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Helium isotope investigation on magnetic reversal boundaries of loess-paleosol sequence at Luochuan, central Chinese Loess Plateau

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Chinese Science Bulletin 2007年第17期52卷 2407-2412页

作者： DU XueQing1,6, WANG YongHong2, REN JianGuo3, YE XianRen4 & LU HuaYu5,1 1 State Key Laboratory of Loess and Quaternary Geology, Institute of Earth environment, Chinese Academy of Sciences, Xi’an 710075, china 2 College of Marine Geosciences, Ocean university of china, Qingdao 266003, china 3 National natural Science Foundation of china, beijing 100085, china 4 Lanzhou Research Center for Petroleum and natural Gas resources, Institute of Geology and Geophysics, Chinese Academy of Sciences, Lanzhou 730000, china 5 Key Laboratory of Coast and Island Development, school of Geographic and Oceanographic Sciences, Nanjing university, Nanjing 210093, china 6 Graduate university of Chinese Academy of Sciences, beijing 100049, china State Key Laboratory of Loess and Quaternary Geology Institute of Earth Environment Chinese Academy of Sciences Xi''an 710075 China

Extraterrestrial particles have higher 3He/4He ratios than those of terrestrial sediments ( > 100 Ra versus < 0.03 Ra, where Ra is the 3He/4He ratio normalized to the atmospheric value of 1.4×10?6). The inter- planetary dust particles (IDPs), which are very rich in 3He, continuously bombard the Earth and can accumulate in deposits. IDPs sedimentation rate changes can significantly influence 3He concentration in the Earth surface sediments. Since IDPs are not easy to detect in terrestrial deposits, measuring helium isotopes is a helpful approach to examine changes in IDPs. Helium concentration and helium isotopic composition magnetic substances and the quartz particles were examined for helium concen- tration and helium isotopic ratio. Results show that the 3He/4He ratio and the 3He concentrations of the magnetic substances are clearly higher than those of the bulk samples and the quartz particles, and, the 3He/4He ratio of the extracted magnetic substances is also higher than that of the average level of the Earth’s crust. The higher helium content in the magnetic fractions can be explained by an influx of IDPs.

关键词：中国黄土高原古土壤氦同位素行星际尘埃颗粒反方向磁化

Relaying Selection with Network-coded Cooperative Protocols in Aeronautical Communications

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Chinese Journal of Aeronautics 2010年第1期23卷 75-83页

作者： Du Bing,Zhang Jun school of Electronics and Information Engineering,beijing university of Aeronautics and Astronautics,beijing 100191,china [a] school of Electronics Information Engineering Beijing University of Aeronautics Astronautics Beijing 100191 China

In this article, we exploit the idea of network-coded cooperative protocol in aeronautical communications which combines different source nodes＇ information at the relay and joint decoding at the destination. Recently, the network coding in cooperative communications has been categorized into two mainstreams, bit-level and signal-level combinations, which are both discussed in the article. And to be exclusively,multiple access relay channel（MARC） is adopted. The mutual information expressions of both above-cited network-coded protocols are deduced, which prove that without proper selected relays to perform network coding, the spatial diversity of the proposed protocol cannot be obtained. This then leads to search for the selection and grouping algorithms. An adjacency matrix is defined to describe the connectivity of the nodes in one radio contact disk, so that, the selection and grouping of algorithm is equivalent to constructing this adjacency matrix to minimize the system outage probability evaluated in term of the mutual information. Besides, a network-coded cooperative protocol requires the acyclic network, of which the construction is to avoid loop-4 in the matrix. The article ends with simulations to demonstrate the viability of the proposed algorithms.

关键词： communication network coding outage probability mutual information bit-level signal-level

Aridity/humidity status of land surface in china during the last three decades

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Science china Earth Sciences 2005年第9期48卷 1510-1518页

作者： WU Shaohong1, YIN Yunhe1,2, ZHENG Du1 & YANG Qinye1 1. Institute of Geographical Sciences and natural resources Research, Chinese Academy of Sciences (CAS), beijing 100101, china 2. Graduate school of the CAS, beijing 100039, china 1. Institute of Geographical Sciences and natural resources Research Chinese Academy of Sciences (CAS) 100101 Beijing China 2. Graduate school of the CAS 100039 Beijing China

