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TEXTURE DETERMINATION OF THIN FILM ZrO_2 BY ELECTRON DIFFRACTION

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Acta Metallurgica Sinica(English Letters) 1993年第12期6卷 472-473页

作者： WAng Yinghua tsinghua university,beij.ng,china department of Materials Science and engineering,tsinghua university,beij.ng 100084,china tsinghua Univ Beijing China

A method for semi-quantitative determination of thin film texture using electron diffrac- tion is *** texture state of a zirconia thin film with a cubic structure has been determined in this way and is presented as an... 详细信息

关键词： texture thin film electron diffraction ZrO_2

Measurement and simulation of the two-phase velocity correlation in sudden-expansion gas-particle flows

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Acta Mechanica Sinica 2011年第4期27卷 494-501页

作者： Li-Xing Zhou.Yang Liu.Yi Xu department of engineering mechanics,tsinghua university,100084 beij.ng,china Marine engineering College,Dalian Maritime university,116026 Dalian,china department of engineering mechanics Tsinghua University Beijing China Marine engineering College Dalian Maritime University Dalian China

In this paper the present authors measured the gas-particle two-phase velocity correlation in sudden expansion gas-particle flows with a phase Doppler particle anemometer （PDPA） and simulated the system behavior by using both a Reynolds-averaged Navier-Stokes （RANS） model and a large-eddy simulation （LES）. The results of the measurements yield the axial and radial time-averaged velocities as well as the fluctuation velocities of gas and three particle-size groups （30μm, 50μm, and 95μm） and the gasparticle velocity correlation for 30μm and 50μm particles. From the measurements, theoretical analysis, and simulation, it is found that the two-phase velocity correlation of sudden-expansion flows, like that of jet flows, is less than the gas and particle Reynolds stresses. What distinguishes the two-phase velocity correlations of sudden-expansion flow from those of jet and channel flows is the absence of a clear relationship between the two-phase velocity correlation and particle size in sudden-expansion flows. The measurements, theoretical analysis, and numerical simulation all lead to the above-stated conclusions. Quantitatively, the results of the LES are better than those of the RANS model.

关键词： PDPA measurement - Simulation Two-phasevelocity correlation Sudden expansion gas-particle flows

ARNOLDI REDUCTION ALGORITHM FOR LARGE SCALE GYROSCOPIC EIGENVALUE PROBLEM

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Acta Mechanica Solida Sinica 1996年第2期9卷 95-103页

作者： Zheng Zhaochang Ren Gexue, department of engineering mechanics, tsinghua university, beij.ng 100084 TSIng HUA UNIV DEPT ENGN MECH BEIJING 100084 PEOPLES R CHINA

Based on Arnoldi's method, a version of generalized Arnoldi algorithm has been developed for the reduction of gyroscopic eigenvalue problems. By utilizing the skew symmetry of system matrix, a very simple recurrence scheme, named gyroscopic Arnoldi reduction algorithm has been obtained, which is even simpler than the Lanczos algorithm for symmetric eigenvalue problems. The complex number computation is completely avoided. A restart technique is used to enable the reduction algorithm to have iterative characteristics. It has been found that the restart technique is not only effective for the convergence of multiple eigenvalues but it also furnishes the reduction algorithm with a technique to check and compute missed eigenvalues. By combining it with the restart technique, the algorithm is made practical for large-scale gyroscopic eigenvalue problems. Numerical examples are given to demonstrate the effectiveness of the method proposed.

关键词： gyroscopic eigenvalue problem skew symmetry Arnoldi reduction algorithm restart technique

A two-dimensional molecular dynamics simulation of liquid-vapor nucleation

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Chinese Science Bulletin 2003年第7期48卷 623-626页

作者： WAng Jinzhao, CHEN Min & GUO Zengyuan department of engineering mechanics, tsinghua university, beij.ng 100084, china 1. department of engineering mechanics Tsinghua University Beijing 100084 China

The molecular dynamics method is employed to simulate the liquid-vapor nucleation processes. The results show that the initial stage of nucleus in nucleation process is cavity or space containing very few vapor molecules. Because of the very limited size of the simulation domain in previous reports, further growth of the nucleus has not been realized. Large scale molecular dynamics simulation of liquid-vapor nucleation indicates that the liquid-vapor nucleation process undergoes at least three stages: cavity growth, cavity coales-cence, bubble formation.

