The inlet deflector rollers of a recoiling line are sprayed rollers. Short scratch lines have been found on the surface of steel sheets during commissioning. By adjusting the control parameters of the line and investi...The inlet deflector rollers of a recoiling line are sprayed rollers. Short scratch lines have been found on the surface of steel sheets during commissioning. By adjusting the control parameters of the line and investigating the manufacturing process of inlet deflector rollers, the root cause of the scratches was found. By modifying the manufacturing process of the rollers, the scratches have been thoroughly eliminated, and quality steel sheets have been consistently produced in the recoiling line.展开更多
The decay of 20Na of astrophysical reactions has been studied deeply via 20Ne(p, n)20Na reaction. A new β-delayed α decay with α energy of 5 896 ± 6 keV and relative intensity of 0. 002 4 ± 0. 000 3 was d...The decay of 20Na of astrophysical reactions has been studied deeply via 20Ne(p, n)20Na reaction. A new β-delayed α decay with α energy of 5 896 ± 6 keV and relative intensity of 0. 002 4 ± 0. 000 3 was discovered. At the same time the 16O recoiling in β+-delayed α decay of 20Na was observed in experiment for the first time. From these, it is inferred that a β-delayed low energy α decay of 20Na with energy of-780 keV and relative intensity of -1.4 was mixed in 16O recoiling. In 16O recoiling and the low energy α decay, the energy loss for low energy charged particles through matter was discussed in detail. At last, two methods for discriminating the β-delayed low energy α decay of 20Na were proposed.展开更多
It is widely recognized by many within the scientific community that the field of seismology faces challenges in aligning with established scientific practices for studying earthquakes. Some views may suggest a relian...It is widely recognized by many within the scientific community that the field of seismology faces challenges in aligning with established scientific practices for studying earthquakes. Some views may suggest a reliance on methods that resemble divination rather than sound scientific inquiry. Despite efforts to understand seismic phenomena over the past three centuries [1], progress in seismology has been perceived as somewhat stagnant. Criticisms have been raised about certain theories, such as Mr. Reid’s Elastic Recoil theory from 1910 [2], and its purported advancements in comprehending seismic processes. While acknowledging various perspectives on this matter [3]-[7], it is important to reflect on the historical context and potential limitations in our understanding. Addressing concerns raised within the discipline involves examining educational practices and fostering a rigorous academic environment to promote scientific excellence. This article aims to explore the underlying factors contributing to the current state of seismology, offering insights into overcoming challenges and fostering advancements that benefit the scientific community and society as a whole.展开更多
State-selective single-and double-electron capture processes in collisions of S^(5+)ions with helium at energies ranging from 50.8 keV to 100 keV were investigated using cold target recoil ion momentum spectroscopy(CO...State-selective single-and double-electron capture processes in collisions of S^(5+)ions with helium at energies ranging from 50.8 keV to 100 keV were investigated using cold target recoil ion momentum spectroscopy(COLTRIMS).Q-value spectra and projectile scattering angle distributions were obtained.For single-electron capture,single electron capture into n=3 states of the projectile ion is dominant.As the projectile energy increases,the contribution of single electron capture into n=4 states is observed.Experimental relative cross-sections for single-electron capture into different projectile final states were compared with theoretical predictions based on the molecular orbital close-coupling(MOCC)method.In double-electron capture,two-electron populating into the 3s^(2)3p and 3s3p^(2)states of projectile dominates.The reaction window calculated from the classical molecular Coulombic barrier model can qualitatively explain the experimental results.The scattering angle distribution of the multi-peak structure of the double-electron capture process is observed.The database is openly available in Science Data Bank at https://doi.org/10.57760/sciencedb.j00113.00233.展开更多
We study the fragmentation of NO^(q+)(q=2,3)molecular ions produced by collisions between 96 keV O^(6+)ions and neutral nitric oxide(NO)molecules,using the cold target recoil ion momentum spectrometer(COLTRIMS).The ki...We study the fragmentation of NO^(q+)(q=2,3)molecular ions produced by collisions between 96 keV O^(6+)ions and neutral nitric oxide(NO)molecules,using the cold target recoil ion momentum spectrometer(COLTRIMS).The kinetic energy release(KER)for various dissociation channels is obtained.For the channel NO^(2+)→N^(+)+O^(+),double-electron capture followed by autoionization of the projectile ions is the dominant process,which can be explained by the recapture of loosely bound electrons into highly excited states of the target.For NO3+trication,two dissociation channels,i.e.,(a)N^(+)+O^(2+)and(b)N^(2+)+O^(+),are observed,where channel(b)is the dominant channel.Moreover,for dissociation channels originating from the same parent molecular ion,the dissociation channel with a higher charge for the oxygen ion fragment exhibits a higher most probable KER,which is consistent with studies of CO fragmentation by Rajput et al.Additionally,it is observed that as capture stability increases,the average KER shifts to higher values.展开更多
