1,721,163 research outputs found
Optimization of the Mix-Design System for the Sub-ballast Railroad
No full textBituminous sub-ballast is an alternative solution to the unbound granular sub-ballast used in the railway track due to several benefits that it can provide. Indeed, it contributes to maintain the moisture content in the subgrade unchanged during all year. This decreases the subgrade deterioration process. Moreover, the presence of bituminous sub-ballast can also reduce vertical stiffness variations on the track; it can have a positive effect in the maintenance needs at transition sections (bridge-embankment) and in the attenuation of the vibrations induced by the rail traffic. Despite the importance of the presence of the bituminous sub-ballast to conceive the construction and/or rehabilitation of sustainable infrastructure, in literature, there are only fragmentary information regarding the definition of benchmark criteria for their mix design. The superpave mix design approach used in road domain is applied systematically in the railway domain, without being adjusted for different load configuration of the rail track system. This research work aims at defining the benchmark criteria for the bituminous sub-ballast mix design to reduce the approximations involved in the recipe optimization due to the limitation of applying the superpave system in the railway domain. The methodology proposed aims at selecting the RESAL (rail equivalent single axle load) and therefore, transforming the entire traffic spectrum on the track lines in number of ESALs. Afterwards, the Ndesign has been calculated as function of the rail traffic level. Finally, a case study of bituminous sub-ballast mix design has been investigated for a first verification of the methodology proposed
Procedure for a Temperature-Traffic Model on Rubberized Asphalt Layers for Roads and Railways
Get PDFThe impact of temperature on the mechanical properties and thermal susceptibility of the railway bituminous sub-ballast layer, has served as motivation to develop the advanced measurement of thermal cycles in this layer and, an evaluation of the average seasonal temperatures interpolated by sinusoidal functions, of which characteristic parameters are determined. According to weather situation, Barber’s temperature model was used to prove the effectiveness for the railway superstructure. It is included the assessment of improved modified asphalt mixes performed with coarse rubber from scrap tires, having 1.5 to 3 percent of crumb rubber (particle size 0.2-4 mm) by weight of the total mix, as sub-ballast layer in railway and base layers on roads, recurring to the Superpave mix design compaction enhanced after computer simulations to evaluate real stresses derived from the rail traffic and climatic conditions. This article following the assessment of the average seasonal temperatures, involves the characterization of rubberized materials with attention to crumb rubber properties, designed with dry technology, to enhance the bitumen-rubber and binder-voids ratios. Indirect tensile strength and water sensitivity tests were applied for the evaluation of its mechanical properties including dynamic complex modulus at elevated temperature to measure the amount of bitumen absorbed by the rubber. The rubberized mix-results obtained and the comparison with a conventional HMA (hot mix asphalt) show that these dry rubber bituminous mixtures are particularly effective in damping vibrations. The purpose of using rubber modifiers in hot mix asphalt to obtain a stiffer-elastic sustainable material has been achieved for the assessment of its behavior in sub-ballast/base layers
CHARACTERIZATION OF RUBBERIZED ASPHALT FOR RAILWAYS
Get PDFRubberized asphalt mixtures are regarded as a solution for improving the strength of the rail-track section. The
recycled rubber has become an enhancer of the modified bituminous mixtures. In this work, it has been shown as
a sustainable improvement option in HMA mixes due to the elastic behavior exposed by the rubber particles. The
impact of thermal susceptibility on the mechanical properties of the railway bituminous sub-ballast layer has
served to the advanced measurement of the thermal cycles inside the rail track. Different simulations following
the Kentrack and Kenpave software were employed to be effective with the best mix-design for railways.
According to weather situation, reviewed temperature models were used to prove the effectiveness of the railway
superstructure. It is included the assessment of improved modified asphalt mixes with coarse rubber from scrap
tires, containing 1.5-3% of rubber (sizes 0.2-4mm) by weight of the total mix. Adopting the Volumetric mix design by the dry process was enhanced the characterization of rubberized materials after computer simulations
to evaluate stresses derived from the rail traffic and the average seasonal temperatures. The stiffer-elastic
sustainable rubberized mixes showed that is useful in the reduction of rail track damping vibrations
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe 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
Get PDF“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
Get PDFWe 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
Get PDFWe 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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