1,720,968 research outputs found
Assessment of the performances and limitations of spacetime convective corrections for acoustic metacontinua design
No full textThe acoustic metamaterial extension to aeroacoustic applications is still an open issue principally due to the lack of a reliable methodology for the meta-devices design when they have to operate in a non-quiescent medium. One suitable strategy is to use spacetime coordinate transformations that include the background flow features to tune the meta-device design parameters analytically, and, therefore, the phenomenon must be reinterpreted into the spacetime. However, a change of coordinates capable of including all the convective effects is not known for general flow conditions and analytical approximations are inevitably introduced. This work validates the spacetime framework numerically, providing a better comprehension of the approximation effects on the spacetime-corrected acoustic metacontinuum and its cautious interpretation both from the mathematical and physical points of view
Assessment of the convective correction defect of metacontinua using spurious sources in the aeroacoustic spacetime
No full textThe analytical convective adaptation of statically-design acoustic meta materials could be a suitable strategy to achieve their implementation in the aeronautical context preserving their performances. The adaptation process follows from the application of analytical correction based on coordinate transformation. Their introduction is possible by exploiting the formal invariance of the governing equation when it is rewritten in the space time domain. In the present paper, two analytical corrections based on Taylor’s and Prandtl-Glauert’s coordinate transformation are considered, and the effect of the analytical approximation introduced is investigated for several Mach numbers up to 0.3. The test case considers a cylindrical sound-hard obstacle surrounded by an in viscid fluid model adapted through the corrections, embedded in a conventional medium domain characterized by a uniform background flow where a simple monopole source emits acoustic perturbations. The numerical setup is chosen to make the effect of the spurious terms evident and hence to quantify their influence on the corrections’ goodness. The scattered fields are evaluated in the frequency domain through the commercial FEM solver COMSOL Multi physics
Numerical assessment of the correction defect induced by spacetime coordinate transformations in the design of a convective meta-device
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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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