Compound section is referred to a section the surface of which is made of several sub-sections with different flow characteristics. The difference in the hydraulic and geometry characteristics causes a complexity in f...Compound section is referred to a section the surface of which is made of several sub-sections with different flow characteristics. The difference in the hydraulic and geometry characteristics causes a complexity in flow hydraulic and creates an interaction between the main channel and floodplains, resulting in an apparent shear stress and a transverse momentum transfer. The amount of such a stress plays an important role in many river engineering measures [1]. Due to the flow complexity, the common approximate analytical methods are not enough to identify the flow profile. The FLOW3D Software with its great features in three-dimensional analysis of flow field is used as a tool to investigate the shear stress in a direct symmetrical compound rectangular channel. After the simulation of models, it is found that an increase in the relative width and relative depth parameters decreases the percentage of apparent shear stress and an increase in the relative roughness causes it to be increased [2].展开更多
Modelling and simulations are conducted on velocity slip and interfacial momentum transfer for supersonic two-pha.se (gas-droplet) flow in the transient section inside and outside a Laval jet(LJ). The initial velocity...Modelling and simulations are conducted on velocity slip and interfacial momentum transfer for supersonic two-pha.se (gas-droplet) flow in the transient section inside and outside a Laval jet(LJ). The initial velocity slip between gas and droplets causes an interfacial momentum transfer flux as high as (2.0-5.0) x 104 Pa. The relaxation time corresponding to this transient process is in the range of 0.015-0.090ms for the two-phase flow formed inside the LJ and less than 0.5ms outside the LJ. It demonstrates the unique performance of this system for application to fast chemical reactions using electrically active media with a lifetime in the order of 1 ms. Through the simulations of the transient processes with initial Mach number Mg from 2.783 to 4.194 at different axial positions inside the LJ, it is found that Mg has the strongest effect on the process. The momentum flux increases as the Mach number decreases. Due to compression by the shock wave at the end of the LJ, the flow pattern becomes two dimensional and viscous outside the LJ. Laser Doppler velocirneter (LDV) measurements of droplet velocities outside the LJ are in reasonably good agreement with the results of the simulation.展开更多
The effects of projectile/target impedance matching and projectile shape on energy,momentum transfer and projectile melting during collisions are investigated by numerical simulation.By comparing the computation resul...The effects of projectile/target impedance matching and projectile shape on energy,momentum transfer and projectile melting during collisions are investigated by numerical simulation.By comparing the computation results with the experimental results,the correctness of the calculation and the statistical method of momentum transfer coefficient is verified.Different shapes of aluminum,copper and heavy tungsten alloy projectiles striking aluminum,basalt,and pumice target for impacts up to 10 km/s are simulated.The influence mechanism of the shape of the projectile and projectile/target density on the momentum transfer was obtained.With an increase in projectile density and length-diameter ratio,the energy transfer time between the projectile and targets is prolonged.The projectile decelerates slowly,resulting in a larger cratering depth.The energy consumed by the projectile in the excavation stage increased,resulting in lower mass-velocity of ejecta and momentum transfer coefficient.The numerical simulation results demonstrated that for different projectile/target combinations,the higher the wave impedance of the projectile,the higher the initial phase transition velocity and the smaller the mass of phase transition.The results can provide theoretical guidance for kinetic impactor design and material selection.展开更多
