1,721,627 research outputs found
Singular elliptic problems in general domains
No full textIn this paper, we prove the existence of solutions to nonlinear elliptic equations, which present first-order terms with natural growth with respect to the gradient and lower order terms singular in the variable that represents the solution. The problems are considered on a domain omega, which may have infinite Lebesgue measure
Symmetrization results for parabolic equations with a singular lower order term
No full textWe provide symmetrization results as mass concentration comparisons for solutions to singular parabolic equations in the cylinder Omega x (0,T),T > 0. Here, Omega subset of R-N(N >= 2) is a bounded open set, featuring a lower order term that is singular in the solution variables
Existence of weak solutions to a nonlinear reaction-diffusion system with singular sources
No full textWe discuss the existence of a class of weak solutions to a nonlinear
parabolic system of reaction-diffusion type endowed with singular production
terms by reaction. The singularity is due to a potential occurrence of quenching
localized to the domain boundary. The kind of quenching we have in mind is
due to a twofold contribution: (i) the choice of boundary conditions, modeling
in our case the contact with an in nite reservoir filled with ready-to-react
chemicals and (ii) the use of a particular nonlinear, non-Lipschitz structure
of the reaction kinetics. Our working techniques use fine energy estimates for
approximating non-singular problems and uniform control on the set where
singularities are localizing
Upscaling the interplay between diffusion and polynomial drifts through a composite thin strip with periodic microstructure
No full textWe study the upscaling of a system of many interacting particles through a heterogenous thin elongated obstacle as modeled via a two-dimensional diffusion problem with a one-directional nonlinear convective drift. Assuming that the obstacle can be described well by a thin composite strip with periodically placed microstructures, we aim at deriving the upscaled model equations as well as the effective transport coefficients for suitable scalings in terms of both the inherent thickness at the strip and the typical length scales of the microscopic heterogeneities. Aiming at computable scenarios, we consider that the heterogeneity of the strip is made of an array of periodically arranged impenetrable solid rectangles and identify two scaling regimes what concerns the small asymptotics parameter for the upscaling procedure: the characteristic size of the microstructure is either significantly smaller than the thickness of the thin obstacle or it is of the same order of magnitude. We scale up the diffusion-polynomial drift model and list computable formulas for the effective diffusion and drift tensorial coefficients for both scaling regimes. Our upscaling procedure combines ideas of two-scale asymptotics homogenization with dimension reduction arguments. Consequences of these results for the construction of more general transmission boundary conditions are discussed. We illustrate numerically the concentration profile of the chemical species passing through the upscaled strip in the finite thickness regime and point out that trapping of concentration inside the strip is likely to occur in at least two conceptually different transport situations: (i) full diffusion/dispersion matrix and nonlinear horizontal drift, and (ii) diagonal diffusion matrix and oblique nonlinear drift
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
Homogenization of a reaction-diffusion problem with large nonlinear drift and robin boundary data
No full textWe study the periodic homogenization of a reaction -diffusion problem with large nonlinear drift and Robin boundary condition posed in an unbounded perforated domain. The nonlinear problem is associated with the hydrodynamic limit of a totally asymmetric simple exclusion process (TASEP) governing a population of interacting particles crossing a domain with obstacle. We are interested in deriving rigorously the upscaled model equations and the corresponding effective coefficients for the case when the microscopic dynamics are linked to a particular choice of characteristic length and time scales that lead to an exploding nonlinear drift. The main mathematical difficulty lies in proving the two -scale compactness and strong convergence results needed for the passage to the homogenization limit. To cope with the situation, we use the concept of two -scale compactness with drift, which is similar to the more classical two -scale compactness result but it is defined now in moving coordinates. We provide as well a strong convergence result for the corrector function, starting this way the search for the order of the convergence rate of the homogenization process for our target nonlinear drift problem
Semilinear problems for the fractional laplacian with a singular nonlinearity
No full textThe aim of this paper is to study the solvability of the proble
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