1,721,153 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
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
Synthesis of new transparent polycrystalline ceramics from full glass crystallization
No full textLes céramiques polycristallines transparentes sont une classe émergente de matériaux pour des applications optiques et photoniques. Au cours de cette thèse, nous avons utilisé une méthode innovante pour élaborer de tels matériaux : la cristallisation complète d'un verre parent. Ce procédé permet d'obtenir de nouvelles céramiques polycristallines transparentes grâce à l'absence de porosité, inhérente à la fabrication du verre parent et aussi d'accéder à de nouvelles phases cristallines. Deux études ont été menées pour améliorer la vitrification de la composition BaAl₄O₇ (1ère céramique transparente obtenue par cristallisation complète du verre). Des résultats surprenants ont été obtenus avec la cristallisation d'une nouvelle phase (BaGa₄O₇) ou avec la synthèse de céramiques biphasiques transparentes BaAl₄O₇ - BaAl₂O₄ dont la transparence est fortement améliorée par rapport à la céramique de BaAl₄O₇, grâce à la cristallisation d'une seconde phase BaAl₂O₄, limitant la croissance des grains biréfringents de BaAl₄O₇. Des céramiques polycristallines transparentes appartenant à la famille des mélilites, de formule générale Sr₁₊xRE₁₋xGa₃O₇₊x∕₂ (RE : rare earth), ont aussi été synthétisées. Des propriétés d'émission de lumière visible ont été mises en évidence à partir des compositions SrGdGa₃O₇ et SrYbGa₃O₇. Cette famille de céramiques polycristallines transparentes ouvre la voie à d'autres applications où l'absence totale de porosité ainsi que l'élaboration de nouvelles phases cristallines inaccessibles par réaction à l'état solide sont des facteurs clés. Ces possibilités ont été démontrées dans le cas de céramiques transparentes présentant une importante conductivité ionique.Transparent polycrystalline ceramic is an emerging class of optic and photonic materials. During this thesis, we used an innovative method to elaborate such materials: the full glass crystallization. This process permits to obtain new transparent polycristalline ceramics through the lack of porosity, inherent to the parent glass and to access to new crystalline phases. Two studies were leaded to improve the glass forming ability of the BaAl₄O₇ composition (1st transparent ceramic obtained from full glass crystallization). Surprising results were obtained with the crystallization of a new phase (BaGa₄O₇) or with the synthesis of two-phase transparent ceramics (BaAl₄O₇ – BaAl₂O₄) where the transparency is considerably enhanced compared to the BaAl₄O₇ ceramic thanks to a second phase crystallization (BaAl₂O₄), limiting the growth of the birefringent BaAl₄O₇ grains. Transparent polycristalline ceramics belonging to the melilite family, with Sr₁₊xRE₁₋xGa₃O₇₊x∕₂ (RE: rare earth) general formulae were also synthesized. White light emission properties have been demonstrated from the SrGdGa₃O₇ and SrYbGa₃O₇ compositions. This family opens the way to others applications where the total absence of porosity with the elaboration of new crystalline phases unattainable by solid state reaction are key factors. These possibilities were demonstrated in the case of transparent polycristalline ceramics showing an important ionic conductivity
Development of new transparent ceramics in the Gd2O3-Ga2O3-Nb2O5 pseudo-ternary diagram for LASER applications
No full textCette thèse est consacrée au développement de nouvelles (vitro)-céramiques transparentes dans le diagramme pseudo-ternaire Gd2O3 - Ga2O3 - Nb2O5. Ces matériaux sont susceptibles de posséder de faibles énergies de phonon, facilitant la transparence dans l'infrarouge proche/moyen pour des applications en tant que nouveaux milieux amplificateurs laser. L'utilisation de la lévitation aérodynamique (ADL) couplée au chauffage par laser CO2 a permis la vitrification des certaines compositions au sein du diagramme pour la première fois. En outre, l'utilisation de l'ADL a facilité la synthèse de nouvelles céramiques transparentes par cristallisation directe du liquide surfondu dans la solution solide Gd3+xNb1-xO7-x (0<x<0,4), qui a elle-même été découverte dans le cadre de ce travail de thèse. Les expériences de diffraction des électrons rétrodiffusés ont révélé une microstructure du type monocristal très inhabituelle qui explique la transparence des échantillons. D'un point de vue cristallographique, le sous-réseau cationique de base de la fluorine est respecté dans toute la solution solide, mais il existe trois types différents types de mise en ordre à courte distance en fonction de la composition, comme le montrent la diffraction des rayons X synchrotron et la diffraction des rayons X sur monocristal. L'échantillon x = 0,4 est un nanocomposite complexe avec une interface cohérente entre les deux types de domaines qui