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61.
The microscopic characteristics of melting trace caused by copper wire fault are an important basis for the physical evidence identification of electrical fires. Metallography is an important method in electrical fire research, and computer-aided quantitative analysis on metallographic structure is common in materials aspect. In this study, the metallographic structure and phase composition characteristics of melting trace caused by overcurrent fault were explored with the aid of a metallographic microscope and an X-ray diffractometer (XRD). The results show that the grains are mainly slender dendritic and columnar crystals when the current is 128 A, while they are coarse dendritic and cellular crystals when the current is greater than 192 A; the average grain diameter of melting trace of copper wire grows with the increase in current. The main phases of melting trace caused by overcurrent fault of copper wire are α-Cu base and Cu2O, and the new phases Cu4Si and Cu2Mg are formed when the current is higher than 160 A. In addition, the solidification process of metallographic structure of copper wire under different currents was simulated by the Procast software. It is found that the simulation results are basically in agreement with the experimental data, which suggests that this model can effectively predict the microstructure characteristics of melting trace of copper wire under different currents. The research results can provide a sound basis for the physical evidence identification of electrical fire and improve the accuracy and scientificity of electrical fire investigation. 相似文献
62.
坡地灾害与重庆城市建设 总被引:1,自引:0,他引:1
阐述和探索了重庆地区斜坡的形态和物质结构特征,以及在人为坡活动的影响下与坡地灾害的形成关系,目的在于引起施工人员重视和提高群众的防灾意识。 相似文献
63.
64.
本文结合贵州省"加速发展、加快转型、推动跨越"的主基调、"工业强省"和"城镇化"两大战略的基本精神,在研究近年贵州省相关统计数据的基础上,分析了我省产业结构的合理化、高度化及产业结构效益,提出了现阶段调整产业结构的对策建议,以期为政府提供政策参考。 相似文献
65.
根据2013年4个航次的调查资料,对东山湾春、夏、秋、冬4个季节营养盐结构分布特征及其限制状况进行分析研究。结果表明:营养盐结构平面分布随着季节变化而不同,陆地径流和沿岸流对营养盐分布有较大影响,夏秋冬3个季节Si/P和Si/N比值由北向南递减,春季相反。N/P比值除了冬季外,其他季节都是由北向南递增的趋势。东山湾海域潜在限制性因子主要为P,秋冬两季尤为明显。 相似文献
66.
《Journal of environmental science and health. Part. B》2013,48(4):551-564
Abstract The formation of the insecticide methidathion (S-[(5-methoxy-2-oxo-1,3,4-thiadiazol-3(2H)-yl)methyl] O,O-dimethyl phosphorodithioate) complexes with inorganic cation-saturated (Mg2+, Ca2+, Cu2+, and Ni2+) montmorillonites was investigated. The nature and structure of the complexes was determined by X-ray diffraction and infrared spectroscopy. The arrangement of the pesticide molecule in the interlayer space was also considered from ab initio calculations using simpler related molecules. The insecticide methidathion penetrated the interlayer spaces of the homoionic clay samples. The ligand–cation interactions in these complexes depend on the nature and characteristics of the saturating cations. Mechanisms involving water bridges and direct coordination with the exchange cation were proposed for the adsorption of methidathion by inorganic cation-saturated montmorillonites. The effect of the inorganic cations on the sorption of the cationic surfactant tetradecyltrimethylammonium bromide (TDTMA) by montmorillonite was also studied and the subsequent sorption of methidathion in TDTMA+-Montmorillonite determined. Van der Waals bonds constitute the methidathion adsorption mechanism by montmorillonite saturated with TDTMA+. The arrangements of methidathion and of the cationic surfactant molecules in the montmorillonite interlayer space were demostrated. 相似文献
67.
