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Hong Kong, China

The Hong Kong Polytechnic University is a public university located in Hung Hom, Hong Kong. The history of PolyU can be traced back to 1937, and it assumed full university status in 1994. It is one of the funded institutions of the territory's University Grants Committee .PolyU has an international faculty and student community and has developed a global network with more than 440 institutions in 47 countries and regions. PolyU offers 220 postgraduate, undergraduate and sub-degree programmes for more than 32,000 students every year. It is the largest UGC-funded tertiary institution in terms of number of students. Wikipedia.

Leung C.-H.,Hong Kong Polytechnic University
Research Journal of Information Technology | Year: 2010

This study presents results and findings from a qualitative study on the application of knowledge management in schools of Hong Kong. The aim of the study was to find out whether knowledge management could be implemented successfully in primary and secondary schools in Hong Kong and what problems were encountered. This study will explain and discuss in detail why particular factors are important to the educational knowledge management practices and also suggest some ways to overcome the encountered barriers to knowledge management in schools. Today, knowledge management systems have been widely implemented in organizations like enterprises, government departments and universities, yet the application of knowledge management in the primary and secondary education sector is not yet popular. A total of 65 teachers from 23 schools were invited for interview. It was found that leadership and change management, strategy and goal, organizational learning, technical support, school culture and trust among teachers are the critical factors affecting knowledge management in school contexts. This study concluded that successful knowledge management in a school involves different aspects such as accessibility of information technology, strong leadership, cultural influences, organizational structure and human characteristics (e.g., trust, learning behaviours and habits). © 2010 Academic Journals Inc.

Wang J.-B.,Shenyang Aerospace University | Wang M.-Z.,Dalian University of Technology | Ji P.,Hong Kong Polytechnic University
International Journal of Systems Science | Year: 2012

In this article, we consider a single machine scheduling problem with a time-dependent learning effect and deteriorating jobs. By the effects of time-dependent learning and deterioration, we mean that the job processing time is defined by a function of its starting time and total normal processing time of jobs in front of it in the sequence. The objective is to determine an optimal schedule so as to minimize the total completion time. This problem remains open for the case of -1

Yuan X.,Hong Kong Polytechnic University
IEEE Transactions on Signal Processing | Year: 2012

This paper introduces a novel algorithm to estimate the direction-of-arrival (DOA) and the polarization of a completely-polarized polynomial-phase signal of an arbitrary degree. The algorithm utilizes a polarized vector-sensor, comprising a spatially collocated six-component electromagnetic vector-sensor, a dipole triad, or a loop triad. This ESPRIT-based algorithm is based on a time-invariant matrix-pencil pair, derived from the time-delayed data-sets collected by a single polarized vector-sensor. The high-order difference-function of the signal's phase constructs the invariant-factor used in the ESPRIT algorithm. The steering vector is estimated from the signal-subspace eigenvector of the data-correlation matrix, following which the closed-form DOA and polarization can be obtained. Given the degree of the polynomial-phase signal, this approach resolves the two-dimensional azimuth-elevation angle and the polarization of the source, and requires neither a priori knowledge of the polynomial-phase signal's coefficients nor a priori knowledge of the polynomial-phase signal's frequency-spectrum. The efficacy of the proposed algorithm is verified by Monte Carlo simulations. Estimation accuracies of the DOA and the polarization parameters are evaluated by the closed-form Cramér-Rao bounds, which are independent of the polynomial coefficients, the degree of the polynomial-phase signal, and the azimuth-angle of the source. © 2011 IEEE.

Ni M.,Hong Kong Polytechnic University
International Journal of Energy Research | Year: 2010

A 2D computational fluid dynamics (CFD) model is developed to study the performance of an advanced planar solid oxide fuel cell based on proton conducting electrolyte (SOFC-H). The governing equations are solved with the finite volume method (FVM). Simulations are conducted to understand the transport phenomena and electrochemical reaction involved in SOFC-H operation as well as the effects of operating/structural parameters on SOFC-H performance. In an SOFC based on oxygen ion conducting electrolyte (SOFC-O), mass is transferred from the cathode side to the anode side. While in an SOFC-H, mass is transferred from the anode to the cathode, which causes different velocity fields of the fuel and oxidant gas channels and influences the distributions of temperature and gas composition in the cell. It is also found that increasing the inlet gas velocity leads to an increase in the local current density and a slight decrease in the SOFC-H temperature due to stronger cooling effect of the gas species at a higher velocity. Another finding is that the electrode structure does not significantly affect the heat and mass transfer in an SOFC-H at typical operating voltages. © 2009 John Wiley & Sons, Ltd.

Cheng H.,University of Bedfordshire | Yang S.,De Montfort University | Cao J.,Hong Kong Polytechnic University
Expert Systems with Applications | Year: 2013

Clustering can help aggregate the topology information and reduce the size of routing tables in a mobile ad hoc network (MANET). To achieve fairness and uniform energy consumption, each clusterhead should ideally support the same number of clustermembers. However, a MANET is a dynamic and complex system and its one important characteristic is the topology dynamics, that is, the network topology changes over time due to the factors such as energy conservation and node movement. Therefore, in a MANET, an effective clustering algorithm should efficiently adapt to each topology change and produce the new load balanced clusterhead set quickly. The maintenance of the cluster structure should aim to keep it as stable as possible to reduce overhead. To meet this requirement, the new solution should keep as many good parts in the previous solution as possible. In this paper, we first formulate the dynamic load balanced clustering problem (DLBCP) into a dynamic optimization problem. Then, we propose to use a series of dynamic genetic algorithms (GAs) to solve the DLBCP in MANETs. In these dynamic GAs, each individual represents a feasible clustering structure and its fitness is evaluated based on the load balance metric. Various dynamics handling techniques are introduced to help the population to deal with the topology changes and produce closely related solutions in good quality. The experimental results show that these GAs can work well for the DLBCP and outperform traditional GAs that do not consider dynamic network optimization requirements. © 2012 Elsevier Ltd. All rights reserved.

Deng Y.,Southwest University | Deng Y.,Shanghai JiaoTong University | Chan F.T.S.,Hong Kong Polytechnic University
Expert Systems with Applications | Year: 2011

Supplier selection is a multi-criterion decision making problem under uncertain environments. Hence, it is reasonable to hand the problem in fuzzy sets theory (FST) and Dempster Shafer theory of evidence (DST). In this paper, a new MCDM methodology, using FST and DST, based on the main idea of the technique for order preference by similarity to an ideal solution (TOPSIS), is developed to deal with supplier selection problem. The basic probability assignments (BPA) can be determined by the distance to the ideal solution and the distance to the negative ideal solution. Dempster combination rule is used to combine all the criterion data to get the final scores of the alternatives in the systems. The final decision results can be drawn through the pignistic probability transformation. In traditional fuzzy TOPSIS method, the quantitative performance of criterion, such as crisp numbers, should be transformed into fuzzy numbers. The proposed method is more flexible due to the reason that the BPA can be determined without the transformation step in traditional fuzzy TOPSIS method. The performance of criterion can be represented as crisp number or fuzzy number according to the real situation in our proposed method. The numerical example about supplier selection is used to illustrate the efficiency of the proposed method. © 2011 Published by Elsevier Ltd.

Chan H.K.,University of East Anglia | Chan F.T.S.,Hong Kong Polytechnic University
Decision Support Systems | Year: 2010

Supply chains need to be flexible and adaptive because their operations are always subject to a variety of uncertainties like customer demand and supplier capacity, particularly for Make-to-Order (MTO) supply chains since their flow of materials is only triggered by customer orders. The main objective of this paper is to study how flexibility and adaptability in delivery quantity and due date can improve the performance in a network of two-level multi-product MTO supply chains. Effect of uncertain customer demand and also supplier capacity, and supplier's capacity utilization are studied. Flexibility and adaptability are realized based on two proposed coordination mechanisms. Agent-based simulation is employed in this study to model the operations of supply chains. Performance of the system is measured in terms of a number of cost items and customer demand fill rate. Simulation results indicate that introduction of such flexibility and adaptability can improve the aforementioned performance. However, there is a trade-off in selecting the coordination mechanism between adaptability and flexibility subject to capacity utilization. Details and concluding remarks are discussed in this paper. © 2009 Elsevier B.V. All rights reserved.

Shareholding Cooperatives (SCs) are the officially recognised organisations responsible for managing villagers’ collectively owned assets. In recent years, massive land requisitions in the Pearl River Delta region have led many villages to experience a rapid expansion in their collective assets, highlighting the indispensable role of SCs in reshaping the landscape of local governance. Based upon an in-depth case study of the Guangzhou Luogang District, this study shows that the local state has engaged with shareholding reforms to achieve two main objectives: inducing compliance amongst villagers and promoting the accountability of village cadres in the management of collective assets. These empirical findings suggest that shareholding reforms were not simply a process of market building or property rights reforms driven by local initiatives. Rather, they should also be interpreted as a process of state power reconsolidation, whereby the local government sought to regain its control over the urbanising villages. © 2015, © Urban Studies Journal Limited 2015.

He X.Y.,Nanyang Technological University | Wang Q.J.,Nanyang Technological University | Yu S.F.,Hong Kong Polytechnic University
IEEE Journal of Quantum Electronics | Year: 2012

We investigate dispersion properties of n-layers unit cell metallic-dielectric stratified structures (MDSSs) for the first time to our knowledge. An efficient and flexible numerical method is applied to study optical characteristics of the MDSSs. As an example, we systematically investigate the influences of geometric parameters, operating frequency, and gain material on the dispersion properties of the n-layers unit cell MDSSs in the terahertz regime. The results show that the effective index of the n-layers unit cell MDSSs decreases with the increase of operating frequency. The full-width-half-maximum of the transmittance of the n-layers unit cell MDSSs can be designed wider than that of the binary unit cell MDSSs, which is beneficial for the design of certain optical devices, such as superlenses. Furthermore, the effective index/loss of the proposed structure increases/decreases with the increase of the material gain. Due to the high flexibility of the proposed n-layers unit cell MDSSs, we believe they would have broad applications in the fields of nanophotonics and integrated optoelectronics. © 1965-2012 IEEE.

Lee P.H.,Hong Kong Polytechnic University
International Journal of Environmental Research and Public Health | Year: 2014

In the medical field, many outcome variables are dichotomized, and the two possible values of a dichotomized variable are referred to as classes. A dichotomized dataset is class-imbalanced if it consists mostly of one class, and performance of common classification models on this type of dataset tends to be suboptimal. To tackle such a problem, resampling methods, including oversampling and undersampling can be used. This paper aims at illustrating the effect of resampling methods using the National Health and Nutrition Examination Survey (NHANES) wave 2009–2010 dataset. A total of 4677 participants aged ≥20 without self-reported diabetes and with valid blood test results were analyzed. The Classification and Regression Tree (CART) procedure was used to build a classification model on undiagnosed diabetes. A participant demonstrated evidence of diabetes according to WHO diabetes criteria. Exposure variables included demographics and socio-economic status. CART models were fitted using a randomly selected 70% of the data (training dataset), and area under the receiver operating characteristic curve (AUC) was computed using the remaining 30% of the sample for evaluation (testing dataset). CART models were fitted using the training dataset, the oversampled training dataset, the weighted training dataset, and the undersampled training dataset. In addition, resampling case-to-control ratio of 1:1, 1:2, and 1:4 were examined. Resampling methods on the performance of other extensions of CART (random forests and generalized boosted trees) were also examined. CARTs fitted on the oversampled (AUC = 0.70) and undersampled training data (AUC = 0.74) yielded a better classification power than that on the training data (AUC = 0.65). Resampling could also improve the classification power of random forests and generalized boosted trees. To conclude, applying resampling methods in a class-imbalanced dataset improved the classification power of CART, random forests, and generalized boosted trees. © 2014 by the authors; licensee MDPI, Basel, Switzerland.

Li S.,Zhengzhou University | Ng C.T.,Hong Kong Polytechnic University | Yuan J.,Zhengzhou University
International Journal of Production Economics | Year: 2011

We consider a single-machine scheduling problem involving both the due date assignment and job scheduling under a group technology environment. The jobs (orders) of customers are classified into groups according to their production similarities in advance. To achieve production efficiency and save time/money resource, all jobs of the same group are required to be processed contiguously on the machine. A sequence-independent setup time precedes the processing of each group. The due dates are assignable according to one of the following three due date assignment methods: FML-CON, FML-SLK and DIF, where FML-CON means that all jobs within the same group are assigned a common due date, FML-SLK means that all jobs within the same group are assigned an equal flow allowance, and DIF means that each job can be assigned a different due date with no restrictions. The goal is to determine an optimal combination of the due date assignment strategy and job schedule so as to minimize an objective function that includes earliness, tardiness, due date assignment and flow time costs. An O(nlogn) time unified optimization algorithm is provided for all of the above three due date assignment methods. © 2010 Elsevier B.V. All rights reserved.

Wang X.,Nanjing University of Science and Technology | Xie X.,Nanjing University of Science and Technology | Cheng T.C.E.,Hong Kong Polytechnic University
International Journal of Production Economics | Year: 2013

We consider a two-stage make-to-order production system characterized by limited production capacity and tight order due dates. We want to make joint decisions on order acceptance and scheduling to maximize the total net revenue. The problem is computationally intractable. In view of the fact that artificial bee colony algorithm has been shown to be an effective evolutionary algorithm to handle combinatorial optimization problems, we first conduct a pilot study of applying the basic artificial bee colony algorithm to treat our problem. Based on the results of the pilot study and the problem characteristics, we develop a modified artificial bee colony algorithm. The experimental results show that the modified artificial bee colony algorithm is able to generate good solutions for large-scale problem instances. © 2012 Elsevier B.V. All rights reserved.

Wu Y.I.,University of Electronic Science and Technology of China | Wong K.T.,Hong Kong Polytechnic University | Lau S.-K.,University of Nebraska at Omaha
IEEE Transactions on Signal Processing | Year: 2010

The acoustic vector-sensor is a practical and versatile sound-measurement system, for applications in-room, open-air, or underwater. Its far-field measurement model has been introduced into signal processing over a decade ago; and many direction-finding algorithms have since been developed for acoustic vector-sensors, but only for far-field sources. Missing in the literature is a near-field measurement model for the acoustic vector-sensor. This correspondence fills this literature gap. © 2010 IEEE.

Tsang M.M.Y.,Castle Peak Hospital | Man D.W.K.,Hong Kong Polytechnic University
Schizophrenia Research | Year: 2013

Employment provides schizophrenic patients with a positive identity and hope. Cognitive impairments have been suggested to slow down the progress in work rehabilitation. The purpose of this study was to investigate the efficacy and effectiveness of VR as a cognitive intervention for enhancing vocational outcomes. 95 inpatients with schizophrenia were randomly assigned to a virtual reality-based vocational training group (VRG), a therapist-administered group (TAG) and a conventional group (CG). Twenty-five of them in each group had completed the study. Their performances were evaluated, before and after interventions, by Brief Neuropsychological Cognitive Examination, Digit Vigilance Test, Rivermead Behavioural Memory Test, Wisconsin Card Sorting Test (WCST) and Vocational Cognitive Rating Scale. Patients in the VRG were found to perform better than patients in the TAG and CG in cognitive functioning, as shown by the WCST-percentage of error (F (2, 72) = 7.146, p. <. 0.001) and the WCST-percentage of conceptual level response (F (2, 72) = 8.722, p. <. 0.001). The post-hoc test revealed that the VRG showed a better performance than both the TAG (p = 0.03) and the CG (p. <. 0.001) in the WCST-percentage of error. The VRG also showed a better performance than patients in both the TAG (p = 0.01) and the CG (p. <. 0.001) in the WCST-percentage of conceptual level response. The VRG also showed a better self-efficacy score than CG. Both VRG and TAG showed a better work performance as reflected by the on-site tests. Further studies on the use of VR in schizophrenia rehabilitation and for vocational success are discussed. © 2013 Elsevier B.V.

Choi T.-M.,Hong Kong Polytechnic University
IEEE Transactions on Industrial Informatics | Year: 2011

RFID technology is an important tool in modern supply chain management. This paper analytically studies the use of RFID in a two-echelon single-manufacturer single-retailer supply chain with the vendor managed inventory (VMI) scheme. First, the supply chain models under a retail replenishment problem with and without RFID are constructed. Second, both the levels of risk and the expected profits of the supply chains are explored. Third, measures which can coordinate the supply chains with and without RFID are proposed. Fourth, comparisons between the cases with and without RFID are made. This paper analytically illustrates several important managerial insights which include: (i) when the RFID tag cost is very small, employing the RFID technology yields an improved supply chain with both larger expected profit and smaller risk; (ii) there exist multiple return policies which can coordinate the supply chain with RFID and the respective upper and lower bounds are identified; (iii) it is beneficial for the manufacturer to take the initiative to share the retailer's cost of RFID implementation, and this action not only can help coordinate the supply chain but also lower the manufacturer's risk; and (iv) compared to the case without RFID, the return rate under the coordinating return policy for the case with RFID can be lower if the RFID tag cost is appropriately shared between the retailer and the manufacturer. These insights are important for both industrialists and academicians. © 2011 IEEE.

Kwan M.-P.,University of California at Berkeley | Kwan M.-P.,Hong Kong Polytechnic University
Annals of GIS | Year: 2012

The uncertain geographic context problem (UGCoP), first articulated by Kwan (2012; The uncertain geographic context problem. Annals of the Association of American Geographers, 102 (5), 958-968), refers to the problem that findings about the effects of area-based contextual variables on individual behaviors or outcomes may be affected by how contextual units (e.g., neighborhoods) are geographically delineated and the extent to which these areal units deviate from the true geographic context. It is a significant methodological problem because it means that analytical results can differ for different delineations of contextual units even if everything else is the same. Drawing upon Kwan (2012) and recent social science studies (especially environmental health and neighborhood effects research), this article further elaborates on the nature of the UGCoP and explores how recent advances in geographical information system (GIS) and geospatial technologies can help address the problem. It discusses possible means for mitigating the UGCoP, especially with regard to the collection of detailed individual space-time data with global positioning systems, construction of individual activity spaces, and the use of qualitative and web-based GIS to capture people's activity locations and everyday experiences. It also discusses the challenges for future research that seeks to address the UGCoP. © 2012 Copyright Taylor and Francis Group, LLC.

Chong C.S.,Hong Kong Polytechnic University
Alternative therapies in health and medicine | Year: 2011

This article reports a systematic review and critical appraisal of the effect of yoga on stress management in healthy adults. A systematic literature search was performed to identify randomized controlled trials (RCTs) and clinical controlled trials (CCTs) that assessed the effects of yoga on stress management in healthy adults. Selected studies were classified according to the types of intervention, duration, outcome measures, and results. They were also qualitatively assessed based on Public Health Research, Education and Development standards. The systematic review was based on eight RCTs and CCTs that indicated a positive effect of yoga in reducing stress levels or stress symptoms. However, most of the studies had methodological problems in that the intervention duration was short and limited follow-up data was available. This review revealed positive effects of yoga on stress reduction in healthy adult populations. However, the result should be interpreted with caution due to the small number of studies and the associated methodological problems. Further studies to ascertain yoga's long-term effects and the underlying biological mechanisms leading to its stress reduction effect should be conducted.

Bai X.,Hong Kong Polytechnic University
Ageing and Society | Year: 2016

It is noteworthy that while modernisation, together with population ageing, has happened in Western countries for a rather long period of time, China must confront the challenges of an ageing population before it really becomes an advanced industrial society. Facing rapid societal changes, citizens may react differently to this process. By conducting questionnaire surveys with 445 elders in Wuhan, China, this study examines Chinese older adults' individual modernity modes and reveals its socio-demographic correlates. The results show that facing rapid changes in societal modernisation, participants have reacted differently to this process, with 23.8 per cent of Chinese older participants using an accommodation mode, 27.0 per cent using a resistance mode, 13.3 per cent using a withdrawal mode and 36.2 per cent using a coping mode. In addition, socio-demographic factors such as urban-rural residence, age, gender, socio-economic status, living arrangement and daily activities have been identified as significant correlates of Chinese older participants' individual modernity modes. It is further suggested that governments at all levels should allow for options and opportunities for older people to align themselves in the modernisation process by removing the barriers that may hinder their integration and empowerment efforts. While it is important to respect older adults' different responses in the face of modernisation, their participation in societies should be encouraged and respected by the wider society in the context of modernisation. © 2014 Cambridge University Press.

Dong F.,Chongqing Technology and Business University | Sun Y.,Chongqing Technology and Business University | Fu M.,Chongqing Technology and Business University | Wu Z.,Zhejiang University | Lee S.C.,Hong Kong Polytechnic University
Journal of Hazardous Materials | Year: 2012

This research represents a highly enhanced visible light photocatalytic removal of 450ppb level of nitric oxide (NO) in air by utilizing flower-like hierarchical porous BiOI/BiOCl composites synthesized by a room temperature template free method for the first time. The facile synthesis method avoids high temperature treatment, use of organic precursors and production of undesirable organic byproducts during synthesis process. The result indicated that the as-prepared BiOI/BiOCl composites samples were solid solution and were self-assembled hierarchically with single-crystal nanoplates. The aggregation of the self-assembled nanoplates resulted in the formation of 3D hierarchical porous architecture containing tri-model mesopores. The coupling to BiOI with BiOCl led to down-lowered valence band (VB) and up-lifted conduction band (CB) in contrast to BiOI, making the composites suitable for visible light excitation. The BiOI/BiOCl composites samples exhibited highly enhanced visible light photocatalytic activity for removal of NO in air due to the large surface areas and pore volume, hierarchical structure and modified band structure, exceeding that of P25, BiOI, C-doped TiO 2 and Bi 2WO 6. This research results could provide a cost-effective approach for the synthesis of porous hierarchical materials and enhancement of photocatalyst performance for environmental and energetic applications owing to its low cost and easy scaling up. © 2012 Elsevier B.V.

Guan B.-O.,Jinan University | Jin L.,Jinan University | Zhang Y.,Dalian University of Technology | Tam H.-Y.,Hong Kong Polytechnic University
Journal of Lightwave Technology | Year: 2012

Fiber grating laser sensors have been attracting great interest because of their high signal-to-noise ratio and narrow linewidth that permit high resolution sensing. According to the working principle, fiber grating laser sensors can be classified into two types: wavelength encoding sensor and polarimetric heterodyning sensor. The former responds to external perturbations in terms of shift in the operation wavelength of the fiber laser, which is similar to that of fiber grating sensor. The latter converts measurand into change in beat frequency between the two orthogonal polarization modes from the fiber laser. The polarimetric fiber grating laser sensor not only has almost all advantages of passive fiber grating sensors, but also has a distinctive advantage of ease of interrogation. This is because the beat frequency is in the RF domain, which avoids the employment of expensive wavelength measurement devices. This type of sensor has been demonstrated for measurement of temperature, axial strain, lateral force, hydrostatic pressure, bending, displacement, acceleration, electric current, and acoustic and ultrasonic signal. In this paper, we review the principle, fabrication, characterization, and implementation of the polarimetric heterodyning fiber grating laser sensors, and the sensor multiplexing in the RF domain. © 2011 IEEE.

Chen W.,Hong Kong Polytechnic University
IEEE Photonics Journal | Year: 2016

A novel method using 3-D space is proposed for optical multiple-image encryption. Each input image is divided into a series of particle-like points distributed in 3-D space, and all generated particle-like points are simultaneously encrypted into a phaseonly mask. The proposed method may open up a novel research perspective for optical multiple-image encryption, since a 3-D-space processing strategy is developed and successfully applied. © 2016 IEEE.

Caot Y.,Hong Kong Polytechnic University
Proceedings of the Annual ACM-SIAM Symposium on Discrete Algorithms | Year: 2016

Let interval + kv, interval + ke, and interval - fee denote the classes of graphs that can be obtained from some interval graph by adding k vertices, adding k edges, and deleting k edges, respectively. When k is small, these graph classes are called almost interval graphs. They are well motivated from computational biology, where the data ought to be represented by an interval graph while we can only expect an almost interval graph for the best. For any fixed k, we give linear-time algorithms for recognizing all these classes, and in the case of membership, our algorithms provide also a specific interval graph as evidence. When k is part of the input, these problems are also known as graph modification problems, all NP-complete. Our results imply that they are fixed-parameter tractable parameterized by k, thereby resolving the long-standing open problem on the parameterized complexity of recognizing interval + ke, first asked by Bodlaender et al. [Bioinformatics, 11:49-57, 1995]. Moreover, our algorithms for recognizing interval + kv and interval - ke run in times 0(6k · (n+m)) and 0(8k · (n+m)), (where n and m stand for the numbers of vertices and edges respectively in the input graph, ) significantly improving the 0(k2k n3ro)-time algorithm of Heggernes et al. [STOC 2007; SICOMP 2009] and the 0(10k · n9)-time algorithm of Cao and Marx [SODA 2014; TALG 2015] respectively.

Kwan P.,Hong Kong Polytechnic University
Journal of Aging Research | Year: 2013

Sarcopenia is an aging-associated condition, which is currently characterized by the loss of muscle mass and muscle strength. However, there is no consensus regarding its characterization hitherto. As the world older adult population is on the rise, the impact of sarcopenia becomes greater. Due to the lack of effective treatments, sarcopenia is still a persisting problem among the global older adults and should not be overlooked. As a result, it is vital to investigate deeper into the mechanism underlying the pathogenesis of sarcopenia in order to develop more effective therapeutic interventions and to inscribe a more uniform characterization. The etiology of sarcopenia is currently found to be multifactorial, and most of the pharmacological researches are focused on the muscular factors in aging. Although the complete mechanism underlying the development of sarcopenia is still waiting to be elucidated, we propose in this article that the primary trigger of sarcopenia may be neurogenic in origin based on the intimate relationship between the nervous and muscular system, namely, the motor neuron and its underlying muscle fibers. Both of them are affected by the cellular environment and their physiological activity. © 2013 Ping Kwan.

Ng S.S.,Hong Kong Polytechnic University | Hui-Chan C.W.,University of Illinois at Chicago
Archives of Physical Medicine and Rehabilitation | Year: 2012

Objectives: (1) To determine the relationships of ankle dorsiflexor strength, ankle plantarflexor strength, and spasticity of the ankle plantarflexors with walking endurance; (2) to determine whether affected ankle dorsiflexor strength makes an independent contribution to walking endurance; and (3) to quantify its relative contribution to the walking endurance of people with spastic hemiplegia after stroke. Design: A cross-sectional study. Setting: University-based rehabilitation center. Participants: Subjects (N=62) with spastic hemiplegia. Interventions: Not applicable. Main Outcome Measures: Walking endurance was measured by the distance covered in the six-minute walk test (6MWT). Ankle dorsiflexor and plantarflexor strength were measured using a load-cell mounted on a custom-built foot support. Plantarflexor spasticity was measured using the Composite Spasticity Scale. Results: The six-minute walk distances showed stronger positive correlation with affected dorsiflexor strength (r=.793, P≤.000) when compared with affected plantarflexor strength (r=.349, P=.005). Results of the regression model showed that after adjusting for basic demographic and stroke-related impairments, affected ankle dorsiflexor strength remained independently associated with six-minute walk distance, accounting for 48.8% of the variance. Conclusions: This is the first study, to our knowledge, to document the importance of ankle dorsiflexor strength as an independent determinant of walking endurance in stroke survivors with spastic plantarflexors. Our findings suggest that stroke rehabilitation programs aiming to improve walking endurance should include strengthening exercises for the ankle dorsiflexors. © 2012 American Congress of Rehabilitation Medicine.

Duan H.F.,Hong Kong Polytechnic University
Journal of Water Resources Planning and Management | Year: 2016

Partial blockages are commonly formed in water supply pipelines due to many factors, such as deposition, biofilm, and corrosion in the natural water supply process, as well as valve throttle in the artificial construction and operation process, which may cause additional energy losses and serious water supply accidents in the system. Recently, a transient-based frequency domain method (TBFDM) has been developed by the author for extended partial blockage detection, and it was found to be efficient, nonintrusive, and inexpensive to apply. While this method has been validated and applied for numerical and laboratory experiments in previous studies for a variety of blockage and hydraulic conditions, the application results revealed that the accuracy of the TBFDM may be easily affected by uncertainties in the experimental process. This paper investigates the sensitivity of the developed TBFDM to different uncertainty factors that commonly exist in water pipeline systems, with perspective to better understand and use this efficient and economic method in practice. The methods of firstorder second-moment analysis and Monte Carlo simulation are adopted in this paper for the investigation. The obtained results are discussed for the validity range and limitations of current TBFDM for practical applications. © 2016 American Society of Civil Engineers.

Mak M.,Hong Kong Polytechnic University | Hallett M.,U.S. National Institutes of Health
Clinical Neurophysiology | Year: 2013

Objective: To examine whether training under visual cues could enhance motor cortical excitability and intracortical inhibition in individuals with Parkinson's disease (PD). Methods: This was a single blinded cross-over study. Eight individuals with PD received two sessions of 30-min pinch-grip training with and without visual cues. The visual cue was given in form of an arrow that indicated the pre-set force level on a computer screen. Outcome measures consisted of peak motor evoked potential (MEP) and cortical silent period (CSP) of the first dorsal interosseus as well as behavioural tests including Purdue pegboard test, tapping speed in 30. s, and the maximum pinch grip force exerted by the thumb and index finger. Results: After cued training, there were significant increases in the peak MEP, CSP duration and tapping speed (all p<. 0.05). In contrast, there was no change in all outcome measures after training under the non-cued condition. Conclusions: Thirty minutes of pinch-grip training with visual cues could enhance motor cortical excitability and intracortical inhibition in individuals with PD. Significance: The findings on the neurophysiological changes after cued-training may inform further clinical application of visual cues to maximize motor improvement and corticomotor plasticity in people with PD. © 2012 International Federation of Clinical Neurophysiology.

