			Home About us Contact

Electromagnetic Response (electromagnetic + response)

Distribution by Scientific Domains

Engineering	33%
Earth and Environmental Science	33%

Selected Abstracts

Coupled FEM and lumped circuit model of the electromagnetic response of coaxially insulated windings in two slot cores

EUROPEAN TRANSACTIONS ON ELECTRICAL POWER, Issue 6 2007
Pär Holmberg
Abstract This paper presents a coupled FEM and lumped circuit modelling approach that is primarily intended for high-frequency and overvoltage simulations of rotating electric machines with coaxially insulated windings, such as Powerformer and Motorformer. The magnetic fields and their interaction with the conductors of the winding are simulated with the aid of a FEM-program. The displacement current and its losses are modelled with an external lumped circuit. To consider eddy current losses, the stranded conductors and the laminated steel cores are replaced by homogeneous bodies with similar losses over a wide frequency range. The approach is illustrated and experimentally verified for a set-up with a cable wound around two slot cores. The model agrees well with measurements up to 1,MHz. Copyright © 2007 John Wiley & Sons, Ltd. [source]

A wide-band lumped circuit model of the terminal and internal electromagnetic response of coaxially insulated windings mounted on a core

EUROPEAN TRANSACTIONS ON ELECTRICAL POWER, Issue 3 2003
P. Holmberg
This paper presents a wide-band lumped circuit model of coaxially insulated windings mounted on a core. The polyphase model can be used to simulate the terminal and internal electromagnetic response in DryformerTM, a new oil-free power transformer, and similar electromagnetic power devices. The circuit parameters are based on geometrical and material data. The simulated frequency and transient response of the lumped circuit is compared to measurements on a 20 MVA 140/6.6 kV three-phase transformer of the DryformerTM type. The comparison shows that the model can be used to estimate resonance frequencies and transient overvoltages in the transformer, although the damping is not accurately modelled. The influence of the core is discussed and investigated. [source]

Modelling electromagnetic responses of 2-D structures due to spatially non-uniform inducing fields.

GEOPHYSICAL JOURNAL INTERNATIONAL, Issue 2 2003
Analysis of magnetotelluric source effects at coastlines
SUMMARY In previous works, we presented 2-D and 3-D magnetotelluric modelling methods based on Rayleigh,Fourier expansions. These methods are an alternative to finite-element and finite-difference techniques and are especially suitable for modelling multilayered structures, with smooth irregular boundaries. Here we generalize the 2-D method for the calculation of the electromagnetic response of 2-D structures to arbitrary, spatially non-uniform 2-D and 3-D inducing magnetic fields. These fields are characteristic of low- and high-latitude regions. We calculate the response to different 2-D and 3-D sources, of a 2-D structure representative of the conductivity distribution which could be found at a coastline, which includes deep conductive anomalies in the lower crust and upper mantle. Then, we investigate source effects, comparing these responses to that obtained for a uniform source. These effects become noticeable for periods greater than approximately 6 h and increase with the period of the source. They are highly dependent on the morphology of the source and also on the orientation of the external field relative to the strike direction of the structure. In various cases, they totally mask the uniform source response. [source]

Krylov model order reduction of finite element approximations of electromagnetic devices with frequency-dependent material properties

INTERNATIONAL JOURNAL OF NUMERICAL MODELLING: ELECTRONIC NETWORKS, DEVICES AND FIELDS, Issue 5 2007
Hong Wu
Abstract A methodology is presented for the Krylov subspace-based model order reduction of finite element models of electromagnetic structures with material properties and impedance boundary conditions exhibiting arbitrary frequency dependence. The proposed methodology is a generalization of an equation-preserving Krylov model order reduction scheme for methodology for second-order, linear dynamical systems. The emphasis of this paper is on the application of this method to the broadband model order reduction of planar circuits including lossy strips of arbitrary thickness and lossy reference planes. In particular, it is shown that the proposed model order reduction methodology provides for the accurately modelling of the impact of the frequency dependence of the internal impedance per unit length of the thick lossy strip on the electromagnetic response of the stripline structure over a very broad, multi-GHz frequency band, extending all the way down to frequencies in the DC neighbourhood. In addition, the application of the proposed methodology to the broadband modelling of electromagnetic coupling between strips on either side of a lossy ground plane is demonstrated. Copyright © 2007 John Wiley & Sons, Ltd. [source]

