检索结果-南通市图书馆

SILICA-SUPPORTED NICKEL AND ZIRCONIUM CATALYSTS FOR BRANCHED POLYETHYLENE

在线全文

学校读者我要写书评

暂无评论

chinese Journal of Polymer Science 2003年第4期21卷 453-458页

作者：孙文华 State key laboratory of Engineering Plastics The Center for Molecular {2. Institute of Chemistry chinese academy of sciences beijing 100080 china chinese Acad Sci Inst Chem Ctr Mol Sci State Key Lab Engn Plast Beijing 100080 Peoples R China

8-Aminoquinoline nickel dichloride and bis(cyclopentadienyl)zirconium dichloride (Cp_2.rCl_2. were supportedsimultaneously on silica to produce branched polyethylene successfully by combined polymerization. The supportedpolymerization results showed that the molecular weight of polyethylene increased while the molecular weight distributionbecame wider and the molecular chains of oligomers remaning in the final solution became shorter as compared to theoligomers obtained in polymerization processes with pure 8-aminoquinoline nickel dichloride catalysis, as well as theCp_2.rCl_2.and nickel combination system. With decreasing amount of Ni catalyst in the supported catalyst, the molecular chains of oligomers in the resulting solution became shorter, while α-olefin selectivity increased.

关键词： 8-Aminoquinoline nickel dichloride, Cp_2.rCl_2 Silica supported catalysts Branched polyethylene

Studies on MB-SAR 3D imaging algorithm using Yule-Walker method

在线全文

学校读者我要写书评

暂无评论

Science china(Information sciences) 2010年第9期53卷 1848-1859页

作者： WANG Bin1,2.,WANG YanPing1,HONG Wen1,TAN WeiXian1,2.& WU YiRong1 1National key laboratory of Microwave Imaging Technology,Institute of Electronics,{2.,beijing 100190,china 2.raduate University of {2.,beijing 100049,china 1. National key laboratory of Microwave Imaging Technology Institute of Electronics Chinese Academy of Sciences Beijing 100190 China2. Graduate University of Chinese Academy of Sciences Beijing 100049 China

Multibaseline synthetic aperture radar(MB-SAR) can form a synthetic aperture in the height direction with multiple parallel observations,so it has the resolving capability in the height direction and can realize three-dimensional(3D) imaging for the *** analytic model of MB-SAR based on spectrum estimation is analyzed in this *** on the more general geometric model,we derive the signal model for MB-SAR 3D *** then Yule-Walker algorithm is proposed to realize MB-SAR 3D imaging meanwhile the principle is analyzed and the steps of Yule-Walker algorithm are *** algorithm can get the 3D image of the target with high resolution using fewer ***,the experimental results of MB-SAR 3D imaging using Yule-Walker algorithm are presented,which are generated with the simulated data and the data collected in anechoic chamber.

关键词： MB-SAR 3D SAR imaging algorithm SAR spectrum estimation Yule-Walker method

On designated-weight Boolean functions with highest algebraic immunity

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 Mathematics 2010年第11期53卷 2847-2854页

作者： LIU MeiCheng1,3, DU YuSong2. PEI DingYi2.& LIN DongDai1 1The State key laboratory of Information Security, Institute of Software of {2., beijing 100190, china 2.ollege of Mathematics and Information sciences, Guangzhou University, Guangzhou 510006, china 3Graduate University of {2., beijing 100049, china 1. The State key laboratory of Information Security Institute of Software of Chinese Academy of Sciences Beijing 100190 China3. Graduate University of Chinese Academy of Sciences Beijing 100049 China2. College of Mathematics and Information Sciences Guangzhou University Guangzhou 510006 China

Algebraic immunity has been considered as one of cryptographically significant properties for Boolean functions. In this paper, we study ∑d-1 i=0 (ni)-weight Boolean functions with algebraic immunity achiev-ing the minimum of d and n - d + 1, which is highest for the functions. We present a simpler sufficient and necessary condition for these functions to achieve highest algebraic immunity. In addition, we prove that their algebraic degrees are not less than the maximum of d and n - d + 1, and for d = n1 +2.their nonlinearities equalthe minimum of ∑d-1 i=0 (ni) and ∑ d-1 i=0 (ni). Lastly, we identify two classes of such functions, one having algebraic degree of n or n-1.

