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The influence of thermal radiation on MHD station-point flow past a stretching sheet with heat generation

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Acta Mechanica Sinica 2011年第4期27卷 502-509页

作者： Jing Zhu.Lian-Cun Zheng.Xin-Xin Zhang department of Mathematics and Mechanics,University of Science and technology beijing,100083 beijing,china Thermal engineering department,University of Science and technology beijing,100083 beijing,china Zheng department of Mathematics and Mechanics University of Science and Technology Beijing Beijing China Thermal engineering department University of Science and Technology Beijing Beijing China

This letter is concerned with the plane and axisymmetric stagnation-point flows and heat transfer of an electrically-conducting fluid past a stretching sheet in the presence of the thermal radiation and heat generation or absorption. The analytical solutions for the velocity distribution and dimensionless temperature profiles are obtained for the various values of the ratio of free stream velocity and stretching velocity, heat source parameter, Prandtl number, thermal radiation parameter, the suction and injection velocity parameter and magnetic parameter and dimensionality index in the series form with the help of homotopy analysis method （HAM）. Convergence of the series is explicitly dis- cussed. In addition, shear stress and heat flux at the surface are calculated.

关键词： Thermal radiation MHD Laminar boundarylayers - Homotopy analysis method

The Process of TiB_2-Cu Composite Phase and Structure Formation during Combustion Synthesis

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Journal of Wuhan University of technology(Materials Science) 2006年第4期21卷 113-116页

作者：徐强 School of Materials Science and engineering Beijing Insitute of TechnologyBeijing 100081China

The reaction process of combustion synthesis for TiB2 -Cu was investigated in detail using combustion-wave arresting experiment, X-ray diffraction （ XRD ） analysis, SEM analysis and differential thermal analysis （ DTA ）. The XRD analysis results for the different parts of the quenched specimen show that TiCux intermetallic phase firstly forms with the propagation of combustion wave, and then Ti1.87 B50 and Ti3B4 metastable phases come forth due to the diffusion of B atoms and finally the stable TiB2 phase forms because of the continuous diffusion of B atoms. The formation of TiB2 phase is uot completed by one step, but undergoes several transient processes. The process of reaction synthesis for Ti-B-Cu ternary system can be divided into three main stages： melting of Cu and Ti , and the formation of Cu- Ti melt and few TiCux , TiBx intermetallic phases ; large numbers of TiCux intermetallic phases formation and some fine TiB2 particles precipitation ; and the TiB2 particles coarsening and the stable TiB2 and Cu two phases formation in the final product.

关键词： combustion synthesis reaction process TiB2 phase combustion-wave arresting experiment

A DIFFERENTIAL GEOMETRIC DESCRIPTION FOR TIME-INDEPENDENT CHETAEV'S NONHOLONOMIC MECHANICAL SYSTEM WITH UNILATERAL CONSTRAINTS

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Acta Mechanica Solida Sinica 2002年第1期15卷 62-67页

作者： Zhang Yi (department of Urban Constrution,University of Science & technology of Suzhou,Suzhou 215011,china)Mei Fengxiang (department of Applied Mechanics,beijing institute of technology,beijing 100081,china) department of Urban Construction University of Science and Technology of Suzhou Suzhou 215011 China department of Applied Mechanics Beijing Institute of Technology Beijing 100081 China

By applying the framework of the tangent bundle geometry to the method of Lagrange multi- pliers,a geometric description of Chetaev's nonholonomic systems subjected to unilateral nonholonomic con- straints trod unilat... 详细信息

关键词： analytical mechanics unilateral constraint differential geometry nonholonomic constraint tangent bundle geometry

Two Side Chain β-CD Polysiloxanes Used as New Stationary Phase for Chiral Separation by HRGC

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Chinese Chemical Letters 1997年第2期8卷 165-166页

作者： Han Bang ZHANG Yun LING Ruo Nong FU Yu Xiu WEN(department of Chemical engineering. beijing institute of technology. beijing 100081) beijing INST TECHNOL DEPT CHEM ENGNBEIJING 100081PEOPLES R CHINA

Two new stationary phases : (Ⅰ) [bikis(2,6-di-O-pentyl-3-O-hex-6O-pentyl-3-O-methyl)-β-CD-polysiloxane] and (Ⅱ) [heptkis(2,6-di-O-methyl-3-O-hex-6-enyl)-β-CD-polysiloxane] were synthesized and successfully used fo... 详细信息

关键词： HRGC CD Polysiloxanes Used as New Stationary Phase for Chiral Separation by HRGC Two Side Chain

THE POPULATION DYNAMICS WITH N-INTERSECTIONS

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Systems Science and Mathematical Sciences 1994年第2期7卷 177-186页

作者： GUO Baozhu(department of Applied Mathematics beijing institute of technology,beijing 100081, china)

