Vol 22, No 3 (2019)

The vast majority of guiding structures are described [1–3] by non-self-adjoint electrodynamic operators, which are understood as the totality of the differential equation and the system of boundary conditions. In [1–5], the conditions for the non-self-adjointness of electrodynamic operators are formulated as applied to the method of separation of variables. The indicated operators can be put in accordance with [5–6] integral equations. The boundary problems for cylindrical guiding structures are assigned the Volterra integral equations, using asymptotic solutions of which an a priori determination of the spectra of solutions of boundary-value problems for two-layer open and shielded waveguides is carried out.

The aperture’s amplitude-phase distribution of a linear antenna array, ensuring the formation of frequency-independent direction-finding characteristics in a wide frequency band, is considered. The basic regularities of the choice of the amplitude-phase distribution parameters of linear antenna arrays for the case of frequency independent amplitude distribution and frequency dependent phase distribution are investigated. Using the example of a 45-element linear array designed for operation in a frequency band with a relative overlap of 4:1, the influence of the amplitude and phase distribution’s parameters on the magnitude and deviation’s character of the direction-finding characteristics in the operating frequency band is investigated. It is shown that the introduction of a substantially decreasing amplitude distribution contributes to a decrease in the integral standard deviation of the direction-finding characteristics in the frequency band. The relationship between deviation of frequency dependence of the direction-finding characteristics of the array and variations in the frequency dependence of the phase distribution in the aperture is established. The analysis of the basic regularities of the formation of frequency-independent direction-finding characteristics of broadband antenna arrays has been carried out.

On the basis of the idea of splitting the process into physical factors, using the Fourier method and the green function apparatus, an algorithm for constructing a new class of solutions to the initial boundary value problems of the theory of drying by electromagnetic radiation is developed. A subclass of asymptotic solutions, which are obtained by the limiting transition and give a description of the established drying processes, is distinguished. The dependences of the temperature and moisture content fields on time in such solutions are determined by the first eigenvalues of the Sturm – Liouville problem, and the distributions of these fields in space are the first eigenfunctions of this problem. The analysis of asymptotic solutions allows us to establish and visualize the basic laws of electromagnetic drying, which can be used for engineering estimates of process parameters and the calculation of temperature and moisture content fields in the first approximation.

The issue of transition to discrete time in mathematical models of nonlinear dynamic systems oscillating in continuous time is considered. On the basis of the examples of the Dmitriev – Kislov and van der Pol generators, the approach based on maintaining in the process of time sampling the impulse response of the linear oscillatory circuit included in the generator is described. This «physically reasonable» sampling allows models of non-linear dynamics to be formulated in discrete time, adequately reproducing the characteristics of analog prototypes, which is not always possible with a widely used combination of explicit and implicit Euler methods.

The article presents the research results of semiconductor silicon carbide (porous) structures with the implanted carbon-14. The results of experimental measurements collected data on parameters of photovoltaic energy conversion of light quanta into a photo-EMF to confirm the efficiency of p-n junction, an evaluation of the effectiveness of the introduction of carbon-14 in the molecule silicon carbide electrophysical measurements. In the process used the technology of solid-phase transformation of the surface of the monocrystalline silicon substrate in the phase of monocrystalline silicon carbide by chemical transport of carbon in the environment of hydrogen.