1,721,027 research outputs found
Continuous fragmentation equations in weighted L1 spaces
No full textWe investigate an integro-differential equation that models the evolution of fragmenting clusters. We assume cluster size to be a continuous variable and allow for situations in which mass is not necessarily conserved during each fragmentation event. We formulate the initial-value problem as an abstract Cauchy problem (ACP) in an appropriate weighted L1 space, and apply perturbation results to prove that a unique, physically relevant classical solution of the ACP is given by a strongly continuous semigroup for a wide class of initial conditions. Moreover, we show that it is often possible to identify a weighted L1 space in which this semigroup is analytic, leading to the existence of a unique, physically relevant classical solution for all initial conditions belonging to that space. For some specific fragmentation coefficients, we provide examples of weighted L1 spaces where our results can be applied
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
Qualitative Contributions to Evolutionary Equations
No full textThe theory of evolutionary equations traces back to Prof. Rainer Picard in 2009, when he introduced this general Hilbert space-approach to partial differential equations. Evolutionary equations form a unified model for a plethora of partial differential equations, including many classical equations. This theory provides, amongst many other results, a powerful, very general well-posedness theorem.
This thesis introduces and analyzes a concept of duality for evolutionary equations with the aim to establish concepts of control theory in the setting of evolutionary equations.
Secondly, homogenization in the sense of convergence in the Schur topology, as introduced by Prof. Marcus Waurick in 2018, is studied in the framework of evolutionary equations. A homogenization theorem that allows for systematic computation of the limits is proven and showcased.
Thirdly, a gap in a proof of a central result concerning the Schur topology is closed
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
Stabilization via homogenization
Full text linkIn this short note we treat a 1+1-dimensional system of changing type. On different spatial domains the system is of hyperbolic and elliptic type, that is, formally, ∂t2un−∂x2un=∂tfand un−∂x2un=f on the respective spatial domains ⋃j∈{1,…,n}(j−1n,2j−12n) and ⋃j∈{1,…,n}(2j−12n,jn). We show that (un)n converges weakly to u, which solves the exponentially stable limit equation ∂t2u+2∂tu+u−4∂x2u=2(f+∂tf) on [0,1]. If the elliptic equation is replaced by a parabolic one, the limit equation is not exponentially stable
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