1,720,964 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
Facteurs influençant la capacité d'isolation thermique de différents systèmes de revêtements "barrière thermique"
No full textIn aeronautical gas turbine engines, the metallic materials employed in the hottest sections are subject to very harsh chemical environments at high pressures and temperatures. Therefore, thermal barrier coating systems (TBCs) are applied onto nickel-based superalloy substrates. These multi-layered systems (ceramic yttria-stabilized zirconia (YSZ) / MCrAl or NiPtAl bond coats / cooled substrate) lower the temperature at the components surface, which ensures an adequate thermomechanical behaviour and reduces the oxidation/corrosion rates. However, the increase of the turbine inlet temperature (increased engine performance) brings about new degradation phenomena (e.g. CMAS) and loss of efficiency of the current TBCs. Therefore, understanding the evolution of the insulation ability of TBCs in such harsh environments is key from both the scientific and technological perspectives to estimate the lifetime of these coatings, hence that of the engines. Based on current plasma-sprayed (PS) and electron-beam physical vapour deposited (EB-PVD) YSZ coatings, this thesis seeks to provide a better comprehension on the relationships between the intrinsic properties of the current TBCs and their thermal insulation capacity as a basis for the development of future coatings. Also, this work studies an alternative solution to create a TBC made of hollow alumina microspheres by the slurry route. We will show that the sintering of the YSZ, the evolution of crystal phases, the reactions between YSZ and CMAS and the growth of thermal oxides alter the thermal diffusivity to different extents. In contrast, the evolution of the thermal diffusivity with temperature is less marked with the slurry alumina coatings, which appear more stable when hybrid Ar/air annealing atmospheres are employed upon their synthesis.Dans les turbines à gaz aéronautiques, les matériaux employés dans les parties les plus chaudes sont soumis à des environnements chimiques extrêmes, sous fortes pressions et températures. Ainsi, des systèmes de revêtement « barrière thermique, BT » sont appliqués sur les substrats en superalliage à base nickel. Ces systèmes multicouches (zircone stabilisée à l’yttrine (YSZ) /couche de liaison en MCrAl ou NiPtAl/substrat refroidi) permettent d’abaisser la température à la surface des pièces, conduisant à un comportement thermomécanique adéquat et à une diminution des vitesses d’oxydation/corrosion. Cependant, l’augmentation nécessaire de la température des gaz d’entrée de turbine (augmentation du rendement moteur) entraîne de nouveaux phénomènes de dégradation (CMAS) et une perte d’efficacité des revêtements BT actuels. Par ailleurs, l’évaluation de la durée de vie des revêtements BT s’avère cruciale pour déterminer celle des moteurs. Comprendre l’évolution du pouvoir isolant des revêtements BT en environnement agressif constitue donc un enjeu essentiel du point de vue scientifique et technologique. A partir des revêtements couramment employés (YSZ) déposés par projection plasma (PS) ou en phase vapeur (EB-PVD), la présente étude a visé à mieux comprendre l’effet de l’évolution des propriétés microstructurales et chimiques des revêtements sur leur pouvoir isolant, dans le but de développer des outils nécessaires à la mise au point des revêtements du futur. De plus, une partie des travaux menés a porté sur une solution alternative plus économique et écologique d’élaboration de revêtements BT, fondée sur un procédé par voie barbotine, permettant in fine d’obtenir une barrière constituée de microsphères creuses d’alumine. Ce travail a permis de montrer que l’évolution par frittage des phases céramiques en YSZ, les changements de phase cristalline, les réactions avec les CMAS et la croissance d’oxydes thermiques modifient la diffusivité thermique. En revanche, celle-ci évolue moins avec la température puisque les revêtements en alumine issus de barbotines se sont avérés plus stables et ce, notamment, lorsque leur élaboration a été réalisée sous atmosphères hybrides (mélanges Ar/air)
Facteurs influençant la capacité d'isolation thermique de différents systèmes de revêtements "barrière thermique"
No full textDans les turbines à gaz aéronautiques, les matériaux employés dans les parties les plus chaudes sont soumis à des environnements chimiques extrêmes, sous fortes pressions et températures. Ainsi, des systèmes de revêtement « barrière thermique, BT » sont appliqués sur les substrats en superalliage à base nickel. Ces systèmes multicouches (zircone stabilisée à l’yttrine (YSZ) /couche de liaison en MCrAl ou NiPtAl/substrat refroidi) permettent d’abaisser la température à la surface des pièces, conduisant à un comportement thermomécanique adéquat et à une diminution des vitesses d’oxydation/corrosion. Cependant, l’augmentation nécessaire de la température des gaz d’entrée de turbine (augmentation du rendement moteur) entraîne de nouveaux phénomènes de dégradation (CMAS) et une perte d’efficacité des revêtements BT actuels. Par ailleurs, l’évaluation de la durée de vie des revêtements BT s’avère cruciale pour déterminer celle des moteurs. Comprendre l’évolution du pouvoir isolant des revêtements BT en environnement agressif constitue donc un enjeu essentiel du point de vue scientifique et technologique. A partir des revêtements couramment employés (YSZ) déposés par projection plasma (PS) ou en phase vapeur (EB-PVD), la présente étude a visé à mieux comprendre l’effet de l’évolution des propriétés microstructurales et chimiques des revêtements sur leur pouvoir isolant, dans le but de développer des outils nécessaires à la mise au point des revêtements du futur. De plus, une partie des travaux menés a porté sur une solution alternative plus économique et écologique d’élaboration de revêtements BT, fondée sur un procédé par voie barbotine, permettant in fine d’obtenir une barrière constituée de microsphères creuses d’alumine. Ce travail a permis de montrer que l’évolution par frittage des phases céramiques en YSZ, les changements de phase cristalline, les réactions avec les CMAS et la croissance d’oxydes thermiques modifient la diffusivité thermique. En revanche, celle-ci évolue moins avec la température puisque les revêtements en alumine issus de barbotines se sont avérés plus stables et ce, notamment, lorsque leur élaboration a été réalisée sous atmosphères hybrides (mélanges Ar/air).In aeronautical gas turbine engines, the metallic materials employed in the hottest sections are subject to very harsh chemical environments at high pressures and temperatures. Therefore, thermal barrier coating systems (TBCs) are applied onto nickel-based superalloy substrates. These multi-layered systems (ceramic yttria-stabilized zirconia (YSZ) / MCrAl or NiPtAl bond coats / cooled substrate) lower the temperature at the components surface, which ensures an adequate thermomechanical behaviour and reduces the oxidation/corrosion rates. However, the increase of the turbine inlet temperature (increased engine performance) brings about new degradation phenomena (e.g. CMAS) and loss of efficiency of the current TBCs. Therefore, understanding the evolution of the insulation ability of TBCs in such harsh environments is key from both the scientific and technological perspectives to estimate the lifetime of these coatings, hence that of the engines. Based on current plasma-sprayed (PS) and electron-beam physical vapour deposited (EB-PVD) YSZ coatings, this thesis seeks to provide a better comprehension on the relationships between the intrinsic properties of the current TBCs and their thermal insulation capacity as a basis for the development of future coatings. Also, this work studies an alternative solution to create a TBC made of hollow alumina microspheres by the slurry route. We will show that the sintering of the YSZ, the evolution of crystal phases, the reactions between YSZ and CMAS and the growth of thermal oxides alter the thermal diffusivity to different extents. In contrast, the evolution of the thermal diffusivity with temperature is less marked with the slurry alumina coatings, which appear more stable when hybrid Ar/air annealing atmospheres are employed upon their synthesis
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
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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