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Structural ensemble dynamics based closure model for wall-bounded turbulent flow

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Acta Mechanica Sinica 2009年第5期25卷 731-736页

作者： Zhen-Su She Ning Hu You Wu State Key Laboratory for Turbulence and Complex Systems and Dept Mechanical and Aerospace Engineering,College of Engineering, Peking university,100871 beijing,{2. State Key Laboratory for Turbulence and Complex Systems and Dept Mechanical and Aerospace Engineering College of Engineering Peking University Beijing China

Wall-bounded turbulent flow involves the development of multi-scale turbulent eddies, as well as a sharply varying boundary layer. Its theoretical descriptions are yet phenomenological. We present here a new framework called structural ensemble dynamics （SED）, which aims at using systematically all relevant statistical properties of turbulent structures for a quantitative description of ensemble means. A new set of closure equations based on the SED approach for a turbulent channel flow is presented. SED order functions are defined, and numerically determined from data of direct numerical simulations （DNS）. Computational results show that the new closure model reproduces accurately the solution of the original Navier-Stokes simulation, including the mean velocity profile, the kinetic energy of the streamwise velocity component, and every term in the energy budget equation. It is suggested that the SED-based studies of turbulent structure builds a bridge between the studies of physical mechanisms of turbulence and the development of accurate model equations for engineering predictions.

关键词： Turbulence Closure equation Channel flow Structural ensemble dynamics

Architecture and key technologies of grid geographic information system

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Science china(Technological Sciences) 2008年第S1期51卷 102-113页

作者： FANG Yu,HUANG Zhou,CHEN Bin,WU Lun & YIN DaFei Institute of Remote Sensing and Geographic Information System,Peking university,beijing 100871,{2. Institute of Remote Sensing and Geographic Information System Peking University Beijing China

The highly efficient and stable collaborative computation platform for geospatial information can be constructed on the basis of Grid computing technology,com-bined with Peer-to-Peer (P2.) computing technology and geospatial database technology. This paper proposed the architecture and key technologies of the Grid GIS (Geographic Information System) incorporated with P2. structure,and corre-spondingly a Grid GIS prototype named Nebula was designed and then imple-mented. Nebula is a suite of middleware for geospatial Grid computing,which could be deployed onto various service nodes in network. Based on Grid protocols and infrastructure,Nebula provides invocation interfaces to users in form of Grid services. By using P2. message based communication mechanism,complex geospatial computation tasks could be accomplished by Nebula in a collaborative way. This paper introduced Nebula's architecture and key modules,and according to experimental data,we discussed the Grid GIS's advantages,application scenar-ios and future directions.

关键词： Grid GIS distributed geospatial computing Peer-to-Peer computing

Development of Trusted Network and Challenges It Faces

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ZTE Communications 2008年第1期6卷 13-17页

作者： Lin Chuang 1, Wang Yuanzhuo 1, Tian Liqin 1,2.(1. Department of Computer Science and Technology, Tsinghua university, beijing 100084,{2. 2. Department of Computer, North{2. Institute of Science and Technology, beijing 101601,{2.)

As the information network plays a more and more important role globally, the traditional network theories and technologies, especially those related to network security, can no longer meet the network development requirements. Offering the system with secure and trusted services has become a new focus in network research. This paper first discusses the meaning of and aspects involved in the trusted network. According to this paper, the trusted network should be a network where the network’s and users’ behaviors and their results are always predicted and manageable. The trustworthiness of a network mainly involves three aspects: service provider, information transmission and terminal user. This paper also analyzes the trusted network in terms of trusted model for network/user behaviors, architecture of trusted network, service survivability and network manageability, which is designed to give ideas on solving the problems that may be faced in developing the trusted network.

关键词： Development of Trusted Network and Challenges It Faces

Mobius Isoparametric Hypersurfaces in S^(n+1) with Two Distinct Principal Curvatures

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Acta Mathematica Sinica,English Series 2002年第3期18卷 437-446页

作者： Hai Zhong LI Department of Mathematics, Tsinghua university. beijing 100084. P. R.{2. Hui Li LIU Department of Mathematics, Northeastern university. Shenyang 110000. P. R.{2. Chang Ping WANG Key Laboratory of Pure and Applied Mathematics, School of Mathematical Sciences. Peking university, beijing 100871, P. R.{2. Guo Song ZHAO Department of Mathematics, Sichuan university, Chengdu 610064. P. R.{2. Department of Mathematics Tsinghua University Beijing P. R. China Department of Mathematics Northeastern University Shenyang P. R. China Key Laboratory of Pure and Applied Mathematics School of Mathematical Sciences Peking University Beijing P. R. China Department of Mathematics Sichuan University Chengdu P. R. China

A hypersurface x: M→S^(n+1) without umbilic point is called a Mbius isoparametric hypersurface if its Mbius form Φ=-ρ^(-2.∑_i(ei(H)+∑_j(h_(ij)-Hδ_(ij))e_j(logρ))θ_i vanishes and its Mbius shape operator S=ρ^(-1)(S-Hid) has constant eigenvalues. Here {e_i} is a local orthonormal basis for I=dx·dx with dual basis {θ_i}, II=∑_(ij)h_(ij)θ_iθ_J is the second fundamental form, H=1/n∑_i h_(ij), ρ~2.n/(n-1)(‖II‖~2.nH^2. and S is the shape operator of x. It is clear that any conformal image of a (Euclidean) isoparametric hypersurface in S^(n+1) is a Mbius isoparametric hypersurface, but the converse is not true. In this paper we classify all Mbius isoparametric hypersurfaces in S^(n+1) with two distinct principal curvatures up to Mbius transformations. By using a theorem of Thorbergsson [1] we also show that the number of distinct principal curvatures of a compact Mbius isoparametric hypersurface embedded in S^(n+1) can take only the values 2. 3. 4, 6.

