MDEWMA chart: an efficient and robust alternative to monitor process dispersion

Control chart is the most important statistical process control tool used to monitor changes in process location and dispersion. In this study, an EWMA control chart is proposed for efficient and robust monitoring of process dispersion. The proposed chart, namely the MDEWMA chart, is based on estimating the process standard deviation (σ) using the mean absolute deviations (MD), taken from the sample median. The performance of the proposed chart has been compared with the EWMASR chart (a dispersion EWMA chart based on sample range) and MD chart (a Shewhart-type dispersion chart based on MD), under the existence and violation of normality assumption. It has been observed that the proposed MDEWMA chart is more efficient and robust when compared with both EWMASR and MD charts in terms of run length (RL) characteristics such as average RL, median RL and standard deviation of the RL distribution.     

Distance equalizers

Distance equalizers are introduced as empirical measures of central tendency that make distances to univariate data as similar as possible. These measures are made precise by means of various so-called fluctuation functions which account for distances in different ways. Distance equalizers differ from the mean as well as from the median. Also, distance equalizers relate to dispersion measures. Algorithms and closed-form solutions for special cases are given. Some computations require to perform multiextremal function minimization. Distance equalization is extendable to data from higher dimensions and to function quantization in signal processing.     

On confidence regions of semiparametric nonlinear reproductive dispersion models

This article investigates the confidence regions for semiparametric nonlinear reproductive dispersion models (SNRDMs), which is an extension of nonlinear regression models. Based on local linear estimate of nonparametric component and generalized profile likelihood estimate of parameter in SNRDMs, a modified geometric framework of Bates and Wattes is proposed. Within this geometric framework, we present three kinds of improved approximate confidence regions for the parameters and parameter subsets in terms of curvatures. The work extends the previous results of Hamilton et al. [in Accounting for intrinsic nonlinearity in nonlinear regression parameter inference regions, Ann. Statist. 10, pp. 386–393, 1982], Hamilton [in Confidence regions for parameter subset in nonlinear regression, Biometrika, 73, pp. 57–64, 1986], Wei [in On confidence regions of embedded models in regular parameter families (a geometric approch), Austral. J. Statist. 36, pp. 327–338, 1994], Tang et al. [in Confidence regions in quasi-likelihood nonlinear models: a geometric approach, J. Biomath. 15, pp. 55–64, 2000b] and Zhu et al. [in On confidence regions of semiparametric nonlinear regression models, Acta. Math. Scient. 20, pp. 68–75, 2000].     

论环境影响评价与排污许可制度的互动和衔接——从制度逻辑和构造建议的角度

如何将环境影响评价与排污许可等环境治理工具进行互动与衔接是未来环境治理制度改革的关键。两种制度在现时的环境下都存在各自的问题及相应的变革路径。两种不同的变革路径却有着共同的价值需求，即环境影响评价与排污许可的衔接与互动。在衔接的过程中存在的最大的争议就是维持或简化环境影响评价审批，这种衔接思路的差异制造了两种截然相反的制度逻辑:一种以维持环评审批为核心，另一种以简化环评审批为核心。就中国目前的环境影响评价制度改革方向而言，简化环评审批似乎已是不可阻挡之潮流。是否应当以简化环评审批、强调排污许可为目标进行两种制度的衔接。简化环评审批并不等同于弱化环评制度；在环境影响评价与排污许可的衔接构造上，应当遵循的思路:在宏观上，以效益最大化统领全局；在具体操作上，秉持“在简化环境影响评价的大环境中，寻找强化的契机；以排污许可为核心的进程中，夯实衔接的构造”的理念。     

A Study of Interval Censoring in Parametric Regression Models

Parametric models for interval censored data can now easily be fitted with minimal programming in certain standard statistical software packages. Regression equations can be introduced, both for the location and for the dispersion parameters. Finite mixture models can also be fitted, with a point mass on right (or left) censored observations, to allow for individuals who cannot have the event (or already have it). This mixing probability can also be allowed to follow a regression equation.Here, models based on nine different distributions are compared for three examples of heavily censored data as well as a set of simulated data. We find that, for parametric models, interval censoring can often be ignored and that the density, at centres of intervals, can be used instead in the likelihood function, although the approximation is not always reliable. In the context of heavily interval censored data, the conclusions from parametric models are remarkably robust with changing distributional assumptions and generally more informative than the corresponding non-parametric models.     

Risk of Legionellosis in residential areas around farms irrigating with municipal wastewater

The conservation of freshwater is of both global and national importance, and in the United States, agriculture is one of the largest consumers of this resource. Reduction of the strain farming puts on local surface or groundwater is vital for ensuring resilience in the face of climate change, and one possible option is to irrigate with a combination of freshwater and reclaimed water from municipal wastewater treatment facilities. However, this wastewater can contain pathogens that are harmful to human health, such as Legionella pneumophila, which is a bacterium that can survive aerosolization and airborne transportation and cause severe pneumonia when inhaled. To assess an individual adult's risk of infection with L. pneumophila from a single exposure to agricultural spray irrigation, a quantitative microbial risk assessment was conducted for a scenario of spray irrigation in central Illinois, for the growing seasons in 2017, 2018, and 2019. The assessment found that the mean risk of infection for a single exposure exceeded the safety threshold of 10^–6 infections/exposure up to 1 km from a low-pressure irrigator and up to 2 km from a high-pressure irrigator, although no median risk exceeded the threshold for any distance or irrigator pressure. These findings suggest that spray irrigation with treated municipal wastewater could be a viable option for reducing freshwater consumption in Midwest farming, as long as irrigation on windy days is avoided and close proximity to the active irrigator is limited.     

论排污交易法律关系

论证企业间以排放指标为标的的排污交易、环境主管部门与企业间的排污行政许可及排污费是相互独立的法律关系,三者具有不同的法律性质,提出对它们分别进行法律规制的设想。认为为使环境行政管理不对排污指标的市场配置机制造成障碍,法律应明确排污交易适用商事交易规则,对于排污交易引起的排污权主体变动,应以对出卖排污指标企业进行许可证变更或解除以及由购进排污指标企业申请新排污许可的制度模式进行承认。此外,还论述环境管理部门在排污交易相关管理体系中应具有的法律功能。     

“十二五”时期污染减排面临的机遇挑战及政策建议

"十一五"时期减排取得的成效和经验为完成"十二五"更加严格、全面的减排任务打下了良好的基础,但"十二五"时期我国污染减排也面临存量减排空间缩小、后续减排难度增大、新增减排领域能力建设滞后、企业减排信心不足、污染治理成本上升等一系列问题和困难。为此,应着力推进减排技术与制度创新,进一步加强工程减排、结构减排和管理减排,以确保"十二五"减排目标顺利实现,全面改善环境质量。     

特殊多层结构中电磁波传播特性研究

对各向异性导体-介质-等离子体特殊多层结构中电磁波的传播特性进行了研究。通过理论推导得到了该结构中的色散方程;并通过计算机计算,给出了色散曲线。研究了该结构中是否存在金属网层对色散曲线的影响,证明了金属网层对电磁波的耦合作用,使慢波和等离子体表面波结合产生了慢等离子体表面波。分析了金属网角度、介质厚度和介电常数对色散的影响。     

Estimation of coefficient of dispersion using auxiliary information

In this note, we consider the problem of estimation of coefficient of dispersion of a study variable by making use of known value of the coefficient of dispersion of an auxiliary variable. We propose ratio and regression-type estimators. We derive expressions of bias and variance of the proposed estimators to the first order of approximation. The relative efficiencies of the ratio and regression-type estimators with respect to the naïve estimator are investigated through a simulation study.