature review, a set of decision-making criteria were identified. The weightings of these criteria perceived by homeowners were evaluated using the nonstructural fuzzy decision support system. The results of the analysis showed that cost affordability of maintenance work and existing building conditions generally dominated the decision-making process. Practical implications for urban managers and public administrators in formulating the strategies to promote housing maintenance then follow. © 2012 American Society of Civil Engineers. Source


Kuo W.,City University of Hong Kong | Zhu X.,University of Tennessee at Knoxville
IEEE Transactions on Reliability | Year: 2012

To identify the critical components or sets of components in a system, various importance measures have been proposed with different probabilistic perspectives and applications. Many of these importance measures are actually related to each other in some ways. This paper summarizes the importance measures in reliability, and presents relations and comparisons among them, focusing on their interrelations to the B-importance, the dominant relations among them, the dual relations, their performances in typical systems, and their computations. The early versions of the importance measures are for binary coherent systems, while the recent research is not limited to this type of system. This paper investigates the extensions of importance measures in noncoherent systems, multistate systems, continuum systems, and repairable systems. © 2012 IEEE. Source


Huang F.,Chinese Academy of Sciences | Wang Y.,Chinese Academy of Sciences | Yang T.,City University of Hong Kong
Archive for Rational Mechanics and Analysis | Year: 2012

We study the vanishing viscosity limit of the compressible Navier-Stokes equations to the Riemann solution of the Euler equations that consists of the superposition of a shock wave and a rarefaction wave. In particular, it is shown that there exists a family of smooth solutions to the compressible Navier-Stokes equations that converges to the Riemann solution away from the initial and shock layers at a rate in terms of the viscosity and the heat conductivity coefficients. This gives the first mathematical justification of this limit for the Navier-Stokes equations to the Riemann solution that contains these two typical nonlinear hyperbolic waves. © 2011 Springer-Verlag. Source


He Y.,Huazhong University of Science and Technology | Lai K.K.,City University of Hong Kong
International Journal of Production Economics | Year: 2012

This study builds a conceptual model to describe the relationships among operational integration and strategic integration of supply chain, product-based and customer action-based service provided by industrial manufacturers, and firm performance. Using sample data from Chinese equipment manufacturers, this study finds that operational integration of supply chain has positive direct effect on product-based service, while strategic integration has positive direct effect on customer action-based service. Furthermore, product-based service is the basic transformation strategy for industrial manufacturing companies and it has not only positive direct effect but also indirect effect through customer action-based service on firm performance. © 2011 Elsevier B.V. All Rights Reserved. Source


Xu C.,Zhengzhou University of Light Industry | Arancon R.A.D.,University of Cordoba, Spain | Arancon R.A.D.,City University of Hong Kong | Labidi J.,University of the Basque Country | Luque R.,University of Cordoba, Spain
Chemical Society Reviews | Year: 2014

Research on lignin deconstruction has recently become the center of interest for scientists and companies worldwide, racing towards harvesting fossil-fuel like aromatic compounds which are so durably put together by plants as products of millions of years of evolution. The natural complexity and high stability of lignin bonds (also as an evolutionary adaptation by plants) makes lignin depolymerization a highly challenging task. Several efforts have been directed towards a more profound understanding of the structure and composition of lignin in order to devise pathways to break down the biopolymer into useful compounds. The present contribution aims to provide an overview of key advances in the field of lignin depolymerisation. Protocols and technologies will be discussed as well as critically evaluated in terms of possibilities and potential for further industrial implementation. © the Partner Organisations 2014. Source


Cheung M.,City University of Hong Kong
Journal of Pragmatics | Year: 2011

In today's knowledge-based global economy, understanding the similarities and differences in persuasive messages across languages is essential to effective communication. This study presents a comparison of sales letters written in two languages, namely, Chinese and English, using Halliday's (1994) notion of Theme. Theme is taken as the point of departure for writers' attempts to project their perceptions of the reality of the experiential field onto their readers. The concept of Rheme then provides room for the further development or elaboration of Theme. Of the 7664 sales texts collected, 160 (80 in Chinese and 80 in English) are randomly selected for detailed analysis using the independent conjoinable clause complex as the unit of analysis. The differences identified can be attributed to differences in both cultural expectations and grammatical structures. © 2010. Source


Du K.,Xiamen University | Du K.,City University of Hong Kong
Journal of Computational Physics | Year: 2011

We consider electromagnetic scattering from two-dimensional (2D) overfilled cavities embedded in an infinite ground plane. The unbounded computational domain is truncated to a bounded one by using a transparent boundary condition (TBC) proposed on a semi-ellipse. For overfilled rectangular cavities with homogeneous media, another TBC is introduced on the cavity apertures, which produces a smaller computational domain. The existence and uniqueness of the solutions of the variational formulations for the transverse magnetic and transverse electric polarizations are established. In the exterior domain, the 2D scattering problem is solved in the elliptic coordinate system using the Mathieu functions. In the interior domain, the problem is solved by a finite element method. Numerical experiments show the efficiency and accuracy of the new boundary conditions. © 2011 Elsevier Inc. Source


Sing C.Y.,City University of Hong Kong | Wong W.S.,The Hong Kong Institute of Education
Journal of American College Health | Year: 2011

Objective: This study examined the prevalence of insomnia and its psychosocial correlates among college students in Hong Kong. Participants: A total of 529 Hong Kong college students participated in the study. Methods: Participants completed a self-reported questionnaire that included the Pittsburgh Sleep Quality Index (PSQI), the Revised Life Orientation Test, the Perceived Stress Scale, and the Beck Depression Inventory, and questions about sociodemographic and lifestyle factors. A PSQI global score equal to or greater than 5 indicated insomnia. Results: Results indicated that 68.6% of the participants were insomniacs. Adjusted regression analyses revealed that optimism, stress, and depression significantly predicted insomnia (p .01). Conclusions: These results suggest that insomnia is very common among Hong Kong college students and associated with other psychosocial factors. This study provides preliminary data on sleep quality and risk factors for insomnia, which may be used to guide sleep hygiene promotion and intervention among college students. © 2010 Taylor & Francis Group, LLC. Source


Dou F.F.,University of Electronic Science and Technology of China | Hon Y.C.,City University of Hong Kong
Engineering Analysis with Boundary Elements | Year: 2012

We investigate in this paper a Cauchy problem for the time-fractional diffusion equation (TFDE). Based on the idea of kernel-based approximation, we construct an efficient numerical scheme for obtaining the solution of a Cauchy problem of TFDE. The use of M-Wright functions as the kernel functions for the approximation space allows us to express the solution in terms of M-Wright functions, whose numerical evaluation can be accurately achieved by applying the inverse Laplace transform technique. To handle the ill-posedness of the resultant coefficient matrix due to the noisy Cauchy data, we adapt the standard Tikhonov regularization technique with the L-curve method for obtaining the optimal regularization parameter to give a stable numerical reconstruction of the solution. Numerical results indicate the efficiency and effectiveness of the proposed scheme. © 2012 Elsevier Ltd. All rights reserved. Source


Li W.,City University of Hong Kong
Land Use Policy | Year: 2016

This paper aims to fill the void in the literature by answering the following research question: to what extent has the Chinese central government institutionalized public participation for addressing the challenge of agent control of local land use in China? Focusing on the stated purposes, specified actors, and installed mechanisms of public participation and government accountability, an institutional analysis was conducted on the national land use regulations and policies enacted between 1947 and 2012. It was found, without institutionalized input and surveillance from bottom-up by individual citizens and civil society organizations (CSOs), the top-down approaches remained ineffective and land use was mainly left for manipulation by local governments. The rural-urban dichotomy and lack of institutionalized public participation in land use decision-making have compromised equal economic and social opportunity for farmers, eroded public trust in local governments, and led to social unrest. Thus, the central government needs not only to directly control the discharge of discretionary power by local governments, but also to empower the public for holding the government accountable for land use decisions. © 2015 Elsevier Ltd. Source


Yue D.-W.,Dalian Maritime University | Zhang Q.T.,City University of Hong Kong
IEEE Transactions on Information Theory | Year: 2010

Optimal transmit/receive diversity (TRD) is one of the most important configurations for wireless multiple-input multiple-output (MIMO) systems, due to its good performance and ease of implementation. Though investigated intensively, the performance of optimal TRD in general correlated fading with cochannel interference is still not well understood. Since the optimal TRD's output instantaneous signal-to-interference-plus-noise ratio (SINR) is equal to the largest sample eigenvalue of a quadratic form involving signal and interference channel matrices, directly determining the probability density function (pdf) of this eigenvalue has been a prevailing approach in the literature. Given the nonlinearity involved in the quadratic form, however, finding such a pdf is not simple except for some special channel conditions. In this paper, we formulate the problem, in a totally different framework, as testing the positive-definiteness of a random matrix whereby the theory of matrix-variate distributions can be invoked to obtain exact solutions in terms of special functions. The solutions are very general including most of existing results as a special case and allowing for the correlation structures of both signal and interferers to be arbitrary at both transmitter and receiver ends. Numerical results are presented to validate the theoretical analysis. © 2006 IEEE. Source


Yates D.,University of Maryland University College | Wagner C.,City University of Hong Kong | Majchrzak A.,University of Southern California
Journal of the American Society for Information Science and Technology | Year: 2010

New Web 2.0 technologies such as wikis permit any organizational member of a virtual community of practice (CoP) to dynamically edit, integrate, and rewrite content (what we call knowledge shaping) as well as contribute personal knowledge. Previous research on factors that motivate contribution in virtual CoPs has focused exclusively on factors explaining why people contribute their personal knowledge, with no research focused on why people make the knowledge-shaping contributions (rewriting, integrating, and restructuring pages) which are possible with wikis. We hypothesize that factors that explain frequency of contribution will be different for those who shape from those who contribute only their personal knowledge. The results support our hypotheses. In addition, we find that shapers are not more likely to be managers or members of a community's core group who might typically serve in an administrator role, contrary to prior expectations. The implications of using Web 2.0 tools to encourage this shaping behavior are discussed. © 2009 ASIS&T. Source


In the context of the globalization and localization of business, it is becoming increasingly important to better understand the cross-linguistic persuasive communication conveyed through electronic media. This study compares 40 Chinese and 40 English direct-marketing sales e-mails. These 80 e-mails were randomly selected from a database of 7664 sales e-mails collected from 36 categories of recipients in Hong Kong over a six-month period. Based on a Cross-linguistic Socio-cultural Model proposed by the author, this study investigates the similarities and differences in the encoding of persuasive messages in the two corpora. It considers how far the similarities can be attributed to generic considerations, that is, to the contextual configuration of the field, mode, and tenor of the texts, as well as how far the differences can be attributed to the social and cultural contexts of those texts with regard to their audience, purpose, and content. Depending on the rhetorical goals the makers wish to achieve through these texts, the viewer-maker relationships they would like to establish, and the social and cultural contexts in which the texts unfold, the sales genre is likely to adapt in terms of its discourse strategy and textual features in today's marketplace, which is experiencing not only increased globalization, but also increased localization. © 2009 Elsevier B.V. All rights reserved. Source


We successfully proposed a newly corrected density functional theory plus Hubbard U parameter (DFT + U) based on partial core correction on the orbitals within norm-conserving lanthanide atomic pseudopotentials. A related and comprehensive investigation of native point defects in cerium oxides has also been performed as an examine by practice. © 2014 Taylor and Francis. Source


Zhao M.,Shandong University | Zhang R.,Beijing Computational Science Research Center | Zhang R.,City University of Hong Kong
Physical Review B - Condensed Matter and Materials Physics | Year: 2014

Silicon carbide and other group-IV binary materials with 1:1 stoichiometry are trivial semiconductors. Using first-principles calculations combined with a tight-binding model, we demonstrate two-dimensional (2D) silicon carbide materials (siligraphenes) with 1:3 and 3:1 stoichiometries are topological insulators (TIs) superior to graphene. Dirac cones and topologically nontrivial electronic structures are predicted in these binary honeycomb lattices. The band gaps opened at the Dirac points due to the spin-orbital coupling (SOC) are several orders of magnitude larger than the graphene value. Such interesting properties also exist in their analogs of other group-IV elements, such as g-GeC3, g-Ge3C, g-GeSi3, and g-Ge3Si. The TI states predicted in these unique lattices broaden the application field of group-IV binary materials and open the door to searching for 2D TIs with enhanced SOC. © 2014 American Physical Society. Source


Lam K.F.,City University of Hong Kong
Computers and Industrial Engineering | Year: 2015

In recent years, several mixed integer linear programming (MILP) models have been proposed for determining the most efficient decision making unit (DMU) in data envelopment analysis. However, most of these models do not determine the most efficient DMU directly; instead, they make use of other less related objectives. This paper introduces a new MILP model that has an objective similar to that of the super-efficiency model. Unlike previous models, the new model's objective is to directly discover the most efficient DMU. Similar to the super-efficiency model, the aim is to choose the most efficient DMU. However, unlike the super-efficiency model, which requires the solution of a linear programming problem for each DMU, the new model requires that only a single MILP problem be solved. Consequently, additional terms in the objective function and more constraints can be easily added to the new model. For example, decision makers can more easily incorporate a secondary objective such as adherence to a publicly stated preference or add assurance region constraints when determining the most efficient DMU. Furthermore, the proposed model is more accurate than two recently proposed models, as shown in two computational examples. © 2014 Elsevier Ltd. Source


This article addresses the free vibration analysis of a nonlinear panel coupled with extended cavity. In practice, the cavity length of a panel-cavity system is sometimes longer than the panel length. Therefore, this study examines the effect of cavity length on the natural frequency of a nonlinear panel coupled with extended cavity. The multi-level residue harmonic balance method, which was recently developed by the author and his research partners, is used to solve this nonlinear problem. The present harmonic balance solution agrees reasonably well with the results obtained from a previous classical solution and shows that the cavity length is a very important factor that significantly affects the panel vibration and should not be ignored in the modelling process. The natural frequency of a panel-cavity system is very sensitive to the cavity length and decreases significantly when the cavity is longer, due to its larger volume or weaker stiffness. Moreover, when the cavity is very long and its resonant frequencies are close to that of the panel, multiple frequency solutions are obtained. © 2015 Elsevier Ltd.All rights reserved. Source


Hao X.,Tongji University | Hao X.,Inner Mongolia University of Science and Technology | Zhai J.,Tongji University | Kong L.B.,Nanyang Technological University | Xu Z.,City University of Hong Kong
Progress in Materials Science | Year: 2014

Lead zirconate (PbZrO3 or PZ)-based antiferroelectric (AFE) materials, as a group of important electronic materials, have attracted increasing attention for their potential applications in high energy storage capacitors, micro-actuators, pyroelectric security sensors, cooling devices, and pulsed power generators and so on, because of their novel external electric field-induced phase switching behavior between AFE state and ferroelectric (FE) state. The performances of AFE materials are strongly dependent on the phase transformation process, which are mainly determined by the constitutions and the external field. For AFE thin/thick films, the electrical properties are also strongly dependent on their thickness, crystal orientation and the characteristics of electrode materials. Accordingly, various strategies have been employed to tailor the phase transformation behavior of AFE materials in order to improve their performances. Due to their relatively poor electrical strength (low breakdown fields), most PZ-based orthorhombic AFE ceramics are broken down before a critical switching field can be applied. As a consequence, the electric-field-induced transition between AFE and FE phase of only those AFE bulk ceramics, with compositions within tetragonal region near the AFE/FE morphotropic phase boundary (MPB), can be realized experimentally at room temperature. AFE materials with such compositions include (Pb,A)ZrO3 (A = Ba, Sr), (Pb1-3/2xLa x)(Zr1-yTiy)O 3 (PLZT x/(1-y)/y), (Pb0.97La0.02)(Zr,Sn,Ti) O3 (PLZST) and Pb0.99(Zr,Sn,Ti)0.98Nb 0.02O3 (PNZST). As compared to bulk ceramics, AFE thin and thick films always display better electric-field endurance ability. Consequently, room temperature electric-field-induced AFE-FE phase transition could be observed in the AFE thin/thick films with orthorhombic structures. Moreover, AFE films are more easily integrated with silicon technologies. Therefore, AFE thin/thick films have been a subject of numerous researches. This review serves to summarize the recent progress of PZ-based AFE materials, focusing on the external field (electric field, hydrostatic pressure and temperature) dependences of the AFE-FE phase transition, with a specific attention to the performances of AFE films for various potential applications, such as high energy storage, electric field induced strains, pyroelectric effect and electrocaloric effect. © 2014 Elsevier Ltd. All rights reserved. Source


Wang Y.,City University of Hong Kong
Computers and Geotechnics | Year: 2012

With the rapid development of computer technology and commonly available personal computers, Monte Carlo Simulation (MCS) is gaining popularity in reliability analysis due to its robustness and conceptual simplicity. MCS, however, does not offer insight into the effect of various uncertainties in the reliability analysis. It generally requires many repeated MCS runs to explore the sensitivity on uncertain variables. This paper presents a novel approach to the sensitivity study on uncertain variables in MCS without repeated MCS runs. The proposed approach makes use of the MCS samples that have been generated in the baseline case (i.e., MCS samples corresponding to the nominal set of statistical parameters and distribution type). The MCS samples in the baseline case are grouped by a Bayesian analysis and reassembled to "match" the new set of statistical parameters or distribution type of the uncertain parameter considered in the sensitivity study. Equations are derived for the Bayesian analysis and sample reassembling to obtain the desired sensitivity study results (e.g., failure probability and probability density function). The approach is illustrated through a slope stability problem, and the results are validated against those from repeated runs of MCS simulations. The proposed approach indicates that, by further exploring and properly utilizing the information generated from the MCS samples in the baseline case, it is possible and straightforward to obtain the sensitivity study results of interest. There is practically no additional computational cost, in terms of the number of MCS samples and simulation runs, for the sensitivity study, and a large number of sensitivity study cases can be performed rapidly. This is particularly beneficial when the operator in the MCS involves complex analyses, such as finite element models or tedious system analyses, and requires significant computational effort for each MCS sample. © 2012 Elsevier Ltd. Source


Song T.,Soochow University of China | Lee S.-T.,City University of Hong Kong | Sun B.,Soochow University of China
Journal of Materials Chemistry | Year: 2012

Organic/group IV nanomaterial-based solar cells attract wide research interest in the photovoltaic community because it can benefit from the advantages of both organic and group IV materials. Especially, hybrid composites of conjugated organic materials and nanostructured inorganic materials are potential candidates for cost-effective and efficient solar-energy-harvesting devices. This review highlights recent advances in organic photovoltaics (OPV) as well as organic-inorganic hybrid solar cells (HSCs) based on group IV nanomaterials, including nanostructured carbon and silicon materials which act as acceptors. The donor can be either small molecules or conjugated polymers. The carbon-based functional materials will vary from carbon nanotubes (CNTs) to new emerging graphene sheets, which do not include fullerene and its derivatives. The silicon nanostructures include free-standing silicon nanocrystals (NCs) and silicon nanowires (SiNWs). © 2012 The Royal Society of Chemistry. Source


Ke L.-L.,Beijing Jiaotong University | Wang Y.-S.,Beijing Jiaotong University | Yang J.,RMIT University | Kitipornchai S.,City University of Hong Kong
Journal of Sound and Vibration | Year: 2012

This paper develops a Mindlin microplate model based on the modified couple stress theory for the free vibration analysis of microplates. This non-classical plate model contains an internal material length scale parameter related to the material microstructures and is capable of interpreting the size effect that the classical Mindlin plate model is unable to describe. The higher-order governing equations of motion and boundary conditions are derived using the Hamilton principle. The p-version Ritz method is employed to determine the natural frequencies of the microplate with different boundary conditions. A detailed parametric study is conducted to study the influences of the length scale parameter, side-to-thickness ratio and aspect ratio on the free vibration characteristics of the microplate. It is found that the size effect is significant when the thickness of microplate is close to the material length scale parameter. © 2011 Elsevier Ltd. All rights reserved. Source


Wang Y.-M.,Fuzhou University | Chin K.-S.,City University of Hong Kong
Expert Systems with Applications | Year: 2011

Performance assessment often has to be conducted under uncertainty. This paper proposes a "fuzzy expected value approach" for data envelopment analysis (DEA) in which fuzzy inputs and fuzzy outputs are first weighted, respectively, and their expected values then used to measure the optimistic and pessimistic efficiencies of decision making units (DMUs) in fuzzy environments. The two efficiencies are finally geometrically averaged for the purposes of ranking and identifying the best performing DMU. The proposed fuzzy expected value approach and its resultant models are illustrated with three numerical examples, including the selection of a flexible manufacturing system (FMS). © 2011 Elsevier Ltd. All rights reserved. Source


Leung A.Y.T.,City University of Hong Kong
Computers and Structures | Year: 2011

We investigate the fractal properties on the distribution of natural frequencies of elastic structures. We use the multi-level-multi-scale dynamic substructure method so that we need only to eliminate a few nodes in advancing a fractal level. We shall give four numerical examples including the von Koch curves and the L-system. The natural frequencies and the dynamic power laws are presented. Example 4 has a fractal dimension that is a function of fractal level and has intermittence power laws discovered here for the first time. © 2010 Elsevier Ltd. All rights reserved. Source


Torabi M.,City University of Hong Kong | Aziz A.,Gonzaga University
International Communications in Heat and Mass Transfer | Year: 2012