One of the greatest challenges in the design of a gun is to balance muzzle velocity and recoil,especially for guns on aircrafts and deployable vehicles.To resolve the conflict between gun power and recoil force,a conc...One of the greatest challenges in the design of a gun is to balance muzzle velocity and recoil,especially for guns on aircrafts and deployable vehicles.To resolve the conflict between gun power and recoil force,a concept of rarefaction wave gun(RAVEN)was proposed to significantly reduce the weapon recoil and the heat in barrel,while minimally reducing the muzzle velocity.The main principle of RAVEN is that the rarefaction wave will not reach the projectile base until the muzzle by delaying the venting time of an expansion nozzle at the breech.Developed on the RAVEN principle,the purpose of this paper is to provide an engineering method for predicting the performance of a low-recoil gun with front nozzle.First,a two-dimensional two-phase flow model of interior ballistic during the RAVEN firing cycle was established.Numerical simulation results were compared with the published data to validate the reliability and accuracy.Next,the effects of the vent opening times and locations were investigated to determine the influence rules on the performance of the RAVEN with front nozzle.Then according to the results above,simple nonlinear fitting formulas were provided to explain how the muzzle velocity and the recoil force change with the vent opening time and location.Finally,a better vent venting opening time corresponding to the vent location was proposed.The findings should make an important contribution to the field of engineering applications of the RAVEN.展开更多
As drilling operations move into remote locations and extreme water depths, recoil analysis requires more careful considerations and the incidence of emergency disconnect is increased inevitably. To accurately capture...As drilling operations move into remote locations and extreme water depths, recoil analysis requires more careful considerations and the incidence of emergency disconnect is increased inevitably. To accurately capture the recoil dynamics of a deep-water riser in an emergency disconnect scenario, researchers typically focus on modelling the influential subsystems (e.g., the tensioner, the mud discharge and seawater refilling process) which can be solved in the preprocessing, and then the determined parameters are transmitted into an existing global riser analysis software. Distinctively, the current study devotes efforts into the coupling effects resulting from that the suspended riser reacts the platform heave motion via the tensioner system in the course of recoil and the discharging fluid column follows the oscillation of the riser in the mud discharge process. Four simulation models are established based on lumped mass method employing different formulas for the top boundary condition of the riser and the discharging flow acceleration. It demonstrates that the coupling effects discussed above can significantly affect the recoil behavior during the transition phase from initial disconnect to the final hang-off state. It is recommended to develop a fully- coupled integrated model for recoil analysis and anti-recoil control system design before extreme deep-water applications.展开更多
A two-dimensional mathematical model based on volume-of-fluid method is proposed to investigate the heat transfer,fluidflow and keyhole dynamics during electron beam welding(EBW)on20mm-thick2219aluminum alloy plate.In...A two-dimensional mathematical model based on volume-of-fluid method is proposed to investigate the heat transfer,fluidflow and keyhole dynamics during electron beam welding(EBW)on20mm-thick2219aluminum alloy plate.In the model,anadaptive heat source model tracking keyhole depth is employed to simulate the heating process of electron beam.Heat and masstransport of different vortexes induced by surface tension,thermo-capillary force,recoil pressure,hydrostatic pressure and thermalbuoyancy is coupled with keyhole evolution.A series of physical phenomena involving keyhole drilling,collapse,reopening,quasi-stability,backfilling and the coupled thermal field are analyzed systematically.The results indicate that the decreased heat fluxof beam in depth can decelerate the keyholing velocity of recoil pressure and promote the quasi-steady state.Before and close to thisstate,the keyhole collapses and complicates the fluid transport of vortexes.Finally,all simulation results are validated againstexperiments.展开更多
In this study, a complex analysis of a man-weapon interaction based on experimental effort is presented.The attention is focused on how a shooter can influence on a rifle, opposite to generally considered in literatur...In this study, a complex analysis of a man-weapon interaction based on experimental effort is presented.The attention is focused on how a shooter can influence on a rifle, opposite to generally considered in literature rifle's impact on a shooter. It is shown, based on the kbk AKM weapon, that each support point of the rifle has an substantial impact on the system. It is said that identifying human reactions on weapon may let to describe gun movement and thus may be applied to weapon accuracy determination.展开更多
