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Effects of building aspect ratio,diurnal heating scenario,and wind speed on reactive pollutant dispersion in urban street canyons

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Journal of Environmental Sciences 2012年第12期24卷 2091-2103页

作者： Nelson Y.O.Tong Dennis Y.C.leung Department of Mechanical Engineering The University of Hong Kong

A photochemistry coupled computational fluid dynamics （CFD） based numerical model has been developed to model the reactive pollutant dispersion within urban street canyons, particularly integrating the interrelationship among diurnal heating scenario （solar radiation affections in nighttime, daytime, and sun-rise/set）, wind speed, building aspect ratio （building-height-to-street-width）, and dispersion of reactive gases, specifically nitric oxide （NO）, nitrogen dioxide （NO2） and ozone （O3） such that a higher standard of air quality in metropolitan cities can be achieved. Validation has been done with both experimental and numerical results on flow and temperature fields in a street canyon with bottom heating, which justifies the accuracy of the current model. The model was applied to idealized street canyons of different aspect ratios from 0.5 to 8 with two different ambient wind speeds under different diurnal heating scenarios to estimate the influences of different aforementioned parameters on the chemical evolution of NO, NO2 and 03. Detailed analyses of vertical profiles of pollutant concentrations showed that different diurnal heating scenarios could substantially affect the reactive gases exchange between the street canyon and air aloft, followed by respective dispersion and reaction. Higher building aspect ratio and stronger ambient wind speed were revealed to be, in general, responsible for enhanced entrainment of 03 concentrations into the street canyons along windward walls under all diurnal heating scenarios. Comparatively, particular attention can be paid on the windward wall heating and nighttime uniform surface heating scenarios.

关键词： photochemistry reactive pollutant dispersion building aspect ratio diurnal heating scenario wind speed urban streetcanyon

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Food and Drug:A New Direction in the History of Medicine in China

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Chinese Medicine and Culture 2023年第3期6卷 265-271页

作者： Angela Ki Che leung Chair Professor of History Joseph Needham-Philip Mao Professor in Chinese HistoryScienceand CivilizationHong Kong Institute for the Humanities and Social SciencesThe University of Hong KongHong Kong 518057China

1 Objects and their histories: unraveling the “black box”The history of object is a burgeoning field in contemporary historical studies. An object, like a “black box,” contains rich information that holds the secret code for knowledge construction. Object is a multifaceted being, consisting of aspects like technology, institution, human–object relationship, and human–nature interaction. Medicine and food inform sophisticated questions about society and ideology.

关键词： knowledge holds History

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Mechanistic study of vacuum UV catalytic oxidation for toluene degradation over CeO_(2) nanorods

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Green Energy & Environment 2022年第3期7卷 533-544页

作者： Muyan Wu Yingguang Zhang Haibao Huang Dennis Y.C.leung Department of Mechanical Engineering The University of Hong KongPokfulam RoadHong KongChina School of Environmental Science and Engineering Sun Yat-sen UniversityGuangzhou510275China

The present study specifically investigates vacuum ultraviolet (VUV) catalytic oxidation for toluene degradation over CeO_(2) *** effects of ultraviolet photocatalytic oxidation (UV-PCO) and ozone catalytic oxidation (OZCO) were manifested in the results of toluene removal and COx generation,while the combination of UV-PCO andOZCO (UV-OZCO) did not lead to improvement of *** the processes contribute to ozone decomposition,but no obvious synergetic effects of the different processes can be *** analysis results indicated that more toluene was oxidized into by-products,such as benzyl alcohol and benzaldehyde,by UV-OZCO rather than forming *** hydroxyl radical (·OH) and superoxide radical (·O_(2)^(-)) were found in all the processes of the VUV-PCO-OZCO system(combination of VUV photolysis,UV-PCO,OZCO and UV-OZCO processes).In the UV-OZCO process,the formation of hydroxyl radical was promoted,while that of superoxide radical was impeded,resulting in lower mineralization level of *** mechanistic study of toluene degradation over CeO_(2) nanorods in the VUV-PCO-OZCO system revealed that with the formation of·O_(2)^(-)and·OH,toluene is first oxidized to intermediates,followed by further ring–opening reaction and,finally,degradation into CO_(2) and H_(2)***_(2) nanorods function as both ozonation catalyst and photocatalyst,and the redox pair of Ce^(3+)and Ce^(4+)are interconvertible and can keep a balance.