This work mainly studies the effect of fluid phase momentum transfer mechanisms on the acidizing results,including the retardation effect of the porous structure and the interaction between the fluid phase,such as vis...This work mainly studies the effect of fluid phase momentum transfer mechanisms on the acidizing results,including the retardation effect of the porous structure and the interaction between the fluid phase,such as viscous dissipation and inertial effect.The results show that the acid fluid momentum transfer is influenced by the complex porous structure and fluid viscous dissipation.Eventually,the Stokes-Darcy equation is recommended to be adopted to describe the fluid phase momentum transfer in the following numerical simulation studies of the carbonate acidizing process.Based on this model,a parametric research is carried out to investigate the impact of acid on rock physical characteristics in the stimulation process.Increasing the acid concentration appears to minimize the quantity of acid consumed for the breakthrough.The acid surface reaction rate has a considerable impact on the pore volume to breakthrough and the optimum acid injection rate.The influence of permeability on the acidizing results basically shows a negative correlation with the injection rate.The difference between the acidizing curves of different permeability gradually becomes insignificant with the decrease in injection rate.The existence of isolated fracture and vug significantly reduces acid consumption for the breakthrough.展开更多
A continuum model and numerical methods were established for description of heat,mass and momentum transfers as well as macrosegregation formations in metallic ingots.Numerical simulation of temperature,composition an...A continuum model and numerical methods were established for description of heat,mass and momentum transfers as well as macrosegregation formations in metallic ingots.Numerical simulation of temperature,composition and liquid flow fields during the solidification of an Al-4.5% Cu ingot were performed on an IBM personal computer.The model and numerical methods were verified through two experiments.展开更多
The modified Coulomb-Born approximation with and without the internuclear interaction （MCB-NN and MCB） is used to calculate the fully differential cross sections （FDCS） for the single ionization of helium by lOO M...The modified Coulomb-Born approximation with and without the internuclear interaction （MCB-NN and MCB） is used to calculate the fully differential cross sections （FDCS） for the single ionization of helium by lOO MeV/amu C6＋ impact. The effects of the internuclear interaction on the FDCS are examined in geometries. The results are compared with experimental data and theoretical predictions from a three-body distorted-wave （3DW） model and a time-dependent close-coupling model. It is shown that the present MCB-NN results are in good agreement with the experiments in the scattering plane and the MCB results qualitatively reproduce the experimental structure outside the scattering plane. In particular, the MCB theory predicts the ＇double-peak＇ structure in the perpendicular plane.展开更多
The present paper has investigated the momentum transport phenomena of underwater shock wave generation in terms of photo-acoustic wave with a very thin metal. The shock wave was induced by a pulsed-laser irradiation....The present paper has investigated the momentum transport phenomena of underwater shock wave generation in terms of photo-acoustic wave with a very thin metal. The shock wave was induced by a pulsed-laser irradiation. In order to clarify the momentum transport mechanics in this phenomenon, we have been considered the momentum and energy transport from laser to metal, and metal to water. A numerical solution of thermo-elastic wave in metal has been obtained to estimate a fundamental gain of the longitudinal wave. Then, the underwater shock wave phenomena have been analyzed by adapting compressible fluid dynamics with suitable boundary condition between the solid and liquid. We had performed an experiment as well and observed the shock wave with optical system. The aim of the research is to estimate the underwater shock wave strength theoretically. The metal region was calculated by Laplace transformation of heat conduction and wave equations. The water region was simulated by MacCormack’s method. Some of boundary conditions have been examined and the acceleration condition has been adopted at the interface. The simulated results show a good agreement with experimental result, consequently the momentum transfer mechanism from longitudinal wave to underwater shock wave has been cleared in the present report.展开更多
