Home – Home – Jornals – Avtometriya 2025 number 3

A new approach to constructing optimal algorithms for localization of point signal sources that detect themselves by generating ultra-short pulses at random time instants is presented. The approach is based on the application of the iterative method of back-recursion to this class of problems. An analytically exact solution of the problem is found for the case where a priori probability density of the source sought is given by a piecewise constant function of arbitrary complexity. The whole process associated with the construction of an optimal search algorithm minimizing the mathematical expectation of the total localization time of the pulsed point source sought is fully formalized and implemented as an autonomous software block.

The problem of tracking an object equipped with a marker with spatio-temporal modulation of the emitted signal is considered. Spatio-temporal modulation is provided by both the radiation of a marker with two stationary radiators and a marker with one rotating radiator. The formal synthesis of observation algorithms is based on the use of an approximate solution of the generalized Stratonovich equation, which differs from the traditional representations of this equation by taking into account the dependence of the observation function not only on time, but also on an arbitrary number of other independent variables that allow, for example, the shape of the observed object to be taken into account. The synthesized algorithm for tracking an object with a marker having a rotating emitter actually determines the structure of a multiconnected closed tracking system using a TV sensor for the object coordinates, as well as the initial phase, frequency, and radius of rotation of the marker emitter. The correctness of the synthesis results is confirmed by simulation modeling. The synthesized algorithm provides increased noise immunity of the tracking process in the presence of several stationary interfering radiators falling into the field of view of the TV sensor.

A method is proposed for decomposing the range of values of two-dimensional spectral features according to the values of their constituent correlation coefficients. The basis of the technique is the analysis of the product of the normalized values of spectral features. The peculiarity of the indicator used and the thresholds entered by the user for its values make it possible to decompose the initial statistical data and map the results obtained. Unlike traditional methods, the proposed approach has higher computational efficiency, which is necessary when processing large amounts of statistical data. The results of the application of the technique in processing of remote sensing data of a natural object are considered.

A method of modeling random sequences composed of digital samples of stationary random processes with a given power spectral density (PSD) in systems with digital signal processing (DSP) is proposed. The method takes into account the limitation of the signal spectrum by the input devices of DSP systems and the peculiarities of the transfer function representation using the fast Fourier transform. Digital white noise with the Gaussian or uniform distribution is taken as an initial process for modeling. It is shown that the PSD estimation of the sequences obtained as a result of modeling is unbiased, and its mean value coincides with the samples of the initial PSD. An expression for calculating the RMS error of the estimation is derived.

Two problems can be identified in biomagnetic (magnetocardiographic) studies: firstly, the difficulty of comparing the results of different experimenters due to the lack of a standard for equipment requirements (the research process is still underway), and second, there is no clearly defined processing technique, in particular, determining the location of a "false" (for example, post-infarction) dipole masked by the main current dipole (ECD-equivalent current dipole) of the heart. The paper considers the issues of inference and analysis of the transformation of the results of biomagnetic studies obtained on one structure of the input superconducting converter into another based on spatial-frequency transformations. This method works like an electronic magnifying glass.

The article considers the creation of a control system for the lateral motion of an aircraft based on an approach similar to the control of the total energy in a longitudinal channel. The structure of the control system is presented. It includes an aircraft-independent core and blocks for transition rudder and ailerons deflection commands. These blocks are based on the principle of inverse dynamics. An approach to creating a control system is proposed. Simulation modeling of the behavior of three aircraft with different aerodynamic configurations is carried out. The control quality is studied using a numerical modeling method.

The article considers methods for solving problems of geophysical monitoring of the environment in relation to powerful pulsed sources - quarry explosions, rocket remnants falling on to the ground of during satellite launches, meteorite fragments, etc. The general idea of the study is formulated as solving an inverse problem of restoring the source parameters based on its seismic and acoustic waves. Numerical modeling and experimental studies of the proposed methods for assessing the accuracy of spatial localization of sources are carried out on an example of using calibration spatially distributed explosions.

