1,720,955 research outputs found
Advanced Diagnostics for a Position Control System of the Pantographs of Tilting Trains
No full textHigh speed tilting trains are a smart solution to guarantee shorter travelling time with respect to conventional trains without the need of major investments to renew the railway network. A design issue associated to the train carbody tilting is the need to keep the pantograph centred with respect to the catenary that runs aligned to the rails. The solution used in most tilting trains is to mechanically link the pantograph to the bogie: it is a simple design concept, but the mechanical structure connecting the pantograph to the bogie takes away useful space from the carbody interior. For this reason, a solution used in recent tilting trains is to connect the pantograph to the carbody roof and implement a position control system in order to keep the pantograph centred with the catenary. This paper specifically addresses the case of a pantograph position control performed by two servovalve controlled, spring centred hydraulic actuators mounted in opposite pair, each equipped with a position transducer for position control and system monitoring. The monitoring system presently implemented in this servocontrol detects the servocontrol failures, but in case the two position transducers provide a conflicting information, it is not always able to sort out which of the two transducers is failed. As a result, a position transducer failure always leads to disabling the tilting function and reducing the train speed, and then to remove and replace the entire pantograph, because the functionality of each individual transducer can only be checked at shop level. An advanced diagnostic system was hence developed that can both identify the presence of a failure and recognize which of the two position transducers is the failed one. In case of a transducer failure is thus possible to isolate the failed transducer and keep the pantograph position control operational, thereby retaining the train tilting function. A further merit of the advanced diagnostic system is the reduction of maintenance time and costs because the failed transducer can be replaced without removing the entire pantograph from the train. The merits of the presented health management system were assessed running several simulations of a model representing the dynamic response of a train pantograph. These simulations were performed, both in normal and in failed conditions, in order to assess the ability of the implemented advanced diagnostic system to properly identify a failure of one or both position transducers and to avoid false alarms. The transducers health management process described in this paper was first tested simulating different tracks over the whole range of normal operating and environmental conditions, and appropriate limits for the failure detection were established to prevent false alarms. Then, all types of transducers failures and malfunctionings were injected and the ability of the health management system to recognize them was positively assessed. The results of the entire simulation campaign proved the robustness of the proposed transducers health management system and a confidence was hence gained in its ability to detect a transducer failure or malfunctioning with minimum risk of false alarms or missed failures. The implementation of such health management system on a tilting train will thus enable the tilting operation to continue after a failure of a pantograph lateral position sensor, hence allowing the train to maintain its high speed travel for the remainder of the ride. Furthermore, the positive recognition of a transducer failure would greatly ease the maintenance operation, since the failed transducer can be replaced without the need of removing the entire pantograph assembly from the train roo
Health management system for the pantographs of tilting trains
No full textTilting trains are provided with the ability of rotating their carbodies of several degrees with respect to the bogies about the longitudinal axis of the train. This permits a train to travel at a high speed while maintaining an acceptable passenger ride quality with respect to the lateral acceleration, and the consequent lateral force, received by the passengers when the train travels on a curved track at a speed in excess of the balance speed built into the curve geometry. When the carbody is tilted with respect to the bogie, the train pantograph needs to remain centered with respect to the overhead catenary, which is aligned with the track. The conventional solution is to mechanically link the pantograph to the bogie, but recent tilting trains have the pantograph connected to the carbody roof while a position servoloop continuously control the pantograph position such to keep it centered with the catenary. The merit of this design is to allow a gain of the useful volume inside the carbody. The pantograph position servoloop uses two position sensors providing a redundant position information to close the pantograph feedback loop and perform system monitoring.
The monitoring functions presently implemented in pantograph position controls are able to detect the servocontrol failures, but in case of conflicting information from the two position transducers they are not always able to sort out which of the two transducer is failed because some failures of the position transducers cannot be detected by simply looking at the output signals of the transducer. As a result, if a difference between the output signals of the two position transducers is detected, the tilting function is disabled and the train speed is reduced. Also, the entire pantograph is then removed and replaced because the functionality of each individual transducer can only be checked at shop level.
Developing better diagnostic techniques for the pantograph position control system have been encouraged by the train companies, but no work on this subject has so far been performed. A research activity was hence conducted by the Authors, that was aimed at developing an advanced diagnostic system that can both identify the presence of a failure and recognize which of the two position transducers is the failed one. In case of a transducer failure it is thus possible to isolate the failed transducer and keep the pantograph position control operational, thereby retaining the train tilting function. A further merit of the advanced diagnostic system is the reduction of maintenance time and costs because the failed transducer can be replaced without removing the entire pantograph from the train.
The general architecture of this innovative diagnostic system, the associated algorithms, the mathematical models for the system simulation and validation, the simulation results and the possible future developments of this health management system are presented in the paper
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
- …
