1,721,994 research outputs found
Findings from the SI papers
No full textThis Special Issue (SI) constitutes a small recognition for the research achievements during a half-a-century activity of B. R. Sehgal, G. Yadigaroglu and G. Hewitt. Around forty papers have been collected in the area of Nuclear Thermal-Hydraulics (NTH) to honor the memory of those scientists. Namely, the SI is sub-divided into three parts: the first one (which includes the present paper) provides introductory remarks and (SI) planning information; the second one celebrates the life and the scientific achievements of the three eminent researchers; the third part consists of a collection of technical papers representative of nowadays investigations in nuclear thermal-hydraulics. Rather than summarizing the content of the SI, the present paper aims at identifying (a few lines in each case) the main message from each paper in order to create a chain among several topics which constitute NTH. The summary can be useful for more thorough discussion (i.e. more systematic and more comprehensive than what done within the framework of the present SI) among specialists about what is now NTH and how to identify substantial improvement ways-out
Selected thoughts and writings by Geoffrey Hewitt
No full textThis synopsis depicts selected ideas and the vision of G. Hewitt in relation to nuclear thermal-hydraulics. This task is ambitious and somewhat unrealistic: Geoff worked for half a century and produced several hundred papers and dozens of books. An analytical rather than synthetic work has been completed, considering a dozen selected documents (cited in the list of references) which were co-authored by Geoff. Key statements were extracted from each document. Within the context of these books and papers, these extracts are used to show here the criticism by Geoff of the current state of knowledge and, primarily, his concerns about the capabilities of numerical models. The discussion in the present paper may be of interest to the new generation of scientists in the field of nuclear thermal-hydraulics, by generating critical views when designing experiments or interpreting the outcomes from computational tools and/or model
Preface and framework for nuclear thermal-hydraulics
No full textNuclear Thermal-Hydraulics (NTH) constitutes a fundamental discipline at the basis of the design, the operation and the safety evaluation of Water Cooled Nuclear Reactors (WCNR). Huge research investments that began to be available in 1970 in conjunction with the publication of 10 CFR 50.46 stepwise declined roughly around the year 2000; a further decline is expected nowadays (year 2020) in most of the Countries where nuclear technology was developed. Nevertheless, those investments brought to the current understanding, as characterized in recently issued textbooks; otherwise, ‘new Countries’, where nuclear technology is florescent nowadays, are supposed to provide new impulse to the research. The present Special Issue (SI) aims at collecting ideas for streamlining researches in nuclear thermal-hydraulics. Topics of expertise of renowned authors are collected and form the basis for a reflection. The scope for the papers is limited to NTH with emphasis to the design conditions of WCNR and to accidents within the Design Basis Accident envelope, including countermeasures to be taken in the conditions of core still intact. Papers connecting the fundamentals to the applications of nuclear thermal-hydraulics have been solicited and constitute the main content of the SI. Topics related to Design Extension Conditions (DEC) and/or connected with the application of NTH to nuclear technology are the focus for a few papers: this is also consistent with the dedication of the SI to the memory of deceased scientists as from below
Challenges and concerns for development of nuclear thermal-hydraulics
No full textNuclear Thermal Hydraulics (NTH), following a flourishing growth until the end of the last century entered a phase of slow advancement (this statement does not apply to each sector of NTH). In the area of applications to nuclear reactor design and safety an emblem for this situation is exhibited by system computer codes: their new development began a quarter of a century ago and current predictive capabilities are not better than those available before. Turbulence modeling and averaging techniques, as an example for two-phase flows, are among the key aspects which need improvement since decades; otherwise, attention of decision makers and researchers is oriented towards fashion topics or even research objectives which can be accomplished within an assigned framework of resources (time and budget). A synthesis of today status is provided in the paper after attempting to address the question ‘what is nuclear thermal hydraulics?’ Perspective directions to be pursued are recommended, e.g. the water-fall or the turbulent energy cascade experiment, although it is recognized that quantum leap in modeling (unfortunately not obtainable from present authors) are needed to exit the stagnation
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
- …
