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.     

谈音长在教学和修辞中的作用

语言是声音和意义的结合体。语音是语言的物质外壳。语音的音长决定着言语的速度 ,在交际中 ,对内容的表达起积极作用 ,在教学和修辞的语言实践中 ,应重视音长的作用。     

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。     

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.     

逆向物流及其整合分析

逆向物流是物流管理的一个新的领域,已经引起理论界和企业界越来越多的关注。逆向物流可以降低企业成本,提高顾客满意度,并最终提升企业的竞争力,这对我国企业实践具有重要意义。     

第十届世界杯男排赛中、巴、意发球效果比较研究

根据第十届世界杯男排赛中国男排和冠亚军(巴西、意大利)的两场比赛录像,对三支球队的发球技术进行统计与测量分析。结果显示:中国男排在发球的有效率上与巴、意两队存在显著性差异,发球速度的各项指标均低于巴、意两队。提出了建立新的"一攻"观念、制定特殊政策鼓励大力跳发球等观点。     

甘肃定西马铃薯产业链物流分析

甘肃马铃薯产业的产业链纵向和横向发展都不够完善，而物流是产业链中一个重要的子集，如何发展物流产业，是一个重要的问题。本文分析了目前甘肃定西的物流体系，指出了其中存在的一些问题和认识上的误区，提出了几种整合产业链的思路。     

连锁超市替代农贸市场的对策研究

超市作为一种新型零售业态,在我国已经颇具规模,以连锁超市替代农贸市场已成为可能。本文通过连锁超市与农贸市场的比较,分析了连锁超市具有的优势及替代过程的障碍,提出了连锁超市替代农贸市场的对策。     

价值链理论在跨国经营中的应用

本文剖析了价值链的特点及其变化趋势,阐明了在跨国经营中如何应用价值链理论。旨在为提高我国企业的国际经济竞争力提供参考。