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THREE-DIMENSIONAL NUMERICAL MODELINGOF COHESIVE SEDIMENT TRANSPORT BY TIDAL CURRENTIN PEARL RIVER ESTUARV

International Journal of Sediment Research 1999年第2期14卷 107-123页

作者： Yong CHEN1, Onyx W.H. WAI2. Y. S. Li3 and Qimiao LU4 (l 2.3 department of Civil and Structural engineering, The{2.. Hung Hom, Kowloon, hong kong 4,department of Civil engineering, Daltech, Dalhousie university, Halifax, Can

A three-dimensional numerical model of suspended sediment transport taking into account the effects of cohesiveness between sediments is presented. An efficient operator splitting scheme is employed to solve the equations of mass conservation, momentum and suspended sediment transport. The splitting method partitions a time step into three fractional time steps according to physical phenomena. In the first step, advection and Coriolis force are solved by Eulerian-Lagrangian method (ELM). Horizontal diffusion is approximated by implicit finite element method (FEM) for each horizontal layer in the second step. In the last step, vertical diffusion and pressure gradient are discretized by implicit finite difference method (FDM) for each nodal column. The continuity equation is solved by implicit FEM within an entire time step. The sigma coordinate system for vertical columns and nine-node isoparameteric finite elements for horizontal planes are employed in the model. Empirical functions specifically developed for cohesive sediments in china have been incorporated into the model. The model has been applied to investigate the suspended sediment concentration and seabed evolution in the Pearl River Estuary (PRE) in china. Computed results show that the distribution of sediment concentration and seabed evolution is in agreement with field measurements. In addition, the effect of the size of time step on result is discussed. The computed result shows that larger time steps can be used in this model for saving computation time without losing much accuracy.

关键词： Cohesive sediment Sediment transport model Finite element method Eulerian-Lagrangian method.

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DEVELOPMENT AND APPLICATION OF A EUTROPHICATION WATER QUALITY MODEL FOR RIVER NETWORKS

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Journal of Hydrodynamics 2008年第6期20卷 719-726页

作者： ZHANG Ming-liang SHEN Yong-ming GUO Yakun State Key Laboratory of Coastal and Offshore engineering Dalian University of Technology Dalian 116023 China department of Civil and Structural engineering The Hong Kong Polytechnic University Hong Kong China department of engineering University of Aberdeen Aberdeen AB24 3UE UK

The Preissmann implicit scheme was used to discretize the one-dimensional Saint-Venant equations, the river-junction-fiver method was applied to resolve the hydrodynamic and water quality model for river networks, and the key issues on the model were expatiated particularly in this article. This water quality module was designed to compute time dependent concentrations of a series of constituents, which are primarily governed by the processes of advection, dispersion and chemical reactions. Based on the theory of Water Quality Analysis Simulation Program （WASP） water quality model, emphasis was given to the simulation of the biogeochemical transformations that determine the fate of nutrients, in particular, the simulation of the aquatic cycles of nitrogen and phosphorus compounds. This model also includes procedures for the determination of growth and death of phytoplankton. This hydrodynamic and water quality model was applied to calculate two river networks. As illustrated by the numerical examples, the calculated water level and discharge agree with the measured data and the simulated trends and magnitudes of water quality constituents are generally in good agreement with field observations. It is concluded that the presented model is useful in the pollutant control and in the determination of pollutant-related problems for river networks.

关键词： Preissmann implicit scheme river networks hydrodynamic model water quality model biogeochemical transformations three-step method

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Carbon-neutral pathway to mitigating transport-power grid cross-sector effects

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The Innovation 2024年第3期5卷 27-29页

作者： Jing Ma Huiwen kong Jianxiao Wang Haiwang Zhong Bo Li Jie Song Daniel M.Kammen State Key Laboratory of Alternate Electrical Power System with Renewable Energy Sources School of Electrical and Electronic EngineeringNorth China Electric Power UniversityBeijing 102206China National engineering Laboratory for Big Data Analysis and Applications Peking UniversityBeijing 100871China Peking university Ordos Research Institute of Energy Ordos 017000China State Key Laboratory of Power Systems and Generation Equipment Department of Electrical EngineeringTsinghua UniversityBeijing 100084China School of Electrical engineering Guangxi UniversityNanning 530004China department of Industrial engineering and Management College of EngineeringPeking UniversityBeijing 100871China Energy and Resources Group and Goldman School of Public PolicyUniversity of CaliforniaBerkeleyBerkeleyCA 94720USA

Dear Editor,The growing demand for transportation energy has brought increasing challenges to reducing greenhouse gas ***,many countries or regions have proposed solutions to achieve carbon-neutral transportation such as the rapid expansion of the global electric vehicle(EV)***,these benefits are not *** the goal of decarbonization in electricity is achieved,the“pseudo net zero emissions”effect of the transportation sector will inevitably be accompanied by a quiet shifting of carbon responsibility.1 This shift is undoubtedly fatal for both net zero emissions at the national level and carbon responsibility at the industry level;however,the corresponding effects have not yet been clarified.