Mok P.Y.,Hong Kong Polytechnic University
Computers and Industrial Engineering | Year: 2011

The control of manufacturing systems with variable demands has attracted much research attention over the years. However, only limited results have been obtained due to the difficulty of this production-control problem. In this paper, genetically optimized short-run hedging points are used to construct gain-scheduled adaptive controllers for unreliable manufacturing systems with variable demands. The performance of such adaptive controllers is illustrated for unreliable systems subjected to piecewise-constant demands. It is demonstrated that the performance of these adaptive controllers is superior, in general, to that of genetically optimized non-adaptive controllers. However, such gain-scheduled adaptive controllers are designed for variable demands that are piecewise-constant. Therefore, in order to deal with more general classes of variable demands, a genetic rule-induction design methodology is used to synthesize robust fuzzy-logic controllers to provide automatic closed-loop control for unreliable manufacturing systems. Such robust fuzzy-logic controllers are shown to provide effective control for unreliable manufacturing systems with various kinds of variable demands. © 2011 Elsevier Ltd. All rights reserved.

Chung S.H.,Hong Kong Polytechnic University | Chan H.K.,University of East Anglia
IEEE Transactions on Industrial Electronics | Year: 2012

The economic lot scheduling problem (ELSP) has been studied over 50 years. ELSP is known as NP-hard and hence heuristic algorithms have been developed. In those heuristics, researchers generally adopted two types of rounding-off methods for the production frequency of products, namely, the nearest integer and power-of-two approaches. The production frequency of products defines the number of times that such product being produced during the cycle. Therefore, different production frequency actually leads to different optimization results even for the same set of products. For this reason, this paper proposes a two-level genetic algorithm to deal with this problem. A number of numerical examples found in literature and randomly generated problem sets are used to test and benchmark the performance of the new approach. The comparison shows that the new approach outperforms the other existing approaches and also demonstrates the significance of the production frequency to the optimization results. © 2011 IEEE.

Pun-Cheng L.S.C.,Hong Kong Polytechnic University
IEEE Transactions on Intelligent Transportation Systems | Year: 2012

A comprehensive and presentable public transport information system is deemed invaluable for local residents and tourists all over the world. This is particularly necessary in view of the complex city structure and transportation system in Hong Kong. There are more than ten public transportation modes available, all with different operation schedules, fare structures, and routing characteristics. To assist commuters in making better use of public transport, the system needs to be not only user friendly and informative but intelligent enough to provide optimal route choices in terms of users' travelling behavior or preference as well. The web-map public transport enquiry system, as described in this paper, gives a good example of providing bilingual (English and Chinese) information on all public transports run in Hong Kong in the form of interactive maps and texts, as well as real-time derivation of optimal travelling routes for users in terms of multiple criteria, i.e., preferred mode, least changes, shortest travelling time, or lowest fare. © 2012 IEEE.

Hsu C.-J.,Nan Kai University of Technology | Cheng T.C.E.,Hong Kong Polytechnic University | Yang D.-L.,National formosa University
Information Sciences | Year: 2011

Zhao et al. (2009) [24] study the m identical parallel-machine scheduling problem with rate-modifying activities to minimize the total completion time. They show that the problem can be solved in O(n2m+3) time. In this study we extend the scheduling environment to the unrelated parallel-machine setting and present a more efficient algorithm to solve the extended problem. For the cases where the rate-modifying rate is (i) larger than 0 and not larger than 1, and (ii) larger than 0, we show that the problem can be solved in O(nm+3) and O(n2m+2) time, respectively. © 2011 Elsevier Inc. All rights reserved.

Cheng T.C.E.,Hong Kong Polytechnic University | Hsu C.-J.,Nan Kai University of Technology | Yang D.-L.,National formosa University
Computers and Industrial Engineering | Year: 2011

We study the problem of unrelated parallel-machine scheduling with deteriorating maintenance activities. Each machine has at most one maintenance activity, which can be performed at any time throughout the planning horizon. The length of the maintenance activity increases linearly with its starting time. The objective is to minimize the total completion time or the total machine load. We show that both versions of the problem can be optimally solved in polynomial time. © 2010 Published by Elsevier Ltd. All rights reserved.

Ni M.,Hong Kong Polytechnic University
Chemical Engineering Journal | Year: 2010

In this study, two models are developed to investigate the performance of a solid oxide electrolysis cell (SOEC) for CO2 electrolysis at different levels. The first model is a one-dimensional model which is basing on a previously developed electrochemical model for steam electrolysis and considered all overpotentials in the SOEC. The second model is a two-dimensional thermal-fluid model consisting of the 1D model and a computational fluid dynamics (CFD) model. It is found that the mean electrolyte temperature initially decreases with increasing operating potential, reaches the minimum at about 1.1V and increases considerably with a further increase in potential. At the thermal-neutral voltage (1.463V at 1173K), the calculated mean electrolyte temperature matches the inlet gas temperature. Increasing the operating potential increases both the local current density and the electrolyte Nernst potential. The electrochemical performance can be improved by increasing the inlet gas velocity from 0.2ms-1 to 1.0ms-1 but further increasing the inlet gas velocity will not considerably enhance the SOEC performance. It is also found that a change of electrode permeability in the order of 10-16m2 to 10-13m2 does not noticeably influence the SOEC performance in the present study, due to negligible convection effect in the porous electrodes. © 2010 Elsevier B.V.

Yu T.,University of Wollongong | Teng J.G.,Hong Kong Polytechnic University
Journal of Composites for Construction | Year: 2013

Hybrid fiber-reinforced polymer (FRP) concrete steel, double skin tubular columns (DSTCs) are a new form of hybrid columns. The most common sectional form of hybrid DSTCs consists of a layer of concrete sandwiched between a circular inner steel tube and a circular outer FRP tube whose fiber directions are close to the hoop detection to provide effective confinement to the concrete. Much recent research has been conducted on circular hybrid DSTCs, which has demonstrated that the combination of the three constituent materials leads to several advantages not available with existing forms of columns. In practical applications, for aesthetic and other reasons, square hybrid DSTCs may be needed. This paper thus extends the existing work on circular hybrid DSTCs to square hybrid DSTCs in which the outer FRP tube is square while the inner steel tube is still circular. Results from a series of axial compression tests are presented and interpreted to examine the compressive behavior of square hybrid DSTCs. In these tests, FRP tubes formed through a wet-layup process were used instead of filament-wound FRP tubes because the latter were not readily available to the authors at the time of the study. The test results show that the concrete in these square hybrid DSTCs is effectively confined by the two tubes, and the behavior of the confined concrete is similar to that of concrete in FRP-confined solid columns. A stress-strain model for concrete in square hybrid DSTCs is also proposed and is shown to provide reasonably accurate predictions of the test results. © 2013 American Society of Civil Engineers.

Yang S.-J.,Nan Kai University of Technology | Yang D.-L.,National formosa University | Cheng T.C.E.,Hong Kong Polytechnic University
Computers and Operations Research | Year: 2010

Due-window assignment and scheduling are important issues in modern manufacturing management. In this note we consider single-machine due-window assignment and scheduling with job-dependent aging effects and deteriorating maintenance. The objective is to find jointly the optimal time to perform maintenance, the optimal location and size of the due-window, and the optimal job sequence to minimize the total earliness, tardiness, and due-window related costs. We show that the problem can be optimally solved in O (n4) time. We also show that a special case of the problem can be optimally solved by a lower order algorithm. © 2009 Elsevier Ltd. All rights reserved.

Cheung K.,Hong Kong Polytechnic University
Journal of Clinical Nursing | Year: 2010

Aims: To determine the cumulative incidence (CI) of and risk factors for musculoskeletal problems among nursing students in Hong Kong. Background: Although low back problems have been identified internationally as one of the major work-related hazards among nursing personnel, only a few studies have examined the problem among nursing students. Design: Two-year prospective cohort study; data collected at baseline and 2 (T1), 12 (T2) and 26 (T3) months after baseline. Methods: Three cohorts [i.e. two full-time (FT) and one part-time (PT) cohorts] of nursing students were recruited from one of the universities in Hong Kong. They were invited to complete a baseline and three follow-up questionnaires. CIs of low back problems among the three cohorts were calculated and tested for their association. The multivariate logistic regression was also used to identify the risk factors for low back problems. Results: Initially, the seven-day, 30-day and 12-month prevalence in baseline as well as the T1 (64%) and T2 (94%) CIs of low back problems for the PT cohort were significantly higher than those of the two FT cohorts (their CIs ranged from 45-67%). However, the CIs for the FT cohorts were increased from 45% at T1-83% at T3, while the CIs for the PT cohort was only increased from 64-80%, respectively. At T3, the CIs for both FT cohorts caught up with the CI for the PT cohort (χ2 = 0·068, p = 0·07). As expected, the risk factors for low back problems were multifactorial, i.e. personal, psychosocial and physical. Conclusion: Nursing students had similar CI of low back problems as registered nurses 26 months after baseline, i.e. during their nursing training and before becoming a registered nurse. Relevance to clinical practice: The results of this study, for the first time, identified that low back problems were developed during the period of nursing school training rather than after nurses enter the workforce. These findings have crucial implications for reducing low back problems among nursing personnel. There is a need to evaluate nursing students' experience in their nursing study and provide appropriate support to them to reduce their personal, physical and psychosocial stress. The ability of nursing students to deliver high quality patient care depends in part on their ability to conserve their own health and well-being. © 2010 The Author. Journal compilation © 2010 Blackwell Publishing Ltd.

Cho V.,Hong Kong Polytechnic University
Knowledge-Based Systems | Year: 2010

Nowadays, stock market is becoming a popular investment platform for both institutional and individual investors. The current financial information systems serve to provide latest information. However, they lack sophisticated analytical tools. This paper proposes a new architecture for financial information systems. The developed prototype is entitled as the Multi-level and Interactive Stock Market Investment System (MISMIS). It is specially designed for investors to build their financial models to forecast stock price and index. The performance of the financial models can be evaluated on a virtual trading platform. There are other features in MISMIS that are tailor-made to handle financial data; these include synchronized time frame, time series prediction techniques, preprocessing and transformation functions, multi-level modeling and interactive user interface. To illustrate the capability of MISMIS, we have evaluated strategies of trading the future options of Hang Seng Index (HSI). We find that historical HSI, Dow Jones Index, property price index, retailing sales figure, prime lending rate, and consumer price index in Hong Kong are essential factors affecting the performance of the trading of HSI's future option. Alòso there are some feedbacks from the in-depth interviews of six financial consultant upon how they perceived the prototype MISMIS. © 2010 Elsevier B.V. All rights reserved.

Jing X.,Hong Kong Polytechnic University
Neural Networks | Year: 2012

Feedforward neural networks (FNNs) have been extensively applied to various areas such as control, system identification, function approximation, pattern recognition etc. A novel robust control approach to the learning problems of FNNs is further investigated in this study in order to develop efficient learning algorithms which can be implemented with optimal parameter settings and considering noise effect in the data. To this aim, the learning problem of a FNN is cast into a robust output feedback control problem of a discrete time-varying linear dynamic system. New robust learning algorithms with adaptive learning rate are therefore developed, using linear matrix inequality (LMI) techniques to find the appropriate learning rates and to guarantee the fast and robust convergence. Theoretical analysis and examples are given to illustrate the theoretical results. © 2012 Elsevier Ltd.

Lun Y.H.V.,Hong Kong Polytechnic University
Resources, Conservation and Recycling | Year: 2011

This study aims to investigate the elements of green management practices (GMP) and its association with firm performance. A GMP model that consists of the key elements of GMP is proposed and firm performance indicators are formulated to provide a foundation for the adoption of GMP. Hutchison Port Holding (HPH) is selected as the case to illustrate the application of the proposed GMP model in a real-life situation. The findings suggest that GMP consists of the following elements: (1) cooperation with supply chain partners, (2) environmentally friendly operation, and (3) internal management support. Findings of this study also indicate a positive relationship exists between the adoption of GMP and firm performance. Hence, operators in the container terminal industry should strive to adopt GMP in order to achieve good firm performance including improvement in terminal throughput, profitability, and efficient and cost-effective operation. © 2010 Elsevier B.V. All rights reserved.

Fong L.H.,Hong Kong Polytechnic University
Journal of gambling studies / co-sponsored by the National Council on Problem Gambling and Institute for the Study of Gambling and Commercial Gaming | Year: 2014

Gambling is a leisure activity, which is enjoyed by many people around the world. Among these people, Chinese are known for their high propensity to gamble and are highly sought after by many casinos. In this exploratory study, the effect of two types of fallacy bias-positive recency and negative recency-on the betting behavior of Chinese gamblers is investigated. Although the influence of fallacy bias on a betting decision is well documented, little is known about the interaction of the factors that dictate fallacy bias. Drawing from an analysis of 2,645 betting decisions, the results show that Chinese gamblers primarily endorse positive recency, especially when the latest outcome is more frequent. This is contrary to most findings on Western subjects in which negative recency is more common. Current findings have meaningful implications to casino gaming entertainment businesses and public policymakers.

Lai W.-F.,Hong Kong Polytechnic University
Ageing Research Reviews | Year: 2013

Prolongation of longevity is a history-long desire of humans. Driven by the genetic contribution to longevity and the remarkable plasticity of healthy lifespan as demonstrated in animal models, arduous efforts have been directed to aging and longevity research over the years. Today, our understanding of lifespan determination is much greater than it was in the past, but administrable interventions for longevity enhancement are still virtually absent. The aim of this article is to highlight the technical gap between basic biogerontological research and intervention development, and to explore the importance of nucleic acid (NA) delivery technologies in bridging the gap. It is hoped that this article can engender more awareness of the roles of NA delivery technologies in biogerontological interventions, particularly NA therapy. © 2012 Elsevier B.V.

Ruan X.,Nanjing University of Aeronautics and Astronautics | Ruan X.,Huazhong University of Science and Technology | Tan S.-C.,Hong Kong Polytechnic University | Yang Y.,Nanjing University of Aeronautics and Astronautics | Ye Z.,Lite-On Technology
IEEE Transactions on Power Electronics | Year: 2012

The electrolytic capacitor is the key component that limits the operating lifetime of LED drivers. If an ac-dc LED driver with power factor correction (PFC) control is allowed to output a pulsating current for driving the LEDs, the electrolytic capacitor will no longer be required. However, this pulsating current will introduce light flicker that varies at twice the power line frequency. In this paper, a configuration of flicker-free electrolytic capacitor-less single-phase ac-dc driver for LED lighting is proposed. The configuration comprises an electrolytic capacitor-less PFC converter and a bidirectional converter, which serves to absorb the ac component of the pulsating current of the PFC converter, leaving only a dc component to drive the LEDs. The output filter capacitor of the bidirectional converter is intentionally designed to have a large voltage ripple, thus its capacitance can be greatly reduced. Consequently, film capacitors can be used instead of electrolytic capacitors, leading to the realization of a flicker-free ac-dc LED driver that has a long lifetime. The proposed solution is generally applicable to all single-phase PFC converters. A prototype with 48-V, 0.7-A output is constructed and tested. Experimental results are presented to verify the effectiveness of the flick-free electrolytic capacitor-less ac-dc LED driver. © 2012 IEEE.

Centrifugation accompanied by flocculation of fine biosolids is often utilized in wastewater treatment. Unfortunately, commonly used laboratory jar tests often over-estimate the size of the flocculated solids (flocs) that can be realized in-situ in the centrifuge as the fragile flocs can be easily broken by shear and turbulence during feed acceleration in the centrifuge. Currently, there is no satisfactory method to predict in-situ floc size in the centrifuge, despite the floc size is critical to separation and solids recovery. The difficulty in making predictions also leads to inaccuracy in predicting solids recovery by decanter centrifuge and scale-up between centrifuges of different sizes, designs, and operating conditions, which is an even more serious issue. This study attempts to address these hurdles. In this study, first the flow pattern in a decanter centrifuge in form of moving layer at the pool surface is demonstrated by two different experiments. Second, a model on separation of suspended flocs in the moving layer in a centrifuge is developed. Further, a two-parameter model is proposed to represent the floc size distribution wherein the first parameter represents the minimum floc size (primary particle without coagulation or flocculation) and the second parameter represents the median floc size. A closed form analytical solution for the model is obtained with results expressed by the ratio of minimum-to-median floc size and a dimensionless Leung number which measures feed rate to the clarification rate of the centrifuge. Third, a Buckingham-π analysis has been conducted on separation in a moving layer under centrifugal field confirming these two governing dimensionless parameters can also be derived independently from the more basic dimensionless π groups. Fourth, by matching the solids recovery obtained from field tests with the model prediction, the median floc size can be inferred. In this matching process, the minimum floc size is assumed to be equal to the size of the primary, unflocculated solids. Fifth, four sets of tests (over 20 runs) have been carried out using two decanter centrifuges of different sizes and designs operating, respectively, under different pool depths, feed rates, polymer dosages and rotation speeds in a wastewater treatment plant processing mixed sludge with 48% primary sludge and 52% waste activated sludge. The median floc size inferred from the present method is in the range of 4–9 mm from the three series of tests (14 tests). The improved feed acceleration design with speed matching closely that of the rotating pool results in less pool turbulence, larger flocs, and lower polymer dosage (7 kg polymer/ton sludge); while the poorer feed acceleration with more pool disturbance from the under-accelerated feed results in smaller flocs, and higher polymer dosage (9 kg/t). Sixth, an important application of the model is to predict solids recovery using an estimated median floc size and this approach has predicted the solids recovery reasonably well on the fourth set of tests (9 tests). Seventh, the scale-up for predicting solids recovery of flocculated suspension from decanter centrifuges of different sizes, designs, and operating conditions has been demonstrated using the dimensionless Leung number and the minimum-to-median floc size ratio. © 2016 Elsevier B.V.

Xu X.,Huazhong University of Science and Technology | Yu J.,Huazhong University of Science and Technology | Wang S.,Hong Kong Polytechnic University | Wang J.,Huazhong University of Science and Technology
Applied Energy | Year: 2014

The society and the building professionals have paid much concern in recent years on building energy efficiency and the development and applications of low energy technologies for buildings/green buildings allowing the elimination, or at least reduction of dependence on electricity or fossil fuel while maintaining acceptable indoor environment. Utilizations of favorable diurnal temperature difference and ground thermal source for air conditioning are among these low energy technologies. Utilization of the hollow cores in the prefabricated slab for ventilation and the mass of the slab for thermal storage is widely used in building systems in Europe by exploiting the low energy source of the ambient air. These hollow core slabs aim at enlarging the heat transfer surface between the slab mass and the air in the core, which permits substantial heat flows even for relatively small temperature differences. This, in turn, allows the use of low energy cooling or heating sources, such as the ground, outside air or recovered process heat.In this paper, we present a comprehensive review of the research and application of active hollow core slabs in building systems for utilizing low energy sources. The principle and development of active hollow core slabs in building systems for leveling the indoor temperature fluctuation by ventilation air passing the cores are described. Calculation models of the active hollow core concrete slab as well as the practical applications and performance evaluation of the slab applied in building systems for air conditioning are also critically reviewed, One-dimensional, two-dimensional and three-dimensional models can be found in the literature for successfully simulating these heat transfer process. A finite element or finite difference method is often used for problem solving of two-dimensional or three-dimensional models. These detailed numerical solutions usually require lots of computation demand and limit the practical application in conventional building simulation packages. Simplified thermal network models are simple and easy to be developed, the parameters of these thermal network models were determined manually based on the geometry description of the slab which may deteriorate the modeling accuracy. Simulation-based performance evaluations and in situ measurements show that significant energy and operation cost could be saved, the peak cooling load or heat load can also be reduced significantly when conventional air-conditioning systems are used as supplements. Finally, this review shows that more works on the active slab are worthwhile for further promoting these slabs to be used in low energy architecture for improving energy efficiency and occupant thermal comfort wherever the climate is appropriate. © 2013 Elsevier Ltd.

Kocaguneli E.,West Virginia University | Menzies T.,West Virginia University | Keung J.W.,Hong Kong Polytechnic University
IEEE Transactions on Software Engineering | Year: 2012

Background: Despite decades of research, there is no consensus on which software effort estimation methods produce the most accurate models. Aim: Prior work has reported that, given M estimation methods, no single method consistently outperforms all others. Perhaps rather than recommending one estimation method as best, it is wiser to generate estimates from ensembles of multiple estimation methods. Method: Nine learners were combined with 10 preprocessing options to generate 9 × 10 = 90 solo methods. These were applied to 20 datasets and evaluated using seven error measures. This identified the best n (in our case n=13) solo methods that showed stable performance across multiple datasets and error measures. The top 2, 4, 8, and 13 solo methods were then combined to generate 12 multimethods, which were then compared to the solo methods. Results: 1) The top 10 (out of 12) multimethods significantly outperformed all 90 solo methods. 2) The error rates of the multimethods were significantly less than the solo methods. 3) The ranking of the best multimethod was remarkably stable. Conclusion: While there is no best single effort estimation method, there exist best combinations of such effort estimation methods. © 2012 IEEE.

Cheung R.T.,Hong Kong Polytechnic University
The American journal of sports medicine | Year: 2010

BACKGROUND: The motion control shoe is a well-developed technology in running shoe design for controlling excessive rearfoot pronation and plantar force distribution. However, there is little information on the leg muscle activation with different shoe conditions. HYPOTHESIS: The motion control shoe can prevent excessive shank muscle activation and delay fatigue. STUDY DESIGN: Controlled laboratory study. METHODS: Twenty female recreational runners with excessive rearfoot pronation were tested with running 10 km on a treadmill on 2 days. Participants wore either a motion control running shoe or neutral running shoe on each day. Activities of their right tibialis anterior and peroneus longus were recorded with surface electromyography. The normalized root-mean-square electromyography and median frequency were compared between the 2 shoe conditions. RESULTS: Significant positive correlations were found between the root-mean-square eletromyography and running mileage in both the tibialis anterior and peroneus longus in the neutral shoe condition (P <.001). The median frequency dropped in both shoe conditions with mileage, but paired t tests revealed a significantly larger drop in the neutral shoe (P < .001 for peroneus longus, P = .074 for tibialis anterior). CONCLUSION: The motion control shoe may facilitate a more stable activation pattern and higher fatigue resistance of the tibialis anterior and peroneus longus in individuals with excessive rearfoot pronation during running. CLINICAL RELEVANCE: The motion control shoe may increase the running endurance, thus reduce overuse injuries, in athletes with unstable feet during long-distance running.

Garg A.,Nanyang Technological University | Tai K.,Nanyang Technological University | Savalani M.M.,Hong Kong Polytechnic University
Rapid Prototyping Journal | Year: 2014

Purpose: The empirical modelling of major rapid prototyping (RP) processes such as fused deposition modelling (FDM), selective laser sintering (SLS) and stereolithography (SL) has attracted the attention of researchers in view of their contribution to the overall cost of the product. Empirical modelling techniques such as artificial neural network (ANN) and regression analysis have been paid considerable attention. In this paper, a powerful modelling technique using genetic programming (GP) for modelling the FDM process is introduced and the issues related to the empirical modelling of RP processes are discussed. The present work aims to investigate the performance of various potential empirical modelling techniques so that the choice of an appropriate modelling technique for a given RP process can be made. The paper aims to discuss these issues. Design/methodology/approach: Apart from the study of applications of empirical modelling techniques on RP processes, a multigene GP is applied to predict the compressive strength of a FDM part based on five given input process parameters. The parameter setting for GP is determined using trial and experimental runs. The performance of the GP model is compared to those of neural networks and regression analysis. Findings: The GP approach provides a model in the form of a mathematical equation reflecting the relationship between the compressive strength and five given input parameters. The performance of ANN is found to be better than those of GP and regression, showing the effectiveness of ANN in predicting the performance characteristics of the FDM part. The GP is able to identify the significant input parameters that comply with those of an earlier study. The distinct advantages of GP as compared to ANN and regression are highlighted. Several vital issues related to the empirical modelling of RP processes are also highlighted in the end. Originality/value: For the first time, a review of the application of empirical modelling techniques on RP processes is undertaken and a new GP method for modelling the FDM process is introduced. The performance of potential empirical modelling techniques for modelling RP processes is evaluated. This is an important step in modernising the era of empirical modelling of RP processes. © Emerald Group Publishing Limited.

Awad M.K.,American University of Kuwait | Wong K.T.,Hong Kong Polytechnic University
IEEE Transactions on Aerospace and Electronic Systems | Year: 2012

An acoustic vector-sensor (a.k.a. vector-hydrophone) is composed of three acoustic velocity-sensors, plus a collocated pressure-sensor, all collocated in space. The velocity-sensors are identical, but orthogonally oriented, each measuring a different Cartesian component of the three-dimensional particle-velocity field. This acoustic vector-sensor offers an azimuth-elevation response that is invariant with respect to the source's center frequency or bandwidth. This acoustic vector-sensor is adopted here for recursive least-squares (RLS) adaptation, to track a single mobile source, in the absence of any multipath fading and any directional interference. A formula is derived to preset the RLS forgetting factor, based on the prior knowledge of only the incident signal power, the incident source's spatial random walk variance, and the additive noise power. The work presented here further advances a multiple-forgetting-factor (MFF) version of the RLS adaptive tracking algorithm, that requires no prior knowledge of these aforementioned source statistics or noise statistics. Monte Carlo simulations demonstrate the tracking performance and computational load of the proposed algorithms. © 2011 IEEE.

Ni M.,Hong Kong Polytechnic University
International Journal of Hydrogen Energy | Year: 2012

A two dimensional model is developed to study the transport and reaction processes in solid oxide fuel cells (SOFCs) fueled by partially pre-reformed gas mixture, considering the direct internal reforming (DIR) of methane and water gas shift (WGS) reaction in the porous anode of SOFC. Electrochemical oxidations of H2 and CO fuels are both considered. The model consists of an electrochemical, a chemical model, and a computational fluid dynamics (CFD) model. Two chemical models are compared to examine their effects on SOFC modeling results. Different from the previous studies on hydrogen fueled SOFC, higher gas velocity is found to slightly decrease the performance of SOFC running on pre-reformed gas mixture, due to suppressed gas composition variation at a higher gas velocity. The current density distribution along the gas channels at an inlet temperature of 1173K is quite different from that at 1073K, as DIR reaction is facilitated at a higher temperature. It is also found that neglecting the electrochemical oxidation of CO can considerably underestimate the total current density of SOFC running on pre-reformed hydrocarbon fuels. An alternative method is proposed to numerically determine the open-circuit potential of SOFC running on hydrocarbon fuels. Electrochemical reactions are observed at open-circuit potentials. © 2011, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.

Xiao B.,Hong Kong Polytechnic University | Hua Y.,Huazhong University of Science and Technology
IEEE Transactions on Parallel and Distributed Systems | Year: 2010

One widely used mechanism for representing membership of a set of items is the simple space-efficient randomized data structure known as Bloom filters. Yet, Bloom filters are not entirely suitable for many new network applications that support network services like the representation and querying of items that have multiple attributes as opposed to a single attribute. In this paper, we present an approach to the accurate and efficient representation and querying of multiattribute items using Bloom filters. The approach proposes three variant structures of Bloom filters: Parallel Bloom Filter (referred as PBF) structure, PBF with a hash table (PBF-HT), and PBF with a Bloom filter (PBF-BF). PBF stores multiple attributes of an item in parallel Bloom filters. The auxiliary HT and BF provide functions to capture the inherent dependency of all attributes of an item. Compared to standard Bloom filters to represent items with multiple attributes, the proposed PBF facilitates much faster query service and both PBF-HT and PBF-BF structures achieve much lower false positive probability with a result to save storage space. Simulation and experimental results demonstrate that the new space-efficient Bloom filter structures can efficiently and accurately represent multiattribute items and quickly respond queries at the cost of a relatively small false positive probability. © 2010 IEEE.

Liu K.P.Y.,University of Western Sydney | Chan C.C.H.,Hong Kong Polytechnic University
Archives of Physical Medicine and Rehabilitation | Year: 2014

Objective To test the efficacy of self-regulation (SR) for promoting task performance and motor and cognitive functions. Design Pilot randomized controlled trial. Setting Rehabilitation unit. Participants Inpatients with acute poststroke (N=44) after a cerebral infarction aged ≥60 years. Interventions Patients were randomly assigned to the SR (n=24) or functional rehabilitation (control; n=20) intervention. The SR intervention consisted of 1 week of therapist-supervised practices of daily tasks using SR of one's own performance (five 1-h sessions). Patients in the control intervention practiced the same daily tasks with a therapist's demonstration and guidance. Main Outcome Measures Performance of tasks, including household and monetary transaction tasks; FIM; Fugl-Meyer Assessment (FMA); and Color Trails Test (CTT). Results The SR group showed significant improvement in all tasks (median difference, 1-2; effect size [r]=.74-.89) versus none (median difference, 0-0.5) in the control group. Results of the FIM (P<.001, r=.87 in the motor subscale; P<.001, r=.49 in the cognitive subscale), FMA (P<.001, r=.84 for upper extremity motor function and r=.63 for lower extremity motor function), and CTT (P=.002, r=.72) of the SR group improved. The SR group outperformed their control counterparts in 4 of the 5 tasks (median difference, 1; r=.30-.52) and in the FIM motor subscale (P=.002, r=.47), but not in the cognitive subscale and motor and cognitive functions. Conclusions SR appears useful for improving task performance that demands both motor and cognitive abilities by promoting information processing and active learning. © 2014 by the American Congress of Rehabilitation Medicine.

