1,721,045 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
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
Study of physical, chemical and electronic properties of binaries and ternaries uranium compounds in the U-Si-B and U-Pt-Si systems
No full textCe travail de thèse repose sur deux axes d'étude : (i) l'influence des éléments légers solides, B et C sur la stabilité des phases binaires U-Si, et (ii) la recherche de nouvelles phases et leurs caractérisations physiques dans le système ternaire U-Pt-Si. Des ajouts mineurs de carbone ou de bore au sein d'échantillons U-Si ont montré que la formation de la phase de composition U₅Si₄ était corrélée à la présence de ces éléments légers, conduisant à mettre en doute son existence au sein du système binaire U-Si. Afin d'étudier le potentiel du bore comme simulant des non-métaux de la seconde période (C, N, O), la section isotherme à 927 °C du diagramme de phases ternaire U-Si-B a été tracée, révélant des équilibres entre les axes U-B et U-Si majoritairement et l'existence d'une nouvelle phase U₂₀Si₁₆B₃ isotype du composé ternaire au carbone. Ces résultats tendent à montrer les spécificités physico-chimiques de chacun de ces éléments légers sur le diagramme de phase U-Si. L'étude du diagramme de phases ternaire U-Pt-Si a été effectuée pour la section isotherme à 900 °C. Elle a abouti à la découverte de 14 nouvelles phases, dont U₃Pt₆Si₄ et U₃Pt7Si, présentant des arrangements structuraux inédits. Au préalable de cette étude, un examen du système U-Pt a été entrepris pour la zone de composition 30-70 at.% Pt, conduisant à une nouvelle évaluation du diagramme de phases binaire, intégrant le nouveau composé U₃Pt₄. La température des transformations a été mesurée par ATD. Nos résultats couplés aux données de la littérature ont permis une modélisation par la méthode Calphad. Les caractérisations physiques du nouveau composé binaire U₃Pt₄, indique un comportement de fermion lourd ordonné ferromagnétiquement en dessous de Tc = 7(1)K. En parallèle de ces travaux, l'étude de la famille U₃TGe₅ de type structural anti-Hf₅CuSn₃ a permis la découverte de neuf nouveaux composés pour T = V, Cr, Mn, Zr, Nb, Mo, Hf, Ta et W en plus du composé U₃TiGe₅ déjà répertorié. Leurs propriétés magnétiques et électroniques ont été évaluées, révélant des composés aux corrélations électroniques modérés avec des comportements évoluant en fonction du nombre d'électrons de valence du métal de transition d. Pour les composés avec T = Ti et V des corrélations entre ondes de densités de spin et de charge sont suspectées en dessous de la température d'ordre magnétique.Two main research axes were defined for this Ph-D work : (i) studying the effect of light elements (B, C) on the stability of U-Si compounds, and (ii) identifying and physically characterizing new phases in the U-Pt-Si system. Minor additions of carbon and boron in U-Si samples revealed that the formation of U₅Si₄ would be correlated to the presence of these light elements, questioning its existence in the U-Si system. To evaluate the boron potential as a stimulant for non-metallic light elements of the second period (C, N, O), the isothermal section of the ternary phase diagram U-Si-B has been drawn at 927 °C, disclosing solid equilibrium mainly between the U-B and U-Si binary axes and the existence of the novel compound U₂₀Si₁₆B₃, isostructural to the carbon equivalent one. These results suggest a specific behavior for a given light element on the U-Si phase relations. The isothermal section at 900 °C of the U-Pt-Si ternary system was experimentally determined, leading to the discovery of 14 new phases, among which U₃Pt₄Si₆, U₃Pt₆Si₄ and U₃Pt7Si crystallized in their own structural type. As a prerequisite for this study, the phase relations in the U-Pt binary phase diagram were re-examined for the composition range 30 at.% and 70 at.% Pt, leading to a new assessment of the phase diagram which comprises the new U₃Pt₄ compound . The temperature of the transformations has been measured by DTA. By coupling our experimental results to the literature data, a modeling of the phase diagram by the Calphad method was performed. Physical characterizations of the new U₃Pt₄ compound revealed a moderate heavy fermion behavior, with ferromagnetic ordering below Tc = 7(1) K. As a side project, a study of the U₃TGe₅ family with the anti-Hf₅CuSn₃ structural type lead to the discovery of nine new compounds for T = V, Cr, Mn, Zr, Nb, Mo, Hf, Ta and W in addition to the previously reported U₃TiGe₅. Their magnetic and electronic properties were evaluated, disclosing moderate heavy-fermion compounds, with behavior evolving with valence electron count of the transition metal. For T = Ti, V compounds, correlation between spin and charge density waves are suspected below the magnetic ordering temperature
High-density membrane of energy and life cycle optimized for systems of electrochemical storage of the energy
No full textCette thèse a consisté en la fabrication d’électrodes de charbon actif frittées par SPS destinées aux supercondensateurs à double couche électrochimique. L’influence des paramètres de frittage (température, pression, durée du palier isotherme et vitesses de chauffe et de refroidissement) sur les propriétés structurales et microstructurales des pastilles de charbon actif a été évaluée par diffraction des rayons X, microscopie électronique à balayage et en transmission, spectrométrie de photoélectrons X, mesures de surface spécifique et de volume microporeux et détermination des propriétés mécaniques. Les performances électrochimiques des pastilles de charbon actif frittées sélectionnées pour leurs bonnes propriétés de volume microporeux, de résistance mécanique à l’électrolyte et de masse volumique élevée ont été déterminées par mesures galvanostatiques et de spectrométrie d’impédance. Un gain en capacité volumique de 31% a été obtenu