1,720,960 research outputs found
An Improved Method for the Calculation of the Internal Impedances of Solid and Hollow Conductors With the Inclusion of Proximity Effect
No full textWe present a new method for the evaluation of the per unit length (p.u.l.) internal impedances of solid and hollow conductors. Our method is semianalytical, and takes into account the proximity effect arising from currents mutually induced by nearby conductors which, in turn, modify their internal current density distribution and, hence, their impedance. We eventually apply the developed method to the case of a three-core cable and we calculate the voltages induced in its screens by a lightning current
Sur la prise en compte des effets de proximité dans les câbles multipolaires: proposition d’un modèle semi-analytique
No full textEvaluation of the impact of proximity effect in the calculation of the internal impedance of cylindrical conductors
No full textIn this paper we discuss how the inclusion of proximity effect influences the evaluation of the internal impedances of cylindrical conductors. After recalling the classical analytical formulation used for calculating internal impedance, we use a Finite Element Method (FEM) code, in order to take into account the proximity effect. We show that in a low voltage cable, at frequency higher than the industrial ones, and particularly above the kilohertz range, the impact of proximity effect is rather relevant and cannot be neglected when dealing with EMC issues related to cable networks
A method for the evaluation of the sea return impedance and application of the stochastic collocation technique to take into account the uncertainty of input parameters
No full textWe present a method for the evaluation of the sea return impedance term to be employed in the construction of the per-unit-length parameter matrix which is required to describe submarine cables in Electromagnetic Transient software. We evaluate the sea return impedance using the quasi Monte Carlo technique, and an adapted sequence of pseudo-random variables to get a faster convergence. In the calculation of the impedance integral we employ a change of variable in order to reduce its oscillatory behavior and allow it to converge. We also introduce the stochastic collocation technique in order to analyze the impact of uncertainties on the knowledge of the input parameters. This technique is well adapted to numerical calculations; it gives results similar to those obtained with a standard Monte Carlo method, but requires a minor number of computations, some units, instead of the thousands needed with the Monte Carlo method; this is an advantage because the computation time with the latter method would be too long. Furthermore this technique is non intrusive and thus does not necessitate a modification of the function. We show that for the evaluation of the sea return impedance a certain inaccuracy in the knowledge of the cables laying configuration and of the conductivities of the soil can be tolerated in some cases
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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