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Anomalous magnetotransport in LaMn_(1-x)Te_xO_3

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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, beijing normal university, beijing 100875, China 2 beijing Radiation Center, beijing 100875, China 3 Laboratory of Optical physics, Institute of physics, Chinese Academy of Sciences, beijing 100080, China 4.Key Laboratory of Advanced Materials of the Ministry of Education, department of Materials Science and Engineering, Tsinghua university, beijing 100084. China 5 beijing National Center for Electron Microscopy, Tsinghua university, beijing 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

Eigenvalues, inequalities and ergodic theory

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Chinese Science Bulletin 2000年第9期45卷 769-774页

作者： CHEN Mufadepartment of Mathematics, beijing normal university, beijing 100875, China department of Mathematics Beijing Normal University Beijing China

This paper surveys the main results obtained during the period 1992-1999 on three aspects mentioned in the title. The first result is a new and general variational formula for the lower bound of spectral gap (i.e. the first non-trivial eigenvalue) of elliptic operators in Euclidean space, Laplacian on Riemannian manifolds or Markov chains (?). Here, a probabilistic method -coupling method is adopted. The new formula is a dual of the classical variational formula. The last formula is actually equivalent to Poincare inequality. To which, there are closely related logarithmic Sobolev inequality, Nash inequality, Liggett inequality and so on. These inequalities are treated in a unified way by using Cheeger’s method which comes from Riemannian geometry. This consists of ?2. The results on these two aspects are mainly completed by the author joint with F. Y. Wang. Furthermore, a diagram of the inequalities and the traditional three types of ergodicity is presented (?3). The diagram extends the ergodic

关键词： eigenvalue inequality ergodic theory Markov process.

Theoretical Study on the Pyrolysis Mechanism and Kinetics of 3-Hydroxy-3-Methyl-2-Butanone

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Chinese Chemical Letters 1998年第11期9卷 0-0页

作者： Wen Lin FENG Jie Hao CHEN Yan WANG (department of chemistry, beijing normal university, beijing 100875) department of Chemistry Beijing Normal University Beijing 100875 China

The mechanism and kinetics for the decomposition of 3-hydroxy-3-methyl-2-butanone have been studied by using the ab initio RHF/3-21G method. The calculated activation barrier of the reaction is 24..6kJ/mol which is in reasonable agreement with the experimental data (222.2±3kJ/mol). The calculated results show that the decomposition is a concerted process with hydrogen transferring and bond breaking via a five-membered cyclic transition state. The thermal rate constants of the decomposition are obtained by calculating microcanonical probability fluxes through transition state1.

关键词： Kinetics mechanism theoretical study rate constants

Coupling, spectral gap and related topics (Ⅱ)

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Chinese Science Bulletin 1997年第18期42卷 1409-1416页

作者： CHEN Muf adepartment of Mathematics, beijing normal university, beijing 100875, China department of Mathematics Beijing Normal University Beijing China

THIS is the second one of a series of three reviews. The ideas introduced in the last review are used to study the estimate of spectral gap and four classes of typical eigenvalue problems on manifolds. The comparison ... 详细信息

关键词： diffusions manifold Markov chains spectral gap couplings.

Refraction of light in media

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Science China(physics,Mechanics & Astronomy) 2007年第5期50卷 591-600页

作者： ZHANG Tao Key Laboratory of Beam Technology and Material Modification of Ministry of Education, Institute of Low Energy Nuclear physics, beijing normal university, beijing 100875, China beijing Radiation Center, beijing 100875, China Key Laboratory of Beam Technology and Material Modification of Ministry of Education Institute of Low Energy Nuclear Physics Beijing Normal University Beijing China beijing Radiation Center Beijing China

The roles of the magnetic field and electric field of the light are investigated when the light is refracted in the medium. The model of the electron cloud conductor is presented. Electron cloud in a molecule is treated as a conductor and the Faraday’s Law is applied to this conductor that is in the alternating magnetic field of the light. dBM/dt of the light gives rise to an alternating induced current on the electron cloud conductor, and the light exchanges energy, i.e. the refractive energy, with the elec- tron cloud conductor. Formulas of refractive index, which is the ratio of light speed in vacuum to that in the medium, are derived with this model. These formulas are tested with several mediums and Langevin’s diamagnetic susceptibility of helium gas, and the results are in good agreement with the measured data. The anisotropy and the nonlinearity of the refractive index are explained with the theory described in this work.

