Pressure characteristics and dynamic response of coal mine refuge chamber with underground gas explosion

Coal mine refuge chambers are new devices for coal mine safety which can provide basic survival conditions after gas explosion. In order to simulate the propagation of underground methane/air mixture blast wave, and check structural safety of coal mine mobile refuge chamber, an underground tunnel model and a refuge chamber model have been established based on explicit nonlinear dynamic ANSYS/LS-DYNA 970 program. Results show that the reflected wave pressure on the impact surface was about two times higher than that on the incident one. The relationship between the pressure fields of the chamber was analyzed. The maximum pressure of gas explosion reached about 0.71 MPa, and the pulse width was 360 ms. The maximum absolute displacement and stress occurs at the main door center and the connection of stiffeners and the front plate, respectively. The entire coal mine mobile refuge chamber was in elastic state and its strength and stiffness meet the safety requirements. The cabin door, the front plate and the connecting flange at cabin back as well as the stiffeners on each side were the most critical components. Suggestions were put forward for the refuge chamber.     

Impact of a shock wave on a structure on explosion at altitude

The number of explosive attacks on civilian buildings has recently increased and the pattern of damage inflicted on structures when an explosion takes place at altitude remains quite difficult to predict. The primary aim of the work reported here was to enhance the understanding of how blast waves from an explosion at altitude interact with the ground and with a structure. Small-scale experiments were conducted using a propane–oxygen stoichiometric mixture as explosive. This approach is original because it models high-explosive detonation in terms of gaseous charge explosion using TNT equivalents. Several non-dimensional laws are expressed and validated by experiments. These relationships allow determination of the propagation of a blast wave and its interaction with a structure as a function of the position of the explosive charge when the explosion occurs at altitude. Then, from knowledge of the blast loading, using Hopkinson's scaling law and TNT equivalents, we can predict the interaction of blast waves with the ground and a structure on a real scale. Simulations were performed using the Autodyn code, and good correlation with the experimental results was obtained.     

Structure of flames propagating through aluminum particles cloud and combustion process of particles

Structure of flames propagating through aluminum particles clouds and combustion processes of the particles have been examined experimentally to understand the fundamental behavior of a metal dust explosion. The combustion process of individual aluminum particles in a flame propagating through the aluminum particles cloud has been recorded by using a high-speed video camera with a microscopic optical system, and analyzed. The flame is shown to be consisted of a preheat zone of about 3 mm thick, followed by a combustion zone of 5–7 mm thick. In the combustion zone, discrete gas phase flames are observed around each aluminum particle. Also an asymmetric flame around a particle is observed, which might be caused by an ejection of aluminum vapor from a crack of oxide shell surrounding the particle.     

隔声罩的结构形式及隔声效果研究

介绍了隔声罩的结构类型及隔声罩的设计计算以及隔声罩的应用实例,结果表明:隔声罩的隔声能力取决于其形状和尺寸、结构刚性、罩上开口、缝隙面积、平均吸声系数、隔声材料的隔声量和耗损因数等多种因素.     

论昆山市产业结构调整的环境约束

以昆山市经济发展、产业结构调整的实际情况为依据,从土地资源、水环境、大气环境、社会环境等方面,研究产业结构调整的环境约束,并提出如何提高土地效益、保护水源地、控制水环境污染、建立严格的环境管治、控制人口增长、提升劳动力素质和进行投资转型的发展策略,以此优化产业结构,促进经济发展.     

基于饮用水健康风险评价的江苏省产业结构调整对策研究

将产业结构调整与饮用水健康风险评价结合起来,从宏观角度提出对策分析,有利于整体水环境(包括饮用水源地)的改善.基于长江流域、太湖流域和淮河流域饮用水源地2007～2009年水质监测数据,应用美国环境保护署( U.S.EPA)推荐的健康风险模型计算、分析、评价了江苏省3大流域的水环境健康风险.研究结论揭示了3大流域饮用水...     

