1,720,986 research outputs found
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
Investigation on the fluid and structural dynamic behavior of steam turbine inlet valves at part load operation
No full textDie hier vorliegende Arbeit thematisiert das strömungs- und das strukturdynamische Verhalten von Hochdruckventilen, die in Großkraftwerken zur Regelung von Dampfturbinenanlagen genutzt werden.
Der Fokus der Arbeit liegt auf der Untersuchung der Strömungszustände und des daraus resultierenden Schwingungsverhaltens des Ventilkegels im Teillastbetrieb der Anlage. Bei Teillastbetrieb herrscht eine hohe Druckdifferenz zwischen dem Ein- und Austritt des Ventils, die dazu führt, dass im Bereich der Drosselstelle die Strömung extrem stark beschleunigt wird und als Strahl in den Ventildiffusor eintritt. Bei der anschließenden Dissipation des Strahls treten verschiedene Strömungsinstabilitäten auf. Diese rufen in bestimmten Betriebspunkten starke Druckfluktuationen hervor, die letztendlich den Ventilkegel zum Schwingen anregen.
Durch die aktuell zunehmende Nutzung volatil verfügbarer regenerativer Energieträger ist die Betriebsweise von Dampfkraftwerken signifikanten Änderungen unterworfen. An die Stelle des Volllastbetriebs mit wenigen Anfahrvorgängen tritt eine Betriebsweise mit häufigem Teillastbetrieb, stark variabler Lastabgabe und häufigen Anfahrvorgängen.
Da der zuvor wenig beachtete Teillastbetrieb von Dampfventilen aufgrund dieser Änderungen zunehmend an Bedeutung gewinnt, herrscht in diesem Bereich vermehrt Forschungsbedarf. Die aerodynamischen und strukturdynamischen Untersuchungen werden mit numerischen Methoden durchgeführt.
Voruntersuchungen an Validierungsfällen ergeben, dass zur Modellierung von typischen Strömungsinstabilitäten zeitabhängige CFD-Berechnungen mit klassischen Zweigleichungsturbulenzmodellen (RANS) nicht ausreichend sind. Stattdessen wird ein hybrides Turbulenzmodell genutzt, die eine Zwischenstellung zwischen den Zweigleichungsmodellen und den Large Eddy Simulationen einnehmen, genutzt.
Die CFD Untersuchungen zeigen, dass Wandstrahlablösungen, die bei bestimmten Betriebsbedingungen im Ventildiffusor auftreten, einen maßgeblichen Einfluss auf das Strömungsverhalten haben sowie die Intensität der dynamischen und statischen Lateralkräfte signifikant erhöhen.
Aus der Analyse der Berechnungsergebnisse geht hervor, dass das Auftreten der ungünstigen Wandstrahlablösungen direkt mit dem Versagen des Coandă-Effekts in unterexpandierten Wandstrahlen korreliert.
Weitere Untersuchungen zeigen, dass bei einem angelegten Strahl ein wesentlicher Teil der dynamischen Axialkraft durch einen akustischen Raummode auf den Ventilkegel aufgeprägt wird. Der Raummode wird durch eine Scherschicht im Ventildiffusor angeregt. Störungen dieser Scherschicht, die durch Einbauten oder Schwingungen des Kegels hervorgerufen werden können, führen zu einer Verminderung der Anregung.
Ist der Strahl abgelöst, treten im Ventil durch instationäre Wiederanlegevorgänge des Strahls sowie durch die Oszillation von schrägen Verdichtungsstößen hohe Druckfluktuationen und damit eine hohe dynamische Kraft, die auf den Kegel wirkt, auf.
Generell ist unter strömungsmechanischen Gesichtspunkten die angelegte Strömung als günstiger zu bewerten als die abgelöste Strömung. Die strukturdynamischen Analysen, die zum Teil gekoppelt mit den aerodynamischen Untersuchungen durchgeführt werden, zeigen, dass im Fall der abgelösten Strömung intensivere Schwingungen des Ventilkegels auftreten als im Fall der angelegten Strömung.In this thesis the aero dynamic and structural dynamic behavior of high pressure turbine inlet valves used for large power stations is investigated. Emphasis is put on the investigation of the flow field and the flow induced vibrations at part load operation. At this operational range a large pressure difference exists between the inlet and the outlet of the valve causing an extreme acceleration of the flow in the valve gap between the valve plug and the valve seat. The high speed flow being discharged from the gap forms a jet in the valve diffuser. There the kinetic energy of the jet is dissipated by various flow instabilities causing pressure fluctuations. These pressure fluctuations act on the valve plug and hence cause intense vibrations.
