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

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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 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

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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 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

A new class of impulse stochastic control models with non-negative control quantity

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Science China(Information Sciences) 2011年第3期54卷 638-652页

作者： LIU XiaoPeng & LIU KunHui College of Science, beijing Jiaotong University, beijing 100044, China College of Science Beijing Jiaotong University Beijing China

This paper advances and studies a new class of impulse stochastic control models. Its state structure is defined by a linear stochastic differential equation of the semi-martingale, its control cost function is a twovariable function of pre-control state quantity and control quantity, and its control quantity is kept non-negative. First this paper constructs a new type of variational equations and proves its solution exists. Using a series of stochastic analysis methods to research the solution function of this type of variational equations, this paper proves the existence of optimal control and analyzes its structure in depth. Because of the big difference between the model in this paper and stochastic control models in previous papers, the analysis method here is quite different from previous ones. It is expected that this paper will have important theoretical significance for stochastic control research, along with wide applicative value in finance control and security management.

关键词： impulse stochastic control control quantity variational equation optimal control semi-martingale

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

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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 Department of Mathematics School of Science Beijing Jiaotong University 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

Surface embeddability of graphs via homology

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Science China Mathematics 2010年第11期53卷 2889-2892页

作者： LIU Yan PeiInstitute of Mathematics, beijing Jiaotong University, beijing 100044, China Institute of Mathematics Beijing Jiaotong University Beijing China

This paper presents a characterization of the embeddability on a surface of genus arbitrarily given for a graph. Its specific case for the surface of genus zero leads to the famous planarity theorems given independent... 详细信息

关键词： surface graph embedding duality homology

Determination of the packing number D_λ(3,W_4^((3)),v)

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Science China Mathematics 2009年第11期52卷 2537-2548页

作者： WU Yan & CHANG YanXun Institute of Mathematics,beijing Jiaotong University,beijing 100044,China Institute of Mathematics Beijing Jiaotong University Beijing China

A t-hyperwheel(t≥3) of length l(or W l(t) for brevity) is a t-uniform hypergraph(V,E) ,where E = {e1,e2,. . .,el} and v1,v2,. . .,vl are distinct vertices of V = il=1 ei such that for i = 1,. . .,l,vi,vi+1 ∈ ei and ei ∩ ej = P,j ∈/{i-1,i,i + 1},where the operation on the subscripts is modulo l and P is a vertex of V which is different from vi,1 i l. In this paper,we investigate the maximum packing problem of MPλ(3,W 4( 3) ,v) . Finally,the packing number Dλ(3,W 4( 3) ,v) is determined for any positive integers v 5 and λ.

关键词： t-(v Γ λ) packing leave packing number group divisible(Γ t) -design candelabra(Γ t) -system

Tree　ring　analysis　for　determination　of　pollution　history　of　Chengde　City，north　China

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Journal of Environmental Sciences 1996年第1期8卷 77-85页

作者： Jiang Gaoming(Institute of Botany, Chinese Academy of Sciences,beijing 100044,China ) Inst Botany Chinese Acad of Sci Beijing China China

Air pollution history of sulphur and heavy metals since 1800 in Chengde City , north China,was studied by analyzing the concentrations of sulphur and heavy metals in growth rings of Pinus tabulaeformis Carr. Sulphur concentrations in the tree rings of 1910-1920, 1970-1980,and 1980-1990 have increased 1-2 , 3-5 and 10 times respectively as those in the tree ring of 1810-1820 (P<0. 05). This is ascribed to the result of urbanization, especially the appearance and aggravation of industrialization, in the city of Chengde since 1950s. Fe appeared to increase during 1920-1940, possibly due to the opening of Damiao Iron Mine by the Japanese in 1927; Mn increased throughout the whole history, from 4. 1 μg/g(1840- 1850) to 10. 4 μg/g (1980 1990,P <0. 05);Pb did not increase until 1980 but increased sharply during the last 10 years by 560%(P<0. 001). This is caused by the increased number of automobiles in the city. The contents of Cu,Zn, Ni have changed little. The concentrations of sulphur and heavy metals in the tree rings at the beginning of 1800s were the lowest and could be regarded as the background *** calculated that S, Fe, Pb, Mn, Ni, and Zn in the tree rings have increased 10, 2.4,1.8,1.5,1.0 and 0. 8 times respectively during the past 190 years or so. The results showed that serious environmental pollution, especially air pollution of SO2,has occurred since 1949 when the People's Republic of China was founded.

关键词： tree rings Pinus tabulaeformis sulphur and heavy metals pollution history Chengde

ON THE SINGLE SERVER RETRIAL QUEUE WITH PRIORITY SUBSCRIBERS AND SERVER BREAKDOWNS

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Journal of Systems Science & Complexity 2008年第2期21卷 304-315页

作者： Jinting WANG Department of Mathematics Beijing Jiaotong University Beijing 100044 China

The author concerned the reliability evaluation as well as queueing analysis of M1, M2/G1, G2/1 retrial queues with two different types of primary customers arriving according to independent Poisson flows. In the case of blocking, the first type of customers can be queued whereas the second type of customers must leave the service area but return after some random period of time to try their luck again. The author assumes that the server is unreliable and it has a service-type dependent, exponentially distributed life time as well as a service-type dependent, generally distributed repair time. The necessary and sufficient condition for the system to be stable is investigated. Using a supplementary variable method, the author obtains a steady-state solution for queueing measures, and the transient as well as the steady-state solutions for reliability measures of interest.

关键词： Priority queues reliability retrial queues server breakdowns.

A new method for counting trees with vertex partition

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Science China Mathematics 2008年第11期51卷 2000-2004页

作者： LIU YanPei Institute of Mathematics, beijing Jiaotong University, beijing 100044, China Institute of Mathematics Beijing Jiaotong University Beijing China

A direct and elementary method is provided in this paper for counting trees with vertex partition instead of recursion, generating function, functional equation, Lagrange inversion, and matrix methods used before.

关键词： tree planted tree joint tree model vertex partition code 05C30 05C10