Estimating the distribution function using k-tuple ranked set samples

The basic assumption underlying the concept of ranked set sampling is that actual measurement of units is expensive, whereas ranking is cheap. This may not be true in reality in certain cases where ranking may be moderately expensive. In such situations, based on total cost considerations, k-tuple ranked set sampling is known to be a viable alternative, where one selects k units (instead of one) from each ranked set. In this article, we consider estimation of the distribution function based on k-tuple ranked set samples when the cost of selecting and ranking units is not ignorable. We investigate estimation both in the balanced and unbalanced data case. Properties of the estimation procedure in the presence of ranking error are also investigated. Results of simulation studies as well as an application to a real data set are presented to illustrate some of the theoretical findings.     

Nonparametric estimation of the conditional distribution function in a semiparametric censorship model

In this paper we propose a new nonparametric estimator of the conditional distribution function under a semiparametric censorship model. We establish an asymptotic representation of the estimator as a sum of iid random variables, balanced by some kernel weights. This representation is used for obtaining large sample results such as the rate of uniform convergence of the estimator, or its limit distributional law. We prove that the new estimator outperforms the conditional Kaplan–Meier estimator for censored data, in the sense that it exhibits lower asymptotic variance. Illustration through real data analysis is provided.     

Bayesian analysis of outlier problems using divergence measures

A Bayesian approach is presented for detecting influential observations using general divergence measures on the posterior distributions. A sampling-based approach using a Gibbs or Metropolis-within-Gibbs method is used to compute the posterior divergence measures. Four specific measures are proposed, which convey the effects of a single observation or covariate on the posterior. The technique is applied to a generalized linear model with binary response data, an overdispersed model and a nonlinear model. An asymptotic approximation using Laplace method to obtain the posterior divergence is also briefly discussed.     

PES-C,(PP/Bis-T)PES的次级松驰与转变

描述了酚酞型聚芳醚砜(PES-C)的次级松驰和转变与其结构的关系.TBA和动态力学实验结果表明:PES-C及其共聚物(PP/Bis-T)PES分别在0～50℃和-100℃附近呈现出两个次级松驰峰;双酚T单元的引入导致了PES-C在0～50℃之间的次级松驰位置改变.证实了Cardo侧基的存在对-100℃的次级松驰有较大的贡献.     

Two point priors and Γ-minimax estimating in families of uniform distributions

It is shown that when a parameter lying in a sufficiently small interval is to be estimated in a family of uniform distributions, a two point prior is least favourable under squared error loss. The unique Bayes estimator with respect to this prior is minimax. The Γ-minimax estimator is derived for sets Γ of priors consisting of all priors that give fixed probabilities to two specified subintervals of the parameter space if a two point prior is least favourable in Γ.     

学科教学知识新突破:教学策略“U-S”双向共创机理

教学策略由学科知识、教学知识、学生心理引导和教学监控等条件性知识以及教师教学经验、反思、行为习惯等组成,具有理论与实践一体化特征。其中知识部分属于学科教学知识(PCK)范畴,具有情境性和多种知识融合的特征。学科教学知识的“特殊整合”,不仅需要相应的学科知识和教学知识,还需要情境性教学经验。然而,中小学教师有经验缺理论、高校教师有理论没经验的问题普遍存在,形成教学策略与教学行为之间双向转化的瓶颈。为此,大学和中小学教师需要以外部利益驱动构建协同共创平台,在相同教学旨趣吸引下组成优势互补的研发团队,形成突破教学策略转化瓶颈的分层赋能与共创机制。“大学―中小学”(“U-S”)协同共创,应注重从教学策略理论知识传授到教师教学行为转变、从学习名师经验及其教学策略创新到新教学策略文本形成的转化与共创过程,形成特色鲜明的学科教学策略知识,将其以陈述性、程序性、策略性知识形式融入师范生实训教学,进而实现对现有学科教学知识的新突破。只有构建“U-S”共同体,协同实现教学策略的“理—实”双向共创,才能赋予教学策略以“内容、形式和旨趣”三个维度的理论和实践生命力,才能发挥双方优势,形成规模更大的教学策略创新平台。     

A probablistic analysis for an optimal screening problem

Summary We consider a lotL formed byN apparently similar unitsW ₁,…,W _N, where each of theW _i may come from one of two different populationsP ₁ andP ₂;T ₁,…,T _N denote the corresponding lifetimes. The units fromP _i undergo a failure of kindi and their survival function isS _i (t). We assume that the failure rate function are known and that the units fromP ₁ are ?substandard?: λ ₁ (t)≥λ ₂ (t), ∀t≥0. We want to putW ₁,…,W _N under a pre-operational test (burn-in test) in order to eliminate at least a great part of the substandard units and we face the problem of obtaining a rule for stopping the test under the assumption that, with the failure of a unit, it is possible to recognize the population from which the unit comes. Such a problem will be formalized as an optimal stopping problem for a suitably defined Markov process. Our study shall evidentiate some fundamental aspects of the problem and the role of the prior distribution of the (random) numberM ₀ of those units inL coming fromP ₁ (substandard). The latter distribution has a great influence on the form of the solution. This research was supported by the C.N.R. Project ?Statistica Bayesiana e Simulazione in Affidalità e Modellistica Biologica?.     

中国二板市场应无限期推迟——从海外二板市场的教训看中国开设二板的艰难性

德国、日本、澳大利亚及香港等海外二板市场失败的原因是由于其大幅度降低了公司入市的标准和要求,有其必然性。美国纳斯达克市场尚存的原因是其特性与主板有重叠之处,从超长期看,其是否成功还难以确定。本文指出中国拟创立的二板市场理由、目标与海外二板市场衰败的原因如出一辙;加之中国A股市场股本结构分裂,股价高企,没有做空机制,二板市场贸然推出,不仅本身可能会蹈海外多数二板市场的覆辙,而且可能对主板A股市场形成严重影响,故建议中国二板市场无限期推迟。在主板市场可通过附设一个科技创业分板,并应尽快恢复深圳证券市场新股发行工作。     

澳大利亚OESC保护中小学生上网安全的途径研究

随着网络技术的发展和社交软件使用的低龄化,发生在中小学校的网络欺凌现象越来越普遍。澳大利亚政府高度关注该问题,专门成立网络安全专员办公室（OESC）,用以支持和推动中小学生网络安全措施的实施。具体而言：（1）提供安全的网络使用指导,引导中小学生养成网络安全行为习惯;（2）为学校和家庭提供相关的教育资源,培养中小学生的网络安全意识和能力;（3）对网络服务供应商设立监管机制,确保中小学生网络安全措施的顺利实施。     

中小学教师依法治教的困境与对策

中小学教师是依法治教的实践者、宣讲者、推动者,是推动依法治教的关键因素之一。但是,在中小学教师依法治教的过程中,还存在着中小学教师法治素养良莠不齐,教育立法滞后、执法不严、司法不公以及中小学教师职前、职后法治教育缺失等现象。全面推进依法治国,实现教育治理体系和治理能力现代化,必须深刻把握和充分发挥中小学教师在依法治教中的价值和作用,增强其依法治教的自觉性;必须深刻分析中小学教师在依法治教中面临的各种困境与原因,采取针对性措施,做到有的放矢,综合施策。