Nano-sized aluminum(Nano-Al)powders hold promise in enhancing the total energy of explosives and the metal acceleration ability at the same time.However,the near-detonation zone effects of reaction between Nano-Al wit...Nano-sized aluminum(Nano-Al)powders hold promise in enhancing the total energy of explosives and the metal acceleration ability at the same time.However,the near-detonation zone effects of reaction between Nano-Al with detonation products remain unclear.In this study,the overall reaction process of 170 nm Al with RDX explosive and its effect on detonation characteristics,detonation reaction zone,and the metal acceleration ability were comprehensively investigated through a variety of experiments such as the detonation velocity test,detonation pressure test,explosive/window interface velocity test and confined plate push test using high-resolution laser interferometry.Lithium fluoride(LiF),which has an inert behavior during the explosion,was used as a control to compare the contribution of the reaction of aluminum.A thermochemical approach that took into account the reactivity of aluminum and ensuing detonation products was adopted to calculate the additional energy release by afterburn.Combining the numerical simulations based on the calculated afterburn energy and experimental results,the parameters in the detonation equation of state describing the Nano-Al reaction characteristics were calibrated.This study found that when the 170 nm Al content is from 0%to 15%,every 5%increase of aluminum resulted in about a 1.3%decrease in detonation velocity.Manganin pressure gauge measurement showed no significant enhancement in detonation pressure.The detonation reaction time and reaction zone length of RDX/Al/wax/80/15/5 explosive is 64 ns and 0.47 mm,which is respectively 14%and 8%higher than that of RDX/wax/95/5 explosive(57 ns and 0.39 mm).Explosive/window interface velocity curves show that 170 nm Al mainly reacted with the RDX detonation products after the detonation front.For the recording time of about 10 ms throughout the plate push test duration,the maximum plate velocity and plate acceleration time accelerated by RDX/Al/wax/80/15/5 explosive is 12%and 2.9 ms higher than that of RDX/LiF/wax/80/15/5,respectively,indicating that the aluminum reaction energy significantly increased the metal acceleration time and ability of the explosive.Numerical simulations with JWLM explosive equation of state show that when the detonation products expanded to 2 times the initial volume,over 80%of the aluminum had reacted,implying very high reactivity.These results are significant in attaining a clear understanding of the reaction mechanism of Nano-Al in the development of aluminized explosives.展开更多
A deep understanding of explosive sensitivities and their factors is important for safe and reliable applications.However,quantitative prediction of the sensitivities is difficult.Here,reactive molecular dynamics simu...A deep understanding of explosive sensitivities and their factors is important for safe and reliable applications.However,quantitative prediction of the sensitivities is difficult.Here,reactive molecular dynamics simulation models for high-speed piston impacts on explosive supercells were established.Simulations were also performed to investigate shock-induced reactions of various high-energy explosives.The fraction of reacted explosive molecules in an initial supercell changed linearly with the propagation distance of the shock-wave front.The corresponding slope could be used as a reaction rate for a specific shock-loading velocity.Reaction rates that varied with the shock-loading pressure exhibited two-stage linearities with different slopes.The two inflection points corresponded to the initial and accelerated reactions,which respectively correlated to the thresholds of shock-induced ignition and detonation.Therefore,the ignition and detonation critical pressures could be determined.The sensitivity could then be a quantitative prediction of the critical pressure.The accuracies of the quantitative shock sensitivity predictions were verified by comparing the impact and shock sensitivities of common explosives and the characteristics of anisotropic shock-induced reactions.Molecular dynamics simulations quantitatively predict and rank shock sensitivities by using only crystal structures of the explosives.Overall,this method will enable the design and safe use of explosives.展开更多
