1,720,963 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
Characterization of glass-polymers composite materials for the high pressure storage of hydrogen
Full text linkThis thesis investigates glass capillaries and structures consisting of borosilicate glass (Simax) for high pressure hydrogen storage. The finite element method (FEM) is used for the mechanical analyses and the design optimization.
The necessary characteristic values for the material descriptions are determined by experimental tests. The strength, the shear strength of the interface glass/adhesives, the coefficient of hydrogen permeation, the time-temperature behavior and the upper temperature limit are in particular important for this topic.
The strength of the glass is highly dependent on the surface quality. Therefore it is important to draw capillaries and coated this in one step. The influence of the coating on the glass strength will be tested with burst pressure tests. The polymers were used in the thesis are characterized by push-out tests, dynamic mechanical analyses (DMA) and permeation tests.
Aditionally, a viscoelastic material model will be determined from the DMA test. This model is used for the time-temperature depending simulation.
Under consideration of the experimental results and and based on the simulations it is possible to create an optimized storage design. Furthermore, we gain knowledge about the application limits.In der vorliegenden Arbeit werden Glaskapillaren und Strukturen aus Borosilikatglas (Simax) für die Hochdruckspeicherung von Wasserstoff betrachtet. Um die mechanischen Belastungen zu analysieren und anschließend ein optimiertes Speicherdesign abzuleiten, findet die Finite Element Methode (FEM) Einsatz.
Die notwendigen Materialkennwerte werden zuvor experimentell ermittelt. Dazu gehören die Festigkeit, die Schubfestigkeit der Grenzfläche Klebung/Glas, der Wasserstoffpermeationskoeffizient, das Temperatur-Zeit-abhängige Verhalten, sowie die obere Temperatureinsatzgrenze.
Die Glasfestigkeit ist stark abhängig von der Oberflächengüte. Daher werden in dieser Arbeit Kapillaren selber gezogen und beschichtet. Der Einfluss auf die Festigkeit wird mit Hilfe von Berstversuchen untersucht. Die eingesetzten Polymere werden zusätzlich mit dem Push-out Versuch, der dynamisch mechanischen Analyse und der Permeationsmessung charakterisiert.
Darüber hinaus wird aus den DMA Versuchen ein viskoelastisches Materialmodell abgeleitet, womit der Temperatur- und Zeiteinfluss auf die mechanische Belastung simuliert wird.
Unter Beachtung der experimentell gewonnenen Erkenntnisse, sowie der durchgeführten Simulation ist es möglich, ein optimiertes Speicherdesign zu erstellen und Aussagen über die Einsatzgrenzen zu treffen
Glaskapillaren für die Wasserstoffhochdruckspeicherung
No full textWasserstoff spielt eine wichtige Rolle im Bereich der erneuerbaren Energien. Um die hohe gravimetrische Energiedichte auszunutzen, bietet sich die die Hochdruckspeicherung an.
Um die theoretische Festigkeit, die geringe Wasserstoffpermeabilität vom Werkstoff „Glas“ und das Wissen von Griffith auszunutzen, sollten Glaskapillaren zum Einsatz kommen. Glas bietet diverse Möglichkeiten solche Kapillaren anzuordnen. Es beginnt bei der Bündelung von Einzelkapillaren und geht bis hin zu ganzen Strukturen.
Allerdings stellt sich auch die Frage wie die Berstdruckfestigkeit optimal ausgenutzt und dabei noch die Permeation und das mechanische Langzeitverhalten beachtet werden kann. Ziel dieser Arbeit ist es, die wichtigen Einzelkomponenten diesbezüglich zu untersuchen und einen Langzeitspeicher mithilfe von Simulationen auszulegen
Charakterisierung einer polymerbeschichteten Glaskapillare für den Einsatz der Wasserstoffspeicherung
No full textDispelling 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
Simulation der mechanischen Belastung einer Glaskapillare für die Verwendung zur Wasserstoffhochdruckspeicherung
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