Journal of Communications Technology and Electronics最新文献

Abstract—

The paper presents the results of experimental determination of the spin Hall angle in a Pt/La_0.7Sr_0.3MnO₃ bilayer metal/ferromagnetic structure inferred from angular dependences of longitudinal and transverse spin magnetoresistance in configuration of the planar Hall effect. The value of the spin Hall angle determined from the longitudinal magnetoresistance is θ_Hx ≈ 0.016, and that from the transverse magnetoresistance is θ_Hy ≈ 0.018, whereas for SrIrO₃/La_0.7Sr_0.3MnO₃ heterostructures the ratio of values of the transverse spin Hall angle to the longitudinal one appears to be substantially higher, θ_Hy/θ_Hx ≈ 9, which is apparently caused by a layer with a high spin conductance formed at the SrIrO₃/La_0.7Sr_0.3MnO₃ interface.

Abstract

The dependence of radiation losses in a liquid on the value of displacement component U₃ normal to the plate on the surface of a piezoelectric plate for Lamb waves of various orders has been experimentally investigated. The waves whose phase velocity V_n in the plate is greater than velocity V_l of the longitudinal volumetric acoustic wave in the liquid are considered. It is shown that at low values of U₃, there is no radiation into the liquid and the value of radiation losses is close to zero even at V_n > V_l, at high values of U₃, the value of radiation losses is large and for Lamb waves in the YZ–LiNbO₃ plate with a normalized wavelength thickness of 1.75 and a frequency of 16.97 MHz, it reaches a value of 4 dB/mm, comparable to the radiation losses of surface acoustic waves in the same material.

Abstract—

All currently known methods and ways for the formation of the fractal features of polarimetric radar images have been given. A new textural-fractal feature has been briefly considered: a directional multifractal signature measured morphologically by an iterative coverage method. In relation to the analysis of polarimetric images generated by a synthetic aperture radar, a new concept of their processing based on the possibility of considering the polarization differences of terrestrial spatially distributed objects by identifying the multifractal and anisotropic properties of their texture has been proposed. The variant of interpretation of the results for automation of further successful solution of specific problems of segmentation (classification) of the underlying surface and detection and recognition of ground objects has been shown.

Abstract—In the modernization of Global Navigation Satellite System (GNSS), Binary offset carrier (BOC) modulation signal has been applied as a new modulation method, but it also brings the complexity of signal acquisition process. To reduce the data required for BOC signal acquisition and eliminate acquisition ambiguity, an unambiguous compression acquisition method is proposed. The core ideas are as follows: (1) Based on the principle of disambiguation by side-peak superposition, a matrix operation model is constructed for signal sparse transformation; (2) Extract the basic elements of compressed sensing (CS) theory, select a measurement matrix based on singular value decomposition (SVD) for compression measurement, and use the Orthogonal Matching Pursuit (OMP) algorithm for signal reconstruction. The simulation results show that the method can completely remove the side-peaks of the acquisition curve. The acquisition performance is more than 3 dB better than the compressed sensing acquisition method based on singular value decomposition (SVD-CS). The sampling rate is more than 57% lower than that of the BOC signal acquisition based on side-peak superposition (BASS), overcoming the limitation of Nyquist sampling theorem. Finally, it can be explained that the proposed method can realize the unambiguous acquisition of BOC signal under low sampling rate.

Abstract

A series of studies of the structure of aluminum films deposited on single-crystal silicon substrates in different temperature regimes has been carried out. The roughness and grain size of 20-nm thick films of nuclei deposited at elevated temperatures and also dusted over the nucleus layer at room temperature to a thickness of 150 nm was studied using an atomic force microscope. The film profile was measured in an electron microscope. It is found that films on a hot sublayer turn out to be smoother, more rigid (less friable), and make it possible to expect the creation of superconductor–insulator–superconductor and superconductor–insulator–normal metal transitions with a higher current density and lower capacitance, respectively.

Abstract

The possibility of constructing wavelets based on convolutions with a rectangular impulse of exponential and harmonic atomic functions has been studied. Some properties of exponential and harmonic atomic functions are considered. The values of the uncertainty constants of the constructed wavelets are calculated.

Abstract

The results of the development of a meander-line slow-wave system (SWS) with metal supports for a miniature high-power W-band traveling-wave tube (TWT) with two sheet electron beams are presented. Using a three-dimensional finite element software package, the electromagnetic parameters of the SWS were studied. A two-section model of a TWT amplifier with a sever to prevent self-excitation has been developed. Three-dimensional modeling of the beam–wave interaction has been carried out. It was found that with a total beam current of 200 mA in the linear mode, the gain exceeds 30 dB in the frequency band 95.4–97.75 GHz, and the output power in the saturation mode reaches 120 W. A technology for manufacturing SWSs based on laser micromachining of thin copper plates is proposed. Test samples of the SWS were fabricated and verified using optical and scanning electron microscopy.

Abstract

We study magnetism in the 2D magnets with a (d)-metal sub-lattice based on the density functional theory and Monte-Carlo simulations. The phenomena of ligand field and the macroscopic nature of (p{text{-}}d) orbitals hybridization has been discussed widely. For a magnetism in the 2D materials with a honeycomb and hexagonal (d)-metal sub-latices we derive an effective Hamiltonian for a spin subsystem with and without inclusion next nearest-neighbors interaction and higher-order terms. Based on the proposed models critical temperature ({{T}_{{text{C}}}}) for a wide range of compounds estimated.

Abstract

A TiNi shape memory alloy plate has been simulated at different crystallographic orientations in the free LAMMPS classical molecular dynamics simulator. It has been found that the crystallographic orientation of the plate significantly affects the phase transition temperature. The temperature dependence of the surface energy at the (100), (110), (112), and (122) crystallographic orientations has been built. The stability of the model used has been examined and thereby its applicability to the calculation made has been confirmed.

Abstract

In this paper, we developed and investigated superconducting integrated circuits designed to match the impedances of a generator represented by a flux-flow oscillator based on a long Josephson junction and a detector based on a superconductor–insulator–superconductor tunnel junction in the subterahertz frequency range. The structures were modeled using the transfer matrix method. Designs were also calculated in the program of numerical three-dimensional modeling. A qualitative agreement was found between the results obtained by two methods. Three samples with different topologies were designed, covering the frequency range of 250–680 GHz at a level of –2 dB.