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Science china Chemistry 2006年第6期49卷 492-498页

作者： QI Yuanhua1.2. GUAN Daren1.& LIU Chengbu1.1. Institute of Theoretical Chemistry, Shandong {1., Jinan 2.01.0, china 2. School of Physics and Microelectronics, Shandong {1., Jinan 2.0061. china 1. Institute of Theoretical Chemistry Shandong University Jinan 250100 China 2. School of Physics and Microelectronics Shandong University Jinan 250061 China

The density functional theory (DFT) combining with the non-equilibrium Green functions (NEGF) method is applied to the study of the electronic transport properties for a Di-thiol-benzene (DTB) molecule coupled to two Au(1.1. surfaces. The dependence of the transport properties on the bias, the coupling geometry of the molecule-electrode interface, and the intermolecular interaction are examined in detail. The results show that the existence of the hydrogen atom at the end of the DTB molecule would significantly decrease the transmission coefficients, and then the differential conductance (dI/dV). By changing the position of the DTB molecule located between two electrodes a maximum value of calculated current is observed. It is also found that the intermolecular interaction will strongly influence the transport properties of the system studied.

关键词： non-equilibrium Green functions method, transmission spectrum, the molecular projected selfconsistent Hamiltonian, projected density of state.

A complex variable meshless method for fracture problems

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Science china(Physics,Mechanics & Astronomy) 2006年第1期49卷 46-59页

作者： CHENG Yumin1.& LI Jiuhong2.1. Shanghai Institute of Applied Mathematics and Mechanics, Shanghai {1., Shanghai 2.0072. china 2. Department of Building Engineering, Xi’an {1. of Technology, Xi’an 71.048, china Shanghai Institute of Applied Mathematics Mechanics Shanghai University Shanghai 200072 China Department of Building Engineering Xi’an University of Technology Xi’an 710048 China

Based on the moving least-square (MLS) approximation, the complex variable moving least-square approximation (CVMLS) is discussed in this paper. The complex variable moving least-square approximation cannot form ill-conditioned equations, and has greater precision and computational efficiency. Using the analytical solution near the tip of a crack, the trial functions in the complex variable moving least-square approxi- mation are extended, and the corresponding approximation function is obtained. And from the minimum potential energy principle, a complex variable meshless method for fracture problems is presented, and the formulae of the complex variable meshless method are obtained. The complex variable meshless method in this paper has greater precision and computational efficiency than the conventional meshless method. Some examples are given.

关键词： moving least-square approximation, complex variable moving least-square approximation, meshless method, complex variable meshless method, fracture.

Predicting the behavior of large scale P2. systems by parallel discrete event simulation

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Science china(Information Sciences) 2010年第6期53卷 1109-1121页

作者： ZHENG WeiMin1.YU HongLiang1.SHI GuangYu2.& CHEN Jian2.1.epartment of Computer Science and Technology,tsinghua university,Beijing 1.0084,{2. 2.uawei Technologies Co.,Ltd,shenzhen 51.1.0},{2. 1. Department of Computer Science and Technology Tsinghua University Beijing 100084 China2. Huawei Technologies Co. Ltd Shenzhen 518129 China

P2. systems are becoming the dominator of *** systems are typically composed of thousands to millions of physical computers,which make it difficult to predict their behaviors without a large scale distributed system *** paper is an attempt to predict the behavior of large scale P2. systems by building a novel parallel simulator:AegeanSim,which provides parallel discrete event simulation of such systems on high performance server *** abstract the execution of P2. applications with a specific event model,and parallel the simulation of events in a cluster,thus expanding the simulation scale and boosting the simulation process dramatically.A 1.stage synchronization method is proposed to improve the *** event callback interface is designed to implement their application logic easily while keeping the simulator *** use AegeanSim to predict the behavior of a typical P2. system:*** comparing the simulation behavior of BT with that of related BT studies and verifying its efficiency,scalability and accuracy,we make predictions about the behavior of BT system assuming they are assaulted by different man-made system *** reasonable results are found:(1. Tracker isolation can hardly work because of its short attacking time window.(2. Limiting the bandwidth of BT may be an efficient way to control it.

