Parameter selection in modified histogram estimates

A multivariate modified histogram density estimate depending on a reference density g and a partition P has been proved to have good consistency properties according to several information theoretic criteria. Given an i.i.d. sample, we show how to select automatically both g and P so that the expected L ₁ error of the corresponding selected estimate is within a given constant multiple of the best possible error plus an additive term which tends to zero under mild assumptions. Our method is inspired by the combinatorial tools developed by Devroye and Lugosi [Devroye, L. and Lugosi, G., 2001, Combinatorial Methods in Density Estimation (New York, NY: Springer–Verlag)] and it includes a wide range of reference density and partition models. Results of simulations are also presented.     

Fast On-Line/Off-Line Algorithms for Optimal Reinforcement of a Network and its Connections with Principal Partition

The problem of computing the strength and performing optimal reinforcement for an edge-weighted graph G(V, E, w) is well-studied. In this paper, we present fast (sequential linear time and parallel logarithmic time) on-line algorithms for optimally reinforcing the graph when the reinforcement material is available continuously on-line. These are the first on-line algorithms for this problem. We invest O(|V|³|E|log|V|) time (equivalent to (|V|) invocations of the fastest known algorithms for optimal reinforcement) in preprocessing the graph before the start of our algorithms. It is shown that the output of our on-line algorithms is as good as that of the off-line algorithms. Thus our algorithms are better than the fastest off-line algorithms in situations when a sequence of more than (|V|) reinforcement problems need to be solved. The key idea is to make use of ideas underlying the theory of Principal Partition of a Graph. Our ideas are easily generalized to the general setting of polymatroid functions. We also present a new efficient algorithm for computation of the Principal Sequence of a graph.     

Goodness of fit for thei ordered categories discrete uniform distribution

Goodness of fit for thei ordered categories discrete uniform distribution can be carried out using Pearson's X² _pstatistic and its components. Applications of this technique are considered and comparisons made with recently suggested empirical uniform distribution     

从体制区隔走向协同治理：兰考精准脱贫的实践与思考

2017年3月,经国务院扶贫开发领导小组评估及河南省政府批准,兰考县正式摘掉了贫困县的帽子,正式从脱贫攻坚阶段走向全面建成小康社会新阶段。兰考之问——“兰考是如何脱贫的”、“兰考经验是否可复制”,迫切需求答案。贫困治理属于国家治理的一个领域,其理念与手段深受国家治理理念转变的影响,同时也借鉴、改造与创新其他领域问题治理的探索实践。文章在回顾贫困治理理论与中国贫困治理实践的基础上,反思传统扶贫方式的缺陷与不足,梳理“十八大”以来的贫困治理新思路,总结提炼兰考精准脱贫样本的经验。兰考脱贫故事发生在中国整体性国家贫困治理理念与制度创新转型的时代背景下,找到了制约传统贫困治理方式存在问题的深层次因素,在政府部门关系与层级关系、多元主体协同共治方面有所突破,在贫困治理机制上有所创新,是国家治理、政府治理、社区治理等多元主体协同治理有机结合的产物。     

A class of dynamic piecewise exponential models with random time grid

A novel fully Bayesian approach for modeling survival data with explanatory variables using the Piecewise Exponential Model (PEM) with random time grid is proposed. We consider a class of correlated Gamma prior distributions for the failure rates. Such prior specification is obtained via the dynamic generalized modeling approach jointly with a random time grid for the PEM. A product distribution is considered for modeling the prior uncertainty about the random time grid, turning possible the use of the structure of the Product Partition Model (PPM) to handle the problem. A unifying notation for the construction of the likelihood function of the PEM, suitable for both static and dynamic modeling approaches, is considered. Procedures to evaluate the performance of the proposed model are provided. Two case studies are presented in order to exemplify the methodology. For comparison purposes, the data sets are also fitted using the dynamic model with fixed time grid established in the literature. The results show the superiority of the proposed model.     

The role of selection in socioeconomic homophily: Evidence from an adolescent summer camp

Socioeconomic homophily in friendship networks is the result of several co-occurring processes, which are extremely challenging to disentangle. We propose to study the particular context of a three-week summer camp in France that gathered teenagers from varied socioeconomic backgrounds. We argue that this camp provides a unique opportunity to observe the sociability of adolescents in well-bounded settings with equalized meeting opportunities, thus helping us to narrow down the specific role of homophilic selection - the process by which individuals actively select similar friends. We use Stochastic Actor-Oriented Models to analyze the declared friendships of participants. Furthermore, we introduce a novel longitudinal extension of the Exponential Random Partition Model (ERPM), a model developed for relational data organized in discrete groups, which we apply to observed meal-sharing among adolescents. Results point to weak to non-existent homophilic selection during the stay. In turn, this suggests that structural opportunities and contextual moderators might be essential in explaining the amount of socioeconomic homophily found at school or in other contexts.     

Improved testing for the binomial distribution using chi-squared components with data-dependent cells

A power study suggests that a good test of fit analysis for the binomial distribution is provided by a data-dependent Chernoff–Lehmann X ² test with class expectations greater than unity, and its components. These data-dependent statistics involve arithmetically simple parameter estimation, convenient approximate distributions and provide a comprehensive assessment of how well the data agree with a binomial distribution. We suggest that a well-performed single test of fit statistic is the Anderson–Darling statistic.     

A note on current methods of partitioning the contigency x2 statistic

Comparisons are made between the two values of the chisquare statistic in three dimensional contigency tables as defined respectively by the ‘multiplicative’ an ‘additive’ models of zero second order interaction. It is shown that in practice the two definitions frequently give comparable values for the statistics, and it is concluded that interaction measures, and paritioning of the overall association chisuare, are more useful than the considerable writing on the models' deficiencies would seem to indicate. There seems to be a slight bias in favour of the multiplicative model.     

信息共享环境的数据与技术模块研究

信息共享环境与国家安全和国际安全密切相关,近几年才受到国内外政府与学者的广泛关注和高度重视.数据模块与技术模块是构建信息共享环境的核心.数据模块探讨了功能标准、模块构架、数据描述的抽象模型、数据环境的抽象模型和数据共享的抽象模型等.技术模块探讨了模块架构、服务接入与输出模型、服务平台与基础设施模型、框架模型、以及服务界面与集成模型等.