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Vol 69, No 11 (2024)
Articles
Method of auxiliary sources for the problem of subsurface sensing of two-dimensional dielectric bodies by ultra-wideband electromagnetic impulses
Abstract
The modified method of auxiliary source (MMAS) is investigated for solving the diffraction problem of an ultra-wideband (UWB) electromagnetic impulse on a subsurface dielectric cylinder with an arbitrary cross-sectional shape (circular, elliptical, and drop-shaped). A dielectrically homogeneous half-space and a subsurface cylinder were excited by impulse electrical current source. It is shown that the fields calculated in time domain using the MMAS coincide with the results obtained from finite-difference method within a specified accuracy. It has been established that doubling the refractive index (the average value for the host medium and the filled cylinder) necessitates a similar twofold increase in the number discrete source (DS) and collocation points to maintain the accuracy of the solution. In the case of monochromatic excitation, it is shown that when K is reduced from 0.99 to 0.2, and also when the current frequency is increased from 300 MHz to 900 MHz, the mutual number of DS and collocation points must be increased approximately three times to maintain the same solution accuracy.
1039-1052
Electrodynamic models magnetized graphene diffraction gratings, based on the solution of integral equations for plasmonic anisotropic structures
Abstract
Two methods have been used to solve the boundary value problem of diffraction of a plane electromagnetic wave on a diffraction grating of graphene strips in the presence of a magnetic field. In solving the obtained integral and paired adder equations, the Galerkin method was used with a basis in the form of Legendre and Hegenbauer polynomials. As a result, systems of linear algebraic equations with fast internal convergence were obtained. All matrix elements of the system are expressed explicitly.
1053-1059
Interrelation of energy, spectrum and duration of an ultrashort electromagnetic pulse with its temporary form
Abstract
An ultrashort electromagnetic pulse energy and duration propagating along the radiation axis in the far zone are determined in two ways: by the shape of its electric field strength and by the energy spectrum. In both cases, the pulse energy is the same and the duration as well as peak amplitude differ by tens of percent. A comparative assessment is given for the energy dissipated in semiconductor elements of automated technical means irradiated by ultrashort and rectangular microwave frequency pulses. It is shown that the impact of a microwave pulse is better effective at carrier frequencies of the order of hundreds of megahertz and less.
1060-1066
Use of ytterbium porphyrins complexes in cancer theranostics
Abstract
The principles of new cancer theranostics methods based on nanosized Yb-porphyrins complexes have been developed. The obtained data indicate the promise of using synthesized nanoparticles based on Yb-porphyrins complexes for the development of sensitive luminescent diagnostics and theranostics methods for tumors of visually and endoscopically accessible localization. It is shown that laser photothermolysis at a wavelength of 750...800 nm in combination with near-IR luminescent diagnostics (in the spectral range of 900...1100 nm) is a pioneering development in the medical biophotonics. It is predicted that the synthesized structure of the Lexan-polymer matrix + Yb-porphyrin complex + FeOx can be in demand for the purposes of neoplasms magneto-luminescent theranostics. It has been established that tumors luminescent diagnostics in combination with photodynamic therapy in the porphyrin absorption band (wavelength 635 nm at an optical exposure dose of ~300 J/cm2) using the Fluroscan-type pharmaceutical composition can be used for malignant neoplasms of the skin and mucous membranes.
1067-1075
On the influence of oxygen bombardment on the structure formation of hafnium oxide films
Abstract
Hafnium oxide films were deposited by magnetron reactive sputtering under oxygen bombardment conditions. Structural analysis showed that the presence of oxygen bombardment during film growth leads to changes in the short-range order in the crystal structure of the films obtained.
1076-1078
1079-1094
Diagnostics of a high-current non-sputtering magnetron discharge in hydrogen
Abstract
The experiments were carried out to characterize plasma of a non-sputtering millisecond discharge in hydrogen at a pressure of ~ 1 Torr, pulse duration and a maximum impulse power near 1 ms and 80 kW, correspondingly. It has been demonstrated that the implementation of impulse non-sputtering modes of a magnetron discharge in light gases enables generation of dense non-constricted plasma with no lines of cathode or anode material present in its optical emission spectra.
1095-1098
Features of laser beam diffraction on periodic phase gratings with a rectangular shape relief
Abstract
The results of research on the diffraction of laser radiation on reflective phase diffraction grat-ings (DG), which are formed by a rectangular relief on the surface of a flat substrate, and the use of such DR for the construction of optoelectronic sensors of angular vibrations of objects are presented. Formulas for calculating the power of diffraction orders are given, calculated graphs of the dependences of the radiation power of diffraction orders on the angle of incidence of the optical wave on the DR at different depths of the relief of the DR are presented. The pos-sibility of using an optoelectronic circuit with a reflective DR for the construction of sensors of angular vibrations of the surface, seismometers and a modulator of laser radiation power is shown.
1099-1109
Motion noise compensation of the marine electrode sensor of the electric field
Abstract
The possibility of compensation of the noise component of the electrode sensor caused by pulsations of the liquid velocity relative to the electromagnetic field sensor electrodes and the possibility of increasing the sensitivity of the receiving device several times is shown. The scheme of the device for reception and measurement of low-frequency electric field in the sea, in which the specified compensation is realized, is offered.
1121-1125
Lorenz system as nonlinearly connected first-order radiophysical RC-filters
Abstract
A radiophysical implementation of the Lorenz system demonstrating a chaotic attractor is proposed. It is shown that the form of the Lorenz equation allows it to be represented as a set of low-frequency first-order RC filters connected by nonlinear connections using electronic multipliers. A circuit consisting of three first-order radiotechnical RC filters and two multipliers is proposed. An electronic circuit is considered that allows for the effective implementation of a generator demonstrating the chaotic Lorenz attractor.
1126-1131
Noise figure analysis of receiver based on current-driven mixer
Abstract
An analysis of the noise characteristics of the receiver based on a current-driven passive mixer is presented, taking into account the noise of the following blocks: the low-noise amplifier at input of the mixer, the mixer itself, and the transimpedance amplifier at output of the mixer. The noise at the output of the receiver, which is generated by the listed groups of noise sources, is analyzed. The noise figure of the receiver and its optimal (minimum) value are found taking into account the influence of parasitic capacitances of the switches of the mixer. The calculation results are confirmed by the simulation results.
1110-1120
The contributon of capacitive and induced currents in total currents on metal electrodes and Shockley-Ramo theorem
Abstract
The position of Shockley-Ramo theorem (SRT) in the theory of electric circuits is considered. A brief history of problem is given. The conditions are analyzed, when current sources in SRT in the case of potential electric fields are reduce to induced and capacitive currents.
1132-1138