Based on the boundary support conditions of overlying high-position,hard and thick strata,a Winkler foundation beam mechanical model was built.Computational expressions for the characteristics and position of the bend...Based on the boundary support conditions of overlying high-position,hard and thick strata,a Winkler foundation beam mechanical model was built.Computational expressions for the characteristics and position of the bending moment for high-position,hard and thick strata were constructed by theoretical analysis,and the initial breaking position of high-position,hard and thick strata was also analyzed.The breaking process and evolution law of mining stress in high-position,hard and thick strata were studied by similar material simulation tests.Studies show that:due to the foundation deformation effect of the lower strata,the initial break position in high-position,hard thick layers is in the middle of goaf;vertical tension fractures first occur under the middle surface,then tilt tension fractures form at both sides and a non-uniform thickness of the fracture structure forms and produces subsidence deformation;behind the coal wall tilt fractures extend and eventually complete the migration.Mining stress produces obvious changes before and after the breakage of the high,hard and thick stratum;high stress concentration forms in front of the coal wall before breakage and fracture stress concentration significantly reduces after migration.Coal seam mining under high-position,hard thick strata can easily induce dynamic phenomena.展开更多
We propose a novel scheme for generating and accelerating simultaneously a dozen-GeVisolated attosecond electron bunch via phase-compressed injection in a radiative-wakefield-breaking process from an electron beam-dri...We propose a novel scheme for generating and accelerating simultaneously a dozen-GeVisolated attosecond electron bunch via phase-compressed injection in a radiative-wakefield-breaking process from an electron beam-driven hollow-channel plasma target.During the beam-target interaction,transverse oscillations of plasma electrons are induced,and subsequently,a radiative wakefield is generated.Meanwhile,a large number of plasma electrons of close to the speed of light are injected transversely toward the center of the hollow channel from the position of the transverse electric field of radiative wakefield,forming an isolated attosecond electron bunch due to the phase compression in the radiative-wakefield-breaking process.The injected attosecond electron bunch is then located just in the acceleration phase of the longitudinal electric field of the radiative wakefield and is importantly accelerated to high energies by the radiative wakefield.It is demonstrated theoretically and numerically that this scheme can efficiently generate an isolated attosecond electron bunch with a charge of more than 2 nC,a peak energy up to 13 GeV of more than 2 times that of the driving electron beam,a peak divergence angle of less than 5 mrad,a duration of 276 as,and an energy conversion efficiency of 36.7%as well as a high stability as compared with the laser-beam drive case.Such an isolated attosecond electron bunch in the range of GeV would provide critical applications in ultrafast physics and high-energy physics.展开更多
基金financially supported by the National Natural Science Foundation of China (No.51374139)the Natural Science Foundation of Shandong Province (No.ZR2013EEM018)the Scientific Research Innovation Team Support Plan of Shandong University of Science and Technology
文摘Based on the boundary support conditions of overlying high-position,hard and thick strata,a Winkler foundation beam mechanical model was built.Computational expressions for the characteristics and position of the bending moment for high-position,hard and thick strata were constructed by theoretical analysis,and the initial breaking position of high-position,hard and thick strata was also analyzed.The breaking process and evolution law of mining stress in high-position,hard and thick strata were studied by similar material simulation tests.Studies show that:due to the foundation deformation effect of the lower strata,the initial break position in high-position,hard thick layers is in the middle of goaf;vertical tension fractures first occur under the middle surface,then tilt tension fractures form at both sides and a non-uniform thickness of the fracture structure forms and produces subsidence deformation;behind the coal wall tilt fractures extend and eventually complete the migration.Mining stress produces obvious changes before and after the breakage of the high,hard and thick stratum;high stress concentration forms in front of the coal wall before breakage and fracture stress concentration significantly reduces after migration.Coal seam mining under high-position,hard thick strata can easily induce dynamic phenomena.
基金supported by Project of Gamma-Gamma Collider and Integrated Beam Flow Facility(Phase I)Validation Device at SYSU(2403-000000-05-03-714165)Guangdong Provincial Key Laboratory of Advanced Particle Detection Technology(2024B1212010005)+3 种基金Guangdong Provincial Key Laboratory of Gamma-Gamma Collider and Its Comprehensiv Applications(2024KSY001)Research Project of SYSU(74140-71020003 and 74140-71020006)National Natural Science Foundation of China(grant nos.12375244 and 12135009)Natural Science Foundation of Hunan Province of China(grant no.2025JJ30002).
文摘We propose a novel scheme for generating and accelerating simultaneously a dozen-GeVisolated attosecond electron bunch via phase-compressed injection in a radiative-wakefield-breaking process from an electron beam-driven hollow-channel plasma target.During the beam-target interaction,transverse oscillations of plasma electrons are induced,and subsequently,a radiative wakefield is generated.Meanwhile,a large number of plasma electrons of close to the speed of light are injected transversely toward the center of the hollow channel from the position of the transverse electric field of radiative wakefield,forming an isolated attosecond electron bunch due to the phase compression in the radiative-wakefield-breaking process.The injected attosecond electron bunch is then located just in the acceleration phase of the longitudinal electric field of the radiative wakefield and is importantly accelerated to high energies by the radiative wakefield.It is demonstrated theoretically and numerically that this scheme can efficiently generate an isolated attosecond electron bunch with a charge of more than 2 nC,a peak energy up to 13 GeV of more than 2 times that of the driving electron beam,a peak divergence angle of less than 5 mrad,a duration of 276 as,and an energy conversion efficiency of 36.7%as well as a high stability as compared with the laser-beam drive case.Such an isolated attosecond electron bunch in the range of GeV would provide critical applications in ultrafast physics and high-energy physics.
