1,720,960 research outputs found
The effect of copolymerisation on the performance of acrylate-based hybrid sol-gel coating for corrosion protection of AA2024-T3
No full textThe study was focused on the optimisation of the copolymerisation process of acrylate-based hybrid sol-gel coating to obtain long-lasting corrosion protection of AA2024-T3. The coating was synthesised using the radical copolymerisation process of methyl methacrylate (MMA) and 3-methacryloxypropyl trimethoxysilane (MAPTMS) performed under air and nitrogen (oxygen-free) atmospheres, followed by acidic hydrolysis and polycondensation in the presence of silica prepared from tetraethyl orthosilicate (TEOS). The sol synthesis was evaluated at various stages using real-time infrared spectroscopy, multinuclear liquid- and solid-state magnetic resonance spectroscopy and gel permeation chromatography. After deposition on AA2024-T3 substrate and curing, the coating properties were further evaluated by contact profilometer and focused ion beam/scanning electron microscopy coupled with energy-dispersive X-ray spectrometry. The corrosion performance was evaluated in 0.1 M NaCl solution using electrochemical impedance spectroscopy and salt spray chamber testing. The results indicated that the reaction performed in the nitrogen atmosphere increases the degree of the copolymerisation of acrylates groups, resulting in a larger molecular weight of the formed copolymer. After curing, both sol-gels formed continuous, smooth, ∼4 μm thick coatings that provided excellent barrier properties. However, when coating synthesised under nitrogen atmosphere, the coating provided better long-term corrosion resistance reaching almost 1 GΩ cm2 after 6 months immersion in 0.1 M NaCl solution. Superior corrosion resistance was also confirmed in the salt spray chamber where the coating prepared under N2 atmosphere remained unchanged more than 500 hours
The synergistic effect of cerium acetate and sodium sulphate on corrosion inhibition of AA2024-T3 at various temperatures
No full textThe present work examines the corrosion inhibition of aluminium alloy 2024-T3 immersed in NaCl+Ce(OAc)3 and NaCl+Ce(OAc)3+Na2SO4 solutions to evaluate the synergetic effect between cerium and sulphate ions at various temperatures (5 °C, 25 °C and 50 °C). The electrochemical properties were studied using short-term potentiodynamic measurements and long-term electrochemical impedance measurements. The surface topography, morphology and composition of cerium deposits formed on the alloy surface after two days of immersion were evaluated using scanning electron microscopy combined with energy-dispersive X-ray spectroscopy and X-ray photoelectron spectroscopy. The results revealed an efficient long-term (up to 8 weeks) corrosion inhibition in NaCl+Ce(OAc)3 that was superior in the NaCl+Ce(OAc)3+Na2SO4 solution, especially at lower temperatures (5 °C > 25 °C > 50 °C). The composition of the Ce-based film varied with the temperature and the presence of Na2SO4, resulting in different mixtures of Ce(III) and Ce(IV) species. The synergistic effect of cerium and sulphate ions on corrosion inhibition was reflected by a higher degree of cerium oxidation from Ce3+ to Ce4+ at a low temperature and the incorporation of sulphates into the formed film, which protected the surface from the corrosion medium more efficiently
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
The effect of surface preparation on the protective properties of Al2O3 and HfO2 thin films deposited on cp-titanium by atomic layer deposition
Full text linkAtomic layer deposition (ALD), a method that allows the formation of thin and conformal films on substrates of interest, was employed to prepare thin films of alumina (Al2O3) and hafnia (HfO2), with the aim of protecting the surface of the commercially pure titanium (cp-Ti) used in biomedical applications. Prior to deposition, cp-Ti specimens have been prepared in two ways – grinding and grinding followed by polishing. Such surfaces have been denoted as rough and smooth, respectively. The thickness, composition, morphology and topography of alumina and hafnia films have been determined using ellipsometry, focused ion beam microscopy with energy dispersive X-ray spectroscopy, time-of-flight secondary ion mass spectrometry and 3D profilometry. A homogeneous stoichiometric composition of alumina and hafnia was obtained with a layer thickness of ca. 150 nm. The anti-corrosive properties of ALD thin films were measured in simulated body fluid solution, using electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization curves. The roughness of the cp-Ti surface plays an important role in the protective properties of these films, especially those of hafnia. In general, when deposited on a smooth surface, ALD films with better anti-corrosive properties were obtained, as evidenced by EIS long-term, 40-day tests. ALD films showed very low porosity, calculated from electrochemical parameters, and significantly lower corrosion current densities, compared with those from bare cp-Ti specimens. Lower porosity and slightly better protective properties were provided by films of hafnia. On the other hand, according to EIS long-term tests, alumina retained slightly greater impedance values than hafnia. Since both alumina and hafnia are biocompatible materials, this study confirms the possibility of their use to reduce the risk of failure of medical implants made of cp-Ti, in the human body environment
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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