1,720,990 research outputs found
Analysis of the hydrodynamic loads on RBMK fuel pins in the event of Pressure Tube Cracking
No full textThe accidental reduction of the mass flow rate through a channel of a RBMK type nuclear reactor is expected to determine, besides other effects, the failure of the pressure tube. Due to the steam exiting with high velocity from the crack on the pressure tube, strong static pressure gradients interest the fuel pins closest to the opening. As a result, a “suction effect” takes place which might be strong enough to break the fuel pins and to cause them to be entrained out of the pressure tube.
After introducing some hypotheses about the parameters governing the steam flow throughout the tube and the geometry crack, a CFD model was developed aimed at estimating, to a first approximation, the hydrodynamic loads acting on the fuel pins, and assessing the influence of several geometric and physical parameters on the loads.
In addition, a simplified structural model for the fuel pin was used in order to estimate a range of loads which are expected to cause the failure of the pin, and a comparison was made against the hydrodynamic loads obtained through the CFD model. The result is that if the crack is large enough the loads are sufficient to cause the fuel pin collapse
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
Modelling of Thermal-Hydraulic Loads of WWER-1000 RPV and Structural Integrity Assessment
No full textCFD Code Validation and Benchmarking Against Stratified Air-Water Flow Experimental Data
No full textPressurized thermal shock (PTS) modelling has been identified as one of the most important industrial needs related to nuclear
reactor safety. A severe PTS scenario limiting the reactor pressure vessel (RPV) lifetime is the cold water emergency core cooling
(ECC) injection into the cold leg during a loss of coolant accident (LOCA). Since it represents a big challenge for numerical
simulations, this scenario was selected within the European Platform for Nuclear Reactor Simulations (NURESIM) Integrated
Project as a reference two-phase problem for computational fluid dynamics (CFDs) code validation. This paper presents a CFD
analysis of a stratified air-water flow experimental investigation performed at the Institut de M ́ecanique des Fluides de Toulouse
in 1985, which shares some common physical features with the ECC injection in PWR cold leg. Numerical simulations have
been carried out with two commercial codes (Fluent and Ansys CFX), and a research code (NEPTUNE CFD). The aim of this
work, carried out at the University of Pisa within the NURESIM IP, is to validate the free surface flow model implemented in
the codes against experimental data, and to perform code-to-code benchmarking. Obtained results suggest the relevance of threedimensional
effects and stress the importance of a suitable interface drag modelling
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