The prediction of the fragment velocity distribution of a cylindrical cased charge with end caps is one of the key issues to assess the damage efficiency of the warhead. However, limited work has been conducted to pre...The prediction of the fragment velocity distribution of a cylindrical cased charge with end caps is one of the key issues to assess the damage efficiency of the warhead. However, limited work has been conducted to predict the fragment velocity distributions along the axis of cylindrical cased charges with end caps. This paper presents a study of the velocity distribution of fragments caused by the explosion of a cylindrical cased charge with end caps. The fragment velocity distribution and the end cap velocity were determined by an X-ray radiography method, and the axial fragment distribution was determined by witness plates. It was found that the velocities of fragments, especially near the edge, were increased when the end caps were added, and the position of maximum velocity is closer to the non-detonation end. The fragment velocities were increased, and the fragment projection range was decreased with the increase of the thickness of the end cap. A formula for fragment velocity distributions of a cylindrical cased charge with end caps, which is based on Huang’s formula, was proposed by the theoretical analysis and data fitting and validated experimentally. The results indicate that the proposed formula is accurate in predicting the fragment velocity distribution along the axis of a cylindrical cased charge with end caps detonated at one end.展开更多
Pressure is one of the important measures to control the surface accuracy of the reflector of inflatable antenna. Experiments and numerical analysis were carried out to highlight the effect of pressure on accuracy. Th...Pressure is one of the important measures to control the surface accuracy of the reflector of inflatable antenna. Experiments and numerical analysis were carried out to highlight the effect of pressure on accuracy. The rapid, contactless and low-cost digital photogrammetry system （DIES） was employed to investigate the effect according to its lightweight and flexible characteristics. Measurement data show that the best pressure and the best area in this pressure can be obtained. Numerical analysis was conducted to check the measurement result. It is indicated that there is a little difference between them attributed to wrinkle. Results of analysis and experiments show that surface accuracy of the reflector can be adjusted by controlling pressure.展开更多
Copolymers of 9,9-dioctylfluorene(DOF)and 2-thienyl-benzothiadiazole(DBT)were synthesized by Suzuki reaction and end-capped by N-hexyl-carbazole and benzene,which were abbreviated as PDOF-DBT-Cz and PDOF-DBT-B,respect...Copolymers of 9,9-dioctylfluorene(DOF)and 2-thienyl-benzothiadiazole(DBT)were synthesized by Suzuki reaction and end-capped by N-hexyl-carbazole and benzene,which were abbreviated as PDOF-DBT-Cz and PDOF-DBT-B,respectively.The photophysical,electrochemical and thermal properties of the copolymers were studied.The results indicated that replacement of N-hexyl-carbazole as end-capping group of PDOF-DBT can vary light color and improve luminescence efficiency.展开更多
基金financial support from the exploratory project of State Key Laboratory of Explosion Science and Technology, China (No. QNKT19-09)。
文摘The prediction of the fragment velocity distribution of a cylindrical cased charge with end caps is one of the key issues to assess the damage efficiency of the warhead. However, limited work has been conducted to predict the fragment velocity distributions along the axis of cylindrical cased charges with end caps. This paper presents a study of the velocity distribution of fragments caused by the explosion of a cylindrical cased charge with end caps. The fragment velocity distribution and the end cap velocity were determined by an X-ray radiography method, and the axial fragment distribution was determined by witness plates. It was found that the velocities of fragments, especially near the edge, were increased when the end caps were added, and the position of maximum velocity is closer to the non-detonation end. The fragment velocities were increased, and the fragment projection range was decreased with the increase of the thickness of the end cap. A formula for fragment velocity distributions of a cylindrical cased charge with end caps, which is based on Huang’s formula, was proposed by the theoretical analysis and data fitting and validated experimentally. The results indicate that the proposed formula is accurate in predicting the fragment velocity distribution along the axis of a cylindrical cased charge with end caps detonated at one end.
文摘Pressure is one of the important measures to control the surface accuracy of the reflector of inflatable antenna. Experiments and numerical analysis were carried out to highlight the effect of pressure on accuracy. The rapid, contactless and low-cost digital photogrammetry system （DIES） was employed to investigate the effect according to its lightweight and flexible characteristics. Measurement data show that the best pressure and the best area in this pressure can be obtained. Numerical analysis was conducted to check the measurement result. It is indicated that there is a little difference between them attributed to wrinkle. Results of analysis and experiments show that surface accuracy of the reflector can be adjusted by controlling pressure.
基金Supported by the Major Project of Science Foundation Ministry of Education of China(Grant No.207015)the National Natural Science Foundation of China(Grant No.20671068)
文摘Copolymers of 9,9-dioctylfluorene(DOF)and 2-thienyl-benzothiadiazole(DBT)were synthesized by Suzuki reaction and end-capped by N-hexyl-carbazole and benzene,which were abbreviated as PDOF-DBT-Cz and PDOF-DBT-B,respectively.The photophysical,electrochemical and thermal properties of the copolymers were studied.The results indicated that replacement of N-hexyl-carbazole as end-capping group of PDOF-DBT can vary light color and improve luminescence efficiency.
