Estimation of coefficient of dispersion using auxiliary information

In this note, we consider the problem of estimation of coefficient of dispersion of a study variable by making use of known value of the coefficient of dispersion of an auxiliary variable. We propose ratio and regression-type estimators. We derive expressions of bias and variance of the proposed estimators to the first order of approximation. The relative efficiencies of the ratio and regression-type estimators with respect to the naïve estimator are investigated through a simulation study.     

Phase type stress–strength models with reliability applications

The stress–strength model has attracted a great deal of attention in reliability analysis, and it has been studied under various modeling assumptions. In this article, the stress–strength reliability is studied for both single unit and multicomponent systems when stress and strength distributions are of phase type. Phase-type distributions, besides their analytical tractability, are a versatile tool for modeling a wide range of real life systems/processes. In particular, matrix-based expressions are obtained for the stress–strength reliability, and mean residual strength for an operating system. The results are illustrated for Erlang-type stress–strength distributions for a single unit system and a system having a general coherent structure. An example on the comparison of two multi-state units in stress–strength ordering is also presented.     

Copula-based reliability analysis for a parallel system with a cold standby

The traditional reliability models cannot well reflect the effect of performance dependence of subsystems on the reliability of system, and neglect the problems of initial reliability and standby redundancy. In this paper, the reliability of a parallel system with active multicomponents and a single cold-standby unit has been investigated. The simultaneously working components are dependent and the dependence is expressed by a copula function. Based on the theories of conditional probability, the explicit expressions for the reliability and the MTTF of the system, in terms of the copula function and marginal lifetime distributions, are obtained. Let the copula function be the FGM copula and the marginal lifetime distribution be exponential distribution, a system with two parallel dependent units and a single cold-standby unit is taken as an example. The effect of different degrees of dependence among components on system reliability is analyzed, and the system reliability can be expressed as the linear combination of exponential reliability functions with different failure rates. For investigating how the degree of dependence affects the mean lifetime, furthermore, the parallel system with a single cold standby, comprising different number of active components, is also presented. The effectiveness of the modeling method is verified, and the method presented provides a theoretical basis for reliability design of engineering systems and physics of failure.     

Correlation coefficient of response variances in compound noise and product array experiments

In robust parameter design, a compound noise experiment has been frequently used for reducing the number of experimental runs compared to a product array experiment. However, the results obtained by the compound noise experiment and the product array experiment are often much different. This paper derives an expression of the correlation coefficient of response variances in the compound noise and the product array experiments, which gives an explanation of that difference.     

Quickly variable selection for varying coefficient models with missing response at random

This paper focuses on the variable selections for a varying coefficient models with missing response at random. A procedure is presented by basis function approximations with smooth-threshold estimating equations. Furthermore, the proposed method selects significant variables and estimates coefficients simultaneously avoiding the problem of solving a convex optimization, which reduced the burden of computation. Compared to existing equation based approaches, our procedure is more efficient and quick. With proper choices the regularization parameter, the resulting estimates perform an oracle property. A cross-validation for tuning parameter selection is also proposed, a numerical study confirms the performance of the proposed method.     

A note on multivariate linear regression

In this note, a hypothesis test based on relevant statistical differences is proposed for multivariate linear regression models whose design matrix rank does not equal the number of regression variables. A statistical example is also provided to illustrate the proposed hypothesis test.     

资源环境约束下中国工业环境技术效率的地区差异及动态演变

本文通过构建环境污染综合指数来全面反映环境污染非期望产出,运用基于非径向、非角度包含非期望产出的DEA—SBM模型测算了资源环境约束下2001—2015年中国30个省份的工业环境技术效率,然后运用Dagum基尼系数及其子群分解方法、kernel 密度估计方法和空间Markov链对资源环境约束下中国工业环境技术效率的地区差异及其分布动态演变进行了实证分析。研究表明：资源环境约束下中国工业环境技术效率在地理空间上具有集聚特征,呈现“东高西低”非均衡的空间分布格局;中国工业环境技术效率水平在不断提高的同时,也呈现明显的两极分化的分布状态;资源环境约束下中国工业环境技术效率地区差异整体上呈现不断扩大趋势,地区间差异和超变密度是造成资源环境约束下中国工业环境技术效率地区差异的主要来源;中国工业环境技术效率分布的演变总体上受到邻域空间滞后类型的影响,但在传统粗放型的工业发展方式下,中国工业环境技术效率具有很强的路径依赖性,在时长1年内很难实现短期跨越式发展。最后,针对研究结论,提出相应的政策建议。     

基于失效情景的应急设施选址评估指标体系与模型

突发事件具有巨大的破坏性、不确定性,应急设施有可能失效,本文研究基于失效情景的应急设施选址评估指标体系与评估模型。首先基于定义的失效情景研究应急设施选址评估指标。构建全局性、可靠性、时效性、均衡性、经济性评估指标。可靠性作为重要评估指标有助于提高应急设施对需求区域的物资保障程度,保证系统的稳定性,采用多重覆盖率刻画。然后,设计具有不同侧重评估目标的一般情景评估指标体系、设施失效情景评估指标体系以及多区域情景评估指标体系。最后,由于应急设施选址评估具有多影响因素特征,涉及输入和输出多个指标的测度,选取处理多输入\多输出问题具有优势的评估方法—数据包络法,对应急设施选址的合理性进行评估。实例验证评估指标体系的实用性和有效性。     

Three New Life Distribution Models for Modeling Field Failure Data

Intrinsic and extrinsic factors affect the field reliability of a product. This makes the field reliability generally different from the inherent reliability. It is desired that a field reliability model can provide the information about the inherent reliability and quantify the effects of main extrinsic factors on reliability. This article presents three such life distribution models that can quantitatively reflect the effect of tests, transport and storage process, or/and operating variability on reliability. A real-world example is included to illustrate the appropriateness and usefulness of these models. The significance and interpretation of the felid reliability model are also discussed.     

农村居民消费不平等的微观结构分析

提出了个体微观数据基尼系数的组群、要素统一分解式,并利用该分解式考察消费结构、区域结构和收入不平等对农村居民消费不平等的影响.采用了2009年福建省农村居民生活状况调查数据进行分析,得出结论:食品、衣着类消费的增长可以降低农村居民的消费不平等,其中谷物、薯类、食用油、蔬菜及制品、肉禽蛋奶及制品的消费增长对消费公平性的提高产生积极的作用;组内不平等在总体消费不平等中占80％以上,消费差异主要表现为内部的差异;农村居民的消费不平等受收入不平等影响显著.