1,720,998 research outputs found
Fixed points for some non-obviously contractive operators
No full textThe use of K-normed spaces gives us the possibility of proving that a fixed point theorem due to B. D. Lou [Proc. Amer. Math. Soc. 127 (1999), no. 8, 2259–2264; MR1646199 (99m:47065)] is equivalent to the Banach contraction principle. This confirms the conspiracy among fixed point theorems. Moreover, the theorem of Luo is improved and extended to different contexts. A counterexample about the fixed points of the sum of a contraction and an integral operator is given. The usefulness of the K-norm is tested on a Volterra integral equation as wel
Oltre la pittura
No full textIl saggio, incluso nel catalogo della mostra tenutasi nel 2013 al Museo di Santa Giulia di Brescia, presenta una delle sezioni della mostra stessa, dedicata ad alcune esperienze artistiche che si sviluppano in Italia negli anni '50 e '60, e che costituiscono un superamento di esperienze coeve in direzione di una sorta di annullamento, di grado zero della pittura, che assume molteplici connotazioni: le spirali spazialiste e cosmiche di Roberto Crippa; i rivoluzionari "buchi" e "tagli" di Lucio Fontana, concettualmente concentratissimi; la provocante affermazione di libertà del giovane Piero Manzoni; le tele estroflesse di Enrico Castellani (un movimento della superficie dell'opera reso effettivo mediante l'inserimento di chiodi sotto il supporto); il moltiplicarsi dei piani sovrapposti riscontrabile nelle "intersuperfici" di Paolo Scheggi; l'"anti-pittura" di Arturo Vermi, che elimina il colore e adotta un'ascetica reiterazione del segmento, sempre uguale e sempre diverso su campo bianco; le prospettive pop degli smalti di Franco Angeli e dei décollages di Mimmo Rotella (dove il manifesto strappato soppianta il pigmento). Persino Bruno Munari, in apparenza più "tradizionale", arriva a negare, con i suoi "Negativi-positivi", i presupposti stessi della sintassi pittorica, disattivandone uno degli elementi essenziali, cioè la distinzione tra figura e sfondo
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
Nonlinear spectral theory
No full textThis book provides a comprehensive and self-contained treatment of the theory, methods, and applications of nonlinear spectral theory.The first chapter briefly recalls the definition and properties of the spectrum and several subspectra for bounded linear operators. Then some numerical characteristics for nonlinear operators are introduced which are useful for describing those classes of operators for which there exists a spectral theory. Since spectral values are closely related to solvability results for operator equations, various conditions for the local or global invertibility of a nonlinear operator are collected in the third chapter. The following two chapters are concerned with spectra for certain classes of continuous, Lipschitz continuous, or differentiable operators. These spectra, however, simply adapt the corresponding definitions from the linear theory which somehow restricts their applicability. Other spectra which are defined in a completely different way, but seem to have useful applications, are defined and studied in the following four chapters. The remaining three chapters are more application-oriented and deal with nonlinear eigenvalue problems, numerical ranges, and selected applications to nonlinear problems
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
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