The restriction of KB averaging method is discussed and asymptotic solution of the weakly nonlinear and forced oscillation u″+ω20u=εkcos ωt-εu3 is obtained by Struble technique. The conclusion about this oscillat...The restriction of KB averaging method is discussed and asymptotic solution of the weakly nonlinear and forced oscillation u″+ω20u=εkcos ωt-εu3 is obtained by Struble technique. The conclusion about this oscillation derived with other method is discussed. The results show that KB method will break down when a and θ in the zeroth solution of above eqation are not slowly varying functions of time t. The stationary solution of weakly nonlinear oscillation, u″+ω20u=εkcosω(ε)t-εu3 is also analysed.展开更多
Inspired by the phenomenon of superhydrophobic plants and animals in nature,1,3,5,7-tetranitro-1,3,5,7-tetrazocane(HMX)@copper stearate(CS)core-shell composites with similar properties was prepared.A rough shell layer...Inspired by the phenomenon of superhydrophobic plants and animals in nature,1,3,5,7-tetranitro-1,3,5,7-tetrazocane(HMX)@copper stearate(CS)core-shell composites with similar properties was prepared.A rough shell layer on the surface of the HMX was observed by scanning electron microscopy(SEM),and a series of in-depth characterization confirmed the successful generation of CS and the coreshell structure of the samples.Differential scanning calorimeter(DSC)proves that the crystal transition temperature(204℃)and high temperature decomposition exothermal temperature(284℃)of HMX@CS is almost unchanged compared with pure HMX,which means HMX and CS have good compatibility.Then,the H50 of the samples also increased continuously(16.6 cm→33.7 cm)when the CS shell content increased from 1%to 5%,indicating that the CS shell has a certain buffering performance,and CS will absorb some heat and melt under the stimulation of impact due to its low melting point,which improved impact sensitivity of HMX effectively further.Moreover,HMX@CS has excellent hydrophobic and oleophilic performance,shows excellent wettability with lipid binder,and samples with appropriate CS shell content can continue to combustion stably after covering water.This waterproof and low sensitivity coating provides a new way for the development of multifunctional energetic materials.展开更多
To explore the response law of non-lethal large-size kinetic energy projectiles to blunt attack on skin tissue,and to evaluate the skin injury characteristics of the attacked personnel and the use safety of kinetic en...To explore the response law of non-lethal large-size kinetic energy projectiles to blunt attack on skin tissue,and to evaluate the skin injury characteristics of the attacked personnel and the use safety of kinetic energy projectiles.Based on the LS-DYNA simulation software,a three-layer skin simulation model and a Flash-Ball rubber bullet model are established,and the force-time and deformation-time biomechanical corridors of the Flash-Ball rubber bullet impacting human skin tissue are obtained.The corridor curve and the energy transfer and diffusion are analyzed and compared.The safety evaluation of the damage caused by the rubber bullet shooting a human body at different distances is carried out using the empirical formula of the penetration limit.Finally,the safe shooting distance is obtained.The results show that the model used in the simulation has a good correlation with the experimental data,its biomechanical corridor characteristics are different from those of conventional vehicle impact and smallsize projectile response characteristics.The energy transfer and action time of medium and low-speed impact may cause greater damage.The fat layer is the largest energy absorption unit.The minimum safe shooting distance to ensure skin tissue from penetrating damage is 15.8 m,and the limit specific kinetic energy of skin damage is 7.88 J/cm^(2).This study can be extended to the study of biomechanical response law and safety evaluation under the impact of the same type of large kinetic energy projectile,which provides an important theoretical reference for the police to use large kinetic energy projectiles to conduct safe shooting in peacekeeping operations.展开更多
The aim was to examine the biotransformation of chemical compounds during the fermentation of litchi wine.S.bccyanus BV818 was inoculated to litchi juice(Heiye)to initiate the fermentation.Acetic acid decreased dramat...The aim was to examine the biotransformation of chemical compounds during the fermentation of litchi wine.S.bccyanus BV818 was inoculated to litchi juice(Heiye)to initiate the fermentation.Acetic acid decreased dramatically,succinic acid and DL-malic acid increased sharply.Saturated free fatty acid increased,especially the concentration of the free fatty acid with long carbon chain(more than 10 carbons)increased significantly.The unique flavor compounds of fresh litchi including linalool,α-terpineol,β-citronellol and other terpenoids remained in the litchi wine were transformed to other aroma constituents,by which the primary litchi flavor was retained.The wine had a fruity flavor and delicate bouquet and had harmonious sourness and sweetness.The litchi'Heiye'was suitable for being fermented into litchi wine.展开更多
文摘The restriction of KB averaging method is discussed and asymptotic solution of the weakly nonlinear and forced oscillation u″+ω20u=εkcos ωt-εu3 is obtained by Struble technique. The conclusion about this oscillation derived with other method is discussed. The results show that KB method will break down when a and θ in the zeroth solution of above eqation are not slowly varying functions of time t. The stationary solution of weakly nonlinear oscillation, u″+ω20u=εkcosω(ε)t-εu3 is also analysed.
