1,720,980 research outputs found
Effect of calcareous deposit formation on efficiency of cathodic protection on carbon steel in simulated soil solution
Get PDFAbstract: The surface blocking properties of calcareous deposit have been shown to have a beneficial effect for cathodic protection. Though this may be true, the role of calcareous deposit has never been quantified. The purpose of this study was to investigate the effect of the formation of calcareous deposit on carbon steel induced by the application of cathodic polarisation in simulated soil solution. The solution was derived from Evian water, with [Ca2+]:[Mg2+] ratio maintained at 2:1 and chloride concentration of 0.01 mol/L. The behaviour of the metal/electrolyte interface was studied using non-invasive in-situ electrochemical techniques at OCP and at various applied potentials Eapp from –0.7 VSCE to –1.2 VSCE. A combination of voltammetry, electrochemical impedance spectroscopy with X-ray diffraction analysis of the mineral layer were utilised. One week long experiments were conducted. Results showed that at OCP, lepidocrocite, carbonated green rust, calcite and aragonite were found as the corrosion process involved anodic and cathodic zones. For cathodic protection Eapp –0.7 VSCE to –1.2 VSCE, calcite and aragonite was found. At Eapp –1.2 VSCE, brucite was found due to increased interfacial pH and as a result evolution of hydrogen bubble was observed. Normalised current curves for Eapp –1.2 VSCE showed surface coverage not exceeding 60% after 7 days. In contrast –1.1 VSCE ≤ Eapp ≤ –0.7 VSCE surface coverage was 0% at day 7. Quantification of the cathodic protection efficiency done via modelling of polarisation curves illustrated a “passivation” phenomenon which resulted from formation of hydroxyl cations. Modelling of polarisation curves allowed for acquisition of the expression for the anodic component of the current ja as a function of the applied potential Eapp. It could be predicted that the interfacial behaviour had a direct influence on the anodic Tafel coefficient. The influence of the calcareous deposit on cathodic protection efficiency can be quantified by plotting log ja vs Eapp. Eapp –0.7, –0.8 and –1.0 VSCE were shown to offer the best current inhibition with formation of calcareous layer allowing very low current density to be maintained.M.Tech. (Chemical Engineering
Erosion wear behavior of spark plasma-sintered Ti-6Al-4V reinforced with TiN nanoparticles
No full textThe extensive application of titanium alloys is delimited as their erosion wear properties deteriorate when exposed to erosive and harsh environments. The present research investigates the effects of TiN additions (2, 4, and 6 vol.%) on the Ti-6Al-4V alloy prepared by spark plasma sintering technique. Erosion wear behaviour of the composites was investigated by high-velocity solid particle erosion test and tribometer pin-on-disc friction module method. The duration of the test was 10 min, while the mass loss of the sample was recorded after 2-min interval. The surface analysis and phase identifications of the sintered composites were examined by optical microscopy (OM), scanning electron microscopy (SEM), and X-ray diffraction (XRD), respectively. Microstructural analysis revealed a transformation from lamellar with β grain boundaries in Ti-6Al-4V alloy to bimodal structures upon addition of TiN nanoparticles. XRD patterns of the alloy indicated an increase in diffraction peaks from lower intensity to high intensity with an increase in TiN nanoparticle content. Erosion is visible in Ti-6Al-4V alloy, 4 and 6 vol.% TiN, but less severe with 2 vol.% TiN addition for all the test times. However, this is due to grain detachment of the hard phase regions between the matrix and the reinforcing phase of the composites. The results showed the presence of micro-voids on the eroded surfaces. It was found that Ti-6Al-4V alloy with TiN nanoparticle addition was resistant to erosion wear, while the recorded steady-state friction coefficients for all the samples range from 0.2 to 0.4. However, an increase in microhardness values ranges from 342 to 513 HV0.1.Fil: Kganakga, Mokgoba Glodean. Universidad de Johannesburgo; NoruegaFil: Prieto, Germán. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto de Física del Sur. Universidad Nacional del Sur. Departamento de Física. Instituto de Física del Sur; Argentina. Universidad Nacional del Sur. Departamento de Ingeniería; ArgentinaFil: Falodun, Oluwasegun Eso. Universidad de Johannesburgo; NoruegaFil: Tuckart, Walter Roberto. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto de Física del Sur. Universidad Nacional del Sur. Departamento de Física. Instituto de Física del Sur; Argentina. Universidad Nacional del Sur. Departamento de Ingeniería; ArgentinaFil: Obadele, Babatunde Abiodun. Botswana International University of Science and Technology; BotsuanaFil: Ajibola, Olarewaju Olawale. Federal University; NigeriaFil: Olubambi, Peter Apata. Universidad de Johannesburgo; Norueg
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
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
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