Technical Physics最新文献

The effective scattering surface, i.e., the RCS parameter of the graphene nanoribbon array irradiated by a normally incident terahertz TEM-wave (p-polarization) with applying an perpendicular external magnetic field has been simulated using the CST MWS software package. A numerical investigation has been performed of the ratio of the amplitudes of the horizontal E_x and vertical E_y components of the scattered field at the points of the main lobe cross section of the scattering pattern in the absence and with an external magnetic field. It is shown that as a result of diffraction of a linearly polarized TEM-wave on the graphene nanoribbon array with applied magnetic field, the transmitted and reflected waves have an elliptical polarization (the polarization ellipse being strongly elongated), in contrast to the case of zero external magnetic field, when the transmitted and reflected waves have a linear polarization.

Using the MWS CST software, the diffraction of a TEM-wave (with the p-polarization) normally incident on the grating of graphene nanoribbons (GNRs) under applying a magnetic field in the direction perpendicular to the graphene plane is simulated. With the help of the MWS CST software, numerical analysis of the scattering pattern 3D e-Field in the far-field is performed for the vertical Е_y and horizontal Е_х components of the diffracted field for different values of magnetic induction B₀ at the magnetoplasmon resonance frequencies. The results of calculation of the ratio Е_х/Е_у of the horizontal and vertical components of the diffracted field are obtained at the points of cross section (φ = 0) of the main lobe of the 3D e-Field scattering pattern; it is shown that the variation of the horizontal component Е_х of the diffracted field as a function of magnetic induction B₀, which is due to the gyrotropy of the graphene conductivity and the magnetooptical effects emerging in this case, is demonstrated.

The emergence of jumpwise increases and decreases in the isobaric heat capacity of the ternary mixture of ethanol, rapeseed oil, and heterogeneous catalyst Al₂O₃, which are components for obtaining biodiesel fuel, is substantiated theoretically. Temperature ranges of melting, dissolution, and chemical reaction are revealed.

This paper presents a detailed analysis of the effects of global hydrogen production trends on the decarbonization pathway. The study covers clean and low-carbon technologies for industrial-scale hydrogen production, defined as those capable of producing more than 100 nm³ of hydrogen per hour. The study classifies industrial-scale technologies into six categories according to their potential for industrial application within the next 15 years. A comprehensive review of 560 major hydrogen production projects from 49 countries worldwide is conducted. The review is based on the International Energy Agency (IEA) database. It focuses on the location of the projects, the technologies applied, the renewable and non-renewable energy sources used, and the impact of hydrogen technologies on the decarbonization strategy. The hydrogen projects have been clearly classified according to the “color” of hydrogen, which conditionally reflects cleanliness of the process used for hydrogen production. The analysis compares the previous study by the authors with the current study, allowing them to identify unchanged trends and determine the changes in trends of clean and low-carbon technologies that have real prospects for industrial implementation. The demonstrated trends in the development of hydrogen production technology over the period 2000–2038 provide a clear roadmap for scientists, policy makers, industry players, and investors as they navigate the expanding hydrogen energy sector for its sustainable development. The study is based solely on information from publicly available sources.

The study is aimed at developing a universal topological optimization algorithm based on fundamental principles of elasticity theory and continuum mechanics. The objective of the study is to minimize the mass of a structure subjected to dynamic loads while maintaining its strength characteristics, which can be achieved by optimal distribution of material in the volume of the workpiece. An element of a tillage tool—a plate weighing 1.925 kg with maximum stresses of 176.8 MPa operating under variable mechanical stresses—was taken as a basic model Application of parametric modeling and systems approach implemented in the SysML language made it possible not only to select the best element for optimization, but also to develop a new geometry of the structural element (plate). The theory of elasticity, finite element method (FEM), and von Mises stress analysis were used as the physical foundations of the study. This algorithm was found to reduce the mass of the structural element to 1.585 kg, which corresponds to mass reduction by 17.67% while meeting the established requirements for the factor of safety (1.5 to 2.0). The presented method can be used both in aerospace engineering, materials science, machine tool engineering and automotive industry, where similar optimization principles can help to increase the efficiency of design solutions while reducing material consumption.

Mathematical modeling of a plasma flow in coaxial channels with different outer electrode diameters is considered. A numerical model for determining the distribution of density, velocity, and magnetic fields in a channel is proposed based on the system of differential equations describing the mass, momentum, and energy conservation laws. Computational experiments show that depending on the outer electrode diameter, the location of the region of elevated density and velocity field changes, leading to variation of the time of emergence of the main mass of the plasma from the channel, as well as its value and velocity. For complex assessment of these parameters, the plasma momentum in the output cross section is calculated. The performed analysis demonstrates the existence of an optimal value of the outer electrode diameter, for which the maximal magnitude of the momentum is achieved.

A method for calculating the radiation characteristics of diatomic atoms in the conditions of vibration–rotation nonequilibrium is proposed. The method is based on the application of the classical narrow-band k-distribution (kd) model, into which corrections for nonequilibrium are introduced. These corrections include vibrational and rotational distribution functions, as well as the Boltzmann functions averaged over vibrational and rotational temperatures. To verify the calculation technique, a series of nonequilibrium calculations has been performed, which is compared with the exact line-by-line (LBL) technique. The comparison performed in a wide range of pressures as well as translational, rotational, and vibrational temperatures has demonstrated good coincidence. Comparison of the results of calculations with experimental data has also shown satisfactory agreement.

Dynamic changes in the polarization characteristics of radiation propagating along an optical cable are studied using an electrophysical setup that generates artificial lightning under laboratory conditions. The effect of atmospheric electricity on the polarization characteristics of optical signals in the C-band transmitted via fiber-optic communication lines is studied with a time resolution of 40 ns. Changes in the polarization parameter of optical radiation used to transmit information via fiber-optic communication lines are recorded with precise time reference to different stages of atmospheric discharges near the optical cable.

This research introduces an innovative ultrasonic-driven mechanochemical technique for creating protecting coatings, either metallic or ceramic, on metallic surfaces with the purpose of corrosion inhibition. Two variations of the method have been explored. In the first variation, hard balls and powdered metal or ceramics are placed inside a bowl-shaped resonant chamber that is secured beneath the surface to be coated. In the second variation, only the balls are contained in the chamber while the surface has been pre-treated with a mixture of a liquid and powder was applied as a suspension. An ultrasonic transducer affixed to the bottom of the chamber induces high-frequency vibrations, resulting in chaotic movement and collisions between the balls and powder particles, effectively hammering them into the metallic surface. Experimental investigations utilized substrates made of aluminum and stainless steel, along with powders such as titanium, silicon carbide, and alumina, as well as various liquids for the pre-coating process. The findings indicated that the technique facilitates the creation of diverse coatings and protective layers on metal surfaces at ambient temperatures, irrespective of the differences in the properties of the materials employed.