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Electromagnetic Fields (electromagnetic + field)
Kinds of Electromagnetic Fields Selected AbstractsBioreactor Coupled with Electromagnetic Field Generator: Effects of Extremely Low Frequency Electromagnetic Fields on Ethanol Production by SaccharomycescerevisiaeBIOTECHNOLOGY PROGRESS, Issue 5 2007Victor H. Perez The effect of extremely low frequency (ELF) magnetic fields on ethanol production by Saccharomyces cerevisiae using sugar cane molasses was studied during batch fermentation. The cellular suspension from the fermentor was externally recycled through a stainless steel tube inserted in two magnetic field generators, and consequently, the ethanol production was intensified. Two magnetic field generators were coupled to the bioreactor, which were operated conveniently in simple or combined ways. Therefore, the recycle velocity and intensity of the magnetic field varied in a range of 0.6,1.4 m s,1 and 5,20 mT, respectively. However, under the best conditions with the magnetic field treatment (0.9,1.2 m s,1 and 20 mT plus solenoid), the overall volumetric ethanol productivity was approximately 17% higher than in the control experiment. These results made it possible to verify the effectiveness of the dynamic magnetic treatment since the fermentations with magnetic treatment reached their final stage in less time, i.e., approximately 2 h earlier, when compared with the control experiment. [source] Electromagnetic fields in a steel-cased boreholeGEOPHYSICAL PROSPECTING, Issue 1 2005Ki Ha Lee ABSTRACT The development of an electromagnetic numerical modelling scheme for a magnetic dipole in an arbitrary casing segment in an inhomogeneous conductivity background has been difficult, due to the very high electrical conductivity and magnetic permeability contrasts between the steel casing and the background medium. To investigate the effect of steel casing efficiently, we have developed an accurate but simple finite-element modelling scheme to simulate electromagnetic fields in a medium of cylindrically symmetric conductivity structures. In order to preserve the cylindrical symmetry in the resulting electromagnetic fields, a horizontal loop current source is used throughout. One of the main advantages of the approach is that the problem is scalar when formulated using the azimuthal electric field, even if the casing is both electrically conductive and magnetically permeable. Field calculations have been made inside the cased borehole as well as in another borehole which is not cased. Careful analyses of the numerical modelling results indicate that the anomaly observed in a cross-borehole configuration is sensitive enough to be used for tomographic imaging. [source] Electromagnetic fields in jetsMONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 2 2007B. D. Sherwin ABSTRACT The magnetic fields and energy flows in an astronomical jet described by our earlier model are calculated in detail. Though the field distribution varies with the external pressure function p(z), it depends only weakly on the other boundary conditions. Individual field lines were plotted; the lines become nearly vertical at the bottom and are twisted at the top. An animation of a field line's motion was made, which shows the line being wound up by the accretion disc's differential rotation and rising as a result of this. The distribution of Poynting flux within the jet indicates that much of the energy flows up the jet from the inside of the accretion disc but a substantial fraction flows back down to the outside. [source] Induction Ovens and Electromagnetic Interference:PACING AND CLINICAL ELECTROPHYSIOLOGY, Issue 7p1 2003What is the Risk for Patients with Implanted Pacemakers? Electromagnetic fields may interfere with normal pacemaker function. Despite the introduction of modern pacemakers and bipolar lead systems, electromagnetic interference (EMI) still remains to be a concern during daily lives when patients are exposed to cellular phones, electronic security systems, and several household appliances. The aim of this study was to evaluate potential EMI risk of induction ovens, which are increasingly used in private households. The study included 40 consecutive patients (22 men, 18 women; age73 ± 11 years) with implanted DDD, VVI, VDD, and AAI pacemaker systems. The pacemakers were programmed to unipolar sensing and pacing. Sensitivity remained unchanged, if the measured sensing threshold was more than twice the programmed value; otherwise, it was set at half of the measured sensing threshold. Patients were placed in a sitting position at the closest possible distance of about 20 cm between two cooking pots and pacemaker bending the