To investigate the effect of void defects on the shock response of hexanitrohexaazaisowurtzitane(CL-20)co-crystals,shock responses of CL-20 co-crystals with energetic materials ligands trinitrotoluene(TNT),1,3-dinitro...To investigate the effect of void defects on the shock response of hexanitrohexaazaisowurtzitane(CL-20)co-crystals,shock responses of CL-20 co-crystals with energetic materials ligands trinitrotoluene(TNT),1,3-dinitrobenzene(DNB),solvents ligands dimethyl carbonate(DMC) and gamma-butyrolactone(GBL)with void were simulated,using molecular dynamics method and reactive force field.It is found that the CL-20 co-crystals with void defects will form hot spots when impacted,significantly affecting the decomposition of molecules around the void.The degree of molecular fragmentation is relatively low under the reflection velocity of 2 km/s,and the main reactions are the formation of dimer and the shedding of nitro groups.The existence of voids reduces the safety of CL-20 co-crystals,which induced the sensitivity of energetic co-crystals CL-20/TNT and CL-20/DNB to increase more significantly.Detonation has occurred under the reflection velocity of 4 km/s,energetic co-crystals are easier to polymerize than solvent co-crystals,and are not obviously affected by voids.The results show that the energy of the wave decreases after sweeping over the void,which reduces the chemical reaction frequency downstream of the void and affects the detonation performance,especially the solvent co-crystals.展开更多
The influence of crystallographic orientation on the void growth in FCC crystals was numerically simulated with 3D crystal plasticity finite element by using a 3D unit cell including a spherical void, and the rate-dep...The influence of crystallographic orientation on the void growth in FCC crystals was numerically simulated with 3D crystal plasticity finite element by using a 3D unit cell including a spherical void, and the rate-dependent crystal plasticity theory was implemented as a user material subroutine. The results of the simulations show that crystallographic orientation has significant influence on the growth behavior of the void. Different active slip systems of the regions around the void cause the discontinuity in lattice rotation around the void, and the corner-like region is formed. In the case of the void located at grain boundary, large heterogeneous deformation occurs between the two grains, and the equivalent plastic deformation along grain boundary near the void in the case of θ=45^o （θ is the angle between grain boundary direction and X-axis） is larger than the others. Large difference of orientation factor of the two grains leads to large equivalent plastic deformation along grain boundary, and the unit cell is more likely to fail by intergranular fracture.展开更多
目的:探究3 d排尿日记(VD)评估两种儿童严重原发性遗尿(PNE)的价值。方法:采用多中心前瞻性研究,选择2023年1~12月就诊的符合国际儿童尿控协会(ICCS)严重PNE诊断标准(遗尿>4晚/周)的141例患儿(年龄6~15岁),均记录2周VD,分为单症状性P...目的:探究3 d排尿日记(VD)评估两种儿童严重原发性遗尿(PNE)的价值。方法:采用多中心前瞻性研究,选择2023年1~12月就诊的符合国际儿童尿控协会(ICCS)严重PNE诊断标准(遗尿>4晚/周)的141例患儿(年龄6~15岁),均记录2周VD,分为单症状性PNE(MNE)和非单症状性PNE(NMNE)两组;提取3 d VD(第1个周五、周六、周日),比较2周与3 d VD中平均每天排尿次数、平均每次排尿量(AVV)/预期膀胱容量(EBC)、平均最大排尿量(MVV)、平均MVV/EBC、平均夜间排尿量、平均夜间排尿量/EBC的差异。以2周VD是否记录到白天排尿异常为评估NMNE和MNE的金标准,分析3 d VD的诊断效能。结果:128例完成2周VD,其中MNE 87例,NMNE 41例。2周和3 d VD的平均每天排尿次数、AVV/EBC、平均MVV、平均MVV/EBC、平均夜间排尿量、平均夜间排尿量/EBC差异均无统计学意义(P>0.05)。3 d VD诊断MNE和NMNE的敏感度、特异度、准确度、阳性预测值和阴性预测值分别为95.0%、96.6%、96.1%、92.7%和97.7%。结论:3 d VD可以替代2周VD,用于评估、诊断儿童严重MNE和NMNE。展开更多
