1,720,991 research outputs found
Active Control in Railway Vehicles
No full textThe most notable progress which has taken place in the design and development of railway rolling stock over the last few decades is the increasing integration of electronics and control in rail vehicles which used to be purely mechanical systems [1,2].
The aim of this paper is to survey the applications of active control and mechatronics in railway vehicles, providing an overview of active control technologies which have recently been brought to the level of revenue service, of ongoing research topics still under development that have already proven their potential through experimental demonstration, and of more "blue sky" oriented research which is likely to impact upon rail vehicles on a longer timescale. In particular, this review will cover the topics of active primary and secondary suspensions and active pantograph control.
From the implementation point of view, it is noticeable that the introduction of active control remains fairly restricted: tilting of course is now an accepted, relatively mature technology with widespread use [3], but there is only one operational example of any other type of active secondary suspension [4]. Furthermore, although active primary suspension technology is offered by one manufacturer, at present this has not been incorporated into operational trains. With respect to active pantographs, few experimental versions exist (e.g. [5]), but again none have been applied in revenue operation.
History shows, however, that there are inexorable trends toward better performance requirements, and it is likely that sooner or later various types of active technology will become standard within the railway industry: much as has already happened for aircraft and is happening for automobiles. It is not obvious in which way railways are so different from these other transportation modes that they should not follow the lead of these other industries.
There are also significant economic and political pressures to reduce the cost of railways: not only the price of tickets for the passengers, but also the subsidies from national governments. However, the biggest cost reductions are likely to arise from active solutions that affect both sides of the vehicle/track interface, in which case, there are difficulties with realising such innovations when many train operations are financially separated from the infrastructure.
In the longer term, consideration could be given to new configurations, in particular taking advantage of mechanical simplifications afforded by the use of control technology, and essentially trading off mechanical for electronic complexity in the true spirit of a mechatronic approach
Concepts and prospects for actively-controlled railway running gear
No full textAs active suspension control is becoming an established technology for railways, it is time to look forward to further extensions of the basic concept, especially its application in controlling the wheels and wheelsets of rail vehicles. This article reviews the background to the subject, including an identification of basic configurations and technology options, before providing a summary of known concepts and the corresponding control strategies. The final section speculates upon the longer-term trends, in particular, to suggest what will be the overall impact upon suspension design
Active suspension for a two-axle railway vehicle
No full textThe aim of this paper is to investigate how the ride quality of a two-axle railway vehicle with single-stage suspension might be improved by the use of active control, compensating for the lack of the double suspension stage, and thereby taking full advantage of vehicle lightweight construction. The basic requirement is to improve the ride quality on random track unevenness while keeping suspension deflection within acceptable levels when the vehicle negotiates deterministic track features such as a gradient.
Two active suspension configurations are considered – skyhook damping and linear quadratic Gaussian (LQG) optimal control. Finally, actuator dynamics are included in the analysis, to assess the impact on the overall success of an active suspension implementation. The paper shows that both skyhook and LQG control strategies offer significant improvements in ride quality and also that careful design of the actuators and their force control loops is essential
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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