Electromagnetic Waves In Medium Research Articles

Energy and momentum of electromagnetic waves in media

Energy and momentum of electromagnetic waves in media

Technology for combining the processes of salting and heat treatment of offal in a microwave installation

Relevance. With the increase in livestock production, the question of the rational use of by-products arises. Currently, such raw materials are mainly sold without processing. To increase the profitability of production, it is proposed to sell the offal in boiled form. One of the ways to obtain boiled products from small-sized meat raw materials with good consumer properties is the use of endogenous heating during massaging in brine.Methods. Theoretical studies were carried out by analyzing the physical processes associated with the propagation of electromagnetic waves in media with losses; the mass-transfer processes in raw materials with a curing substance during endogenous heating were studied. The visualization of the distribution of the electromagnetic field (EMF) in a cylindrical slotted resonator, the calculation of the intrinsic quality factor and the electric field strength (EF) were carried out using the CST Microwave Studio program. The substantiation of the operating modes of the installation was carried out through regression models obtained using a threefactor experiment of type 23 in the programs Statistica 12.0, Microsoft Excel 10.0. In the Compass-3D 18 program, three-dimensional modeling of the structural design of cylindrical slotted resonators-drums was carried out. Electromagnetic safety was evaluated by the results of studies of the power of the radiation flux by the installation using a PZ-33M, PZ-41 measuring devices.Results. The operating modes of the developed and manufactured microwave installation with a slotted cylindrical resonator-drum for heat treatment and massaging of raw materials are established, taking into account regression models. They are: productivity 10 kg/h; specific power 1.6 W/g; processing time 1.0 h, at a salt concentration of 12.88%; specific energy costs 0.165 kW·h/kg; frequency of rotation of the resonator-drum 23 rpm.

On nonclassical boundary conditions for the contact of thin interlayers with different physical and mechanical properties on wave propagation in anisotropic media

Wave processes are intensively studied in various fields of physics: electrodynamics, plasma physics, radiophysics, acoustics, hydrodynamics, etc. Along with the study of electromagnetic and elastic wave processes, the research of patterns of wave propagation of various physical nature in the presence of mutual transformation are of particular relevance. Wave processes in coupled fields reflect the mutual influence of elastic, electromagnetic and thermal fields. The coupling of electromagnetic fields to the deformation field takes place in a medium with piezoelectric, piezomagnetic and magnetostrictive properties. In the paper, based on the matrix method, the propagation of coupled elastic and electromagnetic waves in media with different physical and mechanical properties is studied. The paper proposes a generalization of non-classical contact conditions for studying the effect of thin layers with different physical and mechanical properties on wave processes. A system of differential equations of the 1st order with variable coefficients is constructed, which describe the propagation of electroelastic waves in anisotropic media of a rhombic system of class 222. The conditions for nonrigid contact for a thin layer with piezoelectric properties are derived. The possibility of studying layers with δ-shaped properties (δ is the Dirac function) is proved.

Ponderomotive forces, Stokes drift, and momentum in acoustic and electromagnetic waves

This work illuminates fundamental connections between three wave-induced phenomena: (i) the ponderomotive force acting on the medium particles, (ii) the Stokes drift of free medium particles, and (iii) the canonical wave momentum. The results are applicable to sound waves in fluids or gases and to electromagnetic waves in media with free electrons.