upper part of the body slightly over the induction oven. The energy was increased stepwise to the maximum. One pot was removed and placed again at the highest oven level. Potential interference was monitored continuously. The study showed no incidence of pacemaker malfunction during the entire test while the patients with intrinsic cardiac rhythms were exposed to the induction oven at varying energy strengths. Likewise, there was no external interference when the patients were paced at heart rates of 10,15 beats/min above their heart rates. The programmed parameters remained unchanged after the study. In conclusion, this study shows no EMI risk of an induction oven in patients with bipolar or right-sided unipolar pacemakers. (PACE 2003; 26[Pt. I]:1494,1497) [source] Electromagnetic fields induced by a concentrated heat source in multiferroic materialsPHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 1 2008X. Wang Abstract Pyroelectric and pyromagnetic effects are important for applications of multiferroic materials in elevated temperature environments. In this paper, we derive exact closed-form electromagnetic Green's function expressions for polarization fields in uniaxial multiferroic materials and bimaterials induced by a steady point heat source. The pyroelectric and pyromagnetic effects as a result of temperature change in multiferroic materials are incorporated in this study. The degen- erate and nondegenerate cases, which pertain to whether the heat conduction characteristic constant is equal to one of the two electromagnetic characteristic constants, are discussed in detail. The Green's functions for a bimaterial composed of two perfectly bonded uniaxial multiferroic half-spaces subjected to a point heat source are further obtained by means of the image method. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Electromagnetic fields (900 MHz) evoke consistent molecular responses in tomato plantsPHYSIOLOGIA PLANTARUM, Issue 2 2006David Roux First page of article [source] Electromagnetic fields alter the expression of estrogen receptor cofactors in breast cancer cellsBIOELECTROMAGNETICS, Issue 3 2008Rainer Girgert Abstract Breast cancer is the most common malignancy of women in Western societies. The increasing exposure to electromagnetic fields has been suspected to contribute to the rising incidence of breast cancer in industrialized countries. The majority of breast tumors is treated with the partial antiestrogen tamoxifen. Most tumors become resistant to tamoxifen in the course of treatment resulting in treatment failure. Electromagnetic fields reduce the efficacy of tamoxifen similar to tamoxifen resistance. In this study we investigated the mechanism by which electromagnetic fields influence the sensitivity to tamoxifen. In cells exposed to 1.2 µT of a 50 Hz electromagnetic field gene expression of cofactors of the estrogen receptors was compared to sham exposed cells. Using a gene array technology several cofactors were found to be differentially expressed. The expression of the coactivators, SRC-1 and AIB1, and of two corepressors, N-Cor and SMRT, was quantified by RT-PCR. Both coactivators were expressed more strongly in the exposed cells while the expression of two corepressors decreased. The RNA analysis was confirmed by Western blots. The contradirectional changes in gene expression of coactivators and corepressors by electromagnetic fields results in a lower sensitivity to tamoxifen. Electromagnetic fields may contribute to the induction of tamoxifen resistance in vivo. Bioelectromagnetics 29:169,176, 2008. © 2007 Wiley-Liss, Inc. [source] Electromagnetic Field Treatment of Nerve Crush Injury in a Rat Model: Effect of Signal Configuration on Functional RecoveryBIOELECTROMAGNETICS, Issue 4 2007Janet L. Walker Abstract Electromagnetic fields (EMFs) have been demonstrated to enhance mammalian peripheral nerve regeneration in vitro and in vivo. Using an EMF signal shown to enhance neurite outgrowth in vitro, we tested this field in vivo using three different amplitudes. The rat sciatic nerve was crushed. Whole body exposure was performed for 4 h/day for 5 days in a 96-turn solenoid coil controlled by a signal generator and power amplifier. The induced electric field at the target tissue consisted of a bipolar rectangular pulse, having 1 and 0.3 ms durations in each polarity, respectively. Pulse repetition rate was 2 per second. By varying the current, the coils produced fields consisting of sham (no current) and peak magnetic fields of 0.03 mT, 0.3 mT, and 3 mT, corresponding to peak induced electric fields of 1, 10, and 100 µV/cm, respectively, at the tissue target. Walking function was assessed over 43 days using video recording and