1,720,976 research outputs found
Elaboration of funtional objects by controlled microextrusion of preceramic polymers
No full textLe besoin de matériaux permettant l’amélioration des systèmes actuels en fonctionnant sous des contraintes de plus en plus extrêmes afin de relever les défis technologiques des prochaines décennies, notamment dans les domaines de l’énergie et de l’aérospatiale, induit la recherche de matériaux plus complexes et réfractaires. Le carbure de silicium (SiC) est identifié comme étant un tel matériau. Néanmoins, l’élaboration de pièce en SiC par fabrication additive se heurte à la complexité de densification de ce matériau sans application de charge mécanique extérieure et/ou d’ajout de frittage. Ainsi, dans le cadre de cette thèse, c’est une voie chimique d’obtention de céramique, la voie Polymer-Derived Ceramics (PDCs) et son implémentation à la fabrication additive qui a été investiguée. La modification chimique d’un polycarbosilane par un complexe de bore a permis de préparer une formulation adaptée au robocasting à partir des poudres SiBC obtenues après pyrolyse. La seconde stratégie a permis de fabriquer des structures lattices à partir de formulations avec des comportements rhéofluidifiants composées de SiC/BN. Enfin, des formulations polymériques thermofusibles ont été développées permettant de mettre en forme des structures lattices et miroirs par Fused Deposition Modeling donnant lieu à des pièces SiC ou SiC/B4C après pyrolyse. L’ensemble des polymères ont été caractérisés par ATR-IRTF, ATG-MS, analyse élémentaire et le comportement des céramiques obtenues ont été caractérisé entre 1000 et 1800 °C par Raman, DRX, MEB-EDS.The need for materials allowing the improvement of current systems by operating under increasingly extreme constraints in order to meet the technological challenges of the coming decades, particularly in the fields of energy and aerospace, induces the search for materials more complex and refractory. Silicon carbide (SiC) is identified as such material. Nevertheless, the development of SiC parts by additive manufacturing comes up against the complexity of densifying this material without applying an external mechanical load and/or adding sintering. Thus, in the context of this thesis, it is a chemical route for obtaining ceramics, the Polymer-Derived Ceramics (PDCs) route and its implementation in additive manufacturing that has been investigated. The chemical modification of a polycarbosilane by a boron complex made it possible to prepare a formulation suitable for robocasting from SiBC powders obtained after pyrolysis. The second strategy made it possible to manufacture lattice structures from formulations with shear-thinning behavior composed of SiC/BN. Finally, thermofusible polymer formulations have been developed to shape lattice and mirror structures by Fused Deposition Modeling giving rise to SiC or SiC/B4C parts after pyrolysis. All the polymers were characterized by ATR-FTIR, ATG-MS, elementary analysis and the behavior of the ceramics obtained were characterized between 1000 and 1800 °C by Raman, DRX, SEM-EDS
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
Fused Deposition Modeling of polycarbosilane to manufacture silicon carbide-based materials
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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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