This paper analytically investigates the thermal performance of convective-radiative T-shape fin with simultaneous variation of thermal conductivity, heat transfer coefficient and surface emissivity with temperature. Unlike some other fin studies, the sink temperatures for convection and radiation are assumed to be non-zero. This model is a more realistic representation of fins in actual engineering practice. The collection of graphs provided should facilitate design and performance evaluation of T-shaped fins. © 2012 Elsevier Ltd. Source


Torabi M.,City University of Hong Kong | Aziz A.,Gonzaga University
International Communications in Heat and Mass Transfer | Year: 2012

This article investigates entropy generation in an asymmetrically cooled hollow cylinder with temperature dependent thermal conductivity and internal heat generation. The inside surface of the cylinder is cooled by convection on its inside surface while the outside surface experiences simultaneous convective-radiative cooling. The thermal conductivity of the cylinder as well as the internal heat generation within the cylinder are linear functions of temperature, introducing two nonlinearities in the one-dimensional steady state heat conduction equation. A third nonlinearity arises due to radiative heat loss from the outside surface of the cylinder. The nonlinear system is solved analytically using the differential transformation method (DTM) to obtain the temperature distribution which is then used to compute local and total entropy generation rates in the cylinder. The accuracy of DTM is verified by comparing its predictions with the analytical solution for the case of constant thermal conductivity and constant internal heat generation. The local and total entropy generations depend on six dimensionless parameters: heat generation parameter Q, thermal conductivity parameter β, conduction-convection parameters Nc 1 and Nc 2, conduction-radiation parameter Nr, convection sink temperature δ and radiation sink temperature ζ. © 2012 Elsevier Ltd. Source


Ngan S.-C.,City University of Hong Kong
Expert Systems with Applications | Year: 2011

Fuzzy set theory, with its ability to capture and process uncertainties and vagueness inherent in subjective human reasoning, has been under continuous development since its introduction in the 1960s. Recently, the 2-tuple fuzzy linguistic computing has been proposed as a methodology to aggregate fuzzy opinions (Herrera & Martinez, 2000a, 2000b), for example, in the evaluation of new product development performance (Wang, 2009) and in customer satisfactory level survey analysis (Lin & Lee, 2009). The 2-tuple fuzzy linguistic approach has the advantage of avoiding information loss that can potentially occur when combining opinions of experts. Given the fuzzy ratings of the evaluators, the computation procedure used in both Wang (2009) and Lin and Lee (2009) returned a single crisp value as an output, representing the average judgment of those evaluators. In this article, we take an alternative view that the result of aggregating fuzzy ratings should be fuzzy itself, and therefore we further develop the 2-tuple fuzzy linguistic methodology so that its output is a fuzzy number describing the aggregation of opinions. We demonstrate the utility of the extended fuzzy linguistic computing methodology by applying it to two data sets: (i) the evaluation of a new product idea in a Taiwanese electronics manufacturing firm and (ii) the evaluation of the investment benefit of a proposed facility site. © 2011 Elsevier Ltd. All rights reserved. Source


Song K.,University of Electronic Science and Technology of China | Mo Y.,University of Electronic Science and Technology of China | Xue Q.,City University of Hong Kong | Fan Y.,University of Electronic Science and Technology of China
IEEE Transactions on Industrial Electronics | Year: 2014

Two new wideband four-way out-of-phase slotline power dividers are proposed in this paper. The half-wavelength slotlines are employed to construct the presented compact power dividers. Based on the proposed power-dividing circuit, a four-way power divider is implemented with compact size and simple structure. To obtain high isolation among the four output ports and good output impedance matching, another four-way out-of-phase slotline power divider with improved isolation performance is designed by introducing an air-bridge resistor and two slotlines with isolation resistors. The simulated and measured results of the proposed power dividers demonstrate reasonable performance of impedance matching, insertion loss, amplitude balancing, and isolation among the output ports. © 1982-2012 IEEE. Source


Differential electricity pricing was promulgated by China's central government to guide the development of high energy-consuming industries, which are significant for energy conservation. This paper examines the twists and turns of the policy implementation at the provincial level, and seeks to elucidate the difficulties in its implementation. Local governments, concerned that following the central directives would hurt local interests, have tried to deviate from the central orders while the central revises the policy from time to time to ensure local compliance. Three difficulties are analyzed: (1) the current relations between the central and local energy regulatory institutions make these local institutions difficult to perform their duties, and affect incentives for local governments to respond to central directives; (2) financial reform puts a great burden on local governments to raise revenues to cover expenditures, making local governments focus mainly on economic development rather than serving merely as political agents of the central government; (3) the aggressive attitude of local governments in pursuing GDP growth is not necessarily driven by the central government, but by pressure from competition among localities and the need to win local support. Solving these difficulties is important for making national energy conservation polices effective and efficient. © 2011 Elsevier Ltd. Source


Ding C.,City University of Hong Kong
International Journal of Law and Psychiatry | Year: 2014

The long-awaited Mental Health Law of China was passed on 26 October 2012 and took effect on 1 May 2013. Being the first national legislation on mental health, it establishes a basic legal framework to regulate mental health practice and recognizes the fundamental rights of persons with mental disorders. This article focuses on the system of involuntary detention and treatment of the mentally ill under the new law, which is expected to prevent the so-called "Being misidentified as mentally disordered" cases in China. A systematic examination of the new system demonstrates that the Mental Health Law of China implicitly holds two problematic assumptions and does not provide adequate protection of the fundamental rights of the involuntary patients. Administrative enactments and further national legislative efforts are needed to remedy these flaws in the new law. © 2014 Elsevier Ltd. Source


Zhang X.,City University of Hong Kong
Journal of Cleaner Production | Year: 2015

The urbanization process is creating dramatic and rapid changes globally, with over half of the world's population living in cities. This rapid urbanization growth has led to the need to understand urbanization as a major contributor to not only economic/social transformation but also resource consumption and environmental damage. In this context, 'sustainable urbanization' came into being. Theoretical debate on 'sustainable urbanization' has been eliminated by the rhetoric and realities of sustainability, while the practical application of this debate to the urbanization process has been both limited and contradictory (Pinches, 1994). From the practical application point of view, many effective urban-rural sustainability practices exist in different situations depending on social, economic, political, cultural development and geographical conditions, which makes it difficult to effectively share the experiences obtained from these practices. It is therefore imperative to establish a fundamental holistic model to share these practical experiences in order to mirror and help transfer the good results already obtained. The aim of the bi-dimensional model for sustainable urbanization is to analyze environmental, social and economic issues in quadrant terms at different stages from a new life cycle perspective of the urban and rural environment. Based on the conceptual model, a Curitiba case is used to demonstrate the way how one of the quadrant I (sustainable urban form) is achieved at city level. It is highlighted that government sponsored urbanization pattern can be efficient. However, practical implementation at city governance/management level is rather more important. This research proposes a roadmap for sustainable urbanization, facilitating the generation of the effective acquisition and sharing of sustainable urbanization experiences to support the decision making processes involved in selecting strategies and solutions. This contribution aims to stimulate innovative methods that are able to cope with current challenging urbanization problems in an integrative manner that is adapted to fluctuating urban demand patterns. © 2015 Elsevier Ltd. Source


Djordjevich A.,City University of Hong Kong
International Journal of Heat and Mass Transfer | Year: 2012

One-dimensional advection-diffusion equation with variable coefficients in semi-infinite media is solved using explicit finite difference method for three dispersion problems: (i) solute dispersion along steady flow through inhomogeneous medium, (ii) temporally dependent solute dispersion along uniform flow through homogeneous medium, and (iii) solute dispersion along temporally dependent unsteady flow through inhomogeneous medium. The continuous point source of uniform nature is considered at the origin of the medium. Results are compared to analytical solutions reported in the literature and good agreement was found. We have shown that explicit finite difference method is effective and accurate for solving advection-diffusion equation with variable coefficients in semi-infinite media, which is especially important when arbitrary initial and boundary conditions are required. © 2012 Elsevier Ltd. All rights reserved. Source


Tong S.-C.,Liaoning University of Technology | Li Y.-M.,Liaoning University of Technology | Feng G.,City University of Hong Kong | Li T.-S.,Dalian Maritime University
IEEE Transactions on Systems, Man, and Cybernetics, Part B: Cybernetics | Year: 2011

In this paper, an adaptive fuzzy backstepping dynamic surface control (DSC) approach is developed for a class of multiple-input-multiple-output nonlinear systems with immeasurable states. Using fuzzy-logic systems to approximate the unknown nonlinear functions, a fuzzy state observer is designed to estimate the immeasurable states. By combining adaptive-backstepping technique and DSC technique, an adaptive fuzzy output-feedback backstepping-control approach is developed. The proposed control method not only overcomes the problem of explosion of complexity inherent in the backstepping-design methods but also overcomes the problem of unavailable state measurements. It is proved that all the signals of the closed-loop adaptive-control system are semiglobally uniformly ultimately bounded, and the tracking errors converge to a small neighborhood of the origin. Simulation results are provided to show the effectiveness of the proposed approach. © 2011 IEEE. Source


Hong L.J.,Hong Kong University of Science and Technology | Liu G.,City University of Hong Kong
Operations Research | Year: 2010

A probability is the expectation of an indicator function. However, the standard pathwise sensitivity estimation approach, which interchanges the differentiation and expectation, cannot be directly applied because the indicator function is discontinuous.In this paper, we design a pathwise sensitivity estimator for probability functions based on a result of Hong [Hong, L. J. 2009. Estimating quantile sensitivities. Oper. Res. 57(1) 118-130]. We show that the estimator is consistent and follows a central limit theorem for simulation outputs from both terminating and steady-state simulations, and the optimal rate of convergence of the estimator is n?2/5 where n is the sample size. We further demonstrate how to use importance sampling to accelerate the rate of convergence of the estimator to n?1/2, which is the typical rate of convergence for statistical estimation. We illustrate the performances of our estimators and compare them to other well-known estimators through several examples. © 2010 INFORMS. Source


Cheung C.M.K.,Hong Kong Baptist University | Lee M.K.O.,City University of Hong Kong
Decision Support Systems | Year: 2010

Online social networks (Facebook, MySpace, LinkedIn and the like) have become truly significant new phenomena in human communication and interaction patterns and may have a profound impact in the way people communicate and connect with each other. In this study, the decision to use an online social network is conceptualized as intentional social action and the relative impact of the three modes of social influence processes (compliance, internalization, and identification) on intentional social action to use (collective intention) is examined. An empirical study of Facebook users (n = 389) found that collective intention to use a social networking site is determined by both subjective norm and social identity. Further, social identity is found to be a second-order latent construct comprised of cognitive, evaluative, and affective (first-order) components. Implications for research and practice are discussed. © 2009 Elsevier B.V. All rights reserved. Source


Jiang J.Q.,City University of Hong Kong | McQuay L.J.,Management Health Solutions
IEEE/ACM Transactions on Computational Biology and Bioinformatics | Year: 2012

Assigning biological functions to uncharacterized proteins is a fundamental problem in the postgenomic era. The increasing availability of large amounts of data on protein-protein interactions (PPIs) has led to the emergence of a considerable number of computational methods for determining protein function in the context of a network. These algorithms, however, treat each functional class in isolation and thereby often suffer from the difficulty of the scarcity of labeled data. In reality, different functional classes are naturally dependent on one another. We propose a new algorithm, Multi-label Correlated Semi-supervised Learning (MCSL), to incorporate the intrinsic correlations among functional classes into protein function prediction by leveraging the relationships provided by the PPI network and the functional class network. The guiding intuition is that the classification function should be sufficiently smooth on subgraphs where the respective topologies of these two networks are a good match. We encode this intuition as regularized learning with intraclass and interclass consistency, which can be understood as an extension of the graph-based learning with local and global consistency (LGC) method. Cross validation on the yeast proteome illustrates that MCSL consistently outperforms several state-of-the-art methods. Most notably, it effectively overcomes the problem associated with scarcity of label data. The supplementary files are freely available at http://sites.google.com/site/csaijiang/MCSL. © 2012 IEEE. Source


Kuo W.,City University of Hong Kong | Zhu X.,University of Tennessee at Knoxville
IEEE Transactions on Reliability | Year: 2012

Many importance measures have been proposed with respect to the diverse considerations of system performance, reflecting different probabilistic interpretations and potential applications. This paper studies importance measures in reliability, including their definitions, probabilistic interpretations, properties, computations, and comparability. It categorizes importance measures into the structure, reliability, and lifetime types based on the knowledge for determining them. It covers importance measures of individual components, and ones of pairs and groups of components. It also investigates importance measures in consecutive-k-out-of-n systems. © 2012 IEEE. Source


Alibeigloo A.,Tarbiat Modares University | Liew K.M.,City University of Hong Kong
Composite Structures | Year: 2014

This paper presents an exact three-dimensional free vibration solution for sandwich cylindrical panels with functionally graded core. Material properties of the FGM core are assumed to be graded in the radial direction, according to a simple power-law distribution in terms of volume fractions of the constituents. Poisson's ratio is assumed to be constant. The governing equation of motions is formulated based on the 3D-theory of elasticity and displacement fields are expanded in Fourier series along the in-plane coordinates which satisfy the simply supported edges boundary conditions. The state space technique is used to obtain natural frequencies analytically. Accuracy and convergence of the present approach are examined by comparing the analytical results with the existing values in literature. The parametric study is carried out to discuss the effects of gradient index, geometrical properties such as span angle, facing layers thickness and axial length to mid radius ratio on the frequency behavior of the sandwich panel. The obtained exact solution shows that the FGM core has significant effects on the vibration behavior of sandwich cylindrical panel. This fist known exact solution serves as a benchmark for assessing the validity of numerical methods or two-dimensional theories used to analyses of sandwich cylindrical panels. © 2014. Source


Zhang F.,Soochow University of China | Han X.,Soochow University of China | Lee S.-T.,City University of Hong Kong | Sun B.,Soochow University of China
Journal of Materials Chemistry | Year: 2012

Hybrid solar cells based on composites of silicon nanopillar arrays (SiNPs) on silicon substrates and conjugated polymer were investigated in this study. SiNPs with three dimensional (3D) geometry could orthogonalize the directions of light absorption and charge transfer while allowing for enhanced light scattering and trapping. In addition, SiNPs were fabricated by a simple process at low temperature and displayed strong light trapping capability over a wide range of incidence angles as well as near infrared light absorption. Furthermore, a method to control the density of SiNPs had been developed to obtain pillar arrays with controllable distance, which allowed conjugated polymer to reach the bottom part of SiNPs. The thickness of organic layer played a critical role on the short-circuit current, open-circuit voltage and fill factor, and optimum thickness was indispensable to achieve the superior performance. A power conversion efficiency of 9.2% was achieved based on the heterojunction with organic thin layer under AM 1.5G illumination at 100 mW cm -2. We believe that this model is appropriate for the fabrication of heterojunction hybrid devices based on alternative organic semiconductors or even inorganic semiconducting nanocrystals. © The Royal Society of Chemistry 2012. Source


Memon S.A.,City University of Hong Kong
Renewable and Sustainable Energy Reviews | Year: 2014

The building sector is the dominant energy consumer with a total 30% share of the overall energy consumption and accounts for one-third of the greenhouse gas emissions around the world. Moreover, in recent years the energy demands for buildings have increased very rapidly due to increase in the growth rate of population and improvement in living standards of people. Furthermore, fossil fuels will continue to dominate the world's primary energy by 2030. Thus, the increase in energy demand, shortage of fossil fuels and environmental concerns has provided impetus to the development of sustainable building and renewable energy resources. Thermal energy storage is an efficient method for applying to building envelopes to improve the energy efficiency of buildings. This, in turn, reduces the environmental impact related to energy usage. The combination of construction materials and PCM is an efficient way to increase the thermal energy storage capacity of construction elements. Therefore, an extensive review on the incorporation of PCM into construction materials and elements by direct incorporation, immersion, encapsulation, shape-stabilization and form-stable composite PCMs is presented. For the first time, the differentiation between shape-stabilized and form-stable composite PCM has been made. Moreover, various construction materials such as diatomite, expanded perlite and graphite, etc. which are used as supports for form-stable composite PCM along with their worldwide availability are extensively discussed. One of the main aims of this review paper is to focus on the test methods which are used to determine the chemical compatibility, thermal properties, thermal stability and thermal conductivity of the PCM. Hence, the details related to calibration, sample preparation, test cell and analysis of test results are comprehensively covered. Finally, because of the renewed interest in integration of PCM in wallboards and concrete, an up-to-date review with focus on PCM enhanced wallboard and concrete for building applications is added. © 2014 Elsevier Ltd. Source


Liu H.-L.,Guangdong University of Technology | Gu F.,Guangdong University of Technology | Zhang Q.,City University of Hong Kong | Zhang Q.,University of Essex
IEEE Transactions on Evolutionary Computation | Year: 2014

This letter suggests an approach for decomposing a multiobjective optimization problem (MOP) into a set of simple multiobjective optimization subproblems. Using this approach, it proposes MOEA/D-M2M, a new version of multiobjective optimization evolutionary algorithm-based decomposition. This proposed algorithm solves these subproblems in a collaborative way. Each subproblem has its own population and receives computational effort at each generation. In such a way, population diversity can be maintained, which is critical for solving some MOPs. Experimental studies have been conducted to compare MOEA/D-M2M with classic MOEA/D and NSGA-II. This letter argues that population diversity is more important than convergence in multiobjective evolutionary algorithms for dealing with some MOPs. It also explains why MOEA/D-M2M performs better. © 2013 IEEE. Source


Leung A.Y.T.,City University of Hong Kong
International Journal of Solids and Structures | Year: 2010

A helical beam has non-zero curvature and tortuosity. When there is a pre-twist, the Frenet triad is not necessary coincident with the principal triad. When an initially straight rod undergoing a large deformation, it will be curved and twisted during each deformation sequence. The purpose of the paper is to establish the governing equations and the associated natural boundary conditions for a pre-twisted helical beam by variational principles and differential geometry. Although circular helix is taken as example, the formulation is valid for inhomogeneous and non-uniform parameters along the centerline that variable curvature and tortuosity can be treated without difficulties. The method can be used to treat helical anisotropy. If the pre-twist rate of a ring is 0.5, we show a thick Möbius ring for the first time. The solution of the natural vibration problem is through Chebyshev discretization and Clenshaw-Curtis integration by means of the Galerkin formulation. © 2010 Elsevier Ltd. All rights reserved. Source


Rogach A.L.,City University of Hong Kong
Nano Today | Year: 2011

Starting from a short introduction on basic properties of colloidal semiconductor nanocrystals and on the FRET formalism, we focus on fluorescence energy transfer in hybrid systems combining organic (dyes, conjugated polymers) and inorganic (nanocrystals) components, providing examples for their application in biological systems and in photovoltaic devices. © 2011 Elsevier Ltd. All rights reserved. Source


Zhang G.,Sun Yat Sen University | Yau K.K.W.,City University of Hong Kong | Chen G.,Sun Yat Sen University
Accident Analysis and Prevention | Year: 2013

With the recent economic boom in China, vehicle volume and the number of traffic accident fatalities have become the highest in the world. Meanwhile, traffic accidents have become the leading cause of death in China. Systematically analyzing road safety data from different perspectives and applying empirical methods/implementing proper measures to reduce the fatality rate will be an urgent and challenging task for China in the coming years. In this study, we analyze the traffic accident data for the period 2006-2010 in Guangdong Province, China. These data, extracted from the Traffic Management Sector-Specific Incident Case Data Report, are the only officially available and reliable source of traffic accident data (with a sample size >7000 per year). In particular, we focus on two outcome measures: traffic violations and accident severity. Human, vehicle, road and environmental risk factors are considered. First, the results establish the role of traffic violations as one of the major risks threatening road safety. An immediate implication is: if the traffic violation rate could be reduced or controlled successfully, then the rate of serious injuries and fatalities would be reduced accordingly. Second, specific risk factors associated with traffic violations and accident severity are determined. Accordingly, to reduce traffic accident incidence and fatality rates, measures such as traffic regulations and legislation - targeting different vehicle types/driver groups with respect to the various human, vehicle and environment risk factors - are needed. Such measures could include road safety programs for targeted driver groups, focused enforcement of traffic regulations and road/transport facility improvements. Data analysis results arising from this study will shed lights on the development of similar (adjusted) measures to reduce traffic violations and/or accident fatalities and injuries, and to promote road safety in other regions. © 2013 Elsevier Ltd. All rights reserved. Source


Yuan L.,Chongqing Technology and Business University | Lu Y.Y.,City University of Hong Kong
Optics Express | Year: 2014

Symmetry breaking is a common phenomenon in nonlinear systems, it refers to the existence of solutions that do not preserve the original symmetries of the underlying system. In nonlinear optics, symmetry breaking has been previously investigated in a number of systems, usually based on simplified model equations or temporal coupled mode theories. In this paper, we analyze the scattering of an incident plane wave by one or two circular cylinders with a Kerr nonlinearity, and show the existence of solutions that break a lateral reflection symmetry. Although symmetry breaking is a known phenomenon in nonlinear optics, it is the first time that this phenomenon was rigorously studied in simple systems with one or two circular cylinders. © 2014 Optical Society of America. Source


Lo Yuk-Ping C.,University of Hong Kong | Thomas N.,City University of Hong Kong
Health Policy and Planning | Year: 2010