measurement of the 1,5 toe-spread, using an imaging program. Comparing injured to uninjured hind limbs, mean responses were evaluated using a linear mixed statistical model. There was no difference found in recovery of the toe-spread function between any EMF treatments compared to sham. Bioelectromagnetics 28:256,263, 2007. © 2007 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] Development of a high-speed electromagnetic repulsion mechanism for high-voltage vacuum circuit breakersELECTRICAL ENGINEERING IN JAPAN, Issue 1 2008Mitsuru Tsukima Abstract This paper presents a design and testing of a new high-speed electromagnetic driving mechanism for a high-voltage vacuum circuit breaker (VCB). This mechanism is based on a high-speed electromagnetic repulsion and a permanent magnet spring (PMS). This PMS is introduced instead of the conventional disk spring due to its low spring energy and more suitable force characteristics for VCB application. The PMS has been optimally designed by the 3D nonlinear finite-elements magnetic field analysis and investigated its internal friction and eddy-current effect. Furthermore, we calculated the dynamic of this mechanism coupling with the electromagnetic field and circuit analysis, in order to satisfy the operating characteristics,contact velocity, response time, and so on, required for the high-speed VCB. A prototype VCB, which was built based on the above analysis, shows sufficient operating performance. Finally, the short circuit interruption tests were carried out with this prototype breaker, and we have been able to verify its satisfying performance. © 2008 Wiley Periodicals, Inc. Electr Eng Jpn, 163(1): 34,40, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.20398 [source] Comparison of electromagnetic field for two different lightning pulse current modelsEUROPEAN TRANSACTIONS ON ELECTRICAL POWER, Issue 4 2001A. Andreotti In this paper the electromagnetic field produced by a lightning current analytically described by the so called double exponential model is compared with the field produced by the same current (same peak, rise and decay time) analytically described by the model proposed by Heidler. The exponential model has been widely used in literature for its simplicity and its relatively good accuracy. The Heidler model is more complex, but removes the main problem shown by the double exponential: the non-zero derivative at the beginning of the lightning pulse in contrast with the physical phenomenon. In the lightning electromagnetic pulse (LEMP) simulations both models are now used. In the paper we aim to make a comparison between the two. In particular we show that the two models are fairly equivalent in the frequency range up to 2 MHz, namely the range of interest of typical lightning phenomena. In addition, the double exponential model is shown to be conservative for higher frequencies. [source] Gauge-independent quantum dynamics on phase-space of charged scalar particlesFORTSCHRITTE DER PHYSIK/PROGRESS OF PHYSICS, Issue 2-3 2003S. Varró On the basis of the Hamiltonian form of the Klein-Gordon equation of a charged scalar particle field introduced by Feshbach and Villars, the gauge-invariant 2×2 Wigner matrix has been constructed whose diagonal elements describe positive and negative charge densities and the off-diagonal elements correspond to cross-densities in phase-space. The system of coupled transport equations has been derived in case of interaction with an arbitrary external electromagnetic field. A gauge-independent generalization of the free particle representation due to Feshbach and Villars is given, and on the basis of it both the nonrelativistic and the classical limits of the general relativistic quantum Boltzmann-Vlasov equation(RQBVE) is discussed. In the non-relativistic limit (p/mc,0) the set of equations of motion decouple to two independent quantum transport equations describing the dynamics of oppositely charged positon and negaton densities separately. In the classical limit(,,0) two relativistic Boltzmann-Vlasov equations result for the diagonal positon and negaton densities. It is obtained that, though in the latter equations the Planck constant , is absent, the real part of the cross-density does not vanish. [source] Fabrication of a Macroporous Microwell Array for Surface-Enhanced Raman ScatteringADVANCED FUNCTIONAL MATERIALS, Issue 19 2009Martina Zamuner Abstract Here, a colloidal templating procedure for generating high-density arrays of gold macroporous microwells, which act as discrete sites for surface-enhanced Raman scattering (SERS), is reported. Development of such a novel array with discrete macroporous sites requires multiple fabrication steps. First, selective wet-chemical