Theoretical calculations serve as an effective method for determining plasma temperatures within planetary atmospheres.To simulate plasma temperature,a comprehensive implementation of the energy equation is used,which...Theoretical calculations serve as an effective method for determining plasma temperatures within planetary atmospheres.To simulate plasma temperature,a comprehensive implementation of the energy equation is used,which is governed by five terms:conductivity,heating,cooling,adiabatic expansion,and advection.The derivations mentioned are strongly dependent on the collision cross section between electrons and other particles(e.g.,neutrals,ions).It is notable that the momentum transfer cross sections between electrons and neutrals have been updated in recent decades.However,the widely used momentum average collision cross sections between electrons and neutrals,derived from the momentum transfer cross sections,are collected in studies dating back nearly half a century.Therefore,it becomes imperative to revise the momentum average collision cross sections relevant to astrophysical contexts,based on the latest studies.In this study,we summarize the momentum average collision cross sections of 13 species common in planetary atmospheres:H,H_(2),He,O,CH_(4),H_(2)O,CO,N_(2),O_(2),Ar,CO_(2),N_(2)O,and NO_(2).All results are derived from the latest studies concerning the electron-neutral collision cross section and are compared with previous studies.Furthermore,we present a comparison of the derived total electron-neutral collision frequency at Mars between this study and previous studies.Prominent differences in the total electron-neutral collision frequency between this and prior studies support the significance of updating the momentum average collision cross section between electrons and neutrals in studying the planetary atmospheres.展开更多
The determination of optical force as a consequence of momentum transfer is inevitably subject to the use of the proper momentum density and stress tensor.It is imperative and valuable to consider the intrinsic scheme...The determination of optical force as a consequence of momentum transfer is inevitably subject to the use of the proper momentum density and stress tensor.It is imperative and valuable to consider the intrinsic scheme of photon momentum transfer,particularly when a particle is embedded in a complex dielectric environment.Typically,we consider a particle submerged in an inhomogeneous background composed of different dielectric materials,excluding coherent illumination or hydrodynamic effects.A ray-tracing method is adopted to capture the direct process of momentum transfer from the complex background medium,and this approach is validated using the modified Einstein–Laub method,which uses only the interior fields of the particle in the calculation.In this way,debates regarding the calculation of the force with different stress tensors using exterior fields can be avoided.Our suggested interpretation supports only the Minkowski approach for the optical momentum transfer to the embedded scatterer while rejecting Peierls’s and Abraham’s approaches,though the momentum of a stably moving photon in a continuous background medium should be considered to be of the Abraham type.Our interpretation also provides a novel method of realizing a tractor beam for the exertion of negative force that offers an alternative to the use of negative-index materials,optical gain,or highly non-paraxial or multiple-light interference.展开更多
We discuss transportation and redistribution of energy and angular momentum in the magnetic connection(MC) process and Blandford-Payne(BP) process.MC results in readjusting the interior viscous torque,and its effects ...We discuss transportation and redistribution of energy and angular momentum in the magnetic connection(MC) process and Blandford-Payne(BP) process.MC results in readjusting the interior viscous torque,and its effects are operative not only in but also beyond the MC region.The BP process is invoked to transfer the "excessive" angular momentum from an accretion disc.In addition,we derive a criterion for the interior viscous torque to resolve the puzzle of the overall equilibrium of angular momentum in disc accretion.It turns out that the efficiency of BP at extracting angular momentum and the intensity of the outflow are required to be greater than some critical values.展开更多
This work tries to identify the relationship between geometric configuration of monolith catalysts, and transfer and reaction performances for selective catalytic reduction of N2O with CO. Monolith catalysts with five...This work tries to identify the relationship between geometric configuration of monolith catalysts, and transfer and reaction performances for selective catalytic reduction of N2O with CO. Monolith catalysts with five different channel shapes (circle, regular triangle, rectangle, square and hexagon), was investigated to make a comprehensive comparison of their pressure drop, heat transfer Nu number, mass transfer Sh number and N2O conversion. It was found that monolith catalysts have a much lower pressure drop than that of traditional packed bed, and for monolith catalysts with different channel shapes, pressure drop decreases in the order of regular triangle > rectangle > square > hexagon > circle. The order of Nu is in regular triangle > rectangle ≈ square > hexagon > circle, similar to that of Sh. N2O conversion follows the order of regular triangle > rectangular ≈ square ≈ circle > hexagon. The results indicate that chemical reaction including internal diffusion is the controlling step in the selective catalytic reduction of N2O removal with CO. In addition, channel size and gas velocity also have influence on N2O conversion and pressure drop.展开更多
