1,720,994 research outputs found
Tribo-corrosion mechanisms of stainless steel in soft drinks
Full text linkTribo-corrosion mechanisms of 316L Stainless Steel in slurries containing common household soft drinks have been studied through investigating the micro-abrasion-corrosion performance using a ball and disk apparatus which has been modified to measure the in-situ corrosion current during the abrasion process. The objective of this study was to evaluate the effect of pH and solution viscosity on the micro-abrasion-corrosion performance of the material. 316L Stainless Steel was selected because it is commonly used as a dental replacement material. This is an important area of work as the use of steel retainers as well as other stainless steel dental replacements is still widespread and the effectiveness of these devices will be determined by their tribological and tribo-corrosion performance. Additionally, an attempt has been made to investigate the importance of the pH and viscosity variables on the tribo-corrosive synergism, wastage and mechanism maps
Mapping erosion-corrosion of carbon steel in oil-water solutions : Effect of velocity and applied potential
No full textIn this study, the combined effects of erosion and corrosion on carbon steel were investigated in three environments containing crude oil, reservoir water, and a mixture of both solutions at a range of applied potentials, velocities and impact angle. The results indicate that the corrosion contribution was augmented with an increase in the percentage of reservoir water. Both the erosion and corrosion contributions increased with impact velocity for all three environments. Following exposure of the carbon steel in the crude oil, the extent of the erosion was greater than that of corrosion, whilst in the reservoir water, the erosion and corrosion contributions were similar. Mechanisms of erosion-corrosion were proposed based on the change in erosion behaviour at various impact angles and applied potentials in the various environments. Erosion-corrosion maps were constructed based on the results, showing the change in mechanisms and wastage rates as a function of impact velocity and applied potential at various impact angles
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
Some views on the construction of bio-tribo-corrosion maps for Ti in Hanks solution : Particle concentration and applied loads effects
No full textTribology of bio-implants is a major limiting issue in materials selection of the appropriate implant for the appropriate patient activity level [1]. For example, for wear of replacement hip joints, wear caused by the sliding action of the bearing surface of the femoral head against the counterface occurs in synovial fluid. Hence, the major challenge of materials scientists in replacement of such materials is to optimize the wear resistance, minimize any potential tribo-corrosion interaction and adverse biocompatibility effects caused by such interactions and reduce wherever possible any adsorption of wear debris into the surrounding tissue. In Tribology, and in Aqueous Corrosion, various mapping methodologies[1-7] have been developed to characterize the various interactions. The wear map developed by Lim and Ashby [2] classifies the wear regimes at ambient conditions in terms of applied load and velocity, illustrating significant temperature rises and attendant corrosion reactions as a function of the tribological variables. The Pourbaix diagram[8] considers various transitions in terms of potential and pH, therefore presenting corrosion regimes as a function of the driving force of the electrochemical reaction and the hydrogen ion concentration. In tribo-corrosion, there is an extensive recent literature combing the concepts of both approaches to construct tribo-corrosion maps [2-8]. Despite such work, there has been very little work carried out until very recently[9] on the construction of tribo-corrosion maps for application to bio-tribo-corrosion environments. This is despite the fact that such maps may have significant application in optimizing materials for specific patient activity/mass combinations, all of which are important in selection of the most appropriate material combination in total replacement joint procedures. In studies of wear of candidate hip joint materials, it has been observed that particle concentration of wear debris can have an adverse effect on loosening of the joint, leading to osteolysis and potential revision of the replacement joint material [10]. In such cases, it is important to identify the effects of wear debris on the tribo-corrosion mechanism [12]. Assessing the effects of such particle concentrations with load is also of significance as it will indicate what dependency, if any, particle concentration has at various body masses as defined by variation of applied load. Hence, in this paper, the effect of applied load and abrasive concentration were assessed at a range of applied loads for Ti rotating against an inert Zirconia ball, in which abrasive particles of SiC were entrained in Hanks solution. The results were used to construct micro-abrasion-corrosion maps for application to biological environments. The significance of the bio-tribo-corrosion map in identifying mechanisms of wastage and the extent of synergy between the tribological and corrosion processes is addressed in this paper
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
A note on threshold velocity criteria for modelling the solid particle erosion of WC/Co MMCs
No full textThe threshold velocity for erosion of a ductile material is considered as the velocity required for initiation of plastic deformation in the substrate. For a brittle material, it defines the velocity required to nucleate a median crack in the elastic/plastic interface beneath the indentation. By invoking models for the solid particle erosion of ductile and brittle materials from the literature, together with a set of criteria based on threshold velocity calculations for erosion of the individual components, various predictions of erosion behaviour of WC/Co MMCs have been made. Qualitative agreement was found between the model predictions and various trends of the solid particle erosion behaviour of WC/Co cermets in the literature. The implications of the findings in addressing some of the puzzling trends of the solid particle erosion of MMCs in the literature, and how such insights may result in a reconsideration of some "classical" solid particle erosion relationships, are addressed in this paper
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