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In order to obtain thermal expansion silicone rubber for composite soft molding with excellent performance and wide adaptability, the flow, heat resistance, thermal expansion and elastic properties of three kinds of thermal expansion silicone rubber were tested. Two kinds of silica particles were added and dispersed into the thermal expansion silicone rubber by the way of grading composite dispersion. Then the flow, heat resistance and thermal expansion of silicone rubber were studied. The results show that silicone rubber Ⅰ have the advantages of slow increase of curing reaction viscosity, long curing time, best heat resistance and thermal expansion properties, and is suitable for soft molding of composite materials. The silicone rubber Ⅰ is filled with a maximum of 2 phr of nano-silica and 60 phr of micron silica which has a better modification effect than that of nano-silica. When the amount of micron silica is 60 phr, the average linear expansion coefficient of silicone rubber is 210.0×10-6 ℃-1 from room temperature to 200 ℃, which is about 22% lower than that of silicone rubber without added filler. The average elastic modulus of silicone rubber is 4.7 MPa from room temperature to 200℃, which is about 96% higher than that of silicone rubber without filler. The results meet the demand for thermal material modification of silicone rubber and expands the application scope of thermal expansion silicone rubber for soft mold molding process.

Nickel-based superalloy (GH4169) and Si3N4 ceramics were connected by AgCuTi composite active filler and high purity W foil which acts as interlayer. The effects of temperature on the microstructure evolution and mechanical properties of GH4169/ Si3N4 brazed joint were systematically studied. The results show that the effective connection of GH4169/Si3N4 brazed joint can be realized by using AgCuTi+W composite filler. The microstructure of the joint is GH4169/TiNi3+TiCu+TiCu2+Ag(s, s)+Cu(s, s)+W+TiN+Ti5Si3/Si3N4. When the brazing temperature is low, the Ti element in liquid filler diffuses to less of the ceramic interface with the filler, and no obvious reaction layer is formed； when the brazed temperature increases to 880 ℃, Ti is enriched on the ceramic side, forming a thickness of 2 μm TiN and Ti5Si3 reaction layer. At this time, the shear strength of the joint is the highest, reaching 190.9 MPa. With the increase in brazing temperature, the content of Ti-Cu compound，which is a brittle compound, increases and the mechanical properties of the joint are greatly reduced. The fracture results show that during the shear process, the crack initiates in the interlayer, and then diffuses into the Si3N4 ceramic matrix， and finally breaks on the side of Si3N4 ceramic.

U-bimetallic finned tube is a new widely used heat exchange component.In order to predict and control the flowinduced vibration damage of U-bimetallic finned heat exchange tubes,their natural frequencies must be calculated accurately.Inplane and out-of-plane vibration modal of U-bimetallic finned tubes were investigated by means of the hammering method and finite element method.The influence of arc bending radius R of U-bimetallic finned tubes on their natural frequencies was analyzed.The finite element simulation results of natural frequencies of U-bimetallic finned tubes were compared with the measured values for free-free boundary condition,the maximum error of the first 18 order frequencies is 7.3%.The natural frequencies of U-bimetallic finned tubes decrease with increasing the arc radius R for clamped-hinged case.

The eutrophication of water in reservoirs and lakes is getting worse year by year and has become a prominent issue of water environmental protection. In order to assess the degree of eutrophication and the changing trend of important drinking water sources in the coastal areas of western Guangdong and ensure the safety of drinking water, this paper takes Gaozhou Reservoir as the research object and based on the long-term monitoring results of eutrophication index of reservoirs from 2012 to 2019, using the comprehensive nutritional status index method and through the spatial and temporal analysis of the evaluation indexes and the comprehensive nutritional status of the reservoir. Based on W-F law the early warning model of reservoir eutrophication and classification and evaluation was established, to provide theoretical support and prevention and control methods for the ecological environment protection of reservoirs. The results show that Gaozhou Reservoir was in the middle nutritive state and the degree of eutrophication was more serious in the high water period than in the low water period. TLI(TN) is the biggest contributor of reservoir eutrophication and shows mild eutrophication in each single nutrient status index, and then Chl a, phosphorus and organic matter had little effect on the degree of eutrophication. The eutrophication status of the monitored sections of the reservoir fluctuates relatively steadily, the total TLI(∑) of Liangde Dam is lower than that of Shigu Reservoir area, and the comprehensive nutritional status of Shigu area is the tail > supply port > center. Based on the W-F law, an early warning model between the comprehensive impact index of eutrophication and the nutritional status index of Gaozhou Reservoir was constructed, to evaluate eutrophication status in different seasons from 2012 to 2019, and the results show that the comprehensive influence index value of dry period is less than that of flood period and consistent with the seasonal results, so the model has good warning effect. [ABSTRACT FROM AUTHOR]

In the context of the complex geological conditions such as large thickness variation of thin-medium-thick coal seam, development of strike fault and broken roof in Southwest China, intelligent fully mechanized mining support technology and equipment for thin-medium-thick coal seam are proposed. Through the implementation of grouting reinforcement and roof-lifting transformation for broken roof in the hanging wall and the footwall of fault layer, as well as the adoption of the coupled support technology of bolt-mesh-anchor combined support+advance reinforcement+blasting roof cutting+pillar hanging net gangue retaining+delayed shotcrete reinforcement+finishing wall in gob-side entry retaining, the stability of the roadway is greatly improved. A lateral self-advancing advanced support group consisting of eight advanced supports and two end supports is designed to realize the coordination and cooperation of the roof support at the end of the working face and the rapid advancement of the advanced supports. The intelligent fully mechanized mining equipment for thin-medium-thick coal seam and its optimal layout scheme are proposed. When the mining height at both ends of the working face is less than the height of the roadway, a cushion frame is used to support the head and tail of the shearer. The length of the scraper conveyor head and tail beyond the coal wall is controlled at 800 mm to ensure that the undercover amount reaches 97 mm so as to clear the floating coal in time. The scraper conveyor head is equipped with a trailer parallel to the floor, and the scraper conveyor head and tail are directly pushed as a whole through the transition support auxiliary pushing device, which effectively solves the problem of mutual interference between the rocker arm of the shearer and the scraper conveyor. The study proposes an active preventive intelligent coal cutting technology in the fault zone, which is composed of end cutting triangular coal following section process and middle oblique cutting following section process. The technology uses half cutting depth and fractional cutting methods to improve the safe coal cutting speed of the shearer under the fault zone condition.