Vol 523, No 1 (2025)

This article considers electro-optical effects in liquid disperse systems with particles comparable with the wavelength of light and exceeding it. Criteria are introduced that allow splitting the extinction constant of particles into two parts, characterizing small (Rayleigh) and larger particles. Using the example of studying diamond and graphite hydrosols containing particles of different sizes, it is demonstrated that the electro-optical method associated with the determination of two distinct effects from the intensity of light passed through a dispersed system (which are pronounced for both small and large particles), is applicable to dispersed systems with a wide distribution of particle sizes. The method is effective in studying the processes of formation of aggregates in dispersed systems and analyzing their stability.

The paper presents a theoretical and numerical study of the sound field mode structure in a wide frequency band (0.2–2 kHz) in a wedge-shaped waveguide with a gradient sound speed profile, associated with the presence of a thermocline. The acoustic track is directed towards increasing depth, so that the sound source and the vertical receiving array of hydrophones are located on different sides of the region where the thermocline touches the bottom. It is shown that in this region, due to mode coupling, the frequency dependences of the amplitudes of normal modes acquire an oscillating character, and the oscillation period depends on the depth of the thermocline. Analysis of the oscillation spectrum of lower mode amplitudes allows us to estimate the distance from the sound source to this region.

The paper examines the phenomenon of relativistic tunnel ionization of heavy atoms under the influence of tightly focused laser beams of extreme intensity using the imaginary-time method. For the general case of non-orthogonal and unequal electric and magnetic fields, an equation determining the complex initial instant of subbarrier motion is derived.

This work presents the results of a numerical simulation of interaction between various bodies and an ice field. Prandtl–Reuss elastoplastic body model is employed with Mises–Schleicher yield condition, and material destruction is accounted for using maximum main stress and maximum plastic deformation criteria. Discontinuous Galerkin method is used to numerically solve the equations. High-energy impact on ice and slow indentation with a massive body are investigated. Based on the momentum change and the global load exerted on moving body the ice resistance force during ice-breaking process was estimated. Results were obtained for different speeds of stationary advancement through the ice field.

We demonstrate an increase in the resolving power of a telescope with the aperture of 1 m when observing astronomical objects on flat terrain using a fast-operating adaptive optical system. This system includes a Rayleigh laser guide star formed at the distance of 3–6 km. In the experiments, the image size (FWHM) of natural stars has been reduced by more than an order of magnitude with an increase in the radiation energy fraction in the diffraction angle to 11% at the Fried parameter ~6 cm and the bandwidth of the turbulent distortions ~50 Hz. These results are in qualitative agreement with the calculation results. It has been demonstrated that adaptive phase correction significantly increases the image details of a non-isoplanar moving object, such as the International Space Station, enabling its reliable identification.

This paper presents an approach allowing to reduce by up to 30–40 dB and more the low-frequency noise critically affecting human health, functional activity and comfort, as well as the instrument accuracy. This paper considers some methodological aspects and results of designing the composites with a polymer matrix and modifying fillers of inorganic and biopolymer polydisperse phase, the algorithms for predicting and analyzing the efficiency of sound insulation by the criterion of transmission loss when the waves pass through a thin single- or multilayer medium. The validity of the approach is confirmed by correctness of applied physical and chemical methods of the composites synthesis, and experimental data obtained for the models tested in the acoustic duct. The results methods of the research can be used in developing the soundproof structures for aircraft of various purposes, and in microelectronics.

This paper presents the results of an optimization process conducted on an all-fiber ps-pulse amplifier with sub-MW peak power, operating at a wavelength of 1064 nm, with a final amplifying stage based on a ytterbium-doped tapered fiber. The double-cladded active fiber was counter-pumped through the side surface. Two tapered fibers, with maximum core and cladding diameters of 39/375 and 58/625 µm, were utilized (in both cases, the thin part of the tapered fibers was single-mode with a geometry of ~8/80 µm). The optimal profile of the pump-feeding fiber was determined, the high-power unstable fixation polymer was eliminated, and a tapered fiber with an additional narrowing at the output end was used to compensate the increased numerical aperture of the injected pump. As a result, 42 W of average power was obtained with 9 ps pulse amplification, and the maximum achieved peak power was 0.62 MW.