检索结果-南通市图书馆

ANALYSIS OF VALENCE ELECTRON STRUCTURE OF Nd2Fe14B DIRECTLY FROM ITS CRYSTAL STRUCTURE

在线全文

学校读者我要写书评

暂无评论

中国科学A辑(英文版) 1988年第12期31卷 1487-1494页

作者：张瑞林吴尚才余瑞璜 institute of Materials Science Jilin university Changchun institute of Nonferrous Metals Guangzhou department of Physics Jilin university Changchun

Based on the experimental data of Nd2Fe14B crystal structure reported by J. F. Herbst, the valence electron structure and the magnetic moment structure of crystal Nd2Fe14B have been analysed by the BLD （bond length difference） method of the empirical electron theory of solids and molecules. The hybridization levels of all kinds of elements at various crystallographic sites in the Nd2Fe14B crystal and their corresponding covalent bond networks are selected as B（g）-6, Nd（f）-1, Nd（g）-1, Fe（c）-A15, Fe（e）-A13, Fe（j1）-A10, Fe（j2）-C3, Fe（k1）-A7 and Fe（k2）-A8. The strongest bond has the number of covalent bond electron pairs n3=0.5819. The distribution of charges around various iron atoms is calculated from the valence electron structure of the crystal. The reason why all the iron atomic magnetic moments are arranged along the direction c is explained by making a comparison between the charge distributions above and below the horizontal atomic plane containing Fe atoms. The dependence of the va

关键词： Nd2Fe14B valence electron structure magnetic moment structure.

Mapping forest fire risk zones with spatial data and principal component analysis

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

Science China(Technological Sciences) 2006年第z1期49卷 140-149页

作者： XU Dong, Guofan Shao, DAI Limin, HAO Zhanqing, TANG Lei & WANG Hui institute of Applied Ecology, Chinese Academy of Sciences, Shenyang 110016, China Graduate university of Chinese Academy of Sciences, Beijing 100039, China department of Forestry and Natural Resources, Purdue university, West Lafayette, IN 47907, USA department of Management, Shenyang institute of Aeronautical Engineering, Shenyang 110034, China department of City Development, Jinan university, Jinan 250002, China institute of Applied Ecology Chinese Academy of Sciences Graduate university of Chinese Academy of Sciences

By integrating forest inventory data with remotely sensed data, new data layers for factors that affect forest fire potentials were generated for Baihe Forestry Bureau in Jilin Province of China. The principle component analysis was used to sort out the relationships between forest fire potentials and environmental factors. The classifications of these factors were performed with GIS, generating three maps: a fuel-based fire risk map, a topography-based fire risk map, and an anthropogenic-factor fire risk map. These three maps were then synthesized to generate the final fire risk map. The linear regression method was used to analyze the relationship between an area-weighted value of forest fire risks and the frequency of historical forest fires at each forest farm. The results showed that the most important factor contributing to forest fire ignition was topography, followed by anthropogenic factors.

关键词： wildfire risk, regression analysis, geographic information system, remote sensing, Baihe Forestry Bureau.

A maximum principle for optimal control problem of fully coupled forward-backward stochastic systems with partial information

在线全文

学校读者我要写书评

暂无评论

Science China Mathematics 2009年第7期52卷 1579-1588页

作者： MENG QingXin1,2 1 department of Mathematical Sciences,Huzhou university,Zhejiang 313000,China 2 institute of Mathematics,Fudan university,Shanghai 200433,China department of Mathematical Sciences Huzhou University Zhejiang China institute of Mathematics Fudan University Shanghai China

The paper is concerned with a stochastic optimal control problem in which the controlled system is described by a fully coupled nonlinear forward-backward stochastic differential equation driven by a Brownian *** is required that all admissible control processes are adapted to a given subfiltration of the filtration generated by the underlying Brownian *** this type of partial information control,one sufficient(a verification theorem) and one necessary conditions of optimality are *** control domain need to be convex and the forward diffusion coefficient of the system can contain the control variable.

关键词： maximum principle stochastic optimal control partial information 93E20 60H10 60H30

North Pacific sea ice cover, a predictor for the Western North Pacific typhoon frequency?

