Showing papers on "Electromagnetic field published in 1990"
TL;DR: In this paper, an accurate and general procedure for the analysis of electromagnetic radiation and scattering by perfectly conducting objects of arbitrary shape embedded in a medium consisting of an arbitrary number of planar dielectric layers is developed.
Abstract: An accurate and general procedure for the analysis of electromagnetic radiation and scattering by perfectly conducting objects of arbitrary shape embedded in a medium consisting of an arbitrary number of planar dielectric layers is developed. The key step in this procedure is a formulation of the so-called mixed-potential electric field integral equation (MPIE) that is amenable to an existing advanced solution technique developed for objects in free space and that employs the method of moments in conjunction with a triangular-patch model of the arbitrary surface. Hence, the goal is to immediately increase analysis capabilities in electromagnetics, yet remain compatible with the large existing base of knowledge concerning the solution of surface integral equations. Three alternative forms of the MPIE in plane-stratified media are developed, and their properties are discussed. One of the developed MPIEs is used to analyze scatterers and antennas of arbitrary shape that penetrate the interface between contiguous dielectric half-spaces. >
773 citations
TL;DR: The photonic band structure of a face-centered-cubic lattice of spheres is calculated using the plane-wave method for Maxwell's equations in this article, and the results show good agreement with the available experimental results, except that they do not find a true gap for this configuration.
Abstract: The photonic band structure of a face-centered-cubic lattice of spheres is calculated using the plane-wave method for Maxwell's equations. Comparisons with the available experimental results show rather good agreement, except that we do not find a true gap for this configuration. This we believe is due to symmetry reasons at the W point.
434 citations
TL;DR: In this article, the development and application of a computer model for analyzing the transient performance of grounding systems based on electromagnetic field theory is described, where the use of a combination of numerical integration techniques, method of moments, adaptive interpolation, and fast Fourier transform constitutes the basis for the computation of various physical quantities such as the electric fields in the ground, longitudinal and leakage currents in ground conductors, and ground impedances.
Abstract: The development and application of a computer model for analyzing the transient performance of grounding systems based on electromagnetic field theory is described. The use of a combination of numerical integration techniques, method of moments, adaptive interpolation, and fast Fourier transform constitutes the basis for the computation of various physical quantities such as the electric fields in the ground, longitudinal and leakage currents in the ground conductors, and ground impedances. It is shown that the analysis of conductors energized by current waves can require computations at frequencies higher than the significant frequencies in the spectrum of the excitation signal, while simpler models may fail to predict accurately the transient performance. The main limitation of the computer model is the time required for the analysis of large or complex grounding systems. >
413 citations
Patent•
22 Aug 1990
TL;DR: In this article, the effects of microwave flooding, plasma torch activation, molecular cracking and selective heating are used to heat the oil within the reservoir, by controlling frequency, intensity, duration, direction and wave form of the electromagnetic field.
Abstract: A method of creating a protocol for oil extraction or for enhancing oil extraction from oil reservoirs. A process of devising and applying a customized electromagnetic irradiation protocol to individual reservoirs. Reservoir samples are tested to determine their content, molecular resonance frequencies and the effects of electromagnetic field on their compounds. Electromagnetic field frequencies, intensities, wave forms and durations necessary to heat and/or crack individual molecules and produce plasma torches is determined. Equipment are selected and installed according to the results of the laboratory tests and the geophysics of the mine. Dielectric constant of the formation is reduced by draining the water and drying it with electromagnetic energy. A combination of the effects of microwave flooding, plasma torch activation, molecular cracking and selective heating are used to heat the oil within the reservoir, by controlling frequency, intensity, duration, direction and wave form of the electromagnetic field. Conditions of there servoir are continuously monitored during production to act as feedback for modification of the irradiation protocol.
377 citations
TL;DR: In this paper, the photon number distribution is shown to display unusual oscillations which are interpreted as interference in phase space, analogous to Franck-Condon oscillations in molecular spectra, and the possibility of detecting these oscillations is discussed, through the photodetection counting statistics of the displaced number states.
