Predicting the ejection velocities of fragments from explosions cylindrical pressure vessels: Uncertainty and sensitivity analysis

The purpose of this study was a refinement of knowledge on predicting the ejection velocities of fragments generated by explosions of cylindrical horizontal pressure vessels. A procedure is proposed for assessing these velocities by means of the stochastic simulation. The procedure is used to quantify uncertainties related to the ejection velocities and to carry out a simulation-based sensitivity analysis. The main finding is that the currently available information on phenomena related to the vessel fragmentation is sparse and, therefore, predicting ejection velocities will require a substantial amount of subjective judgement. It was found that ejection velocities are functions of a relatively large number of random input variables, many of which must be modelled subjectively. The study revealed also the need to choose subjectively between several alternative mathematical models used to specify input variables that influence the ejection velocities. The most critical choice must be made between several models used for an assessment of the energy liberated during vessel explosions. Results of the sensitivity analysis indicate that the ejection velocities are influenced mainly by input variables used to express energies involved in the prediction problem. Increased sensitivity to filling ratio of a two-phase pressure vessel was also detected. Results of the study can be used for an improvement of estimation of fragment impact probabilities and design of protective barriers that are built close to the pressure vessels posing explosion hazard.     

Pollutant loads of surface runo inWuhan City Zoo, an urban tourist area

The pollutant loads of surface runoff in an urban tourist area have been investigated for two years in the Wuhan City Zoo, China. Eight sampling sites, including two woodlands, three animal yards, two roofs and one road, were selected for sampling and study. The results indicate that pollutants ranked in a predictable order of decreasing load （e.g. animal yard〉roof〉woodland〉road）, with animal yards acting as the key pollution source in the zoo. Pollutants were transported mainly by particulate form in runoff. Particulate nitrogen and particulate phosphorous accounted on average for 61%, 78% of total pollutant, respectively, over 13 monitored rainfall events. These results indicate the treatment practices should be implemented to improve particulate nutrient removal. Analysis of the M（V） curve indicate that no first flush effect existed in the surface runoff from pervious areas （e.g. woodland, animal ground yard）, whereas a first flush effect was evident in runoff from impervious surfaces （e.g. animal cement yard, roof, road）.     

产电微生物反应系统内电阻的快速测定

内阻是表征反应器内部状态的重要参数.传统的极化曲线法存在耗时长、对系统日常运行干扰严重等问题.本研究尝试通过减小可变外阻的调节范围,使系统内阻的测定可以在非常接近于系统日常运行状态的有限外阻变化范围内完成,在实现内阻快速测定的同时,有效控制了测定过程对系统运行状态的干扰.在外阻调节步长为10Ω,电压稳定时间1 min条件下,单次测定用时缩短到10 min,测定前后系统电流的变化1.5%.不同稳定时间对内阻测定结果的影响不大.减小外阻调节步长虽然有助于降低测量过程对系统运行的干扰,但在相同万用表精度下,测量误差有增大的趋势.本研究所提出的方法能够比较实时地反映系统内阻的变化情况.     

高效低温聚磷菌的筛选及特性研究

通过人工模拟自然降温的方式,从A2/O反应器驯化污泥中筛选到低温条件下聚磷效果较好的三株功能菌株P1、P2、P3,经试验得到一种分离聚磷菌效果较好的方法 -稀释混合平板法;分析研究三株菌的聚磷效果、生化特性,测定三株菌的多维生长曲线,研究了温度、pH、微量元素对这三株菌的生长量及除磷率的影响,结果表明,三株菌的生长最适温度均为15℃,适宜的生长和除磷pH为中性偏碱。最后用分子生物学的方法对三株菌进行鉴定,三株菌均属于不动杆菌属的约氏不动杆菌(A cinetobacter Johnson ii)。     