Mouratidis K.,Singapore Management University | Yiu M.L.,Hong Kong Polytechnic University
IEEE Transactions on Knowledge and Data Engineering | Year: 2010

The increasing availability of location-aware mobile devices has given rise to a flurry of location-based services (LBSs). Due to the nature of spatial queries, an LBS needs the user position in order to process her requests. On the other hand, revealing exact user locations to a (potentially untrusted) LBS may pinpoint their identities and breach their privacy. To address this issue, spatial anonymity techniques obfuscate user locations, forwarding to the LBS a sufficiently large region instead. Existing methods explicitly target processing in the euclidean space and do not apply when proximity to the users is defined according to network distance (e.g., driving time through the roads of a city). In this paper, we propose a framework for anonymous query processing in road networks. We design location obfuscation techniques that: 1) provide anonymous LBS access to the users and 2) allow efficient query processing at the LBS side. Our techniques exploit existing network database infrastructure, requiring no specialized storage schemes or functionalities. We experimentally compare alternative designs in real road networks and demonstrate the effectiveness of our techniques. © 2006 IEEE.

Herold D.K.,Hong Kong Polytechnic University
Information Society | Year: 2010

Information and communication technologies (ICTs) have increasingly become an integral part of society, enhancing, changing, supporting, and complicating human lives. Although the disregard of technology inventors and designers for the users of ICTs has resulted in disjunctures between ICTs and users, users have refused to become mere agents of the designers. Individual users have developed their own uses of ICTs based on the complex webs of relations and meanings in which they function as social actors. Instead of adjusting these webs to new ICTs, they have fit the ICTs into their preexisting social webs, often resulting in imaginative and creative uses for new technologies, not envisaged by the original designers. Accordingly, human users should be given precedence over ICTs, and studies should focus less on creative uses of given technologies and more on an appropriate design of ICTs that can be integrated into human lives. © Taylor & Francis Group, LLC.

Herold D.K.,Hong Kong Polytechnic University
Computers and Education | Year: 2010

Second Life has become increasingly popular with educators and educational institutions, because of the educational possibilities it seems to offer. While there has been a lot of hype and academic publications about educational design or the theoretical framing of teaching in virtual environments, there have been few publications focussing on actual teaching and learning experiences of lecturers and students in Higher Education institutions. This article uses practical examples from an introductory course on Media studies taught at the Hong Kong Polytechnic University to demonstrate that even simple tasks in Second Life can be used to great effect if properly contextualised into the course being taught. High levels of technical skills, or extraordinary educational designs are less important to employing Second Life successfully in a Higher Education environment, than a proper evaluation of student learning outcomes, and teaching goals. © 2009 Elsevier Ltd. All rights reserved.

Yuen K.K.F.,Hong Kong Polytechnic University
Applied Soft Computing Journal | Year: 2010

In the analytic hierarchy process, prioritization of the reciprocal matrix is a core issue to influence the final decision choice. Various prioritization methods have been proposed, but none of prioritization methods performs better than others in every inconsistent case. To address the prioritation operator selection problem, this paper proposes the analytic hierarchy prioritization process, which is an objective hierarchy model (without using subjective pairwise comparisons) to approximate the real priority vectors with selection of the most appropriate prioritization operator among the various prioritization candidates, for a reciprocal matrix, and on the basis of a list of measurement criteria. Nine important prioritization operators and seven measurement criteria are illustrated in AHPP. Two previous applications are revised and illustrate the validity and usability of the proposed model. The results show that the most appropriate prioritization operator is dependent of the content of the reciprocal matrix and AHPP is an appropriate method to address the prioritization problem to make better decisions. © 2009 Elsevier B.V. All rights reserved.

Lai C.K.Y.,Hong Kong Polytechnic University
Clinical Interventions in Aging | Year: 2014

Objective: The Neuropsychiatric Inventory (NPI) is one of the most commonly used -assessment scales for assessing symptoms in people with dementia and other neurological disorders. This paper analyzes its conceptual framework, measurement mode, psychometric properties, and merits and problems. Method: All articles discussing the psychometric properties and factor structure of the NPI were searched for in Medline via Ovid. The abstracts of these papers were read to determine their relevance to the purpose of this paper. If deemed appropriate, a full paper was then obtained and read. Results: The NPI has reasonably good content validity and internal consistency, and good test-retest and interrater reliability. There is limited information about its sensitivity, specificity, positive and negative predictive values, and, in particular, responsiveness. Merits of the NPI include being comprehensive, avoiding symptom overlap, ease of use, and flexibility. It has problems in scoring (no multiples of 5, 7, and 11) and, therefore, analysis using parametric tests may not be appropriate. The use of individual subscales also warrants further investigation. Conclusion: In terms of its content and concurrent validity, intra- and interrater reliability, test-retest reliability, and internal consistency, the NPI can be considered as valid and reliable, and can be used across different ethnic groups. The tool is most likely unable to deliver as good a performance in terms of discriminating between different disorders. More studies are required to further evaluate its psychometric properties, particularly in the areas of factor structure and responsiveness. The clinical utility of the NPI also needs to be further explored. © 2014 Lai. This work is published by Dove Medical Press Limited.

Lau A.K.W.,Hong Kong University of Science and Technology | Tang E.,Hong Kong Polytechnic University | Yam R.C.M.,City University of Hong Kong
Journal of Product Innovation Management | Year: 2010

While the beneficial impacts of supplier and customer integration are generally acknowledged, very few empirical research studies have examined how an organization can achieve better product performance through product innovation enhanced by such integration. This paper thus examines the impact of key supplier and customer integration processes (i.e., information sharing and product codevelopment with supplier and customer, respectively) on product innovation as well as their impact on product performance. It contributes to existing literature by asking how such integration activities affect product innovation and performance in both direct and indirect ways. After surveying 251 manufacturers in Hong Kong, this study tested the relationships among information sharing, product codevelopment, product innovativeness, and performance with three control variables (i.e., company size, type of industry, and market certainty). Structural equation modeling with correlation and t-tests was used to test the hypothesized research model. The findings indicate a direct, positive relationship between supplier and customer integration and product performance. In particular, this study verifies that sharing information with suppliers and product codevelopment with customers directly improves product performance. In addition, this study empirically examines the indirect effects of supplier and customer integration processes on product performance, mediated by innovation. This has seldom been attempted in previous research. The empirical findings show that product codevelopment with suppliers improves performance, mediated by innovation. However, the sampled firms cannot improve their product innovation by sharing information with their current customers and suppliers as well as codeveloping new products with the customers. If the adoption of supplier and customer integration is not cost free, the findings of this study may suggest firms work on particular supplier and customer integration processes (i.e., product codevelopment with suppliers) to improve their product innovation. The study also suggests that companies codevelop new products only with new customers and lead users instead of current ones for product innovation. For managers, this study has demonstrated that both information sharing and product codevelopment affect performance directly and indirectly. Managers should put more emphasis on these key processes, especially when linked with product innovation. Managers should consider involving their suppliers and customers in the early stages of design. Information sharing with suppliers is also important in product development. As suggested by this study, extensive effort on supplier and customer integration should be made to directly augment current product performance and product innovation at the same time. © 2010 Product Development & Management Association.

Li H.,Bohai University | Jing X.,Hong Kong Polytechnic University | Karimi H.R.,University of Agder
IEEE Transactions on Industrial Electronics | Year: 2014

This paper deals with the problem of output-feedback H∞ control for a class of active quarter-car suspension systems with control delay. The dynamic system of the suspension systems is first formed in terms of the control objectives, i.e., ride comfort, road holding, suspension deflection, and maximum actuator control force. Then, the objective is to the design of the dynamic output-feedback H∞ controller in order to ensure asymptotic stability of the closed-loop system with H∞ disturbance attenuation level and the output constraints. Furthermore, using Lyapnov theory and linear matrix inequality (LMI) approach, the existence of admissible controllers is formulated in terms of LMIs. With these satisfied conditions, a desired dynamic output-feedback controller can be readily constructed. Finally, a quarter-vehicle model is exploited to demonstrate the effectiveness of the proposed method. © 1982-2012 IEEE.

Jing X.,Hong Kong Polytechnic University
Journal of Sound and Vibration | Year: 2011

Block-oriented nonlinear models including Wiener models, Hammerstein models and WienerHammerstein models, etc. have been extensively applied in practice for system identification, signal processing and control. In this study, analytical frequency response functions including generalized frequency response functions (GFRFs) and nonlinear output spectrum of block-oriented nonlinear systems are developed, which can demonstrate clearly the relationship between frequency response functions and model parameters, and also the dependence of frequency response functions on the linear part of the model. The nonlinear part of these models can be a more general multivariate polynomial function. These fundamental results provide a significant insight into the analysis and design of block-oriented nonlinear systems. Effective algorithms are therefore proposed for the estimation of nonlinear output spectrum and for parametric or nonparametric identification of nonlinear systems. Compared with some existing frequency domain identification methods, the new estimation algorithms do not necessarily require model structure information, not need the invertibility of the nonlinearity and not restrict to harmonic inputs. Simulation examples are given to illustrate these new results. © 2011 Elsevier Ltd.

Zhu Q.,Dalian University of Technology | Sarkis J.,Clark University | Lai K.-H.,Hong Kong Polytechnic University
International Journal of Production Research | Year: 2012

Environmental pressures have caused green supply chain management (GSCM) to emerge as an important corporate environmental strategy for manufacturing enterprises. For manufacturers to fully realise the performance potentials of GSCM, they need to integrate internal GSCM practices emphasising functional coordination with external GSCM practices such as cooperation with suppliers and customers in the implementation. Using coordination theory, this article examines three models used to evaluate the mediation relationships between the external and internal practices of GSCM with respect to environmental, economic, and operational performance. We posit that the strategic stance of manufacturing enterprises in improving their overall performance and competitive position requires a joint coordination of internal and external GSCM practices. Survey data collected from 396 Chinese manufacturing enterprises are used to validate our arguments by testing the mediation effects of two categories of GSCM practices. Our empirical results show support for the mediation effects, which indicates the importance for manufacturers to coordinate between the internal and external aspects of implementing GSCM practices to reap the performance benefits. Coordinating internal and external GSCM practices to seek performance improvements is an important aspect of the manufacturing operations strategy. The dynamics of implementing GSCM practices and the performance contingencies are worthwhile topics to pursue in future research. © 2012 Copyright Taylor and Francis Group, LLC.

Lee W.L.,Hong Kong Polytechnic University
Energy and Buildings | Year: 2012

BREEAM, LEED, CASBEE, BEAM Plus and Chinese ESGB have been formally launched at different stages in the last twenty years. How well the certified and rated buildings compare with each other is always an interest of building designers and policy-makers. This paper presents a side-by-side comparison of energy use assessments of the five schemes. The comparisons are on the assessment method and criteria, default parameters, trade-offs allowed, performance scales, approved simulation tools, performance indicators and assessment results. Comparison results showed that all the five schemes are based on relative performance. It was also found that despite the variations in default parameters among the five schemes, market positions of certified buildings are comparable. LEED was found to be the most stringent and relatively less flexible in its assessment criteria. Nonetheless, the energy cost budget approach, adopted only by LEED, is able to fulfil emission reduction and cost saving objectives on the condition that a "fuel neutral" approach should be adopted. © 2011 Elsevier B.V.

Wu Y.I.,Nanyang Technological University | Wong K.T.,Hong Kong Polytechnic University
IEEE Transactions on Aerospace and Electronic Systems | Year: 2012

A new scheme is herein proposed to localize an acoustic source. This new method blends the received signal strength indication (RSSI) approach of geolocation, and the acoustic vector-sensor (AVS) (a.k.a., vector-hydrophone) based direction-finding (DF). Unlike customary RSSI-based source-localization, this proposed approach needs only two (not three or more) passive anchor-nodes: 1) one pressure-sensor, and 2) one physically compact triad of three (collocating, but orthogonally oriented) acoustic velocity-sensors. The latter can estimate the direction-of-arrival (DOA) of an emitter, regardless of that emitters arbitrary/unknown center-frequency, bandwidth, spectrum, and near-field/far-field location. This triads DOA estimates can be distributed processed, locally, apart from the pressure-sensors measured power, to estimate the emitters radial distance. This proposed algorithm is noniterative, requires no initial estimate, is closed form, and can accommodate any prior known propagation-loss exponent. © 2006 IEEE.

Yuan X.,Hong Kong Polytechnic University
IEEE Transactions on Aerospace and Electronic Systems | Year: 2012

A new focusing technique is proposed for the direction-finding with an acoustic vector sensor when the acoustic vector sensor suffers arbitrarily fluctuating misorientation. The data set collected in the total observation time is partitioned into several sub data sets at different time segments. These sub data sets with different orientations are transformed into new data sets aligned with the reference orientation by the proposed focusing transformation matrix. The conventional direction-finding algorithms can then be adopted to the newly constructed data sets. The efficacy of this approach is demonstrated by simulation results. © 1965-2011 IEEE.

Tang S.K.,Hong Kong Polytechnic University
Applied Acoustics | Year: 2010

The screening effect of balconies on a building faade in the case where the noise source is not parallel to the faade is studied using scale model experiment in the present study. Results show that the angle of source inclination to the faade has substantial effects on the balcony insertion loss in the presence of a traffic noise spectrum. Less amount of noise amplification is observed when the source is inclined compared to the case of parallel source in the presence of balcony ceiling reflections. Regression formulae in terms of three independent angles which determine the positions of the balcony and its ceiling relative to the noise source are developed for the prediction of balcony insertion loss. The discrepancy between measurements and predictions is within engineering tolerance. © 2010 Elsevier Ltd. All rights reserved.

Metaparti P.,Hong Kong Polytechnic University
Maritime Policy and Management | Year: 2010

The post-9/11 maritime security scenario was characterized by intense rhetoric in the first few years, during which security measures such as the Container Security Initiative (CSI) and International Ship and Port Security (ISPS) code were adopted. This rhetoric resulted in a hasty implementation that precluded a detailed examination of security measures. Findings show that while rhetoric was useful for facilitating quicker adoption of security measures, it nonetheless prevented a fuller examination of security threats and responses, resulting in security gaps. This paper examines the effectiveness of the security responses and identifies some gaps in security coverage and other inefficiencies. Recommendations are also made to overcome these limitations. © 2010 Taylor & Francis.

Liang H.K.,Nanyang Technological University | Yu S.F.,Hong Kong Polytechnic University | Yang H.Y.,Singapore University of Technology and Design
Applied Physics Letters | Year: 2010

An array of highly disordered i-ZnO:Al(3%) random cavities, which have 1 μm width, 150 nm thickness, and 2 mm length, is sandwiched between n-ZnO:Al(5%) and p-GaN /sapphire substrate to form an array of heterojunctions. The random cavities, which are electrically isolated and optically coupled with the adjacent random cavities, are laterally separated by a 1 μm wide Al 2 O3 dielectric insulator. Stable single-mode operation is observed from the laser diode array under high electrical pumping (i.e., >6×threshold current) at room temperature. © 2010 American Institute of Physics.

Li X.F.,Nanyang Technological University | Yu S.F.,Hong Kong Polytechnic University
Optics Letters | Year: 2010

We performed a rigorous study to reduce threshold gain of Au-nanoparticle lasers in the deep-subwavelength scale with the consideration of strong interband transitions in Au and device dimensions. We found that the high-threshold optical gain of the nanolaser (over 105 cm -1, which is matched with the result estimated from a previous article [Nature 460,1110 (2009)]) arises from the high interband transition of Au near 530 nm. It can be shown that by increasing the background index, as well as optimizing the lasing wavelength and device dimensions, the threshold gain (cavity volume) can be reduced by 43% (90%). © 2010 Optical Society of America.

Lin D.,Sichuan Normal University | Kwok K.W.,Hong Kong Polytechnic University
Journal of the American Ceramic Society | Year: 2010

New lead-free (Bi0.5Na0.5)1-x-y-z(Bi 0.5K0.5)xBaySrzTiO 3 ceramics have been prepared by an ordinary sintering technique and their structure, ferroelectric, and piezoelectric properties have been studied. X-ray diffraction patterns reveal that a morphotropic phase boundary (MPB) of rhombohedral and tetragonal phases is formed at 0.10≤x≤0.20, 0

Yu J.,Hangzhou Dianzi University | Hong R.,Hefei University of Technology | Wang M.,Hefei University of Technology | You J.,Hong Kong Polytechnic University
Pattern Recognition | Year: 2014

Image clustering methods are efficient tools for applications such as content-based image retrieval and image annotation. Recently, graph based manifold learning methods have shown promising performance in extracting features for image clustering. Typical manifold learning methods adopt appropriate neighborhood size to construct the neighborhood graph, which captures local geometry of data distribution. Because the density of data points' distribution may be different in different regions of the manifold, a fixed neighborhood size may be inappropriate in building the manifold. In this paper, we propose a novel algorithm, named sparse patch alignment framework, for the embedding of data lying in multiple manifolds. Specifically, we assume that for each data point there exists a small neighborhood in which only the points that come from the same manifold lie approximately in a low-dimensional affine subspace. Based on the patch alignment framework, we propose an optimization strategy for constructing local patches, which adopt sparse representation to select a few neighbors of each data point that span a low-dimensional affine subspace passing near that point. After that, the whole alignment strategy is utilized to build the manifold. Experiments are conducted on four real-world datasets, and the results demonstrate the effectiveness of the proposed method. © 2014 Elsevier Ltd.

Tse C.K.,Hong Kong Polytechnic University | Li M.,University of Tennessee at Knoxville
International Journal of Bifurcation and Chaos | Year: 2011

Bifurcation analysis has been applied to many power electronics circuits. Literature abounds with results regarding the various ways in which such circuits lose stability under variation of some selected parameters, e.g. via period-doubling bifurcation, Hopf bifurcation, border collision, etc. The current status of research in the identification of bifurcation behavior in power electronics has reached a stage where the salient types of bifurcation behavior, their underlying causes and the theoretical parameters affecting them have been well understood. Currently, the emphasis of research in this field has gradually shifted toward applications that are of direct relevance to practical design of power electronics. One direction is to apply some of the available research results in bifurcation behavior to the design of practical power electronics circuits. The main difficulty is that the abstract mathematical presentations of the available results are not directly applicable to practical design problems. In this paper we will discuss how research efforts may be directed to bridge this gap. © 2011 World Scientific Publishing Company.

Dong W.,Xidian University | Zhang L.,Hong Kong Polytechnic University | Shi G.,Xidian University
Proceedings of the IEEE International Conference on Computer Vision | Year: 2011

This paper proposes a novel sparse representation model called centralized sparse representation (CSR) for image restoration tasks. In order for faithful image reconstruction, it is expected that the sparse coding coefficients of the degraded image should be as close as possible to those of the unknown original image with the given dictionary. However, since the available data are the degraded (noisy, blurred and/or down-sampled) versions of the original image, the sparse coding coefficients are often not accurate enough if only the local sparsity of the image is considered, as in many existing sparse representation models. To make the sparse coding more accurate, a centralized sparsity constraint is introduced by exploiting the nonlocal image statistics. The local sparsity and the nonlocal sparsity constraints are unified into a variational framework for optimization. Extensive experiments on image restoration validated that our CSR model achieves convincing improvement over previous state-of-the-art methods. © 2011 IEEE.

Ye H.-Q.,Hong Kong Polytechnic University | Yao D.D.,Columbia University
Operations Research | Year: 2010

Stochastic programming can effectively describe many decision-making problems in uncertain environments. Unfortunately,such programs are often computationally demanding to solve. In addition, their solution can be misleading when there is ambiguity in the choice of a distribution for the random parameters. In this paper, we propose a model that describes uncertainty in both the distribution form (discrete, Gaussian, exponential, etc.) and moments (mean and covariance matrix). We demonstrate that for a wide range of cost functions the associated distributionally robust (or min-max) stochastic program can be solved efficiently. Furthermore, by deriving a new confidence region for the mean and the covariance matrix of a random vector, we provide probabilistic arguments for using our model in problems that rely heavily on historical data. These arguments are confirmed in a practical example of portfolio selection, where our framework leads to better-performing policies on the "true" distribution underlying the daily returns of financial assets. © 2010 INFORMS.

Gorla N.,American University of Sharjah | Somers T.M.,Wayne State University | Wong B.,Hong Kong Polytechnic University
Journal of Strategic Information Systems | Year: 2010

Increased organizational dependence on information systems drives management attention towards improving information systems' quality. A recent survey shows that "Improve IT quality" is one of the top concerns facing IT executives. As IT quality is a multidimensional measure, it is important to determine what aspects of IT quality are critical to organizations to help Chief Information Officers (CIOs) to devise effective IT quality improvement strategies. In this research, we model the relationship between information systems' (IS) quality and organizational impact. We hypothesize greater organizational impact in situations in which system quality, information quality and service quality are high. We also hypothesize a positive relationship between system quality and information quality. We test our hypotheses using survey data. Our structural equation model exhibits a good fit with the observed data. Our results show that IS service quality is the most influential variable in this model (followed by information quality and system quality), thus highlighting the importance of IS service quality for organizational performance. This paper contributes theoretically to IS success models through the system quality-to-information quality and IS quality-to-organizational impact links. Implications of our results for practice and research are discussed. © 2010 Elsevier B.V. All rights reserved.

Kumar A.,Hong Kong Polytechnic University
IEEE Transactions on Information Forensics and Security | Year: 2014

Automated biometrics identification using finger knuckle images has increasingly generated interest among researchers with emerging applications in human forensics and biometrics. Prior efforts in the biometrics literature have only investigated the major finger knuckle patterns that are formed on the finger surface joining proximal phalanx and middle phalanx bones. This paper investigates the possible use of minor finger knuckle patterns, which are formed on the finger surface joining distal phalanx and middle phalanx bones. The minor finger knuckle patterns can either be used as independent biometric patterns or employed to improve the performance from the major finger knuckle patterns. A completely automated approach for the minor finger knuckle identification is developed with key steps for region of interest segmentation, image normalization, enhancement, and robust matching to accommodate image variations. This paper also introduces a new or first publicly available database for minor (also major) finger knuckle images from 503 different subjects. The efforts to develop an automated minor finger knuckle pattern matching scheme achieve promising results and illustrate its simultaneous use to significantly improve the performance over the conventional finger knuckle identification. Several open questions on the stability and uniqueness of finger knuckle patterns should be addressed before knuckle pattern/image evidence can be admissible as supportive evidence in a court of law. Therefore, this paper also presents a study on the stability of finger knuckle patterns from images acquired with an interval of 4-7 years. The experimental results and the images presented in this paper provide new insights on the finger knuckle pattern and identify the need for further work to exploit finger knuckle patterns in forensics and biometrics applications. © 2014 IEEE.

Xu Z.,Hong Kong Polytechnic University | Ostergaard J.,Technical University of Denmark | Togeby M.,Ea Energianalyse A S
IEEE Transactions on Power Systems | Year: 2011

Relying on generation side alone is deemed insufficient to fulfill the system balancing needs for future Danish power system, where a 50% wind penetration is outlined by the government for year 2025. This paper investigates use of the electricity demand as frequency controlled reserve (DFR), which has a high potential and can provide many advantages. Firstly, the background of the research is reviewed, including conventional power system reserves and the demand side potentials. Subsequently, the control logics and corresponding design considerations for the DFR technology have been developed and analyzed, based on which simulation models have been built using the DIgSILENT Power Factory. The simulation studies of different scenarios confirm that the DFR can provide reliable performance of frequency control. Furthermore, relevant issues regarding implementing DFR in reality have been discussed. © 2011 IEEE.

Amphiphilic core-shell nanoparticle, which is composed of a hydrophobic core and a branched polyethylenimine (PEI) shell, has been designed and synthesized as a novel gene delivery nanocarrier. In our previous study, we demonstrated that the core-shell nanoparticle was not only able to efficiently complex with plasmid DNA (pDNA) and protect it against enzymatic degradation, but also three times less cytotoxic, and threefold more efficient in gene transfection than branched 25 kDa PEI. This paper reports our further studies in the following three aspects: (1) the ability of the PEI-based nanoparticles to deliver gene in various mammalian cell lines; (2) intracellular distributions of the nanoparticles and their pDNA complexes in HeLa cells; and (3) incorporation of nuclear targeting agent into the nanoparticle/pDNA complexes to enhance the nuclear targeting ability. The PEI-based nanoparticles were able to transfect both human and non-human cell lines and their transfection efficiencies were cell-dependent. Within our four tested cell lines (MCF-7, BEL 7404, C6 and CHO-K1), gene transfer using PEI-based core-shell nanoparticles displayed gene expression levels comparable to, or even better than, the commercial Lipofectamine™ 2000. Confocal laser scanning microscopy showed that the nanoparticles and their pDNA complexes were effectively internalized into the HeLa cells. The in vitro time series experiments illustrated that both the nanoparticle/pDNA complexes and PEI-based nanoparticles were distributed in the cytoplasmic region after transfection for 10 and 60 min, respectively. Nuclear localization was also observed in both samples after transfection for 20 and 60 min, respectively. Incorporation of the high mobility group box 1 (HMGB1) protein for nuclear targeting has also been demonstrated with a simple approach: electrostatic complexation between the PEI-based nanoparticles and HMGB1. In the in vitro transfection study in MCF-7 cells, the expression level of the firefly luciferase gene encoded by the pDNA increased remarkably by up to eightfold when the HMGB1 protein was incorporated into the nanoparticle/pDNA complexes. Our results demonstrate that the PEI-based core-shell nanoparticles are promising nanocarriers for gene delivery.

Jing X.J.,Hong Kong Polytechnic University | Lang Z.Q.,University of Sheffield | Billings S.A.,University of Sheffield
Systems and Control Letters | Year: 2011

The nonlinear influence on system output spectrum is studied for a class of nonlinear systems which have Volterra series expansion. It is shown that under certain conditions the system output spectrum can be expressed in an alternating series with respect to some model parameters which define system nonlinearities. The magnitude of the system output spectrum can therefore be suppressed by exploiting the properties of alternating series. Sufficient (and necessary) conditions in which the output spectrum can be cast into an alternating series are studied. These results reveal a novel frequency-domain insight into the nonlinear influence on a system, and provide a new method for the analysis and design of nonlinear systems in the frequency domain. Examples are given to illustrate the results. © 2011 Elsevier B.V. All rights reserved.

Fang Y.P.,University of Sichuan | Meng K.,Southwest Jiaotong University | Yang X.Q.,Hong Kong Polytechnic University
Operations Research | Year: 2012

In this paper we study piecewise linear multicriteria programs, that is, multicriteria programs with either a continuous or discontinuous piecewise linear objective function and a polyhedron set constraint. We obtain an algebraic representation of a semi-closed polyhedron and apply it to show that the image of a semi-closed polyhedron under a continuous linear function is always one semi-closed polyhedron. We establish that the (weak) Pareto solution/point set of a piecewise linear multicriteria program is the union of finitely many semi-closed polyhedra. We propose an algorithm for finding the Pareto point set of a continuous piecewise linear bi-criteria program and generalize it to the discontinuous case. We apply our algorithm to solve the discontinuous bi-criteria portfolio selection problem with an l ∞ risk measure and transaction costs and show that this algorithm can be improved by using an ideal point strategy. © 2012 INFORMS.

Wirman H.,Hong Kong Polytechnic University
Games and Culture | Year: 2015

From gold farmers and '100 million brain-damaged online gamers' to the world's biggest game company and more players than US citizens, China seems like the cabinet of curiosities for the whole world of digital gaming. This article focuses on news coverage around Chinese gaming and presents three phases of such journalism. China's emerging games market was most prominently featured between 1999 and 2005, while 2006-2011 focused on extreme play behavior in China. Most recently, a discourse of vast business opportunities and stabilizing markets has been presented by Western news media. In total more than 853 news articles are explored in parallel to the theoretical concept of Sinological-orientalism. This article suggests significant historical changes in the ways in which knowledge of Chinese gaming has been produced in English language news media. © SAGE Publications.

Pang K.-W.,Hong Kong Polytechnic University
Expert Systems with Applications | Year: 2011

Vehicle routing problem with time windows (VRPTW) is a generalisation of the classical vehicle routing problem, where a group of customers with given capacity demand are required to be serviced, and the servicing of the customer demands has to be started within a restricted available time window at the customer locations. This class of routing problems can be used to solve many practical problems such as container truck routing, delivery service scheduling and many logistics system problems. In this paper, we present a route construction heuristic with an adaptive parallel scheme. The result from extensive computation experiments shows the proposed parallel route construction heuristic is efficient and effective for routes construction, which is particularly useful for generation of the initial solutions for many metaheuristic approaches with improved solution quality and convergence of the solution process. © 2011 Elsevier Ltd. All rights reserved.

Wong C.Y.,University of Hull | Boon-Itt S.,Thammasat Business School | Wong C.W.Y.,Hong Kong Polytechnic University
Journal of Operations Management | Year: 2011

This paper extends prior supply chain research by building and empirically testing a theoretical model of the contingency effects of environmental uncertainty (EU) on the relationships between three dimensions of supply chain integration and four dimensions of operational performance. Based on the contingency and organizational information processing theories, we argue that under a high EU, the associations between supplier/customer integration, and delivery and flexibility performance, and those between internal integration, and product quality and production cost, will be strengthened. These theoretical propositions are largely confirmed by multi-group and structural path analyses of survey responses collected from 151 of Thailand's automotive manufacturing plants. This paper contributes to operations management contingency research and provides theory-driven and empirically proven explanations for managers to differentiate the effects of internal and external integration efforts under different environmental conditions. © 2011 Elsevier B.V.

