Bayesian model selection for D‐vine pair‐copula constructions

In recent years analyses of dependence structures using copulas have become more popular than the standard correlation analysis. Starting from Aas et al. ( 2009 ) regular vine pair‐copula constructions (PCCs) are considered the most flexible class of multivariate copulas. PCCs are involved objects but (conditional) independence present in data can simplify and reduce them significantly. In this paper the authors detect (conditional) independence in a particular vine PCC model based on bivariate t copulas by deriving and implementing a reversible jump Markov chain Monte Carlo algorithm. However, the methodology is general and can be extended to any regular vine PCC and to all known bivariate copula families. The proposed approach considers model selection and estimation problems for PCCs simultaneously. The effectiveness of the developed algorithm is shown in simulations and its usefulness is illustrated in two real data applications. The Canadian Journal of Statistics 39: 239–258; 2011 © 2011 Statistical Society of Canada     

基于集对理论分析比较上证50ETF和上证180ETF跟踪误差

上证50ETF和上证180ETF无论从指数编制还是从指数特征来看都极其相似,因此本文拟选择上证50ETF和上证180ETF作为实证研究对象,运用三种测定方法,实证分析了两者对其目标指数即上证50指数和上证180指数的跟踪误差状况。在此基础上,运用集对分析理论,综合判断测定结果,探讨上证50ETF和上证180ETF跟踪误差的差异性。     

英语音位分析

音位作为语言中最基本和抽象的语音单位，通常以音位变体的形式出现．最小的对立的概念可以帮助理解音泣，但要真正区分音位至少必须遵从三条原则：语音相似原则，互补分布原则和模式匀整原则．     

集对分析(SPA)方法在教学研究中的应用

利用集对分析的方法,对学生英语课、计算机基础相关课考试成绩进行比较,虽然客观上呈现为模糊状态,但分析结果得出相关系数较大,说明两门学科的学习有一定内在的共同规律,在教学上具有类比和互补性。     

Competition and evolutionary stability of plants in a spatially structured habitat

We modelled the population dynamics of two types of plants with limited dispersal living in a lattice structured habitat. Each site of the square lattice model was either occupied by an individual or vacant. Each individual reproduced to its neighbors. We derived a criterion for the invasion of a rare type into a population composed of a resident type based on a pair-approximation method, in which the dynamics of both average densities and the nearest neighbor correlations were considered. Based on this invasibility criterion, we showed that, when there is a tradeoff between birth and death rates, the evolutionarily stable type is the one that has the highest ratio of birth rate to mortality. If these types are different species, they form segregated spatial patterns in the lattice model in which intraspecific competitive interactions occur more frequently than interspecific interactions. However, stable coexistence is not possible in the lattice model contrary to results from completely mixed population models. This clearly shows that the casual conclusion, based on traditional well mixed population models, that different species can coexist if intraspecific competition is stronger than interspecific competition, does not hold for spatially structured population models.     

原子轨道杂化态与非过渡元素的立体化学

本文提出公式化的方法确定分子的杂化轨道数,进而推断分子的杂化轨道类型,确定主族元素共价分子的成键情况和几何构型,并且探讨了影响杂化态的因素。     

两对非相容映象的一个新的公共不动点定理

利用度量空间中自映象对的非相容性条件，建立了一类关于三次方幂型压缩映象新的公共不动点定理，这一结果不同于相关的文献．     

一种预测轨道杂化类型的简便方法

根据用杂化轨道理论和价层电子对互斥理论预测和判断共价多原子分子或离子 (不包括配合物 )空间构型的原理 ,导出了一种用价层电子对数直接预测中心原子轨道杂化类型的简便方法     

液压设备的固体污染分析及防治措施

液压系统中的固态杂质,是污染油液的主要原因,也是液压泵和液压马达效率降低,液压阀卡死,噪声和振动等现象发生的主要原因。因此,固体污染物分析与控制的研究具有积极而重要的意义。     

Improving Ratio Estimators of Second Order Point Process Characteristics

Ripley's K function, the L function and the pair correlation function are important second order characteristics of spatial point processes. These functions are usually estimated by ratio estimators, where the numerators are Horvitz–Thompson edge corrected estimators and the denominators estimate the intensity or its square. It is possible to improve these estimators with respect to bias and estimation variance by means of adapted distance dependent intensity estimators. Further improvement is possible by means of refined estimators of the square of intensity. All this is shown by statistical analysis of simulated Poisson, cluster and hard core processes.