etching of the distal face of a coherent optical fiber bundle produces a microwell array. The microwells are then selectively filled with a macroporous structure by electroless template synthesis using self-assembled nanospheres. The fabricated arrays are structured at both the micrometer and nanometer scale on etched imaging bundles. Confocal Raman microscopy is used to detect a benzenethiol monolayer adsorbed on the macroporous gold and to map the spatial distribution of the SERS signal. The Raman enhancement factor of the modified wells is investigated and an average enhancement factor of 4,×,104 is measured. This demonstrates that such nanostructured wells can enhance the local electromagnetic field and lead to a platform of ordered SERS-active micrometer-sized spots defined by the initial shape of the etched optical fibers. Since the fabrication steps keep the initial architecture of the optical fiber bundle, such ordered SERS-active platforms fabricated onto an imaging waveguide open new applications in remote SERS imaging, plasmonic devices, and integrated electro-optical sensor arrays. [source] Gold Nanorods: From Synthesis and Properties to Biological and Biomedical ApplicationsADVANCED MATERIALS, Issue 48 2009Xiaohua Huang Abstract Noble metal nanoparticles are capable of confining resonant photons in such a manner as to induce coherent surface plasmon oscillation of their conduction band electrons, a phenomenon leading to two important properties. Firstly, the confinement of the photon to the nanoparticle's dimensions leads to a large increase in its electromagnetic field and consequently great enhancement of all the nanoparticle's radiative properties, such as absorption and scattering. Moreover, by confining the photon's wavelength to the nanoparticle's small dimensions, there exists enhanced imaging resolving powers, which extend well below the diffraction limit, a property of considerable importance in potential device applications. Secondly, the strongly absorbed light by the nanoparticles is followed by a rapid dephasing of the coherent electron motion in tandem with an equally rapid energy transfer to the lattice, a process integral to the technologically relevant photothermal properties of plasmonic nanoparticles. Of all the possible nanoparticle shapes, gold nanorods are especially intriguing as they offer strong plasmonic fields while exhibiting excellent tunability and biocompatibility. We begin this review of gold nanorods by summarizing their radiative and nonradiative properties. Their various synthetic methods are then outlined with an emphasis on the seed-mediated chemical growth. In particular, we describe nanorod spontaneous self-assembly, chemically driven assembly, and polymer-based alignment. The final section details current studies aimed at applications in the biological and biomedical fields. [source] Some Parameters of Correlated Current and Radiated Field Pulses from Lightning to the Gaisberg TowerIEEJ TRANSACTIONS ON ELECTRICAL AND ELECTRONIC ENGINEERING, Issue 1 2010Hannes Pichler Non-member Abstract Simultaneous measurements of lightning current and associated radiated electromagnetic field are of fundamental interest for various applications in lightning research. These data can be used for the evaluation of return stroke (RS) models or to investigate the so-called tower effect when lightning hits an elevated object. In this paper, we show the results of simultaneous measurements of current pulses from lightning strikes on the instrumented Gaisberg tower (Austria) and the correlated vertical E-field components at a distance of 78.8 and 108.7 km, respectively. We have analyzed some main lightning current parameters (peak current Ip, 30,90% rise time TI_30-90, and full width at half maximum TI_FWHM and the time-correlated field waveform parameters (Ep, 30,90% rise time TE_30-90, TE_FWHM, and the peak-to-zero time TE_PTZ. With a geometric mean of TI_FWHM = 19 ,s and Ip = 9.6 kA (N = 73) of the RS current pulses used in this study, those strokes are very similar to the strokes in triggered lightning in Florida and Alabama1. With a TE_PTZ of about 10 µs, the zero-crossing time of the radiated E-fields from the tower strokes are significantly shorter than the typical values of 30 , 40 µs (e.g.2). Correlation between the current and field parameters TI_FWHM versus TE_FWHM and TE_PTZ, respectively, is low (R2 = 0.29 and 0.14). We assume that the relatively short lightning channel in the case of the RSs in object-triggered upward flashes is the main reason for the observed short zero-crossing time. Copyright © 2010 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc. [source] A review of studies on the electric field