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Search Results: 1 - 10 of 254825 matches for " David W. K. Yeung "
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Optimal Consumption under Uncertainties: Random Horizon Stochastic Dynamic Roy’s Identity and Slutsky Equation  [PDF]
David W. K. Yeung
Applied Mathematics (AM) , 2014, DOI: 10.4236/am.2014.52028
Abstract:

This paper extends Slutsky’s classic work on consumer theory to a random horizon stochastic dynamic framework in which the consumer has an inter-temporal planning horizon with uncertainties in future incomes and life span. Utility maximization leading to a set of ordinary wealth-dependent demand functions is performed. A dual problem is set up to derive the wealth compensated demand functions. This represents the first time that wealth-dependent ordinary demand functions and wealth compensated demand functions are obtained under these uncertainties. The corresponding Roy’s identity relationships and a set of random horizon stochastic dynamic Slutsky equations are then derived. The extension incorporates realistic characteristics in consumer theory and advances the conventional microeconomic study on consumption to a more realistic optimal control framework.

The Use of Neural Network Analysis of Brain 18F-FDG PET in Diagnosis of Dementia Subjects  [PDF]
Eric S. K. See, David Wai Chow Yeung
Journal of Biomedical Science and Engineering (JBiSE) , 2019, DOI: 10.4236/jbise.2019.122009
Abstract: Since the world population is aging rapidly, the prevalence of dementia is also rising rapidly thus causing a great impact on individuals, families and societies. Accurate classification and level measurement of dementia are very importance in the disease management. Numerous studies show that 18F-FDG-brain scan can differentiate various types of dementia. However, correct and accurate interpretation of nuclear images requires physicians who are well experienced. Therefore, it is worthwhile to build an automatic diagnostic system for it. In this paper, we present a novel method by using an artificial neural network (ANN) to analyze CortexID of brain PET-CT scan with clinical and laboratory data for dementia classification. Moreover, the ANN was trained to indicate the clinical severity of the disease as reflected by MMSE score. All ANNs were trained and tested again with an experienced physician’s seventy diagnosis and the results were very promising. The dementia classifier achieved 96% accuracy and the mapper network could correctly predict the MMSE score with 0.782 regression value.
APPLICATION OF ADVANCED MODELING IN SOCIAL WORK RESEARCH: A DEMONSTRATION OF MULTILEVEL PATH MODELING ANALYSIS BY MPLUS
Jerf W. K. YEUNG,Evans LI
Revista de Cercetare ?i Interven?ie Social? , 2011,
Abstract: Social work research has a crucial role in steering development, implementation and intervention of quality services and programs, in which application of more advanced statistical modeling analyses may redress the inaccuracy of findings and Type I error, that are mostly likely derived from conventional statistical procedures at individual-level analyses, such as ANOVA and OLS Regression. A multilevel path modeling analysis demonstrated by Mplus, an easy-to-use statistical program for advanced modeling, is suggested as a preliminary step to open up the window for other more sophisticated and useful statistical modeling procedures that are imperative for us to comprehend influences of multi-layer social situations on human behaviors and outcomes. Results showed that, in addition to knowledge on effects from a higher level, the multilevel path model increased explanatory power and rectify some augmented path parameters at individual level. Procedures and construction of model command syntaxes for the usage of Mplus are also reported in detail.
Case 2
Jacky Y.T. Yeung,David T.W. Wong
University of Toronto Medical Journal , 2004, DOI: 10.5015/utmj.v81i2.716
Abstract:
From the Physics of Interacting Polymers to Optimizing Routes on the London Underground
Chi Ho Yeung,David Saad,K. Y. Michael Wong
Physics , 2013, DOI: 10.1073/pnas.1301111110
Abstract: Optimizing paths on networks is crucial for many applications, from subway traffic to Internet communication. As global path optimization that takes account of all path-choices simultaneously is computationally hard, most existing routing algorithms optimize paths individually, thus providing sub-optimal solutions. We employ the physics of interacting polymers and disordered systems to analyze macroscopic properties of generic path-optimization problems and derive a simple, principled, generic and distributed routing algorithm capable of considering simultaneously all individual path choices. We demonstrate the efficacy of the new algorithm by applying it to: (i) random graphs resembling Internet overlay networks; (ii) travel on the London underground network based on Oyster-card data; and (iii) the global airport network. Analytically derived macroscopic properties give rise to insightful new routing phenomena, including phase transitions and scaling laws, which facilitate better understanding of the appropriate operational regimes and their limitations that are difficult to obtain otherwise.
Framing and Consolidating the Assessment of Outcome-Based Learning (OBL) in higher institutes in Hong Kong: An example case demonstration
Jerf W. K. YEUNG,Ai-Choo ONG
Revista de Cercetare ?i Interven?ie Social? , 2012,
Abstract: Aiming at providing quality teaching and learning in higher education, the pendulum of education has recently swung back to Outcome-Based Learning (OBL), in which higher education institutes need to assess the extent to which they have attained those learning outcomes planned for their students. However, OBL assessment is still at its developmental stage with amorphous nature. For this, the present paper proposes a mixed-method approach and consolidates the assessment by providing different methods, namely expert-panel assessment, qualitative longitudinal study, institute-level survey, and course-level evaluation, as means of obtaining more precise results. Integrating findings from different methods is also briefly discussed.