To clarify aridity/humidity status of land surface is helpful for studying environmental background and regional differences, seeking causes of environmental change, and providing a scientific basis for researches on climate change in the future. In this paper, the authors calcu- lated potential evapotranspiration of china using data from 616 meteorological stations during the period of 1971―2000 with the Penman-Monteith model recommanded by FAO in 1998. Vy- sothkii’s model was used to calculate aridity/humidity index. Then the calculated results of sta- tions were interpolated to land surface using ArcGIS. Results show that the annual average po- tential evapotranspiration is 400―1500 mm in the whole country, 600―800 mm in most parts of it; and 350―1400 mm in growing season (April―Octobor), which is nearly 200 mm less than the annual average. According to the aridity/humidity indexes of 1.0, 1.5 and 4.0, the aridity/humidity status is categorized to four types, namely, humid, subhumid, semiarid and arid. A majority of stations (76%) are more humid in growing season than the annual average. Results of com- prisons between the distribution map of aridity/humidity index with that of precipitation and vegetation indicate a good consistence of aridity/humidity status with natural environment. Therefore potential evapotranspiration calculated with modified FAO’s Penman-Monteith model in combination with aridity/humidity index that considers water balance can more reasonably explain the actual land surface aridity/humidity status of china.

关键词： potential evapotranspiration, aridity/humidity status, land surface, regional differences, Penman-Monteith.

The localization of 1-cohomology of transitive Lie algebroids

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Science china Mathematics 2006年第2期49卷 277-288页

作者： CHEN Zhuo & LIU Zhangju Department of Mathematics, Capital Normal university, beijing 100037, china school of Mathematical Science, Peking university, beijing 100871, china 1. Department of Mathematics Capital Normal University Beijing 100037 China 2. school of Mathematical Science Peking University Beijing 100871 China

For a transitive Lie algebroid A on a connected manifold M and its representation on a vector bundle F, we define a morphism of cohomology groups rk: Hk(A,F) → Hk(Lx,Fx), called the localization map, where Lx is the adjoint algebra at x ∈ M. The main result in this paper is that if M is simply connected, or H (LX,FX) is trivial, then T is injective. This means that the Lie algebroid 1-cohomology is totally determined by the 1-cohomology of its adjoint Lie algebra in the above two cases.

关键词： transitive Lie algebroid representation cohomology localization.

Preparation of semi-solid AlSi7Mg alloy slurry with big capability

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Rare Metals 2010年第6期29卷 642-645页

作者： LI Sha and MAO Weimin school of Materials Science and Engineering,university of Science and Technology beijing,beijing 100083,china school of Materials Science and Engineering University of Science and Technology Beijing Beijing China

Semi-solid AlSi7Mg alloy slurry was prepared by low superheat pouring and weak traveling-wave electromagnetic *** effects of pouring temperature and stirring power on the microstructure of AlSi7Mg alloy slurry were *** results show that the semi-solid AlSi7Mg alloy slurry of 5 kg can be *** new technology can save energy and make the pouring process *** the pouring temperature is decreased at a stirring power of 0.41 kW,the shape of primary α-Al grains gradually changes from dendritic-like to *** the alloy melt is poured at the temperature（630°C） with a certain superheat,the pouring process becomes easier,and the spherical microstructure of AlSi7Mg alloy slurry can be prepared by the weak traveling-wave electromagnetic *** the pouring temperature is 630°C,increasing the stirring power appropriately can result in better spherical primary α-Al grains,but if the stirring power is increased to a certain value（1.72 kW）,the shape of primary α-Al grains does not obviously improve when the stirring power is continually increased.

关键词： aluminum alloys metal forming semisolid slurry electromagnetic stirring microstructure

Search for B_c (ns) via the B_c (ns) → B_c (ms) π^+ π^- transition at LHCb and Z^0 factory

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Science china(Physics,Mechanics & Astronomy) 2010年第11期53卷 2019-2024页

作者： KE HongWei 1 & LI XueQian 2 1 school of Science,Tianjin university,Tianjin 300072,china 2 school of Physics,Nankai university,Tianjin 300071,china 1. school of Science Tianjin University Tianjin 300072 China2. School of Physics Nankai University Tianjin 300071 China

It is interesting to study the characteristics of the whole family of B c which contains two different heavy *** and the proposed Z 0 factory provide an opportunity because a large database of the B c family will be achieved.B c and its excited states can be identified via their decay *** suggested by experimentalists,B-c (ns) → B c +γ is not easy to be clearly measured,instead,the trajectories of π + and π- occurring in the decay of B c (ns) → B c (ms) + π + π( n > m ) can be unambiguously identified,thus the measurement seems easier and more reliable;therefore this mode is more favorable at the early running stage of LHCb and the proposed Z 0 *** this work,we calculate the rate of B c (ns) → B c (ms) + π + π-in terms of the QCD multipole-expansion and the numerical results indicate that the experimental measurements with the luminosity of LHC and Z 0 factory are feasible.

