Home About us Contact
|
Home About us Contact | ||
|
|
||
Electromagnetic Waves (electromagnetic + wave)
Selected AbstractsDetermination of moisture content in a deformable soil using time-domain reflectometry (TDR)EUROPEAN JOURNAL OF SOIL SCIENCE, Issue 1 2000D. J. Kim Summary Time-domain reflectometry (TDR) is being used increasingly for measuring the moisture content of porous media. However, successful application for measuring water in soil has been limited to non-deformable soils, and it would be a valuable extension of the technique if it could be used for soils that shrink on drying. We have recently investigated its application to soils rich in clay and organic matter and peats. Here we propose a method for determining moisture content in deformable soils based on the relation between the dielectric constant, K, and the volumetric moisture content, ,, measured by TDR. Parallel TDR probes with a length of 15 cm and a spacing of 2 cm were placed horizontally in soil cores with a diameter of 20 cm and height of 10 cm taken from a forest. The soil is very porous with large proportions of both silt and clay. The sample weight and travel time of the electromagnetic wave guided by parallel TDR probes were simultaneously measured as a function of time, from saturation to oven-dryness during which the core samples shrank considerably. Vertical and horizontal components of shrinkage were also measured to take the air-exposed region of TDR probe into account in the determination of K. The effect of deformation on volumetric moisture content was formulated for two different expressions, namely actual volumetric moisture content (AVMC) and fictitious (uncorrected) volumetric moisture content (FVMC). The effects of air-exposure and expressions of volumetric moisture content on the relation between K and, were examined by fitting the observations with a third-order polynomial. Neglecting the travel time in the air-exposed part or use of the FVMC underestimated the , for a given K. The difference was more pronounced between AVMC and FVMC than between two different dielectric constants, i.e. accounting for air-exposure, Kac, and not accounting for air-exposure, Kau. When the existing empirical models were compared with the fitted results, most underestimated the relation based on the AVMC. This indicates that published empirical models do not reflect the effect of deformation on the determination of , in our forest soil. Correct use of the , expression has more impact on determining moisture content of a deformable soil than the accommodation of travel time through the air-exposed region of TDR probe. [source] Numerical simulation grounding system buried within horizontal multilayer earth in frequency domainINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN BIOMEDICAL ENGINEERING, Issue 1 2007Zhong-Xin Li Abstract A novel mathematical model for accurately calculating the currents flowing along the conductors of grounding system below high voltage a.c. substations and nearby floating metallic structure buried in horizontal multilayer earth model has been developed in this paper. Not only the mutual conductive and capacitive coupling influences of leakage currents, but also mutual inductive coupling influence of network currents flowing along the conductors of grounding system and nearby floating metallic structure in the horizontal multilayer earth model have been considered in this model, and only propagation effect of electromagnetic wave within limited area of the substation has been neglected. The quasi-static complex image method and closed form of Green's function are introduced into this model to accelerate the calculation. The model is then implemented in a computer program, which can be used to calculate currents distribution along the conductors of any configuration of grounding system, and with or without floating metallic structure under some hundreds of kHz frequency harmonic wave. Copyright © 2006 John Wiley & Sons, Ltd. [source] Measurements of photon interference X-ray absorption fine structure (,XAFS)JOURNAL OF SYNCHROTRON RADIATION, Issue 2 2001Larc Tröger Experimental data are presented which demonstrate the existence of a fine structure in extended X-ray absorption spectra due to interference effects in the initial photon state (,XAFS). Interference occurs between the incident electromagnetic wave and its coherently scattered waves from neighboring atoms. Using fine platinum and tungsten powders as well as polycrystalline platinum foil, ,XAFS was measured in high-precision absorption experiments at beamline X1 at HASYLAB/DESY over a wide energy range. ,XAFS is observed below and above absorption-edge positions in both transmission and total-electron-yield detection. Based on experimental data it is shown that ,XAFS is sensitive to geometric atomic structure. Fourier-transformed ,XAFS data carry information, comparable with that of EXAFS, about the short-range-order structure of the sample. Sharp structures occur in ,XAFS when a Bragg backscattering condition of the incident X-rays is fulfilled. They allow precise measurement of long-range-order structural information. Measured data