1,720,960 research outputs found
Electrochemistry and capillary condensation theory reveal the mechanism of corrosion in dense porous media
Full text linkCorrosion in carbonated concrete is an example of corrosion in dense porous media of tremendous socio-economic and scientific relevance. The widespread research endeavors to develop novel, environmentally friendly cements raise questions regarding their ability to protect the embedded steel from corrosion. Here, we propose a fundamentally new approach to explain the scientific mechanism of corrosion kinetics in dense porous media. The main strength of our model lies in its simplicity and in combining the capillary condensation theory with electrochemistry. This reveals that capillary condensation in the pore structure defines the electrochemically active steel surface, whose variability upon changes in exposure relative humidity is accountable for the wide variability in measured corrosion rates. We performed experiments that quantify this effect and find good agreement with the theory. Our findings are essential to devise predictive models for the corrosion performance, needed to guarantee the safety and sustainability of traditional and future cements
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
Influence of mortar resistivity on the rate-limiting step of chloride-induced macro-cell corrosion of reinforcing steel
Full text linkThe influence of mortar bulk resistivity on the kinetics of chloride-induced macro-cell corrosion of the reinforcement was experimentally studied. It was found that the corrosion process was limited by a combination of anodic, ohmic and cathodic control for the geometrical conditions tested (small anodes (Ø 6mm) and large cathode-to-anode ratio (685)). The cathodic partial process was independent of the bulk resistivity. Both the anodic and the ohmic partial processes were influenced by local conditions around the anode but were not directly related to the bulk concrete resistivity. The findings indicate that a unique relationship does not exist between bulk concrete resistivity and the corrosion rate for chloride induced macro-cell corrosion
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
Dispelling 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
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
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