Vol 524, No 1 (2025)

The frequency multiplication effect in a gyrotron operating under conditions of a large excess of the operating current over the starting value (large supercriticality) was studied. It was shown that in a gyrotron with an operating frequency of 0.5 THz at the first cyclotron harmonic in the frequency multiplication mode at the sixth cyclotron harmonic it is possible to excite random sequences of ultrashort pulses in the range of 3 THz with a peak power of up to 200 W, which is two orders of magnitude higher than the background value.

A new conceptual interpretation of the nature of depolarized light is presented. According to this view, light undergoing multiple scattering in a turbid, disordered medium, although formally unpolarized, retains a hidden coherent structure. In contrast to light from incoherent sources (e.g., natural sunlight), which consists of short, uncorrelated wave packets, scattered coherent laser light can be understood as a systematically organized superposition of circularly polarized components with opposite helicities and stable phase relationships. It is shown that the apparent depolarization of scattered light arises not from complete randomization, but from a structured overlap of left- and right-circularly polarized wave packet pairs, indicating the presence of macroscopic phase correlations in the scattered field within optically dense dispersive medium, such as a biological tissue. These findings significantly expand the potential of biomedical polarimetry, revealing its capability to act as a functional analogue of quantum sensing, capable of detecting and exploiting entangled phase states that emerge naturally from coherent scattering events in biological medium.

The paper studies spectral singularities of multi-fractal measure f(α) of a number of non-equilibrium processes and shows that dissipative structure cascades on various time-scale levels statistically have self-similar distributions. A multi-fractal comparative analysis of quantitative dissipative structure characteristics in tera- and gigapascal regions and time intervals of non-equilibrium states t ∼ 10⁻¹⁰ s, t ∼ 10⁻⁸ s, t ∼ 10⁻⁵ s has been conducted for the first time.

This paper presents the results of numerical modeling of the penetration of a sonic boom into a room through a building window. The calculation results are validated by field measurements of a sonic boom caused by a supersonic aircraft flying at cruising altitude. It is found that the main transmission mechanism is the displacement of the window frame in the window opening as a whole, and not the excitation of the first natural mode of the window. The influence of the stiffness and damping of the sealing of the window unit in the window opening on the passage of a sonic boom is studied. It is found that an increase in both of these parameters significantly reduces the amplitude of the sonic boom inside the room.

In this paper, we construct an exact solution to the well-known boundary value problem of the theory of elasticity on the tension of a free half-strip with a rigidly clamped end. The solution is represented by series in Papkovich—Fadle eigenfunctions, the coefficients of which are determined in an explicit form. The solution is based on the Papkovich orthogonality relation and Lagrange expansions. The behavior of stresses near the corner points of the half-strip is investigated. A comparison of the exact solution and numerical one obtained on the basis of the finite element method is given.