1,721,059 research outputs found
Optimisation of railway wheel profiles using a genetic algorithm
No full textThis paper presents the procedures and preliminary results of a novel method for designing wheel profiles
for railway vehicles using a genetic algorithm. Two existing wheel profiles are chosen as parents and
genes are formed to represent these profiles. These genes are mated to produce offspring genes and then
reconstructed into profiles that have random combinations of the properties of the parents. Each of the
offspring profiles are evaluated by running a computer simulation of the behaviour of a vehicle fitted with
these wheel profiles and calculating a penalty index. The inverted penalty index is used as the fitness
value in the genetic algorithm.
The method has been used to produce optimised wheel profiles for two variants of a typical vehicle, one
with a relatively soft primary suspension and the other with a relatively stiff primary suspension
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
The Dynamics of Railway Freight Wagon Wheelset with Dry Friction Damping in the Suspension
No full textNon-linear dynamic techniques v. equivalent conicity methods for rail vehicle stability assessment
No full textThis paper is to record a special discussion meeting held on 26 th August 2003 during the 18th IAVSD Symposium in Atsugi, Kanagawa, Japan, with the particular objective of answering the question "Should we use the term Equivalent Conicity?". The subject is introduced, the subsequent discussion is documented, and some final conclusions and recommendations are given
The Dynamics of the Three-Piece-Freight Truck
Get PDFAlthough the three-piece-freight truck is a simple design its mathematical model is very complicated. The model is definitely a nonlinear dynamical system, where the nonlinearities arise from the nonlinear kinematic and dynamical contact relations between wheels and rails, the suspensions and the nonlinear dry friction damping with hysteresis and stick-slip action. The bolster moves both vertically and laterally relative to the truck frames, so the friction forces on the contact surfaces of the wedges must be treated as two-dimensional vectors, and the same holds for the dry friction on the surfaces of the adapters. Due to the clearances between the car body and the side supports on the bolster, the side supports must be modelled as nonlinear dead-band springs. The stick-slip action and the play between elements of the truck makes the dynamical model a structure varying system. We present the dynamical system that models the dynamics of the moving wagon and show the result of numerical dynamical investigations such as the calculation of the critical speed, and the dynamics of the wagon on an irregular track and compare them with test results and simulation results using NUCARS
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
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