2020 Issue №2

The features of modeling the dynamics of the rotational movement of a cy­lindrical rod in a homogeneous flow of a viscous liquid are considered. The angle of attack, the angle of rotation, and the angular velocity of the rod are studied numerically. The results of solving the boundary value problem using the numerical method in Mathcad are presented. Graphs are presented in di­mensionless variables. It is obtained that the angular velocity of the rod under the action of gravity increases to the maximum value over time, and then tends to zero. In this case, the angle stops changing, which means that the equilibrium position has been reached.

The possibility of modernization of atmospheric optical channel by using orbital angular momentum MIMO system has been studied. An assessment of the increase in the performance of the communication channel after moder­nization is given.

The paper is dedicated to modelling of the meaningful and relatively sta­ble visual-figurative and verbal-sign representation of the real problems in medical diagnostics. In the paper, we introduce concepts «a task» and «a method». In addition, here we introduce the method and model for the for­mation of schemes-images of methods for solving tasks from decomposition of a diagnostic problem. All concepts are interpreted in terms of the language of the description of relations and connections. A. V. Kolesnikov introduced it for predicative coding of the verbal-sign knowledge about the subject area.

This work is related to the field of applied electrodynamics and is devoted to the improvement of transmitting antenna systems used in radio frequency methods of substance research. The operation of search and other devices in remote mode imposes certain conditions on the parameters of transmitting contours, which must be taken into account when building them. The authors outline ways to optimize a number of design characteristics of transmitting antenna systems, which will increase the efficiency of radio engineering sys­tems used for detecting and analyzing objects that are in the volume of poly­crystalline substances.

The application of the cooperative game theory model, Shapley value, for the estimation of the regression coefficients and the contribution of predictors to the general explainability of the model is considered. The necessary theoret­ical apparatus is systematized and the construction of Shapley estimates based on the coefficient of determination is given.

The work relates to the field of applied electrodynamics and is devoted to improving antenna-feeder devices of communication means. The article at­tempts to justify one of the ways to expand the range properties of a short-wave pin antenna by creating conditions for constant wave resistance along the antenna. The authors propose a physical model of an asymmetric vibrator that allows us to determine the set of measures necessary to obtain an antenna design with improved range properties. The questions of experimental evalua­tion of the effects of the electromotive force generator on the capacitive and in­ductive components of the antenna system are considered.

The paper presents the results of a study of spin States in the main elec­tronic state of the only nitrogen-vacancy center (NV–) in a 13C-enriched dia­mond. The analysis is based on applying a method that uses a full set of com­muting operators. The results show that there are two double degenerations of energy levels in this system, which can be considered as a special case of LAC. Changes in the properties of the spin States of the NV–-center at the quasi-intersection level are considered as a possible cause of changes in the photolu­minescence intensity of NV–-centers.