Home – Home – Jornals – Avtometriya 2022 number 2

This paper proposes a new method for investigating the elastic properties of bio-relevant films, based on the study of object deformation under the action of a steel ball, used as an intendor, placed in a magnetic field. Varying the distance between the magnet and the steel ball allows varying the amount of the applied force in a wide range, which opens up a great potential of the proposed method for studying a large class of biologically relevant objects. The capabilities of the proposed method are demonstrated by an example of determining Young's modulus of hydrogel films of different stiffness, made on the basis of gelatin.

In a new Russian kilogram mass standard based on the Watt balance, it is proposed to use an interferometer for measuring the displacements and velocities of the electromagnetic coil and the proofmass in the vertical direction. Based on the formalism of Jones matrices, the paper describes the optical scheme of a three-channel homodyne displacement interferometer with a quadrature principle of phase detection. The results of modeling an algorithm for compensating for nonlinear effects arising from quadratic detection of interference signals are considered. The results of experimental studies of the layout of a homodyne quadrature displacement interferometer are presented, and it is shown that the displacement measurement error according to the PV criterion does not exceed 0.2 nm.

Functioning of the system for automatic focusing of technological lasers on optical 3D surfaces, implemented in the optical recording head of the LGI-2 model laser image generator, is analyzed. The reasons for serious restrictions on the allowable inclination of the recording surface are discussed. An alternative solution is proposed that makes it possible to significantly increase the permissible angle of inclination of axisymmetric surfaces on which the topology of microstructures should be recorded.

For quantitative assessment of the spectral sensitivity of matrix photodetectors, the authors propose a method based on Fourier transforms for a more detailed analysis of characteristics in the frequency and time domains by the value of the broadband index, the shape of the pulse (time) characteristic curve, the degree of vibration, the value of the damping coefficient, and the energy losses. A strong influence of the electron-phonon interaction in a semiconductor on the formation of noise in matrix photodetectors relative to the human eye is found.

Various issues of localization of magnetic field sources in magnetocardiography using the 1-D multidipole model are considered. In real conditions, the experimenter deals with an underdetermined ill-conditioned system. Regularizing procedures are used to obtain a stable solution. The issues under investigation are the resolution of the method and the quality of recovery (determination of the spatial parameters of the multidipole: the depth of occurrence and the amplitude of the dipole moment), as well as the issues of solution stability. In computer modeling, the following methods are used: the method of matrix decomposition by singular numbers and Tikhonov regularization.

Refractive index changes induced in a Cu-doped surface layer of a lithium niobate crystal are experimentally studied. The refractive index changes are induced via point-by-point exposure of the experimental sample by the a focused laser beam at a wavelength of λ = 532 nm.

Methods for determining the domain structure of thin ferroelectric films from the time dependence of the pyroelectric response to short pulsed surface heating are considered. The problem of finding the distribution of the pyroelectric constant over the thickness from the time dependence of the pyroelectric current is the solution of the Fredholm equation of the first kind. Despite the fact that this problem is ill-posed in general, it can be solved under additional assumptions about the resolvent. The assumption that the domains are wedges allows the depth distribution of the pyroelectric constant in a thin barium-strontium niobate film to be determined.

Various methods of adaptive space-time signal processing in a survey radar system with a digital antenna array and wideband sounding signals intensively influenced by active and passive interferences are considered. Approaches to simulation of interferences acting on radars and their suppression by adaptive signal processing are discussed. It is proposed to simulate signals and interferences and their processing after transformation to the complex envelope in the frequency domain.

The problem of segmentation of natural and anthropogenic objects from panchromatic satellite images of very high spatial resolution (< 1 m) using texture analysis is considered. The effectiveness of various statistical methods for extracting texture features is analyzed. Based on the results of numerical experiments represented in this paper, we have selected methods that make it possible to segment the main types of natural and anthropogenic objects, as well as various structures of the forest canopy, with high accuracy (> 95%). We proposed the TTSPCA method, which allows the joined use of the most informative features extracted by different statistical methods. The results of numerical experiments show that the method proposed has higher texture segmentation accuracy (> 99%) in comparison with the standard texture extraction methods considered in this paper.

