The debris cloud generated by the hypervelocity impact(HVI)of orbiting space debris directly threatens the spacecraft.A full understanding of the damage mechanism of rear plate is useful for the optimal design of prot...The debris cloud generated by the hypervelocity impact(HVI)of orbiting space debris directly threatens the spacecraft.A full understanding of the damage mechanism of rear plate is useful for the optimal design of protective structures.In this study,the hypervelocity yaw impact of a cylindrical aluminum projectile on a double-layer aluminum plate is simulated by the FE-SPH adaptive method,and the damage process of the rear plate under the impact of the debris cloud is analyzed based on the debris cloud structure.The damage process can be divided into the main impact stage of the debris cloud and the structural response of the rear plate.The main impact stage lasts a short time and is the basis of the rear plate damage.In the stage of structure response,the continuous deformation and inertial motion of the rear plate dominate the perforation of the rear plate.We further analyze the damage mechanism and damage distribution characteristics of the rear plate in detail.Moreover,the connection between velocity space and position space of the debris cloud is established,which promotes the general analysis of the damage law of debris cloud.Based on the relationship,the features of typical damage areas are identified by the localized fine analysis.Both the cumulative effect and structural response cause the perforation of rear plate;in the non-perforated area,cratering by the impact of hazardous fragments is the main damage mode of the rear plate.展开更多
Dried fruit beetles can be cultured easily using an artificial diet,therefore it is notnecessary to provide fruit.The ingredient are:Torula yeast,54g:Dried carrot,162g;Nipagin,2.4g;HCL Conc.7ml;Rain water,800ml.About6...Dried fruit beetles can be cultured easily using an artificial diet,therefore it is notnecessary to provide fruit.The ingredient are:Torula yeast,54g:Dried carrot,162g;Nipagin,2.4g;HCL Conc.7ml;Rain water,800ml.About60g of diet in pressed against one side of ahalf litre yogurt and sprinkled with a teaspoonful of active yeast.Two teaspoons full of diet ontop of the gauze lid and sprinkled with active yeast granules for the adults to eat and also to layeggs into.Up to2000 larvae should be produced from400 parents each week.About200 eggscan be collected,when making observations.The culture is rejuvenated each year with beetlescollected from the wild,kept isolated to avoid contamination of the culture room with mites.展开更多
The damage to the rear surface of fused silica under the action of high power laser is more severe than that incurred by the front surface,which hinders the improvement in the energy of the high power laser device.For...The damage to the rear surface of fused silica under the action of high power laser is more severe than that incurred by the front surface,which hinders the improvement in the energy of the high power laser device.For optical components,the ionization breakdown by laser is a main factor causing damage,particularly with laser plasma shock waves,which can cause large-scale fracture damage in fused silica.In this study,the damage morphology is experimentally investigated,and the characteristics of the damage point are obtained.In the theoretical study,the coupling and transmission of the shock wave in glass are investigated based on the finite element method.Thus,both the magnitude and the orientation of stress are obtained.The damage mechanism of the glass can be explained based on the fracture characteristics of glass under different stresses and also on the variation of the damage zone’s Raman spectrum.In addition,the influence of the glass thickness on the damage morphology is investigated.The results obtained in this study can be used as a reference in understanding the characteristics and mechanism of damage characteristics induced by laser plasma shock waves.展开更多
基金supported by the Innovative Research Groups of the National Natural Science Foundation of China(Grant No.12221002)。
文摘The debris cloud generated by the hypervelocity impact(HVI)of orbiting space debris directly threatens the spacecraft.A full understanding of the damage mechanism of rear plate is useful for the optimal design of protective structures.In this study,the hypervelocity yaw impact of a cylindrical aluminum projectile on a double-layer aluminum plate is simulated by the FE-SPH adaptive method,and the damage process of the rear plate under the impact of the debris cloud is analyzed based on the debris cloud structure.The damage process can be divided into the main impact stage of the debris cloud and the structural response of the rear plate.The main impact stage lasts a short time and is the basis of the rear plate damage.In the stage of structure response,the continuous deformation and inertial motion of the rear plate dominate the perforation of the rear plate.We further analyze the damage mechanism and damage distribution characteristics of the rear plate in detail.Moreover,the connection between velocity space and position space of the debris cloud is established,which promotes the general analysis of the damage law of debris cloud.Based on the relationship,the features of typical damage areas are identified by the localized fine analysis.Both the cumulative effect and structural response cause the perforation of rear plate;in the non-perforated area,cratering by the impact of hazardous fragments is the main damage mode of the rear plate.
文摘Dried fruit beetles can be cultured easily using an artificial diet,therefore it is notnecessary to provide fruit.The ingredient are:Torula yeast,54g:Dried carrot,162g;Nipagin,2.4g;HCL Conc.7ml;Rain water,800ml.About60g of diet in pressed against one side of ahalf litre yogurt and sprinkled with a teaspoonful of active yeast.Two teaspoons full of diet ontop of the gauze lid and sprinkled with active yeast granules for the adults to eat and also to layeggs into.Up to2000 larvae should be produced from400 parents each week.About200 eggscan be collected,when making observations.The culture is rejuvenated each year with beetlescollected from the wild,kept isolated to avoid contamination of the culture room with mites.
基金Project supported by the Key Research and Development Projects of Science and Technology Department of Sichuan Province,China(Grant No.2018FZ0032)the National Natural Science Foundation of China(Grant No.U1730141)
文摘The damage to the rear surface of fused silica under the action of high power laser is more severe than that incurred by the front surface,which hinders the improvement in the energy of the high power laser device.For optical components,the ionization breakdown by laser is a main factor causing damage,particularly with laser plasma shock waves,which can cause large-scale fracture damage in fused silica.In this study,the damage morphology is experimentally investigated,and the characteristics of the damage point are obtained.In the theoretical study,the coupling and transmission of the shock wave in glass are investigated based on the finite element method.Thus,both the magnitude and the orientation of stress are obtained.The damage mechanism of the glass can be explained based on the fracture characteristics of glass under different stresses and also on the variation of the damage zone’s Raman spectrum.In addition,the influence of the glass thickness on the damage morphology is investigated.The results obtained in this study can be used as a reference in understanding the characteristics and mechanism of damage characteristics induced by laser plasma shock waves.
