检索结果-南通市图书馆

Science china Chemistry 2009年第8期52卷 1097-1103页

作者： LI XiangJun,ZHENG Na,HU ZhongBo & YUAN ZhuoBin College of Chemistry and Chemical Engineering,graduate university of chinese academy of sciences,Beijing 100049,china 1. College of Chemistry and Chemical Engineering Graduate University of Chinese Academy of Sciences Beijing 100049 China

A series of Nd1-yDyyFe11-xTiMx(M=Mo,Si) alloys have been prepared by arc melting and studied by X-ray diffraction and neutron *** samples are found to crystallize in the ThMn12-type *** lattice parameters a and c and unit cell volume V of Nd0.5Dy0.5Fe11-xTiMox alloys increase linearly with increasing content of Mo(x),while the lattice parameters a and c and unit cell volume V of Nd0.5Dy0.5Fe11-xTiSix alloys decrease linearly with increasing content of Si(x).In NdyDy1-yFe11-xTiMx(M=Mo,Si) compounds,Ti and Mo atoms preferentially occupy the 8i sites and Si atoms preferentially occupy the 8j and 8f *** measurements show that the substitution of Fe by either Mo or Si leads to a decrease in the Curie temperature.

关键词： rare earth-transition metal compounds crystal structure X-ray diffraction neutron diffraction

A one-dimensional heat transfer model of the Antarctic Ice Sheet and modeling of snow temperatures at Dome A, the summit of Antarctic Plateau

在线全文

学校读者我要写书评

暂无评论

Science china Earth sciences 2010年第5期53卷 763-772页

作者： CHEN BaiLian1,3. ZHANG RenHe2, SUN ShuFen1, BIAN LinGen2, XIAO CunDe4,2 & ZHANG TingJun5 1 Institute of Atmospheric Physics, chinese academy of sciences, Beijing 100029,{3. 2 chinese academy of Meteorological sciences, Beijing 100081,{3. 3.graduate university of chinese academy of sciences, Beijing 100049,{3. 4 Cold and Arid Regions Environmental and Engineering Research Institute, chinese academy of sciences, Lanzhou 73.000,{3. 5 The National Snow and Ice Data Center, university of Colorado, Boulder, CO 803.9-0449, USA 1. Institute of Atmospheric Physics Chinese Academy of Sciences Beijing 100029 China3. Graduate University of Chinese Academy of Sciences Beijing 100049 China2. Chinese Academy of Meteorological Sciences Beijing 100081 China4. Cold and Arid Regions Environmental and Engineering Research Institute Chinese Academy of Sciences Lanzhou 730000 China5. The National Snow and Ice Data Center University of Colorado Boulder CO 80309-0449 USA

A vertical one-dimensional numerical model for heat transferring within the near-surface snow layer of the Antarctic Ice Sheet was developed based on simplified parameterizations of associated physical processes for the atmosphere, radiation, and snow/ice systems. Using the meteorological data of an automatic weather station (AWS) at Dome A (80°22′S, 70°22′E), we applied the model to simulate the seasonal temperature variation within a depth of 20 m. Comparison of modeled results with observed snow temperatures at 4 measurement depths (0.1, 1, 3. 10 m) shows good agreement and consistent seasonal variations. The model results reveal the vertical temperature structure within the near-surface snow layer and its seasonal variance with more details than those by limited measurements. Analyses on the model outputs of the surface energy fluxes show that: 1) the surface energy balance at Dome A is characterized by the compensation between negative net radiation and the positive sensible fluxes, and 2) the sensible heat is on average transported from the atmosphere to the snow, and has an evident increase in spring. The results are considered well representative for the highest interior Antarctic Plateau.

关键词： Antarctic Ice Sheet near-surface layer energy transfer numerical model

Zircon SHRIMP U-Pb geochronology and petrogenesis of the plagiogranites from the Lagkor Lake ophiolite,Gerze,Tibet,china

在线全文

学校读者我要写书评

暂无评论

chinese Science Bulletin 2007年第5期52卷 651-659页

作者： ZHANG YuXiu1,2, ZHANG KaiJun1,3. LI Bing1,2, WANG Yang1,2, WEI QingGuo1,2 & TANG XianChun1,2 1 Key Laboratory of Marginal Sea Geology, Guangzhou Institute of Geochemistry, chinese academy of sciences, Guangzhou 510640,{3. 2 graduate university, chinese academy of sciences, Beijing 10003.,{3. 3.Department of Earth sciences, Nanjing university, Nanjing 210093.{3. Key Laboratory of Marginal Sea Geology Guangzhou Institute of GeochemistryChinese Academy of Sciences Guangzhou 510640 China

