检索结果-南通市图书馆

A new species of Leptocycas (Zamiaceae) from the Upper Triassic sediments of Liaoning Province,China

在线全文

学校读者我要写书评

暂无评论

Journal of Systematics and Evolution 2010年第4期48卷 286-301页

作者： 1,2.3Jian-Wei ZHANG 2.ian-Xin YAO 1Jia-Rui CHEN 1Cheng-Sen LI 1(State Key Laboratory of Systematic and Evolutionary Botany,institute of Botany,chinese academy of sciences,{2. 100093,China) 2.State Key Laboratory of Stratigraphy and Paleontology,institute of Geology,chinese academy of Geological sciences,{2. 100037,China) 3(Graduate University,chinese academy of sciences,beijing 100049,China) (State Key Laboratory of Systematic and Evolutionary Botany Institute of Botany Chinese Academy of Sciences Beijing 100093 China) (State Key Laboratory of Stratigraphy and Paleontology Institute of Geology Chinese Academy of Geological Sciences Beijing 100037 China) (Graduate University Chinese Academy of Sciences Beijing 100049 China)

A new cycad,Leptocycas yangcaogouensis ***.,was found in sediments from the Late Triassic in western Liaoning,*** pinnately compound leaves(Pseudoctenis type)are screwed in a crown on the stem *** leaflets are linear,with parallel veins and decurrent bases on the *** leaf bases are *** cataphylls intermix with the *** female cone is ovoid in *** characteristics of the new plant are more similar to those of Leptocycas gracilis,a Triassic cycad from North America,but the new species differs from *** in the size of its stem(7–8 vs.3–5 cm in diameter,respectively),leaves(length×width 100×16 vs.30×7 cm,respectively)and leaf density along the stem(4–6 vs.1–2.bases/1 cm length,respectively).Both *** and ***,having leaves of the Pseudoctenis type,show a closer relationship to the extant Dioon of *** present study provides evidence for the origin of the genus Dioon,which may have come from Leptocycas plants of the *** would be assumed that the extent cycads in Zamiaceae originate from the pteridosperms in the Late Paleozoic and have evolved through the stage of *** and *** in Late Triassic,and reaching the extant Dioon.

关键词： China Cycadales Leptocycas Upper Triassic Zamiaceae

Investigation into the rotational bands of ^(185)Pt with the particle-rotor model

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) 2011年第S1期54卷 114-118页

作者： LI GuangShun1,2. ZHOU XiaoHong1,2. ZHANG ShuangQuan3, ZHANG YuHu1 & MENG Jie3 1 institute of Modern physics, {2., Lanzhou 730000, China 2.Graduate University of {2., beijing 100049, China 3 School of physics and SK Laboratory of Nuclear physics & Technology, Peking University, beijing 100871, China institute of Modern physics Chinese Academy of Sciences Lanzhou China Graduate University of chinese academy of sciences Beijing China School of physics and SK Laboratory of Nuclear physics & Technology Peking University Beijing China

Theoretical calculations have been performed for the ν9/2.[62.](i13/2. and ν7/2.[503](f7/2. bands of 185Pt in the framework of particle-rotor model. The band properties of signature splitting and configuration mixing have been analyzed. The level energy and signature splitting before the band crossing can be well interpreted by introducing triaxiality. The positive-parity yrast band is pro posed to be dominated by the ν9/2.[62.](i13/2. component, while the negative-parity band shows strong mixing of ν7/2.[503](f7/2. and ν9/2.[505](h9/2. configurations.

关键词： high-spin states particle-rotor model signature splitting configuration mixing

Heavy ion reactions around the Coulomb barrier

在线全文

学校读者我要写书评

暂无评论

中国科学：物理学、力学、天文学英文版 2011年第S1期54卷 6-13页

作者： ZHANG HuanQiao1, LIN ChengJian1, JIA HuiMing1, ZHANG ChunLei1,2. ZHANG GaoLong1,3, YANG Feng1, LIU ZuHua1, AN GuangPeng1, WU ZhenDong1, XU XinXing1 & JIA Fei1 1 China institute of Atomic energy, P. O. Box 2.5(10), {2. 102.13, China 2.Particle Astrophysics Center, institute of high energy physics, chinese academy of sciences, {2. 100039, China 3 School of physics and Nuclear energy Engineering, Beihang University, {2. 100191, China China institute of Atomic energy Beijing China Particle Astrophysics Center Institute of High Energy Physics Chinese Academy of Sciences Beijing China School of physics and Nuclear energy Engineering Beihang University Beijing China

