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Numerical simulation of Richtmyer-Meshkov instability

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Science china Mathematics 2004年第z1期47卷 234-244页

作者： FU Dexun, MA Yanwen, ZHANG Linbo & TIAN BaolinState Key Laboratory of Nonlinear Mechanics, institute of Mechanics, chinese academy of sciences, beijing 100080,{3. State Key Laboratory of Scientific and Engineering Computing, institute of Computational Mathematics, chinese academy of sciences, beijing 100080,{3. State Key Laboratory of Nonlinear Mechanics Institute of Mechanics Chinese Academy of Sciences Beijing China State Key Laboratory of Scientific and Engineering Computing Institute of Computational Mathematics Chinese Academy of Sciences Beijing China

The compressible Navier-Stokes equations discretized with a fourth order accurate compact finite difference scheme with group velocity control are used to simulate the Richtmyer-Meshkov (R-M) instability problem produced by cylindrical shock-cylindrical material interface with shock Mach number Ms=1.2 and density ratio 1:20 (interior density/outer density). Effect of shock refraction, reflection, interaction of the reflected shock with the material interface, and effect of initial perturbation modes on R-M instability are investigated numerically. It is noted that the shock refraction is a main physical mechanism of the initial phase changing of the material surface. The multiple interactions of the reflected shock from the origin with the interface and the R-M instability near the material interface are the reason for formation of the spike-bubble structures. Different viscosities lead to different spike-bubble structure characteristics. The vortex pairing phenomenon is found in the initial double mode simulation. The mode interaction is the main factor of small structures production near the interface.

关键词： R-M instability, direct numerical simulation, shock-interface interaction.

Role of plasminogen activators and inhibitors in reproduction

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chinese Science Bulletin 1999年第8期44卷 673-685页

作者： LIU YixunState Key Laboratory of Reproductive Biology, institute of Zoology , chinese academy of sciences , beijing 100080,{3. State Key Laboratory of Reproductive Biology Institute of Zoology Chinese Academy of Sciences Beijing China

The recent progress in the studies on the role of local and directed fibrinolysis controlled by plasminogen activators (PAs) and regulated by their inhibitors (PAIs) in reproduction is summarized. Hormone-induced coordinated expression of tissue type PA (tPA) and PAI type-1 (PAI-1) in the ovary is involved in the processes of ovulation and luteal regression; increases in urokinase type PA (uPA) and PAI-1 activity in the early stage of luteinized follicles may be responsible for ovarian tissue remodeling and angiogenesis; the PA system has been found to play an important role in spermatogenesis in testis and modulation of sperm maturation in epididymis. PA and matrix matalloproteanase (MMP) and their respective inhibitors have also been identified in trophoblast and uterus. The targeted proteolytic activity generated by the two systems may play an essential role in the processes of the cyclic uterine angiogenesis, implantation and pla-centation as well as parturition.

关键词： plasminogen activator and inhibitor follicle rupture luteolysis angiogenesis spermatogenesis placentation.

THERMALLY STIMULATED SHAPE MEMORY BEHAVIOR OF POLYMERS WITH PHYSICAL CROSSLINKS

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chinese Journal of Polymer Science 1999年第3期17卷 203-213页

作者： Mao Xu Feng-kui Li Polymer Physics Laboratory, institute of Chemistry, chinese academy of sciences, beijing 100080,{3. 中科院化学所高分子物理及化学国家重点实验室北京 100080 中科院化学所高分子物理及化学国家重点实验室北京

The shape memory effect of polymers was investigated for the purpose of improving the processing conditions of their preparation and broadening the list of polymers for shape memory applications. Emphasis was put on the possibility of using polymers with physical crosslinks as shape memory materials and their structure-function relationships. Segmented block polyurethanes and polyethylene/nylon 6 graft copolymers were used as examples of polymers with physical crosslinks. It was found that these copolymers can really be used as thermally stimulated shape memory materials with large recoverable strain and high final recovery rate. The main advantage of using copolymers is their improved processing conditions as compared with polymers with chemical crosslinks. As only physical crosslinks are introduced, all conventional processing techniques for thermal plastics can be used, and the materials become easily reusable. The results indicate that the high crystallinity of these copolymers at room temperature and the formation of stable physical crosslinks are the two prerequisites for these polymers to exhibit shape memory effect. The successful use of block and graft copolymers imply the possibility of using polymers of various structure and properties as shape memory materials.

关键词： shape memory effect segmented polyurethanes polyethylene nylon graft copolymers

THERMODYNAMIC STUDY OF CHROMITE CAUSTIC FUSION PROCESS

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Acta Metallurgica Sinica(English Letters) 2001年第1期14卷 47-55页

作者： S.L. Zheng and Y. Zhang (institute of Chemical Metallurgy, the chinese academy of sciences, beijing 100080,{3.) institute of Chemical Metallurgy the Chinese Academy of Sciences

A new method for chromate cleaning production, named chromite caustic fusion process, is advanced by institute of Chemical Metallurgy, the chinese academy of sciences. With sodium hydroxide as reaction medium, the new process is composed of three procedures: liquid phase oxidation of chromite, metastable phase separation and carbonation ammonium transition. Generally illustrating the new process and its features, this paper mainly studies the thermodynamics of chromite oxidation. The new process has much better practical results than the conventional chromate production process in which sodium carbonate is used as reaction medium. The superiority is also shown through thermodynamic studies.

