Bayesian updating of atmospheric dispersion after a nuclear accident

Summary.  We consider a Bayesian forecasting system to predict the dispersal of contamination on a large scale grid in the event of an accidental release of radioactivity. The statistical model is built on a physical model for atmospheric dispersion and transport called MATCH. Our spatiotemporal model is a dynamic linear model where the state parameters are the (essentially, deterministic) predictions of MATCH; the distributions of these are updated sequentially in the light of monitoring data. One of the distinguishing features of the model is that the number of these parameters is very large (typically several hundreds of thousands) and we discuss practical issues arising in its implementation as a realtime model. Our procedures have been checked against a variational approach which is used widely in the atmospheric sciences. The results of the model are applied to test data from a tracer experiment.     

Temporal pattern in number of staff on sick leave: the effect of downsizing

Summary.  The pattern of absenteeism in the downsizing process of companies is a topic in focus in economics and social science. A general question is whether employees who are frequently absent are more likely to be selected to be laid off or in contrast whether employees to be dismissed are more likely to be absent for the remaining time of their working contract. We pursue an empirical and microeconomic investigation of these theses. We analyse longitudinal data that were collected in a German company over several years. We fit a semiparametric transition model based on a mixture Poisson distribution for the days of absenteeism per month. Prediction intervals are considered and the primary focus is on the period of downsizing. The data reveal clear evidence for the hypothesis that employees who are to be laid off are more frequently absent before leaving the company. Interestingly, though, no clear evidence is seen that employees being selected to leave the company are those with a bad absenteeism profile.     

宋代绍兴城镇发展简论

宋代绍兴地区城镇已得到初步发展 ,并呈现出城市化趋势 ,其原因是社会经济发展、人口增长和交通发达。这一时期城镇的发展 ,无论是数量、规模 ,还是经济发展状况、市镇管理等 ,均居于浙江地区的前列 ,为明清时期的进一步繁荣奠定了基础。但各地城镇的发展又是不平衡的 ,显示了一定的地区差异 ,并从城镇居民的生活中 ,反映出社会的贫富现象。     

Causal inference with generalized structural mean models

Summary.  We estimate cause–effect relationships in empirical research where exposures are not completely controlled, as in observational studies or with patient non-compliance and self-selected treatment switches in randomized clinical trials. Additive and multiplicative structural mean models have proved useful for this but suffer from the classical limitations of linear and log-linear models when accommodating binary data. We propose the generalized structural mean model to overcome these limitations. This is a semiparametric two-stage model which extends the structural mean model to handle non-linear average exposure effects. The first-stage structural model describes the causal effect of received exposure by contrasting the means of observed and potential exposure-free outcomes in exposed subsets of the population. For identification of the structural parameters, a second stage 'nuisance' model is introduced. This takes the form of a classical association model for expected outcomes given observed exposure. Under the model, we derive estimating equations which yield consistent, asymptotically normal and efficient estimators of the structural effects. We examine their robustness to model misspecification and construct robust estimators in the absence of any exposure effect. The double-logistic structural mean model is developed in more detail to estimate the effect of observed exposure on the success of treatment in a randomized controlled blood pressure reduction trial with self-selected non-compliance.     

论科技期刊的品牌资本

科技期刊的品牌资本是其生存和发展的关键因素,品牌资本体现了社会效益与经济效益的同一性。品牌资本的价值回归是一个缓慢但却是相当稳定的过程。通过抽样调查和方差分析,定量说明了上述论点的正确性。     

言语生成及理解的心理模型

言语生成 (speechproduction)和言语理解 (speechunderstanding)是语言交际中十分复杂的心理认知过程 ,也是心理语言学研究中的一个重要内容。本文拟对有关言语生成和理解的几种心理模型予以讨论 ,探讨言语生成及理解的过程和实质。     

密度分布非均匀的反馈控制Logistic单种群模型平衡态的稳定性

本文对种群密度在非均匀分布情形下,考虑了具反馈控制的滞后 Logistic 生态模型平衡位置的稳定性;分别给出了在常时滞和弱连续时滞以及强连续时滞情况下的稳定性条件;其结果是对 Gopalsamy 在密度均匀分布情形下相应结果的推广.     

汉英文化差异与大学英语教学研究

文化和语言是密不可分的,语言是一种社会文化现象,是社会文化发展的产物.任何语言的生存和发展都离不开赖以生存的社会文化环境,社会文化又在一定程度上制约着语言使用者的思维和表达能力.文章通过对汉英文化差异在语言学各个层次上的表现,以及英美文化背景知识对汉英文化影响的探讨,提出英美文化导入在大学英语教学中的方式方法.     

Young helpline callers and difference: exploring gender, ethnicity and sexuality in helpline access and provision

This article, which has its origin in a feasibility study carried out for three youth telephone helplines, focuses on gender, difference and helpline access by young people. During the research process the writers noted that for the three commissioning helplines, as is the case with the majority of other telephone helplines, approximately two‐thirds of callers are female. A helpline for young Muslims where the gender access ratio was 50/50 stood out as being different in this respect. Until recently, literature on gender and help‐seeking has tended towards making a blanket identification of males as experiencing difficulties in negotiating pathways to help. Although this difficulty of males is evident in relation to both help‐seeking and access to helplines, our study suggests that, at least in relation to helpline usage, when we take culture, ethnicity and sexuality into account, the help‐seeking situation may be more nuanced. This has implications in terms of enabling a cross‐section of young people to access helplines as well as with regard to helpline service development.     

Residual analysis for spatial point processes (with discussion)

Summary.  We define residuals for point process models fitted to spatial point pattern data, and we propose diagnostic plots based on them. The residuals apply to any point process model that has a conditional intensity; the model may exhibit spatial heterogeneity, interpoint interaction and dependence on spatial covariates. Some existing ad hoc methods for model checking (quadrat counts, scan statistic, kernel smoothed intensity and Berman's diagnostic) are recovered as special cases. Diagnostic tools are developed systematically, by using an analogy between our spatial residuals and the usual residuals for (non-spatial) generalized linear models. The conditional intensity λ plays the role of the mean response. This makes it possible to adapt existing knowledge about model validation for generalized linear models to the spatial point process context, giving recommendations for diagnostic plots. A plot of smoothed residuals against spatial location, or against a spatial covariate, is effective in diagnosing spatial trend or co-variate effects. Q – Q -plots of the residuals are effective in diagnosing interpoint interaction.