1,721,051 research outputs found
Main Instabilities of Coaxial Jets
No full textAn experimental analysis of the dominant instabilities in the initial merging region of two coaxial jets is presented. Different inner/outer jet velocity pairs U_i,U_o have been tested in order to investigate the effect of both velocity ratio r_u=~U_o/U_i and Reynolds number in the instability characteristics. Three main instabilities have emerged depending on the velocity ratio. For r_u<0.75 the coaxial jets dynamic is driven by the inner shear layer. For r_u>1.6 the outer shear layer dominates the near field vortex dynamics, while for velocity ratios nearly unitary the vortex shedding behind the separating wall imposes its own dynamics
Experimental analysis of dominant instabilities in coaxial jets
No full textAn experimental analysis of the dominant instabilities in the near field of two coaxial jets is presented and discussed. Different inner/outer jet velocity pairs Ui ,Uo have been tested in order to investigate the effect of both velocity ratio ru=Uo /Ui and Reynolds number. Three main instabilities have emerged depending on the velocity ratio. For ru=0.75, the coaxial jets dynamic is driven by the inner shear layer. For ru=1.6, the outer shear layer dominates the near field vortex dynamics while for ru nearly unitary, the vortex shedding behind the separating wall imposes its own dynamics. A new scaling relationship is proposed to improve the estimation of the shedding frequency with respect to the one found in literature
Experiments on aircraft flight parameter detection by on-skin sensors
No full textAir speed and flight attitude angles are fundamental parameters for manual of automatic control of flying bodies. Conventional measuremen methods rely on probes (e.g. Pitot tubes or vanes) having a one-to-one correspondence with the physical quantities of interest and requiring specific placements. Here, a novel measurement approach is proposed, relying on indirect measurement and on a plurality of pressure readings made by thin capacitive sensors directly placed on the aircraft skin. A redundant number of probes relaxes the accuracy requirements posed on the individual units and helps achieving fault detection or fault tolerance. A strategy for efficiently processing/combining sensor data is herein presented together with an error propagation analysis, and experimental data
Numerical Investigation of the AFRODITE Transition Control Strategy
No full textAFRODITE is a financed project by the European Research Council aimed at experimentally investigating passive flow control methods for transition delay and hence skin-friction drag reduction. The transition delay is here obtained by generating longitudinal high speed streaks in the boundary layer (BL) by means of Miniature Vortex Generators (MVGs) mounted on the wall surface. The present work details the Direct Numerical Simulation (DNS) setup designed to reproduce the AFRODITE experiments and provide results showing that the proposed DNS is in good agreement with the experiments. The results of the DNS also show that even a minimal delay of the transition point results in an overall gain in terms of drag when MVGs are installed on the plate
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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