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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, china Academy of Engineering physics, Mianyang 621900, china 2. department of physics, peking university, beijing 100871, china 3. Institute of Atomic and Molecular physics, Sichuan university, Chengdu 610065, china 1. Institute of Nuclear physics and Chemistry China Academy of Engineering Physics Mianyang 621900 China 2. department of physics Peking university Beijing 100871 China 3. Institute of Atomic and Molecular physics Sichuan University Chengdu 610065 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.

ESTIMATING EXTREME-VALUE INDEX FROM RECORDS

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Chinese Annals of Mathematics,Series B 1998年第4期19卷 499-510页

作者： QI YONGCHENG (department of Probability & Statistics, peking university, beijing 100871, china.) peking Univ Dept Stat & Probabil Beijing 100871 Peoples R China

This paper constructs from the record values an estimator of the extreme-value index. It is proved that the estimator is consistent in the domain of attraction of extremesvalue distributions, and that under very mild ... 详细信息

关键词： Record Extreme value distribution Estimator Consistency Asymptotic normality

Multiparty quantum secret sharing of classical and quantum messages

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Progress in Natural Science:Materials International 2007年第1期17卷 26-31页

作者： CHEN Pan, DENG Fuguo and LONG Guilu ( Key Laboratory for Quantum Information and Measurements, and department of physics, Tsinghua university, beijing 100084, china Key Laboratory of Beam Technology and Material Modification, MOE, Institute of Low Energy Nuclear physics, and department of Material Science and Engineering, beijing Normal university, beijing 100875, china beijing Radiation Center, beijing 100875, china Key Laboratory for Atomic and Molecular Nano-Sciences, Tsinghua university, beijing 100084, china) [a]Key Laboratory for Quantum Information and Measurements and Department of Physics Tsinghua University Beijing China [b]Key Laboratory of Beam Technology and Material Modification MOE Institute of Low Energy Nuclear Physics and Department of Material Science and Engineering Beijing Normal University Beijing China [c]beijing Radiation Center Beijing China [d]Key Laboratory for Atomic and Molecular Nano-Sciences Tsinghua University Beijing China

A scheme for multiparty quantum secret sharing of classical and quantum messages is proposed by using entanglement swapping. This scheme can distribute not only the classical information but also the quantum informati... 详细信息

关键词： quantum secret sharing classical message quantum message EPR pair.

Progress in cognitive neuroscientific studies of visual awareness

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Progress in Natural Science:Materials International 2009年第2期19卷 145-152页

作者： Qi Li,Haiyan Geng department of Psychology,peking university,beijing 100871,china [a]department of Psychology Peking University Beijing 100871 China

The psychological and neural mechanisms of consciousness are among the most baffling problems in cognitive neuroscience. In this field,visual awareness is a topic that has been largely investigated,due to easy manipulation and measurable effects. The present arti-cle begins with the phenomena of dissociations between visual awareness and visual stimulus,visual awareness and visual attention,as well as visual awareness and vision-guided behavior,along with the corresponding experimental evidence. Furthermore,the neural mechanism of visual awareness is also discussed. It has been generally believed that visual awareness is the function of higher-order cerebral areas; however,recent discoveries have demonstrated that feedback from higher-to lower-order cortex areas is necessary for generating consciousness. The present article presents an in-depth analysis regarding this feedback process,and exploring its relation-ship with the generation and mechanisms of consciousness. Finally,theoretical controversies and discrepancies,as well as result con-flicts from various studies,have been collected,compared and discussed. Because the field of consciousness continues to be an extremely mysterious and complicated psychological phenomenon,there is a great need for further studies to explore and clarify this topic.

关键词： Visual awareness Neural mechanism Feedback process Cortical areas

The study of two-color excitation upconversion of Pr(0.5)Yb(3):ZBLAN

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Science china(physics,Mechanics & Astronomy) 2006年第2期49卷 169-177页

作者： CHEN Xiaobo1 & SONG Zengfu2 1. Applied Optics beijing Area Major Laboratory, Analysis and testing center, beijing Normal university, beijing 100875, china 2. peking university, physics School, beijing 100871, china Applied Optics beijing Area Major Laboratory Analysis testing center Beijing Normal University Beijing 100875 China physics School Peking University Beijing 100871 China

The excited state absorption upconversion of Pr(0.5)Yb(3):ZBLAN glass material, under two-color excitation of the 960 nm semiconductor laser and the Xe lamp light simultaneously, is reported in this article. It was found that the upconversion emission spectra of 480.1, 519.0, 601.9 and 631.8 nm coincide with the common emission spectra. Meanwhile, the upconversion-excitation spectrum has three obvious peaks under two-color excitation, and they respectively correspond to the 856.0 nm upconversion ex-citation transition [1G4(Pr3+)→1I6(Pr3+) and 1G4(Pr3+)→3P1(Pr3+)], the 789.0 nm upconver-sion excitation transition 1G4(Pr3+)→3P2(Pr3+), and the 803.7 nm upconversion excitation transition 3H6(Pr3+)→1D2(Pr3+). The upconversion excitation transition 1G4(Pr3+)→1I6(Pr3+) is strong because its oscillator strength f = 23.040×10?6 is large, which results in a large peak appearing in the upconversion excitation spectrum. That is just the new interesting two-color excitation upconversion luminescence phenomenon of Pr(0.5)Yb(3):ZBLAN induced by one laser and one continuous normal light simultaneously.

