1,721,167 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
Lower bounds and reconstruction algorithms for sums of affine powers
No full textLe cadre général de cette thèse est l'étude des polynômes comme objets de modèles de calcul. Cette approche permet de définir de manière précise la complexité d'évaluation d'un polynôme, puis de classifier des familles de polynômes en fonction de leur difficulté dans ce modèle. Dans cette thèse, nous nous intéressons en particulier au modèle AffPow des sommes de puissance de forme linéaire, i.e. les polynômes qui s'écrivent f = ∑_{i = 1}^s α_i ℓ_i^{e_i}, avec deg ℓ_i=1. Ce modèle semble assez naturel car il étend à la fois le modèle de Waring f = ∑ α_i ℓ_i^d et le modèle du décalage creux f = ∑ α_i ℓ^{e_i}, mais peu de résultats sont connus pour cette généralisation. Nous avons pu prouver des résultats structurels pour la version univarié de ce modèle, qui nous ont ensuite permis d'obtenir des bornes inférieures et des algorithmes de reconstruction, qui répondent au problème suivant : étant donné f = ∑ α_i (x-a_i)^{e_i} par la liste de ses coefficients, retrouver les α_i, a_i, e_i qui apparaissent dans la décomposition optimale de f. Nous avons aussi étudié plus en détails la version multivarié du modèle, qui avait été laissé ouverte par nos précédents algorithmes de reconstruction, et avons obtenu plusieurs résultats lorsque le nombre de termes dans une expression optimale est relativement petit devant le nombre de variables ou devant le degré du polynôme.The general framework of this thesis is the study of polynomials as objects of models of computation. This approach allows to define precisely the evaluation complexity of a polynomial, and then to classify families of polynomials depending on their complexity. In this thesis, we focus on the study of the model of sums of affine powers, that is polynomials that can be written as f = ∑_{i = 1}^s α_i ℓ_i^{e_i}, with deg ℓ_i=1. This model is quite natural, as it extends both the Waring model f = ∑ α_i ℓ_i^d, and the sparsest shift model f = ∑ α_i ℓ^{e_i}, but it is still not well known. In this work, we obtained structural results for the univariate variant of this model, which allow us to obtain lower bounds and reconstruction algorithms, that solve the following problem : given f = ∑ α_i (x-a_i)^{e_i} as a list of its coefficient, find the values of the α_i’s, e_i’s and a_i’s in the optimal decomposition of f. We also studied the multivariate case and obtained several reconstruction algorithms that work whenever the number of terms in the optimal expression is small in terms of the number of variable or the degree of the polynomial
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
Elimination of Constants from Machines over Algebraically Closed Fields
No full textLet K be an algebraically closed field of characteristic 0. We show that constants can be removed efficiently from any machine over K solving a problem which is definable without constants. This gives a new proof of the transfer theorem of Blum, Cucker, Shub & Smale for the problem P ? = NP. We have similar results in positive characteristic for non-uniform complexity classes. We also construct explicit and correct test sequences (in the sense of Heintz and Schnorr) for the class of polynomials which are easy to compute. An earlier version of this paper appeared as NeuroCOLT Technical Report 96-43. The present paper contains in particular a new bound for the size of explicit correct test sequences. 1 A part of this work was done when the author was visiting DIMACS at Rutgers University. 1 Introduction As in discrete complexity theory, the problem P ? = NP is a major open problem in the Blum-Shub-Smale model of computation over the reals [3]. It has been possible to show that P..
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
Transfer theorems via sign conditions
No full textWe show that P = PSPACE implies the collapse of the boolean polynomial hierarchy over any structure which admits ``efficient enumeration of sign conditions''. This fairly rich class of structures contains in particular R and C.Nous montrons que si P = PSPACE la hiérarchie polynomiale booléenne s'effondre pour toute structure vérifiant la propriétée d'énumération efficace des conditions de signes. Cette classe de structures assez riche contient en particulier R et C
Valiant's model and the cost of computing integers.
No full textLet tau(k) be the minimum number of arithmetic operations required to build the integer k from the constants 1 and 2. A sequence (x_k) is said to be ``easy to compute'' if tau(x_k) is bounded by a polynomial function of log(k). It is natural to conjecture that sequences such as or n! are not easy to compute. In this paper we show that a proof of this conjecture for the first sequence would imply a superpolynomial lower bound for the arithmetic circuit size of the permanent polynomial. For the second sequence, a proof would imply a superpolynomial lower bound for the permanent or P different from PSPACE
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