污泥性质对动态膜形成和膜污染的影响

以一体式尼龙筛网动态膜生物反应器（DMBR）为研究体系,探讨了正常污泥、膨胀污泥和解体污泥的动态膜形成和膜污染特点,并从胞外聚合物（EPS）、相对疏水性（RH）、污泥混合液粘度（μ）、接触角这些物化性质角度定量研究膜污染机理.研究结果表明,膨胀污泥由于丝状菌累积导致严重的泥饼层污染;解体污泥由于胶体颗粒和可溶性物质沉积...     

Experimental and numerical study of CO2 plume diffusion in a confined space

In this paper, heavy gas diffusion in a confined space has been investigated. The effects of barrier and source intensity on CO₂ diffusion are explored by the small-scale experiments and computational fluid dynamics (CFD) methods. Six different turbulence models are selected to predict the gas concentrations. By comparing these experimental values with the simulated ones, it is found that all models can effectively predict the concentration variation with time, and SST k-ω model is most close to the ideal model compared with others. Three source-barrier distances and three CO₂ flow rates have been set up for the study. In this confined space, the main flow is concentrated in the region near the ground. The existence of barriers in the space will have a dilution effect on the high-concentration plume near the ground of the near-source area and a barrier effect on the low-concentration plume in the far-source area. The changes in source intensity have notable impact on the gas concentrations. This study can provide an experimental basis for the risk assessment in the confined spaces, as well as an experimental and data reference for large-scale CFD simulations.     

A case study of promoting CH4 discharge and preventing coal & gas outburst accidents by using cross-layer liquid injection technology

To solve the problem of gas extraction in coal bodies with the outburst risk, the cross-layer drilling fluid injection technology for protecting rock pillars is adopted to promote gas extraction. We combined theoretical calculations, laboratory experiments, and field tests to analyze the degree of fissure development in different parts of the coal body. We also determined the liquid injection parameters and negative extraction pressures. The CH₄ extraction effects of three stages before, during, and after liquid injection was compared. The results show that the possibility of coal outbursts in different parts is reduced by 58%∼70% by using liquid injection and pumping technology. The peak value of CH₄ pure flow in the main pipe is increased by 1.5–2.8 times, and the average value is increased by 1.8–2.6 times. The peak value of gas concentration at the orifice of the extraction hole is increased by 1.6–3.5 times, and the average value is increased by 1.6–4 times. Liquid injection to promote extraction greatly improves the gas extraction efficiency in coal bodies, which is of great significance to reducing cost, shortening the construction period, and ensuring safe production, and providing a reference for similar engineering construction.     

Method to map human and infrastructure vulnerability using CNN land cover: Case study of floating tank explosion at petrochemical plants of LaemChabang,Thailand

Industrial storage tanks, used to store flammable materials in the petrochemical industry, can induce potential fire and explosion under specific conditions. Therefore, it is necessary to map the population and environment vulnerability, and, to develop procedures for emergency responses in order to reduce potential casualties. In order to achieve this, Convolutional Neural Networks (CNN) are used in this study using 6 classes: floating tank, forest, house, road, wasteland and water. Datasets are built for a total of approximately 1.4 million tiles with a resolution of 0.33m/pixel and their size are optimized in function of the class. The 6 associated CNN models are built and optimized to classify each class. The validation of the models shows that, with the exception of road and wasteland where the precision is only 73% and 89% respectively, the other 4 classes have a value higher than 95%. Post-processing is performed on each prediction before aggregating these results to obtain the land cover. For the floating tank class, a 5 step post-processing is used based on a Density-Based Spatial Clustering of Applications with Noise algorithm (DBCAN) after which blast simulation is applied and effects on people, buildings and trees are obtained through 4 steps. Finally, the petrochemical site of LaemChabang in Thailand is used as study case. Except for the road class that is difficult to detect, land cover is well performed. Human casualties and surface of damaged buildings are finally estimated demonstrating the usefulness of the tool to be used for the emergency planning of industrial disasters.     

Study on the effect of explosion suppression equipment on hydrogen explosions

Hydrogen safety is a critical component of modern industrial safety production. In this study, a set of hydrogen explosion suppression equipment is designed independently. The suppression effects of the equipment on hydrogen explosions are studied at normal room temperature and pressure. The experimental results show that the actuation time of the equipment and the spraying mode of the suppressant are the main factors leading to the failure of the hydrogen explosion suppression equipment. The flame, with a hydrogen equivalence ratio of 0.7 and 1.0, spreads out of control when the suppressant touches the flame front. At this time, the addition of the suppressant enhances flame propagation and increases pressure. In addition, because the suppressant does not fully cover the developing flame, the hydrogen flame with the equivalence ratio of 0.5 eventually breaks through the suppressant cloud, and the explosion happens. However, when the initial flame is completely covered by the suppressant, the hydrogen explosion is suppressed by hydrogen explosion suppression equipment. This research provides a solid and reliable foundation for hydrogen explosion suppression equipment in industrial safety and production protection.     

