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The effect of high temperature induced variation of specific heat on the hypersonic turbulent boundary layer and its computation

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Science china(Physics,Mechanics & Astronomy) 2010年第11期53卷 2103-2112页

作者： DONG Ming & ZHOU Heng Department of Mechanics,tianjin University,tianjin 300072,china tianjin University Department of Mechanics Tianjin China (GRID:grid.33763.32) (ISNI:***)

For hypersonic vehicles,as the temperature in its boundary layer usually exceeds 600 K,for which the molecular vibrational degree of freedom is excited,the perfect gas model is no longer *** this paper,the effect of high temperature induced variation of specific heat on the hypersonic turbulent boundary layer of flat plates is investigated by direct numerical simulations with the perfect gas model,*** constant specific heat,as well as with a variable specific heat gas *** comparison of the results from the two gas models has found that the effect of the variation of specific heat on the velocity of the turbulent boundary layers is relatively small,while its effect on temperature,such as the mean temperature,the temperature fluctuations,is *** is also found that the mean specific heat is quite close to the specific heat calculated by using the mean temperature,indicating that it is possible to do turbulence *** modeling is done under the variable specific heat gas model with the mean temperature as the *** feasibility of such consideration is verified by applying the SST model for variable specific heat turbulence computation.

关键词： hypersonic turbulent boundary layer specific heat direct numerical simulation SST model

The improvement of turbulence modeling for the aerothermal computation of hypersonic turbulent boundary layers

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Science china(Physics,Mechanics & Astronomy) 2010年第2期53卷 369-379页

作者： DONG Ming & ZHOU Heng Department of Mechanics,tianjin University,tianjin 300072,china tianjin University Department of Mechanics Tianjin China (GRID:grid.33763.32) (ISNI:***)

The engineering computation of turbulent flows is mainly based on turbulence modeling,however,accurate aerothermal computation of hypersonic turbulent boundary layers is still a not well-solved problem. Aerothermal computation for turbulent boundary layers on a supersonic or hypersonic blunt cone with small bluntness is done firstly by using both direct numerical simulation and BL model,and seven different cases are investigated. Then the results obtained by the two methods are compared,and the reason causing the differences is found to be the incorrect assumption in the turbulence modeling that the ratio between eddy heat conductivity and eddy viscosity is constant throughout the whole boundary layer. Based on certain theoretical arguments,a method of modifying the expression of eddy heat conductivity in the region surrounding the peak location of the turbulent kinetic energy is proposed,which is verified to be effective,at least for the seven cases investigated.

关键词： hypersonic turbulent boundary layer aerothermal supersonic cone direct numerical simulation(DNS) BL model coefficient of eddy heat conductivity

Synthesis and Crystal Structure of Rctt-1-(2-benzoxazolyl)-2-(4-chlorophenyl)-4-phenyl-3-(4-pyridinyl)cyclobutane

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Chinese Journal of Structural Chemistry 2003年第1期22卷 65-69页

作者： ZHUANG Jun-Peng ZHANG Wen-Qin② (Department of Chemistry, tianjin University, tianjin 300072, china) tianjin Univ Dept Chem Tianjin 300072 Peoples R China

The title compound (C28H21ClN2O, Mr = 436.92) was synthesized by the cross- photodimerization of (E)-2-(2-phenylethenyl)benzoxazole and (E)-4-[2-(4-chlorophenyl)ethenyl]- pyridine in sulfuric acid solution. Its molecular structure has been unequivocally determined by X-ray crystallography. The title compound belongs to triclinic system, space group P?with cell parameters: a = 9.648(3), b = 10.458(4), c = 12.106(4) , a = 89.089(7), b = 75.644(6), g = 68.441(7)? V = 1096.7(7) 3, Z = 2, Dc = 1.323 g/cm3, F(000) = 456 and m(MoKa) = 0.198 mm-1. The final R and wR are 0.0627 and 0.1285, respectively for 1737 observed reflections with I > 2s(I). S = 0.921 and (/s)max = 0.001. The cyclobutane ring has a puckered conformation with four different aryl groups substituted on each carbon atom. The dihedral angles of the cyclobutane ring are 20.2 and 20.6? The bond distances of the cyclobutane ring are 1.541, 1.555, 1.560 and 1.563 ? respectively, which are slightly longer than that of the normal CC single bond. The title compound is the only cross-dimer and its two heteroaryl groups are situated at the trans-1,3 position of the cyclobutane ring, revealing that the cross-photodimerization proceeds in a head-to-tail pattern with high stereo-selectivity.

关键词： cyclobutane photodimerization crystal structure

ON THE ORIENTATION OF BUCKLING DIRECTION OF ANISOTROPIC ELASTIC PLATE UNDER UNIAXIAL COMPRESSION

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Acta Mechanica Solida Sinica 2001年第2期14卷 130-137页

作者： Zhang Yitong (Department of Mechanics, tianjin University, tianjin 300072, china) Department of Mechanics Tianjin University Tianjin 300072 China

The theory of small deformation superimposed on a largedeformation of an elastic solid is used to investigate the bucklingof anisotropic elastic plate under uniaxial compression. The bucklingdirec- tion (th direction of buckling direction is obtained. It isfound that the out-of-plane buckling of anisotropic elastic plate ispossible and both buckling conditions for flexural and extensionalmodes are presented.

