1,721,044 research outputs found
Thermal properties of irradiated UO2 and MOX fuels
No full textThe thermal conductivity of UO2 and MOX LWR fuels decreases as a result of reactor burn-up. In this chapter, the phenomena causing this degradation are presented and the effect of the most influent parameters is discussed. Information useful for the interpretation and comparison of in-pile or out-of-pile measurements is given, especially as a function of burn-up and for samples having different irradiation temperatures, in-pile histories and microstructures. The impact of the introduction of plutonium or additives (Gd, Cr) in standard UO2 is also addressed. The evolution of the thermal conductivity as a function of burn-up is non-linear and the numerous approaches and approximations that are used to obtain thermal conductivity correlations are summarised and compared.JRC.E.3 - Materials researc
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
Thermal conductivity of porous UO2: Molecular Dynamics study
No full textClassical Molecular Dynamics was used to investigate the effect of nanometric size pores on the thermal conductivity of irradiated UO2. The Green-Kubo approach was used for the thermal conductivity calculation.
The effects of pores size, volume fraction and separation were simulated. A comparison with existing theoretical models is presented and an analytical model adapted to irradiated fuel is obtained.
The results demonstrate that, for realistic bubbles size and concentrations, the impact on the fuel thermal conductivity is higher than predicted by the correlations used to quantify the impact of porosity: at 500 K the impact of 0.3 vol.% of nanometric pores is of the same order of
magnitude as that of 4.5 vol.% of micrometric pores.JRC.E.3 - Materials researc
Molecular Dynamics study of the effects of non-stoichiometry and oxygen Frenkel pairs on the thermal conductivity of uranium dioxide
No full textIn the present work, calculations of the thermal conductivity of UO2 were carried out applying classical Molecular Dynamics for the isothermal-isobaric (NPT) statistical ensemble, using the Green-Kubo approach. The thermal conductivity calculated for perfect stoichiometric UO2 is in good agreement with the literature data over the temperature range corresponding to heat transfer by phonons (up to 1700 K). The effect of non-stoichiometry on the thermal conductivity was calculated taking into account the presence of polarons. It was found that for the same value of the stoichiometry deviation, the effect of oxygen vacancies (hypo-stoichiometry) is more pronounced than the effect of oxygen interstitials (hyper-stoichiometry). Then, the saturation concentration of the oxygen Frenkel pairs (OFP) in UO2 was investigated and their influence on the thermal conductivity was calculated. The simultaneous impact of non-stoichiometry and OFP on the thermal conductivity was investigated and it was shown that the two effects can be combined using the interpretation obtained with the classical phonons scattering theory. Finally, simplified correlations were deduced for the calculation of the thermal conductivity of UO2 taking into account the effect of non-stoichiometry and of Frenkel pairs, these two effects being present during irradiation.JRC.E.3 - Materials researc
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