Liu Y.,Stevens Institute of Technology | Xin J.H.,Hong Kong Polytechnic University | Choi C.-H.,Stevens Institute of Technology
Langmuir | Year: 2012

This article reports on the fabrication of cotton fabrics with single-faced superhydrophobicity using a simple foam finishing process. Unlike most commonly reported superhydrophobic fabrics, the fabrics developed in this study exhibit asymmetric wettability on their two faces: one face showing superhydrophobic behavior (highly nonwetting or water-repellent characteristics) and the other face retaining the inherent hydrophilic nature of cotton. The superhydrophobic face exhibits a low contact angle hysteresis of θa/ θr = 151/144 (θa, advancing contact angle; θr, receding contact angle), which enables water drops to roll off the surface easily so as to endow the surface with well-known self-cleaning properties. The untreated hydrophilic face preserves its water-absorbing capability, resulting in 44% of the water-absorbing capacity compared to that of the original cotton samples with both sides untreated (hydrophilic). The single-faced superhydrophobic fabrics also retain moisture transmissibility that is as good as that of the original untreated cotton fabrics. They also show robust washing fastness with the chemical cross-linking process of hydrophobic fluoropolymer to fabric fibers. Fabric materials with such asymmetric or gradient wettability will be of great use in many applications such as unidirectional liquid transporting, moisture management, microfluidic systems, desalination of seawater, flow management in fuel cells, and water/oil separation. © 2012 American Chemical Society.

Chen S.,Hong Kong Polytechnic University | Karalewitz A.P.A.,Medical College of Wisconsin | Barbieri J.T.,Medical College of Wisconsin
Biochemistry | Year: 2012

The clostridial neurotoxins are among the most potent protein toxins for humans and are responsible for botulism, a flaccid paralysis elicited by the botulinum toxins (BoNT), and spastic paralysis elicited by tetanus toxin (TeNT). Seven serotypes of botulinum neurotoxins (A-G) and tetanus toxin showed different toxicities and cleave their substrates with different efficiencies. However, the molecular basis of their different catalytic activities with respect to their substrates is not clear. BoNT/B light chain (LC/B) and TeNT light chain (LC/T) cleave vesicle-associated membrane protein 2 (VAMP2) at the same scissile bond but possess different catalytic activities and substrate requirements, which make them the best candidates for studying the mechanisms of their different catalytic activities. The recognition of five major P sites of VAMP2 (P7, P6, P1, P1′, and P2′) and fine alignment of sites P2 and P3 and sites P2 and P4 by LC/B and LC/T, respectively, contributed to their substrate recognition and catalysis. Significantly, we found that the S1 pocket mutation LC/T(K168E) increased the rate of native VAMP2 cleavage so that it approached the rate of LC/B, which explains the molecular basis for the lower kcat that LC/T possesses for VAMP2 cleavage relative to that of LC/B. This analysis explains the molecular basis underlying the VAMP2 recognition and cleavage by LC/B and LC/T and provides insight that may extend the pharmacologic utility of these neurological reagents. © 2012 American Chemical Society.

Ma P.-W.,EURATOM | Dudarev S.L.,EURATOM | Woo C.H.,Hong Kong Polytechnic University
Physical Review B - Condensed Matter and Materials Physics | Year: 2012

We develop a dynamic spin-lattice-electron model for simulating the time-dependent evolution of coupled spin, atomic, and electronic degrees of freedom in a magnetic material. Using the model, we relate the dissipative parameters entering the Langevin equations for the lattice and spin degrees of freedom to the heat transfer coefficients of a phenomenological spin-lattice-electron three-temperature model. We apply spin-lattice-electron dynamics simulations to the interpretation of experiments on laser-induced demagnetization of iron thin films, and estimate the rates of heat transfer between the spins and electrons, and between atoms and electrons. To model the dynamics of energy dissipation in a magnetic material undergoing plastic deformation, we develop an algorithm that separates the local collective modes of motion of atoms from their random thermal motion. Using this approach, we simulate the propagation of compressive shock waves through magnetic iron. We also explore the microscopic dynamics of dissipative coupling between the spin and lattice subsystems, and show that the rate of spin-lattice heat transfer is proportional to the integral of the four-spin time-dependent correlation function. © 2012 American Physical Society.

Gu Y.J.,Hong Kong Polytechnic University
International journal of nanomedicine | Year: 2011

Single-walled carbon nanotubes (SWNTs) have been identified as an efficient drug carrier. Here a controlled drug-delivery system based on SWNTs coated with doxorubicin (DOX) through hydrazone bonds was developed, because the hydrazone bond is more sensitive to tumor microenvironments than other covalent linkers. The SWNTs were firstly stabilized with polyethylene glycol (H(2)N-PEG-NH(2)). Hydrazinobenzoic acid (HBA) was then covalently attached on SWNTs via carbodiimide-activated coupling reaction to form hydrazine-modified SWNTs. The anticancer drug DOX was conjugated to the HBA segments of SWNT using hydrazine as the linker. The resulting hydrazone bonds formed between the DOX molecules and the HBA segments of SWNTs are acid cleavable, thereby providing a strong pH-responsive drug release, which may facilitate effective DOX release near the acidic tumor microenvironment and thus reduce its overall systemic toxicity. The DOX-loaded SWNTs were efficiently taken up by HepG2 tumor cells, and DOX was released intracellularly, as revealed by MTT assay and confocal microscope observations. Compared with SWNT-DOX conjugate formed by supramolecular interaction, the SWNT-HBA-DOX featured high weight loading and prolonged release of DOX, and thus improved its cytotoxicity against cancer cells. This study suggests that while SWNTs have great potential as a drug carrier, the efficient formulation strategy requires further study.

Kwan P.,Hong Kong Polytechnic University
Mechanisms of Ageing and Development | Year: 2013

It has been approximately 25 years since Dr. Rosenberg first brought attention to sarcopenia. To date, this aging-associated condition is recognized as a chronic loss of muscle mass and is usually accompanied by dynapenia. Despite its poly-etiological factors, sarcopenia has a strong neurogenic component underlying this chrono-degeneration of muscle mass, as shown in recent studies. As it seems plausible to explain the origin of sarcopenia through a motor neuron degeneration model, the focus of sarcopenia research should combine neuroscience with the study of the original myocyte and satellite cells. Although a complete mechanism underlying the development of sarcopenia has yet to be elucidated, we propose that the primary trigger of sarcopenia could be gliogenic in origin based on the close relationship between the glia, neurons and non-neural cells, for example, the motor unit and its associated glia in both the central nervous system (CNS) and the peripheral nervous system (PNS). In addition to muscle cells, both of the neural cells are affected by aging. © 2013 Elsevier Ireland Ltd.

Jing X.,Hong Kong Polytechnic University
Neural Networks | Year: 2011

A novel H∞ robust control approach is proposed in this study to deal with the learning problems of feedforward neural networks (FNNs). The analysis and design of a desired weight update law for the FNN is transformed into a robust controller design problem for a discrete dynamic system in terms of the estimation error. The drawbacks of some existing learning algorithms can therefore be revealed, especially for the case that the output data is fast changing with respect to the input or the output data is corrupted by noise. Based on this approach, the optimal learning parameters can be found by utilizing the linear matrix inequality (LMI) optimization techniques to achieve a predefined H∞ "noise" attenuation level. Several existing BP-type algorithms are shown to be special cases of the new H∞-learning algorithm. Theoretical analysis and several examples are provided to show the advantages of the new method. © 2011 Elsevier Ltd.

Pang M.Y.C.,Hong Kong Polytechnic University
World Journal of Orthopaedics | Year: 2010

Due to various physical impairments, individuals with chronic diseases often live a sedentary lifestyle, which leads to physical de-conditioning. The associated muscle weakness, functional decline and bone loss also render these individuals highly susceptible to falls and fragility fractures. There is an urgent need to search for safe and effective intervention strategies to prevent fragility fractures by modifying the fall-related risk factors and enhancing bone health. Whole body vibration (WBV) therapy has gained popularity in rehabilitation in recent years. In this type of treatment, mechanical vibration is delivered to the body while the individual is standing on an oscillating platform. As mechanical loading is one of the most powerful stimuli to induce osteogenesis, it is proposed that the mechanical stress applied to the human skeleton in WBV therapy might be beneficial for enhancing bone mass. Additionally, the vibratory signals also constitute a form of sensory stimulation and can induce reflex muscle activation, which could potentially induce therapeutic effects on muscle strength and important sensorimotor functions such as postural control. Increasing research evidence suggests that WBV is effective in enhancing hip bone mineral density, muscle strength and balance ability in elderly patients, and could have potential for individuals with chronic diseases, who often cannot tolerate vigorous impact or resistance exercise training. This article aims to discuss the potential role of WBV therapy in the prevention of fragility fractures among people with chronic diseases. © 2010 Baishideng.

Mughal A.,Aberystwyth University | Chan H.K.,Trinity College Dublin | Chan H.K.,Hong Kong Polytechnic University | Weaire D.,Trinity College Dublin
Physical Review Letters | Year: 2011

We develop a simple analytical theory that relates dense sphere packings in a cylinder to corresponding disk packings on its surface. It applies for ratios R=D/d (where d and D are the diameters of the hard spheres and the bounding cylinder, respectively) up to R=1+1/sin (π/5). Within this range the densest packings are such that all spheres are in contact with the cylindrical boundary. The detailed results elucidate extensive numerical simulations by ourselves and others by identifying the nature of various competing phases. © 2011 American Physical Society.

Yuan H.,Hong Kong Polytechnic University
Systems and Control Letters | Year: 2012

In this article, we propose a framework studying all possible operations one can generate at any given time on quantum systems in a Markovian environment. A complete characterization of the operations one can simulate at any given time on a qubit in a unital Markovian environment is given and possible extensions on general cases are discussed. © 2012 Elsevier B.V. All rights reserved.

Kumar A.,Indian Institute of Technology Delhi | Kumar A.,Hong Kong Polytechnic University | Passi A.,Indian Institute of Technology Delhi
Pattern Recognition | Year: 2010

The personal identification approaches using iris images are receiving increasing attention in the biometrics literature. Several methods have been presented in the literature and those based on the phase encoding of texture information are suggested to be the most promising. However, there has not been any attempt to combine these approaches to achieve further improvement in the performance. This paper presents a comparative study of the performance from the iris authentication using Log-Gabor, Haar wavelet, DCT and FFT based features. Our experimental results suggest that the performance from the Haar wavelet and Log-Gabor filter based phase encoding is the most promising among all the four approaches considered in this work. Therefore, the combination of these two matchers is most promising, both in terms of performance and the computational complexity. Our experimental results from the all 411 users (CASIA v3) and 224 users (IITD v1) database illustrate significant improvement in the performance which is not possible with either of these approaches individually. © 2009 Elsevier Ltd. All rights reserved.

Zhang H.,Hong Kong Polytechnic University | Darvell B.W.,Kuwait University
Journal of the European Ceramic Society | Year: 2010

Currently-available HA particle-reinforced composites are not suitable for use in large stress-bearing restorations and biomedical substitution due to low strength and poor durability. HA is the most promising because of good biocompatibility and bioactivity, and since reinforcement efficacy is greatly affected by length and aspect ratio, the preparation of long HA whiskers could be important for biomedical applications. Acetamide, formamide, and carbonyl diamide were tested as precipitation agents to modify crystal growth habit. The morphology and composition of the whiskers showed a sensitive dependence on the additive used. Carbonyl diamide and formamide led to contaminated HA; crystals were needle-like but contained carbonate or formate, respectively. In comparison, acetamide showed a low hydrolysis rate under hydrothermal conditions, giving rise to a rapid growth of HA crystals at a low supersaturation. Furthermore, the hydrolysis products of AA affected neither the composition nor the growth habit of the HA. © 2010 Elsevier Ltd.

Cheng C.-T.,Dalian University of Technology | Shen J.-J.,Dalian University of Technology | Wu X.-Y.,Dalian University of Technology | Chau K.-W.,Hong Kong Polytechnic University
Renewable and Sustainable Energy Reviews | Year: 2012

During the past two decades, in particular the past decade, there has been a rapid rate of development of hydropower in China. It is foreseeable that the same rate of development will be maintained in the next decade. The total installed generation capacity of hydropower in China has now surpassed 200 GW and ranks first in the world. The unprecedented rate of expansion, development scale, emergence of large number of hydro plants with high head and huge capacity, and electric power transmission have led to significant changes in management and operation of large-scale hydropower systems which have become one of the significant factors in constraining the security and economic operation of power grid in China. This article gives an overview of the China's hydropower, analyses the new challenges that it faces, highlights the key scientific and technological issues that need to be solved, and pinpoints that the solution of these problems will be the key to the realization of energy saving and emission reduction by China in 2020. © 2012 Elsevier Ltd. All rights reserved.

Ni M.,Hong Kong Polytechnic University
Energy Conversion and Management | Year: 2013

Compact reformers (CRs) are promising devices for efficient fuel processing. In CRs, a thin solid plate is sandwiched between two catalyst layers to enable efficient heat transfer from combustion duct to the reforming duct for fuel processing. In this study, a 2D heat and mass transfer model is developed to investigate the fundamental transport phenomenon and chemical reaction kinetics in a CR for hydrogen production by methane steam reforming (MSR). Both MSR reaction and water gas shift reaction (WGSR) are considered in the numerical model. Parametric simulations are performed to examine the effects of various structural/operating parameters, such as pore size, permeability, gas velocity, temperature, and rate of heat supply on the reformer performance. It is found that the reaction rates of MSR and WGSR are the highest at the inlet but decrease significantly along the reformer. Increasing the operating temperature raises the reaction rates at the inlet but shows very small influence in the downstream. For comparison, increasing the rate of heat supply raises the reaction rates in the downstream due to increased temperature. A high gas velocity and permeability facilitates gas transport in the porous structure thus enhances reaction rates in the downstream of the reformer. © 2012 Elsevier Ltd. All rights reserved.

Ma L.,Nanjing Southeast University | Wang J.,Nanjing Southeast University | Ding F.,Hong Kong Polytechnic University
Angewandte Chemie - International Edition | Year: 2012

Cut to ribbons: Making atomically well-controlled graphene nanoribbons (GNRs) is prerequisite for many graphene applications. Ab initio calculations reveal that, on applying a uniaxial external tensile strain, O atoms adsorbed on graphene form parallel epoxy chains, and subsequent cutting by oxygen attack gives GNRs instead of the quantum dots that are obtained from unstrained graphene (see picture). Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Yao H.,Hong Kong Polytechnic University
Journal of Applied Mechanics, Transactions ASME | Year: 2013

In this paper, a solution to the quasi-static adhesive contact problem between a rigid cylinder and a transversely isotropic substrate is extended to the most general case by taking adhesion hysteresis into account. An analytical solution to the contact stress is obtained by solving the integral equations established on the basis of the Green's function for the two-dimensional transversely isotropic half-space problem. By using equilibrium conditions and Griffith's criterion, the adhesion force and resistant moment to rolling are determined as functions of contact geometries and material properties of the contacting solids. Detailed discussions on the adhesion force and resistant moment are presented for some specific cases, revealing adhesion behaviors that have not been predicted by previous models. As the most generalized solution to the discussed problem, our results would have extensive applications in predicting the adhesion behavior between solids undergoing sophisticated mechanical loadings. © 2013 American Society of Mechanical Engineers.

Li G.,University of New South Wales | Pong T.K.,Hong Kong Polytechnic University
Mathematical Programming | Year: 2015

We adapt the Douglas–Rachford (DR) splitting method to solve nonconvex feasibility problems by studying this method for a class of nonconvex optimization problem. While the convergence properties of the method for convex problems have been well studied, far less is known in the nonconvex setting. In this paper, for the direct adaptation of the method to minimize the sum of a proper closed function g and a smooth function f with a Lipschitz continuous gradient, we show that if the step-size parameter is smaller than a computable threshold and the sequence generated has a cluster point, then it gives a stationary point of the optimization problem. Convergence of the whole sequence and a local convergence rate are also established under the additional assumption that f and g are semi-algebraic. We also give simple sufficient conditions guaranteeing the boundedness of the sequence generated. We then apply our nonconvex DR splitting method to finding a point in the intersection of a closed convex set C and a general closed set D by minimizing the squared distance to C subject to D. We show that if either set is bounded and the step-size parameter is smaller than a computable threshold, then the sequence generated from the DR splitting method is actually bounded. Consequently, the sequence generated will have cluster points that are stationary for an optimization problem, and the whole sequence is convergent under an additional assumption that C and D are semi-algebraic. We achieve these results based on a new merit function constructed particularly for the DR splitting method. Our preliminary numerical results indicate that our DR splitting method usually outperforms the alternating projection method in finding a sparse solution of a linear system, in terms of both the solution quality and the number of iterations taken. © 2015 Springer-Verlag Berlin Heidelberg and Mathematical Optimization Society

Lu X.,Hong Kong Polytechnic University
European journal of preventive cardiology | Year: 2013

Exercise which can improve muscle strength while not compromising arterial compliance is especially needed for older adults. Tai Chi practitioners are known to have better than average arterial compliance and muscle strength. This study was designed to establish a cause and effect relationship between Tai Chi training and both increased arterial compliance and increased muscle strength. In a single blind randomized clinical trial, 31 elderly women were randomly assigned to receive either Tai Chi training or an education programme, three sessions per week for 16 weeks. After training, the subjects in the Tai Chi group showed significant improvements in arterial compliance and eccentric knee extensor strength. The subjects in the control group showed no significant improvement. Practising Tai Chi can improve the eccentric knee extensor strength and arterial compliance of elderly women. Tai Chi maybe a good exercise choice to improve the cardiovascular health and muscle strength of the elderly.

Zheng J.-J.,Zhejiang University of Technology | Dai J.-G.,Hong Kong Polytechnic University
Construction and Building Materials | Year: 2014

This paper attempts to predict the nonlinear pull-out response of fiber reinforced polymer (FRP) rods embedded in steel tubes filled with cement grout. Based on a tri-linear bond-slip model, the whole FRP rod is divided into three zones: linear elastic, softening, and frictional. In each zone, a set of two second-order ordinary differential equations are established in terms of the displacements of the FRP rod and steel tube and solved in an analytical manner. When the thickness of the steel tube approaches infinity, the solution can be applied to the problem of FRP rods embedded in rock. Based on the derived solution, the interfacial bond properties and snapback phenomenon are discussed. After the analytical solution is validated by comparisons with four sets of experimental data, the effects of the radius and length of FRP rods, the local peak bond stress and the residual frictional strength on the maximum pull-out load are evaluated through sensitivity analysis. © 2014 Elsevier Ltd. All rights reserved.

Cheng Z.,Hong Kong Polytechnic University | Nault B.R.,University of Calgary
Information Systems Research | Year: 2012

We examine how one industry's productivity is affected by the IT capital of its customers and how this effect depends on industries' relative concentration. These customer-driven IT spillovers result from customers' IT investments in various information systems that reduce transaction costs through information sharing and coordination and lead to more efficient production and logistics upstream. The magnitude of IT spillovers depends on relative industry concentration because customers in more concentrated industries relative to those of their suppliers are better able to retain the benefits from their IT investments. We model customer-driven effects based on production theory and empirically test the model using two industry-level data sets covering different and overlapping time periods (1987-1999 and 1998-2005), different scopes of the economy (manufacturing only versus all industries), and different levels of industry aggregation. We find that, given an increase in a downstream industry's IT capital, there is a significant increase in downstream industry output as well as significant increases in upstream industry output. Moreover, the magnitude of IT spillovers is related to relative industry concentration: A 1% decrease in a customer's relative industry concentration increases spillovers by roughly 1%. Thus, further increases in IT capital can be justified along the supply chain, and an industry's relative concentration-which can reflect market power-in part determines the distribution of productivity benefits. © 2012 INFORMS.

Chan S.-W.,Hong Kong Polytechnic University | Chan S.-W.,State Key Laboratory of Chinese Medicine and Molecular Pharmacology
International Journal of Food Sciences and Nutrition | Year: 2012

Panax ginseng (Ginseng), Rhodiola rosea (Hong Jing Tian) and Schisandra chinensis (Wu Wei Zi) are well-known herbs in traditional Chinese medicine (TCM). Recently, there have been a number of studies on these three herbs. This review discusses their active components and major pharmacological effects. For P. ginseng, it has been shown to have an anti-inflammatory activity, affects pulmonary function and erectile dysfunction, improves cognition in patients with Alzheimer's disease and promotes sexual arousal in menopausal women as well as prevents cancer. For R. rosea, its effectiveness in alleviating depression and reducing fatigue is summarized in this review. Additionally, anti-cancer and other clinical effects of S. chinensis are also discussed. These three herbs are considered as adaptogens as they bear multiple functions and their effects were found to be very different in patients depending on the circumstances (age, gender, environment, diet, season, etc.). Thus, in most cases, the art of the TCM practitioner is to prescribe these herbs after a complete evaluation of overall heath status of the patients. © 2011 Informa UK, Ltd.

Chen W.,Hong Kong Polytechnic University
IEEE Photonics Journal | Year: 2016

In this paper, a novel method is proposed to optically verify the decoded images via single-shot imaging without reference wave using a binary intensity pattern. Optical imaging without reference wave is applied based on double random phase encoding (DRPE), and the recorded intensity pattern is further compressed, which contains only two quantization levels (i.e., 0 and 1). During the decoding, an iterative phase retrieval algorithm is developed and applied. It is demonstrated that decoded images do not visually render the input information due to the designed optical encoding strategy using only one binary intensity pattern, and optical verification is further conducted to effectively verify the decoded images. An additional security layer is established for the developed optical system, since optical verification is conducted based on optical encoding systems without direct observation of input information from the decoded images. It is the first to report the use of only one 1-bit intensity pattern in the DRPE system based on single-shot imaging without reference wave for secured verification via optical correlation. © 2009-2012 IEEE.

Cheng A.S.K.,Hong Kong Polytechnic University | Lee H.C.,Curtin University Australia
Transportation Research Part F: Traffic Psychology and Behaviour | Year: 2012

The purposes of this study were to identify the relationships between the risk-taking behavior, response inhibition, and risky motorcycle riding behavior of commuter motorcyclists with different levels of impulsivity, and to examine how these behaviors contribute to motorcycle accidents. A total of 255 Chinese commuter motorcyclists were recruited for this study. Their levels of impulsivity were classified according to the Chinese Barratt Impulsiveness Scale version 11th. Their risk-taking behavior was assessed by the Balloon Analogue Risk Task and their response inhibition was assessed by the Chinese version of the Stroop test Victoria version. The Chinese Motorcycle Rider Driving Violation Scale was used to assess risky motorcycle riding behaviors. Results showed that impulsivity was associated with risk-taking behavior and risky motorcycle riding. Highly impulsive motorcyclists carry out more risk-taking behaviors and are less able to inhibit responses than those with low impulsivity. Motorcyclists with medium impulsivity (OR, 4.74; 95% CI, 1.91-11.39) and those with high impulsivity (OR, 4.91; 95% CI, 2.34-10.24) were about 5 times more likely to be actively involved in motorcycle accidents than those with low impulsivity. Postlicense motorcycle riding experience and risky motorcycle riding behavior were two significant predictors of motorcycle traffic accidents after controlling for other sociodemographic variables. These results can facilitate the development of interventions, including the training and testing of motorcyclists, public education, and mass media messages about traffic risk. © 2012 Elsevier Ltd. All rights reserved.

Luo M.,Hong Kong Polytechnic University
Maritime Policy and Management | Year: 2013

In order to curb the trend toward global warming, many technical, operational, and policy options have been proposed to help reduce the emissions from international shipping-the carrier for 80% of the world's trade. However, these options might not only reduce emissions from shipping activities, but could also have a ripple effect on the whole supply chain of traded goods, as well as on those serving shipping activities. These effects could have both positive and negative impacts, not only on emission reduction, but also on world trade, economic efficiency, and the local environment. While most studies have examined the feasibility of the various options and their potential contribution to emission reduction, their secondary impacts have not been studied. However, failing to take them into account could very well obstruct the implementation of the options. Through a review of existing studies, this article aims to identify and explain some of these previously unexamined secondary effects that are associated with emission reduction in international shipping, point out the problems that will arise if they are ignored, and provide a basis for further detailed research in this area. © 2013 Taylor & Francis.

Guo P.,Hong Kong Polytechnic University | Hassin R.,Tel Aviv University
Operations Research | Year: 2011

We consider a single server queueing system in which service shuts down when there are no customers present and is resumed only when the queue length reaches a given critical length. We analyze the strategic response of customers to this mechanism and compare it to the overall optimal behavior, with and without information on delay. The results are significantly different from those obtained when the server is continuously available. We show that there may exist multiple equilibria in such a system and the optimal arrival rate may be greater or smaller than that of the decentralized equilibrium. Finally, the critical length is taken as a decision variable, and the optimal operations policy is discussed by taking strategic customers into consideration. © 2011 INFORMS.

Chong A.Y.-L.,The University of Nottingham Ningbo, China | Chan F.T.S.,Hong Kong Polytechnic University
Expert Systems with Applications | Year: 2012

Structural equation analysis for multi-stage analysis on Radio Frequency Identification (RFID) diffusion in the health care industry. Faced with an increasingly competitive business environment, organizations in the health care industry are applying Radio Frequency Identification (RFID) to improve operational efficiency and to gain a competitive advantage over their competitors. This research provides a multi-stage analysis on the antecedents that affects the diffusion of RFID in the health care industry. Data collected from 182 health care organizations were analyzed using structural equation modeling analysis. The result shows that variables within the Technology-Organization-Environment (TOE) framework and the Diffusion of Innovation (DOI) theory have different effects on the evaluation, adoption, and routinization stages of RFID diffusion. This is one of few empirical studies on the factors influencing the diffusion of RFID in the health care industry. The results of this study will help decision makers in the health care industry to better understand the diffusion process of RFID, and to formulate strategies for successful diffusion of RFID. © 2012 Elsevier Ltd. All rights reserved.

Jiang L.,Hong Kong Polytechnic University
Production and Operations Management | Year: 2015

We consider a setting in which a manufacturer sequentially sources two components and uses reverse auction to select a supplier with the lowest bidding price for each component. The manufacturer chooses a quantity to order from each supplier and a price for selling the final product. We show that the interplay between the direct competition faced by suppliers in providing their respective components and the sequence whereby the manufacturer sources components influence system performance in a subtle, and sometimes dramatic, way. As the direct competition for the early sourced component intensifies, the profit of its supplier will deteriorate while the profits of the other firms will improve. As the direct competition for the late sourced component intensifies, however, the profit of its supplier may improve, and the profits of the other supplier, the manufacturer, and the system can all decrease. Compared with when the manufacturer simultaneously sources the components, sequentially sourcing the components can benefit the manufacturer and every supplier. Furthermore, all the channel parties can unanimously agree on a specific sourcing sequence. All of these signify the importance for manufacturers to take appropriate measures to manage their sourcing procedures and the competition environments faced by their suppliers. © 2014 Production and Operations Management Society.

Lun Y.H.V.,Hong Kong Polytechnic University | Quaddus M.A.,Curtin University Australia
Expert Systems with Applications | Year: 2011

In this study, we examine the relationship between firm size and the use of electronic commerce (EC) by container transport operators in Hong Kong and their performance implications. Using data collected from a sample of container shipping operators in Hong Kong, we identified internal and external drivers that affect the use of EC by container transport operators. Our findings indicate that large firms tend to adopt EC at a higher level of sophistication. This study also investigates the relationship between the use of EC and firm performance. Our results show that sales growth is positively related to the use of EC and firm size. To understand how firm size affects firm performance, we use a structural equation model (SEM) to examine their structural relationships. Our findings indicate that firm size positively influences sales growth. On the other hand, sales growth affects the profitability of a firm. Although customer satisfaction does not have a direct impact on profitability, our SEM suggests that customer satisfaction is a significant variable that affects the sales growth of firms. © 2010 Elsevier Ltd. All rights reserved.

Leung D.P.,Hong Kong Polytechnic University
Alternative therapies in health and medicine | Year: 2011

The evidence of tai chi for balance improvement and fall reduction in older adults was updated and reviewed. A systematic review was carried out by two independent reviewers among nine electronic databases to identify randomized controlled trials (RCTs) that examined the effects of tai chi on balance improvement and fall reduction in older adults using such key words as tai chi, falls, balance, and randomized trial. The results based on 13 RCTs indicated that tai chi was effective in improving balance of older adults but may not necessarily be superior to other interventions. Results also showed that in the absence of other interventions, tai chi reduced falls in the nonfrail elderly. Tai chi is recommended as an alternative treatment for improving balance so as to reduce falls. Future research with improved research designs such as more consistent outcome measures on balance and fall reduction and longer postintervention follow-up should be conducted to unravel the efficacy of different types of tai chi.

Hsieh J.J.P.-A.,Hong Kong Polytechnic University | Rai A.,Georgia State University | Keil M.,Georgia State University
Information Systems Research | Year: 2011

Digital inequality, or unequal access to and use of information and communication technologies (ICT), is a severe problem preventing the socioeconomically disadvantaged (SED) from participating in a digital society. To understand the critical resources that contribute to digital inequality and inform public policy for stimulating initial and continued ICT usage by the SED, we drew on capital theories and conducted a field study to investigate: (1) the forms of capital for using ICT and how they differ across potential adopters who are SED and socioeconomically advantaged (SEA); (2) how these forms of capitals are relatively impacted for the SEA and the SED through public policy for ICT access; and (3) how each form of capital influences the SED's intentions to use initially and to continue to use ICT. The context for our study involved a city in the southeastern United States that offered its citizens free ICT access for Internet connectivity. Our results show that SED potential adopters exhibited lower cultural capital but higher social capital relative to the SEA. Moreover, the SED who participated in the city's initiative realized greater positive gains in cultural capital, social capital, and habitus than the SEA. In addition, we find that the SED's initial intention to use ICT was influenced by intrinsic motivation for habitus, self-efficacy for cultural capital, and important referents' expectations and support from acquaintances for social capital. Cultural capital and social cultural capital also complemented each other in driving the SED's initial use intention. The SED's continued use intention was affected by both intrinsic and extrinsic motivations for habitus and both knowledge and self-efficacy for cultural capital but was not affected by social capital. We also make several recommendations for future research on digital inequality and ICT acceptance to extend and apply the proposed capital framework. © 2011 INFORMS.