Abstract: Recent developments in quantum optics have led to new proposals to generate number states of the electromagnetic field using conditioned measurement techniques or the properties of atom-field interactions in microwave cavities in the micromaser. The number-state field prepared in such a way may be transformed by the action of a displacement operator; for the microwave micromaser state this could be implemented by the action of a classical current that drives the cavity field. We evaluate some properties of such displaced number states, especially their description in phase space. The photon number distribution is shown to display unusual oscillations, which are interpreted as interference in phase space, analogous to Franck-Condon oscillations in molecular spectra. The possibility of detecting these oscillations is discussed, through the photodetection counting statistics of the displaced number states. We show that the displaced-number-state quantum features are relatively robust when dissipation of the field energy is included.
286 citations
TL;DR: In this article, a spherical reflector illuminated by a point source is found to be capable of launching an electromagnetic missile, but the surfaces of the reflector are not complete spherical surfaces, and the problem cannot be solved by simple boundary matching.
Abstract: A spherical reflector illuminated by a point source is found to be capable of launching an electromagnetic missile. Since the surfaces of the reflector are not complete spherical surfaces, the problem cannot be solved by simple boundary matching. The electromagnetic fields have to be solved in three regions separately. The general solutions are matched on the boundaries to obtain a set of coefficient equations. Under the conditions for an electromagnetic missile, the coefficient equations are solved asymptotically. The evaluation of the Poynting vector shows that the energy radiated from the reflector has the same slow rate of decay as for the spherical lens.
270 citations
TL;DR: In this paper, the theory of chirowaveguides is discussed and their salient features are analyzed, and the corresponding dispersion relations, cutoff frequencies, and propagating and evanescent modes are obtained.
Abstract: The theory of chirowaveguides is discussed, and their salient features are analyzed. It is shown that the Helmholtz equations for the longitudinal components of electric and magnetic fields in chirowaveguides are always coupled and that, consequently, in these waveguides individual transverse electric (TE), transverse magnetic (TM), or transverse electromagnetic (TEM) modes cannot be supported. As an illustrative example, the parallel-plate chirowaveguide is analyzed in detail and the corresponding dispersion relations, cutoff frequencies, and propagating and evanescent modes are obtained. In the dispersion (Brillouin) diagram for a chirowaveguide, three regions are identified: the fast-fast-wave region, the fast-slow-wave region and the slow-slow-wave region. For each of these regions, the electromagnetic field components in a parallel-plate chirowaveguide are analyzed and the electric field components are plotted. Potential applications of chirowaveguides in integrated optical devices, communications systems, and printed circuit antennas are mentioned. >
247 citations
TL;DR: The LLK paraxial approximation to a Maxwellian exact solution for a Gaussian beam shows a polarization dependence if only the transversal optical components are used, and including the exact longitudinal fields results in the experimentally proven polarization independence.
Abstract: The discovery of Lax, Louisell, and Knight (LLK) [Phys. Rev. 9, 378 (1974)] that electromagnetic beams in vacuum do have a longitudinal component can be proved experimentally from the polarization independence of the energy of electrons from the focus of a laser. For this purpose we had to develop the LLK paraxial approximation to a Maxwellian exact solution for a Gaussian beam. Inserting the exact solutions into the Maxwellian stress tensor expression of the nonlinear force for the electron acceleration demonstrates a polarization dependence if only the transversal optical components are used. Including the exact longitudinal fields results in the experimentally proven polarization independence.
176 citations
TL;DR: Using Tolman's and Landau and Lifshitz's definitions, the energy associated with a Kerr-Newman black hole is calculated and the total energy is found to be shared by its interior as well as exterior.
Abstract: Using Tolman's as well as Landau and Lifshitz's definitions, the energy associated with a Kerr-Newman black hole is calculated. Both definitions give exactly the same result and the total energy is found to be shared by its interior as well as exterior. Switching off the charge parameter (i.e., {ital Q}=0) one finds that no energy is shared by the exterior of the Kerr black hole. Thus the gravitational field seems to have a remarkable difference from the electromagnetic field as the energy in the latter case is shared by the interior as well as exterior of the system producing the electromagnetic field.
