Distribution of luminescence centers in the bulk of undoped,Fe-doped,and Cr-doped CVD ZnSe polycrystals studied by two-photon confocal microscopy

Edge and defective-impurity luminescence in polycrystalline CVD ZnSe has been studied in the range 0.46–0.73 μm by two-photon confocal microscopy. We have obtained luminescence intensity distribution maps for undoped, iron-doped, and chromium-doped ZnSe samples at depths of up to 1 mm with a spatial resolution of a few microns. It has been shown that crystal regions with low dopant concentrations contain centers that luminesce in the ranges 520–580 and >670 nm. The parts of the crystals with high iron and chromium concentrations contain centers that suppress the edge and defective-impurity (520–580 nm) luminescence. We discuss the nature of these centers and demonstrate the possibility of assessing the luminescence characteristics of grain boundaries in CVD ZnSe.     

A modified tank in series model for cogeneration of hydroxylamine and electricity in the nitric oxide/hydrogen fuel cell

This work presents a modified TSR model of the nitric oxide/hydrogen fuel cell operating in potentiostatic mode with the co-current flow direction. The developed model accounts for the component and the energy balances in gas channels, liquid catholyte and catalyst layers together with charge balances at electrode/electrolyte interfaces. The simulation results indicate the influence of catalyst selectivity and mass transfer on the distribution of concentration, temperature and current density.     

Influence of the microprojection geometry on the elastic contact of surfaces with regular microrelief

The influence of surface microprojections—their shape and additional harmonics—on the elastic contact of a flat surface and a surface with regular microrelief is considered on the basis of the elastic contact of a half-plane and an undulatory surface. It is shown that the contact-pressure curve depends on the surface gradient of the microprojection and the mutual influence of adjacent microprojections.     

Synthesis of composite coatings using rapid laser sintering of metallic powder mixtures

Presented here is a brief review of research of an authors’ collective dealing with laser treatment of materials, sintering metallic powders, and multiscale simulation. A theoretical analysis of the processes of structure formation upon the rapid laser synthesis of composite coatings has been performed. The experimentally obtained structural and phase characteristics of the sintered layers have been explained based on an analytical and numerical simulation of the dynamics of thermal fields in the zone of treatment, processes of melting, and subsequent solidification of porous materials. Upon rapid sintering and solidification, the effect of impurity trapping has been taken into account, which determines the chemical composition of the powders under nonequilibrium conditions of their formation. It has been shown that rapid laser treatment retains the composite structure of the powder layer due to the high rates of local heating/cooling and high rate of solidification comparable with the rate of diffusion of chemical components. The results obtained are applicable in the development of a wide class of functional-gradient composite materials.     

GaAs structures with a gate dielectric based on aluminum-oxide layers

Different types of dielectrics obtained by low-temperature electron-beam sputtering are studied; these dielectrics include Al₂O₃ layers and Al₂O₃/SiO₂/Al₂O₃ three-layer compositions. The dependence of the electrical strength of Al₂O₃ layers on their thickness is determined. It is established that formation of the three-layer dielectric Al₂O₃/SiO₂/Al₂O₃ makes it possible to increase the range of operating voltages up to 60 V for structures with a gate electrode. It is shown that it is possible to control the density of charge carriers (holes) in the two-dimensional conduction channel of GaAs structures by changing the gate voltage when the Al₂O₃/SiO₂/Al₂O₃ structure is used as a gate dielectric.     

Relation of the genetic and technological parameters adopted in classification to the structural parameters of the coal’s organic mass

Statistical analysis of a representative database reveals the relation of the vitrinite reflection coefficient, the yield of volatiles, and the heat of combustion of solid fuels to the structural parameters of the organic component. This relationship is of great practical interest.     

Rejector and coupling filters in planar realization

In this paper it is considered possibilities of rejectors development and improvement of filter with ring resonator, based on planar waveguide with principal TEM mode. Experimental results and computer simulation of mentioned structures results are given.     

On the string averaging method for sparse common fixed-point problems

We study the common fixed-point problem for the class of directed operators. This class is important because many commonly used nonlinear operators in convex optimization belong to it. We propose a definition of sparseness of a family of operators and investigate a string-averaging algorithmic scheme that favorably handles the common fixed-point problem when the family of operators is sparse. The convex feasibility problem is treated as a special case and a new subgradient projections algorithmic scheme is obtained.