BACKGROUND Small intestine disease endangers human health and is not easy to locate and diagnose.AIM To observe the effect of the MS series of small intestine endoscopes on the gastrointestinal tract,the changes in se...BACKGROUND Small intestine disease endangers human health and is not easy to locate and diagnose.AIM To observe the effect of the MS series of small intestine endoscopes on the gastrointestinal tract,the changes in serum gastrin levels and intestinal tissue,and the time required for the examination.METHODS In vivo experiments in 20 Living pigs were conducted,Bowel preparation was routinely performed,Intravenous anesthesia with propofol and ketamine was applied,the condition of the small intestine was observed and the detection time of the MS series of small intestine endoscopes were recorded,The changes in intestinal tissue using the MS series of small intestine endoscopes observed and compared before and after the examination,Venous blood(3-5 mL)from pigs was collected before and after the experiment;changes in intestinal tissue after use of the MS series of small intestine endoscopes observed after examination.After completion of each type of small intestine endoscope experiment,the pigs were allowed to rest and the next type of small intestine endoscope experiment was performed after 15 days of normal feeding.The detection time data of the single-balloon small intestine endoscope and doubleballoon small intestine endoscope were collected from four hospitals.RESULTS One case of Ascarislumbricoides,one of suspected Crohn’s disease,one small intestinal diverticulum and one anesthesia accident were observed in pigs.The small intestine showed no differences in the MS series of small intestine endoscopes and there were no differences in serum gastrin between the groups(P>0.05).The time required for inspection was recorded,and the overall detection time for the Japanese small intestine endoscopes was approximately 1.68±0.16 h.CONCLUSION Intestinal ascariasis is a common disease in pigs.Some pigs have abnormal intestinal variation.After continuous upgrade and improvement,the MS-3 and MS-4 small intestine endoscope appear superior in terms of detection time.展开更多
Impact flash occurs when objects collide at supersonic speeds and can be used for real-time damage assessment when weapons rely on kinetic energy to destroy targets.However,the mechanism of impact flash remains unclea...Impact flash occurs when objects collide at supersonic speeds and can be used for real-time damage assessment when weapons rely on kinetic energy to destroy targets.However,the mechanism of impact flash remains unclear.A series of impact flash experiments of flat-head long-rod projectiles impacting thin target plates were performed with a two-stage light gas gun.The impact flash spectra for 6061 aluminum at 1.3e3.2 km/s collision speeds were recorded with a high-speed camera,a photoelectric sensor,and a time-resolved spectrometer.The intensity of the impact flash exhibited a pulse characteristic with time.The intensity(I)increased with impact velocity(V0)according to IfVn 0,where n?4.41 for V0>2 km/s.However,for V0<2 km/s,n?2.21,and the intense flash duration is an order of magnitude less than that of higher V0.When V0>2 km/s,a continuous spectrum(thermal radiation background)was observed and increased in intensity with V0.However,for V0<2 km/s,only atomic line spectra were detected.There was no aluminum spectral lines for V0<2 km/s,which indicated that it had not been vaporized.The initial intense flash was emission from excited and ionized ambient gases near the impact surface,and had little relationship with shock temperature rise,indicating a new mechanism of impact flash.展开更多
AIM To assess the feasibility and safety of a novel enteroscope,negative-pressure suction endoscope in examining the small intestine of a porcine model.METHODS In vitro experiments in small intestinal loops from 20pig...AIM To assess the feasibility and safety of a novel enteroscope,negative-pressure suction endoscope in examining the small intestine of a porcine model.METHODS In vitro experiments in small intestinal loops from 20pigs and in vivo experiments in 20 living pigs were conducted.RESULTS In in vitro experiments,a negative pressure of>0.06MPa was necessary for optimal visualization of the intestine,and this pressure did not cause gross or histological damage to the mucosa.For satisfactory examination of the small intestine in vivo,higher negative pressure(>1.00 MPa)was required.Despite this higher pressure,the small intestine did not show any gross or microscopic damage in the suctioned areas.The average time of examination in the living animals was 60±7.67 min.The animals did not experience any apparent ill effects from the procedure.CONCLUSION Small intestine endoscope was safely performed within a reasonable time period and enabled complete visualization of the intestine in most cases.展开更多
