1,720,988 research outputs found
3D simulation of impurity transport in a fusion edge plasma using a massively parallel Monte-Carlo code
No full textThermonuclear fusion of deuterium (D) and tritium (T) has the potential to be an efficient, sustainable and safe source of energy. The international tokamak fusion experiment ITER (Latin: "the way"), which is scheduled to start operation in 2027, is a key project for the realization of this technology. Reliable predictions on the plasma-wall interaction (PWI) are critical to the success of ITER and further upcoming fusion reactors, since these will significantly impact their efficiency and lifespan. An important PWI process is the erosion of the reactor wall. It determines the lifetime of wall components and is also a source of impurities in the plasma, namely beryllium (Be) and tungsten (W) in the case of the metallic ITER first wall. Codeposition and retention of radioactive T with eroded Be is a significant issue for ITER, since its T wall inventory has an administrative limit of 700 g for safety and fuel cycle reasons. The penetration of impurities (in particular of W, which can reach a high degree of ionization) into the plasma core leads to its cooling due to radiative energy losses, which has a deteriorating impact on confinement and stability. The three-dimensional Monte Carlo (MC) code ERO is an established tool for the investigation and prediction of PWI and plasma impurity transport in fusion experiments. However, due to technical aspects, such as most importantly the limited code performance, ERO was used so far for examining small simulation volumes (under 1m), which is a small fraction of the ITER plasma volume( 800m). Thus, addressing the interdependent problem of impurity transport and PWI in the tokamak has demanded additional assumptions (for example, on the impurity content in the plasma). Moreover, the possibilities of code validation based on measurements in fusion experiments were limited, since only local diagnostics could be used. In the framework of this thesis, the ERO code has been redeveloped from scratch to remove these restrictions. The new code ERO2.0 implements algorithms that allow to study large and complexly shaped wall components in a simulation volume of the ITER plasma vessel size. The resulting increased complexity of the simulation requires to enhance the code performance by orders of magnitude. [...
Going Beyond Counting First Authors in Author Co-citation Analysis
No full textThe 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
No full text“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
No full textWe 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
3D-simulation of impurity transport in a fusion edge plasma by means of a massively parallelized Monte-Carlo code
No full textDie Erosion von Wandkomponenten und die Tritiumrückhaltung begrenzen die Verfügbarkeit und Lebensdauer von ITER und zukünftiger Fusionsreaktoren. Für die Interpretation und Vorhersage der zugrundeliegenden physikalischen Prozesse wurde der Simulationscode ERO2.0 entwickelt. Dieser ermöglicht die 3D-Simulation der Plasma-Wand-Wechselwirkung und des globalen Verunreinigungstransportes im gesamten Randschichtplasmabereich einer Fusionsanlage. Die erforderliche Rechenleistung wird durch effiziente massive Parallelisierung des Codes gewährleistet. In einem ersten Anwendungsfall wurde die Erosion von Beryllium-Wandkomponenten in der Hauptkammer des JET-Tokamaks simuliert. Durch das Verfolgen der vollständigen Trajektorien der erodierten Teilchen konnte der Einfluss der Be-Selbstzerstäubung erstmalig selbstkonsistent beschrieben werden. Die Ergebnisse der Modellierung wurden erfolgreich mit experimentellen Spektroskopiedaten verifiziert.Erosion of wall components and tritium retention limit lifetime and availability of ITER and future fusion reactors. The simulation code ERO2.0 was developed for the interpretation and prediction of the involved physical processes. The code enables a 3D simulation of plasma-wall interaction processes and the global impurity transport in the entire edge plasma region of a fusion device. The required computing power is realized by efficient massive parallelization of the code. In a first application, the erosion of beryllium wall components in the main chamber of the JET tokamak was simulated. For the first time the influence of Be self-sputtering was self-consistently described by tracking the full trajectories of eroded particles. The modelling results were successfully verified by comparison with experimental spectroscopy data
Dispelling the Myths Behind First-author Citation Counts
No full textWe 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
Global SOLPS-ITER and ERO2.0 coupling in a linear device for the study of plasma-wall interaction in helium plasma
No full textPlasma–wall interaction (PWI) is a great challenge in the development of a nuclear fusion
power plant. To investigate phenomena like erosion of plasma-facing components, impurity
transport and redeposition, one needs reliable numerical tools for the description of both the
plasma and the material evolution. The development of such tools is essential to guide the
design and interpretation of experiments in present and future fusion devices. This contribution
presents the first global simulation of PWI processes in a linear plasma device mimicking the
boundary plasma conditions in toroidal ones, including both the description of plasma and
impurity transport and of plasma-facing material evolution. This integrated description is
obtained by coupling two of the state-of-the-art numerical codes employed to model the plasma
boundary and the PWI, namely SOLPS-ITER and ERO2.0. Investigation of helium plasma is
also of primary importance due to the role helium will have during ITER pre-fusion power
operation, when it is planned to be used as one of the main plasma species, as well as fusion ash
in full power operation. The plasma background is simulated by SOLPS-ITER and the set of
atomic reactions for helium plasmas is updated, including charge-exchange and radiative heat
losses. ERO2.0 is used to assess the surface erosion in the GyM vessel, using different wall
materials (e.g. carbon, iron or tungsten) and applying different biasing voltage. Eroded particles
are followed within the plasma to assess their redeposition location. The ionization probability
of the different materials in the GyM plasma is inferred through the energy distribution of
impacting particles and its effects on migration are investigated
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
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