检索结果-南通市图书馆

An efficient algorithm for solving supply chain network equilibria and equivalent supernetwork based traffic network equilibria

在线全文

学校读者我要写书评

暂无评论

Science china(Technological Sciences) 2010年第12期53卷 3264-3274页

作者： XU Meng1 & GAO ZiYou2 1 MOE Key Laboratory for Urban transportation Complex Systems Theory and Technology, beijing jiaotong university, beijing 100044, china 2 Institute of Systems Science, school of traffic and transportation, beijing jiaotong university, beijing 100044, china 1. MOE Key Laboratory for Urban transportation Complex Systems Theory and Technology Beijing Jiaotong University Beijing 100044 China2. Institute of Systems Science School of Traffic and Transportation Beijing Jiaotong University Beijing 100044 China

This paper is concerned with the algorithm of the supply chain network equilibrium model and its equivalent supernetwork based traffic network equilibrium model with elastic demands. Both models are further written as nonlinear complementarity problems. Semismooth least squares reformulations of the complementarity problems are presented and their convergence properties are investigated. Considering the drawbacks of Quasi-Newton method (using the Fischer-Burmeister function), a semi-smooth Levenberg-Marquardt-type method is proposed to solve the problems. Numerical examples show that the Levenberg-Marquardt-type method can solve the supply chain network equilibrium model and its equivalent supernetwork based traffic network equilibrium model significantly, and is more efficient than the Quasi Newton method and the modified projection method. Furthermore, the Levenberg-Marquardt-type method with the equivalent supernetwork based complementarity formulation can be implemented faster than with the supply chain network equilibrium complementarity formulation.

关键词： supply chain networks traffic network equilibrium supernetwork nonlinear complementarity problem Levenberg Marquardt-type method

On time-step in structural seismic response analysis under ground displacement/acceleration

在线全文

学校读者我要写书评

暂无评论

Earthquake Engineering and Engineering Vibration 2009年第3期8卷 341-347页

作者： TianYuji~+ and Yang Qingshan~(++) school of Civil Engineering,beijing jiaotong university,beijing 100044,china +Associate Professor ++Professor school of Civil Engineering Beijing Jiaotong University Beijing 100044 China

There are two models in use today to analyze structural responses when subjected to earthquake ground motions, the Displacement Input Model （DIM） and the Acceleration Input Model （AIM）. The time steps used in direct integration methods for these models are analyzed to examine the suitability of DIM. Numerical results are presented and show that the time-step for DIM is about the same as for AIM, and achieves the same accuracy. This is contrary to previous research that reported that there are several sources of numerical errors associated with the direct application of earthquake displacement loading, and a very small time step is required to define the displacement record and to integrate the dynamic equilibrium equation. It is shown in this paper that DIM is as accurate and suitable as, if not more than, AIM for analyzing the response of a structure to uniformly distributed and spatially varying ground motions.

关键词： integration time step multi-supported structure displacement input model acceleration input model spatially varying ground motions

A new seismic isolation system and its feasibility study

在线全文

学校读者我要写书评

暂无评论

Earthquake Engineering and Engineering Vibration 2010年第1期9卷 75-82页

作者： Jia Gaofeng~+ and Shi Zhifei~(++) school of Civil Engineering,beijing jiaotong university,beijing 100044,china Graduated Student ++ Professor school of Civil Engineering Beijing Jiaotong University Beijing 100044 China

This paper introduces a new seismic isolation system called a periodic foundation （PF）, where inclusions are periodically arranged. The PF is different from traditional base isolation in that it causes a fundamental frequency shift in the structure, thus reducing its response and generating a frequency gap. If the frequency contents of a seismic wave fall into the gap, it can not propagate in the foundation. Thus, it will exert no influence on the structure above. A systematic study of the band of frequency gap for a 2D PF is conducted. The influence of physical and geometrical parameters such as density and elastic modulus as well as filling fraction of the PF and its materials on the band of frequency gap are investigated, and a design with a frequency gap as low as 2.49-3.72 Hz is achieved. This band of frequency gap corresponds well to the design spectra in earthquake engineering. Numerical simulations of a six-story frame structure with different foundations demonstrate that a proposed PF can greatly reduce the seismic response of an isolated structure. This investigation shows that PFs have great potential in future applications of seismic isolation technology.

关键词： seismic isolation periodic foundation band of frequency gap

Techniques for searching first integrals by Lie group and application to gyroscope system

在线全文

学校读者我要写书评

暂无评论

Science china Mathematics 2005年第8期48卷 1135-1143页

作者： HU Yanxia & GUAn Keying Department of Mathematics, school of Science, beijing jiaotong university, beijing 100044, china 1. Department of Mathematics School of Science Beijing Jiaotong University 100044 Beijing China

In the paper, the methods of finding first integrals of an autonomous system using one-parameter Lie groups are discussed. A class of nontrivial one-parameter Lie groups admitted by the classical gyroscope system is found, and based on the properties of first integral determined by the one-parameter Lie group, the fourth first integral of the gyroscope system in Euler case, Lagrange case and Kovalevskaya case can be obtained in a uniform idea. An error on the fourth first integral in general Kovalevskaya case (A=B=2C,zG=0), which appeared in literature is found and corrected.

