Home – Home – Jornals – Avtometriya 2021 number 6

The influence of the interferometer optical system characteristics on the distribution of spectral power density of partially coherent light passing through the system is investigated. The results of effective wavelength measurements for partially coherent light sources are presented. It is shown that the optical system transforms the spectra, which leads to a systematic error of interference measurements using the scattered light phase. With atomically smooth surfaces used as a reference mirror, the influence of this system on the phase distortion is investigated. The systematic error is found to be approximately 5 nm in terms of height owing to phase distortion. It is shown that the use of atomically smooth surfaces as a perfect measurement surface allows this error to be significantly reduced down to 0.12 nm. The results of measuring an echelon of atomic steps with a countable number of monoatomic layers on the silicon crystal surface are reported. The interatomic (interplane) distance in the crystal lattice of Si with orientation [111] is experimentally measured for the first time by low-coherence optical interferometry, and its value is found to be 3.145 0.003Å.

The unique variability of modern fiber and integrated optics and also the development of physics of complex nonlinear optical phenomena and nanophotonics have contributed to the development of qualitatively new approaches to the implementation and control of pulsed lasing in fiber lasers in the last decade. In this paper, we present a structured review and comparative analysis of current methods for static and dynamic control of the regimes and parameters of generation in mode-locked fiber lasers.

Modified holographic photopolymer materials developed at NIOCH SB RAS, which, as a result of post-processing, provide high diffraction efficiency with a small thickness of the recording layer, have been studied by the method of recording reflection and transmission volume elementary holograms. Samples of volume reflection holograms with a diffraction efficiency of about 90% are obtained with a recording layer thickness of about 6 μm and refractive index modulation ∆n of no less than 0.036. The obtained holograms have high transparency in the entire visible range of the spectrum, low shrinkage, and good uniformity of the spatial structure of the grating, as evidenced by a clear picture of the side lobes of the spectral response contour.

The method and the possibility of realizing isotropic Bessel-Hilbert diagnostics of the phase optical density fields of gaseous, condensed, and reacting media are discussed. The probing field in such systems is formed as a mono- or polychromatic configuration of the Bessel beams. The spatial-frequency Fourier spectrum of the Bessel beams is optically coupled with the concentric phase structure of the isotropic Hilbert filter, and the color structure corresponds to the spectral sensitivity of the photomatrix of a video camera connected to a computer, which analyzes the frame-by-frame sequence of the resulting images. The structure of such a probing field is resistant to diffraction disturbances induced by the medium under study and their influence on the isotropy of the Hilbert visualization of the phase optical density. The area of possible applications is experimental hydro and gas dynamics, thermal physics, oceanology, as well as the corresponding industrial technologies.

It is shown that the use of an ensemble of reading heads of a certain format, consistent with the parameters of the measuring raster and the matrix of indicator rasters in readheads, can significantly reduce the distorting effect of the systematic component of the instrumental error of the raster. It is noted that the specific technical solution considered in the present paper for matching the parameters of complementary lattice filters is not the only one for the raster used.

The results of experiments aimed at studying the concentration dependences and the time and temperature stability of the quadratic response of guest-host type materials based on polycarbonate and original synthesized dyes are presented. It is shown that modifications of the chromophore by dendronic side substituents significantly improve the solubility, which allows construction of polymer materials with a high content of optically active particles. The materials have high time and temperature stability and exhibit d₃₃ up to 80 pm/V at a chromophore concentration of 2.5^.10²⁰ cm^-3.

The main approaches to identifying the contours of objects in hyperspectral images are considered. Algorithms for extracting the contours of spectrally selective objects based on the spatial spectral correlation and interspectral difference of gradients are presented. The efficiency of the proposed algorithms for processing real hyperspectral images under the condition of additive Gaussian noise is demonstrated.

