1,720,955 research outputs found
Adaptively Refined Mesh for Collocation-Based Dynamic Optimization
No full textDiese Arbeit befasst sich mit der effizienten, numerischen Lösung dynamischer Optimierungsprobleme auf Basis direkter Kollokation und unter Verwendung von Algorithmen zur adaptiven Meshverfeinerung. Eine neuartige h-Methode, eingebettet in ein neu entwickeltes Framework für dynamische Optimierung, wird vorgestellt. Das Framework basiert auf direkten Kollokationsmethoden mit gespiegelten Legendre-Gauss-Radau Punkten. Das adaptive Meshverfeinerungsverfahren zielt darauf ab, die Trajektorien der Steuervariablen auf Grundlage einer Steigungs- und Krümmungsanalyse in jedem Intervall durch sukzessive Bisektion zu homogenisieren. Unter Annahme der Konvergenz des Kollokationsansatzes für glatte Probleme kann die Terminierung des Verfahrens gezeigt werden. Der Algorithmus weist signifikante Vorteile im Bezug auf Laufzeit und Genauigkeit gegenüber traditionellen direkten Kollokationsmethoden auf. Zusätzlich ermöglicht das Framework eine zugängliche und ausdrucksstarke Modellierung und erweist sich bei einer Vielzahl von akademischen und realen Beispielproblemen als ausgesprochen effektiv. Die vorgeschlagene -Methode bietet jedoch Raum für Verbesserungen, da keine direkten Fehlerabschätzungen verwendet werden. Darüber hinaus wird gezeigt, dass die in dieser Arbeit untersuchte Problemklasse eine Erweiterung der Methode zu einer pseudospektralen Meshverfeinerungsmethode ermöglicht. Zusätzlich birgt die Integration des Algorithmus in eine moderne Modellierungs- und Simulationssoftware erhebliche Vorteile, da dies eine gesteigerte Performance, bessere symbolische Verarbeitung und eine Fehleranalyse sowie Validierung der Optimallösung bieten kann.This thesis deals with the topic of efficient numerical solutions to dynamic optimization problems using a direct collocation approach with adaptive mesh refinement. A novel h-method is proposed and implemented in a newly developed dynamic optimization framework that utilizes direct collocation with flipped Legendre-Gauss-Radau points. The mesh refinement algorithm aims to uniformize control trajectories by successive bisection based on slope and curvature analysis in each interval. For smooth problems and under suitable convergence, a termination guarantee is established. The algorithm has significant advantages over traditional direct collocation approaches without mesh refinement in terms of accuracy and computation time. The dynamic optimization framework allows for accessible and expressive modeling and proves to be very effective when applied to a variety of example problems, including academic and real-world physical applications. However, the proposed -method offers room for improvement since no direct error estimates are incorporated, and it is shown that the problem class studied in this thesis allows for an extension to the broad and advanced class of pseudospectral mesh refinement algorithms.Moreover, it is demonstrated that embedding the method in a modern modeling and simulation environment would greatly benefit in terms of performance, symbolic handling, and for error analysis as well as validation of optimal solutions
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
Enhancing Collocation-Based Dynamic Optimization through Adaptive Mesh Refinement
Full text linkDirect collocation-based dynamic optimization plays animportant role in the optimization of equation-basedmodels. With this approach, continuous problems aretranscribed into sparse nonlinear programs (NLPs) that canbe solved efficiently. The open-source Modelica environmentOpenModelica provides an implementation using Radau IIAcollocation, but has major limitations, such as the lack ofparameter optimization, no adaptive mesh refinement, and nosupport for higher-order integration schemes. This paperpresents (1) a comprehensive reimplementation thataddresses these limitations and (2) a novel -method meshrefinement algorithm. Implemented in the custom Python /C++ optimization framework GDOPT, the approach demonstratessignificant performance improvements, solving typicalproblems 2 to 3 times faster than OpenModelica underequivalent conditions. Using the proposed mesh refinementalgorithm, the framework correctly identifies non-smoothregions and increases resolution accordingly, requiringonly a small increase in computation time. Theimplementation lays the foundation for a future integrationinto the OpenModelica toolchain
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
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
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
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