Variance-based importance analysis measure for mission reliability of phased mission system

Importance measures are used to estimate the relative importance of components to system reliability. Phased mission systems (PMS) have many components working in several phases with different success criteria, and their component structural importance is distinct in different phases. Additionally, reliability parameters of components in PMS always have uncertainty in practice. Therefore, existing component importance measures based on either the partial derivative of system structure function or component structural importance may have difficulties in PMS importance analysis. This paper presents a simulation method to evaluate the component global importance for PMS based on the variance-based method and the Monte-Carlo method. To facilitate the practical use, we further discuss the correlation relationship between the component global importance and its possible influence factors, and present here a fitting model for evaluating component global importance. Finally, two examples are given to show that the fitting model displays quite reasonable component importance.     

Numerical Method for Reliability Analysis of Phased-Mission System Using Markov Chains

This article presents a numerical method for solving continuous time Markov chain (CTMC) model for reliability evaluation of phased-mission system. The method generates infinitesimal matrix based on the statistical independence of subsystem failure and repair process. The infinitesimal generator matrix is stored by the use of sparse matrix-compressed storage schemes, and the transient solution of the CTMC model is obtained by using three methods including the uniformization method, forward Euler method, and Runge-Kutta method, which take advantage of the sparseness of the infinitesimal generator matrix. An example PMS is used to compare the preconditioning methods for sparse matrix and numerical methods. Experiment results show that compressed row storage scheme (CRS) saves more storage than other storage formats, and uniformization method combined with CRS achieves the best efficiency and accuracy.     

体育锻炼对女大学生经前期紧张应激能力的影响

经《DSM—Ⅲ—R》普查筛选,从有经前期症状反应的98名女大学生中随机抽取46名女生进行经前期指导性体育锻炼,一个学年后,其症状程度发生率锻炼组低于非体育锻炼组,经前期症状反应中的躯体症状和心理症状各两项总分经比较（x±s）,存在明显差异（P＜0．05）．考试时间内经前期应激身心健康水平,经SCL－90测评,9个症状因素和阳性的项目数经比较（x±s）,除敌对、偏执、精神病性3个因素外,其余存在明显差异（P＜0．05～P＜0．01）．结果表明,体育锻炼能改善经前期紧张综合症中内分泌生理功能和心理活动状态,提高由生理变化刺激应激阈值,科学地体育锻炼是女大学生对经前期紧张应激的一种有效的应对防御手段．     

交互业绩控制对组织绩效的影响——基于组织敏捷性的中介作用

基于资源基础理论,考虑动态环境因素,以组织敏捷性为中介变量,考察交互业绩控制对组织绩效的影响机理。以企业中高层管理者为研究对象,利用191份管理者的问卷调查数据,采用结构方程模型的方法,研究发现:交互业绩控制对组织敏捷性产生正面影响,而且组织敏捷性对组织绩效产生正面影响。组织敏捷性在交互业绩控制与组织绩效的关系中扮演中介角色。交互业绩控制不仅直接影响组织绩效,而且还通过组织敏捷性间接影响组织绩效。研究结论不仅诠释了交互业绩控制的沟通特征与重要性,而且拓展了管理控制和资源基础理论文献,为实现我国企业在实践中的高质量发展提供有价值借鉴。     

大学英语四级成绩多因素影响分析

英语四级(CET-4)成绩是检验大学生英语掌握水平的重要标准。本文以某高校2001级本科生为调查对象,运用多种统计方法分析影响CET-4成绩的一些客观因素。研究发现,男女大学生CET-4成绩存在显著性差异;高考英语成绩、主干课程成绩和性别与(CET-4)成绩存在相关性。同时本文建立了CET-4成绩通过情况预测模型。通过以上结果,旨在为高校英语教与学提供有价值的参考。     

具有多阶段任务需求的温备份系统可靠性分析

实际工程中很多系统的任务都具有多个阶段,且不同阶段的外界环境及系统需求均可能发生变化,而工作元件可在任意阶段发生失效,为系统的可靠性分析与建模带来了挑战。为增加系统的可靠性,一种常用的设计方法是配置备份元件。针对多阶段任务下基于需求的温备份系统可靠性建模问题,首先提出了一种基于多值决策图的方法,其次给出了处于不同状态的元件可靠性计算公式,最后通过算例表明该模型适用于具有多阶段任务需求的温备份系统可靠性分析。