Geant4 based Monte Carlo study has been carried out to assess the improvement in efficiency of the planar structure of Silicon Carbide(SiC)-based semiconductor fast neutron detector with the stacked structure. A proto...Geant4 based Monte Carlo study has been carried out to assess the improvement in efficiency of the planar structure of Silicon Carbide(SiC)-based semiconductor fast neutron detector with the stacked structure. A proton recoil detector was simulated, which consists of hydrogenous converter, i.e., high-density polyethylene(HDPE) for generating recoil protons by means of neutron elastic scattering(n, p) reaction and semiconductor material SiC, for generating a detectable electrical signal upon transport of recoil protons through it. SiC is considered in order to overcome the various factors associated with conventional Si-based devices such as operability in a harsh radiation environment, as often encountered in nuclear facilities. Converter layer thickness is optimized by considering 10~9 neutron events of different monoenergetic neutron sources as well as ^(241)Am-Be neutron spectrum. It is found that the optimized thickness for neutron energy range of 1–10 MeV is ~400 μm. However, the efficiency of fast neutron detection is estimated to be only 0.112%,which is considered very low for meaningful and reliable detection of neutrons. To overcome this problem, a stacked juxtaposition of converter layer between SiC layers has been analyzed in order to achieve high efficiency. It is noted that a tenfold efficiency improvement has been obtained—1.04% for 10 layers stacked configuration vis-à-vis 0.112% of single converter layer detector. Further simulation of the stacked detector with respect to variable converter thickness has been performed to achieve the efficiency as high as ~3.85% with up to 50 stacks.展开更多
Leader propagation is a fundamental issue in lightning physics. The propagation characteristics of positive leaders and negative leaders are summarized and compared based on data from high-speed camera and electromagn...Leader propagation is a fundamental issue in lightning physics. The propagation characteristics of positive leaders and negative leaders are summarized and compared based on data from high-speed camera and electromagnetic field in rocket-triggered lightning and tower-initiated lightning discharges; available channel base current data recorded in rocket-triggered lightning are also used. The negative leaders propagate in a stepped fashion accompanied by many branches. The stems ahead of the negative leader tip determine the manner and direction of the leader propagation, and even the branching and winding of the lightning channel. The impulsive current, electromagnetic field, and related optical images suggest that the positive leader may develop in a step-like fashion at its initial stage of triggered lightning. However, the stepping processes of the positive leader are obviously different from those of the negative leader. Tower-initiated lightning revealed that the most conspicuous characteristics of the stepwise positive leader involve the intermittent brush-like corona zone in front of the leader tip and the luminosity enhancement of the channel behind the tip. In rockettriggered lightning flashes, the charge transferred during an individual step for the negative leader was nearly an order greater than for the positive counterpart. The successive streamers ahead of the leader tip are essential for both negative and positive leader propagation, and the stems could be formed from one or more streamers in the previous negative streamer zone with the main leader channel dim. High-resolution observation of tower lightning also revealed a new type of bidirectional recoil leader, with polarity contrary to the traditional one, traversing in negative channels associated with tower-initiated and rocket-triggered lightning.展开更多
A measurement of the ^235U prompt fission neutron spectrum (PFNS) by the recoil proton method was performed at the Institute of Nuclear Physics and Chemistry, China. Details of the method, which include the calculatio...A measurement of the ^235U prompt fission neutron spectrum (PFNS) by the recoil proton method was performed at the Institute of Nuclear Physics and Chemistry, China. Details of the method, which include the calculation and validation of the response matrix, are presented. The PFNS for ^235U in the energy range 1–12 MeV, induced by thermal neutrons, was obtained. The measured spectrum in the low-energy region was in good agreement with previous work and the ENDF/B-VII library, except for minor differences. In the high-energy region, however, the relative height of the measured spectrum was greater, and an analysis of the experiment indicated uncertainties of 13% at 10 MeV and 24% at 12 MeV. Experimental results showed that the recoil proton method could be used to measure prompt fission neutron spectra. Some directions for future work are included.展开更多
文摘The inlet deflector rollers of a recoiling line are sprayed rollers. Short scratch lines have been found on the surface of steel sheets during commissioning. By adjusting the control parameters of the line and investigating the manufacturing process of inlet deflector rollers, the root cause of the scratches was found. By modifying the manufacturing process of the rollers, the scratches have been thoroughly eliminated, and quality steel sheets have been consistently produced in the recoiling line.
