1,721,043 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
Identification of resistivity parameter by meta-model methods
No full textLa tomographie électrique est une méthode permettant d'identifier la résistivité d'un milieu grâce à la résolution d'un problème inverse. Le milieu sondé est modélisé par la méthode des éléments finis puis la paramétrisation se fait en sous-domaines de résistivité constante dont on cherche à identifier les valeurs. Numériquement cela revient à minimiser l'écart entre un jeu de données mesurées et un jeu de données calculées en faisant varier les paramètres du modèle. Dans le cas de la résistivité, ces jeux de données sont des mesures de potentiels. Ce problème est résolu en géophysique par la méthode de Newton grâce aux hyptothèses permettant de calculer analytiquement les directions de descente de l'algorithme de minimisation. Dans le cas de milieux finis, l'impossibilité d'évaluer analytiquement les directions de descente de l'algorithme de minimisation entraîne une augmentation substantielle du temps de calcul. Dans le but d'effectuer un suivi des structures en milieu maritime, cette méthode est adaptée au domaine du génie civil. Il est ainsi proposé de substituer au modèle éléments finis direct de propagation du courant électrique, un modèle approché de faible rang. La méthode d'identification adaptée ainsi proposée est une méthode à gradient basée sur des évaluations du modèle approché. Ses performances sont évaluées à travers des tests numériques par comparaison avec une méthode d'identification classique. Les avantages de l'utilisation de ces modèles approximés sont mis en avant, notamment la possibilité d'obtenir un gradient explicite non disponible sur le modèle direct. Enfin, le suivi du port est détaillé via une application au quai de Saint-Nazaire mettant en avant les corrélations entre la température et la résistivité. Puis une méthode de suivi de résistivité pour une structure in situ est proposée dans une dernière partie.Electrical tomography is a method for identifying the resistivity of a medium by solving an inverse problem. The probed medium is modelled by the finite element method and then the parameterisation is done in sub-domains of constant resistivity whose values are to be identified. Numerically, this amounts to minimising the difference between a set of measured data and a set of computed data by varying the model parameters. In the case of resistivity, these data sets are potential measurements. This problem is solved in geophysics by Newton's method thanks to the hypotheses allowing to compute analytically the directions of descent of the minimisation algorithm. In the case of finite medium, the impossibility of analytically evaluating the directions of descent of the minimisation algorithm leads to a substantial increase in computation time. In order to monitor structures in a maritime environment, this method is adapted to the civil engineering domain. It is thus proposed to substitute the direct finite element model of electric current propagation with an approximate model of low rank. The proposed adapted identification method is a gradient method based on evaluations of the approximated model. Its performance is evaluated through numerical tests by comparison with a classical identification method. The advantages of using these approximate models are highlighted, in particular the possibility of obtaining an explicit gradient not available on the direct model. Finally, the monitoring of the harbor is detailed, with an application to the Saint-Nazaire wharf highlighting the correlations between temperature and resistivity. Then a resistivity monitoring method for an in situ structure is proposed in the last part
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
Sur une nouvelle approche en calcul dynamique transitoire, incluant les basses et les moyennes fréquences
No full textThe computational method proposed is a frequency approach in which the low-frequency part is obtained through a classical technique, while the medium-frequency part is handled using the Variational Theory of Complex Rays (VTCR) initially introduced for forced vibrations.La stratégie de calcul proposée est une approche fréquentielle dans laquelle la partie basses fréquences est traitée grâce aux éléments finis classiques, alors que les moyennes fréquences sont calculées grâce à la Théorie Variationnelle des Rayons Complexes (TVRC) initialement introduite pour des problèmes de vibration forcée
Model reduction based on domain decomposition and tensor approximation methods for multiscale stochastic models with localized uncertainties
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