1,721,303 research outputs found
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
3D zinc-air microbatteries, a way of pushing limits of lithium-ion technologies
No full textCes travaux de thèse se sont focalisés sur la miniaturisation d'une batterie zinc-air, dispositif qui présente l'avantage d'avoir une densité d'énergie massique et volumique théorique supérieure à celle de la technologie lithium-ion, majoritairement étudiée dans la littérature. Le micro-usinage d'un substrat de silicium permet de définir le squelette d'électrodes à forte surface spécifique : le gain géométrique des structures 3D se répercute alors sur les performances de stockage des charges des électrodes de la microbatterie. Différentes géométries de microstructures 3D ont été étudiées : à titre d'exemple, des tubes de taille micrométrique (4,2μm de diamètre), profonds de 109μm (rapport d'aspect de 60: 1) permettent d'obtenir un rapport entre la surface spécifique et l'empreinte surfacique de 70. Ce squelette est ensuite recouvert de matériaux actifs à l'aide de procédés de dépôts conformes. Cette démarche a permis la mise au point d'une électrode métallique 3D en zinc (couche mince de 300nm) présentant une capacité spécifique de 1mAh.cm-2 en milieu aqueux (hydroxyde de potassium 0,7M). La tension de la cellule est de 1,2V. Pour la première fois, une électrode à air miniaturisée a été fabriquée, basée sur la création d'un réseau de micro-canaux poreux sur la face avant du substrat silicium, et la gravure d'une cavité sur la face arrière. Dès lors que le silicium est usiné, un dépôt de platine permet d'assurer le caractère conducteur de l'électrode tandis qu'un dépôt de dioxyde de manganèse lui apporte des propriétés catalytiques. Ce concept original d'électrode à air 30 présente un fonctionnement similaire à une électrode commerciale, malgré une taille bien plus réduite.The studies presented in the frame of this thesis are focused on zinc-air battery miniaturization, an electrochemical energy storage system that shows a higher volumetric and gravimetric energy density than the lithium-ion technology, mostly investigated in literature. The micromachining of a silicon substrate allows designing a high specific surface scaffold: 3D geometrical gain enhances the properties of charge storage for the electrodes of the microbattery. 3D microstructures exhibiting various geometrical designs have been studied: for instance, silicon micro-tubes (4,2μm outer diameter) 109 μm-depth (60:1 aspect ratio) provide a specific surface to the footprint ratio close to 70. Then, this scaffold is coated by the active materials using conformal depositions methods. This process leads to a 3D zinc metallic anode (300nm-thick) exhibiting a surface capacity of 1mAh.cm-2 in aqueous electrolyte (potassium hydroxide 0,7M). Cell voltage is 1,2V. For the first time in literature, a miniaturized air electrode has been manufactured, based on a porous microchannel network on the front side of silicon substrate, and the etching of a cavity on the back side. Once silicon wafer is micromachined, a platinum conformal thin film provides the conductive properties to the electrode while a manganese dioxide layer enhances the catalytic activity. This original concept of 3D air electrode presents a behavior similarly to a commercial one, but with a significant reduced size
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
Elaboration and in operando stuctural characterizations of a 3D microbattery made of thin films deposited by atomic layer deposition (ALD)
No full textAfin de subvenir aux besoins énergétiques des nouvelles technologies électroniques nomades et miniatures, le développement de microdispositifs de stockage électrochimique d’énergie suffisamment performants telles que les microbatteries (MB) Li-ion est nécessaire. Pour ce faire, l’élaboration de MB Li-ion en topologie tridimensionnelle est une voie attractive qui permet le déploiement de surface spécifique tout en conservant l’empreinte surfacique initiale (de l’ordre du mm2), exacerbant ainsi la densité d’énergie délivrée par la MB. Cette solution est rendue possible grâce au développement de technique de dépôt couches minces telle que l’ALD qui est capable de réaliser des dépôts conformes. Dans le cadre de cette thèse, un électrolyte solide (Li3PO4) a été développé et optimisé de façon conforme, par ALD, sur un substrat de silicium structuré au préalable par des techniques de micro-fabrication. Une électrode positive de type spinelle (LiMn1.5Ni0.5O4) a également été élaborée par pulvérisation cathodique RF. Les performances ont été optimisées en fonction des paramètres de dépôt sur un substrat Si/Al2O3/Pt. Une capacité volumique de 63 µAh.cm-2.