Vol 24, No 2 (2021)

The problem of asymptotic fluctuations of temperature and moisture content in a half-space whose boundary is blown by an air flow with a temperature varying according to the harmonic law is solved by the method of complex amplitudes. The material filling the half-space consists of a solid base (capillary-porous body) and water. The well-known Fourier solution for temperature fluctuations in half-space in the absence of moisture and under the boundary conditions of heat exchange of the first kind is generalized to the case of a wet material under the boundary conditions of Newton for temperature and Dalton for moisture content. The results of the work can be used in geocryology to model seasonal changes in the thermophysical state of frozen rocks and soils, in the theory of building structures to study the thermal regime of indoor premises with fluctuations in ambient temperature, in the theory of drying by electromagnetic radiation to study the processes of heat and mass transfer in oscillating modes.

In order to further improve the methods of protecting the onboard spacecraft equipment from the effects of electrostatic discharges, based on a comprehensive study of the problem of the occurrence of electrostatic discharges, the authors carried out the studies described in this article to analyze the functioning of the onboard spacecraft equipment under the influence of electrostatic discharges. In the course of the research, the methodology for assessing the resistance of the onboard equipment of the spacecraft to the effects of electrostatic discharges was refined, based on the generalization of the calculation and analytical work. The analysis of the resistance of the onboard equipment of the spacecraft was carried out taking into account the main mechanisms of the effect of electrostatic discharges on the onboard space network. Taking into account the need to assess the resistance of the onboard space network equipment to electrostatic discharges outside real operating conditions, the authors assess the resistance of the onboard space network equipment on the basis of mathematical and physical modeling. As a result of the study, an algorithm was developed for assessing the resistance of the onboard equipment of a spacecraft to the effects of electrostatic discharges, which is described in detail in this article.

This article presents the methods of complex computational and analytical assessment of ensuring electromagnetic compatibility of technical means (electrical, electronic and radio-electronic means of launch vehicles and spacecraft). These methods allow us to conduct a comprehensive computational and analytical assessment of the electromagnetic compatibility of the technical means of rocket and space technology, which in its essence allows us to assess the mutual influence of the technical means of rocket and space technology already at the design stage of rocket and space technology objects. The analysis of the results of the assessment of the electromagnetic compatibility of the technical means of rocket and space technology allows us to develop organizational and technical measures aimed at ensuring the electromagnetic compatibility of the technical means of rocket and space technology at all stages of the life cycle of objects of rocket and space technology. To assess the electromagnetic compatibility of the technical means of rocket and space technology, an integrated approach was chosen due to the large dimension of the initial data and the variety of possible variants of interference penetration.

This article is devoted to the analysis of a queuing system formed by two flows with density functions of the gamma distribution law in order to derive a solution for the average delay of requests in the queue, which is the main characteristic for any queuing system. According to this characteristic, for example, packet delays in packet-switched networks are estimated when they are modeled using the queuing system. In queuing theory, studies of G/G/1 systems are especially relevant because there is no solution in the final form for the general case. Therefore, in the study of such systems, various particular distribution laws are used as an arbitrary distribution law for G. In the study of G/G/1 systems, an important role is played by the method of spectral decomposition of the solution of the Lindley integral equation, and most of the results in the theory of queuing were obtained using this method. The article presents the derivation of the calculation formula for the average delay of requests in the queue in the system under consideration, also based on the spectral decomposition method.

Waveguide structures are used to transmit energy and information signals in a wide range of wavelengths and, in terms of wave-guiding physical properties, usually have mutual (identical) properties in forward and backward directions. The asymmetry of the structure and external influences can often cause non-reciprocity of structures for waves, propagating in mutually opposite directions (this property, although limited, is already used in the so-called nonreciprocal devices of microwave, EHF and optical ranges such as ferrite valves, circulators, phase shifters). At the same time, the nonreciprocal properties of wave-guiding structures, independent of their physical nature, were not considered. It is found, that the motion of the medium filling the acoustic waveguide leads to nonreciprocity of its parameters in the forward and backward directions. The degree of nonreciprocity is proportional to the velocity of the medium. The velocity of the medium also affects the propagation velocity of acoustic waves and leads to a change in the critical frequencies or critical wavelengths of the waveguide modes. As the velocity of the medium increases, the number of modes for which the propagation condition is satisfied increases as well.

Connecting to the Internet whenever and wherever you travel is no longer a luxury. All people have the ability to connect to the Internet and share data away from home. Satellite communications are now an integral part of successful and high-quality communications. Satellite communications antennas are usually installed on mobile ground terminals. Due to its wide coverage and versatility, satellite communications are continuously improving and adapting to the telecommunications needs of many countries, despite the fact that broadband, Internet and fiber - optic communications are used almost everywhere. We know that more than 50 % of all satellites in orbit are communications satellites.

Analysis of a pulse voltage regulator from the point of view of transition to an unstable position and possible bifurcation states. Calculation of the stability condition when changing the parameters of the system. Obtaining the pulse voltage regulator stability surface. This voltage stabilizer can have the basic intrinsic parameters of the system, such as, for example, the load resistance, the value of which can change over time according to unknown laws. In the course of the work, the stability limits for static and dynamic bifurcations were obtained with respect to many parameters of the system, including with respect to the value of the load conductivity. To obtain numerical results, a system with the following main parameters was used: U = 4,1 V, d′0 = 0,4, C = 600 μF, L = 2 mH, f1 = 0,8 Ohm, G = 0,5 V–1, RL = 2 Ohm.