1,720,969 research outputs found
The performance of marine coatings and pipe materials under fluid-borne sand erosion
No full textA program of tests is described in which pipe materials and steel substrates with various coatings were subjected to fluid-borne sand particle erosion conditions. Sand-water slurry jets were used at velocities between 2–30 m/s and at a jet impingement angle of 90° to create a range of erosive conditions to evaluate the performance of the pipe materials carbon steel AISI 1020, stainless steel AISI 316. Cupro-Nickel 90/10, medium density polyethylene and glass reinforced plastic test coupons. Further tests at an impingement angle of 30° and at 10 and 20 m/s velocity compared the performance of the carbon and stainless steels with various polymeric, metallic and ceramic coatings. Flexible polyurethane seems to have promise for future use in fluid-borne sand particle erosion environments. The erosion mechanisms of flexible polyurethane have been identified as micro-cutting at low angle impingement and fatigue/crack propagation at normal impact
Electrochemical noise analysis of polyurethane coated steel subjected to erosion-corrosion
No full textThis paper presents the degradation mechanisms of porous and non-porous PU coatings on steel subjected to slurry erosion–corrosion using a purpose-built apparatus. The samples were subjected to a slurry jet made of 3.5% wt. NaCl solution, containing 0–3% wt. sand particles (90° impact angle, jet velocity 4 m/s). Prior to testing the corrosion reactions present on the steel substrate were examined by Electrochemical Impedance Spectroscopy (EIS) and during the test by Electrochemical Noise Analysis (ENA) on the corrosion current. The non-porous coatings remained fully protective at least 10 months when exposed to a purely corrosive solution, and until total stripping by the sand particles when exposed to a corrosive slurry. In contrast, for the porous coatings, corrosion reactions were rapidly initiated on the substrate after solution transport, via defects in the coating, to the coating/metal interface. However, no synergism was detected between the erosion and the corrosion under these test conditions. Analysis of corrosion current fluctuations provided information on the coating degradation mechanisms. The mean and standard deviation were found to act as effective qualitative indicators of the extent of coating damage. The skewness, kurtosis and PSD slope indicated the initiation of the corrosion reactions on the substrate, i.e. the beginning of coating breakdown
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
Development of a knowledge-based system for materials management
No full textIn the past, many mistakes have been made in selecting the best materials for a given task. Thus, tools for humans to optimise the selection of materials will be valuable assets, particularly when the field of application is broad, the problem complex, the operating envelope variable, or the environment is aggressive. In this paper, a methodology for construction of a generic computer materials selector is described. A knowledge structure is presented in which materials selection and failure analysis are at opposite ends of a spectrum of materials performance. An example of the selection of a coating for marine use is given. Besides being of great value to designers, the tool is of considerable potential use for general materials information systems and computer-based learning module
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
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