Ye Q.,Harbin Institute of Technology | Law R.,Hong Kong Polytechnic University | Gu B.,University of Texas at Austin | Chen W.,University of California at San Diego
Computers in Human Behavior | Year: 2011

The increasing use of web 2.0 applications has generated numerous online user reviews. Prior studies have revealed the influence of user-generated reviews on the sales of products such as CDs, books, and movies. However, the influence of online user-generated reviews in the tourism industry is still largely unknown both to tourism researchers and practitioners. To bridge this knowledge gap in tourism management, we conducted an empirical study to identify the impact of online user-generated reviews on business performance using data extracted from a major online travel agency in China. The empirical findings show that traveler reviews have a significant impact on online sales, with a 10 percent increase in traveler review ratings boosting online bookings by more than five percent. Our results highlight the importance of online user-generated reviews to business performance in tourism. © 2010 Elsevier Ltd. All rights reserved.

Wang F.,Sun Yat Sen University | Lai X.,Hong Kong Polytechnic University | Shi N.,Sun Yat Sen University
Decision Support Systems | Year: 2011

In this paper, we study a supply chain network design problem with environmental concerns. We are interested in the environmental investments decisions in the design phase and propose a multi-objective optimization model that captures the trade-off between the total cost and the environment influence. We conduct a comprehensive set of numerical experiments. The results show that our model can be applied as an effective tool in the strategic planning for green supply chain. Meanwhile, the sensitivity analysis provides some interesting managerial insights for firms. © 2010 Elsevier B.V. All rights reserved.

Fu X.,Hong Kong Polytechnic University | Zhang A.,University of British Columbia
Journal of Transport Economics and Policy | Year: 2010

This paper studies the competitive and welfare implications when an airport offers airlines the option of sharing its concession revenue. By studying a non-congested airport whose aeronautical charge is regulated, we find that revenue sharing allows the airport and airlines to internalise a positive demand externality between aeronautical services and concession services, which may improve welfare. However, revenue sharing may cause a negative effect on airline competition. An airport may strategically share the revenue with its dominant airlines, which can further strengthen these firms' market power. Such exclusive revenue sharing may or may not improve welfare. Implications for a general airport-airline vertical relationship are discussed.

Choi T.-M.,Hong Kong Polytechnic University
IEEE Transactions on Systems, Man, and Cybernetics: Systems | Year: 2016

This paper explores supply chain systems coordination challenges in the presence of multiple heterogeneous risk sensitive retail buyers using the commonly seen markdown contract under both information symmetric and asymmetric settings. For each setting, we explore two scenarios. The first scenario allows the upstream manufacturer to freely set a separate contract to each risk averse retailer, whereas the second scenario specifies that the manufacturer has to grant the same contract to each risk averse retailer under the fair trade rule. We analytically show that the markdown contract which can achieve "perfect coordination" only exists in the first scenario (without the fair trade rule) under the information symmetric setting. For all the other scenarios, we find that perfect coordination cannot be achieved by the markdown contract, and hence we develop the computational algorithms to help identify the markdown contract parameter(s) which can achieve the "best possible coordination." In addition, we reveal that the manufacturer's risk attitude does significantly affect the achievability of perfect coordination. The findings of this paper also provide analytical evidence to show that the fair trade rule would do more harm than good for supply chain systems optimization under simple supply contracts. © 2015 IEEE.

Sung-Chan P.,Hong Kong Polytechnic University | Sung Y.W.,Chinese University of Hong Kong | Zhao X.,Tongji University | Brownson R.C.,Washington University in St. Louis
Obesity Reviews | Year: 2013

Effective interventions are needed to address the growing epidemic of childhood obesity. In the past 35 years, family-based approach has gradually developed as a preferred intervention. This review aimed to examine the methodological rigour and treatment effectiveness of family-based interventions according to intervention types and theoretical orientations. A total of 15 randomized controlled trials (RCTs) of family-based lifestyle interventions for children and adolescents aged 2-19 years were included. The adapted Methodological Quality Rating Scales (MQRS) and a four-grade qualitative scoring scheme were adopted to evaluate the methodological rigour and the effectiveness of treatment, respectively. The average MQRS score was 7.93 out of 14 points. Ten of the 15 RCTs had well aligned their research questions with appropriate research methods. The overall short-term outcome of the15 RCTs were satisfactory with an average score of 3.1. Family-based interventions rooted in behaviour theory achieved better results than those theoretically connected to family systems theory in terms of treatment effectiveness. Results suggest future studies to improve the methodological design and continue to explore the potential of the family systems approach. © 2012 The Authors. Obesity Reviews. © 2012 International Association for the Study of Obesity.

Xu B.G.,Hong Kong Polytechnic University
Expert Systems with Applications | Year: 2012

Flexible rotor is a crucial mechanical component of a diverse range of rotating machineries and its condition monitoring and fault diagnosis are of particular importance to the modern industry. In this paper, Bayesian belief network (BBN) is applied to the fault inference for rotating flexible rotors with attempt to enhance the reasoning capacity under conditions of uncertainty. A generalized three-layer configuration of BBN for the fault inference of rotating machinery is developed by fully incorporating human experts' knowledge, machine faults and fault symptoms as well as machine running conditions. Compared with the Naive diagnosis network, the proposed topological structure of causalities takes account of more practical and complete diagnostic information in fault diagnosis. The network tallies well with the practical thinking of field experts in the whole processes of machine fault diagnosis. The applications of the proposed BBN network in the uncertainty inference of rotating flexible rotors show good agreements with our knowledge and practical experience of diagnosis. © 2011 Elsevier Ltd. All rights reserved.

Ngan H.W.,Hong Kong Polytechnic University
Energy Policy | Year: 2010

The electricity industry of China has been in a process of reforms since the 1980s. This paper gives a review on the three main stages of reforms in China so as to trace out key features of various reform measures including those for power investment financing, the separation between government and power enterprises, and the division between power generation firms and power grids. The findings suggest that further regulatory change in China's electricity market reform is necessary when integration of the electricity markets and increased competition are paving the way ahead for a market-oriented structure. Prospective electricity regulation in the form of a strong legal system and effective institutions that protect market competition and promote appropriate incentives for efficiency are suggested in the paper. © 2009 Elsevier Ltd. All rights reserved.

Mak M.K.Y.,Hong Kong Polytechnic University
Pediatric Physical Therapy | Year: 2010

PURPOSE: To investigate the performance of reaching and grasping a moving target in children with developmental coordination disorder (DCD). METHODS: Sixteen children with DCD and 11 age-matched controls were instructed to reach and grasp a toy car that was sliding down an 8° or 15° slope. Reaction time (RT), movement time (MT), and peak force (PF) were recorded. RESULTS: Children with DCD failed 35% of total test trials. Within the successful trials, children with DCD had significantly longer RTs and MTs and generated larger PF than control children (P < .05). When the slope increased from 8° to 15°, both groups of children could adjust MT and PF (P < .01). CONCLUSION: Children with DCD were slower and generated larger force to reach and grasp a moving target than their age-matched peers. However, the ability to modify the MT and grip force appeared to be preserved in children with DCD. Copyright © 2010 Wolters Kluwer Health | Lippincott Williams & Wilkins and Section on Pediatrics of the American Physical Therapy Association.

Zheng J.-J.,Zhejiang University of Technology | Dai J.-G.,Hong Kong Polytechnic University
Engineering Structures | Year: 2014

Fiber-reinforced polymer (FRP) rods have been increasingly used in grouted ground anchors due to their high strength-to-weight ratio, excellent corrosion resistance, and convenience in incorporating the fiber sensing technology. To establish their pull-out capacity, FRP rods are usually embedded within a grouted steel tube and then subjected to pull-out in the laboratory. The aim of this paper is to develop a numerical method for predicting the nonlinear pull-out response of FRP rods embedded in steel tubes filled with cement grout. In the method, the cement grout is assumed to be subject to simple shear, the local interfacial bond stress-slip model of the bar-to-grout interface is represented by a piece-wise curve comprising elastic, softening, and frictional stages, and the unloading effect is also taken into account. A set of two second-order ordinary differential equations are derived in terms of the displacements of the FRP rod and steel tube and solved analytically to formulate the element transfer matrix. When the thickness of the steel tube approaches infinity, this method can be applied to the problem of FRP rods embedded in rock. Based on the developed numerical method, the interfacial bond properties and snapback phenomenon are analyzed. After the method is validated by comparisons with four sets of experimental data, the effects of the radius and length of FRP rods, the local peak bond stress and the residual frictional strength on the maximum pull-out load are evaluated in a quantitative manner. © 2014 Elsevier Ltd.

Hughes B.R.,Heriot - Watt University Dubai | Mak C.M.,Hong Kong Polytechnic University
Energy and Buildings | Year: 2011

Commercial wind towers have been the focus of intensive research in terms of their design and performance. There are two main forces which drive the flow through these devices, external wind and buoyancy due to temperature difference. This study examines the relationship between these two forces and the indoor ventilation rate achieved. The work uses computational fluid dynamics (CFD) modeling to isolate and investigate the two forces and draw comparisons. The study found that as expected the external driving wind is the primary driving force providing 76% more internal ventilation than buoyancy driven flow, which is deemed secondary. Moreover the study found that the effect of buoyancy is insignificant without an external airflow passage other than the wind tower itself. The addition of an external airflow passage such as a window in combination with buoyancy force increased the indoor ventilation by 47%. Therefore the careful positioning of windows in conjunction with internal heat source has the potential to overcome the lack of external wind driven forces in dense urban environments. © 2011 Elsevier B.V. All rights reserved.

Xu Y.,Harbin Institute of Technology | Zhang D.,Hong Kong Polytechnic University
Optical Engineering | Year: 2010

Multibiometrics can obtain a higher accuracy than the single biometrics by simultaneously using multiple biometric traits of the subject. We note that biometric traits are usually in the form of images. Thus, how to properly fuse the information of multiple biometric images of the subject for authentication is crucial for multibiometrics. We propose a novel image-based linear discriminant analysis (IBLDA) approach to fuse two biometric traits (i.e., bimodal biometric images) of the same subject in the form of matrix at the feature level. IBLDA first integrates two biometric traits of one subject into a complex matrix and then directly extracts low-dimensional features for the integrated biometric traits. IBLDA also enables more information to be exploited than the matching score level fusion and the decision level fusion. Compared to linear discriminant analysis (LDA), IBLDA has the following advantages: First, it can overcome the small sample size problem that conventional LDA usually suffers from. Second, IBLDA solves the eigenequation at a low computational cost. Third, when storing the scatter matrices IBLDA will not bring as heavy a memory burden as conventional LDA. We also clearly show the theoretical foundation of the proposed method. The experiment result shows that the proposed method can obtain a high classification accuracy. © 2010 Society of Photo-Optical Instrumentation Engineers.

He X.Y.,Nanyang Technological University | Wang Q.J.,Nanyang Technological University | Yu S.F.,Hong Kong Polytechnic University
Plasmonics | Year: 2012

A numerical transfer matrix method (TMM) is applied to investigate hybrid surface plasmon polaritons (HySPPs) waveguide structure, which consists of a high permittivity dielectric fiber separated from a metal surface with a low permittivity dielectric gap. The results obtained from the TMM agree well with those from the finite element method but with a faster calculation speed. As a demonstration example, we have systematically investigated the propagation properties of the gain-assisted HySPPs waveguide in the terahertz regime by using this method, studying the influences of structure parameters, frequency, temperature, and material gain. The results manifest that the effective index and the propagation loss decrease with the increase of temperature. In addition, as the frequency increases, the effective index increases and the propagation loss shows a peak. Furthermore, lossless propagation can be achieved when certain gain materials are applied into the HySPPs structure. Our method provides an efficient approach to investigate HySPPs waveguide and other plasmonic devices. © 2012 Springer Science+Business Media, LLC.

Luo W.,Hong Kong Polytechnic University
BMC bioinformatics | Year: 2012

The discovering of interesting patterns in drug-protein interaction data at molecular level can reveal hidden relationship among drugs and proteins and can therefore be of paramount importance for such application as drug design. To discover such patterns, we propose here a computational approach to analyze the molecular data of drugs and proteins that are known to have interactions with each other. Specifically, we propose to use a data mining technique called Drug-Protein Interaction Analysis (D-PIA) to determine if there are any commonalities in the fingerprints of the substructures of interacting drug and protein molecules and if so, whether or not any patterns can be generalized from them. Given a database of drug-protein interactions, D-PIA performs its tasks in several steps. First, for each drug in the database, the fingerprints of its molecular substructures are first obtained. Second, for each protein in the database, the fingerprints of its protein domains are obtained. Third, based on known interactions between drugs and proteins, an interdependency measure between the fingerprint of each drug substructure and protein domain is then computed. Fourth, based on the interdependency measure, drug substructures and protein domains that are significantly interdependent are identified. Fifth, the existence of interaction relationship between a previously unknown drug-protein pairs is then predicted based on their constituent substructures that are significantly interdependent. To evaluate the effectiveness of D-PIA, we have tested it with real drug-protein interaction data. D-PIA has been tested with real drug-protein interaction data including enzymes, ion channels, and protein-coupled receptors. Experimental results show that there are indeed patterns that one can discover in the interdependency relationship between drug substructures and protein domains of interacting drugs and proteins. Based on these relationships, a testing set of drug-protein data are used to see if D-PIA can correctly predict the existence of interaction between drug-protein pairs. The results show that the prediction accuracy can be very high. An AUC score of a ROC plot could reach as high as 75% which shows the effectiveness of this classifier. D-PIA has the advantage that it is able to perform its tasks effectively based on the fingerprints of drug and protein molecules without requiring any 3D information about their structures and D-PIA is therefore very fast to compute. D-PIA has been tested with real drug-protein interaction data and experimental results show that it can be very useful for predicting previously unknown drug-protein as well as protein-ligand interactions. It can also be used to tackle problems such as ligand specificity which is related directly and indirectly to drug design and discovery.

Guo H.,Hong Kong Polytechnic University
Building and Environment | Year: 2011

Indoor volatile organic compound (VOC) data obtained in 100 Hong Kong homes were analyzed to investigate the nature of emission sources and their contributions to indoor concentrations. A principal component analysis (PCA) showed that off-gassing of building materials, household products, painted wood products, room freshener, mothballs and consumer products were the major sources of VOCs in Hong Kong homes. The source apportionments were then evaluated by using an absolute principal component scores (APCS) technique combined with multiple linear regressions. The results indicated that 76.5 ± 1% (average ± standard error) of the total VOC emissions in Hong Kong homes attributes to the off-gassing of building materials, followed by the room freshener (8 ± 4%), household products (6 ± 2%), mothballs (5 ± 3%) and painted wood products (4 ± 2%). Analysis on the source strength in the monitored homes revealed that although six indoor sources were identified and quantified in the Hong Kong homes, only some homes were responsible for the elevated concentrations of target VOCs emitted from these sources. The findings provide us the mechanism of reducing levels of indoor VOCs and ultimately lead to cost effective reduction in population exposures. © 2011 Elsevier Ltd.

Li X.,Tsinghua University | Po-An Hsieh J.J.,Hong Kong Polytechnic University | Rai A.,Georgia State University
Information Systems Research | Year: 2013

We identify two post-acceptance information system (IS) usage behaviors related to how employees leverage implemented systems. Routine use (RTN) refers to employees' using IS in a routine and standardized manner to support their work, and innovative use (INV) describes employees' discovering new ways to use IS to support their work. We use motivation theory as the overarching perspective to explain RTN and INV and appropriate the rich intrinsic motivation (RIM) concept from social psychology to propose a conceptualization of RIM toward IS use, which includes intrinsic motivation toward accomplishment (IMap), intrinsic motivation to know (IMkw), and intrinsic motivation to experience stimulation (IMst). We also consider the influence of perceived usefulness (PU)-a representative surrogate construct of extrinsic motivation toward IS use-on RTN and INV. We theorize the relative impacts of the RIM constructs and PU on RTN and INV and the role of personal innovativeness with IT (PIIT) in moderating the RIM constructs' influences on INV. Based on data from 193 employees using a business intelligence system at one of the largest telecom service companies in China, we found (1) PU had a stronger impact on RTN than the RIM constructs, (2) IMkw and IMst each had a stronger impact on INV than either PU or IMap, and (3) PIIT positively moderated the impact of each RIM construct on INV. Our findings provide insights on managing RTN and INV in the post-acceptance stage. © 2013 Informs.

Ni Y.-H.,Tianjin Polytechnic University | Li X.,Hong Kong Polytechnic University
Systems and Control Letters | Year: 2013

In this paper, the consensus problems of the continuous-time integrator systems under noisy measurements are considered. The measurement noises, which appear when agents measure their neighbors' states, are modeled to be multiplicative. By multiplication of the noises, here, the noise intensities are proportional to the absolute value of the relative states of an agent and its neighbor. By using known distributed protocols for integrator agent systems, the closed-loop system is described in the vector form by a singular stochastic differential equation. For the fixed and switching network topology cases, constant consensus gains are properly selected, such that mean square consensus and strong consensus can be achieved. Especially, exponential mean square convergence of agents' states to the common value is derived for the fixed topology case. In addition, asymptotic unbiased mean square average consensus and asymptotic unbiased strong average consensus are also studied. Simulations shed light on the effectiveness of the proposed theoretical results. © 2013 Elsevier B.V. All rights reserved.

Chen W.,Hong Kong Polytechnic University
IEEE Photonics Journal | Year: 2016

Single-pixel imaging via phase extraction is presented for optical security and flexibility enhancement. A series of random intensity patterns are pregenerated as principal security keys and are sequentially encoded into phase-only masks. Since different optical sensing infrastructures can be arbitrarily designed for the extraction of phase-only masks and object encoding, high flexibility and high security with a largely indirect space for phase are achieved in the proposed optical security system. This finding may advance single-pixel correlated imaging as a quantum or classical technology with potential for significantly enriching the security field. © 2009-2012 IEEE.

Zhu Q.,Dalian University of Technology | Sarkis J.,Clark University | Lai K.-H.,Hong Kong Polytechnic University
Journal of Engineering and Technology Management - JET-M | Year: 2012

Drawing on diffusion of innovation and ecological modernization theories, we identify three types of industrial manufacturers, namely early adopters, followers, and laggards, based on the adoption of green supply chain management (GSCM) practices among Chinese manufacturers. Test results indicate that differences exist between the three types of GSCM adopters in terms of their environmental, operational, and economic performance. Understanding how Chinese manufacturers adopt GSCM practices and if this adoption affects their performance contributes theoretical advancement to the diffusion of innovation theory. Practically, the results provide managerial insights for manufacturers to benchmark for environmental management practices and performance improvement. © 2011 Elsevier B.V. All rights reserved.

Gunasekaran A.,University of Massachusetts Dartmouth | Ngai E.W.T.,Hong Kong Polytechnic University
International Journal of Production Economics | Year: 2012

Managing operations in both manufacturing and service organizations have evolved tremendously over the years with the change in market requirements. The market has become global, thereby compelling enterprise operations to keep up. The application of information technology/information systems (IT/IS) and outsourcing in managing operations have significantly altered the landscape of operations management (OM) strategies, techniques, and technologies. Consciousness towards environmental and safety also urges companies to examine their OM approach and manufacturing from various perspectives. Recently, energy cost and protection against terrorism have changed the portfolio of enterprise operations and therefore the approach to OM. Now, it is time to revisit the OM principles, curriculum, and training at the institution of higher learning and industries. Moreover, manufacturing has become more of a service activity, indicating significant service OM, including project management. The profile of service industries has also changed in view of the emergence of globalization, outsourcing, and IT, coupled with the rapid economic growth of emerging economies such as Brazil, Russia, India, and China (BRIC). In fact, services account for approximately 80% of the US gross domestic product (GDP); this is also a growing figure of the GDPs of other countries over the world. Again, service OM needs to be revisited in the context of the abovementioned paradigm shifts. In considering the significance of the above-mentioned changes in the market and society as a whole, an attempt is made to study the evolution of OM and subsequently to develop a framework for new OM strategies and tactics that will support the competitiveness of organizations within the next 1020 years. © 2011 Elsevier B.V. All Rights Reserved.

Yuan Q.,East China Normal University | Ding F.,Hong Kong Polytechnic University
Angewandte Chemie - International Edition | Year: 2015

Owing to the unique structure of zigzag (ZZ) carbon nanotubes (CNTs), their ring-by-ring growth behavior is different from that of chiral or armchair (AC) CNTs, on the rims of which kinks serve as active sites for carbon attachment. Through first-principle calculations, we found that, because of the high energy barrier of initiating a new carbon ring at the rim of a ZZ CNT, the growth rate of a ZZ CNT is proportional to its diameter and significantly (10-1000 times) slower than that of other CNTs. This study successfully explained the broad experimental observation of the lacking of ZZ CNTs in CNT samples and completed the theory of CNT growth. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Ma L.,Nanjing Southeast University | Wang J.,Nanjing Southeast University | Ding F.,Hong Kong Polytechnic University
ChemPhysChem | Year: 2013

Graphene, the thinnest two-dimensional material in nature, has abundant distinctive properties, such as ultrahigh carrier mobility, superior thermal conductivity, very high surface-to-volume ratio, anomalous quantum Hall effect, and so on. Laterally confined, thin, and long strips of graphene, namely, graphene nanoribbons (GNRs), can open the bandgap in the semimetal and give it the potential to replace silicon in future electronics. Great efforts are devoted to achieving high-quality GNRs with narrow widths and smooth edges. This minireview reports the latest progress in experimental and theoretical studies on GNR synthesis. Different methods of GNR synthesis - unzipping of carbon nanotubes (CNTs), cutting of graphene, and the direct synthesis of GNRs - are discussed, and their advantages and disadvantages are compared in detail. Current challenges and the prospects in this rapidly developing field are also addressed. Making ribbons: Synthetic methods for graphene nanoribbons, including unzipping of carbon nanotubes, lithographic patterning and plasma etching of graphene, cutting of graphene sheets by metal nanoparticles or oxidation, and chemical synthesis (see picture), are reviewed from both experimental and theoretical viewpoints, and advantages and disadvantages of these methods are compared. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Hong L.,Lanzhou University | Wang R.,Lanzhou University | Wang R.,Hong Kong Polytechnic University
Advanced Synthesis and Catalysis | Year: 2013

The asymmetric organocatalysis is definitely one of the most powerful and versatile tools for the rapid construction of various spirocyclic oxindoles. In the past few years, a number of successful strategies based on organocatalysis have been developed for the construction of 3,3′-spirocyclic oxindoles in high yields and excellent enantioselectivities under mild conditions. In this review, recent advances in this area are summarized and classified according to the spiro ring fused at the 3-position of the oxindole core. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Zhang X.,Hong Kong Polytechnic University | Shen L.,Chongqing University | Zhang L.,Harbin Institute of Technology
Renewable and Sustainable Energy Reviews | Year: 2013

The generation of significant amount of emissions from building construction process has led the promotion of controlling emissions as an important strategy for implementing sustainable development principles in the built environment. The emissions incurred during various stages include carbon dioxide, methane, nitrous oxide, sulphur dioxide, carbon monoxide, nitrogen oxide, non methane volatile organic compounds and particulate matter. This paper conducts the life cycle assessment of the air emissions by using a particular case to examine emissions during construction stage. This study examines the emissions sources in each of the six stages and presents an inventory analysis method to measure air emissions to quantify the air emissions during the six life cycle stages for buildings. This method can help evaluating the impacts of implementing a building on the air quality, thus actions can be taken in early stages to reduce the environmental impacts during building life cycle. A case study is presented to demonstrate the practical application of the method with reference to the building practices for all life cycle stages in Hong Kong. © 2012 Elsevier Ltd.

Xiang R.,Hong Kong Polytechnic University
Chaos (Woodbury, N.Y.) | Year: 2012

Recently, a framework for analyzing time series by constructing an associated complex network has attracted significant research interest. One of the advantages of the complex network method for studying time series is that complex network theory provides a tool to describe either important nodes, or structures that exist in the networks, at different topological scale. This can then provide distinct information for time series of different dynamical systems. In this paper, we systematically investigate the recurrence-based phase space network of order k that has previously been used to specify different types of dynamics in terms of the motif ranking from a different perspective. Globally, we find that the network size scales with different scale exponents and the degree distribution follows a quasi-symmetric bell shape around the value of 2k with different values of degree variance from periodic to chaotic Rössler systems. Local network properties such as the vertex degree, the clustering coefficients and betweenness centrality are found to be sensitive to the local stability of the orbits and hence contain complementary information.

Mandal S.K.,Indian National Institute of Foundry and Forge Technology | Chan F.T.S.,Hong Kong Polytechnic University | Tiwari M.K.,Indian Institute of Technology Kharagpur
Expert Systems with Applications | Year: 2012

The generation of leak along the pipeline carrying crude oils and liquid fuels results enormous financial loss to the industry and also affects the public health. Hence, the leak detection and localization problem has always been a major concern for the companies. In spite of the various techniques developed, accuracy and time involved in the prediction is still a matter of concern. In this paper, a novel leak detection scheme based on rough set theory and support vector machine (SVM) is proposed to overcome the problem of false leak detection. In this approach, 'rough set theory' is explored to reduce the length of experimental data as well as generate rules. It is embedded to enhance the decision making process. Further, SVM classifier is employed to inspect the cases that could not be detected by applied rules. For the computational training of SVM, this paper uses swarm intelligence technique: artificial bee colony (ABC) algorithm, which imitates intelligent food searching behavior of honey bees. The results of proposed leak detection scheme with ABC are compared with those obtained by using particle swarm optimization (PSO) and one of its variants, so-called enhanced particle swarm optimization (EPSO). The experimental results advocate the use of propounded method for detecting leaks with maximum accuracy. © 2011 Elsevier Ltd. All rights reserved.

Yang W.,Nanjing Southeast University | Sun C.,Nanjing Southeast University | Zhang L.,Hong Kong Polytechnic University
Pattern Recognition | Year: 2011

In this paper, we propose a Multi-Manifold Discriminant Analysis (MMDA) method for an image feature extraction and pattern recognition based on graph embedded learning and under the Fisher discriminant analysis framework. In an MMDA, the within-class graph and between-class graph are, respectively, designed to characterize the within-class compactness and the between-class separability, seeking for the discriminant matrix to simultaneously maximize the between-class scatter and minimize the within-class scatter. In addition, in an MMDA, the within-class graph can represent the sub-manifold information, while the between-class graph can represent the multi-manifold information. The proposed MMDA is extensively examined by using the FERET, AR and ORL face databases, and the PolyU finger-knuckle-print databases. The experimental results demonstrate that an MMDA is effective in feature extraction, leading to promising image recognition performance. © 2011 Elsevier Ltd. All rights reserved.

Nie C.,Nanjing University | Leung H.,Hong Kong Polytechnic University
ACM Transactions on Software Engineering and Methodology | Year: 2011

Combinatorial Testing (CT) involves the design of a small test suite to cover the parameter value combinations so as to detect failures triggered by the interactions among these parameters. To make full use of CT and to extend its advantages, this article first gives a model of CT and then presents a theory of the Minimal Failure-causing Schema (MFS), including the concept of the MFS, proof of its existence, some of its properties, and a method of finding the MFS. Then we propose a methodology for CT based on this MFS theory and the existing research. Our MFS-based methodology emphasizes that CT should work on accurate testing requirements, and has the following advantages: 1) Detect failure to the greatest degree with the least cost. 2) Effectiveness is improved by emphasizing mining of the information in software and making full use of the information gained from test design and execution. 3) Determine the root causes of failures and reveal related faults near the exposed ones. 4) Provide a foundation and model for regression testing and software quality evaluation of CT. A case study is presented to illustrate the MFS-based CT methodology, and an empirical study on a real software developed by us shows that the MFS really exists and the methodology based on MFS can considerably improve CT. © 2011 ACM.

Ni M.,Hong Kong Polytechnic University
Journal of Power Sources | Year: 2011

A two-dimensional model is developed to study the performance of a planar solid oxide fuel cell (SOFC) running on steam/methane mixture. The model considers the heat/mass transfer, electrochemical reactions, direct internal reforming of methane (CH4), and water gas shift reaction in an SOFC. It is found that at an operating potential of 0.8 V, the upstream and downstream of SOFC work in electrolysis and fuel cell modes, respectively. At the open-circuit voltage, the electricity generated by the downstream part of SOFC is completely consumed by the upstream through electrolysis, which is contrary to our common understanding that electrochemical reactions cease under the open-circuit conditions. In order to inhibit the electrolytic effect, the SOFC can be operated at a lower potential or use partially pre-reformed CH 4 as the fuel. Increasing the inlet gas velocity from 0.5 m s -1 to 5.0 m s-1 does not reduce the electrolytic effect but decreases the SOFC performance. © 2010 Elsevier B.V.

