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Anomalous magnetotransport in LaMn_(1-x)Te_xO_3

Science china(Physics,Mechanics & Astronomy) 2009年第7期52卷 987-992页

作者： TAN GuoTai1,2. chen ZhengHao3 & ZHANG XiaoZhong4,5 1 Key Laboratory of Beam technology & Materials Modification of the Ministry of Education, Institute of Low Energy Nuclear Physics, {2. Normal university, {2. 100875, china 2.{2. Radiation Center, {2. 100875, china 3 Laboratory of Optical Physics, Institute of Physics, Chinese Academy of Sciences, {2. 100080, china 4 Key Laboratory of Advanced Materials of the Ministry of Education, department of Materials Science and Engineering, Tsinghua university, {2. 100084, china 5 {2. National Center for Electron Microscopy, Tsinghua university, {2. 100084, china Key Laboratory of Beam technology & Materials Modification of the Ministry of Education Institute of Low Energy Nuclear Physics Beijing Normal University Beijing China beijing Radiation Center Beijing China Laboratory of Optical Physics Institute of Physics Chinese Academy of Sciences Beijing China Key Laboratory of Advanced Materials of the Ministry of Education Department of Materials Science and Engineering Tsinghua University Beijing China beijing National Center for Electron Microscopy Tsinghua University Beijing China

The LaMn1-xTexO3+δ (x=0.1, 0.2. 0.3) were synthesized using solid-state reaction method for the first time. X-ray photoemission spectrum (XPS) shows that in the samples the Te ions have a valence of Te4+, and Mn3+ ions are partly converted into Mn2. and Mn4+ due to the excess oxygen and Te doping. The magnetotransport associated with Mn2., Mn3+ and Mn4+ was investigated. The experimental results show that the samples are insulator at 0 T when the amount of Mn3+ is much larger or less than the sum of Mn2. and Mn4+; by contrast, the samples display metal to insulator transition with increasing temperature when the amount of Mn3+ is close to the sum of Mn2. and Mn4+. These anomalous magnetotransport behaviors were analyzed in the frame of the double-exchange (DE) mechanism.

关键词： colossal magnetoresistance La-Te-Mn-O magnetotransport

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Existence of unbiased estimate of regression parameters in simple linear EV models

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Science china Mathematics 2005年第7期48卷 915-928页

作者： LIU Jixue & chen Xiru department of Statistics and Finance, {2. of Science and technology of china, Hefei 2.002., china department of Mathematics, Graduate School of Chinese Academy of Sciences, beijing 100049, china department of Statistics and Finance University of Science and Technology of China Hefei 230026 China department of Mathematics Graduate School Chinese Academy of Sciences Beijing 100049 China

It is well known that for one-dimensional normal EV regression model X = x+ u,Y =α+βx+e, where x, u, e are mutually independent normal variables and Eu=Ee=0, the regression parameters a and β are not identifiable without some restriction imposed on the parameters. This paper discusses the problem of existence of unbiased estimate for a and β under some restrictions commonly used in practice. It is proved that the unbiased estimate does not exist under many such restrictions. We also point out one important case in which the unbiased estimates of a and β exist, and the form of the MVUE of a and β are also given.

关键词： EV regression model unbiased estimate identiflability.

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One-step disposal of Cr (Ⅵ)-bearing wastewater by natural pyrrhotite

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Chinese Science Bulletin 2000年第17期45卷 1614-1616页

作者： LU Anhuai, chen Jie, SHI Junxian, LU Xiaoying, TANG Junli & GUO Min1. Departmenl of Geology, Peking university, {2. 100871, china 2. National Laboratory of Mineral and Rock Materials, china university of Geosciences, beijing 100083, china (e-mail: luanhuai department of Geology Peking University Beijing China National Laboratory of Mineral and Rock Materials China University of Geosciences Beijing China

Cr(Ⅵ)-bearing wastewater can be treated by natural pyrrhotite which is used for reductant to reduce Cr(Ⅵ) and precipitant to precipitate Cr(Ⅲ) simultaneously. The disposal products can be divided into three parts in the beakers, namely supernatant in the upper part, the yellowish colloidal precipitates in the middle part and the pyrrhotite in the lower part. The content of total Cr=Cr(Ⅵ)+Cr(Ⅲ) in the supernatant liquid is 0.06 mg/L, which is lower than 1.5 mg/L of the discharge standard of china and near to 0.05 mg/L of the standard of potable water. This one-step disposal composing of both reduction and precipitation which is traditionally divided into two independent steps called reducing technology and precipitating technology respectively. The new method is of obvious economic advantage and favourable to decreasing surplus mud derived from adding Ca(OH)2.to precipitate Cr(Ⅲ) traditionally so as to avoid recontamination. In fact, sodium sulfite (Na2.O3) used in disposal of Cr(Ⅵ) was

关键词： natural pyrrhotite Cr(Ⅵ)-bearing wastewater reduction Cr(Ⅵ) precipitation Cr(Ⅲ) one-step disposal rational use of mineral resources.

