1,720,961 research outputs found
Fracture Mechanics Analysis in a Pressurized Heavy Water Reactor Vessel during LOCA Scenario
No full textThe Reactor Pressure Vessel (RPV) has long been considered one of the most reliable components in Pressurized Water Reactor (PWR). Nowadays, a general target for the countries that produce nuclear energy is to extend the operation life of existing plants. From this point of view, the RPV is one of the major components that may limit the useful life of the nuclear plant. The risk for the RPV structural integrity is connected to the presence of a flaw of sufficient size, a high level of embrittlement due to radiation damage, and the occurrence of a thermal-hydraulic transient inducing strong stresses in the vessel wall.
Severe loading conditions are produced during a Pressurized Thermal Shock (PTS) event, in which an overcooling may induce strong thermal stresses while the internal pressure can be maintained at high level or the system can be re-pressurized during the transient. Such conditions are generated in a Loss Of Coolant Accident (LOCA) transient during the emergency injection.
In recent years, important progresses have been made in the development of analysis methods and tools for the best estimation of the thermal and pressure loads on the vessel wall. In this direction, the US-NRC published in 2007 a document aimed at reviewing the rules adopted in PTS analysis, established in the 1980s, containing significant conservatisms, for a Best Estimate (BE) approach combined with uncertainty assessment.
In this paper, the methodology for Fracture Mechanics analysis developed at University of Pisa aimed to perform parametric analysis assuming various shapes and locations of the flaw is applied to a Pressurized Heavy Water Reactors (PHWR) during a LOCA scenario. Four steps can be identified starting from the thermal hydraulic analysis of the Nuclear Power Plant (NPP) behaviour with Relap5-3D© in order to calculate the cooling loads of the Emergency Core Coolant Systems (ECCS). The second step is the analysis by mean a CFD code (CFX) of the mixing phenomena occurring in the Down-Comer (DC) and the calculation of the thermal load on the RPV internal surface. The third step is represented by the evaluation of the stresses inside the RPV wall by mean a Finite Element (FE) code (Ansys) under the thermal and pressure loads calculate in the previous steps. The last step is represented by the calculation of the Stress Intensity Factor (SIF) KI by mean the Weight Function method and the comparison with the critical SIF KIc of the material, once the stresses inside the undamaged RPV wall are known.
The goal of this work is the evaluation of the safety margin for the operation of the RPV, adopting a BE approach in all the steps of the analysis. This result will be compared with the one obtained with the application of the ASME XI criteria for the KI evaluation with the aim to show that the BE approach leads to a larger safety margin
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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