Том 70, № 9 (2025)

Based on the previously developed method for identifying narrow-spectrum wave events, a threshold discrimination criterion for internal gravity waves (IGWs) has been established and substantiated upon fulfillment of which the analyzed fluctuations can be considered as wave manifestations. This method is universal in the sense that it can be used to analyze specified vertical profiles obtained by any methods both in the Earth’s atmosphere and in the atmosphere of other planets. Application of the developed method to temperature profiles reconstructed from radio occultation measurements of the Magellan satellite gave us the opportunity to identify narrow-spectrum wave events in the Venus’s atmosphere and to determine key IGW characteristics, such as: intrinsic frequency, amplitudes of vertical and horizontal disturbances of wind speed, vertical and horizontal wavelengths, intrinsic vertical and horizontal phase velocities, and others.

Based on the Markov theory of estimation of random processes by the method of reassignment of values of continuous parameters, analytical expressions are obtained for the variance of the quasi-optimal conditional error of phase estimation and for the probability of erroneous reception of a discrete parameter of the received signal. The problem is solved with respect to noise-like signals and, in particular, BOC signals intended for use in global navigation satellite systems such as GPS (USA), Galileo (European Union), GLONASS (Russia) and BeiDou (China). The results of calculating the characteristics of accuracy and noise immunity of these parameters, obtained using the application software package, are presented. The corresponding graphs are constructed.

It is shown that spin-injection terahertz (THz) radiation can be excited at almost any angle of mismatch between the magnetization vectors of the magnetic transition layers. The main characteristics of the magnetic layers influencing the process of THz radiation excitation are determined. Experimental results are presented that prove the non-thermal nature of the radiation produced in a spin-injection radiator with unidirectional orientation of the magnetization vectors of the magnetic transition layers.

The morphology and structure of thin films were studied during the deposition of Au+Ge on the GaAs surface by thermal evaporation in a vacuum in order to create metal-semiconductor contacts with a reduced barrier height. It was found that the addition of germanium to the evaporated sample ensures the formation of a layer, doped with donors and prevents the transformation of GaAs into a hexagonal structure.

A comprehensive approach to processing the responses of Lamb acoustic waves propagating in piezoelectric plates with a liquid coating has been developed, which allows for the differentiation of liquids with similar chemical composition and electrical conductivity. The technique is based on the registration of the amplitudes of zero-order and higher-order Lamb modes in a multi-channel sensor system and the application of polar histogram visualization and principal component analysis (PCA) methods to process the measured data arrays. The technique was tested using 33 acoustic modes for 8 samples of mineral water collected from various sources in the North Caucasus. It was found that even when the compositions are similar, the analyzed liquids exhibit differences in their histograms that are more than an order of magnitude. Changes in the responses were observed during the storage of the samples, indicating the “aging” of the substance. A comparative analysis of the results obtained using polar histograms and the standard PCA classification method was performed. The obtained results are of interest for the development of sensors that do not require sensitive coatings, as well as for integration with machine learning algorithms when working with other types of sensor data.

The effect of Bragg diffraction occurring in the tangential geometry of the acousto-optic (AO) interaction on the speckle structure of the zero and first diffraction orders is investigated. It is established that in the first order, the fine-grained background of the speckle structure is significantly suppressed in comparison with the zero-order structure. Experiments have been performed on filtering speckle-containing optical radiation with a wavelength of 0.63 microns using an AO cell from TeO₂ operating in tangential diffraction geometry at a sound frequency of 100 MHz. A decrease in the fine-grained background in the first order was revealed by ~7 times in comparison with the speckle structure of the zeros order of diffraction.