Estimating rating transition probabilites with missing data

In this article we provide a rigorous treatment of one of the central statistical issues of credit risk management. GivenK-1 rating categories, the rating of a corporate bond over a certain horizon may either stay the same or change to one of the remainingK-2 categories; in addition, it is usually the case that the rating of some bonds is withdrawn during the time interval considered in the analysis. When estimating transition probabilities, we have thus to consider aK-th category, called withdrawal, which contains (partially) missing data. We show how maximum likelihood estimation can be performed in this setup; whereas in discrete time our solution gives rigorous support to a solution often used in applications, in continuous time the maximum likelihood estimator of the transition matrix computed by means of the EM algorithm represents a significant improvement over existing methods.     

On Block Updating in Markov Random Field Models for Disease Mapping

Gaussian Markov random field (GMRF) models are commonly used to model spatial correlation in disease mapping applications. For Bayesian inference by MCMC, so far mainly single-site updating algorithms have been considered. However, convergence and mixing properties of such algorithms can be extremely poor due to strong dependencies of parameters in the posterior distribution. In this paper, we propose various block sampling algorithms in order to improve the MCMC performance. The methodology is rather general, allows for non-standard full conditionals, and can be applied in a modular fashion in a large number of different scenarios. For illustration we consider three different applications: two formulations for spatial modelling of a single disease (with and without additional unstructured parameters respectively), and one formulation for the joint analysis of two diseases. The results indicate that the largest benefits are obtained if parameters and the corresponding hyperparameter are updated jointly in one large block. Implementation of such block algorithms is relatively easy using methods for fast sampling of Gaussian Markov random fields ( Rue, 2001 ). By comparison, Monte Carlo estimates based on single-site updating can be rather misleading, even for very long runs. Our results may have wider relevance for efficient MCMC simulation in hierarchical models with Markov random field components.     

情商成功的客观存在性对经济运行的影响

情商效应的客观存在性增添了经济理论与经济研究的函数变量 ,其对传统经济理论与经济研究是一个较大的冲击与挑战。人们可以充分利用情商效应获取经济生活最大限度的成功。同时 ,也可以在充分认识情商客观存在性对社会经济生活起决定性影响作用这一原理 ,进一步强化对社会经济制度的建立与执行 ,降低经济生活中的交易成本 ,实现经济资源配置的帕累托改善效应。     

高等学校学术权力运行机制探析

高校学术权力的运行机制是为了保证高校学术权力公正、高效、廉洁、有序运转而在学术权力运作方面提出的各种相互联系与制约关系及其实际运作状态的总和。当前我国高校学术权力存在配置不合理、信息反馈迟钝、缺乏有效民主机制协商和规范等诸多问题。为此,应理顺政府与高校的权力关系;优化权力结构,明确权限;完善信息传递与反馈机制;将各种权力行为制度化、程序化;完善监督机制,以权力制约权力。     

供应链企业间的合作轨道模型

文章主要介绍了轨道模型在供应链企业合作中的应用 ,根据合作程度的不同 ,伙伴企业处于以核心企业为中心的不同轨道。文章分别从静态和动态的角度运用轨道模型分析了企业间合作关系以及这种合作关系的变化。一方面使企业间的合作问题简单化 ;另一方面 ,轨道模型便于对合作问题进行深入的定量化研究。     

基于需求不确定性的供应链库存控制研究

通过建立需求不确定性环境下供应链成员的独立存货成本模型,运用模拟退火法对该模型进行52周的仿真,求解存货最佳订购数量与最佳再订购点,从而比较出不同存货控制策略的供应链存货总成本及订单满足率的差异。     

基于科学发展观的创建和谐企业运行机制体系论纲

基于创建和谐企业是贯彻落实科学发展观，构建社会主义和谐社会的一项战略性工程，和谐企业运行机制体系是创建和谐企业的关键所在，论述了创建和谐企业的意义，提出了创建和谐企业的战略选择，界定了创建和谐企业运行机制体系的内涵、特点、功能与创建原则，构建了和谐企业运行机制体系的基本框架。     

粮田经营方式创新探讨

在新的经济社会条件下，现有粮田经营方式与我国对粮食安全、农民增收、农业现代化发展的需求不相适应。粮田经营方式应该进行创新。创新从两个方面进行：一是在农业内部实行粮田适度规模经营，二是在农业外部实行粮食产业化经营。     

Bayesian analysis of directed graphs data with applications to social networks

Summary.  A fully Bayesian analysis of directed graphs, with particular emphasis on applica- tions in social networks, is explored. The model is capable of incorporating the effects of covariates, within and between block ties and multiple responses. Inference is straightforward by using software that is based on Markov chain Monte Carlo methods. Examples are provided which highlight the variety of data sets that can be entertained and the ease with which they can be analysed.     

新中国农村四荒地资源产权运作的历史变迁

资源匮乏,人均占有资源严重不足是我国的基本国情。然而大量的四荒地资源又不能得到充分的开发利用。怎样促进四荒地资源的开发利用,是理论和实践中一个重要的经济问题。本文从农村四荒地资源产权运作的历史变迁入手,分别对三年改造时期、合作社时期、人民公社时期及改革以来农村四荒地资源的产权安排及其变迁进行了描述与评价,进而得出结论,旨在对实践中不断高涨的四荒地资源开发利用有一定的借鉴意义。