The percentile residual life up to time t0: Ordering and aging properties

Motivated by practical issues, a new stochastic order for random variables is introduced by comparing all their percentile residual life functions until a certain instant. Some interpretations of these stochastic orders are given, and various properties of them are derived. The relationships to other stochastic orders are studied and also an application in reliability theory is described. Finally, we present some characterization results of the decreasing percentile residual life up to time t₀ aging notion.     

课外科技活动对材料专业大学生培养“补强”作用的研究

以2006级材料专业毕业生为研究对象,对学生参加课外科技活动后的学习成绩和获奖情况、CET4通过率、考研率以及就业率进行了跟踪和调研。重点分析和评价了课外科技活动对学生在大学学习成绩、价值观培养、考研率和就业率的影响。结果表明,课外科技活动对材料学科的学生补强作用明显。     

Assessing safety at the end of clinical trials using system organ classes: A case and comparative study

Recent approaches to the statistical analysis of adverse event (AE) data in clinical trials have proposed the use of groupings of related AEs, such as by system organ class (SOC). These methods have opened up the possibility of scanning large numbers of AEs while controlling for multiple comparisons, making the comparative performance of the different methods in terms of AE detection and error rates of interest to investigators. We apply two Bayesian models and two procedures for controlling the false discovery rate (FDR), which use groupings of AEs, to real clinical trial safety data. We find that while the Bayesian models are appropriate for the full data set, the error controlling methods only give similar results to the Bayesian methods when low incidence AEs are removed. A simulation study is used to compare the relative performances of the methods. We investigate the differences between the methods over full trial data sets, and over data sets with low incidence AEs and SOCs removed. We find that while the removal of low incidence AEs increases the power of the error controlling procedures, the estimated power of the Bayesian methods remains relatively constant over all data sizes. Automatic removal of low-incidence AEs however does have an effect on the error rates of all the methods, and a clinically guided approach to their removal is needed. Overall we found that the Bayesian approaches are particularly useful for scanning the large amounts of AE data gathered.     

Complete consistency for the estimator of nonparametric regression model based on martingale difference errors

Abstract

In this paper, we study the complete consistency for the estimator of nonparametric regression model based on martingale difference errors, and obtain the convergence rates of the complete consistency by using the inequalities for martingale difference sequence. Finally, some simulations are illustrated.     

Shared gamma frailty models based on reversed hazard rate for modeling Australian twin data

In this paper, we consider shared gamma frailty model with the reversed hazard rate (RHR) with two different baseline distributions, namely the generalized inverse Rayleigh and the exponentiated Gumbel distributions. With these two baseline distributions we propose two different shared frailty models. We develop the Bayesian estimation procedure using Markov Chain Monte Carlo technique to estimate the parameters involved in these models. We present a simulation study to compare the true values of the parameters with the estimated values. A search of the literature suggests that currently no work has been done for these two baseline distributions with a shared gamma frailty with the RHR so far. We also apply these two models by using a real life bivariate survival data set of Australian twin data given by Duffy et a1. (1990) and a better model is suggested for the data.     

节点分析法在分层注采系统中的应用研究

针对二层油藏分层注采实际情况，在分析水平管流、垂直管流、配水嘴嘴流等沿程压降的基础上，基于节点分析原理，建立了二层油藏分层注采系统节点分析数学模型，考虑了层间、注采井间相互作用，大大提高了节点分析的可靠性；通过理论分析和实例计算，确定了分层配产配注量和注入压力，使注采系统处于平衡生产状态，并对多层油藏的节点分析具有一定借鉴意义和理论意义。     

A new destructive Poisson odd log-logistic generalized half-normal cure rate model

We propose a new cure rate survival model by assuming that the initial number of competing causes of the event of interest follows a Poisson distribution and the time to event has the odd log-logistic generalized half-normal distribution. This survival model describes a realistic interpretation for the biological mechanism of the event of interest. We estimate the model parameters using maximum likelihood. For different sample sizes, various simulation scenarios are performed. We propose the diagnostics and residual analysis to verify the model assumptions. The potentiality of the new cure rate model is illustrated by means of a real data.     

Promotion Time Cure Rate Model with Bivariate Random Effects

In this article, we consider the inclusion of random effects in both the survival function for at-risk subjects and the cure probability assuming a bivariate normal distribution for those effects in each cluster. For parameter estimation, we implemented the restricted maximum likelihood (REML) approach. We consider Weibull and Piecewise Exponential distributions to model the survival function for non-cured individuals. Simulation studies are performed, and based on a real database we evaluate the performance of our proposed model. Effect of different follow-up times and the effect of considering independent random effects instead of bivariate random effects are also studied.     

基于部分延迟支付期限的易损品经济批量订货模型研究

已有考虑延期付款的EOQ订货模型多为单层延期支付,而忽略了供应商与其上级供应商,或零售商与其下级零售商的关系。而实际易损品,由于资金约束导致零售商和下游顾客都延迟支付,不同层级延迟支付期限对运营成本与订货周期的策略影响如何?为此,文章在Huang’s模型基础上,考虑零售商、顾客都存在部分延期支付情况下,易损商品三阶段经济批量订货策略,证明了最优订货策略的存在性及唯一性,并分析了参数的影响特征。研究结果表明:(1)当零售商的延迟支付期限大于顾客的延迟支付期限时,零售商最优订货周期和最优订货数量随着变质率的增大而减小,此时零售商应该选择增加订货频率,减少订货数量的策略。(2)当零售商的延迟支付期限小于顾客延迟支付期限时,零售商的最优订货周期和最有订货数量随着变质率的增大而增大,此时零售商应该选择减少订货频率,增加每次订货的订货数量策略。     

宫内节育器使用效果的调查分析

对2659例已婚育龄妇女放置宫内节育器(IUD)后1年进行了调查,了解IUD的使用效果。结果显示,农村妇女IUD放置后1年使用率为84.2%,低于城市妇女(P<0.001);带器妊娠和IUD脱落是IUD停止使用的主要原因。应加强技术服务,提高IUD的续用率。