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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
Etude expérimentale de l’interdiffusion Ge-Si à partir de sources solides Germanium sur Silicium. Application à la formation de couches graduelles Si1-xGex pour les transistors pMOSFETs
Get PDFDans la course à la miniaturisation des dispositifs de la microélectronique, les alliages SiGe sont des matériaux remarquables pour poursuivre l’amélioration des performances des composants de type CMOS, le Silicium atteignant aujourd’hui ses limites physiques. En effet, une méthode originale pour appliquer une contrainte de compression uniaxiale au canal de conduction Silicium, afin d’augmenter la mobilité des trous des transistors pMOS, consiste à remplacer le Silicium dans les régions Source et Drain par des couches SiGe pseudomorphiques. L’utilisation de sources solides sacrificielles de Germanium peut être une solution pour la fabrication de telles structures. Dans ce travail, nous avons ainsi étudié l’interdiffusion Ge-Si, induite par recuit thermique à haute température, à partir d’hétérostructures Ge/Si dont la couche de Germanium est déposée par CVD. Le développement de la méthodologie SIMS MCs2+, que nous réalisons dans cette thèse, assure la caractérisation chimique de couches graduelles Si1-xGex dans la gamme complète de concentrations (0 ≤ x ≤ 1). Nous montrons que l’interdiffusion Ge-Si est fortement dépendante de la composition en Germanium mais également des défauts structuraux formés aux interfaces Ge-Si. Nous avons alors développé un modèle qui permet de reproduire fidèlement les profils expérimentaux. L’effet du dopage Bore tend à réduire légèrement l’interdiffusivité. Finalement, nous montrons que l’utilisation de couches de Germanium polycristallin est prometteuse pour la fabrication de couches graduelles Si1-xGex. En effet, elle permet de réduire la densité de défauts structuraux initialement présents dans les films monocristallins.------------------------------------------------------------------------As Silicon limits are reached, Ge-based materials are expected to be progressively introduced in the fabrication of advanced microelectronic devices. SiGe layers are already used as Source/Drain regions to induce uniaxial compressive stress in the Si channel, which results in the enhancement of hole mobility in PMOS. In this work, we study an alternative method for the fabrication of shallow SiGe regions, in which a pure Ge layer is deposited on a Si substrate and the Ge in-diffusion is induced by a subsequent anneal. The optimisation of such a technology requires the accurate measurement of the Ge concentration in the full range of Ge composition and the understanding of the Si-Ge interdiffusion occurring during the formation of the SiGe layers. Pure Ge(:B) layers were grown on Si substrates by CVD. We present a novel SIMS MCs2+ methodology for the accurate measurement of the Ge diffused profiles. Boltzmann-Matano analysis was used to extract the interdiffusion coefficients. Si-Ge interdiffusion is found to be strongly dependent on the Ge concentration. Also, an effect of dislocations near the Ge/Si original interface is suggested by our results. A physical model including the various observed effects is proposed, that gives a very good agreement with experiments. We also show that the effect of the in-situ B doping of the pure Ge layer is to reduce the interdiffusion. Finally, we suggest that the use of polycristalline Ge films is a promising route for the formation of gradual Si1-xGex layer
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
Development and technological realization of Gallium Nitride (GaN) HEMTs transistors with a "Normally-Off" functionality
No full textL'augmentation de la consommation électrique et l'évolution des besoins en électronique de puissance nécessitent de nouveaux composants intégrés de puissance ayant une forte densité de courant et assurant une meilleure efficacité de conversion d'énergie. La technologie des transistors à haute mobilité électronique en nitrure de gallium (HEMT GaN) est très prometteuse et répond à ces exigences énergétiques. Cependant, ces transistors présentent l'inconvénient d'être normally-on : le canal sous la grille est peuplé d'électrons même à une tension de grille nulle. Pour des raisons de sûreté de fonctionnement, la fonctionnalité normally-off s'avère être un réel besoin. Ce travail se consacre au développement technologique d'un transistor HEMT normally-off avec une grille à barrière P-GaN. La nouvelle structure proposée consiste à introduire une couche GaN dopé p (P-GaN) sous le contact de grille. Les résultats de de simulation sous Sentaurus TCAD ont montré que des tensions de seuil élevées peuvent être obtenues en réduisant l'épaisseur de l'AlGaN sous le P-GaN. Ce travail s'est focalisé sur la mise en place des briques technologiques nécessaires pour la réalisation de cette nouvelle structure, en particulier l'ouverture de grille et la reprise d'épitaxie localisée. Le développement de la gravure de grille en mode RIE à base du Cl2 a permis une maîtrise d'ordre nanométrique des profondeurs de l'AlGaN gravé. La rugosité obtenue après gravure, bien que plus élevée que celle initiale des couches, reste acceptable pour un mode de gravure RIE. La reprise d'épitaxie localisée du P-GaN a été testée avec les deux techniques de croissance que sont la MOCVD et la MBE. Cette dernière a permis l'obtention de meilleurs résultats en termes d'uniformité de couche. Une étude sur les contacts ohmiques et