In the closing decade of the 20th century the myriad challenges posed by infectious disease in a globalized environment began to be re-conceptualized as threats to national and human security. The most widely applied model for identifying and responding to such threats is securitization theory, as proposed by the Copenhagen School. Although its analytical framework is generally accepted, its utility remains contested; especially in non-European and non-state settings. The papers in this special edition have several aims: (1) to analyse ways by which Asian states and international organizations have identified health challenges as security threats, (2) to draw upon the securitization model as a way of understanding the full extent to which these states and international organizations have responded to the health threat, and (3) to identify areas where the theory might be strengthened so as to provide greater analytical clarity in areas of health security. This paper acts as a broad introduction to a set of papers on 'Unhealthy governance' and explores some of the key findings from the subsequent papers. © The Author 2010; all rights reserved. Source


Zhu Z.-L.,Northeastern University China | Zhang W.,Northeastern University China | Wong K.-W.,City University of Hong Kong | Yu H.,Northeastern University China
Information Sciences | Year: 2011

In recent years, a variety of chaos-based digital image encryption algorithms have been suggested. Most of these algorithms implement permutations and diffusions at the pixel level by considering the pixel as the smallest (atomic) element of an image. In fact, a permutation at the bit level not only changes the position of the pixel but also alters its value. Here we propose an image cryptosystem employing the Arnold cat map for bit-level permutation and the logistic map for diffusion. Simulations have been carried out and analyzed in detail, demonstrating the superior security and high efficiency of our cryptosystem. © 2010 Published by Elsevier Inc. All rights reserved. Source


Lee C.K.,City University of Hong Kong
Applied Energy | Year: 2010

A model for a ground-source heat pump (GSHP) fitted with a variable-speed compressor was developed. A frequency inverter (FI) was used to modulate the GSHP capacity for improving the part-load performance of the system. Year-round dynamic simulations were made using TRNSYS for a general office based on the weather conditions in Hong Kong (HK), Kunming (KM) and Beijing (BJ). Different control schemes for the part-load control were tried and the results compared. It was found that the adoption of a variable-speed part-load control to the GSHP in both the cooling and heating mode operations was better. A reduction in the compressor energy input by minimum 27% could be achieved although a slight increase in the borefield fluid circulating pump energy consumption was inevitable. The peak borefield fluid temperatures were also reduced which allowed the borehole lengths to be shortened by at least 4% and the initial cost lowered accordingly. An economic analysis indicated that with the reduced borehole lengths, the payback periods were no longer than 0.4. months. This highlighted the merit of employing a variable-speed part-load in a GSHP system as the initial cost might also be saved besides the running costs under a wide range of climatic conditions. © 2010 Elsevier Ltd. Source


Phan D.D.,St. Cloud State University | Vogel D.R.,City University of Hong Kong
Information and Management | Year: 2010

As more retailers evolve into customer-centric and segment-based business, business intelligence (BI) and customer relationship management (CRM) systems are playing a key role in achieving and maintaining competitive advantage. For the past ten years, the authors have had the rare opportunity of observing and interviewing employees and managers of three different management teams at three separate Fingerhut companies as they experimented with various ITs for their companies. When the first Fingerhut company peaked in 1998, as many as 200 analysts and 40 statisticians mined the database for insights that helped predict consumer shopping patterns and credit behaviour. Data mining and BI helped Fingerhut spot shopping patterns, bring product offerings to the right customers, and nurture customer relationships. By 1998, Fingerhut was the second largest catalogue retailer in the U.S. with revenues nearing $2 billion. However, after Federated acquired Fingerhut in 1999 and made it a subsidiary, Fingerhut Net, it suffered great losses and was eventually liquidated. Finally, a new company, Fingerhut Direct Marketing, was resurrected in 2002 under a new management team, and it once again became successful. What went right? What went wrong? The paper concludes with CRM and BI systems success factors and a discussion of lessons learned. © 2009 Elsevier B.V. All rights reserved. Source


A modified three-dimensional finite difference model for the borehole ground heat exchangers of a ground-source heat pump (GSHP) system was developed which accounted for multiple ground layers with different thermal properties in the borefield at no groundwater flow. The present model was used to investigate the impact of ignoring ground layers in the thermal response test (TRT) analysis and the subsequent system simulation. It was found that the adoption of an effective ground thermal conductivity and an effective ground volumetric heat capacity for a multi-layer ground determined from a TRT analysis led to very little error in the simulated long term system performance under various ground compositions investigated. The maximum difference occurred for a 3 × 3 borefield in a dual-layer ground which measured 0.5 °C or 3.9% in the rise of the borefield fluid leaving temperature with a cooling-dominated loading profile for 10 years. With the same borefield and ground composition, a dynamic simulation of the complete GSHP system was performed using the TRNSYS simulation software. It was found that the overall system performance based on the present and the old models differed very little. It was concluded that the assumption of a homogeneous ground in a TRT analysis and subsequent system simulation was appropriate and impact of ignoring ground layers was small. A single-ground-layer model, including the analytical models, was sufficient even for a multi-layer ground. This could reduce the computation time significantly, especially when simulating a large borefield. © 2011 Elsevier Ltd. Source


Kwok S.S.K.,City University of Hong Kong
Energy Conversion and Management | Year: 2011

Building cooling load prediction is one of the key factors in the success of energy-saving measures. Many computational models available in the industry today have been developed from either forward or inverse modeling approaches. However, most of these models require extensive computer resources and involve lengthy computation. This paper discusses the use of data-driven intelligent approaches, a probabilistic entropy-based neural (PENN) model to predict the cooling load of a building. Although it is common knowledge that the presence and activity of building occupants have a significant impact on the required cooling load of buildings, practices currently adopted in modeling the presence and activity of people in buildings do not reflect the complexity of the impact occupants have on building cooling load. In contrast to previous artificial neural network (ANN) models, most of which employ a fixed schedule or historic load data to represent building occupancy in simulating building cooling load, this paper introduces two input parameters, dynamic occupancy area and rate and uses it to mimic building cooling load. The training samples used include weather data obtained from the Hong Kong Observatory and building-related data acquired from an existing grade A mega office buildings in Hong Kong with tenants including many multi-national financial companies that require 24-h air conditioning seven days a week. The dynamic changes that occur in the occupancy of these buildings therefore make it very difficult to forecast building cooling load by means of a fixed time schedule. The performance of simulation results demonstrate that building occupancy data play a critical role in building cooling load prediction and that their use significantly improves the predictive accuracy of cooling load models. © 2011 Elsevier Ltd. Source


Liu L.,City University of Hong Kong
IEEE Transactions on Automatic Control | Year: 2015

In this technical note, an adaptive cooperative output regulation problem for a class of nonlinear multi-agent systems is considered. The cooperative output regulation problem is first converted into an adaptive stabilization problem for an augmented multi-agent system. A distributed adaptive control law with adoption of Nussbaum gain technique is then proposed to globally stabilize this augmented system. This control scheme is designed such that, in the presence of unknown control direction and large parameter variations in each agent, the closed-loop system maintains global stability and the output of each agent tracks a class of prescribed signals asymptotically. © 2014 IEEE. Source


Teoh W.Y.,City University of Hong Kong
Materials | Year: 2013

The synthesis of functional nanoparticles via one-step flame spray pyrolysis (FSP), especially those of catalytic nature, has attracted the interests of scientists and engineers, as well as industries. The rapid and high temperature continuous synthesis yields nanoparticles with intrinsic features of active catalysts, that is, high surface area and surface energetics. For these reasons, FSP finds applications in various thermally inducible catalytic reactions. However, the design and synthesis of photocatalysts by FSP requires a knowledge set which is different from that established for thermal catalysts. Unknown to many, this has resulted in frustrations to those entering the field unprepared, especially since FSP appears to be an elegant tool in synthesising oxide nanoparticles of any elemental construct. From simple oxide to doped-oxide, and mixed metal oxide to the in situ deposition of noble metals, this Perspective gives an overview on the development of photocatalysts made by FSP in the last decade that led to a better understanding of the design criteria. Various challenges and opportunities are also highlighted, especially those beyond simple metal oxides, which perhaps contain the greatest potential for the exploitation of photocatalysts design by FSP. © 2013 by the authors; licensee MDPI, Basel, Switzerland. Source


Chen G.-R.,City University of Hong Kong
Zidonghua Xuebao/Acta Automatica Sinica | Year: 2013

This article addresses some new problems and challenges faced by the conventional control theory under complex dynamical network environments. After introducing the network science and engineering background, it discusses some research issues regarding pinning control of complex dynamical networks, controllability of directed networks, as well as "network of networks" and its modeling and control. Copyright © 2013 Acta Automatica Sinica. Source


Francesch-Huidobro M.,City University of Hong Kong
Applied Energy | Year: 2016

Despite growing interest in China's response to climate change and energy security, studies undertaken at the subnational level are rare. In the context of the multilevel governance paradigm, this article examines the governance of climate change and energy policy in Shanghai, a rapidly growing Chinese megacity highly vulnerable to the effects of climate change. Although the energy and carbon intensity of Shanghai's economy have fallen significantly since China launched its economic reforms, overall carbon emissions in the municipality continue to rise. Through examining the Shanghai case, this article argues that Chinese subnational climate mitigation policy is dominated by hierarchical governance arrangements. Nevertheless, shifts in national climate and energy policy since 2007 have mandated provincial-level governments, including Shanghai, to develop their own climate and energy policies while offering greater local autonomy for incorporating climate and energy issues into development goals: is this attributable to a decentred form of multilevel governance? The article concludes that Shanghai's climate mitigation and energy policy is dominated by hierarchical governance whereby policies are 'downloaded' from the central government. Perspectives for other cities and insights for policymakers are discussed. © 2015 Elsevier Ltd. Source


Li M.,City University of Hong Kong
Theoretical Computer Science | Year: 2011

Dynamic Voltage Scaling techniques allow the processor to set its speed dynamically in order to reduce energy consumption. It was shown that if the processor can run at arbitrary speeds and uses power sα when running at speed s, the online heuristic AVR has a competitive ratio ( 2α)α2. In this paper we first study the online heuristics for the discrete model where the processor can only run at d given speeds. We propose a method to transform online heuristic AVR to an online heuristic for the discrete model and prove a competitive ratio 2α-1( α-1)α-1(δα-1)α(δ-1) (δα-δ)α-1+1, where δ is the maximum ratio between adjacent non-zero speed levels. We also prove that the analysis holds for a class of heuristics that satisfy certain natural properties. We further study the throughput maximization problem when there is an upper bound for the maximum speed. We propose a greedy algorithm with running time O( n2logn) and prove that the output schedule is a 3-approximation of the throughput and a (α-1)α-1(3α-1) α2αα(3α-1-1)α-1- approximation of the energy consumption. © 2010 Elsevier B.V. All rights reserved. Source


Fan R.,City University of Hong Kong
Theoretical Medicine and Bioethics | Year: 2011

The family is the exemplar community of Chinese society. This essay explores how Chinese communitarian norms, expressed in thick commitments to the authority and autonomy of the family, are central to contemporary Chinese bioethics. In particular, it focuses on the issue of surrogate decision making to illustrate the Confucian family-grounded communitarian bioethics. The essay first describes the way in which the family, in Chinese bioethics, functions as a whole to provide consent for significant medical and surgical interventions when a patient has lost decision-making capacity. It is argued that the practice of not having an established order for surrogate decision makers (e.g., spouse, children, and then parents), as it is done in the United States, reflects the acknowledgment that the family as a social reality cannot be reduced to a stereotype of the appropriate order of default decision makers. This description of the family as being in authority to make surrogate decisions for an incompetent family member is enriched by an elaboration of the differences among the concepts of patient autonomy, family autonomy, and moral autonomy. The Chinese model, as well as the Confucian communitarian life of families, engages a family autonomy that is supported by a Confucian understanding of moral autonomy, rather than individual autonomy. Finally, the issue of possible conflicts between patient and family interests in relation to a patient's past wishes in the Chinese model is addressed in light of the role of the physician. © 2011 Springer Science+Business Media B.V. Source


Zhou G.,Tsinghua University | Chung W.,City University of Hong Kong | Zhang X.,Tsinghua University
Energy | Year: 2013

Undesirable output-oriented Data Envelopment Analysis (DEA) models with different return of scales are used to study the CO2 (Carbon dioxide) emissions performance of the transport sector throughout China's 30 administrative regions. Empirical results show that the number of efficient regions has decreased since 2004, hitting the lowest record in 2006, and improving slightly afterwards. The overall average performance rating reached its peak in 2004 and continuously decreased until it hit its lowest record in 2006. Although it slightly increased in 2007, performance rating has decreased since 2008. This pattern is consistent with the policy guidance of the transport sector in the 11th Five-Year Plan (2006-2010). In general, Eastern China performed better than Central and Western by adjusting undesirable output (CO2). However, Central performed better than Eastern and Western by adjusting both CO2 emissions and desirable outputs. It may be because that transport infrastructure facilities are heavily concentrated in Eastern and spatial clusters. The clusters are like stair steps decreasing from the higher Eastern to Central then to the lower Western. This indicates that the development of transport infrastructure go hand in hand in China. Hence, Eastern may not have too much improvement room by adjusting desirable outputs. © 2012 Elsevier Ltd. Source


Wang Q.,Beihang University | Chen G.,City University of Hong Kong
Chaos | Year: 2011

We study the dependence of synchronization transitions in scale-free networks of bursting neurons with hybrid synapses on the information transmission delay and the probability of inhibitory synapses. It is shown that, irrespective of the probability of inhibitory synapses, the delay always plays a subtle role during synchronization transition of the scale-free neuronal networks. In particular, regions of irregular and regular propagating excitatory fronts appear intermittently as the delay increases. These delay-induced synchronization transitions are manifested as well-expressed minima in the measure for spatiotemporal synchrony. In addition, it is found that, for smaller and larger probability of inhibitory synapses, intermittent synchronization transition is relatively profound, while for the moderate probability of inhibitory synapses, synchronization transition seems less profound. More interestingly, it is found that as the probability of inhibitory synapses is large, regions of synchronization are upscattering. © 2011 American Institute of Physics. Source


Lowry P.B.,City University of Hong Kong | Gaskin J.,Brigham Young University
IEEE Transactions on Professional Communication | Year: 2014

Problem: Partial least squares (PLS), a form of structural equation modeling (SEM), can provide much value for causal inquiry in communication-related and behavioral research fields. Despite the wide availability of technical information on PLS, many behavioral and communication researchers often do not use PLS in situations in which it could provide unique theoretical insights. Moreover, complex models comprising formative (causal) and reflective (consequent) constructs are now common in behavioral research, but they are often misspecified in statistical models, resulting in erroneous tests. Key concepts: First-generation (1G) techniques, such as correlations, regressions, or difference of means tests (such as ANOVA or ${\rm t}$-tests), offer limited modeling capabilities, particularly in terms of causal modeling. In contrast, second-generation techniques (such as covariance-based SEM or PLS) offer extensive, scalable, and flexible causal-modeling capabilities. Second-generation (2G) techniques do not invalidate the need for 1G techniques however. The key point of 2G techniques is that they are superior for the complex causal modeling that dominates recent communication and behavioral research. Key lessons: For exploratory work, or for studies that include formative constructs, PLS should be selected. For confirmatory work, either covariance-based SEM or PLS may be used. Despite claims that lower sampling requirements exist for PLS, inadequate sample sizes result in the same problems for either technique. Implications: SEM's strength is in modeling. In particular, SEM allows for complex models that include latent (unobserved) variables, formative variables, chains of effects (mediation), and multiple group comparisons of these more complex relationships. © 2014 IEEE. Source


Wu J.,Hong Kong Baptist University | Chan R.K.Y.,Hong Kong Baptist University | Chan R.K.Y.,City University of Hong Kong
Optics Express | Year: 2013

We report a fast fluorescence imaging flow cytometer for phytoplankton analysis that can achieve a volume flow rate up to 1ml/min. The instrument shows a high immunity to motion blur in image captured with a lateral resolution of 0.75 0.06 ?m for a wide size range ~1 ?m to ~200 ?m. This is made possible by suppressing the out-of-focus light using thin light sheet illumination and image deconvolution, and by precluding the motion-blur with a unique flow configuration. Preliminary results from untreated coastal water samples show the technique has high potential as a practical field instrument for monitoring phytoplankton abundance and species composition. ©2013 Optical Society of America. Source


Chen L.,Chinese University of Hong Kong | He S.,City University of Hong Kong | Zhang S.,University of Minnesota
Operations Research | Year: 2011

In this paper we develop tight bounds on the expected values of several risk measures that are of interest to us. This work is motivated by the robust optimization models arising from portfolio selection problems. Indeed, the whole paper is centered around robust portfolio models and solutions. The basic setting is to find a portfolio that maximizes (respectively, minimizes) the expected utility (respectively, disutility) values in the midst of infinitely many possible ambiguous distributions of the investment returns fitting the given mean and variance estimations. First, we show that the single-stage portfolio selection problem within this framework, whenever the disutility function is in the form of lower partial moments (LPM), or conditional value-at-risk (CVaR), or value-at-risk (VaR), can be solved analytically. The results lead to the solutions for single-stage robust portfolio selection models. Furthermore, the results also lead to a multistage adjustable robust optimization (ARO) solution when the disutility function is the second-order LPM. Exploring beyond the confines of convex optimization, we also consider the so-called S-shaped value function, which plays a key role in the prospect theory of Kahneman and Tversky. The nonrobust version of the problem is shown to be NP-hard in general. However, we present an efficient procedure for solving the robust counterpart of the same portfolio selection problem. In this particular case, the consideration of the robustness actually helps to reduce the computational complexity. Finally, we consider the situation whereby we have some additional information about the chance that a quadratic function of the random distribution reaches a certain threshold. That information helps to further reduce the ambiguity in the robust model. We show that the robust optimization problem in that case can be solved by means of semidefinite programming (SDP), if no more than two additional chance inequalities are to be incorporated. © 2011 INFORMS. Source


He Y.,Soochow University of China | Fan C.,CAS Shanghai Institute of Applied Physics | Lee S.-T.,Soochow University of China | Lee S.-T.,City University of Hong Kong
Nano Today | Year: 2010

There has been rapidly increasing interest in design and synthesis of siliconbased nanostructured materials for bioapplications. In this review, we focus on recent research progress in design, synthesis and bioapplications of two silicon-based nanostructures, zero-dimensional silicon quantum dots and one-dimensional silicon nanowires. These two low-dimensional silicon nanomaterials have found important applications in ultrasensitive biomolecular detection and fluorescent cellular imaging. We further highlight major challenges and promises in this area. © 2010 Elsevier Ltd. Source


Huang L.,Harbin Institute of Technology | So H.C.,City University of Hong Kong
IEEE Transactions on Signal Processing | Year: 2013

Numerous methodologies have been investigated for source enumeration in sample-starving environments. For those having their root in the framework of random matrix theory, the involved distribution of the sample eigenvalues is required. Instead of relying on the eigenvalue distribution, this work devises a linear shrinkage based minimum description length (LS-MDL) criterion by utilizing the identity covariance matrix structure of noise subspace components. With linear shrinkage and Gaussian assumption of the observations, an accurate estimator for the covariance matrix of the noise subspace components is derived. The eigenvalues obtained from the estimator turn out to be a linear function of the corresponding sample eigenvalues, enabling the LS-MDL criterion to accurately detect the source number without incurring significantly additional computational load. Furthermore, the strong consistency of the LS-MDL criterion for m,n\ura{} ∞ and m/n\ura{} c in (0,∞) is proved, where m and n are the antenna number and snapshot number, respectively. Simulation results are included for illustrating the effectiveness of the proposed criterion. © 1991-2012 IEEE. Source


Yang Q.,City University of Hong Kong
Lecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics) | Year: 2012

This paper proposes a recursive implementation of the bilateral filter. Unlike previous methods, this implementation yields an bilateral filter whose computational complexity is linear in both input size and dimensionality. The proposed implementation demonstrates that the bilateral filter can be as efficient as the recent edge-preserving filtering methods, especially for high-dimensional images. Let the number of pixels contained in the image be N, and the number of channels be D, the computational complexity of the proposed implementation will be O(ND). It is more efficient than the state-of-the-art bilateral filtering methods that have a computational complexity of O(ND 2) [1] (linear in the image size but polynomial in dimensionality) or O(Nlog(N)D) [2] (linear in the dimensionality thus faster than [1] for high-dimensional filtering). Specifically, the proposed implementation takes about 43 ms to process a one megapixel color image (and about 14 ms to process a 1 megapixel grayscale image) which is about 18 × faster than [1] and 86× faster than [2]. The experiments were conducted on a MacBook Air laptop computer with a 1.8 GHz Intel Core i7 CPU and 4 GB memory. The memory complexity of the proposed implementation is also low: as few as the image memory will be required (memory for the images before and after filtering is excluded). This paper also derives a new filter named gradient domain bilateral filter from the proposed recursive implementation. Unlike the bilateral filter, it performs bilateral filtering on the gradient domain. It can be used for edge-preserving filtering but avoids sharp edges that are observed to cause visible artifacts in some computer graphics tasks. The proposed implementations were proved to be effective for a number of computer vision and computer graphics applications, including stylization, tone mapping, detail enhancement and stereo matching. © 2012 Springer-Verlag. Source


Valentine S.V.,City University of Hong Kong
Renewable and Sustainable Energy Reviews | Year: 2014

