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Effects of Positron Diffusion and Its Application in Composite System

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Journal of Materials science & Technology 2000年第3期16卷 311-314页

作者： Jian JIANG, Xinzhang ZHOU and ChiWei LUNG (International center for Materials physics, Institute of Metal Research, chinese academy of sciences, Shenyang 110015, china) International center for Materials physics Institute of Metal Research Chinese Academy of Sciences Shenyang 110015 China

The effects of positron diffusion on the measured S parameter have been investigated by a point-source diffusion model and a δ function method. Firstly, the theoretical analyses of the effects are presented for the samples of a homogeneous semi-infinite medium and a film of definite thickness. Then the results are used to analyze the S parameters in several composite systems and interface models.

关键词： Effects of Positron Diffusion and Its Application in Composite System

Single crystal β-Ga_2O_3: Cr grown by floating zone technique and its optical properties

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science china(Technological sciences) 2007年第1期50卷 51-56页

作者： ZHANG JunGang1, 2, LI Bin3, XIA ChangTai1, XU Jun1, DENG Qun4, XU XiaoDong1, WU Feng1, XU WuSheng4, SHI HongSheng4, PEI GuangQing1, 2 & WU YongQing1,2 1 Shanghai Institute of Optics and Fine Mechanics, chinese academy of sciences, Shanghai 201800, china 2 Graduate School of the chinese academy of sciences, beijing 100039, china 3 Shanghai Institute of Applied physics, chinese academy of sciences, Shanghai 201800, china 4 GE (china) Research and Development center Co. Ltd., Shanghai 201203, china 1. Shanghai Institute of Optics and Fine Mechanics Chinese Academy of Sciences Shanghai 201800 China 2. Graduate School of the chinese academy of sciences Beijing 100039 China 3. Shanghai Institute of Applied physics Chinese Academy of Sciences Shanghai 201800 China 4. GE (china) Research and Development center Co. Ltd. Shanghai 201203 China

β-Ga2O3: Cr single crystals were grown by floating zone technique. Absorption spectra and fluorescence spectra were measured at room temperature. The values of field splitting parameter Dq and Racah parameter B were obtained by the peak values of absorption spectra. The value 10Dq/B=23.14 manifests that in β-Ga2O3 crystals Cr3+ ions are influenced by low energy crystal field. After high temperature annealing in air, the Cr3+ intrinsic emission was enhanced and the green lumines-cence disappeared. The strong and broad 691 nm emission was obtained at 420 nm excitation due to the electron transition occurred from 4T2 to 4A2. The studies manifest that the β-Ga2O3 crystals have the potential application for tunable laser.

关键词： β-Ga2O3: Cr single crystals floating zone technique tunable laser spectrum.

Collision dynamics of He@C_(60)+He@C_(60) at low energies

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science china(physics,Mechanics & Astronomy) 2008年第7期51卷 765-772页

作者： ZHAO Qiang1,2, ZHANG FengShou1,2,3 & ZHOU HongYu1,2 1 Key Laboratory of Beam Technology and Material Modification of Ministry of Education, Institute of Low Energy Nuclear physics, beijing Normal University, beijing 100875, china 2 beijing Radiation center, beijing 100875, china 3 center of theoretical Nuclear physics, National Laboratory of Heavy Ion Accelerator of Lanzhou, Lanzhou 730000, china 1. Key Laboratory of Beam Technology and Material Modification of Ministry of Education Institute of Low Energy Nuclear Physics Beijing Normal University Beijing 100875 China 2. beijing Radiation center Beijing 100875 China 3. center of theoretical Nuclear physics National Laboratory of Heavy Ion Accelerator of Lanzhou Lanzhou 730000 China

A semi-empirical molecular dynamics model is developed. The central collisions of C60+C60 and He@C60+He@C60 at different incident energies are investigated based on this model. It is found that the dimer structures have been produced at proper incident energies and these fullerene dimers could be formed by a self-assembly of C60 fullerene and He@C60. The He atom has a significant effect at higher incident energy and this embedded He atom can enhance the stability of the dimer structure.