The influence of pre-deformation on aging precipitates of three near peak-aged Al–Cu–Li alloys,1460 alloy with a low Cu/Li ratio（1.46）,2050 alloy with a high Cu/Li ratio（4.51） and 2A96 alloy with a medium Cu/Li ...The influence of pre-deformation on aging precipitates of three near peak-aged Al–Cu–Li alloys,1460 alloy with a low Cu/Li ratio（1.46）,2050 alloy with a high Cu/Li ratio（4.51） and 2A96 alloy with a medium Cu/Li ratio（2.97）,was investigated.The strength of the aged alloys is enhanced by the pre-deformation.The effectiveness of pre-deformation on precipitates is dependent on the alloy＇s composition.With increasing the pre-deformation,the population density of T1（Al2Cu Li） precipitates increases in all three Al–Cu–Li alloys and their diameter decreases in 2050 and 2A96 alloys,and the greatest effectiveness is observed in 2A96 alloy.The pre-deformation also increases the population density of θ＇（Al2Cu）precipitates and decreases their diameter in 2050 and 2A96 Al–Li alloys,but the effectiveness is smaller compared to that on T1 precipitates.In 1460 alloy subjected to two-step aging at 130 ℃ for 20 h followed by 160 ℃ for 12 h,the main precipitates are δ＇（Al3Li）.At 2%–6% pre-deformation,GP-I zones form and pre-deformation displays little influence.Eight percentage pre-deformation promotes θ＇＇/θ＇ precipitation and increases their population density.展开更多
The microstructure evolution and the corrosion feature of Al–x Cu– y Li–Mg alloys( x : y = 0.44, 1.65 and 4.2) were systematically investigated under the same artificial aging conditions. The relationships between ...The microstructure evolution and the corrosion feature of Al–x Cu– y Li–Mg alloys( x : y = 0.44, 1.65 and 4.2) were systematically investigated under the same artificial aging conditions. The relationships between types of precipitates and mechanical performance, as well as electrochemical behaviors, were discussed. Our results show that different types of precipitates can be obtained in alloys with different Cu/Li mass ratios, which significantly influences the mechanical performance of the alloys and substantial corrosion behaviors. Specifically, the analogous corrosion evolution in the aging Al– x Cu– y Li–Mg alloys was first ascertained to be derived from the growth mechanism of the precipitates at the grain boundary(GB). Moreover, a small number of GB precipitates can be obtained in the aged alloy with the lowest Cu/Li mass ratio, thereby resulting in the largest intergranular corrosion resistance. A higher proportion of the GB T1 phase in the continuous precipitates induces higher corrosion sensitivity in alloy with a high Cu/Li mass ratio.展开更多
基金The authors would like to acknowledge National Natural Science Foundation of China(Grant No.11832006)Open Project of State Key Laboratory of Explosion Science and Technology in Beijing Institute of Technology(Grant No.KFJJ20-04 M)to provide fund for conducting experiments.
文摘Nano-sized aluminum(Nano-Al)powders hold promise in enhancing the total energy of explosives and the metal acceleration ability at the same time.However,the near-detonation zone effects of reaction between Nano-Al with detonation products remain unclear.In this study,the overall reaction process of 170 nm Al with RDX explosive and its effect on detonation characteristics,detonation reaction zone,and the metal acceleration ability were comprehensively investigated through a variety of experiments such as the detonation velocity test,detonation pressure test,explosive/window interface velocity test and confined plate push test using high-resolution laser interferometry.Lithium fluoride(LiF),which has an inert behavior during the explosion,was used as a control to compare the contribution of the reaction of aluminum.A thermochemical approach that took into account the reactivity of aluminum and ensuing detonation products was adopted to calculate the additional energy release by afterburn.Combining the numerical simulations based on the calculated afterburn energy and experimental results,the parameters in the detonation equation of state describing the Nano-Al reaction characteristics were calibrated.This study found that when the 170 nm Al content is from 0%to 15%,every 5%increase of aluminum resulted in about a 1.3%decrease in detonation velocity.Manganin pressure gauge measurement showed no significant enhancement in detonation pressure.The detonation reaction time and reaction zone length of RDX/Al/wax/80/15/5 explosive is 64 ns and 0.47 mm,which is respectively 14%and 8%higher than that of RDX/wax/95/5 explosive(57 ns and 0.39 mm).Explosive/window interface velocity curves show that 170 nm Al mainly reacted with the RDX detonation products after the detonation front.For the recording time of about 10 ms throughout the plate push test duration,the maximum plate velocity and plate acceleration time accelerated by RDX/Al/wax/80/15/5 explosive is 12%and 2.9 ms higher than that of RDX/LiF/wax/80/15/5,respectively,indicating that the aluminum reaction energy significantly increased the metal acceleration time and ability of the explosive.Numerical simulations with JWLM explosive equation of state show that when the detonation products expanded to 2 times the initial volume,over 80%of the aluminum had reacted,implying very high reactivity.These results are significant in attaining a clear understanding of the reaction mechanism of Nano-Al in the development of aluminized explosives.