In addition to providing a review of electricity generation developments in China, this paper features the development of a framework for understanding the socio-political economy influencing electricity market development. It documents and presents a critical evaluation of the social, technological, economic and political forces which influence electricity generation policy in China. The analysis provides insight into why China's electricity generation shopping basket is being filled with both coal and CO2-reduced electricity generation technologies. It concludes that installed capacity of hydro power, wind power, nuclear power and solar PV power will outpace government projections due to inter alia a proclivity on the part of the Chinese government to set conservative (and achievable) targets, waning apathy toward pollution associated with coal-fired power, progressive improvements in grid connection and resilience, increased economic viability of these alternative energy sources and government support for these industries as strategic commercial sectors. © 2014 Elsevier Ltd. All rights reserved. Source


Chan C.H.-Y.,City University of Hong Kong
Computer Assisted Language Learning | Year: 2013

This paper reports on a blended-learning project that aims to develop a web-based library of interpreting practice resources built on the course management system Blackboard for Hong Kong interpretation students to practise outside the classroom. It also evaluates the library's effectiveness for learning, based on a case study that uses it to assist in-class instruction of a first-year undergraduate interpretation course. Future improvements and modification of the library design and contents, and the implications of this case study for course design in blended learning and computer assisted interpreter training are also discussed. © 2013 Copyright Taylor and Francis Group, LLC. Source


Brimblecombe P.,City University of Hong Kong
Journal of the Institute of Conservation | Year: 2014

A changing climate places shifting risks on heritage. Future English climate can be difficult to interpret and the outcomes may be probabilistic and subtle. In spite of this it can be tempting to reduce our future to one that is warmer or wetter or windier. There is some truth to such a future, but particularly in the case of water-related variables the changes are likely to be complex. In terms of total rainfall and average relative humidity the English climate is likely to become drier. We have to think more in terms of the heritage climate; the particular variables likely to threaten heritage. Meteorological parameters affect heritage in different ways. Heavier rainfall is likely to affect drainage, while an increasing humidity range may be important for salt damage. Yet in the case of fungal attack on outdoor wood it might well be that temperature could be a more important variable than precipitation. This article calls for a careful consideration of the observed change in heritage damage and the climate factors to which this is attributed. © 2014 Icon, The Institute of Conservation. Source


Lang G.,City University of Hong Kong | Xu Y.,Chinese University of Hong Kong
Environmental Politics | Year: 2013

As China rapidly urbanises, many cities are building incinerators to try to reduce the growing pressure of rising volumes of municipal waste on landfills. Incinerator projects have provoked NIMBY protests in many countries, but China is an authoritarian one-party state with a demonstrated readiness to suppress protests which challenge government projects. However, some of these protest campaigns have led to cancellation or indefinite postponement of government-supported projects at particular sites. We review three recent campaigns against incinerators - in Beijing, Guangzhou, and Wujiang - explain the successful outcomes of each campaign, and then place these conflicts within the spectrum of environmental protest-politics in China. Finally, we consider whether these outcomes contribute to 'ecological modernisation' in the management of municipal waste. © 2013 Taylor and Francis Group, LLC. Source


Feng Y.,City University of Hong Kong | Chen Y.F.,Chinese University of Hong Kong
Operations Research | Year: 2011

This note considers a joint inventory-pricing control problem in an infinite-horizon periodic-review system. Demand in a period is random and depends on the posted price. Besides the holding and shortage costs, the system incurs inventoryreplenishment costs that consist of both variable and fixed components. At the beginning of each period, a joint inventory and pricing decision is made. Under the long-run average profit criterion, we show that an optimal policy exists within the class of so-called 4s1 S1p5 policies. This is established based on our algorithmic development, which also results in an algorithm for finding an optimal 4s1 S1p5 policy. Subject classifications: joint pricing and inventory control; setup cost; price dependent demand; stochastic inventory model. Area of review: Manufacturing, Service, and Supply Chain Operations. History: Received May 2003; revisions received May 2004, August 2005, July 2007, May 2009; accepted April 2010. © 2011 INFORMS. Source


Cheng J.,City University of Hong Kong
International journal of nanomedicine | Year: 2011

Carbon nanotubes have shown broad potential in biomedical applications, given their unique mechanical, optical, and chemical properties. In this pilot study, carbon nanotubes have been explored as multimodal drug delivery vectors that facilitate antiangiogenic therapy in zebrafish embryos. Three different agents, ie, an antiangiogenic binding site (cyclic arginine-glycin-easpartic acid), an antiangiogenic drug (thalidomide), and a tracking dye (rhodamine), were conjugated onto single-walled carbon nanotubes (SWCNT). The biodistribution, efficacy, and biocompatibility of these triple functionalized SWCNT were tested in mammalian cells and validated in transparent zebrafish embryos. Accumulation of SWCNT-associated nanoconjugates in blastoderm cells facilitated drug delivery applications. Mammalian cell xenograft assays demonstrated that these antiangiogenic SWCNT nanoconjugates specifically inhibited ectopic angiogenesis in the engrafted zebrafish embryos. This study highlights the potential of using SWCNT for generating efficient nanotherapeutics. Source


Ou C.X.J.,University of Tilburg | Davison R.M.,City University of Hong Kong
Decision Support Systems | Year: 2011

The use of instant messaging (IM) technology at work is controversial, due to the interruptions it may cause and the difficulties associated with quantifying its benefits for individuals, teams and organizations. In this study, we investigate the use and impact of IM tools in the workplace. Based on theories of communication performance and social networks, we propose that while the use of IM will cause work interruption, it will also lead to improved communication quality and the establishment of trust between colleagues. These mediating variables will in turn influence group outcomes. We validate our research model with data collected through a survey of 253 working professionals. The data suggests IM can significantly contribute to communication performance in the workplace, where the benefits overwhelm the negative effects associated with work interruption. The theoretical and practical contribution and implications of the research are discussed. © 2011 Elsevier B.V. All rights reserved. Source


Chu A.M.Y.,City University of Hong Kong | Chau P.Y.K.,University of Hong Kong
Decision Support Systems | Year: 2014

Information security deviant behavior (ISDB) of employees is a serious threat to organizations. However, not much empirical research on ISDB has been carried out. This paper attempts to develop and validate instruments of ISDB using an empirical method. Two instruments of ISDB are proposed and tested, including a four-item instrument of resource misuse (ISDB that is related to the misuse of information systems resources) and a three-item instrument of security carelessness (ISDB that is related to the employees' omissive activities when using computers or handling data). A rigorous instrument development process which includes three surveys and addresses six crucial measurement properties (content analysis, factorial validity, reliability, convergent validity, discriminant validity, and nomological validity) is adopted. The implications of these two instruments for future empirical studies on ISDB are discussed. © 2014 Elsevier B.V. All rights reserved. Source


Deng F.,City University of Hong Kong
BMC genomics | Year: 2013

Single nucleotide polymorphisms (SNPs) are the most common form of genetic variation in human DNA. The sequence of SNPs in each of the two copies of a given chromosome in a diploid organism is referred to as a haplotype. Haplotype information has many applications such as gene disease diagnoses, drug design, etc. The haplotype assembly problem is defined as follows: Given a set of fragments sequenced from the two copies of a chromosome of a single individual, and their locations in the chromosome, which can be pre-determined by aligning the fragments to a reference DNA sequence, the goal here is to reconstruct two haplotypes (h1, h2) from the input fragments. Existing algorithms do not work well when the error rate of fragments is high. Here we design an algorithm that can give accurate solutions, even if the error rate of fragments is high. We first give a dynamic programming algorithm that can give exact solutions to the haplotype assembly problem. The time complexity of the algorithm is O(n × 2t × t), where n is the number of SNPs, and t is the maximum coverage of a SNP site. The algorithm is slow when t is large. To solve the problem when t is large, we further propose a heuristic algorithm on the basis of the dynamic programming algorithm. Experiments show that our heuristic algorithm can give very accurate solutions. We have tested our algorithm on a set of benchmark datasets. Experiments show that our algorithm can give very accurate solutions. It outperforms most of the existing programs when the error rate of the input fragments is high. Source


Yao M.Z.,City University of Hong Kong | Zhong Z.-J.,Sun Yat Sen University
Computers in Human Behavior | Year: 2014

This study aims to examine the causal priority in the observed empirical relationships between Internet addiction and other psychological problems. A cross-lagged panel survey of 361 college students in Hong Kong was conducted. Results show that excessive and unhealthy Internet use would increase feelings of loneliness over time. Although depression had a moderate and positive bivariate relationship with Internet addiction at each time point, such a relationship was not significant in the cross-lagged analyses. This study also found that online social contacts with friends and family were not an effective alternative for offline social interactions in reducing feelings of loneliness. Furthermore, while an increase in face-to-face contacts could help to reduce symptoms of Internet addiction, this effect may be neutralized by the increase in online social contacts as a result of excessive Internet use. Taken as a whole, findings from the study show a worrisome vicious cycle between loneliness and Internet addiction. © 2013 Elsevier Ltd. All rights reserved. Source


Lo K.K.-W.,City University of Hong Kong
Topics in Organometallic Chemistry | Year: 2010

The rich photophysical and photochemical properties of organometallic rhenium(I) and iridium(III) complexes have been well studied. The interesting luminescence behaviour has been exploited in various areas such as emissive supramolecular assemblies, photovoltaic cells, chemosensing, and light-emitting device fabrication. Recently, the applications of these luminescent complexes in biological studies have received much attention. Herein, we review luminescent organometallic rhenium(I) and iridium(III) complexes that have been employed as biological probes, with an emphasis on biological targets including DNA, proteins, and cellular components. In particular, the molecular structures, spectroscopic and photophysical properties of the complexes, emissive behaviour, and potential applications of the labelled bioconjugates are described. © 2010 Springer-Verlag Berlin Heidelberg. Source


Wang Y.,City University of Hong Kong
Geotechnique | Year: 2011

In this paper a general reliability-based design (RBD) approach for spread foundations is developed that addresses, explicitly and simultaneously, the ultimate limit state (ULS), serviceability limit state (SLS), reliability and economic requirements. The design process is formulated as an expanded reliability problem that is evaluated by a single run of Monte Carlo simulations (MCS). Design parameters (i.e. foundation width B, length L and depth D) are artificially treated as discrete uniform random variables, and the design process is considered as a process of finding failure probabilities for designs with various combinations of B, L and D (i.e. conditional probability p(Failure{pipe}B,L,D)) and comparing them with target probability of failure pT. Feasible designs are those with p(Failure{pipe}B,L,D) < pT, and the feasible design with the minimum construction cost is selected as the final design. Equations are derived for this expanded reliability-based design (RBDE) approach and criteria are established for the minimum number of MCS samples to ensure a desired level of accuracy. The RBDE approach with MCS is illustrated through a design example of a square spread foundation with a fixed depth that has been used for the evaluation of Eurocode 7. The results are consistent with those from previous reliability analysis reported in the literature. In addition, the RBDE approach with MCS offers design engineers insights into how the expected performance level of spread foundations changes as B, L and D change, and it allows design engineers to adjust pT, without additional computational efforts, to cater for the needs of particular projects. It also provides design engineers with flexibility in modeling the uncertainties and selecting proper deterministic ULS and SLS calculation models. Source


Yau Y.,City University of Hong Kong
Habitat International | Year: 2011

Management of apartment buildings is never straightforward because of the need for collective homeowner action. Mancur Olson suggests that a rational individual will not participate in collective action which provides no positive net benefit for him or her. Based on this premise, it would seem that rationality drives homeowners to free-ride on others' efforts and that, as a result, no collective action will take place. However, some homeowners do actively participate in housing management, and it is worthwhile to examine why some participate and others do not. Building on the wide-ranging applications of the collective interest model (CIM) in explaining political participation and environmental activism, this paper expands its relevance to the arena of housing management. The explanatory analysis which is based on the findings of a structured questionnaire survey in Hong Kong corroborates the central propositions of the CIM and provides a theoretical account of housing management activism. In brief, housing management activism is a function of beliefs about personal and group efficacy, the value of the collective good, and the selective benefits and costs of participation. These findings have far-reaching implications for the formulation of government policies promoting homeowners' active involvement in housing management in Hong Kong and other megacities. © 2010 Elsevier Ltd. Source


la Grange A.,City University of Hong Kong
Urban Studies | Year: 2011

This paper investigates the relationship between neighbourhood cohesion and organisation and class in Hong Kong. It draws on a survey of 1200 face-to-face interviews in an up-market private housing estate on Hong Kong Island, a large, neither rich nor poor public housing estate in the New Territories and a mixed-use, low-income inner-city neighbourhood in Kowloon. Four indexes measure interneighbourhood and intraneighbourhood differences-namely, attraction to neighbourhood, neighbouring and psychological sense of community adapted from the Buckner scale of social cohesion, and social organisation developed by the author. There are significant differences between the neighbourhoods. However, these differences are not duplicated between occupation-defined class within the neighbourhoods, although there are some differences based on self-defined social class. The likely explanation lies in the character of the three neighbourhoods, government policy, the effect of private housing management and the low level of spatial differentiation by income across the city. © 2010 Urban Studies Journal Limited. Source


Yung Y.,City University of Hong Kong
Housing Studies | Year: 2011

In 2003, the Housing Department launched a marking scheme which aimed to improve environmental hygiene in public housing estates in Hong Kong. Although the scheme can potentially stop anti-social behaviour and other misconduct in public housing estates, the choice of public housing tenants as the sole target of control has not been clearly explained. Therefore, this study attempts to justify this administration-driven marking scheme. It appears that welfare conditionality cannot fully justify the scheme because public housing tenants are not the only recipients of housing welfare in Hong Kong. In addition, discriminating between public housing tenants and the most deprived is not defensible. More importantly, not all the offences prescribed in the marking scheme are socially undesirable. However, the substance of the scheme seems to match the ideologies of Chinese legalism quite well, and the scheme appears to be an initiative by the Hong Kong Housing Authority to strengthen its sovereignty over public housing resources in the city. © 2011 Taylor & Francis. Source


Wu J.,Hong Kong Baptist University | Li J.,Hong Kong Baptist University | Chan R.K.Y.,Hong Kong Baptist University | Chan R.K.Y.,City University of Hong Kong
Optics Express | Year: 2013

This paper reports a light sheet fluorescence imaging flow cytometer for 3D sectioning of phytoplankton. The instrument developed has the inherent advantages of high cell counting throughput and high spatial resolution information derived from flow cytometry and light sheet microscopy. The throughput of the instrument is quantified by the sample volume flow rate of 0.5 μl/min with a spatial resolution as achieved by light sheet microscopy. Preliminary results from 3D morphology of the internal chlorophyll-a structure of two dinoflagellates species show promising application potentials of the method for phytoplankton taxonomy of selected species and species groups. © 2013 Optical Society of America. Source


Zhong L.Y.,City University of Hong Kong
International Journal of Offender Therapy and Comparative Criminology | Year: 2010

From the perspective of prosocial behavior, bystander intervention is conditioned by situational factors; from an informal social control perspective, bystander intervention has been demonstrated to be associated with level of crime and violence at the community level. By drawing on findings in two contrasting communities within a Chinese city, this study investigates the effects of fear of crime and type of community on bystander intervention. It shows that fear of crime and type of community have robust and consistent effects on bystander intervention, controlling for demographic characteristics including sex, age, and education. The implications of the findings are discussed in terms of bystander intervention as both prosocial behavior and informal social control. The findings also question the usefulness of simply casting bystander nonintervention as corrupted morality in China. © 2010 SAGE Publications. Source


Yuan L.,Chongqing Technology and Business University | Lu Y.Y.,City University of Hong Kong
Optics Express | Year: 2013

Nonlinear optical effects can be enhanced by photonic crystal microcavities and be used to develop practical ultra-compact optical devices with low power requirements. The finite-difference time-domain method is the standard numerical method for simulating nonlinear optical devices, but it has limitations in terms of accuracy and efficiency. In this paper, a rigorous and efficient frequency-domain numerical method is developed for analyzing nonlinear optical devices where the nonlinear effect is concentrated in the microcavities. The method replaces the linear problem outside the microcavities by a rigorous and numerically computed boundary condition, then solves the nonlinear problem iteratively in a small region around the microcavities. Convergence of the iterative method is much easier to achieve since the size of the problem is significantly reduced. The method is presented for a specific two-dimensional photonic crystal waveguide-cavity system with a Kerr nonlinearity, using numerical methods that can take advantage of the geometric features of the structure. The method is able to calculate multiple solutions exhibiting the optical bistability phenomenon in the strongly nonlinear regime. © 2013 Optical Society of America. Source


Huang X.,Shanghai JiaoTong University | Zhi C.,City University of Hong Kong | Jiang P.,Shanghai JiaoTong University | Golberg D.,Japan International Center for Materials Nanoarchitectonics | And 2 more authors.
Advanced Functional Materials | Year: 2013

Dielectric polymer composites with high thermal conductivity are very promising for microelectronic packaging and thermal management application in new energy systems such as solar cells and light emitting diodes (LEDs). However, a well-known paradox is that conventional composites with high thermal conductivity usually suffer from the high dielectric constant and high dielectric loss, while on the other hand, composite materials with excellent dielectric properties usually possess low thermal conductivity. In this work, an ideal dielectric thermally conductive epoxy nanocomposite is successfully fabricated using polyhedral oligosilsesquioxane (POSS) functionalized boron nitride nanotubes (BNNTs) as fillers. The nanocomposites with 30 wt% fraction of POSS modified BNNTs exhibit much lower dielectric constant, dielectric loss tangent, and coefficient of thermal expansion in comparison with the pure epoxy resin. As an example, below 100 Hz, the dielectric loss of the nanocomposites with 20 and 30 wt% BNNTs is reduced by one order of magnitude in comparison with the pure epoxy resin. Moreover, the nanocomposites show a dramatic thermal conductivity enhancement of 1360% in comparison with the pristine epoxy resin at a BNNT loading fraction of 30 wt%. The merits of the designed composites are suggested to originate from the excellent intrinsic properties of embedded BNNTs, effective surface modification by POSS molecules, and carefully developed composite preparation methods. An ideal, dielectric, thermally conductive epoxy nanocomposite is successfully fabricated using polyhedral oligosilsesquioxane (POSS) functionalized boron nitride nanotubes (BNNTs) as fillers. Compared with the pure epoxy resin, the nanocomposites with POSS modified BNNTs not only exhibit much lower dielectric constant and dielectric loss tangent but also have high thermal conductivity and a low coefficient of thermal expansion Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. Source


Liu M.,Chongqing University | Chiang K.S.,City University of Hong Kong
Optics Express | Year: 2010

It is known that a decoupled two-core fiber can prevent monochromatic light at a specific wavelength (the decoupling wavelength) launched into one core from coupling to the other core. In this paper, we show that a pulse at the decoupling wavelength launched into one core of such a fiber inevitably splits into two pairs of pulses propagating in the two cores along the fiber. The minimum distance required for pulse splitting to be visible is inversely proportional to the coupling-coefficient dispersion in the fiber and linearly proportional to the pulse width. It would take only several centimeters of a recently demonstrated decoupled two-core photonic-bandgap fiber to observe the pulse-splitting effect with a 100-fs pulse. We also study the effects of self-phase modulation on the pulse propagation dynamics in a decoupled two-core fiber in both the normal and anomalous dispersion regimes. © 2010 Optical Society of America. Source


Au S.-K.,City University of Hong Kong | To P.,Arup
Journal of Structural Engineering (United States) | Year: 2012

This paper presents work on validating the dynamic wind load predicted by a wind tunnel model with the values identified from full-scale field vibration data of a super-tall building in Hong Kong. Dynamic wind load in this work refers to the power spectral density (PSD) of the modal force near the natural frequency of a particular mode of the building, in the context of random vibration with stationary loading and response. This quantity reflects the turbulence characteristics integrated over the building body and is of importance in wind engineering design. This study presents a method to predict the modal PSD of wind load of the first two translational modes of a tall building. The method combines wind tunnel test information and mean wind data available in the free field; the latter taken to be at the Waglan Island station maintained by the Hong Kong Observatory. On the full-scale side, although the modal PSD is not directly observable, it is identified from field vibration data measured at the building top during strong wind events. A Bayesian modal identification method is used for determining the most probable value and the uncertainty of the modal parameters including the natural frequency, damping ratio, and the modal PSD. A number of recent strong wind events are analyzed. Reasonable agreement is observed between the wind tunnel model predictions and the values identified from field data. Factors that can potentially lead to discrepancy are discussed. As the same random vibration modeling consistent with conventional wind engineering design has been used in the wind tunnel prediction model and field identification model, the results are directly transferable among these three disciplines. © 2012 American Society of Civil Engineers. Source


Lim C.W.,City University of Hong Kong
Applied Mathematics and Mechanics (English Edition) | Year: 2010

