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Gas kinetic algorithm for flows in Poiseuille-like microchannels using Boltzmann model equation

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Science china(Physics,Mechanics & Astronomy) 2005年第4期48卷 496-512页

作者： LI Zhihui1,2. zhang Hanxin1 & FU Song2.⒈ National Laboratory for CFD, Hypervelocity Aerodynamics Institute,china Aerodynamics Research and Development Center,Mianyang 62.000,china 2.department of Engineering Mechanics,tsinghua university,Beijing 100084,china 1. National Laboratory for CFD Hypervelocity Aerodynamics Institute China Aerodynamics Research and Development Center 621000 Mianyang China 2. department of Engineering Mechanics Tsinghua University 100084 Beijing China

The gas-kinetic unified algorithm using Boltzmann model equation have been extended and developed to solve the micro-scale gas flows in Poiseuille-like micro-channels from Micro-Electro-Mechanical Systems (MEMS). The numerical modeling of the gas kinetic boundary conditions suitable for micro-scale gas flows is presented. To test the present method, the classical Couette flows with various Knudsen numbers, the gas flows from short microchannels like plane Poiseuille and the pressure-driven gas flows in two-dimensional short microchannels have been simulated and compared with the approximate solutions of the Boltzmann equation, the related DSMC results, the modified N-S solutions with slip-flow boundary theory, the gas-kinetic BGK-Burnett solutions and the experimental data. The comparisons show that the present gas-kinetic numerical algorithm using the mesoscopic Boltzmann simplified velocity distribution function equation can effectively simulate and reveal the gas flows in microchannels. The numerical experience indicates that this method may be a powerful tool in the numerical simulation of micro-scale gas flows from MEMS.

关键词： Boltzmann model equation, discrete velocity ordinate method, finite-difference scheme, Couette flow, Poiseuille flow, gas flow in short-microchannel.

Computational fluid dynamics modeling and hemolysis analysis of axial blood pumps with various impeller structures

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Progress in Natural Science:Materials International 2006年第9期16卷 993-997页

作者： XIA Dongdong, ZHAO Chunzhang, zhang Xiwen and BAI Jing ( {2. of Biomedical Engineering, tsinghua university, Beijing 100084, china {2. of Engineering Mechanics, tsinghua university, Beijing 100084, china) [a]department of Biomedical Engineering Tsinghua University Beijing China [b]department of Engineering Mechanics Tsinghua University Beijing China

The flow fields in the blood pump were analyzed three- dimensionally using computational fluid dynamics (CFD). Hemolysis of the pump was calculated based on the changes in shear stress and related exposure times along the particle trace lines using a forward Euler approach. In this "way, how different impeller structures and rotational speeds affect the hemolysis was particularly acquired. As a result, impeller with long-short alternant vanes behaved best in hemolysis property and can be utilized to axial blood pumps development and design.

关键词： axial blood pump computational fluid dynamics hemolysis.

Semi-solid Processing of Al-7Graghite Composite

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Journal of university of Science and Technology Beijing 2001年第3期8卷 203-206页

作者： Peng zhang, Yunhui Du, Daben Zeng department of Mechanical Engineering, {2., Beijing 100084, china Tsing Hua Univ Dept Engn Mech Beijing 100084 Peoples R China

Al-7graphite composite was processed using Al-7graphite mushy prepared by electromagnetic-mechanical stirring method, and the influence of solid fraction on the distributing of graphite particles in ingot was studied. The results shows that the relationship between solid fraction and stirring temperature of mushy is: f(s) = 591.5-0.897 t (where f(s) is the solid fraction, t is the stirring temperature). For Al-7graphite composite, with the increasing of solid fraction, the aggregation extent of graphite particles reduced gradually, and when solid fraction was larger than 30%, graphite particles could distribute evenly in ingot.