关键词： buckling buckling direction anisotropic elastic plate

A QUASI-NEWTON METHOD IN INFINITE-DIMENSIONAL SPACES AND ITS APPLICATION FOR SOLVING A PARABOLIC INVERSE PROBLEM

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Journal of Computational Mathematics 1998年第4期16卷 305-318页

作者： Wen-huan Yu(Department of Mathematics, tianjin University, tianjin 300072, P.R. china.) Department of Mathematics Tianjin University Tianjin 300072 China

A Quasi-Newton method in Infinite-dimensional Spaces (QNIS) for solving operator equations is presellted and the convergence of a sequence generated by QNIS is also proved in the paper. Next, we suggest a finite-dimensional implementation of QNIS and prove that the sequence defined by the finite-dimensional algorithm converges to the root of the original operator equation providing that the later exists and that the Frechet derivative of the governing operator is invertible. Finally, we apply QNIS to an inverse problem for a parabolic differential equation to illustrate the efficiency of the finite-dimensional algorithm.

关键词： Quasi-Newton method parabolic differential equation inverse problems in partial differential equations linear and Q-superlinear rates of convergence

ON OUT-OF-PLANE BUCKLING OF ANISOTROPIC ELASTIC PLATE SUBJECTED TO A SIMPLE SHEAR

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Acta Mechanica Solida Sinica 2002年第3期15卷 236-243页

作者： Zhang Yitong (Department of Mechanics,tianjin University,tianjin 300072,china) Department of Mechanics Tianjin University Tianjin 300072 China

Out-of-plane buckling of anisotropic elastic plate subjected to asimple shear is investigated. From exact 3-D equilibrium conditionsof anisotropic elastic body with a plane of elastic symmetry atcritical Configuration, the equation for buckling direction (bucklingwave direction) parameter is derived and the Shape functions ofpossible buckling modes are obtained. The traction free boundaryconditions which must Hold on the upper and lower surfaces of platelead to a linear eigenvalue problem whose nontrivial solutions Arejust the possible buckling modes for the plate.

关键词： nonlinear elasticity buckling bifurcation anisotropic elastic plate

Diffraction of plane SV waves by a cavity in poroelastic half-space

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Earthquake Engineering and Engineering Vibration 2009年第1期8卷 29-46页

作者： Liang Jianwen and Liu Zhongxian Department of Civil Engineering, tianjin University, tianjin 300072, china Professor PhD Candidate Department of Civil Engineering Tianjin University Tianjin 300072 China

This paper presents an indirect boundary integration equation method for diffraction of plane SV waves by a 2-D cavity in a poroelastic *** Green＇s functions of compressive and shear wave sources are derived based on Biot＇s theory. The scattered waves are constructed using fictitious wave sources close to the boundary of the cavity, and their magnitudes are determined by the boundary conditions. Verification of the accuracy is performed by：（1） checking the satisfaction extent of the boundary conditions, （2） comparing the degenerated solutions of a single-phased case with well- known solutions, and （3） examining the numerical stability of the solutions. The nature of diffraction of plane SV waves around a cavity in a poroelastic half-space is investigated by numerical examples.

关键词： poroelastic half-space cavity diffraction plane SV waves compressive wave source shear wave source Green's function pore pressure

A　COMPLETE　METRIC　OF　POSITIVE　CURVATURE　ON　R^n　AND　EXISTENCE　OF　CLOSED　GEODESICS

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Chinese Annals of Mathematics,Series B 1994年第3期15卷 293-298页

作者： ZHU DAXIN(Department of Mathematics, tianjin Universityl tianjin 300072, china.) 天津大学数学系天津 300072

An example of complete Riemannian metric of positive (or nonnagative) curvature on Resuch as aam = a(x)dx' is obtained by direct caculations. Furthermore, by using a geodesic convex condition and a theorem for complete noncompact Riemannian manifold, an existence resultof periodic solution of prescribed energy for a singular Handltonian system is also obtained.

关键词： Positive curvature Complete metric Geodesic Riemannian manifold Hamiltonian system.

Views on “Principle of limitation of physical quantities and cyclic universe”

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Science china(Physics,Mechanics & Astronomy) 2010年第9期53卷 1772-1774页

作者： LI LianGang Department of Physics,School of Sciences,tianjin University,tianjin 300072,china tianjin University Department of Physics School of Sciences Tianjin China (GRID:grid.33763.32) (ISNI:***)

This paper presents an analysis of a paper entitled "Principle of limitation of physical quantities and cyclic universe" and proposes different results for some formulae from that *** addition,this paper shows that the principle of limits coupling may lead to an approximation of current theories(i.e.,quantum theory and relativistic theory),which have interesting correlations with the Plank formula and the special theory of relativity.

关键词： principle of limitation of physical quantities limits coupling formulae Plank formula theory of relativity