Teng J.G.,Hong Kong Polytechnic University | Yu T.,University of Wollongong | Fernando D.,ETH Zurich
Journal of Constructional Steel Research | Year: 2012

Over the past two decades, fiber-reinforced polymer (FRP) composites have gradually gained wide acceptance in civil engineering applications due to their unique advantages including their high strength-to-weight ratio and excellent corrosion resistance. In particular, many possibilities of using FRP in the strengthening and construction of concrete structures have been explored. More recently, the use of FRP to strengthen existing steel structures has received much attention. This paper starts with a critical discussion of the use of FRP in the strengthening of steel structures where the advantages of FRP are appropriately exploited. The paper then provides a critical review and interpretation of existing research on FRP-strengthened steel structures. Topics covered by the review include steel surface preparation for adhesive bonding, selection of a suitable adhesive, bond behavior between FRP and steel and its appropriate modeling, flexural strengthening of steel beams, fatigue strengthening of steel structures, strengthening of thin-walled steel structures against local buckling, and strengthening of hollow or concrete-filled steel tubes through external FRP confinement. The paper concludes with comments on future research needs. © 2012 Elsevier Ltd. All rights reserved.

Kim N.,Hong Kong Polytechnic University
Journal of Product Innovation Management | Year: 2013

As different types of knowledge may have different effects on new product positional advantage, knowledge portfolio management in concert with the firm's strategic orientation is indispensable for new product success. However, previous research has not dealt with the knowledge resources and strategic implementations that affect new product development (NPD). To fill in this gap, the current study focuses on two dimensions of knowledge type (knowledge complexity and knowledge tacitness) and two forms of strategic orientation (technological orientation and market orientation), which influence the positional advantages as determinants of NPD outcomes. Drawing on the resource-based view, this study explains how these knowledge and strategic orientation variables influence new product creativity, which comprised the novel and meaningful characteristics of new products. Finally, it demonstrates how these two dimensions of new product creativity differentially provide product advantages in terms of customer satisfaction and product differentiation, which lead to superior new product performance. A conceptual framework is developed and the related hypotheses provided to incorporate the study variables and to test their relationships in a sample based on data collected from both marketing and project managers from 100 U.S. high-technology firms. The model estimation results from path analysis demonstrate that reliance on knowledge of high tacitness harms meaningfulness, while reliance on knowledge of high complexity increases both novelty and meaningfulness of new product. As expected, market orientation and technological orientation improve the meaningfulness and novelty dimensions of the new product, respectively. New product novelty and meaningfulness are shown to enhance new product advantage in terms of product differentiation and customer satisfaction, both of which contribute to new product performance. It is also found that the combinative use of market orientation and knowledge complexity, and technological orientation and knowledge tacitness positively influence both the novelty and meaningfulness of new products. This study, using the product-level analysis, contributes to the literature by clarifying how the firm's different knowledge properties and strategic orientations both play a role as a source of new product creativity, and how new product creativity, as a valuable and rare resource, enhances new product advantage. The study results suggest that project/product managers should increase the transferability and codifiability of unstructured knowledge by stimulating intraorganizational knowledge sharing among NPD team members, and that they should promote both technology and market-orientated practices to fully develop creativity of new products. © 2012 Product Development & Management Association.

Li H.,Central South University | Wu B.,Hong Kong Polytechnic University
ISPRS Journal of Photogrammetry and Remote Sensing | Year: 2013

Geo-information (GI) service automated composition according to user demands is a crucial task in spatial data infrastructures. State-of-the-art GI service composition approaches face serious limitations in terms of effectiveness and stability as the general GI processing service chain (GIPSC) must be generated from individual user specifications from scratch. This paper presents a novel approach called an adaptive geo-information service evolution (AgiSE) method which overcomes these limitations by adaptively reusing and modifying previously generated GIPSC. In this method, an influence domain minimisation (IDM) criterion is employed to modify the existing GIPSC to fit the new (changed) user demands through minimum revisions. The correction of local modification is ensured by process and integrity constraints. An innovative algorithm called influence domain pursuit is developed to find the optimised solution through a heuristic backward search based on the defined IDM. Experimental analysis shows the significant improvements of using AgiSE in GI services compared with existing traditional methods. The benefits of AgiSE are the improved efficiency of GI service composition and the improved executing stability of GIPSC which were achieved by reducing the service provider load. The AgiSE presented in this paper is crucial in reusing a general unified framework for GI service composition. © 2013 International Society for Photogrammetry and Remote Sensing, Inc. (ISPRS).

Ghadikolaei M.A.,Hong Kong Polytechnic University
Renewable and Sustainable Energy Reviews | Year: 2016

In recent years, the effect of alcohols as an alternative fuel on emissions of IC engines has been investigated in a lot of experimental works. However there is a lack of a comprehensive review study about the definition and type of emissions (regulated and unregulated emissions) and alcohols and the influence of alcohols on unregulated emissions of IC engines. Therefore, this literature review study is presented. In the current literature review work, two sections are provided. A brief detail of the effect of alcohols (methanol and ethanol) in blended and fumigation modes on regulated emissions in IC engines is presented in the first section. And the second section (main section of this work) is a comprehensive review part of the literatures related to the effect of methanol and ethanol in blended and fumigation modes on unregulated emissions in IC engines. In this literature review work, a wide type of IC engines, such as SI and CI engines and motorcycles were collected with different operation conditions. Different percentages of alcohol blend and fumigation were summarized to get informations about the effect of alcohol on regulated and unregulated emissions of IC engines. For regulated emissions, it was found that application of alcohols as alternative fuels in fumigation mode in IC engines led to reduction of NOX and CO2 in most tests and PM in all cases. However, an increase of CO and HC was observed with using alcohols in fumigation mode in most cases. It is noticeable that a diverse effect of alcohol application in blended mode compared to fumigation mode on regulated emissions was recorded in considerable tests except PM. For unregulated emissions, it was found a reduction of BTEX (benzene, toluene, ethylbenzene and o-xylene, m/p-xylenes) in blended mode in most cases, polycyclic aromatic hydrocarbons (PAHs) in blended mode in major experiments and 1,3-butadiene, ethyne and ethene in both modes in all tests with using alcohols compared to fossil fuels. On the other hand, it was seen an increase of unburned ethanol and methanol and total carbonyls in both modes in all tests. And, an increase of formaldehyde and acetaldehyde which are the predominant carbonyls in the exhaust for vehicles was recorded in most and major experiments, respectively for both modes. In addition, soluble organic fraction (SOF) had an increase in both modes in major tests. And an increase of benzene, toluene, xylene (BTX) was observed in fumigation mode in significant tests. © 2015 Elsevier Ltd. All rights reserved.

Ng A.K.Y.,Hong Kong Polytechnic University | Cetin I.B.,Dokuz Eylul University
Regional Studies | Year: 2012

Ng A. K. Y. and Cetin I. B. Locational characteristics of dry ports in developing economies: some lessons from Northern India, Regional Studies. Contemporary economic development has triggered the importance of establishing distribution centres at appropriate locations in developing economies. However, so far, academic studies addressing this issue are rather scarce. Hence, by investigating dry ports within two industrial clusters in Northern India, this paper investigates the locational characteristics of distribution centres in developing economies. Analytical results indicate that the spatial dynamics of dry ports in developing economies are different from Western, advanced economies due to geographical diversifications, the different paces of regional development and local practices. This paper also suggests that dry ports in developing economies are more cluster (rather than supply chain) oriented. © 2012 Copyright Regional Studies Association.

Wang X.,Tsinghua University | Zhang D.,Hong Kong Polytechnic University
Expert Systems with Applications | Year: 2013

In order to improve the quality and consistency of tongue images acquired by current imaging devices, this research aims to develop a novel imaging system which records human tongue information faithfully and precisely for medical analysis. A thorough demand analysis is firstly conducted to summarize requirements for reliable rendering of all possible medical clues, i.e., color, texture and geometric features. Then a series of system design criteria are illustrated accordingly, and by following them, three hardware modules of the imaging system, including illuminant, lighting path and imaging camera, are optimally proposed. Moreover, one built-in software module, the color correction process, is also provided to compensate color variations caused by system components. Finally, several important performance indicators, including illumination uniformity, system reproducibility and accuracy, are elaborately tested. Experimental results show that captured images are in high quality and keep stable when acquisitions are repeated. The largest color difference between any two acquired images is 1.6532, which is hardly to be distinguished by human observation. Compared to existing devices, the proposed system could provide much more accurate and stable solution for tongue image acquisition. Besides, this developed imaging system has been evaluated by doctors of Traditional Chinese Medicine for almost three years and over 9,000 tongue images have been collected, analysis results based these data also validate the effectiveness of the proposed system. © 2013 Elsevier Ltd. All rights reserved.

Li R.,Hong Kong Polytechnic University | Leung G.C.,University of Manchester | Leung G.C.,Hong Kong Baptist University
Energy Policy | Year: 2012

The aim of this paper is to re-examine the relationship between coal consumption and real GDP of China with the use of panel data. This paper applies modern panel data techniques to help shed light on the importance of the heterogeneity among different regions within China. Empirical analyses are conducted for the full panel as well as three subgroups of the panel. The empirical results show that coal consumption and GDP are both I(1) and cointegrated in all regional groupings. Heterogeneity is found in the GDP equation of the full panel. The regional causality tests reveal that the coal consumption-GDP relationship is bidirectional in the Coastal and Central regions whereas causality is unidirectional from GDP to coal consumption in the Western region. Thus, energy conservation measures will not adversely affect the economic growth of the Western region but such measures will likely encumber the economy of the Coastal and Central regions, where most of the coal intensive industries are concentrated. © 2011 Elsevier Ltd.

Xue W.,Xian Jiaotong University | Zhang L.,Hong Kong Polytechnic University | Mou X.,Xian Jiaotong University
Proceedings of the IEEE Computer Society Conference on Computer Vision and Pattern Recognition | Year: 2013

General purpose blind image quality assessment (BIQA) has been recently attracting significant attention in the fields of image processing, vision and machine learning. State-of-the-art BIQA methods usually learn to evaluate the image quality by regression from human subjective scores of the training samples. However, these methods need a large number of human scored images for training, and lack an explicit explanation of how the image quality is affected by image local features. An interesting question is then: can we learn for effective BIQA without using human scored images? This paper makes a good effort to answer this question. We partition the distorted images into overlapped patches, and use a percentile pooling strategy to estimate the local quality of each patch. Then a quality-aware clustering (QAC) method is proposed to learn a set of centroids on each quality level. These centroids are then used as a codebook to infer the quality of each patch in a given image, and subsequently a perceptual quality score of the whole image can be obtained. The proposed QAC based BIQA method is simple yet effective. It not only has comparable accuracy to those methods using human scored images in learning, but also has merits such as high linearity to human perception of image quality, real-time implementation and availability of image local quality map. © 2013 IEEE.

Ling T.-C.,Hong Kong Polytechnic University
Construction and Building Materials | Year: 2012

A wide variety of recycled waste has been successfully used in the production of concrete paving blocks. It is known that the mechanical properties of these concrete products tend to be inconsistent, which is understandable in view of the range of mix designs as well as the variety of materials and compaction methods that were adopted in the production. In this study, recycled waste tyre (crumb rubber) was used to replace sand by volume at the level of 0%, 10%, 20% and 30% in order to investigate how the soft rubber particles behave under plant-machine compaction method during the production of rubberized concrete paving blocks (RCPB). In the hardened stage, the physical properties as well as mechanical properties of RCPB including density, compressive strength, bending strength and skid resistance were studied. The results showed that as a small proportion (∼10%) of soft rubber particles was included in the mixture, the particles easily distorted and filled the voids between the solid particles. This filling mechanism reduced the porosity of concrete mixtures and effectively developed an adequate adhesion between the particles, resulting in higher gain in strengths. On the contrary, as the rubber ratio increased more than 10%, which the deformability is more predominant than the filling mechanism, this results in higher total stress concentrations and rebound stress of rubber particles, thus, increasing the porosity and micro-cracks, resulting in loss in strengths. Nevertheless, the presence of rubber in concrete did not demonstrate brittle failure, but rather a ductile which had an ability to withstand post-failure loads. In comparison, the mechanical properties of plant-made RCPB performed better than that of corresponding manually-made RCPB. Therefore, plant-compaction method is recommended for future RCPB production and crumb rubber content used to replace sand by volume should be kept at or less than 10%. © 2011 Elsevier Ltd. All rights reserved.

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.

Ma H.,Shenzhen Polytechnic | Chan K.W.,Hong Kong Polytechnic University | Liu M.,South China University of Technology
IEEE Transactions on Industrial Informatics | Year: 2013

The intelligent control of power systems is one of the main tasks for realizing a smart grid. Because of the high-dimensional dynamics and discrete control of power systems, realizing an optimal control to support system voltages is a hard combinatorial optimization problem. In this paper, a new intelligent scheme based on a genetic learning progress for optimal voltage control is proposed. This learning control scheme combines the genetic algorithm (GA) with a memory which saves knowledge accumulated from past experiences. In each run of search by GA, past experiences in memory is exploited to speed up the searching of GA and improve the quality of the solutions while the knowledge in memory is also refined by the new solutions. With the help of this learning capability, a fast and self-healing voltage control is realized and the control performance can be improved gradually over time. A case study on the New England 39-bus power system showed that the purposed learning control can successfully prevent the system from voltage instability and at the same time a fast and adaptive system response is provided. © 2005-2012 IEEE.

Chow W.K.,Hong Kong Polytechnic University
Journal of Fire Sciences | Year: 2014

Relationship between internal fire whirls generated in a vertical shaft model was studied. A vertical shaft model of height 145 cm was constructed. Four fuels including methanol, ethanol, propanol, and gasoline of different pool sizes were used. Ventilation was provided from a sidewall for onsetting internal fire whirl. In the experiments, the flame height and mass loss rate of fuel while burning the pool fires were observed to increase at the same time. A linear correlation between flame height and mass fuel burning rate can be found for different liquid fuels. A parameter α, which describes the burning rate, calorific value, and the pool size of liquid fuel, was used to develop the correlation between the burning rate and flame height. The flame height was found to be linearly correlated with α. However, the normalized average flame height was found to be roughly constant with different values of α. © The Author(s) 2013.

Cheng T.C.E.,Hong Kong Polytechnic University | Lee W.-C.,Feng Chia University | Wu C.-C.,Feng Chia University
Computers and Industrial Engineering | Year: 2010

Recently, interest in scheduling with deteriorating jobs and learning effects has kept growing. However, research in this area has seldom considered setup times. We introduce a new scheduling model in which job deterioration and learning, and setup times are considered simultaneously. In the proposed model, the actual processing time of a job is defined as a function of the setup and processing times of the jobs already processed and the job's own scheduled position in a sequence. In addition, the setup times are assumed to be proportional to the actual processing times of the already scheduled jobs. We derive polynomial-time optimal solutions for some single-machine problems with or without the presence of certain conditions. © 2009 Elsevier Ltd. All rights reserved.

Shek D.T.L.,Hong Kong Polytechnic University
International Journal on Disability and Human Development | Year: 2013

Students were invited to write personal reflections about the subject, called Tomorrow ' s Leaders, to examine its effectiveness in promoting holistic development in students. Based on the reflections of 104 students, data were separately rated by two independent raters using a standardized rating form. Intra-rater and interrater reliability analyses revealed that the coding of reflections was reliable. Results showed that the informants generally had positive feedbacks about the subject and lecturers. Furthermore, they perceived that the subject promoted their overall development in different domains. Exemplar cases were highlighted in this paper.

Lai J.H.K.,Hong Kong Polytechnic University
Habitat International | Year: 2011

Urbanised areas are increasingly developed with housing estates. Further to their design and construction, the services provided for managing the estates' facilities are crucial to the living quality of numerous habitants there. Holistic study findings on the importance, performance and cost-effectiveness of such facility management (FM) services, especially those between like estates, have yet to be seen. For bridging this knowledge gap, a study was conducted, under which the main aspects of the typical services namely security, cleaning, repair & maintenance, leisure & landscape, and general management were identified in the first stage. In the second stage, the costs of FM services in two comparable estates and the users' perceived importance and performance of the services were collected. The responses drawn from their consistent judgments, after processing by an analytical hierarchy process, were examined against a performance-importance evaluation matrix. Statistical tests were applied to identify the services with different qualities, and a set of weighted performance indicators was computed for representing the cost-effectiveness of the services. Comparisons made between these indicators informed which service or aspect was provided in a more, or less, cost-effective way. Wider adoption of this evaluation approach would facilitate performance benchmarking across estates, which is conducive to attaining quality and cost-effective services. © 2010 Elsevier Ltd.

Wang J.,Shenzhen University | Yuan H.,Hong Kong Polytechnic University
International Journal of Project Management | Year: 2011

Risk-based decision making (RBDM) is critical in successful construction project management, in which decision makers' attitudes towards risks play an important role. Most previous studies in construction project risk management have been focusing on the factors contributing to the success of risk management, but little attention was given to factors significantly affecting decision makers' risk attitudes in construction projects. To improve RBDM, we investigate the critical factors affecting contractors' risk attitudes in construction projects in China in this research. Literatures reviews, interviews and questionnaires are used for the identification of factors affecting contractors' risk attitudes. Statistical methods of ranking analysis and factor analysis are also implemented for verification and further analysis. The results show that the most important three factors are: "consequences of decision making", "engineering experience", and "completeness of project information" Results from factor analysis on the identified critical factors reveal that they can be grouped into four categories, namely: (1) knowledge and experience; (2) contractors' character; (3) personal perception; and (4) economic environment. The significance of this research is that the findings do not only provide decision making support for contractors by deepening their understandings of the factors that affect their risk attitudes, but also serve as a useful reference for further studies under this topic. © 2010 Elsevier Ltd and IPMA.

Yuan X.,Hong Kong Polytechnic University
IEEE Workshop on Statistical Signal Processing Proceedings | Year: 2011

A new spatially-spread electromagnetic vector-sensor consisting of six non-collocating dipoles / loops is proposed in [1] to (i) reduce the mutual coupling across antennas, (ii) adopt the Poynting-vector estimator to estimate the direction-of-arrival of the source, and (iii) improve the direction-finding accuracy by extending the spatial aperture. The improvement in estimation accuracy was characterized by the Cramér-Rao bound for one pure-tone signal in [1]. In contrast, this paper will derive a new Cramér-Rao bound by modeling the incident source as a zero-mean complex Gaussian random sequence. This signal model is applicable when there is no prior knowledge of the incident source's time-frequency structure. © 2011 IEEE.

Ding A.,Nanjing University | Wang T.,Hong Kong Polytechnic University | Fu C.,Nanjing University
Journal of Geophysical Research: Atmospheres | Year: 2013

Transport characteristics and origins of carbonmonoxide (CO) and ozone (O3) transported to Hong Kong were investigated using backward Lagrangian particle dispersion modeling (LPDM) and measurement data collected at a regional background station, Hok Tsui, in South China during 2005-2007. LPDM was conducted using the Hybrid Single-Particle Lagrangian Integrated Trajectory model (HYSPLIT) driven by Global Data Assimilation System (GDAS) data and emission inventories of CO. The LPDM simulations showed very good performance in characterizing temporal variations in CO on both seasonal and synoptic scales during the 3 years. Based on the LPDM simulations, the seasonal cycles of the source origins and transport age of CO were investigated. Carbon monoxide at the background station was found to originate mainly from the coastal regions in southern China and from eastern China, with averaged transport time of about 1 day and 2-4 days, respectively. The O3 annual maximum in autumn was influenced by regional transport of O3 precursors originating from eastern China, suggesting a strong continental outflow and its regional impacts. Photochemical processes contributed to occurrence of O3 episodes with sharp daytime O3 peaks produced from fresh subregional emissions from Hong Kong and the Pearl River Delta region, mixed with inland continental air. By examining the O3-CO relationship and Lagrangian transport time, the roles of transport and photochemical processes in different seasons at Hok Tsui were also investigated. This study demonstrated unique applications of backward LPDM in observational data analysis as well as in understanding source-receptor relationships and multiscale transport of CO and O3. © 2013. Her Majesty the Queen in Right of Canada. American Geophysical Union.

Yuan X.,Hong Kong Polytechnic University
ICASSP, IEEE International Conference on Acoustics, Speech and Signal Processing - Proceedings | Year: 2012

A pre-processing technique is developed to track a polynomial-phase signal using an electromagnetic vector-sensor, which can be collocated or spatially-spread. The performance of the single-forgetting-factor algorithm incorporating the proposed pre-processing approach is improved significantly, and it even surpasses the performance of the multiple-forgetting-factor algorithm in a polynomial-phase source scenario. Simulation results verify the efficacy of the proposed technique. © 2012 IEEE.

Yang X.-L.,Central South University | Yin J.-H.,Hong Kong Polytechnic University
Rock Mechanics and Rock Engineering | Year: 2010

The upper bound theorem of limit analysis is employed to calculate the equivalent MC cohesion coefficient and friction angle to meet the demands of software written in terms of the Mohr-Coulomb (MC) failure criterion when the rock mass failure follows the modified HB failure criterion for slopes in limit state. A MC failure criterion, which is tangent to the actual modified HB failure criterion, is used to calculate the rate of external work and internal energy dissipation. The equivalent MC friction angle is obtained when the objective function is minimized. The equivalent MC friction angles and cohesion depend not only on the nonlinear HB failure criterion but also on the rock slope angles.

Zhao J.-L.,China Agricultural University | Zhou L.-G.,China Agricultural University | Wu J.-Y.,Hong Kong Polytechnic University
Applied Microbiology and Biotechnology | Year: 2010

This study examined the effects of biotic and abiotic elicitors on the production of diterpenoid tanshinones in Salvia miltiorrhiza cell culture. Four classes of elicitors were tested, heavy metal ions (Co2+, Ag +, Cd2+), polysaccharides (yeast extract and chitosan), plant response-signaling compounds (salicylic acid and methyl jasmonate), and hyperosmotic stress (with sorbitol). Of these, Ag (silver nitrate), Cd (cadmium chloride), and polysaccharide from yeast extract (YE) were most effective to stimulate the tanshinone production, increasing the total tanshinone content of cell by more than ten-fold (2.3 mg g-1 versus 0.2 mg g-1 in control). The stimulating effect was concentration-dependent, most significant at 25 μM of Ag and Cd and 100 mg l-1 (carbohydrate content) of YE. Of the three tanshinones detected, cryptotanshinone was stimulated most dramatically by about 30-fold and tanshinones I and IIA by no more than 5-fold. Meanwhile, most of the elicitors suppressed cell growth, decreasing the biomass yield by about 50% (5.1-5.5 g l-1 versus 8.9 g l-1 in control). The elicitors also stimulated the phenylalanine ammonia lyase activity of cells and transient increases in the medium pH and conductivity. The results suggest that the elicitor-stimulated tanshinone accumulation was a stress response of the cells. © 2010 Springer-Verlag.

Mak M.K.Y.,Hong Kong Polytechnic University
Clinical Neurology and Neurosurgery | Year: 2013

Objectives: Previous studies found that people with Parkinson's disease (PD) walked at a slower speed and with significantly shorter stride length and/or increase in variability of stride length than control subjects. The present study aimed to examine whether difference existed in amplitude and variability of step length between control and PD subjects if they walked at a similar speed. Methods: This was a cross-sectional study. Thirteen PD patients and 15 healthy control subjects were instructed to walk at a similar speed on a treadmill under 2 randomized conditions: walking alone (Walko) and walking with digit subtraction of 3 (Walkcalculation). Amplitude of step length (cm), variability of step length (%), and percent accuracy of the calculation task (%) were recorded and analysed. Results: During both Walk o and Walkcalculation, PD patients had significantly shorter step length and larger step length variability than control subjects (p < 0.05). When a cognitive task was added to walking, PD patients showed a significant decrease in step length without further change in step length variability (p < 0.05). Conclusion: As reduced step length persisted when the control subjects walked at a speed similar to that of patients, our finding suggests that PD patients had a fundamental problem in regulating the amplitude of step length during walking. © 2012 Elsevier B.V.

Chiu T.M.L.,Hong Kong Polytechnic University | Eysenbach G.,Center for Global eHealth Innovation
International Journal of Medical Informatics | Year: 2011

Purpose: The purpose of this qualitative study was to improve understanding of family caregivers' use of Web-based intervention support by integrating three theoretical models. The study applied the Anderson's model of health service utilization, Venkatesh's theory of technology acceptance, and Chatman's and Wilson's information behavior theories. Methods: This qualitative study is part of a larger study. An interpretive grounded theory approach was used to conduct in-depth interviews with Chinese caregivers of family members with dementia. The caregivers received Internet-based information support and personalized e-mail intervention. A purposive sample of fourteen caregivers was selected to participate in the interviews. Constant comparison, analytic memoing, case analysis, and concept mapping were used to conduct theoretical triangulation analysis. Results: Three main factors influenced the use of the intervention: (a) caregiver needs, which are influenced by personal capacity, social support available, and caregiving belief; (b) information communication technology (ICT) factors, including accessibility barriers and perceived efforts to use the technology; and (c) style of using the technology, such as preference for using e-mail or the customized Website. The personal capacity of caregivers was influenced by many factors, including computer and language proficiency, health service knowledge, caregiving competence and competing roles and responsibilities. Social support available for caregivers included available computer, language or caregiving support and health service knowledge. Caregiving belief included traditional belief of giving care, and health belief of the illness. New caregivers needed a different kind of support intervention compared with experienced caregivers. Caregivers with different amounts of experience tended to have different learning styles, with new caregivers preferring interactive intervention and more experienced caregivers preferring more reflective learning. Conclusions: This study reinforced the findings of the larger quantitative study that it is important to address both care-giving needs and technology factors in Internet-based intervention. The quantitative study found that less competent caregivers with more positive attitudes towards technology tended to use the intervention more frequently. In this qualitative research, the findings revealed that caregiver needs, ICT factors, and style of use explained the pattern of intervention use. This new conceptualization has integrated information acceptance, health service utilization, and information behavior theories. More studies will be needed to confirm if the proposed concept can explain or predict the usage behavior in other Web-based interventions. © 2011 Elsevier Ireland Ltd.

Pang S.-K.,Hong Kong Polytechnic University
Electrochimica Acta | Year: 2015

Methanol crossover on the cathodes causes significant performance loss in direct methanol fuel cells, and the parasitic current induced by the electrochemical oxidation of methanol on the cathodes is believed to be the cause. Palladium cathodes are known to bear resistance to methanol but not platinum cathodes. By means of the density functional theory (DFT), the distorted molecular structure of the adsorbed methanol on platinum was revealed, and this distorted molecular structure indicates that platinum makes methanol has a tendency toward the elimination of the first hydrogen (involved in the first step of electrochemical oxidation of methanol) in electric neutrality, and loss of an electron can reinforce this tendency. However, palladium cannot distort the molecular structure of the adsorbed methanol, even in the loss of electron condition. The activation energies and the reaction energies calculated by means of DFT also show that after losing an electron, the elimination of the first hydrogen on platinum is more kinetically and thermodynamically favourable than that on palladium. These computational results can explain the experimental findings that no parasitic current is induced at palladium cathodes, but not at platinum cathodes; therefore, palladium cathodes have a methanol-resistance property. © 2015 Elsevier Ltd. All rights reserved.

Chan Z.C.Y.,Hong Kong Polytechnic University
Nurse Education in Practice | Year: 2014

Nursing is a profession that closely related to human life, and nurses are required to demonstrate critical thinking and creativity in providing health care services. However, traditional teaching approaches usually limit students' autonomy and freedom of expressing their thoughts and feelings. In order to develop the corresponding competence of nursing students, I adopted three teaching innovations, namely writing poems, composing songs, and using role plays in a nursing problem-based learning class in a university in Hong Kong. According to students' reflective notes and comments from two international expert reviewers, participating in these activities is a valuable experience and students were able to develop clinical reasoning, empathy, team spirit, motivation to learn, creativity, and ability to summarise and reconstruct knowledge. It is hoped that more innovative learning activities will be implemented, to prepare professional and ethical nurses in the future. It is also hoped that this study could provide other PBL educators some insights in innovative problem-based learning activities. © 2014 Elsevier Ltd.

Wong H.,Hong Kong Polytechnic University | Hu B.Q.,Wuhan University
Journal of Hydrology | Year: 2013

The extension evaluation method (EEM) has been applied to evaluate water quality. However, in real-life applications, sample data may be given as intervals because of errors produced in measurement, poor data brought by poor information, and imprecise data induced by human errors. To deal with data set in the form of a number of intervals, the interval extension evaluation method (IEEM) has been previously introduced. However, the correlative degrees that are obtained from IEEM may yield negative numbers. In evaluating water quality one generally assigns ranks or grades that are non-negative. Then it is expected that correlative degrees must be non-negative. This paper provides a novel method, i.e., the interval clustering approach (ICA), which is based on the grey clustering approach (GCA) and interval-valued fuzzy sets, to overcome this negativity issue. The method also introduces the notion of weightings in the form of intervals, by which interval samples can be analyzed with a view to delineating the important attributes via the interval weights. To demonstrate our proposed approach, the ICA is applied to evaluate the water quality of three different cross-sections of the Fen River, the second major branch river of the Yellow River in China. Our proposed method is a useful tool for the analysis of poorly measured data, poorly collected data and imprecise hydrological data which are very commonly encountered in water research. In brief, our method is novel for analyzing interval data. The GCA is a special case of the ICA, as these intervals are degenerated single values. © 2013 Elsevier B.V.