This paper has successfully addressed three critical but overlooked issues in nonlocal elastic stress field theory for nanobeams: (i) why does the presence of increasing nonlocal effects induce reduced nanostructural stiffness in many, but not consistently for all, cases of study, i.e., increasing static deflection, decreasing natural frequency and decreasing buckling load, although physical intuition according to the nonlocal elasticity field theory first established by Eringen tells otherwise? (ii) the intriguing conclusion that nanoscale effects are missing in the solutions in many exemplary cases of study, e.g., bending deflection of a cantilever nanobeam with a point load at its tip; and (iii) the non-existence of additional higher-order boundary conditions for a higher-order governing differential equation. Applying the nonlocal elasticity field theory in nanomechanics and an exact variational principal approach, we derive the new equilibrium conditions, domain governing differential equation and boundary conditions for bending of nanobeams. These equations and conditions involve essential higher-order differential terms which are opposite in sign with respect to the previously studies in the statics and dynamics of nonlocal nano-structures. The difference in higher-order terms results in reverse trends of nanoscale effects with respect to the conclusion of this paper. Effectively, this paper reports new equilibrium conditions, governing differential equation and boundary conditions and the true basic static responses for bending of nanobeams. It is also concluded that the widely accepted equilibrium conditions of nonlocal nanostructures are in fact not in equilibrium, but they can be made perfect should the nonlocal bending moment be replaced by an effective nonlocal bending moment. These conclusions are substantiated, in a general sense, by other approaches in nanostructural models such as strain gradient theory, modified couple stress models and experiments. © 2010 Shanghai University and Springer Berlin Heidelberg. Source


Feng B.,South China University of Technology | Fan Z.-P.,Northeastern University China | Li Y.,City University of Hong Kong
International Journal of Production Economics | Year: 2011

Although supplier selection in multi-service outsourcing is a very important decision problem, research concerning this issue is still relatively scarce. This paper proposes a decision method for selecting a pool of suppliers for the provision of different service process/product elements. It pioneers the use of collaborative utility between partner firms for supplier selection. A multi-objective model is built to select desired suppliers. This model is proved to be NP-hard, so we develop a multi-objective algorithm based on Tabu search for solving it. We then use an example to show the applicability of the proposed model and algorithm. Extensive computational experiments are also conducted to further test the performance of the proposed algorithm. © 2011 Elsevier B.V. All rights reserved. Source


Hu J.,University of Electronic Science and Technology of China | Feng G.,City University of Hong Kong
Asian Journal of Control | Year: 2011

This paper presents a study of a tracking control problem for a multiagent system with an active leader and quantized communication constraints. We first design a discrete-time distributed estimator-based tracking control for each follower-agent and analyze the tracking convergence with the help of the Riccati equation and common Lyapunov function when the communication channel is perfect and the interconnection topology is time-varying. Then a stochastic quantization strategy is applied to model the information communication in the agent coordination and the corresponding solution to the tracking control problem is also given. Finally, a numerical example is given to illustrate the tracking control algorithm. © 2010 John Wiley and Sons Asia Pte Ltd and Chinese Automatic Control Society. Source


Wang Q.,Beihang University | Chen G.,City University of Hong Kong | Perc M.,University of Maribor
PLoS ONE | Year: 2011

This paper investigates the dependence of synchronization transitions of bursting oscillations on the information transmission delay over scale-free neuronal networks with attractive and repulsive coupling. It is shown that for both types of coupling, the delay always plays a subtle role in either promoting or impairing synchronization. In particular, depending on the inherent oscillation period of individual neurons, regions of irregular and regular propagating excitatory fronts appear intermittently as the delay increases. These delay-induced synchronization transitions are manifested as wellexpressed minima in the measure for spatiotemporal synchrony. For attractive coupling, the minima appear at every integer multiple of the average oscillation period, while for the repulsive coupling, they appear at every odd multiple of the half of the average oscillation period. The obtained results are robust to the variations of the dynamics of individual neurons, the system size, and the neuronal firing type. Hence, they can be used to characterize attractively or repulsively coupled scalefree neuronal networks with delays. © 2011 Wang et al. Source


Fung A.L.-C.,City University of Hong Kong | Raine A.,University of Pennsylvania
Journal of Personality Disorders | Year: 2012

There has been no prior research on peer victimization and child or adolescent schizotypal personality. This study tests the hypothesis that increased peer victimization is associated with increased schizotypal personality. Schizotypy was assessed using the SPQ-C (Schizotypal Personality Questionnaire-Child) in 3,508 male and female schoolchildren aged 8 to 16 years. All forms of peer victimization (physical, verbal, social manipulation, attack on property) were associated with schizotypal personality in both males and females across all age groups. Signifcant victimization more than doubled schizotypy scores. It is hypothesized that peer victimization may predispose to paranoid ideation, social anxiety, and lack of close friends, and consequently heightened schizotypal personality. © 2012 The Guilford Press. Source


Wang J.,City University of Hong Kong
IEEE Transactions on Services Computing | Year: 2011

Service-Oriented Architecture (SOA) is emerging as the next inevitable technology for application developments. One fundamental issue of SOA is service composition, i.e., to seamlessly compose distributed services into more complex applications. In the mobile environment, a service composition may face disruptions caused by the movement of both users and service providers. Thus, a dependable service composition is desired to handle the mobility in the environment. In this paper, we propose to achieve dependable service composition by taking the mobility prediction of the service providers into consideration. We exploit the fact that the service providers can predict their stay time in the current environment. However, some uncertainty may exist in the prediction such that a service provider may move out of the current environment earlier than the prediction. We use two models to characterize the uncertainty, a probability-free model and a probabilistic model. Our objective is to design dependable service composition under these two models such that the service composition solution can have the maximum tolerance to the uncertainty of the mobility prediction. We focus on the case of sequential service composition, prove the NP-hardness of the problem, then present heuristic algorithms, derive the upper and lower bounds of the problem. Simulation results have showcased the effectiveness of the heuristic algorithms. © 2008 IEEE. Source


Wen G.,Peking University | Duan Z.,Peking University | Yu W.,Nanjing Southeast University | Chen G.,City University of Hong Kong
International Journal of Robust and Nonlinear Control | Year: 2013

This paper is concerned with the problem of consensus in directed networks of multiple agents with intrinsic nonlinear dynamics and sampled-data information. A new protocol is induced from a class of continuous-time linear consensus protocols by implementing data-sampling technique and a zero-order hold circuit. On the basis of a delayed-input approach, the sampled-data multi-agent system is converted to an equivalent nonlinear system with a time-varying delay. Theoretical analysis on this time-delayed system shows that consensus with asymptotic time-varying velocities in a strongly connected network can be achieved over some suitable sampled-data intervals. A multi-step procedure is further presented to estimate the upper bound of the maximal allowable sampling intervals. The results are then extended to a network topology with a directed spanning tree. For the case of the topology without a directed spanning tree, it is shown that the new protocol can still guarantee the system to achieve consensus by appropriately informing a fraction of agents. Finally, some numerical simulations are presented to demonstrate the effectiveness of the theoretical results and the dependence of the upper bound of maximal allowable sampling interval on the coupling strength. Copyright © 2012 John Wiley & Sons, Ltd. Source


Wei K.-K.,City University of Hong Kong | Teo H.-H.,National University of Singapore | Chan H.C.,National University of Singapore | Tan B.C.Y.,National University of Singapore
Information Systems Research | Year: 2011

The digital divide has loomed as a public policy issue for over a decade. Yet, a theoretical account for the effects of the digital divide is currently lacking. This study examines three levels of the digital divide. The digital access divide (the first-level digital divide) is the inequality of access to information technology (IT) in homes and schools. The digital capability divide (the second-level digital divide) is the inequality of the capability to exploit IT arising from the first-level digital divide and other contextual factors. The digital outcome divide (the third-level digital divide) is the inequality of outcomes (e.g., learning and productivity) of exploiting IT arising from the second-level digital divide and other contextual factors. Drawing on social cognitive theory and computer self-efficacy literature, we developed a model to show how the digital access divide affects the digital capability divide and the digital outcome divide among students. The digital access divide focuses on computer ownership and usage in homes and schools. The digital capability divide and the digital outcome divide focus on computer self-efficacy and learning outcomes, respectively. This model was tested using data collected from over 4,000 students in Singapore. The results generate insights into the relationships among the three levels of the digital divide and provide a theoretical account for the effects of the digital divide. While school computing environments help to increase computer self-efficacy for all students, these factors do not eliminate knowledge the gap between students with and without home computers. Implications for theory and practice are discussed. © 2011 INFORMS. Source


Liu Z.-Q.,City University of Hong Kong | Liu Y.-K.,Hebei University
Soft Computing | Year: 2010

This paper proposes an axiomatic framework from which we develop the theory of type-2 (T2) fuzziness, called fuzzy possibility theory. First, we introduce the concept of a fuzzy possibility measure in a fuzzy possibility space (FPS). The fuzzy possibility measure takes on regular fuzzy variable (RFV) values, so it generalizes the scalar possibility measure in the literature. One of the interesting consequences of the FPS is that it leads to a new definition of T2 fuzzy set on the Euclidean space Rm which we call T2 fuzzy vector, as a map to the space instead of on the space. More precisely, we define a T2 fuzzy vector as a measurable map from an FPS to the space Rm of real vectors. In the current development, we are suggesting that T2 fuzzy vector is a more appropriate definition for a T2 fuzzy set on Rm In the literature, a T2 fuzzy set is usually defined via its T2 membership function, whereas in this paper, we obtain the T2 possibility distribution function as the transformation of a fuzzy possibility measure from a universe to the space Rm via T2 fuzzy vector. Second, we develop the product fuzzy possibility theory. In this part, we give a general extension theorem about product fuzzy possibility measure from a class of measurable atom-rectangles to a product ample field, and discuss the relationship between a T2 fuzzy vector and T2 fuzzy variables. We also prove two useful theorems about the existence of an FPS and a T2 fuzzy vector based on the information from a finite number of RFV-valued maps. The two results provide the possible interpretations for the concepts of the FPS and the T2 fuzzy vector, and thus reinforce the credibility of the approach developed in this paper. Finally, we deal with the arithmetic of T2 fuzzy variables in fuzzy possibility theory. We divide our discussion into two cases according to whether T2 fuzzy variables are defined on single FPS or on different FPSs, and obtain two theorems about T2 fuzzy arithmetic. © Springer-Verlag 2009. Source


Cao X.,City University of Hong Kong | Yang F.,Hefei University of Technology
Enterprise Information Systems | Year: 2011

In exploring the business operation of Internet companies, few researchers have used data envelopment analysis (DEA) to evaluate their performance. Since the Internet companies have a two-stage production process: marketability and profitability, this study employs a relational two-stage DEA model to assess the efficiency of the 40 dot com firms. The results show that our model performs better in measuring efficiency, and is able to discriminate the causes of inefficiency, thus helping business management to be more effective through providing more guidance to business performance improvement. © 2011 Taylor & Francis. Source


Yu L.,CAS Academy of Mathematics and Systems Science | Lai K.K.,City University of Hong Kong
Decision Support Systems | Year: 2011

In this paper, a distance-based group decision-making (GDM) methodology is proposed to solve unconventional multi-person multi-criteria emergency decision-making problems. In this model, some decision-makers are first identified to formulate a group decision-making framework. Then a standard multi-criteria decision-making (MCDM) process is performed on specific decision-making problems and different decision results are obtained from different decision-makers. Finally, these different decision results are aggregated into a group consensus to support the final decision-making. For illustration and verification purposes, a numerical example and a practical unconventional emergency decision case are presented. Experimental results obtained demonstrate that the proposed distance-based multi-criteria GDM methodology can improve decision-making objectivity and emergency management effectiveness. © 2010 Elsevier B.V. All rights reserved. Source


Wang H.J.,University of Delaware | Zhao J.L.,City University of Hong Kong
Decision Support Systems | Year: 2011

In a globalized economic environment with volatile business requirements, continuous process improvement needs to be done regularly in various organizations. However, maintaining the consistency of workflow models under frequent changes is a significant challenge in the management of corporate information services. Unfortunately, few formal approaches are found in the literature for managing workflow changes systematically. In this paper, we propose an analytical framework for workflow change management through formal modeling of workflow constraints, leading to an approach called Constraint-centric Workflow Change Analytics (CWCA). A core component of CWCA is the formal definition and analysis of workflow change anomalies. We operationalize CWCA by developing a change anomaly detection algorithm and validate it in the context of procurement management. A prototype system based on an open-source rule engine is presented to provide a proof-of-concept implementation of CWCA. © 2011 Elsevier B.V. All rights reserved. Source


Dong J.-G.,City University of Hong Kong
Computers and Mathematics with Applications | Year: 2010

Oscillation criteria are established for second order nonlinear neutral differential equations with deviating arguments of the form (r (t) | z′ (t) |α - 1 z′ (t))′ + f (t, x [σ (t)]) = 0, t ≥ t0 where α > 0 and z (t) = x (t) + p (t) x [τ (t)]. Our results improve and extend some known results in the literature. Some illustrating examples are also provided to show the importance of our results. © 2010 Elsevier Ltd. All rights reserved. Source


Chen S.,Zhejiang University of Technology | Li Y.,City University of Hong Kong | Kwok N.M.,University of New South Wales
International Journal of Robotics Research | Year: 2011

In this paper we provide a broad survey of developments in active vision in robotic applications over the last 15 years. With increasing demand for robotic automation, research in this area has received much attention. Among the many factors that can be attributed to a high-performance robotic system, the planned sensing or acquisition of perceptions on the operating environment is a crucial component. The aim of sensor planning is to determine the pose and settings of vision sensors for undertaking a vision-based task that usually requires obtaining multiple views of the object to be manipulated. Planning for robot vision is a complex problem for an active system due to its sensing uncertainty and environmental uncertainty. This paper describes such problems arising from many applications, e.g. object recognition and modeling, site reconstruction and inspection, surveillance, tracking and search, as well as robotic manipulation and assembly, localization and mapping, navigation and exploration. A bundle of solutions and methods have been proposed to solve these problems in the past. They are summarized in this review while enabling readers to easily refer solution methods for practical applications. Representative contributions, their evaluations, analyses, and future research trends are also addressed in an abstract level. © SAGE Publications 2011. Source


Jones R.H.,City University of Hong Kong
Sport, Education and Society | Year: 2011

This paper explores the role of digital media and creativity in the processes of learning that occur in groups of urban skateboarders. In particular, it examines how the production and consumption of amateur videos contribute to both skaters' mastery of the techniques of the sport and their integration into the culture of the sport. The data come from an ethnographic study of skateboarders in Hong Kong, which included in-depth interviews, participant observation and the collection of texts and artifacts like magazines, blog entries and amateur skating videos. Skateboarders use video in a number of ways that significantly impact their learning and integration into their communities. They use it to analyze tricks and techniques, to document the stages of their learning and socialization into the group, to set community standards, to build a sense of belonging with their 'crews' and to imagine 'idealized futures' for themselves and their communities. Understanding the value and function of such 'semiotic mediation' in learning and socialization into sport cultures, I suggest, can contribute to helping physical educators design tasks that integrate training in physical skills with opportunities for students to make meaning around their experiences of sport and physical education. © 2011 Copyright Taylor and Francis Group, LLC. Source


Sutanto J.,ETH Zurich | Palme E.,Newscron Ltd. | Tan C.-H.,City University of Hong Kong | Phang C.W.,Fudan University
MIS Quarterly: Management Information Systems | Year: 2013

Privacy has been an enduring concern associated with commercial information technology (IT) applications, in particular regarding the issue of personalization. IT-enabled personalization, while potentially making the user computing experience more gratifying, often relies heavily on the user's personal information to deliver individualized services, which raises the user's privacy concerns. We term the tension between personalization and privacy, which follows from marketers exploiting consumers' data to offer personalized product information, the personalization-privacy paradox. To better understand this paradox, we build on the theoretical lenses of uses and gratification theory and information boundary theory to conceptualize the extent to which privacy impacts the process and content gratifications derived from personalization, and how an IT solution can be designed to alleviate privacy concerns. 1 Set in the context of personalized advertising applications for smartphones, we propose and prototype an IT solution, referred to as a personalized, privacy-safe application, that retains users' information locally on their smartphones while still providing them with personalized product messages. We validated this solution through a field experiment by benchmarking it against two more conventional applications: a base non-personalized application that broadcasts non-personalized product information to users, and a personalized, non-privacy safe application that transmits user information to a central marketer's server. The results show that (com-pared to the non-personalized application), while personalized, privacy-safe or not increased application usage (reflecting process gratification), it was only when it was privacy-safe that users saved product messages (reflecting content gratification) more frequently. Follow-up surveys corroborated these nuanced findings and further revealed the users' psychological states, which explained our field experiment results. We found that saving advertisements for content gratification led to a perceived intrusion of information boundary that made users reluctant to do so. Overall our proposed IT solution, which delivers a personalized service but avoids transmitting users' personal information to third parties, reduces users' perceptions that their information boundaries are being intruded upon, thus mitigating the personalization-privacy paradox and increasing both process and content gratification. Source


Xi Z.,University of New South Wales | Feng G.,City University of Hong Kong | Hesketh T.,University of New South Wales
IEEE Transactions on Fuzzy Systems | Year: 2011

This paper addresses piecewise sliding-mode control for Takagi-Sugeno (T-S) fuzzy models. A novel sliding-mode control (SMC) design approach is developed which is based on individual sliding surface in each local region of the T-S fuzzy systems. Conditions of existence of sliding mode in the associated region are given. The chattering effect around region boundaries is analyzed, and prevention of such chattering is discussed. Two illustrative examples are finally given to illustrate the effectiveness and performance of the proposed controller. © 2006 IEEE. Source


Ye R.R.,City University of Hong Kong
Environmental science and pollution research international | Year: 2011

BDE-47 is one of the most widely found congeners of PBDEs in marine environments. The potential immunomodulatory effects of BDE-47 on fish complement system were studied using the marine medaka Oryzias melastigma as a model fish. Three-month-old O. melastigma were subjected to short-term (5 days) and long-term (21 days) exposure to two concentrations of BDE-47 (low dose at 290 ± 172 ng/day; high dose at 580 ± 344 ng/day) via dietary uptake of BDE-47 encapsulated in Artemia nauplii. Body burdens of BDE-47 and other metabolic products were analyzed in the exposed and control fish. Only a small amount of debrominated product, BDE-28, was detected, while other metabolic products were all under detection limit. Transcriptional expression of six major complement system genes involved in complement activation: C1r/s (classical pathway), MBL-2 (lectin pathway), CFP (alternative pathway), F2 (coagulation pathway), C3 (the central component of complement system), and C9 (cell lysis) were quantified in the liver of marine medaka. Endogenous expression of all six complement system genes was found to be higher in males than in females (p < 0.05). Upon dietary exposure of marine medaka to BDE-47, expression of all six complement genes were downregulated in males at day 5 (or longer), whereas in females, MBl-2, CFP, and F2 mRNAs expression were upregulated, but C3 and C9 remained stable with exposure time and dose. A significant negative relationship was found between BDE-47 body burden and mRNA expression of C1r/s, CFP, and C3 in male fish (r = -0.8576 to -0.9447). The above findings on changes in complement gene expression patterns indicate the complement system may be compromised in male O. melastigma upon dietary exposure to BDE-47. Distinct gender difference in expression of six major complement system genes was evident in marine medaka under resting condition and dietary BDE-47 challenge. The immunomodulatory effects of BDE-47 on transcriptional expression of these complement components in marine medaka were likely induced by the parent compound instead of biotransformed products. Our results clearly demonstrate that future direction for fish immunotoxicology and risk assessment of immunosuppressive chemicals must include parallel evaluation for both genders. Source


Ghose A.,New York University | Goldfarb A.,University of Toronto | Han S.P.,City University of Hong Kong
Information Systems Research | Year: 2013

We explore how Internet browsing behavior varies between mobile phones and personal computers. Smaller screen sizes on mobile phones increase the cost to the user of browsing for information. In addition, a wider range of offline locations for mobile Internet usage suggests that local activities are particularly important. Using data on user behavior at a (Twitter-like) microblogging service, we exploit exogenous variation in the ranking mechanism of posts to identify the ranking effects. We show that (1) ranking effects are higher on mobile phones suggesting higher search costs: links that appear at the top of the screen are especially likely to be clicked on mobile phones and (2) the benefit of browsing for geographically close matches is higher on mobile phones: stores located in close proximity to a user's home are much more likely to be clicked on mobile phones. Thus, the mobile Internet is somewhat less "Internet-like": search costs are higher and distance matters more. We speculate on how these changes may affect the future direction of Internet commerce. © 2013 Informs. Source


Natarajan K.,City University of Hong Kong | Teo C.P.,National University of Singapore | Zheng Z.,National University of Singapore
Operations Research | Year: 2011

In this paper, we analyze mixed 0-1 linear programs under objective uncertainty. The mean vector and the second-moment matrix of the nonnegative objective coefficients are assumed to be known, but the exact form of the distribution is unknown. Our main result shows that computing a tight upper bound on the expected value of a mixed 0-1 linear program in maximization form with random objective is a completely positive program. This naturally leads to semidefinite programming relaxations that are solvable in polynomial time but provide weaker bounds. The result can be extended to deal with uncertainty in the moments and more complicated objective functions. Examples from order statistics and project networks highlight the applications of the model. Our belief is that the model will open an interesting direction for future research in discrete and linear optimization under uncertainty. © 2011 INFORMS. Source


Liu G.,City University of Hong Kong | Hong L.J.,Hong Kong University of Science and Technology
Operations Research | Year: 2011

