1,720,965 research outputs found
The Wentzell telegraph equation: asymptotics and continuous dependence on the boundary conditions
No full textSi prova che le soluzioni dell'equazione del telegrafo in molte classi di domini non limitati corrispondono asintoticamente a soluzioni dell'equazione del calore, con diverse condizioni al bordo, tra cui quelle di Wentzell generali. Si provano anche risultati di dipendenza continua dalle condizioni al bordo
Selfadjointness of degenerate elliptic operators on higher order Sobolev spaces
No full textLet us consider the operator A_nu:=(-1)^{n+1}\alpha (x)u^(2n) on H^n_0(0,1) with domain D(A_n):={u\in H^n_0(0,1)\cap H^{2n}_{loc}(0,1): A_n u\in H^n_0(0,1)}, where n\in\bold N, \alpha\in H^n_0(0,1), \alpha (x)>0 in (0,1).Under additional boundedness and integrability conditions on \alpha with respect to x^{2n} (1-x)^{2n}, we prove that (A_n, D(A_n)) is nonpositive and selfadjoint, thus it generates a cosine function, hence an analytic semigroup in the right half plane on H^n_0(0,1). Analyticity results are also proved in H^n(0,1). In particular, all results work well when \alpha (x)=x^j (1-x)^j, for |j-n|<1/2. Hardy type inequalities are also obtained
Nonlinear boundary conditions for nonlinear second order differential operators on C[0,1]
No full textOf concern is the operator script A sign defined formally by (script A sign u)(x) = φ((x,u′(x))u″(x) + ψ(x, u(x), u′(x)), with certain assumptions on φ, ψ. Realizations A of script A sign will be definedon C[0,1] and determined by boundary conditions. In earlier work we look ψ ≡ 0 and used mixed Wentzell-Robin boundary conditions of the form aj(Au)(j) + bju′(j) + cju(j) = 0, j = 0,1 where (aj,bj,cj) ≠ (0,0,0). In this paper we consider more general boundary conditions of the form αj(Au)(j) + βju′(j) ∈ γj(u(j)) where γj is a maximal monotone graph in ℝ2 and (αj,βj) ≠ (0,0). The conclusion (under suitable hypotheses) is that A is m-dissipative and Cauchy problem du/du = script A sign u, u(0) + f is well-posed
The heat equation with nonlinear general Wentzell boundary condition
No full textLet Omega be a bounded subset of R^n with a C^{2,epsilon}- boundary partialOmega, alpha in C^2(ar{Omega}) with alpha>0 in arOmega and Athe operator defined by Au:=
abla(alpha
abla u with thenonlinear general Wentzell boundary condition
Au+brac{partial u}{partial n}in ceta(.,u) on partialOmega, where n(x) is the unit outer normal at x,b,c are real-valued functions in C^1(partialOmega) and eta(x,.) is a maximal monotone
graph. Then, under additional
assumptions on b,c,eta we prove the existence of a contraction semigroup generated by the closure of A onsuitable L^p spaces, 1le
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
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
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe 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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