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Synthesis,field emission and microwave absorption of carbon nanotubes filled with ferromagnetic nanowires

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Science China(Technological Sciences) 2010年第6期53卷 1453-1459页

作者： LV RuiTao1,KANG FeiYu1,GU JiaLin1,WANG KunLin2.& WU DeHai2.1 Laboratory of Advanced Materials,department of Materials Science and Engineering,tsinghua {2.,beijing 100084,China 2.department of Mechanical Engineering,tsinghua {2.,beijing 100084,China 1. Laboratory of Advanced Materials Department of Materials Science and Engineering Tsinghua University Beijing 100084 China2. Department of Mechanical Engineering Tsinghua University Beijing 100084 China

Carbon nanotubes filled with ferromagnetic metal nanowires (M-CNTs) were synthesized by using chlorine-contained benzene (***) as *** wall thicknesses of M-CNTs synthesized by trichlorobenzene are much thinner than those by precursor without Cl (***).As-synthesized thin-walled M-CNTs exhibit remarkably enhanced field electron emission performance with a low turn-on field of 0.3 V/μm and better field-emission ***-absorption coatings were made by dispersing as-synthesized M-CNTs into epoxy resin *** is found that the reflection losses in S-band (2.4 GHz),C-band (4-8 GHz) and X-band (8-12.GHz) are enhanced in the order of FeCoNi-CNTs 2.35 kg/m2.when the coating thickness is 2.0 *** demonstrates that M-CNTs are promising to be used as lightweight and wide-band microwave absorbers.

关键词： carbon nanotubes ferromagnetic nanowires field emission microwave absorption

SUPERSATURATED DESIGN WITH MORE THAN TWO LEVELS

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Chinese Annals of Mathematics,Series B 2001年第2期22卷 183-194页

作者： LU XUAN SUN YIZHOU department of Mathematical Science, tsinghua university,{2., China. department of Mathematical Science Tsinghua Univeristy Beijing 100084 China

Supersaturated designs are useful in screening experiments. This paper discusses the topic of multi-level supersaturated design. Two quantities, E(d2. and Df, are proposed to evaluate the optimality of supersaturated designs. A lower bound of E(d2. is obtained with a necessary condition for achieving it. Some E(d2.-optimal supersaturated designs of 3, 4, and 5 levels are given.

关键词： D-efficiency Screening experiment Fractional factorial design Orthogonality

Study on Numerical Simulation of Mold Filling and Heat Transfer in Die Casting Process

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Journal of Materials Science & Technology 2000年第3期16卷 269-272页

作者： Liangrong JIA, Shoumei XIONG and Baicheng LIU (department of Mechanical Engineering, tsinghua university,{2., China) department of Mechanical Engineering Tsinghua University Beijing 100084 China

A 3-D mathematical model considering turbulence phenomena has been established based on a computational fluid dynamics technique, so called 3-D SOLA-VOF (Solution Algorithm-Volume of Fluid), to simulate the fluid flow of mold filling process of die casting. In addition, the mathematical model for simulating the heat transfer in die casting process has also been established. The computation program has been developed by the authors with the finite difference method (FDM) recently. As verification, the mold filling process of a S-shaped die casting has been simulated and the simulation results coincide with that of the benchmark test. Finally, as a practical application, the gating design of a motorcycle component was modified by the mold filling simulation and the dies design of another motorcycle component was optimized by the heat transfer simulation. All the optimized designs were verified by the production practice.

关键词： Study on Numerical Simulation of Mold Filling and Heat Transfer in Die Casting Process Mold Simulation

A Hierarchy of Multidimensional Hénon-Heiles Systems

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Acta Mathematica Sinica,English Series 2000年第3期16卷 527-534页

作者： Yunbo Zeng department of Mathematical Sciences,tsinghua {2.,beijing 100084 P.R.China department of Mathematical Sciences Tsinghua University Bejing 100084 P. R. China

A hierarchy of multidimensional Hénon-Heiles(M-H-H)systems are constructed via the x-and t_n-higher-order-constrained flows of KdV *** Lax representation for the M-H-H hierarchy is determined from the adjoint representation of the auxiliary linear problem for the KdV *** using the Lax representation the classical Poisson structure and r-matrix for the hierarchy are found and the Jacobi inversion problem for the hierarchy is constructed.

