Linear <Emphasis Type="Italic">s</Emphasis>-polarized surface waves in a medium inhomogeneous in one dimension

Linear s-polarized surface waves can exist at the boundary between an isotropic homogeneous medium and a medium inhomogeneous in one dimension (1D-inhomogeneous medium). This is related to deformation of the spatial envelope of the electric and magnetic components of the surface wave propagating in the 1D-inhomogeneous medium (in particular, in a plane-stratified medium). Such linear s-polarized surface waves can appear only provided that the refractive index of the inhomogeneous medium increases with the distance from the interface.     

A front problem concerning the decomposition of gas hydrates in natural strata on exposure to high-frequency electromagnetic radiation

We consider a one-dimensional axial problem of gas filtration in front decomposition of gas hydrates in a porous medium on exposure to high-frequency electromagnetic radiation. Depending on the permeability of the medium, two basic regimes of the process are distinguished that differ in temperature distribution in the medium. The behavior of the hydrate decomposition front and of the pressure in this front depending on the absorption length of the medium is studied. The presence of an optimum regime for the most rapid decomposition of hydrate in a porous medium of prescribed dimensions is established. Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 71, No. 2, pp. 263–267, March–April, 1998.     

Feasibility evaluation of intracavity solid state laser cooling to cryogenic temperatures

The requirements for obtaining cryogenic temperatures (i.e. 150 K and below) by anti-Stokes fluorescence cooling are analysed for a dielectric cooling medium located inside the cavity of a diode-pumped solid state laser. The cooling efficiency is derived in terms of pump beam parameters, intracavity loss associated with the cooling medium, reabsorption and saturation effects in the gain medium, radiative and conductive heat load on the cooling medium, and finally bulk and surface heating effects. Using experimental data for a Yb³⁺:ZrF₄–BaF₂–LaF₃–AlF₃–NaF [ZBLAN] cooling medium and a Yb³⁺:KY(WO4)₂ [KYW] gain medium, the conditions for optimum cooling efficiency are obtained. Based on realistic materials properties, the analysis shows that it is feasible to obtain a cooling efficiency (i.e. cooling power per input diode pump power) of approximately 0.1% at an operating temperature of 150 K, with a heat lift up to 30 mW.     

Occurrence of bacteria in industrial fluid power systems

Water hydraulic systems use water as a pressure medium to minimize the adverse environmental impacts of oil-using hydraulics. Microbial growth in the systems may restrict the applicability of this technology. In this work, occurrence of bacteria in three different full-scale water hydraulic applications operating in different industries was studied. Bacteria were found from different parts of diesel engine direct water injection (DWI) systems in the range of 1.8×10⁵–1.0×10⁷ cells/ml. Filters designed for removal of mechanical particles released bacteria and particles into the pressure medium indicating that a more frequent change of filters was needed or better filters for microbial control should be developed. The microbiological quality of the pressure medium in the DWI systems did not significantly change during the hydraulic circuit indicating suitability for long-term operation. The DWI studies showed that tap water quality is sufficient to ensure the long-term operation of full-scale water hydraulic applications. The microbiological quality of the pressure medium in a nuclear power plant remained stable (1.4–2.1×10⁵ cells/ml) over long-term operation. The results confirmed that water hydraulics, with demineralized water as a pressure medium, can be used in such demanding applications as nuclear power plants. In the pressure medium of the hydraulic system of a wood processing plant, microbial growth resulted in malfunction. Bacteria should be controlled by a better quality pressure medium rather than the use of a biocide. Electronic Publication     

