1,721,016 research outputs found
Regularity of the symbolic calculus in Besov algebras
No full textWe consider Besov and Lizorkin-Triebel algebras, that is, the real-valued function spaces B-p,q(s) (R-n) boolean AND L-infinity(R-n) and F-p,q(s) (R-n) n L-infinity (R-n) for all s > 0. To each function f : R -> R one can associate the composition operator T-f which takes a real-valued function g to the composite function f circle g. We give necessary conditions and sufficient conditions on f for the continuity, local Lipschitz continuity, and differentiability of any order of T-f as a map acting in Besov and Lizorkin-Triebel algebras. In some cases, such as for n = 1, such conditions turn out to be necessary and sufficient
Functional Calculus in Hoelder-Zygmund Spaces
Get PDFIn this paper we characterize those functions
of the real line to itself,
such that the nonlinear superposition operator
defined by maps the H\"older-Zygmund space
\HSn{s} to itself, is
continuous, and is times continuously differentiable. Our
characterizations cover all cases in which is real and , and
seem
to be novel in case is integer
Functional Calculus on BMO and related spaces
Get PDFLet be a Borel measurable function of the
complex plane to itself. We consider the nonlinear operator
defined by , when belongs to a certain
subspace of the space BMO(\euclid) of functions with bounded mean
oscillation on the Euclidean space. In particular, we investigate the case in
which is the
whole of , the case in which is the
space of functions with vanishing mean oscillation, and the
case in which is the closure in of the smooth functions with
compact support. We characterize those 's for which maps
to itself, those 's for which is continuous from
to itself, and those 's for which is differentiable in
Superposition operators and functions of bounded p-variation (vol 22, pg 455, 2006)
No full textWe characterize the set of all functions of to itself such that the associated superposition operator maps the class into itself. Here , , denotes the set of primitives of functions of bounded -variation, endowed with a suitable norm. It turns out that
such an operator is always bounded and sublinear.
Also, consequences for the boundedness of superposition operators defined on Besov spaces are discussed
Superposition operators and functions of bounded p-variation II
No full textWe continue the study of the superposition
operator
, on the space
of primitives of real-valued
functions of bounded
-variation on an interval .
We give first a characterization of the functions such that
takes to itself.
Then we characterize the functions for which is continuous,
uniformly continuous, and differentiable, as a mapping of
to itself, respectively. By exploiting the Peetre's Imbedding
Theorem and the Fubini property, we derive partial results on
continuity of in
Besov spaces , for a smoothness
parameter satisfying
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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