Wave propagation and resonance phenomena in inhomogeneous media

The waveguide and resonance properties of inhomogeneous penetrable one–dimensional–periodical structures that consist of two different media are studied within the framework of a one–dimensional approximation. The pass and stop bands are determined. A dispersion relation for all the waveguide modes is obtained. Explicit expressions for low waveguide frequencies and corresponding phase velocities of waveguide modes for mono– and polydisperse media are found. The influence of the polydispersity of the sizes of heterogeneities on the low frequencies of a pass band is considered. A pass band in the range of low frequencies is detected. It is shown that the polydispersity does not affect the waveguide properties of a medium at low frequencies of the first pass band. The resonance phenomena in periodical media and structures are investigated. The resonance phenomena are shown to occur for an unlimited discrete set of frequencies if the group velocity of the waveguide mode for them is zero; in this case, the growth of the oscillation amplitude is localized in the neighborhood of a source (localization of the resonance). A synchrophasotron resonance at which the infinite chain of oscillation sources has the oscillations phase of a corresponding traveling wave from the pass band is detected.     

New X-Ray Techniques for Flow Visualization and Measurement of Hydrodynamic Flow Parameters in Opaque Heterogeneous Media

This paper proposes and validates a method for the quantitative analysis of multiphase flows and objects of complex composition with image registration on a charge-coupled-device array taking into account the X-ray spectral characteristics. The method was tested on objects of known composition and shape. New approaches are formulated to solve a number of research problems related to the use of modern registration techniques and computer-based tools for X-ray image processing. __________ Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 46, No. 6, pp. 159–170, November–December, 2005.     

Spherical striations in a glow discharge

The stratification of a volume glow discharge is observed experimentally. Spherically symmetric stationary striations are detected. Pis’ma Zh. éksp. Teor. Fiz. 66, No. 11, 679–682 (10 December 1997)     

Phase transitions in self-assembled monolayers of alkanethiols containing the polar group

Equilibrium states of the system of self-assembled monolayers (SAMs) of n-alkanethiol molecules HS(CH₂) _n−1(X) with polar group X chemiabsorbed on the Au(111) crystal surface are considered. The couplings between the atoms (C, H) of the n-alkanethiols are approximated by the Lennard-Jones potential. The couplings between the n-alkanethiols and the crystal surface are approximated by the 12-3 potential. The interactions of polar groups and the self-images with the metal substrate are taken into consideration. The phase-transition temperatures, the structural order and equilibrium tilt, and the twist and azimuthal angles of the macromolecules, which depend on the dipole moments, are found. Zh. éksp. Teor. Fiz. 114, 208–221 (July 1998) Published in English in the original Russian journal. Reproduced here with stylistic changes by the Translation Editor.     

Wakes in a Dust Plasma. Comparison of Numerical Methods

A self-consistent model for plasma polarization around an isolated dust particle with a size of 10^?6 m under the action of an external electric field is presented. It is shown that there are self-consistent potential oscillations for various intensities of the external electric fields behind the dust particle. The calculation results are compared with data obtained by using the known numerical approaches.     

Propagation of non-diffracting intense ultraviolet beams

Ultraviolet pulses of 200 ps duration are focused in vacuum, and launched into the atmosphere through an aerodynamic window. Instead of diffracting, above a threshold of 100 mJ, the beam propagates in a self-induced waveguide in air. The peak electric field and beam profile are consistent with the eigenfunction of a modified nonlinear Schrödinger equation. The evolution of the beam waist with distance is calculated by a combination of the nonlinear Schrödinger equation and an equation for the nonlinear losses.