are compared with simulations based on ,XAFS theory. Although ,XAFS structures are similarly observed in two detection techniques, the importance of scattering off the sample for the measurements needs to be investigated further. Disentangling ,XAFS, multielectron photoexcitations and atomic XAFS in high-precision measurements close to absorption edges poses a challenge for future studies. [source] Double-resonance grating mirror for polarization control in solid-state lasersLASER PHYSICS LETTERS, Issue 4 2006M. A. Ahmed Abstract The spectral width of the polarizing effect of a coupling grating on a standard quarter-wave multilayer laser mirror can be increased by applying dual-duty-cycle gratings. As an example this is discussed considering the requirements to polarize a Yb:YAG thin-disk laser. By applying dual-duty-cycle gratings the spectral tolerance can be widened by a factor of two as compared to single-duty-cycle designs and at the same time achieve a high reflectivity and low losses for the oscillating polarized laser mode. The calculations of the structures were carried out with the help of an exact modelling code based on the modal method. The code simulates the interaction of a plane electromagnetic wave with the corrugated multilayer structure to compute amplitude and power of all reflected and transmitted diffraction waves. (© 2006 by Astro, Ltd. Published exclusively by WILEY-VCH Verlag GmbH & Co. KGaA) [source] Resonant scattering of a photon by an electron in the field of a circularly polarized electromagnetic waveLASER PHYSICS LETTERS, Issue 4 2005A. I. Voroshilo Abstract This paper presents, for general relativistic case, a theoretical study of Compton effect in the field of a circularly polarized wave under resonant condition , resonances related to a virtual intermediate particle that falls within the mass shell. We derive the expressions for the resonant amplitude and the differential cross section when the invariant intensity parameter of the wave is small (, , 1) and absent interference of the scattering and annihilation reaction amplitudes. It is demonstrated that the resonant cross section of scattering may be several orders of magnitude higher than the cross section of Compton effect in the absence of the external field. (© 2005 by Astro, Ltd. Published exclusively by WILEY-VCH Verlag GmbH & Co. KGaA) [source] Scattering relations for point-source excitation in chiral mediaMATHEMATICAL METHODS IN THE APPLIED SCIENCES, Issue 1 2006Christodoulos Athanasiadis Abstract A spherical electromagnetic wave propagating in a chiral medium is scattered by a bounded chiral obstacle which can have any of the usual properties. Reciprocity and general scattering theorems, relating the scattered fields due to scattering of waves from a point source put in any two different locations are established. Applying the general scattering theorem for appropriate locations and polarizations of the point source we prove an associated forward scattering theorem. Mixed scattering relations, relating the scattered fields due to a plane wave and the far-field patterns due to a spherical wave, are also established. Copyright © 2005 John Wiley & Sons, Ltd. [source] Combined far-ield operators in electromagnetic inverse scattering theoryMATHEMATICAL METHODS IN THE APPLIED SCIENCES, Issue 5 2003Fioralba Cakoni Abstract We consider the inverse scattering problem of determining the shape of a perfect conductor D from a knowledge of the scattered electromagnetic wave generated by a time-harmonic plane wave incident upon D. By using polarization effects we establish the validity of the linear sampling method for solving this problem that is valid for all positive values of the wave number. We also show that it suffices to consider incident directions and observation angles that are restricted to a limited aperture. Copyright © 2003 John Wiley & Sons, Ltd. [source] High harmonic generation by two color field-mixing in n-type low-doped GaAsPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 5 2003D. Persano Adorno Abstract Monte Carlo simulations for high harmonic generation by two mixed electric fields linearly polarized with frequency in the far-infrared range in GaAs crystal are examined. The wave-mixed signal conversion efficiency is calculated by the use of the appropriate Maxwell equation for the propagation of an electromagnetic wave along a given direction in a medium. We show how the efficiency of the harmonics and their polarization depend on: (i) the frequencies and the intensities of the incident waves; (ii) the angle between the polarization of the two incident fields. [source] Novel properties of wave propagation in biaxially anisotropic left-handed materialsANNALEN DER PHYSIK, Issue 6 2004J.Q. Shen Abstract Some physically interesting properties and effects (including the quantum effects) of wave propagation in biaxially anisotropic left-handed materials are investigated in this paper: (i) we show that in the biaxially gyrotropic left-handed material, the left-right coupling of circularly polarized light arises due to the negative indices in permittivity and permeability tensors of gyrotropic