1,720,965 research outputs found
The study of α-quartz reactivity towards alkali-silica reaction by X-ray powder diffraction
No full textThe present study is a contribution to the understanding of α-quartz reactivity towards the alkali-silica reaction (ASR), based on the use of X-ray powder diffraction (XRPD) line broadening. In particular the relationship between α-quartz structural disorder and its potential alkali reactivity towards ASR was investigated by combining traditional and advanced analytical techniques. Two aggregates were characterised by means of optical, physical and chemical analyses. Their potential alkali-reactivity was then tested by the ultra-accelerated mortar-bar test (RILEM AAR-2). Moreover a full profile analysis by XRPD was performed to extract the microstructural features (crystallite size and microstrain) of α-quartz in two aggregates, revealing its degree of structural order. By comparing the mortar bar results with those from the XRPD analysis, a correlation between α-quartz microstructural features and its reactivity towards ASR is highlighted, even if the microstructural features of α-quartz were not the only parameter to be considered. Thomas Telford Lt
Synchrotron radiation XRPD study on the early hydration of cements
Full text linkSynchrotron radiation X-ray powder diffraction has been used to monitor the evolution of hydrous phases during the first hours of the hydration process on synthetic clinker phases and on commercial cements. In order to collect data as soon as water is added to the system, the hydration of the paste was achieved using a remote controlled system. The data were quantitatively analysed via full-profile Rietveld method. The results of quantitative analysis (phase composition) and the lattice parameters determination are very useful to obtain detailed information on the structural evolution of the hydrous phases, in particular during the early stages of the hydration processes
Chromatic weathering of black limestone quarried in Varenna (Lake Como, Italy)
No full textThe causes of chromatic weathering in black limestone have been investigated on samples from the main quarry of Varenna (Lake
Como, Italy), which provided building stones for Lombard architecture. Our studies have been carried out combing colorimetric,
mineralogical, chemical, microstructural and geochemical observations. The results suggest that the chromatic weathering affecting
the surfaces of black limestone is not due to oxidation of the original organic matter present in the bulk, as believed. Chemical and
mechanical weathering associated with the deposition of new organic matter are the most important phenomena occurring on the
surface, leading to a diffuse roughness of surface and de-cohesion
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
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