1,720,957 research outputs found
Des matériaux carbonés au stockage de l'énergie : étude des mécanismes de sodation d'électrodes négatives pour batteries sodium-ion
No full textIn the current context of the energy transition, energy storage is a major challenge where lithium-ion batteries dominate the market. This technology is currently raising questions about the critical materials it uses. A great deal of research is going into identifying solutions to replace this type of accumulators, which is already well established in industry, including sodium-ion batteries. This technology mainly uses hard carbons as the negative electrode material. These non-graphitisable carbons have a complex structure and porous texture, which makes it difficult to analyse these materials, leading to disagreement within the scientific community concerning their electrochemical sodation mechanisms. The aim of this thesis is to contribute to the understanding of the behaviour of hard carbons in Na-ion batteries, through a detailed multi-technique and multi-scale analysis. To this purpose, a method for developing carbon materials was specifically developed, and the samples obtained were compared with commercial carbons. A study of their electrochemical sodiation confirmed a three-stage mechanism. Among other things, this work highlights the importance of developing “closed” porosity to improve the specific capacity of materials. In addition, TiO2/carbon nanocomposites were prepared using an innovative method and considered as an alternative anode for Na-ion battery.Dans le contexte de la transition énergétique actuel, le stockage de l'énergie est un enjeu majeur pour lequel les batteries lithium-ion dominent le marché. Cette technologie interroge aujourd'hui quant aux matériaux critiques qu'elle emploie. De nombreuses recherches visent à identifier des solutions pour substituer ce type d'accumulateurs déjà bien implanté dans l'industrie, parmi lesquelles figurent les batteries sodium-ion. Cette technologie emploie principalement des carbones durs en tant que matériau d'électrode négative. Ces carbones non graphitisables présentent une structure et une texture poreuse complexes rendant difficile l'analyse de ces matériaux, d'où des désaccords au sein de la communauté scientifique quant à leurs mécanismes de sodation électrochimique. L'objectif de cette thèse est de contribuer à la compréhension du comportement des carbones durs en batterie Na-ion, par le biais d'une analyse fine multitechnique et multiéchelle. Pour cela, une méthode d'élaboration de matériaux carbonés a été spécifiquement développée, et les matériaux obtenus ont été comparés à des carbones commerciaux. Une étude de leur sodation électrochimique a conforté un mécanisme en trois étapes. Ce travail souligne entre autres l'importance de développer une porosité « fermée » permettant d'améliorer la capacité spécifique des matériaux. Par ailleurs, des nanocomposites TiO₂/carbone ont été préparés à l'aide d'une méthode novatrice et considérés en tant qu'anode alternative pour batterie Na-ion
Des matériaux carbonés au stockage de l'énergie : étude des mécanismes de sodation d'électrodes négatives pour batteries sodium-ion
No full textIn the current context of the energy transition, energy storage is a major challenge where lithium-ion batteries dominate the market. This technology is currently raising questions about the critical materials it uses. A great deal of research is going into identifying solutions to replace this type of accumulators, which is already well established in industry, including sodium-ion batteries. This technology mainly uses hard carbons as the negative electrode material. These non-graphitisable carbons have a complex structure and porous texture, which makes it difficult to analyse these materials, leading to disagreement within the scientific community concerning their electrochemical sodation mechanisms. The aim of this thesis is to contribute to the understanding of the behaviour of hard carbons in Na-ion batteries, through a detailed multi-technique and multi-scale analysis. To this purpose, a method for developing carbon materials was specifically developed, and the samples obtained were compared with commercial carbons. A study of their electrochemical sodiation confirmed a three-stage mechanism. Among other things, this work highlights the importance of developing “closed” porosity to improve the specific capacity of materials. In addition, TiO2/carbon nanocomposites were prepared using an innovative method and considered as an alternative anode for Na-ion battery.Dans le contexte de la transition énergétique actuel, le stockage de l'énergie est un enjeu majeur pour lequel les batteries lithium-ion dominent le marché. Cette technologie interroge aujourd'hui quant aux matériaux critiques qu'elle emploie. De nombreuses recherches visent à identifier des solutions pour substituer ce type d'accumulateurs déjà bien implanté dans l'industrie, parmi lesquelles figurent les batteries sodium-ion. Cette technologie emploie principalement des carbones durs en tant que matériau d'électrode négative. Ces carbones non graphitisables présentent une structure et une texture poreuse complexes rendant difficile l'analyse de ces matériaux, d'où des désaccords au sein de la communauté scientifique quant à leurs mécanismes de sodation électrochimique. L'objectif de cette thèse est de contribuer à la compréhension du comportement des carbones durs en batterie Na-ion, par le biais d'une analyse fine multitechnique et multiéchelle. Pour cela, une méthode d'élaboration de matériaux carbonés a été spécifiquement développée, et les matériaux obtenus ont été comparés à des carbones commerciaux. Une étude de leur sodation électrochimique a conforté un mécanisme en trois étapes. Ce travail souligne entre autres l'importance de développer une porosité « fermée » permettant d'améliorer la capacité spécifique des matériaux. Par ailleurs, des nanocomposites TiO₂/carbone ont été préparés à l'aide d'une méthode novatrice et considérés en tant qu'anode alternative pour batterie Na-ion
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
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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