Practical Maximum Pseudolikelihood for Spatial Point Patterns(with Discussion)

This paper describes a technique for computing approximate maximum pseudolikelihood estimates of the parameters of a spatial point process. The method is an extension of Berman & Turner's (1992) device for maximizing the likelihoods of inhomogeneous spatial Poisson processes. For a very wide class of spatial point process models the likelihood is intractable, while the pseudolikelihood is known explicitly, except for the computation of an integral over the sampling region. Approximation of this integral by a finite sum in a special way yields an approximate pseudolikelihood which is formally equivalent to the (weighted) likelihood of a loglinear model with Poisson responses. This can be maximized using standard statistical software for generalized linear or additive models, provided the conditional intensity of the process takes an 'exponential family' form. Using this approach a wide variety of spatial point process models of Gibbs type can be fitted rapidly, incorporating spatial trends, interaction between points, dependence on spatial covariates, and mark information.     

Estimation of geodesic tortuosity and constrictivity in stationary random closed sets

We investigate the problem of estimating geodesic tortuosity and constrictivity as two structural characteristics of stationary random closed sets. They are of central importance for the analysis of effective transport properties in porous or composite materials. Loosely speaking, geodesic tortuosity measures the windedness of paths, whereas the notion of constrictivity captures the appearance of bottlenecks resulting from narrow passages within a given materials phase. We first provide mathematically precise definitions of these quantities and introduce appropriate estimators. Then, we show strong consistency of these estimators for unboundedly growing sampling windows. In order to apply our estimators to real data sets, the extent of edge effects needs to be controlled. This is illustrated using a model for a multiphase material that is incorporated in solid oxide fuel cells.     

A general central limit theorem and a subsampling variance estimator for α‐mixing point processes

We establish a central limit theorem for multivariate summary statistics of nonstationary α‐mixing spatial point processes and a subsampling estimator of the covariance matrix of such statistics. The central limit theorem is crucial for establishing asymptotic properties of estimators in statistics for spatial point processes. The covariance matrix subsampling estimator is flexible and model free. It is needed, for example, to construct confidence intervals and ellipsoids based on asymptotic normality of estimators. We also provide a simulation study investigating an application of our results to estimating functions.     

Stress-strength reliability of exponentiated Fréchet distributions based on Type-II censored data

In this paper, we consider inference of the stress-strength parameter, R, based on two independent Type-II censored samples from exponentiated Fréchet populations with different index parameters. The maximum likelihood and uniformly minimum variance unbiased estimators, exact and asymptotic confidence intervals and hypotheses testing for R are obtained. We conduct a Monte Carlo simulation study to evaluate the performance of these estimators and confidence intervals. Finally, two real data sets are analysed for illustrative purposes.     

省域经济洼地区域中心城市发展战略研究——以江苏淮安为例

省域经济洼地地区是实现区域协调发展的重要板块和关键区域。以江苏省淮安市为例,从战略角度审视淮安建设成为苏北重要中心城市的意义和基础,并提出淮安在区域经济和流域经济层面上两个维度的发展定位和三个方向的发展路径。通过纵向融入京沪高铁和京杭运河两条复合发展轴,横向建设淮河流域生态经济带,打造苏皖在江北地区的跨界合作示范区等战略,推动淮安苏北重要中心城市的建设和省域经济协调发展格局的形成。     

从盖恩斯《刑前一课》看小说视点与叙事层面的建构

盖恩斯在《刑前一课》里从零视点与悬念的建构、外视点与悖论的建构、内视点与意识流、多视点聚焦与立体感等方面来研究小说视点与叙事层面的相互关联。他从零视点的角度建构人称悬念、瞬间悬念和期待性悬念,从外视点的角度设置了主题悖论、言辞悖论和语境悖论。为了克服零视点和外视点描述的单调性和乏味性,盖恩斯把内视点与意识流进行了有机结合,从触景生情式意识流、内心独白式意识流和交织式意识流等方面探究人物心理与社会环境的内在关联。他还在人物评述和场景氛围等方面采用了多视点策略,从多层次和多侧面的角度来聚焦于具体的人物、物件或场景,构建了叙事层面的立体感,拓展了现代黑人小说创作的美学认知空间。     

模糊语义研究方法论纲

研究模糊语义必须以查德的“模糊集”理论作指导．运用现代语言学和现代语义学以及相关学科的研究成果来进行研究。这样也就使得研究方法具有多角度、多层次的特点,从而形成一个方法论系统：从整体方法上看,可实行宏观研究与微观分析相结合、定性研究与定量描述相结合、一般规律研究与特殊规律研究相结合的方法;从具体方法上看,应该注重模糊语义学的“综合性的边缘学科”属性,强调不同学科之间的渗透,融合各相关学科的理论和知识,来对模糊语义展开全面而深入的研究。     

Two-step estimation for inhomogeneous spatial point processes

Summary.  The paper is concerned with parameter estimation for inhomogeneous spatial point processes with a regression model for the intensity function and tractable second-order properties ( K -function). Regression parameters are estimated by using a Poisson likelihood score estimating function and in the second step minimum contrast estimation is applied for the residual clustering parameters. Asymptotic normality of parameter estimates is established under certain mixing conditions and we exemplify how the results may be applied in ecological studies of rainforests.     

A Bayesian model for multiple change point to extremes,with application to environmental and financial data

Abrupt changes often occur for environmental and financial time series. Most often, these changes are due to human intervention. Change point analysis is a statistical tool used to analyze sudden changes in observations along the time series. In this paper, we propose a Bayesian model for extreme values for environmental and economic datasets that present a typical change point behavior. The model proposed in this paper addresses the situation in which more than one change point can occur in a time series. By analyzing maxima, the distribution of each regime is a generalized extreme value distribution. In this model, the change points are unknown and considered parameters to be estimated. Simulations of extremes with two change points showed that the proposed algorithm can recover the true values of the parameters, in addition to detecting the true change points in different configurations. Also, the number of change points was a problem to be considered, and the Bayesian estimation can correctly identify the correct number of change points for each application. Environmental and financial data were analyzed and results showed the importance of considering the change point in the data and revealed that this change of regime brought about an increase in the return levels, increasing the number of floods in cities around the rivers. Stock market levels showed the necessity of a model with three different regimes.