1,721,015 research outputs found
A single-station prediction model as a contribution to instantaneous mapping
No full textThe paper presents two opposite approaches for single-station prediction and forecast. Both methods are based on different assumptions of physical processes in the ionosphere and need the different set of incoming data. Different heliogeophysical data, mainly f0F2 parameters from the past were analyzed for f0F2 obtaining for the requested period ahead. In the first method - the autocovariance prediction method - the time series of f0F2 from one station are used for daily forecast at that point. The second method may be used for obtaining f0F2 not only at the particular ionospheric station, but also at any point within the considered area.JCR Journalope
Forecasting of ionospheric characteristics during quiet and disturbed conditions
No full textAn autocovariance forecasting procedure for single location ionospheric characteristics is presented. Its accuracy is illustrated as a function of the amount of time extrapolation for selected European stations under quiet and disturbed conditions.PublishedJCR Journalope
A single-station prediction model as a source of additional screen-points for PRIME model
No full textThe aim of this paper is to present a possible improvement to the global map of the f0F2 parameter obtained using statistical or any other model, by adding to it the additional screen points. The proposed method is illustrated by combining the CCIR model and a set of single points data. The comparison of the pure global CCIR model and CCIR model modified by the additional screen-points with measurements for different seasons and different solar activity is presented. The results show significant improvement of the f0F2 map.JCR Journalope
Impact of variability of space environmenton communications:Working Group 1 overview
No full textThe paper presents an overview of the scientific research carried out in the frames of Working Group 1 activities of the COST Action 271. The basic objective of this Working Group was the study of the impact of ionospheric variability on communications. The main achievements and an overall evaluation are reported.PublishedJCR Journalope
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
Regional study of the ionosphere quietness over Europe
No full textRegional catalogues of the ionospherically disturbed and quiet days are developed on the basis of the analysis of vertical-incidence sounding data over European area during 1964-1990. This paper presents the results obtained by comparing and combining two regional catalogues of the ionospheric disturbed and quiet days into one definitive catalogue recommended for implementation in the PRIME oriented and other studies. According to the criteria applied to the F region peak parameters, only 10 to 20% days per year manifest quietness of acceptable level. Comparison of ionospherically quiet days with geomagnetically quiet periods during 1976-1988 shows coincidence of quiet days in both fields not more than 30% of times considered. Conventional practice of analysis of the ionosphere state by comparing it with the geomagnetic conditions should be forerun by specification of the proper ionospheric quiet and disturbed periods.JCR Journalope
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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