基金supported by the National Natural Science Foundation of China (22275018)the Project of State Key Laboratory of Explosion Science and Technology (Beijing Institute of Technology)(Grant No.QNKT20-04)。
文摘To investigate the effect of void defects on the shock response of hexanitrohexaazaisowurtzitane(CL-20)co-crystals,shock responses of CL-20 co-crystals with energetic materials ligands trinitrotoluene(TNT),1,3-dinitrobenzene(DNB),solvents ligands dimethyl carbonate(DMC) and gamma-butyrolactone(GBL)with void were simulated,using molecular dynamics method and reactive force field.It is found that the CL-20 co-crystals with void defects will form hot spots when impacted,significantly affecting the decomposition of molecules around the void.The degree of molecular fragmentation is relatively low under the reflection velocity of 2 km/s,and the main reactions are the formation of dimer and the shedding of nitro groups.The existence of voids reduces the safety of CL-20 co-crystals,which induced the sensitivity of energetic co-crystals CL-20/TNT and CL-20/DNB to increase more significantly.Detonation has occurred under the reflection velocity of 4 km/s,energetic co-crystals are easier to polymerize than solvent co-crystals,and are not obviously affected by voids.The results show that the energy of the wave decreases after sweeping over the void,which reduces the chemical reaction frequency downstream of the void and affects the detonation performance,especially the solvent co-crystals.
基金Project(2005CB623706) supported by the Major State Basic Research Development Program of China
文摘The influence of crystallographic orientation on the void growth in FCC crystals was numerically simulated with 3D crystal plasticity finite element by using a 3D unit cell including a spherical void, and the rate-dependent crystal plasticity theory was implemented as a user material subroutine. The results of the simulations show that crystallographic orientation has significant influence on the growth behavior of the void. Different active slip systems of the regions around the void cause the discontinuity in lattice rotation around the void, and the corner-like region is formed. In the case of the void located at grain boundary, large heterogeneous deformation occurs between the two grains, and the equivalent plastic deformation along grain boundary near the void in the case of θ=45^o （θ is the angle between grain boundary direction and X-axis） is larger than the others. Large difference of orientation factor of the two grains leads to large equivalent plastic deformation along grain boundary, and the unit cell is more likely to fail by intergranular fracture.
文摘目的:探究3 d排尿日记(VD)评估两种儿童严重原发性遗尿(PNE)的价值。方法:采用多中心前瞻性研究,选择2023年1~12月就诊的符合国际儿童尿控协会(ICCS)严重PNE诊断标准(遗尿>4晚/周)的141例患儿(年龄6~15岁),均记录2周VD,分为单症状性PNE(MNE)和非单症状性PNE(NMNE)两组;提取3 d VD(第1个周五、周六、周日),比较2周与3 d VD中平均每天排尿次数、平均每次排尿量(AVV)/预期膀胱容量(EBC)、平均最大排尿量(MVV)、平均MVV/EBC、平均夜间排尿量、平均夜间排尿量/EBC的差异。以2周VD是否记录到白天排尿异常为评估NMNE和MNE的金标准,分析3 d VD的诊断效能。结果:128例完成2周VD,其中MNE 87例,NMNE 41例。2周和3 d VD的平均每天排尿次数、AVV/EBC、平均MVV、平均MVV/EBC、平均夜间排尿量、平均夜间排尿量/EBC差异均无统计学意义(P>0.05)。3 d VD诊断MNE和NMNE的敏感度、特异度、准确度、阳性预测值和阴性预测值分别为95.0%、96.6%、96.1%、92.7%和97.7%。结论:3 d VD可以替代2周VD,用于评估、诊断儿童严重MNE和NMNE。
