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To solve the water hazard problem of Jurassic coal seam roof sandstone in Yinxing No.1 Coal Mine of Ningxia Province, the direct relationship between the sedimentary environment of Jurassic coal seam roof sandstone and water abundance was analyzed and the water abundance of sandstone aquifer was evaluated on the basis of combing the geological and hydro-geological conditions of the mine. The mechanism and characteristics of water disaster in Jurassic coal seam roof sandstone were analyzed based on the study of the mechanical properties, mineral composition, water stability characteristics and water-conducting fracture development law of coal seam roof strata. In this paper, we propose the idea of comprehensively applying various measures of “exploration, drainage, discharge, interception and monitoring”, and focusing on the basic exploration work, using hydrophobic and depressurizing technology to control water damage. The water damage control effect of 110301 working face show that it was feasible to control the sandstone water damage on the roof of Jurassic coal seam through hydrophobic depressurization.

In the process of deep coal seam mining, confined water pressure and complex structural environment are important factors threatening mine safety production. In order to study the water inrush law of floor under the influence of fault on confined water, based on the basic mechanical principle, the mechanical model of surrounding rock under the influence of coal seam mining on confined water is established to solve the critical water pressure of fault water inrush. At the same time, based on the control variable method and fluid solid coupling theory, using FLAC3D numerical simulation software, from the perspective of the joint coupling of stress field, displacement field, seepage field and failure area, the water inrush law of coal seam floor under different fault shape and confined water pressure is analyzed. The results show that when the working face is mined near the fault area, the fault dip angle has a great influence on the vertical stress on the surrounding rock. When the dip angle changes from 30° to 60°, the average change rate of the vertical stress is about -29%; the fault width mainly affects the damage degree of the fault near the bottom of the working face. The wider the fault width, the smaller the damage degree; the aquifer water pressure plays a leading role in the pore water pressure in the fault. The greater the dip angle and the smaller the width of the fault, the higher the pressure of confined water in the aquifer, and the stronger the risk of water inrush in the floor.

With the depletion of shallow coal resources, the existing production mines in Fengfeng Mining Area have entered the era of deep coal mining. Deep coal mining will face the problems of high ground stress, high temperature, high karst water pressure, complex water conduction structure and strong mining disturbance. All kinds of new problems and new characteristics of water inrush are gradually emerging, showing different hydrogeological laws from shallow mining. Based on the analysis of 72 water inrush cases in Fengfeng Mining Area over the years, the water inrush types are divided by single factor and the water inrush modes are summarized by multiple factors. According to the recharge source of water inrush source and the spatial relationship between coal seam exploitation and water inrush aquifer and channel, the water inrush types are divided into 7 categories, 28 subclasses and 50 types. At the same time, the paper systematically summarizes the various factors of disaster causes, analyzes the manifestation of water inrush from multiple angles, sums up 9 kinds of water inrush modes based on different key disaster causing factors, and illustrates the main characteristics and mechanism of water inrush modes combined with typical water inrush cases.

Bimetallic PtSn catalysts with notable activity and selectivity are widely used in propane dehydrogenation to propylene. However, at high temperature, catalysts are prone to carbon deposition, leading to a decrease in stability. CO2-oxidative propane dehydrogenation (CO2-PDH) has become a new research hotspot due to its potential to eliminate carbon deposition and promote the forward movement of dehydrogenation reaction while converting propane. The reverse water-gas shift catalyst β-Mo2C with propane dehydrogenation catalyst PtSn@S-1 were mixed in CO2-PDH, aiming to develop highly active, selective and stable catalysts. The catalysts were characterized by XRD, CO2-TPD, C3H6-TPD, and thermogravimetric analysis. The research results indicate that in CO2-PDH, the stability of the powder-mixed tandem catalyst PtSn@S-1& β-Mo2C significantly improves by adding β-Mo2C in series to PtSn@S-1, and the catalyst remains active without deactivation during continuous operation for 1440 min, and the high stability of the catalyst is attributed to the removal of partial carbon deposition by CO2 during the reaction process. After optimizing the reaction conditions, it is found that when n(CO2): n(C3H8) is 1.0 and m(PtSn@S-1):m(β-Mo2C) is 1.0: 0.4, the powder-mixed tandem catalyst PtSn@S-1& β-Mo2C exhibites the best performance in CO2-PDH. The propane conversion rate remains stable at above 43.0% after 500 min and propylene selectivity exceeds 99%. [ABSTRACT FROM AUTHOR]

In order to meet the needs of high-altitude, long-endurance, high mobility, functional and economic requirement for the future unmanned aerial vehicle(UAV), advanced composite materials have been increasingly applied in UAVs at home and abroad, and even many all-composite UAVs are manufactured. However, there are still some gaps in the proportion and technical level of composite materials used in UAVs in China compared with foreign countries. The cost of composite parts is one of the main factors restricting its application. This paper introduces the development process of UAV at home and abroad, and summarizes the application of composite materials on UAVs. Some key technologies and development trends of UAV composite materials are proposed. Some questions and suggestions are raised on the application of domestic composite materials on drones. For accelerating the application of composite materials in UAV industry in China, it is necessary to design the composite structure based on the process feasibility and stability with introducing foreign automation technology to reduce composite structure cost, actively develop various liquid forming technology, bag vacuum only-out of autoclave(BVO-OoA) materials and technology, and improve the traditional moulding technology research.