关键词： toluene catalytic vacuum

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A review on the generation, determination and mitigation of Urban Heat Island

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Journal of Environmental Sciences 2008年第1期20卷 120-128页

作者： RIZWAN Ahmed Memon DENNIS Y.C. leung LIU Chunho Department of Mechanical Engineering the University of Hong Kong Hong Kong China.

Urban Heat Island （UHI） is considered as one of the major problems in the 21st century posed to human beings as a result of urbanization and industrialization of human civilization. The large amount of heat generated from urban structures, as they consume and re-radiate solar radiations, and from the anthropogenic heat sources are the main causes of UHI. The two heat sources increase the temperatures of an urban area as compared to its surroundings, which is known as Urban Heat Island Intensity （UHII）. The problem is even worse in cities or metropolises with large population and extensive economic activities. The estimated three billion people living in the urban areas in the world are directly exposed to the problem, which will be increased significantly in the near future. Due to the severity of the problem, vast research effort has been dedicated and a wide range of literature is available for the subject. The literature available in this area includes the latest research approaches, concepts, methodologies, latest investigation tools and mitigation measures. This study was carded out to review and summarize this research area through an investigation of the most important feature of UHI. It was concluded that the heat re-radiated by the urban structures plays the most important role which should be investigated in details to study urban heating especially the UHI. It was also concluded that the future research should be focused on design and planning parameters for reducing the effects of urban heat island and ultimately living in a better environment.

关键词： urban heat island (UHI) urbanization temperature rise mitigation

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Comparative Genomic Study Reveals a Transition from TA Richness in Invertebrates to GC Richness in Vertebrates at CpG Flank-ing Sites:An Indication for Context-Dependent Mutagenicity of Methylated CpG Sites

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Genomics, Proteomics & Bioinformatics 2008年第3期6卷 144-154页

作者： Frederick C.C. leung School of Biological Sciences and Genome Research Centre The University of Hong Kong

Vertebrate genomes are characterized with CpG deficiency, particularly for GCpoor regions. The GC content-related CpG deficiency is probably caused by context-dependent deamination of methylated CpG sites. This hypothesis was examined in this study by comparing nucleotide frequencies at CpG flanking positions among invertebrate and vertebrate genomes. The finding is a transition of nucleotide preference of 5＇ T to 5＇ A at the invertebrate-vertebrate boundary, indicating that a large number of CpG sites with 5＇ Ts were depleted because of global DNA methylation developed in vertebrates. At genome level, we investigated CpG observed/expected （obs/exp） values in 500 bp fragments, and found that higher CpG obs/exp value is shown in GC-poor regions of invertebrate genomes （except sea urchin） but in GC-rich sequences of vertebrate genomes. We next compared GC content at CpG flanking positions with genomic average, showing that the GC content is lower than the average in invertebrate genomes, but higher than that in vertebrate genomes. These results indicate that although 5＇ T and 5＇ A are different in inducing deamination of methylated CpG sites, GC content is even more important in affecting the deamination rate. In all the tests, the results of sea urchin are similar to vertebrates perhaps due to its fractional DNA methylation. CpG deficiency is therefore suggested to be mainly a result of high mutation rates of methylated CpG sites in GC-poor regions.

关键词： CpG deficiency DNA methylation invertebrate genomes GC content

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Alcoholic ketoacidosis in two Chinese patients

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Chinese Medical Journal 2000年第11期113卷 91-93页

作者： Rossa WKChiu Hok-leung Tai and Ching-Wan Lam DepartmentofChemicalPathology TheChineseUniversityofHongKongPrinceofWalesHospitalHongKongChinaDepartmentofChemicalPathologyTheChineseUniversityofHongKongPrinceofWalesHospitalHongKongChina

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A Sub-Grid Structure Enhanced Discontinuous Galerkin Method for Multiscale Diffusion and Convection-Diffusion Problems

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Communications in Computational Physics 2013年第7期14卷 370-392页

作者： Eric T.Chung Wing Tat leung Department of Mathematics The Chinese University of Hong KongHong Kong

In this paper,we present an efficient computational methodology for diffusion and convection-diffusion problems in highly heterogeneous media as well as convection-dominated diffusion *** is well known that the numerical computation for these problems requires a significant amount of computermemory and ***,the solutions to these problems typically contain a coarse component,which is usually the quantity of interest and can be represented with a small number of degrees of *** are many methods that aim at the computation of the coarse component without resolving the full details of the *** proposed method falls into the framework of interior penalty discontinuous Galerkin method,which is proved to be an effective and accurate class of methods for numerical solutions of partial differential equations.A distinctive feature of our method is that the solution space contains two components,namely a coarse space that gives a polynomial approximation to the coarse component in the traditional way and a multiscale space which contains sub-grid structures of the solution and is essential to the computation of the coarse *** addition,stability of the method is *** numerical results indicate that the method can accurately capture the coarse behavior of the solution for problems in highly heterogeneous media as well as boundary and internal layers for convection-dominated problems.