Using data mining technology to explore causes of inaccurate reliability data and suggestions for maintenance management

Reliability data reflects equipment safety and provides a reference for setting inspection period, thereby serving as crucial information for the implementation of equipment integrity management policies. The calculation foundation of reliability data is maintenance records of adequate data quality. However, maintenance records of doubtful quality are common. Despite excluding poor quality recodes and using only the remaining maintenance recodes to calculate the reliability data, the calculated results generally lack a sufficient degree of confidence. This study applied data mining technology, including quality metrics, the association rule, and clustering, to explore the cause of low-quality maintenance data. The results revealed that the low data quality of maintenance records was due to ineffective maintenance policies, the low integrity of key system columns, nonadherence to the policy, and misunderstanding of column definitions. The proposed method successfully identified the causes of low-quality maintenance records. By incorporating the method into the function module of a CMMS, operators can equip the system with self-diagnosis, self-supervision, and continuous optimization functions.     

高压击穿电弧作用下开关柜内典型阻燃绝缘件引燃特性的实验研究

高压开关柜内的绝缘件失效故障,易引发火灾事故、区域停电甚至影响电网系统的稳定运行。基于高压击穿电弧模拟与材料引燃机理综合模拟实验平台,针对4 mm厚支柱绝缘子和固封极柱,开展了15 kV击穿电弧作用下的系列引燃实验研究。结果表明,高压电极横向击穿后,电弧迅速上翻形成自上而下“夹持”样品的倒“U”形弧柱,弧根与弧顶首先炭化或引燃。阻燃绝缘件样品顶部形成火焰后,随着燃烧的进行,逐渐从顶部形成穿透样品的内部击穿电弧,该电弧易诱发剧烈燃烧的水平喷射火焰。内部击穿电弧位置向下移动呈“2阶段”特征:在初始阶段较慢,支柱绝缘子和固封极柱样品内击穿点下移速度分别约为2.55 mm/s和1 .74 mm/s,而在第2阶段分别增大至78.50 mm/s和35.03 mm/s。此外,高压起弧瞬间,在紧邻电极上方的绝缘材料表面,升温速率可达180 ℃/s。研究结果可用于高压开关柜各类阻燃绝缘件的科学选型与优化设计,为开关柜防火安全性能的提升提供科学依据。     

重大疫情下疫苗冷链物流在物联网环境中的风险评估*

为识别和应对重大疫情下疫苗冷链过程中的风险,研究物联网环境中在人-机-环-管理下,以加工包装、储存、运输、装卸搬运、接种为风险链的评估指标体系,全面分析各个环节风险因素,提炼16个影响疫苗冷链质量安全风险点。根据因果关系将风险评价指标体系转换为贝叶斯网络结构,建立基于贝叶斯网络的风险评估模型,并使用GeNIe软件进行计算,搜索相关数据,以印度新冠疫苗冷链物流为实证案例检验模型。研究结果表明:重大疫情下疫苗冷链物流存在风险敏感点,必须明确防控重点,制定针对性控制措施,如加强人员培训、合理规划路径及接种点位置、加大设施设备检查与更新等,研究结果可为实现疫苗冷链物流的高效安全运转提供参考。     

APEC会议前后北京地区PM2.5污染特征及气象影响因素

为分析APEC会议前后北京地区PM_2.5变化特征,利用中国科学院大学雁栖湖校区超级站在2014年10—12月的连续观测数据,对APEC会议前后北京地区污染物分布及变化特征、气象影响因素和气团传输路径特征进行了分析. 结果表明:APEC会议期间北京地区减排效果显著,ρ(PM_2.5)平均值比会前下降了60.5%. 气象条件对污染物扩散起到积极作用,APEC期间平均风速为1.40 m/s,平均相对湿度为31.9 %,近地面气象条件优于APEC会前、会后. 北京地区受到外来污染物输送的影响,在2.00~3.00 m/s的南风下易发生来自南部地区的PM_2.5和SO₂输送. APEC会议期间北京地区主要受来自西北地区的高速、高海拔气团控制,其出现频率为39.6%,远低于APEC会前 (15.9%)和会后(20.8%),而来自南部地区的低速、低海拔污染气团的出现频率仅为2.1%,扩散条件总体良好. 研究显示,除了减排措施有效削减了污染物排放以外,有利的气象条件也是APEC会议期间北京地区保持良好空气质量的重要因素.      

Effects of humidity on minimum ignition energy of gaseous epoxypropane/air mixtures

The minimum ignition energy (MIE) is an important property for designing safety standards and understanding the ignition process of combustible mixtures. The minimum ignition energy (MIE) of gaseous epoxypropane/air mixtures is measured using capacitive spark discharge. The effect of humidity on MIE is studied. It is shown that the MIE is not constant when the relative humidity increases from 40% to 88% at room temperature. The relative humidity has no significant influence on the MIE of gaseous epoxypropane/air mixtures at the lower volume fraction of gaseous epoxypropane in air. But, it has significant influence on that at the higher volume fraction. The MIEs of gaseous epoxypropane/air mixtures vary with the fraction of gaseous epoxypropane in air and the humidity. The lowest value of MIE (0.12 mJ) of gaseous epoxypropane/air mixtures is reached at around 10% in the examined ranges of the concentrations for the humidity 40%. The lowest values of MIE (0.1 mJ) of the mixtures are reached also at around 10% in the examined ranges of the concentrations for the humidity 66% and 88% respectively.