Short Electromagnetic Waves Research Articles

The contributions of Gilbert-damping and inhomogeneous exchange effects on the electromagnetic short waves propagation in saturated ferrite films

Numerical simulations of the non-integrable generalized Kraenkel-Manna-Merle (GKMM) system are performed to study the effects of Gilbert-damping and inhomogeneous exchange on the propagation of short waves in various saturated garnet ferrite films. It is observed that the Gilbert-damping mainly acts on reducing the amplitude and velocity of loop-solitons during propagation and the decay rates are slower than that in the linear theory. It is of interesting that such conclusions are suitable for multi-solitons. For different parameter ranges of the inhomogeneous exchange effect and the frequency of short electromagnetic wave, our simulations reveal four types of inhomogeneous exchange processes that effect on the loop-solitons in different ways. The domains of existence are presented and examples of each case are illustrated. Furthermore, the combined effects are discussed while taking both damping and inhomogeneous exchange into account.

The effect of gamma radiation on the structure of graphene oxide and graphene oxide functionalized with amino-PEG

The functionalization of graphene oxide (GO) with polyethylene glycol (PEG) has been widely used in drug delivery systems. This nanocomposite exhibits excellent stability in the presence of high concentrations of salts and proteins and shows to be less toxic than its raw form in vitro and in vivo. However, it must be sterilized before use in the medical field and the gamma irradiation shows a promising option for this purpose. Sterilization by ionizing energy through gamma rays, generated by Cobalt-60 self-disintegration, consists in exposing the materials to short electromagnetic waves. The irradiation process provides substantial advantages when compared to thermal and chemical processes such as more precise control of the process, production of products with superior qualities, lower energy consumption and less environmental pollution. In this work the effect of gamma radiation on the structure of GO and GO functionalized com Amino-PEG (GO-PEG-NH2) irradiated with different doses (15, 25, 35 and 50 kGy) and rate dose 7.31 kGy.h - 1 was evaluated. The analyses were performed by Fourier-transform infrared spectroscopy (FT-IR) and Raman spectroscopy. The results showed that the methods for the synthesis of GO and GO-PEG-NH2 was effective since there was confirmation of the surface oxidation of materials and functionalization with the PEG-NH2 and the sterilization by gamma radiation does not caused any defects on materials.

The effect of gamma radiation on the structure of graphene oxide and graphene oxide functionalized with amino-PEG

The functionalization of graphene oxide (GO) with polyethylene glycol (PEG) has been widely used in drug delivery systems. This nanocomposite exhibits excellent stability in the presence of high concentrations of salts and proteins and shows to be less toxic than its raw form in vitro and in vivo. However, it must be sterilized before use in the medical field and the gamma irradiation shows a promising option for this purpose. Sterilization by ionizing energy through gamma rays, generated by Cobalt-60 self-disintegration, consists in exposing the materials to short electromagnetic waves. The irradiation process provides substantial advantages when compared to thermal and chemical processes such as more precise control of the process, production of products with superior qualities, lower energy consumption and less environmental pollution. In this work the effect of gamma radiation on the structure of GO and GO functionalized com Amino-PEG (GO-PEG-NH2) irradiated with different doses (15, 25, 35 and 50 kGy) and rate dose 7.31 kGy.h - 1 was evaluated. The analyses were performed by Fourier-transform infrared spectroscopy (FT-IR) and Raman spectroscopy. The results showed that the methods for the synthesis of GO and GO-PEG-NH2 was effective since there was confirmation of the surface oxidation of materials and functionalization with the PEG-NH2 and the sterilization by gamma radiation does not caused any defects on materials.

Calling Inspector Gadget [Microwave Surfing

Unless you were away earlier this year on an intergalactic mission, you probably picked up the heavy media buzz around the claim [1] made by an “important government source”: There was an article this week that talked about how you can surveil someone through their phones, through their . . . certainly through their television sets, any number of different ways. And microwaves that turn into cameras, et cetera. So we know that that is just a fact of modern life. So: is it really a fact of modern life that microwaves can spy on you? It depends on the meaning of microwaves. According to the Merriam-Webster Online Dictionary [2], the word means either “a comparatively short electromagnetic wave; especially: one between about one millimeter and one meter in wavelength” or a “microwave oven.”