基金supported by the National Natural Science Foundation of China(Grant No.11832006).
文摘A deep understanding of explosive sensitivities and their factors is important for safe and reliable applications.However,quantitative prediction of the sensitivities is difficult.Here,reactive molecular dynamics simulation models for high-speed piston impacts on explosive supercells were established.Simulations were also performed to investigate shock-induced reactions of various high-energy explosives.The fraction of reacted explosive molecules in an initial supercell changed linearly with the propagation distance of the shock-wave front.The corresponding slope could be used as a reaction rate for a specific shock-loading velocity.Reaction rates that varied with the shock-loading pressure exhibited two-stage linearities with different slopes.The two inflection points corresponded to the initial and accelerated reactions,which respectively correlated to the thresholds of shock-induced ignition and detonation.Therefore,the ignition and detonation critical pressures could be determined.The sensitivity could then be a quantitative prediction of the critical pressure.The accuracies of the quantitative shock sensitivity predictions were verified by comparing the impact and shock sensitivities of common explosives and the characteristics of anisotropic shock-induced reactions.Molecular dynamics simulations quantitatively predict and rank shock sensitivities by using only crystal structures of the explosives.Overall,this method will enable the design and safe use of explosives.
基金Supported by the 2020 Liaoning Provincial Natural Science Foundation General Project,No.2020-MS-332。
文摘BACKGROUND Small intestine disease endangers human health and is not easy to locate and diagnose.AIM To observe the effect of the MS series of small intestine endoscopes on the gastrointestinal tract,the changes in serum gastrin levels and intestinal tissue,and the time required for the examination.METHODS In vivo experiments in 20 Living pigs were conducted,Bowel preparation was routinely performed,Intravenous anesthesia with propofol and ketamine was applied,the condition of the small intestine was observed and the detection time of the MS series of small intestine endoscopes were recorded,The changes in intestinal tissue using the MS series of small intestine endoscopes observed and compared before and after the examination,Venous blood(3-5 mL)from pigs was collected before and after the experiment;changes in intestinal tissue after use of the MS series of small intestine endoscopes observed after examination.After completion of each type of small intestine endoscope experiment,the pigs were allowed to rest and the next type of small intestine endoscope experiment was performed after 15 days of normal feeding.The detection time data of the single-balloon small intestine endoscope and doubleballoon small intestine endoscope were collected from four hospitals.RESULTS One case of Ascarislumbricoides,one of suspected Crohn’s disease,one small intestinal diverticulum and one anesthesia accident were observed in pigs.The small intestine showed no differences in the MS series of small intestine endoscopes and there were no differences in serum gastrin between the groups(P>0.05).The time required for inspection was recorded,and the overall detection time for the Japanese small intestine endoscopes was approximately 1.68±0.16 h.CONCLUSION Intestinal ascariasis is a common disease in pigs.Some pigs have abnormal intestinal variation.After continuous upgrade and improvement,the MS-3 and MS-4 small intestine endoscope appear superior in terms of detection time.
基金This work was supported by the National Key R&D Programof China(Grant No.2016YFC0801204)the National Programon Key Basic Research Project of China(973 Program,Grant No.613312).
