In order to search the pointing accuracy degradation and the wheel-rail contact of the National astronomical observatory 50m radio telescope, according to the actual wheel-rail structure and design indicators, the wheel rail contact problem with the finite element analysis based on non-Hertz rolling contact theory is analyzed. The results show that the maximum deformation should be less than 1 mm. Then the measurement scheme of rail horizontal error and deformation is formulated. The mean value of the rail horizontal error is 2.89mm, while the maximum rail horizontal error is 1.5mm. The rail maintenance scheme is put forward after the flaw detection which finds large areas of cracks at the rail junction and the welded joint. The measurement is taken after rail maintenance; the experimental data coincide with the simulation results and then verify the correctness of the wheel-rail contact model, also the solution scheme of rail cracks. The reason for the pointing accuracy degradation is verified finally, which also can provide an effective method for the wheel-rail design and maintenance of large radio telescope.
This paper educes the mathematics formula of solid-liquid phase dielectric constant by employing two methods of mixture’s dielectric constant, building on the electromagnetic wave through the medium theory, this paper thus obtains the mathematic theory model of online microwave water content detection in iron concentrate. Finally, this paper identifies and revises the mathematic model through experiments.
Abstract. In order to improve the stability of feed movement in high speed CNC system, the feedrate planning algorithm based on piece-wise polynomial function was proposed. The flexible transition of feedrate was realized through maintaining linear continuous jerk. The principle of the proposed algorithm was introduced and the method to generate smooth motion profile based on the proposed algorithm was presented. The rapidity, stability and tracking accuracy of the feedrate planning algorithm to linearity, S curve and the proposed one were analyzed. The proposed algorithm is simple and it can be applied in acceleration/deceleration before interpolation in high speed feed movement to improve the stability of it. The proposed algorithm was applied in multi-contour high speed processing and the result indicated that it could improve the stability of large-scale parts motion.
The vehicular LNG(Liquefied Natural Gas) tank is a key component in the land transportation of-163°C LNG. The cryo-insulation performance of vehicular tank directly affects the security of LNG transport greatly. Based on a 40m3 vehicular LNG tank, a structural design of the vehicular LNG tank is completed, which includes its body,nozzles,heat-insulating layer,sealing devices,saddles and so on. With the safety requirements of less than 2% LNG evaporation rate, the leakage heat of LNG tank is analyzed completely. Then, a heat-insulating layer outside of LNG tank is completed with thermal design. Finally, with thermal software, the effectiveness of heat-insulating layer is proved.
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