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IN738LC alloy is a typical γ’ phase precipitation-strengthened nickel-based superalloy, commonly used in high-temperature components such as gas turbines and aero-engines.In order to further enhance its high-temperature wear resistance, IN738 alloy samples were prepared using laser cladding technology with four different laser powers in a 99.99%pure nitrogen environment, followed by heat treatment at 850 ℃for 24 h.The microstructure and properties were studied using X-ray diffraction (XRD), scanning electron microscopy (SEM), high-temperature friction and wear testing machines and JMatPro software.Results showed that with the increase in laser power, the mean hardness of the samples without heat treatment increased gradually from 40.74 HRC to 41.92 HRC, while the mean hardness of the samples after heat treatment was 43.0 HRC.The average friction coefficients of the samples without heat treatment and after heat treatment at normal temperature were 0.70 and 0.65, respectively.The average friction coefficient at 800 ℃of the samples after heat treatment was 0.35.The wear resistance of the samples first increased and then decreased with the increase in laser power within a certain range of laser power.The wear resistance of the samples prepared at room temperature and at 800 ℃was highest when the laser power was 750 W and 650 W,respectively.The wear resistance of samples prepared under the same laser power at a high temperature of 800 ℃was much better than that at room temperature.

Laser additive martensite stainless steel can be applied to high temperature parts below 600 ℃.In order to further improve its high temperature wear resistance，four kinds of martensite stainless steel samples with different aluminum content (0，1%，2%and 3%，mass fraction) were prepared.The four types of martensitic stainless steel samples were heat treated at temperatures of 25，200，400，and 600 ℃using a box type resistance furnace.Moreover，the metallographic structure and high-temperature friction and wear properties of the samples were studied by OM，XRD，SEM，3D depth-of-field microscope，high-temperature friction and wear testing machine and JMatPro software.Results showed that with the increase of the aluminum content，the average hardness of the specimen decreased from 57.87 HRC to 42.46 HRC.With the extension of the insulation time at 600 ℃，the hardness of the samples decreased rapidly and stabilized，and its value decreased from 44.79 HRC to 28.70 HRC.In addition，the increase in aluminum content had no obvious effect on the friction coefficient of the sample at 25 ℃，and its values were in the range of 0.8～0.9.When the aluminum content reached 3%，the friction coefficient of the sample in 600 ℃environment was reduced to about 0.45，which was about 52.94%of that at 25 ℃.The volume wear amount declined to 0.021 4 mm3，which was approximately 9%of that at 25 ℃.Meanwhile，the main phase of the sample was composed of martensite and a small amount of precipitated phases such as carbide.In general，the addition of 3%aluminum could significantly improve the high-temperature friction wear performance of martensite stainless steel prepared by laser additive.

With the continuous renewal and rise of various flight equipment, this article designs a method of water data collection, which is realized through the coordination of an unmanned surface vehicle (USV) carrying unmanned aerial vehicles (UAVs, commonly called drones). In reality, multiple UAVs take-off and landing sites, energy consumption, and other complex issues closely related to USV recovery, UAVs must be considered. If mixed integer linear programming (MILP) is used directly, it is difficult to get satisfactory results in an acceptable time range. Therefore, a heuristic algorithm is proposed to solve the problem of data collection by these devices, which can not only quickly solve the large-scale collaborative optimization problem, but also rationally utilize the total energy consumption of the equipment. The effectiveness of the proposed algorithm is verified and analyzed by experimenting a different number of monitoring nodes, different number of UAVs and different task time. It can not only shorten the cycle of data acquisition task, but also reduce the waiting time of the UAV and USV., Author(s): Zhigang Wang [1,2]; Liqin Tian (corresponding author) [1,2]; Lianhai Lin [2]; Jianfei Xie [1]; Wenxing Wu [2]; Yinghua Tong [2] 1. Introduction Unmanned equipment with strong flexibility and extensibility [...]

A series of SO42−/TiO2 solid superacid catalysts were prepared under different conditions. The effect of different preparation conditions on the SO42−/TiO2 catalyst was investigated by evaluating the change of its crystallinity, chemical structure and acid content. The catalytic performance of the SO42−/TiO2 catalyst was evaluated by α-pinene isomerization in a continuous fixed bed reactor. When ammonia was used as the precipitation agent, the concentration of sulfuric acid impregnation solution was 2 M, and the calcination temperature was 500 °C, the activity of the SO42−/TiO2 catalyst reached the maximum, the conversion rate of α-pinene was stable at about 95%, and the selectivity of camphene reached 40%. It was found that the structure and textural properties of the SO42−/TiO2 catalyst did not change significantly after regeneration by studying the regeneration performance of the SO42−/TiO2 catalyst. [ABSTRACT FROM AUTHOR]

A simple equivalent circuit model (ECM) for a reflective polarization converter (RPC) comprising anisotropic metasurfaces is presented in this paper. The impedance matrix of an anisotropic metasurface in x and y axis is derived by the impedance matrix in a diagonal axis multiply with a rotated matrix, while the diagonal impedance matrix can be calculated by a simple L C network, which contains a series of capacitors and inductors. The presence of the dielectric substrates is considered using the transmission line theory. Some typical RPCs with different metasurface shapes are used to verify the effectiveness of the ECM. The methodology provides a simple approach for the design and optimization of RPC. Finally, we designed a polarization converter based on the proposed method, and the measured results are in good agreement with the theoretical results. [ABSTRACT FROM AUTHOR]