1,721,099 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
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
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
Polynômes orthogonaux : processus limites et modèles exactement résolubles
No full textThèse par articlesCette thèse porte sur l’étude des familles de polynômes orthogonaux et leurs liens avec les modèles
exactement résolubles. Elle se décline en deux parties. Dans la première, on caractérise quatre
nouvelles familles de polynômes orthogonaux à l’aide de processus limites appliqués à des familles
appartenant aux schéma d’Askey et de Bannai-Ito. Des troncations singulières des polynômes de
Wilson et d’Askey-Wilson sont considérées. Deux premières extensions bivariées de polynômes
appartenant au tableau de Bannai-Ito sont également introduites. La deuxième partie présente
quatre modèles exactement résolubles en lien avec la théorie des polynômes orthogonaux. Les
propriétés de transfert parfait d’information quantique et de partage d’intrication d’un modèle de
chaîne de spin XX dont les couplage sont liés aux polynômes de para-Racah sont examinées. Deux
modèles superintégrables contenant des opérateurs de réflexions sont proposés. Leurs solutions
sont obtenues et leurs symétries s’encodent respectivement dans l’algèbre de Bannai-Ito de rang
deux et de rang arbitraire ce qui mène à conjecturer l’apparition des polynômes de Bannai-Ito
multivariés comme coefficients de connection. Finalement, par la théorie des représentations de la
superalgèbre osp(1|2), deux identités de convolution pour des familles de polynômes du tableau de
Bannai-Ito sont offertes. Une réalisation en termes d’opérateurs de Dunkl conduit à une fonction
génératrice bilinéaire pour les polynômes de Big −1 Jacobi.This thesis is concerned with the study of families of orthogonal polynomials and their connection
to exactly solvable models. It comprises two parts. In the first one, four novel families of orthogonal
polynomials are caracterized through limit processes applied to families belonging to the Askey
and Bannai-Ito schemes. Singular truncations of the Wilson and Askey-Wilson polynomials are
considered. The first two bivariate extensions of families of the Bannai-Ito tableau are also
introduced. The second part presents four exactly solvable models connected to the theory of
orthogonal polynomials. The perfect transfer of quantum information and entanglement generation
properties of an XX spin chain model whose couplings are linked to the para-Racah polynomials are
examined. Two superintegrable models containing reflexion operators are proposed. Their solutions
are obtained and their symmetries are encoded respectively in the rank two and arbitrary rank
Bannai-Ito algebra which leads to conjecture the apparition of multivariate Bannai-Ito polynomials
as overlaps. Finally, via the representation theory of the osp(1|2) Lie superalgebra, two convolution
identities for families of orthogonal polynomials of the Bannai-Ito tableau are offered. Realizations
in terms of Dunkl operators lead to a bilinear generating function for the Big −1 Jacobi polynomials
Le problème de Coulomb-Dunkl dans le plan
Full text linkCe mémoire, composé d'un article en collaboration avec Monsieur Luc Vinet et
Vincent X. Genest, est la suite du travail effectué sur les systèmes quantiques
super-intégrables définis par des Hamiltoniens de type Dunkl. Plus particulièrement,
ce mémoire vise l'analyse du problème de Coulomb-Dunkl dans le plan qui
est une généralisation du système quantique de l'atome d'hydrogène impliquant des
opérateurs de réflexion sur les variables x et y.
Le modèle est défini par un potentiel en 1/r. Nous avons tout d'abord remarqué
que l'Hamiltonien est séparable en coordonnées polaires et que les fonctions d'onde
s'écrivent en termes de produits de polynômes de Laguerre généralisés et des harmoniques de Dunkl sur le cercle. L'algèbre générée par les opérateurs de symétrie
nous a également permis de confirmer le caractère maximalement super-intégrable
du problème de Coulomb-Dunkl. Nous avons aussi pu écrire explicitement les représentations de cette même algèbre. Nous avons finalement trouvé le spectre de
l'énergie de manière algébrique.This master's thesis, composed of an article in collaboration with Luc Vinet
and Vincent X. Genest, is the result of a work done on superintegrable quantum
systems defined by Hamiltonians of the Dunkl kind. More specifically, the aim
of this paper is to analyse the Coulomb-Dunkl problem in the plane which is a
generalization of the quantum system of hydrogen involving operators of reflection
on the variables x and y.
The model is defined by a potential in 1/r. First, we notice that the Hamiltonian
is separable in polar coordinates and the wave functions are written in terms of
products of generalized Laguerre polynomials and Dunkl harmonics on the circle.