The angular distributions of fission fragments for the 32.+184W reaction near Coulomb barrier energies are measured. The ex perimental fission excitation function is obtained. The measured fission cross sections are decomposed into fusion-fission, quasi-fission and fast fission contributions by the dinuclear system (DNS) model. The hindrance to completing fusion both at small and large collision energies is explained. The fusion excitation functions of 32.+90,96Zr in an energy range from above to below the Coulomb barrier are measured and analyzed within a semi-classical model. The obvious effect of positive Q-value multi-neutron transfers on the sub-barrier fusion enhancement is observed in the 32.+96Zr system. In addition, the excitation functions of quasi-elastic scattering at a backward angle have been measured with high precision for the systems of 16O+2.8Pb, 196Pt, 184W, and 154,152.m at energies well below the Coulomb barrier. Considering the deformed coupling effects, the extracted diffuseness parameters are close to the values extracted from the systematic analysis of elastic and inelastic scattering data. The elastic scattering angular distribution of 17F+12. at 60 MeV is measured and calculated by using the continuum-discretized coupled-channels (CDCC) approach. It is found that the diffuseness parameter of the real part of core-target potential has to be increased by 2.% to reproduce the experimental result, which corresponds to an increment of potential depth at the surface re gion. The breakup cross section and the coupling between breakup and elastic scattering are small.

关键词： fusion-fission quasi-fission fusion hindrance fusion enhancement surface diffuseness parameter exotic nuclei

Cyclic Heating-Annealing and Boltzmann Distribution of Free Energies in a Spin-Glass System

在线全文

学校读者我要写书评

暂无评论

Communications in Theoretical physics 2007年第7期48卷 179-182页

作者： ZHOU Hai-Jun institute of Theoretical physics,the {2.,beijing 100080,China institute of Theoretical physics the Chinese Academy of Sciences Beijing 100080 China

Ergodicity of a spin-glass is broken at low temperatures;the system is trapped in one of many ergodicconfigurational *** between different ergodic domains are achievable through a *** this experiment is repeated infinite times,all ergodic configurational domains will be visited with frequencesthat decreasing exponentially with their free *** mean free energy density of a spin-glass system on a randomgraph is calculated based on this free energy Boltzmann distribution in the present work,by means of the cavity approach.

关键词： spin-glass ergodicity-broken cavity method

Semi-analytical analysis of the response of the air temperature over the land surface to the global vegetation distribution

在线全文

学校读者我要写书评

暂无评论

chinese Science Bulletin 2009年第14期54卷 2499-2505页

作者： LIU Fei1,2.& CHAO JiPing3,4 1 institute of Atmospheric physics, {2., beijing 10002., China 2.Graduate University of {2., beijing 100049, China 3 National Marine Environmental Forecasting Center, beijing 100081, China 4 First institute of Oceanography, State Oceanic Administration of China, Qingdao 2.6061, China institute of Atmospheric physics {2. Beijing China Graduate University of chinese academy of sciences Beijing China National Marine Environmental Forecasting Center Beijing China First institute of Oceanography State Oceanic Administration of China Qingdao China

Response of the air temperature over the land surface to the global vegetation distribution is investigated, using a three-dimensional governing equation to simulate the steady, large-scale, limited amplitude perturbation of the free, inviscid and adiabatic atmosphere. The adoption of the static equation leads to a temperature governing equation in the terrain following coordinate. With the prescribed temperature as the upper boundary condition and the radiation balance as the lower boundary condition, the semi-analytical solution of the global circulation temperature can be calculated. In this article, only the air temperature (at 2.m height) over the land surface is analyzed, and the result suggests that this model can simulate the air temperature pattern over the land surface reasonably. A better simulation occurs when a simple feedback of the albedo on the temperature is included. Two sensitivity experiments are analyzed through this model. One suggests that the air temperature over the land surface descends obviously when the land surface is covered with ice all over, while another suggests that the air temperature rises a little when the land surface is covered with forest except the ice-covered area. This model appears to be a good tool to study the response of the air temperature to the vegetation distribution. Limitations of the model are also discussed.

关键词：空气温度植被分布陆地表面反应解析分析模拟模式控制方程边界条件

Optimization of mathematical models for thematic maps

在线全文

学校读者我要写书评

暂无评论

Science China(Technological sciences) 2010年第S1期53卷 15-24页

作者： QI QingWen1,ZHANG An1,JIANG LiLi1,ZOU XiuPing2.XU Li3 & CHENG Xi1,4 1 institute of Geographical sciences and Natural Resources Research,{2.,beijing 100101,China 2.institute of Policy and Management,{2.,beijing 100080,China 3 Taishan University,Taian 2.102.,China 4 Graduate University of {2.,beijing 100049,China institute of Geographical sciences and Natural Resources Research Chinese Academy of Sciences Beijing China institute of Policy and Management Chinese Academy of Sciences Beijing China Taishan University Taian China Graduate University of chinese academy of sciences Beijing China

The thematic map is a major class of maps designed to demonstrate particular features or concepts,functioning as an indispensable tool in geographical *** process of thematic mapping is one into which geographical research goes deeply and *** key activity and course of thematic map production is the use of mathematical models to create thematic data ***,the selection and optimization of mathematical models is in the forefront of thematic map *** theoretical foundations,mechanisms and methods of mathematical model optimization are expounded in this paper,including two approaches,the phase by phase mode and the multi-aim scheme balance *** studies in eco-environment mapping and emergency mapping are described and analyzed,with a hierarchical analysis method being used in the model optimization for eco-environment fragility and sensitivity assessment mapping in Beibuwan (Guangxi) District,the dynamic system (DS) method being used in the model optimization for ecological security adjustment mapping in Xishuang Banna,Yunnan province,and the multi-phase mode being used in the models for forest fire and infectious diseases mapping.

