Residential House and Zone Volumes in the United States: Empirical and Estimated Parametric Distributions

This research reports empirical distributions and estimated univariate parametric probability distributions for house volume and certain zone volumes within households for residential structures in the United States. The author derived the distributions from two separate databases. The volumes were found to be exceptionally well fit by lognormal distributions (adjusted R² >> 0.95) in almost all cases. In addition, data from one database indicates that the correlation between house volume and air changes per hour is very weak.     

大气污染对杉木生长影响的初步研究

对资江氮肥厂附近大乘山杉木生长情况所作的研究工作包括大气监测、杉叶叶绿素、钾离子外渗率、电解质外渗率及其营养元素N、P、K、Ca、Mg、全S含量的测定,树干解析,结果表明:离厂越近,大气污染物SO_2、NO_2、和NH_3等的浓度越高,杉叶叶绿素及其P、K、Ca、Mg等营养元素含量:对照区>污染区;而杉叶钾离子外渗率和电解质外渗率及其全S、全N含量为:污染区>对照区,且叶中全S和全N含员随着时间的推移逐渐增加,分析表明:大气污染是大乘山杉木衰亡的重要原因。     

Predicted Infant Exposure to Tetrachloroethene in Human Breastmilk

Based on a variety of maternal occupational and residential inhalation exposure scenarios, estimates of infant exposure to the dry-cleaning solvent tetrachlorothylene (perchloroethylene, PCE) in breastmilk were made. Physiologically based pharmacokinetic (PBPK) modeling indicates that infants may be exposed to elevated levels of PCE in breastmilk due to their mothers' inhalation of PCE. The PBPK-predicted breastmilk PCE concentrations agree very well with measured concentrations, where available. Based on this analysis, infants may be exposed to this workplace chemical via breastmilk at doses corresponding to rather high levels of risk. Predicted breastmilk doses provide the infant with little margin of exposure to doses associated with adverse health effects. In addition, the estimated increased cancer risks associated with these infant exposures are large under certain exposure scenarios. The actual concentrations of PCE in breastmilk of exposed mothers can only be known with certainty if monitoring is conducted. Due to the widespread exposure potential, monitoring studies should be undertaken so that the appropriate risk management alternatives can be better evaluated.     

Effects of Surface Material,Ventilation, and Human Behavior on Indirect Contact Transmission Risk of Respiratory Infection

Infectious particles can be deposited on surfaces. Susceptible persons who contacted these contaminated surfaces may transfer the pathogens to their mucous membranes via hands, leading to a risk of respiratory infection. The exposure and infection risk contributed by this transmission route depend on indoor surface material, ventilation, and human behavior. In this study, quantitative infection risk assessments were used to compare the significances of these factors. The risks of three pathogens, influenza A virus, respiratory syncytial virus (RSV), and rhinovirus, in an aircraft cabin and in a hospital ward were assessed. Results showed that reducing the contact rate is relatively more effective than increasing the ventilation rate to lower the infection risk. Nonfabric surface materials were found to be much more favorable in the indirect contact transmission for RSV and rhinovirus than fabric surface materials. In the cases considered in this study, halving the ventilation rate and doubling the hand contact rate to surfaces and the hand contact rate to mucous membranes would increase the risk by 3.7–16.2%, 34.4–94.2%, and 24.1–117.7%, respectively. Contacting contaminated nonfabric surfaces may pose an indirect contact risk up to three orders of magnitude higher than that of contacting contaminated fabric surfaces. These findings provide more consideration for infection control and building environmental design.     

基于系统GMM估计的京津冀数字金融对空气质量动态效应研究

数字金融兼顾金融发展与数字化技术,是绿色金融发展的重要推动力,对空气污染治理的长效机制有着重要意义。文章基于2014—2020年京津冀地区13个城市的面板数据,构建动态GMM模型重点考察了数字金融发展对空气质量水平的动态影响。结果表明,京津冀地区空气质量发展状况分区现象明显;数字金融能够显著改善空气质量,这一影响过程是长期有效的,这一结论在多种方法稳健性检验的基础上依然成立;数字金融指数三个子维度的空气污染治理效果具有明显差异,数字金融覆盖广度与数字化程度能够有效改善空气质量,数字金融使用深度存在不显著的抑制作用,在影响程度上数字化程度>覆盖广度>使用深度。     

