1,720,989 research outputs found
Singular limit of dissipative hyperbolic systems with memory
No full textWe consider a class of weakly damped semilinear hyperbolic equations with memory, expressed by a convolution integral. We study the passage to the singular limit when the memory kernel collapses into the Dirac mass at zero, and we establish a convergence result for a proper family of exponential attractor
Singular limit of differential systems with memory
No full textWe consider differential systems with memory terms,
expressed by convolution integrals, which account for the past
history of one or more variables. The aim of this work is to analyze
the passage to the singular limit when the memory kernel collapses
into a Dirac mass. In particular, we focus on the reactiondiffusion
equation with memory, and we discuss the convergence
of solutions on finite time-intervals. When enough dissipativity
is present, we also establish convergence results of the global and
the exponential attractors. Nonetheless, the techniques here devised
are quite general, and suitable to be applied to a large variety
of models
Strongly damped wave equations in R^3 with critical nonlinearities
No full textWe prove the existence of a global attractor for a strongly damped
semilinear wave equation in the whole space, with a quite general nonlinearity at
critical growth and a nonlinear weak damping term, generalizing some previously
known results
Continuous families of exponential attractors for singularly perturbed equations with memory
No full textWe establish, for a family of semigroups S_(ε:) H_ε→H_ε depending on aperturbation parameter ε∈[0,1], where the perturbation is allowed tobecome singular at ε=0, a general theorem on the existenceof exponential attractors E_ε satisfying a suitableHölder continuity property with respect tothe symmetric Hausdorff distanceat every ε∈[0,1]. The result is appliedto the abstract evolution equations with memoryx_t (t)+∫_0^∞▒█(k_ε (s) B_0 (x(t-s) )ds+B_1 (x(t) )=0, ε∈(0,1] )where k_ε (s)=1/ε k(s/ε)is the rescaling of a convex summable kernel k with unit mass.Such a family can be viewed as a memory perturbationof the equation x_t (t)+B_0 (x(t) )+B_1 (x(t) )=0formally obtained in the singular limit ε→0
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
On the strongly damped wave equation
No full textWe prove the existence of the universal attractor for
the strongly damped semilinear
wave equation, in presence of
a quite general nonlinearity of critical growth.
When the nonlinearity is subcritical, we prove
the existence of an exponential attractor of optimal
regularity, having a basin of attraction coinciding with the
whole phase-space.
As a byproduct, the universal attractor is
regular and of finite fractal dimension.
Moreover, we carry out a detailed analysis of the asymptotic behavior
of the solutions in dependence of the damping coefficient
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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