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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 university of Science and Technology, beijing 100083. China b School of physics, beijing university of Chemical Technology, beijing 100029, China c department of physics, tsinghua university, beijing 100084, China [a]Institute of Applied physics Beijing University of Science and Technology Beijing 100083 China [b]School of Physics Beijing University of Chemical Technology Beijing 100029 China [c]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 2b 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

Analytic Solution of Strongly Coupling Schrdinger Equations

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Communications in Theoretical physics 2004年第4期 502-508页

作者： LIAO Jin-Feng ZHUANG Peng-Fei physics department,tsinghua university,{3.,China physics department Tsinghua UniversityBeijing 100084China

A recently developed expansion method for analytically solving the ground states of strongly couplingSchr(?)dinger equations by Friedberg,Lee,and Zhao is extended to excited states and applied to power-law central forcesfor which scaling properties are *** examples for application of the extended method,the Hydrogen atomproblem is resolved and the low-lying states of Yukawa potential are approximately obtained.

关键词： strong coupling Schrdinger equation Yukawa potential

Large eddy simulation of stably stratified turbulence

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Science China(physics,Mechanics & Astronomy) 2010年第1期53卷 135-146页

作者： SHEN Zhi, LI YuPeng, CUI GuiXiang & ZHANG ZhaoShun department of Engineering Mechanics, tsinghua university, beijing 100084, China 1. department of Engineering Mechanics Tsinghua University Beijing 100084 China

Stable stratification turbulence, as a common phenomenon in atmospheric and oceanic flows, is an important mechanism for numerical prediction of such flows. In this paper the large eddy simulation is utilized for investigating stable stratification turbulence numerically. The paper is expected to provide correct statistical results in agreement with those measured in the atmosphere or ocean. The fully developed turbulence is obtained in the stable stratification fluid by large eddy simulation with different initial velocity field and characteristic parameters, i.e. Reynolds number Re and Froude number Fr. The evolution of turbulent kinetic energy, characteristic length scales and parameters is analyzed for investigating the development of turbulence in stable stratification fluid. The three-dimensional energy spectra, horizontal and vertical energy spectrum, are compared between numerical simulation and real observation in the atmosphere and ocean in order to test the reliability of the numerical simulation. The results of numerical cases show that the large eddy simulation is capable of predicting the properties of stable stratification turbulence in consistence with real measurements at less computational cost. It has been found in this paper that the turbulence can be developed under different initial velocity conditions and the internal wave energy is dominant in the developed stable stratification turbulence. It is also found that the characteristic parameters must satisfy certain conditions in order to have correct statistical property of stable stratification turbulence in the atmosphere and ocean. The Reynolds number and Froude number are unnecessarily equal to those in atmosphere or ocean, but the Reynolds number must be large enough, say, greater than 10 2 , and Froude number must be less than 0.1. The most important parameter is ReFr 2 which must be greater than 10.

关键词： stratified turbulence internal wave potential vortex large eddy simulation

Global analysis theory of climate system and its applications

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Chinese Science Bulletin 2003年第10期48卷 1034-1039页

作者： LI Jianping1,2 & CHOU Jifan2,3.1. LASG, Institute of Atmospheric physics, Chinese Academy of Sciences, beijing 100029, China 2. department of Atmospheric Sciences, Lanzhou {3., Lanzhou 73.000, China 3. Training center for China Meteorological Administration, beijing 100081, China department of Atmospheric Sciences Lanzhou University Lanzhou 730000 China LASG Institute of Atmospheric Physics Chinese Academy of Sciences Beijing 100029 China

The idea and main theoretical results of the global analysis theory of climate system are briefly summarized in this paper. A theorem on the global behavior of climate system is given, i.e. there exists a global attractor in the dynamical equations of climate, any state of climate system will be evolved into the global attractor as time increases, indicating the nonlinear adjustment process of climate system to external forcing. The different effects of external forcing, dissipation and nonlinearity on the long-term behavior of solutions are pointed out, and some main applications of the global analysis theory are also introduced. Especially, three applications, the adjustment and evolution processes of climate, the principle of numerical model design and the optimally numerical integration, are discussed.

关键词：整体分析理论气侯体系应用不定性计算法则气侯科学数字模型

Constraints on smoothness parameter and dark energy using observational H(z) data

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Research in Astronomy and Astrophysics 2011年第2期11卷 125-136页

作者： Hao-Ran Yu1,Tian Lan1,Hao-Yi Wan2,Tong-Jie Zhang1,3.and Bao-Quan Wang4 1 department of Astronomy,beijing Normal university,beijing 100875,China 2 Business Office,beijing Planetarium,beijing 100044,China 3.center for High Energy physics,Peking university,beijing 100871,China 4 department of physics,Dezhou university,Dezhou 253.23.China department of Astronomy Beijing Normal University Beijing 100875 China Business Office Beijing Planetarium Beijing 100044 China center for High Energy physics Peking University Beijing 100871 China department of physics Dezhou University Dezhou 253023 China