关键词： one-parameter Lie group first integral gyroscope system

Reliability analysis of M/G/1 queues with general retrial times and server breakdowns

在线全文

学校读者我要写书评

暂无评论

Progress in Natural Science:Materials International 2006年第5期16卷 464-473页

作者： WANG Jinting (Department of Mathematics, beijing jiaotong university, beijing 100044, china) Department of Mathematics Beijing Jiaotong University Beijing 100044 China

This paper concerns the reliability issues as well as queueing analysis of M/G/1 retrial queues with general retrial times and server subject to breakdowns and repairs. We assume that the server is unreliable and customers who find the server busy or down are queued in the retrial orbit in accordance with a first-come-first-served discipline. Only the customer at the head of the orbit queue is allowed for access to the server. The necessary and sufficient condition for the system to be stable is given. Using a supplementary variable method, we obtain the Laplace-Stieltjes transform of the reliability function of the server and a steady state solution for both queueing and reliability measures of interest. Some main reliability indexes, such as the availability, failure frequency, and the reliability function of the server, are obtained.

关键词： retrial queues general retrial times reliability server breakdowns and repairs.

A geometrical and physical nonlinear finite element model for spatial thin-walled beams with arbitrary section

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

Science china(Technological Sciences) 2010年第3期53卷 829-838页

作者： YANG QingShan 1 &WANG XiaoFeng 2 1 school of Civil Engineering,beijing jiaotong university,beijing 100044,china 2 College of Civil Engineering,Tongji university,Shanghai 200092,china 1. school of Civil Engineering Beijing Jiaotong University Beijing 100044 China2. College of Civil Engineering Tongji University Shanghai 200092 China

Based on the theories of Bernoulli-Euler beams and Vlasov's thin-walled members,a new geometrical and physical nonlinear beam element model is developed by applying an interior node in the element and independent interpolations on bending angles and warp,in which factors such as traverse shear deformation,torsional shear deformation and their coupling,coupling of flexure and torsion,and second shear stress are all ***,geometrical nonlinear strain in total Lagarange(TL) and the corresponding stiffness matrix are *** plastic model is applied to physical nonlinearity to comply with the yield rule of Von Mises and incremental relationship of *** stiffness matrix is derived by numerical integration on the basis of the finite segment *** show that the developed model is feasible in analysis of thin-walled structures with high accuracy.

关键词： Spatial beams thin-walled structures geometrical and physical nonlinearity finite element arbitrary section

An improved reduced-rank STAP interference suppression method in design of GNSS receivers

在线全文

学校读者我要写书评

暂无评论

Science china(Information Sciences) 2012年第10期55卷 2329-2342页

作者： GONG WenFei & SUN Xin school of Electronics and Information Engineering,beijing jiaotong university,beijing 100044,china 1. school of Electronics and Information Engineering Beijing Jiaotong University Beijing 100044 China

In this paper,we address the problem of interference cancellation in global positioning system(GPS) receiver using an adaptive reduced-rank space-time adaptive processing(STAP) interference suppression method based on multistage nested Wiener filter(MSNWF).This improved adaptive reduced-rank method is based on the improved Gerschgorin radii ***,the cross-correlations between the desired signals of the adjacent stages of MSNWF are directly used to calculate the Gerschgorin radii instead of employing the eigenvalue decomposition of the covariance ***,a heuristic decision rule based on Gerschgorin disk estimator(GDE) is employed to estimate the rank of interference *** optimal rank can be adaptively selected without increasing the *** and results of the experiment show that the proposed method further reduces the computation of STAP and enhances its real-time property with the interference suppression performance unaffected.

关键词： global positioning system reduced-rank space-time adaptive processing multistage nested Wiener filter Gerschgorin disk estimator

Inferring playback rate and rate resets of P2P video streaming transmissions by piecewise line envelope approximation

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

The Journal of china Universities of Posts and Telecommunications 2009年第2期16卷 58-62,79页

作者： LI Chun-xi CHEN Chang-jia school of Electronics and Information Engineering,beijing jiaotong university,beijing 100044,china [a]school of Electronics and Information Engineering beijing jiaotong university beijing 100044 china

Conventionally, P2P video is regarded as CBR traffic. However, our measurements have shown that the rate reset cannot be neglected in a practical IPTV system because each rate reset often leads to performance degradation. Thus, addressing the problem of inferring playback rate and rate reset in a P2P video system is significant. In this article, an algorithm termed piecewise linear envelope approximation （PLEA） is proposed, in which a follow-up time is introduced to smooth rate fluctuations in a small time scale and to adapt rate jumps in a large time scale automatically. With the PLEA algorithm, discontinuity introduced by blind segmentations adopted by current methods is avoided. Furthermore, unlike existing algorithms in which both segmentation and combinations are performed in multiple runs, only a single computation path is involved in the PLEA algorithm. This makes PLEA algorithm amenable to implementation of low complexity by either software or hardware. Both theoretical analysis and experiment based on measured data show that the PLEA outperforms existing algorithms based on segmentation.

关键词： P2P video playback rate rate reset convex hull linear program

Optimization model and algorithm for mixed traffic of urban road network with flow interference

在线全文

学校读者我要写书评

暂无评论

Science china(Technological Sciences) 2008年第12期51卷 2213-2222页

作者： SI BingFeng,LONG JianCeng & GAO ZiYou State Key Laboratory of Rail traffic Control and Safety,beijing jiaotong university,beijing 100044,china State Key Laboratory of Rail traffic Control and Safety Beijing Jiaotong University Beijing 100044 China

In this paper,the problem of interferences between motors and non-motors in urban road mixed traffic network is considered and the corresponding link impedance function is presented based on travel *** the base of this,the main factors that influence travelers' traffic choices are all considered and a combined model including flow-split and assignment problem is *** a bilevel model with its algorithm for system optimization of urban road mixed traffic network is *** the application of the model and its algorithm is illus-trated with a numerical example.

关键词： mixed traffic impedance function user equilibrium optimization