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Science china chemistry 2007年第4期50卷 483-487页

作者： chen feiwu department of chemistry, university of Science and {2. beijing, beijing 100083, china (email: chenfeiwu@***) department of chemistry University of Science and Technology Beijing Beijing China

The size consistency of the second and third order energies of the multireference perturbation theory(chen F, Davidson E, Iwata S. Int J Quant Chem, 2.02. 86: 2.6) is investigated theoretically with a su-per-molecular model composed of N-hydrogen molecules separated by a large distance. It is found that the two perturbation series corresponding to two Hamiltonian partitions are not size consistent at the second and third order. However, two size consistent forms are suggested for two Hamiltonian parti-tions at the second order, if some approximations to the denominators of the original second order energies are assumed.

关键词： size consistency multireference perturbation theory

MEAM Potential with Angular Dependence for TiAl

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Rare Metals 2001年第1期20卷 13-17页

作者： Xiaodong Ni, Xitao Wang, Guoliang chen (Physics department, {2. of Science and technology beijing, beijing 100083, china State Key Laboratory for Advanced Metals and Materials, {2. of Science and technology beijing, beijing 100083, china) 北京科技大学新金属材料国家重点实验室北京 100083 北京科技大学北京 100083

The modified embedded atom method (MEAM) is an empirical extension of the embedded atom method (EAM) that includes angular forces. By fitted to the lattice constants, the cohesive energy, the APE (anti-phase boundary) energy, and the vacancy formation energy of TiAl, an accurate MEAM potential is obtained for the TiAl system with L10 structure. The calculation results of the properties of TiAl are in good agreement with experiments and the results of first principle (F.P.) calculations.

关键词： embedded atom method TiAl alloy angular dependence potential intermetallics

NON-EQUILIBRIUM SEGREGATION OF Si ON Al-0.35 wt-% Si ALLOY SURFACE

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Acta Metallurgica Sinica(English Letters) 1993年第8期6卷 98-101页

作者： chen Niug YU Zongsen university of Science and {2. beijing,beijing,china professor,department of Materials Physics,university of Science and {2. beijing,beijing 100083,china beijing Univ of Science and Technology Beijing China

Si segregation was observed in the vacancy condensation pits,formed by supersaturated vacancies beneath the oxidation layer of Al-0.35wt-％Si alloy,by optical microscopy,X- ray photoelectron spectroscopy and microhard... 详细信息

关键词： non-equilibrium segregation vacancy AI-Si alloy surface Si

Novel thermal expansion of lead titanate

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Rare Metals 2003年第4期22卷 294-297页

作者： XING Xianran, DENG Jinxia, chen Jun and LIU Guirongdepartment of Physical {2., university of Science & technology beijing, beijing 100083, china department of Physical chemistry University of Science & Technology Beijing 北京 100083

Lattice parameters of lead titanate were precisely re-determined in thetemperature range of-150-950 deg C by high precision XRPD measurements. It was clarified that therewas no any evidence for a new phase transition at low tempera-lures. Tetragonal distortion straindecreases with temperature increasing. A novel thermal expansion was observed, positive thermalexpansion from -150 deg C to room temperature (RT) and above 490 deg C, and the negative thermalexpansion in the temperature range of RT-490 deg C. A big jump of thermal expansion coefficient isattributed to the tetragonal-cubic phase transition. A rationalization for the negative thermalexpansion of PbTiO_3 is due to the decrease of anion-anion repulsion as polyhedra become moreregular at heating. The mechanisms of positive and negative thermal expansions were elucidated asthe same nature in the homogenous tetragonal phase at present case.