关键词： Mobius geometry Isoparametric hypersurface Principal curvature

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随机双目标焊接车间调度建模与仿真

系统仿真学报 2009年第13期21卷 3906-3909,3913页

作者：樊坤张人千夏国平北京林业大学经济管理学院北京100083 北京航空航天大学经济管理学院北京100083

针对一个生产大型机械产品(如架桥机等)的企业的焊接车间的调度问题进行研究,对m位工人加工n个结构件的随机调度问题建立数学模型,并以最小化最大的加工完成时间的期望与方差为优化目标。为求解该模型,对二进制粒子群算法(BPSO)进行改进... 详细信息

针对一个生产大型机械产品(如架桥机等)的企业的焊接车间的调度问题进行研究,对m位工人加工n个结构件的随机调度问题建立数学模型,并以最小化最大的加工完成时间的期望与方差为优化目标。为求解该模型,对二进制粒子群算法(BPSO)进行改进,并采用动态领域策略、新的粒子个体极值选择以及一维优化方法求解双目标优化问题。通过实例仿真,结果证实修改后的算法是有效的,并能够找到Pareto前沿解。

关键词：调度双目标 Pareto 二进制粒子群优化(BPSO)

Fabrication of MgB2.superconducting films by different methods

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Progress in Natural Science:Materials International 2006年第2期16卷 175-177页

作者： WANG Shufang, ZHOU Yueliang, ZHU Yabin, CHEN Zhenghao, LU Huibin and YANG Guozhen ( Physics & Technology College, Hebei university, Baoding 071002. china {2. National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, {2. 100080, china) Physics and Technology College Hebei University Baoding 071002 China beijing National Laboratory for Condensed Matter Physics Institute of Physics Chinese Academy of Sciences Beijing 100080 China

MgB2.superconducting films have been successfully fabricated on single crystal MgO(111) and c-AL2.3.substrates by different methods. The film deposited by pulsed laser deposition is c-axis oriented with zero resistance transition temperature of 3..4 K, while the other two films fabricated by chemical vapor deposition and electrophoresis are c-axis textured with the zero resistance transition temperature of 3. K and 3. K, respectively. Magnetization hysteresis measurements yield critical current density Jc of 107 A/cm2.at 15 K in zero field for the thin film and of 105 A/cm2.for the thick film. For the thin film deposited by chemical vapor deposition, the microwave surface resistance at 10 K is found to be as low as 100μΩ, which is comparable with that of a high-quality high-temperature superconducting thin film of YBCO.

关键词： MgB2.superconducting films chemical vapor deposition pulsed laser deposition electrophoresis.

ISSR-based genetic diversity of tung tree,a potential biodiesel plant species native to china

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ISSR-based genetic diversity of tung tree,a potential biodie...

ALGEBRAICALLY CONSTRUCTED COSTAS ARRAYS WITH SMALL NUMBER OF CROSS-COINCIDENCES

The Second International Symposium on Bioenergy and Biotechnology——in Conjunction with Miscanthus Workshop

作者： Lingling Zhang1,2.3.and Junhua Peng1,2.1 Wuhan Botanical Garden,Chinese Academy of Science,Wuhan,Hubei 43.074,{2. 2.Key Lab of Plant Germplasm Enhancement and Specialty Agriculture,Chinese Academy of Sciences,Wuhan,Hubei 43.074,{2. 3.graduate {3. of Chinese Academy of Sciences,19 Yuquan Road,beijing 100049,{2.

Tung tree, Vernicia fordii, is a woody oil plant native to china. The Chinese have used its oil for thousands of years to make lacquers, varnishes and other products. The

关键词： Vernicia fordii,tung tree,ISSR,biodiesel plant

来源： cnki会议评论

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Systems Science and Mathematical Sciences 2000年第3期13卷 242-249页

作者： YANG Yixian(Information Security Center, Depertment of Information Engineering, beijing university of Posts and Telecommunication, beijing 100876,{3.) 北京 100876

Eight families of Costas arrays with ideal cross-coincidence are algebraically constructed under the assumptin that the vertical shifts are appropriately *** Costas arrays are useful for designing multiple Costas wavforms with small crossambiguities, if the potential Doppler shifts are restricted to a small portion of the wavform bandwidth.

关键词： Costas arrays signal design coding optical orthogonal codes

Dissolved inorganic carbon and CO_(2. fluxes across Jiaozhou Bay air-water interface

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Acta Oceanologica Sinica 2004年第2期23卷 279-285页

作者： LIXuegang LINing GAOXuelu SONGJinming InstituteofOceanology ChineseAcademyofSciencesQingdao266071China graduateSchool ChineseAcademyofSciencesBeijing100039China

On the basis of data collected in the Jiaozhou Bay in June and July 2.03. the DIC distribution in seawater is studied, and an average air-sea flux of CO2.is estimated. The results show that the content of DIC inside the bay is markedly higher than outside the bay in June, but the content of DIC outside the bay is markedly higher than inside the bay in July. The trend of DIC distribution inside the bay is similar, viz. the content is the maximum in the northeast, then decreases gradually toward the west, and the content is the minimum in the west. The total trend of vertical distribution is to increase gradually from surface to bottom. This characteristic of DIC distribution is determined by Jiaozhou Bay hydrology and there is a close relation between DIC and particulate N,P. Average CO2.lux across the air-sea interface is 0.55 mol/(m2.a) in June and 0.72.mol/(m2.a) in July. Jiaozhou Bay is considered as a net annual source for atmospheric CO2.in June and July, and the total CO2.flux from seawater into atmosphere is about 740t in June and 969 t in July.

关键词： DIC flux of CO_2 Jiaozhou Bay