Cross-country income disparity and its effect on carbon emissions

This study is motivated by the interesting relationship between the income Kuznets curve and the carbon Kuznets curve.This paper focuses on the interaction effects of income distribution and income per capita on CO₂ emissions using country group panel data over the period of 1980 to 2006 by employing fixed effects（FE）,random effects（RE）and feasible generalized least squares（FGLS）estimation methods.The main findings are as follows.（1）There exists an inverted-U relationship between CO₂ emissions per capita and income per capita in all sample countries and high-income groups.（2）The cross-country income disparity has a negative effect on the average level of CO₂ emissions but a positive effect on the aggregate income elasticity of CO₂ emissions.（3）This negative effect of income disparity on the average level of CO₂emissions decreases along with the growth of per capita income.Thus,economic growth contributes to the reduction of this negative impact.     

民航旅客行李托运差异化安检设备联合响应研究*

为提高行李托运差异化安检系统安全性,基于安检设备的依赖关系,提出行李托运安检设备联合响应研究;根据旅客风险属性对其托运行李实施差异化安检,利用二维正态分布建立安检设备的响应分布函数,进行安检设备响应值的数据融合;将系统错误率作为评价指标对比设备联合响应与设备独立响应,分析设备之间的相关系数、报警阈值对系统安全性的影响,并借助ROC曲线得到最优设备报警阈值。研究结果表明:在行李托运差异化安检系统中,设备联合响应优于设备独立响应。研究结果可为民航旅客行李托运安检提供设备支持。     

River Channel Geometry and Rating Curve Estimation Using Height above the Nearest Drainage

River channel geometry is an important input to hydraulic and hydrologic models. Traditional approaches to quantify river geometry have involved surveyed river cross sections, which cannot be extended to ungaged basins. In this paper, we describe a method for developing a synthetic rating curve to relate flow to water level in a stream reach based on reach‐averaged channel geometry properties developed using the Height above Nearest Drainage (HAND) method. HAND uses a digital elevation model (DEM) of the terrain and computes the elevation difference between each land surface cell and the stream bed cell to which it drains. Taking increments in water level in the stream, HAND defines the inundation zone and a water depth grid within this zone, and the channel characteristics are defined from this water depth grid. We apply our method to the Blanco River (Texas) and the Tar River (North Carolina) using 10‐m terrain data from the United States Geological Survey (USGS) 3D Elevation Program (3DEP) dataset. We evaluate the method's performance by comparing the reach‐average stage‐river geometry relationships and rating curves to those from calibrated Hydrologic Engineering Center's River Analysis System (HEC‐RAS) models and USGS gage observations. The results demonstrate that after some adjustment, the river geometry information and rating curves derived from HAND using national‐coverage datasets are comparable to those obtained from hydraulic models or gage measurements. We evaluate the inundation extent and show our approach is able to capture the majority of the Federal Emergency Management Agency (FEMA) 100‐year floodplain.     

大气环境容量系数A值频率曲线拟合及其应用

在用A值法确定大气环境容量的方法研究中,给出了大气环境容量系数的理论定义、特性及其累积频率曲线的PIII型拟合,同时证明该系数亦可定义为空气自洁指数.以北京为例探讨了各重现期的大气环境容量系数在不同控制区面积、时段所对应的容量及其相应空气质量的关联.按1951~2014的气象数据计算的北京百年一遇的年均A值为4.47,而百日一遇的日均A值仅为0.23.研究结果表明大气环境容量系数的频率分析或可成为大气环境管理中的一个重要工具.     

Medium ‐ pressure ‐ liquid ‐ extraction (MPLE) of selected polychlorinated biphenyls from soil (MPLE II) 1

The extraction of PCBs from spiked soils using the Medium‐Pressure Liquid‐Extraction method showed good recovery rates. Comparison of MPLE and Soxhlet extraction of naturally contaminated soil showed similar results. However, too large quantities of solvents have to be used in MPLE procedure and the elution profile makes it unlikely, that the aspired separation from PAHs would be sufficient.