1,721,024 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
Caméra à capteur courbe pour l'imagerie en ultraviolet des aurores polaires depuis l'espace
No full textAu cours de cette thèse, a été étudié pour la première fois l’avantage d’inclure une surface focale courbe dans un système réfractif grand champ pour l’observation d'aurore boréale dans l'ultraviolet (UV). La principale contrainte dans l’UV est le manque de matériaux ayant une haute transmissivité. Habituellement les imageurs utilisant des miroirs sont privilégiés pour les observations UV. Cependant ces systèmes sont limités à un petit champ d'observation et une faible ouverture. Ces limitations peuvent être levées par l'utilisation de surface focales courbes. Un système optique réfractif peut atteindre un large champ de vision. Associé à une surface focale courbe, il est également possible d'obtenir une sensibilité plus élevée en réduisant le nombre d'éléments optiques. Dans cette étude, une relation directe entre la sensibilité et l’amplitude de courbure a été établie. Le nombre d’éléments optiques et l’uniformité des performances sur le champ de vue ont également été analysés. Grâce à cette innovation technique, il est montré la possibilité d'observer de faibles aurores boréales depuis l’espace avec une sensibilité élevée. Puis, un procédé de courbure a été mis au point. Plusieurs capteurs CMOS ont été courbés avec succès suivant des formes convexes et concaves pour différents rayons de courbure. Une caméra UV compacte à grand champ et sensible a été conçue grâce à l’introduction d’une surface focale sphérique. Des prototypes de capteurs courbes ont été réalisés et caractérisés. L’imagerie grand champ peut être considérablement améliorée par des capteurs d’image courbes, bénéficiant ainsi à la communauté scientifiqueDuring this thesis, the advantage of including a curved focal surface in a wide field refractive system for the observation of the aurora in the ultraviolet (UV) was investigated for the first time. The main constraint in UV is the lack of materials with high transmissivity. Usually, imagers using mirrors are preferred for UV observations. However, these systems are limited to a small field of view and a low aperture. These limitations can be overcome by the use of curved focal surfaces. A refractive optical system can provide a wide field of view. In combination with a curved focal surface, it is also possible to achieve higher sensitivity by reducing the number of optical elements. In this study, a direct relationship between sensitivity and amplitude of curvature was established. The number of optical elements and the uniformity of performance over the field of view were also analyzed. Thanks to this technical innovation, it is shown the possibility of observing faint aurora from space with high sensitivity. Then, a bending process was developed. Several CMOS sensors have been successfully bent into convex and concave shapes for different radii of curvature.A compact, wide-field, and sensitive UV camera was designed with the introduction of a spherical focal surface. Prototypes of curved sensors have been produced and characterized. Wide-field imaging can be greatly enhanced by curved image sensors, thus benefiting the scientific communit
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
Co-phasing measurement for segmented mirrors
No full textLa prochaine génération de télescopes collectera la lumière avec des miroirs dont la surface équivaux à environ 82 copies sur papier A4 imprimé sur un seul coté du présent manuscrit ou 4,37.10 puissance 20 UA2 (si les unités astronomique vous parlent mieux). La fabrication et le transport d'un miroir fait d'une seule pièce de verre de cette dimension est un défi titanesque. Á l'heure de l'écriture de ces lignes, la seule solution est de recomposer ce miroir à partir de segments de miroirs plus petits, de l'ordre de 1,22m2 (soit environ 20 pages A4). En contrepartie il faudra déployer un système complexe de méthodes de mesures et d'ordinateurs, aussi appelé système de phasage, pour que le télescope produise des images de haute qualité. Ces méthodes doivent être capables de mesurer des variations plus petites que la taille du virus SARS-CoV-2 (soit environ 100nm). Un système de phasage optique est utilisé environ toutes les deux semaine. Il est difficile d'utiliser ce système plus souvent, car son utilisation perturbe les observations astronomiques. Ce doctorat traite des méthodes de mesures optiques, ou senseurs de phasage, qui ne troublent pas les observations. Ces senseurs seraient complémentaires des senseurs existants et permettraient un contrôle plus fréquent. Ce manuscrit fera d'abord l'état de l'art des méthodes optiques disponibles puis détaillera deux approches. L'état de l'art aborde les avancées des analyseurs phasage les plus populaires. Cette partie se conclut