# Vol 510, No 1 (2023)

**Year:**2023**Articles:**13**URL:**https://journals.rcsi.science/2686-7400/issue/view/7145

## ФИЗИКА

### THE IMPACT OF THE WAVEFRONT ON A NONLINEAR WAVE IN A DISSIPATIVE MEDIUM

#### Abstract

Presented a method for generating solutions of the Burgers equation, which describe the interaction of waves in a nonlinear dissipative medium and a linearly growing wavefront. Exact solutions are used that describe these interactions, as well as the symmetry properties of the equation. It is shown that the rising wavefront is able to compete with dissipation and compress the signal in time. On the contrary, the wavefront with decreasing steepness “stretches” the signal.

**Doklady Rossijskoj akademii nauk. Fizika, tehničeskie nauki**. 2023;510(1):3-5

### THE PROBABILISTIC MODEL OF ULTRASHORT PULSES SCATTERING ON A FREE ELECTRON

#### Abstract

We devoted our study to the generalization of the traditional approach for the description of photon scattering on free electrons in the case of ultrashort laser pulses (USLP). In the framework of the second order of quantum mechanical perturbation theory with the use of the Klein–Nishina formula, we derived the expression for the total scattering probability during the whole time of the pulse action that is applicable in the relativistic limit. The redshift of scattered pulse spectra at the scattering angle increase in the relativistic case was studied. The trends of the total scattering probability on the USLP duration were categorized.

**Doklady Rossijskoj akademii nauk. Fizika, tehničeskie nauki**. 2023;510(1):6-9

### MULTISTABILITY IN A CHIRAL SEMICONDUCTOR MICROCAVITY

#### Abstract

The features of the bi- and multistability effects in the semiconductor Bragg microcavity with chiral photonic crystal slab on the upper mirror are investigated theoretically. It is shown that the response of such a chiral structure under a linearly polarized coherent resonant pump demonstrates sharp multistable transitions with abrupt jumps of the exciton intensity and degree of circular polarization. It is shown that of the thresholds of bistable transitions in the system with different sense of circular polarization differ slightly, i.e. in case of a non-optimized structure, we can expect to obtain even a larger amplitude of the jumps of the degree of circular polarization of the excitonic response due to the multistability than in a specially optimized chiral structure with a high degree of circular polarization at low pump intensity.

**Doklady Rossijskoj akademii nauk. Fizika, tehničeskie nauki**. 2023;510(1):10-15

### NONLINEAR PHENOMENA DURING THE PROPAGATION OF POWERFUL NANOSECOND ELECTROMAGNETIC PULSES IN A LARGE-SCALE STRIPE LINES WITH A GAS AT REDUCED PRESSURE

#### Abstract

Experiments of propagation of the high-power high-voltage nanosecond and subnanosecond pulses in large-scale transmitting lines in various gases make it possible to solve a wide range of fundamental and applied problems, from simulating the propagation of electromagnetic pulses (EMP) through the atmosphere to estimating the electrical strength of elements of pulsed high-voltage gas-filled systems. At the IAP RAS, experiments with stripe lines up to 5 m in length are performed in Krot and Sprite devices. During the propagation of EMP with an electric field strength up to 100 kV/m in a low pressure gas, the effects are observed such as the formation of non-uniform and essentially non-stationary glow, nonlinear absorption and dispersion transformation of the shape of high-power pulses, due to gas ionization in the EMP field.

**Doklady Rossijskoj akademii nauk. Fizika, tehničeskie nauki**. 2023;510(1):16-21

### INFLUENCE OF A UNIFORM MAGNETIC FIELD ON THE GENERATION OF STRONG SMALL-SCALE MAGNETIC FIELDS DURING THE INJECTION OF A PLASMA WITH HOT ELECTRONS INTO AN INHOMOGENEOUS COLD PLASMA LAYER

#### Abstract

We carry out a numerical modeling of plasma injection with hot electrons into a thin layer of cold plasma in the presence of an external magnetic field. We show that the latter can significantly affect the emerging small-scale current filaments and sheets, even if it does not magnetize the particles and does not change the overall dynamics of the redistribution of the total plasma density in the process of injection. The effect observed depends on the orientation of the external magnetic field that is parallel to the plane that bounds the cold plasma layer, if the injection occurs from a narrow strip lying in this plane. In this situation, which corresponds to the ablation of a flat target by a femtosecond laser beam using cylindrical focusing, we study the evolution of the characteristic structures of the formed small-scale magnetic field. It is established that its generation is associated with instabilities of the anisotropic velocity distribution of electrons, and its value can be many times greater than the value of the external magnetic field.

