1,721,370 research outputs found
Sozialer und semiotischer Raum
No full textIn den Gesellschafts- wie in den Kulturwissenschaften hat der Begriff des ‚Raums‘ in den letzten Jahren sehr viel Aufmerksamkeit erfahren. Zahlreiche Einzelstudien, Sammelbände und Handbücher loten den Bedeutungsumfang dieses Begriffs, aber auch die Schwierigkeiten aus, die sich einerseits aus der Vielfalt vorhandener Raumkonzepte und andererseits aus der Fülle ihrer keineswegs deckungsgleichen Anwendungsmöglichkeiten ergeben. Hinzu kommt die Schwierigkeit, den Begriff des Raums von verwandten Ausdrücken wie Platz und Ort, Umgebung und Territorium oder gar Welt abzugrenzen – ganz zu schweigen von den Verschiebungen, die zwischen verschiedenen Sprachen hinsichtlich der Auffassung von ‚Raum‘, ‚espace‘, ‚space‘ usw. bestehen.
Vor diesem Hintergrund erscheint es nicht nur zweckmäßig, sondern notwendig, im Rahmen einer transversalen Betrachtung nach strukturellen Ähnlichkeiten zwischen den Raumkonzepten unterschiedlicher Disziplinen Ausschau zu halten. Einen Versuch in dieser Richtung stellen die folgenden Überlegungen zu Querbezügen und Übergängen zwischen Raumsoziologie und Raumsemiotik dar
Entwurf und Anwendung eines Fluidik-Aktuators zur aktiven Strömungskontrolle an Hochauftriebskonfigurationen
No full textIn dieser Dissertation wird der Forschungsfortschritt von der Entwicklung eines neuartigen Aktuatorsystems bis zu dessen Anwendung im Rahmen von Strömungskontrollexperimenten an dem komplexen dreidimensionalen Modell eines Außenflügels bei relevanten Strömungsbedingungen beschrieben. Dabei bilden drei Veröffentlichungen den Hauptbestandteil dieser Arbeit, in denen nacheinander unterschiedliche Aspekte des Forschungsthemas adressiert werden: die Entwicklung eines Strömungskontrollaktuators und dessen Validierung an einer generischen 2D-Zweielementkonfiguration [Bauer2014], die Übertragung des Strömungskontrollansatzes auf eine komplexe Geometrie [Bauer2015a] und schließlich die Zusammenführung dieser Arbeiten und die Anwendung von lokaler aktiver Strömungskontrolle an einem Modell mit für zivile Verkehrsflugzeuge repräsentativer Geometrie und bei nominellen Anströmbedingungen für den Startfall [Bauer2015b].
Der Ansatz der Strömungskontrolle basiert auf der Erhöhung der Durchmischung von energiereicher Außenströmung und energiearmer wandnaher Strömung mittels periodischen gepulsten Ausblasens. Die Ergebnisse aller drei Veröffentlichungen belegen den positiven aerodynamischen Effekt des Einsatzes von lokaler aktiver Strömungskontrolle an der Modellvorderkante.
Zunächst wurde an einer 2D-Zweielementkonfiguration demonstriert, dass unter Einsatz des entwickelten zweistufigen Fluidik-Aktuatorsystems der Maximalanstellwinkel deutlich erhöht werden kann mit einhergehender Steigerung des Maximalauftriebs um bis zu 10%. Im Folgenden wurde der Stömungskontrollansatz auf eine komplexe 3D-Geometrie, das Modell eines für moderne Zivilflugzeuge typischen Außenflügelsegments, übertragen, um daran die Möglichkeiten aufzuzeigen, dass durch die Nutzung von lokaler aktiver Strömungskontrolle den ablösebedingten Anstiegs des Widerstands zu höheren Anstellwinkeln hin verschoben werden kann. In diesen Experimenten wurde belegt, dass durch die untersuchte Aktuationsmethode und unter Aufwendung eines moderaten Impulsbeiwertes von 0.62% eine Verbesserung der Gleitzahl um bis zu 80% möglich ist. Schließlich wurden sowohl das Aktuatorsystem als auch die Aktuationsmethode auf ein industrienahes Außenflügelmodell übertragen und bei der für den Startfall eines Verkehrsflugzeugs relevanten Anströmmachzahl von Ma = 0.2 untersucht. Auch unter diesen relevanten Strömungsbedingungen konnte die aerodynamische Leistungsfähigkeit des Modells durch den Einsatz von aktiver Strömungskontrolle verbessert werden, wobei sich eine deutliche Abhängigkeit des Kontrolleffekts von der spannweitigen Verteilung der Einbringung von Impuls- und Massenstrom zeigte. Für die als am effektivsten identifizierte Verteilung wurde bei einem Impulsbeiwert von 0,59% eine Erhöhung des Maximalanstellwinkels um 2,4 Grad und des Maximalauftriebs um 10,5% nachgewiesen. Damit einhergehend konnte eine Widerstandsreduktion um bis zu 37% bezogen auf den Wert der unkontrollierten Grundströmung gezeigt werden.This dissertation delineates the path of research from the design of a novel actuator system to its application for local active flow control on a highly three-dimensional outer wing model under relevant flow conditions. The core of this contribution consists of three individual publications, which address different aspects of the research topic: the development of a flow control actuator system and its validation on a generic geometry [Bauer2014], the extension of local active separation control to an industry relevant geometry [Bauer2015a], and consecutively, the application of local active flow control to an outer wing geometry representative for civil airliners and at the nominal take-off Mach number using the devised actuator system [Bauer2015b].