media; (ii) it is well known that the geometric phases of photons inside a curved fiber in previous experiments often depend on the cone angles of solid angles subtended by a curve traced by the direction of wave vector of light, at the center of photon momentum space. Here, however, for the light propagating inside certain anisotropic left-handed media we will present a different geometric phase that is independent of the cone angles; (iii) the extra phases of electromagnetic wave resulting from the instantaneous helicity inversion at the interfaces between left- and right-handed (LRH) media is also studied in detail by using the Lewis-Riesenfeld invariant theory. Some interesting applications (e.g., controllable position-dependent frequency shift, detection of quantum-vacuum geometric phases and helicity reversals at the LRH interfaces etc.) of above effects and phenomena in left-handed media is briefly discussed. [source] Predicted SAR in sprague-dawley rat as a function of permittivity values,,BIOELECTROMAGNETICS, Issue 6 2001P. Gaj Abstract Specific absorption rate (SAR) value is dependent on permittivity value. However, variability in the published permittivity values for human and animal tissue and the development of sophisticated 3-dimensional digital anatomical models to predict SAR values has resulted in the need to understand how model parameters (permittivity value) affect the predicted whole body and localized SAR values. In this paper, we establish the partial derivative of whole body SARs and localized SAR values (defined as SAR for individual organs with respect to a change in the permittivity values of all tissue types, as well as for those tissues with the most variable permittivity values. Variations in the published permittivity values may substantially influence whole body and localized SAR values, but only under special conditions. Orientation of the exposed object to the incident electromagnetic wave is one of the most crucial factors. Bioelectromagnetics 22:384,400, 2001. Published 2001 Wiley-Liss, Inc. [source] On the Modelling of a Nonequilibrium Spherical Microwave Discharge at Atmospheric PressureCONTRIBUTIONS TO PLASMA PHYSICS, Issue 3 2007I. R. Rafatov Abstract The work presents results of calculation of a spherical microwave discharge characteristics in an argon at atmospheric pressure against the external parameters (the mode, frequency and power of the applied electromagnetic field and the size of the discharge chamber). Model assumes a thermal and ionization non-equilibrium of discharge plasma and takes into account first three modes of incident electromagnetic waves. Calculation results are compared with the results for the ionization equilibrium model. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Screening Breakdown in a Plasma by Two Laser Fields and Strong DC Magnetic FieldCONTRIBUTIONS TO PLASMA PHYSICS, Issue 1 2005D. F. Miranda Abstract The effective static dielectric constant of an electron plasma system in the simultaneous presence of two electromagnetic waves and a strong DC magnetic field is calculated. It is found that as the difference ,, of the two electromagnetic wave frequencies matches the plasma frequency ,, a breakdown in screening occurs thereby increasing the plasma heating rate via the external fields due to inverse Bremmstrahlung. An application is made by considering the typical parameters of a hot plasma. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Understanding the partial discharge activity of conducting particles in GIS under DC voltages using the UHF techniqueEUROPEAN TRANSACTIONS ON ELECTRICAL POWER, Issue 5 2010R. Sarathi Abstract The major cause of failure of DC-GIS is due to presence of foreign particles causing partial discharges in the insulation structure. The particle movement in gas insulated system (GIS) radiates electromagnetic waves and the bandwidth of the signal lies in the range 1,2,GHz. Increase in applied DC voltage/pressure has not altered the frequency content of the ultra high frequency (UHF) signal generated due to partial discharge formed by particle movement. The UHF sensor could recognize the breakdown of sulfur-hexa-fluoride (SF6) gas under DC and Lightning impulse voltages and the frequency content of the signal captured by the UHF sensor lies up to 500,MHz. Mounting UHF sensor in GIS could allow one to classify internal partial discharges from breakdown, at the time of testing/during operation. Copyright © 2009 John Wiley & Sons, Ltd. [source] Recent trend of the partial discharge measurement technique using the UHF electromagnetic wave detection methodIEEJ TRANSACTIONS ON ELECTRICAL AND ELECTRONIC ENGINEERING, Issue 5 2007Masayuki Hikita Member Abstract The ultra high frequency (UHF) electromagnetic wave detection method has been widely studied and used in partial discharge (PD) measurement and as a diagnostic technique for insulation performance in gas-insulated switchgears (GIS) and transformers. The UHF method has advantages such as high sensitivity, wide detection range and reduced external disturbances. On the other hand, there are still some issues to be solved in the UHF methods, such