1,720,994 research outputs found
Full Wave Computation of the Electromagnetic Field in Chaotic Reverberation Chambers
No full textThe geometry deformation of a rectangular shaped reverberation chamber (RC) improves the field mixing and the chaoticity within the RC, in addition to traditional stirring techniques. We noted how the position and number of hemispherical diffractors affect the RC, evaluating their typical key performance parameter such as the number of uncorrelated stirrer positions. Full wave finite-difference time-domain simulations were performed for the analysis
On the Field Statistics in Nested Reverberation Chambers
No full textWe study the normalized field statistics inside nested reverberation chambers, through the analysis of the shielding effectiveness of enclosures and material samples. Accurate knowledge of field statistics allows to improve the estimation of probability distributions for high field values inside electrically large enclosures. Furthermore, the study allows for better selection of the measurement model for both shielding effectiveness of enclosures and materials and gaskets. We find the correct procedures to achieve such distributions. We study basic cases of single and electrically small coupling apertures filtering single or double field components and we show the theoretical statistics of the field components inside NRCs. The change of inner field distributions is driven by the electrical size of coupling apertures and has been verified experimentally. The theory developed to obtain such statistics is based upon physics and the results are supported by measurements. The procedures and results shown in this paper are applicable to predict the statistics in NRCs as well as in adjacent RCs
Accurate Analysis of Reverberation Field Penetration into an Equipment-Level Enclosure
No full textThe paper focuses on the reverberation chamber method for the shielding properties evaluation of equipment-level enclosures. The enclosure under test is numerically modeled by an in-house finite-difference time-domain code that is able to predict the field inside the enclosure and the voltage captured by the probe placed inside it. The chamber fields have been modeled by applying the plane-wave superposition. The code is validated by measurements in our reverberation chamber. Subsequently, the effect of probe positioning and length on the induced voltage is analyzed. Finally, the enclosure shielding effectiveness is evaluated by applying two different definitions, and a statistical analysis is carried out, thus allowing an estimation of the measurement uncertainty
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
Evaluation of Stochastic Electromagnetic Field in Multi-Volume Reverberation Chamber Configurations
No full textFull wave simulations of a reverberation chamber were performed in order to evaluate the stirring efficiency when the overall volume of the chamber was varied, progressively enlarged. The stirrer geometry, position and geometry, do not change during the analysis. We evaluated the stirrer uncorrelated positions, K-factor and the power max-to-mean ratio
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