具扩散项的停止-损失再保问题的破产概率

本文在具有扩散项的假定下,研究了原保险公司、再保险公司的破产问题.在索赔随机变量为指数情形,得到了免赔额与破产概率之间的关系,并且得到了如下的结果:1.随机风险模型生存概率的表达公式,从而得到了由扰动导致的破产概率的表达公式.2.分别得到了两类保险公司破产概率的表达公式.所得结果不仅推广了文献[1]的结果,而且使用的方法具有一定的独立价值.     

Combining Probability Distributions From Experts in Risk Analysis

This paper concerns the combination of experts' probability distributions in risk analysis, discussing a variety of combination methods and attempting to highlight the important conceptual and practical issues to be considered in designing a combination process in practice. The role of experts is important because their judgments can provide valuable information, particularly in view of the limited availability of hard data regarding many important uncertainties in risk analysis. Because uncertainties are represented in terms of probability distributions in probabilistic risk analysis (PRA), we consider expert information in terms of probability distributions. The motivation for the use of multiple experts is simply the desire to obtain as much information as possible. Combining experts' probability distributions summarizes the accumulated information for risk analysts and decision-makers. Procedures for combining probability distributions are often compartmentalized as mathematical aggregation methods or behavioral approaches, and we discuss both categories. However, an overall aggregation process could involve both mathematical and behavioral aspects, and no single process is best in all circumstances. An understanding of the pros and cons of different methods and the key issues to consider is valuable in the design of a combination process for a specific PRA. The output, a combined probability distribution, can ideally be viewed as representing a summary of the current state of expert opinion regarding the uncertainty of interest.     

The VL control measure for symmetric networks

In this paper we measure “control” of nodes in a network by solving an associated optimisation problem. We motivate this so-called VL control measure by giving an interpretation in terms of allocating resources optimally to the nodes in order to maximise some search probability. We determine the VL control measure for various classes of networks. Furthermore, we provide two game theoretic interpretations of this measure. First it turns out that the VL control measure is a particular proper Shapley value of the associated cooperative network game. Secondly, we relate the measure to optimal strategies in an associated matrix search game.     

Extreme behaviour for bivariate elliptical distributions

The authors examine the asymptotic behaviour of conditional threshold exceedance probabilities for an elliptically distributed pair (X, Y) of random variables. More precisely, they investigate the limiting behaviour of the conditional distribution of Y given that X becomes extreme. They show that this behaviour differs between regularly and rapidly varying tails.     

论谢灵运山水审美的发生机制——兼论当下学界对谢诗“玄言尾巴”解读的失据

魏晋玄学与魏晋山水审美的联姻主要是通过三种途径完成的,具体到谢灵运来讲,他的山水审美则主要是从把山水之爱当作人的本能需求的角度切入的.由于把人的山水之爱归结为人的生命本性对自然美本身的本能追寻,而并不像有的士人那样,只将山水视为某种哲理或某种生命境界的展现,如此就使谢灵运的山水审美在形式上发生了重大改变:一是一改对景物静观默照式的悟赏,而为兴味盎然,近似疯狂的邀游;二是在山水诗创作鼢中对山水美本身有了更多的关注.谢灵运山水审美机制的改变与魏晋玄学对人性至善的积极肯定密切相联系,所以,我们认为他的诗歌总有一个玄言尾巴,主要是由于对于他的山水审美切入方式发生误读造成的.     

L'analyse de la variation saisonniére quand l'amplitude et la taille sont faibles

Studies of seasonal variation are valuable in biomedical research because they can help to discover the etiology of diseases that are not well understood. Generally in these studies the data have certain characteristics that require specialized tests and methods for the statistical analysis. But the effectiveness of these specialized tests is variable, especially according to the seasonal variation, the dimension of the amplitude in the seasonal variation, and the sample size. The purpose of this paper is to present a test and methods appropriate for the analysis and modeling of data whose seasonal variation has small amplitude and whose sample size is small. This test can detect different kinds of seasonal variation. The results from a simulation study show that the test performs very well. The application of these methods is illustrated by two examples.     

Bayesian Dividend Optimization and Finite Time Ruin Probabilities

We consider the valuation problem of an (insurance) company under partial information. Therefore, we use the concept of maximizing discounted future dividend payments. The firm value process is described by a diffusion model with constant and observable volatility and constant but unknown drift parameter. For transforming the problem to a problem with complete information, we derive a suitable filter. The optimal value function is characterized as the unique viscosity solution of the associated Hamilton-Jacobi-Bellman equation. We state a numerical procedure for approximating both the optimal dividend strategy and the corresponding value function. Furthermore, threshold strategies are discussed in some detail. Finally, we calculate the probability of ruin in the uncontrolled and controlled situation.     

Comparison of the several parameterized estimators for the positive extreme value index

In the paper we compare several parameterized estimators for the positive extreme value index, which is a very important parameter appearing in the estimation of the probability of rare events. Firstly, asymptotic comparison at optimal levels of the corresponding tail index estimators is performed. Secondly, the practical validation of asymptotic results for moderate finite samples is done by means of Monte-Carlo simulations. We demonstrate that theoretical domination of the positive extreme value index estimators, which are asymptotically normal with a null asymptotic bias, is not reflected in Monte-Carlo simulations. Moreover, the estimators of such type do not demonstrate stability in the sense of empirical mean-squared error.     

Application of box-cox transformations to discrimination for the two-class problem

The performance of Box-Cox power transformations in classification using Hinkley's (1975) method is studied. Misclassification probabilities before and after transformation are compared. It is found that the use of Box-Cox transformations can sometimes substantially reduce the error probabilities. Estimates of error probabilities are obtained and certain properties are derived. Examples for a number of distributions are given.