We discuss the technology of data processing for the AIRS hyperspectral suite and AMSU-A microwave sounder installed on board the Aqua satellite. This technology makes it possible to retrieve geophysical parameters of the Earth’s atmosphere and surface even with 80 % coverage of an observation area by clouds. The failure of the AMSU-A sounder in 2016 led to exclusion of its readings from the AIRS data processing scheme and to implementation of the simplified AIRS Only algorithm used today by NASA. In this paper we propose an approach to repair the AIRS «all-weather mode» using data from the ATMS scanning microwave radiometer on board the Suomi-NPP and NOAA-20 satellites. It is shown that the inclusion of the ATMS readings in the data processing algorithm makes it possible to obtain geophysical results that practically coincide with the original AIRS/AMSU data.

A method for estimating the nonlinear functional of the probability density of a three-dimensional random variable is proposed. It is relevant in the implementation of procedures for fast bandwidths selection in the problem of optimizing kernel estimates of the probability density. Solving this problem can significantly improve the computational efficiency of nonparametric decision rules. The proposed approach is based on the analysis of the formula for the optimal bandwidths of the kernel probability density estimate. The bandwidths of the kernel functions are represented as the product of an undefined parameter and the standard deviations of the analyzed random variables. The main component of the undefined parameter is a nonlinear functional of the probability density. The considered functional for a family of unimodal distribution laws is determined by the form of the probability density and does not depend on the density parameters. It is determined by the approximation of the functional dependence on the antikurtosis and skewness coefficients, which are estimated from the initial statistical data. To simplify the problem of restoring the desired dependence, the antikurtosis and skewness coefficients are transformed into a generalized parameter. The initial information is made up of a family of lognormal distribution laws. The errors of approximation of the considered nonlinear functional of the probability density are estimated by the values of the introduced generalized parameter for a family of three-dimensional lognormal distribution laws of independent random variables. The possibility of using the proposed methodology for estimating nonlinear functionals of the probability densities that differ from lognormal distribution laws is investigated. The influence of the arising approximation errors on the mean square criteria for recovering a nonparametric probability density estimate of a three-dimensional random variable is analyzed.

The features of carrying out X-ray lithography by synchrotron radiation (SI) using masks on thin (up to 50 microns) and thick (up to 1 mm) layers of X-ray resists are described with an illustration on specific examples of X-ray lithography stations of the VEPP-3 storage ring. The calculated graphs of the spectral dependence of the resolution of X-ray lithography on the size of the gap between the working surfaces of the X-ray mask and the substrate being processed, graphs of the dependences of the SI beam intensity and the absorbed power density on the depth of radiation penetration into the resist, and similar graphs for the contrast of the X-ray mask are presented. A description of self-supporting perforated (with through holes) metal X-ray masks is given. Reaching a new qualitative level of their production by laser cutting with a femtosecond pulse duration is illustrated by SEM photos, which will allow obtaining samples of planar elements of terahertz optics in the form of metal microstructures formed by means of the LIGA technology, varying the cell sizes, the width of “the line” of structures, and their thickness in a significantly wider range than was done earlier.

The optimal design of a cooled flip-chip photodetector in the infrared spectral range for installation in a cryostat is determined both with the possibility of bending during cooling and with rigid attachment to a pedestal through a sapphire plate. A numerical calculation is carried out for a radially symmetric photodetector model: GaAs (first layer) - Indium (ring structures) - Si - GaAs (second layer) with a plate diameter of 10 mm. The maximum deformation loads in the edge indium ring are determined for plates of different thicknesses (from 0 to 700 μm), which occur when the photodetector is cooled to 77 K. For the photodetector model, when it is fixed on a cooled cryostat pedestal with the possibility of bending, the optimal design is determined - GaAs(1) and Si plates with a thickness of about 50 μm and without GaAs(2;, the maximum deformation loads in the edge indium ring (width 15 μm, thickness 5 µm) with this configuration are approximately 427 MPa. When the model is rigidly mounted on the pedestal of the cryostat, the optimal design is GaAs(1) and Si plates 50 µm thick and a GaAs(2) compensation layer 100 µm thick; the maximum deformation loads in the edge indium ring under these conditions are 600 MPa.