1,720,978 research outputs found
Mass-lumped high-order cell methods for the time-dependent Maxwell's equations
No full textOur goal is the efficient numerical approximation of solutions to the time-domain linear Max-well system. Methods like the classical finite-difference time-domain method rely on the approximation of the electric and the magnetic
field on two interlaced (Cartesian) grids respectively. Our method expands this idea to general triangular/tetrahedral meshes by defining a dual grid using the barycentric subdivision of the primal mesh. The resulting primal and dual ements are both composed of the same set of quadrilateral (in 2d) and hexahedral (in 3d) cells. We use Lagrangian polynomial basis functions with respect to tensor product integration points on the unit square/cube which are mapped to the physical cells and suitably combined to obtain differing, element-wise conforming bases on the dual and primal mesh respectively. This approach provides generically computable, stable high order bases. Using lumped mass matrices with respect to the defining points of the basis functions leads to block diagonal mass matrices with block-size independent of the polynomial degree. Thus the combination of the spatial discretization with explicit time-stepping schemes yields an efficient method with very little memory requirement
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
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe 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
Hardy-Space Infinite Elements
Get PDFEs existieren zwei unterschiedlichen Arten von Problemen, die bei der Untersuchung von zeit-harmonischen Wellen entstehen. Bei Streuprobleme sind eine Quelle und eine Frequenz vorgegeben. Bei Resonanzproblemen werden Frequenzen gesucht, für die das Problem nicht mehr eindeutig lösbar ist. Der Fokus dieser Arbeit liegt auf letzterem. Außerdem betrachten wir für diese Arbeit zwei Arten von Wellen, nämlich akustische und elektromagnetische. Erstere werden durch die Helmholtz-Gleichung, zweitere durch die zeitharmonische Maxwell-Gleichung beschrieben. Das unbeschränkte Gebiet, auf dem sich die Wellen bewegen, ist vom Typus eines Wellenleiters. Diesen unterteilen wir in einen beschränkten Innenund einen unbeschränkten Außenraum, in den die Welle ausstrahlt oder ausläuft. Der Innenraum wird mithilfe der Finiten Elemente Methode bearbeitet. Für den unbeschränkt Außenraum benötigen wir spezielle Infinite Elemente, die von einem Parameter und der Anzahl der Freiheitsgrade im Außenraum abhängig sind. Diese speziellen Infiniten Elemente sind der Hauptgegenstand dieser Arbeit. In den numerischen Beispielen am Ende der Arbeit zeigen wir exponentielles Abfallverhalten des Fehlers bezüglich der Anzahl der Freiheitsgrade in Ausstrahlungsrichtung. Außerdem zeigen wir, wie sich die Resonanzen anhand des Parameters verhalten.Wave phenomena can be divided into two categories. Scattering problems, where the right side, i.e. a source and a frequency are given. In the case of resonance problems, we look for frequencies, for which the problem is not uniquely solvable. This work deals with the latter. In addition, we consider two types of waves for this work: acoustic and electromagnetic waves. The former are described by the Helmholtz equation, the second by the time-harmonic Maxwell equation. The unrestricted area on which the waves move is of a waveguide type. We subdivide this into a restricted inner and an unrestricted outer space into which the wave radiates or leaks. The interior is processed using the Finite Element Method. For the unrestricted outer space, special Infinite Elements are required, which depend on a parameter and the number of outer degrees of freedom. These special Infinite Elements are the main subject of this work. In the numerical examples at the end of the work, we show exponential falling behavior of the error in the direction of emission with respect to the number of degrees of freedom. We also show how the resonances behave, depending on the parameter
Komplexe Skalierungsprofile für Wellengleichungen in offenen Systemen
Get PDFOpen boundary simulations are the subject of great interest when considering wave phenomena. Methods using complex coordinate stretchings can be employed to generate exponentially decaying outgoing solutions in space for time-harmonic equations. Applying a Fourier transform to the resulting system in space leads to a system in time domain which can be discretized using the Finite Element Method and an appropriate time-stepping. In this thesis we consider different versions of complex scalings for the wave equation and the Klein-Gordon equation. We study the effects of using different coordinate systems and scaling functions and give numerical results in one and two dimensions
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
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