在线全文

学校读者我要写书评

暂无评论

Science China Earth Sciences 2007年第8期50卷 1251-1257页

作者： FAN Ke institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing 100029, China department of Atmospheric Science, Yun-nan university, Kunming 650091, China institute of Atmospheric Physics Chinese Academy of Sciences Beijing China department of Atmospheric Science Yunnan University Kunming China

The relationship between the sea ice cover in the North Pacific and the typhoon frequency has been studied in this paper. It follows that the index for the sea ice cover in the North Pacific (ISA) both in December-January-February (DJF) and in March-April-May (MAM) is negatively correlated with annual typhoon number over the western North Pacific (TNWNP) during 1965―2004, with correlation coeffi-cients of -0.42 and -0.49 respectively (above 99% significant level). Large sea ice cover in the North Pacific tends to decrease TNWNP. Positive ISA (MAM) is associated with the tropical circulation and SST anomalies in the North Pacific, which may lead to unfavorable dynamic and thermal conditions for typhoon genesis over WNP from June to October (JJASO). The variability of the atmospheric circula-tion over the North Pacific, associated with the ISA anomaly in MAM is connected to the tropical at-mospheric circulation variability in MAM via the teleconnection wave train. Besides, as the tropical circulation has strong seasonal persistency from the MAM to JJASO, thus, the ISA in MAM-related variability of the tropical atmospheric circulation as well as the SST can affect the typhoon activity over the western North Pacific.

关键词： typhoon sea ice cover North Pacific teleconnection

Synthesis, Crystal Structure and Electrochemical Properties of 2-Chlorobenzaldehyde Thiosemicarbazone

在线全文

学校读者我要写书评

暂无评论

Chinese Chemical Letters 1997年第5期8卷 459-460页

作者： Sheng Yi ZHANG Yu Peng TIAN(department of chemistry, Anhui university, Hefei, 230039)(Coordination Chemistry institute State Key Laboratory of Naning university. Nanjing. 210093) department of Chemistry Anhui University Hefei 230039 China Coordination Chemistry institute State Key Laboratory Nanjing University Nanjing 210093 China

The title compound crystallized in space goups P2(1)/c with Z=4, in a unit cell of dimensions, a=12.964(4), b=5.131(5), c=14.970(1)Angstrom; V=9331(1) Angstrom(3) Dc=1.429gcm(-3), mu=0.541mm(-1), R=0.045, Rw=0.059. The equilibrium constant of the ligand with CdBr2 was obtained by polarographic method. Crystal structure determination revealed that the molecule is in transconformation and non-hydrogen atoms of the molecule are in one plane except N(3) atom.

关键词： Crystal Structure and Electrochemical Properties of 2-Chlorobenzaldehyde Thiosemicarbazone Synthesis

A paleontological perspective of vertebrate origin

在线全文

学校读者我要写书评

暂无评论

Chinese Science Bulletin 2003年第8期48卷 725-735页

作者： SHU Degan Early Life institute & department of Geology, Northwest university, Xi抋n, 710069, China School of Earth Sciences and Resources, China university of Geosciences, Beijing, 100083, China (e-mail: elidgshu@ ***) Early Life institute & department of Geology Northwest University China School of Earth Sciences and Resources China University of Geosciences

The Early Cambrian Haikouichthys and Haikouella have been claimed to be related to contribute in an important way to our understanding of vertebrate origin, but there have been heated debates about how exactly they are to be interpreted. New discoveries of numerous speci-mens of Haikouichthys not only confirm the identity of pre-viously described structures such as the dorsal and the ven-tral fins, and chevron-shaped myomeres, but also reveal many new important characteristics, including sensory or-gans of the head (e.g. large eyes), and a prominent notochord with differentiated vertebral elements. This 揻irst fish?ap-pears, however, to retain primitive reproductive features of acraniates, suggesting that it is a stem-group craniates. A new order (Myllokunmingiida) and a new family (Myllo-kunmingiidae) are erected, and a new species, Zhongjianich-thys rostratus (gen. et sp. nov.), is described herein. Over 1400 newly-discovered specimens of Haikouella provide a wealth of anatomical information on this organism. It differs from chordates in many organs and organ systems, including the skin, muscles, respiratory, circulatory and nervous sys-tems. In contrast, its body-design resembles that of vetuli-colians, and the presence of a 搕ransitional?nervous system with both dorsal and ventral nerve cords suggests an affinity with living hemichordates. On the basis of these and other recent findings of fossil deuterostomes, a five-step hypothesis for vertebrate origin is proposed, intended to bridge the long- standing gap between protostomes and vertebrates. Four of the five steps accord with established ideas current in modern evolutionary zoology. Evidence for the first step is obtainable only from fossils, and specifically from fossils found from South China, hence the crucial importance of S. China sites for our understanding of early vertebrate origins and evolution. Accordingly, South China is suggested as the oldest-known birthplace of the whole vertebrates.