关键词： neutral doubt shifting

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Structural and electronic properties of single-walled carbon nanotubes adsorbed with 1-pyrenebutanoic acid,succinimidyl ester

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Science china Chemistry 2008年第12期51卷 1203-1210页

作者： FAN WenJie & ZHANG RuiQin Centre of Super-Diamond and Advanced Films (COSDAF) and department of Physics and Materials Science, City university of{2.,{2. SAR, china Centre of Super-Diamond and Advanced Films (COSDAF) and department of Physics and Materials Science City University of Hong Kong Hong Kong SAR China

The adsorption of a 1-pyrenebutanoic acid, succinimidyl ester (PSE) interacting with metallic armchair (n, n) carbon nanotubes (CNTs) (n= 3-13) was investigated by using a density-functional tight-binding method with an empirical van der Waals force correction. In this study of large systems involving weak interactions, our calculations showed that the pyrene ring of PSE could be spontaneously absorbed onto the CNTs surface through π-π stacking at the physisorption distances. Increasing of the CNTs diameter leads to a higher adsorption energy. After adsorption of PSE on its sidewall, the geometric and electronic structures of CNTs are basically undamaged. CNTs contribute to the main peak of the electron excitation procedure in the UV/vis spectrum, with a slight red shift after adsorption of PSE.

关键词： SWNTs PSE π-π stacking density-functional tight-binding method

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PULSED Nd-YAG LASER WELDING OF AN AI-SiC_p METAL MATRIX COMPOSITE

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Chinese Journal of Aeronautics 1997年第1期10卷 75-80页

作者： Xu Jiukua Jiang Chengyu(Mechanical engineering Institute, Nanjing university of Aeronauticsand Astronautics, Nanjing, 2.0016,{2.)Yu Damin Liu Weicheng(department of Manufacturing engineering, hong kong polytechnic university) Mechanical engineering Institute Nanjing Univ. Aero. and Astronaut. Nanjing 210016 China Dept. of Manufacturing engineering Hong Kong Polytechnic University Hong Kong

A study is presented of the laser welding behaviour of an SiC particulate re-inforced Al-alloy comPOsite using a pulsed Nd-YAG laser. The influences of laser weldingparameters of laser intensity, pulse duration and the beamjs focus position on the depth ofweld penetration as well as the size of weld bead width were investigated. A typical mi-crostructure of a weld section reveals that the three distinct zones are present. Cracks andporosity were fOund to be two major defects in laser welded metal matrix composites(MMC). These investigations have led to an optimum welding condition proposed forlaser welding of SiC partiulate reinforced aluminium alloy comPosites with minimum de-fects.

关键词： metal matrix composites laser welding laser intensity peak power

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EXPERIMENTAL STUDY ON INSTANTANEOUS DISCHARGE OF UNSORTED PARTICLE CLOUD IN CROSS-FLOW

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Journal of Hydrodynamics 2008年第1期20卷 10-16页

作者： GU Jie HUANG Jing LIC. W. College of Marine Science and Technology Shanghai Fisheries University Shanghai 200090 China department of Civil and Structural engineering The Hong Kong Polytechnic University Hong Kong China

A series of extensive laboratory experiments were conducted to investigate the transport and mixing of instantaneous discharge of unsorted particle cloud in cross-flow. The following experimental results were obtained：（1） the vertical frontal position and the longitudinal width of the particle cloud in the cross-flow is much larger than those in stagnant water, （2. the smaller cross-flow velocity will normally cause the larger non-dimensional frontal position for the same particle size range and initial volume, （3） the non-dimensional longitudinal width of the particle cloud in the cross-flow increases with the increase of cross-flow velocity. The empirical constants （α1, α3 and α2. and their variance range, which can be used to determine the relationships of non-dimensional vertical frontal position and time, longitudinal width and time, and vertical frontal position and longitudinal width were also obtained through the analysis of experimental data.

关键词： instantaneous discharge particle cloud cross-flow buoyancy hydrodynamic behavior

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Monitoring and Warning of Landslides and Debris Flows Using an Optical Fiber Sensor Technology

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Journal of Mountain Science 2011年第5期8卷 728-738页

作者： PEI Huafu CUI Peng YIN Jianhua ZHU honghu CHEN Xiaoqing PEI Laizheng department of Civil and Structural engineering the Hong Kong Polytechnic University Hong Kong China Institute of Mountain Hazards and Environment CAS Chengdu 610041 China School of Earth Sciences and engineering Nanjing University Nanjing 210093 China

Landslides and debris flows are typical geo-hazards which occur in hilly or mountainous regions. Debris flows may result from landslides. Geotechnical instrumentation plays an important role in monitoring and warning of landslides and resulted debris flows. Traditional technologies for monitoring landslides and debris flows have certain limitations. The new optical fiber sensors presented in this paper can overcome those limitations. This paper presents two new optical fiber sensor systems: one is the Fiber Bragg Grating (FBG)-based in-place inclinometer for monitoring landslides and the other is the FBG-based column-net system for monitoring debris flows. This paper presents the calibration results of FBG-based in-place inclinometers in laboratory. It is found that the calibration results are in good agreement with theoretical results. Both the FBG-based in-place inclinometers and the FBG-based column-net system have been installed at a site in Weijiagou valley, Beichuan County, Sichuan Province of china. Some preliminary results have been obtained and reported in the paper. The advantages of the FBG monitoring systems and their potential applications are also presented.