关键词： Multiscale problem sub-grid capturing multiscale basis function boundary layer internal layer

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Is artificial intelligence the final answer to missed polyps in colonoscopy?

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World Journal of Gastroenterology 2020年第35期26卷 5248-5255页

作者： Thomas K L Lui Wai K leung Department of Medicine Queen Mary HospitalUniversity of Hong KongHong KongChina

Lesions missed by colonoscopy are one of the main reasons for post-colonoscopy colorectal cancer,which is usually associated with a worse *** the adenoma miss rate could be as high as 26%,it has been noted that endoscopists with higher adenoma detection rates are usually associated with lower adenoma miss *** intelligence(AI),particularly the deep learning model,is a promising innovation in *** studies have shown that AI is not only accurate in colorectal polyp detection but can also reduce the miss ***,the application of AI in real-time detection has been hindered by heterogeneity of the AI models and study design as well as a lack of long-term ***,we discussed the principle of various AI models and systematically reviewed the current data on the use of AI on colorectal polyp detection and miss *** limitations and future prospects of AI on colorectal polyp detection are also discussed.

关键词： Artificial intelligence Adenoma Colonoscopy Colorectal cancer Polyps

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Structure and sequence analysis of influenza A virus nucleoprotein

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Science China(Life Sciences) 2009年第5期52卷 439-449页

作者： NG Andy Ka-leung SHAW Pang-Chui Molecular Biotechnology Programme Department of Biochemistry and Centre for Protein Science and Crystallography The Chi-nese University of Hong Kong

Influenza A virus nucleoprotein (NP) forms homo-oligomers and multiple copies of NP wrap around genomic RNA, along with a trimeric polymerase making up ribonucleoprotein (RNP) complex. Sequence comparison of more than 2500 influenza A NP showed that this protein contains 30.1 % of polymorphic residues. NP is composed of a head and a body domain and a tail loop/ linker region. The head domain is more conserved than the body domain, as revealed from the structure-based sequence alignment. NP oligomerization is mediated by the insertion of the non-polymorphic and structurally conserved tail loop of one NP molecule to a groove of another NP. The different form of NP oligomers is due to the flexibility of the polymorphic linkers that join the tail loop to the rest of the protein. The RNA binding property of NP is known to involve the protruding element and the flexible basic loop between the head and body domains, both having high degree of primary sequence conservation. To bind RNA, NP may first capture the RNA by the flexible basic loop and then the RNA is clamped by the protruding element.

关键词： Influenza H5N1 nucleoprotein oligomerization RNA binding

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MATRIX-AGENT FRAMEWORK: A VIRTUAL PLATFORM FOR MULTI-AGENTS

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Journal of Systems Science and Systems Engineering 2006年第4期15卷 436-456页

作者： Clement H.C. leung Gitesh K. RAIKUNDALIA School of Computer Science and Mathematics Victoria University PO Box 14428 Melbourne City MC 8001 Australia

Multi-agent technology has been applied extensively to many areas, including Decision Support Systems （DSS）. However, the applications of multi-agent technology in DSS are still very preliminary. Most of the current agent frameworks, such as middle-agent-based or agent-facilitator-based frameworks, are basically agent-to-agent model. These agent-based frameworks often neglect the living environment for agents and they suffer from：（i） inability to adapt to the environment, （ii） inability to self-upgrade, and （iii） inefficiency in information acquisition. Here, we introduce a recently proposed multi-agent framework, namely Agent-based Open Connectivity for Decision Support Systems （AOCD）. In this new framework, the communication and cooperation between agents are through a key component, the Matrix, which provides a virtual platform for agents. We use a unified Matrices framework to solve the bottleneck problem in the AOCD framework. Our experimental results based on different agent network topologies indicate that the hybrid topology presents superior performance compared with the centralised and decentralised topologies.

关键词： Multi-agent agent topology analysis DSS virtual agent society AOCD

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