宇宙膨胀中的能量问题

现有的标准宇宙模型是从爱因斯坦引力场方程中获得的,而不是从能量守恒角度考察的,但如果宇宙空间中存在暗能量,那么随着宇宙空间的膨胀,必然存在其他形式的能量和暗能量的转化问题.文中从相对论的质量和空间关系入手,研究了宇宙膨胀中的能量问题,得出宇宙膨胀同样必须遵守能量守恒定律,并在忽略非能量转化引起的宇宙膨胀条件下,考察了宇宙是否会无限膨胀的问题.     

哈勃参量限制宇宙学模型的优势

1998年对Ia型超新星的观测结果表明,宇宙是加速膨胀的,暗能量是可能导致宇宙加速膨胀的一个重要模型.宇宙学中状态方程w是了解暗能量本质的一个重要的物理量,我们在假定暗能量状态方程w=w(z)随红移变化的情况下,通过计算哈勃参量和光度距离,得到用光度距离来限制暗能量状态方程会有信息损失的结论,进一步比较哈勃参量和光度距离,发现哈勃参量在限制宇宙学模型和宇宙学参数方面比光度距离更有优势.     

震荡宇宙的热力学性质

震荡宇宙暗能量的状态方程是ω(a)=-cos(bln a).我们证明,该模型没有粒子视界和事件视界,解决了一致性问题的困扰.无论物质项怎样演化,暗能量总能追踪上与之一致,且不需要精细调整,并且暗能量刚好可以反映整个宇宙的热力学状态.我们也发现表观视界是个非常好的全息屏,可以作为保持热力学性质的边界.作为一个热力学整体,当前相变下,震荡宇宙的演化情况非常好.在表观视界以内,宇宙处于热力学平衡状态,也就是说热力学第一定律和第二定律都满足,并且物质项不影响此平衡状态.     

具有奇异物质与暗能量作用的宇宙模型

研究了具有奇异物质与暗能量作用的4维宇宙模型,获得了一些新的宇宙解,这些解可用于解释宇宙加速膨胀;采用天文观测数据确定宇宙中物质与暗能量比例,此外,还根据观测数据估计了宇宙年龄.     

ΛCDM宇宙中的弦圈演化

研究了∧CDM宇宙中的宇宙弦圈的演化，弦圈是否会从收缩相转入膨胀相将由暗能量的态方程参数确定．在当前的观测值范围内，现时宇宙不存在弦圈膨胀相，但在将来某一时刻t＊进入膨胀相．特别地，对于∧CDM宇宙t＊-t0=4．89Gyr。     

加速膨胀的宇宙

提出一个加速膨胀的宇宙模型.假设宇宙的外面仍然是一个物质的世界,称其为广义宇宙.宇宙就像一个吸积的黑洞.从广义宇宙的概念和宇宙是吸积的概念出发,说明宇宙是由于本身引力势能的原因在加速膨胀,不需要一种排斥能量或暗能量.     

宇宙发展的第三种可能:大撕裂

据英《新科学家》2003年3月8日报道 :新汉普郡达特茅斯大学的RobertCaldwell提出了宇宙发展的第三种可能性 ,即宇宙“大撕裂” ;而过去人们认为 ,宇宙或者是再次毁灭 ,或者是一直膨胀到无限稀薄的状态。宇宙是否发生大撕裂取决于撕开宇宙的神秘暗能量的性质。我们知道 ,宇宙正在加速膨胀。大多数物理学家认为这种加速很可能保持不变 ,或者加速在随时间减弱。但现在Caldwell提出了不同的观点 ,他认为暗能量可能引起的膨胀似乎增长得更加强烈 ,超乎人们的想象。暗能量是一种称为“假想能量”的神秘物质。在暗能量的影响下 ,失控的宇宙膨胀可…     

含三个实标量场的暗能量模型

近年来型超新星的观测结果表明宇宙在加速膨胀,并且驱动宇宙加速膨胀的暗能量占据宇宙总能量密度的2/3.目前,物理学家们已经根据实验观测结果提出了一些暗能量的模型.这些模型的最主要的区别是它们预测了暗能量的不同的态方程,近而给出了不同的宇宙论,但是它们的态方程参数叫都限制在-1<ω<-1/3的范围内.然而最近的观测数据似乎支持暗能量的态方程参数ω由之前的ω-1[1]演化到当今时代的ω<-1.在本文中我们考虑了一个含三个实标量场的暗能量模型来实现上述情况.在本文的讨论中我们均考虑ρm≤ρφ     

洛伦兹对称破缺与宇宙加速膨胀

1998年的超新星观测表明当今宇宙正在加速膨胀.暗能量是指宇宙加速膨胀的宇宙介质.正的宇宙学常数L是暗能量的重要候选者,但导致宇宙加速膨胀的原因并非L莫属.洛伦兹不变性是物理学最严格的对称性之一,然而所有的量子引力理论都预言了洛伦兹对称性的破缺.基于大尺度洛伦兹破缺(LargeScale Lorentz Violation, LSLV)的宇宙学模型,讨论了有效引力理论修正的Friedmann方程,由此可以得到,大尺度上的洛伦兹破缺和宇宙学常数项的综合效应会产生后期观测到的宇宙加速膨胀.     

彭加莱规范宇宙和状态诊断

利用状态诊断法,讨论了引力彭加莱规范理论的加速膨胀宇宙.发现该模型的状态参数演化具有一些与其他宇宙模型不一样的性质.     

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