1,721,011 research outputs found
The application of advanced beamforming techniques for the noise characterization of installed counter rotating open rotors
No full textThis paper reports on the results of a series of aeroacoustic measurements of a counter rotating open rotor (CROR) installed on a 1=7th scale model of an advanced regional aircraft design. The tests were conducted in a large low speed wind tunnel for a variety of aircraft geometries, angles of attack and low speeds. Data were acquired on three far field beamforming arrays. The study attempts to characterize the installed CROR noise source through the application of several beamforming techniques applied to each individual array and to a global array of the three arrays in combination. Although some results have been achieved in this preliminary study, there are also drawbacks and limitations of the beam-forming processes for the case of model with CRORs, therefore a deeper investigation will be necessary. This work has been conducted as part of the European Clean Sky funded
WENEMOR project which will be completed in August 2013, the testing phase of which was completed in May 2013
The application of advanced beamforming techniques for the noise characterization of installed counter rotating open rotors
No full text
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
Etude expérimentale du bruit de bord de fuite à large bande d'une grille d'aubes linéaire et de sa réduction par dispositifs passifs
No full textBroadband trailing edge noise is one of the main contributors to modern turbofan noise. The current need for both understanding and reducing those sources motivated the present work. This study focuses on the cascade effect which is produced by the scattering of acoustic waves on neighbouring blades. A seven blade linear cascade is set up for acoustic measurements in the downstream sector with varying speed and angle of attack. Broadband trailing edge noise is thus the main noise source in the facility on a wide frequency range. Acoustic resonances in the cascade and far field interferences as well as specific velocity dependence are proofs of the sought blade interactions. To give a more quantitative insight in the cascade effect, Amiet isolated airfoil trailing edge noise model is first used. Its input data which are a statistical description of the turbulent boundary layer are directly measured on the suction surface of the center blade. The noise levels are fairly well predicted suggesting that the cascade effect only moderately affects the far-field acoustic spectra. Glegg's cascade model is then modified to fit the experimental set-up and used with the same input data. The estimates differ from the isolated airfoil predictions from ±3dB confirming the preceeding conclusions. However far field interferences are well recovered by Glegg's model. Noise reduction is then assessed in this study. First, brushes are inserted in an isolated airfoil trailing edge and a broadband noise reduction of 4,5 dB is obtained. A hot wire coherence study is carried out in the near wake of the brush showing that spanwise decorrelation could be partly responsible for the observed noise reduction. Trailing edge serrations are finally applied on the cascade trailing edges and the same reduction potential than on isolated airfoil with the same device is recovered. This shows that the cascade effet has little influence on the noise reduction process. This mechanism is more likely to be threefold. Particle image velocimetry measurements show that the suction side boundary layer is thrown out from the airfoil surface which could result in smaller induced surface pressure. Secondly, the vorticity sheet shed in the wake because of the Kutta condition is necessarily less coherent in the spanwise direction with the serrations than with the straight edge. Last, the reduced relative angle between the flow and the local trailing edge could also theorically reduce the far-field noise. This has been investigated analytically by means of a modification of Amiet's model to account for the sweep angle of the blade.Le bruit de bord de fuite à large bande est l'un des contributeurs principaux du bruit des soufflantes de turboréacteurs modernes. La double nécessité de mieux comprendre sa génération et de le réduire a suscité le présent travail, essentiellement expérimental. L'étude se focalise sur l'effet de grille provoqué par la diffraction des ondes acoustiques sur les aubes adjacentes. Une grille d'aubes linéaire de solidité 1,43 est instrumentée et adaptée à la mesure acoustique dans le secteur aval pour plusieurs vitesses d'écoulement et plusieurs angles d'attaque. Le bruit de bord de fuite de la grille d'aubes prédomine ainsi sur une large gamme de fréquence. L'effet de grille se manifeste à travers des résonances dans la grille, des interférences dans le champ lointain et à travers la dépendance en vitesse des spectres acoustiques. Les données d'entrée de modèles analytiques décrivant statistiquement la turbulence des couches limites sont directement mesurées sur les aubages. Le modèle de bruit de profil isolé d'Amiet fournit une estimation convenable des niveaux de bruit suggérant que la déformation des spectres par l'effet de grille est de faible amplitude. Nous avons ensuite adapté à la configuration expérimentale le modèle de Glegg qui tient compte des interactions entre pales. Il fournit des estimations de spectres acoustiques s'écartant de 3 dB de la prédiction de profil isolé, confirmant la conclusion précédente. Cependant ce dernier modèle décrit mieux les interférences observées en champ lointain. La réduction du bruit de bord de fuite est ensuite abordée, dans un premier temps sur profil isolé au moyen de brosses insérées au bord de fuite. Une réduction de 4,5 dB est ainsi obtenue sur une large gamme de fréquences. Une étude de corrélation aérodynamique aux fils chauds dans le sillage des brosses montre qu'elles décorrèlent les structures turbulentes dans la direction de l'envergure ce qui peut expliquer partiellement la réduction du bruit observée. Dans un deuxième temps, des chevrons dessinant des dents de scie dans la direction de l'envergure sont appliqués aux bords de fuite de la grille d'aubes. Nous retrouvons alors les observations faites avec ces dispositifs sur les profils isolés. Aucun effet de couplage entre la réduction du bruit et l'effet de grille n'est observé. Des mesures de vélocimétrie par images de particules dans le sillage des chevrons montrent que la couche limite de l'extrados est éloignée de la surface du profil fournissant un mécanisme admissible de réduction du bruit. Un deuxième mécanisme crédible est la décorrélation dans la direction de l'envergure de la nappe de vorticité lâchée dans le sillage suite à la condition de Kutta. Enfin, nous étudions l'effet de l'inclinaison du bord de fuite par rapport 'a l'écoulement et montrons par une prise en compte de cette géométrie dans le modèle d'Amiet qu'il peut également aboutir à une réduction acoustique
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