Estimation of Vulnerable Zones Due to Accidental Release of Toxic Materials Resulting in Dense Gas Clouds

Heavy gas dispersion models have been developed at IIT (hereinafter referred as IIT heavy gas models I and II) with a view to estimate vulnerable zones due to accidental (both instantaneous and continuous, respectively) release of dense toxic material in the atmosphere. The results obtained from IIT heavy gas models have been compared with those obtained from the DEGADIS model [Dense Gas Dispersion Model, developed by Havens and Spicer (1985) for the U.S. Coast Guard] as well as with the observed data collected during the Burro Series, Maplin Sands, and Thorney Island field trials. Both of these models include relevant features of dense gas dispersion, viz., gravity slumping, air entrainment, cloud heating, and transition to the passive phase, etc. The DEGADIS model has been considered for comparing the performance of IIT heavy gas models in this study because it incorporates most of the physical processes of dense gas dispersion in an elaborate manner, and has also been satisfactorily tested against field observations. The predictions from IIT heavy gas models indicate a fairly similar trend to the observed values from Thorney Island, Burro Series, and Maplin experiments with a tendency toward overprediction. There is a good agreement between the prediction of IIT Heavy Gas models I and II with those from DEGADIS, except for the simulations of IIT heavy gas model-I pertaining to very large release quantities under highly stable atmospheric conditions. In summary, the performance of IIT heavy gas models have been found to be reasonably good both with respect to the limited field data available and various simulations (selected on the basis of relevant storages in the industries and prevalent meteorological conditions performed with DEGADIS). However, there is a scope of improvement in the IIT heavy gas models (viz., better formulation for entrainment, modification of coefficients, transition criteria, etc.). Further, isotons (nomograms) have been prepared by using IIT heavy gas models for chlorine, which provide safe distance for various storage amounts for 24 meteorological scenarios prevalent in the entire year. These nomograms are prepared such that a nonspecialist can use them easily for control and management in case of an emergency requiring the evacuation of people in the affected region. These results can also be useful for siting and limiting the storage quantities.     

The Benefits of Probabilistic Exposure Assessment: Three Case Studies Involving Contaminated Air,Water, and Soil1

Probabilistic risk assessments are enjoying increasing popularity as a tool to characterize the health hazards associated with exposure to chemicals in the environment. Because probabilistic analyses provide much more information to the risk manager than standard “point” risk estimates, this approach has generally been heralded as one which could significantly improve the conduct of health risk assessments. The primary obstacles to replacing point estimates with probabilistic techniques include a general lack of familiarity with the approach and a lack of regulatory policy and guidance. This paper discusses some of the advantages and disadvantages of the point estimate vs. probabilistic approach. Three case studies are presented which contrast and compare the results of each. The first addresses the risks associated with household exposure to volatile chemicals in tapwater. The second evaluates airborne dioxin emissions which can enter the food-chain. The third illustrates how to derive health-based cleanup levels for dioxin in soil. It is shown that, based on the results of Monte Carlo analyses of probability density functions (PDFs), the point estimate approach required by most regulatory agencies will nearly always overpredict the risk for the 95^th percentile person by a factor of up to 5. When the assessment requires consideration of 10 or more exposure variables, the point estimate approach will often predict risks representative of the 99.9^th percentile person rather than the 50^th or 95^th percentile person. This paper recommends a number of data distributions for various exposure variables that we believe are now sufficiently well understood to be used with confidence in most exposure assessments. A list of exposure variables that may require additional research before adequate data distributions can be developed are also discussed.     

试论科室心理

如何提高科室工作的效率,已越来越为决策者及管理者们所重视.作者认为.在提高科室人员业务素质的同时,也应注重科室人员心理素质的培养,才能有效地提高并保持科室工作的效率,本文从造就良好的科室氛围、减轻工作压力感,保持科室成员间的积极交流以及倡导协作的人际环境等方面对此进行了初步探讨.     

