"最严格水资源管理制度"对京津冀地区农业干旱的影响

京津冀地区多年来一直是水资源匮乏的区域，近年来随着"最严格水资源管理制度"的落实，当地的农业生产和社会经济的发展受到了严重制约。因此，系统研究京津冀地区的干旱情况，精确预测和评估旱情发生的规律和危害，可为区域水资源调控和相关部门决策提供科学依据，并对未来农业用水提供合理的解决方案。基于2000-2016年5-10月份MODIS NDVI和LST月数据，利用TVDI模型对京津冀地区进行干旱监测，探讨其干旱的时空分布，在此基础上，结合MCD12Q1 Land cover type2土地覆盖数据的马里兰分类方案，将土地覆盖分类修改合并为两大类：农用地和非农用地，作为提取农用地TVDI的底图，并进一步分析农用地受灾的情况。结果表明：2013年之后，"最严格水资源管理制度"的提出对京津冀农用地影响非常大，在很大程度上导致农用地干旱面积增加。     

地方党政主要领导职位空缺的现状、成因及对策

地方党政主要领导职位空缺是指在领导干部选任和调配过程中,由于诸多常规或非常规原因导致某一地区的党委或政府部门主要领导职位在较长时间内空缺,进而直接或间接影响地方党政工作的特殊现状,广泛存在于各级、各地党政部门。由于我国有关干部职位空缺的制度建设和管理规范尚不完善,地方党政主要领导职位空缺产生一些消极影响,主要表现为不利于地方党政机关运行,存在腐败风险,触发舆论风险等。在充分认识空缺危害性的基础上,深入分析造成职位空缺的干部调配因素、选任导向变革因素以及其他非常规因素等,从完善遴选机制、衔接制度、保障机制、舆论生态治理、干部教育等五个方面切实解决地方党政主要领导职位空缺带来的一系列问题。     

Analysis of non-repairable cold-standby systems in Bayes theory

ABSTRACT

In this paper, we seek to analyse the reliability of k-out-of-n cold-standby system with components having Weibull time-to-failure distribution in view of Bayes theory. At first, we review the existing methods exhaustively and find that all these methods have not considered Bayes theory. Then we modify the simplest method and propose new methods based on Monte Carlo simulation. Next, we combine all the information to derive the posterior distribution of Weibull parameters. A robust and universal sample-based method is proposed according to the Monte Carlo Markov Chain method to draw the sample of parameters to obtain the Bayes estimate of reliability. The drawn samples are proved to be rather satisfactory. Conducting a simulation study to compare all the methods in terms of accuracy and computational time, we have presented some useful recommendations from the simulation results. These conclusions would provide insight on the application for k-out-of-n cold-standby system.     

On a system of nonhomogeneous components sharing a common frailty

The components of a reliability system subjected to a common random environment usually have dependent lifetimes. This paper studies the stochastic properties of such a system with lifetimes of the components following multivariate frailty models and multivariate mixed proportional reversed hazard rate (PRHR) models, respectively. Through doing stochastic comparison, we devote to throwing a new light on how the random environment affects the number of working components of a reliability system and on assessing the performance of a k-out-of-n system.     

Optimal design and maintenance of a repairable multi-state system with standby components

The configuration of a repairable system directly influences its performance measures, such as mean time between failures and steady state availability. Additionally, maintenance strategies such as corrective, preventive, and condition-based can affect the performance of the system. The objective of this work is to investigate the trade-offs between the configuration of a repairable multi-state system with binary components and its maintenance strategy. The corresponding stochastic process for the proposed model is formulated using the continuous-time Markov process and important performance measures of such a multi-state system are derived. An optimization model is introduced for the cost-effective design of this repairable multi-state system. The results are demonstrated using a numerical example for a power generation system.     

Idempotent and multivariate copulas with fractal support

Using special iterated function systems (IFS) Fredricks et al. (2005) constructed two-dimensional copulas with fractal supports and showed that for every s∈(1,2)$s\in (\mathrm{1,2})$ there exists a copula A whose support has Hausdorff dimension s. In the current paper we present a stronger version and prove that the same result holds for the subclass of idempotent copulas. Additionally we show that every doubly stochastic idempotent matrix N (having neither minimum nor maximum rank) induces a family of idempotent copulas such that, firstly, the corresponding Markov kernels transform according to N   and, secondly, the set of Hausdorff dimensions of the supports of elements of the family covers (1,2). Furthermore we generalize the IFS approach to arbitrary dimensions d≥2$d\ge 2$ and show that for every s∈(1,d)$s\in (1,d)$ we can find a d-dimensional copula whose support has Hausdorff dimension s.     

The ℓ1 oblique procrustes problem

In this paper, we reconsider the well-known oblique Procrustes problem where the usual least-squares objective function is replaced by a more robust discrepancy measure, based on the ₁ norm or smooth approximations of it.We propose two approaches to the solution of this problem. One approach is based on convex analysis and uses the structure of the problem to permit a solution to the ₁ norm problem. An alternative approach is to smooth the problem by working with smooth approximations to the ₁ norm, and this leads to a solution process based on the solution of ordinary differential equations on manifolds. The general weighted Procrustes problem (both orthogonal and oblique) can also be solved by the latter approach. Numerical examples to illustrate the algorithms which have been developed are reported and analyzed.     

一种适用于非齐次指数增长序列的直接型离散灰色模型

基于灰色模型的背景值表达式及非齐次指数增长序列的形式1,得到了一种一次累加序列与原始序列的关系,给出了系数确定方法,获得了适用于非齐次指数增长序列的直接型离散灰色模型,并给出了系数确定的方法。实例研究表明：本优化模型不仅具有可操作性,而且精度高,效果好。     

UMPU tests based on sequential order statistics

Sequential order statistics with conditional proportional hazard rates form a regular exponential family in the model parameters. This finding is used to establish uniformly most powerful unbiased (UMPU) tests for a variety of hypotheses.     

我国农民科学素质测评指标体系的构建

农民科学素质低下一直是制约我国社会发展的重要因素。国家意识到这一点,开始逐步重视对农民科学素质的研究工作。作为后续研究的基础和依据,如何科学准确地测量农民的科学素质是研究工作的首要问题。我国现行的农民科学素质测评中还存在着缺乏专用的农民科学素质测评体系、忽略农民的异质性、测评方法降低结果的科学性、单一视角的设计影响测评的全面性等不足。提出了构建科学合理的农民科学素质测评指标体系应遵循科学性、针对性、综合性、稳定性和与时俱进等5个原则。在界定中国农民科学素质的内涵与外延的基础上,探讨并建构了中国农民科学素质测评指标体系。