1,720,993 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
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
Numerical simulation of magnetic reconnection : kinetic mechanisms underlying the fluid description of the ions
No full textLa capacité à libérer l’énergie stockée dans le champ magnétique et à briser le théorème du gel font de la reconnexion magnétique un des phénomènes les plus importants de la physique des plasmas. Lorsqu’elle se produit dans un environnement non-collisionel comme la magnétosphère terrestre, une modélisation cinétique est à priori nécessaire. Cependant la plupart de notre compréhension du phénomène se base sur un interprétation fluide, plus intuitive. Dans quelle mesure ces deux interprétations d’un même phénomène sont-elles reliées ? C’est la problématique à laquelle cette thèse s’intéresse, dans le cas de la reconnexion antiparallèle et pour la population ionique du plasma. La première partie de ce travail s’intéresse à l’accélération fluide et cinétique des protons au sein de la région de reconnexion. Il est montré comment le mouvement individuel des particules joue un rôle du point de vue fluide via la force de pression, jusqu’alors négligée dans les modèles. Ces résultats ont également mené dans une seconde partie à des prédictions et vérifications observationnelles basées sur les données des satellites Cluster. Dans un troisième temps, nous montrons le rôle important joué par le flux d’énergie thermique dans le transfert d’énergie au cours du processus de reconnexion, dans le cas symétrique et asymétrique. Enfin la dernière partie de ce manuscrit propose une solution au problème fondamental consistant décrire une couche de courant tangentielle asymétrique dans un état d’équilibre cinétiqueBecause of its ability to transfer the energy stored in magnetic field together with the breaking of the flux freezing constraint, magnetic reconnection is considered as one of the most important phenomena in plasma physics. When it happens in a collision less environment such as the terrestrial magnetosphere, it should a priori be modelled with in the framework of kinetic physics. The evidence of kinetic features has incidentally for a long time, been shown by researchers with the help of both numerical simulations and satellite observations. However, most of our understanding of the process comes from the more intuitive fluid interpretation with simple closure hypothesis which do not include kinetic effects. To what extent are these two separate descriptions of the same phenomenon related? What is the role of kinetic effects in the averaged/fluid dynamics of reconnection? This thesis addresses these questions for the proton population in the particular case of antiparallel merging with the help of 2D Hybrid simulations. We show that one can not assume, as is usually done, that the acceleration of the proton flow is only due to the La place force. Our results show, for symmetric and asymmetric connection, the importance of the pressure force, opposed to the electric one on the separatrices, in the decoupling region. In the symmetric case, we emphasize the kinetic origin of this force by analyzing the proton distribution functions and explain their structure by studying the underlying particle dynamics. Protons, as individual particles, are shown to bounce in the electric potential well created by the Hall effect. The spatial divergence of this well results in a mixing in phase space responsible for the observed structure of the pressure tensor. A detailed energy budget analysis confirms the role of the pressure force for the acceleration ; but, contrary to what is sometimes assumed, it also reveals that the major part of the incoming Poynting flux is transferred to the thermal energy flux rather than to the convective kinetic energy flux, although the latter is generally supposed dominant. In the symmetric case, we propose the pressure tensor to be an additional proxy of the ion decoupling region in satellite data and verify this suggestion by studying a reconnection event encountered by the Cluster spacecrafts. Finally, the last part of this thesis is devoted to the study of the kinetic structure of asymmetric tangential current sheets where connection can develop. This theoretical part consists in finding a steady state solution to the Vlasov-Maxwell system for the protons in such a configuration. We present the theory and its first confrontation to numerical tests
Étude statistique des contraintes globales gouvernant la reconnexion magnétique à la magnétopause terrestre
No full textLa reconnexion magnétique est le mécanisme principal à l'œuvre dans le couplage entre la magnétosphère terrestre et le vent solaire magnétisé. L'efficacité du processus dépend grandement d'où il se déroule sur la magnétopause. La localisation de la ligne X en fonction des propriétés du milieu interplanétaire reste, à ce jour, l'une des questions clés de la physique magnétosphérique en raison de son caractère multi-échelles. L'une des principale difficulté tient dans notre quasi complète méconnaissance de l'environnement plasma et magnétique à grande échelle sur la magnétopause, et comment celles-ci évoluent avec les conditions interplanétaires. Ces propriétés sont aujourd'hui accessibles uniquement au travers de modèles, analytiques ou numériques. Cette thèse apporte de nouvelles contraintes observationnelle au problème de la localisation de la reconnexion en proposant la reconstruction et l'analyse des variations spatiales et grande échelle des variations spatiales du plasma et champ magnétique dans la magnétogaine et sur la magnétopause Un nouvelle méthode est développée afin de collecter et traiter deux décennies de données in-situ des missions Cluster, Double Star, THEMIS et MMS. Nous proposons en premier lieu de reconstruire la structure globale et 3D du champ magnétique drapé dans la magnétogaine, démontrant que l'hypothèse d'un drapé magnétostatique sans courant ne correspond pas aux observations pour environ 30% des orientations du champ interplanétaire. Nous examinons ensuite la variation, dans la magnétogaine, de l'amplitude du champ magnétique et de la densité du plasma, ainsi que leur dépendance en l'orientation du champ interplanétaire, en soulignant leur couplage non linéaire avec la reconnexion à la magnétopause. Enfin, la reconstruction des variations spatiales, sur la magnétopause, du cisaillement magnétique, de la densité de courant et du taux de reconnexion, en fonction de l'orientation du champ interplanétaire et du dipôle terrestre, nous a permis de mieux comprendre les rôles respectifs des contraintes globales et locales dans la localisation possible de la X-line.Magnetic reconnection is the primarymechanism through which the Earth's magnetosphere couples to the surrounding magnetized solar wind. The efficiency of this coupling largely depends on where the reconnection occurs on themagnetopause. Determining the location of so-called reconnection X-lines, as a function of the upstream interplanetary conditions, remains a long-standing challenge in magnetospheric physics due to its multiscale character. Progress is hampered by the fact that the plasma and field properties that constrain where reconnection can develop on the magnetopause are themselves poorly understood, and so far only accessed through global magnetohydrodynamics simulations. This thesis brings new observational constraints to this problem through the reconstruction of 3D global spatial variations of the plasma and magnetic field on the dayside magnetosheath and magnetopause. A newmethodology was developed to collect and process two decades of in-situ measurements from the Cluster, Double Star, THEMIS, andMMS missions. We first reconstructed the global 3Dmagnetic draping of the interplanetary magnetic field (IMF) in the magnetosheath, whose structure is demonstrated to be controlled by the plasma flow in this region in a way that invalidates widely used vacuum magnetostatic draping assumptions in about 30% of the IMF orientations. We then examine the variation of magnetic field amplitude and plasma density in the magnetosheath and their dependence on the IMF orientation, and highlight their nonlinear coupling with magnetopause reconnection. Finally reconstructions of the spatial distributions magnetic shear, current density and reconnection rate on the dayside magnetopause,for different dipole tilts and IMF orientations, allowed us to better understand the interplay between local and global constraints on the location of reconnection X-lines
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
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