Technical Physics Letters最新文献

Current research on plasma-assisted methods for affecting gas-dynamic flows in order to control active aerodynamic flows is reviewed. Linearly stabilized discharges, surface barrier discharges, and dc surface glow discharges are briefly described. Several approaches to controlling the boundary layer separation and reducing the aerodynamic drag in advanced aircraft are presented.

Based on the solution of a nonlinear 3D diffraction problem (Maxwell’s equations combined with the equation of motion of the magnetization vector in a ferromagnet) using a computational algorithm developed using the cross-sectional method, mathematical modeling of the diffraction and interaction of microwaves with a nonlinear gyromagnetic (ferrite) inclusion in a strip-slot line has been performed. Using the nonlinear autonomous block method, results have been obtained based on electrodynamic calculations of the amplitudes of reflected (at the input cross sections of the nonlinear gyromagnetic inhomogeneity) second-harmonic waves depending on the longitudinal size of the ferrite inclusion at various amplitudes of the incident (fundamental mode) first-harmonic wave.

Using the MWS CST software package, the frequency dependences of the transmission and reflection coefficients of a normally incident TEM-wave (p- and s-polarized) through graphene nanoribbon (GNR) lattices have been calculated by using the Floquet channel method for various values of the external magnetic field applied perpendicular to the graphene plane in the terahertz range. The results of 3D scattering diagram simulations (radar cross section RCS, μm²) of a single-layer and multilayer (N = 3) GNR lattice cell at a magnetoplasmon resonance frequency of f_0res = 10.614 THz under an applied magnetic field (B₀ = 10 T) have been obtained. An increase in the RCS parameter of the transmitted and, especially, reflected wave from the multilayer GNR (compared to the single-layer GNR) has been demonstrated.

We describe a new kind of gas and metal ion source based on a planar magnetron discharge with electron injection from a vacuum-arc plasma. Additional injection of electrons, accelerated in the magnetron discharge cathode layer, enables the source’s operating pressure to be shifted to a lower range, down to 2 × 10^–4 Torr. At this pressure it is possible to effectively select ions from the plasma to form an energetic ion beam. The pressure drop between plasma generation region and ion acceleration region allows a lower pressure in the ion beam transport zone, down to 4 × 10^–5 Torr. For an accelerating voltage of 30 kV, magnetron discharge current of 80 A, and pulse duration of up to 1 ms the total ion beam current was 140 mA. By regulating the current of injected electrons one can independently control the magnetron discharge voltage and, along with the capability of changing the discharge current, this permits wide variation of the gas/metal ion ratio in the plasma and hence in the ion beam.

This paper investigates the long-time behaviour of solutions to the (varepsilon )-perturbed Fokker–Planck–Kolmogorov (FPK) equation in the context of ship roll dynamics under stochastic sea excitation. Starting from a stochastic model of a ship navigating in a transverse sea, we derive the associated FPK equation governing the time evolution of the joint probability density function (PDF) of the roll angle, angular velocity, and wave-induced excitation. The theoretical analysis focuses on the asymptotic behaviour of the PDF as time tends to infinity, demonstrating that the probability of capsize stabilises and eventually becomes time-invariant. This result offers new insights into the probabilistic stability of ships subjected to random sea conditions. To support these theoretical findings, we implement a finite-difference numerical scheme that accurately captures the transient dynamics and confirms convergence towards the steady-state distribution. The simulations validate the analytical predictions and underline the robustness of the proposed approach for long-term stability assessments in marine engineering applications.

Patch antennas are integral components of modern wireless communication systems, valued for their compact size and high efficiency. This study focuses on enhancing patch antenna performance for terahertz frequency applications. Polytetrafluoroethylene (PTFE) is employed as the substrate material, and comprehensive simulations are carried out using Ansys Electronics Desktop Software. To improve antenna performance, a two-dimensional photonic crystal (PhC) structure is incorporated by introducing air holes into the substrate. By precisely varying the dimensions of these air gaps, the antenna’s key parameters are optimized. The simulation results demonstrate notable improvements in return loss, gain, radiation pattern, directivity, and other critical performance metrics compared to a conventional antenna without the PhC structure. This research highlights the potential of photonic crystal-based designs to significantly advance next-generation terahertz wireless communication technologies.

Dense plasma generators—plasma torches—have found wide application in various industries. The most common of them are electric arc gas heaters. Among electric arc plasma generators, plasma generators with gas discharge stabilization are the most widely used. The advantages of these plasma torches are high efficiency in various technological processes and a relatively simple design. This paper proposes a fairly versatile design calculation methodology for most possible gas-stabilized plasma torches, which is applicable to plasma torches with other methods of discharge stabilization. This methodology allows one to determine the main design dimensions of a plasma torch for a selected configuration and the main operating parameters of the process, or to perform a test calculation for a plasma torch with known dimensions.

Based on the general theory of transducers and Mason’s equations for the thermodynamic state of a piezoelectric medium, the transfer functions of a piezoelectric motor with an elastic multiplier for the developed force, velocity, and load displacement are obtained. Analytical expressions relating the parameters of the transfer functions to the design and piezoelectric characteristics of the multiplier and piezo actuator are determined. As a result, an approach to deriving the transfer functions of piezoelectric motors with external elastic elements is proposed.

The article examines ways to improve the technological flexibility of a robotic production line and enhance safety for human operators when interacting with it. This combined problem is a priority in the design and operation of robotic systems. Life-threatening emergencies may occur during the production process. They can cause equipment failure, necessitating urgent repairs or changing the speed of the production line, which will lead to changes in the production time of finished products. Therefore, this article focuses on the third stage of the robotic system’s life cycle, which involves human interaction with electrical devices, systems, and electrical machines. The problem of interaction between a process assembly module and a human specialist to increase technological flexibility was solved by implementing a voice assistant [1]. Comparing the resulting solution with recent research on this topic, we note the novelty of using a voice assistant, as opposed to ideas for standard, safe collaboration between humans and manipulators [2]. It is worth noting that the presented solution is one of the leaders in industrial robotics in terms of safety [3] and will allow enterprises to create jobs for people with disabilities.