1,720,982 research outputs found
Mechanism of Electrochemical Chloride Removal
No full textThis paper presents the first laboratory results obtained from continuous monitoring of the free chloride content in concrete blocks during electrochemical chloride removal (ECR). Chloride sensitive electrodes have been embedded at different depths in concrete specimens and the free chloride concentration was measured during ECR. The total chloride content was determined prior to and after the electrochemical treatment. Time and space resolved data on the removal of chloride ions and information concerning the relationship between bound and free chloride was obtained. Due to the removal of free chloride during the treatment, bound chloride is dissolved in order to re-establish the equilibrium between bound and free chlorides. The rate of release of bound chloride is slow compared to the rate of chloride removal and thus the ECR process quickly becomes inefficient. Current off periods allow the system to re-establish the equilibrium between bound and free chlorides. Subsequently, the process is efficient again. The results are discussed with respect to treatment efficiency, treatment procedure and current distribution. It is concluded that the ECR process is currently applied in an inefficient manner and the charge required for the desalination can be reduced significantly. This is also of interest with regard to the risk of undesirable side-effects that currently limit the use of ECR
Considerations on the effect of sample size for the critical chloride content in concrete
No full textIn order to perform reliable service life predictions of reinforced concrete structures, realistic values for the critical chloride content are needed. With regard to the large scatter in the literature as well as the development of modern cement types, agreement has been reached that the test methods for this parameter must be improved. Many of the setups in use are not practice-related.
In the present work, the effect of the size of reinforced concrete samples is discussed. It is shown that this parameter is not critical when considering electrochemical or physical aspects of the corrosion mechanism. From a probabilistic point of view, on the other hand, it has some implications since the critical chloride content decreases with increasing rebar length. Further research should concentrate on finding the critical sample size, i.e. the minimal specimen size that is required to give proper critical chloride contents. Moreover, some aspects of evaluating experimental results are pointed out
Diffusion potentials in porous mortar in a moisture state below saturation
No full textDiffusion potentials (membrane potentials) were measured in mortar in a moisture state below saturation for the first time. In contrast to conventional diffusion cell setups, the experimental approach was based on embedded ion selective electrodes. A numerical model with coupled Nernst-Planck equations for the most abundant species in the pore solution allowed simulating ion transport processes and the correspondingly arising diffusion potentials. It was found that Portland cement mortar with a water/cement ratio of 0.6 does not exhibit any significant permselective behaviour – even not in an unsaturated state determined by self-desiccation. Apparently, the stable radius of water-filled capillaries is still large enough to allow ionic transport through those fractions of pore solution that are unaffected by double layer effects. In addition, the relative importance of liquid junction potentials at the reference electrode / sample interface and internal diffusion or membrane potentials are discussed with respect to application of direct potentiometry to cement based materials
sj-docx-1-ces-10.1177_1478422X241227829 - Supplemental material for Tafel slopes and exchange current densities of oxygen reduction and hydrogen evolution on steel
No full textSupplemental material, sj-docx-1-ces-10.1177_1478422X241227829 for Tafel slopes and exchange current densities of oxygen reduction and hydrogen evolution on steel by M. C. van Ede and U. Angst in Corrosion Engineering, Science and Technology</p
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
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