1,721,148 research outputs found
Systematic Validation of a Mathematical Model of ACAS Operations for Safety Assessment Purposes
No full textInternational audienceCurrent international regulations and policies do not consider the effect of airborne safety nets in the analysis of safety risks. This widely accepted practice tends to create significant tension between the realization of the ambitious safety improvement targets of SESAR and NextGEN, and standing regulations. In order to close this gap, there is a need for systematic development of safety risk analyses of airborne safety nets within an Air Traffic Management context. The aim of the research described in this paper is to address the systematic validation of an unambiguous mathematical model of Airborne Collision Avoidance System (ACAS) operations, together with its interactions with own and other pilots and with air traffic controllers. The specific modelling formalism used for this is Stochastically and Dynamically Coloured Petri Nets (SDCPN); which supports both mathematical analysis as well as Monte Carlo simulation. In order to build confidence, the focus of this paper is on the performance of a systematic validation of the developed model. This validation includes both comparisons against " real data " and comparison with the results of Eurocontrol's ACAS simulation model. Initial application of this validation process to the novel model shows that it is at least as good as the existing ACAS simulation model. However, the added value is that the novel model defines both an unambiguous mathematical model as well as an unambiguous simulation model
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
Development, validation and application of stochastically and dynamically coloured Petri net model of ACAS operations for safety assessment purposes
No full textInternational audienceIn view of the SESAR and NextGEN objectives of increasing both the capacity and the safety of the Air Traffic Management (ATM) system, there is a need to conduct safety risk analysis of current or new operations, covering the joint effect of airborne and ground-based safety nets in ATM. The subject of the research presented in this paper is Airborne Collision Avoidance System (ACAS) which presents an airborne safety net within an ATM context, for current practices as well as advanced concepts. The aim of the research described in this paper is fivefold: (a) to verify existing ACAS models regarding their coverage of evaluation needs of ACAS operations; (b) to develop a stochastic and dynamical model of ACAS II including interactions with pilots and air traffic control; (c) to develop a systematic validation process that allows building model confidence; (d) to initially apply this validation process to the newly-developed ACAS model; and (e) to use the ACAS model to assess the potential collision risk reduction by ACAS II for a historical en-route mid-air collision event. The specific modelling formalism used for this is Stochastically and Dynamically Coloured Petri Nets (SDCPN). The developed SDCPN-based ACAS model contains the technical, human and procedural elements of ACAS operations and fully supports mathematical analysis as well as rare event Monte Carlo simulation of aircraft encounters. In order to build confidence into the developed model and to judge model credibility, a systematic multilevel validation process is defined and is successfully applied. The SDCPN-based ACAS model is demonstrated to work well for a historical en-route mid-air collision event and is very powerful in determining the most critical elements contributing to the non-zero collision risk of ACAS operation
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