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Numerical exploration of new features on three-dimensional transition of a cylinder wake

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Science China Mathematics 2004年第z1期47卷 69-80页

作者： LING Guocan, XIONG Jun & ZHU KeqinState key laboratory of Nonlinear Mechanics, Institute of Mechanics, chinese academy of sciences, Beijing 100080, China Department of Engineering Mechanics, Tsinghua University, Beijing 100084. China chinese Acad Sci Inst Mech State Key Lab Nonlinear Mech Beijing 100080 Peoples R China Tsing Hua Univ Dept Engn Mech Beijing 100084 Peoples R China

The three-dimensional transition of the wake flow behind a circular cylinder is studied in detail by direct numerical simulations using 3. incompressible N-S equations for Reynolds number ranging from 200 to 3.0. New features and vortex dynamics of the 3. transition of the wake are found and investigated. At Re = 200, the flow pattern is characterized by mode A instability. However, the spanwise characteristic length of the cylinder determines the transition features. Particularly for the specific spanwise characteristic length linear stable mode may dominate the wake in place of mode A and determine the spanwise phase difference of the primary vortices shedding. At Re = 250 and 3.0 it is found that the streamwise vortices evolve into a new type of mode "dual vortex pair mode" downstream. The streamwise vortex structures switch among mode A, mode B and dual vortex pair mode from near wake to downstream wake. At Re = 250, an independent low frequency fm in addition to the vortex shedding frequency fs is identified. Frequency coupling between fm and fs occurs. These result in the irregularity of the temporal signals and become a {4. feature in the transition of the wake. Based on the formation analysis of the streamwise vorticity in the vicinity of cylinder, it is suggested that mode A is caused by the emergence of the spanwise velocity due to three dimensionality of the incoming flow past the cylinder. energy distribution on various wave numbers and the frequency variation in the wake are also described.

关键词： cylinder, wake, 3. transition, Fourier-spectral-spectral-element method, direct numerical simulation (DNS).

Surface effects of monolayer-protected gold nanoparticles on the redox reactions between ferricyanide and thiosulfate

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Science China Chemistry 2005年第5期48卷 424-430页

作者： LI Di1, SUN Chunyan1, HUANG Yunjie1, LI Jinghong1,2 & CHEN Shaowei3.1. State key laboratory of Electroanalytical Chemistry, Changchun Institute of Applied Chemistry, chinese academy of sciences, Changchun 13.022, China 2. Department of Chemistry, Tsinghua University, Beijing 100084. China 3. Department of Chemistry, University of California, Santa Cruz, Santa Cruz, CA 95064. USA 1. State key laboratory of Electroanalytical Chemistry Changchun Institute of Applied Chemistry Chinese Academy of Sciences 130022 Changchun China 2. Department of Chemistry Tsinghua University 100084 Beijing China 3. Department of Chemistry University of California 95064 Santa Cruz Santa Cruz CA USA

Electron transfer through the self-assembled monolayers (SAMs) on gold nanopar-ticles is investigated by using the monolayer protected gold nanoclusters (MPCs) as elec-tron-transfer mediators. 3.Mercaptopropionic acid (MPA) and 11-meraptoundecanoic acid (MUA) MPCs were employed to catalyze the redox reaction between potassium ferricyanide and sodium thiosulfate. The catalytic mechanism was proposed that the MPCs act as diffusing elec-tron-mediators and electron transfers to and from the MPCs surface. Therefore the electron transfer rate through the capping layers would be proportional to the MPCs catalyzed reaction rate, which was monitored by the UV absorbance of ferricyanide. The calculated apparent rate constant was orders of magnitude smaller than that of the maximum of tunneling current, which was attributed to the splited energy level of the nanoscale particles.

关键词： electron transfer, three-dimensional self-assembled monolayers, redox reaction, electron transfer mediator, surface effect.

Ultrafast excitation relaxation in light-harvesting complex LH2 from *** 601

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Science China Chemistry 2004年第3期47卷 192-199页

作者： GUO Lijun1,2, LIU Yuan3. LIU Weimin2, GUO Junhua1, XU Chunhe3.& QIAN Shixiong2 1. School of Physics and Information Optoelectronics, Henan University, Kaifeng 4.5001, China 2. Physics Department, Fudan University, Shanghai 2004.0}, China 3. Shanghai Institute of Plant Physiology, {4., Shanghai 20003., China 1. School of Physics and Information Optoelectronics Henan University 475001 Kaifeng China 2. Physics Department Fudan University 200433 Shanghai China 3. Shanghai Institute of Plant Physiology Chinese Academy of Sciences 200032 Shanghai China

The energy relaxation and kinetic evolution of transient spectra of bacteriochloro- phylls (BChls) in light-harvesting complex LH2 from Rb. sphaeroides 601 were investigated using femtosecond pump-probe technique. Upon 783.nm excitation, the energy at B800 BChls ex-periences an intramolecular redistribution with 0.3. ps time constant before transferring to B850 BChls. With tuning the excitation wavelength, the dynamical evolution of excited BChls was clearly observed, which indicates an obvious competition between the ground state bleaching and excited state absorption (ESA) of BChls involved and an isosbestic point near 818 nm, and also demonstrates that from the lower electronic excited state of B800 BChls to the higher exci-tonic state of B850 BChls is an efficient routine for energy transfer. The excitation energy in higher excitonic states of B850 BChls relaxes rapidly to the next lowest excitonic state by inter-conversion, delocalization to adjacent molecular, populating the lowest excitonic state and the change of molecular conformation.