Due to the increasing use of renewable energy, the operational mode of steam turbine installations is changed from base load operation to intermediate operation with highly variable power output and frequent startup operations. As long time part load operation was not previously considered, there is a demand for research. The study on the aero and structural dynamic phenomena is carried out with numerical models.
Pre-studies on validation cases show that classical two-equation turbulence models are not capable to model flow instabilities and the generation of pressure fluctuations properly. A Hybrid turbulence model combining the advantages of the RANS and the SAS-method is used instead.
The CFD simulations reveal that wall jet separations existing at certain operation conditions have a significant effect on the flow topology in the valve diffuser and increase the level of the dynamic lateral forces acting on the valve plug.
The analysis of the CFD study shows, that the wall jet separation is related to the failure of the Coandă effect in underexpanded wall jets.
In case of the flow topology with the attached wall jet CFD simulations predict that a significant amount of the dynamic force is related to an acoustic mode acting on the valve plug. The acoutic mode is excited by a shear layer in the valve diffuser. Pertubations of the shear layer being caused by vortex-generatig devieces or by vibrations of the plug reduce the excitaion of the mode and the level of the dynamic axial forces.
If the jet is detached, the oscialtion of oblique shocks and the partial unsteady reattachment of the jet cause intense pressure fluctuations and hence high dynamic forces acting on the valve plug.
From an aerodynamic point of view, the flow topology with the attached jet is more favorable than the detached flow topology. Structural dynamic simulations are preformed to analyse the impact of the flow topology on the vibrations of the valve plug. One one way as well as two way coupled calculations are conducted. The structural dynamic analysis predict that the detached flow topology causes higher structural vibrations than the attached flow topology
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
Author Under Sail The Imagination of Jack London, 1893-1902
No full textIn Author Under Sail, Jay Williams offers the first complete literary biography of Jack London as a professional writer engaged in the labor of writing. It examines the authorial imagination in London's work, the use of imagination in both his fiction and nonfiction, and the ways he defined imagination in the creative process in his business dealings with his publishers, editors, and agents. In this first volume of a two-volume biography, Williams traverses the years 1893 to 1902, from London's "Story of a Typhoon" to The People of the Abyss. The Jack London who emerges in the pages of Author Under Sail is a writer whose partnership with publishers, most notably his productive alliance with George Brett of Macmillan, was one of the most formative in American literary history. London pioneered many author models during the heyday of realism and naturalism, blurring the boundaries of these popular genres by focusing on absorption and theatricality and the representation of the seen and unseen. London created an impassioned, sincere, and extremely personal realism unlike that of other American writers of the time. Author Under Sail is a literary tour de force that reveals the full range of London as writer, creative citizen, and entrepreneur at the same time it sheds light on the maverick side of machine-age literature.Intro -- Title Page -- Copyright Page -- Dedication -- Contents -- Acknowledgments -- Introduction -- 1. Spirit Truth -- 2. From Absorption to Theatricality and Back Again -- 3. "I Will Build a New Present" -- 4. Sons as Authors -- 5. Fathers as Publishers -- 6. The Daughter as Author -- 7. Lovers as Authors -- 8. At Sea with the Family -- 9. Yellow News, Yellow Stories -- 10. The Return Home -- Notes -- Bibliography -- Index -- About Jay WilliamsIn Author Under Sail, Jay Williams offers the first complete literary biography of Jack London as a professional writer engaged in the labor of writing. It examines the authorial imagination in London's work, the use of imagination in both his fiction and nonfiction, and the ways he defined imagination in the creative process in his business dealings with his publishers, editors, and agents. In this first volume of a two-volume biography, Williams traverses the years 1893 to 1902, from London's "Story of a Typhoon" to The People of the Abyss. The Jack London who emerges in the pages of Author Under Sail is a writer whose partnership with publishers, most notably his productive alliance with George Brett of Macmillan, was one of the most formative in American literary history. London pioneered many author models during the heyday of realism and naturalism, blurring the boundaries of these popular genres by focusing on absorption and theatricality and the representation of the seen and unseen. London created an impassioned, sincere, and extremely personal realism unlike that of other American writers of the time. Author Under Sail is a literary tour de force that reveals the full range of London as writer, creative citizen, and entrepreneur at the same time it sheds light on the maverick side of machine-age literature.Description based on publisher supplied metadata and other sources.Electronic reproduction. Ann Arbor, Michigan : ProQuest Ebook Central, YYYY. Available via World Wide Web. Access may be limited to ProQuest Ebook Central affiliated libraries
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