关键词：脊椎动物动物起源寒武纪中国南部地区

Effect of rare earths on phase transformation in as-cast ZA27 alloy dur-ing compressive creep

在线全文

学校读者我要写书评

暂无评论

Rare Metals 2003年第4期22卷 259-264页

作者： WEIXiaowei SHENBaoluo DepamnentofAppliedPhysics UniversityofElectronicScienceandTechnologyofChinaChengdu610045China DeparlanentofMetalScience SichuanUniversityChengdu610065China

The effect of the mixed rare earths of Ce on the phase transformation in ascast ZA 27 alloy during compressive was investigated under 37 MPa and at 160 deg C by X-raydiffraction technique and SEM. The results showed that the as cast microstructure of ZA 27-RE alloyconsisted of a dendritic Al-rich alpha' surrounded by Zn-rich beta' phase, interdendritic epsilonphase and Zn-rich eta phase together with a complex Z phase which was a complex constitute compound,(RE,Cu)Al_5Zn_(16), dispersed in crystal interfaces or branch crystal interfaces and stable duringcompressive creep test at 160 deg C. The phase transformations of ZA 27-RE alloy, decomposition ofbeta' phase arid four transformation, were delayed by the addition of rare earths, also the lamellarstructure and the spheroidized structure in ZA 27-RE alloy were finer than in ZA 27 alloy duringcompressive creep test at 160 deg C at the same creep time, and the compressive creep resistance ofZA 27-RE alloy was higher than that of ZA 27 alloy.

关键词： microstructure change compressive creep rare earths ZA 27 alloy

The Synthesis, Photoconductivity, Photoinduced Charge Transfer, and Other Properties of HEC-TCNQ

在线全文

学校读者我要写书评

暂无评论

Chinese Chemical Letters 1997年第1期8卷 75-78页

作者： Qi FANG Hong LEI Dong XU Duo Rong YUAN(institute of Crystal Materials, Shandong university, Jinan 250100department of Electronic Engineering, Shandong university, Jinan 250100) institute of Crystal Materials Shandong University Jinan 250100 China department of Electronic Engineering Shandong University Jinan 250100 China

The donor-acceptor complex HEC-TCNQ (HEC = 9-hydroxyethylcarbazole; TCNQ = tetracyanoquinodimethane) has been synthesized. Under the illumination of Ar+ laser, the photoinduced charge transfer salt HEC(+)TCNQ(-) can b... 详细信息

关键词： HEC The Synthesis Photoconductivity Photoinduced Charge Transfer and Other Properties of HEC-TCNQ

The existence of global solution and their weak limit of generalized Ginzburg-Landau equations in two dimensions

在线全文

学校读者我要写书评

暂无评论

Progress in Natural Science:Materials International 2006年第5期16卷 458-463页

作者： YANG Ling'e and GUO Boling (department of Mathematics, Foshan university, Foshan 528000, China institute of Applied Physics and Computational Mathematics, Beijing 100088, China) department of Mathematics Foshan University Foshan 528000 China institute of Applied Physics and Computational Mathematics Beijing 100088 China

By the uniform a priori estimate of solution about parameters, we prove the existence of global solution and inviscid lim- it to a generalized Ginzburg-Landau equations in two dimensions. We also prove that the solution to the Ginzburg-Landau equations converges to the weak solution to the derivative nonlinear Schrodinger equations.

关键词： Ginzburg-Landau equation global solution inviscid limits.