1,721,018 research outputs found
Assessment of THEMA Code against Spreading Experiments
No full textIn the frame work of Severe Accident research, the spreading code THEMA, developed at CEA/DRN, aims at predicting the spreading extent of molten core after a vessel melt-through. The code solves fluid balance equations integrated over the fluid depth for oxidic and/or metallic phases under the shallow water assumption, using a finite difference scheme. Solidification is taken into account through crust formation on the substrate and at contact with the surroundings, as well as increase of fluid viscosity with solid fraction in the melt. A separate energy equation is solved for the solid substrate, including possible ablation. The assessment of THEMA code against the spreading experiments performed in the framework of the Corium Spreading and Coolability project of the European Union is presented. These experiments use either simulating materials at medium (RIT), or at high temperature (KATS), or corium (VULCANO, FARO), conducted at different mass flow rates and with large or low solidification interval. THEMA appears to be able to simulate the whole set of the experiments investigated. Comparison between experimental and computed spreading lengths and substrate temperatures are quite satisfactory. The results show a rather a rather large sensitivity at mass flow rate and inlet temperature, indicating that, generally, efforts should be made to improve the accuracy of the measurements of such parameters in the experiments
TOLBIAC Code Simulations of some Molten Salt RASPLAV Exsperiments
No full textIn the frame of severe accidents studies, the behaviour of a corium pool has to be predicted. Numerous physical processes are involved in these studies, and a predictive tool is of great interest in order to investigate several situations, geometries or events. The TOLBIAC code, developed by CEA/Grenoble, is devoted to the simulation of the thermalhydraulic behaviour of a corium pool both in-vessel and ex-vessel situations, with natural convection.Some molten salt RASPLAV experiments have been simulated for the TOLBIAC code assessment. An adiabatic condition at the free surface of the molten pool is used. The comparisons between TOLBIAC calculations and RASPLAV data concern the pool temperatures, the local wall heat fluxes and the crust thickness (if any). The wall heat transfer correlations are the key parameter for the agreement between calculations and data, and are discussed. Concerning the crust thickness, the results are sensitive to their physical properties, and mainly to the thermal conductivity
Preliminary Assessment of an In-Vessel Core Retention Strategy Using Best Estimate Tools
No full textThe In-Vessel Core Retention Strategy (IVCRS) is proposed as an innovative and complementary approach to the currently adopted ex-vessel core melt management. Within the frame of an international cooperation CEA (F) and ENEA (I) have performed some preliminary calculations, aimed at identifying the lacks and the needs of the analytical models available for a comprehensive assessment of an IVCRS technical solution. For this purpose, a best estimate approach has been adopted for the theoretical assessment of the Dual In-Vessel Retention (DIVER) concept, proposed by CEA for high power PWRs. Such concept combines the two strategies which have been investigated up to now for future reactors: external cooling of the RPV and presence of a core catcher inside. Both generic phenomena involved in a IVCRS (e.g. behavior of the corium pool) and specific phenomena associated to the coolability of the particular concept studied (gap between the crucible and the RPV wall) have been taken into account. The calculations have been performed with best estimate French codes under CEA supervision
Politik und Theorie in der politischen Theorie - am Beispiel von John Rawls' Theorie der Gerechtigkeit
No full textIorio M. Politik und Theorie in der politischen Theorie - am Beispiel von John Rawls' Theorie der Gerechtigkeit. In: Jobmann A, Spindler B, eds. "Theorien über Theorien über Theorien": Tagungsdokumentation. IWT-Paper ; 24. Bielefeld: Inst. f. Wissenschafts- und Technikforschung, Univ. Bielefeld; 1999: 53-61
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
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