1,721,167 research outputs found
On a one-phase Stefan problem
No full textIn this paper we introduce a new way to approach the one-phase Stefan problem
partial_t(u +chi) = Delta u + fchi, u(0) = g, chiin H(u(t)),
with both g and f non-negative and where H : R
ightarrow P([0; 1]) is the usual
maximal monotone Heavyside graph. Our idea is to introduce a discrete
in time approximation scheme involving, step by step, suitable one-phase
Hele-Shaw problems. With natural regularity hypotheses on data we are
able to solve them, by means of results similar to a joint work of the second author with P. Tilli.
Using the qualitative behavior of these solutions we can then construct a discrete in
time approximate solution for the Stefan problem endowed with suitable
a-priory estimates. So we can ̄finally pass to the limit, getting existence of
solutions, uniqueness, monotonicity and regularity results
The evolution of photovoltaic thecnologies for energy production: State-of-the-art context and recent developments
No full textELECTRONIC-STRUCTURE OF PRBA2CU3O7 - A LOCAL-SPIN-DENSITY APPROXIMATION WITH ON-SITE COULOMB INTERACTION
No full textElectronic structure calculations based on the local-spin-density approximation (LSDA) fail to reproduce the antiferromagnetic ground state of PrBa2Cu3O7 (PBCO). We have performed linear muffin-tin orbital-atomic sphere approximation calculations, based on the local-spin-density approximation with on-site Coulomb correlation applied to Cu(1) and Cu(2) 3d states. We have found that inclusion of the on-site Coulomb interaction modifies qualitatively the electronic structure of PBCO with respect to the LSDA results, and gives Cu spin moments in good agreement with the experimental values. The Cu(2) upper Hubbard band lies about 1 eV above the Fermi energy, indicating a Cu-II oxidation state. On the other hand, the Cu(1) upper Hubbard band is located across the Fermi level, which implies an intermediate oxidation state for the Cu(1) ion, between Cu-I and Cu-II. The metallic character of the CuO chains is preserved, in agreement with optical reflectivity [K. Takenaka et al., Phys. Rev. B 46, 5833 (1992)] and positron annihilation experiments [L. Hoffmann et al., Phys. Rev. Lett. 71, 4047 (1993)]. These results support the view of an extrinsic origin of the insulating character of PrBa2Cu3O7
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
Adaptive estimation of spectral parameters for myoelectric signalsby means of AR modelling
No full textVariations 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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