171 citations
TL;DR: In this paper, three essentially different current loop models are analyzed and the expression for the force on a magnetic dipole is derived and analyzed for all models, which differs from what usually appears in the educational literature.
Abstract: Recent controversies about torque and force on a magnetic dipole are discussed. Three essentially different current loop models are analyzed. Although all models yield the same expression for the torque, N=m×B, the detailed mechanisms that give rise to the torque in each case are very different. The expression for the force on a magnetic dipole is derived and analyzed for all models. The force expression is the same for all current loop models but it differs from the force on a magnetic charge dipole. The expression, obtained for the force on a current loop magnetic dipole, FCL=■(m⋅B)−(d/dt)(m×E/c), differs from what usually appears in the educational literature. The standard ‘‘naive’’ calculation of the force yields the correct expression for the rate of change of the total momentum, dP/dt=∇(m⋅B). However, the current loop in an externa l electric field has an internal ‘‘hidden momentum’’ m×E/c, which is not related to the motion of the center of mass of the dipole. Thus, for the force, defined as mass t...
151 citations
TL;DR: In this article, the authors derived the uniform asymptotic behavior of solutions to linear field equations in Minkowski space, based on geometric consideration and generalized energy estimates, using a systematic use of the invariance properties of the field equations with respect to the conformal group of the MINKowski space and thus departs substantially from the classical method of analyzing the fundamental solution.
Abstract: The aim of this paper is to derive the uniform asymptotic behavior of solutions to linear field equations in Minkowski space, based on geometric consideration and generalized energy estimates. Our method relies on a systematic use of the invariance properties of the field equations with respect to the conformal group of the Minkowski space and thus departs substantially from the classical method of analyzing the fundamental solution
TL;DR: In this paper, the effect of an external magnetic field, magnetic anisotropy, energy dissipation and finite dimensions of the sample on the propagation of nonlinear electromagnetic-spin waves is considered.
TL;DR: The proper-time expression for the electron propagator in a background constant electromagnetic field to include a nonvanishing density of electrons or positrons is generalized and has the correct limits as either the magnetic field or the chemical potential is taken to zero.
Abstract: We generalize the proper-time expression for the electron propagator in a background constant electromagnetic field to include a nonvanishing density of electrons or positrons. In the case where only a magnetic field is present, we derive therefrom the effective Lagrangian, and show that it has the correct limits as either the magnetic field or the chemical potential is taken to zero. We extract the relativistic Landau levels from the poles in the propagator.
TL;DR: In this article, the hybrid moment and finite element methods are used to obtain 3D scattering and/or absorption from inhomogeneous, arbitrarily shaped objects, where the surface of an object is approximated by triangles and the volume of the object is estimated by tetrahedrons.
Abstract: The hybrid moment and finite element methods are used to obtain 3-D scattering and/or absorption from inhomogeneous, arbitrarily shaped objects. The surface of the object is approximated by triangles and the volume of the object is approximated by tetrahedrons. The electrical parameters are assumed constant in each tetrahedron. The Galerkin testing procedure is used. To avoid contaminations of spurious mode, a divergenceless vector basis function is used in finite elements. The calculated internal field and scattered field for a homogeneous sphere, a layered sphere, and a lossy prolate spheroid are compared with Mie series solutions and other numerical techniques. The accuracy and rate of convergence of the solution are discussed. >
TL;DR: In this paper, the problem of generating squeezed states of the electromagnetic field in a one-dimensional resonator with a moving wall was considered, and the squeezing and correlation coefficients for a harmonic law of motion of the wall were calculated.
TL;DR: In this article, a magnetic type solution of the classical electroweak equations with the property that for fields larger than mw2/e a W- and Z-condensate is formed was discussed.
TL;DR: The theory of electromagnetic induction by motional sources in the ocean is examined from a first principles point of view in this paper, where the electromagnetic field is expanded mathematically in poloidal and toroidal magnetic modes based on the Helmholtz decomposition.
