1,720,977 research outputs found
Image analysis for determination of cement content in concrete to improve accuracy of chloride analysis
No full textThe chloride content at the level of the reinforcement expressed as %Cl by weight of cement is an important parameter in condition assessment of reinforced concrete structures. Whereas standardized procedures are available to determine the chloride content in concrete powder, the cement content is assumed equal to the mix design or even as constant value. This work shows that the cement content in thin slices of 50 mm diameter concrete cores with maximal aggregate diameter 32 mm varies between 8.4% and 24.1% (bulk: 13.8%). A procedure based on colouring the cement paste, scanning the specimen surface, and image analysis allows the non-destructive determination of the cement content with good accuracy. It is concluded that a reliable determination of the chloride content in terms of %Cl by weight of cement requires the analysis of both the chloride and cement content in a concrete specimen
Experimental protocol to determine the chloride threshold value for corrosion in samples taken from reinforced concrete structures
No full textWe propose a method to measure a parameter highly relevant for corrosion assessments or predictions of reinforced concrete structures. The main advantage is that the method permits testing samples taken from engineering structures. This ensures real conditions at the steel-concrete interface, which is crucial to avoid artefacts of laboratory-made samples
Chloride threshold values in concrete - A look back and ahead
No full textOver the last 60 years, extensive research efforts aimed at determining the so-called chloride threshold value in reinforced concrete. The belief that such a threshold exists is the root of all efforts to measure and model chloride ingress into concrete. This paper addresses the usefulness of this established concept by evaluating the experience available for portland cement systems. Additionally, it is critically discussed whether the concept can be applied to modern materials, particularly SCMs. Finally, suggestions for future research are made. It is concluded that the pronounced stochastic nature of the chloride threshold currently permits only corrosion prognoses with large uncertainties. It is shown that even the most sophisticated chloride transport model in concrete will not significantly improve this. Instead of refining mass transport models, future research should thus aim at finally understanding the relevant parameters governing corrosion initiation in concrete. There is strong indication that a number of such parameters are overlooked in the current concept of the chloride threshold value. We believe that as long as initiation of chloride-induced corrosion is not fully understood, it does not make sense to continue applying the (unsuccessful) concept of the chloride threshold value to modern materials
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
Impact of IR Drops on the −850 mVCSE Cathodic Protection Criterion for Coated Steel Pipes in Soil
No full textDispelling 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
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