MODELING THE LIFETIME OF LONGITUDINAL ELEMENTS

In the study of the stochastic behaviour of the lifetime of an element as a function of its length, it is often observed that the failure time (or lifetime) decreases as the length increases. In probabilistic terms, such an idea can be expressed as follows. Let T be the lifetime of a specimen of length x, so the survival function, which denotes the probability that an element of length x survives till time t, will be given by S_T (t, x) = P(T > t/α(x), where α(x) is a monotonically decreasing function. In particular, it is often assumed that T has a Weibull distribution. In this paper, we propose a generalization of this Weibull model by assuming that the distribution of T is Generalized gamma (GG). Since the GG model contains the Weibull, Gamma and Lognormal models as special and limiting cases, a GG regression model is an appropriate tool for describing the size effect on the lifetime and for selecting among the embedded models. Maximum likelihood estimates are obtained for the GG regression model with α(x) = cx^b . As a special case this provide an alternative to the usual approach to estimation for the GG distribution which involves reparametrization. Related parametric inference issues are addressed and illustrated using two experimental data sets. Some discussion of censored data is also provided.     

Nonlinear and non-gaussian state estimation: A quasi-optimal estimator

The rejection sampling filter and smoother, proposed by Tanizaki (1996, 1999), Tanizaki and Mariano (1998) and Hiirzeler and Kiinsch (1998), take a lot of time computationally. The Markov chain Monte Carlo smoother, developed by Carlin, Poison and StofFer (1992), Carter and Kohn (1994, 1996) and Geweke and Tanizaki (1999a, 1999b), does not show a good performance depending on noniinearity and nonnormality of the system in the sense of the root mean square error criterion, which reason comes from slow convergence of the Gibbs sampler. Taking into account these problems, we propose the nonlinear and non-Gaussian filter and smoother which have much less computational burden and give us relatively better state estimates, although the proposed estimator does not yield the optimal state estimates in the sense of the minimum mean square error. The proposed filter and smoother are called the quasi-optimal filter and quasi-optimal smoother in this paper. Finally, through some Monte Carlo studies, the quasi-optimal filter and smoother are compared with the rejection sampling procedure and the Markov chain Monte Carlo procedure.     

基于语言规划观的澳大利亚语言政策模型构建及启示

从语言作为问题、语言作为权利、语言作为资源三个角度考察,澳大利亚百年来的语言政策可划分为四个时期,即放任化时期、同化时期、多元化时期和优先化时期。在全面分析影响澳大利亚制定语言政策的基本规划观念的基础上,我们建立了一个基于语言规划观的,能够反映澳大利亚语言政策演变情况的澳大利亚语言政策模型。这个模型对分析中国或其他国家的语言政策也有一定价值。     

论公民社会与社会工作——公民社会视角下的中国社会工作

回顾改革开放以来的几十年,中国正在由一个高度政治化的社会向一个多元化的公民社会演变,政府职能开始转变,民间社会从政治权力中逐渐分离出来,并显示了巨大的能量。大政府、小社会的政治格局正在发生变化,社会工作在这一背景下也在悄悄的改变。本文就是具体论述在这一转变之后,社会工作和公民社会间的关系。首先对公民社会中的社会工作进行宏观考察,分析公民社会下社会工作、国家权力和公民三者之间的关系。公民社会与社会工作之间存在互动的关系。两者之间相互影响,相互作用。社会工作对公民社会的作用有:社会工作为公民提供帮助,救助公民于危难之时;社会工作帮助公民解困;社会工作帮助公民更好地发展。公民社会对社会工作的作用:公民社会监督社会工作组织;公民社会监督和保护社会工作者;公民社会在经济上支持社会工作。     

认知框架下的借代现象及其语篇功能探究

同隐喻一样,借代也是一种重要的思维方式和认知工具.然而,长期以来,借代研究仍然拘泥于修辞范畴,其功能得不到充分体现.本文从认知角度出发,在引入理想化认知模型(ICM)的基础上对借代的工作机制进行重新探讨和认识,同时对其在语篇连贯和衔接方面所发挥的重要作用也进行了初步研究.     

总体镜下的中国模式

随着＂华盛顿共识＂的式微,＂中国模式＂正日益兴起。当前,理论界热议中的＂中国模式＂尚处于一种能指的狂欢状态。从方法论上来看,分析还原论的方法堵塞了认知＂中国模式＂的道路,这种方法表征的是思维的初级阶段。打破目前僵局的唯一路径,就是要彻底变革思维方式,用马克思的方法——总体性的方法研究马克思主义中国化进程中的事物——＂中国模式＂,这种方法的基本运思理路是面向总体,维护总体与获得总体。惟此,＂中国模式＂方能走向澄明之境。     

A pattern-mixture odds ratio model for incomplete categorical data

Most models for incomplete data are formulated within the selection model framework. Pattern-mixture models are increasingly seen as a viable alternative, both from an interpretational as well as from a computational point of view (Little 1993, Hogan and Laird 1997, Ekholm and Skinner 1998). Whereas most applications are either for continuous normally distributed data or for simplified categorical settings such as contingency tables, we show how a multivariate odds ratio model (Molenberghs and Lesaffre 1994, 1998) can be used to fit pattern-mixture models to repeated binary outcomes with continuous covariates. Apart from point estimation, useful methods for interval estimation are presented and data from a clinical study are analyzed to illustrate the methods.     

“现代化”之后的东亚农业和农村社会——日本、韩国和台湾地区的案例及其历史意蕴

日本、韩国和台湾地区的农业和农村通常被看作中国大陆农业和农村的样板。但是,以粮食大量依赖进口,农村的空洞化、老龄化和劳动力不足,以及与"新娘短缺"相伴的"外籍新娘"的涌入为代表,这三个国家和地区的粮食和人口的再生产都处于难以持续的状态,"现代化"之后的农业和农村实际上都处于严重的危机之中。这种状况与其具有高度竞争力的工业和拥挤的城市形成鲜明对照,它是"东亚模式"或"东亚资本主义"的一种必然结局,也对中国大陆农业和农村的未来演变趋势提出了警示。     

Analysis of a continuous-time proportional hazard model using discrete duration data

Many economic duration variables are often available only up to intervals, and not up to exact points. However, continuous time duration models are conceptually superior to discrete ones. Hence, in duration analyses, one faces a situation with discrete data and a continuous model. This paper discusses (i) the asymptotic bias of a conventional approximation procedure in which a discrete duration is treated as an exact observation; and (ii) the efficiency of a correct maximum likelihood estimator which appropriately accounts for the discrete nature of the data.     

Robust methods in econometrics

This survey of recent developments in robust estimation and inference is directed primarily toward econometricians. It is argued that many of the techniques in common use in econometrics are highly sensitive to unverified hypotheses. Recent progress in designing alternative robust procedures is described and some prospects for future developments are discussed.