The problem of momentum and heat transfer in a compressible boundary layerbehind a thin expansion wave was solved by the application of the similarity transformation and theshooting technique. Utilizing the analytical...The problem of momentum and heat transfer in a compressible boundary layerbehind a thin expansion wave was solved by the application of the similarity transformation and theshooting technique. Utilizing the analytical expression of a two-point boundary value problem formomentum transfer, the energy boundary layer solution was represented as a function of thedimensionless velocity, and as the parameters of the Prandtl number, the velocity ratio, and thetemperature ratio.展开更多
Large momentum transfer( LM T) beamsplitting in atom interferometry is review ed,focusing on the use of Bloch Oscillations to achieve high momentum separation w ithout loss of visibility. Phase sensitivity w ith a fri...Large momentum transfer( LM T) beamsplitting in atom interferometry is review ed,focusing on the use of Bloch Oscillations to achieve high momentum separation w ithout loss of visibility. Phase sensitivity w ith a fringe visibility of 7% is observed in a horizontally guided,acceleration-sensitive atom interferometer w ith a momentum separation of 80k betw een its arms.In addition,a 510 k beamsplitter is demonstrated.展开更多
N^(3+)离子与基态He原子碰撞过程在天体物理、星际空间和实验室等离子体环境中具有重要研究意义.本文采用从头算的多参考单双激发组态相互作用方法精确计算了[NHe]^(3+)碰撞体系的分子结构参数,包括势能曲线和耦合矩阵元等.基于计算得...N^(3+)离子与基态He原子碰撞过程在天体物理、星际空间和实验室等离子体环境中具有重要研究意义.本文采用从头算的多参考单双激发组态相互作用方法精确计算了[NHe]^(3+)碰撞体系的分子结构参数,包括势能曲线和耦合矩阵元等.基于计算得到的结构参数,采用全量子分子轨道强耦合方法开展了低能N^(3+)离子与He原子碰撞电荷转移过程研究,获得了能量在3.16×10^(–3)e V—24 ke V(即2.25×10^(–4)e V/u—1.73 ke V/u)范围内的总单电荷、双电荷转移截面和态选择截面.在计算中考虑了电荷平动因子、高角动量态对碰撞过程的影响,发现高角动量态对电荷转移截面具有显著影响.与现有实验和理论结果相比,当前计算的单电荷和双电荷转移截面与实验测量值更为接近.相较于Liu等(2011 Phys.Rev.A 84042706)未考虑高角动量态的研究,当碰撞能量大于10 e V/u时,其总单电荷转移截面约高出当前计算值2—3倍,表明高角动量态对电荷转移过程具有显著影响.同时研究表明单电荷转移截面远大于双电荷转移截面,在碰撞电荷转移过程中占据主导地位.展开更多
文摘Compound section is referred to a section the surface of which is made of several sub-sections with different flow characteristics. The difference in the hydraulic and geometry characteristics causes a complexity in flow hydraulic and creates an interaction between the main channel and floodplains, resulting in an apparent shear stress and a transverse momentum transfer. The amount of such a stress plays an important role in many river engineering measures [1]. Due to the flow complexity, the common approximate analytical methods are not enough to identify the flow profile. The FLOW3D Software with its great features in three-dimensional analysis of flow field is used as a tool to investigate the shear stress in a direct symmetrical compound rectangular channel. After the simulation of models, it is found that an increase in the relative width and relative depth parameters decreases the percentage of apparent shear stress and an increase in the relative roughness causes it to be increased [2].
基金Supported by the National Natural Science Foundation of China (No. 29876022) and Grant of State Key Laboratory of High Speed Hydrodynamics (No. 2007).
文摘Modelling and simulations are conducted on velocity slip and interfacial momentum transfer for supersonic two-pha.se (gas-droplet) flow in the transient section inside and outside a Laval jet(LJ). The initial velocity slip between gas and droplets causes an interfacial momentum transfer flux as high as (2.0-5.0) x 104 Pa. The relaxation time corresponding to this transient process is in the range of 0.015-0.090ms for the two-phase flow formed inside the LJ and less than 0.5ms outside the LJ. It demonstrates the unique performance of this system for application to fast chemical reactions using electrically active media with a lifetime in the order of 1 ms. Through the simulations of the transient processes with initial Mach number Mg from 2.783 to 4.194 at different axial positions inside the LJ, it is found that Mg has the strongest effect on the process. The momentum flux increases as the Mach number decreases. Due to compression by the shock wave at the end of the LJ, the flow pattern becomes two dimensional and viscous outside the LJ. Laser Doppler velocirneter (LDV) measurements of droplet velocities outside the LJ are in reasonably good agreement with the results of the simulation.
