射线截曲率有负下界且大体积增长的开流形

研究一类具有Ric_M≥-(n-1)c和大体积增长的完备非紧黎曼流形.证明在射线截面曲率有负下界以及流形M上测地球与欧氏空间上单位球的体积增长相差不大的条件下,流形M微分同胚于R~n.将曲率条件及体积增长条件改进,所得结果是文献(Xia C.London Math Soc,2002,34(2):229-235.)中相关结论的推广.     

渐进非负曲率流形的Poisson方程解的估计

M为完备非紧的K(a)hler流形有非负的全纯双截曲率和极大体积增长且数量曲率二次退化的条件下,可以通过研究Poisson方程来解Poincaré-Lelong方程,并应用Poinicaré-Lelong方程研究和分析流形M的几何性质,文章主要研究了完备非紧非抛物的有渐近非负曲率n维K(a)hler流形M的Poisso...     

次大体积增长条件下非紧黎曼流形的拓扑结构

研究一类具有非负Ricci曲率和次大体积增长的完备非紧的黎曼流形,利用Toponogov型比较定理和临界点理论,证明在临界半径有正下界以及函数(vol[B(p,r)])/(I_n(r)r~(n-1))是单调递减条件下,流形M微分同胚于R~n,从而丰富了前人关于这类流形的研究结果.     

爱因斯坦卷积流形的不存在性问题

讨论了带有完备非紧基流形且Ricci平坦的爱因斯坦卷积流形的存在性问题.证明了若基流形上总数量曲率非正或卷积函数有界,且体积增长满足一定条件,则不存在非平凡的Ricci平坦的爱因斯坦卷积流形.     

一个关于Kahler平坦的定理

文章主要研究完备非紧的Kahler流形,得到2个定理.首先在Kahler流形有非负有界的全纯双截曲率和平均数量曲率满足一定的条件下得到关于数量曲率的一个积分估计和流形在不同时刻度量条件下体积保持极大增长的条件;其次在Kahler流形有非负的全纯双截曲率,Ricci曲率有界和平均数量曲率满足一定条件下得到它双全纯等价于平坦的Kahler流形的结果.     

流形上的调和函数空间

本文主要研究截曲率渐近非负完备的流形上的函数理论,通过证明此流形上的体积比较定理和Poincare不等式,得到了此流形上具有多项式增长的调和函数空间的维数估计.     

次大体积增长的流形的曲率与拓扑研究

该文研究了一类具有非负Ricci曲率和α(α∈[0,2])次衰减截曲率下界的完备非紧黎曼流形.利用Toponogov型比较定理和临界点理论,证明了该流形在一定次大体积增长条件下具有有限拓扑型,从而推广了J.Sha、Z.Shen和C.Xia的关于这类流形的一系列结果.     

非负曲率的完备黎曼流形上的平行射线

讨论了具非负典率的完备非紧黎曼流形M上平行射线的性质,证明了此时两平行射线对应于M上的同一个Busemann函数.同时证明了具完全平行性质的非负曲率的完备非紧黎曼流形M=Rk×S,其中S为核心.     

具有渐近非负Ricci曲率完备非紧的黎曼流形

研究了一类具有渐近非负Ricci曲率完备非紧的n维黎曼流形,利用推广的Excess函数和Busemann函数,证明了具有渐近非负Ricci曲率完备非紧的n维黎曼流形在k_p(r)≥-C/(1+r)α和大体积增长的条件下具有有限拓扑型,从而推广了已有的一系列结果。     

非负里奇曲率的完备极值射影Blaschke流形

本文在里奇曲率非负的假定下,解决了李-赵关于极值射影Blaschke流形的一个猜想,得到:若M为非负里奇曲率的n维完备极值射影Blaschke流形,则M等距于En/Γ,其中Γ为自由、纯不连续作用在M上的等距离散子群,M～为M的万有覆盖流形.     

An Index mechanism for multi-scale view in spatial databases

There are numerous geometric objects stored in the spatial databases. An importance function in a spatial database is that users can browse the geometric objects as a map efficiently. Thus the spatial database should display the geometric objects users concern about swiftly onto the display window. This process includes two operations:retrieve data from database and then draw them onto screen. Accordingly, to improve the efficiency, we should try to reduce time of both retrieving object and displaying them. The former can be achieved with the aid of spatial index such as R-tree, the latter require to simplify the objects. Simplification means that objects are shown with sufficient but not with unnecessary detail which depend on the scale of browse. So the major problem is how to retrieve data at different detail level efficiently. This paper introduces the implementation of a multi-scale index in the spatial database SISP (Spatial Information Shared Platform) which is generalized from R-tree. The difference between the generalization and the R-tree lies on two facets: One is that every node and geometric object in the generalization is assigned with a importance value which denote the importance of them, and every vertex in the objects are assigned with a importance value,too. The importance value can be use to decide which data should be retrieve from disk in a query. The other difference is that geometric objects in the generalization are divided into one or more sub-blocks, and vertexes are total ordered by their importance value. With the help of the generalized R-tree, one can easily retrieve data at different detail levels.Some experiments are performed on real-life data to evaluate the performance of solutions that separately use normal spatial index and multi-scale spatial index. The results show that the solution using multi-scale index in SISP is satisfying.     

