1,721,143 research outputs found
Streamline curvature effects in confined isothermal recirculating flowfields behind an axisymmetric bluff body - Numerical calculations with the k-epsilon turbulence model
No full textThe confined turbulent recirculating flowfield due to the isothermal mixing of dual coaxial streams in the near-wake region of an axisymmetric bluff body is numerically investigated. The finite-difference computations based upon the Reynolds-averaged Navier-Stokes equations and the k-epsilon turbulence model examine modifications to the turbulence model to account for the effects of streamline curvature and for the preferential influence of normal stresses on turbulence dissipation. This examination is facilitated by a comparison of the predicted and measured results of the axial and radial distributions of the mean and rms axial velocity, the centerline stagnation points, and the axial decay of the centerline CO2 concentration
Isothermal Predictions of Recirculating Turbulent Flow fields of Confined Dual Coaxial Jets Behind an Axisymmetrec Bluff Body
No full textFinite-difference numerical computations are presented to predict the isothermal, turbulent, recirculating flowfields in a centerbody combustor configuration which involves confined dual coaxial jet mixing in the near-wake region of an axisymmetric bluff body. The calculations based upon the Reynolds-averaged Navier-Stokes equations and the k-epsilon turbulence model consider the influence of the annular and central flow rates on the nature of the flowfield downstream of the bluff body. Other questions addressed include the effects of inlet turbulence length scales and streamline curvature. The recirculating flowfield structure is studied by examining the axial and radial distributions of the mean and rms velocity fields, the centerline stagnation points, the vortex center, and the zero mean axial velocity contour. The present numerical results demonstrate the complex nature of the flowfield interactions in the near-wake region and refine the understanding of the centerbody combustor flowfields
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe 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
Get PDF“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
Get PDFWe 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
Get PDFWe 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
Numerical Calculation of a Confined Two-Dimensional Turbulent Mixing Layer
No full textNumerical simulation of a recent Stanford University experiment on the mixing layer downstream of a splitter plate is reported. The splitter plate, located midway between confining walls of a 4-cm-high and 10-cm-wide test section, separates upper and lower nitrogen streams of initial velocities of 6 and 3 m/s respectively. The flowfield computations, based upon Reynolds-averaged Navier-Stokes equations and k-epsilon turbulence model, investigate the influence of inlet velocity profiles and turbulence length scales, differencing schemes, streamline curvature effects, and exit boundary location on the mean and rms velocity fields. The numerical predictions are compared with the available hot-wire anemometry data
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