Zhang G.,Lanzhou University | Zhang Y.,Lanzhou University | Wang R.,Lanzhou University | Wang R.,Hong Kong Polytechnic University
Angewandte Chemie - International Edition | Year: 2011

Simple and efficient: A one-pot oxidative and catalytic enantioselective alkylation of α-C sp 3-H bonds adjacent to a nitrogen atom was realized for the first time. This novel strategy provides a simple, efficient, and environmentally friendly access to diverse optically active α-alkyl α-amino acid and C1-alkylated tetrahydroisoquinoline derivatives. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Deng H.-Y.,Hong Kong Polytechnic University
Physics Letters, Section A: General, Atomic and Solid State Physics | Year: 2011

We study the incipient ferroelectricity in strontium titanate (ST) by focusing on the Ti-sublattice, which is considered to carry the polar degrees of freedom. The O variables are eliminated to obtain an effective model for the Ti atoms, which are further subjected to an on-site double-well potential. The dielectric constant is calculated exactly on the mean-field level. Good agreement with experiment is achieved with only two parameters as inputs. Moreover, the inputs are tightly constrained by physical reasons. Our study sheds light on the transition-like behaviors that were observed in ST [K.A. Müller, H. Burkard, Phys. Rev. B 19 (1979) 3593]. According to the present analysis, such behaviors are argued to follow from the hopping between high energy intra-well states, and hence intrinsic to the double-well model. © 2011 Elsevier B.V. All rights reserved.

Yuen M.,Hong Kong Polytechnic University
Physics Letters, Section A: General, Atomic and Solid State Physics | Year: 2011

In this Letter, we construct a new class of blowup or global solutions with elementary functions to the 3-dimensional compressible or incompressible Euler and Navier-Stokes equations. And the corresponding blowup or global solutions for the incompressible Euler and Naiver-Stokes equations are also given. Our constructed solutions are similar to the famous Arnold-Beltrami-Childress (ABC) flow. The obtained solutions with infinite energy can exhibit the interesting behaviors locally. Furthermore, due to divu→=0 for the solutions, the solutions also work for the 3-dimensional incompressible Euler and Navier-Stokes equations. © 2011 Elsevier B.V. All rights reserved.

Yuen M.,Hong Kong Polytechnic University
Physics Letters, Section A: General, Atomic and Solid State Physics | Year: 2011

We construct non-radially symmetry solutions for the compressible 1-dimensional adiabatic Euler equations in this Letter. In detail, we perturb the linear velocity with a drifting term:u=c(t)x+b(t), to seek new solutions. Then, we transform the problem into the analysis of ordinary differential equations. By investigating the corresponding ordinary differential equations, a new class of blowup or global solutions can be given. Here, our constructed solutions can provide the mathematical explanations for the drifting phenomena of some propagation wave like Tsunamis. And when we adopt the Galilean-like transformation to a drifting frame, the constructed solutions are self-similar. © 2011 Elsevier B.V.

Cao Y.,Lanzhou University | Jiang X.,Lanzhou University | Liu L.,Lanzhou University | Shen F.,Lanzhou University | And 3 more authors.
Angewandte Chemie - International Edition | Year: 2011

A-spiro-ing: The title reaction of α-isothiocyanato imides and methyleneindolinones has been realized for the first time using 1 as the catalyst. This newly developed synthetic method provides a simple, efficient, and environmentally friendly way to access, in an enantioselective manner, densely functionalized spirooxindoles having three contiguous stereogenic centers. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Tang S.K.,Hong Kong Polytechnic University
Journal of the Acoustical Society of America | Year: 2012

The present study investigates the sound transmission loss across a section of an infinitely long duct where one or more narrow sidebranch tubes are installed flushed with the duct wall. The finite-element method is used to compute the wave propagation characteristics, and a simplified theoretical analysis is carried out at the same time to explain the wave mechanism at frequencies of high sound reduction. Results show that the high sound transmission loss at a particular frequency is due to the concerted actions of three consecutive sidebranch tubes with the most upstream one in the resonant state. The expansion chamber effect of the setup also plays a role in enhancing sound attenuation at non-resonance frequencies. Broadband performance of the device can be greatly enhanced by appropriate arrangements of tube lengths and/or by coupling arrays on the two sides of the duct. © 2012 Acoustical Society of America.

Jung H.-S.,University of Seoul | Lu Z.,U.S. Geological Survey | Zhang L.,Hong Kong Polytechnic University
IEEE Transactions on Geoscience and Remote Sensing | Year: 2013

The European Space Agency's Sentinel-1, a C-band imaging radar mission to be launched in mid-2013, will provide a continuity of radar data for monitoring the changing Earth. The azimuth resolution of Sentinel-1's background mode, interferometric wide-swath (IW) mode, is four times lower than that of European remote-sensing satellite (ERS) and Envisat systems. Therefore, the measurement accuracy of along-track displacement from Sentinel-1 IW images presumably will be significantly reduced. In this paper, we test the feasibility of along-track displacement measurement from Sentinel-1 IW mode. We simulate Sentinel-1 IW synthetic aperture radar (SAR) images from the ERS raw data that captured the coseismic deformation of the 1999 Hector Mine earthquake in California. Along-track displacement maps are generated using multiple-aperture interferometric SAR (MAI) and intensity tracking techniques, respectively, and are compared with GPS measurements. The root-mean-square (rms) error between the synthetic Sentinel-1 MAI and GPS measurements is about 9.6 cm, which corresponds to only 0.5 % of the azimuth resolution. The rms error between the along-track displacements from synthetic Sentinel-1 offset tracking and GPS is about 27.5 cm, which is about 1.4 % of the azimuth resolution. These results suggest that the MAI method will still be useful to measure along-track displacements from Sentinel-1 IW InSAR imagery and that it would be difficult to effectively measure the along-track displacements by the Sentinel-1 offset tracking method. © 2012 IEEE.

Decoursey C.A.,Hong Kong Polytechnic University
Computers and Education | Year: 2012

This paper explores the attitudes of teachers, as adult learners, towards learning to do animation. A part of popular culture which second-language students enjoy, until recently, animation has been technically too demanding for non-specialists to learn. Adult learners can experience e-learning as transformative, but also as a barrier. Thus, teacher reception is crucial in exploring the feasibility of animation as an instructional tool in language teaching. In all, 44 Hong Kong and mainland Chinese teachers were taught animation over ten weeks. Subsequently, three surveys elicited both quantitative and qualitative data. Appraisal analysis indicated teachers positively realised animation as valuable, worthwhile and satisfactory, but also difficult and time-consuming.; entailed high levels of communication. Quantitative data indicated their view that animation would be well-received by both colleagues and secondary language learners, as an instructional tool. © 2012 Elsevier Ltd. All rights reserved.

Huang K.,Hong Kong Polytechnic University | Lau V.K.N.,Hong Kong University of Science and Technology
IEEE Transactions on Information Theory | Year: 2012

This paper addresses the stability and queueing delay of space-division multiple access (SDMA) systems with bursty traffic, where zero-forcing beamforming enables simultaneous transmissions to multiple mobiles. Computing beamforming vectors relies on quantized channel state information (CSI) feedback (limited feedback) from mobiles. Define the stability region for SDMA as the set of multiuser packet-arrival rates for which the steady-state queue lengths are finite. Given perfect feedback of channel-direction information (CDI) and equal power allocation over scheduled queues, the stability region is proved to be a convex polytope having the derived vertices. A similar result is obtained for the case with perfect feedback of CDI and channel-quality information (CQI), where CQI allows scheduling and power control for enlarging the stability region. For any set of arrival rates in the stability region, multiuser queues are shown to be stabilized by the joint queue-and-beamforming control policy that maximizes the departure-rate-weighted sum of queue lengths. The stability region for limited feedback is found to be the perfect-CSI region multiplied by one minus a small factor. The required number of feedback bits per mobile is proved to scale logarithmically with the inverse of the above factor as well as linearly with the number of transmit antennas minus one. The effect of limited feedback on queueing delay is also quantified. CDI quantization errors are shown to multiply average queueing delay by a factor $M > 1$. For given $M\rightarrow 1$, the number of feedback bits per mobile is proved to be $O(-\log-{2}(1-1/M))$. © 1963-2012 IEEE.

Wong C.W.Y.,Hong Kong Polytechnic University
Journal of Supply Chain Management | Year: 2013

Although environmental sustainability has emerged as an important organizational capability to protect the environment and sustain businesses, there is little knowledge on how it is developed. This is of particular importance when environmental management no longer relies solely on an individual firm's efforts, but on its supply chain partners as well. Building on dynamic capabilities theory, environmental information integration (EII) is defined as the organizational capacity of sharing information on environmental management with supply chain partners to facilitate coordination of environmental management practices. This study examines how EII contributes to environmental management capabilities in terms of corporate environmental innovativeness and adaptability. The research model is empirically tested using data collected from 230 firms. The findings show that supplier EII is insufficient in improving environmental management capabilities. Internal EII contributes to corporate environmental adaptability, while customer EII engenders both corporate environmental innovativeness and adaptability. This study suggests that strategic values of EII go beyond the sharing of environmental management information between supply chain partners, simultaneously contributing to the environmental management capabilities of firms. This study contributes substantially to environmental management research by providing empirical evidence on the specific dimensions of EII in supply chains that contribute to environmental management capabilities and business values. © 2013 Institute for Supply Management, Inc.

Chan F.T.S.,Hong Kong Polytechnic University
International Journal of Advanced Manufacturing Technology | Year: 2010

In the fast-changing fashion market, being flexible and adaptive is a key to survival. Therefore, supply chain strategy like quick response is important in the fashion or textile industry. Selection of suppliers to support such strategies is thus one of the most critical activities, but is not well studied. Traditionally, suppliers are selected usually based on quantity requirement and cost, which are not the only important issues in the operation of a textile supply chain nowadays. This study presents an example on solving the supplier selection problem in the apparel industry by using the Analytical Hierarchy Process (AHP), which takes the operational performance (for example, flexibility, cost, and delivery) into account for supporting supply chain strategies. The system was implemented with the aid of the commercial software package Expert Choice. Based on the results from the AHP model, benefits of implementing quick response in apparel supply chains can also be verified. © 2010 Springer-Verlag London Limited.

Yuen M.,Hong Kong Polytechnic University
Journal of Mathematical Physics | Year: 2010

In this article, we study the self-similar solutions of the 2-component Camassa-Holm equations ρt+uρx+ρux=0, mt+2uxm+umx+σρρx=0, with m=u-α2uxx. By the separation method, we can obtain a class of blowup or global solutions for σ=1 or -1. In particular, for the integrable system with σ=1, we have the global solutions, ρ(t,x)=f(η)/a(3t)1/3 for η2<α2/ξ, ρ(t,x)=0 for η2≥α2/ξ, u(t,x)=ȧ(3t)/a(3t)x, ä(s)-ξ/3a(s)1/3=0,a(0)=a0>0,ȧ(0)=a1, f(η)=ξ-1/ξη2+(α/ξ)2, where η=xa(s)1/3 with s=3t; ξ>0 and α≥0 are arbitrary constants. Our analytical solutions could provide concrete examples for testing the validation and stabilities of numerical methods for the systems. © 2010 American Institute of Physics.

Chien W.T.,Hong Kong Polytechnic University | Thompson D.R.,Australian Catholic University
British Journal of Psychiatry | Year: 2014

Background Psychoeducation programmes for people with schizophrenia are shown to reduce relapses but few studies have indicated significant improvements in patients' illness awareness and insight, functioning, symptom severity or rates of readmission to hospital. Aims To examine the effects of a mindfulness-based psychoeducation programme for Chinese people with schizophrenia. Method A multisite randomised controlled trial was conducted with 107 out-patients with schizophrenia: 36 and 35 received a 6-month mindfulness-based psychoeducation and a conventional psychoeducation programme, respectively, and 35 received routine care alone. Patient outcome measures were psychiatric symptom severity, psychosocial functioning, social support, insight into illness/treatment, and frequency and duration of readmissions to hospital (ClinicalTrials.gov: trial registration NCT01667601). Results The mindfulness-based psychoeducation group reported significantly greater improvements in psychiatric symptoms, psychosocial functioning, insight into illness/treatment and duration of readmissions to hospital over 24 months when compared with the other two groups. Conclusions Mindfulness-based psychoeducation appears to be a promising approach to treatment for Chinese patients with schizophrenia. Declaration of interest None.

Garg A.,Nanyang Technological University | Tai K.,Nanyang Technological University | Savalani M.M.,Hong Kong Polytechnic University
International Journal of Advanced Manufacturing Technology | Year: 2014

The rapid prototyping (RP) processes, specifically selective laser melting (SLM), are popular for building complex 3D parts directly from the metal powder. The literature reveals that the properties such as surface roughness, waviness, bead width, compressive strength, tensile strength, wear, and dimensional accuracy of an SLM-fabricated prototype depend on the parameter settings of the SLM setup and can be improved by appropriate adjustment. For the selection of an optimal parameter setting, multi-gene genetic programming (MGGP), which develops the model structure and its coefficients automatically, can be applied. The model participating in the evolutionary stage of the MGGP method is a linear weighted sum of several genes (model trees) regressed using the least squares method. In this combination mechanism, the occurrence of gene of lower performance in the MGGP model can degrade its performance. This paper proposes a modified MGGP (M-MGGP) method using a stepwise regression approach such that the genes of lower performance are eliminated, and only the high performing genes are combined. The M-MGGP approach is applied on the bead width data obtained from the experiments conducted on the SLM machine, and its performance is found to be better than that of the standardized MGGP and artificial neural network (ANN) models. Between MGGP and ANN, ANN has shown better performance. Further, the parametric and sensitivity analysis conducted validates the robustness of our proposed model and is proved to capture the dynamics of the SLM process by unveiling important process parameters and the hidden non-linear relationships. © Springer-Verlag London 2014.

Chen X.,Hong Kong Polytechnic University | Ng M.K.,Hong Kong Baptist University | Zhang C.,Beijing Jiaotong University
IEEE Transactions on Image Processing | Year: 2012

Nonsmooth nonconvex regularization has remarkable advantages for the restoration of piecewise constant images. Constrained optimization can improve the image restoration using a priori information. In this paper, we study regularized nonsmooth nonconvex minimization with box constraints for image restoration. We present a computable positive constant θ for using nonconvex nonsmooth regularization, and show that the difference between each pixel and its four adjacent neighbors is either 0 or larger than θ in the recovered image. Moreover, we give an explicit form of θ for the box-constrained image restoration model with the non-Lipschitz nonconvex l p-norm (0

Lam J.S.L.,Nanyang Technological University | Lai K.-H.,Hong Kong Polytechnic University
Journal of Cleaner Production | Year: 2015

As a key trade facilitator, the impact of shipping on the global economy and societies cannot be underestimated. However, there are increasing trends of carbon emission caused by the shipping industry and the related cargo flow activities. As such, the adoption of green shipping practices (GSP) is increasingly popularized by shipping companies. This study aims to develop a decision-support model with systematic metrics for shipping companies to attain environmental sustainability in their operations. An integrated analytical approach which combines Analytical Network Process (ANP) with Quality Function Deployment (QFD) is proposed to serve this purpose. A case study of an international tanker shipping company is used to demonstrate the application of this approach to enhance eco-efficiency. The case results show how the ANP-QFD model can be deployed to understand customers' expectation for environmental management and develop operational measures for shipping companies to achieve environmental and market-oriented outcomes. Accordingly, this study develops the concept of Customer Cooperation Programme for Sustainability in the shipping management context. From the practical standpoint, shipping firms that emphasize sustainability as a competitive priority will benefit by communicating sustainability efforts to better serve their customers, particularly those keen on environmental preservation. The ANP-QFD approach is an integrative method helpful for shipping managers to incorporate the 'voice' of customers for greening into their decision-making and operations processes. The decision-support tool is useful for shipping companies to meet customer requirements for environmental performance and thus progress towards achieving more sustainable performance outcomes. © 2014 Elsevier Ltd. All rights reserved.

Chen J.,Hong Kong Polytechnic University
Social science & medicine (1982) | Year: 2013

China's rapid economic growth has had a serious impact on the environment. Environmental hazards are major sources of health risk factors. The migration of over 200 million people to heavily polluted urban areas is likely to be significantly detrimental to health. Based on data from the 2009 national household survey "Chinese Attitudes toward Inequality and Distributive Injustice" (N = 2866) and various county-level and municipal indicators, we investigate the disparities in subjective exposure to environmental hazards and associated health outcomes in China. This study focuses particularly on migration-residency status and county-level socio-economic development. We employ multiple regressions that account for the complex multi-stage survey design to assess the associations between perceived environmental hazards and individual and county-level indicators and between perceived environmental hazards and health outcomes, controlling for physical and social environments at multiple levels. We find that perceived environmental hazards are associated with county-level industrialization and economic development: respondents living in more industrialized counties report greater exposure to environmental hazards. Rural-to-urban migrants are exposed to more water pollution and a higher measure of overall environmental hazard. Perceived environmental risk factors severely affect the physical and mental health of the respondents. The negative effects of perceived overall environmental hazard on physical health are more detrimental for rural-to-urban migrants than for urban residents. The research findings call for restructuring the household registration system in order to equalize access to public services and mitigate adverse environmental health effects, particularly among the migrant population. Copyright © 2012 Elsevier Ltd. All rights reserved.

Tan S.-C.,Hong Kong Polytechnic University
IEEE Transactions on Industrial Electronics | Year: 2010

Power-electronics interface and the technique of pulsewidth modulation have been the heart of controlling the illumination intensity of lighting devices. It is, however, observed that for some lighting devices, the use of such a methodology leads to a lower energy-conversion efficiency (with a lower light intensity for the same amount of electrical input power) than potentially possible. The main problem is related to the saturable characteristic of the electrical-to-optical energy conversion, which follows that of an exponential characteristic, and the fast nature of this reaction in these lighting devices. This paper presents an in-depth discussion on the phenomenon and offers a solution to the problem. Specifically, it is proposed that an n -level type of driving approach to be adopted in the design and construction of power-electronic drivers for fast-response saturable lighting devices to achieve a quasi-optimal lighting efficacy. The result is energy saving for the same required light illumination. Theoretical proofs and experimental results are provided for verification. The topic of discussion in this paper and the proposed approach are not only applicable to the area of electronic circuits and lighting devices, but also to general controlled systems which comprise components that inherit a saturable and fast-reactive energy conversion characteristic. © 2010 IEEE.

Wu Q.,Nanjing Southeast University | Law R.,Hong Kong Polytechnic University
Information Sciences | Year: 2010

This paper proposes a robust loss function that penalizes hybrid noise (i.e., Gaussian noise, singularity points, and larger magnitude noise) in a complex fuzzy fault-diagnosis system. A mapping relationship between fuzzy numbers and crisp real numbers that allows a fuzzy sample set to be transformed into a crisp real sample set is also presented. Furthermore, the paper proposes a novel fuzzy robust wavelet support vector classifier (FRWSVC) based on a wavelet base function and develops an adaptive Gaussian particle swarm optimization (AGPSO) algorithm to seek the optimal unknown parameter of the FRWSVC. The results of experiments that apply the hybrid diagnosis model based on the FRWSVC and the AGPSO algorithm to fault diagnosis demonstrate that it is both feasible and effective. Tests comparing the method proposed in this paper against other fuzzy support vector classifier (FSVC) machines show that it outperforms them. © 2010 Elsevier Inc. All rights reserved.

Wonga W.K.,Hong Kong Polytechnic University | Zhao H.,East China University of Science and Technology
Information Fusion | Year: 2013

Recently, a number of studies have demonstrated that thermal infrared (IR) imagery offers a promising alternative to visible imagery in face recognition problems due to its invariance to visible illumination changes. However, thermal IR has other limitations such as being opaque to glass. As a result, thermal IR imagery is very sensitive to facial occlusion caused by eyeglasses. Fusion of the visible and thermal IR images is an effective way to solve this problem. In this paper, using the face reconstruction information of the visible images, we propose two thermal image reconstruction algorithms, called the visible information aided eyeglasses removing algorithm (VIAER) and the refined visible information aided eyeglasses removing algorithm (refined VIAER). Experiments on publicly available data set show the excellent performance of our algorithms. © 2012 Elsevier B.V. All rights reserved.

Zhang K.,Hong Kong Polytechnic University | Zhang K.,Chinese University of Hong Kong | Song H.,Chinese University of Hong Kong
Pattern Recognition | Year: 2013

Adaptive tracking-by-detection methods have been widely studied with promising results. These methods first train a classifier in an online manner. Then, a sliding window is used to extract some samples from the local regions surrounding the former object location at the new frame. The classifier is then applied to these samples where the location of sample with maximum classifier score is the new object location. However, such classifier may be inaccurate when the training samples are imprecise which causes drift. Multiple instance learning (MIL) method is recently introduced into the tracking task, which can alleviate drift to some extent. However, the MIL tracker may detect the positive sample that is less important because it does not discriminatively consider the sample importance in its learning procedure. In this paper, we present a novel online weighted MIL (WMIL) tracker. The WMIL tracker integrates the sample importance into an efficient online learning procedure by assuming the most important sample (i.e., the tracking result in current frame) is known when training the classifier. A new bag probability function combining the weighted instance probability is proposed via which the sample importance is considered. Then, an efficient online approach is proposed to approximately maximize the bag likelihood function, leading to a more robust and much faster tracker. Experimental results on various benchmark video sequences demonstrate the superior performance of our algorithm to state-of-the-art tracking algorithms. © 2012 Elsevier Ltd All rights reserved.

Guilbert E.,Hong Kong Polytechnic University
GeoInformatica | Year: 2013

Contour lines are important for quantitatively displaying relief and identifying morphometric features on a map. Contour trees are often used to represent spatial relationships between contours and assist the user in analysing the terrain. However, automatic analysis from the contour tree is still limited as features identified on a map by sets of contours are not only characterised by local relationships between contours but also by relationships with other features at different levels of representation. In this paper, a new method based on adjacency and inclusion relationships between regions defined by sets of contours is presented. The method extracts terrain features and stores them in a feature tree providing a description of the landscape at multiple levels of detail. The method is applied to terrain analysis and generalisation of a contour map by selecting the most relevant features according to the purpose of the map. Experimental results are presented and discussed. © 2012 Springer Science+Business Media, LLC.

Cheng G.,The Hong Kong Institute of Education | Chau J.,Hong Kong Polytechnic University
Internet and Higher Education | Year: 2013

This study explores the relationship between students' self-regulated learning (SRL) ability and their ePortfolio achievement in a language enhancement programme. Undergraduate students (N = 26) were asked to create several ePortfolio showcases to demonstrate their English language learning experience over a period of three months. Upon completion of the programme, participants' SRL ability was measured by the Motivated Strategies for Learning Questionnaire (MSLQ) and their achievement was assessed using an ePortfolio scoring system. Our findings reveal that higher-order cognitive skills (i.e. elaboration, organization, critical thinking), metacognitive control strategies (i.e. self-regulation) and collaborative learning strategies (i.e. peer learning) were positively correlated with the ePortfolio achievement of participants. The results not only provide evidence to support that ePortfolio development is a complex process that cannot simply be driven by surface learning strategies, but also suggest that students should be equipped with appropriate SRL strategies to successfully participate in and benefit from ePortfolio activities. © 2012 Elsevier Inc.

Dong M.,University of Alberta | Meira P.C.M.,University of Campinas | Xu W.,University of Alberta | Chung C.Y.,Hong Kong Polytechnic University
IEEE Transactions on Smart Grid | Year: 2013

This paper presents a technique to extract load signatures non-intrusively by using the smart meter data. Load signature extraction is different from load activity identification. It is a new and important problem to solve for the applications of non-intrusive load monitoring (NILM). For a target appliance whose signatures are to be extracted, the proposed technique first selects the candidate events that are likely to be associated with the appliance by using generic signatures and an event filtration step. It then applies a clustering algorithm to identify the authentic events of this appliance. In the third step, the operation cycles of appliances are estimated using an association algorithm. Finally, the electric signatures are extracted from these operation cycles. The results can have various applications. One is to create signature databases for the NILM applications. Another is for load condition monitoring. Validation results based on the data collected from three actual houses and a laboratory experiment have shown that the proposed method is a promising solution to the problem of load signature collection. © 2013 IEEE.

Liu J.,University of West Florida | Wang Z.-A.,Hong Kong Polytechnic University
Journal of Biological Dynamics | Year: 2012

We establish the existence of global classical solutions and non-trivial steady states of a one-dimensional attraction-repulsion chemotaxis model subject to the Neumann boundary conditions. The results are derived based on the method of energy estimates and the phase plane analysis. © 2012 Copyright Taylor and Francis Group, LLC.

Lam C.-H.,Hong Kong Polytechnic University | Tsui O.K.C.,Boston University
Physical Review E - Statistical, Nonlinear, and Soft Matter Physics | Year: 2013

We study the driven flow of an unentangled glassy polymer film with a free upper surface and supported below by a substrate using nonequilibrium molecular dynamics simulations based on a bead-spring model. Above the glass transition temperature Tg, simple Poiseuille laminar flow is observed with the film mobility defined as the flow current density per unit pressure gradient scaling as h3 with the film thickness h. Below Tg, the film mobility becomes independent of h, signifying surface transport. This is in full agreement with recent experiments on the time evolution of capillary waves in polystyrene films supported by silica. A mobile layer is found responsible for the surface transport, as previously conjectured. Our result also shows that it has a velocity profile decaying exponentially into the bulk. © 2013 American Physical Society.

Dong W.,Xidian University | Zhang L.,Hong Kong Polytechnic University | Shi G.,Xidian University | Li X.,West Virginia University
IEEE Transactions on Image Processing | Year: 2013

Sparse representation models code an image patch as a linear combination of a few atoms chosen out from an over-complete dictionary, and they have shown promising results in various image restoration applications. However, due to the degradation of the observed image (e.g., noisy, blurred, and/or down-sampled), the sparse representations by conventional models may not be accurate enough for a faithful reconstruction of the original image. To improve the performance of sparse representation-based image restoration, in this paper the concept of sparse coding noise is introduced, and the goal of image restoration turns to how to suppress the sparse coding noise. To this end, we exploit the image nonlocal self-similarity to obtain good estimates of the sparse coding coefficients of the original image, and then centralize the sparse coding coefficients of the observed image to those estimates. The so-called nonlocally centralized sparse representation (NCSR) model is as simple as the standard sparse representation model, while our extensive experiments on various types of image restoration problems, including denoising, deblurring and super-resolution, validate the generality and state-of-the-art performance of the proposed NCSR algorithm. © 1992-2012 IEEE.

Lee P.K.C.,Hong Kong Polytechnic University | To W.M.,Macao Polytechnic Institute | Yu B.T.W.,Macao Polytechnic Institute
International Journal of Production Economics | Year: 2013

Teams have been regarded as an integral element of a number of operations management (OM) strategies and many of their related concepts such as group dynamics and people issues are considered important for knowledge of behavioral operations. In practice, the management of operational service teams is challenging for OM managers because of its potential problems such as unstructured tasks and negative member behavior. In this study, operational service teams' attribute patterns and their associated performance levels were examined using a configuration approach. Based on the data collected from 201 operational service teams in Hong Kong and Macao (China), an empirical taxonomy was developed, comprising team attributes including team use, organizational support, clear goals, collaborative climate, coercive influence and adaptation difficulty. The taxonomy indicated that there were three attribute patterns among the sample teams. The analyzed results indicated that the sample teams of different attribute patterns achieved markedly different levels of team performance. The study contributes to the literature by providing empirical evidence that team attributes and their combined patterns are determinants of operational service teams' performance. It also contributes to practitioners by reporting the current status of operational service team management and offering guidelines on enhancement of team performance. © 2012 Elsevier B.V. All rights reserved.

Wong P.K.,University of Macau | Wong K.I.,University of Macau | Vong C.M.,University of Macau | Cheung C.S.,Hong Kong Polytechnic University
Renewable Energy | Year: 2015

This study presents the optimization of biodiesel engine performance that can achieve the goal of fewer emissions, low fuel cost and wide engine operating range. A new biodiesel engine modeling and optimization framework based on extreme learning machine (ELM) is proposed. As an accurate model is required for effective optimization result, kernel-based ELM (K-ELM) is used instead of basic ELM because K-ELM can provide better generalization performance, and the randomness of basic ELM does not occur in K-ELM. By using K-ELM, a biodiesel engine model is first created based on experimental data. Logarithmic transformation of dependent variables is used to alleviate the problems of data scarcity and data exponentiality simultaneously. With the K-ELM engine model, cuckoo search (CS) is then employed to determine the optimal biodiesel ratio. A flexible objective function is designed so that various user-defined constraints can be applied. As an illustrative study, the fuel price in Macau is used to perform the optimization. To verify the modeling and optimization framework, the K-ELM model is compared with a least-squares support vector machine (LS-SVM) model, and the CS optimization result is compared with particle swarm optimization and experimental results. The evaluation result shows that K-ELM can achieve comparable performance to LS-SVM, resulting in a reliable prediction result for optimization. It also shows that the optimization results based on CS is effective. © 2014 Elsevier Ltd.

Drug analysis is an indispensable task in controlling drug abuse, which is a serious problem worldwide nowadays. In this study, we report a simple and rapid approach for detection and quantitation of drugs-of-abuse in urine and oral fluid by wooden-tip electrospray ionization mass spectrometry (WT-ESI-MS). We demonstrated that ketamine, one of the most common abused drugs, and its major metabolite, norketamine, in raw urine and oral fluid could be readily detected and quantified by WT-ESI-MS with only little sample preparation and no chromatographic separation, and the analytical performances, including the linear range, accuracy, precision, LOD and LOQ, were well acceptable for analysis of real samples.

Wang X.,Nanjing University of Science and Technology | Xie X.,Nanjing University of Science and Technology | Cheng T.C.E.,Hong Kong Polytechnic University
International Journal of Production Economics | Year: 2013

We study the order acceptance and scheduling problem in a two-machine flowshop. The firm receives a pool of orders before a planning period, each of which is characterized by revenue, processing times on machines 1 and 2, a due date, and a tardiness penalty. The firm seeks to decide on the orders to accept and schedule the accepted orders so as to maximize the total net revenue. We formulate the problem as mixed-integer linear programming models, and develop a heuristic and a branch-and-bound (B&B) algorithm based on some derived dominance rules and relaxation techniques. We assess the performance of the B&B algorithm and the heuristic via computational experiments. The computational results show that the B&B algorithm can solve problem instances with up to 20 jobs within a reasonable time while the heuristic is efficient in approximately solving large instances of the problem. © 2012 Elsevier B.V. All rights reserved.