基金Project supported by the Chinese Academy of Sciences and the National Natural Science Foundation of China.
文摘The decay of 20Na of astrophysical reactions has been studied deeply via 20Ne(p, n)20Na reaction. A new β-delayed α decay with α energy of 5 896 ± 6 keV and relative intensity of 0. 002 4 ± 0. 000 3 was discovered. At the same time the 16O recoiling in β+-delayed α decay of 20Na was observed in experiment for the first time. From these, it is inferred that a β-delayed low energy α decay of 20Na with energy of-780 keV and relative intensity of -1.4 was mixed in 16O recoiling. In 16O recoiling and the low energy α decay, the energy loss for low energy charged particles through matter was discussed in detail. At last, two methods for discriminating the β-delayed low energy α decay of 20Na were proposed.
文摘It is widely recognized by many within the scientific community that the field of seismology faces challenges in aligning with established scientific practices for studying earthquakes. Some views may suggest a reliance on methods that resemble divination rather than sound scientific inquiry. Despite efforts to understand seismic phenomena over the past three centuries [1], progress in seismology has been perceived as somewhat stagnant. Criticisms have been raised about certain theories, such as Mr. Reid’s Elastic Recoil theory from 1910 [2], and its purported advancements in comprehending seismic processes. While acknowledging various perspectives on this matter [3]-[7], it is important to reflect on the historical context and potential limitations in our understanding. Addressing concerns raised within the discipline involves examining educational practices and fostering a rigorous academic environment to promote scientific excellence. This article aims to explore the underlying factors contributing to the current state of seismology, offering insights into overcoming challenges and fostering advancements that benefit the scientific community and society as a whole.
基金Project supported by the National Key Research and Development Program of China(Grant No.2022YFA1602500)the National Natural Science Foundation of China(Grant No.11974358)。
文摘State-selective single-and double-electron capture processes in collisions of S^(5+)ions with helium at energies ranging from 50.8 keV to 100 keV were investigated using cold target recoil ion momentum spectroscopy(COLTRIMS).Q-value spectra and projectile scattering angle distributions were obtained.For single-electron capture,single electron capture into n=3 states of the projectile ion is dominant.As the projectile energy increases,the contribution of single electron capture into n=4 states is observed.Experimental relative cross-sections for single-electron capture into different projectile final states were compared with theoretical predictions based on the molecular orbital close-coupling(MOCC)method.In double-electron capture,two-electron populating into the 3s^(2)3p and 3s3p^(2)states of projectile dominates.The reaction window calculated from the classical molecular Coulombic barrier model can qualitatively explain the experimental results.The scattering angle distribution of the multi-peak structure of the double-electron capture process is observed.The database is openly available in Science Data Bank at https://doi.org/10.57760/sciencedb.j00113.00233.
基金supported by the National Key Research and Development Program of China(Grant No.2022YFA1602500)the National Natural Science Foundation of China(Grant Nos.11934004,12064040,and 11974358)Strategic Key Research Program of the Chinese Academy of Sciences(Grant No.XDB34020000).