关键词：二维分子动力学仿真液-汽成核现象晶核空穴合并

Simulation study and function analysis of the dynamic aortic valve

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Progress in Natural Science:Materials International 2006年第5期16卷 512-517页

作者： XIA Dongdong and BAI Jing (department of Biomedical engineering, tsinghua university, beij.ng 100084, china) department of Biomedical engineering Tsinghua University Beijing 100084 China

The dynamic aortic valve (DAV) is a new left ventricular assist device, a micro-axial blood pump implemented at the position of the aortic valve, pumping blood from the left ventricle into the aortic artery. The present dynamic aortic valve operates at 7 different rotation speeds, ranging from 3000 r/min (speed 1) to 9000 r/min (speed 7). Because in vivo experiments need a lot of live animals and take a long period of time, modeling and simulation have been widely used to simulate and analyze hydra-dynamic property of the DAV and its assisting effects. With the measurements from the mock circulatory loop, a mathematic model of the DAV is established and embedded into the previously developed canine circulatory system. Using this model, the effect of the DAV on the failing heart at each rotation speed level is investigated. The vital cardiac variables are computed and compared with in vivo experimental results, which are in good agreement with an acceptable difference mostly 15%. The establishment of the DAV model and its simulation are useful for further improvement of the DAV device.

关键词： dynamic aortic valve mathematic model computer simulation.

Synchrotron Radiation Tomography for Reconstruction of Layer Structures and Internal Defects of Composite Materials

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Chinese Journal of Lasers 1999年第6期8卷 24-29页

作者： LI Xide (department of engineering mechanics, tsinghua university, beij.ng 100084, china)HU Xiaofang (department of Modern mechanics and engineering, university of Science and Technology of china, Hefei 230026, china) HU Yiguan KAN Ya (National Sy 清华大学工程力学系北京 100084 中国科学技术大学近代力学与工程系安徽合肥 230026 中国科学技术大学同步辐射国家实验室安徽合肥 230026 中国科学技术大学同步辐射国家实验室安徽合肥

Synchrotron radiation tomography has been used as a non intrusive technique to study layer structures and internal defects of composite materials with carbon aluminum fibers and boron carbon fibers. A rotatable platform, which is positioned in a vacuum chamber of a beam line, is used to hold specimens and to get multi directional scanning images. The scanning images are recorded on a PMMA film firstly by use of the single exposure method, resampled by a microscopic system, and reconstructed with computerized tomography to yield their three dimensional descriptions. This reconstruction makes it possible to identify different layers and structures of composite materials. Particularly the defects inside composite materials can also be detected and evaluated.

关键词： composite material synchrotron radiation computerized tomography reconstruction nondestructive evaluation

Finite Element Simulation for Interfacial Evolutions

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Communications in Nonlinear Science and Numerical Simulation 1998年第2期3卷 3-5页

作者： Jianming HUAng and Wei YAng (department of engineering mechanics, tsinghua university, beij.ng 100084, china) E mail: yw dem@*** department of engineering mechanics Tsinghua University Beijing 100084 China

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ＩｎｔｒｏｄｕｃｔｉｏｎＩｎｔｅｒｆａｃｅｍｏｔｉｏｎｐｌａｙｓａｄｅｃｉｓｉｖｅｒｏｌｅｉｎｄｅｓｉｇｎｉｎｇｔｈｅｍｉｃｒｏｓｔｒｕｃｔｕｒｅ，ｆａｂｒｉｃａｔｉｎｇｍａｔｅｒｉａｌｓ，ａｎｄｓｈａｐｉｎｇｔｈｅｓｔｒｕｃｔｕｒｅｇｅｏｍｅｔｒ...

关键词： finite element scheme energetics and kinetics interface motion

Design of policy mechanism to promote cleaner production in china

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Journal of Environmental Sciences 2001年第3期13卷 346-350页

作者： ZHAng Tian zhu(department of Environmental Science and engineering, tsinghua university, beij.ng 100084, china. department of Environmental Science and engineering Tsinghua University Beijing 100084 China. zhangtz@***

In order to promote cleaner production in china, a package of policy options was presented based on the identification of the barriers encountered in the CP demonstration project and the effectiveness and feasibility of policy options for the CP implementation were analyzed. Furthermore, the policy mechanism framework was given, which composes of compulsory, economic incentive, social pressure and supportive function. Finally, the implementation strategy of the policy mechanism, in which the emphasis will be changed from compulsory policy options towards economic and social pressure policy options, was proposed.

关键词： cleaner production barrier identification policy mechanism china

A molecular dynamics study on melting point and specific heat of Ni_3Al alloy

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Science china(Physics,mechanics & Astronomy) 2007年第4期50卷 407-413页

作者： YAng Hong,Lü YongJun,CHEN Min & GUO ZengYuan department of engineering mechanics,tsinghua university,beij.ng 100084,china 1. department of engineering mechanics Tsinghua University Beijing 100084 China

Using the Embedding Atom Method(EAM)for highly undercooled Ni3Al alloy,the melting point and the specific heat were studied by a molecular dynamics *** simulation of melting point was carried out by means of the sandwich method and the NVE ensemble method,and the results show a good agreement,whereas are larger than the experimental value of 1663 *** difference is attrib-uted to the influence of surface melting on experimental results,which causes the smaller measurements compared with the thermodynamic melting *** simulated specific heat of Ni3Al alloy weakly and linearly increases with the in-crease of undercooling in the temperature range from 800 K to 2000 K.

关键词： Ni3Al alloy undercooled melting point specific heat