Doklady Physics最新文献

On the basis of the condition of the flow potentiality of the hydrodynamic stream flowing around a stationary rotating ball, a detailed analytical derivation of the formula for the Magnus force describing the nondissipative lateral impact from the direction of the progressively moving viscous flow is given for the first time.

A 1D hyperbolic equation is derived for the Rayleigh wave induced by prescribed surface loading. The wave operator turns out to be independent of the vertical coordinate, which appears only in the right hand side of the equation as a parameter within the pseudo-differential operator acting on the given load. It is shown that in case of the classical 2D Lamb problem this operator causes smoothening of the surface concentrated impulse as the depth increases. The suggested formulation enables revealing of the peculiarities of surface elastic wave.

A new definition of the hydroacoustic field invariant based on a stable estimate of the invariance of orthogonal projections of the sound-pressure-phase gradients on the “distance–frequency” plane is introduced. Such a definition generalizes the concept of an invariant to all existing zones of shallow and deep seas including the near and far zones of illumination of the deep sea in which it is impossible to estimate and apply the Chuprov interference invariant. In the zone of existence of the Chuprov invariant, its values almost coincide with the values of the new invariant.

A technique for synthesizing Tb nanoparticles using laser ablation in various liquid media (MQ water, ethanol, isopropyl alcohol, and isobutanol) is considered with the aim of preparing colloidal solutions of Tb nanoparticles, containing different amounts of oxidized particles. The synthesis of nanoparticles in isobutyl alcohol exhibits the lowest percentage of oxidized particles relative to the total number of particles in the resulting colloid, with a final ratio of oxidized Tb₂O₃ particles to all particles close to 5%. The influence of oxidized particles on the intensity of physicochemical processes (formation of plasma, shock waves, acoustic signals, and chemical products as a result of dissociation of water molecules) occurring during optical breakdown of colloidal solutions, has been investigated. The general tendency of the influence of oxidized particles consists in an increase in the intensity of the aforementioned characteristics upon laser breakdown with an increase in the Tb₂O₃ fraction with respect to the total number of particles in the colloid. The observed effect is presumably related to the high aggregability of Tb₂O₃ particles, while the absorption coefficient of particles is of minor importance.

The results of comparison of the efficiency and radiation resistance of solar cells made of single-crystal silicon and polycrystalline silicon (multisilicon) are presented. It is shown that film solar cells synthesized with using the chloride process when using multisilicon as a substrate material are not inferior in their characteristics to solar cells made of single-crystal silicon.

The heating of the surface of a blunted plate made of a material with low thermal conductivity is experimentally investigated in a wind tunnel under the strong interaction regime. The flow in the boundary layer on the plate is nonstationary, since the temperature of the plate surface continuously increases during the start-up, and its distribution over the surface is variable. The installation of a wedge in the vicinity of the trailing edge of the plate leads to changes in the area of the perturbed flow and in the temperature distribution on the surface of the plate in front of it up to the leading edge as compared to the case of flow around a plate without a wedge. These changes are explained by the propagation of pressure perturbations caused by the installation of the wedge along the subsonic part of the boundary layer against the flow.

Based on the analysis of the physical processes that occur during a steam explosion, it is shown that, in plants of this type, it is necessary to provide the homogeneous-nucleation mode with the fluctuation frequency of formation of viable vapor-phase nuclei in the unit volume of liquid of at least 10⁸ m^–3 s^–1 and the relative value of liquid overheating of ~1. On the basis of a standard autoclave, a steam-explosion plant that meets the specified requirements is designed and manufactured.

A method for selective heating of a cavity shell filled with liquid using heated submerged jets generated by laser heating of a liquid at the end of an optical fiber introduced into the cavity is investigated. It is experimentally shown that the jets, passing through the “cold” surrounding liquid, collide with the shell and heat it, while the temperature of the surrounding liquid rises insignificantly. Numerical simulation of this process allows us to estimate the heating time of closed shells to the temperature of thermal modification of the walls of pathological objects and sanitation of surfaces depending on the power of laser radiation. It is important to consider the obtained result during laser-induced precision cleaning and sanitation of surfaces in closed volumes when developing medical technologies for laser surgical treatment of pathologically altered vessels, cysts, and other applications.

Methods to obtain solutions describing traveling waves in strongly inhomogeneous media are discussed within a linear wave equation with a variable speed (speed of sound). It is shown that there is a wide range of propagation speed variations that allow for the existence of waves that do not reflect despite the strong inhomogeneity of the medium. In this case, the shape of the wave and its characteristics change with distance. These waves can transfer energy over long distances without loss.

Alternative scenarios for the development of world energy, based on low options for the change in the population of the planet, are being explored from the point of view of preventing dangerous global climate change. It has been shown that in order to keep the increase in the average global temperature within safe limits while maintaining the current growth rates of energy consumption and the population of the planet, a radical restructuring of the world energy industry is necessary—the “great energy transition”—with a complete rejection of the use of fossil fuels in the coming decades, which seems impossible given the inertia of development and spread of energy technologies. Using the author’s approaches to forecasting the volume and structure of world energy consumption, alternative scenarios for carbon dioxide emissions have been formed in the implementation of low, but quite realistic trends for demographic dynamics. Based on simulations of models of the global carbon cycle and climate, it is shown that the development of natural demographic processes is able to restrain growth and ensure a further decrease in the concentration of carbon dioxide in the Earth’s atmosphere, limiting the increase in the average global temperature to a completely safe level of 1.8 degrees compared to the pre-industrial period without large-scale restructuring of the world energy.