Home – Home – Jornals – Avtometriya 2017 number 1

A simplified method of plane trajectory calculation is proposed for solving the problem of planning the path defined by a sequence of turning points. The trajectory consists of oriented segments of straight lines joined by clothoids (Cornu spirals). The efficiency of the method is validated by means of numerical simulations in the MATLAB/Simulink environment.

Various aspects of mathematical modeling of the inclination parameter converter based on two double-axis accelerometers in a single integrated design are considered. Possible variants of design patterns of such a converter are presented. Additional turns of the accelerometer sensors mounted in the transducer body are considered. Generalized static mathematical models for two double-axis accelerometers as part of the inclination parameter converter are obtained, which ensure accurate determination of the spatial orientation angles of an object: zenith and sighting (apsidal) angles.

An automated system of acquisition of raw experimental data and a control system for operation modes of an experimental large-scale separation column are described. The influence of a new method of refluxing of structured packing on the separation column efficiency is studied. Based on the data obtained by the developed automated system, a 20-30 % increase in the efficiency of mixture separation on structured packing is expected.

A problem of control of quadcopters in a leader-follower group is considered. A method is proposed, which allows control actions for the follower robot to be formed only on the basis of information about the follower motion parameters and the relative positions of the leader and follower.

The efficiency of methods of the spectral-spatial classification of difficult-to-distinguish types of vegetation on the basis of hyperspectral data of remote sensing of the Earth, which take into account local neighborhoods of analyzed image pixels, is experimentally studied. Algorithms that involve spatial pre-processing of the raw data and post-processing of map charts of pixel-by-pixel spectral classification are considered. Results obtained both for a large-scale hyperspectral image and for its test fragment with different methods of learning sample formation are reported. The classification accuracy in all cases is estimated through comparisons of sub-satellite data and map charts of classes formed by using the compared methods. The reasons for the differences in these estimates are discussed.

This paper presents a method for determining the spatial coordinates of a moving radiation source on the basis of a two-position system from measurements of one bearing and relative energy measurements of the received signal taking into account the effect of its reflection from the Earth surface.пThe passive location problem is solved for low elevation angles taking into account the curvature of the Earth and using a polynomial model of source motion. An algorithm is developed for the parametric identification of this model based on a sample of measurements of increasing size in a regularized formulation, and the accuracy characteristics of the method are analyzed.

A method of optimal output-uniform coding for a set of sources consisting of a union of a countable number of source sets is proposed. It is shown that the coding for a union of finite-memory Markov sources is asymptotically optimal. It is established that the proposed coding is weakly universal for a set of stationary sources.

The phenomenon of four-wave mixing that occurs in passive optical networks with wavelength-division multiplexing of channels has been studied.пResults of modeling the distribution of combination frequencies over the spectrum depending on the number and frequency interval between the channels are given. To suppress crosstalk between the channels at combination frequencies, it is proposed to divide the range into two bands and select a guard interval between them. The effect of combination frequencies on the signal transmission quality is considered as a function of the power level in the channels, frequency interval, and transmission length.

This paper presents the results of experimental studies of the spectral properties of layered structures consisting of two volume reflective holographic gratings separated by an optically homogeneous layer. When such structures are exposed to polychromatic light, the interference interaction of the waves formed by these gratings leads to the formation of a plurality of narrow spectral passbands. The period of arrangement of the passbands is determined by the optical thickness of the intermediate layer, and their envelope coincides with the spectral selectivity contour of one grating. The existence of this type of spectra with local passbands arranged at a periodicity 2-8 Å (in different experiments) has been experimentally confirmed. A high-resolution Ramanor U1000 spectrometer and an optical Fabry-Perot interferometer were used. It is found that the irregularities in the internal structure of the holographic gratings due to the imperfection of the recording medium substantially distort the spectral characteristics of the studied structures in comparison with their simple theoretical models: the spectrum is asymmetric and the local bandwidth is significantly less than the estimated value. Similarity between experimental data and simulation results is achieved by selecting the parameters of said irregularities.

This paper presents the results of a computer simulation of the process of measuring the parameters of MIOL-Akkord type bifocal refractive-diffractive lenses in which the central area of the diffraction element is reduced and compensation of spherical aberrations of the eye is provided. The spatial-energy characteristics of an ideal diffractive lens is preliminarily calculated using existing formulas. The simulation of the process of controlling intraocular lens parameters showed that the intensity distribution along the optical axis does not characterize the diffraction efficiency, which is the total (integrated) intensity in the beam cross section at the focus.пIt is found that due to the coupling of diffraction orders, it is difficult to measure the absolute diffraction efficiency and it is better to evaluate only the relative efficiency.

The luminescent properties of gradient activated crystals of lithium niobate with the concentration profiles of the optical centers of ytterbium and erbium ions are studied. It is shown that the spectral-luminescent properties of the gradient crystal are correlated with the concentration profiles of the optical centers of Yb^{3 +} donors and Er³⁺ acceptors.

This paper shows that the near-surface layer of a lithium niobate single layer 15 μm in depth is essentially different from the rest of the volume of the material from the standpoint of composition, structure, and mechanical properties. The pointed out difference are due to the effect of cutting, polishing, and smoothing of the lithium niobate plates, which result in an increase in the density of point defects and dislocations. The increasing density of the structural defects leads to uncontrollable changes in the conditions of the formations of waveguides and the drifting of characteristics of integrated optical circuits. The results obtained are very important for the manufacture of lithium niobate based integrated optical circuits.

This paper describes the technological approach to the implementation of quasioptical high-pass subterahertz filters with the use of high-aspect pseudometallic structures. The approach is based on microstructuring of the solid polymer layer of polymethylmethacrylate by synchrotron X-ray lithography with subsequent metallization of the entire surface of the structure. This paper also presents the example of the manufactured sample and the operational characteristics of the high-pass filter with a cut-off frequency of 0.275 THz, whose thickness is 1 mm and which was formed by hexagonally packed open-end hexangular holes separated by partitions 70 μm. The electrodynamic analysis and design basics of high-pass structures are given too.

This paper describes the stochastic models of recombination of electrons and holes in inhomogeneous semiconductors in two-dimensional and three-dimensional cases, which were developed on the basis of discrete (cellular automation) and continuous (Monte Carlo method) approaches. The mathematical model of electron and hole recombination constructed on the basis of a system of spatially inhomogeneous nonlinear integro-differential Smoluchowski equations is described. The continuous algorithm of the Monte Carlo method and the discrete cellular automation algorithm used for the simulation of particle recombination in the semiconductors is described.