Uncertain Numbers and Uncertainty in the Selection of Input Distributions—Consequences for a Probabilistic Risk Assessment of Contaminated Land

Risks from exposure to contaminated land are often assessed with the aid of mathematical models. The current probabilistic approach is a considerable improvement on previous deterministic risk assessment practices, in that it attempts to characterize uncertainty and variability. However, some inputs continue to be assigned as precise numbers, while others are characterized as precise probability distributions. Such precision is hard to justify, and we show in this article how rounding errors and distribution assumptions can affect an exposure assessment. The outcome of traditional deterministic point estimates and Monte Carlo simulations were compared to probability bounds analyses. Assigning all scalars as imprecise numbers (intervals prescribed by significant digits) added uncertainty to the deterministic point estimate of about one order of magnitude. Similarly, representing probability distributions as probability boxes added several orders of magnitude to the uncertainty of the probabilistic estimate. This indicates that the size of the uncertainty in such assessments is actually much greater than currently reported. The article suggests that full disclosure of the uncertainty may facilitate decision making in opening up a negotiation window. In the risk analysis process, it is also an ethical obligation to clarify the boundary between the scientific and social domains.     

语言冗余现象在英语教学中的作用初探

冗余是人类语言的固有特征。冗余现象的研究在语言学中占据重要地位,它对语言教学的影响也日益受到重视。本文利用语言测试手段,通过实验验证了冗余理论在英语教学中的积极作用     

The design of organizations and the right to act

Recent innovations in the structure of formal organizations suggest possible directions for the design of schools to bring about high achievement. The structure of output-driven in contrast to administratively-driven schools is described, and designs are described which address both the goal of high achievement and the goal of reduced inequality.An earlier version of this paper was presented as the author's Sorokin Lecture at the annual meeting of the Eastern Sociological Society, Boston, March 1993.     

经济收敛理论与检验方法研究综述

在大量文献研究的基础上,对收敛问题的产生及收敛概念的发展作了全面概括,并对绝对收敛、条件收敛、俱乐部收敛和σ收敛作了深入辨析,对各种识别方法作了全面归纳。归纳了对世界大多数国家和地区数据所作识别的结果。还从收敛理论与传统理论的冲突与协调方面作了深入分析。最后对近年收敛研究的深化与扩展研究的趋势作了概括。     

A new test for multivariate normality by combining extreme and nonextreme BHEP tests

In this article, we propose a new multiple test procedure for assessing multivariate normality, which combines BHEP (Baringhaus–Henze–Epps–Pulley) tests by considering extreme and nonextreme choices of the tuning parameter in the definition of the BHEP test statistic. Monte Carlo power comparisons indicate that the new test presents a reasonable power against a wide range of alternative distributions, showing itself to be competitive against the most recommended procedures for testing a multivariate hypothesis of normality. We further illustrate the use of the new test for the Fisher Iris dataset.     

Affirmation effects on math scores: The importance of high school track

Stereotype threat has been shown to affect academic performance of minority racial groups. Minority girls may experience the burdens of both race and gender - a “double bind” theorized to affect the underrepresentation of women in STEM fields. A randomized controlled trial focused on alleviating stereotype threat in three high schools in a large U.S. metro demonstrates the effects of affirmative writing interventions, which have previously shown positive effects for minority and female students. Results indicate effects for these groups were insignificant. However, results also show that student track is highly significant at p < 0.001, and interactive analyses suggest that the intervention may help alleviate threat for higher-achieving students.     

Robust block bootstrap panel predictability tests*

This article develops two block bootstrap-based panel predictability test procedures that are valid under very general conditions. Some of the allowable features include cross-sectional dependence, heterogeneous predictive slopes, persistent predictors, and complex error dynamics, including cross-unit endogeneity. While the first test procedure tests if there is any predictability at all, the second procedure determines the units for which predictability holds in case of a rejection by the first. A weak unit root framework is adopted to allow persistent predictors, and a novel theory is developed to establish asymptotic validity of the proposed bootstrap. Simulations are used to evaluate the performance of our tests in small samples, and their implementation is illustrated through an empirical application to stock returns.     

矿渣MTC胶结物抗腐蚀性能研究

随着矿渣MTC技术的发展和应用,矿渣MTC胶结物的抗腐蚀性能日益受到人们的关注。矿渣MTC胶结物的抗腐蚀性能直接关系到矿渣胶结物后期性能,并影响井和套管的使用寿命。分析了矿渣MTC胶结物可能受到的几种腐蚀类型及其机理,实验验证了矿渣胶结物具有较强的抗NaCl、Na₂CO₃、Na₂SO₄、MgSO₄侵蚀的能力,但易受酸性介质腐蚀;实验发现了加入胶乳能较大幅度提高矿渣胶结物抗酸性介质腐蚀的能力,并对胶乳提高矿渣胶结物抗酸蚀能力的原因进行了分析。