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To study the effects of bamboo fiber and steel wire mesh on the flexural ductility of basalt fiber reinforced polymer（BFRP）bar concrete beams, 7 BFRP bar concrete beams with bamboo fiber and steel wire mesh were tested with different bamboo fiber lengths (0 mm, 30 mm and 45 mm) and different steel wire mesh layout ranges (0, 1/2 maximum bending moment point layout and full beam length layout). The flexural failure tests of the 7 beams were carried out, and the initial crack loads, the crack developments, the ultimate loads and the deformations were detected. The effects of the fiber length and the wire mesh layout range on the crack resistance and the deformation resistance of the specimens were analyzed based on the test data. With the function model, the equivalent yield points of the 7 test beams were obtained, and their ductility coefficients were calculated. The results show that, the addition of bamboo fiber and steel wire mesh increases the cracking loads of BFRP bar concrete beams by 12%~68%, decreases the crack spacings and the crack length development speed, reduces the test beam deformation under the same load, and increases the ductility coefficient by 1.58%~31.75%. [ABSTRACT FROM AUTHOR]

Plant protection spraying has been the main way to prevent crops from pests and diseases at present. However, the average utilization rate of pesticides is only 20% to 30% in manual sprayers and large-capacity rain spraying, particularly with water consumption of 600-1 200 L/hm2 . The current pesticide spraying cannot fully meet the requirement of intensive agriculture in recent years. Among them, a large number of droplets with small particle sizes are susceptible to drifting by ambient wind. In this study, the mesh atomization of droplets was applied to reduce the wind drift for the high utilization rate of pesticides in the process of plant protection spraying. A systematic optimization was also made to investigate the secondary atomization characteristics of the droplets and the deposition effect of the droplets after the spray hits the mesh. The experimental variables were set as the pore size and the distance between the nozzle and the mesh. Phase Doppler Anemometry (PDA) was used to measure the velocity and particle size distribution of droplets after secondary atomization. A high-speed camera was selected to capture the spray angle. A 0.5 g/L methyl orange aqueous solution was prepared as a spray solution. The water-sensitive and filter tests were carried out to determine the droplet coverage and deposition amount, in order to evaluate the droplet deposition characteristics of the mesh atomization. The test results showed that: 1) the mesh effectively reduced the speed of the droplets. The average velocities of the measurement points were 1.80, 2.02, and 1.67 m/s under the mesh with pore sizes of 461, 350, and 227 μm, respectively. There were 23.40%, 13.90%, and 29.00% lower than those without the mesh (2.35 m/s). 2) The mesh reduced the particle size of the droplets. The maximum average particle sizes of the measurement points were 155.0, 165.6, and 173.3μm under the mesh with the pore size of 461, 350, and 227 μm, respectively, which were 19.5%, 14%, and 10% lower than those without the mesh (192.5 μm). 3) The spray angle of the droplet was varied in the pore size of the mesh and the distance between the nozzle and the mesh. Specifically, the maximum spray angle was 84.179° for the secondary atomized droplets at the pore size of 461 μm and the 10cm distance between the nozzle and the mesh, which was 20.366° larger than that without the mesh. 4) There was a great influence of pore size on the uniformity and penetration of the droplet deposition. The coefficient of variation of the deposition rate was between 33.51% and 88.08% at the sampling point of the mesh with the pore size of 350 and 227 μm, respectively, indicating similar deposition uniformity. By contrast, the maximum coefficient of variation of the deposition rate was 162.98% at the sampling points in each mesh layer with a pore size of 461 μm, indicating relatively less deposition uniformity. The better penetration of droplets was achieved in the mesh with the pore size of 350 μm, where the coefficient of variation of deposition between layers was between 0.8 % and 10.08 %. The better deposition was obtained in the mesh with the pore size of 461 μm in this case, compared with the pore size of 461 and 227 μm. There was no significant effect of the distance between the nozzle and the grid on the droplet coverage and deposition volume. In terms of the grids and large spraying droplets, the average droplet drift in the non-target area was 7.58 % of the deposition in the target area, indicating better performance after optimization. This finding can provide a strong reference to select the spraying and mesh parameters for the combination of plant protection UAV spray and mesh atomization. [ABSTRACT FROM AUTHOR]

The icing of helicopter rotor blades will lead to the destruction of its aerodynamic shape and seriously affect the flight quality. In order to improve the flexibility and fatigue resistance of helicopter rotor anti-icing system, the metal mesh braided with nickel alloy filaments is used as heating element, and the heating element is arranged in the blade in an extended way. Through the design, the diameter of wire and the size of mesh are determined. Combining with the existing composite material forming process, the electrical heating test pieces are prepared. The electrothermal performance test, mechanical property test and laboratory simulated deicing test of the prepared heating pad are carried out. The results show that the temperature rising speed of the heating pad is 2.5 ℃/s, the temperature uniformity in the plane is less than 2 ℃, and the simulated deicing effect in the laboratory is good.

Copyright of Journal of PLA University of Science & Technology (Natural Science Edition) / Jiefangjun Ligong Daxue Xuebao is the property of Magazine of PLA University of Science and Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)