The Greeks are the derivatives (also known as sensitivities) of the option prices with respect to market parameters. They play an important role in financial risk management. Among many Monte Carlo methods of estimating the Greeks, the classical pathwise method requires only the pathwise information that is directly observable from simulation and is generally easier to implement than many other methods. However, the classical pathwise method is generally not applicable to the Greeks of options with discontinuous payoffs and the second-order Greeks. In this paper, we generalize the classical pathwise method to allow discontinuity in the payoffs. We show how to apply the new pathwise method to the first- and second-order Greeks and propose kernel estimators that require little analytical efforts and are very easy to implement. The numerical results show that our estimators work well for practical problems. © 2011 INFORMS. Source


Kankanhalli A.,National University of Singapore | Lee O.-K.,University of Massachusetts Boston | Lim K.H.,City University of Hong Kong
Information and Management | Year: 2011

Organizations are implementing electronic repository systems to facilitate knowledge reuse but with varying degrees of success. There is a lack of understanding of how individual and technical factors interact in determining knowledge reuse and the performance benefits that could be derived from electronic knowledge repositories. We proposed a model to explain the impact of user motivation and the user's perception of the value of the available knowledge repository on knowledge reuse and the individual's performance benefits through using the system. Through a field survey, we found that perceived knowledge repository capability and intrinsic motivation positively affected knowledge reuse, which in turn impacted the benefits derived from using the system. We also found that perceived knowledge repository capability moderated the relationship between extrinsic reward and knowledge reuse. © 2011 Elsevier B.V. All rights reserved. Source


Chow N.-K.,City University of Hong Kong
Journal of Global Information Management | Year: 2011

This study explores key factors affecting the usage of information technology (IT) tools in support of knowledge sharing in service organizations in Hong Kong. In a case study of five firms, the usage of IT tools is influenced by an array of factors acting as enablers, barriers, and motivators. The findings support extant theories on knowledge management (KM). This research discovers relationships between multiple factors and the usage of IT tools for knowledge sharing at various hierarchical levels. Operational factors like perceived usefulness, perceived ease of use, staff capability, and nature of work induce higher usage of IT for knowledge sharing. These findings and related analyses have managerial implications for firms engaging in service business. Copyright © 2011, IGI Global. Source


Yu Y.T.,City University of Hong Kong | Lau M.F.,Swinburne University of Technology
Information and Software Technology | Year: 2012

Context: Existing test suite prioritization techniques usually rely on code coverage information or historical execution data that serve as indicators for estimating the fault-detecting ability of test cases. Such indicators are primarily empirical in nature and not theoretically driven; hence, they do not necessarily provide sound estimates. Also, these techniques are not applicable when the source code is not available or when the software is tested for the first time. Objective: We propose and develop the novel notion of fault-based prioritization of test cases which directly utilizes the theoretical knowledge of their fault-detecting ability and the relationships among the test cases and the faults in the prescribed fault model, based on which the test cases are generated. Method: We demonstrate our approach of fault-based prioritization by applying it to the testing of the implementation of logical expressions against their specifications. We then validate our proposal by an empirical study that evaluates the effectiveness of prioritization techniques using two different metrics. Results: A theoretically guided fault-based prioritization technique generally outperforms other techniques under study, as assessed by two different metrics. Our empirical results also show that the technique helps to reveal all target faults by executing only about 72% of the prioritized test suite, thereby reducing the effort required in testing. Conclusions: The fault-based prioritization approach is not only applicable to the instance empirically validated in this paper, but should also be adaptable to other fault-based testing strategies. We also envisage new research directions to be opened up by our work. © 2011 Elsevier B.V. All rights reserved. Source


Yang T.,CAS Technical Institute of Physics and Chemistry | Wang H.,CAS Technical Institute of Physics and Chemistry | Ou X.-M.,CAS Technical Institute of Physics and Chemistry | Lee C.-S.,City University of Hong Kong | Zhang X.-H.,CAS Technical Institute of Physics and Chemistry
Advanced Materials | Year: 2012

A new 1D core-shell strategy is demonstrated for a hydrogen-generation photo-electrochemical cell (PEC). This Si/iodine-doped poly(3,4- ethylenedioxythiophene) (PEDOT) 1D nanocable array shows an encouraging solar-to-chemical energy-conversion efficiency. Coating with iodine-doped PEDOT can effectively enhance the photocatalytic efficiency and stability of SiNW arrays. The PEC model proposed shows a potentially promising structure for H2 production using solar energy. © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. Source


Yau Y.,City University of Hong Kong
Urbani Izziv | Year: 2012

Because of aggravating antisocial behaviour (ASB) or the 7neighbourhood problem in housing, many western governments have given ASB control a central place in their policy agendas. However, tackling ASB often involves a great deal of politics. Although ASB and controlling it have attracted much scholarly attention, the focus has almost always been placed on social housing. It is unclear whether this problem does not exist in other types of housing or if it is simply ignored. Drawing on a study of private housing developments in Hong Kong, this article examines the extent and seriousness of ASB as a problem in private housing. It shows that the problem does raise wide concerns among residents, and that many residents complain about noise nuisances and littering in their living places. On the other hand, most residents feel that the efforts of housing management agents in countering the problem are in vain or inadequate. In fact, when reacting to ASB, housing managers inevitably face a number of issues that originate from the joint appointment of managers by all homeowners and the lack of enforcement powers. In particular, controlling some neighbourhood nuisances is difficult and costly. This article concludes with an agenda for empirical research to explain the proliferation of ASB from the transaction-cost perspective. Source


Li J.C.M.,City University of Hong Kong
International Journal of Offender Therapy and Comparative Criminology | Year: 2013

Violence against sex workers is considered a global phenomenon. Despite this, very little is known about the patterns and nature of this form of violence. This article is concerned with violence against Chinese female sex workers in Hong Kong. Based on a systematic analysis of 75 police case files, it was found that violent attacks on sex workers display clear temporal and spatial patterns, and that perpetrators share certain characteristics. The article concludes that violence against female sex workers in the Chinese context is largely opportunity driven and goes on to argue that situational measures offer the greatest potential for preventive gains. Barriers to effective implementation such as the inappropriate or unfavourable responses of the government, the police, community leaders, and local residents toward commercial sexual activity are also discussed. © The Author(s) 2012. Source


Teoh W.Y.,City University of Hong Kong | Scott J.A.,University of New South Wales | Amal R.,University of New South Wales
Journal of Physical Chemistry Letters | Year: 2012

The field of heterogeneous photocatalysis has expanded rapidly in the last four decades, having undergone various evolutionary phases related to energy and the environment. The two most significant applications of photocatalysis are geared toward solar water splitting and the purification of air and water. Notably, the interdisciplinary nature of the field has increased significantly, incorporating semiconductor physics, surface sciences, photo and physical chemistry, materials science, and chemical engineering. Whereas this forms the basis on which the field continues to grow, adequate bridging of multidisciplinary knowledge remains essential. By recalling some of the classical fundamentals of photocatalysis, this Perspective provides contemporary views on heterogeneous photochemical conversion, encompassing charge transport characteristics, radical chemistry and organic degradation mechanisms, photocatalyst design, and photoreactor engineering. © 2012 American Chemical Society. Source


Zhu L.,Hong Kong Polytechnic University | Lu J.,City University of Hong Kong
International Journal of Plasticity | Year: 2012

Rendering a bimodal grain size distribution in nanostructured materials has been proved to effectively achieve both higher strength and higher ductility, which is based on the ansatz that large grains provide hardening ability and small grains provide larger yield stress. Here we propose a theoretical model focusing on the behaviour of nano/microcracks, which nucleate in the nano/ultrafine grained phase and stop at the boundary of large grains during the plastic deformation. We found that nano/microcracks do not lead to catastrophic failure; instead, they induce the back stress for the strain hardening and also the variation of the mechanical behaviour in the nano/ultrafine grained phase. With the aid of the modified mean field approach, the stress-strain relationship of the bimodal metals can be derived by combining the constitutive relations of the nano/ultrafine grained phase and the coarse grained phase. Numerical results show that the proposed model can successfully describe the enhanced strength and ductility of the bimodal metals. The predictions of the bimodal nickels are in good agreement with the experimental results. It is further noted that the strength and ductility of a bimodal metal are sensitive to the volume fraction of constituents and the distribution of nano/microcracks. This theoretical model can be utilized to optimize the mechanical properties of the bimodal metals, by tuning the constituent fractions and the size of the microstructures. © 2011 Elsevier Ltd. All rights reserved. Source


Chu P.K.,City University of Hong Kong
IEEE Transactions on Plasma Science | Year: 2013

Despite the tremendous potential of biodegradable magnesium alloys in surgical implants, the intrinsic degradation rates of Mg-based biomedical implants may be too fast in the physiological environment, particularly in the early stage after surgery. This shortcoming has been hampering wider clinical applications. In this respect, surface modification by plasma-based techniques is a good means to tailor the surface structure and degradation rate of magnesium alloys. The work conducted in the Plasma Laboratory of the City University of Hong Kong in the past two to three years in this area is summarized and discussed in a chronological order in this paper. Different physiologically important elements such as aluminum, titanium, oxygen, zinc, and chromium have been plasma implanted into various biomedical magnesium alloys to alter the surface chemistry and corrosion behavior. This paper discusses the roles played by these plasma-implanted elements and the subsequent effects pertaining to the control of surface degradation from the perspective of orthopedic and cardiovascular applications. © 1973-2012 IEEE. Source


Lo T.W.,City University of Hong Kong
British Journal of Criminology | Year: 2010

In view of the smuggling out of democratic leaders after the Tiananmen crackdown in 1989 and China's resumption of sovereignty of Hong Kong in 1997, China applied a 'united front' tactic to recruit Hong Kong triad societies to the Communist camp. Consequently, triad leaders were able to set foot in China and bridge up with officials and state enterprises. Against this backdrop, this paper argues that when political dynamics is involved, both the traditional structural and social network approaches are insufficient to explain triad-organized crime. Therefore, social capital perspective is proposed. Using two case studies, it was discovered that the triad leaders converted the social capital they developed in mainland China into economic capital through illegitimate means in the stock market. The paper concludes by highlighting the similarities and differences between this triad-organized crime and other forms of Chinese organized crime. The Author 2010. Published by Oxford University Press on behalf of the Centre for Crime and Justice Studies (ISTD). All rights reserved.2010 © The Author 2010. Published by Oxford University Press on behalf of the Centre for Crime and Justice Studies (ISTD). All rights reserved. Source


Yau Y.,City University of Hong Kong
Waste Management | Year: 2010

Efficacy of waste recycling is one of the key determinants of environmental sustainability of a city. Like other pro-environmental activities, waste recycling cannot be successfully accomplished by just one or two people, but only by a concerted effort of the community. The collective-action dilemma creates a common underlying difficulty in formulating workable solutions to many environmental problems. With a view to the non-excludability of the outcome, rationality drives people to free-ride efforts of others in waste recycling. To solve this free-rider problem, some scholars suggest the use of economic incentive. This article attempts to study the impacts of reward schemes on waste recycling behaviour of residents in 122 private housing estates in Hong Kong. The study is differentiable from the others as the latter mainly focus on domestic waste recycling in low-rise low-density housing while this one looks into the same in a high-rise high-density residential setting. According to the results of analyses on a set of aggregate data, reward schemes are found to have a significant positive relationship with the per-household weight of recyclables collected, keeping other things constant. The research findings suggest that economic incentives do work in promoting waste recycling in Hong Kong. Practical and policy implications follow. © 2010 Elsevier Ltd. Source


Wang X.,Soochow University of China | Wang C.,Soochow University of China | Cheng L.,Soochow University of China | Lee S.-T.,City University of Hong Kong | Liu Z.,Soochow University of China
Journal of the American Chemical Society | Year: 2012

Single-walled carbon nanotubes (SWNTs) with various unique optical properties are interesting nanoprobes widely explored in biomedical imaging and phototherapies. Herein, DNA-functionalized SWNTs are modified with noble metal (Ag or Au) nanoparticles via an in situ solution phase synthesis method comprised of seed attachment, seeded growth, and surface modification with polyethylene glycol (PEG), yielding SWNT-Ag-PEG and SWNT-Au-PEG nanocomposites stable in physiological environments. With gold or silver nanoparticles decorated on the surface, the SWNT-metal nanocomposites gain an excellent concentration and excitation-source dependent surface-enhanced Raman scattering (SERS) effect. Using a near-infrared (NIR) laser as the excitation source, targeted Raman imaging of cancer cells labeled with folic acid (FA) conjugated SWNT-Au nanocomposite (SWNT-Au-PEG-FA) is realized, with images acquired in significantly shortened periods of time as compared to that of using nonenhanced SWNT Raman probes. Owing to the strong surface plasmon resonance absorption contributed by the gold shell, the SWNTs-Au-PEG-FA nanocomposite also offers remarkably improved photothermal cancer cell killing efficacy. This work presents a facile approach to synthesize water-soluble noble metal coated SWNTs with a strong SERS effect suitable for labeling and fast Raman spectroscopic imaging of biological samples, which has been rarely realized before. The SWNT-Au-PEG nanocomposite developed here may thus be an interesting optical theranostic probe for cancer imaging and therapy. © 2012 American Chemical Society. Source


Lee E.W.M.,City University of Hong Kong
Applied Soft Computing Journal | Year: 2011

This paper presents a probabilistic-entropy-based neural network (PENN) model for tackling online data regression problems. The network learns online with an incremental growth network structure and performs regression in a noisy environment. The training samples presented to the model are clustered into hyperellipsoidal Gaussian kernels in the joint space of the input and output domains by using the principles of Bayesian classification and minimization of entropy. The joint probability distribution is established by applying the Parzen density estimator to the kernels. The prediction is carried out by evaluating the expected conditional mean of the output space with the given input vector. The PENN model is demonstrated to be able to remove symmetrically distributed noise embedded in the training samples. The performance of the model was evaluated by three benchmarking problems with noisy data (i.e., Ozone, Friedman#1, and Santa Fe Series E). The results show that the PENN model is able to outperform, statistically, other artificial neural network models. The PENN model is also applied to solve a fire safety engineering problem. It has been adopted to predict the height of the thermal interface which is one of the indicators of fire safety level of the fire compartment. The data samples are collected from a real experiment and are noisy in nature. The results show the superior performance of the PENN model working in a noisy environment, and the results are found to be acceptable according to industrial requirements. © 2010 Elsevier B.V. All rights reserved. Source


Majchrzak A.,University of Southern California | Majchrzak A.,Ramon Llull University | Wagner C.,City University of Hong Kong | Yates D.,U.S. Air force
MIS Quarterly: Management Information Systems | Year: 2013

In this study, we explore the Wiki affordance of enabling shaping behavior within organizational intranets supported by Wikis. Shaping is the continuous revision of one's own and others' contributions to a Wiki. Shaping promotes knowledge reuse through improved knowledge integration. Recognizing and clarifying the role of shaping allows us to theorize new ways in which knowledge resources affect knowledge reuse. We examine the role of three knowledge resources of a Wiki contributor: knowledge depth, knowledge breadth, and assessment of the level of development of the Wiki community's transactive memory system. We offer preliminary evidence based on a sample of experienced organizational Wiki users that the three different knowledge resources have differential effects on shaping, that these effects differ from the effects on the more common user behavior of simply adding domain knowledge to a Wiki, and that shaping and adding each independently affect contributors' perceptions that their knowledge in the Wiki has been reused for organizational improvement. By empirically distinguishing between the different knowledge antecedents and consequences of shaping and adding, we derive implications for theory and research on knowledge integration and reuse. Source


Yu W.,Nanjing Southeast University | Yu W.,RMIT University | Chen G.,City University of Hong Kong | Cao M.,University of Groningen
IEEE Transactions on Automatic Control | Year: 2011

This technical note studies the consensus problem for cooperative agents with nonlinear dynamics in a directed network. Both local and global consensus are defined and investigated. Techniques for studying the synchronization in such complex networks are exploited to establish various sufficient conditions for reaching consensus. The local consensus problem is first studied via a combination of the tools of complex analysis, local consensus manifold approach, and Lyapunov methods. A generalized algebraic connectivity is then proposed to study the global consensus problem in strongly connected networks and also in a broad class of networks containing spanning trees, for which ideas from algebraic graph theory, matrix theory, and Lyapunov methods are utilized. © 2006 IEEE. Source


Zhou P.-P.,Beijing Computational Science Research Center | Zhou P.-P.,Lanzhou University | Zhang R.-Q.,City University of Hong Kong
Physical Chemistry Chemical Physics | Year: 2015

A series of benzene derivatives with different substituents adsorbed on graphene was investigated using a density-functional tight-binding method with a dispersion correction. Compared to benzene, the derivative with either an electron-withdrawing or -donating substituent exhibits stronger physisorption. Moreover, the steric size of the substituent is important in determining the adsorption strength, while the direction and the number of H atoms in the substituent affect the electron transfer from graphene. NBO analysis reveals that the stereoelectronic effect of the conjugation between the substituent and the benzene ring strongly influences the π⋯π interaction region between the molecule and graphene. The findings can deepen the understanding of the interaction between an aromatic molecule and graphene as well as the corresponding adsorption mechanism. © the Owner Societies 2015. Source


Wang D.,City University of Hong Kong
Mechanical Systems and Signal Processing | Year: 2016

Gears are the most commonly used components in mechanical transmission systems. Their failures may cause transmission system breakdown and result in economic loss. Identification of different gear crack levels is important to prevent any unexpected gear failure because gear cracks lead to gear tooth breakage. Signal processing based methods mainly require expertize to explain gear fault signatures which is usually not easy to be achieved by ordinary users. In order to automatically identify different gear crack levels, intelligent gear crack identification methods should be developed. The previous case studies experimentally proved that K-nearest neighbors based methods exhibit high prediction accuracies for identification of 3 different gear crack levels under different motor speeds and loads. In this short communication, to further enhance prediction accuracies of existing K-nearest neighbors based methods and extend identification of 3 different gear crack levels to identification of 5 different gear crack levels, redundant statistical features are constructed by using Daubechies 44 (db44) binary wavelet packet transform at different wavelet decomposition levels, prior to the use of a K-nearest neighbors method. The dimensionality of redundant statistical features is 620, which provides richer gear fault signatures. Since many of these statistical features are redundant and highly correlated with each other, dimensionality reduction of redundant statistical features is conducted to obtain new significant statistical features. At last, the K-nearest neighbors method is used to identify 5 different gear crack levels under different motor speeds and loads. A case study including 3 experiments is investigated to demonstrate that the developed method provides higher prediction accuracies than the existing K-nearest neighbors based methods for recognizing different gear crack levels under different motor speeds and loads. Based on the new significant statistical features, some other popular statistical models including linear discriminant analysis, quadratic discriminant analysis, classification and regression tree and naive Bayes classifier, are compared with the developed method. The results show that the developed method has the highest prediction accuracies among these statistical models. Additionally, selection of the number of new significant features and parameter selection of K-nearest neighbors are thoroughly investigated. © 2015 Elsevier Ltd. All rights reserved. Source


Wu L.F.,City University of Hong Kong
European Physical Journal B | Year: 2011

Research on the growth of online tagging systems not only is interesting in its own right, but also yields insights for website management and semantic web analysis. Traditional models that describing the growth of online systems can be divided between linear and nonlinear versions. Linear models, including the BA model [A.L. Barabasi, R. Albert, Science 286, 509 (1999)], assume that the average activity of users is a constant independent of population. Hence the total activity is a linear function of population. On the contrary, nonlinear models suggest that the average activity is affected by the size of the population and the total activity is a nonlinear function of population. In the current study, supporting evidences for the nonlinear growth assumption are obtained from data on Internet users' tagging behavior. A power law relationship between the number of new tags (F) and the population (P), which can be expressed as F~P γ (γ > 1), is found. I call this pattern accelerating growth and find it relates the to time-invariant heterogeneity in individual activities. I also show how a greater heterogeneity leads to a faster growth. © 2011 EDP Sciences, SIF, Springer-Verlag Berlin Heidelberg. Source


Valentine S.V.,City University of Hong Kong
Journal of Cleaner Production | Year: 2016

Many environmental networks form around specific initiatives with prescribed outcome objectives. When the objectives are met, the networks frequently disband. Technological transfer halts and the social capital built up during the initiative fragments, in many cases, disappearing altogether. In an era of globally unsustainable economic activity, encouraging progressive innovation and broadening the scale and scope of knowledge transfer is one strategy for helping to attenuate ecological damage. This paper presents empirical field work which explores the Kalundborg Symbiosis in Denmark - a network of economic actors that has organically come together to implement industrial ecology principles - and documents how this network has managed to foster progressive innovation. The four drivers which emerged as central for fostering collaboration are i) a pragmatic environmental mindset, ii) the existence of opportunities to explore possibilities, iii) mutually beneficial initiatives and iv) the presence of dominant needs which stimulate a proactive search for solutions. The paper also contributes to sustainable public policy and urban planning literature by considering how municipal involvement can foster progressive and sustained development within the Kalundborg Symbiosis. © 2016 Elsevier Ltd. Source


Tsang P.W.M.,City University of Hong Kong | Poon T.-C.,Virginia Polytechnic Institute and State University
Optics Express | Year: 2015

This paper reports a fast method for generating a 2048x2048 digital Fresnel hologram at a rate of over 100 frames per second. Briefly, the object wave of an image is nonuniformally sampled and generated on a wavefront recording plane (WPR) that is close to the object scene. The sampling interval at each point on the WRP image is then modulated according to the depth map. Subsequently, the WRP image is converted into a hologram. The hologram generated with our proposed method, which is referred to as the warped WRP (WWRP) hologram, is capable of presenting a 3-D object with faster speed as compared with existing methods. © 2015 OSA. Source


