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831.
A Kernel Variogram Estimator for Clustered Data   总被引:3,自引:0,他引:3  
Abstract.  The variogram provides an important method for measuring the dependence of attribute values between spatial locations. Suppose that the nature of the sampling process leads to the presence of clustered data; it would be advisable to use a variogram estimator that aims to adjust for clustering of samples. In this setting, the use of a non-parametric weighted estimator, obtained by considering an inverse weight to a given neighbourhood density combined with the kernel method, seems to have a satisfactory behaviour in practice. This paper pursues a theoretical study of the cluster robust estimator, by proving that it is asymptotically unbiased as well as consistent and by providing criteria for selection of the bandwidth parameter and the neighbourhood radius. Numerical studies are also included to illustrate the performance of the considered estimator and the suggested approaches.  相似文献   
832.
文章从区域空间的角度,建立城市土地集约利用的指标体系,采用主成分分析法和聚类分析法,对安徽省17个地市城市土地集约利用情况进行了分类和评价,以期为政府决策提供参考。  相似文献   
833.
详细介绍了中小企业集群的概念及发展状况,在定义知识价值链和分析集群创新的知识特征的基础上,研究了知识管理与集群创新的机理关系,通过知识管理构建集群学习型组织,提高集群组织的学习与创新能力,从而最终提高中小企业集群的核心竞争力,促进整体经济的发展。  相似文献   
834.
Various bootstrap methods for variance estimation and confidence intervals in complex survey data, where sampling is done without replacement, have been proposed in the literature. The oldest, and perhaps the most intuitively appealing, is the without-replacement bootstrap (BWO) method proposed by Gross (1980). Unfortunately, the BWO method is only applicable to very simple sampling situations. We first introduce extensions of the BWO method to more complex sampling designs. The performance of the BWO and two other bootstrap methods, the rescaling bootstrap (Rao and Wu 1988) and the mirror-match bootstrap (Sitter 1992), are then compared through a simulation study. Together these three methods encompass the various bootstrap proposals.  相似文献   
835.
本文使用Schlenk操作技术,以Fe3(CO)(12)与phNCS在温和条件下反应,除了制得一取代物外,还制得一个新的二取代产物,通过元矛分析、IR、MS、1HNMR和13CNhIR表征,确定它们的化学式为Fe3(CO)3(CNPh)(μ3-S)2和Fe3(CO)7(CNPh)2(μ3-S)2。  相似文献   
836.
Suppose particles are randomly distributed in a certain medium, powder or liquid, which is conceptually divided into N cells. Let pi denote the probability that a particle falls in the ith cell and Yi denote the number of particles in the ith cell. Assume that the joint probability function of the Yi follows a multinomial distribution with cell probabilities pi respectively. Take n (≤N) cells at random without replacement and put each of the cells separately through a mixing mechanism of dilution and swirl. These n cells constitute the first stage samples and the number of particles in these cells are not observable. Now conceptually divide each of n cells into M subcells of equal size and let Xij denote the number of particles in the jth subcell of the ith cell selected in the first stage; i=1,2,…,N and j=1,2,…,M. Consequently assume that the conditional joint probability function of the Xij given Yi=yi follows a multinomial distribution with equal cell probabilities. Now take m (≤M) subcells at random from each of the cells selected in the first stage sample. Assume that the numbers of particles in M×N subcells are observable. The properties of the estimator of the particle density per sample unit are investigated under the modified two-stage cluster sampling method. A laboratory experiment for Xanthan Gum Products is analyzed in order to examine the appropriateness of the model assumed in this paper.  相似文献   
837.
Following the murder of a young child by her stepfather a ministerial review of child protection across Scotland was established. It was carried out by a multidisciplinary team of representatives from education, health‐nursing, health‐medical, police, social work and the Reporter to the Children's Hearing. The review comprised a number of subprojects and included a direct audit of the practice of all the key agencies. The views of the general public, parents, children and professionals were obtained via a set of consultation subprojects. The audit of practice was built around a set of individual, in‐depth case studies. The cases were drawn from the spectrum of child care and protection cases by sampling from cases known to health visitors, education departments, the police and social work departments. The audit considered compliance with guidance, but the key focus was on outcomes for children. The findings indicated that although there were many examples of good practice with children, a significant number of children were left unprotected or their needs were not met. The issues were not unique to Scotland and are discussed under four key areas. The paper sets out the extent of chronic need amongst the child population that the audit revealed, looks at the messages from consultation about issues of accessing help for children or by children directly, and describes some shortcomings of the current system. Finally the paper analyses the ways that the different agencies interact and sets out a model for how the system can provide a protective network for children who are in need of protection and support.  相似文献   
838.
利用循环伏安法对双二茂铁丙烷.6-乙炔基双二茂铁丙烷及其钴簇合物的电化学性质和氧化还原行为进行了研究.研究结果表明.在6-乙炔基双二茂铁丙烷及其钴簇合物中乙炔取代基、簇骨架C2Co2等均能使其两个铁原子中的电子具有更大的交互性.  相似文献   
839.
区域科技发展水平的综合评价   总被引:1,自引:0,他引:1  
建立了区域科技发展水平综合评价指标体系,并采用2002年中国各地区科技发展情况的最新数据,运用系统聚类方法和因子分析模型对各地区科技发展水平进行了综合评价。  相似文献   
840.
跨国公司理论新进展:基于区位与集群的视角   总被引:10,自引:0,他引:10  
区位优势为跨国公司重要的竞争优势来源之一,空间集群则成为当代跨国公司突出的区位选择变量。当前的集群研究中,忽略了跨国公司的参与和对集群开放性的认识,因此本文基于跨国公司的视角,从知识的维度对这种类型的集群进行了分析,并阐述了两者间的互动模式。  相似文献   
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