Transmission enhancement effect of electromagnetic wave in non-uniform collisional plasma

The effect of plasma on the transmission properties of electromagnetic waves and its application have always been one of the key research directions of electromagnetic theory and technology and plasma physics. The enhancement effect of collisional plasma on electromagnetic waves is a classic subject of the interaction between electromagnetic waves and plasma. Based on the transmission characteristics of electromagnetic waves in medium, this paper takes plasma as a special medium, and carries out experimental, theoretical and simulation studies on the transmission characteristics of high power microwave (HPM) atmospheric plasma and a certain range of electromagnetic waves under certain experimental conditions. The study found that the plasma formed by the S-band HPM under a vacuum of 50 Pa has a great influence on the electromagnetic wave transmission characteristics of different frequencies, and the electromagnetic wave transmission signal enhancement effect occurs regularly within a certain frequency range. A series of transmission waveforms of continuous electromagnetic waves of different frequencies passing through the HPM plasma area were obtained, and the waveforms were normalized. At 32.4 GHz, the transmission coefficient of continuous electromagnetic waves passing through the plasma area with plasma is about twice as high as that through the area without plasma. A simulation model was established, and the transmission coefficient distribution curve in the range of 31.5−32.5 GHz was obtained. The electromagnetic wave passing through the plasma showed a transmission enhancement effect, and at some frequency points, there was a transmission enhancement of about 1.9 times. The research results provides important technical support for the application of plasma in stealth, emergency communications, and black barrier communications.

Phase-Plane Analysis of Solutions of the Helmholtz Equation for Electromagnetic Waves in Media with Self-Action

We describe the application of the phase plane method to analyze the behavior of stationary harmonic plane electromagnetic waves. The phase plane method allows one to describe qualitatively all possible solutions of the Helmholtz nonlinear differential equation without performing a numerical integration. All types of phase portraits for waves in the media with self-action are presented and their physical interpretation is discussed. The consideration is carried out on the model of cubic nonlinearity without specifying the physical mechanism of this nonlinearity. The features of the nonlinear case are discussed. The phenomenon of the self-limitation of the transmitted wave power in a medium with negative nonlinearity is described.

Nonlinear Interaction of Electromagnetic Waves in a Dense Plasma

We discuss the nonlinear phenomena caused by the quadratic interaction of electromagnetic waves in a dense charged medium (Coulomb systems and plasma), including the parametric generation and second harmonic generation of the electromagnetic radiation. To determine the quadratic reaction functions describing the interaction of electromagnetic waves in a medium, an approach based on the explicit approximations for the reaction functions with adjustable parameters is used. The parameters are found from the exact frequency moments of the reaction functions. Using the data on the reaction functions, the conditions for the experimental implementation of the above-mentioned phenomena in a laboratory dense plasma in a dc magnetic field are estimated.

Нелинейное взаимодействие электромагнитных волн в плотной плазме

Nonlinear phenomena caused by the quadratic interaction of electromagnetic waves in a dense charged medium (Coulomb systems, plasma) are considered: parametric generation and generation of the second harmonic of electromagnetic radiation. To determine the quadratic reaction functions describing the interaction of electromagnetic waves in the medium, an approach based on the use of explicit approximations for reaction functions with fitting parameters is applied. Parameters are found from the exact frequency moments of the reaction functions. Using data on reaction functions, the conditions for the experimental implementation of these phenomena in a laboratory dense plasma in a constant magnetic field were evaluated.

Wave propagation in and around negative-dielectric-constant discharge plasma

The modes of wave propagation in media with a negative dielectric constant are not simple, unlike those for electromagnetic waves in media with a positive dielectric constant (where modes propagate inside the media with positive phase velocity since the refractive index is usually positive). Instead, they depend on the permeability sign, either positive or negative, and exhibit completely different features. In this report, we investigated a wave confined on the surface of a negative-dielectric-constant and a positive-permeability plasma medium for which the refractive index is imaginary. The propagation mode is similar to surface plasmon polaritons on the metal containing free electrons, but its frequency band is different due to the significant spatial gradient of the dielectric constant and a different pressure term. We also studied a wave with a negative dielectric constant and negative permeability, where the refractive index is negative. This wave can propagate inside the media, but its phase velocity is negative. It also shares similar qualities with waves in plasmonic devices with negative permeability in the photon range.

