1,721,135 research outputs found
MARTIN, J.R. e ROSE, D. Genre relations ”“ maping culture . Equinox: London/Oakvile, 289 páginas, 2008.
Full text linkMARTIN, J.R. e ROSE, D. Genre relations ”“ maping culture . Equinox: London/Oakvile, 289 páginas, 2008
Rotating gravity current and channel flows
No full textA theoretical and laboratory Investigation of rotating gravity currents and channel flows is presented. The study is applicable to buoyancy driven flows through straits, mid ocean ridge valleys and fracture zones, and intermittent gravity currents. In the theoretical study two extensions are achieved to the energy conserving theory of Hacker (1996). Hacker considered three flow geometries, case A - weak rotation, case B - intermediate rotation and case C - strong rotation. Firstly, the theory is extended to include dissipation. This is achieved in a similar manner to that used by Benjamin (1968) to include energy loss in the non-rotating gravity current theory. The governing equations and numerical solutions for the three flow geometries are presented. For shallow currents the energy loss theory predicts that the Froude number tends to 2* irrespective of the rotation rate. For deeper currents the Froude number increases with rotation. The second extension to the energy conserving theory is the inclusion of an upstream potential vorticity boundary conditionin the current. The approach taken is based on a method used by van Heijst (1985). The governing equations and preliminary solutions for each case are derived. The potential vorticity theory provides an insight into the circulation that develops within the current.However, varying the pre-set potential vorticity in the source region does not appear to have a significant effect upon the front speed and the other principle variables.In the laboratory investigation the effects of fractional depth and rotation rate on the velocity and other parameters which characterise the flow are quantified. For weakly rotating currents, w/R < 0.7 (where w is the width of the channel and R the Rossby radius), the measured front speed is in fair agreement with the energy loss and potential vorticity theories. At higher rotation rates the front speed is lower than predicted. However, the theories assume that the fluid is inviscid, the no-slip condition is not applied at the boundary, potential vorticity is conserved and that energy loss is uniform across the channel. The theory does not include factors such as the enhanced vertical mixing and the development of a geostrophic eddy. These are associated with strong rotation rates and could account for the divergence of the experimental results from the theory
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
Rotating gravity currents. Part 1. Energy loss theory
No full textA comprehensive energy loss theory for gravity currents in rotating rectangular channels is presented. The model is an extension of the non-rotating energy loss theory of Benjamin (J. Fluid Mech. vol. 31, 1968, p. 209) and the steady-state dissipationless theory of rotating gravity currents of Hacker (PhD thesis, 1996). The theory assumes the fluid is inviscid, there is no shear within the current, and the Boussinesq approximation is made. Dissipation is introduced using a simple method. A head loss term is introduced into the Bernoulli equation and it is assumed that the energy loss is uniform across the stream. Conservation of momentum, volume flux and potential vorticity between upstream and downstream locations is then considered. By allowing for energy dissipation, results are obtained for channels of arbitrary depth and width (relative to the current). The results match those from earlier workers in the two limits of (i) zero rotation (but including dissipation) and (ii) zero dissipation (but including rotation). Three types of flow are identified as the effect of rotation increases, characterized in terms of the location of the outcropping interface between the gravity current and the ambient fluid on the channel boundaries. The parameters for transitions between these cases are quantified, as is the detailed behaviour of the flow in all cases. In particular, the speed of the current can be predicted for any given channel depth and width. As the channel depth increases, the predicted Froude number tends to , as for non-rotating flows
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