浅议我国木材国际贸易的比较优势

在世贸组织体制下 ,我国木材国际贸易的环境将发生重大变化。木材国际贸易对缓解我国森林资源紧张矛盾 ,促进木材产业适应国际竞争要求 ,提高产业竞争力具有重要意义。我国木材产业在我国产业体系中处于相对落后位置 ,但不等于其产品完全没有国际贸易的比较优势。该文主要通过对我国木材产业部分产品贸易比较优势的分析 ,说明我国木材产业部分产品参与国际竞争的可能性和现实性。同时 ,提出我国保持现有产品比较优势和培育新的产品比较优势的战略立足点     

Ambivalences: a challenge to permanency for children

A key to determining a permanent plan for children in placement lies in determining and working with the history and relative intensity of parental ambivalence in the parent-child relationship as it is acted out in the placement experience. A study of cases in a public department disclosed not only indicators of parental ambivalence but also the reinforcement of that ambivalence by agency policy, working conditions, and lack of resources.     

An iterative Monte Carlo method for nonconjugate Bayesian analysis

The Gibbs sampler has been proposed as a general method for Bayesian calculation in Gelfand and Smith (1990). However, the predominance of experience to date resides in applications assuming conjugacy where implementation is reasonably straightforward. This paper describes a tailored approximate rejection method approach for implementation of the Gibbs sampler when nonconjugate structure is present. Several challenging applications are presented for illustration.     

Low-Income Children's Participation in a Public Health Insurance Program in Georgia

To expand health care coverage to uninsured, low-income children, the Congress created the State Children's Health Insurance Program (SCHIP) in 1997. Given ample evidence that state Medicaid programs have failed to enroll many eligible children, experts questioned whether SCHIP could successfully enroll low-income children. Using Georgia state SCHIP data, we analyzed enrollment patterns and identified factors contributing to program enrollment. This study found that the children's enrollment is explained by perceived costs and benefits of joining the program as well as the underlying family structure, demographic factors, and health status. We discuss implications of these findings on the participation of low-income families in public sector programs.     

Inference in model-based cluster analysis

A new approach to cluster analysis has been introduced based on parsimonious geometric modelling of the within-group covariance matrices in a mixture of multivariate normal distributions, using hierarchical agglomeration and iterative relocation. It works well and is widely used via the MCLUST software available in S-PLUS and StatLib. However, it has several limitations: there is no assessment of the uncertainty about the classification, the partition can be suboptimal, parameter estimates are biased, the shape matrix has to be specified by the user, prior group probabilities are assumed to be equal, the method for choosing the number of groups is based on a crude approximation, and no formal way of choosing between the various possible models is included. Here, we propose a new approach which overcomes all these difficulties. It consists of exact Bayesian inference via Gibbs sampling, and the calculation of Bayes factors (for choosing the model and the number of groups) from the output using the Laplace–Metropolis estimator. It works well in several real and simulated examples.     

Detecting active effects in unreplicated designs

Unreplicated factorial designs pose a difficult problem in analysis because there are no degrees of freedom left to estimate the error. Daniel [Technometrics 1 (1959), pp. 311-341] proposed an ingenious graphical method that does not require σ to be estimated. Here we try to put Daniel's method into a formal framework and lift the subjectiveness that carries. A simulation study has been conducted that shows that the proposed method behaves better than Lenth's [Technometrics 31 (1989), pp. 469-473] popular method.     

Kurtosis and spread

An increase in kurtosis is achieved through the location- and scale-free movement of probability mass from the “shoulders” of a distribution into its centre and tails. We introduce a coherent structure of ordering and measures, requiring no symmetry assumption, that represent different formalizations of this movement. For this purpose spread functions and spread-spread plots are defined. The orderings impose growth patterns on the spread-spread plot of the distributions involved, and the weakest involve both a specific scale-matching technique and placement of “shoulders”. The role of existing kurtosis orderings and measures in this general context is identified and examples discussed throughout.