关键词： metallurgical physical chemistry thermal expansion X-ray powder diffraction(XRPD) lead titanate phase transition

The steady-state solution of dendritic growth from the undercooled binary alloy melt with the far field flow

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Science china(Technological Sciences) 2009年第8期52卷 2280-2287页

作者： chen MingWen1,2. WANG ZiDong2.& XU JianJun2.3,4 1 School of Applied Sciences, university of Science and {2. beijing, beijing 100083, china 2.School of Materials Science and Engineering, university of Science and {2. beijing, beijing 100083, china 3 School of Mathematical Sciences, Nankai university, Tianjin 300071, china 4 department of Mathematics and Statistics, McGill university, Montreal H3A 2.6, Canada School of Applied Sciences University of Science and Technology Beijing Beijing China School of Materials Science and Engineering University of Science and Technology Beijing Beijing China School of Mathematical Sciences Nankai University Tianjin China department of Mathematics and Statistics McGill University Montreal Canada

The steady-state dendritic growth from the undercooled binary alloy melt with the far field flow is considered. By neglecting the interface energy, interface kinetics and buoyancy effects in the system, we obtaine the steady-state solution for the case of the large Schmidt number, in terms of the multiple variable expansion method. The changes of the temperature and concentration fields, the morphology of the interface, the normalization parameter and the Peclet number of the system induced by uniform external flow are derived. The results show that, compared with the system of dendritic growth from undercooled pure melt, the convective flow in the system of growth from undercooled binary alloy has stronger effects on the morphology of the interface. Nevertheless, the shape of the interface still remains nearly a paraboloid.

关键词： binary alloy melt convection dendritic growth interfaces steady-state solution multiple variable expansion method

The evolution and morphological stability of a spherical crystal

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Science china(Technological Sciences) 2008年第3期51卷 225-243页

作者： chen MingWen1,2. WANG ZiDong2.& XU JianJun3,4 1 School of Applied Sciences, university of Science and {2. beijing, beijing 100083, china 2.School of Materials Science and Engineering, university of Science and {2. beijing, beijing 100083, china 3 School of Mathematical Sciences, Nankai university, Tianjin 300071, china 4 department of Mathematics and Statistics, McGill university, Montreal H3A 2.6, Canada School of Applied Sciences University of Science and Technology Beijing Beijing China School of Materials Science and Engineering University of Science and Technology Beijing Beijing China School of Mathematical Sciences Nankai University Tianjin China department of Mathematics and Statistics McGill University Montreal Canada

The growth model of a spherical crystal in the undercooled melt including the surface energy, interfacial kinetics and convective flow is established. The effect of the convective flow induced by a small far field flow on the evolution and morphological stability of the interface of the spherical crystal is studied. The interface shape of the spherical crystal, which is affected by the far field flow, and the dispersion relation of the growth rate of amplitude of the perturbed interface are derived. It is shown that the convection induced by the far field flow makes the interface of the growing spherical crystal further grow in the upstream direction of the far field flow and inhibit growth in the downstream direction; the interface of the decaying spherical crystal further decays in the upstream direction and inhibits decay in the downstream direction. The theoretical result suggests that both the growth of the sphere in the upstream direction and the decay of the sphere in the downstream direction make the spherical crystal tend to evolve into an oval; the morphological stability of the interface depends on a certain radius R c such that the spherical crystal is unstable when its radius is greater than R c and stable when its radius is less than R c . The surface energy and interfacial kinetics have strong stabilizing effects on the growth of the spherical crystal. In the meantime interfacial kinetics is a table factor of the interface when the interface of the sphere is growing; it is an unstable factor of the interface when the interface is decaying.

关键词： solid-liquid interface spherical crystal convective flow crystal growth morphological stability

Electrical Properties of Expanded Graphite Intercalation Compounds

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Journal of Materials Science & technology 2001年第3期17卷 371-374页

作者： Xiuyun CHUAN department of Geology, Peking university, {2. 100871, china Daizhang chen and Xunruo ZHOU department of Materials Science, china university of Geosciences, beijing 100083, china E-mail: cxyljhcj@*** Dept. of Geol. Beijing Univ. Beijing 100871 China

The intercalation compounds of CuCl2.were synthesized with expanded graphite, whose magnitude of the electrical conductivity is about 10(3)S(.)cm(-1). Their electrical conductivity is 3 similar to6 times as high as that of the expanded graphite, and about 10 times as high as that of GIC made of the non-expanded graphite. The microanalysis results of chemical compounds by X-ray energy spectrum scanning of TEM testified that the atomic ratio of chloride and cupric is nonstoichoimetric. The multivalence and exchange of electrovalence of the cupric ion was confirmed by the XPS-ESCA. Vacancy of chlorine anion increases the concentration of charge carrier. The special stage structure, made of graphite and chloride, produces a weak chemical bond belt and provides a carrier space in the direction of GIC layer. These factors develop the electrical properties.

