检索结果-南通市图书馆

Relative importance of water, energy, and heterogeneity in determining regional pteridophyte and seed plant richness in China

在线全文

学校读者我要写书评

暂无评论

Journal of Systematics and Evolution 2011年第2期49卷 95-107页

作者： 1,2,3 Sheng-Bin CHEN § 1 Gao-Ming JIANG 3 Zhi-Yun OUYANG 3 Wei-Hua XU 3 Yi xiao 1 (State key laboratory of Vegetation and Environmental Change, institute of Botany, chinese academy of sciences, beijing 100093, China) 2 (Graduate University of the chinese academy of sciences, beijing 100049, China) 3 (State key laboratory of Urban and Regional Ecology, Research Center for Eco-Environmental sciences, chinese academy of sciences, beijing 100085, China) (State key laboratory of Vegetation and Environmental Change Institute of Botany Chinese Academy of Sciences Beijing 100093 China) (Graduate University of the chinese academy of sciences Beijing 100049 China) (State key laboratory of Urban and Regional Ecology Research Center for Eco-Environmental Sciences Chinese Academy of Sciences Beijing 100085 China)

Environmental variables, such as ambient energy, water availability, and environmental heterogeneity have been frequently proposed to account for species diversity gradients. How taxon-specific functional traits define large-scale richness gradients is a fundamental issue in understanding spatial patterns of species diversity, but has not been well documented. Using a large dataset on the regional flora from China, we examine the contrast spatial patterns and environmental determinants between pteridophytes and seed plants which differ in dispersal capacity and environmental requirements. Pteridophyte richness shows more pronounced spatial variation and stronger environmental associations than seed plant richness. Water availability generally accounts for more spatial variance in species richness of pteridophytes and seed plants than energy and heterogeneity do, especially for pteridophytes which have high dependence on moist and shady environments. Thus, pteridophyte richness is disproportionally affected by water-related variables; this in turn results in a higher proportion of pteridophytes in regional vascular plant floras (pteridophyte proportion) in wet regions. Most of the variance in seed plant richness, pteridophyte richness, and pteridophyte proportion explained by energy is included in variation that water and heterogeneity account for, indicating the redundancy of energy in the study extent. However, heterogeneity is more important for determining seed plant distributions. Pteridophyte and seed plant richness is strongly correlated, even after the environmental effects have been removed, implying functional linkages between them. Our study highlights the importance of incorporating biological traits of different taxonomic groups into the studies of macroecology and global change biology.

关键词： habitat heterogeneity pteridophytes seed plants species richness water-energy hypothesis.

Direct numerical simulation of shock/turbulent boundary layer interaction in a supersonic compression ramp

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) 2010年第9期53卷 1651-1658页

作者： lI Xinliang1,FU DeXun2,MA YanWen2 & lIANG Xian1 1 key laboratory of high Temperature Gas Dynamics,institute of Mechanics,chinese academy of sciences,beijing 100190,China 2 The State key laboratory of Nonlinear Mechanics,institute of Mechanics,chinese academy of sciences,beijing 100190,China key laboratory of high Temperature Gas Dynamics Institute of Mechanics Chinese Academy of Sciences Beijing China The State key laboratory of Nonlinear Mechanics Institute of Mechanics Chinese Academy of Sciences Beijing China

A direct numerical simulation of the shock/turbulent boundary layer interaction flow in a supersonic 24-degree compression ramp is conducted with the free stream Mach number *** blow-and-suction disturbance in the upstream wall boundary is used to trigger the *** the mean wall pressure and the velocity profiles agree with those of the experimental data,which validates the *** turbulent kinetic energy budget in the separation region is *** show that the turbulent production term increases fast in the separation region,while the turbulent dissipation term reaches its peak in the near-wall *** turbulent transport term contributes to the balance of the turbulent conduction and turbulent *** on the analysis of instantaneous pressure in the downstream region of the mean shock and that in the separation bubble,the authors suggest that the low frequency oscillation of the shock is not caused by the upstream turbulent disturbance,but rather the instability of separation bubble.