ELECTROMAGNETIC INTERFERENCE IMPACT ON FRONT-END RECEIVERS OUTSIDE THE ANTENNA BANDWIDTH

Impact of electromagnetic interference on front-end receiver behaviour is theoretically and experimentally studied outside the bandwidth of the antennas. Microwave chaotic generation is observed. Under certain conditions, re∞ected waves combined to the non linearity of the front-end receiver leads to a chaotic signal generation between the antenna and the front-end receiver. Difierent antennas, such as patch, loop, monopole and horn, are tested. Theoretical and experimental results are presented for each antenna. When an intentional or an unintentional electromagnetic interference is applied outside of the bandwidth of an antenna, re∞ection waves are generated between the antenna radiation impedance which is in the case of a few ohms and the nonlinear impedance of the front-end circuit of the receiver which is interconnected to the antenna via a transmission line. Under certain conditions, the efiects of the re∞ected waves due to antenna mismatch combined to those of the nonlinear impedance of the front-end circuits lead to chaos generation. This can have an impact on the electrical behaviour of the receiver particularly for high speed receiver systems and short electromagnetic interference wave lengths. The chaotic behaviour has already been observed in a microwave limiter circuit (1), in 'R-L-diode' circuits (2{7) and also in VHF microstrip oscillator (8). The doubling period has been observed

Eikonal waves, caustics and mode conversion in tokamak plasmas

Ray optics is used to model the propagation of short electromagnetic plasma waves in toroidal geometry. The new RAYCON code evolves each ray independently in phase space, together with its amplitude, phase and focusing tensor to describe the transport of power along the ray. Particular emphasis is laid on caustics and mode conversion layers, where a linear phenomenon splits a single incoming ray into two. The complete mode conversion algorithm is described and tested for the first time, using the two space dimensions that are relevant in a tokamak. Applications are shown, using a cold plasma model to account for mode conversion at the ion-hybrid resonance in the Joint European Torus.

Localization of Intense Electromagnetic Waves in a Relativistically Hot Plasma

We consider nonlinear interactions between intense short electromagnetic waves (EMWs) and a relativistically hot electron plasma that supports relativistic electron holes (REHs). It is shown that such EMW-REH interactions are governed by a coupled nonlinear system of equations composed of a nonlinear Schro dinger equation describing the dynamics of the EMWs and the Poisson-relativistic Vlasov system describing the dynamics of driven REHs. The present nonlinear system of equations admits both a linearly trapped discrete number of eigenmodes of the EMWs in a quasistationary REH and a modification of the REH by large-amplitude trapped EMWs. Computer simulations of the relativistic Vlasov and Maxwell-Poisson system of equations show complex interactions between REHs loaded with localized EMWs.

Current and Future Status of Pulse Elecromagnetic Wave Generation Using Plasma

Novel frequency upshift phenomena, a flash ionization and a photon acceleration process, are reviewed. The flash ionization is the frequency upshift that the quick creation of the plasma around a electromagnetic wave, on time scales on the order of a cycle of the wave. The photon acceleration is that the frequency of the electromagnetic wave propagating with the plasma density perturbation is upshifted because of the difference of the phase velocity. Furthermore, the generation of the short pulse electromagnetic wave in the THz region is also introduced.

Research in Medical Sciences

THE experiments of Faraday on electricity and of Helmholtz on heat and on light were incorporated during the latter half of the nineteenth century into a comprehensive electromagnetic theory inter relating light and electric and magnetic fields. Clerk Maxwell (1831-79) proposed the theory that light waves consist of oscillating electric fields at right angles to which are magnetic fields. The velocity of light, three hundred million meters (or 186,000 miles) per second, is the same for impulses of short and long wave-lengths and is one of the most impor tant of physical constants, comparable in its universality to the force of gravity. Indeed Einstein, in 1905, deduced, in terms of the velocity of light, the relation between mass and energy which made possible the prediction of atomic fission. Since the velocity is the same for all electromagnetic waves, includ ing light, differences in property are associated with the length of the wave or with its frequency. The propagation of electromagnetic waves, first studied by Hertz (1857-94), led to wireless telegraphy. Improve ments in technique have made it possible to transmit both very long and very short wave-lengths, ranging from centimeters to thousands of meters. The bands of the modern radio generally extend from 150 to 600 meters. Waves of these lengths may be absorbed by biological sys tems and give rise to considerable heating effects. Radio waves are very long in comparison with those of visible light, which range from about 0.0000007 meters, characteristic of red light, to about 0.0000004 meters for violet light. For convenience, different units are generally used in describing waves of short length, namely Angstrom units, one Angstrom unit being equal to one billionth of a meter. In these terms, red light has a wave length of 7,000 and violet light of 4,000 Angstrom units. The visibility of cells through the microscope depends upon the fact that their diameters are of the same order as the wave-length of light. Objects smaller than cells cannot be observed with ordinary light even through the most powerful microscope. In 1895, Wilhelm R?ntgen (1845-1923), studying the discharge of electricity through gases, noted that photographic plates, placed near the tubes, fogged when the gas in the tubes was largely exhausted. The action was not due to light, but to very short electromagnetic waves which passed through the tubes. The chance nature of the observation of this previously unknown type of radiation, X ray, is reminiscent of Galvani's earlier observation of the nature of electricity and of Bec querel^ later observation of radioactivity. In each instance, discoveries in new fields of the greatest importance were made because, to quote the

Methods to generate femto- and attosecond electron and X-ray pulses

Abstract Short electromagnetic wave pulses of wavelength λ can be used to modulate the energy of a charged particle beam on a scale of λ 2 , which in turn can generate particle bunching of dimension ≲ λ 2 , in the usual manner. These short bunches can then radiate correspondingly short photon bunches, including higher energy photons. Four types of devices are discussed which can achieve the requisite energy modulation on a scale of λ 2 : Vacuum, Cherenkov, resonator, and klystron modulators. The first is the simplest, and for short bunches its performance approaches, or is superior to that of the last two. For broadband short pulses it is generally to be preferred.

