1,720,964 research outputs found
Simulation of a transient supersonic jet
No full textThis study investigates the evolution of under-expanded jets into a quiescent atmosphere using two-dimensional numerical simulation. The test case consists of two chambers separated by a wall with a small orifice. Initial pressure ratios between the two chambers were varied between 88 and 700, and the jet gas type was high pressure air exhausting into a low pressure, quiescent air chamber. During the initial transient, a Mach shock forms by rapid lateral expansion of the gas near the corner of the orifice and is initially absent at the jet centreline. As the flow evolves, the Mach shock becomes fully formed and vortex rings develop by Kelvin-Helmholtz and baroclinic instabilities at the interface of the barrel shocks and the quiescent air. After further flow evolution, the inner structure of the jet, enclosed by a barrel shock and Mach shock, resembles the structure of a steady under-expanded jet.</p
Transient start-up of a sonic jet in hypersonic crossflow
No full textThis paper presents a numerical study of the transient start-up of a sonic jet into a hypersonic crossflow. Implicit large-eddy simulations were performed using OpenFOAM for a round, sonic, perfect air jet issuing normal to a Mach 5 crossflow, over a flat plate with a laminar boundary layer, at a jet-to-crossflow momentum ratio of 5.3. The evolution of shock and vortex structures, the jet penetration, and the control force have been quantified during the jet start-up. Initially, a lead shock forms, which is quickly deformed and convected downstream by the crossflow. The obstruction caused by the jet leads to formation of barrel shocks, a bow shock, and a Mach disk. The obstruction also results in upstream flow separation, which facilitates the formation of the horseshoe vortices within an upstream recirculation region. Shear-layer vortices begin to form and shed periodically once the barrel shock structure is established, while longitudinal counter-rotating vortices and wake vortices are not formed until the jet flow has penetrated far downstream. The control force develops on the same time-scale as the longitudinal counter-rotating vortices. An overshoot is observed in the control force after the lead shock and initial jet flow has convected downstream beyond the edge of the plate, and is related to the re-compression of the free-stream flow downstream of the jet outlet, and the development of re-circulation regions.</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
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
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
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