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The development of the world ocean shelf requires the use of a variety of underwater communication equipment. The results of simulation of the shape of electrical pulses generated by 1-ns optical pulses from a photodetector are presented. These pulses propagate through a water layer containing only nanobubble clusters. Scattering from the volume behind the emitter was also taken into account. Attenuation was calculated using Bouguer's law. Cluster scattering efficiency factors were estimated using Mie theory for submicron particles with a refractive index lower than that of water. It was found that the broadening of a 1-ns pulse caused by scattering only by bubstons taking into account the volume behind the emitter does not exceed 0.1 ns at a distance of 20 m. It is shown that nanobubble clusters in transparent water limit the length of underwater optical wireless communication lines by attenuating the radiation. The results can be used in the development of devices for underwater wireless optical communication.

The propagation of high-power femtosecond laser pulses under conditions of their filamentation in air of different pressures is theoretically studied. This approach allows predicting the formation of a nonlinear focus during self-focusing and the filamentation domain on real atmospheric paths hundreds of meters long. This is possible due to the scaling laws that relate the pressure in a propagation medium to the initial parameters of high-power ultrashort laser pulses. Thus, the results of laboratory studies under conditions of increased pressure at distances of several meters are transformed into extended air paths hundreds of meters long at atmospheric pressure. The results allow better understanding of the complex and multifactorial dynamics of filamentation of high-power ultrashort laser radiation and open up new prospects for optimizing and expanding the range of applications based on this phenomenon, in particular, remote diagnostics of atmospheric components and long-range energy delivery. Numerical simulation in this work was performed based on the reduced (time-integrated) nonlinear Schrödinger equation for the optical field envelope during propagation of high-power femtosecond pulses of a titanium-sapphire laser under conditions of a 16-fold change in air pressure. The formation of a multifocal structure of the filamentation domain, which is especially evident under these conditions, is considered in detail.

This review addresses the problem of water body eutrophication and approaches to monitoring this process. It describes key biophysical and chemical markers of water object eutrophication, including the content of chlorophyll- a , suspended solids, and nutrients in the aquatic environment, as well as volatile molecular markers of eutrophication which can be present in the air near the water surface. The comparative analysis of experimental, process-based, and theoretical models of this process is performed. Since the volume and quality of experimental data significantly affect the predictive accuracy of eutrophication models, the review focuses on methods for accumulating these data, including remote and local sensing of water body parameters. Among the latter, laser gas analysis methods for detecting volatile markers of eutrophication near the water surface are considered. Based on a literature review, a list of the most informative volatile molecular markers of eutrophication emitted from the water surface into the atmosphere has been compiled: carbon dioxide (CO₂), hydrogen sulfide (H₂S), methane (CH₄), nitric oxide (N₂O), geosmin, and 2-methylisoborneol. The importance of monitoring phosphorus derivative phosphine (PH₃) as an indicator of the phosphorus cycle and a potential greenhouse gas is noted. The back of data on its sources and the processes leading to its synthesis is emphasized. Based on data on quantum spectral transitions, recommendations are provided for recording PH₃ and other volatile markers of eutrophication near the water-air interface using IR gas absorption spectroscopy.

The fabrication of Al-metallic glass (Fe₆₆Cr₁₀Nb₅B₁₉) composites with low residual porosity and varying component concentrations is presented. During sintering, no interfacial interactions between the composite components are observed. The hardness and thermal conductivity of the Al-metallic glass composites are experimentally determined. The experimental data are compared with values calculated using the rule of mixtures. The measured thermal conductivity of composites containing 20 and 80 vol.% metallic glass closely matches values predicted by models for parallel and series phase connectivity, respectively. The hardness values for these composites are consistent with those calculated using the Reuss and Voigt models.

A numerical study of the effect of a perturbation generated by a vortex-generator fin on the local flow structure and turbulence of a bubbly flow in a planar channel behind a backward-facing step is performed. An Eulerian approach is employed to describe the flow dynamics and heat and mass transfer in both the carrier gas and dispersed phases. The problem is solved using the Reynolds-averaged Navier-Stokes equations, modified to account for the presence of bubbles. The influence of air bubble concentration, initial bubble diameter, and vortex generator height on the turbulent flow structure and the length of the separation region is investigated. The presence of the vortex-generator fin induces a significant (twofold) increase in the turbulence level in both single-phase and two-phase bubbly separated flows. The fin is found to exert a substantial effect on turbulence in the separated flow, with the turbulence level increasing by up to 60%. The addition of bubbles reduces the recirculation zone length (by 60% for ∆/H = 1/3).

Some experimental results on the penetration of polyconical penetrators made of EP637 steel into M400 concrete blocks and sandy soil are presented. The critical velocity is determined through successive iterations over a range of impact velocities characteristic of the transition from an intact penetrator (defined as a reduction in model length of less than 5%, excluding cavitator blunting) to a failed penetrator (defined as a length reduction exceeding 5% or a breach of penetrator integrity). The critical impact velocity above which penetrator failure occurs is identified.

Results of experiments on the fabrication of a composite material based on PTS-1 titanium with a TiN reinforcing phase at volume fractions of 4, 8, 12, and 21% by hot pressing are presented. A powder mixture of titanium and titanium nitride, mechanically processed in a high-energy planetary ball mill, is sintered at temperatures of 1200, 1300, and 1400°C. The sintered samples are shown to contain primary (α-Ti and β-Ti) and secondary phases (δ-TiN and ε-Ti₂N). With increasing titanium nitride concentration, a polymorphic transformation (β ↔ α) occurs, forming the α-Ti-TiN eutectoid. Elevating the sintering temperature is found to increase the grain size of the β-Ti phase by 250%. Owing to the high titanium nitride concentration, the composite structure is transformed, leading to an increase in relative density to 99%, an improvement in material hardness by 97%, and an increase in elastic modulus by 63%.

Results of experimental investigations into the effect of impact energy on the residual compressive strength of high-strength laminated carbon fiber reinforced polymer specimens are presented. To study the influence of residual stress levels induced by impact on the residual strength of the specimens, additional measurements are performed using electronic speckle pattern interferometry in conjunction with the drilling of small probe holes. Residual stress values are determined in the mid-plane of the specimens at the boundaries of the impacted zones. The scatter in the experimental data, arising from distributed damage within the material microstructure, prevents establishing a correlation between residual stresses after impact with energies of 0-110 J and the residual strength of the specimens.

An exact solution to the two-dimensional Wiener-Hopf integral equation is obtained for the first time. This solution is used to solve mixed problems in acute-angled wedge-shaped domains. Mixed problems are considered for an arbitrary multilayer anisotropic composite. The block element method is employed in combination with topological and factorization approaches. The constructed solution has an integral representation that can be utilized in standard software packages for evaluating integrals in the study of anisotropic composites. The solution contains singular sets where it becomes infinite, which complicates the direct numerical solution of such mixed problems. An exact solution to the two-dimensional Wiener-Hopf integral equation is equivalent to solving the mixed problem in a wedge-shaped domain with an angle of 90°. This result may be used together with topological methods to solve these equations in arbitrary acute-angled wedge-shaped domains. A theory of contact problems for wedge-shaped punches with an acute angle is developed.