Time evolution of few-cycle pulse in a dense V-type three-level medium

Propagation of a few-cycle laser pulse in a dense V-type three-level atomic medium is investigated by the numerical solution of the full Maxwell–Bloch equations without the rotating wave and slowly varying envelope approximations, and the numerical solution is obtained by using the predictor–corrector method and the finite-difference time-domain method. It is shown that, due to the strength of the electric field induced by the macroscopic polarization in a dense medium being stronger than that in a dilute medium and the influence of the near dipole–dipole (NDD) interaction, the time evolution of a few-cycle pulse in the dense medium is remarkably different from that in the corresponding dilute medium. In the dilute medium, oscillation arises at the trailing edge of the pulse; while in the dense medium, it appears at both the leading and trailing edges of the pulse; moreover, the oscillation at the leading edge is more obvious with the pulse area decreasing. The carrier-envelope phase has an obvious difference in the two cases with and without NDD interaction. The ratio, γ, of the transition dipole moments has strong influence on the time evolution and split of the pulse. In the dense medium, when?γ?= 1, NDD interaction delays propagation and split of the pulse; while when?γ?> 1, NDD interaction accelerates propagation and split of the pulse, moreover, the phenomenon is more obvious with the input pulse area decreasing. In the dilute medium, the larger area pulse doesn't split when?γ?= 1 while it splits when?γ?> 1.     

On wave propagation in laminated composites—I. propagation parallel to the laminates

The problem of elastic wave propagation in a laminated medium is considered. Using asymptotic expansions in terms of a small parameter given by the ratio of wave velocities of the two constituents a continuum model is deduced in which microstructure effects appear as a consequence of “non-locality” in time of the laminated medium. This is manifested by a history-dependence of the current state of the medium, which results in a system of integro-differential equations. The laminated medium is found to be highly dissipative. The asymptotic behavior of this system is then examined and two differential systems are obtained for the early and late phases of the motion. It is found that the entire dynamic behavior of a laminated medium consists of two distinct phases of motion which are described as follows. During an early phase, the motion is confined to an O(l) boundary-layer where l is a typical macro-scale, and is characterized by damped waves. During this phase of the motion an applied pulse undergoes substantial attenuation. At a later phase and beyond this layer, the behavior is predominantly that of a macroscopically homogeneous medium, where the attenuated pulse emerging from the boundary-layer propagates essentially without distortion. As a result, it is concluded that the early phase boundary-layer motion constitutes the crucial phase of motion in a laminated medium, whereas the later phase is of no practical consequence inasmuch as pulse attenuation is essentially completed during the early phase. Thus, current efforts aimed at a continuum characterization of the later phase motion appear entirely unwarranted.     

Unit-impulse response matrix of unbounded medium by finite-element based forecasting

In this novel forecasting algorithm to calculate the unit-impulse response matrix of an unbounded medium to analyse dynamic medium-structure interaction in the time domain based on the substructure method, a finite-element region adjacent to the structure–medium interface consisting of two or three rows only is introduced. Its exterior boundary is chosen to be similar to the interior boundary which coincides with the structure–medium interface. At similar boundaries of the unbounded medium the unit-impulse response matrices are a function of the dimensionless time. The unit-impulse response matrix at the exterior boundary can be forecasted from that at the interior boundary via this dimensionless time by taking advantage of the time delay of waves propagating between these two boundaries. The forecasting algorithm based solely on the finite-element method is exact in the finite-element sense in modelling the unbounded medium.     

On thermal waves in random nonsimple relaxing medium

In this paper, a study has been made of the nature of thermal waves in a random nonsimple medium exhibiting thermal relaxation properties, using the model of Chen. Gurtin and Williams for nonsimple medium and Lord-Shulman's theory for thermal relaxation in time. The method of perturbation for random medium developed by Karal and Keller has been utilised to determine the equation satisfied by the mean temperature. The results have been applied to the particular problem of penetration of temperature waves in a semi-infinite medium.     

On the J-integral in periodically layered composites

When a heterogeneous elastic material is represented by an effective homogeneous elastic solid, average stress and strain fields are used. The meaning of the J-integral in the effective homogeneous solid is investigated. A periodically layered medium is considered. The relation between the J-integrals in the original layered medium and the effective medium is derived.     