Short acoustic, electromagnetic, and elastic waves in random media

First and second one- and two-point moments of the phase, the amplitude, and the field of a periodic wave in a random medium are calculated. Acoustic, electromagnetic, and elastic waves are treated. In the electromagnetic and elastic cases the Stokes matrix is determined, and the depolarization of the wave is found. The medium is assumed to be nearly uniform and statistically homogeneous and isotropic. A high-frequency expansion is used together with a perturbation expansion in the magnitude of the inhomogeneity.

Influence of electron-positron pairs on the wakefields in plasmas

It is shown that the presence of electron-positron pairs can drastically reduce the amplitude and wavelength of electrostatic wakefields that are generated by coherent, short electromagnetic wave packets in unmagnetized plasmas. The relevance of our work to laboratory and cosmic plasmas is pointed out.

Complex Permittivity for an Ideal Dielectric of Stochastic Structure

AbstractThe effective complex permittivity is calculated of a microheterogeneous dielectric, which is a composite material or a polycrystal. The Bourret approximation is used and the binary correlation function of the permittivity tensor is taken to be exponential. Asymptotic formulas are presented for long, short, and ultrashort electromagnetic waves. The results are presented in the form of plotted frequency dependences of the imaginary and real parts of the effective permittivity and the Cole‐Cole diagrams for real and virtual waves.

Interaction of short surface and electromagnetic waves with ocean fronts

The interaction of short surface waves with shearing and converging currents is investigated by means of an approximate analytical solution of the wave action spectral transport equation. Spectral perturbations of less than 10% are predicted at centimeter wavelengths for moderately strong ocean fronts, although much larger perturbations are expected at wavelengths of the order of 1 m. These results, when combined with a simple Bragg electromagnetic scattering model, do not explain the large backscatter variations observed at X band and C band in the vicinity of ocean fronts. A two‐scale electromagnetic scattering model provides an effective coupling between the long‐wave spectral perturbations and the radar backscatter at small incidence angles, but this mechanism becomes less effective at intermediate incidence angles. Observation of large backscatter variations at these angles may thus be an indication of additional hydrodynamic and/or electromagnetic scattering mechanisms that are not yet accounted for.

Generation of density and magnetic field fluctuations by an electromagnetic wave packet in a magnetized plasma

Nonlinear interaction of a high-frequency short electromagnetic wave packet with a background magnetized electron plasma is considered. The possibility of excitation of both the low-frequency electrostatic potential and magnetic field fluctuations by the electromagnetic radiation pressure is demonstrated. The enhanced fluctuations can influence the propagation of the electromagnetic wave packet as well as the electron transport properties.

Effect of interconvertibility of electromagnetic and gravitational waves in strong external electromagnetic fields and the propagation of waves in the field of a charged “black hole”: PMM vol. 38, n≗ 6, 1974, pp. 1122–1129