基金the National Natural Science Foundation of China(Grant Nos.62227901,12202068)the Civil Aerospace Pre-research Project(Grant No.D020304).
文摘The effects of projectile/target impedance matching and projectile shape on energy,momentum transfer and projectile melting during collisions are investigated by numerical simulation.By comparing the computation results with the experimental results,the correctness of the calculation and the statistical method of momentum transfer coefficient is verified.Different shapes of aluminum,copper and heavy tungsten alloy projectiles striking aluminum,basalt,and pumice target for impacts up to 10 km/s are simulated.The influence mechanism of the shape of the projectile and projectile/target density on the momentum transfer was obtained.With an increase in projectile density and length-diameter ratio,the energy transfer time between the projectile and targets is prolonged.The projectile decelerates slowly,resulting in a larger cratering depth.The energy consumed by the projectile in the excavation stage increased,resulting in lower mass-velocity of ejecta and momentum transfer coefficient.The numerical simulation results demonstrated that for different projectile/target combinations,the higher the wave impedance of the projectile,the higher the initial phase transition velocity and the smaller the mass of phase transition.The results can provide theoretical guidance for kinetic impactor design and material selection.
基金financial support from the Key Project of the National Natural Science Foundation of China(No.52034010)the China Scholarship Council(201906450038)
文摘This work mainly studies the effect of fluid phase momentum transfer mechanisms on the acidizing results,including the retardation effect of the porous structure and the interaction between the fluid phase,such as viscous dissipation and inertial effect.The results show that the acid fluid momentum transfer is influenced by the complex porous structure and fluid viscous dissipation.Eventually,the Stokes-Darcy equation is recommended to be adopted to describe the fluid phase momentum transfer in the following numerical simulation studies of the carbonate acidizing process.Based on this model,a parametric research is carried out to investigate the impact of acid on rock physical characteristics in the stimulation process.Increasing the acid concentration appears to minimize the quantity of acid consumed for the breakthrough.The acid surface reaction rate has a considerable impact on the pore volume to breakthrough and the optimum acid injection rate.The influence of permeability on the acidizing results basically shows a negative correlation with the injection rate.The difference between the acidizing curves of different permeability gradually becomes insignificant with the decrease in injection rate.The existence of isolated fracture and vug significantly reduces acid consumption for the breakthrough.
文摘A continuum model and numerical methods were established for description of heat,mass and momentum transfers as well as macrosegregation formations in metallic ingots.Numerical simulation of temperature,composition and liquid flow fields during the solidification of an Al-4.5% Cu ingot were performed on an IBM personal computer.The model and numerical methods were verified through two experiments.
基金Supported by the National Natural Science Foundation of China under Grant No 11274215the Natural Science Foundation of Shanxi Province under Grant No 2010011009
文摘The modified Coulomb-Born approximation with and without the internuclear interaction （MCB-NN and MCB） is used to calculate the fully differential cross sections （FDCS） for the single ionization of helium by lOO MeV/amu C6＋ impact. The effects of the internuclear interaction on the FDCS are examined in geometries. The results are compared with experimental data and theoretical predictions from a three-body distorted-wave （3DW） model and a time-dependent close-coupling model. It is shown that the present MCB-NN results are in good agreement with the experiments in the scattering plane and the MCB results qualitatively reproduce the experimental structure outside the scattering plane. In particular, the MCB theory predicts the ＇double-peak＇ structure in the perpendicular plane.