The paper is devoted to solving the problem of constructing a state estimation of a finite discrete-time Markov chain. A Markov chain is considered as a linear dynamic system with incomplete state information. The state estimation is based on the Luenberger observer. The conditions for state estimation invariance to perturbations of transition probabilities in a Markov chain are obtained. A numerical example is considered.

The article proposes a method for selecting stable feature points of images obtained using the BRISK and AKAZE algorithms. The method is based on the selection of points that remain in the image after its significant transformation. The results of numerical experiments, based on 1000 images, confirming the effectiveness of the proposed method are presented. It is found that the sets of points obtained using the proposed method contain three to five times more stable points than random sets of the same size. It is shown that, for the selection of stable points, it is more efficient to use significant transformations of images.

The properties of the method for testing the hypothesis of theindependence of random variables based on the use of a nonparametric pattern recognition algorithm corresponding to the maximum likelihood criterion are investigated. The distribution laws in the classes are estimated on the basis of the initial statistical data, assuming the independence and dependence of the compared random variables. Under these conditions, the estimates of the probability of an error in pattern recognition in classes are calculated. Based on their minimum value, a decision is made on the independence or dependence of random variables. The application of the proposed technique allows us to circumvent the problem of decomposition of the range of values of random variables into multidimensional intervals. The effectiveness of the proposed technique with the complication of the relationship between random variables and changes in the volume of the initial statistical data is investigated by the method of computational experiments.

On the basis of the previously developed mathematical model and algorithms for functioning of the mirror system control system of the Millimetron Observatory, the results of numerical simulation of obtaining permissible values of the errors of the on-board 3D scanner during the preliminary measurement of the geometric parameters of the spatial location of the mirror system of the Millimetron Observatory using optical control marks on the surface of the mirror system are presented. When modeling the measurement of the geometric parameters of the spatial arrangement of the control marks, two options for their execution on the panels of the main mirror of the telescope are considered: Option 1 - the control marks are given in the form of mirror spheres with a diameter of 10 mm, located at the four corners of the panels of the main mirror; Option 2 - the control labels of Option 1 are complemented with miniature swivel mirrors. The miniature mirrors allow the measuring beam to be rotated so that through the mirror it is possible to measure the geometric parameters of the control marks located on adjacent (for mirrors) panels of the main mirror. It is revealed that, when the permissible values of errors in the operation of the 3D scanner are reached (9 μm for the rangefinder channel and 2 angular sec for the angle channels) and combined control marks are used (option 2), it is potentially possible to build a device for pre-tuning the mirror system.

The article presents the structure and implementation of a digital model of a coalmine face. The digital model contains the parameters of the coal seam, the technical parameters of the mining machines, and economic indicators. The digital model can be used to support decision-making to increase the productivity of the coalmine face and to assess the effect of using new mining machines or new technology. An example of using the digital model to determine the dependence the financial indicators of functioning of the face on the face length and technological schemes of coal mining is given.

The article is devoted to the development of a numerical algorithm for determining the optimal regime parameters of a chemical process. The statement of the problem of multi-purpose optimization of the chemical process conditions is formulated in the general form. To solve this problem, a genetic algorithm is presented. The algorithm is based on the FFGA method, which allows one to determine many Pareto-optimal solutions. A computational experiment is carried out for the thiol aminomethylation reaction in order to determine the optimum temperature and reaction time, ensuring the maximum conversion of the starting materials and the maximum selectivity of the formation of the target reaction product.

The paper suggests an approach to the construction of equipment for diagnostics of dangerous states caused by destruction of bearing elements in propulsion systems like gas-turbine engines. The approach is based on continuous monitoring of external factors affecting the bearing assembly and of the presence of metal particles in the engine lubrication system, which are carried out using original single-coil eddy-current sensors, modeling of the wear of bearings, and expert verification of the remaining resources in changing operating conditions. This makes it possible to determine the residual life of the bearing assembly and predict the time until its intensive destruction. Thus, the possibility of taking measures to prevent the development of emergency situations is provided.