1,720,975 research outputs found
FEM-DBEM procedure for crack analysis in baffle module of Wendelstein 7-X
No full text“Wendelstein 7-X” is the world’s largest nuclear fusion experiment of “stellarator type” in which a
hydrogen plasma is confined in a magnet field, generated with external superconducting coils, allowing the
plasma to be heated up to fusion temperature. The water-cooled Plasma Facing Components (PFC) protect the
Plasma Vessel (PV) against radiative and convective heat from the plasma.
After the manufacturing process of the heat shields and baffles, several cracks have been found in the braze and
in the cooling pipes. Due to heat loads occurring during each Operational Phase (OP), thermal-stresses are
generated in the heat sinks, brazes and cooling pipes, that encourage cyclic crack-growth and, eventually, the
water leak through the pipes.
The aim of this study is to predict the operational limits of the baffles and heat shields under cyclic heat loads,
by using a numerical model based on a FEM-DBEM approach, in order to provide an assessment on the risks of
premature failure for segments assembled in the PV
Fatigue life assessment in lateral support element of a magnet for nuclear fusion experiment "Wendelstein 7-X"
Get PDFWendelstein 7-X (W7X), a nuclear fusion experiment of modular stellarator type, started operation in 2015 and will be upgraded with a water cooled first wall for steady state operation in 2020. A hot hydrogen plasma of ultra-low density is confined in a plasma vessel by an electromagnetic field generated by specially shaped superconducting coils. Such coils, embedded in a cryostat working at 4. K, are kept by a central support ring and joined together by welded lateral support elements (LSEs). In this paper, a coupled FEM-DBEM (Dual BEM) submodelling approach is adopted for crack-growth simulations of the cracks detected in LSEs and driven by a fatigue load spectra.A global analysis on one fifth of the fivefold symmetric magnet system is performed by FEM, whereas the submodelling approach is adopted to solve the crack propagation by DBEM. In particular, the adopted approach is based on the application of the superposition principle to solve a LEFM problem: the only boundary conditions for the DBEM submodel consist of tractions, calculated by the FEM global analysis and applied to the crack faces in the local submodel. The obtained speed of crack advance and crack kinking are compared with literature results to highlight the accuracy of the proposed approach together with inherent computational advantages
Nonlinear fatigue crack propagation in a baffle module of Wendelstein 7‐X under cyclic bending loads
Get PDFSimulation of the fatigue crack propagation in a Wendelstein 7‐X baffle module is performed in this study using both a finite element method‐based software and the UniGrow nonlinear model for small‐scale yielding (SSY) conditions. Some experimental fatigue tests of several cracked baffle modules have been performed through a servo‐hydraulic machine. One of these experimental tests
has been considered to simulate fatigue crack propagation in the baffle module. Before starting the experimental test, a first crack partly contained in the welding seam and partly in the steel pipe is found. Subsequently, owing to the applied load, the crack propagated both into the welding seam and into the steel pipe until the plastic zone in the near field attains SSY conditions.
Finally, owing to the increase in the extension of the plastic zone, SSY conditions are not more valid, and the breakage of the steel pipe is produced by plastic collapse
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
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