sur l'utilisation des méthodes optiques dans les télescopes segmentés présents et à venir, etc...The next generation of telescopes will have light collecting surfaces that can be covered by about 82 A4 -paper single sided copies of the present work or 4,37.10 power 20 AU2 (if you prefer astronomical units). Producing and handling such a large, monolithic glass mirror would be a considerable challenge. So far, the only foreseen solution is to slice this surface into more manageable segments of roughly 1,22m2 (or 20 A4-pages). All these segments still need to behave like a single piece of glass for the telescope to deliver high quality images. This is achieved through a complex set of measurement devices and computers working together. The measurements need to be precise enough to detect variations below the size of SARS-CoV-2 (about 100nm). The system of computers and measurement devices are called a phasing system. The phasing system are used with a certain frequency to reduce the competition with observations for astronomy. This PhD is about exploring measurement devices or phasing sensors that do not compete with astronomy and allow more frequent non-intrusive controls for segmented telescope. The phasing sensors would be complementary of the already existing ones. After a brief description of the state of the art, the details and performances of two techniques are exposed. The state of the art gives an overview of some of the most popular phasing sensors. It also elaborates on their use in current and future segmented telescopes,etc..
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
Deformable curved sensors : multidisciplinary applications
No full textDepuis plusieurs années, les détecteurs courbes ont été proposés comme étant une nouvelle approche pour améliorer les performances des caméras. En courbant les détecteurs, une des aberrations optiques, la courbure de champ, peut en effet être annulée, ce qui permet d’avoir une meilleure résolution ou d’utiliser moins de lentilles pour une même qualité d’image.Ce travail de thèse propose d’étudier cette approche, en essayant de prendre en compte les aspects mécaniques, optiques et technologiques du système final. Tout d’abord, le lien entre la scène et la courbure des capteurs est théorisé. Ainsi, la position et la forme de l’objet par rapport au système optique influent sur la valeur de courbure du capteur optimale. Une forte compacité est permise pour les systèmes optiques possédant cette courbure. Ces études théoriques permettent de créer une nouvelle méthodologie de conception optique. Celle-ci débute par la détermination des limites mécaniques du capteur, pouvant casser lorsque la courbure est élevée. Intégrant ces limites et les changements théoriques observés, une architecture optique est choisie, donnant de hautes performances en compacité, résolution et champ de vue. De nouvelles tolérances sont établies pour la courbure. Ce système est ensuite fabriqué pour être caractérisé. La forme des montre un léger écart à la sphère. La courbure n’a pas d’impact significatif sur les performances électro-optiques des détecteurs. La qualité de l’image caractérisée est perturbée par des tilts ou décentrements probables. Enfin une caractérisation utilisant un capteur plan et l’optique imageant sur une surface courbe permet d’obtenir des informations sur la courbure idéaleIn the past few years, curved sensors have been proposed to enhance optical systems. The curvature of these sensors improves off-axis aberrations, such as field curvature, which provides a better resolution and less complex optical systems.This work studies deformable and curved sensors development in a multidisciplinary approach. Firstly, scene and curved sensors are theoretically linked. The form and the position of the object change the curvature of the best image plane, leading to new relations adapted to optical systems with deformable sensors. Gains in compactness are also demonstrated. These investigations merge into a new methodology adapted to optical systems based on curved sensors that has been developed. The first step is to determine mechanical limits of the sensor such as maximum bending without breakage. Based on these limits, a new compact architecture is developed, providing high resolution and good field of view. New tolerances are determined to manufacture a system with its opto-mechanical mount. Finally, the entire imaging system is characterized. The form of the curved sensor is analyzed, showing few deviations from the ideal sphere. Electro-optical characterizations are realized and the image quality is determined according to the object distance, showing the effects of the deformable curvature. The ideal curved focal plane is also determined by combining a flat sensor to the manufactured optical syste
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