石化系统电子设备的雷电过电压保护

结合国际、国内有关防雷标准,介绍了石化系统电子设备的雷电过电压保护的必要性和雷电过电压保护系统.石化系统电子设备防雷是一系统工程,必须将直击雷防护、等电位连接和系统地安装电涌保护器有机地结合起来,对于电涌保护器,不但要选择好适当的型号,还要注意其安装的位置和彼此配合的层次.     

基于点危险源的危险品运输路径优化研究

为合理选择危险品运输路径,降低危险品运输事故造成的损失,使道路危险品运输风险评价更符合实际情况,建立点危险源风险评价模型。模型综合考虑了运输时间和季节情况影响因子,在准确估算危险品泄漏事故毒害区域面积和后果损失的基础上,结合传统风险评价模型与最大最小模型进行求解。最后通过算例分析,检验该模型的实际运用,通过与传统求和方式所得的最优运输路径的对比,反映2种方式所求得的最优运输路径并不相同,同时也表明,用所建模型求得的运输路径风险值有更高的精确性。计算结果表明:该模型求得的某条运输路径的风险值等于该路径上风险值最大的路段的风险值,而不是该路径上所有路段的风险值之和。     

基于模糊-理想点法的海下采场顶板稳定性分析

为准确评价复杂地质条件下海下采场顶板的稳定性,提出将模糊数学中的隶属度与理想点法相结合的模型。针对海下采场的特殊地质条件,综合考虑水文地质因素、工程地质因素、采场结构因素以及其他因素4个方面,选取9个评价指标。通过对指标进行隶属度化处理,由变异系数法确定指标权重,建立顶板分级模型。最后,根据三山岛金矿5个采场现场调查以及室内试验获得的指标数据,应用该模型对顶板稳定级别进行评判。结果表明,该模型的评判等级结果与工程实际相符,从而验证模型可用于海下采场顶板的稳定性分析。     

驾校考场防雷安全设计探讨

随着驾校考试手段的变化,大量电子、通信设备应用于考场,其雷击风险越来越高。做好驾校考场的雷电综合防护工程对避免和减少雷电灾害损失具有重要作用。通过对邹平安星驾校科目二考场项目的防雷工程进行剖析,指出驾校雷电防护要点,就如何做好直击雷、雷电感应和雷击电磁脉冲防护设计进行了初步探讨。按照安全、经济、有效的原则,对邹平安星驾校科目二考场采用避雷线进行直击雷防护,并运用接地、分流、屏蔽、等电位连接、安装电涌保护器等措施进行雷电感应和雷击电磁脉冲防护。该工程经过5年夏季雷暴季节的考验,没有因雷击造成灾害损失。     

高压聚乙烯装置料仓闪燃隐患综合治理

介绍了茂名石化分公司化工事业部高压聚乙烯装置料仓闪燃隐患治理的情况.根据存在的问题从两个方面进行了改造:采用多重管重力掺混技术,降低气相粉尘浓度,减少静电积聚;在料仓底部增设通风口,增加氮气、空气反吹管等,减少可燃气体积聚.     

Risk and the neoliberal state: why post-Mitch lessons didn't reduce El Salvador's earthquake losses

Although El Salvador suffered light losses from Hurricane Mitch in 1998, it benefited from the increased international aid and encouragement for advance planning, especially mitigation and prevention interventions. Thus, one would have supposed, El Salvador would have been in a very advantageous position, able more easily than its economically crippled neighbours, Honduras and Nicaragua, to implement the 'lessons of Mitch'. A review of the recovery plan tabled by the El Salvador government following the earthquakes of early 2001 shows that despite the rhetoric in favour of 'learning the lessons of Mitch', very little mitigation and prevention had actually been put in place between the hurricane (1998) and the earthquakes (2001). The recovery plan is analysed in terms of the degree to which it deals with root causes of disaster vulnerability, namely, the economic and political marginality of much of the population and environmental degradation. An explanation for the failure to implement mitigation and preventive actions is traced to the adherence by the government of El Salvador to an extreme form of neoliberal, free market ideology, and the deep fissures and mistrust in a country that follow a long and bloody civil war.     

Comparative Evaluation of Three River Water Quality Models1

Abstract: Selection of a biochemical oxygen demand (BOD) reaction model to incorporate into dissolved oxygen (DO) water quality models is an overlooked choice available to river water quality modelers. Data from rivers can serve in screening methods to discriminate between competing water quality models. In this study, 15 published BOD and DO datasets based on a 7 year long study of the Bormida River in Italy are used to calibrate three‐multiorder BOD models: first‐order, three‐halves order, and second‐order, which are then included in three corresponding DO models which incorporate these BOD models. The adequacy of the first‐order, three‐halves order and second‐order BOD models was evaluated by calculating the root mean square error between a model and data. A similar procedure was followed to evaluate three DO models, each of which incorporated one of the three BOD models. The first‐order BOD model most frequently fit the river data best, followed by the three‐halves order and the second‐order BOD models. The DO model incorporating a first‐order BOD model most frequently fit the data best, followed by the DO order incorporating second‐order BOD and the DO model incorporating three‐halves order BOD.     

Achieving Nutrient Water Quality Goals: Bringing Market‐Like Principles to Water Quality Management*1

Abstract: Market‐like trading programs for water quality management begin with enforceable limits on the amount of the pollutant allowed in a watershed. Properly designed market‐like trading programs then create incentives for dischargers to reduce nutrient control costs over time by making pollution prevention innovations. However, the structure of the Clean Water Act can be a barrier to establishing market‐like trading programs. First, we describe the general features and advantages of market‐like trading programs. Then we offer practical suggestions for bringing market‐like design concepts to nutrient trading programs within the existing legal and regulatory setting.     

Conservation‐Induced Wastewater Flow Reductions Improve Nitrogen Removal: Evidence from New York City1

Abstract: Water resources are under increasing pressure to meet potable supply needs while sustaining aquatic ecosystems and fisheries. Growing populations and enforcement of the Total Maximum Daily Load provisions of the Clean Water Act present public water and wastewater utilities with costly options to meet potable water demands and reduce pollutant discharges into receiving waters. This paper documents that New York City’s comprehensive water conservation program – designed to extend the city’s safe yield of potable water—has also resulted in reduced nitrogen discharges from the city’s water pollution control plants during a period of population increases. This paper demonstrates and quantifies the effects that wastewater inflow volume reductions have on increased nitrogen removal, controlling for plant process changes. Conservation programs have saved the city billions of dollars in delayed or avoided capital improvements to both water and wastewater treatment plants, and have enabled the city to meet interim effluent discharge standards.     

The lower explosion point—A good measure for explosion prevention: Experiment and calculation for pure compounds and some mixtures

It is well known that explosive mixtures can exist at temperatures below the flash point (FP). Experiments show that the difference between the FP and the lower explosion point (LEP) may be up to 15 K and in some special cases even more. Consequently, an industrial process even running a few Kelvin below the FP may operate in an explosive vapour/air-atmosphere. Operating at temperatures below the LEP gives sufficient safety. Calculated LEPs are discussed and compared with experimental results.