1,720,974 research outputs found
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
Compact photon sources in multi-PetaWatt facilities : a kinetic numerical investigation
No full textLAUREA MAGISTRALELe prime installazioni di laser multi-PetaWatt stanno venendo ultimate. L’aspettativa
è di poter irraggiare target con intensità superiori a 10 22 Wcm^−2 , riuscendo cosı̀ a ren-
dere accessibili per la prima volta i regimi ultra-intensi dell’interazione laser-plasma.
Quest’ultima può portare ad una vasta varietà di fenomeni fisici, tra cui l’emissione
di radiazione di sincrotrone.
L’obiettivo di questa tesi è quello di raggiungere una migliore comprensione della
fisica e delle proprietà dell’emissione di radiazione nell’interazione laser-plasma ultra-
intensa, fornendo cosı̀ strumenti utili alla progettazione di esperimenti mai stati
possibili fino ad ora. A questo scopo è stato effettuato un vasto studio di simulazioni
numeriche multidimensionali con il codice Particle-In-Cell Smilei.
Un impulso laser, le cui specifiche sono state basate sulle reali condizioni nominali
del laser Apollon (presto ultimato nel sito di Parigi-Saclay), è stato irraggiato su
di un target multistrato composto da uno strato a bassa densità e uno a densità
solida. Dando particolare attenzione alla modellazione numerica, è stata raggiunta
una configurazione risultante dal compromesso tra l’aderenza alla realtà sperimentale
e l’economia delle risorse computazionali.
Progettando opportunamente i set-up delle simulazioni, è stato possibile osservare
una copiosa produzione di fotoni ad alte energie, con efficienza complessiva di con-
versione energetica da laser a radiazione dell’ordine di 10^−1 .The first PetaWatt laser facilities are becoming operational, and are expected to de-
liver on-target intensities exceeding 10 22 Wcm^−2 , making new regimes of laser-matter
interaction experimentally available for the first time. Ultra-intense laser-plasma
interaction can lead to a broad spectrum of physical effects among which synchrotron-
like photon emission. This work aims to reach a better understanding of the physics
and properties of the radiation emission in ultra-intense laser-plasma interaction.
The goal of this thesis is to gain insights on the system behaviour, helping designing
experiments never possible before.
An extensive, kinetic, multidimensional Particle-In-Cell simulation campaign has
been employed. A laser pulse with specifics realistic of the forthcoming Apollon facil-
ity in Paris-Saclay, is used to impact on a multilayered target made of a low-density
layer, and a solid density substrate. Special attention is given to the modelling, where
a balance between physically realistic and computationally affordable configuration
has been used.
Carefully designing the simulation set-up we managed to observe copious high en-
ergy photon production, with energy conversion efficiency from laser to synchrotron
radiation of the order of 10^−1
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
Modification of laser beam coherence in inertial confinement fusion plasmas
No full textLa fusion inertielle par laser requiert l'utilisation de faisceaux lissés aux propriétés de cohérence contrôlables. Ces faisceaux contiennent une multitude de surintensités : les speckles. Lors de leur propagation dans un plasma, les propriétés de cohérence de ces faisceaux peuvent être modifiées, on parle de lissage par plasma. A haute intensité, des instabilités se développant au sein même des speckles induisent la perte de cohérence. A plus basse intensité, des mécanismes collectifs mettant en jeu plusieurs speckles sont responsable du lissage induit. Cette thèse constitue une étude théorique, numérique et expérimentale de ces mécanismes. La prise en compte du caractère incohérent des faisceaux laser requiert l'utilisation d'outils statistiques pour décrire l'interaction laser-plasma. Un modèle est développé pour la diffusion multiple de l'onde laser sur les fluctuations de densité induites par l'ensemble des speckles. Cette diffusion est responsable d'un élargissement du spectre spatial et temporel de l'onde laser. Elle sert de germe à l'instabilité de diffusion Brillouin stimulée vers l'avant, laquelle induit à la fois un élargissement spectral et un décalage vers le rouge de la lumière transmise. Un modèle analytique est développé pour cette instabilité. Un nouveau critère est établi qui détermine une puissance (sous la puissance critique pour la filamentation) au delà de laquelle cette instabilité croît fortement. Des simulations numériques réalisées avec le code PARAX est une expérience réalisée sur le laser ALISE confirment la présence importante de ces mécanismes de diffusion vers l'avant à basse intensité et leur rôle dans le lissage induit par plasma.Inertial confinement fusion by laser requires smoothed laser beam with well-controlled coherenceproperties. Such beams are made