Diesel Emissions and Lung Cancer1

This paper uses two different methods to assess the potential risk of human lung cancer from exposure to diesel engine emissions. One method analyzes the best available epidemiological evidence on the lung cancer risks of persons exposed in their occupations to diesel engine emissions. The second conducts a comparative analysis of laboratory and epidemiological data on diesel engine emissions and two chemically related environmental exposures–coke oven emissions and roofing tar emissions. The estimates of potential risk derived from these two distinct methods are compared. The sources of uncertainty in each method are explicitly characterized. The value of these estimates for comparing the potential lung cancer risks from exposure to diesel engine emissions with other personal and societal risks are discussed. Also considered are the limitations of these results in predicting the possible excess incidence of lung cancer from ambient exposure to diesel emissions.     

Forecasting models for developing control scheme to improve furnace run length

In petrochemical industries, the gaseous feedstock like ethane and propane are cracked in furnaces to produce ethylene and propylene as main products and the inputs for the other plant in the downstream. A problem of low furnace run length (FRL) increases furnace decoking and reduces productivity along with the problem of reducing life of the coil. Coil pressure ratio (CPR) and tube metal temperature (TMT) are the two most important performance measures for the FRL to decide upon the need for furnace decoking. This article, therefore, makes an attempt to develop the prediction models for CPR and TMT based on the critical process parameters, which would lead to take the necessary control measures along with a prior indication for decoking. Regression-based time series and double exponential smoothing techniques are used to build up the models. The effective operating ranges of the critical process parameters are found using a simulation-based approach. The models are expected to be the guiding principles eventually to increase the average run length of furnace.     

基于加权深度的异常曲线探测方法——以空气质量函数型数据为例

基于空气质量数据特征,在B-样条基底拟合曲线的基础上,将曲线本身信息、曲线变化信息引入分析,构造加权曲线深度指标,探索一种异常曲线探测方法。与现有仅考虑离散点信息和曲线本身信息的方法相比较,该探测方法更加符合空气质量数据特点,具备缺失值处理能力及整体异常和局部异常的识别能力。将该方法应用于兰州市空气质量数据采集点的二氧化氮水平曲线异常情况分析,结果表明该方法具有更好的异常情况识别效果。     

儿科医护人员职业压力分析

目的调查儿科医护人员工作的主要压力。方法采用问卷调查法,对川北医学院附属医院儿科20名医生和50名护士进行工作压力方面的调查。结果⑴护士平均压力值高于医生压力平均值;⑵医生的压力来源主要是家长及病人亲属,护士的压力来源主要是儿科专业压力;⑶压力最大的三个因素是风险大,待遇低,工作负荷重和家长要求高,期望值高,过度维权。结论儿科医疗护理是压力较高的行业,儿科医生和护士的压力有所不同。     

高职院校辅导员工作压力与应对方式的现状、问题与对策

为了解专职辅导员感受工作压力的状况,采用问卷法对31名在岗辅导员进行调查。结果显示96．8％的辅导员均感受到有不同程度的工作压力,其中48．4％的辅导员感到压力在相当大以上。有20％左右的辅导员由于过大的工作压力对身心健康造成了一定的影响,表现为压抑、焦虑、失眠等身心问题。面对压力有95．6％的辅导员认为自己有缓解压力的应对能力,多数辅导员采取了较为积极的应对措施。     

Introduction to the Special Issue: Under Pressure

This article introduces this special issue on the theme “Under Pressure.” It uses an analysis of experimental lesbian filmmaker Su Friedrich's Seeing Red (2005) to frame the issue's focus on the ways that the category “lesbian” is placed under pressure and/or the pressure “lesbian” places on twentieth- and twenty-first-century cultural production. After this overview, the introduction summarizes all seven articles in the order that they appear in the issue. These summaries also show the connections between the articles and suggest possibilities for future critical dialogues on the theme.