1,721,041 research outputs found
Honvault, Pascal Euclidean realizations of triangulated polyhedra. (English) £ ¢ ¡ Zbl 07203374
No full textInternational audienceThe author studies (not necessarily convex) triangulated polyhedra in three-dimensional Euclidean space and with genus zero. The focus of the paper is to devise an algorithm to construct an explicit realization of such a polyhedron given by its combinatorial data: • the number n + 1 and a labelling v 0 , v 1 ,. .. , v n of its vertices • degree sequence (d 0 , d 1 ,. .. , d n), where d i is the number of edges incident to the ith vertex v i • a triangulation given by a list of triangles (v i , v j , v k) The algorithm is guided by a set of necessary and sufficient conditions on the length of the edges, and the internal and external angles of the triangles in the triangulation. Reviewer: Matthias Schymura (Cottbus) MSC: 52B05 Combinatorial properties of polytopes and polyhedra (number of faces, shortest paths, etc.) 51N20 Euclidean analytic geometry 52-04 Software, source code, etc. for problems pertaining to convex and discrete geometry 51M20 Polyhedra and polytopes; regular figures, division of space
Honvault, Pascal Euclidean realizations of triangulated polyhedra. (English) £ ¢ ¡ Zbl 07203374
No full textInternational audienceThe author studies (not necessarily convex) triangulated polyhedra in three-dimensional Euclidean space and with genus zero. The focus of the paper is to devise an algorithm to construct an explicit realization of such a polyhedron given by its combinatorial data: • the number n + 1 and a labelling v 0 , v 1 ,. .. , v n of its vertices • degree sequence (d 0 , d 1 ,. .. , d n), where d i is the number of edges incident to the ith vertex v i • a triangulation given by a list of triangles (v i , v j , v k) The algorithm is guided by a set of necessary and sufficient conditions on the length of the edges, and the internal and external angles of the triangles in the triangulation. Reviewer: Matthias Schymura (Cottbus) MSC: 52B05 Combinatorial properties of polytopes and polyhedra (number of faces, shortest paths, etc.) 51N20 Euclidean analytic geometry 52-04 Software, source code, etc. for problems pertaining to convex and discrete geometry 51M20 Polyhedra and polytopes; regular figures, division of space
Gensane, Thierry; Honvault, Pascal Optimal packings of two ellipses in a square. (English) £ ¢ ¡
No full textInternational audienceFor each real number E in ]0, 1], we describe the densest packing P E of two non-overlapping congruent ellipses of aspect ratio E in a square. E belongs to ]0, 1/2], [1/2, E 0 ] where E 0 = √ (6 √ 3 − 3)/11, and [E 0 , 1]. The technique of unavoidable sets-used by Friedman for proving the optimality of square packings-allows to prove the optimality of each packing P E
Combinatorics of triangulated polyhedra
No full textInternational audienceThis paper considers compact triangulated polyhedra of genus zero. Let V n = {v 0 , v 1 ,. .. , v n+2 } be a fixed labeled collection of n + 3 vertex points on the unit sphere S 2 and denote by T n = {T (1) n , T (2) n ,. . .} the set of all triangulations of S 2 whose vertices are the points of V n. For a given triangulation T (i) n let C (i) n = (d(v 0),. .. , d(v n+2)) denote the degree sequence of the triangulation (something the author calls the combinatorics of the triangulation). Two degree sequences are called equivalent if they differ by a permutation of the vertices of V n. This paper presents an algorithm, or procedure, to list all the distinct triangulations, equivalent or not, for a given point set V n. Reviewer: Geir Agnarsson (Fairfax) MSC: 52B05 Combinatorial properties of polytopes and polyhedra (number of faces, shortest paths, etc.
Combinatorics of triangulated polyhedra
No full textInternational audienceThis paper considers compact triangulated polyhedra of genus zero. Let V n = {v 0 , v 1 ,. .. , v n+2 } be a fixed labeled collection of n + 3 vertex points on the unit sphere S 2 and denote by T n = {T (1) n , T (2) n ,. . .} the set of all triangulations of S 2 whose vertices are the points of V n. For a given triangulation T (i) n let C (i) n = (d(v 0),. .. , d(v n+2)) denote the degree sequence of the triangulation (something the author calls the combinatorics of the triangulation). Two degree sequences are called equivalent if they differ by a permutation of the vertices of V n. This paper presents an algorithm, or procedure, to list all the distinct triangulations, equivalent or not, for a given point set V n. Reviewer: Geir Agnarsson (Fairfax) MSC: 52B05 Combinatorial properties of polytopes and polyhedra (number of faces, shortest paths, etc.
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
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
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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