关键词： In Ph Electrical Properties of Expanded Graphite Intercalation Compounds Graphite ESCA

Structure and kinematic analysis of a novel 2.DOF translational parallel robot

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Progress in Natural Science:Materials International 2007年第10期17卷 1213-1219页

作者： chen Tao1, Wu Chao2.and Liu Xinjun2.1. School of Application Science and technology, Harbin {2. of Science and technology, Harbin 150080, china 2. department of Precision Instruments, Tsinghua {2., beijing 100084, china) School of Application Science and technology Harbin University of Science and Technology Harbin 150080 China department of Precision Instruments Tsinghua University Beijing 100084 China

This paper addresses the analysis of a novel parallel robot with 2.translational degrees of freedom (DOFs). The robot can position a rigid body in a plane with constant orientation. The kinematic structure of the robot is first described in detail. Some kinematic problems, such as the inverse and forward kinematics, velocity, and singularity are then analyzed. The working and assembly modes are discussed. Since it is the most important index to design a robot, the workspace of the robot is studied systematically in this paper. Based on the analysis of reachable workspace and singularity, a kind of workspace concept characterizing the region that the end-effector of the robot can reach in practice is defined. The results of this paper will be very useful for the design and application of the robot.

关键词： parallel robot degree of freedom kinematics workspace.

Compactness of the commutators of parabolic singular integrals

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Science china Mathematics 2010年第10期53卷 2633-2648页

作者： chen YanPing1 & DING Yong2.3 1department of Mathematics and Mechanics,{2. of Science and technology beijing,beijing 100083,china 2.chool of Mathematical Science,beijing Normal {2.,beijing 100875,china 3Laboratory of Mathematics and Complex Systems (BNU),Ministry of Education of china,beijing 100875,china department of Mathematics and Mechanics University of Science and Technology Beijing Beijing China School of Mathematical Science Beijing Normal University Beijing China Laboratory of Mathematics and Complex Systems (BNU) Ministry of Education of China Beijing China

In this paper,the authors prove that the commutator [b,T] of the parabolic singular integrals is a compact operator on Lp(Rn)(1 < p < ∞) if and only if b ∈ VMO(Rn,ρ).The result is substantial improvement and extens... 详细信息

关键词： parabolic singular integrals commutators compactness BMO VMO

An atomistic simulation of site preference and vibrational properties of UMxAl12.x (M = Fe, Co, Ni, Cr and Mn) and UMxAl12.xHx

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Progress in Natural Science:Materials International 2009年第8期19卷 983-989页

作者： Huijun Tian a,b, Ping Qian a, Jiang Shen a, Nanxian chen a,c a Institute of Applied Physics, beijing {2. of Science and technology, beijing 100083, china b School of Physics, beijing {2. of Chemical technology, beijing 10002., china c department of Physics, Tsinghua {2., beijing 100084, china Institute of Applied Physics Beijing University of Science and Technology Beijing 100083 China School of Physics Beijing University of Chemical Technology Beijing 100029 China department of Physics Tsinghua University Beijing 100084 China

A series of lattice inversion pair potentials are used to evaluate the phase stability and site preference for uranium intermetallics UMxAl12.x (M = Fe, Co, Ni, Cr and Mn) and their related hydrides. Calculated results show that Fe, Co, Ni, Cr or Mn atoms preferentially substitute Al at the 8f site. Interstitial H atoms only occupy 2. interstitial sites in UMxAl12.x. Calculated lattice constants are found to agree with a report in the literature. Elastic constants and bulk modulus of UMxAl12.x and UMxAl12.xH were also investigated. In particular, the phonon densities of states (DOS) of these actinide compounds were evaluated for the first time.

关键词： Interatomic potentials Site preference Lattice vibration