Monitoring the parameter vector of regression models with time-to-event response in phase II processes

In most of the existing specialized literature, monitoring regression models are a special case of profile monitoring. However, not every regression model always represents appropriately a profile data structure. This is clearly the case of the Weibull regression model (WRM) with common shape parameter γ. Even though it might be thought that existing methodologies (especially likelihood-ratio (LRT)-based methods) for monitoring generalized linear profiles can also be successfully applied to monitoring regression models with time-to-event response, it will be shown in this paper that those methodologies work fairly acceptable just for data structures with 1000 observations at least approximately. It was found out that some corrections, often referred to as Bartlett's adjustments, are needed to be implemented in order to improve the accuracy of using the asymptotic distributional properties of the LRT statistic for carrying out the monitoring of WRM with relatively small and moderate dimensions of the available datasets. Simulation studies suggest that the use of the aforementioned corrections make the resulting charts work quite acceptable when available data structures contain 30 observations at least. Detection abilities of the proposed schemes improve as dataset dimension increases.     

Box-Cox变换下联合均值与方差模型的极大似然估计

在提出Box-Cox变换下联合均值与方差模型的基础上,研究了该模型参数的估计问题.同时利用截面极大似然估计方法对变换参数λ进行估计,并对均值模型和方差模型的参数进行极大似然估计.通过随机模拟和实例研究,结果表明该模型和方法是有效和可行的.     

Towards a job competency profile for agricultural extension instructors: A survey of views of experts

A project is carried out for instructors in the agricultural extension service in Esfahan. Part of the project is study, conducted to inform the process of competency profile development for the instructors. The study, reported in this contribution, focuses on views of experts about competencies needed by the instructors. The survey is based on the methodology for developing models of HRD, in which 257 key experts participated. A mix of methods was used for collecting data. The most important competencies found in this study are subject matter and business understanding, and presentation skill. The most essential outputs are presentation of instructional materials, feedback to learners and equipping learners with new competencies after the course. In this contribution, competencies and outputs are elaborated. Further research is needed regarding performance improvement as a result of the efforts of the instructors, and the views of other stakeholders on the development of the agri-clusters.     

Likelihood approach for evaluating bioequivalence of highly variable drugs

Bioequivalence (BE) is required for approving a generic drug. The two one‐sided tests procedure (TOST, or the 90% confidence interval approach) has been used as the mainstream methodology to test average BE (ABE) on pharmacokinetic parameters such as the area under the blood concentration‐time curve and the peak concentration. However, for highly variable drugs (%CV > 30%), it is difficult to demonstrate ABE in a standard cross‐over study with the typical number of subjects using the TOST because of lack of power. Recently, the US Food and Drug Administration and the European Medicines Agency recommended similar but not identical reference‐scaled average BE (RSABE) approaches to address this issue. Although the power is improved, the new approaches may not guarantee a high level of confidence for the true difference between two drugs at the ABE boundaries. It is also difficult for these approaches to address the issues of population BE (PBE) and individual BE (IBE). We advocate the use of a likelihood approach for representing and interpreting BE data as evidence. Using example data from a full replicate 2 × 4 cross‐over study, we demonstrate how to present evidence using the profile likelihoods for the mean difference and standard deviation ratios of the two drugs for the pharmacokinetic parameters. With this approach, we present evidence for PBE and IBE as well as ABE within a unified framework. Our simulations show that the operating characteristics of the proposed likelihood approach are comparable with the RSABE approaches when the same criteria are applied. Copyright © 2014 John Wiley & Sons, Ltd.     

Monitoring and change-point estimation for spline-modeled non-linear profiles in phase II

In some applications of statistical quality control, quality of a process or a product is best characterized by a functional relationship between a response variable and one or more explanatory variables. This relationship is referred to as a profile. In certain cases, the quality of a process or a product is better described by a non-linear profile which does not follow a specific parametric model. In these circumstances, nonparametric approaches with greater flexibility in modeling the complicated profiles are adopted. In this research, the spline smoothing method is used to model a complicated non-linear profile and the Hotelling T² control chart based on the spline coefficients is used to monitor the process. After receiving an out-of-control signal, a maximum likelihood estimator is employed for change point estimation. The simulation studies, which include both global and local shifts, provide appropriate evaluation of the performance of the proposed estimation and monitoring procedure. The results indicate that the proposed method detects large global shifts while it is very sensitive in detecting local shifts.     

基于光电传感器的目标轮廓提取及其识别

针对物体外形轮廓特征,给出一种基于主动式光电传感器的轮廓特征提取方法,该方法是通过物体经过传感器组视场时各传感器输出状态来获取特征信息;并结合稀疏表示理论,提出一种基于稀疏表示的目标轮廓识别算法,该算法是将测试样本投影到稀疏域,依据系数的稀疏性对测试样本进行分类。数值仿真与实验结果表明：采用光电传感器组获取的信息能够有效地描述物体;且通过本文算法对不同类型物体进行分类,具有良好的识别效果;对不同条件下获得的特征样本进行分类时,具有良好的鲁棒性。     

Likelihood Ratio Tests for Fixed Model Terms using Residual Maximum Likelihood

Likelihood ratio tests for fixed model terms are proposed for the analysis of linear mixed models when using residual maximum likelihood estimation. Bartlett-type adjustments, using an approximate decomposition of the data, are developed for the test statistics. A simulation study is used to compare properties of the test statistics proposed, with or without adjustment, with a Wald test. A proposed test statistic constructed by dropping fixed terms from the full fixed model is shown to give a better approximation to the asymptotic χ²-distribution than the Wald test for small data sets. Bartlett adjustment is shown to improve the χ²-approximation for the proposed tests substantially.     

直齿圆锥齿轮弧齿厚的计算

本文介绍利用球面渐开线方程计算圆锥齿轮背锥齿形弧齿厚的方法,并通过实例指出利用当量圆柱齿轮计算弧齿厚的理论误差。     

英语中名词性间接回指的认知语义解析

根据兰盖克的认知语法,英语中名词性间接回指的语义本质是基体—侧重有机结合体。名词性间接回指含有两个基本构成元素,即先行项和名词性回指项,但二者不共指。回指项的语义预设了先行项的意义,先行项的语义就成为名词性间接回指的基体。分析不同类型的名词性间接回指的语义特征,并指出名词性间接回指的语义是存在于认知主体大脑中的心理实体,它必然受到认知主体的认知域的限制,所以名词性间接回指的解读存在一定的个体差异性。     

Statistical methods for the analysis of high-throughput data based on functional profiles derived from the Gene Ontology

The increasing availability of high-throughput data, that is, massive quantities of molecular biology data arising from different types of experiments such as gene expression or protein microarrays, leads to the necessity of methods for summarizing the available information. As annotation quality improves it is becoming common to rely on biological annotation databases, such as the Gene Ontology (GO), to build functional profiles which characterize a set of genes or proteins using the distribution of their annotations in the database. In this work we describe a statistical model for such profiles, provide methods to compare profiles and develop inferential procedures to assess this comparison. An R-package implementing the methods will be available at publication time.