1,721,015 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
Slow light by parametric amplification in birefringent optical fibers
No full textCette thèse a pour thème le processus physique de ralentissement de la lumière induit par amplification paramétrique vectorielle dans les fibres optiques biréfringentes. Notre première étude porte sur la lumière lente induite par amplification paramétrique vectorielle dans les fibres fortement biréfringentes. Contrairement au processus scalaire, nous montrons théoriquement que le processus vectoriel offre la possibilité de créer des bandes de gain paramétrique étroites et éloignées de la pompe, permettant de générer des retards optiques très importants, un ordre de grandeur supérieurs à ceux obtenus en amplification paramétrique scalaire. Des résultats analytiques et issus de simulations numériques dans le cas de dispersion normale ainsi que dans le cas de dispersion anormale sont présentés. Ensuite, nous discutons des principales limitations au retard optique (élargissement de l’impulsion pompe notamment) et nous étudions l’influence positive de l’effet Raman sur le retard optique. Notre seconde étude est consacrée à la lumière lente induite par amplification paramétrique dans les fibres faiblement biréfringentes. Nous traitons l’ensemble des configurations possibles d’instabilité de polarisation selon l’état initial de polarisation de l’impulsion pompe et du régime de dispersion. Nous démontrons clairement que la configuration correspondant à une impulsion pompe polarisée suivant l’axe lent de la fibre et une impulsion signal polarisée suivant l’axe rapide en régime de dispersion normale donne des retards optiques les plus importantThis thesis aims to the physical process of slow light induced by vector parametric amplification in highly and weakly birefringent optical fibers. Our first study concerns slow light induced by parametric amplification in highly birefringent fibers. Unlike the scalar process, we theoretically demonstrate that large optical delays can be in principle generated in birefringent fibers, one order of magnitude higher than for the scalar case. Both analytical and numerical results in the case of anomalous dispersion are presented. We further discuss the main limitations for slow light optical delays (signal pulse broadening, pump pulse depletion). The influence of the Raman gain is also studied both analytically and numerically. The second study focuses on slow light induced by parametric amplification in weakly birefringent fibers. We consider all possible configurations of polarization modulation instability, depending on the polarization axis of the pump pulse and on the dispersion regime, and we derive the slow-light optical delays. We clearly demonstrate that the configuration corresponding to a pump pulse polarized in the slow axis of the fiber and a signal pulse polarized on the fast axis, in the normal dispersion regime, gives the largest optical delays
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
Nonlinear Optics in Integrated Liquid-filled Optical Fibers
No full textInternational audienceOptofluidic systems based on liquid-filled optical fiber represent an alternative way for nonlinear optics in optical fibers, in particular due to the large nonlinearity of some liquids and specific molecular dynamics of anisotropic molecules. We will present recent results, especially toward supercontinuum generation in an integrated nonlinear optofluidic fiber arrangement.<br&g
Experimental technique for distributed spectral imaging along photonic components in nominal operation
No full textCette thèse de doctorat présente une méthode novatrice de métrologie optique pour réaliser des mesures spectrales distribuées le long de composants photoniques en fonctionnement nominal de manière non destructive et non invasive et avec une résolution spatiale et spectrale élevée. La technique repose sur la détection de la diffusion Rayleigh de la lumière se propageant dans le composant photonique. Nous avons testé cette méthode avec succès sur des fibres optiques effilées de diamètres submicrométriques et de longueurs centimétriques en régime linéaire et non linéaire. En régime linéaire, nous avons pu caractériser l'évolution spatiale de la lumière guidée le long d'une fibre effilée, les pertes et la localisation des défauts, ainsi que les changements de guidage des modes et des battements intermodaux. En régime non linéaire, nous avons observé le processus d'une cascade Raman le long de la nanofibre et la génération d'un supercontinuum optique le long d'une fibre optique incluant une fibre effilée. Nous avons ainsi mesuré le gain Raman pour les différents ordres Stokes et anti-Stokes générés par le processus de cascade Raman. Par ailleurs, nous avons étudié la contribution de chacune des zones constituant la fibre effilée sur la génération du supercontinuum, en comparant les résultats expérimentaux avec les prédictions numériques basées sur l'équation de Schrödinger non linéaire. Cette méthode innovante peut être étendue à l'étude de différents types de composants photoniques avec des géométries complexes et dans des conditions nominales de fonctionnement.This doctoral thesis presents an innovative optical metrology method for performing distributed spectral measurements along photonics components under nominal operating conditions, with high spatial and spectral resolution and without any destructive or invasive effects. The technique relies on detecting Rayleigh scattering of light propagating within the photonics component. We successfully tested this method on submicrometer-diameter tapered optical fibers with centimeter lengths in both linear and nonlinear regimes. In the linear regime, we characterized the spatial evolution of guided light along a tapered fiber, as well as losses, defect localization, mode guidance changes and mode beatings. In the nonlinear regime, we observed the process of Raman cascading along the nanofiber and the generation of an optical supercontinuum throughout the entire fiber. We measured the Raman gain for different Stokes and anti-Stokes orders generated by the Raman cascade process. Additionally, we studied the contribution of each zone constituting the tapered fiber to supercontinuum generation by comparing experimental results with numerical predictions based on the nonlinear Schrödinger equation. This innovative method can be extended to the study of various types of photonics components with complex geometry and under nominal operating conditions
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
- …
