基于复合极值模型的暴雨重现期研究--以川东北地区为例

利用川东北地区29个气象观测站1960—2010年的逐年暴雨日数和暴雨日降水量资料,根据复合极值理论,建立了泊松-广义帕累托复合极值模型,利用该模型对暴雨的重现周期进行了分析.研究结果表明:1)该地区暴雨发生日数序列服从泊松分布,暴雨日降水量序列服从广义帕累托分布;2)复合极值模型不仅综合考虑了暴雨的多要素特征,而且拟合效果良好;3)在当前气候条件下,该地区50年一遇和100年一遇的暴雨日降水量空间分布特征基本一致,总体上呈现山地降水多,平地降水少的特点.     

应用GPD估计国内商业银行操作风险的实证研究

利用从媒体公开报导中搜集的国内商业银行操作风险损失事件,应用广义帕累托分布对损失超出量分布进行拟合,并进行KS检验,进而得到操作风险重现水平。     

Mlinex损失函数下反向帕累托分布形状参数的Bayes估计

文章研究了Mlinex损失函数下反向帕累托分布的参数估计问题。在已知反向帕累托分布位置参数的情况下,给出形状参数的五种估计方法：极大似然估计、最大后验估计、经典Bayes估计、多层Bayes估计、E-Bayes估计,并推导出相应估计方法下的具体表达式。利用MC方法在R软件下进行数值模拟,对比模拟数据确定了参数估计的最优环境,并验证了估计方法的合理性和估计结果的准确性与稳健性,得到了E-Bayes估计为最优估计方法的结论;最后利用最优估计方法对实例进行数据拟合,确定了新疆县市级城市的人均城市道路面积可以利用反向帕累托分布近似拟合,并结合最终数据给出了相应的数据分析。     

广义指数-帕累托(Ⅳ)混合模型

有限多个分布的混合模型在经济学、可靠性分析等方面应用广泛.基于实践中的许多观测数据可能取自于两个或更多的分布总体,构建了广义指数-帕累托(Ⅳ)混合模型,并研究混合模型的相关统计性质.讨论了模型中各参数对密度函数的影响,给出了模型的风险函数的具体计算公式及参数对风险函数的影响.给出了混合模型前四阶矩的解析表达式,进而得出峰度和偏度等相关统计量的计算公式.给出了平均偏差的解析表达式,并且使用EM算法给出混合模型的参数估计.实证方面,使用丹麦火险数据做拟合分析,比较了7个模型的拟合效果.结果显示,广义指数-帕累托(Ⅳ)混合模型拟合效果最优.     

抽水蓄能机组导叶关闭策略优化方法研究

为了解决水电站大波动过渡过程运行安全问题,综合考虑蜗壳水击压力极值和转速上升极值两个目标,建立了抽水蓄能机组导叶关闭策略多目标优化模型,提出了基于改进多目标引力搜索算法(IMOGSA)的抽水蓄能机组导叶关闭策略优化方法.利用该方法得到包含蜗壳水击压力极值和转速上升峰值的帕累托非劣解集,采用模糊满意度评价法在帕累托非劣解集中选出兼容性最好的解,并与多目标粒子群算法进行对比,结果表明利用IMOGSA优选的导叶关闭策略能有效提高对抽水蓄能机组水泵断电工况的控制水平.     

关于上海股市指数日收益尾部的实证研究

基于极值理论（EVT）方法,利用平均超出量函数,结合判断阈值u改变引起参数估计量的变化,找出合适的阈值,建立了上海股市综合指数极端日收益率的广义帕累托模型（GPD）。     

采用广义极值分布的公路桥梁车辆荷载效应极值预测

为改善对汽车荷载效应样本的统计拟合,建立随机变量的均值、偏差系数、变差系数与广义极值分布的形状参数、尺度参数、位置参数的一一对应关系.采用广义极值分布适线法拟合车辆荷载效应区间最大值样本的概率分布.首先,以矩法计算样本均值和变差系数,假定偏差系数,计算广义极值分布的形状参数、尺度参数和位置参数;然后,将样本点和理论频率曲线绘制到海森机率格纸上,按照理论频率曲线与实测数据拟合得最好的原则选定统计参数,并确定汽车荷载效应样本的理论频率曲线;最后,采用经典极值理论建立设计基准期荷载效应最大值分布.采用某公路一个车道39周的动态称重系统(WIM)数据,建立车辆荷载效应模型,并与最大似然法结果进行比较.结果表明:文中方法更能反映样本分布曲线尾部特征,且实际最大基准期车辆荷载效应远大于现行公路-Ⅰ级汽车荷载效应.     

基于极值理论和Copula的灾难风险建模研究

利用极值理论中的广义极值分布(GEVD)对单一灾难事件的特性进行刻画，然后利用Copula函数把不同的灾难风险组合起来，构造其联合分布，并提出了适合模型的蒙特卡罗算法．最后利用实例说明了GEVD-Copula组合建模的应用，得出了有益结论。     

重车荷载作用的简支梁桥荷载效应极值预测

为了准确预测重车荷载作用的简支梁桥荷载效应极值,充分考虑了过桥重车的随机性特征和不同重车荷载事件出现的概率,基于经典极值理论,提出了不同重车荷载事件的组合广义极值分布(CGEV)极值预测方法,通过数学推导和数值算例证明了该方法的合理性.同时,以一座简支梁桥为工程背景,采用CGEV方法预测简支梁桥在重车荷载作用下的荷载效应极值.研究结果表明:采用CGEV方法预测桥梁的车致荷载效应极值精度较高且工程应用方便,最大预测误差为4%,而传统混合数据的单一广义极值分布(SGEV)的桥梁车致荷载效应极值预测误差最小为36.6%;简支梁桥的车致荷载效应可以基于同时过桥的重车数量划分荷载事件类型,其车致荷载效应极值主要受2辆重车过桥事件控制;为了保证简支梁桥的安全运营,建造时应有适当的安全储备,管养时应结合实际情况对过桥重车采取相应的限载措施.     

GPD在地球化学元素异常识别中的应用

根据地球化学元素异常含量分布规律和极值理论(EVT)的广义帕累托分布(GPD)规律具有一致性,采用GPD分布建立了地球化学元素含量异常提取模型,并对模型中的尺度参数、形状参数以及阈值估计方法进行了选取和探讨,研究地球化学元素含量异常分布规律及其找矿标志。在此基础上设计了一种修正阈值函数法。将构建的异常提取方法应用于湖北鸡冠咀铜金矿区地球化学元素含量异常提取,结果显示构建的模型能够有效提取地球化学元素含量异常值,所提取的元素含量异常区域与实际矿体分布趋势一致,得出地球化学找矿标志,圈定出新的找矿靶区。     

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