Vol 510, No 1 (2023)

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.

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.

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.

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.

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.

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.

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.