引入风险价值约束的投资组合理论

风险价值(VaR)是近年来最为流行的风险管理工具．本文在无风险证券情形下，将VaR约束引入到传统的均值一方差投资组合理论中，考察了此时投资组合的有效前沿以及投资组合选择的变化，并指出了VaR约束对证券投资基金组合管理的意义．     

基金绩效评估模型及其在中国的应用

证券投资基金业绩评估是当今西方国家证券界非常时兴的一项工作.它主要包括评估与比较不同投资基金的投资表现,正确评价投资基金的回报及其承担的风险,并根据评估结果对投资基金进行业绩排序,投资基金业绩评估是评价投资基金管理人运作绩效并据以派发管理酬劳的依据,也是投资者     

证券投资基金绩效评估的模型与方法

对投资基金绩效评估理论研究的进展进行了系统的分析．从静态评估模型、动态评估模型和相关理论研究3个方面对证券投资基金绩效评估理论进行研究．综述了国内外基金绩效评估的现状并给出了证券投资基金评估理论的发展趋势．     

我国证券投资基金净值业绩与价格业绩特征的实证比较分析

分别采用基金的股价和净值计算基金的收益率,运用风险调整指数等国内外比较公认的绩效评估方法对我国证券投资基金进行了全面的实证研究和比较分析.结果表明,用净值计算的基金收益普遍优于同期市场基准组合收益,与基金股价计算的收益背离严重;对基金投资能力、基金经理选股能力和择时能力的实证分析得出了与价格法下基本对立的结论.     

证券投资基金中委托代理关系的风险研究

讨论了证券投资基金中投资人和基金管理人在委托代理关系中存在的风险问题，给出了考虑投资总收益作为单一可观测变量的委托代理模型，并进行了风险分析，提出了证券投资基金中风险防范的一些措施．     

VaR及投资灵敏度分析

VaR是一种处理非线性问题、概括证券组合市场风险量化的工具,它解决了传统风险定量化工具对于非线性的衍生金融资产适用性差、难以概括证券组合的市场风险缺点,有利于测量和管理金融风险.通过简要介绍VaR的概念、性质及特点的基础上,对VaR关于投资组合的灵敏度进行了深入分析,给出了VaR关于投资组合一阶、二阶导数的解析表达式,进而说明了VaR的凸性利用.     

风险资产组合均值-CVaR模型的算法分析

CVaR是指损失超过VaR的条件均值,反映了损失超过VaR时可能遭受的平均损失水平,它克服了VaR的非一致性、非凸性等不足.本文基于CVaR风险计量技术,分析了风险证券的投资收益率在服从正态分布下的风险资产组合均值-CVaR模型,给出了该风险资产组合有解的条件,以及在该条件满足下,最小均值-CVaR组合的投资比例解析形式和最小值.     

风险估值在沪深股市风险测量中的应用研究

以中国沪、深股市的风险测量为研究对象,收集了近5年的沪深股市每日指数收盘价;运用风险估值(VaR)常用的方差-协方差法和历史模拟法,通过对单一金融产品和资产组合的风险测量,论证了利用VaR技术计算股市风险的可行性.与传统的风险测量方法相比,方差-协方差法和历史模拟法在精确量化投资风险方面具有简捷易行的显著优势.利用指数加权移动平均方法考察了VaR对股市收益率波动性的描述能力,结果表明VaR计算值基本涵盖了绝大部分交易日的损失,有效降低了"幽灵效应",并且捕捉了波动的聚集性.从资产组合的VaR小于单个金融产品的VaR的结果看,VaR技术在股市风险测量上符合现代投资组合理论的基本思想.     

引入VaR和ES约束的投资组合理论实证

针对机构投资者控制市场风险的需要，将VaR(风险价值)和ES(期望不足)约束引入到均值一方差投资组合理论中，并利用中国A股1995～2002年的数据，实证了VaR和ES约束对组合绩效的影响．实证结果表明：对于有无风险约束、风险约束类型(VaR对ES)、置信水平高低以及约束值的大小这4项选择(任选1项而其他3项任其变化)，存在风险约束或ES约束或置信水平高或约束值小时组合的风险调整绩效均显著好于相应组合的风险调整绩效，而组合绩效表现则完全相反。     

我国证券投资基金市场存在问题及对策

证券投资基金是证券市场中重要的投资力量，是证券市场稳定和发展的基石，也是证券市场主要投资品种之一。随着我国经济的发展，企业筹资对证券市场的依赖性将日趋增强，证券投资基金在我国证券市场的作用将日趋增大。本通过我国证券投资基金与发达国家比较分析，提出我国证券投资基金存在的问题和差距，以及解决问题的对策。     

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.     

Features of Women's language

Language is a means of verbal communication. People use language to communicate with each other. In the society, no two speakers are exactly alike in the way of speaking. Some differences are due to age, gender, statue and personality. Above all, gender is one of the obvious reasons. The writer of this paper tries to describe the features of women＇s language from these perspectives： pronunciation, intonation, diction, subjects, grammar and discourse. From the discussion of the features of women＇s language, more attention should be paid to language use in social context. What＇s more, the linguistic phenomena in a speaking community can be understood more thoroughly.     

Wuhan University Journal of Natural Sciences TOTAL CONTENTS

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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.     

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     

Jane Eyre——A Feminist In The 19th Century

In the 19th century the society was controlled by men, and women were just appendants of them, they had not any rights and freedom. But Jane was an exception, she showed some characteristics of early feminist. Jane showed her characteristics of feminism in three aspects: rebellion, equality, and independence. These characteristics were helpful to her success, and feminism is the only way out for women of that time.     

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.     

Editorial note for the special topic on ＂Nanopore Analysis＂

The concept of nanopore analysis, using the pore-forming protein a-hemolysin to detect individual nucleic acids at a single-molecule level, was first proposed in 1996. Over the past two decades, tremendous progress has been made in the nanopore field, and nanopore analysis has become a label-free and high-throughput method for probing bio- molecules and other analytes with single-molecule sensi- tivity, especially holds the promising for ＂third generation＂ DNA sequencing. However, challenges still remain in the experimental strategies and the design of whole nanopore-based instruments. Here, we proudly present a special topic dedicated to the topic of ＂Nanopore Analysis＂, with 8 reviews/articles providing up to date coverage of the experimental strategies, theoretical calcu- lations and simulations, and instrument design. Reviews and articles on the experimental strategies cover control of DNA partitioning into a nanopore, detection of target DNA, and the advantages of nanopore-based DNA sequencing. The theoretical calculations and simulations discuss the translocation behavior of DNA, and an inte- grated measurement system and data analysis software are presented for instrument design.     

Effects of climate change on biodiversity

1 Rise of studies on climate change＇s effects on biodiversity
Until the 1980s, climate change and biodiversity were studied as two independent disciplines for more than a century. In 1992, the Ecological Society of America＇s annual report named climate change, biodiversity, and the sustainable ecological system as the three major global environmental issues of the twenty-first century [1].     

Discussing the Expansive Learning in Modern Organizations

<正>1 Introduction Endeavours on learning methods have long occupied the mind spaces of scholars and there have been theories abound on how people learn and in what way organisations can use some of the knowledge gained in the art of learning to maximise human productivity.While the theories by themselves are not solutions to problems,they are steps of inquiry that provide us with interesting perspectives that we can use to extend our knowledge of the dimensions of learning.This paper is an exploratory work on the theories postulated by three notable scholars including Zimmerman