关键词： P2. simulation parallel

The Design and Its Application of Cross-Coupled Controller in X-Y Table

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武汉理工大学学报 2006年第S3期28卷 783-787页

作者： XI Lei~1.WANG Xin~2.ZHANG Yi~1.(1.Division of Control and Mechatronics Engineering,Harbin Institute of Technology {1. graduate,{1. 51.055,china, 2.Division of Mechanical Engineering & Automation,Harbin Institute of Technology {1. graduate,{1. 51.055,china) Division of Control and Mechatronics Engineering Harbin Institute of Technology Shenzhen GraduateShenzhen 518055China Division of Mechanical Engineering & Automation Harbin Institute of Technology Shenzhen GraduateShenzhen 518055China

In conventional cross-coupled controller design,the method usually ignored the inherent characteristic of time-vary- ing parameters and model uncertainties in *** this paper,a cross-coupled controller(CCC)using an H~∞control scheme has been proposed to reduce the contouring error for an X-Y ***,the proposed CCC design,which is a typical Multi- Input Multi-Output(MIMO)system with linear time varying(LTV)characteristics,has been verified as being internally stable. The simulations are carried on Matlab simulink to verify the proposed method,and the results showed that the proposed method can reduce the contouring error significantly compared with the conventional one.

关键词： motion control cross-coupled control contour error H∞control

Pole assignment in descriptor periodic systems

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Science china Mathematics 2005年第10期48卷 1309-1332页

作者： FAN Hung-Yuan~1.LIN Wen-Wei~1.& XU Shufang~2.1. Department of Mathematics,Tsing Hua {1.,Hsinchu 30043,china 2. LMAM,School of Mathematical Sciences,Peking {1.,Beijing 1.0871.china 1. Department of Mathematics Tsing Hua University 30043 Hsinchu China 2. LMAM School of Mathematical Sciences Peking University 100871 Beijing China

In this paper a pole assignment problem is considered for the descriptor linear discrete-time periodic systems, which is using the periodic proportional-derivative feedback to modify a given system such that the closed loop system has a specified selfconjugate set of eigenvalues. It is shown that the complete reachability of an open loop periodic system is equivalent to the possibility of assigning an arbitrary set of the eigenvalues to the system by choosing the suitable periodic proportional-derivative feedback.A computational approach is also proposed to solve the problem, which uses the reliable numerical techniques based on the orthogonal transformations. Numerical examples are presented to illustrate the effectiveness of the proposed approach.

关键词： descriptor linear periodic system, pole assignment, proportional and derivative feedback, numerical method, periodic Schur decomposition.

Boundary element-free method for elastodynamics

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Science china(Physics,Mechanics & Astronomy) 2005年第6期48卷 641-657页

作者： CHENG Yumin1.& PENG Miaojuan2.1. Shanghai Institute of Applied Mathematics and Mechanics, Shanghai {1., Shanghai 2.0072. china 2. Department of Civil Engineering, Shanghai {1., Shanghai 2.0072. china 1. Shanghai Institute of Applied Mathematics and Mechanics Shanghai University 200072 Shanghai China 2. Department of Civil Engineering Shanghai University 200072 Shanghai China

The moving least-square approximation is discussed first. Sometimes the method can form an ill-conditioned equation system, and thus the solution cannot be obtained correctly. A Hilbert space is presented on which an orthogonal function system mixed a weight function is defined. Next the improved moving least-square approximation is discussed in detail. The improved method has higher computational efficiency and precision than the old method, and cannot form an ill-conditioned equation system. A boundary element-free method (BEFM) for elastodynamics problems is presented by combining the boundary integral equation method for elastodynamics and the improved moving least-square approximation. The boundary element-free method is a meshless method of boundary integral equation and is a direct numerical method compared with others, in which the basic unknowns are the real solutions of the nodal variables and the boundary conditions can be applied easily. The boundary element-free method has a higher computational efficiency and precision. In addition, the numerical procedure of the boundary element-free method for elastodynamics problems is presented in this paper. Finally, some numerical examples are given.

关键词： moving least-square approximation, improved moving least-square approximation, elastodynamics, boundary integral equation, meshless method, boundary element-free method, Fourier eigen transform.

Commission Strategy of the Auction House

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Wuhan university Journal of Natural Sciences 2006年第3期11卷 507-510页

作者： WANG Yan~ 1.2.1. College of Economics, Fudan {1., Shanghai 2.0433, china 2. School of Mathematics and Statistics, Wuhan {1. , Wuhan 430072. Hubei, china College of Economics Fudan University 200433 Shanghai China School of Mathematics Statistics Wuhan University 430072 Wuhan Hubei China

In a SIPV model, when the commission proportion is not certain, but related with bargain price, generally, it is a linear function of the bargain price, this paper gives bidders＇ equilibrium bidding strategies in the first-and secondprice auctions. We find that the equilibrium strategies in second-price auction are dominant strategies. For seller or auction house, whether the fixed proportion or the unfixed proportion is good is not only related with constant item and the linear coefficient of the linear function, the size of the fixed commission proportion, but also related with the value of the item auctioned. So, in the practical auctions, the seller and the auction house negotiated with each other to decide the commission rules for their own advantage.