关键词： Al-7graphite composite electromagnetic-mechanical stirring method distributing of graphite particles solid fraction stirring temperature

Arbitrarily long distance quantum communication using inspection and power insertion

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Chinese Science Bulletin 2009年第1期54卷 158-162页

作者： WANG WanYing1,2.WANG Chuan1,2.zhang GuangYu1,3 & LONG GuiLu1,2.1 {2. of Physics,tsinghua university,Beijing 100084,china 2.tsinghua National Laboratory for Information Science and Technology,tsinghua university,Beijing 100084,china 3 College of Applied Science,Harbin university of Science and Technology,Harbin 150080,china department of Physics Tsinghua University Beijing 100084 China tsinghua National Laboratory for Information Science and Technology Tsinghua University Beijing 100084 China College of Applied Science Harbin University of Science and Technology Beijing 100084 China

The biggest obstacle for long distance quantum communication is the channel loss and the channel noise on photons. In this paper,a method to solve this problem was analyzed using inspection and power insertion (IPI). It is proved that quantum communication may be established over arbitrarily long distance using this technology. The amount of resources required is a polynomial function of the dis-tance. IPI is proposed as a general technique to prolong quantum secure direct communication where secret messages are transmitted directly over a quantum channel.

关键词：长距离量子通信量子安全通信量子密匙分布噪声

Plant protein kinase genes induced by drought, high salt and cold stresses

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Chinese Science Bulletin 2000年第13期45卷 1153-1157页

作者： LIU Qiang , zhang Yong & Chen Shouyi1. Deparlmenl of Biological Science and Biotechnology, tsinghua university, Beijing {2., china 2. department of Biological Science and Biotechnology, Slate Key Laboratory of Biomembrane and Membrane Biotechnology, tsinghua university, Beijing {2., china 3. Institute of Genetics, Chinese Academy of sciences, Beijing 100101, china department of Biological Science and Biotechnology Tsinghua University Beijing China department of Biological Science and Biotechnology State Key Laboratory of Biomembrane and Membrane Biotechnology Tsinghua University Beijing China Institute of Genetics Chinese Academy of Sciences Beijing China

Drought, high salt and cold are three different kinds of environment stresses that severely influence the growth, development and productivity of crops. They all decrease the water state of plant cells, and consequently result in the harm of plant from water deficit. Several genes encoding protein kinases and induced by drought, high salt and low temperature have been isolated from Arabidopsis. These protein kinases include receptor protein kinase (RPK), MAP kinases, ribosomal-protein kinases and transcription-regulation protein kinase. The expression features of these genes and the regulatory roles of these protein kinases in stress response and signal transduction are discussed.

关键词： protein kinase environment stress signal transduction gene expression.

A counter example for nilpotent groups

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Science china Mathematics 2010年第11期53卷 3041-3048页

作者： LIU HeGuo1, zhang JiPing2.& LIAO Jun2.1{2. of Mathematics, Hubei university, Wuhan 430062. china 2.chool of mathematical sciences, Peking university, Beijing 100871, china 1. department of Mathematics Hubei University Wuhan 430062 China2. School of Mathematical Sciences Peking University Beijing 100871 China

Let R be a ring with 1, I be a nilpotent subring of R (there exists a natural number n, such that In = 0), and I be generated by {xj |j ∈ J} as ring. Write U = 1 + I, and it is a nilpotent group with class ≤ n - 1. Let G be the subgroup of U which is generated by {1 + xj|j ∈ J}. The group constructed in this paper indicates that the nilpotency class of G can be less than that of U.

关键词： nilpotency class nilpotent group nilpotent ring Lie ring

A normalized thoracic coordinate system for atlas mapping in 3D CT images

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Progress in Natural Science:Materials International 2008年第1期18卷 111-117页

作者： Hongkai Wang,Jing Bai*,Yonghong zhang department of Biomedical Engineering,{2.,Beijing 100084,china department of Biomedical Engineering Tsinghua University Beijing 100084 China

In this paper,a normalized thoracic coordinate system(NTCS)is defined for rapidly mapping the 4D thoracic organ atlas into indi- vidual CT volume *** coordinate system is defined based on the thoracic *** coordinate values are normalized by the size of the individual thorax so that this coordinate system is universal to different *** compensating the respiratory motion of the organs,a 4D dynamic torso atlas is introduced.A method for mapping this dynamic atlas into the individual image using the NTCS is also *** this method,the dynamic atlas was mapped into the clinical thoracic CT images and rough positions of the organs were found *** NTCS-based 4D atlas mapping method may provide a novel way for estimating the thoracic organ positions in low-resolution molecular imaging modalities,as well as in modern 4D medical images.

