1,720,955 research outputs found
Disc machine testing to assess the life of surface-damaged railway track
No full textWheel-rail contacts operate in an arduous and contaminated environment. Railway track running surfaces can become damaged either prior to or during operation. This work is aimed at understanding how that surface damage can affect the life of railway track. Pre-damaged surfaces and track damaged by the entrainment of solid contaminants are considered under both oil and water lubrication. A series of small-scale laboratory experiments has been carried out on a twin-disc rolling-sliding test machine. The test discs are artificially indented and run under typical wheel-rail contact conditions. The experimental results revealed that artificial dents only reduce the fatigue life of the contact under oil, but not water lubrication. With oil lubrication the fatigue failure initiates close to the location of the surface defect. However, with water as the lubricant the whole of the surface undergoes cracking with the defect having no preferential effect. Studies have also been carried out to investigate the damage caused by the entrainment of solid particles into the wheel-rail contact. This kind of damage can accelerate surface fatigue and also lead to excessive wear. An attempt has been made to quantify the wear process and develop a simple empirical model
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
Wear and Fatigue of Railway Track Caused by Contamination, Sanding and Surface Damage
Full text linkThe wheel rail contact operates in an arduous
environment. Damage to the surface of either
component is possible during manufacture, installation,
or operation. The question arises as to how tolerant is
the railway wheel or section of track to surface
indentation or damage.
In this work a twin disc simulation has been used
to relate the level of surface damage (as well as the way
it is generated) to the fatigue life of the surfaces. A
related problem is the presence of solid contamination
on the track. Sand (applied for improved adhesion) or
track ballast material can cause damage to the rail and
wheel surfaces. These mechanisms have been explored
to assess the effect on contact fatigue life and wear. The
disc specimens have been either artificially damaged
(with dents and scratches) or run with particles of sand
or ballast material. The discs were then loaded and
rotated at realistic conditions of contact pressure and
controlled slip.
For normal operation of the contact, either dry or
with water lubrication, surface dents and scratches have
little effect on fatigue life. The normal plastic flow in
the rail surface layer acts to close up dents. The failure
of the disc is then by fatigue cracking across the whole
surface with no particular preference to the dent
location. Alternatively, if the contact is lubricated with
oil then this plastic flow is greatly reduced and the dents
act as stress raisers and fatigue cracks initiate from their
trailing edge.
Sand or ballast particles are crushed as they enter
the wheel/rail contact. The fragments indent the surfaces
and rapidly roughen the contact faces. The surface
indentation is relatively minor, but the presence of
particles increases the level of traction (over the wet
case) and promotes further surface plastic flow. This
can reduce the residual fatigue life of the contact.
Further, high concentrations of sand were shown to
promote a low cycle fatigue process that caused very
high wear by the spallation of material.
The twin disc simulations have shown that, under
conditions similar to that of wheel/rail operation,
surface damage is not a primary cause of fatigue failure.
However, wear is greatly accelerated by the presence of
solid contaminants and some evidence of a low cycle
fatigue process was observed for sanded contacts
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
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
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