关键词： cryptography Boolean function algebraic immunity algebraic degree nonlinearity

Topography and functional information of plasma membrane

在线全文

学校读者我要写书评

暂无评论

Science china(Life sciences) 2008年第2期51卷 95-103页

作者： SUN DeLan1, CHEN JianMin1, SONG YanMei1, ZHU ChuanFeng2. PAN GeBo2.& WAN LiJun2.1 key laboratory of Photosynthesis and Environmental Molecular Physiology, Institute of Botany, {2., beijing 100093, china 2.Institute of Chemistry, {2., beijing 100080, china 1. key laboratory of Photosynthesis and Environmental Molecular Physiology Institute of Botany Chinese Academy of Sciences Beijing 100093 China 2. Institute of Chemistry Chinese Academy of Sciences Beijing 100080 China

By using atomic force microscope (AFM), the topography and function of the plasmalemma surface of the isolated protoplasts from winter wheat mesophyll cells were observed, and compared with dead protoplasts induced by dehydrating stress. The observational results revealed that the plasma membrane of living protoplasts was in a state of polarization. Lipid layers of different cells and membrane areas exhibited distinct active states. The surfaces of plasma membranes were unequal, and were characterized of regionalisation. In addition, lattice structures were visualized in some regions of the membrane surface. These typical structures were assumed to be lipid molecular complexes, which were measured to be 15.8±0.09 nm in diameter and 1.9±0.3 nm in height. Both two-dimensional and three-dimensional imaging showed that the plasmalemma surfaces of winter wheat protoplasts were covered with numerous protruding particles. In order to determine the chemical nature of the protruding particles, living protoplasts were treated by proteolytic enzyme. Under the effect of enzyme, large particles became relatively looser, resulting that their width was increased and their height decreased. The results demonstrated that these particles were likely to be of protein nature. These protein particles at plasmalemma surface were different in size and unequal in distribution. The diameter of large protein particles ranged from 2.0 to 440 nm, with a central micropore, and the apparent height of them was found to vary from 12.to 40 nm. The diameter of mid-sized protein particles was between 40―60 nm, and a range of 1.8―5 nm was given for the apparent height of them. As for small protein particles, obtained values were 12.40 nm for their diameter and 0.7―2.2.nm for height. Some invaginated pits were also observed at the plasma membrane. They were formed by the endocytosis of protoplast. Distribution density of them at plasmalemma was about 16 pits per 15 μm2. According to their size, we clas

关键词： atomic force microscope winter wheat protoplast plasma membrane surface membrane protein invaginated pits

Carbon Storage and Vertical Distribution in Three Shrubland Communities in Gurbantünggüt Desert,Uygur AutonomousRegion of Xinjiang,Northwest china

在线全文

学校读者我要写书评

暂无评论

chinese Geographical Science 2012年第5期22卷 541-549页

作者： GONG Yanming 1 ,HU Yukun 1 ,FANG Fei 1 ,LIU Yanyan 1 ,LI Kaihui 1 ,ZHANG Guangming 2.(1.key laboratory of Biogeography and Bioresource in Arid Land,Xinjiang Institute of Ecology and Geography,{2.,Urumqi 830011,china 2.State key laboratory of Vegetation and Environmental Change, Institute of Botany,{2.,beijing 100093,china) 1. key laboratory of Biogeography and Bioresource in Arid Land Xinjiang Institute of Ecology and Geography Chinese Academy of Sciences Urumqi 830011 China 2. State key laboratory of Vegetation and Environmental Change Institute of Botany Chinese Academy of Sciences Beijing 100093 China

