1,720,958 research outputs found
Mitigation of ground motion effects via feedback systems for the Compact Linear Collider
Get PDFDer Compact Linear Collider (CLIC) ist ein zukünftiger multi-TeV Elektron-Positron Linearbeschleuniger, der gegenwärtig am CERN entworfen wird. Um seine ambitionierten Ziele zu erreichen muss CLIC Teilchenstrahlen von höchster Qualität produzieren, was den Beschleuniger empfindlich für Bodenbewegungen macht. Das CLIC Entwurfsteam hat vier Gegenmaßnahmen vorgesehen um dieses kritische Bodenbewegungsproblem zu lösen. Die vorliegende Arbeit beschäftigt sich mit dem Entwurf einer dieser Gegenmaßnahmen, dem sog. Linac-Regler (L-FB), aber auch mit der Simulation und der Validierung aller Gegenmaßnahmen gemeinsam. Zusätzlich wurde eine Methode zur Verbesserung des notwendigen Systemmodells entwickelt.Das L-FB dient zur Unterdrückung von Strahloszillationen entlang des Beschleunigers. Der Reglerentwurf basiert auf der Entkopplung des Beschleunigersystems in unabhängige Systemkanäle. Für jeden Systemkanal wird anschließend mit Hilfe einer automatischen Syntheseprozedur ein individueller Regler bestimmt. Die Prozedur erlaubt es Expertenwissen einzubringen, welches von einem Optimierungsalgorithmus benutzt wird um den Luminositätsverlust zu minimieren. Dieser Ansatz beschleunigt den Entwurfsprozess signifikant während gleichzeitig die Regelgüte im Vergleich zu Standardmethoden verbessert wird. Neben dem L-FB werden auch einfache aber effiziente Entwürfe für den sog.Kollisionspunktregler und Kostenreduktionsoptionen für die Quadrupol-Stabilisation präsentiert. Für den Entwurf all dieser Regler wurden Modelle für den Einfluss der Bodenbewegungen auf Strahlparameter wie Stahlversatz, Strahlgröße und Luminosität durch Adaption von existierenden Modellen hergeleitet. Für den Entwurf und die Validierung der Gegenmaßnahmen wurde eine Simulationsumgebung aufgesetzt. Diese Umgebung beinhaltet einen Bodenbewegungsgenerator, das Strahl-Tracking, die Strahl-Kollisionen sowie alle Gegenmaßnahmen. Die Simulationen zeigen, dass der Luminositätsverlust auf Grund von Bodenbewegungen effizient reduziert werden kann. Dank des L-FB Entwurfs konnten auch die Spezifikationen für die Strahlpositionsmonitore signifikant gelockert werden. Die Robustheit des L-FB wurde bezüglich vieler Imperfektionen getestet. Eine Sensitivität im Bezug auf Strahlenergievariationen wurde festgestellt, welche durch Filterung von dispersiven Strahlversätzen aus den Messdaten behoben wurde. Weitere Simulationen resultierten in Richtlinien für den Neuentwurf des Quadrupol-Stabilisationssystems, welches zu einer signifikanten Reduktion des Luminositätsverlustes führte. Auf Grund der Wichtigkeit von präzisen Systemmodellen wurde ein speziell zugeschnittenes Systemidentifikationsschema entwickelt. Es ist in der Lage die Parameter des Modells des Hauptbeschleunigers während des Betriebs an das aktuelle Beschleunigerverhalten anzupassen. Durch eine Spezialisierung auf die wichtigsten Systemveränderungen konnte im Vergleich zu Standardalgorithmen die Identifikationsgeschwindigkeit stark erhöht werden. Die identifizierten Modellparameter können für Orbitregler, Systemdiagnose, Alignment-Algorithmen und Fehlererkennungstools verwendet werden.The Compact Linear Collider (CLIC) is a future multi-TeV electron positron collider, which is currently being designed at CERN.To achieve its ambitious goals, CLIC has to produce particle beams of the highest quality, which makes the accelerator very sensitive to ground motion. Four mitigation methods have been foreseen by the CLIC design group to cope with the feasibility issue of ground motion. This thesis is concerned with the design of one of these mitigation methods, named linac feedback (L-FB), but also with the simultaneous simulation and validation of all mitigation methods. Additionally, a technique to improve the quality of the indispensable system knowledge has been developed.The L-FB suppresses beam oscillations along the accelerator. Its design is based on the decoupling of the overall accelerator system into independent channels. For each channel an individual compensator is found with the help of a semi- automatic control synthesis procedure.This technique allows the designer to incorporate expert knowledge, which is used by an optimisation algorithm to minimise the luminosity loss due to ground motion. This approach speeds up the design process significantly, while at the same time improving the orbit feedback performance compared to standard methods. Beside the L-FB, simple but effective designs for the interaction point feedback and cost reduction options for the quadrupole stabilisation are presented. For the design of all these feedback systems models of the ground motion influence on different beam parameters such as beam offset, beam size and luminosity have been derived by adapting and extending existent models.To design, improve and validate the ground motion mitigation methods, a simulation framework was set up, which includes a ground motion generator, beam tracking, beam-beam interaction and all mitigation methods. The simulations show that the ground motion mitigation methods can efficiently preserve the CLIC luminosity. Due to our design of the L-FB, the specifications of the beam position monitor resolution could be relaxed significantly. The robustness of the L-FB was also verified with respect to many other imperfections. Only a certain sensitivity to beam energy variations was observed, which could be resolved by filtering dispersive orbits from the measurements. Further simulation results were an essential input for the redesign of the quadrupole stabilisation system leading to a significant performance improvement of the system. Due to the high importance of the system knowledge for many applications, a system identification scheme was developed. It is capable of adapting the parameters of the system model to changes of the main linac behaviour (orbit response matrix) on-line, during the regular operation of the linac. By focusing only on the most significant system changes, the identification speed could be improved strongly compared to standard algorithms. The identified parameters of the orbit response matrix can be used to improve the performance of beam-based alignment algorithms and orbit feedbacks and are an important input for diagnosis and error detection tools
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
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
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
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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