Optical-acoustic transducers (OAPs) can be used in all applications of applied optics, where precision measurements of the electromagnetic radiation power are required. They belong to thermal volumetric receivers of the "full spectrum" have a constant spectral sensitivity in a very wide range (0.3-10000 microns), and allow measuring both constant fluxes of electromagnetic radiation with a power of 10^-11 W with a dynamic range of 80 dB, and femtosecond terawatt laser pulses. The metrological parameters of OAPs are mainly determined by the design of the sensing elements performing the acoustic-mechanical transformation. The methods of increasing the sensitivity of the classical membrane sensing elements through the use of new materials, optimization of geometry, corrugation and edge perforation, as well as the use of cantilevers as new highly sensitive elements of pressure sensors are analyzed. The limiting capabilities of both classical and new methods of precision measurements of the deformation of a sensitive element of an OAP caused by the pressure of an expanding gas are presented.

The properties of optical phonons in InSb nanocrystals synthesized at the Si/SiO₂ interface of a silicon-on-insulator (SOI) structure are studied. The formation of InSb nanocrystals occurs as a result of diffusion of In and Sb atoms from implanted SiO₂ and Si regions to the bonding interface of the SOI structure at annealing temperatures of 1000 and 1100 °C for 0.5-5 hours. The Raman spectra are excited by laser radiation with a wavelength λ_ex = 514.5 nm at room temperature. The Raman scattering bands are observed in the spectra of the annealed structures whose position corresponds to the TO and LO modes in InSb. The effect of the high-frequency shift of the TO and LO modes in InSb nanocrystals is found, which reveals an inverse dependence on the annealing time as the temperature increases. The nature of the observed effect is related to deformations in nanocrystals. Non-hydrostatic deformations are present in nanocrystals formed after annealing at a temperature of 1000 °C. After annealing at a temperature of 1100 °C, deformations are present only at the initial stages of growth and are close to hydrostatic ones.

This study evaluates the laser time-of-flight method for measuring droplet velocities and sizes across a wide range of pressure characteristics of pneumatic nozzles. Determination of droplet sizes is based on high-velocity registration of the delay of scattering orders when the droplet crosses the laser beam. Determination of droplet sizes and velocities is based on high-speed registration of the delay of scattering orders when the droplet crosses the laser beams cross section. Two nozzles are examined as examples: one with coaxial liquid supply and the other with the liquid supplied at an angle to the air stream. A distinctive feature of these nozzles is the requirement for a high air stream pressure relative to the sprayed liquid pressure. The aim of the research is to determine the limitations of the droplet size and velocity ranges detectable by the instrument under conditions of low air pressure, where the spray quality is suboptimal due to the presence of both low-inertia small droplets and high-inertia large droplets, as well as significant jetting. It is found that the AOM-Systems instrument is capable of simultaneously detecting spherical droplets in the size range of 5 to 200 µm with velocities ranging from 2 to 120 m/s. The greatest dispersion in droplet sizes and velocities is observed when the liquid is supplied at an angle to the air stream. The jet structure of the plume generated by the nozzles is detected by means of contre-jour visualization.

The effect of post-exposure heat treatment on the change in the spectral and diffraction characteristics of photopolymer reflection holograms with different initial thicknesses of 8-10 μm and 20-25 μm is studied in two different cases of post-processing: immediately after completion of their recording, and after photopolymer hardening (tanning) by means of UV exposure. It is revealed that long-term heat treatment at 50 °C of unhardened holograms with a thickness of 10 μm leads to an increase in the modulation scale of the refractive index from 0.014 to 0.022. A significant shift of the spectral response to the short-wave region and expansion of its contour are established for untanned holograms, which may be due to photopolymer shrinkage and distortion of the spatial structure of the holographic grating. After the tanning procedure, heat treatment does not induce any significant changes in the spectral and diffraction characteristics of holograms, regardless of their thickness. Heating/cooling of 25-μm thick holograms, mainly at 50-5°C, leads to a bathochromic/hypsochromic stage of the spectral response of the hologram, controlled in real time, while there are no such spectral shifts for a hologram with a thickness of 8 μm, which creates prerequisites for the formation of athermolyzed holographic optical elements insensitive to temperature changes.