Home – Home – Jornals – Avtometriya 2023 number 5

The paper provides a justification for the use of the principal component method for assessing the generalized characteristics of the defect in the processing of multi-parameter acoustic signals of the mirror-shadow multiple reflections method of bar stock testing. The method allows reducing the number of signal parameters in the formation of rejection criteria, developing a methodology for assessing the generalized characteristics of the defect, and forming a complex rejection criterion based on the unacceptable value of the generalized defect characteristic for objects made of any steel grades and of any diameters. The results of approbation of the proposed approach for evaluation of the generalized characteristic of natural defects using the regression dependence produced are satisfactorily consistent with the results of metallographic studies.

A method is proposed that allows determining the optimal values of the parameters p of the detectors of singular points from the local characteristics of the image µ. The method is based on the procedure for finding the extremum of the analytical dependence δ = P(p, µ), where δ is the criterion of detector efficiency, defined as the weighted sum of errors of the first and second kind. The dependence P(p, µ) interpolates a set δ(p_i, µ_j) obtained from a sample chosen from a set of similar images. An experiment is performed with 40 radiographs of the lower part of the human spine, which are processed by the Harris-Stephens and SUSAN detectors. It is found that, when choosing the configurable detector parameters by the proposed method, the criterion δ turns out to be significantly lower than that for the values of these parameters at the boundaries of the recommended intervals.

The analysis of images of the whole core (rock sample extracted from a well) is in demand in modern geophysics. The subject area determines the manner of core image processing and the form of presentation of the results. A common form of representing well data is measured values ordered by depth. Core samples are also ordered by depth, and core sample images are a collection of individual photographs or tomographic scans often with missing data at some depths. A typical image of a core sample contains a meter-long sample of rock. At the same time, in practice, it is often required to evaluate the characteristics of centimeter intervals. This paper proposes an approach to creating an ensemble of textural features of core images, presented in the form of depth-ordered profiles, which allows the results to be used in conjunction with other geological and geophysical data.

The method of hypothesis testing of the independence of random variables, based on a nonparametric pattern recognition algorithm, is used in the analysis of ambiguous dependencies. The pattern recognition algorithm meets the maximum likelihood criterion. The estimation of the distribution laws in classes is carried out according to the initial statistical data under the assumption of independence and dependence of the compared random variables. Nonparametric statistics of the Rosenblatt - Parzen type are used to estimate probability densities in classes. The blur coefficients of kernel functions in nonparametric estimates of probability densities in classes are determined from the condition of the minimum of mean square deviations. Under these conditions, estimates of the probabilities of pattern recognition errors in classes are calculated. According to their minimum value, a decision is made on the independence or dependence of random variables. The hypothesis of a significant difference in the probabilities of pattern recognition errors in classes is tested. The application of the proposed technique allows us to bypass the problem of decomposition of the range of values of random variables into intervals, which is typical for the Pearson criterion. The effectiveness of the proposed method is compared with the Pearson criterion. The results of computational experiments using the studied criteria in the analysis of ambiguous dependencies between random variables are presented.

A method of reconstruction based on one image of curved surfaces is proposed. To reconstruct the surface, the object's silhouette data and a multi-level elevation map are used. Unlike the known approaches to reconstruction of a single angle, the proposed method does not have a depth limit and requires fewer calculations by an order of magnitude. High-resolution 3D models can be generated interactively.

The creation of a system for controlling the longitudinal motion of aircraft based on the principle of the total energy control is considered. The structure of the control system is presented. It includes a core independently of aircraft calculating commands for deflecting the elevator and thrust obtained on the basis of the principle of inverse models. The control system is implemented for models of three aircraft with different aerodynamic configurations. The study of the quality of regulation is carried out using the numerical modeling method.

The development of methods for controlling the flow and heat transfer in submerged turbulent jets (impact jets) impinging on an obstacle is an important task, because such a configuration is used in various technical applications. The active flow control technology and optimization of the signal that controls the external flow disturbance in impact jets can be applied to exploit the inherent properties of the flow to further enhance heat transfer at the wall. IR thermography is used and measurements are carried out using the PIV (Particle Image Velocimetry) method for optical diagnostics of the wall temperature fields and velocity fields under conditions of flow disturbance control, including feedback from a local velocity sensor. It is found that low-amplitude sinusoidal disturbances increase the integral temperature at the wall due to the intensification of flow separation at the wall compared to an undisturbed jet. It is also established that high-amplitude disturbances in the pulsating jet mode make it possible to reduce the integral temperature by increasing the average flow velocity near the wall and compensate for the undesirable effect of flow separation. The genetic programming algorithm makes it possible to find a self-oscillating regime during jet disturbance with feedback, which improves local heat transfer on the wall not worse than in the case of a forced periodic disturbance.

The problem of angular orientation of a moving object using measurements of a strapless inertial navigation system (SINS) and a satellite navigation system (SNS) is solved in the general formulation with the most general assumptions about the nature of the angular motion of the object and the probabilistic characteristics of interference from inertial measurements. The solution is obtained in the form of an extended Kalman filter using the directional cosines of rotation in the inertial coordinate system as the estimated orientation parameters, and the vector of measurements of the SNC and the accelerometers of the BINC as the observation vector. An example is given illustrating the high stability and convergence rate of the process of estimating the selected parameters of the angular orientation of a moving object.

Theoretical studies of the dependence of the optimal thickness of a single-layer antireflective coating of SiO₂ on a silicon photodiode on the characteristics of light incident on the photodiode have been carried out. It is found that the optimal thickness of a single-layer antireflective coating of SiO₂ for various angular intensity distributions increases the quantum efficiency of the photodiode up to 1.1 times compared to the classical single-layer antireflective coating with a thickness of λ/4n, which is an optimal coating in the case of normal incidence of monochromatic light.

Experiments on testing long-term stability of metrological parameters of the CLWS-300 model laser pattern generator used in the technological process of production of goniometric equipment have been carried out. It is shown that the CLWS-300 model laser pattern generator retained the ability to reproduce its indicators practically unchanged over an interval of 18 years.

A coherent fiber optic transmission system for OFDM signals is considered. The channels are formed using spectrally efficient modulation formats - QPSK and M-QAM. It is shown that the nonlinear phase noise arising in the optical path is converted into the amplitude noise and, after mixing with the noise of optical amplifiers, leads to a decrease in the signal quality index. Evaluation formulas are given for determining the noise immunity of channel signals using the Q-factor.

The Fraunhofer diffraction phenomena in coherent light on an extended object of constant thickness in the form of a volumetric asymmetric edge with a bevel and a flat reflecting (gray) inner surface of the object, characterized by the modulus of the amplitude coefficient of light reflection and the phase shift in the reflected wave, are investigated using the model of equivalent transparencies. It is shown that the field in the far zone can be represented in the form of two components: transmitted and reflected, the former corresponding to diffraction of light at an absolutely absorbing asymmetric edge, and the latter describes diffraction phenomena at a volume structure in the form of a biplanar slit illuminated by a plane light wave. On the basis of a constructive approximation of the Fresnel integral function, an expression for the spectrum of the object is obtained in analytical form, which allows studying the behavior of fields in the far-field zone. It is shown that, in the case of a large object obliqueness, the main contribution to the field is given by the reflected component. Methods of determining the geometric parameters of the object by measuring the position of the central maximum of the reflected component and its effective width are proposed.