assure la transparence, comme montré par HAADF-STEM.This thesis is devoted to the development of novel transparent glass-ceramics within the Gd2O3 - Ga2O3 - Nb2O5 pseudoternary diagram. Such materials are expected to have low phonon energies, facilitating transparency in the near/mid infra-red with applications as new laser-gain media. The use of aerodynamic levitation (ADL) coupled with CO2 laser heating, permitted vitrification in the diagram for the first time. Additionally, the use of ADL facilitated the synthesis of new transparent ceramics by direct crystallisation of the supercooled liquid from the Gd3(GdxNb1-x)O7-x (0<x<0.4) solid solution, which itself was discovered as part of this work. Electron back scattering diffraction experiments revealed a highly unusual single-crystal like microstructure which explained the sample's transparency. From a crystallographic perspective, the basic fluorite cation sublattice is respected throughout the solid-solution. However, three types of short-range ordering are observed depending on the composition, as shown by synchrotron X-ray diffraction and single-crystal X-ray diffraction. The x = 0.4 member is a complex, but still transparent, nanocomposite due to coherent interfaces between ordered and disordered domains, as seen by atomic resolution HAADF-STEM
Synthesis of transparent polycrystalline ceramics with optical properties by complete and oriented crystallization of glass
No full textLes matériaux possédant des propriétés de luminescence persistante peuvent être décrits comme étant des « batteries optiques » capables de se charger lorsqu’ils sont soumis à une source excitatrice et de se décharger en émettant un rayonnement lumineux. Un des enjeux majeurs pour ce type de matériaux consiste en la synthèse d’échantillons entièrement cristallisés et transparents, permettant une émission en volume. Ces dernières années, le laboratoire CEMHTI a développé un procédé original de synthèse de céramiques polycristallines transparentes : la cristallisation complète du verre. Ce procédé a été employé au cours de ce travail en vue d’obtenir des matériaux innovants présentant des propriétés de luminescence persistante. Pour ce faire, trois systèmes pseudo-binaires ont été étudiés : SrAl2O4-SrAl2Si2O8, BaAl2O4-BaAl2Si2O8 et CaAl2O4-CaAl2Si2O8. Parmi les principaux résultats obtenus, il a été montré que les solutions-solides Sr1-x/2Al2-xSixO4 et Ba1-x/2Al2-xSixO4 permettaient une modulation des propriétés de luminescence persistante par rapport à leurs composés de référence, respectivement SrAl2O4 et BaAl2O4. Par ailleurs, de nouvelles céramiques transparentes biphasiques, composées des deux nouvelles solutions-solides Ba1-x/2Al2-xSixO4 et Ba1+x/2Al2+xSi2-xO8, ont été synthétisées. Enfin, l’étude ciblée d’une composition proche de CaAl2Si2O8 a permis de mettre en évidence la stabilisation d’une nouvelle phase cristalline, localisée dans le volume de l’échantillon, grâce à un processus original lié au rôle d’agent nucléant joué par l’europium. Ce dernier résultat renforce l’intérêt du pseudo-binaire CaAl2O4-CaAl2Si2O8 dans le but futur d’obtenir des céramiques transparentes de grande taille par cristallisation complète du verre.Materials showing long-lasting luminescence properties can be seen as « optical batteries ». Indeed, they can be charged by an optical excitation source and discharged with the emission of visible light. One of the major challenges long-lasting phosphors are facing is the synthesis of fully crystallized and transparent materials, which would enable an optical emission in the entire volume of the sample. Recently, the CEMHTI laboratory has developed an innovative synthesis process to obtain transparent ceramics: the full crystallization from a parent glass. This approach was used all along this work in order to synthetize new crystalline materials showing long-lasting luminescence properties. Three pseudo-binary systems have been studied: SrAl2O4-SrAl2Si2O8, BaAl2O4-BaAl2Si2O8 and CaAl2O4-CaAl2Si2O8. Among the principal results, it has been shown that Sr1-x/2Al2-xSixO4 and Ba1-x/2Al2-xSixO4 solid-solutions enable the modulation of long-lasting luminescence properties compared to those of their parent materials, respectively SrAl2O4 and BaAl2O4. Moreover, two transparent and biphasic ceramics, composed of the two new Ba1-x/2Al2-xSixO4 and Ba1+x/2Al2+xSi2-xO8 solid-solutions, were synthetized. Finally, the study of a particular composition close to CaAl2Si2O8 showed the possibility to stabilize a new crystalline phase located in the volume of the sample using an original crystallization process caused by the nucleating agent role played by europium. This last result reinforces the interest of the CaAl2O4-CaAl2Si2O8 pseudo-binary system in order to further synthetize large transparent ceramics via glass crystallization
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
- …