Gunawan C.,University of New South Wales | Teoh W.Y.,City University of Hong Kong | Marquis C.P.,University of New South Wales | Amal R.,University of New South Wales
ACS Nano | Year: 2011

The work investigates the source of toxicity of copper oxide nanoparticles (CuO NPs) with respect to its leaching characteristic and speciation. Complexation-mediated leaching of CuO NPs by amino acids was identified as the source of toxicity toward Escherichia coli, the model microorganism used in the current study. The leached copper-peptide complex induces a multiple-fold increase in intracellular reactive oxygen species generation and reduces the fractions of viable cells, resulting in the overall inhibition of biomass growth. The cytotoxicity of the complex leachate is however different from that of equivalent soluble copper salts (nitrates and sulfates). A pH-dependent copper speciation during the addition of copper salts gives rise to uncoordinated copper ions, which in turn result in greater toxicity and cell lysis, the latter of which was not observed for CuO NPs even at comparable pH. Since leaching did not occur with micrometer-sized CuO, no cytotoxicty effect was observed, thus highlighting the prominence of materials toxicity at the nanoscale. © 2011 American Chemical Society. Source


Li M.,Central South University | Lai A.C.K.,City University of Hong Kong
Applied Energy | Year: 2013

Short-time responses of borehole ground heat exchangers (GHEs) are difficult to predict because they involve heat capacity effect and various arrangements of U-shaped tubes within boreholes. To meet this engineering challenge, this paper builds a composite-medium line-source model. The central idea of the new model is that the downward and upward channels of U-shaped tubes (not the borehole) are approximated as line sources or sinks of heat placed in a composite medium. This approach can account for not only the influence of the heat capacity of grouting material but also the difference between properties of soil and grout, whilst it is flexible enough to model various U-pipe configurations. The new composite-medium model is validated by using a reported laboratory experiment; it can yield predictions matching the experimental response profiles with acceptable accuracy for times as short as 5. min. Several uncertainties which may contribute to discrepancies between the model prediction and the laboratory data are analyzed, including heat input rate, thermal conductivities and heat capacities of the composite medium. The potential errors caused by these uncertainties are comparable to the observed discrepancies. © 2012 Elsevier Ltd. Source


Choi K.,City University of Hong Kong
Urban Studies | Year: 2012

Hong Kong Disneyland (HKDL) was seen as the 'Millennium Dream Comes True!' in 1999, but as 'Hong Kong's shame' after its opening in 2005. In this article, interviews and ethnographic research are used to examine the different positions of various actors (HKDL workers, consumers and media practitioners) in their relationship with HKDL. Appropriating Lefebvre's conceptual triad of space, these stories show that Disney brought Hong Kong a physical park, non-transparent values and related management practices. These same stories also demonstrate that HKDL workers and visitors work and consume the park in a local way that Disneyland management finds difficult to control; local people produce and circulate the changed meanings of 'Disney' and change certain Disney management policies. © 2011 Urban Studies Journal Limited. Source


Tuck C.O.,University of Nottingham | Perez E.,University of Nottingham | Horvath I.T.,City University of Hong Kong | Sheldon R.A.,Technical University of Delft | Poliakoff M.,University of Nottingham
Science | Year: 2012

Most of the carbon-based compounds currently manufactured by the chemical industry are derived from petroleum. The rising cost and dwindling supply of oil have been focusing attention on possible routes to making chemicals, fuels, and solvents from biomass instead. In this context, many recent studies have assessed the relative merits of applying different dedicated crops to chemical production. Here, we highlight the opportunities for diverting existing residual biomass - the by-products of present agricultural and food-processing streams - to this end. Source


Cheung C.M.K.,Hong Kong Baptist University | Lee M.K.O.,City University of Hong Kong
Decision Support Systems | Year: 2012

The advance of the Internet facilitates consumers to share and exchange consumption-related advice through online consumer reviews. This relatively new form of word-of-mouth communication, electronic word-of-mouth (eWOM) communication, has only recently received significant managerial and academic attention. Many academic studies have looked at the effectiveness of positive eWOM communication, examining the process by which eWOM influences consumer purchasing decisions. eWOM behavior is primarily explained from the individual rational perspective that emphasizes a cost and benefit analysis. However, we felt there was a need for an extensive study that examines consumers' motives for eWOM. In this paper, we focus on the factors that drive consumers to spread positive eWOM in online consumer-opinion platforms. Building on the social psychology literature, we identified a number of key motives of consumers' eWOM intention and developed an associated model. We empirically tested the research model with a sample of 203 members of a consumer review community, OpenRice.com. The model explains 69% of the variance, with reputation, sense of belonging and enjoyment of helping other consumers significantly related to consumers' eWOM intention. The results of this study provide important implications for research and practice. © 2012 Elsevier B.V. All rights reserved. Source


Ngan S.-C.,City University of Hong Kong
Engineering Applications of Artificial Intelligence | Year: 2013

We frequently use the standard correlation coefficient to quantify linear relation between two given variables of interest in crisp industrial data. On the other hand, in many real world applications involving the opinions of experts, the domain of a variable of interest, e.g. the rating of the innovativeness of a new product idea, is oftentimes composed of subjective linguistic concepts such as very poor, poor, average, good and excellent. In this article, we extend the standard correlation coefficient to the subjective, linguistic setting, so as to quantify relations in imprecise industrial and management data. Unlike the correlation measures for fuzzy variables proposed in the literature, the present approach allows one to develop a correlation coefficient for linguistic variables that can account for and reflect the conditional dependence assumptions underlying a given data set. We apply the proposed method to quantify the degree of correlation between technology and management achievements of 15 large-scale machinery firms in Taiwan. It is shown that the flexibility of the present framework in allowing for the incorporation of appropriate conditional dependence assumptions to derive a correlation measure for linguistic variables can be essential in approximate reasoning applications. © 2012 Elsevier Ltd. All rights reserved. Source


Qiu L.,Peking University | Pang J.,Renmin University of China | Lim K.H.,City University of Hong Kong
Decision Support Systems | Year: 2012

Most B2C websites provide consumers with two types of electronic Word-of-Mouth (eWOM) information, namely aggregated rating and individual review. The present research investigates the effects of a conflicting aggregated rating on the perceived credibility and diagnosticity of individual reviews. The results of our laboratory experiment demonstrate that the presence of a conflicting aggregated rating will decrease review credibility and diagnosticity via its negative effect on consumers' product-related attributions of the review. In addition, these effects are more salient for positive reviews than for negative ones. These findings contribute to a better understanding of the interactions between different types of eWOM information and provide practitioners with actionable suggestions on how to improve the design of their eWOM systems. © 2012 Elsevier B.V. All rights reserved. Source


Dai L.,City University of Hong Kong
IEEE Transactions on Wireless Communications | Year: 2013

Aloha and Carrier Sense Multiple Access (CSMA) are two representative random-access protocols. Despite their simplicity in concept, the performance analysis of Aloha and CSMA networks has long been known as notoriously difficult. Numerous models and analytical approaches have been proposed in the past four decades. Yet how to integrate them into a coherent theory remains an open challenge. Toward this end, a unified analytical framework was recently proposed in , based on which a comprehensive study of throughput, delay and stability performance of Aloha networks was presented. In this paper, the framework is further extended to CSMA networks. The analysis shows that both CSMA and Aloha have the same bi-stable property, and the performance of both networks critically depends on the selection of backoff parameters. Different from Aloha, however, substantial gains can be achieved in CSMA networks by reducing the mini-slot length a and the collision-detection time x. The maximum throughput with CSMA is derived as an explicit function of a and x, and shown to be higher than that with Aloha if a Source


Yau Y.,City University of Hong Kong
Journal of Green Building | Year: 2012

Promotion of green housing is of utmost importance in the achievement of sustainability in the built environment. While the states often use legislation or offer subsidies to motivate developers to build green, market forces can lead to green housing provision without any state intervention if the market players are willing to pay extra for the green attributes of housing. This study aims to explore residents' willingness to pay (WTP) and preferences for green housing attributes based on the findings from a structured questionnaire survey in Hong Kong. Te housing attributes under investigation include the uses of green materials and construction methods (e.g. timber from sustainable sources), energy-efficient technologies (e.g. LED lighting) and water-saving devices (e.g. grey water recycling system). Results indicate that apart from moral or altruistic reasons, residents' WTP was mainly motivated by economic incentives. Green housing attributes which can directly reduce residents' utility bills corresponded to greater WTP. Besides, environmental attitude was found a strong determinant of the WTP. Policy implications of the research findings then follow. Source


Wu L.,City University of Hong Kong
Journal of Environmental Education | Year: 2012

A Chinese version of the revised NEP Scale was generated and adopted in a survey among 507 students (age 10 to 12 years old) from three elementary schools in Shenzhen, China. The results show an acceptable level of internal consistency (Cronbach's alpha =.65) but some abnormalities on the modified NEP scale: items 1 and 7 presented very low item-total correlations (≤.10); factor analysis generated five unclearly-patterned factors. The abnormalities on the modified scale, in light of a focus group interview during item modification stage, are partially attributed to some fundamental problems on the original revised NEP Scale per se on one hand, and may be partially understood as cultural differences in interpreting statements on the scale between China and Western nations on the other. © 2012 Copyright Taylor and Francis Group, LLC. Source


Chen T.-H.,City University of Hong Kong
Current Stem Cell Research and Therapy | Year: 2014

Regenerative medicine offers therapeutic approaches to treating non-regenerative diseases such as spinal cord injury and heart disease. Owing to the limited donor tissue available, cell-based therapy using cultured cells with supporting scaffolds has been proposed to rebuild damaged tissue. Early attempts at repairing skin and cartilage achieved significant success thanks to the simplicity of the tissue architecture, which later fueled enthusiasm for applying the same strategy to other types of tissue. However, more complex tissue functions require a more extensive vasculature and heterogeneous cell arrangements, which together constitute a significant hurdle in practical applications. Accordingly, recent years an increased interest has been in the use of decellularized matrices that retain the natural microarchitecture as the scaffold. However, although a number of engineering approaches have been suggested, self-organizing behavior such as cell proliferation, migration, and differentiation may still disorganize and frustrate the artificial attempts. This mini-review first provides examples of the early history of tissue engineering using skin and cartilage as examples, and then elaborates on the key technologies used to fabricate synthetic acellular scaffolds and cell/scaffold constructs with more complicated architectures. It also summarizes the progress achieved in the use of decellularized matrices for cell seeding as well as the recent success seen in self-organizing two- and three-dimensional tissue formation with the aid of biomathematical modeling. The review concludes by proposing the future integration of biomathematics, developmental biology, and engineering in concert with the self-organization approach to tissue regeneration. © 2014 Bentham Science Publishers. Source


Li D.H.W.,City University of Hong Kong
Applied Energy | Year: 2010

Daylighting is recognized as an important element in architecture and a useful strategy in energy-efficient building designs. Daylight gives a sense of cheeriness and brightness that can have a significant positive impact on the people. There is a scope for integrating daylight with electric light to reduce building energy use. The amount of daylight entering a building is mainly through window openings, which create in the indoor environment a more attractive and pleasing atmosphere, in addition to maximise visual access to the pleasant views of the outside world. Determinations of the exterior and interior daylight and lighting energy savings are key issues to demonstrate the benefits based on daylighting designs. This paper provides a review of daylight illuminance determinations and the lighting energy reductions due to daylighting schemes. The study includes daylight measurements, prediction of daylight illuminance under various sky conditions and potential electric lighting energy savings from daylight-linked lighting controls. The article aims at providing building professionals, practitioners and researchers more information and a better understanding of daylight for promoting effective daylighting designs and evaluations. © 2010 Elsevier Ltd. All rights reserved. Source


Ngan S.-C.,City University of Hong Kong
Computers and Industrial Engineering | Year: 2013

Fuzzy set theory (FST), since its introduction in the 1960s, has been continuously developed. Theory development for FST is highly challenging. For instance, various researchers have devoted substantive efforts in developing methodologies for many fundamental tasks, such as ranking type-1 fuzzy numbers, defining arithmetic and logical operations on type-1 and type-2 fuzzy numbers, and defining correlation measure on type-1 and type-2 numbers, resulting in a multitude of approaches, many of which based on differing postulates and assumptions. On the other hand, by interpreting the membership function of a linguistic concept based on a probabilistic framework, and by abandoning Zadeh's extension principle in favor of relying on probabilistic arguments, many of the technical difficulties in developing theory involving "type-1" like linguistic concepts and variables can be bypassed, with the resulting probabilistic linguistic framework enabling a uniform approach for theory development for a wide range of elementary operations and measures. In this article, the probabilistic linguistic framework is extended to type-2 linguistic sets that allows, with as few postulates as possible, uniform approach for developing methodologies for fundamental tasks such as taking the union and intersection of and performing arithmetic operations on type-2 linguistic numbers. Furthermore, we demonstrate the resulting methodology by applying it to an industrial data set concerning multi-criteria decision making. Source


Tan C.W.,City University of Hong Kong
Proceedings - IEEE INFOCOM | Year: 2011

Heterogeneous wireless networks employ varying degrees of network coverage using power control in a multi-tier configuration, where low-power femtocells are used to enhance performance, e.g., optimize outage probability. We study the worst outage probability problem under Rayleigh fading. As a by-product, we solve an open problem of convergence for a previously proposed algorithm in the interference-limited case. We then address a total power minimization problem with outage specification constraints and its feasibility condition. We propose a dynamic algorithm that adapts the outage probability specification in a heterogeneous network to minimize the total energy consumption and simultaneously guarantees all the femtocell users a min-max fairness in terms of the worst outage probability. © 2011 IEEE. Source


Westman B.J.,University of Dundee | Verheggen C.,French National Center for Scientific Research | Hutten S.,University of Dundee | Lam Y.W.,City University of Hong Kong | And 2 more authors.
Molecular Cell | Year: 2010

Posttranslational SUMO modification is an important mechanism of regulating protein function, especially in the cell nucleus. The nucleolus is the subnuclear organelle responsible for rRNA synthesis, processing, and assembly of the large and small ribosome subunits. Here, we have used SILAC-based quantitative proteomics to identify nucleolar SUMOylated proteins. This reveals a role for SUMOylation in the biogenesis and/or function of small nucleolar ribonucleoprotein complexes (snoRNPs) via the targeting of Nhp2 and Nop58. Using combined in vitro and in vivo approaches, both Nhp2 and Nop58 (also known as Nop5) are shown to be substrates for SUMOylation. Mutational analyses revealed the sites of modification on Nhp2 as K5, and on Nop58 as K467 and K497. Unlike Nop58 and Nhp2, the closely related Nop56 and 15.5K proteins appear not to be SUMO targets. SUMOylation is essential for high-affinity Nop58 binding to snoRNAs. This study provides direct evidence linking SUMO modification with snoRNP function. © 2010 Elsevier Inc. Source


Xi Z.,University of New South Wales | Feng G.,City University of Hong Kong | Hesketh T.,University of New South Wales
IEEE Transactions on Fuzzy Systems | Year: 2011

This paper addresses the issue of piecewise integral sliding-mode control (ISMC) for the TakagiSugeno (TS) fuzzy systems. ISMC is chosen to stabilize the TS fuzzy system because of its superior capability in treating uncertainties. Individual integral sliding surfaces are designed in different operating regions of the TS fuzzy system. Conditions on the existence of the sliding mode in the associated region are given. The chattering phenomenon around region boundaries is analyzed, and the prevention of such chattering is discussed. An illustrative example is finally given to show the efficiency of the proposed method. © 2006 IEEE. Source


Duan L.,Singapore University of Technology and Design | Huang J.,Chinese University of Hong Kong | Shou B.,City University of Hong Kong
IEEE Transactions on Mobile Computing | Year: 2013

Femtocells can effectively resolve the poor connectivity issue of indoor cellular users. This paper investigates the economic incentive for a cellular operator to add femtocell service on top of its existing macrocell service. We model the interactions between a cellular operator and users as a Stackelberg game: The operator first determines spectrum allocations and pricings of femtocell and macrocell services, and then heterogeneous users choose between the two services and the amount of resource to request. In the ideal case where the femtocell service has the same full spatial coverage as the macrocell service, we show that the operator will choose to provide femtocell service only, as this leads to a better user quality of service and a higher operator profit. However, if we impose the constraint that no users' payoffs decrease after introducing the femtocell service, then the operator will always continue providing the macrocell service (with or without the femtocell service). Furthermore, we study the impact of operational cost, limited coverage, and spatial reuse on femtocell service provision. As the operational cost increases, fewer users are served by femtocell service and the operator's profit decreases. When the femtocell service has limited spatial coverage, the operator always provides the macrocell service beside the femtocell service. However, when the coverage is high or the total resource is low, the operator will set the prices such that all users who can access femtocell will choose to use the femtocell service only. Finally, spatial reuse of spectrum will increase the efficiency of femtocell services and gives the operator more incentives to allocate spectrum to femtocells. © 2002-2012 IEEE. Source


Yuen A.N.Y.,University of Hong Kong | Ho S.M.Y.,City University of Hong Kong | Chan C.K.Y.,University of Hong Kong
Psycho-Oncology | Year: 2014

Objective This study aimed to examine the effects of dispositional hope on psychopathology as well as self-perceived positive change in childhood cancer survivors through the potential mediation of cancer-related ruminations. Methods A cross-sectional design was used, and a group of childhood cancer survivors (N = 89; mean age = 23.2 years; age range = 17.2-31.3 years) were studied. Dispositional hope level was measured by the Hope Scale; positive and negative cancer-related ruminations were assessed by the Chinese Cancer-related Rumination Scale; depression symptoms were measured by Beck Depression Inventory; and anxiety symptoms were measured by Beck Anxiety Inventory. Positive adjustment outcome of posttraumatic growth (PTG) was assessed by the Chinese Post-traumatic Growth Inventory. Multiple regressions were used to analyze the relationship between dispositional hope and the outcome variables of PTG, anxiety and depression and the potential mediators of positive and negative cancer-related rumination. Results Dispositional hope was positively related to PTG, and the correlation was specifically mediated by positive cancer-related rumination. Dispositional hope also correlated with lower levels of depression and anxiety, specifically mediated by negative cancer-related rumination. Conclusion The present finding supported hope as a significant positive factor for childhood cancer survivors, which was associated with PTG and better psychological adjustment. The findings may inform development of therapeutic intervention programs aimed at increasing childhood cancer patients' hope levels, which may be correlated with more positive cancer-related thoughts and better adjustment. The present study, which examined survivors diagnosed at young age, may enrich existing studies on the effect of onset age and adjustment outcomes. Copyright © 2013 John Wiley & Sons, Ltd. Source


Lee Y.-Y.,City University of Hong Kong
International Journal of Mechanical Sciences | Year: 2016

This study investigates the sound absorption of a nonlinear perforated panel backed by a cavity with leaking edges. Many other related works assume that the cavity is perfectly enclosed. This is the first study to address the effect of leakage on the sound absorption of a nonlinear perforated panel. The development of the absorption formula is based on the classical nonlinear thin plate theory, the three-dimensional wave equation and micro-perforation acoustic impedance. The recently developed multi-level residue harmonic balance method is introduced to compute the nonlinear vibration responses. Unlike previous harmonic balance methods, the proposed method generates nonlinear algebraic equations in the process of computing zero-level solutions only, and produces linear algebraic equations in the higher-level processes. The theoretical results obtained from the proposed method and the numerical integration method are in reasonable agreement. The effects of various parameters such as the excitation magnitude, damping ratio, cavity depth, perforation ratio and amount of leakage are examined. © 2016 Elsevier Ltd. All rights reserved. Source


Lee S.K.,Korea Institute of Energy Research | Mogi G.,Tokyo University of Technology | Hui K.S.,City University of Hong Kong
Renewable and Sustainable Energy Reviews | Year: 2013

The Low Carbon, Green Growth was declared as Korean national agenda in 2008. Korea has been enhancing the green growth for the sustainable economic development and fostering energy. To improve Korean national energy security and promote the Low Carbon, Green Growth, we established a long term strategic energy technology roadmap. In this paper, five criteria, such as economical impact, commercial potential, inner capacity, technical spin-off, and development cost, were used to assess the strategic energy technologies against high oil prices. We developed the integrated two-stage multi-criteria decision making (MCDM) approach which was used to evaluate the relative weights of criteria and measures the relative efficiency of energy technologies against high oil prices. On the first stage, the fuzzy analytic hierarchy process, reflecting the vagueness of human thought with interval values instead of crisp numbers, allocated the relative weights of criteria effectively instead of the AHP approach. On the second stage, the data envelopment analysis approach measured the relative efficiency of energy technologies against high oil prices with economic viewpoints. The relative efficiency score of energy technologies against high oil prices can be the fundamental decision making data which help decision markers to effectively allocate the limited R&D resources. © 2013 Elsevier Ltd. Source


Pang Z.,Lancaster University | Chen F.Y.,City University of Hong Kong | Feng Y.,Zaragoza Logistics Center
Operations Research | Year: 2012