关键词： compression ramp shock/turbulent boundary layer interaction direct numerical simulation shock oscillation

Correlation of Behavior Changes and BOlD Signal in Alzheimer-like Rat Model

在线全文

学校读者我要写书评

暂无评论

Acta Biochimica et Biophysica Sinica 2004年第12期36卷 803-810页

作者： Zheng-Hui HU#, xiao-Chuan WANG1#, li-Yun lI3, Mai-li lIU3, rong lIU1, Zhiqun lING1, Qing TIAN1, xiao-Wei TANG, Yi-Gen WU2*, and Jian-Zhi WANG1* Department of physics and Bio-X disciplinary laboratory, Zhejiang University, Hangzhou 310027,China 1 Department of Pathophysiology, Tongji Medical College, Huazhong University of Science and Technology, Wuhan 430030, China 2institute of high energy physics and key laboratory of Nuclear Analysis Techniques, chinese academy of sciences, P.O. Box 918, beijing 100039, China 3Wuhan institute of physics and Mathematics, State key laboratory of Magnetic Resonance and Atomic and Molecular physics, chinese academy of sciences, Wuhan 430071, China Department of physics and Bio-X disciplinary laboratory Zhejiang UniversityHangzhou 310027China Department of Pathophysiology Tongji Medical College Huazhong University of Science and TechnologyWuhan 430030 China Wuhan institute of physics and Mathematics State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics Chinese Academy of SciencesWuhan 430071 China institute of high energy physics and key laboratory of Nuclear Analysis Techniques Chinese Academy of SciencesP.O. Box 918 Beijing 100039 China

To explore a potential means for the early diagnosis of Alzheimer disease, we studied the relationship of resting T2* signal and tau hyperphosphorylation/spatial memory deficit. The rat model with tau hyperphosphorylation and spatial memory deficit was established by bilateral hippocampi injection of isoproterenol (IP). Then, the correlative alteration between resting T2* signal and spatial memory retention was assessed with blood oxygenation level dependent (BOlD) functional magnetic resonance imaging (fMRI) study and Morris Water Maze test, and Western blot was employed to confirm tau hyperphosphorylation. The analysis showed following results. (1) Tau phosphorylation at Ser396/Ser404 and Ser199/Ser202 was signifi- cantly increased in IP-injected rats as detected by PHF-1 and tau-1, respectively. (2) An AD-like spatial memory retention disturbance was induced at 24 h after isoproterenol injection. (3) A sensitivity threshold of resting T2* signal intensity, which separated the IP-treated rats from vehicle control, was obtained by applying linear regression analysis, and an estimated sensitivity statistical threshold was at 32.62. These results suggest that resting T2* signal may serve as a noninvasive quantitative marker in predicting AD-like spatial memory deficits and tau hyperphosphorylation.

关键词： Alzheimer disease (AD) functional magnetic resonance imaging (fMRI) isoproterenol (IP) Morris Water Maze diagnosis

An Explicit Function Expression for dc Bias and Temperature Dependence of Magnetoresistances in Magnetic Tunnel Junctions

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

Journal of Materials Science & Technology 2002年第6期18卷 497-501页

作者： Xiufeng HANState key laboratory of Magnetism, institute of physics and Center of Condensed Matter physics, chinese academy of sciences, beijing 100080, China chinese Acad Sci Inst Phys State Key Lab Magnetism Beijing 100080 Peoples R China chinese Acad Sci Ctr Condensed Matter Phys Beijing 100080 Peoples R China

An explicit function expression for the bias voltage or/and temperature dependences of tunnel magnetoresistance ratio and resistances were obtained with a unique set of intrinsic parameters. Two of these intrinsic parameters are the Curie temperature TC and the density of state (DOS) for itinerant majority and minority electrons ξ(ρM/ρm), which are the eigen parameters of ferromagnetic electrodes. Others are the spin-dependent matrix-element ratio (i.e., |Td|2/|TJ|2 ) and the anisotropic-wavelength-cutoff energy ECγ of spin-wave spectrum in magnetic tunnel junction (MTJ), which are the structure parameters of an MTJ. These intrinsic parameters can be predetermined using the experimental measurement or, in principle, using the first-principle calculation method for an MTJ with the three key layers of FM/I/FM. Furthermore, a series of experimental data for an MTJ, for example, a spin-valve-type MTJ of Ta (5 nm)/Ni79Fe21(25 nm)/lr22Mn78(12 nm)/Co75Fe25(4 nm)/AI(0.8 nm)-oxide/Co75Fe25(4 nm)/Ni79Fe21(20 nm)/Ta (5 nm) in this work, can be self-consistently evaluated and explained using such concise explicit function formulations.

