Technical Physics Letters最新文献

Protective coatings are an effective way to increase the wear resistance of various parts, tools, and components. Ti–Al–Ta–Si–N coatings combine the benefits of the Ti–Al–Ta–N and Ti–Al–Si–N systems which provide their improved hardness, toughness, adhesion, thermal stability and oxidation resistance. In this paper, the possibility of increasing the wear resistance of Ti–Al–Ta–Si–N coatings by introducing intermediate Ta layers is investigated. It is shown that the deposition of Ti–Al–Ta–Si–N/Ta multilayer compositions with optimal layer architecture can significantly increase their wear resistance. The wear rate of Ti–Al–Ta–Si–N/Ta coatings containing 15 layers is reduced by ~3.6 times compared to the monolithic Ti–Al–Ta–Si–N coating.

A new method is proposed for thermal protection of high-speed aircraft (HSA) nose cones, which is based on injection of a coolant with a strong temperature dependence of its dynamic viscosity (changing by 3‒5 orders of magnitude upon temperatures variation from 300 to 500 K) into the gas-dynamic boundary layer. This dependence allows the design of an automatic system for coolant delivery through channels formed in the structure onto the blunt cone surface, since, as the temperature of the structure increases, the coolant viscosity drops sharply, its fluidity increases, and, at a constant pressure differential between the coolant reservoir and the surface, its delivery to the boundary layer increases, forming a protective liquid film that flows and evaporates, injecting vapor into the boundary layer. As the structural temperature drops, the coolant delivery decreases. The efficiency of this thermal protection method is related to the fact that, first, the HSA surface temperature does not exceed the coolant evaporation temperature and, second, the HSA structure operates without mass loss and maintains its geometry. Numerical results have been obtained for the mass flow rate, mass evaporation rate of the liquid coolant film, its temperature, and the HSA structure temperature.

The fundamental possibility of identifying a mathematical model of heat transfer in thin ceramic coatings enriched with SiO₂ nanoparticles has been investigated. Thermal tests of samples with different nanoparticle contents (0–1.0%) have been performed to establish the thermophysical properties (thermal conductivity and heat capacity) of the coatings using the inverse heat transfer techniques, in particular, the iterative regularization method. The results obtained make it possible to evaluate the efficiency of the proposed approach to studying these coatings for increasing the durability of thermal protection materials used in aerospace engineering under extreme conditions.

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.