基金financially supported by the National Natural Science Foundation of China (Grant NO.11702268)Sichuan provincial key S&T Special Projects (Grant NO.19DZX0106)
文摘Inspired by the phenomenon of superhydrophobic plants and animals in nature,1,3,5,7-tetranitro-1,3,5,7-tetrazocane(HMX)@copper stearate(CS)core-shell composites with similar properties was prepared.A rough shell layer on the surface of the HMX was observed by scanning electron microscopy(SEM),and a series of in-depth characterization confirmed the successful generation of CS and the coreshell structure of the samples.Differential scanning calorimeter(DSC)proves that the crystal transition temperature(204℃)and high temperature decomposition exothermal temperature(284℃)of HMX@CS is almost unchanged compared with pure HMX,which means HMX and CS have good compatibility.Then,the H50 of the samples also increased continuously(16.6 cm→33.7 cm)when the CS shell content increased from 1%to 5%,indicating that the CS shell has a certain buffering performance,and CS will absorb some heat and melt under the stimulation of impact due to its low melting point,which improved impact sensitivity of HMX effectively further.Moreover,HMX@CS has excellent hydrophobic and oleophilic performance,shows excellent wettability with lipid binder,and samples with appropriate CS shell content can continue to combustion stably after covering water.This waterproof and low sensitivity coating provides a new way for the development of multifunctional energetic materials.
文摘To explore the response law of non-lethal large-size kinetic energy projectiles to blunt attack on skin tissue,and to evaluate the skin injury characteristics of the attacked personnel and the use safety of kinetic energy projectiles.Based on the LS-DYNA simulation software,a three-layer skin simulation model and a Flash-Ball rubber bullet model are established,and the force-time and deformation-time biomechanical corridors of the Flash-Ball rubber bullet impacting human skin tissue are obtained.The corridor curve and the energy transfer and diffusion are analyzed and compared.The safety evaluation of the damage caused by the rubber bullet shooting a human body at different distances is carried out using the empirical formula of the penetration limit.Finally,the safe shooting distance is obtained.The results show that the model used in the simulation has a good correlation with the experimental data,its biomechanical corridor characteristics are different from those of conventional vehicle impact and smallsize projectile response characteristics.The energy transfer and action time of medium and low-speed impact may cause greater damage.The fat layer is the largest energy absorption unit.The minimum safe shooting distance to ensure skin tissue from penetrating damage is 15.8 m,and the limit specific kinetic energy of skin damage is 7.88 J/cm^(2).This study can be extended to the study of biomechanical response law and safety evaluation under the impact of the same type of large kinetic energy projectile,which provides an important theoretical reference for the police to use large kinetic energy projectiles to conduct safe shooting in peacekeeping operations.
基金Supported by the Talent Introduction Project of Guangdong University of Petrochemical Technology(513036)the Innovation Project of the High Education Institutions of Guangdong Province(650465)。
文摘The aim was to examine the biotransformation of chemical compounds during the fermentation of litchi wine.S.bccyanus BV818 was inoculated to litchi juice(Heiye)to initiate the fermentation.Acetic acid decreased dramatically,succinic acid and DL-malic acid increased sharply.Saturated free fatty acid increased,especially the concentration of the free fatty acid with long carbon chain(more than 10 carbons)increased significantly.The unique flavor compounds of fresh litchi including linalool,α-terpineol,β-citronellol and other terpenoids remained in the litchi wine were transformed to other aroma constituents,by which the primary litchi flavor was retained.The wine had a fruity flavor and delicate bouquet and had harmonious sourness and sweetness.The litchi'Heiye'was suitable for being fermented into litchi wine.