文摘We study the fragmentation of NO^(q+)(q=2,3)molecular ions produced by collisions between 96 keV O^(6+)ions and neutral nitric oxide(NO)molecules,using the cold target recoil ion momentum spectrometer(COLTRIMS).The kinetic energy release(KER)for various dissociation channels is obtained.For the channel NO^(2+)→N^(+)+O^(+),double-electron capture followed by autoionization of the projectile ions is the dominant process,which can be explained by the recapture of loosely bound electrons into highly excited states of the target.For NO3+trication,two dissociation channels,i.e.,(a)N^(+)+O^(2+)and(b)N^(2+)+O^(+),are observed,where channel(b)is the dominant channel.Moreover,for dissociation channels originating from the same parent molecular ion,the dissociation channel with a higher charge for the oxygen ion fragment exhibits a higher most probable KER,which is consistent with studies of CO fragmentation by Rajput et al.Additionally,it is observed that as capture stability increases,the average KER shifts to higher values.
基金supported by the National Natural Science Foundation of China(Grant No.11502114)the Fundamental Research Funds for the Central Universities(Grant No.30918011323)
文摘One of the greatest challenges in the design of a gun is to balance muzzle velocity and recoil,especially for guns on aircrafts and deployable vehicles.To resolve the conflict between gun power and recoil force,a concept of rarefaction wave gun(RAVEN)was proposed to significantly reduce the weapon recoil and the heat in barrel,while minimally reducing the muzzle velocity.The main principle of RAVEN is that the rarefaction wave will not reach the projectile base until the muzzle by delaying the venting time of an expansion nozzle at the breech.Developed on the RAVEN principle,the purpose of this paper is to provide an engineering method for predicting the performance of a low-recoil gun with front nozzle.First,a two-dimensional two-phase flow model of interior ballistic during the RAVEN firing cycle was established.Numerical simulation results were compared with the published data to validate the reliability and accuracy.Next,the effects of the vent opening times and locations were investigated to determine the influence rules on the performance of the RAVEN with front nozzle.Then according to the results above,simple nonlinear fitting formulas were provided to explain how the muzzle velocity and the recoil force change with the vent opening time and location.Finally,a better vent venting opening time corresponding to the vent location was proposed.The findings should make an important contribution to the field of engineering applications of the RAVEN.
基金financially supported by the National Natural Science Foundation of China(Grant No.51879161)
文摘As drilling operations move into remote locations and extreme water depths, recoil analysis requires more careful considerations and the incidence of emergency disconnect is increased inevitably. To accurately capture the recoil dynamics of a deep-water riser in an emergency disconnect scenario, researchers typically focus on modelling the influential subsystems (e.g., the tensioner, the mud discharge and seawater refilling process) which can be solved in the preprocessing, and then the determined parameters are transmitted into an existing global riser analysis software. Distinctively, the current study devotes efforts into the coupling effects resulting from that the suspended riser reacts the platform heave motion via the tensioner system in the course of recoil and the discharging fluid column follows the oscillation of the riser in the mud discharge process. Four simulation models are established based on lumped mass method employing different formulas for the top boundary condition of the riser and the discharging flow acceleration. It demonstrates that the coupling effects discussed above can significantly affect the recoil behavior during the transition phase from initial disconnect to the final hang-off state. It is recommended to develop a fully- coupled integrated model for recoil analysis and anti-recoil control system design before extreme deep-water applications.
文摘A two-dimensional mathematical model based on volume-of-fluid method is proposed to investigate the heat transfer,fluidflow and keyhole dynamics during electron beam welding(EBW)on20mm-thick2219aluminum alloy plate.In the model,anadaptive heat source model tracking keyhole depth is employed to simulate the heating process of electron beam.Heat and masstransport of different vortexes induced by surface tension,thermo-capillary force,recoil pressure,hydrostatic pressure and thermalbuoyancy is coupled with keyhole evolution.A series of physical phenomena involving keyhole drilling,collapse,reopening,quasi-stability,backfilling and the coupled thermal field are analyzed systematically.The results indicate that the decreased heat fluxof beam in depth can decelerate the keyholing velocity of recoil pressure and promote the quasi-steady state.Before and close to thisstate,the keyhole collapses and complicates the fluid transport of vortexes.Finally,all simulation results are validated againstexperiments.