Abstract: The theory of electromagnetic induction by motional sources in the ocean is examined from a first principles point of view. The electromagnetic field is expanded mathematically in poloidal and toroidal magnetic modes based on the Helmholtz decomposition. After deriving a set of Green functions for the modes in an unbounded ocean of constant depth and conductivity underlain by an arbitrary one-dimensional conducting earth, a set of exact integral equations are obtained which describe the induction process in an ocean of vertically varying conductivity. Approximate solutions are constructed for the low-frequency (subinertial) limit where the horizontal length scale of the flow is large compared to the water depth, the effect of self induction is weak, and the vertical velocity is negligible, explicitly yielding complex relationships between the vertically-integrated, conductivityweighted horizontal water velocity and the horizontal electric and three component magnetic fields and accounting for interactions with the conductive earth. After introducing geophysically reasonable models for the conductivity structures of the ocean and earth, these reduce to a spatially smoothed proportionality between the electromagnetic field components and the vertically-integrated, conductivity-weighted horizontal water velocity. An upper bound of a few times the water depth for the lateral averaging scale of the horizontal electric field is derived, and its constant of proportionality is shown to be nearly 1 for most of the deep ocean based on geophysical arguments. The magnetic field is shown to have a similar form but is a relatively weak, larger-scale average of the velocity field. Because vertical variations in the conductivity of seawater largely reflect its thermal structure and are weak beneath the thermocline, the horizontal electric field is a spatially filtered version of the true water velocity which strongly attenuates the influence of baroclinicity and accentuates the barotropic component. This is quantified using conductivity profiles and velocity information from a variety of locations.
TL;DR: In this paper, it was shown that there exist electromagnetic knots, which are standard electromagnetic fields in which any pair of magnetic lines whatsoever are linked and the magnetic helicity has the value integral A.Bd 3r-na, n being a topological constant of the motion given by a Hopf index and a certain action constant.
Abstract: It is shown that there exist electromagnetic knots, which are standard electromagnetic fields in which any pair of magnetic lines whatsoever (or of electric lines) are linked and the magnetic helicity has the value integral A.Bd 3r-na, n being a topological constant of the motion given by a Hopf index and a a certain action constant. A family of n=1 knots is obtained, the projection of spin on three-momentum being equal to a.
TL;DR: In this article, a method for shaping electromagnetic field pulses to achieve chemical selectivity is extended and applied to a simple multiple level model system, where both the time-dependent Schrodinger equation and the constant pulse energy are used as constraints on the variational scheme.
Abstract: A previously reported method for shaping electromagnetic field pulses to achieve chemical selectivity is extended and applied to a simple multiple level model system. The pulse shaping approach is based on optimal control theory, where both the time‐dependent Schrodinger equation and the constant pulse energy are used as constraints on the variational scheme. A conjugate gradient direction method is used to direct the convergence of the iterative process used to calculate the optimum pulse shape. The method is applied to a five‐level system interacting with an optical (laser) field. Results demonstrating selectivity and stability are compared to those of other recent related investigations.
TL;DR: In this paper, the authors explored the characteristics of space and surface-wave fields produced by an electromagnetic source in a multilayered structure using the integral transformation technique, and showed that the space and the surface wave modes are orthogonal along the longitudinal direction with respect to an appropriate weighting function.
Abstract: Characteristics of space- and surface-wave fields produced by an electromagnetic source in a multilayered structure are explored. Using the integral transformation technique it is shown that the space and surface-wave modes are orthogonal along the longitudinal direction with respect to an appropriate weighting function. It is demonstrated that these properties, together with reciprocity, can be utilized to determine the amplitudes of various surface-wave modes produced by an arbitrarily shaped source. Numerical results for the space- and surface-wave power for a circular patch antenna are presented. The study may find application for millimeter-wave printed antennas where the surface waves will play an important role in determining the radiation and impedance characteristics. >
TL;DR: In this article, the authors studied the time evolution of a collisionless plasma in the case when the Viasov density is a function of the time, one space variable and two velocity variables.
Abstract: The time evolution of a collisionless plasma is studied in the case when the Viasov density ƒ is a function of the time, one space variable and two velocity variables. The electromagnetic fields E, B also have a special structure, and the magnetic field B is non-trivial. It is shown that smooth, consistent initial values generate a uniquc smooth global solution.