pour un supercondensateur composé d’électrodes de charbon actif pur de 200 μm d’épaisseur frittées à 1100°C – 50 MPa par rapport à un supercondensateur composé d’électrodes de production de Blue Solutions. Cependant sa résistance série est deux fois supérieure à celle d’un supercondensateur de production de volume identique. Des résultats prometteurs de frittage multi-pastilles, possédant des propriétés microstructurales proches, indiquent une voie possible d’industrialisation du procédé SPS pour la fabrication d’électrodes frittées de charbon actif destinées aux supercondensateurs.This thesis has consisted in the manufacturing of activated carbon electrodes sintered by SPS for Electric Double-Layer Capacitors (EDLCs). The influence of sintering parameters (temperature, pressure, isothermal dwell duration, heating and cooling rates) on structural and microstructural properties of sintered activated carbon pellets has been evaluated by X-ray diffraction, scanning and transmission electron microscopy, X-ray photoelectron spectrometry, specific area and microporous volume measurements and determination of mechanical properties. The electrochemical performances of sintered activated carbon pellets selected for their good properties in terms of microporous volume, mechanical resistance in the electrolyte and high density were determined by galvanostatic and impedance spectrometry measurements. A 31% increase of the volumetric capacity was obtained for a supercapacitor composed of 200 μm thick electrodes of pure activated carbon sintered at 1100°C – 50 MPa, relative to a supercapacitor composed of industrial electrodes from Blue Solutions company. However, its serial resistance is twice larger than that of an industrial of identical volume. Promising results of multi-pellet sintering, possessing close microstructural properties, indicate a possible way of industrialization of SPS process for the manufacturing of sintered activated carbon electrodes for supercapacitors
Relationships between morphological and microstructural characteristics of the U₃Si₂ compound and its elaboration processes
No full textCette thèse s’inscrit dans le cadre du développement de combustibles nucléaires haute densité à base U₃Si₂ pour les réacteurs expérimentaux. Ces combustibles se présentent sous forme de plaques dans lesquelles une âme combustible - faite de particules uranifères dispersées dans une matrice aluminium - est gainée dans un alliage d’aluminium. L’ensemble est colaminé, permettant la cohésion et la soudure des éléments entre eux. Pour les réacteurs de recherche les plus performants, ce combustible haute densité est en cours de qualification. Cette thèse exploratoire s’inscrit en parallèle de cet effort de recherche. Dans ce travail, des leviers d’améliorations des procédés de synthèse et de fabrication actuels ont été identifiés. Tout d’abord, une étude microstructurale approfondie du composé U₃Si₂, synthétisé en laboratoire mais également provenant de synthèses industrielles par fusion à l’arc ou par atomisation centrifuge, a été menée pour obtenir des caractéristiques de référence. Un travail visant à obtenir des particules de morphologie arrondie, mieux adaptées au procédé de fabrication de plaques par laminage, a ensuite été mené. Pour ce faire, deux voies ont été testées. Parallèlement, une étude a porté sur le développement d’une nouvelle méthode de synthèse d’U₃Si₂ en passant par une réaction en phase solide entre U et Si. Le suivi in situ par diffraction de neutrons de la réaction 3U+2Si a permis son optimisation. Ce procédé permet d’obtenir des poudres avec des caractéristiques morphologiques et microstructurales significativement différentes de celles produites par les procédés de synthèse classiquement mis en œuvre. Enfin, une dernière étude a porté sur le procédé de fabrication des plaques de combustible. Un procédé de fabrication innovant a été développé, basé sur le frittage SPS. Cette méthode présente de nombreux avantages et notamment la possibilité de contrôler aisément différentes caractéristiques de la plaque finale (dont sa charge en U). Des exemplaires de plaques à échelle réduite ont ainsi été fabriqués.This thesis is part of the development of a high-density U₃Si₂-based fuel for nuclear research reactors. These fuels have a shape of plates in which the “fuel meat” - fissile particles dispersed in an aluminium matrix - is cladded by an aluminium alloy. The plates are then hot and cold rolled to ensure cohesion between the different elements. For the most powerful research reactors, the qualification of these high-loaded fuels are still underway. This exploratory thesis runs parallel to this research effort. Within this work, levers improving the currently applied synthesis and manufacturing process currently were identified. First of all, a thorough microstructural investigation was performed on U₃Si₂, synthesized in the laboratory but also from industrial production batches by arc-melting or centrifugal atomization. It allows a full overview of the properties of U₃Si₂, from the arc-melted ingot to the powder dispersed inside the fuel plate. In parallel, a study focused on the development of a new synthesis process of U3Si2 through solid-state reactions. Among them the 3U+2Si reaction has been followed in situ by neutron diffraction, to understand and optimize it. With this process, powders with significantly different morphological and microstructural characteristics have been obtained, compared to the powders produced with the standard arc-melting+milling synthesis process. Finally, a last study focused on the fuel plate manufacturing process using Spark Plasma Sintering as an innovative manufacturing process. It presents several advantages inclunding its high flexibility to tune the final plate properties. Reduced scale plates were thus produced
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
- …