Floristic composition and vegetation ecology of the Malindi bay coastal dune field, Kenya

A short outline is given of the floristic composition, structure and distribution of coastal dune vegetation found at Malindi Bay, Kenya. The area was studied by air photo interpretation and field sampling to determine the relationship of plants to aeolian features. TWINSPAN classification was used to distinguish geomorphological units on the basis of their species composition. In this paper, an inventory and first quantitative analysis of vegetation distribution is presented. We identified 174 plant species from 62 families in the sand dunes and several plant communities are distinguished based on the species content and the connection with morphological units.Papilionaceae with 18 species andPoaceae with 17 species were the most represented families. A distinct zonal distribution of the plant communities was found. The most important plant species are the pioneer vegetation consisting ofHalopyrum mucronatum, Ipomoea pescaprae andScaevola plumieri. The woody shrub species which have colonized the established primary dunes and hummock dunes areCordia somaliensis, Pluchea discoridis, Tephrosia purpurea (dunensis). Succulent herbs were identified in the dune slacks and salt marsh that are moist and damp environments.     

聚合氯化铝与聚磷硫酸铁絮凝除藻比较研究

针对武汉市莲花湖湖水,采用聚合氯化铝(PAC)和聚磷硫酸铁(PPFS)进行絮凝实验,比较了两种无机絮凝剂的絮凝效果及原水处理前后藻类群落变化。主要结论如下:①PPFS与PAC的最佳投加量分别为1.5mg/L、2.0mg/L;②PPFS在去除藻类细胞、浊度和色度方面均优于PAC,当PPFS投加过量时,因水体中Fe3+过量分布,使水样色度去除率下降;③PPFS絮凝处理微囊藻为主体的水华原水时,其效果比PAC更好。本文研究后表明:PPFS是一种新型高效絮凝剂,其絮凝性能明显优于PAC,当水体以微型藻类为主时,可使用PPFS以替代PAC,能提高絮凝效果。     

Effects of vacuum levels,carbon dioxide,and structural sizes of linked vessels on dump vessel vented

The method of explosion venting is widely used in industrial explosion-proof design due to its simple operation, economical and practical features. A dump vessel vented platform was built. By changing the vacuum level and the gas in the dump vessels and the structural size of linked vessels, the pressure in the explosion vessel and the dump vessel was compared, and the influencing factors of explosion venting investigated. The main conclusions are as follows: In the explosion venting process, the higher the vacuum in the dump vessel, the smaller the pressure peak of the explosion vessel and the dump vessel, and the faster the explosion pressure is lowered. When the dump vessel is under the same vacuum level and the gas in the dump vessel is CO₂, the maximum pressure of the explosion vessel and the dump vessel is less than the maximum pressure when the containment medium is air. Under the same vacuum condition, the larger the volume ratio of the dump vessel and the explosion vessel, the smaller the pressure peak of the explosion vessel, the faster the explosion pressure drops, and the volume of the dump vessel reaches or exceeds the explosion vessel. Increasing the volume ratio of the containment vessel to the explosion vessel facilitates protection of the explosion vessel and the containment vessel. Under the same vacuum condition, when the gas explosion in 113 L vessel vents into 22 L vessel, the longer the length of the pipe, the greater the maximum pressure in the spherical vessel. When the gas explosion in 22 L vessel vents into 113 L dump vessel, as the pipeline grows, the maximum pressure in the two vessels decreases, but the reduction is not significant. In practical application, it is recommended to use a vacuum of 0.08Mpa or more for the dump vessel vented, and the containment medium is CO_2.In terms of the structural size of the container, it is recommended that the ratio of the receiving container to the explosion container be as large as possible, and the pipe length be as long.     

河南环境问题城乡差异的对比研究

消费、教育、医疗等方面的城乡差异一直是社会各界关注的问题,然而,日益突出的城乡环境差异却没有引起足够的重视。河南作为农业大省,其城乡环境差异的表现更具代表性,本文通过对河南省城乡环境压力指标、环境状态指标以及环境保护工作等方面的差异的具体特征和表现形式进行深入的对比分析,发掘出导致城乡二元环境差别产生的认识上、理论上及组织工作上的深层次的问题及原因,为进一步推动和实现城乡环境一体化以及新农村建设提供理论支持。