scholarly journals Eigenmode analysis of the electromagnetic field scattered by an elliptic cone

2011 ◽  
Vol 9 ◽  
pp. 31-37 ◽  
Author(s):  
M. Kijowski ◽  
L. Klinkenbusch
Keyword(s):  
Free Space ◽  
Plane Electromagnetic Wave ◽  
Multipole Expansion ◽  
Neumann Condition ◽  
Electrically Conducting ◽  
Eigenmode Analysis ◽  
Elliptic Cone ◽  
Series Transformation ◽  
Neumann Eigenvalues

Abstract. The vector spherical-multipole analysis is applied to determine the scattering of a plane electromagnetic wave by a perfectly electrically conducting (PEC) semi-infinite elliptic cone. From the eigenfunction expansion of the total field in the space outside the elliptic cone, the scattered far field is obtained as a multipole expansion of the free-space type by a single integration over the induced surface currents. As for the evaluation of the free-space-type expansion it is necessary to apply suitable series transformation techniques, a sufficient number of eigenfunctions has to be considered. The eigenvalues of the underlying two-parametric eigenvalue problem with two coupled Lamé equations belong to the Dirichlet- or the Neumann condition and can be arranged as so-called eigenvalue curves. It has been observed that the eigenvalues are in two different domains: In the first one Dirichlet- and Neumann eigenvalues are either nearly coinciding, while in the second one they are strictly separated. The eigenfunctions of the first (coinciding) type look very similar to free-space modes and do not contribute to the scattered field. This observation allows to significantly improve the determination of diffraction coefficients.

Topological sensitivity analysis revisited for time-harmonic wave scattering problems. Part I: the free space case

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Frédérique Le Louër ◽  
María-Luisa Rapún
Keyword(s):  
Free Space ◽  
Order Term ◽  
Harmonic Wave ◽  
Dirichlet Condition ◽  
Point Sources ◽  
Neumann Condition ◽  
Scattering Problems ◽  
Content Type ◽  
Time Harmonic ◽  
Topological Gradient

PurposeIn this paper, the authors revisit the computation of closed-form expressions of the topological indicator function for a one step imaging algorithm of two- and three-dimensional sound-soft (Dirichlet condition), sound-hard (Neumann condition) and isotropic inclusions (transmission conditions) in the free space.Design/methodology/approachFrom the addition theorem for translated harmonics, explicit expressions of the scattered waves by infinitesimal circular (and spherical) holes subject to an incident plane wave or a compactly supported distribution of point sources are available. Then the authors derive the first-order term in the asymptotic expansion of the Dirichlet and Neumann traces and their surface derivatives on the boundary of the singular medium perturbation.FindingsAs the shape gradient of shape functionals are expressed in terms of boundary integrals involving the boundary traces of the state and the associated adjoint field, then the topological gradient formulae follow readily.Originality/valueThe authors exhibit singular perturbation asymptotics that can be reused in the derivation of the topological gradient function that generates initial guesses in the iterated numerical solution of any shape optimization problem or imaging problems relying on time-harmonic acoustic wave propagation.

Determination of the velocity of short electromagnetic waves by interferometry

1952 ◽  
Vol 213 (1112) ◽  
pp. 123-141 ◽  
Keyword(s):  
Phase Velocity ◽  
Electromagnetic Radiation ◽  
Free Space ◽  
Electromagnetic Waves ◽  
Wave Beam ◽  
Wave Length ◽  
Wave Frequency ◽  
Space Wave

A new measurement of the velocity of electromagnetic radiation is described. The result has been obtained, using micro-waves at a frequency of 24005 Mc/s ( λ = 1∙25 cm), with a form of interferometer which enables the free-space wave-length to be evaluated. Since the micro-wave frequency can also be ascertained, phase velocity is calculated from the product of frequency and wave-length. The most important aspect of the experiment is the application to the measured wave-length of a correction which arises from diffraction of the micro-wave beam. This correction is new to interferometry and is discussed in detail. The result obtained for the velocity, reduced to vacuum conditions, is c 0 = 299792∙6 ± 0∙7 km/s.

