Home – Home – Jornals – Avtometriya 2023 number 3

The presence of an medium-range order in glassy materials, i.e., structural correlations on the nanometer scale, leads to fluctuations of elastic constants with the same characteristic correlation radius. The question of what is the characteristic amplitude of these fluctuations is of great interest both from the applied point of view and from the point of view of fundamental understanding of the structure and dynamics of glassy materials. In this study, we find the value of mean-square fluctuations of the shear modulus at the nanometer scale in salol (phenyl salicylate) molecular glass and its dependence on temperature during glass melting into a supercooled liquid. For this purpose, we use the theory of elasticity in a medium with spatial fluctuations of elastic constants in calculating the phonon free path using the perturbation theory. In addition, in the supercooled state of the material, we take into account the contribution of structure relaxation to phonon damping. Using the Ioffe-Regel criterion for the localization of transverse phonons, we find a relationship between the magnitude of shear modulus fluctuations and the frequency of the so-called boson peak caused by them in the spectrum of vibrational excitations of glasses. We determine this frequency from experimental data on the spectra of low-frequency inelastic light scattering in salol. A comparison with the theory makes it possible to find the temperature dependence of the rms fluctuations of the shear modulus at the nanometer scale. In addition, we compare this dependence with the temperature behavior of the Landau-Placzek parameter in salol. We also determine the temperature dependence of the radius of structural correlations in salol and glycerol and compare it with the temperature dependence of the size of the dynamic inhomogeneity.

The possibility of complete suppression of the instrumental error caused by inaccuracy of manufacturing of an angle-measuring structure, realized at an arbitrary form of the field of interaction of light radiation with the topology of the measuring structure is shown. This possibility is achieved by choosing a necessary structure of the encoder for which the principle of coherence of the complementary comb filters formed in the encoder is provided.

The system "movable electrode - nanometer gap - thin crystalline film of a material with a high value of dielectric permittivity - fixed electrode" is used to create high specific mechanical power microelectromechanical systems (MEMS). Two-dimensional electromechanical waves are found to arise in such a system. The occurrence of such excitations limits the maximum specific power of electromechanical converters - actuators, MEMS motors, and generators. On the other hand, this phenomenon opens up wide possibilities of using such structures.

In real conditions, the experimenter deals with input superconducting converters, whose design in biomagnetic systems depends on the research conditions, presence of magnetic shielding, available cryogenic support, required sensitivity to magnetic field induction, and technological capabilities of developers. It is impossible to compare the results of studies obtained for different biomagnetic systems. The paper considers the issues of describing the source of the magnetic field of the heart based on the spatial-frequency transformations of the 2-D model of the current dipole. The depth of occurrence, location and orientation of the current dipole on the value of magnetic field induction and its spectrum over the space of the magnetic field measurement grid of the heart are investigated.

The results of experimental studies of the deformation of a rail under the force of a moving railway transport are presented. The studies are carried out using a highly sensitive deformation sensor with a limit level of relative deformation of 2 · 10^-7 . The possibilities of optical strain measurement for solving the problem of monitoring the technical condition of the running gear of wagons and the upper structure of the track are analyzed.

The study of the photothermal effect during laser ablation of a 45 nm thick molybdenum oxide film is carried out. A hypothesis on the relationship of the thermal conductivity coefficient of the dielectric film with the limiting value of the photothermal effect is presented. It is shown that, with a thermal conductivity coefficient of more than 5 W / (m• K), the rate of temperature change decreases sharply at the beginning of heating the film, which, together with the peculiarity (singularity?) of the temperature distribution, can have a multidirectional effect on the width of the track being formed. It has been experimentally established that, under the action of continuous laser radiation in the 45 nm thick molybdenum oxide film, it is possible to form tracks with a width almost 2 times smaller than the effective diameter of the laser beam.

The main ideas used in solving the problems of detecting and classifying objects by their images using neural network technologies are reviewed. The key publications devoted to the most popular ways to improve the accuracy of classification are considered. It is shown that neural network methods of object detection have achieved significant success in the last decade due to the use of convolutional technologies and practical implementation of the idea of deep learning using large visual databases. The main disadvantages, limitations, and possible directions of development of existing approaches are considered and analyzed.

Diagnosis of Parkinson's disease is an expensive procedure that includes transcranial sonography and brain tomography. In this regard, simple and accurate screening diagnostic methods are relevant. The article deals with the analysis of handwritten static drawings of spirals and meanders using machine learning methods for diagnosing Parkinson's disease based on the publicly available HandPD dataset. Fuzzy classifiers are constructed using original methods that are able to determine the presence or absence of the disease by drawing. As the Hand PD dataset is unbalanced, oversampling algorithms are used in the work. A statistical comparison of the accuracy of the applied models and methods is carried out. The ranking of features is performed.

Results of the study usingtwo neural networks to solve the problem of detection and classification of microparticles in images obtained by restoring model and experimental holograms of aerosol media with a particle density of 180000 cm^-3 are reported. The first neural network is trained on a database of manually labeled particle images, while the second neural network is trained on a database based on algorithms for automatically distributing certain parts of images into classes. The results of operation of two neural networks are compared, ways of their further improvement are presented.

Modern small and medium-sized enterprises, such as IT companies, law, consulting, and logistics firms, use many electronic tools for management purposes to ensure internal information exchange. However, there are a number of tasks, such as registration of vacations, project reporting, issuance of professional literature, etc., which do not fit into the existing decision models. Some IT companies in such cases create their own services to automate the same type of procedures, but many companies do not have software solutions for automating it. The paper presents the model and architecture of software on an open software platform of the employee appraisal service - one of the above-mentioned non-standard tasks. Using the service will allow small and medium-sized companies to apply this flexible and simple solution to frequently occurring management tasks.

We apply a polynomial approach to low-order optimal controller design for linear stationary SISO systems described by differential-algebraic equations. Critical root diagrams and root polynomials are explored in low-order controller design in classical control systems. The method is illustrated on an unstable controlled plant defined by an improper transfer fraction with a 6th-degree numerator and a 4th-degree denominator. We find the settings of a few stabilizing PI₃-controllers and select the optimal one providing the maximum relative stability; the impulse response calculation confirms that the close loop system is astatic and impulse-free. The method scheme remains the same as that for the classical control systems; however, the arising polynomial systems turn out to be of a higher degree and more difficult for numerical solving.

The possibilities of photographing objects in an aquatic environment on acoustic waves by means of circular aperture synthesis are experimentally tested. An experimental setup has been created to implement a method for reconstructing the image of objects in cross sections using a trajectory Doppler signal. Image reconstruction is carried out by scanning an object placed inside a rotating cylindrical water tank controlled by a circular synthesized aperture focus. The algorithm of focus control and image construction is given. The experiment is conducted with the simplest text objects:metal point object and metal rod with a diameter of 2 mm and a length of 10 cm. The problems of implementing circular aperture synthesis using a cylindrical rotating water tank with piezo sensors attached to the inner wall of the tank are discussed.