Characterization of Ordovician carbonate reservoirs, southeastern Saskatchewan, Canada

The discovery of the prolific Ordovician Red River reservoirs in 1995 in southeastern Saskatchewan was the catalyst for extensive exploration activity which resulted in the discovery of more than 15 new Red River pools. The best yields of Red River production to date have been from dolomite reservoirs. Understanding the processes of dolomitization is, therefore, crucial for the prediction of the connectivity, spatial distribution and heterogeneity of dolomite reservoirs.The Red River reservoirs in the Midale area consist of 3～4 thin dolomitized zones, with a total thickness of about 20 m, which occur at the top of the Yeoman Formation. Two types of replacement dolomite were recognized in the Red River reservoir: dolomitized burrow infills and dolomitized host matrix. The spatial distribution of dolomite suggests that burrowing organisms played an important role in facilitating the fluid flow in the backfilled sediments. This resulted in penecontemporaneous dolomitization of burrow infills by normal seawater. The dolomite in the host matrix is interpreted as having occurred at shallow burial by evaporitic seawater during precipitation of Lake Almar anhydrite that immediately overlies the Yeoman Formation. However, the low δ18O values of dolomited burrow infills (-5.9‰～ -7.8‰, PDB) and matrix dolomites (-6.6‰～ -8.1‰, avg. -7.4‰ PDB) compared to the estimated values for the late Ordovician marine dolomite could be attributed to modification and alteration of dolomite at higher temperatures during deeper burial, which could also be responsible for its 87Sr/86Sr ratios (0.7084～0.7088) that are higher than suggested for the late Ordovician seawaters (0.7078～0.7080). The trace amounts of saddle dolomite cement in the Red River carbonates are probably related to "cannibalization" of earlier replacement dolomite during the chemical compaction.     

A computer generator for randomly layered structures

AcomputergeneratorforrandomlylayeredstructuresYUJia shun1,2,HEZhen hua2(1.TheInstituteofGeologicalandNuclearSciences,NewZealand;2.StateKeyLaboratoryofOilandGasReservoirGeologyandExploitation,ChengduUniversityofTechnology,China)Abstract:Analgorithmisintrod…     

Perspherical Approaches for Electrons in Atoms and Charged Excitons in Quantum Wells

Instead of following Fock’s expansion,we solve the Schrodinger equation for some quantum mechanical manybody systems such as electrons in atoms and charged excitons in quantum wells in a similar way in hyperspherical coordinates by expanding the wave functions into orthonormal complete basis sets of the hyperspherical hannonics(HHs)of hyperangles and generalized Laguerre polynomials(GLPs)of the hyperradius.This leads the equation to     

Advances in broadband wireless communications under high-mobility scenarios

Future mobile communication systems aim at providing very high data transmission rates, even in high-mobility scenarios such as high-speed wheel-track trains, maglev trains, highway vehicles, airplanes, guided missiles or spacecraft. A particularly important commercial application is the strong and increasing worldwide demand for high- speed broadband wireless communications （up to 574.8 km/ h test speeds or 380 km/h commercial speeds） in railways, providing data, voice and video services for applications such as onboard entertainment services to passengers, train control, train dispatch, train sensor status handling and sur- veillance. In such high-mobility scenarios, there are a number of communication challenges, including fast hand- over, location updating, high-speed channel modeling, estimation and equalization, anti-Doppler spreading tech- niques, fast power control, and dedicated network architec- ture. Because signal transmission in very high-speed scenarios will inevitably experience serious deterioration, it is imperative to develop key broadband mobile communi- cation techniques for such high-speed vehicles.     

Wuhan University Journal of Natural Sciences TOTAL CONTENTS

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海南岛地体及其毗邻陆缘晚中生代—新生代古地磁研究和构造演化

本文叙述了对海南岛及其毗邻大陆边缘白垩纪到第四纪地层岩石进行古地磁研究的全部工作过程。通过分析岩石中剩余磁矢量的磁偏角及磁倾角的变化,提出海南岛白垩纪以来经历的构造演化模式如下:早期伴随顺时针旋转而向南迁移,后期伴随逆时针转动并向北运移。联系该地区及邻区的地质、地球物理资料,对海南岛上述的构造地体运动提出以下认识:北部湾内早期有一拉张作用,主要是该作用使湾内地壳显著伸长减薄,形成北部湾盆地。从而导致了海南岛的早期构造运动,而海南岛后期的构造运动则主要是受南海海底扩张的影响。海南地体运动规律的阐明对于了解北部湾油气盆地的形成演化有重要的理论和实际意义。     

Scale-based spatial data model for GIS

Being the primary media of geographical information and the elementary objects manipulated, almost all of maps adopt the layer-based model to represent geographic information in the existent GIS. However, it is difficult to extend the map represented in layer-based model. Furthermore, in Web-Based GIS, It is slow to transmit the spatial data for map viewing. In this paper, for solving the questions above, we have proposed a new method for representing the spatial data. That is scale-based model. In this model we represent maps in three levels: scale-view, block, and spatial object, and organize the maps in a set of map layers, named Scale-View, which associates some given scales.Lastly, a prototype Web-Based GIS using the proposed spatial data representation is described briefly.     

Exciton Seebeck in Molecular Systems

Various applications relevant to the exciton dynamics,such as the organic solar cell,the large-area organic light-emitting diodes and the thermoelectricity,are operating under temperature gradient.The potential abnormal behavior of the exicton dynamics driven by the temperature difference may affect the efficiency and performance of the corresponding devices.In the above situations,the exciton dynamics under temperature difference is mixed with     

Achieving Unusual States of Matter Under High Pressure

The elongation method,originally proposed by Imamura was further developed for many years in our group.As a method towards O(N)with high efficiency and high accuracy for any dimensional systems.This treatment designed for one-dimensional(ID)polymers is now available for three-dimensional(3D)systems,but geometry optimization is now possible only for 1D-systems.As an approach toward post-Hartree-Fock,it was also extended to