关键词： C60 He@C60 collision molecular dynamics

Containerless solidification of Zr_(41)Ti_(14)Cu_(12.5)Ni_(10)Be_(22.5) glass-forming alloy in drop tube

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chinese science Bulletin 2002年第20期47卷 1700-1703页

作者： LI Gong, SUN Liling & WANG WenkuiCollege of Material sciences and Engineering, Yanshan University, Qinhuangdao 066004, china center for Condensed Matter physics, Institute of physics, chinese academy of sciences, beijing 100080, china National Microgravit Coll. of Mat. Sci. and Engineering Yanshan University Qinhuangdao 066004 China center for Condensed Matter physics Institute of Physics Chinese Academy of Sciences Beijing 100080 China National Microgravity Laboratory Chinese Academy of Sciences Beijing 100080 China

Droplets of Zr41Ti14Cu12.5Ni10Be22.5 glass forming alloys with different sizes are solidified in a drop tube containerless processing. Glass transition behavior, crystallization kinetics, and the phase evolution during annealing of the Zr41Ti14Cu12.5Ni10Be22.5 glassy spheres are investigated. The experimental results indicate that the apparent activation energy of the glass transition (Eg=435.5 kJ/mol), and the activation energy of the main crystallization reaction (Ep1 = 249.6 kJ/mol) are obviously different from those of bulk glass samples prepared by water quenched (Eg=559.1 kJ/mol and Ep1=192.5 kJ/mol). The difference is discussed in the view point of the atomic configuration of the liquid state of the metallic glass and nucleation mechanism.

关键词： ZrTiCuNiBe alloy containerless processing activation energy drop tube.

Mechanisms of the pancake vortex and vortex line movement in the high T_c superconductors Bi_2Sr_2CaCu_2O_8+δ and La_(1.93)Sr0.0_7CuO_4+δ

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science china(physics,Mechanics & Astronomy) 2007年第2期50卷 240-248页

作者： WANG WeiXian1,ZHOU Fang2,TAN Shun1,WU Huan1 & ZHANG YuHeng1 1 National High Magnetic Field Laboratory,University of science and Technology of china,Hefei 230026,china 2 National Laboratory for Superconductivity,lnstitute of physics and the center for Condensed Matter physics,chinese academy of sciences,beijing 100080,china 1. National High Magnetic Field Laboratory University of Science and Technology of China Hefei 230026 China 2. National Laboratory for Superconductivity Institute of Physics and the Center for Condensed Matter Physics Chinese Academy of Sciences Beijing 100080 China

In the strict sense, it is not very clear why with magnetic field increasing, the normal-superconductive (NS) transition becomes broad for Bi2Sr2CaCu208+δ(Bi2212) while the NS transitions are almost parallel for La193Sroo7Cu04+δ(La214). In this paper, R-T relations are measured by the six-probe method. We propose a moving mechanism of the pancake vortex and vortex line for Bi2212. The theoretical curves fit the experiment data well.

关键词： superconductivity superconductive pancake vortex dynamics

Estimating surface evapotranspiration using combined MODIS and CBERS-02 data

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science china(Technological sciences) 2005年第S2期48卷 145-160页

作者： XIN Xiaozhou1,2, LIU Qinhuo1, TANG Yong1,3, TIAN Guoliang1, GU Xingfa1, LI Xiaowen1,2, ZHENG Hongsheng4 & CHEN Jiayi4 1. State Key Laboratory of Remote Sensing science, Institute of Remote Sensing Applications, chinese academy of sciences, beijing 100101, china 2. Research center for Remote Sensing and GIS, Department of Geography, beijing Normal University, beijing 100875, china 3. Graduate University of chinese academy of sciences, beijing 100039, china 4. Department of Atmospheric physics, Peking University, beijing 100871, china 1. State Key Laboratory of Remote Sensing science Institute of Remote Sensing Applications Chinese Academy of Sciences 100101 Beijing China2. Research Center for Remote Sensing and GIS Department of Geography Beijing Normal University 100875 Beijing China3. Graduate University of Chinese Academy of Sciences 100039 Beijing China4. Department of Atmospheric Physics Peking University 100871 Beijing China

Spatial scale error is one of the most serious problems in the estimates of land surface heat fluxes of sensible and latent from satellite-borne data such as MODIS 1km resolution reflectance and emissive data. One of the feasible and economic ways to decrease the spatial scale error is to use high resolution land use class data together with the MODIS data. CBERS-02 data were used to produce land use class of Baiyangdian area, Hebei Province, china in the autumn of 2004. The area ratio of each class in MODIS pixel was calculated, and used to derive the heat fluxes of the mixed pixel. The results showed that the estimated heat fluxes of soil, sensible and latent have been changed remarkably after using the high resolution land class data. It could be concluded from the comparison between simulated and ground-measured fluxes as well as the theoretical analysis that high resolution land class data are useful to diminishing the scale error of heat fluxes estimated from low resolution satellite data.

