1,720,962 research outputs found
Identification of memory kernels depending on time and on an angular variable
No full textWe deal with the problem of recovering a memory kernel k(t, η), depending on time t and on an angular variable η, in a parabolic integrodifferential equation related to a toric domain. We show that the problem can be uniquely solved locally in time if the kernel k is not assumed to be necessarily periodic with respect to η. On the contrary, under a periodicity condition for k(t, ·), we show uniqueness assuming existence
Gradient estimates for solutions of parabolic differential equations degenerating at infinity
No full textFor p ∈ (1,+∞) we derive a weighted Lp estimate for the (spatial) gradient of the solution u of a degenerate parabolic differential equation. Here the underlying domain ω ⊂ Rn, n ≥ 2, is unbounded and the equation may degenerate only at infinity along some unbounded branch of ω. Our estimate is strictly related with the still-open problem of giving a concrete characterization of the interpolation space between W2,p(ω) and Lp(ω) to which the (spatial) gradient of u belongs
Parabolic integro-differential identification problems related to memory kernels with special symmetries
No full textWe are concerned with the problem of recovering the kernel k, depending on time and having a special spatial symmetry, in the parabolic integro-differential equation (1.1) and related to a domain which is union of level sets of each function k(t, ·). We single out a special class of differential operators A and two pieces of suitable additional information for which the problem of identifying k can be uniquely solved locally in time
Recovering a leading coefficient and a memory kernel in first-order integro-differential operator equations
No full textAbstractWe are concerned with the identification of the scalar functions a and k in the convolution first-order integro-differential equation u′(t)−a(t)Au(t)−k∗Bu(t)=f(t), 0⩽t⩽T, k∗v(t)=∫0tk(t−s)v(s)ds, in a Banach space X, where A and B are linear closed operators in X, A being the generator of an analytic semigroup of linear bounded operators. Taking advantage of two pieces of additional information, we can recover, under suitable assumptions and locally in time, both the unknown functions a and k. The results so obtained are applied to an n-dimensional integro-differential identification problem in a bounded domain in Rn
Fractional Powers and Interpolation Theory for Multivalued Linear Operators and Applications to Degenerate Differential Equations
No full textdepartmental bulletin pape
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
- …