关键词： refractive index, light, speed, medium, propagation

Development and application of ergodicity model with FRCM and FLAR for hydrological process

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Science China(Technological Sciences) 2009年第2期52卷 379-386页

作者： WANG HongRui1, FENG QiLei2, LIN Xin3 & ZENG WenYi4.1 College of Water Science, Key Laboratory for Water and Sediment Sciences of the Ministry of Education, beijing normal university, beijing 100875, China 2 School of Science, beijing Institute of Education, beijing 100011, China 3 School of Mathematical Sciences, beijing normal university, beijing 100875, China 4.College of Information Science and Technology, beijing normal university, beijing 100875, China College of Water Science Key Laboratory for Water and Sediment Sciences of the Ministry of Education Beijing Normal University Beijing China School of Science Beijing Institute of Education Beijing China School of Mathematical Sciences Beijing Normal University Beijing China College of Information Science and Technology Beijing Normal University Beijing China

In this paper, a new ergodic property analysis model of hydrological process is proposed based on fuzzy-rough c-means clustering (FRCM), autocorrelogram, and fuzzy least absolute regression (FLAR). A precipitation time series (1951―2004. from Shanghai Hydrology Station is then analyzed with the model. The results show that the precipitation time series of April, May, June, and September has er-godic property. We conclude that in the long run, the precipitation of April, May, June, and September will not keep decreasing; it will converge to its mean value in some period.

关键词： hydrological process ergodic autocorrelogram fuzzy-rough c-means clustering fuzzy least absolute regression

On the stability of diffusion processes with state-dependent switching

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Science China Mathematics 2006年第9期49卷 1258-1274页

作者： XI Fubao & ZHAO Liqin department of Mathematics, beijing Institute of Technology, beijing 100081, China School of Mathematical Sciences, beijing normal university,{4., China department of Mathematics Beijing Institute of Technology Beijing China School of Mathematical Sciences Beijing Normal University Beijing China

In this paper we consider the stability for diffusion processes with state-dependent switching. We first prove their Feller continuity by the coupling methods. Furthermore, we also prove their strong Feller continuity and their exponential ergodicity under some reasonable conditions. Finally, we append a very brief discussion about the regularity of these processes.

关键词： Feller continuity, coupling, strong Feller continuity, exponential ergodicity,state-dependent switching.

Direct Electrochemistry of Myoglobin in DDAB-Clay Composite Films

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Chinese Chemical Letters 2000年第1期11卷 79-80页

作者： Nai Fei HU Zhen LI Hong Yan MA (department of Chemistry, beijing normal university, beijing, 100875) department of Chemistry Beijing Normal University Beijing 100875 China

Ordered films were made by casting a mixture of aqueous dispersions of didodecyldimethylammonium bromide (DDAB)-clay composite and myoglobin (Mb) solution on pyrolytic graphite (PG) electrodes. The Mb-DDAB-clay film electrodes showed stable and reversible cyclic voltammetric responses in buffers and can catalyze the reduction of id (TCA).

关键词： myoglobin didodecyldimethylammonium bromide clay composite film electrode electrochemistry electrocatalysis

AVERAGE σ-K WIDTH OF CLASS OF L_p(R^n) IN L_q (R^n)

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Chinese Annals of Mathematics,Series B 1995年第3期16卷 351-360页

作者： LIU YONGPING(department of Mathematics, beijing normal university, Beliing 100875, China.) beijing normal UNIV DEPT MATHBEIJING 100875PEOPLES R CHINA

The average σ-K width of the Sobolev-Wiener class in Lq(Rn) is studied for and the asymptotic behaviour of this quantity is determined. The exact value of average σ-K width of some class of smooth functions in L2(Rn... 详细信息

关键词： Average σ-K width Optimal subspace,Sobolev-Wiener class,Riesz potential.