Joint modelling of longitudinal and repeated time-to-event data using nonlinear mixed-effects models and the stochastic approximation expectation–maximization algorithm

We propose a nonlinear mixed-effects framework to jointly model longitudinal and repeated time-to-event data. A parametric nonlinear mixed-effects model is used for the longitudinal observations and a parametric mixed-effects hazard model for repeated event times. We show the importance for parameter estimation of properly calculating the conditional density of the observations (given the individual parameters) in the presence of interval and/or right censoring. Parameters are estimated by maximizing the exact joint likelihood with the stochastic approximation expectation–maximization algorithm. This workflow for joint models is now implemented in the Monolix software, and illustrated here on five simulated and two real datasets.     

Asymptotic properties of numbers of observations in random regions determined by central order statistics

In this paper, we extend the concept of near order statistic observation by considering observations that fall into a random region determined by a given order statistic and a Borel set. We study asymptotic properties of numbers of such observations as the sample size tends to infinity and the order statistic is a central one. We show that then proportions of these numbers converge in probability to some population probabilities. We also prove that these numbers can be centered and normalized to yield normal limit law. First, we derive results for one order statistic; next we give extensions to the multivariate case of two or more order statistics.     

中国的横向政府竞争:问题与对策

在官员选拔制下,中国的横向政府竞争体现出典型"囚徒困境"的特征,其表现就在于严重的地方保护主义和重复建设问题。如果中央政府能够充分发挥地方政府横向竞争的"调控者"作用,中国的横向政府竞争将能达致一个较优的结果。     

诗不厌改贵乎精也——简评许渊冲教授对“三美”的不断追求

大凡文学作品,其中包括诗歌,创作之初都会有所不足,需经反复修改才能不断完善,以臻完美。许渊冲教授是一位著名的古诗英译学者,凭他那译笔优美的诸多古诗英译本驰名中外。从他所提出的古诗英译中应具的“意美”、“音美”和“形美”三个方面着眼,通过对他先后出版的不同译本中的若干源于同一原诗的译诗进行分析比较,探索许渊冲教授对译诗反复修改、精益求精的执着精神,并以此论证他对“三美”的不断追求。     

钢铁行业投资趋同的羊群效应研究

对企业投资行为的研究是解释钢铁行业重复建设的微观基础。由于制度和技术的路径依赖,中国钢铁工业形成了区域寡占型市场结构,大型国有企业和中小民营企业并存,前者在国家兼并政策下以扩大市场份额为目标,后者以利润为目标且通过大型企业的投资来形成市场需求预期。大型钢铁企业之间的投资趋同,以及中小企业的跟风行为产生了羊群效应。文章对上市钢铁企业的实证研究证实了这种效应。政策建议是减轻制度和技术的路径依赖,加强企业之间的信息交流。     

东亚区域合作机制:促进中日合作的机制设计

中日之间存在着难以化解的历史问题、现实矛盾与冲突以及未来合作的隐患。这些障碍使两国关系陷入了类似“囚徒困境”博弈的难题。然而,中日在经济上的相互依存关系为双方突破“囚徒困境”奠定了坚实基础。中日实现和解的途径必须是在一定制度模式下进行无限次重复博弈。在多次博弈中,为了获取长期而更大的利益,双方有可能放弃眼前利益而采取合作策略。东亚区域合作机制的构建,为中日进行无限次博弈提供了现实支持。两国在区域合作中有可能逐渐增强共识和理解,走出“囚徒困境”。     

西方经济学中的信誉理论及其启示

信誉机制是保证契约诚实执行的重要机制,在现代市场经济中,信誉越来越成为影响现代企业成长的重要因素。在一个社会中,企业的信誉主要受博弈次数、产权和法律制度、竞争的环境以及政府行为的影响。信誉理论给我们的启示是:必须建立现代产权制度,加大对产权的保护力度;进一步消除垄断,引入更为开放的竞争政策;加快建立对失信者的惩罚机制;建立健全信息传输体系,发展我国的信用管理行业;政府应加强社会信用观念的培养,提高全社会的信用意识。     

优化长株潭三市产业结构的对策研究

目前长株潭三市的产业结构存在着"同构化"、"低度化"、"低层次化"等诸多因素.加入WTO后,这些矛盾进一步存在将使长株潭三市经济面临更大的挑战,从而影响长株潭三市经济的发展,及时研究并确立相应的策略具有紧迫的现实意义.     

《许三观卖血记》重复叙事的意蕴

余华擅长重复叙事的运用,几乎驾轻就熟,其名作《许三观卖血记》的重复叙事不仅是作品结构的主要手段,也是构成细节的主要手法,并造就了作品一种无尽的意蕴:形式的审美和主题的深邃。     

Relative smoothing of discrete distributions with sparse observations

Quite often we are faced with a sparse number of observations over a finite number of cells and are interested in estimating the cell probabilities. Some local polynomial smoothers or local likelihood estimators have been proposed to improve on the histogram, which would produce too many zero values. We propose a relativized local polynomial smoothing for this problem, weighting heavier the estimating errors in small probability cells. A simulation study about the estimators that are proposed show a good behaviour with respect to natural error criteria, especially when dealing with sparse observations.