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The Design and Implementation of Qinghai Province Geological Hazards Management Information System

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地学前缘 2009年第S1期16卷 42-43页

作者： Quan Xu~1,Qun Wang~1,Jun chen~2.Wenqian Jiang~1 1.School of Information technology,{2. university of Geosciences(beijing),beijing 100083,{2.. 2.department of Information,{2. Institute of Geo-Environment Monitoring,beijing 100081,{2.

The formation and development of geological hazards are extremely complex,depending on factors such as the topography,geology,meteorology, project,human activity,and so on;the geological hazards data include remarkable spatial characteristics and complex attribute *** the amount of geological hazards data is rapidly growing,it has become an urgent demand for geologists to

关键词： geological hazards mapGIS web services ajax

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EAM Analysis of the Lattice Parameter Effect in Order-Disorder Transformation

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Journal of university of Science and technology {2. 2001年第3期8卷 189-194页

作者： Timoth■e Nsongo, Xiaodong Ni, Guoliang chen State Key Laboratory for Advanced Metals and Materials, university of Science and {2. beijing, beijing 100083, china Faculty of Science, Physics department, P. O. Box 69, Brazzaville (CONGO) Applied Scie State Key Lab. for Adv. Met. Mat. Univ. of Sci. and Technol. Beijing Beijing 100083 China

The embedded atom method (EAM) was used to theoretically analyze the effect of the lattice parameter variation on the order-disorder transformation in binary alloys. Based on EAM, it is found that only one kind of order-disorder transition (second-order transition) exists for AB alloy. Three groups of order-disorder transformation can be observed for the A(3)B or AB(3) compounds. For group I, the order-disorder is a completely first-order transition. For group II, the order-disorder transformation is a classical first-order transition. For group III, the order-disorder transformation is found to be a second-order transition. The lattice parameter variations have a significant effect on E-2.coefficient, which is related to the ordering energy. These results are in good agreement with experiments.

关键词： order-disorder transformation embedded atom method (EAM) phase transformation binary alloy

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Electronic structure and magnetism of R(Fe,Si)_(12. (R=Y,Nd)

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Science china(Physics,Mechanics & Astronomy) 2006年第2期49卷 195-202页

作者： SUN Guang’ai1, chen Bo1, DU Honglin2. FAN Zhijian1, GAO Tao3 & QI Xinhua31. Institute of Nuclear Physics and chemistry,{2.Academy of Engineering Physics, Mianyang 62.900, china 2. department of physics, Peking university, beijing 100871, china 3. Institute of Atomic and Molecular Physics, Sichuan university, chengdu 610065, china Institute of Nuclear Physics and chemistry China Academy of Engineering Physics Mianyang China department of physics Peking university Beijing China Institute of Atomic and Molecular Physics Sichuan University Chengdu China

The newly developed full-potential linearized augmented plane wave (LAPW) and local orbitals (lo) based on standard APW methods are briefly introduced, and the structure and magnetic properties of R(Fe, Si)12.compounds (R = Y, Nd) are calculated using the method. The distribution of Si at different sites is analyzed based on total energy of one crystal unit with structure having been optimized. The characters of magnetic mo-ments, total density of states (TDOS) and partial density of states (PDOS) for different crystal sites Si occupies are obtained and analyzed. The results show that the total mag-netic moments of RFe10Si2.(R = Y, Nd) are larger than those of RFe10M2.(M = Ti, V, Cr, Mn, Mo and W) and the hybridization mechanism is seen as follows. Si(8j) reduce the mag-netic moments of Fe at three sites, however, Si(8f) mainly reduce the magnetic moments of Fe(8i) and Fe(8j) atoms. The Curie temperature is markedly enhanced by the introduc-tion of Si atoms according to spin fluctuation of DOS at Fermi level.

关键词： (L)APW+lo method R(Fe Si)12.R = Y Nd) magnetic moment Density of state.

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Dynamic behavior of polymer surface and the time dependence of contact angle

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Science china chemistry 2005年第6期48卷 553-559页

作者： WANG Xinping1, chen Zhifang1 & SHEN Zhiquan2.1. Key Laboratory of Advanced Textile Materials and Manufacturing technology of Education Ministry, {2. of Applied chemistry, Zhejiang Institute of Science and technology, Hangzhou 310033, china 2. {2. of Polymer Science and Engineering, Zhejiang university, Hangzhou 31002., china department of Applied chemistry Zhejiang Institute of Science and Technology Key Laboratory of Advanced Textile Materials and Manufacturing Technology of Education Ministry Hangzhou China department of Polymer Science and Engineering Zhejiang University Hangzhou China

