Russian Physics Journal最新文献

The Green’s functions are compared for the Maxwell, Beltrami and Helmholtz equations as applied to effective infinite isotropic media, including electromagnetic metamaterials. The Dyadic and scalar Green’s functions are calculated based on the 3D and 2D Fourier transforms and the residue theory without using the so-called concept of a negative refractive index.

The paper studies parameters of the snow-ice cover and forest ground determined by the integrated approach based on the global navigation satellite system reflectometry. Experimental data on the amplitude and time response of satellite navigation signals are processed by fast Fourier transform and then analyzed using mathematical methods based on the multipath echoes model in terms of geometrical optics. Using a combination of reflectometry and numerical simulation of the surface layers based on local weather data, it is possible to evaluate not only the current state of these layers, but also predict their dynamic development.

A multiwave Cherenkov generator with an asymmetric oversized slow-wave structure and an azimuthally inhomogeneous electron beam has been experimentally studied. At a diode voltage of 680 kV and a beam current of 10 kA transported in a magnetic field of 0.5 T, pulses of linearly polarized radiation with a wavelength of 3.26 cm, a duration of 30 ns, and a power of 1.7 GW have been obtained.

Blue aluminum silicate phosphors of Sr₁Al₂Si₂O₈, Sr_0.98Al₂Si₂O₈:0.02Eu²⁺ and Sr_0.98–xAl₂Si₂O₈:0.02Eu²⁺, xTm³⁺ (x = 0.005, 0.01, 0.02, 0.04, 0.08) compositions are prepared by high temperature solid phase method. Their XRD, fluorescence emission and excitation luminescence properties, afterglow attenuation, afterglow luminescence, thermoluminescence and photostimulated luminescence properties are investigated. The results show that a high purity crystallized phosphor can be successfully prepared at 1350°C for 4 h. It is proven that Eu²⁺ as the luminescent center is replaced by Sr²⁺ with a coordination number of 12; Eu²⁺ and Tm³⁺ are substituted for Sr²⁺, which is the reason for a decrease in the unit cell parameter values. The sample excitation and emission spectra have peak wavelengths of 330 nm and 405 nm. Sr_0.97Al₂Si₂O₈:0.02Eu²⁺, 0.01Tm³⁺ has a minimum afterglow decay rate of 0.61389, which is suitable for use as a long-lasting luminescent blue phosphor. The pyroluminescence indicates that doping with Tm³⁺ significantly deepens the trap level. The photostimulated luminescence proves that the co-doped Tm³⁺ greatly improves the initial intensity and the optical storage performance of the photostimulated luminescence, especially the Sr_0.96Al₂Si₂O₈:0.02Eu²⁺; the 0.02Tm³⁺ sample trap level is 0.8999 eV. The initial photostimulated luminescence intensity of the co-doped sample is shown to be 1000 times that of the single doped Eu²⁺, and the optical storage – 1.8 times that of the single doping case.

The main disadvantage of encoders currently used to measure the object motion, is the required mechanical coupling with the observed object, that significantly limits its scope of application. The paper presents theoretical results of the contactless (without mechanical contact with the observed object) encoder based on the Doppler effect. The block diagram and the analysis are presented for the proposed contactless encoder.

The changes in the wear and contact structure of steel specimens are determined in dry sliding against steel under an alternating electric current at different values of the nominal contact area. It is shown that the wear rate decreases with the contact area. The formation of transfer layers (tribolayers) on the contact surfaces containing FeO and α-Fe is observed. The plastic deformation of these tribolayers is accompanied by the formation of morphology consisting of two sectors on the sliding surface. One of them has traces of a viscous liquid. It is hypothesized that this factor contributes to a rapid stress relaxation in the tribolayer, followed by a corresponding wear intensity decrease.

Heat engines based on the rotation of fullerenes C60 and C80 are considered. A theoretical description based on models of classical particle dynamics is used. Chiral effects of fullerenes C60 and C80 have been studied. The work of the heat engine during one operating cycle of the heat engine is found. Molecules of the monatomic gas helium are used as the environment molecules.

The paper reviews research results of the ultrafine grained structure of titanium alloy and Zr–1Nb, Ti–45Nb, and Mg–Y–Nd alloys affecting their thermal properties and energy dissipation and storage during deformation. It was found that substructural strengthening during severe plastic deformation of ultrafine grained titanium and Zr–1Nb alloys reduces their heat capacity and thermal diffusivity by ~10% and changes the deformation and thermal behavior, especially at the initial stage of loading. It has been shown that dispersion hardening of the Ti–45Nb alloy with ω-phase nanoparticles and Mg–2.9Y–1.3Nd alloy with Mg₂₄Y₅-phase nanoparticles decreases the effect of the ultrafine grained structure on their thermal properties and energy dissipation and storage at the initial stage of tensile deformation.

An algorithm for erosive fracture of solid bodies during high-velocity interactions is presented. The algorithm is implemented using the finite element method. The proposed mechanism for describing erosive fracture and restructuring of the computational mesh ensures the conservation of mass law. To accelerate the data preparation for the erosive fracture algorithm, optimization of the algorithm for searching adjacent element faces has been performed.

Methods of reconstructing holographic images of objects made of the composite based on carbon fibermodified acrylonitrile-butadiene styrene and a thin electrically conductive film are presented. Holograms are obtained in the axial scheme when the collimating lens is placed on the source axis. Results of comparison of the calculated frequency response of the model transmission coefficient with measurements on an experimental setup are presented.