Technical Physics Letters最新文献

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.

Abstract

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.

Abstract

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.

Abstract—The growth of InGaN layers on hybrid SiC/Si substrates with orientations (100), (110), and (111) by the HVPE method was studied at temperatures that wittingly exceed the temperature of InN decomposition onto nitrogen atoms and metallic In (1000°C). On substrates with orientations (110) and (111), the formation of InGaN whisker nanocrystals was observed. The shape and growth mechanisms of nanocrystals were investigated. It is shown that nanocrystals nucleate on the (111) surface only inside V-defects formed at the points where screw dislocations exit onto the surface. On the (110) surface, nanocrystals are formed only on pedestals that arise during the film growth. An explanation is given for the difference in the growth mechanisms of nanocrystals on substrates of different orientations.

Abstract

Using a model representation of the motion of the Earth’s core in a viscous continuum, its equation of motion has been obtained and the linear size of the barysphere has been analytically found. A completely adequate estimate of the distance from the Earth’s center to the center of mass of the core has been given, which does not contradict modern geodetic concepts. It has been shown that the proposed model, which is not related to measuring the velocities of longitudinal and transverse seismic waves, makes it possible to determine quite satisfactorily all the basic geometric parameters of the barysphere.

Abstract

The principal aim of this study is to find a solution to the inverse problem of diffraction on cylindrical bodies located in free space. This problem can be applied in the diagnosis of breast cancer.. It is proposed to reduce the initial boundary value problem for the Helmholtz equation to an integral equation. This equation will be solved numerically. A two-step algorithm is used to solve the inverse problem. Graphic images are presented to illustrate the permittivity inside a body for the initial problem and for reconstructed values. A numerical method for finding the wave function is proposed and implemented, which makes it possible to identify the structure of an object without damaging or destroying it.

Abstract

Based on the principles of correlation theory, the dependence is calculated of dry friction sliding factor (k) in the form of a function from Poisson coefficients of both bodies (sigma ) and (sigma ') and temperature (T). The research method is based on the application of Green’s temperature functions for unbalanced processes. The dependence of the dry friction factor on the Poisson coefficients of both bodies and temperature has been found. A mathematical description is given of the dry friction factor depending on the parameters, meaning the function (k = kleft( {sigma ,sigma ',T} right)), which this is extremely important for the practical application of the resulting dependency.