µm-1 a ainsi été mesurée pour un dépôt de 420 nm à 0,01 mbar recuit sous air à 700°C. Enfin, un prototype de cellule électrochimique en vue d’un suivi in situ/operando par DRX d’une électrode en couche mince, a été proposé.In order to address the demand on energetic needs to sustain nomad and miniaturized electronic devices, micro-devices performance for energy storage such as Li-ion microbatteries (MB) have to be improved. An attractive way to meet the required performance consists in using 3D topology increasing the specific surface while keeping the initial surface footprint (in the mm2 range) which is significantly enhancing the delivered energy density of the MB. The development of thin film technologies such as ALD enabling conformal deposition makes it possible. In the framework of this thesis, a solid electrolyte (Li3PO4) has been developed and optimized by ALD, on a 3D micro-architectured silicon substrate obtained by microfabrication techniques. A positive electrode (LiMn1.5Ni0.5O4) has also been developed and optimized as a function of the deposition parameter by RF sputtering deposition on a Si/Al2O3/Pt substrate. A volumetric capacity of 63 µAh.cm-2.µm-1 has been measured for a film of 420 nm thick obtained at 0.01 mbar and then annealed at 700°C under air atmosphere. Finally, a prototype has been proposed to realize an electrochemical cell for the purpose of in situ/operando follow-up by XRD of a thin film electrode deposited on silicon substrate
Thin films sputtering deposition for chalcopyrite and kesterite solar cells (Cu(In,Ga)Se2 or Cu2ZnSnS4)
No full textMa thèse a permis d’initier l’activité de recherche sur les cellules en couche mince à base de matériaux chalcopyrite et kësterite (CIGS et CZTS) et d’entamer leur réalisation technologique. En intégrant des critères économiques et environnementaux, nous avons défini une stratégie en deux points (i) utilisation de la pulvérisation cathodique comme unique procédé de dépôt pour tous les matériaux et utilisation de cibles uniques pour les matériaux composés. (ii) remplacement des matériaux toxiques et rares. J’ai alors développé le contact arrière en molybdène déposé sur verre sodocalcique, ayant les propriétés électriques requises et une bonne adhésion au substrat. Nous avons vérifié que le sodium présent dans le substrat migre jusqu’à la surface du molybdène. Après une étude bibliographique du dépôt de CIGS par cible unique, j’évalue les avantages et difficultés afférentes à cette méthode. Après une étude bibliographique des méthodes de formation du CZTS et après une étude de pulvérisation de CZTS à partir d’une cible unique, je justifie le choix d’une méthode originale de pulvérisation à partir de trois sources. Je présente ensuite une étude bibliographique évaluant la possibilité de déposer une couche tampon en Zn(O,S) par pulvérisation pour remplacer le CdS déposé par bain chimique. Enfin, après une étude montrant que notre équipement ne permet pas d’obtenir des couches d’AZO ayant les propriétés électriques requises, une étude matériau des couches d’ITO déposées par pulvérisation RF est réalisée. Des couches d’ITO amorphe ayant d’excellentes propriétés électriques et optiques sont obtenues et leur utilisation en tant que fenêtre optique des cellules est proposée.Thin film photovoltaic cells based on CIGS and CZTS materials has been initiated in this work. Environmental and economic issues have been taken into account to define an original strategy. We aim to substitute all the toxic and rare materials by abundant and non-toxic materials. In order to simplify the fabrication process, we also decide to deposit all layers using sputtering technique. The molybdenum back contact has been developed on a soda lime glass (SLG) substrate, with adequate electrical properties and good adhesion to the substrate even after thermal treatments similar to those used during the absorber formation. We have verified the required sodium migration from the SLG substrate to the molybdenum surface. A bibliographic study has been done to evaluate a single-target sputtering method to form CIGS and CZTS films. CZTS thin film deposition from a single target has been studied, with unsatisfactory results. We finally suggest an original multi-target method. Then, a bibliographic study has been done to evaluate the relevance of a sputtered Zn(S,O) buffer layer to replace the CBD-CdS conventional buffer layer. A study of RF-sputtered AZO films has been carried out, but we didn’t obtain the required electrical conductivity. We finally study RF-sputtering of ITO films. We developed amorphous ITO thin films with excellent electrical and optical properties. We suggest using this material as the window layer of solar cells
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