关键词： photosynthesis, light-harvesting complex, energy transfer, ultrafast, dynamics, purple bacteria.

Origins of intraseasonal rainfall variations over the southern South China Sea in boreal winter

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Atmospheric and Oceanic Science Letters 2017年第1期10卷 44-50页

作者： CAO Xi WU Ren-Guang Center for Monsoon System Research chinese academy of sciences State key laboratory of Numerical Modeling for Atmospheric {3. and Geophysical Fluid Dynamics Center for Monsoon System Research Institute of Atmospheric Physics Chinese Academy of Sciences Beijing China State key laboratory of Numerical Modeling for Atmospheric sciences and Geophysical Fluid Dynamics Institute of Atmospheric Physics Chinese Academy of Sciences Beijing China

This study investigates the origins of intraseasonal rainfall variations over the southern South China Sea（SCS） region in boreal *** is found that intraseasonal rainfall variations over the southern SCS have different origins on the 10-20-day and 3.-60-day time *** the 10-20-day time scale,large rainfall anomalies over the southern SCS are preceded by strong northerly wind anomalies associated with the East Asian winter monsoon（EAWM）,by about two *** the 3.-60-day time scale,the strong EAWM-related northerly wind anomalies almost appear simultaneously with large rainfall anomalies over the southern *** addition,obvious large rainfall anomalies occur over the southeastern tropical Indian Ocean about one week before the peak southern SCS rainfall *** indicates that the convection and related circulation anomalies with origins over the tropical Indian Ocean may play an important role in inducing intraseasonal rainfall variations over the southern SCS on the 3.-60-day time scale,but not on the 10-20-day time scale.

关键词： Intraseasonal rainfall anomalies southern South China Sea boreal winter 10-20-day and 3.-60-day time scales

A Detailed Dynamics Study of the Reaction CH_4.Cl→HCl+CH_3

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chinese Chemical Letters 1998年第8期9卷 771-774页

作者： Li Jin XU Xue Bin WANG Ji Min YAN Fan Ao KONG (State key laboratory of Molecular Reaction Dynamics, Institute of Chemistry,chinese academy of sciences, Beijing 100080) chinese Acad Sci Inst Chem State Key Lab Mol React Dynam Beijing 100080 Peoples R China

The detailed dynamics of the CH4.Cl→HCl+CH3.reaction has been investigated by means of the quasiclassical trajectory approach. The properties analyzed can be interpreted in terms of the main topological featUres of the potential energy surface used. on the basis of the theoretical results, two reaction channels are proposed: one is a direct channel and the other is a complex one.

关键词： quasiclassical trajectory calculation LEPS potential energy surface

Different roles of Ekman pumping in the west and east segments of the South China Sea Warm Current

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Acta Oceanologica Sinica 2011年第3期30卷 1-13页

作者： WANG Qiang WANG Yinxia BO Hong ZHOU Weidong WANG Dongxiao key laboratory of Tropical Marine Environmental Dynamics South China Sea Institute of Oceanology Chinese Academy of Sciences Guangzhou 510301 China Graduate School of the chinese academy of sciences Beijing 100049 China South China Sea Marine Engineering and Environment Institute of State Oceanic Administration Guangzhou 510300 China Virginia Institute of Marine Science College of William and Mary VA 23062 USA

A three-dimensional model is used to investigate the mechanism of the South China Sea （SCS） winter counter-current （also known as the SCS Warm Current, or the SCSWC）, which flows against the wind. The model can reproduce the structure of the band-like currents over the northern shelf of the SCS, including the westward coastal current and slop current, and the SCSWC sandwiched in between. Sensitivity experiments are designed to understand the different roles of Ekman pumping of the SCSWC at different longitude. The results show that the Ekman pumping drives the SCSWC in the west segment. In the east, it is not the Ekman pumping but the intrusion of the Kuroshio that drives the SCSWC.

