Estimation of the marginal expected shortfall under asymptotic independence

We study the asymptotic behavior of the marginal expected shortfall when the two random variables are asymptotic independent but positively associated, which is modeled by the so-called tail dependent coefficient. We construct an estimator of the marginal expected shortfall, which is shown to be asymptotically normal. The finite sample performance of the estimator is investigated in a small simulation study. The method is also applied to estimate the expected amount of rainfall at a weather station given that there is a once every 100 years rainfall at another weather station nearby.     

Beyond tail median and conditional tail expectation: Extreme risk estimation using tail Lp-optimization

The conditional tail expectation (CTE) is an indicator of tail behavior that takes into account both the frequency and magnitude of a tail event. However, the asymptotic normality of its empirical estimator requires that the underlying distribution possess a finite variance; this can be a strong restriction in actuarial and financial applications. A valuable alternative is the median shortfall (MS), although it only gives information about the frequency of a tail event. We construct a class of tail L^p-medians encompassing the MS and CTE. For p in (1,2), a tail L^p-median depends on both the frequency and magnitude of tail events, and its empirical estimator is, within the range of the data, asymptotically normal under a condition weaker than a finite variance. We extrapolate this estimator and another technique to extreme levels using the heavy-tailed framework. The estimators are showcased on a simulation study and on real fire insurance data.     

On a Dualization of Graphical Gaussian Models: A Correction Note

Abstract.  We correct two proofs concerning Markov properties for graphs representing marginal independence relations.     

两个随机变量的独立性和相关性之比较

从随机变量的独立性和相关性概念出发,运用反例和定理的形式详细探讨二者的区别和联系.     

Weakly implementable social choice rules

Previous investigations have shown that a social choice function which is partially implementable must be characterized by pervasive veto power. This paper investigates how much additional latitude in the design of social choice functions, and how much relief from this vetoers result, can be achieved by examining multi-valued social choice rules and relaxing the requirement of partial implementability to a requirement that we call weak partial implementability. We find that the power structures which characterize partially implementable social choice functions, including the veto properties, also characterize weakly partially implementable social choice rules. The conclusion is that invoking multi-valuedness and implementation of appealing social choice rules in strong Nash equilibria. Our results apparently exhaust the possibilities for implementation in strong Nash equilibrium. If any implementation possibility results are to be achieved, they can apparently come only by weakening the equilibrium requirement.     

浅析《紫色》的书信体风格

《紫色》(TheColorPurple)是美国当代黑人女作家艾丽斯·沃克(AliceWalker)的代表作品之一。小说采用书信体形式,全书由92封书信构成。在小说中,艾丽斯·沃克娴熟运用现代叙述技巧,采用第一人称作为叙述人称的主线,但又不局限于第一人称,并从人物的视角进行叙述,让读者在阅读文本时,随着人物的视角,直接感受到人物的思想情绪与主观体验,从而清晰透视到女主人公茜莉从麻木、觉醒、抗争到独立的心灵感受和生活历程。本文从《紫色》的叙述技巧和主人公个性的成长两个方面分析《紫色》的书信体风格及其产生的艺术效果。     

Weak disintegrability as a form of preservation of coherence

Summary Weak disintegrations are investigated from various points of view. Kolmogorov's definition of conditional probability is critically analysed, and it is noted how the notion of disintegrability plays some role in connecting Kolmogorov's definition with the one given in line with de Finetti's coherence principle. Conditions are given, on the domain of a prevision, implying the equivalence between weak disintegrability and conglomerability. Moreover, weak sintegrations are characterized in terms of coherence, in de Finetti's sense, of, a suitable function. This fact enables us to give, an interpretation of weak disintegrability as a form of “preservation of coherence”. The previous results are also applied to a hypothetical inferential problem. In particular, an inference is shown to be coherent, in the sense of Heath and Sudderth, if and only if a suitable function is coherent, in de Finetti's sense. Research partially supported by: M.U.R.S.T. 40% “Problemi di inferenza pura”.     

论拉伦茨氏裁判方法的实质

使用传统的判案理论系统分析了拉伦茨氏的方法论体系。指出，拉伦茨氏方法论的基础是欧洲传统“名判”逻辑，其设定目标乃个案公决。拉伦茨氏强调了法官“续造法”的权力。所续造的“法”不是条法，而是曾经自主运用诸条法的模式，它理应有“现行法”的拘束力。“条法库”的缺漏由审判员以法律运用技术补足。诸准则之不谐或与宪法条法的不谐需赖“法益衡量”调谐。分析结论是，拉伦茨氏片面突出法官的自主地位，其方法论在本质上是现代法治社会一种尚需调制的折衷系统。     

略论自主创新环境下我国图书馆人力资源管理

我国图书馆人力资源令人堪忧的现实表明我国图书馆人力资源管理存在许多不足。加强图书馆人力资源管理,需要强化图书馆自身人力资源管理意识;需要建立图书馆职业资格认证制度;需要建立新型的干部考核制度;需要改革现行的技术职务评审与评聘制度;需要建立与健全竞争激励机制;需要加大人才的投资力度,抓好员工的继续教育。只有这样,才能确保我国各级各类图书馆在自主创新环境下的高质量服务。