关键词： auction commission proportion Bayesian equilibrium bidding strategy

Analysis on ignition and extinction of n-heptane in homogeneous systems

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Science china(Technological Sciences) 2005年第5期48卷 556-569页

作者： LIU Yongfeng1.& PEI Pucheng2.1. Mechanical and Electrical Engineering Department, Beijing Institute of Civil Engineering and Architec-ture, Beijing 1.0044,{1. 2. State Key Laboratory of Automotive Safety and Energy, tsinghua university, Beijing 1.0084,{1. 1. Mechanical and Electrical Engineering Department Beijing Institute of Civil Engineering and Architecture 100044 Beijing China 2. State Key Laboratory of Automotive Safety and Energy Tsinghua University 100084 Beijing China

To calculate ignition delay times, the governing equations about species and temperature, which are in a closed volume based on the theory of thermal explosion and in a continuously stirred flow reactor, are deducted. The method referred to steady state assumptions is based on the observation that due to very fast chemical processes in combustion problems many chemical species and reactions are in a quasi-steady state or partial equilibrium. When a species is assumed to be in the steady state, the corresponding differential equation can be replaced by an algebraic relation, which reduces the computational costs. The steady state solution of the reactor equations describes the three ignition temperature regimes and get “S-shaped curve”. The reduced simplified 4-step mechanism for n-heptane from 1.1. elementary reactions leads with the steady state assumptions to linear differential equations, which is solved. The simulation results of the 4-step reduced mechanism for n-heptane are fitted well with the experiment data. At last, two important parameters are discussed thoroughly and the temperature perturbation is given. It reduces the computational efforts considerably without losing too much accuracy and further supplies numerical methods for turbulent combustion in the diesel engine.

关键词： ignition delay times, thermal runaway, steady state assumptions, continuously stirred flow reactor.

Uniform estimate for maximum of randomly weighted sums with applications to insurance risk theory

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Science china Mathematics 2005年第10期48卷 1379-1394页

作者： WANG Dingcheng~1.SU Chun~2.& ZENG Yong~1.1. School of Management and School of Applied Mathematics,{1. of Electronic Science and Technology of china,Chengdu 61.054,{2. 2. Department of Statistics and Finance,{1. of Science and Technology of china,Hefei 2.002.,{2. 1. School of Management and School of Applied Mathematics University of Electronic Science and Technology of China 610054 Chengdu China 2. Department of Statistics and Finance University of Science and Technology of China 230026 Hefei China

This paper obtains the uniform estimate for maximum of sums of independent and heavy-tailed random variables with nonnegative random weights, which can be arbitrarily dependent of each other. Then the applications to ... 详细信息

关键词： dependent stochastic return, discount factor, heavy-tails, discrete time insurance risk model, maxima of randomly weighted sums, ruin probability, tail probabilities, uniformly asymptotic estimate.

Mechanical model of vulnerable atherosclerotic plaque rupture

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Science china(Physics,Mechanics & Astronomy) 2004年第4期47卷 452-462页

作者： SU Haijun1. ZHANG Mei2.& ZHANG Yun2.1. School of Mathematics and System Science, Shandong university, Jinan 2.01.0, china 2. Qilu Hospital, Shandong university, Jinan 2.001.0} china 1. School of Mathematics and System Science Shandong University 250100 Jinan China 2. Qilu Hospital Shandong University 250012 Jinan China

Rupture of atherosclerotic plaque is the main trigger of acute cardiovascular events, but the mechanism of plaque rupture is still unknown. We have constructed a model describing the motion of the fibrous cap of the plaque using the theory of elastic mechanics and studied the stability of the plaque theoretically. It has shown that plaque rupture is the result of a dynamic interplay between factors intrinsic to the plaque itself and extrinsic factors. We have proposed a new mechanism of plaque rupture, given a new explanation about the nonlinear dynamic progress of atherosclerosis and suggested a method to identify the vulnerable plaques to manage atherosclerosis.

关键词： fibrous cap, parametric resonance, stability, mechanism, identification.