Том 512, № 1 (2023)

The conditions and dynamics of electron runaway in a gas gap with an inhomogeneous distribution of the electric field due to the use of a conical cathode are analyzed. Significant differences in the behavior of electrons at cone opening angles larger and smaller than the threshold value of 98.6 degrees are revealed. For a weakly inhomogeneous field distribution (cones with angles exceeding the threshold), electrons are continuously accelerated throughout the gap. In a strongly inhomogeneous field (cones with relatively small opening angles), electrons can gain maximum energy inside the gap, and begin to decelerate in the near-anode region. Despite this, they reach the anode with high energies comparable to the work of the electric field. This difference leads to the need to use different criteria for the runaway of free electrons in the gas gap.

For the first time, the properties of the phase invariant of sound to vector-scalar fields formed in a waveguide by directional multipole sources are studied. It is shown that when even such complex sources are used, the phase invariant is valid for sound pressure and for projections of the vibrational velocity vector. It practically does not depend on the directivity and frequency of the source, the distance between the receiver and the source, and on the parameters of the waveguide.

In the article, based on the analysis of the features of the trajectory of a charged particle in an inhomogeneous electromagnetic wave, the physical processes that determine the nature of pondermotive forces are specified. In particular, the reason for changing the accelerated motion of a particle when passing through zero of the electric field amplitude in the direction perpendicular to the electric field to deceleration with increasing electric field amplitude is detailed. The influence of the inertial mass on the trajectory of a charged particle in an inhomogeneous electromagnetic wave is determined.

The basic principles of thermal explosion were studied and outlined by 1980. It seemed that fundamental research had been completed, but in 1984 A.A. Filippov discovered that the “ignition” condition obtained by Ya.B. Zeldovich did not correlate with the data of the experiment on ignition of a gas mixture by incandescent cylinders. Since Zeldovich’s “Theory of Incandescent surface ignition” has long been the basis of the ignition theory, its analysis was carried out and an error was found. It is proved that the above-mentioned work is not related to ignition, but to the self-ignition of infinite fuel. It is shown that a thermal explosion of fuel from an incandescent body can develop not only as ignition, but also as self-ignition. The conditions of self-ignition of infinite fuel by a flat surface and a cylinder are given, as well as the probable condition of ignition of fuel between parallel walls of different temperatures.

A methodology for constructing three-dimensional shell models for the layer-by-layer study of the stress and strain state of irregular sandwich shells, which are increasingly used in practice, is proposed. An original approach is considered for obtaining approximating displacement functions in the finite elements of the core layer, which does not lead to a discontinuity in the generalized displacements on the interfaces with moment skin layers. The development of such models makes it possible to significantly expand the class of problems to be solved and, with the necessary accuracy and degree of detail, for the first time to study the stress and strain state in the general case of irregular sandwich shells in a wide range of variation in the geometric and physical and mechanical characteristics of the layers. The possibilities of the proposed methodology are illustrated by the example of the study of the stress and strain state of conical sandwich shells with rectangular cutouts.

In the present paper paper the dynamic problem of thermoelasticity with a localized inclusion in the medium is considered. It is shown that in the resonant regime an important role is played by the coupling coefficient of the temperature and strain fields. The coupling of the problem and the presence of a discrete spectrum lead to the appearance of an additional term in the expression for temperature, which is localized and does not describe the diffusion process.

Samples of the Murchison meteorite (carbonaceous chondrite, type CM2) were kept isothermally in a specially designed device at temperatures of 200, 500 and 800°C. After the samples cooled down in an inert helium atmosphere, Raman scattering spectra were taken. An increase in the intensity of the G- and D-lines of graphite was detected depending on the degree of heating. It is shown that using such a characteristic parameter of these lines as the area ratio, S_D/S_G, it is possible to define a geothermometer to determine the maximum temperature of thermal metamorphism of the parent bodies of carbonaceous chondrites. A comparison with the known data for carbonaceous chondrite Allende (CM3), which has experienced a significant thermal metamorphism, is carried out.

A vector method for recording phase-dynamic radio images is proposed by forming and numerically analyzing the S-parametric scattering matrix of multidisciplinary signatures of material media and objects. The key advantages of aperture capture of signal radio images by the method of frequency-synthesized power spectral density function of a scattered wave radio profile are determined. On the basis of a vector analyzer of microwave circuits and broadband antennas of the Vivaldi type, an experimental laboratory installation for signal registration of time-scale radio images in the spectral region of 0.03…6.0 GHz has been built. The dependences of the influence of the angular characteristics of the object on the spectral-temporal structure of the formation of phase-dynamic radio images have been experimentally established. As a time-scale postprocessing of radio images, a method of cepstral transformation of S-parametric characteristics with convolution of basic signatures in the radiogenic of the irradiated object is proposed. A series of cepstral convolutions of phase-dynamic radio images was obtained, establishing a functional relationship between the change of the signature of an object in time with its radio genome.