182 research outputs found
Direct sampling method to inverse wave-number-dependent source problems (part I): determination of the support of a stationary source
This paper is concerned with a direct sampling method for imaging the support
of a frequency-dependent source term embedded in a homogeneous and isotropic
medium. The source term is given by the Fourier transform of a time-dependent
source whose radiating period in the time domain is known.
The time-dependent source is supposed to be stationary in the sense that its
compact support does not vary along the time variable.
Via a multi-frequency direct sampling method, we show that the smallest strip
containing the source support and perpendicular to the observation direction
can be recovered from far-field patterns at a fixed observation angle. With
multiple but sparse observation directions, the shape of the convex hull of the
source support can be recovered. The frequency-domain analysis performed here
can be used to handle inverse time-dependent source problems.
Our algorithm has low computational overhead and is robust against noise.
Numerical experiments in both two and three dimensions have proved our
theoretical findings
catena-Poly[[trimethylÂtin(IV)]-μ-phenylÂseleninato-κ2 O:O′]
In the title polymeric coordination compound, [Sn(CH3)3(C6H5O2Se)]n, the SnIV atom has a distorted trigonal–bipyramidal geometry, with two O atoms of two symmetry-related bridging phenylÂseleninate anions in axial positions and three methyl groups in equatorial positions. In the crystal, the complex exhibits a chain structure parallel to the b axis
Evolution of modes in a metal-coated nano-fiber.
We report on the evolution of modes in cylindrical metal/dielectric systems. The transition between surface plasmon polaritons and localized modes is documented in terms of the real and imaginary parts of the effective refractive index as a function of geometric and optical parameters. We show the evolution process of SPP and localized modes. New phenomena of coupling between SPP and core-like modes, and of mode gap and super-long surface plasmon polaritons are found and discussed. We conclude that both superluminal light and slow light can be solutions of metallically coated dielectric fibers
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