It is shown that the behavior of an arbitrary wave propagating in the field of a nonrotating charged black hole is defined (with the use of quadratures) by four functions. Each of these functions obeys its second order equation of the wave kind. Short electromagnetic waves falling onto a black hole are reflected by its field in the form of gravitational and electromagnetic waves whose amplitude was explicitly determined. In the case of the wave carrying rays winding around the limit cycle the reflection and transmission coefficients were obtained in the form of analytic expressions. Various physical processes taking place inside, as well as outside a collapsing star, may induce perturbations of the gravitational, electromagnetic and other fields, and lead to the appearance in the surrounding space of waves of various kinds which propagate over a distorted background and are dissipated along its inhomogeneities. In the absence of rotation and charge in a star, the analysis of small perturbations of the gravitational fields is based on the system of Einstein equations linearized around the Schwarzschild solution. In [1, 2] this system of equations, after expansion of perturbations in spherical harmonics and Fourier transformation with respect to time, was reduced to two independent linear ordinary differential equations of second order of the form of the stationary Schrödinger equation for a particle in a potential force field. Each of these equations defines one of two possible independent perturbation kinds: “even” and “odd” (the different behavior of spherical tensor harmonics at coordinate inversion is the deciding factor in the determination of the kind of perturbation [1, 2]). Although these equations were derived with the superposition on the perturbations of the metric of specific coordinate conditions, they define, as shown in [4], the behavior of invariants of the perturbed gravitational field, which imparts to the potential barriers appearing in these equations an invariant meaning. The system of Maxwell equations on the background of Schwarzschild solution also reduces to similar equations, which differ from the above only by the form of potential barriers appearing in these [5]. In the presence in the unperturbed solution of a strong electromagnetic field the gravitational and electromagnetic waves interact with each other, and transmutation takes place. The train of short periodic electromagnetic waves generates the accompanying train of gravitational waves. This phenomenon was first analyzed in [6] on and arbitrary background. It was shown in [7, 8] that dense stars surrounded by hot plasma may acquire a charge owing to splitting of charges by radiation pressure and the “sweeping out” of positrons nascent in vapors in strong electrostatic fields. The interaction of waves becomes particularly clearly evident in the neighborhood of black holes which may serve as “valves” by maintaining equilibrium between the relict electromagnetic and gravitational radiation in the Universe. Rotation of black holes intensifies this effect [6]. If a nonrotating star possesses an electrostatic charge, the definition of perturbations of the electromagnetic and gravitational fields must be based on the complete system of Einstein-Maxwell equations linearized around the Nordström-Reissner solution. (Small perturbations of electromagnetic field outside a charged black hole were considered in [9, 10] on the basis of the system of Maxwell equations on a “rigid” background of the Nordström-Reissner solution, without taking into account the interconvertibility of gravitational and electromagnetic waves, which materially affects their behavior in the neighborhood of a charged black hole). Here this system of equations which define the interacting gravitational and electromagnetic perturbations are reduced to four independent second order differential equations, two for each kind of perturbations (an importsnt part is played here by the coordinate conditions imposed on the perturbations of the metric, proposed by the authors in [4]). Perturbation components of the metric and of the electromagnetic field are determined in quadratures by the solutions of these equations. If the charge of a star tends to vanish, two of the derived equations convert to equations for gravitational waves on the background of the Schwarzschild solution [1, 2], while the twoothers become equations which are equivalent to Maxwell solutions on the same background. The short-wave asymptotics of derived equations is determined throughout including the neighborhood of the limit cycle for the wave carrying rays. These solutions far away from the point of turn coincide with those obtained in [6] for any arbitrary background. Approximation of geometric optics does not provide correct asymptotics for impact parameters of rays which are close to critical for which the Isotropie and geodesic parameters wind around the limit cycle. This case is investigated below. A similar situation in the Schwarzschild field was analyzed in [11], where analytic expressions for the wave reflection and transmission coefficients were determined, and the integral radiation stream trapped by a black hole produced by another radiation component of the dual system was calculated.

Scattering of short electromagnetic waves by an oscillating body of complex shape

Scattering of short electromagnetic waves by an oscillating body of complex shape

The third Clerk Maxwell Memorial Lecture. “The diffraction of short electromagnetic waves”

The third Clerk Maxwell Memorial Lecture. “The diffraction of short electromagnetic waves”

Nonreflecting absorbers for microwave radiation

The absorption of very short electromagnetic waves by absorbing systems, which avoid reflection of the incident wave is a problem of practical interest. Three different methods are applicable: 1. Complete absorption of the incident energy can be obtained for one wavelength by using resonance systems of relatively small thickness; e.g., a resistance card having a surface resistivity equal to the wave impedance of free space and placed a quarter of the wavelength in front of a metal sheet; a dielectric layer of lossy material on a metal sheet, with the thickness of the layer equal to about a quarter of the wavelength in the material; a two-dimensional periodic structure of concentric resonant circuits arranged within the metal sheet itself. 2. The reflecting object can be covered by a thick layer of absorbing material, so that in a wide wavelength range most energy of the incident wave will be absorbed before reaching the reflecting surface. To avoid reflection, the absorption material can be tapered or arranged in different layers in such a manner that the loss tangent steadily increases towards the base plate. 3. The bandwidth of resonance absorbers can be widened without an increase of its thickness by combination of two specially dimensioned resonant circuits.

Proposed use of a cylindrical surface wave resonator for the determination of the velocity of short electromagnetic waves

It is proposed to set up a surface wave resonator consisting of a length of smooth bare wire acting as the guide and short-circuited at both ends by large flat conducting plates mounted at right angles with the guide. Energy would be supplied to the resonator at a frequency between 1000 and 40 000 Mc/s using either a coaxial or loop coupling and a similar device would be employed for the detector. From a knowledge of the guide wavelength, the frequency and the radial propagation coefficient of the wave in the air surrounding the guide, the corresponding T.E.M. wave velocity can be determined and thence c deduced for vacuum conditions. Attention is drawn to certain helpful features of the method but no attempt is made to assess its ultimate accuracy in comparison with other techniques whose value has been established for this purpose.