TL;DR: In this article, the authors present the modifications of the spontaneous radiation rate in a cavity and the shifts of energy levels, with an outline of a theoretical framework in which the experiments may be understood.
Abstract: Publisher Summary This chapter focuses on cavity quantum electrodynamics. It presents the modifications of the spontaneous radiation rate in a cavity and the shifts of energy levels. The chapter focuses on experimental work, with an outline of a theoretical framework in which the experiments may be understood. In the laboratory, the study of atoms in cavities is a relatively young field in which much of the effort is still aimed at elucidating the basic physical principles at work and demonstrating the elementary modifications of energies and the rates of an atom in a cavity. However, the ability to adjust the electromagnetic spectrum of the vacuum is leading into a remarkable new domain of quantum physics in which atoms can decay from the ground state to an excited state, radiative corrections can be far larger than fine structure, and electromagnetic fields can be prepared with an exact number of photons. This realm of physics is now known as “cavity quantum electrodynamics.”
IBM1
TL;DR: In this article, a full-wave approach is presented for calculating the scattered fields produced by structures that involve finite-size dielectric regions, and the matrix elements are calculated, depending upon the distance between the source and field locations.
Abstract: A full-wave approach is presented for calculating the scattered fields produced by structures that involve finite-size dielectric regions. The dielectric is first approximated by an array of interlocking thin-wall sections; the electric field boundary conditions are then applied through the use of appropriate surface impedances. Rooftop basis functions, chosen to represent the surface current, are appropriately placed on the thin-wall sections in such a way as to accurately represent the polarization current while preventing fictitious charge within the dielectric. Rooftop currents are also used to represent the current on any conductor that may be present. The matrix elements are calculated, depending upon the distance between the source and field locations, through a scheme that employs Taylor series expansions and point source approximations. The technique is applied to scattering from dielectric cubes and composite dielectric-conductor structures, and to radiation from microstrip structures. Numerical convergence and agreement with the literature are demonstrated. >
TL;DR: In this paper, a computational approach for including the effects of a dispersive loss in direct time-domain solutions for electromagnetic (EM) field problems is discussed, which involves a distribution function that has properties between those of a Dirac delta function and a doublet.
Abstract: A computational approach for including the effects of a dispersive loss in direct time-domain solutions for electromagnetic (EM) field problems is discussed. If such problems are solved in the frequency domain, a dispersive impedance that models the loss can be easily incorporated in the solution. In the time domain, this effect is taken into account through a convolution integral, which involves a distribution function that has properties between those of a Dirac delta function and a doublet. A few simple examples of these distribution functions are presented, and comments as to their use in calculations are made. >
07 May 1990
TL;DR: An efficient numerical procedure for the analysis and computation of electromagnetic scattering by arbitrarily shaped three-dimensional complex material/conducting objects is presented based on integral equations, the equivalence principle, and the method of moments as discussed by the authors.
Abstract: An efficient numerical procedure for the analysis and computation of electromagnetic scattering by arbitrarily shaped three-dimensional complex material/conducting objects is presented based on integral equations, the equivalence principle, and the method of moments. The surface triangular basis functions are used to represent the equivalent electric current residing on the interface of material boundaries, and a new basis function defined on polygons enclosing the triangle vertices is developed to express and equivalent magnetic current which is approximately spatially orthogonal to the electric current. Four types of integral equations, electric (EFIE), magnetic (MFIE), and combined (CFIE) field integral equations, and the PMCHW formulation are used to compute the field scattered by a dielectric sphere. Numerical results compared with the Mie series solution illustrate the numerical characteristics of the new basis function and the flexibility and efficiency of the CFIE approach. >
Patent•
09 Aug 1990
TL;DR: In this article, a method for restoring visual functions in cases of affected optic nerve and retina comprises an electromagnetic field radiator emitting the latter field into the region of the eyeball and an EM receiver adapted to interact with the radiator, both of them exerting an electrostimulation effect on the optic nerve.
