1,720,975 research outputs found
FESTUNG: A MATLAB/GNU Octave toolbox for the discontinuous Galerkin method. Part III: Hybridized discontinuous Galerkin (HDG) formulation
No full textThe third paper in our series on open source MATLAB / GNU Octave implementation of the discontinuous Galerkin (DG) method(s) focuses on a hybridized formulation. The main aim of this ongoing work is to develop rapid prototyping techniques covering a range of standard DG methodologies and suitable for small to medium sized applications. Our FESTUNG package relies on fully vectorized matrix / vector operations throughout, and all details of the implementation are fully documented. Once again, great care is taken to maintain a direct mapping between discretization terms
and code routines as well as to ensure full compatibility to GNU Octave. The current work formulates a hybridized DG scheme for a linear advection problem, describes hybrid approximation spaces on the mesh skeleton, and compares the performance of this discretization to the standard (element-based) DG method for different polynomial orders.The stay of A. Jaust at the University of Erlangen-Nurnberg was supported by the Research Foundation - Flanders (FWO) with a grant for a short study visit abroad and by the Special Research Fund (BOF) of Hasselt University
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
Neue implizite unbeschränkt stabile Zeitschrittverfahren für DG-artige Verfahren und zugehörige Themen
No full textThe thesis is concerned with the improvement and evaluation of hybridized discontinuous Galerkin (HDG) methods for problems from computational fluid dynamics (CFD). HDG methods and high order methods in general promise to improve the quality of simulations
used in research and development due to their high accuracy. However, due to their relatively young age there are open question regarding their stability, efficiency and applicability to a wide range of different problems. This thesis focuses on tackling some of these points.
The main concern of this thesis are time-dependent, viscous flow problems that are often described by Euler or Navier-Stokes equations. Therefore, we investigate different types of
implicit time integration methods of high order that have not been applied earlier to the HDG methods. This includes implicit general linear methods and multiderivative time integrators. The multiderivative time integrators introduce additional time derivatives that need to be approximated. We find that the approach used for explicit time integrators fails to deliver a
uniformly stable discretization. Thus, we devise a new approach for implicit multiderivative integrators that remedies the stability issues.
The efficient implementation of the numerical method is important to limit the required run-time of simulations. During this thesis we have developed several implementations which led to the contribution of an implementation of an HDG method to FESTUNG, an open source framework for MATLAB / GNU Octave. Besides efficiency we focus on a code that is well documented, extendable and easy to use.
Many equations used for CFD are nonlinear and thus their solutions are prone to develop shocks. In order to handle shocks properly with the HDG method, a shock capturing method must be employed. We identify a suitable shock capturing method and justify our decision
by comparing the method to other approaches. Additionally, we show that our choice allows to approximate several demanding test cases that contain shocks.
The approximation of a solution to the equations we study requires to solve linear systems of equations. The solving process is a very time and memory consuming part of a simulation. Thus, it is necessary to have an efficient solution strategy. We discuss a newly introduced linear solver that makes use of the special structure of discontinuous Galerkin methods. We apply the new solver to nonlinear problems, which has not been done before, and compare it to an established linear solver to find good agreements in the results of both solvers.UHasselt; RWTH Aachen University; FW
Neue implizite unbeschränkt stabile Zeitschrittverfahren für DG-artige Verfahren und zugehörige Themen
No full textThe thesis is concerned with the improvement and evaluation of hybridized discontinuous Galerkin (HDG) methods for problems from computational fluid dynamics (CFD). HDG methods and high order methods in general promise to improve the quality of simulations
used in research and development due to their high accuracy. However, due to their relatively young age there are open question regarding their stability, efficiency and applicability to a wide range of different problems. This thesis focuses on tackling some of these points.
The main concern of this thesis are time-dependent, viscous flow problems that are often described by Euler or Navier-Stokes equations. Therefore, we investigate different types of
implicit time integration methods of high order that have not been applied earlier to the HDG methods. This includes implicit general linear methods and multiderivative time integrators. The multiderivative time integrators introduce additional time derivatives that need to be approximated. We find that the approach used for explicit time integrators fails to deliver a
uniformly stable discretization. Thus, we devise a new approach for implicit multiderivative integrators that remedies the stability issues.
The efficient implementation of the numerical method is important to limit the required run-time of simulations. During this thesis we have developed several implementations which led to the contribution of an implementation of an HDG method to FESTUNG, an open source framework for MATLAB / GNU Octave. Besides efficiency we focus on a code that is well documented, extendable and easy to use.
Many equations used for CFD are nonlinear and thus their solutions are prone to develop shocks. In order to handle shocks properly with the HDG method, a shock capturing method must be employed. We identify a suitable shock capturing method and justify our decision
by comparing the method to other approaches. Additionally, we show that our choice allows to approximate several demanding test cases that contain shocks.
The approximation of a solution to the equations we study requires to solve linear systems of equations. The solving process is a very time and memory consuming part of a simulation. Thus, it is necessary to have an efficient solution strategy. We discuss a newly introduced linear solver that makes use of the special structure of discontinuous Galerkin methods. We apply the new solver to nonlinear problems, which has not been done before, and compare it to an established linear solver to find good agreements in the results of both solvers.UHasselt; RWTH Aachen University; FW
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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