1,720,959 research outputs found
Influence of re-deposited layer thickness and sample structure on deuterium retention in tungsten
No full textDynamic erosion and stability analysis of nano-columnar tungsten
Full text linkDie Wahl des ersten Wandmaterials für künftige Fusionsreaktoren ist eine der Herausforderungen, die es zu bewältigen gilt, um die Aufwärtsskalierung zu kommerziellen Kraftwerken zu ermöglichen. Aufgrund seiner Hitzebeständigkeit, seiner hohen Sputtering-Schwelle und vieler weiterer vorteilhafter Eigenschaften ist Wolfram (W) bisher einer der vielversprechendsten Kandidaten. Dennoch gibt es eine Reihe von nachteiligen Effekten, wenn W in Fusionsgeräten mit magnetischem Einschluss verwendet wird, wie z. B. Blasen- und "W-Fuzz"-Bildung, die die Effizienz der Reaktoren beeinträchtigen. In früheren Studien wurde gezeigt, dass die Nanostrukturierung von W in Form von Nanosäulen zu einer höheren Strahlungsresistenz und einer geringeren Sputterausbeute führt.Um den Erosionsprozess von nanosäulenförmigem W (NCW) besser zu verstehen, wurde eine dünne Schicht von NCW, die zuvor auf einen mit Gold-Elektroden ausgestatteten Quarzkristall abgeschieden worden war, unter 2 keV Ar Ionenbestrahlung bei einem Einfallswinkel des Ionenstrahls von ° zur Oberflächennormalen schrittweise erodiert. Nach jedem Erosionsschritt wurde die winkelabhängige Sputterausbeute gemessen und die Oberflächentopographie mittels SEM und AFM abgebildet. Zusätzlich wurden die AFM-Messungen und eine nach den verfügbaren SEM-Bildern modellierte Struktur als Input für einen Simulationscode (SPRAY-Code) verwendet, der auf Basis der sogenannten binary collision approximation (BCA) in Kombination mit einem Raytracing Algorithmus entwickelt wurde.Es wurde festgestellt, dass die SPRAY-Simulationen die gemessene statische Sputterausbeute erst nach einer signifikanten Erosion der NCW-Probe gut reproduzieren konnten. Dies wurde hauptsächlich auf die Ungenauigkeiten bei der Reproduktion der Oberflächentopologie mittels AFM-Abbildung zurückgeführt. Andererseits stellt die Modellstruktur zwar die tiefen Kanäle in den NCW-Topologien besser dar, gibt aber die Oberflächenrauheit nicht genau wieder und konnte daher auch keine fehlerfreien simulierten Sputtererträge für NCW liefern.Die Messung der dynamischen Sputterausbeute liefert die erste experimentell ermittelte Quantifizierung der Stabilität von NCW bei längerem Sputtern mit energiereichen (keV-Bereich) Ionen. Während die anwendbaren Fluenzen bisher nur durch Simulationen untersucht wurden, untermauert das Experiment den vorhergesagten Wert mit guter Übereinstimmung. Darüber hinaus wurde die Betriebszeit des NCW unter fusionsrelevanten Bedingungen abgeschätzt, sodass Hochrechnungen für die Betriebszeit in unterschiedlichen Betriebsmodi möglich ist.The choice of the first wall material in future fusion reactors is one of the challenges that need to be addressed, in order to enable the up scaling of research reactors to commercial power plants. Because of its heat resistance, high sputtering threshold and many other beneficial properties, to date, tungsten (W) is one of the most promising candidates. Nevertheless, there are a number of detrimental effects when using W in Magnetic Confinement Fusion (MCF), such as blistering and W-fuzz formation, which inhibit the efficiency of the reactors. In previous studies, it was shown that nano-structuring of W into nano-columns or nano-foam results in higher radiation resistance and lower sputter yield.In order to better understand the erosion process of nano-columnar W (NCW), a thin layer of NCW deposited onto a quartz crystal was gradually eroded under 2\,keV Ar ion irradiation at an ion beam incidence angle of ° towards the surface normal. After each erosion step the angle dependence of the sputter yield was measured and the surface topography was imaged via SEM and AFM. Additionally, the AFM measurements and a structure modeled according to the available SEM images were used as input for a simulation code (SPRAY), which was developed on the basis of the so-called Binary Collision Approximation (BCA) in combination with a ray-tracing algorithm.It was found that the SPRAY simulations could only reproduce the measured static sputter yield well after significant erosion of the NCW sample. This was mainly attributed to the inaccuracies in the reproduction of the surface topology via AFM imaging. On the other hand, the model structure, while better representing the deep channels present in the NCW topologies, did not reproduce the surface roughness precisely and, therefore as well, could not provided accurate simulated sputter yields for NCW.The dynamic sputter yield measurement provides the first experimentally determined quantification of the stability of NCW under prolonged sputtering with energetic (keV range) ions. While previously the applicable fluences were only investigated through simulations, the experiment supports the predictions with good agreement. Furthermore, an operational time of NCW in fusion relevant conditions was estimated, which can be up-scaled to possible reactor scenarios
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
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
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