This study was carried out in the Gurbantünggüt Desert,Uygur Autonomous Region of Xinjiang,Northwest china in August,*** quantify the storage,contribution and vertical distribution patterns of plant biomass carbon (PBC)and soil organic carbon(SOC)in the study area,we investigated the carbon concentrations and its vertical distribution in three different desert shrubland communities dominated by Reaumuria soongorica,Haloxylon ammodendron+*** and Tamarix ramosissima+***,*** analyzed vertical distribution of root biomass carbon and soil carbon contents by excavating soil profiles for each dominated *** results show that SOC is considerably the larger carbon pool in the soil layers of 1.0-3.0 m(the mean value of three shrubland communities is 38.46%)and 3.0-5.0 m(the mean value is 40.2.%).In contrast,70.74%of belowground biomass carbon storage in 0-1.0 m layer,and its content decrease with increasing soil *** Haloxylon ammodendron+R. soongorica shrubland community has the highest belowground biomass carbon among three selected communities. This study highlights the importance of SOC stored in deep soil layers(lower than 3.0 m from the surface)in arid shrubland communities in the global carbon *** addition,it provides the data support for revealing deep soil solid carbon potential,and offers scientific basis for the further research in the carbon cycle of terrestrial ecosystem.

关键词： shrubland community plant biomass carbon soil organic carbon vertical distribution Gurbantünggüt desert

Analysis of a kind of quantum cryptographic schemes based on secret sharing

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(Physics,Mechanics & Astronomy) 2009年第9期52卷 1313-1316页

作者： ZHANG XingLan1 & JI DongYao2.1 College of Computer Science and Technology, beijing University of Technology, beijing 10012., {2. 2.State key laboratory of Information Security, Graduate University of chinese academy of sciences, beijing 100049, {2. College of Computer Science and Technology Beijing University of Technology Beijing 100124 China State key laboratory of Information Security Graduate University of Chinese Academy of Sciences Beijing 100049 China

Recently, Yang et al. proposed a kind of quantum cryptographic schemes based on secret sharing. The main idea is drawn from the case, where any n participants who share a secret K can co-operate as K does. This process can be applied to encryption, authentication, signature and so on. Unfortunately, since there is no identity authentication of the share's holder, these schemes inherit the limitation of secret sharing in practice. If some participants do not follow the protocol, the protocol would be a failure at last. Moreover, these schemes encounter another serious attack. Any two participants can co-operate to defeat the schemes by sending different shares to the parties unknown to the distributor of the secret K, such that these parties can execute the protocol as well. The attack proves that it is not enough for quantum cryptographic schemes that only the secret key is secure.

关键词： quantum identity authentication quantum secure direct communication quantum signature secret sharing

AN ITERATIVE PROCEDURE FOR DOMAIN DECOMPOSITION METHOD OF SECOND ORDER ELLIPTIC PROBLEM WITH MIXED BOUNDARY CONDITIONS

在线全文

学校读者我要写书评

暂无评论

Journal of Computational Mathematics 1997年第4期15卷 319-326页

作者： Lie-heng Wang (State key laboratory of Scientific and Engineering Computing, ICMSEC, {2., beijing, china) 中科院计算数学与科学工程计算所科学与工程计算国家重点实验室北京

This paper is devoted to study of an iterative procedure for domain decomposition method of second order elliptic problem with mixed boundary conditions (i.e., Dirichlet condition on a part of boundary and Neumann condition on the another part of boundary). For the pure Dirichlet problem, Marini and Quarteroni [3], [4] considered a similar approach, which is extended to more complex problem in this paper.