文摘In this study, a complex analysis of a man-weapon interaction based on experimental effort is presented.The attention is focused on how a shooter can influence on a rifle, opposite to generally considered in literature rifle's impact on a shooter. It is shown, based on the kbk AKM weapon, that each support point of the rifle has an substantial impact on the system. It is said that identifying human reactions on weapon may let to describe gun movement and thus may be applied to weapon accuracy determination.
基金supported by the grant of a research fellowship from Indira Gandhi Centre for Atomic Research,Department of Atomic Energy,India
文摘Geant4 based Monte Carlo study has been carried out to assess the improvement in efficiency of the planar structure of Silicon Carbide(SiC)-based semiconductor fast neutron detector with the stacked structure. A proton recoil detector was simulated, which consists of hydrogenous converter, i.e., high-density polyethylene(HDPE) for generating recoil protons by means of neutron elastic scattering(n, p) reaction and semiconductor material SiC, for generating a detectable electrical signal upon transport of recoil protons through it. SiC is considered in order to overcome the various factors associated with conventional Si-based devices such as operability in a harsh radiation environment, as often encountered in nuclear facilities. Converter layer thickness is optimized by considering 10~9 neutron events of different monoenergetic neutron sources as well as ^(241)Am-Be neutron spectrum. It is found that the optimized thickness for neutron energy range of 1–10 MeV is ~400 μm. However, the efficiency of fast neutron detection is estimated to be only 0.112%,which is considered very low for meaningful and reliable detection of neutrons. To overcome this problem, a stacked juxtaposition of converter layer between SiC layers has been analyzed in order to achieve high efficiency. It is noted that a tenfold efficiency improvement has been obtained—1.04% for 10 layers stacked configuration vis-à-vis 0.112% of single converter layer detector. Further simulation of the stacked detector with respect to variable converter thickness has been performed to achieve the efficiency as high as ~3.85% with up to 50 stacks.
基金supported by the National Natural Science Foundation of China (Grant Nos. 41630425, 41761144074)
文摘Leader propagation is a fundamental issue in lightning physics. The propagation characteristics of positive leaders and negative leaders are summarized and compared based on data from high-speed camera and electromagnetic field in rocket-triggered lightning and tower-initiated lightning discharges; available channel base current data recorded in rocket-triggered lightning are also used. The negative leaders propagate in a stepped fashion accompanied by many branches. The stems ahead of the negative leader tip determine the manner and direction of the leader propagation, and even the branching and winding of the lightning channel. The impulsive current, electromagnetic field, and related optical images suggest that the positive leader may develop in a step-like fashion at its initial stage of triggered lightning. However, the stepping processes of the positive leader are obviously different from those of the negative leader. Tower-initiated lightning revealed that the most conspicuous characteristics of the stepwise positive leader involve the intermittent brush-like corona zone in front of the leader tip and the luminosity enhancement of the channel behind the tip. In rockettriggered lightning flashes, the charge transferred during an individual step for the negative leader was nearly an order greater than for the positive counterpart. The successive streamers ahead of the leader tip are essential for both negative and positive leader propagation, and the stems could be formed from one or more streamers in the previous negative streamer zone with the main leader channel dim. High-resolution observation of tower lightning also revealed a new type of bidirectional recoil leader, with polarity contrary to the traditional one, traversing in negative channels associated with tower-initiated and rocket-triggered lightning.
基金supported by the National Natural Science Foundation of China(No.11775196)the Chinese Special Project for ITER(No.2015GB108006)
文摘A measurement of the ^235U prompt fission neutron spectrum (PFNS) by the recoil proton method was performed at the Institute of Nuclear Physics and Chemistry, China. Details of the method, which include the calculation and validation of the response matrix, are presented. The PFNS for ^235U in the energy range 1–12 MeV, induced by thermal neutrons, was obtained. The measured spectrum in the low-energy region was in good agreement with previous work and the ENDF/B-VII library, except for minor differences. In the high-energy region, however, the relative height of the measured spectrum was greater, and an analysis of the experiment indicated uncertainties of 13% at 10 MeV and 24% at 12 MeV. Experimental results showed that the recoil proton method could be used to measure prompt fission neutron spectra. Some directions for future work are included.