The algebra generated by the symmetry operators has also allowed us to confirm
the maximally superintegrable character of the Coulomb-Dunkl problem. We also
write explicitly the representations of the same algebra. We finally found the energy
spectrum algebraically
Structures algébriques, systèmes superintégrables et polynômes orthogonaux
Full text linkCette thèse est divisée en cinq parties portant sur les thèmes suivants: l’interprétation physique et algébrique de familles de fonctions orthogonales multivariées et leurs applications, les systèmes quantiques superintégrables en deux et trois dimensions faisant intervenir des opérateurs de réflexion, la caractérisation de familles de polynômes orthogonaux appartenant au tableau de Bannai-Ito et l’examen des structures algébriques qui leurs sont associées, l’étude de la relation entre le recouplage de représentations irréductibles d’algèbres et de superalgèbres et les systèmes superintégrables, ainsi que l’interprétation algébrique de familles de polynômes multi-orthogonaux matriciels. Dans la première partie, on développe l’interprétation physico-algébrique des familles de polynômes orthogonaux multivariés de Krawtchouk, de Meixner et de Charlier en tant qu’éléments de matrice des représentations unitaires des groupes SO(d+1), SO(d,1) et E(d) sur les états d’oscillateurs. On détermine les amplitudes de transition entre les états de l’oscillateur singulier associés aux bases cartésienne et polysphérique en termes des polynômes multivariés de Hahn. On examine les coefficients 9j de su(1,1) par le biais du système superintégrable générique sur la 3-sphère. On caractérise les polynômes de q-Krawtchouk comme éléments de matrices des «q-rotations» de U_q(sl_2). On conçoit un réseau de spin bidimensionnel qui permet le transfert parfait d’états quantiques à l’aide des polynômes de Krawtchouk à deux variables et on construit un modèle discret de l’oscillateur quantique dans le plan à l’aide des polynômes de Meixner bivariés. Dans la seconde partie, on étudie les systèmes superintégrables de type Dunkl, qui font intervenir des opérateurs de réflexion. On examine l’oscillateur de Dunkl en deux et trois dimensions, l’oscillateur singulier de Dunkl dans le plan et le système générique sur la 2-sphère avec réflexions. On démontre la superintégrabilité de chacun de ces systèmes. On obtient leurs constantes du mouvement, on détermine leurs algèbres de symétrie et leurs représentations, on donne leurs solutions exactes et on détaille leurs liens avec les polynômes orthogonaux du tableau de Bannai-Ito. Dans la troisième partie, on caractérise deux familles de polynômes du tableau de Bannai-Ito: les polynômes de Bannai-Ito complémentaires et les polynômes de Chihara. On montre également que les polynômes de Bannai-Ito sont les coefficients de Racah de la superalgèbre osp(1,2). On détermine l’algèbre de symétrie des polynômes duaux -1 de Hahn dans le cadre du problème de Clebsch-Gordan de osp(1,2). On propose une q - généralisation des polynômes de Bannai-Ito en examinant le problème de Racah pour la superalgèbre quantique osp_q(1,2). Finalement, on montre que la q -algèbre de Bannai-Ito sert d’algèbre de covariance à osp_q(1,2). Dans la quatrième partie, on détermine le lien entre le recouplage de représentations des algèbres su(1,1) et osp(1,2) et les systèmes superintégrables du deuxième ordre avec ou sans réflexions. On étudie également les représentations des algèbres de Racah-Wilson et de Bannai-Ito. On montre aussi que l’algèbre de Racah-Wilson sert d’algèbre de covariance quadratique à l’algèbre de Lie sl(2). Dans la cinquième partie, on construit deux familles explicites de polynômes d-orthogonaux basées sur su(2). On étudie les états cohérents et comprimés de l’oscillateur fini et on caractérise une famille de polynômes multi-orthogonaux matriciels.This thesis is divided into five parts concerned with the following topics: the physical and algebraic interpretation of families of multivariate orthogonal functions and their applications, the study of superintegrable quantum systems in two and three dimensions involving reflection operators, the characterization of families of orthogonal polynomials of the Bannai-Ito scheme and the study of the algebraic structures associated to them, the investigation of the relationship between the recoupling of irreducible representations of algebras and superalgebras and superintegrable systems, as well as the algebraic interpretation of families of matrix multi-orthogonal polynomials. In the first part, we develop the physical and algebraic interpretation of the Krawtchouk, Meixner and Charlier families of multivariate orthogonal polynomials as matrix elements of unitary representations of the SO(d + 1), SO(d, 1) and E(d) groups on oscillator states. We determine the transition amplitudes between the states of the singular oscillator associated to the Cartesian and polyspherical bases in terms of the multivariate Hahn polynomials. We examine the 9j coefficients of su(1,1) through the generic superintegrable system on the 3-sphere. We characterize the q-Krawtchouk polynomials as matrix elements of "q-rotations" of U_q(sl_2). We show how to design a two-dimensional spin network that allows perfect state transfer using the two-variable Krawtchouk polynomials and we construct a discrete model of the two-dimensional quantum oscillator using the two-variable Meixner polynomials. In the second part, we study superintegrable systems of Dunkl type, which involve reflections. We examine the Dunkl oscillator in two and three dimensions, the singular Dunkl oscillator in the plane and the generic system on the 2-sphere with reflections. We show that each of these systems is superintegrable. We obtain their constants of motion, we find their symmetry algebras as well as their representations, we give their exact solutions and we exhibit their relationship with the orthogonal polynomials of the Bannai-Ito scheme. In the third part, we characterize two families of polynomials belonging to the Bannai-Ito scheme: the complementary Bannai-Ito polynomials and the Chihara polynomials. We also show that the Bannai–Ito polynomials arise as Racah coefficients for the osp(1,2) superalgebra. We determine the symmetry algebra associated with the dual − 1 Hahn polynomials in the context of the Clebsch-Gordan problem for osp(1,2). We introduce a q -generalization of the Bannai-Ito polynomials by examining the Racah problem for the quantum superalgebra osp_q(1,2). Finally, we show that the q-deformed Bannai-Ito algebra serves as a covariance algebra for osp_q(1,2). In the fourth part, we determine the relationship between the recoupling of representations of the su(1,1) and osp(1,2) algebras and second-order superintegrable systems with or without reflections. We also study representations of Racah–Wilson and Bannai-Ito algebras. Moreover, we show that the Racah Wilson algebra serves as a quadratic covariance algebra for sl(2). In the fifth part, we explicitly construct two families of d-orthogonal polynomials based on su(2). We investigate the squeezed/coherent states of the finite oscillator and we characterize a family of matrix multi-orthogonal polynomials
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