Abstract: A device for restoration of visual functions in cases of affected optic nerve and retina comprises an electromagnetic field radiator emitting the latter field into the region of the eyeball and an electromagnetic field receiver adapted to interact with the radiator, both of them exerting an electrostimulation effect on the optic nerve and the retina. The electromagnetic field radiator is essentially a source of a pulsed magnetic field and is shaped as an electromagnet provided with an adjuster of a distance between the end of the electromagnet and the electromagnetic field receiver, which is in effect an inductor having lead wires furnished with electrodes whose active surface exceeds 10 mm 2 . A method for restoration of visual functions in cases of affected optic nerve and retina consists in conducting electrostimulation of the eyeball, for which purpose an inductor is implanted into the orbit on the sclera of the posterior portion of the eyeball in such a manner that one of the inductor electrodes is positioned nearby the external tunic of the optic nerve, while the other electrode is fixed on the sclera in the area of the eyeball equator, whereupon a pulsed magnetic flux is applied remotely to the eyeball portion carrying the inductor, the magnetic field induction being from 0.1 T to 0.25 T, while the pulsed magnetic field is simultaneously brought in synchronism with pulsation of the internal carotid artery.
Proceedings Article•
21 May 1990
TL;DR: In this paper, the authors studied the amplification of a single-mode electromagnetic field by an atomic system with a three-level cascade structure in two-photon resonance conditions when the top and bottom levels are mixed coherently by a strong external resonant field.
Abstract: We have studied the amplification of a single-mode electromagnetic field by an atomic system with a three-level cascade structure in two-photon resonance conditions when the top and bottom levels are mixed coherently by a strong external resonant field. We find different kinds of phase-sensitive amplification for different values of the driving field strength. For a very high driving field and near one-photon resonance, the system approaches an ideal parametric amplifier.
TL;DR: An explicit time-domain integration scheme is developed for finite-element spatial discretization of the Maxwell equations, using a generalized wave equation in weak form which is free of vector parasites when discretized on single C/sup 0/ elements.
Abstract: An explicit time-domain integration scheme is developed for finite-element spatial discretization of the Maxwell equations. A generalized wave equation is used in weak form, which is free of vector parasites when discretized on single C/sup 0/ elements. The use of integral lumping renders the mass matrix diagonal with no necessary degradation in accuracy. The explicit method which results combines the economy of established finite-difference techniques with the geometric flexibility of finite elements. Test problems representative of practical hyperthermia applications show agreement with analytic and frequency-domain finite-element methods, and confirm scaling arguments on run-time and memory. >
TL;DR: In this article, the frequency response of the microstrip line has been analyzed by simulating the illuminating field with a plane wave arbitrarily incident on the line, and indications for reducing the circuit susceptibility have been obtained.
Abstract: The voltages and currents induced by external electromagnetic fields on a planar microstrip line have been studied with the use of a distributed-source transmission-line model. The frequency response of the microstrip line has been analyzed by simulating the illuminating field with a plane wave arbitrarily incident on the line. The influence of the microstrip geometrical and electrical characteristics on the voltages and currents induced on the line has been examined, and indications for reducing the circuit susceptibility have been obtained. The model adopted can be used for studying the response of the line to any type of external field arbitrarily varying in space time. Numerical results show that for lines loaded with the characteristic impedance at both terminals, voltage amplitudes on the order of some millivolts and currents of some hundreds of microamperes can be induced at f=3 GHz by an incident plane wave with an electric-field intensity of 1 V/m and for various angles of incidence. The voltages and currents induced on a microstrip circuit can be reduced by using substrates of sufficiently high permittivity. >
TL;DR: In this paper, the electromagnetic field generated by a vertical electric dipole on or near the surface of the Earth is studied for continuous-wave excitation, and simple explicit new formulas are derived for the three components of the electromagnetic spectrum and represented graphically.
Abstract: The electromagnetic field generated by a vertical electric dipole on or near the surface of the Earth is studied for continuous-wave excitation. The analytical foundation established by Sommerfeld and developed by many others is reviewed, and simple explicit new formulas are derived for the three components of the electromagnetic field and represented graphically. Their range of validity is defined. They show that the surface waves constitute the entire far field along the air-earth boundary.