关键词： Magnetic tunnel junction TMR Spin-electron transport Magnon excitation Spin-polarization Magnetotransport

Simulation of aerodynamic performance affected by vortex generators on blunt trailing-edge airfoils

在线全文

学校读者我要写书评

暂无评论

Science China(Technological sciences) 2010年第1期53卷 1-7页

作者： YANG Ke1,2,ZHANG lei1,3 & XU JianZhong1,2 1 institute of Engineering Thermophysics,chinese academy of sciences,beijing 100190,China 2 key laboratory of Wind energy Utilization,chinese academy of sciences,beijing 100190,China 3 Graduate School of chinese academy of sciences,beijing 100190,China institute of Engineering Thermophysics Chinese Academy of Sciences Beijing China key laboratory of Wind energy Utilization Chinese Academy of Sciences Beijing China Graduate School of chinese academy of sciences Beijing China

An investigation was carried out by numerical simulation on a wind turbine airfoil and a blunt trailing-edge airfoil with and without vortex generators (VGs), and the performance of the airfoils was analyzed. By the simulation of airfoil DU 91-W2-250 it was verified that the numerical method and model were credible. Based on this airfoil, a new one with a blunt trailing edge of 6% chord was blended by symmetrically adding thickness, and its characteristics curves were obtained through computing at key angles of attack. Additionally, the pressure distribution on blended airfoil was analyzed by comparing to the airfoil without blend. The interaction of streamwise vortices induced by VGs with trailing vortex or separation vortex was considered, followed by the uncovery of how VGs can suppress the boundary layer separation.

关键词： vortex generators airfoil blunt trailing-edge

Progress in multi-waveband observations of supernova remnants

在线全文

学校读者我要写书评

暂无评论

Progress in Natural Science:Materials International 2008年第9期18卷 1057-1062页

作者： Xuejuan Yang a,b, Fangjun lua, Wenwu Tian c,d,* a particle astrophysics Center, institute of high energy physics, chinese academy of sciences, beijing 100049, China b Department of Astronomy, beijing Normal University, beijing 100875, China c National Astronomical Observatories, chinese academy of sciences, 20A Datun Road, Chaoyang District, CAS, beijing 100012, China d Department of physics & Astronomy, University of Calgary, Alberta, Canada T2N 1N4 particle astrophysics Center Institute of High Energy Physics Chinese Academy of Sciences Beijing 100049 China Department of Astronomy Beijing Normal University Beijing 100875 China National Astronomical Observatories Chinese Academy of Sciences 20A Datun Road Chaoyang District CAS Beijing 100012 China Department of physics & Astronomy University of Calgary Alberta Canada T2N 1N4

The development of observational techniques has enriched our knowledge of supernova remnants. In this paper, we review the main progresses in the last decade, including new discoveries of supernova remnants and the associated (rare type of) pulsars, nucleosynthesis, the interaction between supernova remnants and molecular clouds, dust in the supernova remnants, shock physics, and cosmic ray accelerations.

关键词： Supernova remnant Observations

Atomistic mechanism of high ionic conductivity in lithium ytterbium-based halide solid electrolytes:A first-principles study

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

Journal of Rare Earths 2024年第1期42卷 155-162,I0006页

作者： limin Wang Wei xiao lu Sun rong Yang Jinqiu Yu ligen Wang State key laboratory of Nonferrous Metals and Processes China GRINM Group Co.Ltd.Beijing100088China GRIMAT Engineering institute Co. Ltd.Beijing101407China General Research institute for Nonferrous Metals Beijing100088China China Automotive Battery Research institute Co. Ltd.Beijing101407China Rare Earth Functional Materials(Xiong'an)Innovation Center Co. Ltd.Xiong'an071700China

