1,720,988 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
Extension non-linéaire des méthodes FFT accélérées par gradient conjugué
No full textInternational audienceLes méthodes de résolution par Transformée de Fourier Rapide permettent de résoudre des problèmes mécaniques (ou thermiques, ou autre...) sur des cellules hétérogènes, discrétisées sous forme de grilles régulières 2D ou 3D, soumises à des conditions aux limites périodiques. Ces méthodes, hautement parallélisables, constituent une alternative performante à la méthode des éléments finis. Proposées dans les années 90, elles sont en plein essor tant du point de vue de leur application que de leur développement. Parmi les développements récents, on note la proposition d'accélérer la résolution itérative de problèmes linéaires par l'utilisation de solveurs itératifs type gradient conjugué. On propose ici d'étendre cette proposition à la résolution de problèmes non-linéaires
FFT-based simulations of heterogeneous conducting materials with combined non-uniform Neumann, Periodic and Dirichlet boundary conditions
No full textInternational audienceBecause of their simplicity, efficiency and ability for parallelism, FFT-based methodsare very attractive in the context of numerical periodic homogenization, especiallywhen compared to standard FE codes used in the same context. The purpose of thepaper is to go beyond the use of periodic Boundary Conditions (BC), but keeping theadvantages of FFT-based implementations. The present paper focuses on conductivityproblems, considered as a first step towards mechanical problems. The proposedimplementation is highly flexible, allowing to apply non-uniform loadings, to choosebetween periodic, Neumann and Dirichlet BC for each face of the unit-cell (of couple offaces for periodic BC), and to choose between different types of Finite Differencesschemes (two types are considered here). The implementation relies on the use ofDiscrete Trigonometric Transforms and their relation with the Discrete FourierTransform on 4 times extended signals. The implementation has been preciselyvalidated for various types of loading (uniform or non-uniform, full or combined,Dirichlet, Neumann and periodic BC) from a direct comparison with the same FEsimulations
Simulations FFT de matériaux hétérogènes avec conditions aux limites de type Dirichlet, Neumann et Périodiques, combinées et non uniformes
No full textNational audienceLes méthodes FFT, très performantes pour la simulation numérique du comportement de matériaux hétérogènes, sont utilisées sous l’hypothèse de conditions aux limites périodiques. On se propose ici d’étendre ces méthodes à des chargements variés combinant sur chacune des faces des conditions de type Neumann, Dirichlet ou périodiques, uniformes ou non. On s’intéresse dans un premier temps aux problèmes de conduction, première étape vers les problèmes mécaniques. De plus amples détails seront disponibles prochainement dans un article récemment accepté [1]
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
Un solveur FFT précis et robuste pour la diffusion transitoire dans les matériaux hétérogènes
Full text linkInternational audienceThe purpose of the present letter is to propose an efficient, accurate and robust FFT-based solver for transient diffusion in heterogeneous materials with ‘realistic’ BC, taking advantage of two recent advances in terms of boundary conditions and finite difference schemes to overcome their actual limitations (periodic BC and spurious oscillations). It is an essential step towards couplings between mechanics and other physics (such as the diffusion of species) through FFT-based solvers. Discrete Trigonometric Transform are used to implement non-periodic boundary conditions, and a finite difference (FD) scheme recently proposed by Finel is advantageously compared to the common hexahedral FD scheme. ‘Accurate’ refers to two properties: accurate in term of locality with a small size of Finite Difference pencil to capture fluctuations around material heterogeneities, and accurate in term of precision with the absence of spurious spatial oscillations (at least in the reported cases with well-separated inclusions). The ‘robustness’ is here associated to the stability of the solver, especially associated to the implicit time integration method. The description of the method focuses on thermal diffusion but applies to any other similar diffusion process (with the same type of parabolic equation). As a by-product, the FD scheme proposed by Finel is introduced in a more general (for mixing finite different schemes) and simple way (no introduction of FCC subgrids), extending its usage to any type of grid parity (not only even grids).Cette note propose un solveur FFT efficace, précis et robuste pour la diffusion transitoire dans des matériaux hétérogènes avec des conditions aux limites (CL) dites « réalistes » . Cette approche exploite deux avancées récentes : le traitement des conditions aux limites non périodiques et l’utilisation d’un nouveau schéma de différences finies limitant les oscillations parasites. Il s’agit d’une étape essentielle vers le couplage entre la mécanique et d’autres phénomènes physiques (comme la diffusion d’espèces) à l’aide de solveurs FFT. Les Transformées Trigonométriques Discrètes sont utilisées pour implémenter des conditions aux limites non périodiques, tandis qu’un schéma de différences finies (DF) récemment proposé par Finel est comparé avantageusement au schéma DF classique hexaédrique.Le terme « précis » se réfère à deux aspects : (1) la précision locale, grâce à un schéma de DF de petite taille permettant de capturer les fluctuations autour des hétérogénéités du matériau, et (2) la précision en termes de fidélité, avec l’absence d’oscillations spatiales parasites (au moins dans les cas étudiés avec des inclusions bien séparées). La « robustesse » fait référence à la stabilité du solveur, notamment grâce une méthode d’intégration temporelle implicite. Bien que la description se concentre sur la diffusion thermique, la méthode s’applique à tout processus de diffusion similaire (régie par une équation parabolique du même type).En complément, le schéma DF proposé par Finel est présenté de manière plus générale (pour mélanger différents schémas de différences finies) et simplifiée (sans introduction de sous-grilles FCC), élargissant également son usage à tout type de parité de grille (et pas seulement aux grilles paires)
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
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