预氧化聚丙烯腈/g-C3N4光催化降解罗丹明B

以聚丙烯腈(PAN)和g-C_3N_4为原料,采用超声波辅助分散的溶液浸渍法及煅烧法制备了具有共轭结构的预氧化聚丙烯腈/g-C_3N_4复合光催化剂(CPAN/g-C_3N_4),采用XRD、SEM、FTIR、UV-Vis DRS、EIS等技术对光催化剂进行了表征,考察了CPAN/g-C_3N_4对罗丹明B(Rh B)的可见光催化降解性能。结果表明:CPAN与g-C_3N_4具有良好的协同作用,使g-C_3N_4片状结构堆叠体颗粒显著减小,明显增强了光催化剂在全部光谱范围内的光吸收,有效提高了光生电子-空穴分离效率;在PAN与g-C_3N_4质量比为1∶200、煅烧温度250 ℃、煅烧时间1 h条件下所制备的CPAN/g-C_3N_4光催化活性最高,且具有良好的光催化活性稳定性。超氧自由基和光生空穴为CPAN/g-C_3N_4复合光催化剂光降解罗丹明B的主要活性物种。     

基于多孔环形喷嘴的可燃爆粉尘分散特征的密度效应研究*

为了研究不同密度的可燃爆粉尘在内置多孔环形喷嘴的20 L爆炸特性测试装置中的分散特征，基于负载粒子流方法、耦合DPM动量平衡方程和时间平均 Navier Stokes控制方程组，实现3种不同密度的煤粉、铝粉和锆粉在20 L爆炸测试装置中粉尘分散全过程的数值模拟。研究结果表明:多孔环形喷嘴的分散较为均匀，但是约束管道末端存在局部粉尘残留区，致使爆炸仓内真实粉尘浓度远低于形式浓度；爆炸仓中心位置的最大湍动能随着粉尘密度的增加而减小，只有显著地变化粉尘密度才能展示区分度较高的浓度峰值和抵达浓度峰值的时间。     

Study into influence of different types of igniters on the explosion parameters of dispersed nitrocellulose powder

Nitrocellulose is a flammable compound produced by cellulose nitration. The nitrocellulose production and handling are associated with a risk of fire and explosion. Nitrocellulose is used as either collodion cotton (<12.5% N) or as an explosive (>12.5% N). Nitrocellulose is a fibrous or powdered substance and may detonate or burn upon certain conditions. The article compares the combustion parameters of dry nitrocellulose in the KV-150M2-UIBE explosion chamber at the concentrations of 250, 500 and 750 g m⁻³. To ignite a nitrocellulose sample, six different types of igniters were used. A commercially available 5 kJ pyrotechnic igniter was used as the standard. Also used were a nitrocellulose igniter, a pyrotechnic igniter with magnesium powder and KNO₃/KClO₃, and an exploding wire (Kanthal and tungsten wire). The examined igniters were found to affect the explosion parameters of dispersed nitrocellulose. The deviation of the explosion constant K_st reached 50% of the standard value. The highest pressure of 12.73 bar g was reached at a concentration of 750 g m⁻³ and an igniter exploding wire with Kanthal wire. The highest K_st value of 287.9 bar.m.s⁻¹ was achieved at a concentration of 750 g m⁻³, when using the pyrotechnic igniter with KClO₃ and magnesium powder.     

Numerical investigation of powder aerosolization in a mining rock dust dispersion chamber

We have conducted numerical simulations of dust dispersion within the NIOSH Rock Dust Dispersion Chamber. The apparatus consists of a low-speed background ventilation flow down a long box in which is placed a tray containing a rock dust powder. A nozzle upstream of the tray introduces a short pulse of a turbulent horizontal jet flow just above the powder surface. We have utilized an incompressible Reynolds-Averaged Navier-Stokes k-ω model for the turbulent flow; particles are incorporated within a one-way Euler-Lagrangian formalism. The Rock Dust Dispersion Chamber ventilation flow exhibits a recirculation zone just above the powder-containing tray. Aerosolization proceeds via the interplay of the jet pulse flow with the background recirculation flow. The air flow is not well-mixed. The aerosolized dust is convected as a concentration cloud downstream towards the detection zone. For larger particles, gravitational settling depletes the convected cloud, so the instrument behaves as a horizontal elutriator. The instrument is robust with respect to misalignment of the jet nozzle. However, reduced streamwise drift velocity allows mixing to disperse the optically detected dust cloud concentration pulse. Our large particle simulation results compare favorably with published experimental results for large, polydisperse calcium carbonate rock dust.     

