Dynamic Reliability Evaluation of Consecutive-k-Within-m-Out-of-n:F System

A consecutive k-within-m-out-of-n:F system consists of n linearly ordered components and fails if and only if there are m consecutive components which include among them at least k failed components. This system model generalizes both consecutive k-out-of-n:F and k-out-of-n:F systems. In this article, we study the dynamic reliability properties of consecutive k-within-m-out-of-n:F system consisting of exchangeable dependent components. We also obtain some stochastic ordering results and use them to get simple approximation formulae for the survival function and mean time to failure of this system.     

Some reliability characteristics and stochastic ordering of series and parallel systems of bivariate generalized exponential distribution

In this paper, the reliability properties of two-component parallel and series systems are considered for bivariate generalized exponential (BVGE) distribution introduced by Kundu and Gupta [Bivariate generalized exponential distribution. J Multivar Anal. 2009;100:581–593]. For this model, the moments and mean residual life functions of these systems and the regression mean residual life function are derived. Stochastic comparisons of series and parallel systems of BVGE distribution are investigated. Moreover, various ordering results for the comparisons of series and parallel systems arising from BVGE random vectors are obtained with respect to the usual stochastic, reversed hazard rate and likelihood ratio orderings.     

Uncovering bias in order assignment

To mitigate sequencing effects in decision-making, many situations require a set of items to be considered in a random order. When such orderings are repeated, one can test whether randomization indeed obtains, or whether some orderings have been manipulated in order to achieve a favorable result. This paper articulates the key features of this problem and presents three general tests for randomness. These methods are used to analyze the order in which lottery numbers are drawn in Powerball, contestants perform on American Idol, and candidates are placed on election ballots. This last application features frequent manipulation, with potentially serious consequences.     

Extensions of empirical likelihood and chi-squared-based tests for ordered alternatives

Several methods for comparing k populations have been proposed in the literature. These methods assess the same null hypothesis of equal distributions but differ in the alternative hypothesis they consider. We focus on two important alternative hypotheses: monotone and umbrella ordering. Two new families of test statistics are proposed, including two known tests, as well as two new powerful tests under monotone ordering. Furthermore, these families are adapted for testing umbrella ordering. We compare some members of the families with respect to power and Type I errors under different simulation scenarios. Finally, the methods are illustrated in several applications to real data.     

文化哲学的沉思:转型期社会文化心态变迁规律阐释

转型期社会文化心态变迁的规律,不同于社会形态更替时期大破大立的规律,也不同于社会常态时期积累渐进的规律,而是特定历史时期、特定经济、政治、文化条件下的社会文化心态嬗变的规律.主要包括:有序重组规律,即社会文化心态系统内各要素在与外部环境不断进行信息、能量和物质交换中,能够进行自组织,使某些要素的变化得以强化或抑制,使之达到有序化;涨落突变规律,即社会文化心态系统内部经常随机发生不同形式的微观涨落,当某种微观涨落被正反馈作用放大超过临界点,形成巨涨落,随之引发突变;连锁感应规律,即社会文化心态系统内各要素或子系统之间存在传感过程,其中某一个要素变化引发另一个或多个要素的变化,从而产生轰动效应.我们理解和把握这三条规律,对于发挥社会文化心态变迁的正值效应,克服其负值效应,都具有重大的理论和实践意义.     

抑制恶性出口竞争的制度化对策

探讨了我国对外贸易迅速增长中出现的恶性出口竞争问题,指出恶性出口竞争导致出口秩序混乱,不仅降低出口效益,还容易引起国外反倾销,从而使我国丧失出口产品的国际市场。认为解决问题的关键是制度化建设,并从设置出口企业进入的门槛、出口政策导向与措施相配套、对大型成套设备及国际承包工程企业实行严格的出口许可制度,以及切实加强产品出口限制以保护国内资源、依托商会协调企业间关系等方面提出了依法对出口实行有效管制的对策建议。     

物料价格随时间波动及完工期随机的MTO订购决策

对于订单式中小生产企业,物料供应是否及时以及生产进度是否按计划进行是影响订单交货期的关键因素。实际中,某些产品的物料价格随时间连续波动并具有规律性,而生产过程中由于插单多、工人流动性大、设备故障、质量返工等,生产完工期有一定的随机性。对于物料订购决策,传统方法主要考虑订单的投产日期以及物料采购成本最小化,而未考虑订单完工期的随机性特点。基于企业内部供应链集成及总成本最小化的系统思想,综合考虑物料价格的变化趋势以及随机生产完工期的统计规律,分别建立单一物料或多种物料订购情形下总生产成本(包括订购成本、制造成本、延迟完工或提早完工成本等)与订购日期的关系模型,并对其最优解进行讨论、分析与求解。当物料种类单一时,采用极值法对模型极小值点的存在性进行讨论;当物料种类较多时,构建了有约束条件的多决策变量非线性优化模型,并采用最优化理论中的拉格朗日乘子法(即PHR算法)进行求解。通过实例分析,得出的结论是物料最佳订购时间点与物料初始价格、价格波动周期、波动幅度、单位延迟或提早完工成本等因素相关。上述采购与生产集成的思想、模型构建的思路以及求解方法等可供有关人员参考。     

The one-way analysis of variance with ordered alternatives: A modification of bartholomew's Ē2 Test

Tests of homogeneity of normal means with the alternative restricted by an ordering on the means are considered. The simply ordered case, μ₁ ≤ μ₂ ≤ ··· ≤ μ_k, and the simple tree ordering, μ₁ ≤ μ_j, for; j= 2, 3,…, k, are emphasized. A modification of the likelihood-ratio test is proposed which is asymptotically equivalent to it but is more robust to violations of the hypothesized orderings. The new test has power at the points satisfying the hypothesized ordering which is similar to that of the likelihood-ratio test provided the degrees of freedom are not too small. The modified test is shown to be unbiased and consistent.     

Two-moment approximations to some null distributions in order-restricted inference: Unequal sample sizes

Bartholomew's statistics for testing homogeneity of normal means with ordered alternatives have null distributions which are mixtures of chi-squared or beta distributions according as the variances are known or not. If the sample sizes are not equal, the mixing coefficients can be difficult to compute. For a simple order and a simple tree ordering, approximations to the significance levels of these tests have been developed which are based on patterns in the weight sets. However, for a moderate or large number of means, these approximations can be tedious to implement. Employing the same approach that was used in the development of these approximations, two-moment chisquared and beta approximations are derived for these significance levels. Approximations are also developed for the testing situation in which the order restriction is the null hypothesis. Numerical studies show that in each of the cases the two-moment approximation is quite satisfactory for most practical purposes.