关键词： Melting Oxidation Recycling Sodium compounds Thermodynamics

LEAST-SQUARES MIXED FINITE ELEMENT METHOD FOR SADDLE-POINT PROBLEM

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Journal of Computational Mathematics 2000年第4期18卷 353-364页

作者： Lie-heng Wang Huo-yuan Duan (LSEC, institute of Computational Mathematics and Scientific/Engineering Computing, academy of Mathematics and System sciences,{3., beijing, 100080, china) 中科院计算数学与科学工程计算所科学与工程计算国家重点实验室北京 100080

In this paper, a least-squares mixed finite element method for the solution of the primal saddle-point problem is developed. It is proved that the approximate problem is consistent ellipticity in the conforming finite element spaces with only the discrete BB-condition needed for a smaller auxiliary problem. The abstract error estimate is derived. [ABSTRACT FROM AUTHOR]

关键词： least-squares method mixed finite element approximation saddle-point problem

Algebraically explicit analytical solu-tions for the unsteady non-Newtonian swirling flow in an annular pipe

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Science china(Physics,Mechanics & Astronomy) 2006年第4期49卷 396-400页

作者： CAI Ruixian1 & GOU Chenhua1,2 1. institute of Engineering Thermophysics, chinese academy of sciences, beijing 100080,{3. 2. Graduate School, chinese academy of sciences, beijing 100080,{3. institute of Engineering Thermophysics Chinese Academy of Sciences Beijing 100080 China

This paper presents two algebraically explicit analytical solutions for the incompressible unsteady rotational flow of Oldroyd-B type in an annular pipe. The first solution is derived with the common method of separation of variables. The second one is deduced with the method of separation of variables with addition developed in recent years. The first analytical solution is of clear physical meaning and both of them are fairly simple and valuable for the newly developing computational fluid dynamics. They can be used as the benchmark solutions to verify the applicability of the existing numerical computational methods and to inspire new differencing schemes, grid generation ways, etc. Moreover, a steady solution for the generalized second grade rheologic fluid flow is also presented. The correctness of these solutions can be easily proven by substituting them into the original governing equation.

关键词： analytical solution, Oldroyd-B type fluid, swirling flow, non-Newtonian.

From quantum spectra to classical orbits: Varying rectangular billiards

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Progress in Natural Science:Materials International 2008年第8期18卷 927-930页

作者： Jun Lu * Department of Foundational Science, beijing Union University, beijing 100101, china {3. of Theoretical Physics, chinese academy of sciences, beijing 100080, china Department of Foundational Science Beijing Union University Beijing 100101 China institute of Theoretical Physics Chinese Academy of Sciences Beijing 100080 China

The quantum-spectrum function is introduced by means of the eigenvalues and the eigenfunctions in the system of varying rectangular billiards. It is found that the Fourier transform of the quantum-spectrum function corresponds with the classical orbits in the system. These results give new evidence about the classical-quantum correspondence.

关键词： Quantum spectrum Classical-quantum correspondence Semiclassical physics

Central simple Poisson algebras

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Science china Mathematics 2004年第2期47卷 245-263页

作者： SU Yucai & XU XiaopingDepartment of Mathematics, Shanghai Jiaotong University, Shanghai 20003., china institute of Mathematics, academy of Mathematics and System {3., chinese academy of sciences, beijing 100080, china Department of Mathematics Shanghai Jiaotong University Shanghai China institute of Mathematics Academy of Mathematics and System Sciences Chinese Academy of Sciences Beijing China

Poisson algebras are fundamental algebraic structures in physics and symplectic geometry. However, the structure theory of Poisson algebras has not been well developed. In this paper, we determine the structure of the central simple Poisson algebras related to locally finite derivations, over an algebraically closed field of characteristic *** Lie algebra structures of these Poisson algebras are in general not finitely-graded.

关键词： Poisson algebra, locally-finite operator, derivation, finitely-graded, isomorphism class.

ELTA-WAVE IN A SIMPLE 1-D 2 x 2 HYPERBOLIC PROBLEM

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Journal of Computational Mathematics 1996年第4期14卷 311-318页

作者： S.L. Yang(institute of Applied Mathematics, chinese academy of sciences, beijing,{3.) institute of Applied Mathematics Chinese Academy of Sciences Beijing China

A simple one-dimensional 2 x 2 hyperbolic system is considered in the *** model contains a linear hyperbolic equation, as well as a hyperbolic equation ofwhich the coefficients are about the solution of the linear one. The exact solution ispresented and discussed, then numerical experiments are given by TVD (or MmB)type schemes for Riemann problems. From the results, we know that the solutionsdo have δ-waves for some suitable initial data.

关键词： Zhang Figure DELTA-WAVE IN A SIMPLE 1-D 2 HYPERBOLIC PROBLEM