1,721,076 research outputs found
Composants micro-optiques popur systèmes miniatures d'imagerie à base de technologie MEMS
No full textLa miniaturisation des systèmes d'imagerie présente aujourd'hui un fort potentiel dans plusieurs domaines, dont le développement de nouveaux dispositifs biomédicaux. Les exigences associées concernant l'imagerie demandent un effort substantiel dans le développement de composants optiques de haute qualité. Un meilleur contrôle de la propagation de la lumière ou de ses caractéristiques dans de tels systèmes est également important. Les composants doivent donc, par exemple, contenir les aberrations optiques pouvant affecter la résolution, la mise en œuvre de composants optiques dont le profil de phase continu est bien contrôlé est une voie intéressante. Ces composants devraient, de plus, être réalisés à partir de matériaux robustes en vue de leur assemblage au sein de dispositifs miniatures. Ce manuscrit de thèse de doctorat porte donc sur la conception et la fabrication parallèle de tels micro-composants optiques réfractifs réalisés en verre. Dans ce but, deux technologies ont été étudiées et optimisées, la lithographie à niveaux de gris et un procédé de soufflage de verre. En exemple, des microaxicons en verre ont été fabriqués et la génération de faisceaux de Bessel démontrée. Ce type de faisceau est caractérisé par une longue distance de propagation non-diffractive le long de l'axe optique, suivie d'une forme de faisceaux creux, qui les rend très utiles dans de nombreux domaines. Ces travaux de thèse ont été soutenus par le projet SMYLE (Small Systems for a Better Life) et le conseil Régional de Franche-Comté.Miniaturization of imaging systems shows nowadays a strong potential for many applications, in particular, e. g., for novel biomedical devices. Related imaging specifications require a substantial effort onto the development of high quality microoptical components. better control of light propagation and features in such system sis also of particular interest. Components should then e.g. contain optical aberrations in order to reach high resolutions. In purpose of searching higher diffraction efficiencies or resolutions, optical components with well-controlled continuous phase profiles are sought. In addition, they also should be made of robust materials to handle their further assembly into miniaturized devices. Consequently, the manuscript focuses on the design and the parallel fabrication of such microoptical components made of glass. To that end, two technologies have been studied and optimized, namely gray-scale lithography and glass-blowing processes. As an example, glass-based microaxicons have been fabricated and Bessel beams generation has been demonstrated. This type of beam exhibits a long non-diffractive propagation distance along the optical axis followed by a dark hollow shape which makes them useful in many different applications. This work has been supported by the SMYLE (Smart Systems for a Better Life) European project and the Ranche-Comté Regional Council
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
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
Microwave atomic clock with improved microcell technology and pulsed interrogation regime
No full textCe travail de thèse a visé à proposer des solutions scientifiques et technologiques innovantes pour la démonstration d’une horloge atomique CPT à cellule micro-fabriquée à la stabilité de fréquence long-terme améliorée.Un premier axe d’étude a concerné la mise en place de protocoles d’interrogation impulsionnels pour réduire les déplacements de fréquence induits lors de l’interaction entre les atomes et le champ d’interrogation lumineux. La mise en œuvre d’une séquence avancée nommée Symmetric Auto-Balanced Ramsey (SABR) a notamment permis une réduction de la sensibilité de la fréquence d’horloge aux variations du champ laser par plus de deux ordres de grandeur, bénéficiant à la stabilité de fréquence pour des temps d’intégration supérieurs à 100 s.Un second axe de recherche a porté sur la preuve de concept et le développement d’une nouvelle technologie de microcellule à vapeur de césium reposant sur l’exploitation de vannes ouvrantes et fermantes micro-fabriquées actionnables par laser, combinées à l’utilisation de substrats de verre à faible perméation, permettant un choix étendu et un contrôle renforcé de son atmosphère interne. Une réduction du taux de perméation par un facteur supérieur à 1000 a été démontrée dans des cellules avec verres aluminosilicatés et revêtements d’alumine. Des études pour le développement de cellules exploitant de nouveaux mélanges de gaz tampon et pouvant ainsi opérer à haute température (>90°C) ont été entreprises.Enfin, les résultats complémentaires de ces deux axes de recherche ont été valorisés par la démonstration d’une horloge à microcellule Cs-Ne à verres aluminosilicatés exploitant la séquence d’interrogation SABR. La combinaison de ces approches, renforcées par la mise en œuvre de contrôles actifs de paramètres expérimentaux clés, a mené à une stabilité relative de fréquence de 7x10-11 à 1 s et 1.4x10-12 à 105 s. Ces performances de stabilité journalières sont compétitives avec celles des meilleures horloges microondes à micro-cellule.This PhD thesis work aims to propose innovative scientific and technological solutions for the demonstration a microcell-based CPT atomic clock with improved long-term frequency stability.The first research axis has concerned the implementation of pulsed interrogation sequences used to reduce light-shifts induced during the interaction between the atoms and the optical interrogation field. The use of an advanced sequence named Symmetric Auto-Balanced Ramsey (SABR) has in particular allowed a reduction of the clock frequency sensitivity to variations of the optical field by more than two orders of magnitude, benefiting to the frequency stability for integration times higher than 100 s.A second research axis has led to the proof-of-concept and the development of a new alkali vapor microfabricated cell tehnology, based on hermetic laser-actuated break- and make-seals, combined with the use of low permeation glass substrates, for enhanced choice and reinforced control of the cell inner atmosphere. A reduction of the permeation rate by a factor higher than 1000 was demonstrated in cells filled with helium using aluminosilicate glass coupled with Al2O3 coatings. Studies for the development of cells using new buffer gas mixtures and working at high temperature (>90°C) have been undertaken.Complementary results of these two research axis led to the demonstration of a CPT atomic clock using a Cs-Ne microcell with aluminosilicate glass and operating with the SABR interrogation sequence. The combination of these approaches, reinforced by additional active stabilization loops of some key experimental parameters, has led to a fractional frequency stability of 7x10-11 at 1 s and 1.4x10-12 at 105 s. These stabilities at one day are competitive with those of best microcell-based microwave clocks
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
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
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