Determination of Parameters of the Europium Ion Crystal Field by the Luminescence Spectra Obtained by Means of an Acousto-Optical Spectrometer

The parameters of the europium ion crystal field in dipic acid salts have been determined by their luminescence spectra. The sample preparation procedure and the luminescence-measuring technique using an original spectrometer based on an acousto-optical tunable filter have been described. It has been shown that the methods and equipment used permit reliable proximate analysis of the quality of compounds of this type.     

Elastic and photoelastic properties of KGd(WO4)2 single crystals

The elastic and photoelastic properties of a potassium-gadolinium tungstate KGd(WO₄)₂ crystal are determined. A complete matrix of elastic constants for the material is obtained for the first time and the velocity diagrams in the five most practically important planes are constructed on its basis. The coefficients of acoustooptic quality M ₂ are measured for the first time for the crystal in the case of isotropic diffraction for all basic configurations of acoustooptic interaction, which makes it possible to reveal the directions of the most effective interaction.     

Complex noise suppression using a sparse representation and 3D filtering of images

A novel method for the filtering of images corrupted by complex noise composed of randomly distributed impulses and additive Gaussian noise has been substantiated for the first time. The method consists of three main stages: the detection and filtering of pixels corrupted by impulsive noise, the subsequent image processing to suppress the additive noise based on 3D filtering and a sparse representation of signals in a basis of wavelets, and the concluding image processing procedure to clean the final image of the errors emerged at the previous stages. A physical interpretation of the filtering method under complex noise conditions is given. A filtering block diagram has been developed in accordance with the novel approach. Simulations of the novel image filtering method have shown an advantage of the proposed filtering scheme in terms of generally recognized criteria, such as the structural similarity index measure and the peak signal-to-noise ratio, and when visually comparing the filtered images.     

Analysis of nonstationary signals and fields with the use of enclosed semi-Markov processes

In this study, the possibility to describe the signals scattered by various physical objects such as underlying surfaces of land and sea, the segments of “clear sky,” and processes of various physical natures, such as fluctuations of the refractive index of the troposphere and electromagnetic and acoustic radiation of a lithospheric nature, by enclosed semi-Markov processes is investigated. This approach makes it possible to construct statistic models for a broad class of signals and processes. In some cases, statistics based on atomic functions and WA systems of the Kravchenko-Rvachev functions show the best results.