Design of Stealthy Devices Made of Metamaterials with Material Properties

2013 ◽  
Vol 661 ◽  
pp. 95-98 ◽  
Author(s):  
Ye Liu ◽  
Zhu Ying Li ◽  
Wang Zhou Zhang ◽  
Yu Hong Sun
Keyword(s):  
Material Properties ◽  
Coordinate Transformation ◽  
Plane Electromagnetic Wave ◽  
Electromagnetic Devices ◽  
Specific Distribution ◽  
Permittivity And Permeability ◽  
Permeability Distribution ◽  
Electromagnetic Characteristics ◽  
Forming Condition

Using the method of electromagnetic coordinate transformation, through determination of the relation of permittivity and permeability distribution in different spaces, the forming condition of electromagnetic stealthy cloak made of metamaterial is discussed. On the specific distribution of permittivity and permeability, finite element method is used to analyze the electromagnetic characteristics of stealthy cloak which is radiated by plane electromagnetic wave. And the cloak shows excellent stealthy characteristic in theory at certain frequency of the wave. The result shows that the artificial metamterials, which are not found in nature, have the ability of controlling the electromagnetic field and changing the transmission path of wave. Besides stealthy cloak, new electromagnetic devices such as transparent device and concentrator, which are made of metamaterials designed by the coordinate transformation, are preliminarily discussed. They all have excellent stealthy characteristics.

Determination of free space, growth, solute concentrations and parameters of water relations of suspension-cultured tobacco cells

1986 ◽  
Vol 9 (9) ◽  
pp. 693-701 ◽  
Author(s):  
M. DRACUP ◽  
J. GIBBS ◽  
C. E. E. STUIVER ◽  
H. GREENWAY ◽  
T. J. FLOWERS
Keyword(s):  
Water Relations ◽  
Free Space ◽  
Tobacco Cells

Determination of Forces in a Magnetic Bearing Actuator: Numerical Computation With Comparison to Experiment

1992 ◽  
Vol 114 (4) ◽  
pp. 796-801 ◽  
Author(s):  
J. D. Knight ◽  
Z. Xia ◽  
E. McCaul ◽  
H. Hacker
Keyword(s):  
Relative Permeability ◽  
Free Space ◽  
Flux Distribution ◽  
Magnetic Bearing ◽  
Two Dimensional ◽  
Metal Parts ◽  
A Value ◽  
Axis Of Symmetry ◽  
Good Agreement

Calculations of the forces exerted on a journal by a magnetic bearing actuator are presented, along with comparisons to experimentally measured forces. The calculations are based on two-dimensional solutions for the flux distribution in the metal parts and free space, using finite but constant permeability in the metals. Above a relative permeability of 104 the effects of changes in permeability are negligible, but below 104 decreases in permeability cause significant decreases in the force. The calculated forces are shown to depend on the metal permeability more strongly when the journal is displaced from its centered position. The predicted forces in the principal attractive direction are in good agreement with experiment when a relatively low value of permeability is chosen. The forces measured normal to the axis of symmetry when the journal is displaced from that axis, however, are significantly higher than predicted by theory, even with a value of relative permeability larger than 5000. These results indicate a need for futher work including nonlinear permeability distributions.

scholarly journals The Determination of the Salt Relations of the Cytoplasmic Phase in Cells of Beetroot Tissue

1963 ◽  
Vol 16 (3) ◽  
pp. 647 ◽  
Author(s):  
MG Pitman
Keyword(s):  
Free Space ◽  
Cell Type ◽  
In Cells

An analysis of the rate at which isotope diffuses out of disks of beetroot tissue shows that there are at least two components of the non-free space. As tlwse components are not due to differences in cell type within the tissue, it is suggested they are due to a cytoplasmic phase in the parenchymatou's cells, and to the vacuoles.

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