1,720,961 research outputs found
Multicomponent rogue waves
No full textWe overview theoretical and experimental advances in the field of rogue wave solutions of multi-component optical wave systems. In these systems, the transfer of energy among the coupled waves may lead to novel and complex extreme wave phenomena. We focus our attention on the case of vector field co-propagation in randomly birefringent optical fibers, and on the coupling among counter propagating waves in a periodic nonlinear waveguide
Complex rogue wave in the fiber optics
No full textCe manuscrit de thèse présente l’étude d’instabilités non-linéaires et la génération d’ondes scélérates complexes liées à la propagation de la lumière dans des fibres optiques standards des télécommunications optiques. Un rappel est tout d’abord présenté sur les phénomènes physiques linéaires et non-linéaires impliqués et qui peuvent présenter une analogie directe avec le domaine de l’hydrodynamique. Les différentes formes d’ondes scélérates liées au processus d’instabilité de modulation, aussi appelées « breathers », sont alors présentées, elles sont obtenues par la résolution de l’équation de Schrödinger non-linéaire. À partir de ces solutions exactes, divers systèmes expérimentaux sont alors conçus par simulation numérique à partir de deux méthodes d’excitation d’ondes scélérates. La première est une génération exacte à partir des solutions analytiques en effectuant une mise en forme spectrale en intensité et en phase d’un peigne de fréquence optique. La seconde méthode est basée sur des conditions initiales approchées avec des ondes continues modulées sinusoïdalement. Les mesures expérimentales réalisées avec ces deux méthodes démontrent parfaitement la génération d’ondes scélérates complexes (solutions d’ordre supérieur du système) issues de la superposition non-linéaire ou collisions de « breathers » de premier ordre. Enfin, nous avons également étudié un système non-linéaire équivalent au modèle de Manakov, qui fait intervenir la propagation de deux ondes distinctes avec des polarisations orthogonales dans une fibre optique. L’analyse de stabilité et des simulations numériques de ce système multi-variable mettent en évidence un nouveau régime d’instabilité de modulation vectorielle ainsi que de nouvelles solutions d’ondes scélérates noires et couplées en polarisation. Un nouveau système expérimental mis en place a permis de confirmer ces prédictions théoriques avec un excellent accord quantitatif.This manuscript presents the generation of complex rogue waves related to nonlinear instabilities occurring through the propagation of light in standard optical fibers. Linear and nonlinear physical phenomena involved are first listed, in particular some of them by analogy with the field of hydrodynamics. The different forms of rogue waves induced by the modulation instability process are then presented. They are also known as "breathers", and they are obtained by solving the nonlinear Schrödinger equation. From these exact solutions, various experimental systems were designed by means of numerical simulations based on two rogue-wave excitation methods. The first one is an exact generation of mathematical solutions based on the spectral shaping of an optical frequency comb. The second method uses approximate initial conditions with a simple sinusoidal modulation of continuous waves. For both cases, experimental measurements demonstrate the generation of complex rogue waves (i.e., higher-order solutions of the system) arising from the nonlinear superposition or collision of first-order breathers. Finally, we also studied a nonlinear fiber system equivalent to the Manakov model, which involves the propagation of two distinct waves with orthogonal polarizations. The stability analysis and numerical simulations of this multi-component system highlight a novel regime of vector modulation instability and the existence of coupled dark rogue-wave solutions. A new experimental system setup was conceived and theoretical predictions are confirmed with an excellent quantitative agreement
Ondes scélérates complexes dans les fibres optiques
No full textThis manuscript presents the generation of complex rogue waves related to nonlinear instabilities occurring through the propagation of light in standard optical fibers. Linear and nonlinear physical phenomena involved are first listed, in particular some of them by analogy with the field of hydrodynamics. The different forms of rogue waves induced by the modulation instability process are then presented. They are also known as "breathers", and they are obtained by solving the nonlinear Schrödinger equation. From these exact solutions, various experimental systems were designed by means of numerical simulations based on two rogue-wave excitation methods. The first one is an exact generation of mathematical solutions based on the spectral shaping of an optical frequency comb. The second method uses approximate initial conditions with a simple sinusoidal modulation of continuous waves. For both cases, experimental measurements demonstrate the generation of complex rogue waves (i.e., higher-order solutions of the system) arising from the nonlinear superposition or collision of first-order breathers. Finally, we also studied a nonlinear fiber system equivalent to the Manakov model, which involves the propagation of two distinct waves with orthogonal polarizations. The stability analysis and numerical simulations of this multi-component system highlight a novel regime of vector modulation instability and the existence of coupled dark rogue-wave solutions. A new experimental system setup was conceived and theoretical predictions are confirmed with an excellent quantitative agreement.Ce manuscrit de thèse présente l’étude d’instabilités non-linéaires et la génération d’ondes scélérates complexes liées à la propagation de la lumière dans des fibres optiques standards des télécommunications optiques. Un rappel est tout d’abord présenté sur les phénomènes physiques linéaires et non-linéaires impliqués et qui peuvent présenter une analogie directe avec le domaine de l’hydrodynamique. Les différentes formes d’ondes scélérates liées au processus d’instabilité de modulation, aussi appelées « breathers », sont alors présentées, elles sont obtenues par la résolution de l’équation de Schrödinger non-linéaire. À partir de ces solutions exactes, divers systèmes expérimentaux sont alors conçus par simulation numérique à partir de deux méthodes d’excitation d’ondes scélérates. La première est une génération exacte à partir des solutions analytiques en effectuant une mise en forme spectrale en intensité et en phase d’un peigne de fréquence optique. La seconde méthode est basée sur des conditions initiales approchées avec des ondes continues modulées sinusoïdalement. Les mesures expérimentales réalisées avec ces deux méthodes démontrent parfaitement la génération d’ondes scélérates complexes (solutions d’ordre supérieur du système) issues de la superposition non-linéaire ou collisions de « breathers » de premier ordre. Enfin, nous avons également étudié un système non-linéaire équivalent au modèle de Manakov, qui fait intervenir la propagation de deux ondes distinctes avec des polarisations orthogonales dans une fibre optique. L’analyse de stabilité et des simulations numériques de ce système multi-variable mettent en évidence un nouveau régime d’instabilité de modulation vectorielle ainsi que de nouvelles solutions d’ondes scélérates noires et couplées en polarisation. Un nouveau système expérimental mis en place a permis de confirmer ces prédictions théoriques avec un excellent accord quantitatif
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
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
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