Electromagnetic waves in media with permittivity dispersion

A technique for the numerical simulation of electromagnetic wave propagation in materials with permittivity depending on the frequency is presented. The technique is based on numerical solutions of Maxwell equations with additional integral components in the bias current density. The technique to calculate the bias current density in dispersive media is represented and the corresponding modification of finite-difference scheme for Maxwell equations developed earlier is carried out. The electromagnetic pulse propagation in solid-fuel power systems is calculated.

Electromagnetic Waves in Media With Correlated Inhomogeneity of Permittivity and Permeability

The propagation of electromagnetic waves is examined in inhomogeneous media where the product of the permittivity and permeability is independent of position. A plasma-like frequency dispersion of the refractive index in these media is predicted. It is established that there is a cutoff frequency below which electromagnetic waves cannot be excited in these media. In general, two types of inhomogeneous waves can propagate in these media: transverse electric and transverse magnetic. The magnetic field of the transverse electric waves has a longitudinal component and is elliptically polarized in the plane formed by the wave normal and the gradient of the parameters of the medium. The electric field of the transverse magnetic waves has similar properties.

Metamaterials for ballistic electrons

This article presents a metamaterial for ballistic electrons, which consists of a quantum barrier formed in a semiconductor with negative effective electron mass. This barrier is the analog of a metamaterial for electromagnetic waves in media with negative electrical permittivity and magnetic permeability. Besides applications similar to those of optical metamaterials, a nanosized slab of a metamaterial for ballistic electrons, sandwiched between quantum wells of positive effective mass materials, reveals unexpected conduction properties, e.g., single or multiple room temperature negative differential conductance regions at very low voltages and with considerable peak-to-valley ratios, while the traversal time of ballistic electrons can be tuned to larger or smaller values than in the absence of the metamaterial slab. Thus, slow and fast electrons, analogous to slow and fast light, occur in metamaterials for ballistic electrons.

Design of Linear-to-Circular Polarization Transformers Made of Long Densely Packed Metallic Helices

In this work, we study the realization of realistic polarization transformers formed by long metallic helices. To this end, we propose a new homogenization model to characterize the propagation of electromagnetic waves in medium formed by infinitely long helices. We derive approximate analytical expressions for the effective permittivity, effective permeability and the magnetoelectric tensor of the composite material, taking into account the effects of spatial dispersion. We apply the new homogenization model to characterize novel linear-to-circular polarization transformers. Our results show that the metamaterial screen may be designed in such a way that an incoming linearly polarized wave may be transformed into a circularly polarized transmitted wave, and that the transmission efficiency of such polarization transformer may be as high as 95%. The theoretical results are supported by full wave simulations.

Propagation of Electromagnetic Waves in Media Undergoing Complex Motions

Results of a theoretical and experimental investigation into new effects in moving-media optics are presented. An exact analytical solution is obtained for the trajectory of the wave vector of a monochromatic electromagnetic plane wave in a medium undergoing a complex motion. It is shown that the spatial dragging of the electromagnetic wave by the moving medium can be described correctly in the general case only if relativistic terms of order β2 are taken into account. Also, in this investigation a spatial effect of the light drag was observed at a wavelength of λ =0· 63299 μm by means of an optical disk with a refractive index n=1· 4766, a radius of R0 =0· 06 m rotating at a frequency of ω =25 Hz. A relative shift of the interference pattern, monitored by the time of the interference band motion across the aperture of a photodetector for the disk rotating in the opposite directions, amounted to \(\Delta_\Sigma^{\rm exp} =0\cdot 0076\pm 0\cdot 0030\) of the interference bandwidth. The results of theoretical calculations of the expected interference pattern shift on the basis of the total solution of the dispersion equation in the experiment are in agreement with the experimental results. Analysis of the results obtained suggests that the detected effects determine a wide class of observed phenomena, even when the velocities of moving media are non-relativistic.