文摘The present paper has investigated the momentum transport phenomena of underwater shock wave generation in terms of photo-acoustic wave with a very thin metal. The shock wave was induced by a pulsed-laser irradiation. In order to clarify the momentum transport mechanics in this phenomenon, we have been considered the momentum and energy transport from laser to metal, and metal to water. A numerical solution of thermo-elastic wave in metal has been obtained to estimate a fundamental gain of the longitudinal wave. Then, the underwater shock wave phenomena have been analyzed by adapting compressible fluid dynamics with suitable boundary condition between the solid and liquid. We had performed an experiment as well and observed the shock wave with optical system. The aim of the research is to estimate the underwater shock wave strength theoretically. The metal region was calculated by Laplace transformation of heat conduction and wave equations. The water region was simulated by MacCormack’s method. Some of boundary conditions have been examined and the acceleration condition has been adopted at the interface. The simulated results show a good agreement with experimental result, consequently the momentum transfer mechanism from longitudinal wave to underwater shock wave has been cleared in the present report.
基金the National Natural Science Foundation of China through Grants 42261160643,42441806,42241114,and 42304166supported by the open project funded by the Key Laboratory of Geospace Environment,Chinese Academy of Sciences,University of Science and Technology of China.
文摘Theoretical calculations serve as an effective method for determining plasma temperatures within planetary atmospheres.To simulate plasma temperature,a comprehensive implementation of the energy equation is used,which is governed by five terms:conductivity,heating,cooling,adiabatic expansion,and advection.The derivations mentioned are strongly dependent on the collision cross section between electrons and other particles(e.g.,neutrals,ions).It is notable that the momentum transfer cross sections between electrons and neutrals have been updated in recent decades.However,the widely used momentum average collision cross sections between electrons and neutrals,derived from the momentum transfer cross sections,are collected in studies dating back nearly half a century.Therefore,it becomes imperative to revise the momentum average collision cross sections relevant to astrophysical contexts,based on the latest studies.In this study,we summarize the momentum average collision cross sections of 13 species common in planetary atmospheres:H,H_(2),He,O,CH_(4),H_(2)O,CO,N_(2),O_(2),Ar,CO_(2),N_(2)O,and NO_(2).All results are derived from the latest studies concerning the electron-neutral collision cross section and are compared with previous studies.Furthermore,we present a comparison of the derived total electron-neutral collision frequency at Mars between this study and previous studies.Prominent differences in the total electron-neutral collision frequency between this and prior studies support the significance of updating the momentum average collision cross section between electrons and neutrals in studying the planetary atmospheres.
基金CWQ acknowledges financial support from the National University of Singapore(Grant No.R-263-000-678-133)ZW acknowledges support from the Packard Fellowship in Science and Engineering and the Alfred P.Sloan Research Fellowship.CWQ and WD contributed equally。
文摘The determination of optical force as a consequence of momentum transfer is inevitably subject to the use of the proper momentum density and stress tensor.It is imperative and valuable to consider the intrinsic scheme of photon momentum transfer,particularly when a particle is embedded in a complex dielectric environment.Typically,we consider a particle submerged in an inhomogeneous background composed of different dielectric materials,excluding coherent illumination or hydrodynamic effects.A ray-tracing method is adopted to capture the direct process of momentum transfer from the complex background medium,and this approach is validated using the modified Einstein–Laub method,which uses only the interior fields of the particle in the calculation.In this way,debates regarding the calculation of the force with different stress tensors using exterior fields can be avoided.Our suggested interpretation supports only the Minkowski approach for the optical momentum transfer to the embedded scatterer while rejecting Peierls’s and Abraham’s approaches,though the momentum of a stably moving photon in a continuous background medium should be considered to be of the Abraham type.Our interpretation also provides a novel method of realizing a tractor beam for the exertion of negative force that offers an alternative to the use of negative-index materials,optical gain,or highly non-paraxial or multiple-light interference.