Spectroscopic ellipsometry and vector network analysis for determination of the electromagnetic response in two wavelength regions

PHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 5 2008
C. Åkerlind
Abstract In this work, spectroscopic ellipsometry and vector network analysis are used to determine the electromagnetic response of three samples, an epoxy polymer, a sample with ferrit-based nanoparticles in a polymer matrix and silicon, in the wavelength ranges 0.4-30 ,m and 0.75-7.59 cm. Both methods measure amplitude and phase changes due to interaction with a sample and can be used to measure the full complex-valued dielectric response to electromagnetic radiation. The data from the two methods show similar levels of the response at the two ends of the spectral gap between the ranges of the two methods. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

Memory-based or afferent processes in mismatch negativity (MMN): A review of the evidence

PSYCHOPHYSIOLOGY, Issue 1 2005
Risto Näätänen
Abstract The mismatch negativity (MMN) is an electromagnetic response to any discriminable change in regular auditory input. This response is usually interpreted as being generated by an automatic cortical change-detection process in which a difference is found between the current input and the representation of the regular aspects of the preceding auditory input. Recently, this interpretation was questioned by Jääskeläinen et al. (2004) who proposed that the MMN is a product of an N1 (N1a) difference wave emerging in the subtraction procedure used to visualize and quantify the MMN. We now evaluate this "adaptation hypothesis" of the MMN in the light of the available data. It is shown that the MMN cannot be accounted for by differential activation of the afferent N1 transient detectors by repetitive ("standard") stimuli and deviant ("novel") stimuli and that the presence of a memory representation of the standard is required for the elicitation of MMN. [source]

Ground-penetrating radar and geo-electrical simulations of data from the Floridablanca archaeological site

ARCHAEOLOGICAL PROSPECTION, Issue 1 2005
M. de la Vega
Abstract In this work we characterize the electromagnetic response of archaeological remains of a Spanish fortress situated on the Atlantic coast in Patagonia (Argentina). The fortress, part of the Floridablanca colony, founded in the eighteenth century, has been surveyed with non-invasive electromagnetic techniques (ground-penetrating radar (GPR) and the geo-electric method). The surveys indicate the presence of adobe walls of various sizes and width having different preservation states. Use of inversion algorithms alone to interpret the data has not been conclusive in obtaining a reliable model, because many uncertainties remained. To aid the interpretation, we make use of modelling methods to simulate the low- and high-frequency electromagnetic responses of the structures. The walls can be differentiated in spite of the low resistivity contrast with the surrounding media. The resolution of the 500,MHz antenna allows a satisfactory determination of the location of the walls and their conservation state. Similarly, the geo-electrical response has enough sensitivity to detect the inner and major walls. Copyright © 2005 John Wiley & Sons, Ltd. [source]

Colloidal Films That Mimic Cilia

ADVANCED FUNCTIONAL MATERIALS, Issue 18 2010
Fang Liu
Abstract Cilia are wavy hair-like structures that extend outward from surfaces of various organisms. They are classified into two general categories, primary cilia, which exhibit sensing attributes, and motile cilia, which exert mechanical forces. A new poly(2-(N,N -dimethylamino)ethyl methacrylate- co -n-butyl acrylate- co - N,N -(dimethylamino) azobenzene acrylamide) (p(DMAEMA/nBA/DMAAZOAm) copolymer is prepared using colloidal synthesis, which, upon coalescence, form films capable of generating surfaces with cilia-like features. While film morphological features allow the formation of wavy whiskers, the chemical composition of the copolymer facilitates chemical, thermal, and electromagnetic responses manifested by simultaneous shape and color changes as well as excitation wavelength dependent fluorescence. These studies demonstrate that synthetically produced polymeric films can exhibit combined thermal, chemical, and electromagnetic sensing leading to locomotive and color responses, which may find numerous applications in sensing devices, intelligent actuators, defensive mechanisms, and others. [source]