Machine learning based quantitative consequence prediction models for toxic dispersion casualty

Incidental release of toxic chemicals can pose extreme danger to life in the vicinity. Therefore, it is crucial for emergency responders, plant operators, and safety professionals to have a fast and accurate prediction to evaluate possible toxic dispersion life-threatening consequences. In this work, a toxic chemical dispersion casualty database that contains 450 leak scenarios of 18 toxic chemicals is constructed to develop a machine learning based quantitative property-consequence relationship (QPCR) model to estimate the affected area caused by toxic chemical release within a certain death rate. The results show that the developed QPCR model can predict the toxic dispersion casualty range with root mean square error of maximum distance, minimum distance, and maximum width less than 0.2, 0.4, and 0.3, which indicates that the constructed model has satisfying accuracy in predicting toxic dispersion ranges under different lethal consequences. The model can be further expanded to accommodate more toxic chemicals and leaking scenarios.     

对核磁共振成像仪建设项目环境影响评价的研究

核磁共振作为一种分析手段广泛应用于物理、化学、生物、医疗等领域.本文从核磁共振原理出发,分析核磁共振成像仪主要环境影响,结合环评现状,分析环评管理存在的主要问题,结合相关法规条文,查找存在这些问题的主要原因,结合目前核磁共振仪的建设情况和使用条件,从切合实际角度出发,提出核磁共振成像仪建设项目环评管理建议.     

核设施营运单位邻避问题应对策略研究

邻避问题激发的群体性事件是当前危险设施选址面临的主要问题,而核设施则是邻避设施中负外部性等级较高的一类设施.通过分析各行业邻避问题的九因素分析框架引入核设施邻避问题的研究,并结合国内外核行业和值得借鉴的非核行业典型案例进行分析,发现了影响邻避问题的核心要素包括程序公正、企业与政府公众形象、行业污名化倾向和补偿不合理等方面内容.核设施运营单位应在这些方面制定针对性策略和措施以减小邻避问题对核行业发展的影响.     

Method to analyze the regional life loss risk by airborne chemicals released after devastating earthquakes: A simulation approach

Widespread chemical plants render human life more vulnerable to major natural disasters such as earthquakes. Recognizing the potential cascading threats initiated by a devastating earthquake, a general methodology for assessing the life loss risks introduced by airborne hazardous chemical dispersion following seismically induced chemical release (SICR) was proposed. With a 600 km × 600 km region in North China as a demonstrative study area, the dispersion of ammonia released from multiple relevant chemical plants that were supposed to be damaged by a devastating earthquake was simulated in a probabilistic manner. Using an ammonia toxicity-fatality relationship and its toxicity concentration threshold, regional life loss and spatial spread were evaluated. The life loss risk was found to be non-prominent but would be very contingent on unfavorable meteorological conditions. Non-parametric correlation analysis revealed that the respective effects of meteorological mixing parameters on the risk exhibit new features in a disaster context, that is, stronger mixing would cause elevation of risk in a region. This preliminary research implied that the risk of chemical-induced life loss after a devastating earthquake deserves attention and a thorough uncertainty evaluation in the future.     

基于熵值法和物元可拓模型的核电站安全运行状态评价

我国核电事业发展迅速,核电安全是核电产业发展的重要基础.针对我国核电的发展和安全运行现状,建立了安全运行状况指标体系,通过构建物元可拓模型获得各指标在各评价等级上的关联度,将关联度与熵值法求得的指标权重合成得到加权综合关联度,继而确定核电站安全运行状况评价等级.在对核电站整体运行状况进行综合评价的同时,也能实现对安全运行状况各指标的分类评价.     

飞机撞击下核电厂安全壳载荷曲线相关问题研究

针对大型商用飞机对核电厂反应堆安全壳恶意撞击的安全评估需求,综述了国外确定飞机撞击安全壳载荷曲线的基础理论、试验测试技术和数值模拟方法.首先,从理论上对飞机撞击安全壳的载荷特性和Riera撞击模型进行分析,给出了Riera模型的基本假设、模型各项物理意义及模型的求解方法,明确了靶体碰撞表面的冲击载荷(力)由静载项和动载项组成;其次,分析总结了确定Riera模型中压损载荷参数的试验方法和真实飞机撞击载荷测量的试验技术和实施方法,指出大型商用飞机对核电厂反应堆安全壳恶意撞击属"软冲击"范畴,撞击载荷可用Riera模型计算得到;再者,在数值模拟方面,总结了采用有限元技术进行飞机撞击载荷计算和安全评估的数值模拟方法及其发展趋势;最后,在分析国内开展飞机撞击载荷研究面临问题的基础上,指出从理论上建立飞机撞击载荷-时间曲线计算模型及方法,并通过试验和数值模拟验证是国内确定大型商用飞机撞击安全壳结构载荷曲线比较可行的技术路线.