In this paper, we study the dynamic behavior and quasi-energy spectrum of multiband superlattice Bloch electrons in quantum kicked potential. We show analytically and numerically the avoided crossing and band suppress...In this paper, we study the dynamic behavior and quasi-energy spectrum of multiband superlattice Bloch electrons in quantum kicked potential. We show analytically and numerically the avoided crossing and band suppression about the quasi-energy spectrum, the dynamic nonlocalization, and the electron oscillation behavior between two bands.展开更多
By taking into account spatial degrees of freedom of atoms, we study the internal-state disentanglement dynamics of two atoms interacting with a vacuum multi-mode noise field. We show that the complete internal-state ...By taking into account spatial degrees of freedom of atoms, we study the internal-state disentanglement dynamics of two atoms interacting with a vacuum multi-mode noise field. We show that the complete internal-state disentanglement of the two atoms, caused due to the atomic spontaneous emission can be achieved in a finite time.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
The paper presents an energy iterative method to determine the second critical velocity by comparing the time histories of the kinetic energy and the buckling deformation based on the finite element model of the impac...The paper presents an energy iterative method to determine the second critical velocity by comparing the time histories of the kinetic energy and the buckling deformation based on the finite element model of the impact system. To design anti-impact structures of the thin-wall cylindrical tubes with this new method, the cost of the experiment can be considerably reduced. The feasibility and validity of this method are demonstrated by a dropping hammer experiment. In addition, this paper deals with the influence of constrained damping layers on the anti-impact capability and energy-absorption of thin-wall cylindrical tubes. Results show that the constrained damping layers make the energy-absorption and the anti-impact capability increased comparing with the naked tubes; the thickness of the damping layer should be restricted in a range, or else the anti-impact capability will decrease with the increase of the damping layer thickness; for the constrained layer, the anti-impact capability will increase with the augment of its thickness.展开更多
For civil structures founded on shallow foundations, the ground underneath the foundation often holds the greatest risks of the total structure. This can be due to of a very soft soil layer, an inhomogeneous subsurfac...For civil structures founded on shallow foundations, the ground underneath the foundation often holds the greatest risks of the total structure. This can be due to of a very soft soil layer, an inhomogeneous subsurface or a hidden dangerous object. It would be most favorable when a cheap and quick kind of seismic ＂tap-and-listen＂ technique can be used to detect those risks. The problem is however that an applied pulse or blast always creates a combination of compression-, shear- and surface-waves. These types of waves have different wave velocities and will return therefore at different time intervals. For a shallow subsurface technique, all these waves will overlap, which makes the interpretation very hard. Both the single pulse technique and the single-frequency, multiple wave technique （constant vibration） have been studied, but both techniques have their limitations. It can be concluded from finite element calculations that it will be difficult or even impossible to design good seismic techniques for surveying the underground of shallow foundations for hidden shallow potholes, etc.. The main reason is that the relative amount still present original wave. objects like water pipelines, undetonated bombs, dead bodies, coffins, of reflected energy is simply too low in comparison to the energy of the展开更多
文摘In this paper, we study the dynamic behavior and quasi-energy spectrum of multiband superlattice Bloch electrons in quantum kicked potential. We show analytically and numerically the avoided crossing and band suppression about the quasi-energy spectrum, the dynamic nonlocalization, and the electron oscillation behavior between two bands.
基金Supported by Foundation of the Education Department of Liaoning Province under Grant No.20060160the Natural Science Foundation of Zhejiang Province under Grant No.Y6100098+1 种基金the National Natural Scinece Foundation of China under Grant No.11074062the funding support from Hangzhou Normal University
文摘By taking into account spatial degrees of freedom of atoms, we study the internal-state disentanglement dynamics of two atoms interacting with a vacuum multi-mode noise field. We show that the complete internal-state disentanglement of the two atoms, caused due to the atomic spontaneous emission can be achieved in a finite time.
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The paper presents an energy iterative method to determine the second critical velocity by comparing the time histories of the kinetic energy and the buckling deformation based on the finite element model of the impact system. To design anti-impact structures of the thin-wall cylindrical tubes with this new method, the cost of the experiment can be considerably reduced. The feasibility and validity of this method are demonstrated by a dropping hammer experiment. In addition, this paper deals with the influence of constrained damping layers on the anti-impact capability and energy-absorption of thin-wall cylindrical tubes. Results show that the constrained damping layers make the energy-absorption and the anti-impact capability increased comparing with the naked tubes; the thickness of the damping layer should be restricted in a range, or else the anti-impact capability will decrease with the increase of the damping layer thickness; for the constrained layer, the anti-impact capability will increase with the augment of its thickness.
文摘For civil structures founded on shallow foundations, the ground underneath the foundation often holds the greatest risks of the total structure. This can be due to of a very soft soil layer, an inhomogeneous subsurface or a hidden dangerous object. It would be most favorable when a cheap and quick kind of seismic ＂tap-and-listen＂ technique can be used to detect those risks. The problem is however that an applied pulse or blast always creates a combination of compression-, shear- and surface-waves. These types of waves have different wave velocities and will return therefore at different time intervals. For a shallow subsurface technique, all these waves will overlap, which makes the interpretation very hard. Both the single pulse technique and the single-frequency, multiple wave technique （constant vibration） have been studied, but both techniques have their limitations. It can be concluded from finite element calculations that it will be difficult or even impossible to design good seismic techniques for surveying the underground of shallow foundations for hidden shallow potholes, etc.. The main reason is that the relative amount still present original wave. objects like water pipelines, undetonated bombs, dead bodies, coffins, of reflected energy is simply too low in comparison to the energy of the
