1,721,020 research outputs found
Aeroacoustics of Transonic Shock-Boundary Layer Interactions
No full textThe interaction of a spatially developing supersonic turbulent boundary layer with a normal shock wave is analyzed by means of direct numerical simulation of the compressible Navier-Stokes equations. At the selected flow conditions, corresponding to a mild shock, no mean flow separation is observed. However, the flow is strongly unsteady, and inter- mittent regions of flow reversal are found near the wall, while large vortical structures are observed away from it. Such structures are mainly responsible for the amplification of noise and turbulence across the interaction zone. The intense acoustic loads occurring in the interaction zone are found to be strictly related to the Reynolds shear stress distribu- tion. The analysis of the pressure energy spectra shows a behavior consistent with that observed in incompressible boundary layers in adverse pressure gradient. In particular, a power-law scaling is recovered: at low frequencies the spectra scale as St0.4, while at high frequencies they decay as St-5. The results show that the interacting shock primarily acts as a low-pass filter for the turbulence spectra. © 2007 by Sergio Pirozzoli and Francesco Grasso
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
CFD simulations of flow in LREs rectangular cooling channels
No full textIn the design of liquid propellant rocket engines, the regenerative cooling of the thrust chamber represents one of the most challenging issues. In this respect, the importance of numerical prediction of pressure losses and wall temperatures is crucial. Among the flow models used as a support in the engine design phase, Reynolds-Averaged Navier-Stokes (RANS) equation solvers play an important role, since they represent a fast tool to reproduce turbulent flow phenomena. However, flow in liquid rocket engine cooling channels is characterized by complex and coupled phenomena. In particular, cooling channels typically exhibit rectangular cross section. This leads to the presence of secondary motions that have an influence on both skin friction and heat transfer. RANS turbulence closure models based on the linear eddy-viscosity ansatz are not able to predict secondary eddies, thus inhibiting additional momentum and heat transfer from the duct center toward the corners. In this work, quadratic constitutive relations (QCR) have been implemented in an in-house RANS solver equipped with the Spalart-Allmaras turbulence model. These relations add a nonlinear
term to the linear Reynolds stress tensor in order to improve the eddy-viscosity approximation and the accuracy of RANS solvers. In particular, the effect of QCR on skin friction and heat transfer is investigated through a comparison with direct numerical simulations (DNS) of square and rectangular ducts
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
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
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