高水速凝材料浆体流变特性研究 总被引:1,自引:0,他引:1
刘文永 《中国安全科学学报》1997,(4)
高水速材料是一种新型无机材料,其体积比合水率达90%,称为“点水成石”。高水材料加水制成净浆可用于煤矿巷旁充填和灌注:高水材料具有不同于水泥的团结特性,可团结粘土、污泥和矿山尾砂等工业废料,高水材料与上述骨料加水后制成砂浆,输送浓度为60~75%,具有良好的流动性和输送性。在此重点介绍高水材料浆体的流变特性研究的成果,包括高水材料浆体的类型、流变特性、屈服应力、结构粘度与浆体浓度的关系,以及高水材料浆体的输送特性和管道阻力的计算公式,以便更好的推广和广泛使用。 相似文献
68.
Effects of Vehicle Impact Velocity and Front-End Structure on Dynamic Responses of Child Pedestrians
《Traffic injury prevention》2013,14(4):337-344
To investigate the effects of vehicle impact velocity and front-end structure on the dynamic responses of child pedestrians, an extensive parametric study was carried out using two child mathematical models at 6 and 15 years old. The effect of the vehicle impact velocity was studied at 30, 40, and 50 km/h in terms of the head linear velocity, impact angle, and head angular velocity as well as various injury parameters concerning the head, chest, pelvis, and lower extremities. The variation of vehicle front-end shape was determined according to the shape corridors of modern vehicles, while the stiffness characteristics of the bumper, hood edge, and hood were varied within stiffness corridors obtained from dynamic component tests. The simulation results show that the vehicle impact speed is of great importance on the kinematics and resulting injury severity of child pedestrians. A significant reduction in all injury parameters can be achieved as the vehicle impact speed decreases to 30 km/h. The head and lower extremities of children are at higher injury risks than other body regions. Older children are exposed to higher injury risks to the head and lower leg, whereas younger ones sustain more severe impact loads to the pelvis and upper leg. The results from factorial analysis indicate that the hood-edge height has a significant effect on the kinematics and head impact responses of children. A higher hood edge could reduce the severity of head impact for younger children, but aggravate the risks of head injury for older ones. A significant interaction exists between the bumper height and the hood-edge height on the head impact responses of younger child. Nevertheless, improving the energy absorption performance of the hood seems effective for mitigating the severity of head injuries for children. 相似文献
69.
WBS-RBS与AHP方法在土建工程施工安全风险评估中的应用 总被引:10,自引:2,他引:10
结合土建工程施工安全风险管理的特点,提出了WBS-RBS与AHP相结合的土建工程施工安全风险评估方法,把评估过程分为工程项目资料调研、风险辨识、风险衡量和风险度计算4个步骤,并详细介绍了WBS-RBS风险辨识方法、专家调查风险衡量方法和AHP风险度计算方法在土建工程施工安全风险评估中的应用。WBS-RBS与AHP相结合的土建工程施工安全风险评估方法在系统分析计算的基础上,能够全面的辨识土建工程项目施工安全的典型风险和计算总的风险度,为工程项目的施工安全风险评价提供了一个可行的方法和为有效防范风险奠定了基础。 相似文献
70.
安全裕度研究与应用进展 总被引:5,自引:0,他引:5
随着人们对安全认识和需求的不断提高 ,安全裕度的概念越来越多受到工程设计界及人们日常生活的关注。笔者综述了安全裕度概念在不同工程技术领域应用情况 ,重点讨论了在压力容器设计、机械加工、电力系统运行、航空飞行管理、军备等复杂系统研究中安全裕度的含义、安全裕度设计方法以及应用安全裕度进行安全评定的方法。通过对安全裕度应用情况分析 ,表明安全裕度已经成为现代科学技术领域和日常生活中不可缺少的重要概念 ,广泛受到科技工作者和管理人员的高度重视。笔者还分析了目前安全裕度研究和应用方面存在的问题 ,提出了应尽快开展安全裕度理论的系统研究 ,使这一重要概念从目前主要以定性讨论为主上升到定量计算 ,建立安全裕度学科 ,并且使安全裕度理论成为安全科学重要组成部分的观点。 相似文献