关键词： Atlas mapping Registration Segmentation Molecular imaging

Diagnostics for the structure of AGNs'broad line regions with reverberation mapping data:confirmation of the two-component broad line region model

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Science china(Physics,Mechanics & Astronomy) 2010年第S1期53卷 196-201页

作者： ZHU Ling1 & zhang ShuangNan2.1 {2. of Physics and tsinghua Center for Astrophysics,tsinghua university,Beijing 100084,china 2.Key Laboratory of Particle Astrophysics,Institute of High Energy Physics,Chinese Academy of sciences,Beijing 100049,china 1. department of Physics and tsinghua Center for Astrophysics Tsinghua University Beijing 100084 China 2. Key Laboratory of Particle Astrophysics Institute of High Energy Physics Chinese Academy of Sciences Beijing 100049 China

We re-examine the ten Reverberation Mapping(RM) sources with public data based on the two-component model of the Broad Line Region(BLR).In fitting their broad Hβ Mlines,six of them only need one Gaussian component,one of them has a double-peak profile,one has an irregular profile,and only two of them need two components,i.e.,a Very Broad Gaussian Component(VBGC) and an Inter-Mediate Gaussian Component(IMGC).The Gaussian components are assumed to come from two distinct regions in the two-component model;they are the Very Broad Line Region(VBLR) and the Inter-Mediate Line region(IMLR).The two sources with a two-component profile are Mrk 509 and NGC *** time lags of the two components of both sources satisfy tIMLR/tVBLR=V 2.BLR/V 2.MLR,where tIMLR and tVBLR are the lags of the two components while VIMLR and VVBLR represent the mean gas velocities of the two regions,supporting the two-component model of the BLR of Active Galactic Nuclei(AGNs).The fact that most of these ten sources only have the VBGC confirms the assumption that RM mainly measures the radius of the VBLR;consequently,the radius obtained from the R-L relationship mainly represents the radius of ***,NGC 4051,with a lag of about 5 days in the one component model,is an outlier on the R-L relationship as shown in Kaspi et al.(2.05);however this problem disappears in our two-component model with lags of about 2.and 6 days for the VBGC and IMGC,respectively.

关键词： broad line region AGN Reverberation Mapping cross correlation

Cloning and characterization of 37 kDa laminin receptor precursor in pearl oyster,Pinctada fucata

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Progress in Natural Science:Materials International 2008年第2期18卷 233-238页

作者： Yaopeng Fu a,Liping Xie a,b,,Rongqing zhang a,b,a Institute of Marine Biotechnology,department of Biological {2. and Biotechnology,tsinghua university,Beijing 100084,china b Protein Science Laboratory of the Ministry of Education,tsinghua university,Beijing 100084,china Institute of Marine Biotechnology Department of Biological Sciences and Biotechnology Tsinghua University Beijing 100084 China Protein Science Laboratory of the Ministry of Education Tsinghua University Beijing 100084 China

A 1063 bp cDNA clone encoding a putative 37 kDa laminin receptor precursor (37 kDa LRP) is isolated from the mantle tissue of pearl oyster,Pinctada fucata. The amino acid sequence predicted from the cDNA sequence is 301 residues long,with a calculated molec-ular mass of 33.5 kDa. RT-PCR analysis shows that 37 kDa LRP mRNA is especially highly expressed in the mantle while widely expressed in several tissues. In situ hybridization analysis reveals that 37 kDa LRP is expressed in the outer epithelial cells of the mantle edge,suggesting its involvement in cell proliferation and secretion in P. fucata. The identification and characterization of 37 kDa LRP in the pearl oyster will help us to further understand the signal transduction in the processes of mantle epithelial cell proliferation and tissue formation.

关键词： 37 kDa laminin receptor precursor Mantle epithelial cell Pearl oyster