Analysis of dark spot formation in absorbing liquid media

Abstract

A theoretical analysis based on coupled field-matter equations is given to describe the recently observed phenomenon of a central dark spot formation of a Gaussian beam transmitted through an absorbing defocusing liquid medium. We find that such a pattern formation, which is accompanied by normal defocusing rings in the far field, originates from interplay between the wave-front curvature of the Gaussian beam and strong spatial self-phase medulation arising from thermally induced refractive index change in the medium. Results of numerical analysis for a thin medium are shown to be in a good quantitative agreement with our experimental findings. Further, the dark spot formation is also predicted by using a focused Gaussian beam and self-focusing medium.     

Mass transfer in aggregated porous media with nonlinear compressibility

The problem of the squeezing out of a solution from aggregates in a porous medium has been considered and investigated. A specific feature of the problem lies in taking account of the existence of two compaction zones in deforming aggregates of a porous medium. Features essential to mass transfer in a deformable aggregated porous medium have been determined and analyzed. Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 81, No. 4, pp. 646–651, July–August, 2008.     

Using a quantum-chemical approach for the investigation of corrosion on surfaces of metals and alloys

We analyze results of using quantum chemistry methods for simulating and calculating the interaction of surfaces of metals and alloys with a corrosive medium in the cluster approximation. Models of corrosion dissolution of brass and intermetallics of an aluminum alloy are constructed, and energy characteristics of the interaction of components of a chloride-containing medium with their surfaces are determined. We determine energy barriers of ionization of clusters of the components of brass and the CuAl₂ intermetallic in a medium, which enables us to propose the mechanism of their fracture. A model of the contact interaction of dissimilar metals Al–Fe, Al–Cr, Cu–Al, and Cu–Fe in the presence of particles of the corrosive medium is considered, the values of the adhesion energy of the corresponding clusters of dissimilar metals is computed, and its dependence on the composition of the medium is found. The prospects and efficiency of the quantum chemistry methods for the study of corrosion fracture of metals and alloys are shown.     

Wave four-vectors for the electromagnetic waves in relatively moving dielectric media

Abstract

The wave four-vectors are deduced for the general case where the reflection and transmission of a plane electromagnetic wave are at the interface between a stationary dielectric medium and a dielectric medium moving with an arbitrary velocity. It is demonstrated that the frequency shift in the reflected wave not only depends on the velocity v of the moving medium but also markedly depends on the refractive index n ₁ of the incident medium; the frequency shift in the transmitted wave varies with n ₁ and the refractive index n ₂ of the moving medium, as well as on v Total reflection not only occurs when n ₁ > n ₂ but also may occur when n ₁ ≤ n ₂ if 0 < v/c < 1. The law of reflection, the Snell law and the equivalent refractive index of the moving medium are discussed according to the wave four-vectors as well.     

Flow structure of the active medium of a HF laser with a radially expanding nozzle unit

Measurements have been made of gasdynamic characteristics of the flow of the active medium as well as energy and spectral characteristics of radiation generated by a continuous chemical HF laser with a radially expanding nozzle unit. Based on the analysis of measurement results, the flow structure of the active medium has been determined, which is formed by the “nozzle–injector” reactant mixing scheme. It has been shown that only a part of the active medium is involved in the radiation generation. Measures for improving the efficiency of its use have been proposed.     

Influence of Kerr-like medium on the dynamics of a two-mode Raman coupled model

Abstract

We study the quantum dynamics of an effective two-level atom interacting with two modes via Raman process inside an ideal cavity in the presence of Kerr non-linearity. The cavity modes interact both with the atom as well as the Kerr-like medium. The unitary transformation method presented here, not only solves the time-dependent problem, but also provides the eigensolutions of the interacting Hamiltonian at the same time. We study the atomic-population dynamics and the dynamics of the photon statistics in the two cavity modes. The influence of the Kerr-like medium on the statistics of the field is explored and it is observed that Kerr medium introduces antibunching in mode 1 and this effect is enhanced by a stronger interaction with the non-linear medium. In the high non-linear coupling regime anticorrelated beam become correlated. Kerr medium also introduces non-classical correlation between the two modes.     