As the next generation of commercial automotive power batteries begins replacing liquid lithium batteries,many look towards all-solid-state batteries to pioneer the ***-so lid-state batteries have attracted the attention of countless researchers around the world because of their high safety and high energy *** recent times,halide solid-state electrolytes have become a research hotspot within solid-state electrolytes because of their potentially superior *** this paper,in the framework of DFT,we investigated the atomic mechanisms of improving the ionic conductivity and stability of li_(3)YbCl_(6).Our calculations show that both trigonal and orthorhombic li_(3)YbCl_(6) exhibit wide electrochemical windows and metastable properties(100 meV/atom>Ehull>0 meV/atom).However,the orthorhombic li_(3)YbCl_(6) can be stabilized at high temperatures by taking the vibrational entropy into account,which is supported by the experimental ***,it is expected that because of the Yb/li synergistic interactions that,due to their strong mutual coulomb repulsion,influence the li^(+)transport behavior,the orthorhombic li_(3)YbCl_(6) might have superior ionic conductivities with appropriate li+migration paths determined by the Yb^(3+) ***,higher ionic conductivities can be obtained by regulating the random distribution of li^(+) *** li^(+)-deficiency can also largely increase the ionic conductivity by invoking *** study helps gain a deeper understanding of the laws that govern ionic conductivities and stabilities and provides a certain theoretical reference for the experimental development and design of halide solid-state electrolytes.

关键词： Halide solid-state electrolytes Phase stability Ionic conductivity First-principles calculations Rare earths

Exploration of combined adjustment laws about IGV,stator and rotational speed in off-design conditions in an axial compressor

在线全文

学校读者我要写书评

暂无评论

中国科学：技术科学英文版 2010年第4期53卷 969-975页

作者： HU YanMing1,2 & NIE ChaoQun1 1 key laboratory of Advanced energy and Power Technology,institute of Engineeting Thermophysics,chinese academy of Science,beijing 100190,China 2 Graduate School of chinese academy of sciences,beijing 100190,China key laboratory of Advanced energy and Power Technology Institute of Engineeting Thermophysics Chinese Academy of Science Beijing China Graduate School of chinese academy of sciences Beijing China

Experimental investigations are performed in a three-stage low-speed axial compressor with variable inlet guide vanes(IGV) and adjustable *** characteristics of the compressor,especially the efficiency and stall margin,are analyzed in design and off-design operation conditions by adjusting stagger angles of IGV and stators as well as changing the rotational *** experimental results show that the off-design performance of the multistage axial compressor is improved by restaggering of IGV and stators related to rotational *** the background of engineering applications,digital signal processing(DSP) technique is used to realize online adjustment of stagger angles according to the corresponding relations between incidence angles of rotor and rotational speed.

关键词： axial compressor IGV surge DSP techniques off-design

Transport　of　atmospheric　trace　elements　and　dust－soil　to　the　Western　Pacific　Ocean

在线全文

学校读者我要写书评

暂无评论

Journal of Environmental sciences 1996年第4期8卷 460-465页

作者： Yang Shaojin Chen Bingru Yang Yinan(institute of high energy physics,chinese academy of sciences,beijing 100080,China) institute of high energy physics Chinese Academy of Sciences Beijing 100080 China

Atmospheric aerosol and rainwater samples collected in the different Western Pacific area were analyzed by instrumental neutron activation and proton induced X-ray emission to (1) determine the atmospheric concentrations of trace elements over the Western Pacific and (2) to esti mate the atmospheric deposition of trace elements and dust-soil material to this region. high abundance of pollutant and crustal elements relative to oceanic sources was observed. Some characteristics of marine atmosphere relating to long-range transport of crustal and anthropogenic elements from continent to the remote ocean are discussed. The total dust-soil particle mass is estimated to be 0. 066-1.2 μg/m￣3 over the Western Pacific Ocean areas. Atmospheric inputs of dust-soil particles control the marine particle concentrations of crustal elements. In addition, the characteristics of marine rain water are discussed.

关键词： dust-soil marine rain-water atmospheric trace elements.