Technical Physics Letters最新文献

Abstract—For deeply supercooled bulk water, known are anomalies of thermodynamic quantities near the Widom line, the locus of increased fluctuations of entropy and density. In this work, we measured the reflected power of microwave radiation at the frequency of 18 GHz from a silicate sorbent sample moistened with a hydrogen peroxide solution. In the experiment, we observed variations in the recorded reflected radiation power in the range of –46 to –47°C determined by structural changes in the liquid. Thus, it is shown that fluctuations of water parameters near the Widom line manifest themselves in changes not only in thermodynamic, but also in electrophysical quantities.

A technique has been developed for frequency analysis of the IR reflection spectrum to determine the thickness and order of the layers in the epitaxial structure of silicon carbide. Calculations for the 4H-SiC epitaxial structure have been performed. The method has been shown to be highly sensitive to optical boundaries resulting from a sequential increase in the doping level during the layer growth.

The parameters of a high-current electron beam extracted from the self-focusing zone through a hole in the anode into a vacuum chamber are investigated. The beam parameters were determined from the measurement of the spatial distribution of destruction and glow arising in polymethyl methacrylate samples installed at different distances from the anode (electron beam autographs). The formation of two electron beams—a self-focused with a high energy density, propagating along the axis of the cone facing the base to the anode with an apex angle of ~7° and a high-energy beam of low density, propagating in a hollow truncated cone and surrounding self-focused, was found. The oscillograms of the current and the energy of the electron beams were measured.

The influence of the coating method (spray-coating or drop-casting onto horizontal substrate) on the electrochromic characteristics of the layers of water-soluble polyaniline–polyacid complex was investigated. It was shown that, in the case of adding single-wall nanotubes, the polyaniline–polyacid layers prepared by the scalable spray-coating technology demonstrate high coloration speed and electrochromic efficiency.

Abstract—The irradiation of silicon nanowires with Ar⁺ ions with the energy of 250 keV and fluences of 10¹³ to 10¹⁶ cm^–2 was carried out. The dependence of the destruction of the structure under ion irradiation on the fluence was investigated by Raman spectroscopy. It was shown that the amorphization of porous silicon occurs at higher values of displacement per atom than in thin silicon films.

Abstract—A model of spontaneous formation of the core-shell structure in (In,Ga)As nanowire grown via molecular beam epitaxy without independent radial growth is proposed. Within the framework of the proposed model, the distribution of In across the axis of the nanowire was fitted.

Abstract—A harmonic effect on a modified Anishchenko–Astakhov generator capable of demonstrating two-frequency quasi-periodic oscillations in the autonomous mode is considered. The possibility of doubling the three-frequency tori in a non-autonomous system is shown. The possibility of the effect of chaos suppression by an external signal is demonstrated, which leads not only to periodic, but also to quasi-periodic modes when the influence amplitude exceeds a certain threshold.

The paper presents the results of a theoretical study of the dispersion characteristics of electromagnetic waves (EMW) existing in a transversely magnetized antiferromagnetic (AFM) semiconductor with loss. An AFM semiconductor is an infinite bi-gyrotropic medium, the effective material parameters of which are twice negative in several frequency ranges. It was found that these frequency bands are in the terahertz range, and there are four backward EMEs in them, two of which are TE waves, and the other two are TM waves.

An experimental study of pulsations characteristics of the zone of flow separation arising at a small airplane- type UAV with a pushing two-blade propeller were carried out. The measurements were done in wind tunnel by unsteady pressure sensors and microphones built into the skin of the UAV for the test cases with and without a rotating propeller. A significant effect of the propeller on the level of pulsations was found. An increase of the incoming flow velocity led to a weakening of this effect. Analysis of the spectral data of the disturbances did not reveal a direct relationship between the propeller noise and the unsteady characteristics of the separation zone.

Abstract—The possibility of the existence of laminar chaos in coupled time-delayed feedback systems is investigated. The cases of unidirectional and mutual coupling of time-delay systems are considered. It is shown for the first time that laminar chaos can exist not only in a system with a variable delay time, but also in a system with a constant delay time, if it is coupled with a system in the regime of laminar chaos.