1,720,959 research outputs found
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
Comparative modal analysis of NRD parallelepiped dielectric resonators
No full textThe resonance modes of dielectric resonators having parallelepiped shape are extensively investigated in this work referring to the nonradiative dielectric (NRD) topology. Different numerical techniques, both rigorous and approximated (boundary elements, point matching, finite elements, transmission line approaches), are proposed and implemented to compute the relevant resonance spectrum as a function of the involved geometric and electromagnetic parameters. The theoretical results are discussed and compared also in connection with experimental investigations, carried out on suitable prototypes of NRD components. Qualitative and quantitative information is thus achieved to characterize with accuracy and efficiency the basic parameters (resonant frequencies, field configurations, etc.) involved in filter design and in other applications at microwaves and millimeter waves
BEM applications in electromagnetics: advantageous features of an original implementation for the modal analysis of dielectric waveguides
No full textStepped leaky-wave antennas for microwave and millimeterwave applications
No full textThis work presents the complete general features of a recently proposed class of leaky-wave antennas, derived from stepped rectangular-section waveguides with radiating slits. Based on very favorable topological features, straightforward but extremely effective design procedures are shown to be possible for achieving sophisticated radiation properties. Furthermore, new possibilities are considered as concerns in both the use of linear arrays to scan in two dimensions, and in the introduction of dielectric parts to improve the angular pointing range and to also protect the radiating elements. The analysis of all these properties illustrates very attractive characteristics and perspectives for this type of antenna which can profitably find applications both at microwaves and at millimeter waves
A Boundary-Element-Method formulation for the electromagnetic coupling between dielectric waveguides and resonators
No full textThe Boundary Element Method has been applied to evaluate the electromagnetic coupling between dielectric waveguides and resonators. A two-dimensional integral-equation formulation has been developed, using dyadic Green's functions. A numerical solution as a function of electromagnetic and geometrical quantities has been obtained for the scattering parameters of a filtering device, consisting of a “Non-Radiative Dielectric” waveguide and a “pillbox” resonator
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
- …
