1,720,956 research outputs found
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
Simulation of multicomponent spray combustion in gas turbine engines
Get PDFLiquid fuels are the dominant source of energy from combustion and will continue to be so until the maturity of emerging technologies. During this transition phase the use of Sustainable Aviation Fuels (SAF) as blends or in totality inside existing infrastructure is an attractive option. The operational aspects of these new fuels inside the combustion chambers are not known in detail. Further, gas turbine engines operate under high pressure ratios and lean conditions to achieve emission targets making them susceptible to thermo-acoustic oscillations. Large Eddy Simulations (LES) have proven to be a successful tool in understanding fuel combustion processes. The focus of this thesis is on the modelling and simulation of complex multicomponent spray flame combustion in realistic systems. First step deals with the multi-component evaporation of the liquid fuel. Realistic fuels have hundreds of components each with their vapourisation characteristics. The Abramzon-Siringnano evaporation in the AVBP solver is extended to handle this complex compositional aspect of realistic fuels. Comparison of the implemented model with experimental and numerical studies show a good agreement and ability to capture the preferential evaporation characteristics of multicomponent fuels. Second, this multicomponent evaporation model is used in a canonical 1D laminar spray flame setup. A three-component jet fuel surrogate is coupled with Analytically Reduced Chemistry (ARC) to study the effects of droplet sizes, equivalence ratios and relative velocities on the spray flame structures. Correlations developed to estimate the spray flame speed agree with the numerical experiments indicating the correct physical parameters have been chosen to describe multicomponent spray flame propagation. Third part of the thesis deals with the simulations of swirled multicomponent spray flames in a large-scale LOTAR configuration. A three component description of conventional jet fuel and sustainable aviation fuel spray is coupled with turbulent combustion models and complex chemistry description to perform 3D-LES. The fuels composition effects on the overall vapour distribution and its effects on the spray flame structure indicate the role of preferential evaporation on flame stabilisation and combustion regimes. Finally, the forced response of the spray flame in the configuration is studied. The flame transfer function extracted using global chemistry agrees well with the experimental trends. Varying injection patterns to account for the effects of forcing on the droplet distribution shows a change in the flame response. The multicomponent spray flame response shows a strong role of composition and volatility of the fuel components
Simulation de la combustion multicomposant diphasique dans les moteurs aéronautiques
No full textLa plupart des combustibles utilisés pour la propulsion sont aujourd’hui sous forme liquide et vont le rester jusqu’à la maturité des nouvelles technologies énergétiques. Pendant cette phase de transition l’utilisation des Carburants Aéronautiques Renouvelables (SAF en anglais) mélangés aux carburants existants ou purs est une solution attractive. Le comportement de ces carburants dans les chambres de combustion dans des conditions opérationnelles n’est, à l’heure actuelle, pas complètement compris. Les turbines à gaz fonctionnent à haute pression et avec des mélanges pauvres en combustible d’atteindre leurs objectifs d’émission, ce qui les rend susceptibles de générer des oscillations thermo-acoustiques, ajoutant un autre niveau de complexité à leur étude. La Simulation aux Grandes Échelles (SGE) s’est montrée très utile pour modéliser et comprendre les mécanismes complexes et leurs interactions dans les flammes turbulentes. Cette thèse se concentre sur la modélisation et la simulation de flammes diphasiques de carburant complexe dans des systèmes réalistes. Dans une première partie, l’évaporation multi-composants d’un carburant liquide est etudiee. Les carburants réalistes se composent en effect de centaines d’espèces chimiques ayant chacune des caractéristiques de vaporisation différentes. Le modèle d’évaporation d’Abramzon-Sirignano implémenté dans le solveur AVBP est étendu pour prendre en compte la composition multi-composants du combustible. Des comparaisons avec des précédentes études expérimentales et numériques montrent que la présente implémentation est en bon accord avec celles-ci et est capable de capturer l’évaporation préférentielle des carburants multi-composants.Dans une deuxième étape, le modèle d’évaporation multi-composants est utilisé dans une flamme laminaire 1D diphasique canonique. Un carburant aéronautique représenté par un modèle à 3 composants couplé à une Chimie Analytiquement Réduite (Analytically Reduced Chemistry ou ARC en anglais) est utilisé afin d’étudier l’effet de la taille de goutte, de la richesse et de la vitesse relative sur la structure des flammes diphasiques. La cohérence des corrélations développées pour estimer la vitesse de flamme diphasique avec les expériences numériques indique que des paramètres physiques pertinents ont été choisis pour décrire la propagation de ces flammes. Dans une troisième partie, des flammes diphasiques swirlées multi-composants sont simulées dans la configuration grande échelle LOTAR mesurée à l’ONERA Fauga. Une description multi-composants d’un spray de carburant aéronautique conventionnel et de carburant renouvelable couplée avec un modèle de combustion turbulente et une description complexe de la chimie sont utilisés pour réaliser et analyser les SGE. Les effets du carburant sur la structure de flamme et les régimes de combustion sont discutés. Enfin, la réponse acoustique forcée de la flamme diphasique dans cette configuration est étudiée. La fonction de transfert de flamme extraite de la simulation est en bon accord avec les tendances expérimentales. La variation du schéma d’injection pour simuler l’effet du forçage sur la distribution des gouttes montre un changement dans la réponse de la flamme. La réponse forcée de la flamme multi-composants diphasique montre l’impact de la description du carburant sur la réponse thermo-acoustique du système.Liquid fuels are the dominant source of energy from combustion and will continue to be so until the maturity of emerging technologies. During this transition phase the use of Sustainable Aviation Fuels (SAF) as blends or in totality inside existing infrastructure is an attractive option. The operational aspects of these new fuels inside the combustion chambers are not known in detail. Further, gas turbine engines operate under high pressure ratios and lean conditions to achieve emission targets making them susceptible to thermo-acoustic oscillations. Large Eddy Simulations (LES) have proven to be a successful tool in understanding fuel combustion processes. The focus of this thesis is on the modelling and simulation of complex multicomponent spray flame combustion in realistic systems. First step deals with the multi-component evaporation of the liquid fuel. Realistic fuels have hundreds of components each with their vapourisation characteristics. The Abramzon-Siringnano evaporation in the AVBP solver is extended to handle this complex compositional aspect of realistic fuels. Comparison of the implemented model with experimental and numerical studies show a good agreement and ability to capture the preferential evaporation characteristics of multicomponent fuels. Second, this multicomponent evaporation model is used in a canonical 1D laminar spray flame setup. A three-component jet fuel surrogate is coupled with Analytically Reduced Chemistry (ARC) to study the effects of droplet sizes, equivalence ratios and relative velocities on the spray flame structures. Correlations developed to estimate the spray flame speed agree with the numerical experiments indicating the correct physical parameters have been chosen to describe multicomponent spray flame propagation. Third part of the thesis deals with the simulations of swirled multicomponent spray flames in a large-scale LOTAR configuration. A three component description of conventional jet fuel and sustainable aviation fuel spray is coupled with turbulent combustion models and complex chemistry description to perform 3D-LES. The fuels composition effects on the overall vapour distribution and its effects on the spray flame structure indicate the role of preferential evaporation on flame stabilisation and combustion regimes. Finally, the forced response of the spray flame in the configuration is studied. The flame transfer function extracted using global chemistry agrees well with the experimental trends. Varying injection patterns to account for the effects of forcing on the droplet distribution shows a change in the flame response. The multicomponent spray flame response shows a strong role of composition and volatility of the fuel components
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
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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