亚轨道商业飞行的法律规制

近年来,已有多家企业利用新研发的亚轨道飞行器,开展了以旅游观光为目的的亚轨道商业飞行,亚轨道飞行的商业运输发展势头愈来愈猛.由于空气空间和外层空间的定界一直悬而未决,亚轨道飞行的法律地位也因此处于模糊地带.目前仍缺乏具体有效的国际公约对亚轨道商业飞行进行法律规制,现有的航空法公约和空间法公约能否适用以及如何适用于亚轨道商业飞行成为关键问题.与此同时,以美国、欧盟为代表的国家和地区纷纷制定了亚轨道商业飞行的相关法律规则,以国内法对亚轨道商业飞行活动进行监管并促进其发展.结合相关国际法和国内法的相关规定,对亚轨道商业飞行器的管辖权问题及其造成的损害赔偿责任等方面进行深入研究分析,旨在系统梳理亚轨道商业飞行的法律规制现状,为中国发展亚轨道商业飞行并建立相关监管制度提出初步建议.     

Simulations and computations of nonparametric density estimates for the deconvolution problem

The nonparametric density function estimation using sample observations which are contaminated with random noise is studied. The particular form of contamination under consideration is Y = X + Z, where Y is an observable random variableZ is a random noise variable with known distribution, and X is an absolutely continuous random variable which cannot be observed directly. The finite sample size performance of a strongly consistent estimator for the density function of the random variable X is illustrated for different distributions. The estimator uses Fourier and kernel function estimation techniques and allows the user to choose constants which relate to bandwidth windows and limits on integration and which greatly affect the appearance and properties of the estimates. Numerical techniques for computation of the estimated densities and for optimal selection of the constant are given.     

中国传统养生文化的传承与发展探究

中国传统养生文化源远流长,是中华民族优秀传统文化的重要组成部分。然而,在生产方式变革、社会、经济和政治不断发展的综合作用下,我国传统养生文化传承与发展也遇到了新的问题。文章着重从中国传统养生文化的起源与形成、呈现形式、传统养生文化传承与发展中的问题及对策和建议四个方面进行深入剖析。对解决当代传统养生文化传承与发展中遇到的问题,推进中国传统养生文化的发展,弘扬中华民族优秀传统文化具有重要的理论与现实意义。     

改制谐波励磁发电机的简便设计

本文针对改制谐波励磁发电机时,由于原产品型号或生产年代不同而产生的性能差异较大的情况,提出根据发电机铁芯的极弧系数αP 进行电枢绕组结构选择,给出了进行谐波绕组可靠匝数计算的实用公式 W_(3K)=(W_1·U_(BH)·(δ_m/a)~(1/2))/(m_3·U_1·αp~3·K_(r3)),并讨论了凸极铁芯参数对谐波励磁发电机性能的影响及其处理方法.     

Quantification of Variability and Uncertainty for Censored Data Sets and Application to Air Toxic Emission Factors

Many environmental data sets, such as for air toxic emission factors, contain several values reported only as below detection limit. Such data sets are referred to as "censored." Typical approaches to dealing with the censored data sets include replacing censored values with arbitrary values of zero, one-half of the detection limit, or the detection limit. Here, an approach to quantification of the variability and uncertainty of censored data sets is demonstrated. Empirical bootstrap simulation is used to simulate censored bootstrap samples from the original data. Maximum likelihood estimation (MLE) is used to fit parametric probability distributions to each bootstrap sample, thereby specifying alternative estimates of the unknown population distribution of the censored data sets. Sampling distributions for uncertainty in statistics such as the mean, median, and percentile are calculated. The robustness of the method was tested by application to different degrees of censoring, sample sizes, coefficients of variation, and numbers of detection limits. Lognormal, gamma, and Weibull distributions were evaluated. The reliability of using this method to estimate the mean is evaluated by averaging the best estimated means of 20 cases for small sample size of 20. The confidence intervals for distribution percentiles estimated with bootstrap/MLE method compared favorably to results obtained with the nonparametric Kaplan-Meier method. The bootstrap/MLE method is illustrated via an application to an empirical air toxic emission factor data set.