1,720,974 research outputs found
Un metodo rigoroso per l’analisi di fenomeni propagativi e radiativi in guide periodiche stampate
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A full-wave numerical approach for modal analysis of 1D periodic microstrip structures
No full textIn this paper, a full-wave numerical approach for
the analysis and design of one-dimensional (1-D) printed periodic structures is presented. Electromagnetic-bandgap structures and
leaky-wave antennas are important special cases of structures that
can be analyzed. The proposed technique is based on a mixed-potential integral equation in a unit-cell environment solved by the
method of moments in the spatial domain through a triangular
Delaunay mesh. The 1-D periodic vector and scalar Green’s
functions are derived in the spectral domain and an efficient sum
of spectral integrals is carried out to obtain the spatial-domain
quantities. An appropriate choice of the spectral integration path
is used in order to consider leakage effects. The method developed
here can thus analyze both bound and leaky modes on printed
structures that have an arbitrary metallization within the unit cell
Surface-wave propagation in a metamaterial formed by arrayed pairs of planar conductors
No full textAbstrac
Leaky modes at backward endfire on periodic printed structures
No full textIn this work, the transition at backward endfire between bound (nonleaky) and leaky
modes on one-dimensional periodic structures printed on a grounded dielectric substrate is
examined. This mode evolution has been characterized for a class of structures with a
finite-width cross section. Such structures support leakage into surface waves as well as
into space due to the presence of the substrate. The solutions in this transition region are
calculated using an accurate full-wave moment-method approach that allows for the
determination of both physical and nonphysical solutions, both of which play an important
role in the transition region
Modal analysis of a metamaterial layer formed by arrayed pairs of planar conductors
No full textIn this paper, the dispersion analysis is proposed for the characterization of natural modes of a metamaterial
formed by pairs of metallic Jerusalem crosses separated by a thin dielectric layer. It is
shown that the modal spectrum includes bound (proper real) and leaky (proper and improper complex)
waves. An interesting observation is that at low frequencies a peculiar dominant TM improper
leaky wave occurs, which is shown to be related to peaks of complete transmission
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe 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
Full text link“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
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
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