1,720,975 research outputs found
Corrigendum/Erratum to: Aerodynamic sound production in low speed flow ducts [79 (2) (1981) 263-289]
No full textAn error has occurred in the presentation of experimental data in Figs. 7, 9, and 10. The error can be corrected by subtracting 6 dB from the vertical scales; equivalently, the values of K2(St) presented in these figures should be divided by 4. The correction applies to all data presented in Figs. 7, 9, and 10
Active control of source sound power in uniform flow
No full textThis paper is mainly a theoretical study of the minimum sound power radiated by two point volume velocity sources situated in an unbounded uniform fluid which moves with a uniform steady velocity. The paper also calculates the maximum sound power that can be absorbed by a point volume velocity source from an incident plane wave in a uniform flow field. The study is in response to the growing interest in applying active control to reduce the sound radiated from aircraft turbofan intakes on approach. For the idealised volume velocity source distribution used in this paper convection effects, to leading term, are found to be of order M2, where M is the Mach number. Mean flows with high subsonic Mach numbers are therefore found to cause a significant deterioration in the radiated sound power that can be reduced at a fixed source separation distance.</p
Active control of source sound power radiation in uniform flow
No full textMany suggested applications of active noise control involve the presence of a background air flow such as in ventilation ducts, exhaust stacks and the radiation from turbofan engines. This paper is a theoretical study aimed at assessing the effect of a uniform flow on the ability of simple sources actively to control free field sound power radiation. In particular, the minimum sound power radiated by two point volume velocity sources situated in an unbounded uniform fluid which moves with a uniform steady velocity is determined. Also the maximum sound power that can be absorbed by a point volume velocity source from an incident plane wave is determined.</p
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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