Green's functions for composite media

A method is given on construction of Green's functions for finding field excited by a point (or line) source in a layered composite medium. The concept of Green's function for a composite medium as a whole is introduced in a rigorous manner by showing that it possesses all properties of the Green's function for an uniform medium. The appropriate Green's function for the whole composite medium is constructed through two solutions of the corresponding homogeneous equation over the whole multiregion. The method enables one to write down, directly, the explicit expression for the field in an arbitrary region produced by a point (or line) source located in another arbitrary region without resort to images, Fourier-Bessel integrals, integral transforms of quasi-orthogonal functions. It is an extension of the existing method, which constructs the Green's functions for uniform media through the generalized Fourier expansions and two solutions of the corresponding homogeneous equations, to cases heretofore beyond its scope.     

Thermal deformation of the active medium in a solid-state laser with natural cooling

An analytical expression is derived for the transient thermal deformation of the active medium in a periodic duty laser with natural cooling.Notation W thermooptical constant of the active medium - n refractive index of the active medium - k thermal expansivity of the active medium - thermal conductivity of the active medium - a thermal diffusivity of the active medium - L length of the active medium - 2R diameter of the active medium - H distance from axis of the pump lamp to the axis of the active medium - _i=t_i – t_a excess temperature - t_i temperature of the i-th element - t_a ambient temperature - P_i power of heat generation within the i-th element - C_i total thermal capacity of the i-th element - P_ij thermal flux from body i to body j (i, j=1, 2, 3) - _ij thermal conductance between body i and body j (i, j=1, 2, 3) - _ij heat-transfer coefficient from body i to body j (i, j=1, 2, 3) - P average pump power - time - 1 pump lamp - 2 active medium - 3 luminaire envelope Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 42, No. 1, pp. 85–91, January, 1982.     

Intensity noise reduction of twin beams by a passive semiconductor medium

Abstract

A passive optical system is proposed to explore the intensity quantum correlation of two twin beams to reduce the photon noise of one of them. It consists of using a semiconductor medium inside an optical cavity, which behaves as a nonlinear medium presenting a crossed Kerr effect. The intensity fluctuations of one beam modify the resonance condition of the cavity for the other beam and therefore its intensity. The medium is described microscopically within the two-level atom model. It is shown that, under typical experimental conditions, this system may produce noise reduction.     

Bactericide glasses developed by Na+/Ag+ ionic exchange

The action of bacteria and fungi in residential, industrial and hospital environments offers high risk to human health. In this context, the development and use of antimicrobial materials has been an efficient method of handling risk situations. This work presents preliminary results of powdered glass showing bactericide effect obtained by ionic exchange between sodium ions, present in the glass composition, and silver ions, present in the ionic exchange medium. Powdered glass was submitted to ionic exchange in an ionic medium containing different concentrations of silver species. The bactericide effect was dependent on AgNO₃ concentration in the ionic medium. The Agar Diffusion Test on Escherichia coli bacteria, EDS and ICP-MS analyses were applied to the samples; the results showed that a critical concentration of silver ions incorporated into the powdered glass occurred and a limit to the bactericide effect. Tests and analyses revealed that 6 wt.% of AgNO₃ in the ionic medium was the critical concentration.     

Preparation of RuO2-silica gel composite microspheres from silicon ethoxide complex dispersion

A suspension polymerization method was modified for producing composite microspheres of silica gel or silica glass coated by a layer of fine RuO₂ particles. Pre-hydrolysed silicon tetraethoxide (TEOS) was dispersed into a mixed medium comprising cyclohexane and cyclohexanol or cyclohexane and cyclohexanone with pre-dispersed RuO₂ powders. The rate of gelation of TEOS sensitively increased with increasing content of alcohol or ketone in the dispersing medium. Faster gelation brought about smaller composite particles. Better dispersion of RuO₂ in cyclohexanone containing medium resulted in the better coating of RuO₂.