A new algorithm to estimate monotone nonparametric link functions and a comparison with parametric approach

The generalized linear model (GLM) is a class of regression models where the means of the response variables and the linear predictors are joined through a link function. Standard GLM assumes the link function is fixed, and one can form more flexible GLM by either estimating the flexible link function from a parametric family of link functions or estimating it nonparametically. In this paper, we propose a new algorithm that uses P-spline for nonparametrically estimating the link function which is guaranteed to be monotone. It is equivalent to fit the generalized single index model with monotonicity constraint. We also conduct extensive simulation studies to compare our nonparametric approach for estimating link function with various parametric approaches, including traditional logit, probit and robit link functions, and two recently developed link functions, the generalized extreme value link and the symmetric power logit link. The simulation study shows that the link function estimated nonparametrically by our proposed algorithm performs well under a wide range of different true link functions and outperforms parametric approaches when they are misspecified. A real data example is used to illustrate the results.     

马与草原文明的形成和发展

马是游牧文明的标志性核心载体之一。马的驯化,特别是马的承骑不仅造就了游牧文明,推动草原文化走向新的发展阶段,也对整个人类社会的政治、经济、军事、交通、商贸和文化交流产生过深远的影响。游牧形态的形成与发展空前加强和提升了草原文化的内聚力、外张力,出现很多彼此联系紧密、特征相近的游牧民族、游牧帝国,将亚欧草原变成游牧文明天下,对世界的民族、文化格局带来深刻变化。     

Cities evolution tree and applications to predicting urban growth

China’s unprecedented urbanization and economic modernization have brought about significant growth and land use changes in cities and their surroundings. Traditional analyses of the relationship between urbanization and land use change have not fully incorporated important factors like city function or developmental stage. We define and apply a new visualization and analysis tool—an evolution tree—showing how an understanding of evolutionary pathways taken by growing cities contributes to visualization and forecasting of urban development and spatial expansion. We clustered 253 Chinese cities by type and developmental stage, arranging them in a “tree” structure, with types grouped as branches and leaf position along branches reflecting developmental stage. Urban growth rates are higher for business-oriented, manufacturing-oriented, and functionally comprehensive cities than for those oriented toward tourism. Extent of spatial growth is dominated by city type and developmental stage. Cities evolve along typical pathways, punctuated by occasional leap developments across functional types.     

小识王宁的书画艺术

笔墨语言的表达能力，对于一个精确表达思想的人是十分重要的。对王宁来说，他的书法、篆刻、诗词、绘画等创作，能将笔墨经营出无限丰富的层次来，并将多种表现手法的试验，进一步介入到当代书画艺术发展的主流上来，这是非常难得的。王宁从中国历代经典的书法作品中，采足了雄健、宽博、飘逸、清净之气，乃至篇幅不论大小，同样使我们体会到宏大的精神境界和超于物象之上的精神表达。     

我国农业传统文化与后现代农业发展的相关思考

现代农业的发展是以功利性为特征的,受经济目标的逐利影响,正逐渐步入生态困境。后现代农业发展阶段将出现农业生态观的原始回归,这将为我国农业传统文化功能的发挥创造机遇。我国后现代农业发展阶段应重视传统农业文化的诉求,挖掘本土农业文化资源,加强对外引文化的审视,提高农业自我创新能力。     

农村地区彝族青年婚姻困境破解的公共政策支持

当前,农村地区彝族青年的婚姻困境问题明显,形式变异的"买卖婚"在强大的社会心理支撑下普遍存在,婚姻困境中的性别差异明显,青年男女的婚姻自由受到限制,固守传统婚姻形式造成多种社会问题。破解农村地区彝族青年婚姻困境,需要给予公共政策支持的外力推动,形成解决这一问题的内生动力,并最终帮助彝族青年男女突破婚恋的物质和精神束缚,促进农村地区婚姻进步和经济社会发展。     

自我网络特征对电信客户流失的影响

近年来，随着移动通信行业的蓬勃发展，市场饱和度越来越高，企业获取新用户的成本也越来越大。随着中国三大运营商竞争的加剧，产品和服务的同质化程度也越来越高，这使企业在老客户的保留上变得异常困难，客户流失率也在逐年上升，如何识别高风险流失客户并有效防止客户流失已经成为该行业管理者普遍关心的问题之一。 着眼于客户流失影响因素研究，运用社交网络分析方法，通过构造与网络结构相关的变量进行影响因素的探讨，运用逻辑回归方法构建客户流失预警模型。从社交网络的视角出发，利用客户的通话详单数据建立客户之间的通信网络，在自我网络的相关理论框架下，构建个体的度、联系强度、个体的信息熵3个自我网络特征变量。运用中国某移动运营商公司的月度客户数据(包括基础通信数据和通话详单数据)，通过逻辑回归构建基于社交网络变量的客户流失预警模型。 研究结果表明，个体的度、联系的强度和个体的信息熵都对预测客户流失有显著效果。具体的，个体的度越大，联系强度越强，个体的信息熵越大，客户越不容易流失。外样本AUC值平均可以达到0.75以上，模型具有良好的预测精度。 研究结果对企业实践具有非常重要的意义，合作企业应用客户流失预警模型进行高风险流失客户的识别，预测精度可以达到70%，达到了企业的实践预期。客户流失预警模型可以帮助企业提前识别高风险流失客户，极大地降低企业维系客户的成本。建议企业管理者在未来更加关注与客户社交网络有关的变量，从网络结构的视角理解消费者行为，更好地进行客户关系管理。     

基于双因子的公平偏好模型研究

基本公平偏好模型虽然能较好地解释现实中存在的“投桃报李”等互惠互利现象,但却忽略了这样一个基础问题:这种“公平”比较的基点本身是否满足“公平性”.文章通过对基本公平偏好模型的修正,构建了双因子收入公平偏好模型,从而弥补和修正了原有模型中存在的基础假设缺失的难题.由双因子模型可得结论:双因子呈反向变化关系;双因子放大了净收入变化所带来的效用改变程度.其研究的意义在于:双因子模型能够解释基本公平偏好所不能解释的一些激励问题;定量说明了交易中委托方应当如何根据代理方双因子的特征(而非仅依据公平偏好单因子),提供合理收益分配方案,以促进合作成功.     

Bayesian quantile regression for parametric nonlinear mixed effects models

We propose quantile regression (QR) in the Bayesian framework for a class of nonlinear mixed effects models with a known, parametric model form for longitudinal data. Estimation of the regression quantiles is based on a likelihood-based approach using the asymmetric Laplace density. Posterior computations are carried out via Gibbs sampling and the adaptive rejection Metropolis algorithm. To assess the performance of the Bayesian QR estimator, we compare it with the mean regression estimator using real and simulated data. Results show that the Bayesian QR estimator provides a fuller examination of the shape of the conditional distribution of the response variable. Our approach is proposed for parametric nonlinear mixed effects models, and therefore may not be generalized to models without a given model form.