基金supported by the National Natural Science Foundation of China (Grant No. 10873005)the Research Fund for the Doctoral Program of Higher Education (Grant No. 200804870050)the National Basic Research Program of China (Grant No. 2009CB824800)
文摘We discuss transportation and redistribution of energy and angular momentum in the magnetic connection(MC) process and Blandford-Payne(BP) process.MC results in readjusting the interior viscous torque,and its effects are operative not only in but also beyond the MC region.The BP process is invoked to transfer the "excessive" angular momentum from an accretion disc.In addition,we derive a criterion for the interior viscous torque to resolve the puzzle of the overall equilibrium of angular momentum in disc accretion.It turns out that the efficiency of BP at extracting angular momentum and the intensity of the outflow are required to be greater than some critical values.
基金Supported by the National Natural Science Foundation of China （21121064, 21076008） the Projects in the National Science ＆ Technology Pillar Program During the 12th Five-Year Plan Period （2011BAC06B04）
文摘This work tries to identify the relationship between geometric configuration of monolith catalysts, and transfer and reaction performances for selective catalytic reduction of N2O with CO. Monolith catalysts with five different channel shapes (circle, regular triangle, rectangle, square and hexagon), was investigated to make a comprehensive comparison of their pressure drop, heat transfer Nu number, mass transfer Sh number and N2O conversion. It was found that monolith catalysts have a much lower pressure drop than that of traditional packed bed, and for monolith catalysts with different channel shapes, pressure drop decreases in the order of regular triangle > rectangle > square > hexagon > circle. The order of Nu is in regular triangle > rectangle ≈ square > hexagon > circle, similar to that of Sh. N2O conversion follows the order of regular triangle > rectangular ≈ square ≈ circle > hexagon. The results indicate that chemical reaction including internal diffusion is the controlling step in the selective catalytic reduction of N2O removal with CO. In addition, channel size and gas velocity also have influence on N2O conversion and pressure drop.
基金This work was supported by the "Cross-Century Talents Projects of the Educational Ministry of China"the "Projects of Investigations of Post Graduate School, University of Science and Technology Beijing".
文摘The problem of momentum and heat transfer in a compressible boundary layerbehind a thin expansion wave was solved by the application of the similarity transformation and theshooting technique. Utilizing the analytical expression of a two-point boundary value problem formomentum transfer, the energy boundary layer solution was represented as a function of thedimensionless velocity, and as the parameters of the Prandtl number, the velocity ratio, and thetemperature ratio.
基金support of the Australian Research Council Discovery program
文摘Large momentum transfer( LM T) beamsplitting in atom interferometry is review ed,focusing on the use of Bloch Oscillations to achieve high momentum separation w ithout loss of visibility. Phase sensitivity w ith a fringe visibility of 7% is observed in a horizontally guided,acceleration-sensitive atom interferometer w ith a momentum separation of 80k betw een its arms.In addition,a 510 k beamsplitter is demonstrated.
文摘N^(3+)离子与基态He原子碰撞过程在天体物理、星际空间和实验室等离子体环境中具有重要研究意义.本文采用从头算的多参考单双激发组态相互作用方法精确计算了[NHe]^(3+)碰撞体系的分子结构参数,包括势能曲线和耦合矩阵元等.基于计算得到的结构参数,采用全量子分子轨道强耦合方法开展了低能N^(3+)离子与He原子碰撞电荷转移过程研究,获得了能量在3.16×10^(–3)e V—24 ke V(即2.25×10^(–4)e V/u—1.73 ke V/u)范围内的总单电荷、双电荷转移截面和态选择截面.在计算中考虑了电荷平动因子、高角动量态对碰撞过程的影响,发现高角动量态对电荷转移截面具有显著影响.与现有实验和理论结果相比,当前计算的单电荷和双电荷转移截面与实验测量值更为接近.相较于Liu等(2011 Phys.Rev.A 84042706)未考虑高角动量态的研究,当碰撞能量大于10 e V/u时,其总单电荷转移截面约高出当前计算值2—3倍,表明高角动量态对电荷转移过程具有显著影响.同时研究表明单电荷转移截面远大于双电荷转移截面,在碰撞电荷转移过程中占据主导地位.