as a clear understanding of the propagation characteristics of electromagnetic waves arising from the structure of the equipment, optimization of antenna design, calibration of charge, etc. This article deals with the present status and future trend of the technology of this promising UHF method of PD measurement, together with recent activities and results from our laboratory. Copyright © 2007 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc. [source] Dynamic fade restoration in Ka-band satellite systemsINTERNATIONAL JOURNAL OF SATELLITE COMMUNICATIONS AND NETWORKING, Issue 4 2002A. Paraboni Atmospheric precipitation can seriously affect the propagation of centimeter and millimeter electromagnetic waves. As a consequence, in some applications, it is necessary to make use of a fade countermeasure technique in order to satisfy the system availability and quality requirements. This study analyses the performance of a satellite-based system in geo-stationary orbit operating at 20 GHz, dynamically assigning the antenna directivity pattern to counteract tropospheric attenuation. The on-board power is spatially distributed over the covered region to minimize, at any time, the number of users undergoing outage because of the tropospheric attenuation. Both the aspects of broadcasting and telecommunication services are addressed. The reflector antenna of the system is supposed to be illuminated by a cluster of feeds driven by a set of excitation coefficients, continuously modified and optimized according to the meteorological information derived by processing METEOSAT satellite data and ECMWF (European Centre for Medium-Range Weather Forecasts) data. Copyright © 2002 John Wiley & Sons, Ltd. [source] Direct and inverse problems for electromagnetic scattering by a doubly periodic structure with a partially coated dielectricMATHEMATICAL METHODS IN THE APPLIED SCIENCES, Issue 2 2010Guanghui Hu Abstract Consider the problem of scattering of electromagnetic waves by a doubly periodic Lipschitz structure. The medium above the structure is assumed to be homogenous and lossless with a positive dielectric coefficient. Below the structure there is a perfect conductor with a partially coated dielectric boundary. We first establish the well-posedness of the direct problem in a proper function space and then obtain a uniqueness result for the inverse problem by extending Isakov's method. Copyright © 2009 John Wiley & Sons, Ltd. [source] Electromagnetic scattering by a perfectly conducting obstacle in a homogeneous chiral environment: solvability and low-frequency theoryMATHEMATICAL METHODS IN THE APPLIED SCIENCES, Issue 11 2002C. Athanasiadis Abstract The scattering of plane time-harmonic electromagnetic waves propagating in a homogeneous isotropic chiral environment by a bounded perfectly conducting obstacle is studied. The unique solvability of the arising exterior boundary value problem is established by a boundary integral method. Integral representations of the total exterior field, as well as of the left and right electric far-field patterns are derived. A low-frequency theory for the approximation of the solution to the above problem, and the derivation of the far-field patterns is also presented. Copyright © 2002 John Wiley & Sons, Ltd. [source] On interaction of electromagnetic waves with infinite bianisotropic layered slabMATHEMATISCHE NACHRICHTEN, Issue 9-10 2007Tengiz Buchukuri Abstract A stratified general bianisotropic medium is considered, consisting of several infinite slabs either between two half-spaces filled with isotropic material, or grounded. The slab is illuminated by an incident plane wave from one of the half-spaces. The excited electromagnetic field inside the bianisotropic slab and in the isotropic domains is described. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Fast and accurate calculation of transmission coefficients for an EBG microstrip structureMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 4 2010Shao Ying Huang Abstract In this article, an approach is proposed to provide an accurate and fast calculation on the transmission coefficients of an electromagnetic band-gap (EBG) structures where patches are periodically inserted into the microstrip line (capacitive loaded EBG microstrip structure). The stopband performance, such as the center frequency, bandwidth, and attenuation, of these EBG structures can be predicted at a high degree of accuracy through the calculation of the transmission coefficient. The dispersion relation of electromagnetic waves in the structure is derived, plotted, and analyzed. The grating nature of the structure is demonstrated. This approach can be applied to periodic microstrip structures of a similar nature to simplify the analysis and design procedures. © 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52:793,797, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.25046 [source] Scattering and absorption of electromagnetic waves on a plane with hemispherical bossesMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 11 2007Xiaoxiong Gu Abstract We apply multiple scattering equations to study the scattering of electromagnetic waves on a perfectly conducting plane surface with a random dense distribution of hemispherical bosses. We derive a multipole solution up to third order to analyze close range interactions between nearby bosses. Results show significant improvement of accuracy compared with the traditional dipole approximation solution. Absorption on a lossy embossed surface is obtained from the field solution for the perfectly conducting surface. The surface current and absorption enhancement factor are further computed numerically. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 2681,2686, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22855 [source] Strong localization of EM waves using open cavities made of left-handed transmission-line mediaMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 8 2006Yao Qin Abstract Open cavities are investigated using properly designed right-handed (RH) and left-handed (LH) transmission-line media (TLM), with detailed formulations to design TLM. We demonstrate large fields and high energies are concentrated at the center because of the resonance, which is a strong localization of electromagnetic waves and energies. © 2006 Wiley Periodicals, Inc. Microwave Opt Technol Lett 48: 1662,1665, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.21689 [source] Directivity of an antenna embedded inside a Fabry,Perot cavity: Analysis and designMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 1 2006H. Boutayeb Abstract The enhancement of directivity of a monopole located in a Fabry,Perot type cavity is studied. The analysis is based on the response of the cavity excited from its inside by electromagnetic waves. To validate the proposed antenna, an experimental prototype is designed, fabricated, and measured. © 2005 Wiley Periodicals, Inc. Microwave Opt Technol Lett 48: 12,17, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.21249 [source] Influence of Mobile Magnetic Resonance Imaging on Implanted PacemakersPACING AND CLINICAL ELECTROPHYSIOLOGY, Issue 1p2 2003RYOJI KISHI KISHI, R., et al.: Influence of Mobile Magnetic Resonance Imaging on Implanted Pacemakers.Purpose: Mobile magnetic resonance imaging (MRI) systems will be widely used in Japan. When traveling, mobile MRI generate alternating electromagnetic waves which may cause electromagnetic interference (EMI). This study was designed to determine whether this may influence the function of implanted pacemakers (PM). Methods and Results: The influence of the static magnetic fields was tested in the first method using a PM-human model (Phantom). Magnetic force was simultaneously measured. The PM was switched to the magnet mode within 90 cm from the vehicle, where the magnetic force was = 2 mT. In the second method, six phantoms were placed on the side of the road, facing in three different directions in X-Y-Z axis orientations, at 1.3 m and 2.0 m above the ground. The mobile MRI passed by at a distance of 1 m from the phantoms at the speed of 20 or 40 km/h. In these experiments, magnet mode switch of the PM was observed for 2 seconds when the vehicle passed close to the phantoms, though no electrical noise was recorded. Conclusion: Mobile MRI vehicles can switch a PM to magnet mode when the distance between patient and vehicle is <90 cm, regardless of whether the vehicle is moving or at a stop. Patients with implanted PM should not approach within <1 m of a mobile MRI. No other EMI-induced PM dysfunction was detected. (PACE 2003; 26[Pt. II]:527,529) [source] Optically and electrically induced dissipation in quantum Hall systemsPHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 2 2008G. Nachtwei Abstract We have studied the onset of dissipation in quantum Hall systems (QHSs), patterned in various geometries (Hall bars, meanders and Corbino rings) from wafers with heterojunctions (GaAs/GaAlAs) and HgTe quantum wells with adjacent HgCdTe barriers. The QH samples were excited by electrical pulses with pulse durations tP of 0.5 ns , tP , 180 ns or by illumination with electromagnetic waves of 1.7 THz , f , 2.5 THz. These waves were either emitted coherently by a pulsed p-Ge laser system or by a thermal source. In the case of excitation by electric pulses, it is necessary to exceed a certain critical pulse length which is a function of various extrinsic parameters and sample properties. For no dissipation occurs inside the QHSs. Also, using THz illumination, the QHSs can be driven to dissipation. We found different mechanisms to be responsible for the photoresponse (PR) of the QHSs: non-resonant (bolometric) and resonant (cyclotron resonance) contributions to the PR of the QHSs. First attempts to develop a quantitative model for the observed data are made. We are able to describe a part of the observations by either a drift model or a two-level model. The quantitative agreement of these calculations with the measured data is, however, limited. This is due to the simplicity of the models applied so far and to the complex behaviour of QHSs when nonlinearly excited. