A parametric study of the clustering transition of a vibration-driven granular gas system is performed by simulation.The parameters studied include the global volume fraction of the system,the size of the system,the f...A parametric study of the clustering transition of a vibration-driven granular gas system is performed by simulation.The parameters studied include the global volume fraction of the system,the size of the system,the friction coefficient,and the restitution coefficient among particles and among particle-walls.The periodic boundary and fixed boundary of sidewalls are also checked in the simulation.The simulation results provide us the necessary“heating”time for the system to reach steady state,and the friction term needed to be included in the“cooling”time.A gas-cluster phase diagram obtained through Kolmogorov-Smirnov(K-S)test analysis using similar experimental parameters is given.The influence of the parameters to the transition is then investigated in simulations.This simulation investigation helps us gain understanding which otherwise cannot be obtained by experiment alone,and makes suggestions on the determination of parameters to be chosen in experiments.展开更多
In order to design the scale model in a wide frequency range,a method based on the reflective loss is proposed according to the high-frequency approximation algorithm,and an example of designing the scale model of a p...In order to design the scale model in a wide frequency range,a method based on the reflective loss is proposed according to the high-frequency approximation algorithm,and an example of designing the scale model of a plate-shaped absorber is given in this paper.In the example,the frequency of the full-size measurement ranges from 2.0 GHz to 2.4 GHz,the thickness of the full-size absorber is 1 mm and the scale ratio is 1/5.A two-layer scale absorber is obtained by the proposed method.The thickness values of the bottom and top layer are 0.4 mm and 0.5 mm,respectively.Furthermore,the scattering properties of a plate model and an SLICY model are studied by FEKO to verify the effectiveness of the designed scale absorber.Compared with the corresponding values from the theoretical scale model,the average values of the absolute deviations in 10 GHz～12 GHz are 0.53 d Bm^2,0.65 d Bm^2,0.76 d Bm^2 for the plate model and 0.20 d Bm^2,0.95 d Bm^2,0.77 d Bm^2 for the SLICY model while the incident angles are 0°,30°,and 60°,respectively.These deviations fall within the Radar cross section（RCS） measurement tolerance.Thus,the work in this paper has important theoretical and practical significance.展开更多
基金Project supported by the National Natural Science Foundation of China(Grant Nos.U1738120,11474326,and 11705256)Young Scholar of CAS”Light of West China”Program for Guanghui Yang(Grant No.2018-98)+1 种基金the Strategic Priority Research Program of Chinese Academy of Sciences(Grant No.XDA21010202)the International Cooperation Project of China Manned Space Program.
文摘A parametric study of the clustering transition of a vibration-driven granular gas system is performed by simulation.The parameters studied include the global volume fraction of the system,the size of the system,the friction coefficient,and the restitution coefficient among particles and among particle-walls.The periodic boundary and fixed boundary of sidewalls are also checked in the simulation.The simulation results provide us the necessary“heating”time for the system to reach steady state,and the friction term needed to be included in the“cooling”time.A gas-cluster phase diagram obtained through Kolmogorov-Smirnov(K-S)test analysis using similar experimental parameters is given.The influence of the parameters to the transition is then investigated in simulations.This simulation investigation helps us gain understanding which otherwise cannot be obtained by experiment alone,and makes suggestions on the determination of parameters to be chosen in experiments.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.61601299 and 11404213)the Shanghai Municipal Science and Technology Commission,China(Grant Nos.17210730900 and 15ZR1439600)the Defense Industrial Technology,China(Grant No.B2120132001)
文摘In order to design the scale model in a wide frequency range,a method based on the reflective loss is proposed according to the high-frequency approximation algorithm,and an example of designing the scale model of a plate-shaped absorber is given in this paper.In the example,the frequency of the full-size measurement ranges from 2.0 GHz to 2.4 GHz,the thickness of the full-size absorber is 1 mm and the scale ratio is 1/5.A two-layer scale absorber is obtained by the proposed method.The thickness values of the bottom and top layer are 0.4 mm and 0.5 mm,respectively.Furthermore,the scattering properties of a plate model and an SLICY model are studied by FEKO to verify the effectiveness of the designed scale absorber.Compared with the corresponding values from the theoretical scale model,the average values of the absolute deviations in 10 GHz～12 GHz are 0.53 d Bm^2,0.65 d Bm^2,0.76 d Bm^2 for the plate model and 0.20 d Bm^2,0.95 d Bm^2,0.77 d Bm^2 for the SLICY model while the incident angles are 0°,30°,and 60°,respectively.These deviations fall within the Radar cross section（RCS） measurement tolerance.Thus,the work in this paper has important theoretical and practical significance.