关键词： surface evapotranspiration spatial scale error MODIS CBERS land class.

High-pressure synthesis and properties of CeO_2-ZrO_2 solid solution

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chinese science Bulletin 2001年第10期46卷 801-806页

作者： XU Dapeng, WANG Quanyong, LU Zhe, LIU Zhiguo, ZHANG Gongmu & SU Wenhui1. Department of physics, Jilin University, Changchun 130023 china 2. International center for Materials physics, chinese academy of sciences, Shenyang 110015, china 3. center for Condensed Matter and Radiation physics, china center of Advanced science and Technology (World Laboratory), beijing 100080, china Department of physics Jilin University Changchun China International center for Materials physics Chinese Academy of Sciences Shenyang China center for Condensed Matter and Radiation physics China Center of Advanced Science and Technology (World Laboratory) Beijing China

Using nanoparticles of CeO2 and ZrO2 prepared by the chemical precipitation method as starting materials, the single-phase cubic Ce0.5Zr0.5O2 solid solution (c-Ce0.5Z0.5O2) has been synthesized under 3.1 GPa at 1073 K for the first time. The structure of the c-Ce0.5Zr0.5O2 has not been changed before and after annealing at 773 K for 1 h. Only an unknown EPR signal (g =1.990) has been observed in the c-Ce0.5Zr0.5O2 and not varied after annealing at 773 K for 1 h, which exhibited that there exists no Ce3+ in the c-Ce0.5Zr0.5O2 and the Ce4+ has not been reduced into Ce3+ after annealing. The transport mechanism is ionic for the c-Ce0.5Zr0.5O2. The bulk conductivity (a =1.2×10-5 S/cm at 823 K, σ=2.1 ×10-3 S/cm at 1123 K) is the same as that of CeO2, but smaller than that of Y2O3-stabilized ZrO2. A marked curvature at T = 823 K has been observed in the Arrhenius plot of the bulk conductivity. The activation energy below 823 K is lower than that above 823 K, and the reason has been discussed.

关键词： CeO2-ZrO2 nanocrystalline high-pressure and -temperature solid-state reaction solid solution.

STUDY ON PYROLYSIS OF POLYPHENYLSILSESQUIOXANE

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chinese Journal of Polymer science 2002年第6期20卷 573-577页

作者： Jun Ma Liang-he Shi Jian-min Zhang Bai-yu Li De-yan Shen Jian Xu State Key Laboratory of Polymer physics & Chemistry center for Molecular science, Institute of Chemistry,chinese academy of sciences, beijing 100080 china chinese Acad Sci Inst Chem State Key Lab Polymer Phys & Chem Ctr Mol Sci Beijing 100080 Peoples R China

X-ray photoelectron spectroscopy and Raman spectroscopy were' used to determine the chemical change of polyphenylsilsesquioxane (PPSQ) during pyrolysis in flowing nitrogen. Two temperature ranges were found for pyrolysed PPSQ below and above 600degreesC, respectively. The former is related to the rearrangement of PPSQ backbone and the latter reflects that most of backbone structure of PPSQ might be broken down and unorganized. Carbon formed in carbonization of PPSQ sample pyrolysed at 900degreesC should be sp(3) bonded carbon with crystallite size effects or defects.

关键词： pyrolysis polyphenylsilsesquioxane

The Real-gas Effect in Single-bubble Sonoluminescence

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Communications in Nonlinear science and Numerical Simulation 1999年第1期4卷 29-34页

作者： Li YUAN (LSEC, Institute of Computational Mathematics and Scientific-Engineering Computing, chinese academy of sciences, beijing 100080, china) Wei WEI (center for Nonlinear sciences, University of science and Technology of china, Hefei 230026,china) LSEC Inst. Compl. Math./Sci.-Eng. Comp. Chinese Academy of Sciences Beijing 100080 China center for Nonlinear sciences Univ. of Sci. and Technol. of China Hefei 230026 China Department of physics Chinese University of Hong Kong Shatin Hong Kong

The full set of hydrodynamic equations governing the oscillation of a bubble is solved numerically by using a modified equation of state with ionization. We show that the hydro-thermal process in the form of compression waves and low-level ionization are dominant inside a sonoluminescing bubble for a wide range of driving pressure. The resulting thermal bremsstrahlung radiation has pulse heights and widths that agree with experimental data for cases considered in this paper.

关键词： single-bubble sonoluminescence ionization bremsstrahlung