1,720,974 research outputs found
Truncated Floquet wave full-wave analysis of large phased arrays of open-ended waveguides with a nonuniform amplitude excitation
No full textRecently, an efficient hybrid asymptotic-method of
moments (MoM) approach has been proposed for the analysis of
large periodic planar arrays of elements excited with equal amplitude
and linear phase. The aforementioned method, which is based
on a Floquet wave diffraction representation of the array Green’s
function (AGF), is here extended to treat arrays with tapered amplitude
excitation. To this end, the asymptotic AGF is refined by
introducing additional “slope” diffraction contributions. An appropriate
“fringe” integral equation, solved via a MoM scheme,
provides the effects of array truncation in addition to the infinite
array solution. The dimension of the corresponding linear algebraic
system is independent of the number of elements of the array.
Numerical results are provided to prove the accuracy and the efficiency
of this method with respect to an ordinary element-by-element
MoM
T(FW)2 analysis of large arrays of open ended waveguides with a global tapered excitation
No full textThe Truncated Floquet Wave Full-Wave (T(FW)2) analysis is generalized to large arrays with a tapered amplitude excitation. Numerical results are given to demonstrate the extreme accuracy and the numerical efficiency of the technique
A Pole-zero matching method for EBG surfaces composed of a dipole FSS printed on a grounded dielectric slab
No full textA method is presented, for the efficient derivation of the dispersion equation associated with electromagnetic bandgap (EBG) structures composed by loss-less frequency selective surfaces (FSS) printed on stratified dielectric media. The method, valid for the range of frequency where a single propagating Floquet mode occurs, is based on Foster's reactance theorem applied to an equivalent transmission line network. This theorem implies that the admittance functions of frequency which represent the FSS satisfy the pole-zero analytical properties of the driving point LC admittance functions. By these basic properties and by the full-wave identification of the FSS resonances, an analytical form of the dispersion equation is obtained. This equation is next solved for both surface wave and leaky wave modes by a conventional numerical technique. The results are successfully compared with those from a full-wave analysis
T(FW)2 analysis of large arrays
No full textThe Truncated Floquet Wave Full-Wave (T(FW)2) analysis is generalized to large arrays with a tapered amplitude excitation. Numerical results are given to demonstrate the extreme accuracy and the numerical efficiency of the technique
UHF-HF RFID Integrated Transponder for Moving Vehicle Identification
No full textThis paper presents a passive HF-UHF RFID integrated transponder for the identification of a moving vehicle. It consists of a single ISO 7810 ID-1 Card where both a UHF meander dipole antenna and an ISO 15693 commercial tag are arranged. The UHF antenna is designed by using a parametric analysis of the optimal shape of the meanders to obtain a proper conjugate matching between the antenna and the RFID microchip. A single-lane identification scenario is presented and simulated. The effects of the electromagnetic reflection and diffraction on the reading range as well as on the identification operations of a tagged vehicle are also investigated. Numerical simulations and experimental results on a prototype of the conduced transponder confirm the possibility of using this technology for the identification of a moving vehicle approaching a road-toll system with a relatively slow speed
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
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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