and the current induced in a human body exposed to electromagnetic fieldsIEEJ TRANSACTIONS ON ELECTRICAL AND ELECTRONIC ENGINEERING, Issue 2 2006Tadasu Takuma Member Abstract How high an electric field or current is induced inside a human body when exposed to an electromagnetic field has recently attracted much attention. The background for this is twofold; concern about the possible health effects of electromagnetic fields (usually called ,EMF issues'), and their positive application to medical treatment or new research subjects. This paper reviews various aspects related to this topic in terms of the following items: basic formulas for field calculation, effect of electromagnetic fields, calculation methods, an Investigation Committee in the IEEJ, and future research subjects. © 2006 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc. [source] Numerical analysis of deformed free surface under AC magnetic fieldsINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN FLUIDS, Issue 12 2004Haruhiko Kohno Abstract A novel numerical scheme for the analysis of large deformation of electrically conducting liquid under alternating current magnetic fields is presented. The main features are characterized by two numerical tools; the level set method to calculate deformed free surface stably and the hybrid finite element method and boundary element method to discretize the electromagnetic field efficiently. Two-dimensional numerical simulation of conducting drop deformation is carried out to demonstrate the effectiveness of the present scheme, and the oscillatory behaviour, which depends on the magnitude of surface tension and Lorentz force, is investigated. Copyright © 2004 John Wiley & Sons, Ltd. [source] An extended Huygens' principle for modelling scattering from general discontinuities within hollow waveguidesINTERNATIONAL JOURNAL OF NUMERICAL MODELLING: ELECTRONIC NETWORKS, DEVICES AND FIELDS, Issue 5 2001Ronald L. Ferrari Abstract The modal fields, generalized scattering matrix (GSM) theory and dyadic Green's functions relating to a general uniform hollow waveguide are briefly reviewed in a mutually consistent normalization. By means of an analysis linking these three concepts, an extended version of the mathematical expression of Huygens' principle is derived, applying to scattering from an arbitrary object within a hollow waveguide. The integral-equation result expresses the total field in terms of the incident waveguide modal fields, the dyadic Green's functions and the tangential electromagnetic field on the surface of the object. It is shown how the extended principle may be applied in turn to perfect conductor, uniform material and inhomogeneous material objects using a quasi method of moments (MM) approach, coupled in the last case with the finite element method. The work reported, which indicates how the GSM of the object may be recovered, is entirely theoretical but displays a close similarity with established MM procedures. Copyright © 2001 John Wiley & Sons, Ltd. [source] Application of the TLM technique to integrated optic component modellingINTERNATIONAL JOURNAL OF NUMERICAL MODELLING: ELECTRONIC NETWORKS, DEVICES AND FIELDS, Issue 2 2001O. Jacquin The TLM algorithm is of high interest to simulate new integrated optical devices as a ,photonic band gap' (PBG) structures. These components are realized with semiconductor material and constituted by a set of abrupt optical discontinuities. The electromagnetic behaviour of these structures does not allow the use of usual simulation methods of integrated optics. Indeed, their validity conditions are not satisfied. Then, we have to use unusual simulation method for integrated optics as TLM software which allows the visualization and understanding of the behaviour of electromagnetic field in the PBG structures. In this paper, the simulation results of different optical devices made from the TLM method are presented. Copyright © 2001 John Wiley & Sons, Ltd. [source] Charged relativistic spheres with generalized potentialsMATHEMATICAL METHODS IN THE APPLIED SCIENCES, Issue 6 2009S. Thirukkanesh Abstract A new class of exact solutions of the Einstein,Maxwell system is found in closed form. This is achieved by choosing a generalized form for one of the gravitational potentials and a particular form for the electric field intensity. For specific values of the parameters it is possible to write the new series solutions in terms of elementary functions. We regain well-known physically reasonable models. A physical analysis indicates that the model may be used to describe a charged sphere. The influence of the electromagnetic field on the gravitational interaction is highlighted. Copyright © 2008 John Wiley & Sons, Ltd. [source] The singular sources method for cracksMATHEMATICAL METHODS IN THE APPLIED SCIENCES, Issue 10 2007Morteza Fotouhi Abstract The singular sources method is given to detect the shape of a thin infinitely cylindrical obstacle from a knowledge of the TM-polarized scattered electromagnetic field in large distance. The basic idea is based on the singular behaviour of the scattered field of the incident point source on the cross-section of the cylinder. We assume that the scatterer is a perfect conductor which is possibly coated by a material and investigate two models with different boundary conditions. Also we give a uniqueness proof for the shape reconstruction. Copyright © 2006 John Wiley & Sons, Ltd. [source] The dressed nonrelativistic electron in a magnetic fieldMATHEMATICAL METHODS IN THE APPLIED SCIENCES, Issue 10 2006Laurent Amour Abstract We consider a nonrelativistic electron interacting with a classical magnetic field pointing along the x3 -axis and with a quantized electromagnetic field. When the interaction between the electron and photons is turned off, the electronic system is assumed to have a ground state of finite multiplicity. Because of the translation invariance along the x3 -axis, we consider the reduced Hamiltonian associated with the total momentum along the x3 -axis and, after introducing an ultraviolet cutoff and an infrared regularization, we prove that the reduced Hamiltonian has a ground state if the coupling constant and the total momentum along the x3 -axis are sufficiently small. We determine the absolutely continuous spectrum of the reduced Hamiltonian and, when the ground state is simple, we prove that the renormalized mass of the dressed electron is greater than or equal to its bare one. We then deduce that the anomalous magnetic moment of the dressed electron is nonnegative. Copyright © 2006 John Wiley & Sons, Ltd. [source] Solution of axisymmetric Maxwell equationsMATHEMATICAL METHODS IN THE APPLIED SCIENCES, Issue 10 2003Franck Assous Abstract In this article, we study the static and time-dependent Maxwell equations in axisymmetric geometry. Using the mathematical tools introduced in (Math. Meth. Appl. Sci. 2002; 25: 49), we investigate the decoupled problems induced in a meridian half-plane, and the splitting of the solution in a regular part and a singular part, the former being in the Sobolev space H1 component-wise. It is proven that the singular parts are related to singularities of Laplace-like or wave-like operators. We infer from these characterizations: (i) the finite dimension of the space of singular fields; (ii) global space and space,time regularity results for the electromagnetic field. This paper is the continuation of (Modél. Math. Anal. Numér. 1998; 32: 359, Math. Meth. Appl. Sci. 2002; 25: 49). Copyright © 2003 John Wiley & Sons, Ltd. [source] Theoretical tools to solve the axisymmetric Maxwell equationsMATHEMATICAL METHODS IN THE APPLIED SCIENCES, Issue 1 2002F. Assous Abstract In this paper, the mathematical tools, which are required to solve the axisymmetric Maxwell equations, are presented. An in-depth study of the problems posed in the meridian half-plane, numerical algorithms, as well as numerical experiments, based on the implementation of the theory described hereafter, shall be presented in forthcoming papers. In the present paper, the attention is focused on the (orthogonal) splitting of the electromagnetic field in a regular part and a singular part, the former being in the Sobolev space H1 component-wise. It is proven that the singular fields are related to singularities of Laplace-like operators, and, as a consequence, that the space of singular fields is finite dimensional. This paper can be viewed as the continuation of References (J. Comput. Phys. 2000; 161: 218,249, Modél. Math. Anal. Numér, 1998; 32: 359,389) Copyright © 2002 John Wiley & Sons, Ltd. [source] Miniaturized antenna using half-mode substrate integrated waveguide structureMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 12 2008Cuilin Zhong Abstract An X-band miniaturized antenna which uses half-mode substrate integrated waveguide structure is designed. We analyzed the electromagnetic field using the cavity model and the electromotive force method. The input impedance, simulated and experimental results of return loss, resonant frequency, and radiation patterns are presented. Its performances are as same as those of the corresponding microstrip antenna, but its size is half of the microstrip antenna. This planar structure can be integrated on the same substrate with other components such as filter and amplifier, and it can also be used to easily form antenna arrays. