1,722,089 research outputs found
Solid particle erosion of CVD diamond coatings
No full textDiamond coatings deposited on both tungsten and tungsten carbide-cobalt substrates were investigated. The thickness of the coatings ranged from 10 to 200mm and the samples were supplied in both as-grown and lapped forms. The coatings were characterised using a number of techniques including X-ray diffraction, Raman spectroscopy, indentation, surface profilometry as well as optical and electron microscopy. The grain size and surface roughness were also measured for comparison with the size of damage features generated in the erosion studies. The results revealed that the coatings were close to natural diamond in both chemical (i.e. negligible graphite content) and mechanical (i.e. hardness and elastic modulus) characteristics. In the erosion studies, two test facilities were used: a water-sand slurry rig and a high velocity air-sand rig. The erodent used was silica sand with average diameters 135mm, 194mm and 235mm with the velocities in the range 16 to 268 m s-1 and 90° nominal impact angle. The erosion rates were plotted against particle kinetic energy and compared with those for cemented tungsten carbide and stainless steel. At 268 m s-1, the most erosion-resistant coating was a 120mm lapped sample, which had an erosion resistance more than 10 times that of cemented WC-7Ni. The coatings were examined both pre- and post-test by scanning electron microscopy in order to determine the degradation mechanisms. Ultrasonic imaging and taper polishing of eroded samples were also performed to reveal sub-surface damage and to elucidate its contribution to coating degradation. The results suggest that the erosion mechanism consists of a three-stage process consisting of micro-chipping, development of pin-holes and interfacial debonding, followed by catastrophic failure.</p
Observations and characterization of damage in diamond coatings due to impact loading
No full textThis paper describes a single-impact study of diamond coatings on tungsten substrates. A gas blast erosion test facility was used to impact 2.38-mm-diameter tungsten carbide spheres onto diamond-coated tungsten at a velocity of 37 m/s. The results show that the impacts result in the formation of ring cracks, whose maximum diameters do not show any significant dependence on the coating thickness. The ring cracks do not agree with the contact diameters as predicted using Hertz’ dynamic impact theory, the ring crack diameters being significantly larger than those predicted by the theory. These discrepancies can be attributed to a modified stress field generated by friction between the sphere and the target, as well as plastic deformation of the spheres during impact. A closer agreement with the Hertz theory was seen in the case of subsurface damage: significant delamination was observed adjacent to impact sites on coatings where the depth of maximum shear stress was close to the coating– substrate interface. This finding needs to be borne in mind when designing coated systems for use in erosive environments or applications where impact resistance is required
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
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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