1,720,974 research outputs found
Complex railway systems: capacity and utilisation of interconnected networks
Full text linkIntroduction Worldwide the transport sector faces several issues related to the rising of traffic demand such as congestion, energy consumption, noise, pollution, safety, etc. Trying to stem the problem, the European Commission is encouraging a modal shift towards railway, considered as one of the key factors for the development of a more sustainable European transport system. The coveted increase in railway share of transport demand for the next decades and the attempt to open up the rail market (for freight, international and recently also local services) strengthen the attention to capacity usage of the system. This contribution proposes a synthetic methodology for the capacity and utilisation analysis of complex interconnected rail networks; the procedure has a dual scope since it allows both a theoretically robust examination of suburban rail systems and a solid approach to be applied, with few additional and consistent assumptions, for feasibility or strategic analysis of wide networks (by efficiently exploiting the use of Big Data and/or available Open Databases). Method In particular the approach proposes a schematization of typical elements of a rail network (stations and line segments) to be applied in case of lack of more detailed data; in the authors’ opinion the strength points of the presented procedure stem from the flexibility of the applied synthetic methods and from the joint analysis of nodes and lines. The article, after building a quasiautomatic model to carry out several analyses by changing the border conditions or assumptions, even presents some general abacuses showing the variability of capacity/utilization of the network’s elements in function of basic parameters. Results This has helped in both the presented case studies: one focuses on a detailed analysis of the Naples’ suburban node, while the other tries to broaden the horizon by examining the whole European rail network with a more specific zoom on the Belgium area. The first application shows how the procedure can be applied in case of availability of fine-grained data and for metropolitan/regional analysis, allowing a precise detection of possible bottlenecks in the system and the individuation of possible interventions to relieve the high usage rate of these elements. The second application represents an on-going attempt to provide a broad analysis of capacity and related parameters for the entire European railway system. It explores the potentiality of the approach and the possible exploitation of different ‘Open and Big Data’ sources, but the outcomes underline the necessity to rely on proper and adequate information; the accuracy of the results significantly depend on the design and precision of the input database. Conclusion In conclusion, the proposed methodology aims to evaluate capacity and utilisation rates of rail systems at different geographical scales and according to data availability; the outcomes might provide valuable information to allow efficient exploitation and deployment of railway infrastructure, better supporting policy (e.g. investment prioritization, rail infrastructure access charges) and helping to minimize costs for users.The presented case studies show that the method allows indicative evaluations on the use of the system and comparative analysis between different elementary components, providing a first identification of ‘weak’ links or nodes for which,
then, specific and detailed analyses should be carried out, taking into account more in depth their actual configuration, the technical characteristics and the real composition of the traffic (i.e. other elements influencing the rail capacity, such as: the adopted operating systems, the station traffic/route control & safety system, the elastic release of routes, the overlap of block sections, etc.)
Procedure di valutazione di capacità/puntualità e misure di accessibilità per reti ferroviarie / Capacity versus punctuality assessment procedures and accessibility measures for rail networks
No full textL’articolo fornisce un riesame e un confronto pratico di diverse metodologie per la valutazione della capacità e puntualità ferroviaria; viene anche proposto e analizzato un approccio semplificato e maneggevole per la loro stima in caso di analisi preliminari o di vasta scala, basato su formulazioni consolidate per il calcolo del tempo di viaggio, dei ritardi e della capacità utilizzata.
Un tale approccio risulta particolarmente rilevante per la stima di alcuni indicatori operativi e di performance
in mancanza di dati dettagliati relativi all’infrastruttura e/o al programma di esercizio. In particolare i suddetti indicatori sono stati anche integrati in un’analisi di accessibilità ferroviaria; i risultati complessivi forniscono ai decisori politici un valido strumento per identificare le aree più o meno accessibili su rotaia e come/dove miglioramenti delle infrastrutture e dei livelli di servizio potrebbero beneficiare gli utenti.The article provides a review and a practical comparison of capacity and punctuality assessment methodologies; it also identifies and evaluates a manageable and streamlined approach to their estimation for preliminary or large-scale analysis based on consolidated formulations for travel time, delay and utilized capacity. This becomes particularly relevant in absence of detailed infrastructure and timetable data as we aim at evaluating some fundamental operational and performance indicators. Secondly, these parameters are integrated in an accessibility analysis by rail; the overall outcomes provide a valuable tool for decision makers to identify areas more or less accessible and how/where improvements in infrastructure and levels of service could benefit users
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
An analysis of the railway access charges regime in the Italian context
No full textAn appropriate access charges regime represents the basis for implementing an open market and for guaranteeing fair competition in the rail sector. In accordance with the recent European and national legislations, the Italian rail infrastructure manager has lately presented a new charges scheme with a better cost orientation and a deeper market segmentation based on the ability to pay. This paper describes and compares the new and the previous regimes, presenting a case study on selected Italian corridors. Interesting insights are added by applying a data envelopment analysis to rank the efficiency of the rail segments considering the different standpoints of three stakeholders: infrastructure manager, rail operators and rail regulator. The results of the case study, beside showing different patterns by applying the two charges schemes, suggest that high-speed services may better respond to the needs of infrastructure manager and rail regulator while the rail operator's perspective ranks better short connections by regional trains (especially under the new regime). This evaluation framework could help policy makers, transport authorities or railway stakeholders to identify where and how benefits could be gained or lost and by whom
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
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