Sampling Strategies for Toxic Air Contaminants

Annual concentrations of toxic air contaminants are of primary concern from the perspective of chronic human exposure assessment and risk analysis. Despite recent advances in air quality monitoring technology, resource and technical constraints often impose limitations on the availability of a sufficient number of ambient concentration measurements for performing environmental risk analysis. Therefore, sample size limitations, representativeness of data, and uncertainties in the estimated annual mean concentration must be examined before performing quantitative risk analysis. In this paper, we discuss several factors that need to be considered in designing field-sampling programs for toxic air contaminants and in verifying compliance with environmental regulations. Specifically, we examine the behavior of SO2, TSP, and CO data as surrogates for toxic air contaminants and as examples of point source, area source, and line source-dominated pollutants, respectively, from the standpoint of sampling design. We demonstrate the use of bootstrap resampling method and normal theory in estimating the annual mean concentration and its 95% confidence bounds from limited sampling data, and illustrate the application of operating characteristic (OC) curves to determine optimum sample size and other sampling strategies. We also outline a statistical procedure, based on a one-sided t-test, that utilizes the sampled concentration data for evaluating whether a sampling site is compliance with relevant ambient guideline concentrations for toxic air contaminants.     

人民币实际汇率波动与中国对美出口

运用协整方法对人民币实际汇率波动与中国对美出口的关系进行实证研究。结果表明：中国对美出口收入效应极强,中国对美出口汇率波动效应较弱,中国对美出口的价格效应不存在。在美国经济可能陷入衰退的情况下,中国政府应暂缓人民币升值和人民币汇率形成机制改革的步伐。     

Accurate estimation for extra-Poisson variability assuming random effect models

In this study, the components of extra-Poisson variability are estimated assuming random effect models under a Bayesian approach. A standard existing methodology to estimate extra-Poisson variability assumes a negative binomial distribution. The obtained results show that using the proposed random effect model it is possible to get more accurate estimates for the extra-Poisson variability components when compared to the use of a negative binomial distribution where it is possible to estimate only one component of extra-Poisson variability. Some illustrative examples are introduced considering real data sets.     

当代先锋文学中的江南文化因素

江南文化的诗性特征和在全国文化版图中得天独厚的领先优势,是当今中国先锋文学的深厚精神和艺术营养。与伦理的北方齐鲁文化以及同处南方的其他文化类型相比,江南文化的审美性带有了某种宗教般的超越性品格。这些深厚的文化积淀在当代先锋文学之中,成为这种新潮审美形式不竭的精神和艺术资源。然而这种继承和吸纳是以一种悖反的方式实现的。     

心律波动信号的1/f噪声特性分析

心律波动信号具有1/f噪声特性,是非平稳的。该文采用平均功率谱密度方法,分析了基于平均功率谱密度和最小二乘拟合法求正常人和心脏充血患者的心律波动信号的谱参数,发现根据谱参数可以定量地区分正常人与心脏充血患者:大部分正常人的心律波动信号的谱参数大于1,而大部分心脏充血患者的心律波动信号的谱参数小于1,该结论可为心脏病的诊断与预诊断提供一种辅助手段。     

论语言变体和语用失误之间的互相影响

第二语言习得的过程是一个自然的连续体。语言变体研究第二语言习得过程中连续体的节．属于语言习得过程的输入。语言变体由系统变体和非系统变体构成,其中又含有个体变体和语境变体。语用失误则将研究的重点放在语用上,注重语言使用者运用语言过程中出现的失误,属于语言交际过程中的输出。语用失误由语用语言失误和社会语用失误构成。两种不同的理论研究共同的对象——语言习得者,从不同的角度来研究语言的习得和使用,这就极大地丰富了语言习得和使用的内涵,对语言的学和教有着十分重要的价值。     

Increasing Vocal Variability in Children with Autism Using a Lag Schedule of Reinforcement

Variability has been demonstrated to be an operant dimension of behavior (Neuringer, 2002; Page & Neuringer, 1985). Recently, lag schedules have been used to demonstrate operant variability of verbal behavior in persons with a diagnosis of autism (e.g., Lee, McComas, & Jawor, 2002). The current study evaluated the effects of a Lag 1 schedule on the vocal variability of 2 nonverbal children with a diagnosis of autism. Results showed systematic increases in variability during the Lag 1 schedule. Implications of lag schedules for speech and language training are discussed.     

Simultaneous decomposition of the variance by sources and subgroups – new insights

There are two types of decompositions: of linear combinations of random variables into contributions of individual variables (sources) and associations between them, and of populations into contributions of their subpopulations. Simultaneous treatment of the two types is called for, which takes into account the correlations between sources within subpopulations and between subpopulation means. The expected values of the subcomponents are derived and their sensitivity to correlations among sources within groups and among source group means is conducted. An example is provided, in which the correlations contribute 20--25% to total variability. This additional information is hidden when decompositions are not simultaneous.     

中国传统诗学的"异质性"概说

由于西学知识对传统知识谱系的全面替换,中国传统诗学已成为一种"异质"的知识.认识中国传统诗学的这种"异质性"对于中西两种异质的诗学如何在平等对话的基础上达到互补,具有重要的意义.基于这一总体性认识,文章从中西比较的角度对中国传统诗学的谱系结构、知识质态和知识言路作了具体而深入的分析,阐明了中国传统诗学的"异质性"特征.     

Variability in Physical Constant Parameter Values from Standard Data Sources and the Implication of This Variability for Risk Analysis

Physical property values are used in environmental risk assessments to estimate media and risk-based concentrations. However, considerable variability has recently been reported with such values. To evaluate potential variability in physical parameter values supporting a variety of regulatory programs, eight data sources were chosen for evaluation, and chemicals appearing in at least four sources were selected. There were 755 chemicals chosen. In addition, chemicals in seven environmentally important subgroups were also identified for evaluation. Nine parameters were selected for analysis-molecular weight (MolWt), melting point (MeltPt), boiling point (BoilPt), vapor pressure (VP), water solubility (AqSOL), Henry's law constant (HLC), octanol-water partition coefficient (Kow), and diffusion coefficients in air (Dair) and water (Dwater). Results show that while 71% of constituents had equal MolWts across data sources, <3% of the constituents had equivalent parameter values across data sources for AqSOL, VP, or HLC. Considerable dissimilarity between certain sources was also observed. Furthermore, measures of dispersion showed considerable variation in data sets for Kow, VP, AqSOL, and HLC compared to measures for MolWt, MeltPt, BoilPt, or Dwater. The magnitude of the observed variability was also noteworthy. For example, the 95th percentile ratio of maximum/minimum parameter values ranged from 1.0 for MolWt to well over 1.0E + 06 for VP, and HLC. Risk and exposure metrics also varied by similar magnitudes. Results with environmentally important subgroups were similar. These results show that there is considerable variability in physical parameter values from standard sources, and that the observed variability could affect potential risk estimates and perhaps risk management decisions.