ＴＨＥＰＯＰＵＬＡＴＩＯＮＤＹＮＡＭＩＣＳＷＩＴＨＮ－ＩＮＴＥＲＳＥＣＴＩＯＮＳ￥ＧＵＯＢａｏｚｈｕ（ＤｅｐａｒｔｍｅｎｔｏｆＡｐｐｌｉｅｄＭａｔｈｅｍａｔｉｃｓＢｅｉｊｉｎｇＩｎｓｔｉｔｕｔｅｏｆＴｅｃｈｎｏｌｏｇ... 详细信息

ＴＨＥＰＯＰＵＬＡＴＩＯＮＤＹＮＡＭＩＣＳＷＩＴＨＮ－ＩＮＴＥＲＳＥＣＴＩＯＮＳ￥ＧＵＯＢａｏｚｈｕ（ＤｅｐａｒｔｍｅｎｔｏｆＡｐｐｌｉｅｄＭａｔｈｅｍａｔｉｃｓＢｅｉｊｉｎｇＩｎｓｔｉｔｕｔｅｏｆＴｅｃｈｎｏｌｏｇｙ，Ｂｅｉｊｉｎｇ１０００８１，Ｃ...

关键词： Population dynamics stable population logistic model

Small Random Perturbations of One-Dimensional Diffusion Processes

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Acta Mathematica Sinica,English Series 1998年第1期14卷 35-40页

作者： Xi Fubao department of Applied Mathematics, beijing institute of technology, beijing 100081, china

In the present paper we consider the small random perturbations of one-dimensional diffosion processes. By virtue of stochastic analysis methods, we investigate the asymptotics of the mean exit times and probabilistic... 详细信息

关键词： Diffusion processes Small random perturbations Exit times

Multi-Step Amplitude Quantization for Ultralow Sidelobe Phased Arrays by Direct Optimization Synthesis

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Journal of Systems engineering and electronics 2001年第1期12卷 65-69页

作者： Zhu Huan Wang Yixin Xu Xiaowen & Li Shizhi Dept. of electronic engineering, beijing institute of technology, 100081, P. R. china Dept. of electronic engineering Beijing Institute of Technology 100081 P. R. China

In this paper, a new amplitude quantization synthesis method for ultralow sidelobe phased arrays is proposed, which is based on the constrained nonlinear optimization algorithm. By introducing a set of critical constraint conditions into the optimization model, we can directly quantize the amplitude distribution instead of replacing it with a continuous equivalent aperture antenna. The mutual coupling and the element patterns are also considered in the quantization synthesis. Finally, some array simulation results are given to show the effectiveness of the method.

关键词： Algorithms Computer simulation Directional patterns (antenna) Directive antennas Mathematical models Optimization Vector quantization

The numerical method for three-dimensional impact with friction of multi-rigid-body system

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Science china(Physics,Mechanics & Astronomy) 2006年第1期49卷 102-118页

作者： ZHAO Zhen1,2, LIU Caishan2 & CHEN Bin2 1. beijing institute of Graphic Communication, beijing 102600, china 2. department of Mechanics & engineering Science, Peking University, beijing 100871, china beijing institute of Graphic Communication Beijing 102600 China department of Mechanics & engineering Science Peking University Beijing 100871 China

The differential equations for planar impacts reduce to an algebraic form, and can be easily solved. For three dimensional impacts with friction, there is no closed-form solution, and numerical integration is required due to the swerve behavior of tangential impulse during collisions. The dynamic governing equations in the impact process are built up in impulse space based on the Lagrangian equation in this paper. The coefficient of restitution defined by Poisson is used as the condition of impact termination. A valid nu- merical method for solving three-dimensional frictional impact of multi-rigid body system is established. The singular cases of tangential movement in sticking point are especially noticed and analyzed. Several examples are present to reveal the different kinds of tan- gential movement modes varied with the normal impulse during collision.

关键词： multi-rigid body, impact, friction.

On the Iteration of Holomorphic Self Maps of C

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Acta Mathematica Sinica,English Series 1998年第1期14卷 139-144页

作者： Fang Liping department of Applied Mathematics, beijing institute of technology, beijing 100081, china

Let f be a holomorphic self-map of the punctured plane C~*=C\{0} with essentially singular points 0 and ∞. In this note, we discuss the sets I_O(f)={z∈C~*: f^n(z)→0,n→∞} and I_∞(f)={z∈C~*: f^n(z)→∞,n→∞}.We try to find the relation between I_O(f), I_∞(f) and J(f). It is proved that both the boundary of I_O(f) and the boundary of I_∞(f) equal to J(f), I_O(f) ∩J(f)≠ 0 and I_∞(f)∩J(f)≠. As a consequence of these results, we find both I_O(f) and I_∞(f) are not doubly-bounded.

关键词： Iteration Julia set