Karsyan A.Z.,Rostov State Transport University
Journal of Applied Mechanics and Technical Physics | Year: 2014
A steady problem of a slow axisymmetric flow of a viscous incompressible fluid around an oblate spheroid covered by a viscous film is solved analytically with the use of the Stokes approximation. Surface tension on the interface between the fluids is taken into account. Expressions for velocity components and stream functions are presented. A formula for determining the force action of the incoming flow onto the oblate spheroid is derived. © Pleiades Publishing, Ltd., 2014.
Demekhin P.V.,University of Heidelberg |
Demekhin P.V.,Rostov State Transport University |
Hochstuhl D.,Institute For Theoretische Physik Und Astrophysik |
Cederbaum L.S.,University of Heidelberg
Physical Review A - Atomic, Molecular, and Optical Physics | Year: 2013
The time-dependent Schrödinger equation for the hydrogen atom and its interaction with coherent intense high-frequency short laser pulses is solved numerically exactly by propagating single-electron wave packets. Thereby, the wave function is followed in space and time for times longer than the pulse duration. Results are explicitly shown for 3 and 10 fs pulses. Particular attention is paid to identifying the effect of dynamic interference of photoelectrons emitted with the same kinetic energy at different times in the rising and falling sides of the pulse as predicted by Demekhin and Cederbaum. In order to be able to see the dynamic interference pattern in the computed electron spectra, the photoelectron wave packet has to be propagated over long distances. Clearly, the complex absorption potentials often employed to compute the spectra of emitted particles cannot be used to detect dynamic interference. For the considered high-frequency pulses of 3 and 10 fs duration, this requires enormously large spatial grids. The photoionization and above-threshold ionization spectra presently computed are found to exhibit pronounced dynamic interference patterns. The patterns are in very good agreement with previously published results on the photoionization spectra, where available, which were computed using a completely different method, thus supporting the previously made assumption that the above-threshold ionization processes are very weak for the considered pulse intensities and high carrier frequency. The quiver motion in space and time of a free electron in strong laser pulses is also investigated numerically. Finally, a discussion is presented of how fast the atom is ionized by an intense pulse. © 2013 American Physical Society.
Pirogova N.D.,Rostov State Transport University
Radioelectronics and Communications Systems | Year: 2013
A simulation method for nonlinear inertial feedback systems has been proposed. It involves the presenting of each functional block of the system in the form of a set of nonlinear transfer functions. Nonlinear transfer functions of the system as a whole are determined by using the differential Taylor transformations. © 2013 Allerton Press, Inc.
Karsyan A.Z.,Rostov State Transport University
Journal of Applied Mechanics and Technical Physics | Year: 2013
An unsteady flow of a viscous incompressible fluid around a deformable spherical body is considered in the approximation of low Reynolds numbers with a predetermined flow velocity. The hydrodynamic impact of the flow incoming onto the body is determined with allowance for small radial displacements of the body surface. The effect of spherical body surface deformation on the magnitude of the incoming flow impact force is taken into account, in particular, the dependence of small radial displacements of the body surface on the time is found, which makes it possible to minimize the physical impact of the incident flow. © 2013 Pleiades Publishing, Ltd.
Bruhl S.,Bruhl Consulting |
Kochur A.G.,Rostov State Transport University
Journal of Physics B: Atomic, Molecular and Optical Physics | Year: 2012
The Monte Carlo technique is applied to simulate the processes of the cascade relaxation of gaseous boron at atomic density of 2.5×10 22m 3ionized by photons with the energies of 0.725 Ryd passing through a cylindrical interaction zone along its axis. The trajectories of electrons are simulated based on photoionization and electron-impact ionization cross sections calculated in the one-electron configuration-average PauliFock approximation. Numbers of electrons and photons leaving the interaction zone per one initial photoionization, their energy spectra, the energy transferred to the medium and the probabilities of final ion formations are shown to change noticeably as the incident photon energy is scanned through boron atom ionization thresholds. These variations can be explained only if secondary electron-impact-produced processes are considered. The density of secondary events decreases when going from the zone axis to its border, and the profiles of the density along the radial direction are found to be similar for all the initial exciting photon energies. © 2012 IOP Publishing Ltd.