**Doklady Rossijskoj akademii nauk. Fizika, tehničeskie nauki**. 2023;510(1):22-29

### SYNCHRONIZED ACTIVE ANTENNA ARRAYS FOR STUDYING THE PASSAGE OF ULTRA-WIDEBAND SIGNALS IN THE ATMOSPHERE AND IONOSPHERE

#### Abstract

Active synchronized antenna arrays generating ultra-wideband radiation with an electric field strength of about 1 V/m at a distance of several hundred kilometers have been studied. They are designed to study the passage of ultra-wideband signals in the surface layer of the atmosphere and through ionosphere. Synchronous antenna arrays with 4 and 9 radiating modules have been created. Their radiation has a symmetrical radiation pattern along the

**Doklady Rossijskoj akademii nauk. Fizika, tehničeskie nauki**. 2023;510(1):30-34

### CRITICAL CONDITIONS OF SELF-IGNITION AT BIFURCATION POINTS

#### Abstract

The article summarizes the results of the main research in the field of self-ignition theory. For symmetrical vessels, the following are presented: critical conditions of spontaneous ignition in dimensional coordinates, temperature distribution in the vessel, pre-explosive heating of fuel and the critical size of the vessel at the time of explosion. It is noted that the self-ignition conditions for different vessels differ only by a digital multiplier, which indicates that the shape of the vessel does not affect the physic-chemical processes going on in the fuel at the time of the explosion. Each singular point, being a bifurcation point, determines a number that allows finding a single critical condition of self–ignition from the set of solutions to the heat equation. This condition, in the coordinates of its variables, represents a multidimensional surface separating the zone of stationary existence of a combustible system from the zone of “no return”, where a combustible system cannot exist.

**Doklady Rossijskoj akademii nauk. Fizika, tehničeskie nauki**. 2023;510(1):35-38

### DETERMINATION OF THE ELECTRO-OPTICAL COEFFICIENTS OF BARIUM TITANATE

#### Abstract

Within the framework of thermodynamic theory, a method for determining the electro-optical coefficients is proposed. It is shown that for all ferroelectrics whose symmetry admits a diagonal susceptibility, the ratio of some electro-optical coefficients is expressed in terms of the ratio of susceptibilities. For barium titanate, the dependence of the electrooptical coefficients on the electric field has been revealed and studied. It is shown that large values of the electro-optical coefficients of barium titanate are associated with a nonlinear dependence of the dielectric susceptibility on the electric field.

**Doklady Rossijskoj akademii nauk. Fizika, tehničeskie nauki**. 2023;510(1):39-44

## МЕХАНИКА

### DYNAMIC MODEL OF PROCESS OF SEPARATION THE LARGE-SIZED ELASTIC SPACE-ROCKET DESIGNS

#### Abstract

The approach to working out of dynamic model of one of key stages of flight of space-rocket systems – process of separation of large-sized designs is offered. The urgency of the account of own elastic properties of the separated objects, caused by growth of their sizes at simultaneous minimisation of weight of a “dry” design, by application of new materials with good strength and the expressed elastic properties, considerable on size (to hundreds kilonewtons) the concentrated forces created by special means of branch is proved. On the basis of assumptions, characteristic for investigated process (a little angular speeds in the course of relative movement at separation in comparison with the lowest frequencies of divided objects). Transition from the differential equations of elastic fluctuations in private derivatives to system of the ordinary differential equations describing excitation of the limited set of the lowest forms that has allowed to formulate the effective approach supposing evident mechanical interpretation is carried out: full movement at separation is displayed on portable movement (rotary and forward as whole) and the small elastic relative fluctuations described in the universal modal formulation. Process of separation of the aerospace plane and the carrier rocket is analysed. The effect of “loss” of relative speed of branch because of elastic fluctuations is revealed, the recommendation about a rational choice of installation sites of means of branch is formulated.

