1,720,992 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
A non-commutative algorithm for multiplying 5 × 5 matrices using 99 multiplications
No full textWe present a non-commutative algorithm for multiplying 5 × 5 matrices using 99 multiplications. This algorithm is a minor modification of Makarov’s algorithm which exhibit the previous best known bound with 100 multiplications
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
Méthodes seminumériques en algèbre différentielle~; applications à l'étude des propriétés structurelles de systèmes différentiels algébriques en automatique
No full textThe work presented here is based on differential algebra and on the methods of symbolic computation to solve problems of nonlinear control theory which do not lend themselves to a direct numerical resolution. The problem of local algebraic observability consists in deciding if the model state variables can be deduced from perfectly known inputs and outputs. We present a probabilistic algorithm of arithmetic complexity polynomial in the size of the input which allows to test local algebraic observability by determining the non observable variables. The use of modular arithmetic enables to obtain a polynomial bit complexity for this test. This complexity depends linearly on the probability of success which can be arbitrarily fixed. An implementation of this algorithm is available and makes it possible to deal with problems unreachable until now. Taking as a starting point these methods mixing symbolic computation and numerical computation, we propose a generalization of the concept of differential flatness to certain models described by nonlinear partial differential equations. An ordinary differential system is differentialy flat if its solutions can locally be parameterized by arbitrary functions. To study certain nonlinear systems of partial differential equations, one brings back to a system of ordinary differential equations by discretization ; our approach consists in seeking flat discretizations such that the associated parametrization converge when the step of discretization tends towards zero. This method is illustrated by the study of the motion planning problem for three nonlinear models : the semilinear heat equation, the Burger equation with diffusion and a nonlinear model of flexible rod.Les travaux présentés dans ce mémoire se basent sur les apports de l'algèbre différentielle et les méthodes du calcul symbolique pour résoudre des problèmes d'automatique non linéaire qui ne se prêtent pas à une résolution numérique directe.Le problème de l'observabilité algébrique locale consiste à décider si les variables d'état intervenant dans un modèle peuvent être déterminées en fonction des entrées et des sorties supposées parfaitement connues.Nous présentons un algorithme probabiliste de complexité arithmétique polynomiale en la taille de l'entrée permettant de tester l'observabilité algébrique locale en déterminant les variables non observables. L'utilisation du calcul modulaire permet d'obtenir pour ce test une complexité binaire elle aussi polynomiale. Cette complexité dépend linéairement de la probabilité de succès qui peut être arbitrairement fixée. Une implantation de cet algorithme permet de traiter des problèmes inaccessibles jusqu'à présent.À partir de ces méthodes mêlant calcul symbolique et calcul numérique, nous proposons une généralisation de la notion de platitude différentielle à certains modèles non linéaires décrits par des équations aux dérivées partielles. Un système différentiel ordinaire est différentiellement plat si ses solutions peuvent être localement paramétrées bijectivement par des fonctions arbitraires.Pour étudier certains systèmes d'équations aux dérivées partielles non linéaires, on se ramène à un système d'équations différentielles ordinaires par discrétisation ; notre approche consiste à chercher des discrétisations plates telles que les paramétrages associés convergent lorsque le pas de discrétisation tend vers zéro. Cette méthode est illustrée par l'étude du problème de planification de trajectoire réalisée pour trois modèles non linéaires de dimension infinie : l'équation de la chaleur semilinéaire, l'équation de Burger avec diffusion et un modèle non linéaire de tige flexible
A non-commutative algorithm for multiplying 5 × 5 matrices using 99 multiplications
No full textWe present a non-commutative algorithm for multiplying 5 × 5 matrices using 99 multiplications. This algorithm is a minor modification of Makarov’s algorithm which exhibit the previous best known bound with 100 multiplications
Laderman matrix multiplication algorithm can be constructed using Strassen algorithm and related tensor's isotropies
No full textIn 1969, V. Strassen improves the classical~2x2 matrix multiplication algorithm. The current upper bound for 3x3 matrix multiplication was reached by J.B. Laderman in 1976. This note presents a geometric relationship between Strassen and Laderman algorithms. By doing so, we retrieve a geometric formulation of results very similar to those presented by O. Sykora in 1977
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
A non-commutative algorithm for multiplying (7 × 7) matrices using 250 multiplications
No full textWe present a non-commutative algorithm for multiplying (7 × 7) matrices using 250 multiplications and a non-commutative algorithm for multiplying (9 × 9) matrices using 520 multiplications. These algorithms are obtained using the same divide-and-conquer technique
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
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