关键词： meson hadronic decay QCD multipole-expansion

Mixed boundary conditions for piezoelectric plates

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Science china(Physics,Mechanics & Astronomy) 2009年第5期52卷 755-761页

作者： GAO Yang 1 ,XU SiPeng 2 &ZHAO BaoSheng 3 1College of Science,china Agricultural university,beijing 100083,china 2College of Engineering,Ocean university of china,Qingdao 266071,china 3 school of Mechanical Engineering,university of Science and Technology of Liaoning,Anshan 114044,china College of Science China Agricultural University Beijing 100083 China College of Engineering Ocean University of China Qingdao 266071 China school of Mechanical Engineering University of Science and Technology of Liaoning Anshan 114044 China

For plate bending and stretching problems in piezoelectric materials,the reciprocal theorem and the general solution of piezoelasticity are applied in a novel way to obtain the appropriate mixed boundary conditions accurate to all order.A decay analysis technique is used to establish necessary conditions that the prescribed data on the edge of the plate must satisfy in order that it should generate a decaying state within the *** the case of axisymmetric bending and stretching of a circular plate,these decaying state conditions are obtained explicitly for the first time when the mixed conditions are imposed on the plate *** are then used for the correct formulation of boundary conditions for the interior solution.

关键词： boundary conditions piezoelectric plates mixed data bending problems stretching problems

Study on NDVI-T_s space by combining LAI and evapotranspiration

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Science china Earth Sciences 2006年第7期49卷 747-754页

作者： HAN Lijuan1,2,3, WANG Pengxin4, YANG Hua1,2,3, LIU Shaomin1,2,3 & WANG Jindi1,2,3 1. Research Center for Remote Sensing and GIS, school of Geography, beijing Normal university, beijing 100875, china 2. State Key Laboratory of Remote Sensing Science, beijing 100875, china 3. beijing Key Laboratory for Remote Sensing of environment and Digital Cities, beijing 100875, china 4. Department of Information Management, College of Information and Electronic Engineering, china Agricultural university, beijing 100083, china 1. Research Center for Remote Sensing and GIS School of Geography Beijing Normal University Beijing 100875 China 2. State Key Laboratory of Remote Sensing Science Beijing 100875 China 3. beijing Key Laboratory for Remote Sensing of environment and Digital Cities Beijing 100875 China 4. Department of Information Management College of Information and Electronic Engineering China Agricultural University Beijing 100083 China

This paper focuses on interpreting the different spatial relationships between NDVI and Ts, a triangular or a trapezoid, and on analyzing transformation conditions, the physical and ecological meanings of the vegetation index-surface temperature space as well. Further, we use the Tempera-ture-Vegetation Dryness Index (TVDI) to explain the existent meaning of a triangular space after NDVI reaches its saturated state by employing the relationships between NDVI, LAI and evapotranspiration. The specific relations between NDVI and Ts are useful for describing, validating and updating land surface models.

关键词： NDVI, land surface temperature, evapotranspiration, leave area index.

Boundary conditions for the bending of a piezoelectric beam

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Science china(Physics,Mechanics & Astronomy) 2008年第7期51卷 847-856页

作者： GAO Yang1, XU SiPeng2 & ZHAO BaoSheng3 1 College of Science, china Agricultural university, beijing 100083, china 2 College of Engineering, Ocean university of china, Qingdao 266071, china 3 school of Mechanical Engineering, university of Science and Technology Liaoning, Anshan 114044, china 1. College of Science China Agricultural University Beijing 100083 China 2. College of Engineering Ocean University of China Qingdao 266071 China 3. school of Mechanical Engineering University of Science and Technology Liaoning Anshan 114044 China

For beam bending in transversely isotropic piezoelectric media, the reciprocal theorem and the general solution of piezoelasticity are applied in a novel way to obtain the appropriate stress and mixed boundary conditions accurate to all orders for the beam of general edge geometry and loadings. By generalizing the method developed by Gregory and Wan, a set of necessary conditions on the edge-data for the existence of a rapidly decaying solution is established. The prescribed edge-data of the beam must satisfy these conditions in order that they could generate a decaying state within the beam. When stress and mixed conditions are imposed on the beam edge, these decaying state conditions for the case of bending deformation of piezoelectric beam are derived explicitly. They are then used for the correct formulation of boundary conditions for the beam theory solution (or the interior solution). Besides, an analytical solution of elastic beam is formulated to verify validity of our boundary conditions. For the stress data, our boundary conditions coincide with those obtained in conventional forms of beam theories. More importantly, the appropriate boundary conditions with two sets of mixed edge-data are obtained for the first time.

关键词： boundary conditions beam bending piezoelectric media decaying states regular states