**Doklady Rossijskoj akademii nauk. Fizika, tehničeskie nauki**. 2023;510(1):45-50

### DETONATION OF A COMBUSTIBLE GAS MIXTURE UPON THE INTERACTION OF A SHOCK WITH AN ELLIPSOIDAL INERT GAS BUBBLE

#### Abstract

Interaction of a shock wave in a combustible gas mixture with an ellipsoidal region of an inert gas of increased density is numerically simulated using the Euler equations in two-dimensional plane and axisymmetric formulations. Four qualitatively different regimes of indirect initiation of detonation have been found: upon reflection of a wave from the gas interface, upon focusing of secondary transverse shock waves on the axis/plane of symmetry, upon amplification of a transverse wave converging to the axis of symmetry, and upon secondary focusing of waves in front of the bubble. It is shown that the mode of detonation initiation significantly depends on both the intensity of the shock wave and the shape of the bubble. Based on a series of simulations, the dependence of the threshold Mach numbers of the incident wave on the shape of the bubble is determined. In the plane flow, a moderate elongation of the bubble leads to a significant decrease in the threshold Mach number. In an axisymmetric flow, the lower threshold Mach number is less sensitive to the shape of the bubble, and the most effective detonation initiation is carried out using a spherical bubble. The effect of shock wave focusing makes it possible to achieve successful initiation of detonation at a fundamentally lower intensity of the incident wave compared to direct initiation.

**Doklady Rossijskoj akademii nauk. Fizika, tehničeskie nauki**. 2023;510(1):51-58

### FORCED LONGITUDINAL OSCILLATIONS OF GAS AND AEROSOL IN AN OPEN TUBE WITH A CROSS-SECTION JUMP

#### Abstract

The forced longitudinal oscillations of gas and aerosol in an open tube with a cross-section jump near the resonance frequency are investigated experimentally. The intensification of gas oscillations in the tube with a cross-section jump in comparison with a homogeneous tube is observed, while preserving a close to harmonic, continuous pressure waveform. A non-monotone dependence of the aerosol deposition time on the frequency of oscillations with a minimum value at the resonance frequency is observed.

**Doklady Rossijskoj akademii nauk. Fizika, tehničeskie nauki**. 2023;510(1):59-63

### TURBULENT BOUNDARY LAYER ON A PERMEABLE PLATE IN SUPERSONIC FLOW WITH POSITIVE PRESSURE GRADIENT UNDER FOREIGN GAS INJECTION

#### Abstract

A numerical simulation of a turbulent boundary layer on a permeable plate with helium injection into a supersonic xenon flow in the presence of a positive longitudinal pressure gradient has been carried out. The injection regimes are considered, in which the temperature of the injected gas is lower than the temperature of the adiabatic impermeable wall and the stagnation temperature of the oncoming flow. The existence of a minimum temperature of the permeable wall is confirmed, at which the wall temperature is lower than the temperature of the injected gas, while there are two sections along the length of the permeable plate in which the adiabatic conditions are satisfied. The results of calculations of a supersonic flow with a longitudinal pressure gradient differ significantly from the results obtained for a gradientless flow around a plate, both for subcritical and critical injection.

**Doklady Rossijskoj akademii nauk. Fizika, tehničeskie nauki**. 2023;510(1):64-69

### STRUCTURE AND MECHANICAL CHARACTERISTICS OF COMPOSITES WITH HIGH DAMPING PROPERTIES

#### Abstract

The damping characteristics of hybrid composite materials reinforced with elastic spherical and fibrous inclusions with viscoelastic coatings are studied. It is shown that in composites with particles morphology, the effect of significant increase of dissipation loss can be realized, andᵇ the effective composite properties loss can exceed the dissipation loss of viscoelastic coatings more than twenty times. The analytical estimations for optimal parameters of hybrid composite materials are proposed. The influence of possible imperfections in composite structure on their effective dissipation properties are analyzed.

**Doklady Rossijskoj akademii nauk. Fizika, tehničeskie nauki**. 2023;510(1):70-76