A particle-in-cell simulation of symmetric reconnection with zero guide field is carried out to understand the dynamics of ions along the separatrices.Through the investigation of ion velocity distributions at differe...A particle-in-cell simulation of symmetric reconnection with zero guide field is carried out to understand the dynamics of ions along the separatrices.Through the investigation of ion velocity distributions at different moments and locations along the separatrices,a typical distribution is found:two counter-streaming populations in the perpendicular direction,with another two populations accelerated into distinct energy levels in the parallel direction.Backward tracing of ions reveals that the counter-streaming cores are mostly composed of ions initially located at the same side of the separatrix,while the other two accelerated populations in the parallel direction are composed of ions crossing through the neutral sheet.Through analysis of energy conversion of these populations,it is found that the ion energization along the separatrix is attributable primarily to the Hall electric field,while that in the region between the two separatrices is caused primarily by the induced reconnection electric field.For the counter-streaming population,the low-energy ions that cross the separatrix twice are affected by both Hall and reconnection electric fields,while the high-energy ions that directly enter the separatrix from the unperturbed plasma are energized mainly by the Hall electric field.For the two energized populations in the parallel direction,the ions with lower-energy are accelerated mainly by the in-plane electric field and the Hall electric field on the opposite side of the separatrix,whereas the ions with higher-energy not only experience the same energization process but also are constantly accelerated by the reconnection electric field.展开更多
Ti/Al/Mg laminated composites were successfully fabricated by hot roll bonding.The effects of the rolling reduction on the microstructural evolution and mechanical properties of the composites were explored.The result...Ti/Al/Mg laminated composites were successfully fabricated by hot roll bonding.The effects of the rolling reduction on the microstructural evolution and mechanical properties of the composites were explored.The results show that Ti/Al/Mg laminated sheets exhibit good interfacial bonding.The rolling reduction has a significant effect on the deformation inhomogeneity through the thickness of the Al layer.The initial grains of the Al layer near the Ti/Al interface are fragmented into fine equiaxed grains,and the grains at the center and near the Al/Mg interface are elongated.The R-cube shear texture of the Al layer forms near the Ti/Al interface and permeates into the center layer in the samples with greater rolling reductions.The b-fiber rolling texture of the Al layer is observed near the Al/Mg interface and increases with the increase of rolling reduction.The stress–strain curves indicate that the fracture appears first in the Mg layer.With the increasing rolling reduction,the ultimate tensile and yield strength values increase,and the elongation up to the Mg layer fracture decreases.展开更多
基金supported by the NSFC grants 41821003 and 41974192,by the B-type Strategic Priority Program of the Chinese Academy of Sciences(Grant No.XDB41000000)by the pre-research projects on Civil Aerospace Technologies No.D020103 funded by China’s National Space Administration(CNSA).
文摘A particle-in-cell simulation of symmetric reconnection with zero guide field is carried out to understand the dynamics of ions along the separatrices.Through the investigation of ion velocity distributions at different moments and locations along the separatrices,a typical distribution is found:two counter-streaming populations in the perpendicular direction,with another two populations accelerated into distinct energy levels in the parallel direction.Backward tracing of ions reveals that the counter-streaming cores are mostly composed of ions initially located at the same side of the separatrix,while the other two accelerated populations in the parallel direction are composed of ions crossing through the neutral sheet.Through analysis of energy conversion of these populations,it is found that the ion energization along the separatrix is attributable primarily to the Hall electric field,while that in the region between the two separatrices is caused primarily by the induced reconnection electric field.For the counter-streaming population,the low-energy ions that cross the separatrix twice are affected by both Hall and reconnection electric fields,while the high-energy ions that directly enter the separatrix from the unperturbed plasma are energized mainly by the Hall electric field.For the two energized populations in the parallel direction,the ions with lower-energy are accelerated mainly by the in-plane electric field and the Hall electric field on the opposite side of the separatrix,whereas the ions with higher-energy not only experience the same energization process but also are constantly accelerated by the reconnection electric field.
基金This work was supported by the National Natural Science Foundation of China （Nos. 61377033 and 91123008）, the 973 Program of China （No. 2011CB933300）, and the Program for New Century Excellent Talents of the University in China （Grant No. NCET-11-0179）.
基金financial supports from the National Natural Science Foundation of China(No.51421001)the National High Technology Research and Development Program of China(863 Program,No.2013AA031304)+1 种基金the Fundamental Research Funds for the CentralUniversitiesofChina(2019CDQYCL001,2019CDCGCL204,2020CDJDPT001)the Research Project of State Key Laboratory of Vehicle NVH and Safety Technology of China(No.NVHSKL-201706)。
文摘Ti/Al/Mg laminated composites were successfully fabricated by hot roll bonding.The effects of the rolling reduction on the microstructural evolution and mechanical properties of the composites were explored.The results show that Ti/Al/Mg laminated sheets exhibit good interfacial bonding.The rolling reduction has a significant effect on the deformation inhomogeneity through the thickness of the Al layer.The initial grains of the Al layer near the Ti/Al interface are fragmented into fine equiaxed grains,and the grains at the center and near the Al/Mg interface are elongated.The R-cube shear texture of the Al layer forms near the Ti/Al interface and permeates into the center layer in the samples with greater rolling reductions.The b-fiber rolling texture of the Al layer is observed near the Al/Mg interface and increases with the increase of rolling reduction.The stress–strain curves indicate that the fracture appears first in the Mg layer.With the increasing rolling reduction,the ultimate tensile and yield strength values increase,and the elongation up to the Mg layer fracture decreases.
