To investigate the controlling method of interior ballistic stability of bulk-loaded propellant guns,the combustion-gas generator and cylindrical stepped-wall chamber are designed aiming at the injection processes of ...To investigate the controlling method of interior ballistic stability of bulk-loaded propellant guns,the combustion-gas generator and cylindrical stepped-wall chamber are designed aiming at the injection processes of combustion-gases in liquid.The expansion courses of Taylor cavities and the turbulent mixing characteristic of gaseliquid are recorded by means of high speed photographic system.Based on the experiment,three-dimensional unsteady model on the interaction of gas and liquid is established to simulate expansion characteristics of twin combustion-gas jets in liquid under different nozzle diameters.The distribution regularities of characteristic parameter in jet field are obtained and analyzed.The results show the pressure,velocity and temperature distributions under different nozzle diameters are basically the same at the initial time.As time goes on,these characteristic parameters under different nozzle diameters have large differences.展开更多
Current literature on parallel bulk-loading of R-tree index has the disadvantage that the quality of produced spatial index decrease considerably as the parallelism increases. To solve this problem, a novel method of ...Current literature on parallel bulk-loading of R-tree index has the disadvantage that the quality of produced spatial index decrease considerably as the parallelism increases. To solve this problem, a novel method of bulk-loading spatial data using the popular MapReduce framework is proposed. MapReduce combines Hilbert curve and random sampling method to parallel partition and sort spatial data, thus it balances the number of spatial data in each partition. Then the bottom-up method is introduced to simplify and accelerate the sub-index construction in each parti- tion. Three area metrics are used to test the quality of generated index under different partitions. The extensive experiments show that the generated R-trees have the similar quality with the gener- ated R-tree using sequential bulk-loading method, while the execution time is reduced considerably by exploiting parallelism.展开更多
基金supported by National Nature Science Foundation of China (No. 51506096)Foundation Research Project of Jiangsu Province (The Natural Science Fund No. BK20150765)
文摘To investigate the controlling method of interior ballistic stability of bulk-loaded propellant guns,the combustion-gas generator and cylindrical stepped-wall chamber are designed aiming at the injection processes of combustion-gases in liquid.The expansion courses of Taylor cavities and the turbulent mixing characteristic of gaseliquid are recorded by means of high speed photographic system.Based on the experiment,three-dimensional unsteady model on the interaction of gas and liquid is established to simulate expansion characteristics of twin combustion-gas jets in liquid under different nozzle diameters.The distribution regularities of characteristic parameter in jet field are obtained and analyzed.The results show the pressure,velocity and temperature distributions under different nozzle diameters are basically the same at the initial time.As time goes on,these characteristic parameters under different nozzle diameters have large differences.
基金Supported by the National High Technology Research and Development Program of China (863 Program) (2011AA12A306)the National Natural Science Foundation of China (40801160,60902036)
文摘Current literature on parallel bulk-loading of R-tree index has the disadvantage that the quality of produced spatial index decrease considerably as the parallelism increases. To solve this problem, a novel method of bulk-loading spatial data using the popular MapReduce framework is proposed. MapReduce combines Hilbert curve and random sampling method to parallel partition and sort spatial data, thus it balances the number of spatial data in each partition. Then the bottom-up method is introduced to simplify and accelerate the sub-index construction in each parti- tion. Three area metrics are used to test the quality of generated index under different partitions. The extensive experiments show that the generated R-trees have the similar quality with the gener- ated R-tree using sequential bulk-loading method, while the execution time is reduced considerably by exploiting parallelism.
