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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,beijing,China Department of Materials Science and Engineering,Tsinghua University,beijing 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

The quantum general linear supergroup, canonical bases and Kazhdan-Lusztig polynomials

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Science China Mathematics 2009年第3期52卷 401-416页

作者： ZHANG HeChun Department of Mathematical Sciences, Tsinghua University, beijing 100084, China Department of Mathematical Sciences Tsinghua University Beijing China

Canonical bases of the tensor powers of the natural Uq(glm|n)-module V are constructed by adapting the work of Frenkel, Khovanov and Kirrilov to the quantum supergroup setting. This result is generalized in several directions. We first construct the canonical bases of the Z2-graded symmetric algebra of V and tensor powers of this superalgebra; then construct canonical bases for the superalgebra Oq(Mm|n) of a quantum (m, n) × (m, n)-supermatrix; and finally deduce from the latter result the canonical basis of every irreducible tensor module for Uq(glm|n) by applying a quantum analogue of the Borel-Weil construction.

关键词： canonical basis crystal basis Kazhdan-Lusztig polynomial

Modularity of Calabi-Yau varieties and conformal field theory

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Science China Mathematics 2008年第6期51卷 1135-1146页

作者： TAN FuCheng Department of Mathematical Sciences,Tsinghua University,beijing 100084,China Department of Mathematical Sciences Tsinghua University Beijing China

We study the modularity problem of Calabi-Yau varieties from the conformal field theo- retic point of *** express the modular forms associated to all 1-dimensional Calabi-Yau orbifolds in terms of products of Dedekind eta functions,which is hoped to shed light on the modularity questions for higher dimensional Calabi-Yau varieties.

关键词： L-function Calabi-Yau variety Gepner model

THE APPROXIMATIONS OF THE EXACT BOUNDARY CONDITION AT AN ARTIFICIAL BOUNDARY FOR LINEARIZED INCOMPRESSIBLE VISCOUS FLOWS

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Journal of Computational Mathematics 1998年第3期16卷 239-256页

作者： Wei-zhu Bao (Department of Applied Mathematics, Tsinghua University, beijing 100084, P.R. China) 清华大学应用数学系北京

We consider the linearized incompressible Navier-Stokes (Oseen) equations in a flat channel. A sequence of approximations to the exact boundary condition at an artificial boundary is derived. Then the original problem is reduced to a boundary value problem in a bounded domain, which is well-posed. A finite element approximation on the bounded domain is given, furthermore the error estimate of the finite element approximation is obtained. Numerical example shows that our artificial boundary conditions are very effective.

关键词： Oseen equations artificial boundary artificial boundary condition finite element approximation error estimate

AR quivers,exceptional sequences and algorithms in derived Hall algebras

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Science China Mathematics 2010年第6期53卷 1609-1624页

作者： SHENG Jie Department of Mathematical Sciences,Tsinghua University,beijing 100084,China Department of Mathematical Sciences Tsinghua University Beijing China

Consider the canonical isomorphism between the positive part U+ of the quantum group Uq(g) and the Hall algebra H(Λ),where the semisimple Lie algebra g and the finite-dimensional hereditary algebra Λ share a Dynkin *** and Xiao have given two algorithms to decompose the root vectors into linear combinations of monomials of Chevalley generators of U+,respectively induced by the braid group action on the exceptional sequences of Λ-modules and the structure of the Auslander-Reiten quiver of Λ.In this paper,we obtain the corresponding algorithms for the derived Hall algebra DH(Λ),which was introduced by *** show that both algorithms are applicable to the lattice algebra and Heisenberg double in the sense of *** the new recursive formulae have the same flavor with the quantum Serre relations.

