1,720,958 research outputs found
Evaluation of some algorithms and programs for the computation of integer-order Bessel functions of the first and second kind with complex arguments
No full textThe purpose of this article is to provide some insight on the efficiency and accuracy of a few available algorithms for the computation of integer-order Bessel functions. First, the computation of integer-order Bessel functions of the first kind (Jn(z)), using the Fast Fourier Transform (FFT) algorithm as opposed to recurrence techniques, is investigated. It is shown that recurrence techniques are superior to the FFT technique, both in accuracy and speed efficiency. Second, an erroneous algorithm, suggested in the literature and used by commercially available software, specially MATLAB 3.5 and MATHEMATICA 1.2, for computing integer-order Bessel functions of the second kind (Yn(z)), is revealed by comparing these routines with an algorithm developed by the author. Catastrophic errors result from the use of the erroneous algorithm, for the computation of large orders with non-real arguments.Articl
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
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe 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
DIELECTRIC LOADING OF A SMALL RIDGED CAVITY-BACKED SLOT ANTENNA.
No full textThe effects are studied of dielectric loading on the frequency of operation, input impedance, and aperture field distribution of a ridged, cavity-backed slot antenna. The transverse slot is cut in the flat broadwall of a deep, single-ridge waveguide cavity, when the cavity is excited by the center conductor of a coaxial transmission line. The role of the input-probe position in matching the antenna is demonstrated. The experimental parameters are summarized in tabular form. It is concluded that dielectric loading reduces the operating frequency and improves the slot aperture efficiency. The input impedance level is controlled by the probe position. A lossy dielectric increases bandwidth (reduces Q) at the expense of efficiency.Conference Pape
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe 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
The computation of antenna electromagnetic fields at nonasymptotic distances from cylindrical near-field measurements
No full textA technique for the determination of the electric field at arbitrary points in the space surrounding an antenna is described. The cylindrical modal expansion formulation of the electric field can be evaluated using A. C. Ludwig's (1968) algorithm after the factorization of the integrands into slowly and rapidly changing factors. The latter is achieved by factorizing the Hankel functions in the integrands using an asymptotic approximation. The modal coefficients of an E-plane sectoral horn were computed from cylindrical near-field measurements at 3 GHz. Using the method described, the copolarized electric field was computed in the E-plane at distances of 1 and 10 m from the antenna. It is concluded that the method can be used successfully to compute the electric field in the radiating near field and further.Conference Pape
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