关键词： Higher-order constrained flow Multidimensional Hénon-Heiles systems Lax representation Jacobi inversion problem

NUMERICAL DISSIPATION FOR THREE-POINT DIFFERENCE SCHEMES TO HYPERBOLIC EQUATIONS WITH UNEVEN MESHES

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Journal of Computational Mathematics 2003年第4期21卷 519-534页

作者： Zi-niu Wu(department of Engineering Mechanics, tsinghua university,{2., China) department of Engineering Mechanics Tsinghua University Beijing 100084 China

The widely used locally adaptive Cartesian grid methods involve a series of abruptly refined interfaces. The numerical dissipation due to these interfaces is studied here for three-point difference approximations of a hyperbolic equation. It will be shown that if the wave moves in the fine-to-coarse direction then the dissipation is positive (stabilizing), and if the wave moves in the coarse-to-fine direction then the dissipation is negative (destabilizing).

关键词： Refined interfaces Numerical dissipation Three-point difference approxima-tion Hyperbolic equation.

Process data compression based on recursive identification of nonuniformly sampled systems

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控制理论与应用（英文版） 2012年第2期10卷 166-175页

作者： Boyi NI, Deyun XIAO department of Automation, tsinghua university,{2., China department of Automation Tsinghua University Beijing China

A recursive identification method is proposed to obtain continuous-time state-space models in systems with nonuniformly sampled （NUS） data. Due to the nonuniform sampling feature, the time interval from one recursion step to the next varies and the parameter is always updated partially at each step. Furthermore, this identification method is applied to form a combined data compression method in NUS processes. The data to be compressed are first classified with respect to a series of potentially existing （possibly time-varying） models, and then modeled by the NUS identification method. The model parameters are stored instead of the identification output data, which makes the first compression. Subsequently, as the second step, the conventional swinging door trending method is carried out on the data from the first step. Numeric results from simulation as well as practical data are given, showing the effectiveness of the proposed identification method and fold increase of compression ratio achieved by the combined data compression method.

关键词： Nonuniformly sampled system Recursive identification Data compression Swinging door trending

Multiple time step molecular dynamics simulation for interaction between dislocations and grain boundaries

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Acta Mechanica Sinica 2005年第4期21卷 371-379页

作者： X.Y.Li W.Yang department of Engineering Mechanics,tsinghua {2.,beijing 100084.China department of Engineering Mechanics Tsinghua University Beijing 100084 China

A multiple time step algorithm, called reversible reference system propagator algorithm, is introduced for the long time molecular dynamics simulation. In contrast to the conventional algorithms, the multiple time method has better convergence, stability and efficiency. The method is validated by simulating free relaxation and the hypervelocity impact of nano-clusters. The time efficiency of the multiple time step method enables us to investigate the long time interaction between lattice dislocations and low-angle grain boundaries.

关键词： Multiple time step Molecular dynamics ,Dislocation Grain boundary

Thermodynamic Significance of Human Basal Metabolism

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Journal of Thermal Science 1993年第2期2卷 81-86页

作者： Wang Cuncheng Thermal Engineering department tsinghua university,{2., P.R. China 1. Thermal Engineering department tsinghua university 100084 Beijing P.R. China

The human basal state,a non-equilibrium steady state,is analysed in this paper in the light of the First and Second Laws of Thermodynamics whereby the thermodynamic significance of the basal metabolic rate and its distinction to the dissipation function and exergy loss are *** analysis demonstrates the correct expression of the effects of the blood flow on the heat balance in a human-body bio-heat model and the relationship between the basal metabolic rate and the blood perfusion.

关键词： thermodynamic laws basal metabolism blood perfusion dissipation function exergy loss

Fluorescence fluctuation spectroscopy and its artifacts:simulations and tests

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Science China(physics,Mechanics & Astronomy) 2005年第3期48卷 336-344页

作者： MENG Fanbo 1 , CHEN Bo 1 , LIU Guang 1 , DING Jianying 1 & MA Hui 2.1 1. department of physics and Key Laboratory of Atomic and Molecular Nano Sciences, Ministry of Educa- tion,{2., beijing 100084, China 2. Graduate School at Shenzhen,{2., Shenzhen 518055, China 1. department of physics and Key Laboratory of Atomic and Molecular Nano Sciences Ministry of Education Tsinghua University 100084 Beijing China 2. Graduate School at Shenzhen Tsinghua University 518055 Shenzhen China

Fluorescence fluctuation spectroscopy (FFS) technique is capable of monitoring changes in concentration, mass, size and structure of fluorescent-labeled bio-molecules in microscopic volume and is suitable for measuring biological interactions in living cells. FFS data may be affected by many experimental factors in complicated biological systems. Using a Monte Carlo approach, we generate fluorescence fluctuation data for different experimental systems. This approach helps to separate the contributions by different experimental factors in a complicated fluorescence fluctuation spectrum. It also helps to validate new theoretical models and new fitting formulations. We describe the algorithm of the simulation program and tests on its statistical performance. The program is then used successfully to study the effects of several experimental factors on FFS detection.

关键词： fluorescence fluctuation spectroscopy, fluorescence correlation spectroscopy, Monte Carlo simulation.