Time-dependent contact angles were measured by depositing sessile drops of wa-ter on the polymer surfaces and monitoring the drop shape as a function of time. It was found that contact angles decreased sharply with contact time and the equilibrium contact angle was finally attained after a certain time. Values of starting (θ s) and equilibrium contact angles (θ e) obtained by the sessile drop method depend on polymer properties. The Wilhelmy plate technique was used to measure advancing and receding contact angles. The variations of starting (θ s) and equilibrium contact angles (θ e), advancing (θ a) and receding contact angles (θ r) have been studied on the oxidized surface of polymers containing polybutadiene block to explore the cause of time-dependence in contact angle measurement and the meaning of θ s and θ e. The results showed the linear relationships between starting (θ s) and advancing contact angles (θ a), the equilibrium (θ e) and receding contact angles (θ r). The similar relationship was also established between the contact angle hysteresis (θ a?θ r) and differences (θ s ?θ e) in starting contact angles and equilibrium contact angles. Therefore, time-dependence in contact angle measurement was mainly attributed to the surface reconstruction when water drops were deposited on polymer surfaces. The starting contact angle was contributed by the hydrophobic component on polymer surface and the equilibrium contact angle mainly by the hydrophilic component of polymer. These results not only demonstrated the interdependency between two contact angle measurements, the sessile drop method and the Wilhelmy plate technique, but also provided the experimental evidence to explain the cause of time-dependent contact angle. This may also provide a new method to study dynamic behavior of polymer surface.

关键词： contact angle, surface dynamic behavior, polymer surface, dynamic contact angle, time-dependence.

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Research on Theoretical Model of Linear Frequency Modulation Interferometry

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Chinese Journal of Lasers 2000年第3期9卷 28-34页

作者： chen Yan ZHAO Yang (State Key Laboratory of Precision Measurement technology and Instruments, {2. of Precision Instruments,Tsinghua university, beijing 100084,china) 清华大学精密测试技术及仪器国家重点实验室北京 100084

In this paper, the principle of linear frequency-modulation (LFM) with an external microcavity laser is analyzed mathematically and a method to establish the math model of LFM heterodyne interference is presented. The expression of LFM heterodyne interference is deduced by an illustration of a triangular frequency modulation. At present, one application of the LFM technique is non-guide absolute distance measurement. Experimental results of a system for absolute distance measurement based on a microchip solid laser and LFM technique are given. Based on the precisely theoretical model some effective approaches to improve the performance of LFM and decrease the measuring error are discussed.

关键词： linear frequency modulation heterodyne interference absolute distance measurement

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Molecular dynamics simulation of the transmembrane subunit of BtuCD in the lipid bilayer

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Science china(Life Sciences) 2010年第5期53卷 620-630页

作者： SUN TingGuang1,2.LIU Ming1,chen WeiZu1 & WANG CunXin1 1College of Life Science and Bioengineering,beijing {2. of technology,beijing 10012.,china 2.6} of Biological and Chemical Engineering,Guangxi {2. of technology,Liuzhou 545006,china College of Life Science and Bioengineering Beijing University of Technology Beijing China department of Biological and Chemical Engineering Guangxi University of Technology Liuzhou China

Based on the crystal structure of the vitamin B12.transporter protein of Escherichia coli(BtuCD) a system consisting of the BtuCD transmembrane domain(BtuC) and the palmitoyloleoyl phosphatidylcholine(POPC) lipid bilayer was constructed in silica,and a more-than-57-nanosecond molecular dynamics(MD) simulation was performed on it to reveal the intrinsic functional motions of *** results showed that a stable protein-lipid bilayer was obtained and the POPC lipid bilayer was able to adjust its thickness to match the embedded BtuC which underwent relatively complicated *** results may help to understand the mechanism of transmembrane substrate transport at the atomic level.

关键词： BtuCD POPC functional motion principal component analysis

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Effect of bond length and radius on superconducting transition temperature for FeAs-based superconductors

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Science china(Physics,Mechanics & Astronomy) 2010年第1期53卷 59-63页

作者： chen Ning 1 , LIU Yang 1 , JIA YaKui 1 , QU ShaoPeng 1 , ZHANG WanJie 1 & LI Yang 2.1 School of Material Science and Engineering, university of Science and {2. beijing, beijing 100083, china 2.department of Engineering Science and Materials, university of Puerto Rico at Mayaguez, Mayaguez PR 00681-9044, USA School of Material Science and Engineering University of Science and Technology Beijing Beijing China department of Engineering Science and Materials University of Puerto Rico at Mayaguez Mayaguez USA

By comparing the data of lattice parameters of more than 50 new FeAs-based high temperature superconductors in two syetems, the effect of bondlength on superconducting transition temperature (T C ) was found that, for both FeAs superconductor systems with similar ionic radii of cation A, the bond length L As-A between Arsenic atom and its nearest neighbor cation at the A site is in an inverse proportion to T C , i.e. the larger the bond length L As-A , the lower the T C . In addition, we also found a noticeable effect of ionic radius on T C , in which deviation from the tendency line of bond length vs. T C decreases with the increasing ionic radius. Both bond length-T C and ionic radii-T C relations indicate that the interaction of cation A and As ion have significant effect on superconductivity. The analysis on the electronic structure indicates that there exists the proximity of the secondary-outer p-orbit of the cation A and the 4s orbit of the As ion, both in energy space and in real space. Some high frequency individual vibrating modes would be established through exchange coupling on their inner orbits. It is worth of mention that the superconducting condensation is influenced by the interaction between the cation A and the As atoms.

关键词： lattice constant FeAs-based superconductor superconducting transition temperature

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