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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]

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The effect of aeration combined with microorganisms in treating polluted lakes was studied under experimental conditions; then the aeration and microorganisms were integrated into a device to treat polluted lakes. The results show that aeration combined with microorganisms can increase the ability and efficiency of microorganisms to purify pollutants. Intermittent aeration is better than that of continuous aeration in treating polluted lakes, and the operating costs can be reduced using intermittent aeration. Under experimental conditions, the removal rate of COD, NH3-N and TP reached 55.55%, 79.52% and 61.54% respectively after 10 days. In the application study, the water quality was upgraded from Inferior Class V to Class III, and the removal rate of COD, NH3-N and TP reached 59.38%, 81.08% and 82.26% respectively after 3 weeks. The equipment has good application prospects in lake treatment. [ABSTRACT FROM AUTHOR]

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To solve the problems of serious deformation and damage of soft rock roadway in deep well and difficult support, numerical simulation methods and field industrial tests in underground were used to study the stability and support scheme of soft rock roadway in deep well. The results indicated that in comparison with rectangular roadway, the use of arched roadway as the layout shape of the roadway section can effectively improve the stress state and stress value of the surrounding rock after the roadway excavated, and can enhance the stability of the roadway to a certain extent. Based on the related analysis of the original support status of the soft rock roadway outside the vein, a composite support technology of + anchor mesh + sprayed concrete + steel support" was proposed. It was concluded from underground field industrial tests that this adopted composite support scheme can effectively control the deformation and failure of weak and broken surrounding rock roadway. [ABSTRACT FROM AUTHOR]

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The purpose of the present study was to realize the resource utilization of agricultural byproduct. In this paper, we used rice husk as materials for producing activated carbon. Five factors which affected the yield and iodine absorption performance of rice husk-based activated carbon were sifted and optimized by Plackett-Burman (P-B) and Central Composite Design (CCD). Based on those, the prediction models of yield and iodine adsorption rate were determined and validated. The measurement of iodine absorption rate was based on the method of the GB/T 12,496.1-12,496.22-1999. The results showed that the determination coefficients (R²) of regression equations which established for the yield and iodine adsorption rate of activated carbon samples were 0.90 and 0.85, respectively. The first main factor which influenced the yield of activated carbon was activation temperature followed by activation time and concentration of K2CO3. For the iodine adsorption rate of activated carbon, activation temperature still played an important role in the preparation process, and the next were the concentration of K2CO3 and activation time. The impregnation volume ratio and impregnation time had little influence on the performance of rice husk-based activated carbon. The prediction models which were established by the CCD had a highly significant correlation (P<0.0001) and the determination coefficients (R2) reached 0.92 and 0.90, respectively. There was a strong interaction between the activation temperature and activation time. The response surface analysis indicated that when the activation time was at the center value of 0.92 h and the concentration of K2CO3 remained a constant, the iodine adsorption rate increased with the rise of activation temperature. It can be well illustrated that high activation temperature can promote the chemical reaction. However, the iodine adsorption rate decreased with the extension of activation time when the concentration of K2CO3 was at the center value of 1.5 mol/L and activation temperature remained a constant. This was because that long activation time made the micropore of samples sintered, thus it affected the adsorption performance of rice husk-based activated carbon. With the increased concentration of K2CO3, the iodine adsorption rate showed a gradually increasing trend when the activation temperature was at the center value of 1098 K and activation time remained a constant. It was the reason that more active agent can increase the contact area, which accelerated the reaction distinctively. The optimal conditions were that the rice husk was infused in the K2CO3 solution with concentration and impregnation volume ratio (K2CO3/rice husk) of 1.95 mol/L and 3, respectively after impregnating for 11 h, they were heated for 1.17 h at 1173 K. The prediction value of yield and iodine adsorption rate were 13.61%, 1058.83 mg/g, and the adequacy of the model equation for predicting the optimum response values was verified effectively by the experiment, and the experimental values (14.53%, 1021.30 mg/g) agreed with the predicted values of the model equation with 6.33%, 3.67% deviation, respectively. Our results indicated that optimizing the preparation of rice husk-based activated carbon by using CCD was reliable. This study can provide an important reference for the preparation of activated carbons from rice husk in the industrial production. [ABSTRACT FROM AUTHOR]