关键词： derived Hall algebra exceptional sequence AR quiver

Shrinkage Behaviour of Spheroidal Graphite Cast Iron in Green and Dry Sand Molds for the Benchmarking of Solidification Simulation

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Journal of Materials Science & Technology 2001年第6期17卷 610-614页

作者： Wenzhen LI and Baicheng LIU Department of Mechanical Engineering, Tsinghua University, beijing 100084, China Jiarong LI beijing Institute of Aeronautical Materials, beijing 100095, China [Manuscri Dept. of Mech. Eng. Tsinghua Univ. Beijing 100084 China

The effects of metallurgical and processing parameters on the formation of shrinkage cavities and porosities in spheroidal graphite cast iron have been studied, considering the parameters of carbon equivalent, inoculation, casting modulus, mold type (green or dry) and pouring temperature within specific ranges of these variables. Based on the orthogonal experiments, the metallurgical and processing parameters of the minimum casting shrinkage and the maximum casting shrinkage were obtained, and the effects of metallurgical and processing parameters on the formation of shrinkage cavities and porosities in spheroids graphite cast iron castings were discussed. Finally, two regression equations relating these variables to the formation of shrinkage porosity were derived based upon the orthogonal experiments conducted.

关键词： Shrinkage Behaviour of Spheroidal Graphite Cast Iron in Green and Dry Sand Molds for the Benchmarking of Solidification Simulation Graphite Simulation Cast

3D Stochastic Modeling of Grain Structure for Aluminum Alloy Casting

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Journal of Materials Science & Technology 2003年第5期19卷 391-394页

作者： Qingyan XU, Weiming FENG and Baicheng LIUDepartment of Mechanical Engineering, Tsinghua University, beijing 100084, China Dept. of Mech. Eng. Tsinghua Univ. Beijing 100084 China

A 3D stochastic modeling was carried out to simulate the dendritic grains during solidification of aluminum alloys, including time-dependent calculations for temperature field, solute redistribution in liquid, curvature of the dendritic tip, and growth anisotropy. The nucleation process was treated by continuous nucleation. A 3D simplified grain shape model was established to represent the equiaxed dendritic grain. Based on the Cellular Automaton method, a grain growth model was proposed to capture the neighbor cells of the nucleated cell. During growing, each grain continues to capture the nearest neighbor cells to form the final shape. When a neighbor cell was captured by other grains, the grain growth along this direction would be stopped. Three-dimensional calculations were performed to simulate the evolution of dendritic grain. In order to verify the modeling results, the predictions were compared with the observation on samples cast in the sand mold and the metal mold.

关键词： 3D stochastic modeling Nucleation Grain growth

Luminescence of Eu^(2+) in Strontium Aluminum Oxide System with Long Decay Property

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Chinese Chemical Letters 1998年第4期9卷 401-402页

作者： Yong QIU and Hai Tao SUN(Department of Chemistry, Tsinghua University, beijing 100084) Department of Chemistry Tsinghua University Beijing 100084 China

A long decay luminescent powder based upon the strontium aluminum oxide system with Eu2+ as the activator was produced. It was found that the variation of the molar ratio of Al to Sr leads to a change in emission colo... 详细信息

关键词： luminescence of Eu^(2+) strontium aluminum oxide emission

Application and Comparison of Two SGS Models in Large Eddy Simulation of FreeTurbulent Jet Flow

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Communications in Nonlinear Science and Numerical Simulation 1999年第1期4卷 12-19页

作者： Hong YAN and Mingde SU (Department of Engineering Mechanics, Tsinghua University, beijing 100084, China) Department of Engineering Mechanics Tsinghua University Beijing 100084 China

Large eddy simulations of spatially evolved turbulent round jets were presented. The two SGS models called the standard Smagorinsky’s eddy viscosity model and the non-eddy viscosity stimulated small scale(SSS) model developed by Shah & Ferziger were applied. The Reynolds number of the flow was taken as 10000 based on the orifice diameter and the axial velocity in the orifice. The comparison between these two models showed that the standard Smagorinsky’s viscosity model with Smagorinsky’s constant of 0.1 underestimated the turbulent intensity, while the SSS model showed a better agreement with the experiment. Also the SSS model was used to investigate the development of vortex. The convective boundary condition at the outflow boundary was adopted to ensure less effect of noise on the upstream.

关键词： stimulated small scale model smagorinsky’s eddy viscosity model Round jet, Large eddy simulation