We consider a joint inventory-pricing control problem for a periodic-review, single-stage inventory system with a positive order leadtime and a linear order cost. Demands in consecutive periods are independent, but their distributions depend on the price in accordance with a stochastic demand function of additive form. Pricing and ordering decisions are made simultaneously at the beginning of each period. The objective is to maximize the total expected discounted profit over a finite horizon. We partially characterize the structure of the optimal joint ordering and pricing policies. We also show that our structural analysis can be extended to a multistage (or serial) inventory system with constant or stochastic leadtimes and an assemble-to-order system with price-sensitive demand. © 2012 INFORMS. Source


Yang Q.,City University of Hong Kong
IEEE Transactions on Image Processing | Year: 2015

This paper presents a complete proof that the bilateral filter can be implemented recursively, as long as: 1) the spatial filter can be implemented recursively and 2) the range filter can be decomposed into a recursive product. As a result, an O(ND) solution can be obtained for bilateral filtering, where N is the image size and D is the dimensionality. © 1992-2012 IEEE. Source


Ke L.-L.,Beijing Jiaotong University | Wang Y.-S.,Beijing Jiaotong University | Yang J.,RMIT University | Kitipornchai S.,City University of Hong Kong
International Journal of Engineering Science | Year: 2012

Nonlinear free vibration of microbeams made of functionally graded materials (FGMs) is investigated in this paper based on the modified couple stress theory and von Kármán geometric nonlinearity. The non-classical beam model is developed within the framework of Timoshenko beam theory which contains a material length scale parameter related to the material microstructures. The material properties of FGMs are assumed to be graded in the thickness direction according to the power law function and are determined by Mori-Tanaka homogenization technique. The higher-order nonlinear governing equations and boundary conditions are derived by using the Hamilton principle. A numerical method that makes use of the differential quadrature method together with an iterative algorithm is employed to determine the nonlinear vibration frequencies of the FGM microbeams with different boundary conditions. The influences of the length scale parameter, material property gradient index, slenderness ratio, and end supports on the nonlinear free vibration characteristics of the FGM microbeams are discussed in detail. It is found that both the linear and nonlinear frequencies increase significantly when the thickness of the FGM microbeam is comparable to the material length scale parameter. © 2011 Elsevier Ltd. All rights reserved. Source


Guan Z.-H.,Huazhong University of Science and Technology | Wu Y.,Huazhong University of Science and Technology | Feng G.,City University of Hong Kong
IEEE Transactions on Circuits and Systems I: Regular Papers | Year: 2012

This paper discusses consensus problems for multiagent networks under directed communication graphs. The motions of agents are described by impulsive differential equations, and thus, consensus algorithms can be designed in terms of impulsive systems. Different from the standard consensus algorithms which rely on continuous-time or discrete-time models, the proposed algorithms based on impulsive systems take advantages of instantaneous information. It is shown that the proposed algorithms have a faster convergence speed than the standard consensus algorithms. Moreover, conditions under which all agents reach consensus with the desired H ∞ performance are presented for the multiagent networks with external disturbances. Simulation results demonstrate the effectiveness of the proposed algorithms. © 2011 IEEE. Source


Zhang F.,Institute of Functional Nano and Soft Materials FUNSOM | Sun B.,Institute of Functional Nano and Soft Materials FUNSOM | Song T.,Institute of Functional Nano and Soft Materials FUNSOM | Zhu X.,Soochow University of China | Lee S.,City University of Hong Kong
Chemistry of Materials | Year: 2011

Efficient, stable hybrid photovoltaic (PV) devices based on poly(3-hexylthiophene) (P3HT) and silicon nanowire arrays (SiNWs) are reported. A two-step, chlorination/methylation procedure is used to convert Si-H bonds into Si-C ones to reduce the velocity of charge recombination at the silicon surface as well as achieve a favorable alignment of band-edge energies. In addition, Pt nanodots (PtNDs) are deposited onto the surface of the SiNWs to further tune the band-edge alignment and passivate nonmethylated silicon sites. Methylated silicon surfaces modified with PtNDs possess a favorable internal electric field in accord with expectations based on the electron affinity (∼3.7 eV) and net positive surface dipole measured on such surfaces by ultraviolet photoemission spectroscopy. This attests to the degree of chemical control that can be exerted over the internal electric field in such systems by surface functionalization. In concert with methyl termination and decoration with PtNDs, hybrid PV devices based on composites of SiNWs and P3HT achieve an external quantum efficiency (EQE) of 76% at 800 nm and a power conversion efficiency (PCE) of 5.9% under simulated air mass 1.5 solar irradiation at 100 mW cm-2. Moreover, these devices exhibit stable performance for more than 1200 h. In contrast, devices based on composites of hydrogen-terminated planar silicon and P3HT display an EQE of 0.19% at 560 nm and PCE of 0.006%. The ∼800 times enhancement in device performance and improvement in stability are assigned to the facile derivatization of the surface of silicon nanostructures. © 2011 American Chemical Society. Source


Hu J.,University of Electronic Science and Technology of China | Feng G.,City University of Hong Kong
Automatica | Year: 2010

In this paper, a distributed tracking control scheme with distributed estimators has been developed for a leader-follower multi-agent system with measurement noises and directed interconnection topology. It is supposed that each follower can only measure the relative positions of its neighbors in a noisy environment, including the relative position of the second-order active leader. A neighbor-based tracking protocol together with distributed estimators is designed based on a novel velocity decomposition technique. It is shown that the closed loop tracking control system is stochastically stable in mean square and the estimation errors converge to zero in mean square as well. A simulation example is finally given to illustrate the performance of the proposed control scheme. © 2010 Elsevier Ltd. All rights reserved. Source


Lim C.W.,City University of Hong Kong | Xu X.S.,Dalian University of Technology
Applied Mechanics Reviews | Year: 2010

Many of the early works on symplectic elasticity were published in Chinese and as a result, the early works have been unavailable and unknown to researchers worldwide. It is the main objective of this paper to highlight the contributions of researchers from this part of the world and to disseminate the technical knowledge and innovation of the symplectic approach in analytic elasticity and applied engineering mechanics. This paper begins with the history and background of the symplectic approach in theoretical physics and classical mechanics and subsequently discusses the many numerical and analytical works and papers in symplectic elasticity. This paper ends with a brief introduction of the symplectic methodology. A total of more than 150 technical papers since the middle of 1980s have been collected and discussed according to various criteria. In general, the symplectic elasticity approach is a new concept and solution methodology in elasticity and applied mechanics based on the Hamiltonian principle with Legendre's transformation. The superiority of this symplectic approach with respect to the classical approach is at least threefold: (i) it alters the classical practice and solution technique using the semi-inverse approach with trial functions such as those of Navier, Ĺvy, and Timoshenko; (ii) it consolidates the many seemingly scattered and unrelated solutions of rigid body movement and elastic deformation by mapping with a series of zero and nonzero eigenvalues and their associated eigenvectors; and (iii) the Saint-Venant problems for plane elasticity and elastic cylinders can be described in a new system of equations and solved. A unique feature of this method is that bending of plate becomes an eigenvalue problem and vibration becomes a multiple eigenvalue problem. © 2010 American Society of Mechanical Engineers. Source


Brown E.S.,University of California at Los Angeles | Chan T.F.,Hong Kong University of Science and Technology | Bresson X.,City University of Hong Kong
International Journal of Computer Vision | Year: 2012

The active contours without edges model of Chan and Vese (IEEE Transactions on Image Processing 10(2):266-277, 2001) is a popular method for computing the segmentation of an image into two phases, based on the piecewise constant Mumford-Shah model. The minimization problem is non-convex even when the optimal region constants are known a priori. In (SIAM Journal of Applied Mathematics 66(5):1632-1648, 2006), Chan, Esedolu, and Nikolova provided a method to compute global minimizers by showing that solutions could be obtained from a convex relaxation. In this paper, we propose a convex relaxation approach to solve the case in which both the segmentation and the optimal constants are unknown for two phases and multiple phases. In other words, we propose a convex relaxation of the popular K-means algorithm. Our approach is based on the vector-valued relaxation technique developed by Goldstein et al. (UCLA CAM Report 09-77, 2009) and Brown et al. (UCLA CAM Report 10-43, 2010). The idea is to consider the optimal constants as functions subject to a constraint on their gradient. Although the proposed relaxation technique is not guaranteed to find exact global minimizers of the original problem, our experiments show that our method computes tight approximations of the optimal solutions. Particularly, we provide numerical examples in which our method finds better solutions than the method proposed by Chan et al. (SIAM Journal of Applied Mathematics 66(5):1632-1648, 2006), whose quality of solutions depends on the choice of the initial condition. © 2011 Springer Science+Business Media, LLC. Source


Li J.,City University of Hong Kong
Habitat International | Year: 2014

This paper explores the impacts of different land sale venues on the economic growth path, and hence Chinese local officials' incentive structure and their strategic balance between political promotion and rent creation. By investigating the panel data of 30 provinces and municipalities from 2000 to 2009, empirical results suggest that the proportion of land sale through public auction has positive effects on local GDP growth. The implication is that local officials who choose land sale venues may be judged on the basis of their impacts on local economic performance, because China's political promotion is largely GDP-based. However, descriptive statistics further reveal that local officials tend to sell commercial and residential land but not industrial land through public auction, indicating that local officials may have a strategic balance between their political promotion incentive and rent seeking incentive. In conclusion, it is the incentive of climbing further up the career ladder that drives local officials to give up some of, if not all, their rent seeking incentive in urban land transactions. © 2013 Elsevier Ltd. Source


Wong W.S.,City University of Hong Kong | Fielding R.,University of Hong Kong
Journal of Sleep Research | Year: 2011

Prevalence estimates of insomnia in western general populations are well documented, but population-based epidemiological data on insomnia in Chinese adults are scarce. The aims of the present study were to determine the prevalence of insomnia in the general population of Hong Kong, compare components of sleep disturbances and lifestyle factors stratified by sex, and identify risk factors for insomnia. Using a population-based cross-sectional design, a total of 5001 Chinese adults aged ≥18years completed a telephone interview on the Pittsburgh Sleep Quality Index (PSQI), Hospital Anxiety and Depression Scale (HADS) and measures of quality of life (QoL) indexed by Medical Outcomes Study 12-item Short-Form Health Survey (SF12), lifestyle and sociodemographic details. Insomnia was defined by a PSQI global score >5. The resultant weighted prevalence of insomnia was 39.4%, equivalent to 2.2 million affected adults in Hong Kong. Women reported significantly poorer component and global sleep quality (all P<0.05). Fully adjusted stepwise regression analyses identified non-full-time employment status, existing long-term health problems, alcohol consumption four to seven times per week, higher HADS scores, poor mental health component of QoL and low self-perceived health were associated significantly with insomnia (all P<0.05). Our results suggest that insomnia is highly prevalent among Hong Kong Chinese adults and is associated with frequent use of alcohol, poor mental health and QoL. © 2010 European Sleep Research Society. Source


Tjong S.C.,City University of Hong Kong | Tjong S.C.,King Abdulaziz University
Materials Science and Engineering R: Reports | Year: 2013

One-dimensional carbon nanotubes and two-dimensional graphene nanosheets with unique electrical, mechanical and thermal properties are attractive reinforcements for fabricating light weight, high strength and high performance metal-matrix composites. Rapid advances of nanotechnology in recent years enable the development of advanced metal matrix nanocomposites for structural engineering and functional device applications. This review focuses on the recent development in the synthesis, property characterization and application of aluminum, magnesium, and transition metal-based composites reinforced with carbon nanotubes and graphene nanosheets. These include processing strategies of carbonaceous nanomaterials and their composites, mechanical and tribological responses, corrosion, electrical and thermal properties as well as hydrogen storage and electrocatalytic behaviors. The effects of nanomaterial dispersion in the metal matrix and the formation of interfacial precipitates on these properties are also addressed. Particular attention is paid to the fundamentals and the structure-property relationships of such novel nanocomposites. © 2013 Elsevier B.V. All rights reserved. Source


Yang Q.,City University of Hong Kong
IEEE Transactions on Pattern Analysis and Machine Intelligence | Year: 2015

Matching cost aggregation is one of the oldest and still popular methods for stereo correspondence. While effective and efficient, cost aggregation methods typically aggregate the matching cost by summing/averaging over a user-specified, local support region. This is obviously only locally-optimal, and the computational complexity of the full-kernel implementation usually depends on the region size. In this paper, the cost aggregation problem is re-examined and a non-local solution is proposed. The matching cost values are aggregated adaptively based on pixel similarity on a tree structure derived from the stereo image pair to preserve depth edges. The nodes of this tree are all the image pixels, and the edges are all the edges between the nearest neighboring pixels. The similarity between any two pixels is decided by their shortest distance on the tree. The proposed method is non-local as every node receives supports from all other nodes on the tree. The proposed method can be naturally extended to the time domain for enforcing temporal coherence. Unlike previous methods, the non-local property guarantees that the depth edges will be preserved when the temporal coherency between all the video frames are considered. A non-local weighted median filter is also proposed based on the non-local cost aggregation algorithm. It has been demonstrated to outperform all local weighted median filters on disparity/depth upsampling and refinement. © 2015 IEEE. Source


Karmee S.K.,City University of Hong Kong | Karmee S.K.,North West University South Africa
Renewable and Sustainable Energy Reviews | Year: 2016

Depletion of fossil fuels, environmental damage due to pollution and energy security have intensified research on alternative liquid biofuels. A major portion of municipal solid waste is food waste. Huge quantities of food waste is generated worldwide and currently its disposal is becoming a challenge. Food waste contain carbohydrates, lipids, phosphates, vitamins and amino acids. Carbohydrate, lipid and carbon containing materials present in food waste can be converted to bioethanol, biodiesel and biooil. Lipid extracted from food waste is converted to biodiesel in 95-97% yield. On the other hand, 92-96% bioethanol obtained by fermentation of food waste. Along this line, pyrolysis of food waste can be performed to obtain biooil and biochar. In this paper, technical feasibility, prospects and policies for liquid biofuel preparation from food waste was evaluated. Also, limitations of using food waste as a resource for biofuel production is discussed. © 2015 Elsevier Ltd. Allrightsreserved. Source


Qiu J.,Harbin Institute of Technology | Feng G.,City University of Hong Kong | Feng G.,Nanjing University of Science and Technology | Gao H.,Harbin Institute of Technology
IEEE Transactions on Fuzzy Systems | Year: 2013

This paper investigates the problem of robust H∞ output feedback control for a class of continuous-time Takagi-Sugeno (T-S) fuzzy affine dynamic systems with parametric uncertainties and input constraints. The objective is to design a suitable constrained piecewise affine static output feedback controller, guaranteeing the asymptotic stability of the resulting closed-loop fuzzy control system with a prescribed H∞ disturbance attenuation level. Based on a smooth piecewise quadratic Lyapunov function combined with S-procedure and some matrix inequality convexification techniques, some new results are developed for static output feedback controller synthesis of the underlying continuous-time T-S fuzzy affine systems. It is shown that the controller gains can be obtained by solving a set of linear matrix inequalities (LMIs). Finally, three examples are provided to illustrate the effectiveness of the proposed methods. © 1993-2012 IEEE. Source


Song D.,Nanjing University of Aeronautics and Astronautics | Lu Y.Y.,City University of Hong Kong
Journal of Lightwave Technology | Year: 2014

For optical waveguides with high index-contrast and sharp corners, it is challenging to develop efficient, accurate and general full-vectorial mode solvers. The classical mode-matching method is capable of computing modes to high accuracy for waveguides with right-angle corners, but it is not convenient to implement when the waveguide has lossy components. Numerical variants of the mode-matching method, such as the Fourier modal method (as a mode solver), are simpler to implement. In this paper, a recently developed pseudospectral modal method for diffraction gratings is reformulated as a full-vectorial waveguide mode solver. As demonstrated in a number of examples, the method can be used to calculate waveguide modes to high accuracy, and it is relatively simple to implement. © 1983-2012 IEEE. Source


Yu P.K.,City University of Hong Kong
Physics in medicine and biology | Year: 2013

Kilovoltage x-ray beams are used for the treatment of facial cancers when located on the patient's skin or subcutaneous tissue. This is of course due to the sharp depth dose characteristics of these beams delivering much lower doses at depth, than high energy x-ray beams. When treatment is performed, lead shields are often used within the nasal passage, or behind the lips and ears. These shields affect the backscattering patterns of the x-ray beams producing perturbations to upstream dose thus reducing delivered dose to the tumour. Experimental results using radiochromic films have shown that up to 10.5% ± 1.9% reduction in tumour dose can occur for field sizes less than 5 cm circle diameter for x-ray beams of 50 to 150 kVp. These results were confirmed using EGSnrc Monte Carlo techniques. Clinically more than 70% of treatments used fields of diameters less than 3 cm where the reductions were up to 6% ± 1.3%. Using a 1 cm diameter field, which can be used for skin cancer treatment on the nose, reductions up to 2.5% ± 1.3% were seen. Thus corrections need to be applied for dose calculations when underlying lead shields are used clinically in kilovoltage x-rays. The size of the reduction was also found to be dependent on the depth of the shield which will normally clinically vary from approximately 0.5 cm for nasal shields or behind eye lobes and up to approximately 1 cm for lips or cheek areas. We recommend that clinics utilize data for corrections to delivered dose in kilovoltage x-ray beams when lead shields are used in nasal passages, behind lips or behind ears for dose reduction. This can be easily and accurately measured with EBT2 Gafchromic film. Source


Chen X.,University of Electronic Science and Technology of China | Hao G.,City University of Hong Kong | Li L.,Old Dominion University
International Journal of Production Economics | Year: 2014

We investigate a one-period two-echelon supply chain composed of a risk-neutral supplier that produces short life-cycle products and a loss-averse retailer that orders from the supplier via option contracts and sells to end-users with stochastic demand in the selling season. When a single retail season begins, the retailer can obtain goods by purchasing and exercising call options. We derive the loss-averse retailer's optimal ordering policy and the risk-neutral supplier's optimal production policy under these conditions. In addition, we find that the loss-averse retailer may order less than, equal to, or more than the risk-neutral retailer. Further, we show that the loss-averse retailer's optimal order quantity may increase in retail price and decrease in option price and exercise price, which is different from the case of a risk-neutral retailer. Finally, we study coordination of the supply chain and show that there always exists a Pareto contract as compared to the non-coordinating contracts. © 2013 Elsevier B.V. Source


Lau M.,City University of Hong Kong
Asia-Pacific journal of public health / Asia-Pacific Academic Consortium for Public Health | Year: 2010

The aims of this study were to examine the frequency and correlates of problem behaviors among Hong Kong adolescents. It is a cross-sectional survey targeting secondary forms 1 to 3 (equivalent to grades 7-9 in the United States) students (N = 1029). A self-administered questionnaire was used as the measurement tool. The study found that there are intercorrelations of problem behaviors in adolescence, such as tobacco use, alcohol use, drug abuse, and having connections with triad society. Given the intercorrelations among problem behaviors, identification of a single type of problem behavior in adolescents can help discover the likelihood of the occurrence of other problem behaviors. It can facilitate identification and intervention at an early stage. The results provide some insights for the concerned authorities to develop a syndrome approach addressing problem behaviors. Source


Zhu P.,Hunan University | Zhang L.W.,Shanghai Ocean University | Liew K.M.,City University of Hong Kong
Composite Structures | Year: 2014

A meshless local Petrov-Galerkin approach based on the moving Kriging interpolation technique is developed for geometrically nonlinear thermoelastic analysis of functionally graded plates in thermal environments (prescribed a temperature gradient or heat flux). The Kriging interpolation method makes the constructed shape functions possess Kronecker delta function property and thus special techniques for enforcing essential boundary conditions are avoided. In the thermal analysis, the dependency of thermal conductivity of functionally graded materials on temperature is involved, which gives rise to a nonlinear partial differential heat conduction equation. The nonlinear formulation of large deflection of the functionally graded plates is based on the first-order shear deformation plate theory in the von Kármán sense by taking small strains and moderate rotations into account. The incremental form of nonlinear equations is obtained by Taylor series expansion and the tangent stiffness matrix is explicitly developed in two different ways within the framework of the local meshless method. The nonlinear solutions are computed using the Newton-Raphson iteration method. Parametric and convergence studies are conducted to examine the stability of the proposed method and then several selected numerical examples are presented to demonstrate the accuracy and effectiveness of the method for nonlinear bending problems of functionally graded plates in thermal environments. © 2013 Elsevier Ltd. Source


Zhang L.W.,Shanghai Ocean University | Zhu P.,Hunan University | Liew K.M.,City University of Hong Kong
Composite Structures | Year: 2014

The mechanical and thermal buckling behaviors of ceramic-metal functionally grade plates (FGPs) were studied by using a local Kriging meshless method. The local meshless method was developed based on the local Petrov-Galerkin weak-form formulation combined with shape functions having the Kronecker delta function property, constructed by the Kriging interpolation. The cubic spline function of high continuity was used as the weight function to simplify the local weak form of governing equations with the integration on the internal boundaries vanishing. The transverse shear strains of FGPs were incorporated by employing the first-order shear deformation plate theory and plate material properties were assumed to change exponentially along the thickness direction. Convergence and comparison studies examined the stability and accuracy of the presented method. Two types of FGMs, Al/Al2O3 and Ti-6Al-4V/Aluminum oxide, were chosen for mechanical and thermal buckling analyses. The influences of volume fraction exponent, boundary condition, length-to-thickness ratio and loading type on the buckling behaviors of FGPs were discussed. © 2013 Elsevier Ltd. Source