关键词： thematic map mathematic model optimization

X（3872. and Bound State Problem of D0*0（0 D*0）

在线全文

学校读者我要写书评

暂无评论

原子核物理评论 2009年第S1期 16-21页

作者： LIU Yan-rui1,LIU Xiang2.3,DENG Wei-zhen2.(1 institute of high {2. physics,chinese academy of sciences,beijing 100049,China 2.Department of physics,Peking University,beijing 100871,China 3 Centro de Física Terica,Departamento de Física,Universidade de Coimbra,P-3004-516,Coimbra,Portugal)

We have performed a dynamical calculation of the bound state problem of D0D*0 by considering the pion and sigma meson exchange potential. Our preliminary analysis disfavors the molecular interpretation of X(3872. if we use the experimental D*Dπ coupling constant g=0.59 and a reasonable cutoff around 1 GeV,which is the typical hadronic scale. In contrast,there probably exists a loosely bound S-wave BB* molecular state. Such a molecular state would be rather stable since its dominant decay mode is the radiative decay through B*→Bγ.

关键词： X(3872. bound state molecule

Modeling the climate effects of different subregional uplifts within the Himalaya-Tibetan Plateau on Asian summer monsoon evolution

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

chinese Science Bulletin 2012年第35期57卷 4617-4626页

作者： ZHANG Ran 1,JIANG DaBang 1,2.3,LIU XiaoDong 4 & TIAN ZhiPing 2.5 1 Climate Change Research Center,chinese academy of sciences,beijing 10002.,China 2.Nansen-Zhu International Research Centre,{2. of Atmospheric physics,chinese academy of sciences,beijing 10002.,China 3 Key Laboratory of Regional Climate-Environment Research for Temperate East Asia,chinese academy of sciences,beijing 10002.,China 4 State Key Laboratory of Loess and Quaternary Geology,{2. of Earth Environment,chinese academy of sciences,Xi’an 710075,China 5 Graduate University of chinese academy of sciences,beijing 100049,China Climate Change Research Center Chinese Academy of Sciences Beijing China Nansen-Zhu International Research Centre Institute of Atmospheric Physics Chinese Academy of Sciences Beijing China Key Laboratory of Regional Climate-Environment Research for Temperate East Asia Chinese Academy of Sciences Beijing China State Key Laboratory of Loess and Quaternary Geology Institute of Earth Environment Chinese Academy of Sciences Xi’an China Graduate University of chinese academy of sciences Beijing China

Considering the different uplifting time of different subregions of the Himalaya-Tibetan Plateau(TP),a series of numerical simulations have been conducted with the Community Atmosphere Model(CAM4) developed at the National Center for Atmospheric Research to explore the effects of the phased tectonic uplift of the Himalaya-TP on the evolution of Asian summer *** results show that the uplifts of the Himalaya and northern TP significantly affect the evolutions of South Asian summer monsoon and northern East Asian summer monsoon *** is,the tectonic uplift of the Himalaya intensifies the South Asian summer monsoon circulation and increases the precipitation in South Asia,whereas the uplift of the northern TP intensifies the northern East Asian summer monsoon circulation and increases the precipitation in northern East *** with previous simulations,current comparative analyses of modeling results for different subregional uplifts within the Himalaya-TP help deepen our understanding of the evolutionary history of Asian monsoons.

关键词：青藏高原隆升喜马拉雅亚洲季风高原气候夏季季风次区域隆起演化建模

CMQV+:An authenticated key exchange protocol from CMQV

在线全文

学校读者我要写书评

暂无评论

Science China(Information sciences) 2012年第7期55卷 1666-1674页

作者： LI Hui 1,2.& WU ChuanKun 1 1 State Key Laboratory of Information Security,institute of Software,chinese academy of sciences,{2. 100190,China 2.Graduate University of chinese academy of sciences,beijing 100049,China State Key Laboratory of Information Security Institute of Software Chinese Academy of Sciences Beijing China Graduate University of chinese academy of sciences Beijing China

Ustaoglu presents a secure and efficient key exchange protocol named CMQV,based on the design rationales of HMQV and *** with the latter two protocols,on one hand,CMQV achieves high performance of HMQV,and on the other,it is proven secure in eCK model as NAXOS ***,CMQV enjoys the security proof under gap Diffie-Hellman assumption as indicated by its *** this paper,we propose a variant of CMQV,called CMQV+,which is proven secure under a weaker assumption (*** Diffie-Hellman assumption) in eCK model with random oracles while maintaining the high-performance feature of CMQV as much as possible.

关键词： key exchange eCK model trapdoor-test technique provable security CDH assumption