Optimal designs for compartmental models with correlated observations

The flow of internally deposited radioisotope particles inside the body of people exposed to inhalation, ingestion, injection or other ways is usually evaluated using compartmental models (see Sánchez & López-Fidalgo, (2003, and López-Fidalgo & Sánchez, 2005). The International Commission on Radiological Protection (ICRP, 1994) describes the model of the human respiratory tract, represented by two main regions. One of these, the thoracic region (lungs) is divided into different compartments. The retention in the lungs is given by a large combination of ratios of exponential sums depending on time. The aim of this work is to provide optimal times for making bioassays when there has been an accidental radioactivity intake and there is interest in estimating it. In this paper, a large two–parameter model is studied and a simplified model is proposed in order to obtain optimal designs in a more suitable way. Local c-optimal designs for the main parameters are obtained using the results of López-Fidalgo & Rodríguez-Díaz, 2004). Efficiencies for all the computed designs are provided and compared.     

网络最大流Pareto扩充研究

将网络容量定义为最大s-t流的流量,建立了带有时间和费用双重限制下的网络容量扩充问题模型。通过网络变换,将该问题转化为可利用成熟算法求解的线性最小费用流问题。研究了给定网络容量扩充目标要求下,求解所有关于时间和费用的Pareto优化解问题并提供了相应算法。研究内容不仅适用于各种情形的容量扩充问题,而且还可应用于网络规划。最后通过具体例子的求解,说明了算法的正确性和有效性。     

福利经济学视角下的林业资源配置

本文运用福利经济学理论，分析我国林业资源配置的若干问题，其中包括林业生产要素配置中的帕累托改进、森林资源区域配置中的帕累托改进和林业资源配置的动态均衡分析等，并指出了我国林业资源配置结构调整的趋势。文章运用经典的经济学理论表达范式研究林业经济中的具体问题，丰富和完善了我国的林业经济学。     

Robust stochastic dominance: A semi-parametric approach

Lorenz curves and second-order dominance criteria, the fundamental tools for stochastic dominance, are known to be sensitive to data contamination in the tails of the distribution. We propose two ways of dealing with the problem: (1) Estimate Lorenz curves using parametric models and (2) combine empirical estimation with a parametric (robust) estimation of the upper tail of the distribution using the Pareto model. Approach (2) is preferred because of its flexibility. Using simulations we show the dramatic effect of a few contaminated data on the Lorenz ranking and the performance of the robust semi-parametric approach (2). Since estimation is only a first step for statistical inference and since semi-parametric models are not straightforward to handle, we also derive asymptotic covariance matrices for our semi-parametric estimators.     

VaR的若干度量方法及其比较

目前存在较多的度量VaR的方法,不同的方法计算出的结果又有较大差别。针对这种状况,文章给出了GARCH-GPD模型,并将之与几种普遍使用的估算VaR的方法进行了分析比较。结果表明,GARCH-GPD模型能有效捕捉金融收益序列的尖峰厚尾、波动聚集等特性,在较高的置信水平下,GARCH-GPD模型显示的结果更加安全。     

论福利经济学的伦理学基础

本文探讨了三个问题:第一,为了克服实证经济学的理论局限,福利经济学引入了功利主义作为自己的伦理学基础,实现了实证经济学到规范经济学的转变;第二,仅仅以功利主义作为自己的伦理学基础,福利经济学(通过帕累托准则)无法实现社会福利最大化,因此应该改弦更张,进一步将道义主义作为自己的伦理学基础;第三,同时以功利主义和道义主义作为自己的伦理学基础,福利经济学必须引入伦理妥协的方法,以解决可能遇到的理论不一致问题。     

The Asymptotic Distribution of the S–Gini Index

Several generalizations of the classical Gini index, placing smaller or greater weights on various portions of income distribution, have been proposed by a number of authors. For purposes of statistical inference, the large sample distribution theory of the estimators of those measures of economic inequality is required. The present paper was stimulated by the use of bootstrap by Xu (2000) to estimate the variance of the estimator of the S –Gini index. It shows that the theory of L –statistics (Chernoff, Gastwirth & Johns, 1967; Shorack & Wellner, 1986) makes possible the construction of a consistent estimator for the S –Gini index and proof of its asymptotic normality. The paper also presents an explicit formula for the asymptotic variance. The formula should be helpful in planning the size of samples from which the S –Gini index can be estimated with a prescribed margin of error.     

REDUCED DISTANCE MEASURES AND TRANSFORMATIONS IN PROCESSING MULTIVARIATE OUTLIERS

The study of multivariate outliers raises many problems of definition, principle and manipulation. Well-authenticated tests of discordancy exist only for the multivariate normal distribution. Detection of outliers in non-normal distributions involves the adoption of appropriate criteria to represent 'extremeness' of observations in a sample; corresponding tests of discordancy usually require tedious, or even intractable, distributional and computational manipulations. A class of transformations of the data is considered with a view of transferring some of the familiar and desirable features of discordancy tests for normal samples to non-normal situations.     

A Robust Test for Non-nested Hypotheses

We propose a robust version of Cox-type test statistics for the choice between two non-nested hypotheses. We first show that the influence of small amounts of contamination in the data on the test decision can be very large. Secondly, we build a robust test statistic by using the results on robust parametric tests that are available in the literature and show that the level of the robust test is stable. Finally, we show numerically not only the robustness of this new test statistic but also that its asymptotic distribution is a good approximation of its sample distribution, unlike for the classical test statistic. We apply our results to the choice between a Pareto and an exponential distribution as well as between two competing regressors in the simple linear regression model without intercept.     

天然气操作成本影响因素分析方法研究

以HTB气田为例,首先采用帕累托原理和灰关联分析,找出气田操作成本中的主要影响因素和各分项费用与操作成本之间的关联度,再采用指数分析法精确地描述其变动的影响因素,从而全面、准确分析天然气操作成本变动情况,为天然气成本控制和提高气田的经济效益提供科学依据。