1,720,981 research outputs found
A geometric approach to constrained mechanical systems, symmetries and inverse problems
No full textWe introduce a geometrical framework for the description of constrained mechanical systems, and we analyse different kinds of symmetries and their relationships. We propose a new definition for non-holonomic Lagrangian mechanical systems, and we give a geometrical characterization for the Helmholtz conditions related to the inverse problem
The Cauchy problem for metric-affine f(R) gravity in presence of perfect-fluid matter
No full textThe Cauchy problem for metric-affine f(R)-gravity in the manner of Palatini and with torsion, in the presence of perfect fluid matter acting as a source, is discussed following the well-known Bruhat prescriptions for general relativity. The problem results in being well formulated and well posed when the perfect-fluid form of the stress-energy tensor is preserved under conformal transformations and the set of viable f(R)-models is not empty. The key role of conservation laws in the Jordan and in the Einstein frame is also discussed. © 2009 IOP Publishing Ltd
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
- …
