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Viscosity,thermal diffusivity and Prandtl number of nanoparticle suspensions

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Progress in Natural Science:Materials International 2004年第10期14卷 82-86页

作者： WANG Buxuan ,ZHOU Leping and PENG Xiaofeng (Thermal Engineering department,tsinghua university,beijing100084,china) tsinghua Univ Dept Thermal Engn Beijing 100084 Peoples R China

Using our reported experimental data of effective thermal conductivity,specific heat capacity and viscosity for CuO nanoparticle suspensions,the corresponding thermal diffusivity and Prandtl number are *** the hard sphere model and consid-ering effects of particle clustering and surface adsorption,the increase of viscosity for nanoparticle suspension observed is *** is shown that the effective thermal conductivity will be strongly affected by the formation and correlated spatial distribution of nanoparticle clusters when compared to viscosity in hosting liquid.

关键词： nanoparticle suspension viscosity thermal diffusivity Prandtl number

Fusion tracking in color and infrared images using joint sparse representation

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Science china(Information Sciences) 2012年第3期55卷 590-599页

作者： LIU HuaPing1,2,3 & SUN FuChun1,2,3 1department of Computer Science and Technology, tsinghua university, beijing 100084, china 2State Key Laboratory of Intelligent Technology and Systems, beijing 100084, china 3tsinghua National Laboratory for Information Science and Technology, beijing 100084, china 1. department of Computer Science and Technology Tsinghua University Beijing 100084 China2. State Key Laboratory of Intelligent Technology and Systems Beijing 100084 China3. Tsinghua National Laboratory for Information Science and Technology Beijing 100084 China

Currently sparse signal reconstruction gains considerable interest and is applied in many fields. In this paper, a similarity induced by joint sparse representation is designed to construct the likelihood function of particle filter tracker so that the color visual spectrum and thermal spectrum images can be fused for object tracking. The proposed fusion scheme performs joint sparse representation calculation on both modalities and the resultant tracking results are fused using min operation on the sparse representation coefficients. In addition, a co-learning approach is proposed to update the reference templates of both modality and enhance the tracking robustness. The proposed fusion scheme outperforms state-of-the-art approaches, and its effectiveness is verified using OTCBVS database.

关键词： joint sparse representation fusion tracking color image infrared image

THEORY OF MUM FOR METAL SPHERICAL ROTOR WITH CONTACTLESS SUSPENSION

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Chinese Journal of Mechanical Engineering 2004年第2期17卷 243-246页

作者： He Xiaoxia Gao Zhongyu Wang Yongliang department of Precision Instruments and Mechinery,tsinghua university,beijing 100084, china department of Precision Instruments and Machinery Tsinghua University Beijing 100084 China

Based on the motion equations of an unbalanced spherical rotor withcontactless suspension, three methods of MUM (mass unbalance measurement) are put forward to measurethe total mass unbalance, radical mass unbalance and radical mass unbalance of the rotor. Totalmass unbalance is obtained when the unbalanced rotor plays as a simple pendulum in static *** pendulant period and pendulant midpoint indicate magnitude and direction of total massunbalance of the rotor respectively. Analysis of the motion equations by using the averaging methodyields that the rotor will do a special side oscillation when an auxiliary system makes the rotorspin about its pole axis which is orientating toward the local vertical. The radical mass unbalancecan be obtained by building a proper displacement sensor to sense the amplitude of the sideoscillation. Necessary analysis of the motion equations also shows that when the rotor spins at asmall angular velocity and the rotary axis is perpendicular to the vertical, the pole axis of therotor will precess slowly about the vertical by virtue of the axial mass unbalance. The axial massunbalance can be estimated from the time history of the spin vector of the rotor. Finally,measurement precision of the three methods is compared and how the external torque affects themeasurement precision for the three methods are examined.

关键词： Mass unbalance measurement Radical mass unbalance Axial mass unbalance Static balancing Averaging method

Micro-computed tomography for small animal imaging: Technological details

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Progress in Natural Science:Materials International 2008年第5期18卷 513-521页

作者： Hao Li, Hui Zhang , Zhiwei Tang, Guangshu Hu department of Biomedical Engineering, tsinghua university, beijing 100084, china department of Biomedical Engineering Tsinghua University Beijing 100084 China

The high-resolution micro-computed tomography (micro-CT) system has now become an important tool for biological research. The micro-CT system enables a non-invasive inspection to screen anatomical changes in small animals. The promising advantages include high-spatial resolution, high sensitivity to bone and lung, short scan time and cost-e ectiveness. The dose received by the small animal might be a critical concern in the research. In this article, the choice of the components, fundamental physical problems, the image recon- struction algorithm and the representative applications of micro-CT are summarized. Some results from our research group are also pre- sented to show high-resolution images obtained by the micro-CT system.

关键词： Micro-computed tomography Small animal X-ray

Truncation error calculation based on Richardson extrapolation for variable-step collaborative simulation

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Science china(Information Sciences) 2011年第6期54卷 1238-1250页

作者： ZHANG HeMing 1 , LIANG SiLu 2 , SONG ShiJi 1 & WANG HongWei 3 1 department of Automation, TNList, tsinghua university, beijing 100084, china 2 Computer and Information Management Center, tsinghua university beijing 100084, china 3 Engineering Design Centre, Engineering department, Cambridge university, Cambridge CB2 1PZ, UK 1. department of Automation TNList Tsinghua University Beijing 100084 China2. Computer and Information Management Center Tsinghua University Beijing 100084 China3. Engineering Design Centre Engineering Department Cambridge University Cambridge CB2 1PZ UK

Collaborative simulation is an effective approach to performing simulation analysis for complex systems by integrating models developed for different engineering disciplines. Collaborative simulation issues include the modeling of coupled multidisciplinary systems, and the simulation running time integration of these models that are solved parallelly. Estimation of the local truncation error of coupling models is the key to solve multidisciplinary collaborative simulation problem, which is actually used to restrict the simulation step. This paper presents a variable-step method based on Richardson extrapolation for calculating the local truncation error to solve collaborative simulation problem of multidisciplinary coupling models. Formulas for estimating the local truncation error are derived through theoretical analysis by using integration methods and interpolation technologies, respectively. The simulation experiments are illustrated to validate the accuracy and efficiency of proposed collaborative simulation algorithm in comparison with the usual combinative algorithm.

