1,720,966 research outputs found
Etude théorique des amplificateurs sensibles à la phase des fibres pourles applications
No full textFiber optic parametric amplifiers (FOPA) are promising for tomorrow's communication systems. In particular, fiber phase sensitive amplifiers offer attractive functionalities like low noise and high gain which makes it a potential candidate for applications in microwave photonic links. This thesis provides a theoretical investigation of such fiber phase sensitive amplifiers aimed towards applications.The first part of the thesis is dedicated towards development of an analytical model for propagation of seven CW waves through a FOPA. The system was solved exactly when nonlinear effects of the fiber are not strong. The developed model unravelled the important role of the higher order waves in determining the amplification performance of the FOPA. Strategies were formulated to enhance the amplification and the possibility of a phase sensitive frequency conversion with just two pump waves was also predicted.In the second part of this thesis, the possibility of introducing a fiber phase sensitive amplifier in a microwave photonic link for analog signal distribution was investigated. A numerical model was utilized to simulate how the RF nonlinearities in a microwave photonic link are amplified by the FOPA. The performance of the link when the FOPA attains a gain saturation was also studied. The study revealed the possibility of RF nonlinearity mitigation using the fiber nonlinearity. Implementation of such techniques could lead to realization of long-range and highly linear microwave photonic links for antenna remoting applications.Les amplificateurs paramétriques à fibre optique (FOPA) sont prometteurs pour les systèmes de communication de demain. En particulier, les amplificateurs sensibles à la phase des fibres offrent des fonctionnalités intéressantes comme un faible bruit et un gain élevé, ce qui en fait des candidats potentiels pour des applications dans les liaisons photoniques micro-ondes. Cette thèse propose une étude théorique de tels amplificateurs sensibles à la phase destinés à certaines applications.La première partie de la thèse est consacrée au développement d'un modèle analytique pour la propagation de sept ondes continues à travers un FOPA. Le système est résolu lorsque les effets non linéaires de la fibre ne sont pas trop forts. Le modèle développé révèle le rôle important des ondes d'ordre supérieur dans la détermination des performances d'amplification du FOPA. Des stratégies sont formulées pour améliorer l'amplification. La possibilité d'une conversion de fréquence sensible à la phase avec seulement deux ondes de pompe est également prédite.Dans la deuxième partie de cette thèse, la possibilité d'introduire un amplificateur sensible à la phase dans une liaison photonique hyperfréquence pour la distribution de signaux analogiques est étudiée. Un modèle numérique est utilisé pour simuler comment les non-linéarités RF dans une liaison photonique hyperfréquence sont amplifiées par le FOPA. Les performances de la liaison lorsque le FOPA atteint la saturation du gain sont également étudiées. L'étude révèle la possibilité d'une atténuation de la non-linéarité RF en utilisant la non-linéarité de la fibre. La mise en œuvre de telles techniques pourrait conduire à la réalisation de liaisons photoniques hyperfréquences à longue portée et hautement linéaires pour les applications de déport d'antenne
Etude théorique des amplificateurs sensibles à la phase des fibres pourles applications
No full textFiber optic parametric amplifiers (FOPA) are promising for tomorrow's communication systems. In particular, fiber phase sensitive amplifiers offer attractive functionalities like low noise and high gain which makes it a potential candidate for applications in microwave photonic links. This thesis provides a theoretical investigation of such fiber phase sensitive amplifiers aimed towards applications.The first part of the thesis is dedicated towards development of an analytical model for propagation of seven CW waves through a FOPA. The system was solved exactly when nonlinear effects of the fiber are not strong. The developed model unravelled the important role of the higher order waves in determining the amplification performance of the FOPA. Strategies were formulated to enhance the amplification and the possibility of a phase sensitive frequency conversion with just two pump waves was also predicted.In the second part of this thesis, the possibility of introducing a fiber phase sensitive amplifier in a microwave photonic link for analog signal distribution was investigated. A numerical model was utilized to simulate how the RF nonlinearities in a microwave photonic link are amplified by the FOPA. The performance of the link when the FOPA attains a gain saturation was also studied. The study revealed the possibility of RF nonlinearity mitigation using the fiber nonlinearity. Implementation of such techniques could lead to realization of long-range and highly linear microwave photonic links for antenna remoting applications.Les amplificateurs paramétriques à fibre optique (FOPA) sont prometteurs pour les systèmes de communication de demain. En particulier, les amplificateurs sensibles à la phase des fibres offrent des fonctionnalités intéressantes comme un faible bruit et un gain élevé, ce qui en fait des candidats potentiels pour des applications dans les liaisons photoniques micro-ondes. Cette thèse propose une étude théorique de tels amplificateurs sensibles à la phase destinés à certaines applications.La première partie de la thèse est consacrée au développement d'un modèle analytique pour la propagation de sept ondes continues à travers un FOPA. Le système est résolu lorsque les effets non linéaires de la fibre ne sont pas trop forts. Le modèle développé révèle le rôle important des ondes d'ordre supérieur dans la détermination des performances d'amplification du FOPA. Des stratégies sont formulées pour améliorer l'amplification. La possibilité d'une conversion de fréquence sensible à la phase avec seulement deux ondes de pompe est également prédite.Dans la deuxième partie de cette thèse, la possibilité d'introduire un amplificateur sensible à la phase dans une liaison photonique hyperfréquence pour la distribution de signaux analogiques est étudiée. Un modèle numérique est utilisé pour simuler comment les non-linéarités RF dans une liaison photonique hyperfréquence sont amplifiées par le FOPA. Les performances de la liaison lorsque le FOPA atteint la saturation du gain sont également étudiées. L'étude révèle la possibilité d'une atténuation de la non-linéarité RF en utilisant la non-linéarité de la fibre. La mise en œuvre de telles techniques pourrait conduire à la réalisation de liaisons photoniques hyperfréquences à longue portée et hautement linéaires pour les applications de déport d'antenne
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
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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