Study of the basic welding characteristics of Mg alloy

Offering the advantages of lightweight and high specific strength, magnesium (Mg) alloys are extensively used in the manufacture of automotive parts and light-gauge box-type products, such as laptop computers, mobile phones, etc, which are expected to see lighter-weight applications in future. Presently available Mg alloy products, however, are manufactured by molten or semi-molten working in diecasting or thixomoulding processes, with applications technology currently at the development stage. Suitable techniques for the further development of Mg alloy manufacturing technology include plastic working of wrought alloys and assembly of products with complex shapes by welding. This study focuses on TIG welding as a widely practised and convenient technique for assembly of general metal products. The article examines the basic welding characteristics of an Mg alloy equivalent to AZ31 as an Mg alloy in widespread practical use together with the deformation properties of the proposed alloy. A suitable welding procedure is then investigated. Also discussed is an assembly method for products in consideration of the working and welding characteristics of the proposed alloy.     

Characterization of elevated neutrophil-associated IgG in various autoimmune disorders: not anti-neutrophil autoantibodies, but possibly immune complexes, bind to neutrophils

Resistance to toxicants is a convenient model for investigating whether adaptive changes are associated with pleiotropic fitness costs. Despite the voluminous literature devoted to this subject, intraspecific comparisons among toxicant resistance genes are rare. We report here results on the pleiotropic effect on adult survival of Culex pipiens mutants involved in the same adaptation: the resistance to organophosphorus insecticides. This field study was performed in southern France where four resistance genes sequentially appeared and increased in frequency in response to intense insecticide control. By repeated sampling of overwintering females through winter, we analysed the impact of each of three resistance genes on adult survival. We showed that (i) the most recent gene seems to be of no disadvantage during winter, (ii) the oldest affects survival in some environmental conditions, and (iii) the third induces a constant, severe and dominant survival cost. Such variability is discussed in relation to the physiological changes involved in resistance.     

Study of the welding procedure for production of Mg alloy joints for practical use

The previous report describes a study of the welding characteristics of an AZ31-equivalent Mg alloy welded by AC TIG arc welding. The results show this alloy to have some important welding characteristics that differ from those of the similarly welded reference Al alloy.     

浅谈工程建设项目组织管理模式

高水平的工程项目组织管理,无疑是高效率、高质量、低风险地实现工程项目投资建设目标的重要手段。文章结合工作实际,探讨项目组织管理的重点和问题。     

Triggered Seismicity in a Flooded Former Coal Mining Basin (Gardanne Area,France)

We studied the correlation between seismicity and the water table level in an abandoned coal mine (Bouches-du-Rhône, France), closed in 2003, where groundwater has been pumped out since 2010 to prevent underground flooding. Microseismicity was first felt by the population in 2010 and a strongly felt seismic swarm occurred in November 2012. The origin of the seismicity was therefore questioned, in relation to both the potential instability of old, shallow galleries that might generate damage at the surface and a local seismic hazard assessment. A temporary dense seismic network in the area allowed us to analyse the spatial distribution of the seismicity in detail. Most of the seismicity was clearly located under the mine workings, highlighting that an existing fault system crossing the mining operation was being hydraulically activated, in accordance with the known tectonic extension regime. Our analysis clearly shows a spatiotemporal relationship between seismic migration and the level of the mine aquifer between 2013 and 2017. Thus, seismicity will persist with oscillations of the mining aquifer, depending on the pumping capacities and effective rainfall. Continuous hydraulic and seismic monitoring is necessary to better understand these phenomena and assess the associated risks.