地关系与 petrographical 一起， petrological ，和 geochemicalcharacteristics ，和锆石人口，显示从在 Bangong-Nujiang 缝术地区的 Lagkor Lakeophiolite 的 plagiogranites (～ Gerze 县的 20 km 南方，中央西藏，中国)，由在海洋的外壳的运输期间的可锻的砍源于含水的斑粝岩的 anatexis 。因此，这种 plagiogranite 比传播海洋的外壳晚对或很少同时代。锆石虾 166 ±使 2.5 妈变老因为 plagiogranites 显示海洋的盆在中间的侏罗记在 Bangong-Nujiang 地区的西方的部分存在。

关键词：西藏改则县拉果错湖泊蛇绿岩斜长花岗岩锆SHRIMP U-Pb地质年代岩石成因

BIFURCATION OF THE NORTH EQUATORIAL CURRENT DERIVED FROM ALTIMETRY IN THE PACIFIC OCEAN

在线全文

学校读者我要写书评

暂无评论

Journal of Hydrodynamics 2006年第5期18卷 620-626页

作者： WANG Qing-ye HU Dun-xin Institute of Oceanology Chinese Academy of Sciences Qingdao 266071 China graduate School of the chinese academy of {3. Beijing 100039 China

The gridded （1/3.＊1/3.） altimetry data from October 1992 through December 2004 were analyzed to study the seasonal and interannual variabilities of the bifurcation of the North Equatorial Current （NEC） at the surface in the western North Pacific Ocean. Calculations show that on annual average the bifurcation occurs at about 13.4°N at the surface. The geostrophic flow derived from Sea Surface Height （SSH） data shows that the southernmost latitude of the NEC bifurcation at the surface is about 12.9°N in June and the northernmost latitude is about 14.1°N in December. Correlation analyses between the bifurcation latitude and the Southern Oscillation Index （SOl） suggest that the bifurcation latitude is highly correlated with the E1 Nino/Southern Oscillation （ENSO） events. During the E1 Nino years the bifurcation of the NEC takes place at higher latitudes and vice versa.

关键词： bifurcation of the North Equatorial Current altimetry data Pacific Ocean North Equatorial Current (NEC),E1 Nino/Southern Oscillation (ENSO) events

The Koppelman-Leray formula on complex Finsler manifolds

在线全文

学校读者我要写书评

暂无评论

Science china Mathematics 2005年第6期48卷 847-863页

作者： QIU Chunhui & ZHONG Tongde School of Mathematical sciences, Xiamen university, Xiamen 3.1005, china {3. of Mathematics and System sciences, chinese {3. of sciences, Beijing 100080, china 1. School of Mathematical sciences Xiamen University 361005 Xiamen China 2. academy of Mathematics and System sciences Chinese Academy of Sciences 100080 Beijing China

By means of the invariant integral kernel (the Berndtsson kernel), the complex Finsler metric and the non-linear connection associated with the Chern-Finsler connection to research into the integral representation theory on complex Finsler manifolds, theKoppelman and Koppelman-Leray formulas are obtained, and the - -equations are solved.

关键词： complex Finsler manifold, Chern-Finsler connection, invariant integral kernel, Koppelman-Lerayformulas, - -equation.

The establishment of crystal position look-up table for positron emission tomography with block detectors

在线全文

学校读者我要写书评

暂无评论

Science china(Technological sciences) 2009年第8期52卷 2418-2423页

作者： CHAI Pei1,2 & SHAN BaoCi1 1 Key Laboratory of Nuclear Analytical Techniques, Institute of High Energy Physics, chinese academy of sciences, Beijing 100049,{3. 2 graduate university of chinese academy of sciences, Beijing 100049,{3. Key Laboratory of Nuclear Analytical Techniques Institute of High Energy Physics Chinese Academy of Sciences Beijing 100049 China graduate university of chinese academy of sciences Beijing 100049 China

A method has been developed to establish the crystal position look-up table for positron emission tomography with block detectors. It is based on the principle that the counts in crystal position histogram obey the Gaussian mixture model (GMM). This method has taken full consideration of the characteristics of the GMM and the detector itself. The experimental results have proved that it is simple, reliable, and universal.

关键词： positron emission tomography position look-up table 2-D position histogram

Impact of land-use change on hydrological processes in the Maying River basin, china

在线全文

学校读者我要写书评

暂无评论

Science china Earth sciences 2006年第10期49卷 1098-1110页

作者： WANG Genxu1,3. ZHANG Yu2, LIU Guimin2 & CHEN Lin3.1. Institute of Mountain Hazards and Environment, chinese academy of sciences, Chengdu 610041,{3. 2. Cold and Arid Regions Environmental and Engineering Research Institute, chinese academy of sciences, Lanzhou 73.000,{3. 3. Resource and Environment School, Lanzhou university, Lanzhou 73.000,{3. 1. Institute of Mountain Hazards and Environment Chinese Academy of Sciences Chengdu 610041 China 3. Resource and Environment School Lanzhou University Lanzhou 730000 China 2. Cold and Arid Regions Environmental and Engineering Research Institute Chinese Academy of Sciences Lanzhou 730000 China