Operator of Effective Permittivity of a Statistically Inhomogeneous Medium with Strong Fluctuations

The majority of known works on the theory of multiple scattering of electromagnetic waves in media with strong fluctuations are constrained by the assumption of statistical homogeneity of a medium. In this paper, we consider an isotropic lossy random medium, for which the principle value and multipole moments of the permittivity are invariant with respect to arbitrary rotations about a fixed symmetry axis and translations along the axis and are inhomogeneous in the radial direction. This paper is aimed at calculating the effective permittivity operator (EPO) for such a medium for the case of strong permittivity fluctuations.

The 2.5D FDTD and Fourier PSTD methods and applications

AbstractIn this work, 2.5‐dimensional finite‐difference time‐domain (FDTD) and pseudospectral time‐domain (PSTD) algorithms are developed for electromagnetic waves in media that are invariant in one spatial dimension. Both algorithms use Berenger's perfect matched layer (PML) as an absorbing boundary condition. The FDTD method is an extension of Yee's 3D algorithm to 2.5D. The PSTD algorithm uses the fast Fourier transform to approximate spatial derivatives, and gives a much higher accuracy than the FDTD method. Numerical results have been validated by comparing them with analytical solutions. The methods have been applied to ground‐penetrating‐radar and dielectric‐waveguide problems. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 36: 430–436, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.10783

Gaussian beams in hollow metal waveguides

Various families of Gaussian beams have been explored previously to represent the propagation of nearly plane electromagnetic waves in media having at most quadratic transverse variations of the index of refraction and the gain or loss in the vicinity of the beam. However, such beams cannot directly represent the wave solutions for propagation in planar or rectangular waveguides, and sinusoidal mode functions are more commonly used for such waveguides. On the other hand, it is also useful to consider the possibility of recurring Gaussian beams that have an approximately Gaussian transverse profile at certain distinct planes along the propagation path. It is shown here that under some conditions recurring Gaussian beams can describe wave propagation in hollow metal waveguides, and they can also lead to efficient coupling between the waveguide fields and free-space beams.

Intermittency of electromagnetic waves in a regular time-varying medium

A transformation of a plane electromagnetic wave in a medium with permittivity and conductivity changing in time as a finite sequence of rectangular periodic pulses is considered. An exact solution of the problem is derived and the influence of the conductivity on the wave parametric amplifications is investigated. A transition to intermittent chaotic behaviour of the secondary waves is shown to occur and the Hurst index is numerically estimated.

Reflection of electromagnetic waves from nonstationary media (exactly solvable models)

An analysis is made of propagation of electromagnetic waves in media which are nonstationary because of relaxation of the refractive index. A series of models of oscillatory and transient regimes of such relaxation is developed. Several characteristic times are used in these models and exact analytic solutions of the Maxwell equations can be obtained for these regimes. In contrast to the traditional approaches, the exact solutions are obtained without assuming smallness or slowness of temporal variations of the parameters of the medium and these solutions are valid even when the characteristic relaxation time is comparable with the period of oscillations of the wave field. A nonstationary generalisation of the Fresnel formulae is derived. It is shown that waves reflected from a nonstationary surface experience amplitude and frequency modulation, and the modulation effect is localised in an interval of the order of one relaxation time. It is shown that a short broadband perturbation pulse forms in the reflected wave and that this pulse contains one or several oscillations of the field. It should be possible to use nonstationary broadening of the spectrum of a probe wave reflected from a surface perturbed by a powerful laser pulse in estimating the relaxation times of fast optical processes.

Modulational instability of electromagnetic waves in media with varying nonlinearity

The process of modulational instability of nonlinear plane waves is investigated in media with periodically and randomly varying nonlinearity. The wave behavior is analyzed in the parametric instability region under the joint action of periodic modulation and the self-steepening effect, and a recurrence phenomena is observed for the nonlinear wave in the parametric resonance region. Stochastic parametric resonance is predicted in the case of a random media. The increment value of stochastic parametric resonance obtained numerically is in good agreement with the theoretical estimate.