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 3214,3218, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23911 [source] Electromagnetic propagation in unbounded inhomogeneous chiral media using the coupled mode methodMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 11 2007Álvaro Gómez Abstract The coupled mode method (CMM) is a seminumerical method for studying electromagnetic propagation, originally formulated for closed structures. We show how this method can be used for obtaining the propagation constants and electromagnetic field in unbounded isotropic chiral media. We also characterize single and periodic cascade discontinuities made of isotropic chiral slabs by means of the mode matching method combined with the CMM. The results are tested with a robust FDTD technique, modified to model bi-isotropic media and with analytical solutions. In all cases good agreement is found. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 2771,2779, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22863 [source] Optimization of the current integration method for a front-fed parabolic reflector antennaMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 3 2004F. D'Agostino Abstract This work centers on an optimization of the current integration method for determining the field radiated by a centered parabolic reflector fed at its focus. A nonredundant sampling representation of the physical optics (PO) current, induced on the main reflector by the electromagnetic field radiated from the primary field source, and an optimal sampling interpolation algorithm are developed to this end. Such an approach allows one to reduce the number of points where the knowledge of the current is required, so that the computation time decreases remarkably when the evaluation of the field radiated from the feed is burdensome. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 40: 235,239, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.11339 [source] Relativistically expanding cylindrical electromagnetic fieldsMONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 4 2009K. N. Gourgouliatos ABSTRACT We study relativistically expanding electromagnetic fields of cylindrical geometry. The fields emerge from the side surface of a cylinder and are invariant under translations parallel to the axis of the cylinder. The expansion velocity is in the radial direction and is parametrized by v=R/(ct). We consider force-free magnetic fields by setting the total force the electromagnetic field exerts on the charges and the currents equal to zero. Analytical and semi-analytical separable solutions are found for the relativistic problem. In the non-relativistic limit, the mathematical form of the equations is similar to equations that have already been studied in static systems of the same geometry. [source] Unconventional control of excited states of a dimer molecule by a localized light field between metal nanostructuresPHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 5 2009Takuya Iida Abstract We have made a theoretical study of the spatial interplay between the localized light field (LLF) and the electronic wavefunction of molecules. When the LLF has a nanoscale spatial variation comparable to a molecular wavefunction, this interplay is crucial to determine the optical response of molecular excited states. Such a condition can be realized in case that a molecule is lying in the vicinity of a metal nanogap. By using the calculation method applicable to arbitrary-shaped samples, we demonstrate a drastic enhancement of the response electromagnetic field from an optical forbidden state whose magnitude is comparable to that from an allowed state. The obtained result indicates that we have a possibility to control the excited states of molecules by designing the LLF with metal nanostructures. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Electronic excitations and optical spectra of Pt2 and Pt4 on Cu(001) modeled by a clusterPHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 5 2010George Pal Abstract The photoabsorption spectra of Pt2 and Pt4 clusters on the Cu(001) surface are computed using two different theoretical methods: the symmetry-adapted cluster expansion configuration interaction from quantum chemistry and a recently developed linear response approach to treat electron,hole correlations in the presence of an external electromagnetic field. Comparing the energetically low-lying optical excitations, we find very good agreement between the two methods. For different orientations of the adsorbed clusters with respect to the surface, we find that the most intense optical peaks occur when the polarization of the applied laser pulse is parallel to the surface. [source] | ||||||||||||||||||||||||||||