关键词： multidisciplinary systems collaborative simulation variable-step algorithm error estimation

The first-principles study on the doping effect of Re in Ni3Al

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Progress in Natural Science:Materials International 2008年第7期18卷 861-866页

作者： Song Yu a,*, Chongyu Wanga,b, Tao Yua aCentral Iron and Steel Research Institute, beijing 100081, china bdepartment of physics, tsinghua university, beijing 100084, china Central Iron and Steel Research Institute Beijing 100081 China department of physics Tsinghua University Beijing 100084 China

Using first-principles density function for molecules method (DMol) and discrete variational method (DVM) based on the density functional theory, we studied the doping effect of Re in Ni3Al. The structure relaxation and the alloying energy show that Re has a strong Al site preference and leads to the local deformation, which is in agreement with the experimental results and other theoretical results. In addition, the charge density diffierence and the bond order show that Re can strongly enhance the interatomic interaction between the nearest neighbor atoms. From the density of states and the Pauli spectrum, we find that resonance states and localized states are induced by doping Re, and the doped Re atom forms the hybridized bond with the nearest neighbor atoms.

关键词： The first-principles Re Ni3Al

SYNTHESIS OF NOVEL SOLUBLE AROMATIC POLYPYROMELLITIMIDE CONTAINING ORDERED 1,2,4-TRIAZINE IN THE MAIN CHAIN

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Chinese Journal of Polymer Science 2002年第3期20卷 219-224页

作者： Xiao-bing Yi Guo-shi Wu Feng-cai Lu department of Chemistry tsinghua university, beijing 100084 china Institute of Chemistry Chinese Academy of Sciences, beijing 100080, china Tsing Hua Univ Dept Chem Beijing 100084 Peoples R China Chinese Acad Sci Inst Chem Beijing 100080 Peoples R China

A new heat-resistant, soluble polymer, poly(phenyl-1,2,4-triazine imide), has been prepared via a two-step method of polycondensation of N,N'-bis(4-benzil)pyromellitimide and terephthalamidrazone in cresol, followed by curing at higher temperature. The rigid 1,2,4-triazine group increases the solubility of the polyimide so that the polymer is soluble in cresol, N-methyl-2-pyrrolidone (NMP), trifluoroacetic acid and concentrated sulfuric acid, etc. Thermogravimetric analysis (TGA) indicates that this novel polyimide has good thermal stability with a high decomposition temperature of 447degreesC in air and of 423 degreesC in N-2, It has a tensile strength of 107.4 MI'a with an elongation at break of around 7.6%.

关键词： polyimides N,N '-bis(4-benzil)pyromellitimide rigid-rod group 1,2,4-triazine

A SOLUTION PROCEDURE FOR LOWER BOUND LIMIT AND SHAKEDOWN ANALYSIS BY SGBEM

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Acta Mechanica Solida Sinica 2001年第2期14卷 118-129页

作者： Zhang Xiaofeng Liu Yinghua Cen Zhangzhi (department of Engineering Mechanics,tsinghua university,beijing 100084,china) ***

The symmetric Galerkin boundary element method (SGBEM) instead ofthe finite element method is used t perform lower bound limit andshakedown analysis of structures. The self-equilibrium stress fieldsare constructed by a linear combination of several basicself-equilibrium stress fields with parameters to be *** basic self-equilibrium stress fields are expressed as elasticresponses of the body to im- posed permanent strains and obtainedthrough elastic-plastic incremental analysis.

关键词： limit and shakedown analysis SGBEM self-equilibrium stress

A new orthogonality relationship for orthotropic thin plate theory and its variational principle

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Science china(physics,Mechanics & Astronomy) 2005年第3期48卷 371-380页

作者： LUO Jianhui 1 , LONG Yuqiu 2 & LIU Guangdong 1 1. College of Civil Engineering, Hunan university, Changsha 410082, china 2. department of Civil Engineering, tsinghua university, beijing 100084, china 1. College of Civil Engineering Hunan University 410082 Changsha China 2. department of Civil Engineering Tsinghua University 100084 Beijing China

The thought how dual vectors are constructed in a new orthogonality relationship for theory of elasticity is generalized into orthotropic thin plate bending problems by using the analogy theory between plane elasticity problems and plate bending problems. Dual differential equations are directly obtained by using a mixed variables method. A dual differential matrix to be derived possesses a peculiarity of which principal diagonal sub-matrixes are zero matrixes. Two independently and symmetrically orthogonality sub-relationships are discovered. By using the integral form for elastic bending theory of orthotropic thin plate the orthogonality relationship is demonstrated. By selecting felicitous dual vectors a new orthogonality relationship for theory of elasticity can be generalized into elastic bending theory of orthotropic thin plate. By using the integral form a variational principle which is relative to differential form and a whole function expression are proposed.

关键词： theory of elasticity, thin plate theory, dual vectors, orthogonality relationship, orthotropic, variational principle.