文摘Impact flash occurs when objects collide at supersonic speeds and can be used for real-time damage assessment when weapons rely on kinetic energy to destroy targets.However,the mechanism of impact flash remains unclear.A series of impact flash experiments of flat-head long-rod projectiles impacting thin target plates were performed with a two-stage light gas gun.The impact flash spectra for 6061 aluminum at 1.3e3.2 km/s collision speeds were recorded with a high-speed camera,a photoelectric sensor,and a time-resolved spectrometer.The intensity of the impact flash exhibited a pulse characteristic with time.The intensity(I)increased with impact velocity(V0)according to IfVn 0,where n?4.41 for V0>2 km/s.However,for V0<2 km/s,n?2.21,and the intense flash duration is an order of magnitude less than that of higher V0.When V0>2 km/s,a continuous spectrum(thermal radiation background)was observed and increased in intensity with V0.However,for V0<2 km/s,only atomic line spectra were detected.There was no aluminum spectral lines for V0<2 km/s,which indicated that it had not been vaporized.The initial intense flash was emission from excited and ionized ambient gases near the impact surface,and had little relationship with shock temperature rise,indicating a new mechanism of impact flash.
文摘AIM To assess the feasibility and safety of a novel enteroscope,negative-pressure suction endoscope in examining the small intestine of a porcine model.METHODS In vitro experiments in small intestinal loops from 20pigs and in vivo experiments in 20 living pigs were conducted.RESULTS In in vitro experiments,a negative pressure of>0.06MPa was necessary for optimal visualization of the intestine,and this pressure did not cause gross or histological damage to the mucosa.For satisfactory examination of the small intestine in vivo,higher negative pressure(>1.00 MPa)was required.Despite this higher pressure,the small intestine did not show any gross or microscopic damage in the suctioned areas.The average time of examination in the living animals was 60±7.67 min.The animals did not experience any apparent ill effects from the procedure.CONCLUSION Small intestine endoscope was safely performed within a reasonable time period and enabled complete visualization of the intestine in most cases.
基金the National High Technology Research and Development Program of China(No.2013AA032401)Teacher’s Research Foundation of Central South University(No.2013JSJJ 001) for the financial supportNonferrous Metal Oriented Advanced Structural Materials and Manufacturing Cooperative Innovation Centre
文摘The influence of pre-deformation on aging precipitates of three near peak-aged Al–Cu–Li alloys,1460 alloy with a low Cu/Li ratio（1.46）,2050 alloy with a high Cu/Li ratio（4.51） and 2A96 alloy with a medium Cu/Li ratio（2.97）,was investigated.The strength of the aged alloys is enhanced by the pre-deformation.The effectiveness of pre-deformation on precipitates is dependent on the alloy＇s composition.With increasing the pre-deformation,the population density of T1（Al2Cu Li） precipitates increases in all three Al–Cu–Li alloys and their diameter decreases in 2050 and 2A96 alloys,and the greatest effectiveness is observed in 2A96 alloy.The pre-deformation also increases the population density of θ＇（Al2Cu）precipitates and decreases their diameter in 2050 and 2A96 Al–Li alloys,but the effectiveness is smaller compared to that on T1 precipitates.In 1460 alloy subjected to two-step aging at 130 ℃ for 20 h followed by 160 ℃ for 12 h,the main precipitates are δ＇（Al3Li）.At 2%–6% pre-deformation,GP-I zones form and pre-deformation displays little influence.Eight percentage pre-deformation promotes θ＇＇/θ＇ precipitation and increases their population density.
基金Postdoctoral Research Station of Mechanical Engineering of school of Mechanical and Electrical Engineering of Central South Universityfinancially supported by the National Foundation of China(No.TDZX-17-005-1)。
文摘The microstructure evolution and the corrosion feature of Al–x Cu– y Li–Mg alloys( x : y = 0.44, 1.65 and 4.2) were systematically investigated under the same artificial aging conditions. The relationships between types of precipitates and mechanical performance, as well as electrochemical behaviors, were discussed. Our results show that different types of precipitates can be obtained in alloys with different Cu/Li mass ratios, which significantly influences the mechanical performance of the alloys and substantial corrosion behaviors. Specifically, the analogous corrosion evolution in the aging Al– x Cu– y Li–Mg alloys was first ascertained to be derived from the growth mechanism of the precipitates at the grain boundary(GB). Moreover, a small number of GB precipitates can be obtained in the aged alloy with the lowest Cu/Li mass ratio, thereby resulting in the largest intergranular corrosion resistance. A higher proportion of the GB T1 phase in the continuous precipitates induces higher corrosion sensitivity in alloy with a high Cu/Li mass ratio.
