Technical Physics最新文献

The method of numerical-analytical modeling using Maple 18 of the strong buckling of a uniform console with a symmetrical cross-section is presented. The range of plastic deformations in a materials with conditional yield strength (CYS) is studied. Standard profiles and sections made of low-carbon steel, titanium, polyethylene etc. were investigated. Were found and compared with the proper Eulerian values the critical loads of F_cr, N, the shape of buckled console y(z). The quasi-identity of the latter is established for the same slope p_f = dy/dz near the free console end. The method can be applied in robotics, structural mechanics, medical prosthetics, etc. where the materials been used with relatively high Young’s modulus and low the CYS.

Nonlinear transmission lines with ferrite have been actively developed and studied for about two decades. At the same time, the first works on this topic date back to the middle of the last century. Nonlinear transmission lines with ferrite find their application in various problems of electrophysics, with the greatest application being found in the problems of pulse sharpening, as delay lines and generators of highpower pulses of microwave radiation. The main scientific and technical results of the development of technologies of nonlinear transmission lines with ferrite are presented in chronological order, starting from lines for sharpening the fronts of voltage pulses, ending with multichannel microwave sources based on them.

The results of complementary studies of Al films grown by magnetron sputtering at room temperature are presented. The films were obtained on standard Si(111) substrates without and with a ∼20 nm aluminum (homobuffer) layer preliminarily grown on their surface at 400°C. The interdependence of the morphology, microstructure, and hardness of Al films on the state of the substrate surface was studied by the HRXRR, XRD, SEM, EDS, AFM, and Nano Indenter (ASTM) methods. It is shown that the formation of homobuffer layers on the substrate surface makes it possible to control the structural and mechanical properties of thin aluminum films.

As part of the Pulkovo program for the study of near-Earth objects, more than 1500 observations of asteroid 2023 BU, which was discovered at the very beginning of 2023 just a few days before its extremely close approach to the Earth at a distance of about 3.5 × 10⁶ m from its surface, were made at the MTM-500M telescope. It was one of the closest encounters of an asteroid with the Earth ever recorded, which caught the attention of astronomers around the world. Based on the observations of this asteroid, its orbit was refined and the orbital evolution was studied. In addition, estimates of the influence of solar radiation pressure and the Yarkovsky effect were made, which is relevant due to the problem of asteroid and comet hazard.

The properties of Mo/B₄C multilayer X-ray mirrors with periods of 3.74–3.84 nm are studied in this work. The dependences of the transmission band, reflection coefficient and the magnitude of internal stresses in mirrors on the ratio of material thicknesses in the period were investigated. The results of a study of the effect of thermal annealing on the structural parameters and reflective characteristics of mirrors are also presented in the paper.

The method of identifying the direction of the coupling between oscillators based on the simulation of phase dynamics of weakly coupled and weakly noisy periodic processes is used to determine the direction of the coupling between time series extracted from biological signals. Neuronal activity, arterial pressure and respiratory rate of anesthetized rats were used as initial data. Various options for the direction of the coupling between the analyzed time series were revealed.

The article presents the results of a qualitative study of the model of a modern magnetic memory cell, in which the spin Hall effect is used for recording. Cells of square cross-section with longitudinal anisotropy of the active layer are considered. Based on the Landau-Lifshitz-Gilbert vector equation, a mathematical model for controlling the process of writing zero and one into a cell is constructed. In the approximation of a uniform distribution of magnetization, a system of equations is derived that describes the dynamics of magnetization under the action of a magnetic field and spin current. The parameters of the qualitatively equivalent dynamics of the model are determined. It has been established that at zero currents and fields in both cases there are two main stable equilibrium positions. These equilibria, depending on the mutual orientation of the magnetization vector of the active and reference layers, correspond to zero and one, written in the cell. The transition from one cell state to another is described by solving a system of differential equations. A bifurcation diagram of a dynamical system in the variables “field–current” is constructed. It is shown that with a given configuration of the memory element, external influences transfer the magnetization to an intermediate state in the plane of the free layer, which, when the current and field are turned off, leads to writing zero or one to the memory cell. The critical switching current is estimated as a function of the applied external magnetic field.

Electrical resistivity of Co₄₈Fe₂₅Si₄B₁₉Nb₄ amorphous alloy and with small additions of rare-earth metals (= Nd, Sm, Tb, Yb) was studied using the AC four-probe method. It was found that these alloys have a specific behavior of electrical resistivity after crystallization-temperature dependences of resistivity at cooling are non-linear and can be fitted as ln R ~ T^−1/4.

A general approach to the analysis of resonant tunneling and scattering effects is developed within the framework of the Green’s functions method. The proposed mathematical apparatus is based on the biorthogonal formalism of quantum theory that allows one to describe systems with non-Hermitian Hamiltonians. Such operators are typical for problems wherein particle is supposed to leave the physical system and go to infinity. The stationary Schrödinger equation with a particle source is considered in abstract operator form. The solution of that problem is expressed in a general form in terms of the corresponding Green’s operator. Transmission coefficients and their dependences on the particle energy are determined for a single rectangular potential barrier and a double Gaussian barrier. The result of numerical calculation for a single rectangular barrier is compared with the well-known analytical solution of this problem. The proposed method makes it possible to analyze the particles tunneling and scattering in structures with an arbitrary number and shape of potential barriers with high accuracy.

In this paper, model of a surface ion trap for a scalable quantum computer with an RF electrode and a superconducting single-photon detector was studied with an operating temperature of 4 K. The amplitude range of the radio frequency signal varied from 10 to 800 mV at frequencies from 5 to 20 MHz. The effect of the induced external RF field of the trap on the dark and bright count rate of a single-photon detector is studied. The results of this work are important in the design of surface ion traps with planar single-photon detectors.