Zhao X.,Hong Kong Polytechnic University | Tong X.,Beijing Normal University
Computational Statistics and Data Analysis | Year: 2011

This paper discusses regression analysis of panel count data that arise naturally when recurrent events are considered. For the analysis of panel count data, most of the existing methods have assumed that observation times are completely independent of recurrent events or given covariates, which may not be true in practice. We propose a joint modeling approach that uses an unobserved random variable and a completely unspecified link function to characterize the correlations between the response variable and the observation times. For inference about regression parameters, estimating equation approaches are developed without involving any estimation for latent variables, and the asymptotic properties of the resulting estimators are established. In addition, a technique is provided for assessing the adequacy of the model. The performance of the proposed estimation procedures are evaluated by means of Monte Carlo simulations, and a data set from a bladder tumor study is analyzed as an illustrative example. © 2010 Elsevier B.V. All rights reserved.

Choi T.-M.,Hong Kong Polytechnic University
Resources Policy | Year: 2015

Sustainable management of mining operations requires careful considerations of environmental sustainability, economic sustainability and corporate social responsibility (CSR) related issues. Motivated by prior studies on accidents associated with mining operations, this paper builds a formal optimization model to address the above three sustainability related issues for a mining operation with the optimal decision on mining quantity. To be specific, we model the number of accidents as a Poisson distribution with a quantity dependent distribution parameter. We formulate the objective function via the mean-variance approach, and incorporate analytical constraints which relate to environmental sustainability and CSR into the model. We analytically derive the algorithm which can find the globally optimal solution for the optimization problem. After that, we further analyse when the mining company should consider implementing (i) the pollutant reduction technology, and (ii) the accident reduction technology. It is interesting to find that the mining company's degree of risk aversion affects the choice of pollutant reduction technology, but not the choice of accident reduction technology. Several other important insights are also analytically derived. © 2014 Elsevier Ltd.

Zhang H.,Hong Kong Polytechnic University | Darvell B.W.,Kuwait University
Acta Biomaterialia | Year: 2010

Long and uniform HA whiskers with high crystallinity, controlled morphology and high aspect ratio were successfully synthesized by hydrothermal homogeneous precipitation using acetamide. Compared with the additive urea, which is commonly used to raise the pH to drive nucleation and growth of HA crystals, acetamide has a low hydrolysis rate under the required hydrothermal conditions. This allows better and easier control, giving rise to rapid growth of whiskers at a low supersaturation. Whisker length and width were in turn determined by solution conditions, including the concentration of Ca and PO4. Whiskers had a mean length of 60-116 μm and an aspect ratio of 68-103 for starting solutions containing 42-84 mmol L1Ca and 25-50 mmol L 1PO4with a fixed Ca/P ratio of 1.67. Such whiskers are favourable for their improved bone bonding and bioactivity, as well as their mechanical properties. Whiskers were slightly Ca-deficient with Ca/P= 1.60-1.65, with the preferred direction of growth along the c-axis. Variation of acetamide concentration did not affect the constitution, the crystallinity or the crystal growth habit. © 2010 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Zhu X.,Guangxi Normal University | Zhang L.,Hong Kong Polytechnic University | Huang Z.,Queensland University of Technology
IEEE Transactions on Image Processing | Year: 2014

Hashing is becoming increasingly important in large-scale image retrieval for fast approximate similarity search and efficient data storage. Many popular hashing methods aim to preserve the kNN graph of high dimensional data points in the low dimensional manifold space, which is, however, difficult to achieve when the number of samples is big. In this paper, we propose an effective and efficient hashing approach by sparsely embedding a sample in the training sample space and encoding the sparse embedding vector over a learned dictionary. To this end, we partition the sample space into clusters via a linear spectral clustering method, and then represent each sample as a sparse vector of normalized probabilities that it falls into its several closest clusters. This actually embeds each sample sparsely in the sample space. The sparse embedding vector is employed as the feature of each sample for hashing. We then propose a least variance encoding model, which learns a dictionary to encode the sparse embedding feature, and consequently binarize the coding coefficients as the hash codes. The dictionary and the binarization threshold are jointly optimized in our model. Experimental results on benchmark data sets demonstrated the effectiveness of the proposed approach in comparison with state-of-the-art methods. © 1992-2012 IEEE.

Ali G.,Asian Institute of Technology | Abbas S.,Hong Kong Polytechnic University | Mueen Qamer F.,International Center for Integrated Mountain Development
Renewable and Sustainable Energy Reviews | Year: 2013

Backcasting is not a new concept for scientists dealing with carbon mitigation or climate change mitigation issues around the world, but could be an innovative idea for public, local, and national policy planners as they are so far only familiar with forecast scenarios for different issues and sectors. Defining a roadmap to achieving low carbon targets and explaining these targets in quantitative form as much as possible is known as backcasting. Plenty of computer-based quantitative models and tools are used to outline low carbon society scenarios in the Asia-Pacific region and implementations of such models are underway. This paper spotlights these quantitative models and tools which are used to achieve backcasting benchmarks. These models are critically reviewed for their functioning and real possibilities on ground levels and suggestions have been made to improve practical implementation in developing Asia. The study found that all these models are highly acceptable and applicable in Asian countries but actual applications are rare, with Japan as the leading country in implementing such applications, followed by Malaysia. Estimation of CO 2 sinks, open availability, and energy service demands (built-in option) are major weaknesses of the models. We also concluded that these computer-based quantitative models are helpful for almost all of the countries of the Asia-Pacific region facing such issues as data limitation, fewer resources, and lack of government participation. © 2013 Elsevier Ltd.

Xu N.Z.,Hong Kong Polytechnic University | Chung C.Y.,University of Saskatchewan
IEEE Transactions on Smart Grid | Year: 2015

In the foreseeable future, power grids will be managed largely with demand-side management (DSM) programs. With the growing population of electric vehicles (EVs) and the emergence of aggregators, DSM will surely introduce more intense competition to the markets. Since EV charging produces a large amount of time-flexible load in power systems, competition of its management could become a major game. This paper first formulates the game of EV charging management to describe this major form of the future DSM competition and then studies three challenges inherent in it: 1) inefficiency of Nash equilibria; 2) the game of chicken; and 3) cheating on private information. It is found that a central regulator is required to prevent these drawbacks. Solutions are proposed and a central governing procedure is also presented. The notion of the game of EV charging management is compatible with DSM programs that are able to schedule load flexibly over multiple time periods. © 2010-2012 IEEE.

Wong W.K.,Hong Kong Polytechnic University | Zhao H.T.,East China University of Science and Technology
Pattern Recognition | Year: 2012

In the past few years, the computer vision and pattern recognition community has witnessed a rapid growth of a new kind of feature extraction method, the manifold learning methods, which attempt to project the original data into a lower dimensional feature space by preserving the local neighborhood structure. Among these methods, locality preserving projection (LPP) is one of the most promising feature extraction techniques. Unlike the unsupervised learning scheme of LPP, this paper follows the supervised learning scheme, i.e. it uses both local information and class information to model the similarity of the data. Based on novel similarity, we propose two feature extraction algorithms, supervised optimal locality preserving projection (SOLPP) and normalized Laplacian-based supervised optimal locality preserving projection (NL-SOLPP). Optimal here means that the extracted features via SOLPP (or NL-SOLPP) are statistically uncorrelated and orthogonal. We compare the proposed SOLPP and NL-SOLPP with LPP, orthogonal locality preserving projection (OLPP) and uncorrelated locality preserving projection (ULPP) on publicly available data sets. Experimental results show that the proposed SOLPP and NL-SOLPP achieve much higher recognition accuracy. © 2011 Elsevier Ltd. All rights reserved.

Cai X.,Northwest University, China | Li W.,Hong Kong Polytechnic University
IEEE Transactions on Audio, Speech and Language Processing | Year: 2012

Manifold-ranking has been recently exploited for query-focused summarization. It propagates query relevance from the given query to the document sentences by making use of both the relationships among the sentences and the relationships between the given query and the sentences. The sentences in a document set can be grouped into several topic themes with each theme represented by a cluster of highly related sentences. However, it is a well-recognized fact that a document set often covers a number of such topic themes. In this paper, we present a novel model to enhance manifold-ranking based relevance propagation via mutual reinforcement between sentences and theme clusters. Based on the proposed model, we develop two new sentence ranking algorithms, namely the reinforcement after relevance propagation (RARP) algorithm and the reinforcement during relevance propagation (RDRP) algorithm. The convergence issues of the two algorithms are examined. When evaluated on the DUC2005-2007 datasets and TAC2008 dataset, the performance of the two proposed algorithms is comparable with that of the top three systems. The results also demonstrate that the RDRP algorithm is more effective than the RARP algorithm. © 2012 IEEE.

Baba-Kishi K.Z.,Hong Kong Polytechnic University
Journal of Applied Crystallography | Year: 2011

Electron diffraction patterns recorded using a scanning transmission electron microscope (STEM) from PbMg1/3Nb2/3O3 (PMN) crystallites and PbZn1/3Nb2/3O3 (PZN) crystals show weak and systematic continuous diffuse streaking along the 110 directions. Detailed high-angle annular dark-field (HAADF) images recorded via an aberration-corrected STEM show that the B-site cations in PMN and PZN undergo correlated and long-range displacements towards the Pb2+ ions on the (110) planes. The planar B-site displacement measured from the centres of the octahedra is about 0.3-0.5 Å in PMN and about 0.20-0.4 Å in PZN. In the HAADF images of the PMN crystallites and PZN crystals studied, there is insufficient evidence for systematic long-range planar displacements of the Pb2+ ions. The observed Pb2+ ion displacements in PMN and PZN appear randomly distributed, mostly displaced along 110 towards the B-site columns. There is also evidence of possible stress-related distortion in certain unit cells of PMN. In the relaxors studied, two distinct types of displacements were observed: one is the long-range planar B-site spatial displacement on the (110) planes, correlated with the Pb2+ ions, possibly resulting in the observed diffuse streaking; the other is short-range Pb2+ ion displacement on the (110) planes. The observed displacement status indicates a mutual attraction between the Pb ions and the B-site cations in which the B sites undergo the largest spatial displacements towards the Pb ions along 110. © 2011 International Union of Crystallography Printed in Singapore-all rights reserved.

Pin T.W.,Hong Kong Polytechnic University
Archives of Physical Medicine and Rehabilitation | Year: 2014

Objective To systematically review the psychometric evidence on the 2-minute walk test (2MWT). Data Sources Electronic searches of databases including MEDLINE, CINAHL, Academic Search Premier, SPORTDiscus, PsycINFO, EMBASE, the Cochrane Library, and DARE were done until February 2014 using a combination of subject headings and free texts. Study Selection Studies were included if psychometric properties of the 2MWT were (1) evaluated; (2) written as full reports; and (3) published in English language peer-reviewed journals. Data Extraction A modified consensus-based standard for the selection of health measurement instruments checklist was used to rate the methodological quality of the included studies. A quality assessment for statistical outcomes was used to assess the measurement properties of the 2MWT. Data Synthesis Best-evidence synthesis was collated from 25 studies of 14 patient groups. Only 1 study was found that examined the 2MWT in the pediatric population. The testing procedures of the 2MWT varied across the included studies. Reliability, validity (construct and criterion), and responsiveness of the 2MWT also varied across different patient groups. Moderate to strong evidence was found for reliability, convergent validity, discriminative validity, and responsiveness of the 2MWT in frail elderly patients. Moderate to strong evidence for reliability, convergent validity, and responsiveness was found in adults with lower limb amputations. Moderate to strong evidence for validity (convergent and discriminative) was found in adults who received rehabilitation after hip fractures or cardiac surgery. Limited evidence for the psychometric properties of the 2MWT was found in other population groups because of methodological flaws. Conclusions There is inadequate breadth and depth of psychometric evidence of the 2MWT for clinical and research purposes - specifically, minimal clinically important changes and responsiveness. More good-quality studies are needed, especially in the pediatric population. Consensus on standardized testing procedures of the 2MWT is also required. © 2014 by the American Congress of Rehabilitation Medicine.

Ye H.-Q.,Hong Kong Polytechnic University | Yao D.D.,Columbia University
Operations Research | Year: 2012

We study a multiclass stochastic processing network operating under the so-called proportional fair allocation scheme, and following the head-of-the-line processor-sharing discipline. Specifically, each server's capacity is shared among the job classes that require its service, and it is allocated, in every state of the network, among the first waiting job of each class to maximize a log-utility function. We establish the limiting regime of the network under diffusion scaling, allowing multiple bottlenecks in the network, and relaxing some of the conditions required in prior studies. We also identify the class of allocation schemes among which the proportional fair allocation minimizes a quadratic cost objective function of the diffusion-scaled queue lengths, and we illustrate the limitation of this asymptotic optimality through a counterexample. © 2012 INFORMS.

Yang H.Y.,Singapore University of Technology and Design | Han Z.J.,CSIRO | Yu S.F.,Hong Kong Polytechnic University | Pey K.L.,Singapore University of Technology and Design | And 3 more authors.
Nature Communications | Year: 2013

Development of technologies for water desalination and purification is critical to meet the global challenges of insufficient water supply and inadequate sanitation, especially for point-of-use applications. Conventional desalination methods are energy and operationally intensive, whereas adsorption-based techniques are simple and easy to use for point-of-use water purification, yet their capacity to remove salts is limited. Here we report that plasma-modified ultralong carbon nanotubes exhibit ultrahigh specific adsorption capacity for salt (exceeding 400% by weight) that is two orders of magnitude higher than that found in the current state-of-the-art activated carbon-based water treatment systems. We exploit this adsorption capacity in ultralong carbon nanotube-based membranes that can remove salt, as well as organic and metal contaminants. These ultralong carbon nanotube-based membranes may lead to next-generation rechargeable, point-of-use potable water purification appliances with superior desalination, disinfection and filtration properties. © 2013 Macmillan Publishers Limited.

Mouratidis K.,Singapore Management University | Yiu M.L.,Hong Kong Polytechnic University
Proceedings of the VLDB Endowment | Year: 2012

Shortest path computation is one of the most common queries in location-based services (LBSs). Although particularly useful, such queries raise serious privacy concerns. Exposing to a (potentially untrusted) LBS the client's position and her destination may reveal personal information, such as social habits, health condition, shop- ping preferences, lifestyle choices, etc. The only existing method for privacy-preserving shortest path computation follows the obfus- cation paradigm; it prevents the LBS from inferring the source and destination of the query with a probability higher than a threshold. This implies, however, that the LBS still deduces some information (albeit not exact) about the client's location and her destination. In this paper we aim at strong privacy, where the adversary learns nothing about the shortest path query. We achieve this via estab- lished private information retrieval techniques, which we treat as black-box building blocks. Experiments on real, large-scale road networks assess the practicality of our schemes. © 2012 VLDB Endowment.

Hui E.C.M.,Hong Kong Polytechnic University | Bao H.,Zhejiang University of Finance and Economics
Land Use Policy | Year: 2013

Conflicts over land have arisen frequently in China during rapid urbanization and have caused adverse impacts. Different from previous researches on land conflict analyzing its causes, types, consequences, methods of assessment and management, this paper develops a new analytic framework from a behavioral perspective based on game theory. The framework concerns the logic and strategy of conflicts of legal land acquisition, and that of illegal land conversion. The paper has established three innovative models: (1) the dynamic model for conflicts of legal land acquisition, (2) the game model of illegal land acquisition and (3) the game model of the black land market. These models are to explain how disputes and conflicts evolve and illustrate the logic and strategy of conflicts between local governments and farmers. Based on the Nash equilibrium of these models, the paper offers some important insights for policy direction in land acquisition and conflict management. © 2012 Elsevier Ltd.

Wong W.K.,Hong Kong Polytechnic University
Pattern Recognition | Year: 2012

How to define sparse affinity weight matrices is still an open problem in existing manifold learning algorithms. In this paper, we propose a novel unsupervised learning method called Non-negative Sparseness Preserving Embedding (NSPE) for linear dimensionality reduction. Differing from the manifold learning-based subspace learning methods such as Locality Preserving Projections (LPP), Neighbor Preserving Embedding (NPE) and the recently proposed sparse representation based Sparsity Preserving Projections (SPP); NSPE preserves the non-negative sparse reconstruction relationships in low-dimensional subspace. Another novelty of NSPE is the sparseness constraint, which is directly added to control the non-negative sparse representation coefficients. This gives a more ground truth model to imitate the actions of the active neuron cells of V1 of the primate visual cortex on information processing. Although labels are not used in the training steps, the non-negative sparse representation can still discover the latent discriminant information and thus provides better measure coefficients and significant discriminant abilities for feature extraction. Moreover, NSPE is more efficient than the recently proposed sparse representation based SPP algorithm. Comprehensive comparison and extensive experiments show that NSPE has the competitive performance against the unsupervised learning algorithms such as classical PCA and the state-of-the-art techniques: LPP, NPE and SPP. © 2011 Elsevier Ltd All rights reserved.

Cui X.,Shanghai University of Finance and Economics | Li X.,Hong Kong Polytechnic University | Li D.,Chinese University of Hong Kong
IEEE Transactions on Automatic Control | Year: 2014

When a dynamic optimization problem is not decomposable by a stage-wise backward recursion, it is nonseparable in the sense of dynamic programming. The classical dynamic programming-based optimal stochastic control methods would fail in such nonseparable situations as the principle of optimality no longer applies. Among these notorious nonseparable problems, the dynamic mean-variance portfolio selection formulation had posed a great challenge to our research community until recently. Different from the existing literature that invokes embedding schemes and auxiliary parametric formulations to solve the dynamic mean-variance portfolio selection formulation, we propose in this paper a novel mean-field framework that offers a more efficient modeling tool and a more accurate solution scheme in tackling directly the issue of nonseparability and deriving the optimal policies analytically for the multi-period mean-variance-type portfolio selection problems. © 1963-2012 IEEE.

We investigated the mechanism of the intrinsic persistent luminescence of Er2O3 in the A-type lattice based on first-principles calculations. We found that the native point defects were engaged in mutual subtle interactions in the form of chemical reactions between different charge states. The release of energy related to lattice distortion facilitates the conversion of energy for electrons to be transported between the valence band and the trap levels or even between the deep trap levels so as to generate persistent luminescence. The defect transitions that take place along the zero-phonon line release energy to enable optical transitions, with the exact amount of negative effective correlation energy determined by the lattice distortions. Our calculations on the thermodynamic transition levels confirm that both the visible and NIR experimentally observed intrinsic persistent luminescence (phosphor or afterglow) are related to the thermodynamic transition levels of oxygen-related defects, and the thermodynamic transition levels within different charge states for these defects are independent of the chemical potentials of the given species. Lattice distortion defects such as anion Frenkel (a-Fr) pair defects play an important role in transporting O-related defects between different lattice sites. To obtain red persistent luminescence that matches the biological therapeutic window, it is suggested to increase the electron transition levels between high-coordinated O vacancies and related metastable a-Fr defects; a close-packed core-shell structure is required to quench low-coordinated O-related defects so as to reduce the green band luminescence. We further established a conversed chain reaction (CCR) model to interpret the energy conversion process of persistent luminescence in terms of the inter-reactions of native point defects between different charge states. It is advantageous to use the study of defect levels combined with formation energies to suggest limits to doping energy and explain photostimulated luminescence in terms of native point defects. © the Owner Societies.

Confounders can be identified by one of two main strategies: empirical or theoretical. Although confounder identification strategies that combine empirical and theoretical strategies have been proposed, the need for adjustment remains unclear if the empirical and theoretical criteria yield contradictory results due to random error. We simulated several scenarios to mimic either the presence or the absence of a confounding effect and tested the accuracy of the exposure-outcome association estimates with and without adjustment. Various criteria (significance criterion, Change-in-estimate(CIE) criterion with a 10% cutoff and with a simulated cutoff) were imposed, and a range of sample sizes were trialed. In the presence of a true confounding effect, unbiased estimates were obtained only by using the CIE criterion with a simulated cutoff. In the absence of a confounding effect, all criteria performed well regardless of adjustment. When the confounding factor was affected by both exposure and outcome, all criteria yielded accurate estimates without adjustment, but the adjusted estimates were biased. To conclude, theoretical confounders should be adjusted for regardless of the empirical evidence found. The adjustment for factors that do not have a confounding effect minimally effects. Potential confounders affected by both exposure and outcome should not be adjusted for.

Fu T.-C.,Hong Kong Polytechnic University
Engineering Applications of Artificial Intelligence | Year: 2011

Time series is an important class of temporal data objects and it can be easily obtained from scientific and financial applications. A time series is a collection of observations made chronologically. The nature of time series data includes: large in data size, high dimensionality and necessary to update continuously. Moreover time series data, which is characterized by its numerical and continuous nature, is always considered as a whole instead of individual numerical field. The increasing use of time series data has initiated a great deal of research and development attempts in the field of data mining. The abundant research on time series data mining in the last decade could hamper the entry of interested researchers, due to its complexity. In this paper, a comprehensive revision on the existing time series data mining research is given. They are generally categorized into representation and indexing, similarity measure, segmentation, visualization and mining. Moreover state-of-the-art research issues are also highlighted. The primary objective of this paper is to serve as a glossary for interested researchers to have an overall picture on the current time series data mining development and identify their potential research direction to further investigation. © 2010 Elsevier Ltd. All rights reserved.

Zhang J.,Tsinghua University | Chung C.Y.,Hong Kong Polytechnic University | Han Y.,Tsinghua University
IEEE Transactions on Power Systems | Year: 2012

The residue method has been widely used for tuning power system stabilizers (PSSs) in large power systems to improve the damping of interarea oscillations. However, an additional PSS installation may affect the performance of existing PSSs due to interactions among different modes. When contending with several interarea oscillations, compromise among different modes becomes necessary. In this paper, a novel method based on modal decomposition is proposed for tuning PSSs for damping of the concerned interarea mode, while minimizing its effect on other modes by weakening the interactions among different modes. Design considerations, PSS structure and tuning procedure are formulated. The performance of the proposed method has been validated based on a two-area four-machine system and an actual large power system, China Southern Grid. © 1969-2012 IEEE.

Sun Y.-Y.,National Cheng Kung University | Pratt S.,Hong Kong Polytechnic University
Journal of Travel Research | Year: 2014

China outbound tourism contributes substantial foreign receipts but also creates carbon and water footprints at destinations. This study is set out to analyze whether this tourist segment is a preferred market from the economic and environmental perspectives. Using Taiwan as an example, the direct carbon emission per dollar and total carbon footprint per Chinese inbound visitor is about 20% more efficient than other markets because of a high consumption pattern, longer length of stay, and closer distance between the two regions. However, one unsatisfactory area is the total water footprint because of their high spending on food-related souvenirs that generates substantial water requirements from the agriculture sector. When forecasting the estimated growth of Chinese visitors in Taiwan to 2016, an additional 0.8% increase in economic output is expected at the expense of a 2.7% increase in CO2 emissions and a 3.0% increase in water use. © The Author(s) 2014.

Zhang X.,Hong Kong Polytechnic University
International Journal of Consumer Studies | Year: 2015

In addition to canonical political actions, political consumerism, i.e. using market purchases to express political and societal concerns, is becoming a new form of political participation, and it varies significantly among societies. Two society-level distinctions would account for such variations: the level of political freedom and the level of economic development. Using data from the 2004 International Social Survey Program, multilevel models estimate the effects of both individual and structural factors on individuals' political consumerism, i.e. boycotting certain products, across 21 countries (n=30 666). Political consumerism takes place in affluent countries with lower levels of political rights but higher levels of civil liberties. Individual-level political media uses, political orientation and demographics account for boycott behaviours as well. Furthermore, canonical discriminant analysis differentiates political consumption from other types of political behaviours. The study reveals that political consumerism results from the impacts of both individual characteristics and societal determinants. © 2015 John Wiley & Sons Ltd.

Hu B.Q.,Wuhan University | Kwong C.K.,Hong Kong Polytechnic University
Information Sciences | Year: 2014

In this paper, we discuss t-norm extension operations of general binary operation for fuzzy true values on a linearly ordered set, with a unit interval and a real number set as special cases. On the basis of it, t-norm operations of type-2 fuzzy sets and properties of type-2 fuzzy numbers are discussed. © 2013 Elsevier Inc. All rights reserved.

Gahl S.,University of California at Berkeley | Yao Y.,Hong Kong Polytechnic University | Johnson K.,University of California at Berkeley
Journal of Memory and Language | Year: 2012

Frequent or contextually predictable words are often phonetically reduced, i.e. shortened and produced with articulatory undershoot. Explanations for phonetic reduction of predictable forms tend to take one of two approaches: Intelligibility-based accounts hold that talkers maximize intelligibility of words that might otherwise be difficult to recognize; production-based accounts hold that variation reflects the speed of lexical access and retrieval in the language production system. Here we examine phonetic variation as a function of phonological neighborhood density, capitalizing on the fact that words from dense phonological neighborhoods tend to be relatively difficult to recognize, yet easy to produce. We show that words with many phonological neighbors tend to be phonetically reduced (shortened in duration and produced with more centralized vowels) in connected speech, when other predictors of phonetic variation are brought under statistical control. We argue that our findings are consistent with the predictions of production-based accounts of pronunciation variation. © 2011 Elsevier Inc.

Lam C.-H.,Hong Kong Polytechnic University
Journal of Applied Physics | Year: 2010

The pyramid-to-dome transition in Gex Si1-x on Si(100) initiated by step formation on pyramidal quantum dots is atomistically simulated using a multistate lattice model in two-dimensions incorporating effective surface reconstructions. Under quasiequilibrium growth conditions associated with low deposition rates, the transition occurs at island size nc following √ nc ∼ x-1.69 independent of temperature and deposition rate. The shape transition is found to be an activated process. Results are explained by a theory based on simple forms of facet energies and elastic energies estimated using a shallow island approximation. An asymptotic scaling relation nc 1/d ∼ x-2 for x→0 applicable to d=2 or 3 dimensions is derived. The shape transition energy barrier can be dominated by the interface energy between steep and shallow facets. © 2010 American Institute of Physics.

Chang R.C.Y.,Providence University | Kivela J.,Hong Kong Polytechnic University | Mak A.H.N.,University of Surrey
Tourism Management | Year: 2011

Many destination marketers have utilized gastronomy as a source of new products and activities to attract tourists. Despite the substantial rise in the Chinese outbound market, very little is known about how Chinese tourists evaluate their travel dining experiences. By using narrative analysis, this study examines attributes that may affect Chinese tourists' evaluation of their travel dining experiences. On-site participant observation and focus group interviews were conducted, respectively, with Mainland Chinese, Taiwanese, and Hong Kong group tourists, while they were on holiday in Australia. A total of 15 attributes were identified, which were classified under the following six categories: tourists' own food culture, the contextual factor of the dining experience, variety and diversity of food, perception of the destination, service encounter, and tour guide's performance. The respective implications of the attributes on travel dining experience are also discussed. © 2010 Elsevier Ltd.

Chang R.C.Y.,Providence University | Kivela J.,Hong Kong Polytechnic University | Mak A.H.N.,University of Surrey
Annals of Tourism Research | Year: 2010

Given the scarcity of research on tourist food preference, this study is a first attempt to generate in-depth understanding of Chinese tourists' food preferences in a culturally different environment by employing on-site participant observations and focus group interviews. It provides a detailed analysis of the motivational factors underlying the Chinese participants' food preferences when holidaying in Australia, and also proposes a typology that describes and contrasts the participants' tourism dining attitudes, motivations and behaviors. Furthermore, this study elucidates the influence of Chinese food culture on the participants' tourism dining behaviors and explores the disparities in dining behavioral patterns between the participants in terms of their dining motivations and the way they related tourism dining experiences to their daily experiences. © 2010 Elsevier Ltd.

Ni M.,Hong Kong Polytechnic University
International Journal of Hydrogen Energy | Year: 2012

Solid oxide fuel cells (SOFCs) can be operated in a reversed mode as electrolyzer cells for electrolysis of H2O and CO2. In this paper, a 2D thermal model is developed to study the heat/mass transfer and chemical/electrochemical reactions in a solid oxide electrolyzer cell (SOEC) for H2O/CO2 co-electrolysis. The model is based on 3 sub-models: a computational fluid dynamics (CFD) model describing the fluid flow and heat/mass transfer; an electrochemical model relating the current density and operating potential; and a chemical model describing the reversible water gas shift reaction (WGSR) and reversible methanation reaction. It is found that reversible methanation and reforming reactions are not favored in H 2O/CO2 co-electrolysis. For comparison, the reversible WGSR can significantly influence the co-electrolysis behavior. The effects of inlet temperature and inlet gas composition on H2O/CO2 co-electrolysis are simulated and discussed. Copyright © 2012, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights.

Ni M.,Hong Kong Polytechnic University
Journal of Power Sources | Year: 2012

Co-electrolysis of CO 2 and H 2O in a solid oxide electrolyzer cell (SOEC) offers a promising way for syngas production. In this study, an electrochemical model is developed to simulate the performance of an SOEC used for CO 2/H 2O co-electrolysis, considering the reversible water gas shift reaction (WGSR) in the cathode. The dusty gas model (DGM) is used to characterize the multi-component mass transport in the electrodes. The modeling results are compared with experimental data from the literature and good agreement is observed. Parametric simulations are performed to analyze the distributions of WGSR and gas composition in the electrode. A new method is proposed to quantify the contribution of WGSR to CO production by comparing the CO fluxes at the cathode-electrolyte interface and at t