关键词： SCSWC Ekman pumping northern South China Sea numerical model

A study on the sharp knee and fine structures of cosmic ray spectra

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Science China(Physics,Mechanics & Astronomy) 2010年第5期53卷 842-847页

作者： WANG Bo1,YUAN Qiang1,FAN Chao1,2,ZHANG JianLi1,HU HongBo1 & BI XiaoJun1 1 key laboratory of Particle Astrophysics,Institute of High energy Physics,{3.,Beijing 10004.,China 2 Department of Physics,Shandong University,Jinan 250100,China 1. key laboratory of Particle Astrophysics Institute of High Energy Physics Chinese Academy of Sciences Beijing 100049 China2. Department of Physics Shandong University Jinan 250100 China

The paper investigates the overall and detailed features of cosmic ray(CR) spectra in the knee region using the scenario of nuclei-photon interactions around the acceleration *** supernova remnants can be the physical realities of such kind of CR acceleration *** results show that the model can well explain the following problems simultaneously with one set of source parameters:the knee of CR spectra and the sharpness of the knee,the detailed irregular structures of CR spectra,the so-called"component B"of Galactic CRs,and the electron/positron excesses reported by recent *** coherent explanation serves as evidence that at least a portion of CRs might be accelerated at the sources similar to young supernova remnants,and one set of source parameters indicates that this portion mainly comes from standard sources or from a single source.

关键词： cosmic ray knee fine structures e+e-excesses "component B" single source

Evaluating the effect of dislocation on the photovoltaic performance of metamorphic tandem solar cells

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中国科学：技术科学英文版 2010年第9期53卷 2569-2574页

作者： ZHANG Han1,CHEN NuoFu2,3.WANG Yu1,ZHANG XingWang1,YIN ZhiGang1,SHI HuiWei1,WANG YanSuo1,HUANG TianMao1,BAI YiMing2 & FU Zhen11 key laboratory of Semiconductor Materials Science,Institute of Semiconductors,chinese academy of sciences,P.O.Box 912,Beijing 100083.China 2 School of Renewable {3. Engineering,North China Electric Power University,Beijing 102206,China 3.State key laboratory of Silicon Materials,Zhejiang University,Hangzhou 3.0027,China 1. key laboratory of Semiconductor Materials Science Institute of Semiconductors Chinese Academy of Sciences P.O. Box 912 Beijing 100083 China2. School of Renewable Energy Engineering North China Electric Power University Beijing 102206 China3. State Key Laboratory of Silicon Materials Zhejiang University Hangzhou 310027 China

The photovoltaic conversion efficiency for monolithic GaInP/GaInAs/Ge triple-junction cell with various bandgap combination (3.0 suns,AM1.5d) was theoretically *** impressive improvement on conversion efficiency was observed for a bandgap combination of 1.708,1.194.and 0.67 eV.A theoretical investigation was carried out on the effect of dislocation on the metamorphic structure’s efficiency by regarding dislocation as minority-carrier recombination *** results showed that only when dislocation density was less than 1.6×106 cm-2,can this metamorphic combination exhibit its efficiency advantage over the fully-matched *** addition,we also briefly evaluated the lattice misfit dependence of the dislocation density for a group of metamorphic triple-junction system,and used it as guidance for the choice of the proper cell structure.

关键词： tandem solar cell theoretical efficiency dislocation buffer layers

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超声实验中谱比法衰减的散射与本征吸收特性

地球物理学报 2018年第3期61卷 1083-1094页

作者：周浩符力耘矿产地球化学国家重点实验室中国科学院地球化学研究所贵阳550002 中国科学院大学北京100049 中国石油大学(华东)地球科学与技术学院青岛266580

实际地球介质的弹性波衰减,无论是对于地球内部结构反演、含油气储层描述,还是对于地震岩石物理本身的基础研究而言,都十分重要.通过岩石物理实验测量岩石的弹性波衰减是相关研究的基本手段,而谱比法是一种最常用的测量方法.利用谱比法... 详细信息

实际地球介质的弹性波衰减,无论是对于地球内部结构反演、含油气储层描述,还是对于地震岩石物理本身的基础研究而言,都十分重要.通过岩石物理实验测量岩石的弹性波衰减是相关研究的基本手段,而谱比法是一种最常用的测量方法.利用谱比法测量的弹性波衰减,简称谱比法衰减,由介质的本征吸收特性和非均质散射特性共同决定.然而,在谱比法理论中,没有将这两种衰减特性的作用区分对待.因此,实验室测量的谱比法衰减中是否含有散射特性,其散射特性是否可以忽略,常不明确.本文基于对岩石物理实验中样品波形特征的基本认识,通过能流理论描述了弹性波的本征吸收和非均质散射过程,以及对应的尾波形成机理.文章还应用能流理论测量岩石的弹性波衰减,即能流法衰减.无论是通过理论推导,还是通过实验验证,谱比法衰减与能流法衰减都显示出良好的一致性.这两种直达波衰减的一致性暗示了谱比法衰减中存在着两种衰减特性.文中还对比分析了谱比法衰减与喷射流本征衰减的实验结果,该结果同样展示了谱比法衰减中可能存在着散射特性.因此,通过能流理论,可以利用样品波形的尾波特征定性判断谱比法衰减中可能存在的散射特性.即异常明显的尾波振幅可能意味着强烈的直达波非均质散射,谱比法衰减中的散射特性因而不可忽略.

关键词：谱比法散射衰减本征衰减尾波