1,720,960 research outputs found
Prediction of Rail Damage on Underground-Metro Lines
Get PDFSafety and reliability of rails primarily depend on detection, monitoring and maintenance of rolling contact fatigue (RCF) defects. Since when they are undetected and untreated, they can further propagate and increase the risk of rail failures. Thereby, infrastructure managers (IMs) tend to detect these cracks at an early stage in order to manage this risk. After detection, the growth of these cracks should be monitored and efficient maintenance should be carried out to prolong the rail life. However, this requires reliable and sufficient field data with accurate prediction models of RCF damage and its counterpart damage mechanism; wear. Although the current models, which are particularly used on real track conditions, focus on mainline routes and were often validated using rail surface observations, lesser emphasis has been placed on underground-metro system tracks and the use of non-destructive testing (NDT) measurements particularly the crack depth which is a key parameter in the assessment of crack severity and maintenance planning.
In recent years, London Underground (LUL) has put additional effort to improve their rail inspection practices to support the optimisation of their rail maintenance strategy. Besides the use of several different NDT techniques, the magnetic flux leakage based sensor is used to measure the depth of detected cracks. Research suggested that this rail inspection data could be used to improve the accuracy of damage predictions. With the help of successive measurements, the severity of damage could be quantified and the changes in RCF estimations and its interaction with wear over time could be demonstrated. It was proposed that this should increase the confidence in prediction models for maintenance planning and help to support future maintenance optimisation.
Owing to use of different NDT techniques, a significant volume of field defect data was collected and examined in detailed during the research to understand the dominant damage mechanisms and the influential factors promoting RCF crack growth. It was found that severe damage is not limited to mainline and freight routes, with rails on metro lines also suffering from a high number of cracks. In addition, the various track data consisting of wheel-rail profile measurements, track geometry, vehicle speed diagrams and traffic information were also submitted. This provided a good opportunity to build detailed vehicle dynamics simulations for the selected lines to be further studied on LUL.
The Whole Life Rail Model (WLRM) and the Shakedown Map were selected as predictive models since, they can integrate with vehicle dynamics simulations. However, when the main input of WLRM; ‘Tγ’ was initially applied to LUL tracks, it was found that while, it successfully showed the effect of significant factors, it resulted in over-and under-estimation of the RCF damage in several locations. Therefore, the research investigated the interaction between the model parameters and their comparison on sites with and without reported RCF defects to find an optimum solution. The results indicated certain distinctions and hence, new wear and RCF damage prediction methods were developed using a combined Shakedown Map and Tγ approach.
Both of the methods were applied to selected LUL RCF monitoring sites. Whilst the wear method was applied to predict the loss in cross-section area of the rail, the new RCF crack depth prediction model was validated using the MRX-RSCM crack depth measurements. The location and severity of both damage types were successfully predicted. To observe and predict the changes in RCF damage including the interaction of wear over successive measurement intervals brought novelty to the study. In addition, the accuracy of predictions was improved on sites with various track characteristics such as high and low rail of checked and unchecked curved track section and tangent tracks
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
Rail surface damage management through monitoring and modelling
Get PDFRolling contact fatigue (RCF) cracking and wear significantly impact rail surfaces. The interaction between them is crucial; wear dominance can remove initiated cracks, while low wear rates may escalate crack propagation, elevating rail failure risks. Grinding, a preventive maintenance technique, removes remaining cracks, applied in fixed-interval or condition-based regimes. Operational constraints, favouring cyclic regimes, may potentially reduce rail life and increase costs. Thus, an optimal asset management strategy involves grinding based on current RCF condition and its predicted growth rate, considering its interaction with wear. London Underground employs diverse rail inspection methods, including advanced MRX-RSCM technology, to measure crack depth. Research used its measurements, developing a novel Combined Shakedown Map and Tγ approach. This predicts RCF growth under wear interaction, indicating the material to be removed by grinding. Its results are displayed for high and low rails of curved track sites, compared with monitoring measurements, enabling observation of changes in damage susceptibility and related grinding requirements over different rails
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