Evaluation of HemogloBindTM treatment for preparation of samples for cholinesterase analysis  [PDF]
Kevin G. McGarry, Ryan A. Bartlett, Nicholas J. Machesky, Thomas H. Snider, Robert A. Moyer, David T. Yeung, Matthew K. Brittain
Advances in Bioscience and Biotechnology (ABB) , 2013, DOI: 10.4236/abb.2013.412136
Abstract: Acetylcholine is an essential neurotransmitter found throughout the nervous system. Its action on postsynaptic receptors is regulated through hydrolysis by various carboxylesterases, especially cholinesterases (ChEs). The acute toxicity of organophosphate (OP) compounds is directly linked to their action as inhibitors of ChE. One widely used assay for evaluating ChE activity is a spectrophotometric method developed by Ellman et al. When the enzyme source is from tissues or, in particular, blood, hemoglobin displays a spectrophotometric peak at the same wave-length used to analyze cholinergic activity. This creates a substantial background that interferes with the Ellman’s assay and must be overcome in order to accurately monitor cholinesterase activity. Herein, we directly compare blood processing methods: classical method (1.67 ± 0.30 U/mL) and HemogloBindTM treatment (1.51 ± 0.17 U/mL), and clearly demonstrate that pretreatment of blood samples with HemoglobindTM is both a sufficient and rapid sample preparation method for the assessment of ChE activity using the Ellman’s method.
Development and validation of a Chinese family strengths measure for family services intervention in Hong Kong
Jerf W. K. YEUNG,Silvia S. W. LEE,Emily M. S. LEE,John DeFrain
Revista de Cercetare ?i Interven?ie Social? , 2012,
Abstract: This article reports the development and validation of a family strengths measure, the Chinese Family Strengths Measure [CFSM], used for family social service and practice interventions in a Chinese context. Both exploratory factor analysis and hierarchical-order confirmatory factor analysis verified the 28-item CFSM, which demonstrated adequate construct validity and convergent validity. In addition, the CFSM showed good internal consistency by Cronbach alpha and Guttman split-half reliability tests, and had adequate inter-correlation qualities for its respective dimensions by inter-item correlation and mean corrected item-total correlation tests. Implications for administration of this newly-constructed measure in family service setting are briefly suggested.
Skeletal Muscle NADPH Oxidase Is Increased and Triggers Stretch-Induced Damage in the mdx Mouse
Nicholas P. Whitehead,Ella W. Yeung,Stanley C. Froehner,David G. Allen
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0015354
Abstract: Recent studies have shown that oxidative stress contributes to the pathogenesis of muscle damage in dystrophic (mdx) mice. In this study we have investigated the role of NADPH oxidase as a source of the oxidative stress in these mice. The NADPH oxidase subunits gp91phox, p67phox and rac 1 were increased 2–3 fold in tibilais anterior muscles from mdx mice compared to wild type. Importantly, this increase occurred in 19 day old mice, before the onset of muscle necrosis and inflammation, suggesting that NADPH oxidase is an important source of oxidative stress in mdx muscle. In muscles from 9 week old mdx mice, gp91phox and p67phox were increased 3–4 fold and NADPH oxidase superoxide production was 2 times greater than wild type. In single fibers from mdx muscle NADPH oxidase subunits were all located on or near the sarcolemma, except for p67phox,which was expressed in the cytosol. Pharmacological inhibition of NADPH oxidase significantly reduced the intracellular Ca2+ rise following stretched contractions in mdx single fibers, and also attenuated the loss of muscle force. These results suggest that NADPH oxidase is a major source of reactive oxygen species in dystrophic muscle and its enhanced activity has a stimulatory effect on stretch-induced Ca2+ entry, a key mechanism for muscle damage and functional impairment.
Secure Real-Time Streaming Protocol (RTSP) for Hierarchical Proxy Caching
Yeung Siu Fung,John C.S. Lui,David K.Y. Yau
International Journal of Network Security , 2008,
Abstract: Proxies are commonly used to cache objects, especially multimedia objects, so that clients can enjoy better quality-of-service (QoS) guarantees such as smaller start-up latency and lower loss rate. But the use of multimedia proxies increases the risk that data are exposed to unauthorized access by intruders. In this paper, we propose an enhancement of the Internet IETF's Real-time Streaming Protocol (RTSP) which employs a notion of ``asymmetric reversible parametric sequence'' (ARPS) to provide the following security properties: (i) data confidentiality during transmission, (ii) end-to-end data confidentiality, (iii) data confidentiality against proxy intruders, and (iv) data confidentiality against member collusion. We present the Secure Multimedia Library (SML) which is based on ARPS and then realize these security features on a production video streaming server: Apple's Darwin Streaming Server. Our framework guarantees the system resilience against attacks is provably strong given the standard computability assumptions. To reduce the computation demand on the receiving client, our scheme only requires the client to perform a ``single decryption operation'' to recover the original data even though the data packets have been encrypted by multiple proxies along the delivery path. To tradeoff between degree of confidentiality and computational overhead, we also propose the use of a set of ``encryption configuration parameters'' (ECP) to trade off proxy encryption throughput against the presentation quality of audio/video obtained by unauthorized parties. Our implementation prototype shows that one can simultaneously achieve high encryption throughput and extremely low audio/video quality (in terms of audio fidelity, and peak signal-to-noise ratio and visual quality of decoded video frames) for unauthorized access.
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