With large-scale homogeneity,the universe is locally inhomogeneous,clustering into stars,galaxies and larger *** property is described by the smoothness parameter α which is defined as the proportion of matter in the form of intergalactic *** we consider the inhomogeneities over a small scale,there should be modifications of the cosmological distances compared to a homogenous *** and Roeder developed a second-order ordinary differential equation（D-R equation） that describes the angular diameter distance-redshift relation for inhomogeneous cosmological ***,we may obtain the D-R equation for observational H（z） data（OHD）.The density-parameter ΩM,the state of dark energy ω,and the smoothness-parameter α are constrained by a set of OHD in a spatially flat XCDM universe as well as a spatially flat XCDM *** using a χ2 minimization method,we get α = 0.81＋0.19-0.20 and ΩM = 0.3.＋0.12.0.06 at the 1σ confidence *** we assume a Gaussian prior of ΩM = 0.26 ± 0.1,we get α = 0.93.0.07-0.19 and ΩM = 0.3.＋*** the XCDM model,α is constrained to α≥ 0.80 but ω is weakly constrained around-1,where ω describes the equation of state of the dark energy（pX = ωρX）.We conclude that OHD constrains the smoothness parameter more effectively than the data of SNe Ia and compact radio sources.

关键词： cosmology -- dark energy -- cosmological parameters

Temporal study of GRS 1915+105 with rms-flux relation:The importance of magnetic activities in the corona

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Science China(physics,Mechanics & Astronomy) 2010年第S1期53卷 120-124页

作者： HAN Dong1,ZHANG ShuangNan2 & SONG LiMing2 1 department of Engineering physics & 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 Engineering physics & 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

The rms-flux relations for some observations of GRS 1915+105 are *** rms-flux relations of the light curves in only one state,state C or state A,can be described by the simple non-linear model provided Zhang;we thus interpret that such a linear relation reflects the relative importance of magnetic instability for X-ray emission in the corona of the system,compared to the thermal viscous instability for the X-ray emission in the accretion *** rms-flux relations for state B are very scattered,possibly because of the dominance of thermal viscous instability for the X-ray emission in the accretion *** complex rms-flux relations for the observations of transitions between two or three states are caused by the combination of the different rms-flux relations of these *** underlying physical processes are the combination of magnetic topology in the corona and thermal viscous instability in the accretion disk.

关键词： rms-flux relation data analysis GRS 1915+105 magnetic instability

The Process of TiB_2-Cu Composite Phase and Structure Formation during Combustion Synthesis

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Journal of Wuhan university of Technology(Materials Science) 2006年第4期21卷 113-116页

作者：徐强 School of Materials Science and Engineering Beijing Insitute of TechnologyBeijing 100081China

The reaction process of combustion synthesis for TiB2 -Cu was investigated in detail using combustion-wave arresting experiment, X-ray diffraction （ XRD ） analysis, SEM analysis and differential thermal analysis （ DTA ）. The XRD analysis results for the different parts of the quenched specimen show that TiCux intermetallic phase firstly forms with the propagation of combustion wave, and then Ti1.87 B50 and Ti3.4 metastable phases come forth due to the diffusion of B atoms and finally the stable TiB2 phase forms because of the continuous diffusion of B atoms. The formation of TiB2 phase is uot completed by one step, but undergoes several transient processes. The process of reaction synthesis for Ti-B-Cu ternary system can be divided into three main stages： melting of Cu and Ti , and the formation of Cu- Ti melt and few TiCux , TiBx intermetallic phases ; large numbers of TiCux intermetallic phases formation and some fine TiB2 particles precipitation ; and the TiB2 particles coarsening and the stable TiB2 and Cu two phases formation in the final product.

关键词： combustion synthesis reaction process TiB2 phase combustion-wave arresting experiment

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, {3., 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.

Pairwise entanglement and local polarization of Heisenberg model

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Science China(physics,Mechanics & Astronomy) 2008年第10期51卷 1515-1522页

作者： XI XiaoQiang1,2, ZHANG Tao3. YUE RuiHong3.4 & LIU WuMing2 1 department of Applied Mathematics and physics, Xi’an Institute of Post and Telecommunications, Xi’an 710061, China 2 beijing National Laboratory for Condensed Matter physics, Institute of physics, Chinese Academy of Sciences, beijing 100080, China 3.Institute of Modern physics, Northwest university, Xi’an 710069, China 4 department of physics, Ningbo university, Ningbo 3.5211, China department of Applied Mathematics and physics Xi’an Institute of Post and Telecommunications Xi’an 710061 China beijing National Laboratory for Condensed Matter physics Institute of Physics Chinese Academy of Sciences Beijing 100080 China Institute of Modern physics Northwest University Xi’an 710069 China department of physics Ningbo University Ningbo 315211 China

The characteristics of pairwise entanglement and local polarization (LP) are dis-cussed by studying the ground state (states) of the Heisenberg XX model. The re-sults show that: the ground state (states) is (are) composed of the micro states with the minimal polarization (0 for even qubit and 1/2 for odd qubit); LP and the prob-ability of the micro state have an intimate relation, i.e. the stronger the LP, the smaller the probability, and the same LP corresponds to the same probability; the pairwise entanglement of the ground state is the biggest in all eigenvectors. It is found that the pairwise entanglement is decreased by the state degeneracy and the system size. The concurrence approaches a fixed value of about 0.3.12.(for odd-qubit chain) or 0.3.91 (for even-qubit chain) if the qubit number is large enough.

关键词： Heisenberg XX model local polarization pairwise entanglement