# Радиофизика, электроника, акустика

## Two Approaches to the Solution of the Scalar Problem of Diffraction on the Plane Two-periodic Lattice From Bodies of Revolution Located in the Liquid Layer

Background, Objectives and Methods: The problem of diffraction of acoustic waves on the lattices located in the layered media is of great scientific interest in hydroacoustics. There are many methods of the solution of this diffraction problem, such as the method of the surface integral equations, finite element method, boundary element method, etc. One of universal method of solution of diffraction problems is the modified method of discrete sources (MMDS).

## Method for Information Transmission Using a Predictive Model in Coupled Time-delay Systems

Background and Objectives: The object of our study is a system for secure information transmission based on time-delay generators. The choice of the model is justified by the fact that time-delay systems can be easily realized in experiment and they can exhibit chaotic behavior with a large number of positive Lyapunov exponents (hyperchaos). A transmitter uses the modulation of the delay time of a chaotic generator by a binary information signal.

## Calculation of Focusing Spin Wave Transducers Using the Method of Micromagnetic Simulation

Background and Objectives: Researches in the field of electronic circuit development for microwave informational systems based on magnetization oscillations and waves have been performing since the 1960s of the last century. The surge of interest in spin waves (SW) during the last decade is caused by the perspective to use SW as information carriers on the sub-micromagnetic and nanometer scale that leads to the fabrication of devices on magnonic principles and a significant miniaturization of spin-wave devices.

## Synchronization of Chimera States in Ensembles of Nonlocally Coupled Cubic Maps

Background and Objectives: Effects of mutual and external synchronization of chimera states are studied in two coupled ensembles of discrete maps. Each of the ensembles is a onedimensional ring of nonlocally coupled cubic maps in the chaotic oscillation mode. In order to create differences in the dynamics of the ensembles when there is no coupling between them, a mismatch is introduced in the parameters of the individual oscillators of the first and second rings. Effects of external and mutual synchronization of chimera states are explored in detail.

## Lorenz Attractor in a System with Delay: an Example of Pseudogyperbolic Chaos

Background and Objectives: The work contributes to a research direction aimed at search for and construction of physically realizable systems, which could fill the mathematical theory of pseudo-hyperbolic dynamics with physical content. Chaotic attractors belonging to this class generate genuine chaos that does not degrade under small variations of parameters and functions in dynamical equations.

## Numerical Simulation of a Looped Tube 4-Stage Traveling-Wave Thermoacoustic Engine

Background and Objectives: The technology of thermoacoustic energy conversion is one of the most promising technologies for converting thermal energy into electrical one. A brief review of the achievements in development of the multi-stage traveling-wave engines was made. The numerical simulation of a 4-stage engine with a load was done. The aim of research was to determine the engine parameters, required to achieve the maximum of efficiency of the system and the acoustic power on the load.

## Complex Dynamics and Chaos in the Rabinovich – Fabrikant Model

Background and Objectives: In the work we consider a finitedimensional three-mode model of the nonlinear parabolic equation. It was proposed in 1979 by M. I. Rabinovich and A. L. Fabrikant. It describes the stochasticity arising from the modulation instability in a non-equilibrium dissipative medium with a spectrally narrow amplification increment. The Rabinovich – Fabrikant system presents some extremely rich dynamics die to the third-order nonlinearities presented in the equations. The considered system is universal.

## On the Theory of Synchronization of a Two-Mode Electron Maser with a Hard Excitation

Background and Objectives: Medium-power (10–100 W) THz continuous-wave electron cyclotron masers (gyrotrons) are of great interest for many applications, such as spectroscopy with dynamic nuclear polarization, plasma diagnostics, non-destructive testing, remote detection of radioactive materials, biomedical applications, etc. For these applications, a high frequency stability is required, with the possibility of frequency tuning within 1–2 GHz.

## Linear Model of Surface Terahertz Plasmons Amplification in Two Parallel Graphene Sheets

Amplification of terahertz plasmons in a pair of parallel active graphene monolayers is studied theoretically. It is shown that the antisymmetric mode increment of plasmons in the two parallel graphene monolayers may be several times greater than that in a single graphene layer due to deceleration of the antisymmetric plasmon mode as compared to the plasmon mode in a single graphene monolayer.

## Spatiotemporal Structures in an Ensemble of Nonlocally Coupled Nekorkin Maps

Background and Objectives: Studying chimera states is a subject of special attention among specialists in nonlinear dynamics, and the issue on the mechanisms for implementing chimeras is today one of the topic directions. In the paper we consider the mechanism for realizing a chimera state regime which is based on the so-called “solitary states” (SSC) and is actively discussed by experts. The problem is solved by analyzing the dynamics of a one-dimensional ring of nonlocally coupled discrete-time systems.