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Light,matter interaction in finite-size plasma systemsPHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 10 2007W. Hoyer Abstract It is well known that electromagnetic waves with frequencies below the plasma frequency cannot propagate inside an electron plasma. For plasmas with infinite extensions, this property can be mathematically described by a Bogoliubov transformation of the photonic operators. More generally, the presence of finite-size electron plasmas such as laser-induced atmospheric light strings or metallic nano structures including metamaterials leads to a modification of the light,matter interaction. It is shown how this geometric property can be fully accounted for with the help of adapted mode functions used for the quantization of the electromagnetic field. In addition to the analytical derivations, numerical results for luminescence spectra out of quasi-two-dimensional, planar plasma sheets are presented. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Transmission, refraction, and focusing properties of labyrinth based left-handed metamaterialsPHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 4 2007Ekmel Özbay Abstract In this present article, we studied the transmission, refraction and focusing properties of one, two and three dimensional labyrinth based left-handed metamaterials. We demonstrated that the proper periodic arrangement of labyrinth structures and wires results in left-handed transmission. By using a two dimensional labyrinth based left-handed slab, it is shown that it is possible to image the field emitted from source in sub-wavelength detail. Moreover, we demonstrated the focusing and negative refraction of electromagnetic waves by a three dimensional labyrinth based left-handed slab. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Omni-directional gap of 1-D photonic crystals based on porous silicon with a Gaussian profile refractive indexPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 2 2007J. Arriaga Abstract Using the transfer matrix method we calculate the omni-directional band gap of a 1-D photonic crystal consisting of alternating layers of two dielectric materials A and B with refractive index nA and nB, respectively. The refractive index of layer A is constant and the refractive index of layer B varies according to the envelope of a Gaussian function. We find that under certain circumstances it is possible to obtain 100% reflectivity for both polarizations and any value of the incident angle of the electromagnetic waves. Although the structure considered does not posses a higher omni-directional band gap than the periodic sequence of low and high constant refractive indexes, it can be used to produce a new type of omni-directional mirrors without abrupt interfaces. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Surface integral methods for high-frequency electromagnetic scatteringPROCEEDINGS IN APPLIED MATHEMATICS & MECHANICS, Issue 1 2007M. Ganesh Surface integral equation based methods are advantageous for simulation of electromagnetic waves scattered by three dimensional obstacles, because they efficiently reduce the dimension of the problem and are robust for high-frequency problems. However, the cost of setting up the associated discretized dense linear systems is prohibitive due to evaluation of highly oscillatory magnetic and electric dipole surface integral operators using standard cubatures. The computational complexity of evaluating such integrals depends on the incident wave frequency, and the size and shape of the obstacles. In this work we discuss a surface integral reformulation of the scattering problem that involves evaluation of surface integrals with a highly oscillatory physical density, and discuss methods for efficient evaluation of such integrals for a class of smooth three dimensional scatterers whose diameter is a large multiple of the incident wavelength. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] On linear electromagnetic constitutive laws that define almost-complex structuresANNALEN DER PHYSIK, Issue 3 2007D.H. Delphenich Abstract It is shown that not all linear electromagnetic constitutive laws will define almost-complex structures on the bundle of 2-forms on the spacetime manifold when composed with the Poincaré duality isomorphism, but only a restricted class of them that includes linear spatially isotropic and some bi-isotropic constitutive laws. Although this result does not trivialize the formulation of the basic equations of pre-metric electromagnetism, it does affect their reduction to metric electromagnetism by its effect on the types of media that are reducible, and possibly its effect on the way that such media support the propagation of electromagnetic waves. [source] Electromagnetic waves in a rotating frame of referenceANNALEN DER PHYSIK, Issue 5 2003J.C. Hauck Abstract We discuss the electromagnetic measurements of rotating observers and study the propagation of electromagnetic waves in a uniformly rotating frame of reference. The phenomenon of helicity-rotation coupling is elucidated and some of the observational consequences of the coupling of the spin of a particle with the rotation of a gravitational source are briefly examined. [source] | |||||||||||||||||||||||||||||||