1,720,961 research outputs found
Étude de cercles tangents à des coniques
No full textL'objet de la thèse est de déterminer le nombre maximal de cercles (réels) tangents à trois coniques réelles données. Dans la première partie, nous démontrons d'abord que, au voisinage d'une configuration de trois coniques dégénérées, le nombre maximal de cercles tangents est seulement 136, contre 184 solutions complexes. Pour expliquer cette différence de 48, nous observons qu'un cercle est une conique passant par deux points complexes conjugués particuliers. Nous étudions comment varie le nombre de coniques tangentes à trois coniques et passant par deux points lorsque les deux points sont perturbés pour passer de réels à complexes conjugués. La deuxième partie contient l'étude complète du cas particulier des cercles tangents à une hyperbole et une droite fixées et passant par un point fixé. La technique utilisée précédemment permet de construire seulement 8 cercles solutions. Nous démontrons que le nombre maximal de cercles est en fait 10 et donnons une construction
Distance-preserving moves always keep a point fixed
No full textA fixed point is a point that does not move when subjected to a given transformation. Theorems guaranteeing the existence of such points have a wide application not only in mathematics, but also in economics or in Google\u27s search engine. Such a new theorem has recently been discovered: every isometry has a fixed point when viewed in an extended space
Correspondance Kervaire - Milnor d'août 1958 à juin 1961
No full textCorrespondance échangée entre Michel Kervaire et John Milnor d'août 1958 à juin 1961, telle que nous l'avons trouve dans le bureau de Kervaire à la Section de Mathématiques de l'Université de Genève en février 2009. Il s'agit de 13 lettres concernant deux des articles écrits en commun par Kervaire et Milnor: 1) J. Milnor and M. Kervaire: Bernoulli numbers, homotopy groups and a theorem of Rohlin" Proc. Int. Congress of Math. Edinburgh (1958). 2) M. Kervaire and J. Milnor: Groups of homotopy spheres I" Ann. of Math. 77(1963) p. 504-537
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
L'expérience des cafés mathématiques
No full textNous présentons une expérience de vulgarisation mathématique nommée Café des Sciences ayant cours dans les écoles du bassin genevois depuis quelques années. Notre présentation se base sur l'analyse d'une des activités présentées, à savoir l'élucidation d'une tablette babylonienne
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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