关键词： EH Math AN ITERATIVE PROCEDURE FOR DOMAIN DECOMPOSITION METHOD OF SECOND ORDER ELLIPTIC PROBLEM WITH MIXED BOUNDARY CONDITIONS

MB_8^(2.) (M=Be,Mg,Ca,Sr,and Ba):Planar octacoordinate alkaline earth metal atoms enclosed by boron rings

在线全文

学校读者我要写书评

暂无评论

Science china Chemistry 2010年第8期53卷 1737-1745,1829-1832页

作者： PU ZhiFeng1,GE MaoFa1 & LI QianShu2.1State key laboratory for Structural Chemistry of Unstable and Stable Species {2. National laboratory for Molecular sciences (BNLMS) Institute of Chemistry,chinese academy of sciences,beijing 100190,china 2.enter for Computational Quantum Chemistry,South china Normal University,Guangzhou 510631,china 1. State key laboratory for Structural Chemistry of Unstable and Stable Species beijing National laboratory for Molecular {2. (BNLMS) Institute of Chemistry Chinese Academy of Sciences Beijing 100190 China2. Center for Computational Quantum Chemistry South China Normal University Guangzhou 510631 China

Complexes involving planar octacoordinate alkaline earth metal atoms in the centers of eight-membered boron rings have been investigated by two density functional theory (DFT) ***82.with D8h symmetry is predicted to be stable,both geometrically and electronically,since a good match is achieved between the size of the central beryllium atom and the eight-membered boron *** contrast,the other alkaline earth metal atoms cannot be stabilized in the center of a planar eight-membered boron ring because of their large *** following the out-of-plane imaginary vibrational frequency,pyramidal C8v MgB82.,CaB82.,SrB82.,and BaB82.structures are *** presence of delocalized π and σ valence molecular orbitals in D8h BeB82.gives rise to aromaticity,which is reflected by the value of the nucleus-independent chemical *** D8h BeB82.structure is confirmed to be the global minimum on the potential energy surface.

关键词： density functional theory octacoordinate alkaline earth metal aromatic molecular orbital

Chronology of Holocene lacustrine sediments in Co Ngoin, central Tibetan Plateau

在线全文

学校读者我要写书评

暂无评论

Science china Earth sciences 2006年第9期49卷 991-1001页

作者： WU Yanhong1, WANG Sumin1& HOU Xinhua1,3 1. key laboratory of Lake Sedimentation and Environment, Nanjing Institute of Geography and Limnology, {2., Nanjing 2.0008, china 2. Institute of Tibetan Plateau Research, {2., beijing 10085, china 3. Graduate University of {2., beijing 100039, china 1. key laboratory of Lake Sedimentation and Environment Nanjing Institute of Geography and Limnology Chinese Academy of Sciences Nanjing 210008 China 2. Institute of Tibetan Plateau Research Chinese Academy of Sciences Beijing 10085 China 3. Graduate University of chinese academy of sciences Beijing 100039 China

Chronology is the basis for using lacustrine sediments to reconstruct the history of en-vironmental change. Radioactive-nuclides such as 14C, 2.0Pb and 137Cs dating are mainly used to establish the chronology for recent several ten thousand years. Because of being mixed with “dead carbon”, the measured 14C age is always older than the actual age which is recognized as “reservoir effect”. Cs is a kind of active metal element, and easy to migrate vertically in the sediment that leads to the error of the time marker. 2.0Pb dating should make sure to select CIC model or CRS model. On the Tibetan Plateau, most of the lakes are alkaline closed lake where Cs is more moveable in the sediment and the reservoir effect caused by “dead carbon” on 14C dating is stronger. Based on the analysis on results of 14C, 2.0Pb and 137Cs of the lacustrine sediments from Co Ngoin, central Tibetan Plateau, we use the simple regression method to re-calculate the 14C calendar ages, and establish the time sequence for cores CE-1 and CE-2.with result of 2.0Pb CRS model for the upper 35 cm and re-calculated 14C calendar age for sediments bellow 35 cm. Since 1400 cal. a BP, sedimentation inter-rupted for more than 1000 years. According to this time sequence, variations of environmental proxies confidently reflect the major climatic events in Holocene.

关键词： 14C, 2.0Pb and 137Cs, chronology, lacustrine sediments, climatic event, Co Ngoin, central Tibetan Plateau.