Schottky a aussi été menée dans le but de déterminer les empilements métalliques adaptés à la structure proposée. Une optimisation des étapes élémentaires du procédé technologique, comme les paramètres d'insolation, la passivation et l'isolation des composants, a été effectuée en vue de réaliser le dispositif proposé.Thanks to their high breakdown voltage and ultrahigh power density operation, AlGaN/GaN HEMTs stand out as promising candidates for next-generation of high-speed switching devices. While most of the demonstrated AlGaN/GaN HEMTs are inherently normally-on with a negative gate threshold voltage, normally-off mode is strongly demanded to fulfill the requirements of power electronics applications; normally-off devices are inherently secure and suitable for energy converters requiring specifically high system reliability. In this work, a new normally-off AlGaN/GaN HEMT structure is proposed. The regrowth of a p-doped GaN (P-GaN) layer on the AlGaN/GaN heterostructure after the gate recess allows the achievement of the enhancement mode. A shift in the threshold voltage to positive values has been proved through simulation results. This work has focused on the development of the critical technological steps of the fabrication of the new normally-off HEMT structure. Particular attention has been paid to the opening of the gate and of the P-GaN localized regrowth. A precise AlGaN etching was achieved by adjusting Cl2-RIE etching parameters. The roughness surface after etching was three times higher than the non-etched one but remains acceptable for a RIE mode. The P-GaN regrowth was tested using two methods: MOCVD and MBE. The last one provided better results in terms of layer uniformity. A study of ohmic and Schottky contacts was also carried out in order to determine the most adequate metal stacks for the proposed structure. An optimization of the elementary steps of the technological process such as the parameters of insolation, passivation and isolation of the components was carried out in order to realize the proposed device
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
Etude expérimentale de l'interdiffusion Ge-Si à partir de sources solides Germanium sur Silicium. Application à la formation de couches graduelles Si1-xGex pour les transistors pMOSFETs
No full textAs Silicon limits are reached, Ge-based materials are expected to be progressively introduced in the fabrication of advanced microelectronic devices. SiGe layers are already used as Source/Drain regions to induce uniaxial compressive stress in the Si channel, which results in the enhancement of hole mobility in PMOS. In this work, we study an alternative method for the fabrication of shallow SiGe regions, in which a pure Ge layer is deposited on a Si substrate and the Ge in-diffusion is induced by a subsequent anneal. The optimisation of such a technology requires the accurate measurement of the Ge concentration in the full range of Ge composition and the understanding of the Si-Ge interdiffusion occurring during the formation of the SiGe layers. Pure Ge(:B) layers were grown on Si substrates by CVD. We present a novel SIMS MCs2+ methodology for the accurate measurement of the Ge diffused profiles. Boltzmann-Matano analysis was used to extract the interdiffusion coefficients. Si-Ge interdiffusion is found to be strongly dependent on the Ge concentration. Also, an effect of dislocations near the Ge/Si original interface is suggested by our results. A physical model including the various observed effects is proposed, that gives a very good agreement with experiments. We also show that the effect of the in-situ B doping of the pure Ge layer is to reduce the interdiffusion. Finally, we suggest that the use of polycristalline Ge films is a promising route for the formation of gradual Si1-xGex layers.Dans la course à la miniaturisation des dispositifs de la microélectronique, les alliages SiGe sont des matériaux remarquables pour poursuivre l'amélioration des performances des composants de type CMOS, le Silicium atteignant aujourd'hui ses limites physiques. En effet, une méthode originale pour appliquer une contrainte de compression uniaxiale au canal de conduction Silicium, afin d'augmenter la mobilité des trous des transistors pMOS, consiste à remplacer le Silicium dans les régions Source et Drain par des couches SiGe pseudomorphiques. L'utilisation de sources solides sacrificielles de Germanium peut être une solution pour la fabrication de telles structures. Dans ce travail, nous avons ainsi étudié l'interdiffusion Ge-Si, induite par recuit thermique à haute température, à partir d'hétérostructures Ge/Si dont la couche de Germanium est déposée par CVD. Le développement de la méthodologie SIMS MCs2+, que nous réalisons dans cette thèse, assure la caractérisation chimique de couches graduelles Si1-xGex dans la gamme complète de concentrations (0 d x d 1). Nous montrons que l'interdiffusion Ge-Si est fortement dépendante de la composition en Germanium mais également des défauts structuraux formés aux interfaces Ge-Si. Nous avons alors développé un modèle qui permet de reproduire fidèlement les profils expérimentaux. L'effet du dopage Bore tend à réduire légèrement l'interdiffusivité. Finalement, nous montrons que l'utilisation de couches de Germanium polycristallin est prometteuse pour la fabrication de couches graduelles Si1-xGex. En effet, elle permet de réduire la densité de défauts structuraux initialement présents dans les films monocristallins
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