Since the 1960s, dramatic changes have taken place in land-use patterns characterized by the persistent expansion of cultivated land and a continuous decrease in natural woodland and grassland in the arid inland river basins of china. It is very important to assess the effects of such land-use changes on the hydrological processes so vital for water resource management and sustainable development on the catchment scale. The Maying River catchment, a typical arid inland watershed located in the middle of the Hexi Corridor in northwest china, was the site chosen to investigate the hydrological responses to land-use changes. The annual runoff, base flow, maximum peak flow, and typical seasonal runoff in both spring and autumn flood periods were selected as the variables in the hydrological processes. Statistical-trend analysis and curvilinear regression were utilized to detect the trends in hydrological variables while eliminating the climatic influence. The relationship between cultivated land-use and hydrological variables was analyzed based on four periods of land-use variation data collected since 1965. A runoff model was established composed of two factors, i.e., cultivated land use and precipitation. The impact of land use changes, especially in the large ar- eas of upstream woodland and grassland turned into cultivated lands since 1967, has resulted in a mean annual runoff decrease of 28.12%, a base flow decline of 3..3.%, a drop in the maximum peak discharge of 3..77%, and mean discharge decreases in spring and autumn of 3..05% and 24.87% respectively, of which the contribution of cultivated land expansion to the influence of annual runoff amounts to 77%-80%, with the contribution to the influence of spring discharge being 73.-81%, and that to the influence of base flow reaching 62%-65%. Thus, a rational regulation policy of land use patterns is vitally important to the sustainable use of water resources and the proper development of the entire catchment.

关键词： land-use change, arid inland river catchment, hydrological process, impact, Maying River.

Testing local realism in P → VV decays

在线全文

学校读者我要写书评

暂无评论

Science china(Physics,Mechanics & Astronomy) 2010年第5期53卷 870-875页

作者： LI JunLi1 & QIAO CongFeng1,2 1Department of Physics,graduate university of chinese academy of sciences,Beijing 100049,china 2Theoretical Physics Center for Science Facilities(TPCSF),chinese {3. of sciences,Beijing 100049,china 1. Department of Physics Graduate University of Chinese Academy of Sciences Beijing 100049 China2. Theoretical Physics Center for Science Facilities (TPCSF) Chinese Academy of Sciences Beijing 100049 China

It was found that the vector meson pair from the pseudoscalar decays can form an entangled *** this work we give out detailed explanations on the polarization correlation of the two entangled vector *** is demonstrated that an experimental test of the Clauser-Horne inequality can be carried out through measuring the azimuthal distribution of four pseudoscalars in the cascade decay ηc→ VV →(PP)(PP),and the measurement of this process is feasible with the current running experiments in tau-charm ***,a brief discussion on the polarization correlation of the two vector mesons from B → VV decays is also presented.

关键词： nonlocality test high energy experiment meson decays

Existence of unbiased estimate of regression parameters in simple linear EV models

在线全文

学校读者我要写书评

暂无评论

Science china Mathematics 2005年第7期48卷 915-928页

作者： LIU Jixue & CHEN Xiru Department of Statistics and Finance, university of Science and Technology of china, Hefei 23.026, china Department of Mathematics, {3. School of chinese academy of sciences, Beijing 100049, china Department of Statistics and Finance University of Science and Technology of China Hefei 230026 China Department of Mathematics Graduate School Chinese Academy of Sciences Beijing 100049 China

It is well known that for one-dimensional normal EV regression model X = x+ u,Y =α+βx+e, where x, u, e are mutually independent normal variables and Eu=Ee=0, the regression parameters a and β are not identifiable without some restriction imposed on the parameters. This paper discusses the problem of existence of unbiased estimate for a and β under some restrictions commonly used in practice. It is proved that the unbiased estimate does not exist under many such restrictions. We also point out one important case in which the unbiased estimates of a and β exist, and the form of the MVUE of a and β are also given.

关键词： EV regression model unbiased estimate identiflability.

IMPLICITIZATION USING UNIVARIATE RESULTANTS

在线全文

学校读者我要写书评

暂无评论

Journal of Systems Science & Complexity 2010年第4期23卷 804-814页

作者： Liyong SHEN Chunming YUAN School of Mathematical sciences Graduate University Chinese Academy of Sciences Beijing 100049 China Key Laboratory of Mathematics Mechanization Institute of Systems Science Academy of Mathematics and Systems Science Chinese Academy of Sciences Beijing 100190 China

Among several implicitization methods, the method based on resultant computation is a simple and direct one, but it often brings extraneous factors which are difficult to remove. This paper studies a class of rational space curves and rational surfaces by implicitization with univaxiate resultant computations. This method is more efficient than the other algorithms in finding implicit equations for this class of rational curves and surfaces.

关键词： Implicitization rational space curves rational surfaces resultants.