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
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
This study investigated the effects of torrefaction on forest residue(FR)and its subsequent ap-plication as a bulk-loading filler in polylactic acid(PLA)composites.Torrefaction enhanced the chemical properties of FR,i...This study investigated the effects of torrefaction on forest residue(FR)and its subsequent ap-plication as a bulk-loading filler in polylactic acid(PLA)composites.Torrefaction enhanced the chemical properties of FR,improving its compatibility with PLA,and the crystallinity increased from 24.9%to 42.5%.The process also improved the hydrophobicity of PLA/biomass composites,as demonstrated by the water contact angle of 76.1°,closely matching that of neat PLA(76.4°).With the introduction of 20%modified biomass properties after torrefaction treatment,the tensile strength of PLA/biomass composite increased from 58.7 to 62.3 MPa.Additionally,the addition of torrefied forest residue(TFR)accelerated biodegradation by increasing the onset of degrada-tion and inhibiting crystallization.After 90 d,the biodegradability of PLA/biomass composites reached 94.9%,which had a 6.9%increase compared to the neat PLA(88.8%).Overall,this study highlights the potential of torrefaction in enhancing both the physical properties and biodegrad-ability of PLA-based composites,contributing to a more sustainable approach to reducing plastic pollution.展开更多
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.
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 Korea Research Institute of Chemical Technology(KRICT)Project(No.KS2442-10)the R&D Program(No.20017973)of the Ministry of Trade,Industry,and Energy(MOTIE/KEIT).
文摘This study investigated the effects of torrefaction on forest residue(FR)and its subsequent ap-plication as a bulk-loading filler in polylactic acid(PLA)composites.Torrefaction enhanced the chemical properties of FR,improving its compatibility with PLA,and the crystallinity increased from 24.9%to 42.5%.The process also improved the hydrophobicity of PLA/biomass composites,as demonstrated by the water contact angle of 76.1°,closely matching that of neat PLA(76.4°).With the introduction of 20%modified biomass properties after torrefaction treatment,the tensile strength of PLA/biomass composite increased from 58.7 to 62.3 MPa.Additionally,the addition of torrefied forest residue(TFR)accelerated biodegradation by increasing the onset of degrada-tion and inhibiting crystallization.After 90 d,the biodegradability of PLA/biomass composites reached 94.9%,which had a 6.9%increase compared to the neat PLA(88.8%).Overall,this study highlights the potential of torrefaction in enhancing both the physical properties and biodegrad-ability of PLA-based composites,contributing to a more sustainable approach to reducing plastic pollution.