关键词： Landslide Debris flow Fiber Bragg Grating In-place inclinometer Column-net system

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A matrix version of the Wielandt inequality and its application to statistics

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Chinese Science Bulletin 1999年第2期44卷 118-121页

作者： WANG Songgui Wai-Cheung Ipdepartment of Applied Mathematics, Beijing polytechnic {2., Beijing 10002., china Institute of Applied Mathematics, Chinese Academy of Sciences, Beijing 100080, china department of Applied Mathematics, hong kong polytechnic university, hong kong, china department of Applied Mathematics Beijing Polytechntc University Beijing China Institute of Applied Mathematics Chinese Academy of Sciences Beijing China department of Applied Mathematics Hong Kong Polytechnic University Hong Kong China

Suppose that A is an n×n positive definite Hemitain matrix. Let X and Y ben×p and n×q matrices（p+q≤n）, such that X*Y=O. The following inequality is provedX*AY（YAY）-Y*AX≤（（λ1-λn）/（λ1+λn）2./sup>）X*AX,where λ1 and λn are respectively the largest and smallest eigenvalues of A, and M- stands for a generalized inverse of M. This inequality is an extension of the well-known Wielandt inequality in which both X and Y are vectors. The inequality is utilized to obtain some interesting inequalities about covariance matrix and various correlation coefficients including the canonical correlation, multiple and simple correlation.

关键词： Wielandt inequality Cauchy-Schwarz inequality Wishart matrix.

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Equivalent distributed capacitance model of oxide traps on frequency dispersion of C-V curve for MOS capacitors

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Chinese Physics B 2016年第11期25卷 645-651页

作者：卢汉汉徐静平刘璐黎沛涛邓咏雯 School of Optical and electronic Information Huazhong University of Science and Technology department of Electrical and electronic {2. The University of Hong Kong department of Applied Physics The Hong Kong Polytechnic University

An equivalent distributed capacitance model is established by considering only the gate oxide-trap capacitance to explain the frequency dispersion in the C-V curve of MOS capacitors measured for a frequency range from 1 kHz to1 *** proposed model is based on the Fermi-Dirac statistics and the charging/discharging effects of the oxide traps induced by a small ac *** validity of the proposed model is confirmed by the good agreement between the simulated results and experimental *** indicate thatthe capacitance dispersion of an MOS capacitor under accumulation and near flatband is mainly caused by traps adjacent to the oxide/semiconductor interface,with negligible effects from the traps far from the interface,and the relevant distance from the interface at which the traps can still contribute to the gate capacitance is also *** addition,by excluding the negligible effect of oxide-trap conductance,the model avoids the use of imaginary numbers and complex calculations,and thus is simple and intuitive.

关键词： capacitance conductance intuitive negligible imaginary validity explain capacitor biased leakage

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THREE-DIMENSIONAL SIMULATION OF MEANDERING RIVER BASED ON 3-D RNG k-ε TURBULENCE MODEL

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Journal of Hydrodynamics 2008年第4期20卷 448-455页

作者： ZHANG Ming-liang SHEN Yong-ming State Key Laboratory of Coastal and Offshore engineering Dalian University of Technology Dalian 116024China department of Civil and Structural engineering The Hong Kong Polytechnic University Hong Kong China

A 3-D numerical model for calculating flow in non-curvilinear coordinates was established in this article. The flow was simulated by solving the full Reynolds-averaged Navier-Stokes equations with the RNG κ-ε turbulence model. In the horizontal x-y-plane, a boundary-fitted curvilinear co-ordinate system was adopted, while in the vertical direction, a σ co-ordinate transformation was used to represent the free surface and bed topography. The water level was determined by solving the 2.D Poisson equation derived from 2.D depth averaged momentum equations. The finite-volume method was used to discretize the equations and the SIMPLEC algorithm was applied to acquire the coupling of velocity and pressure. This model was applied to simulate the meandering channels and natural rivers, and the water levels and the velocities for all sections were given. By contrasting and analyzing, the agreement with measurements is generally good. The feasibility studies of simulating flow of the natural fiver have been conducted to demonstrate its applicability to hydraulic engineering research.

关键词： non-orthogonal curvilinear coordinates RNG κ-ε turbulence model 2.D Poisson equation SIMPLEC algorithm depth averaged equation

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