关键词： upconversion volumetric three-dimensional display two-color excitation.

Right prefrontal laterality of Chinese boys during a Chinese high conflict Stroop task measured by multi-channel near-infrared spectroscopy imaging

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Progress in Natural Science:Materials International 2007年第9期17卷 1023-1028页

作者： Liu Jiacheng1,Bai Jing1,Peng Miao2,Fan Xiaofei1 and Guo Qiyong3(1.department of Biomedical Engineering,Tsinghua university,beijing 100084,china 2.department of Electroneurophysiology,the Sixth Hospital of peking university,beijing 100085,china 3.department of Radiology,The Second Hospital of china Medical university,Shenyang 110003,china) department of Biomedical Engineering Tsinghua University Beijing 100084 China 2. department of Electroneurophysiology the Sixth Hospital of Peking University Beijing 100085 China 3． department of Radiology The Second Hospital of China Medical University Shenyang 110003 China

Some studies have shown that native Chinese speakers have different laterality in matched Stroop tasks from native English ***,many imaging data,which show left laterality of English-matched Stroop interference,have been *** a few functional imaging studies have been conducted to investigate the phenomenon of the Chinese version of Stroop *** this study,functional activity in the lateral prefrontal cortex of a group of normal Chinese boys with functional near-infrared imaging during a Stroop color-word task was measured to show different Stroop interferences in the prefrontal *** results show obvious fluctuation of the cerebral blood volume in the right prefrontal cortex in all boys,which agrees with the finding of previous studies,that is,Chinese native boys have right laterality in their brain when the Chinese version of Stroop color-word task is applied.

关键词： laterality Stroop effect prefrontal cortex near-infrared

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.

Study on the two and three-parameter working stability regions of 3Y-TZP suspension

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Science china(Technological Sciences) 2006年第5期49卷 547-568页

作者： CHEN Youqiang1, 2, ZHANG Xinni3, CHEN Sha’ou3 & QI Ping3 1. department of Chemistry, Qingdao university, Qingdao 266071, china 2. department of Chemistry, Tsinghua university, beijing 100084, china 3. department of physics, Qingdao university, Qingdao 266071, china 1. department of Chemistry Qingdao University Qingdao 266071 China 2. department of Chemistry Tsinghua University Beijing 100084 China 3. department of physics Qingdao University Qingdao 266071 China

We determined the variation tendency of viscosity (η) at various solids load- ing (α) for 3Y-TZP suspension as a function of dispersant concentration (Cw) using vis- cosity measurement, measured the diameter of particles as a function of Cw in very dilute suspension using light scattering method, and obtained the surface features of the sedi- ment of suspension with different Cw using SEM. We also discussed the influence of the microstructure of adsorbed polymer layers on particles and their interactions in the dis- persing medium on the stability of suspension. Then two different stable states and two different unstable states for 3Y-TZP suspension were given. Accordingly, the (Cw, η), (Cw, α), and (α, η) two-parameter, and (Cw, α, η) three-parameter stability maps were con- structed. Based on the DLVO theory calculations, the dispersant concentration, particle distance (r), and interparticle potential energy (VT) maps with various solids loading for 3Y-TZP aqueous suspension were also constructed. In (Cw, r) two-parameter coordinate system, the stable motion region map for particles was established. The Cw, α, and VT,max (the highest potential energy) surface of the potential barrier map was obtained through calculation and simulation on the basis of the surfaces of Cw, r, VT maps introduced above. The (Cw, α) two-parameter stability map was then obtained from the Cw, α, VT,max map. The results showed that this theoretical map can qualitatively prove the experimentally obtained results—the existence of different dispersed states of particles in suspension system and the variation tendency of suspension stability with changing each parame- ter—were reasonable.

关键词： 3Y-TZP, suspension, stability, DLVO theory, interparticle potential energy.

Lie map for the nonlinear transport of continuous intense beams in the axial-symmetric electrostatic fields

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Progress in Natural Science:Materials International 2008年第7期18卷 795-800页

作者： Jianqin L*, Xiaosong Zhao Institute of Heavy Ion physics, peking university, beijing 100871, china Institute of Heavy Ion physics Peking University Beijing 100871 China

Nonlinear transport of intense continuous beam in the axial-symmetric electrostatic fields is analyzed with the Lie algebraic method. The K-V particle distribution is adopted in the analysis. The results obtained can be used in the calculations of the intense continuous beam dynamics in the beam optical systems consisting of drift spaces, electrostatic lenses, and DC electrostatic accelerating tubes. A com- puter code has been designed for practical simulations. To meet the needs of accurate calculation, all the elements are divided into many small segments, the electric fields in each segment are regarded as uniform fields, and the dividing points are treated as thin lenses. Iter- ation procedures are adopted in the code to obtain self-consistent solutions. The code can be used to design low energy dc beam transport systems, electrostatic accelerators, and ion implantation machines.

关键词： Intense continuous beam Lie algebraic analysis Nonlinearity