What to Do at Low Doses: A Bounding Approach for Economic Analysis

To quantify the health benefits of environmental policies, economists generally require estimates of the reduced probability of illness or death. For policies that reduce exposure to carcinogenic substances, these estimates traditionally have been obtained through the linear extrapolation of experimental dose-response data to low-exposure scenarios as described in the U.S. Environmental Protection Agency's Guidelines for Carcinogen Risk Assessment (1986). In response to evolving scientific knowledge, EPA proposed revisions to the guidelines in 1996. Under the proposed revisions, dose-response relationships would not be estimated for carcinogens thought to exhibit nonlinear modes of action. Such a change in cancer-risk assessment methods and outputs will likely have serious consequences for how benefit-cost analyses of policies aimed at reducing cancer risks are conducted. Any tendency for reduced quantification of effects in environmental risk assessments, such as those contemplated in the revisions to EPA's cancer-risk assessment guidelines, impedes the ability of economic analysts to respond to increasing calls for benefit-cost analysis. This article examines the implications for benefit-cost analysis of carcinogenic exposures of the proposed changes to the 1986 Guidelines and proposes an approach for bounding dose-response relationships when no biologically based models are available. In spite of the more limited quantitative information provided in a carcinogen risk assessment under the proposed revisions to the guidelines, we argue that reasonable bounds on dose-response relationships can be estimated for low-level exposures to nonlinear carcinogens. This approach yields estimates of reduced illness for use in a benefit-cost analysis while incorporating evidence of nonlinearities in the dose-response relationship. As an illustration, the bounding approach is applied to the case of chloroform exposure.     

论林业建设与贫困山区可持续发展

在广大乡村，特别是山区，林业对于乡村群众生活水平的提高和生活质量的改善起着重要作用。林业发展是山区经济发展的核心之一，是解决农村贫困问题的关键。针对贫困山区林业发展存在的问题，提出林业发展必须与山村经济发展要相互协调发展的途径。     

“全面小康”与国民教育的发展

全面建设小康社会,需要教育发展作基础;更高水平的小康社会又为教育发展提供了新的机遇。国民教育作为公共事业,关系到国家经济建设和可持续发展,又代表最广大人民群众的根本利益,必须从制度上创新,激发全社会的关注和重视,保证教育的利益最大化、公平化,促进教育的跨越式发展。     

全面建设小康社会条件下精神文明建设的思考

党的十六大提出的全面建设小康社会的奋斗目标,为我国的社会主义精神文明建设提出了新的时代要求。论文从我国全面建设小康社会条件下的社会主义精神文明建设的意义入手,客观分析了我国社会主义精神文明建设面临的新形势,并对新形势下如何推进社会主义精神文明建设进行了探讨。     

Robust confidence interval for a residual standard deviation

The residual standard deviation of a general linear model provides information about predictive accuracy that is not revealed by the multiple correlation or regression coefficients. The classic confidence interval for a residual standard deviation is hypersensitive to minor violations of the normality assumption and its robustness does not improve with increasing sample size. An approximate confidence interval for the residual standard deviation is proposed and shown to be robust to moderate violations of the normality assumption with robustness to extreme non-normality that improves with increasing sample size.     

Uncertainty Analysis for Computer Model Projections of Hurricane Losses

Projecting losses associated with hurricanes is a complex and difficult undertaking that is wrought with uncertainties. Hurricane Charley, which struck southwest Florida on August 13, 2004, illustrates the uncertainty of forecasting damages from these storms. Due to shifts in the track and the rapid intensification of the storm, real-time estimates grew from 2 to 3 billion dollars in losses late on August 12 to a peak of 50 billion dollars for a brief time as the storm appeared to be headed for the Tampa Bay area. The storm hit the resort areas of Charlotte Harbor near Punta Gorda and then went on to Orlando in the central part of the state, with early poststorm estimates converging on a damage estimate in the 28 to 31 billion dollars range. Comparable damage to central Florida had not been seen since Hurricane Donna in 1960. The Florida Commission on Hurricane Loss Projection Methodology (FCHLPM) has recognized the role of computer models in projecting losses from hurricanes. The FCHLPM established a professional team to perform onsite (confidential) audits of computer models developed by several different companies in the United States that seek to have their models approved for use in insurance rate filings in Florida. The team's members represent the fields of actuarial science, computer science, meteorology, statistics, and wind and structural engineering. An important part of the auditing process requires uncertainty and sensitivity analyses to be performed with the applicant's proprietary model. To influence future such analyses, an uncertainty and sensitivity analysis has been completed for loss projections arising from use of a Holland B parameter hurricane wind field model. Uncertainty analysis quantifies the expected percentage reduction in the uncertainty of wind speed and loss that is attributable to each of the input variables.     

论政治语言的结构

分析和研究政治语言的系统结构及结构要素之间的相互关系 ,是研究政治语言的重要内容 ,有利于更好地认识和把握政治语言。政治语言结构是一种特殊的层级系统 ,其要素包括符号、符号系统、符码、文本、语境和话语。政治语言结构的要素之间相互作用、相互关联 ,共同构成了政治语言的系统 ,并以其特有的方式表达政治意义 ,服务于政治活动     

以课程建设为核心，加强素质教育

指出素质教育是一种“以人为本”的教育观 ,注重人的全面发展。强调课程建设是实施素质教育的基础性工作 ,对提高人才培养质量起到关键性的作用。以东北大学平台课程建设为例 ,分析了目前高等学校课程建设的现状 ,并提出课程建设的中心任务是更新教育观念 ,改革教学内容和课程体系 ,以适应学生创新能力培养的需要 ,为高等学校课程建设工作的改革与发展提供理论依据。     

两相交流伺服电机动态性能的研究

对于两相交流电机的速度伺服系统,分析在幅值控制时系统的机械特性与调节特性,提出了影响两相交流伺服电机动态性能的因素是系统的机械时间常数及增益系数的变化。为了防止因机械时间常数及增益系数的变化而引起的动态特性变差,采用一种简易跟随模型参考自适应控制方法,通过模型与自适应机构的调节作用,改善两相交流伺服电机系统的动态特性和控制精度。计算机仿真结果表明,电机的动态持性良好。     

网络环境下的学习模式探索

教育模式是教育观念、教育思想、教与学理论的集中体现,网络的出现为学习者提供了适应个性化需求的自主学习的机会,建立满足不同学生需要的网络学习模式,是网络教学的当务之急。