1,721,047 research outputs found
On the denseness of Herglotz wave functions and electromagnetic Herglotz pairs in Sobolev spaces
No full textLet D subset of R-3 be a bounded domain with connected boundary partial derivativeD of class C-2. It is shown that Herglotz wave functions are dense in the space of solutions to the Helmholtz equation with respect to the norm in H-1(D) and that the electric fields of electromagnetic Herglotz pairs are dense in the space of solutions to curl curl E = k(2)E with respect to the norm in H-curl(D). Two proofs are given in each case, one based on the denseness of the traces of Herglotz wave functions on partial derivativeD and the other on variational methods. Copyright (C) 2001 John Wiley & Sons, Ltd
An exact linear method for solving non linear electromagnetic inverse scattering problems
No full textInequalities for inverse scattering problems in absorbing media
No full textIn this paper we derive two inequalities concerning two two-dimensional scattering problems: in the first one the infinite cylinder is an obstacle and the electric field satisfies an impedance boundary condition while in the second one the scatterer is inhomogeneous. When the impedance and the refractive index are two known constants these two inequalities can be used to obtain lower bounds on the size of the scatterer. By means of some numerical applications for the impedance problem, we show that the corresponding lower bound is reliable both in the case of full-aperture data and in the case of scattering from a limited aperture
The simple method for solving electromagnetic inverse scattering problems: the case of TE polarized waves
No full textIn two previous papers in this journal we presented a simple method for determining the support of a scattering object from noisy far-field data for transverse magnetic polarized electromagnetic waves. This method was based on the solution of a linear integral equation of the first kind with the mathematical analysis being based on an investigation of an interior transmission problem. In this paper we consider the case of transverse electric polarized electromagnetic waves and again obtain a linear integral equation whose solution yields the support of the scattering object. The mathematical analysis in this case is based on an interior transmission problem different from the one previously considered. Numerical examples are given in the limiting case of a perfect conductor and limited aperture data
A simple method using Morozov's discrepancy principle for solving inverse scattering problems
No full textThis paper is a continuation of earlier research in which a simple inversion scheme was given for inverse scattering problems in the resonance region which is easy to implement and is relatively independent of the geometry and physical properties of the scatterer. The purpose of the paper is to give new and improved theorems establishing the mathematical basis of this method and to show how noisy data can be treated using Morozov's discrepancy principle where the regularization parameter is a function of an auxiliary parameter appearing in the inversion scheme
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
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