1,721,009 research outputs found
Development of a new isogeometric finite element and its application for Lamb wave based structural health monitoring
Get PDFIn this work, a three-dimensional isogeometric piezoelectric finite element is developed, tested in several benchmarks and compared to other numerical higher order approaches with respect to their ability to model Lamb wave propagation problems. The research results are used to recommend an optimal discretization scheme. To illustrate the advantage of the new isogeometric finite element two structural health monitoring (SHM) specific problems are investigated, namely the dynamic behavior of a piezoceramic actuator and the material induced continuous mode conversion. Both problems are studied numerically as well as experimentally. Results, advantages, disadvantages and extensions of the findings are in detail explained and discussed
Higher order finite elements and the fictitious domain concept for wave propagation analysis
Get PDFMagdeburg, Univ., Fak. für Maschinenbau, Diss., 2014von Sascha Ducze
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
Prediction of the airborne sound transmission through a car front end model including poroelastic acoustic treatments
No full textAkustik und Schwingungen Vorgaben spielen eine wichtige Rolle in der Entwicklung
von Personenkraftwagen. Die Auslegung und die Bewertung von passiven akustischen
Maßnahmen erfordert, dass zuverlässige Vorhersage-Tools zur Verfügung stehen.
Diese Modelle müssen die Anwendungsbedingungen realitätsnah berücksichtigen und
sollen eine detaillierte Darstellung der Anwendungsumgebung beinhalten. Der aktuelle
Auslegungsprozess basiert meist auf experimentellen Analysen, die während der ersten
virtuellen Entwicklungsphasen dennoch nicht anwendbar sind. Zur Überwindung dieser
Begrenzung stellt diese Dissertation ein hybrides Verfahren vor, das numerisch und experimentell ermittelte Daten integriert, um die Schallübertragung durch komplexe Systeme zu beschreiben.
Im ersten Schritt wird die Übertragungskette in ihre wesentlichen drei Komponenten
bestehend aus der Anregung, dem strukturelle System und dem Empfangsgebiet geteilt.
Anschließend wird jedes System getrennt untersucht. Der größte Vorteil dabei ist, dass
der geeignete Ansatz abhängig von der vorhandenen Information entweder numerisch
oder experimentell ausgewählt werden kann. Zum einen steigert die Beschreibung des
strukturellen Bauteils mittels einer Simulation die Flexibilität, unterschiedliche Konfigurationen mit reduziertem Aufwand zu analysieren. Zum anderen umfasst die Verwendung von experimentellen Daten automatisch eine realistische Repräsentation der Anregungs- und Empfangsdomänen. Schließlich werden die Ergebnisse der partiellen Modelle zusammengefügt.
Ein zentraler Aspekt die erforderliche Robustheit der Simulationsergebnisse zu sichern
ist die genaue Beschreibung von den akustischen Maßnahmen. Diese bestehen in weitem
Umfang aus poroelastischen Medien. Die Mechanismen der Energiedissipation dieser Materialien sind aufgrund der zweiphasigen Natur schwierig zu modellieren. In dieser Dissertation werden drei unterschiedlichen Materialformulierungen zur Definition des poroelastischen Verhaltens mit Hilfe der Finite Elemente Methode verglichen. Ihre Funktionsfähigkeit wird für verschiedene Konzepte in zwei Kon gurationen überprüft, wobei Messungen in einem Fensterprüfstand die Referenzdaten liefern. Daraus zeichnet sich die
Materialcharakterisierung als ein entscheidender Faktor für die Auswahl und die Anwendung einer Materialformulierung aus.
Nach der Verifikation der numerischen Modelle wird das hybride Verfahren am Beispiel
eines vereinfachten Vorderwagens umgesetzt. Die gemessene einfallende Druckverteilung
sowie die reziprok ermittelten Empfangstransferfunktionen werden mit der numerischen
Information kombiniert. Dadurch kann die gesamte Übertragungskette beschrieben werden.
Abschließend wird das Potenzial des vorgestellten Ansatzes einschließlich der Optionen
zur Effizienzsteigerung diskutiert.Noise, vibration and harshness speci cations play an important part in the development
of passenger vehicles. The design and evaluation of the passive noise control treatments
requires that reliable prediction tools are at one's disposal. These models have to realistically
take into account the application environment and should include a detailed
representation of the sound packages. The current acoustic design process is mostly based
on experimental analyses, which are however not suitable during the early virtual stages of
development. To overcome this limitation the present thesis proposes a hybrid technique
that integrates numerically and experimentally determined data to describe the sound
propagation through complex systems.
The first step consists in the division of the transmission chain into its essential components,
namely, the excitation, the structural system and the reception domain. Next,
each system is separately investigated. The main advantage of this method is that the
most appropriate approach, either numerical or experimental, can be chosen depending on
the available information. On the one hand, the description of the structural component
with a simulation increases the flexibility to study different con gurations with reduced
effort. On the other hand, the use of experimental data automatically comprises a lifelike
representation of the excitation and reception domains. As a last step, the results of the
partial models are merged.
One key aspect to ensure the robustness of the simulation results of the structural subsystem
is the accurate representation of the noise control treatments. To a large extent, the
noise packages are composed of poroelastic media. The energy dissipation mechanisms
inside such materials are difficult to model due to their biphasic nature. Throughout this
thesis three material formulations to de ne the poroelastic behavior are investigated with
the help of the Finite Element Method. Their performance is inspected for different noise
control treatment concepts in two con gurations for which measurements in a window
test bench provide the reference data. Thereby the material characterization stands out
as a decisive factor in the choice and the application of a material formulation.
After the veri cation of the numerical models, the hybrid approach in put into practice
in the example of a simpli ed vehicle front end. The measured incident pressure distribution
as well as the reciprocally determined reception transfer functions are combined
with the numerical information to describe the complete transmission chain. Finally, the
potential of the presented methodology, including options for the efficiency enhancement,
are discussed
Aufbau und Regelung einer aktiven Motorlagerung zur Reduktion von Körperschallen
Get PDFMagdeburg, Univ., Fak. für Maschinenbau, Diss., 2013von Martin Zorneman
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
Aktive und passive Schallreduktion am Dieselmotor
Get PDFOtto-von-Guericke-Universität Magdeburg, Fakultät für Maschinenbau, Dissertation, 2016von Dipl.-Ing. Tommy LuftLiteraturverzeichnis: Seite 119-12
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
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