of many randomly distributed intensity maxima: the so-called speckles.As the laser beam propagates through a plasma its temporal and spatial coherence can be reduced.This phenomenon is called plasma induced smoothing. For high laser intensities, instabilities developpingindependently inside the speckles are responsible for the coherence loss. At lower intensities, onlycollective effects, involving many speckles, can lead to induced smoothing. This thesis is a theoretical,numerical and experimental study of these mecanisms.Accounting for the partially incoherent behavior of the laser beams requires the use of statisticaldescription of the laser-plasma interaction. A model is developped for the multiple scattering of thelaser light on the self-induced density perturbations that is responsible for a spreading of the temporaland spatial spectra of the transmitted light. It also serves as a strong seed for the instability of forwardstimulated Brillouin scattering that induces both, angular spreading and red-shift of the transmittedlight. A statistical model is developped for this instability. A criterium is obtained that gives a laserpower (below the critical power for lamentation) above which the instability growth is important.Numerical simulations with the interaction code PARAX and an experiment performed on the ALISElaser facility conrm the importance of these forward scattering mecanisms in the modication of thelaser coherence properties
Modifications des propriétés de cohérence des faisceaux laser dans les plasmas de fusion par confinement inertiel
Full text linkInertial confinement fusion by laser requires smoothed laser beam with well-controlled coherenceproperties. Such beams are made of many randomly distributed intensity maxima: the so-called speckles.As the laser beam propagates through a plasma its temporal and spatial coherence can be reduced.This phenomenon is called plasma induced smoothing. For high laser intensities, instabilities developpingindependently inside the speckles are responsible for the coherence loss. At lower intensities, onlycollective effects, involving many speckles, can lead to induced smoothing. This thesis is a theoretical,numerical and experimental study of these mecanisms.Accounting for the partially incoherent behavior of the laser beams requires the use of statisticaldescription of the laser-plasma interaction. A model is developped for the multiple scattering of thelaser light on the self-induced density perturbations that is responsible for a spreading of the temporaland spatial spectra of the transmitted light. It also serves as a strong seed for the instability of forwardstimulated Brillouin scattering that induces both, angular spreading and red-shift of the transmittedlight. A statistical model is developped for this instability. A criterium is obtained that gives a laserpower (below the critical power for lamentation) above which the instability growth is important.Numerical simulations with the interaction code PARAX and an experiment performed on the ALISElaser facility conrm the importance of these forward scattering mecanisms in the modication of thelaser coherence properties.La fusion inertielle par laser requiert l'utilisation de faisceaux lissés aux propriétés de cohérence contrôlables. Ces faisceaux contiennent une multitude de surintensités : les speckles. Lors de leur propagation dans un plasma, les propriétés de cohérence de ces faisceaux peuvent être modifiées, on parle de lissage par plasma. A haute intensité, des instabilités se développant au sein même des speckles induisent la perte de cohérence. A plus basse intensité, des mécanismes collectifs mettant en jeu plusieurs speckles sont responsable du lissage induit. Cette thèse constitue une étude théorique, numérique et expérimentale de ces mécanismes. La prise en compte du caractère incohérent des faisceaux laser requiert l'utilisation d'outils statistiques pour décrire l'interaction laser-plasma. Un modèle est développé pour la diffusion multiple de l'onde laser sur les fluctuations de densité induites par l'ensemble des speckles. Cette diffusion est responsable d'un élargissement du spectre spatial et temporel de l'onde laser. Elle sert de germe à l'instabilité de diffusion Brillouin stimulée vers l'avant, laquelle induit à la fois un élargissement spectral et un décalage vers le rouge de la lumière transmise. Un modèle analytique est développé pour cette instabilité. Un nouveau critère est établi qui détermine une puissance (sous la puissance critique pour la filamentation) au delà de laquelle cette instabilité croît fortement. Des simulations numériques réalisées avec le code PARAX est une expérience réalisée sur le laser ALISE confirment la présence importante de ces mécanismes de diffusion vers l'avant à basse intensité et leur rôle dans le lissage induit par plasma
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
- …