The results of all three individual papers prove the aerodynamic benefit of applying active separation control by means of periodic pulsed blowing from near the leading edges of different wing models.
First, it was demonstrated that active flow control applied to a 2D two-element wind tunnel model using the developed staged fluidic actuator system is capable of delaying the onset of stall significantly, while simultaneously increasing maximum lift by up to 10%. Subsequently, those results were transferred to the control of local separation on a model of a highly three-dimensional modern civil aircraft outer wing configuration to the end of drag reduction (i.e. the offset of drag increase to higher angles of attack). Those experiments exemplified the capability of pulsed jet actuation to enhance the aerodynamic efficiency of the wing segment by up to 80% for a moderate momentum coefficient of 0.62% invested. Finally the successful synthesis of the two-stage actuator system approach and of the insights gained on controlling a complex flow is detailed along the lines of their application to a high fidelity model in experiments conducted at the nominal take-off incidence Mach number of Ma = 0.2. It was shown that although all the forcing parameter variations tested improve the aerodynamic performance, the control effect is highly sensitive to the local distribution of momentum and mass introduction. For the most effective set of forcing parameters found, a momentum coefficient of 0.59% sufficed to offset the stall angle by 2.4 degrees, to increase maximum lift by 10.5%, and to decrease drag at the maximum angle of attack by 37%.
The individual publications and this dissertation as a whole therefore contribute to closing the gap between research aimed at enhancing the understanding of flow control aerodynamics and its application to industry relevant geometries and flow conditions
BOX Ligands in Biomimetic Copper-Mediated Dioxygen Activation: A Hemocyanin Model
No full textThe mu-eta(2):eta(2)-peroxodicopper(II) core found in the oxy forms of the active sites of type III dicopper proteins have been a key target for bioinorganic model studies. Here, it is shown that simple bis(oxazoline)s (BOXs), which are classified among the so-called "privileged ligands", provide a suitable scaffold for supporting such biomimetic copper/dioxygen chemistry. Three derivatives (BOX)-B-R,H-Me-2 (R = H, Me, tBu) with different backbone substituents have been used. Their bis(oxazoline)-copper(I) complexes bind dioxygen to yield biomimetic mu-eta(2):eta(2)-peroxodicopper(II) species. O-2 can be reversibly released upon an increase in temperature. Their formation kinetics have been studied under cryo-stopped-flow conditions for the tBu derivative, giving activation parameters. Delta H-on(double dagger) = (2.27 +/- 0.18) kcal mol(-1), Delta H-on(double dagger) = (-46.3 +/- 0.8) cal K-1 mol(-1) for the binding event and. Delta H-off(double dagger) = (11.7 +/- 1.9) kcal mol(-1), Delta H-off(double dagger) = (-16.1 +/- 8.2) calK(-1) mol(-1) for the release of O-2, as well as thermodynamic parameters. Delta H degrees = (-10.0 +/- 1.7) kcal mol(-1) and. Delta S = (-32.7 +/- 7.4) calK(-1) mol(-1) for this equilibrium. The mu-eta(2):eta(2)-peroxodicopper(II) complexes have been isolated as surprisingly stable solids and investigated in depth by a variety of methods, both in solution and in the solid state. Resonance Raman spectroscopy revealed a characteristic isotope-sensitive stretch. (nu) over tilde (O-O) = 731-742 cm(-1) (Delta[O-18(2)] approximate to -39 cm(-1)) and an intense feature around 280 cm(-1) diagnostic for the fundamental symmetric Cu2O2 core vibration. A slight butterfly-shape of the Cu2O2 core has been derived from EXAFS data and DFT calculations. SQUID magnetic data evidenced strong antiferromagnetic coupled Cu-II(2) (-2J >= 1000 cm(-1)). Thermal degradationinsolutionyieldsbis(hydroxo)-bridged[((BOX)-B-tBu,H-Me-2)(L)-Cu(OH)](2)(PF6)(2) (L = H2O, MeCN or THF); whereas in the case of (BOX)-B-H,H-Me-2, ligand oxygenation has been detected. Preliminary reactivity studies with the substrate 2,4-di-tert-butylphenol indicate the formation of the C-C coupling product 3,3',5,5'-tetra-tert-butyl-2,2'-biphenol, whereas orthohydroxylation was not observed. The copper(I) complex [((BOX)-B-tBu,H-Me-2)Cu(MeCN)]PF6 as well as two dicopper(II) complexes [(L)((BOX)-B-tBu,H-Me-2)Cu(OH)](2)(PF6)(2) have been characterised by single-crystal X-ray diffraction. Considering the vast number of known BOX derivatives, a rich and versatile Cu/O-2 chemistry based on this platform is anticipated.European COST program [CM 1003
Ancient Myths and Cultural Change: Phaedra's Illicit Love in Twentieth-Century Anglo-American Drama
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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
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