1,720,971 research outputs found
Modeling the topside ionosphere by means of electron density values as recorded by the Swarm constellation
Full text linkThe topside part of the ionosphere lies above the ionospheric F2 layer peak and extends up to the plasmasphere. Since it contains a considerable part of the ionospheric plasma, its modeling is important for telecommunication’s purposes. In this work, electron density values recorded by Langmuir Probes on board the Swarm constellation are used as top anchor points by definite analytical functions (α-Chapman, β-Chapman, Epstein and Exponential) to investigate the variability of the topside plasma scale height H, a parameter which is crucial to perform a reliable modeling of the topside ionosphere. Bottom anchor points are provided by the IRIUP (International Reference Ionosphere UPdate) method, which is a method developed to update the IRI model relying on the assimilation of foF2 and M(3000)F2 data routinely recorded by a network of ionosonde stations. The IRIUP method calculates updated effective indices IG12eff and R12eff at each station of the network and, applying a universal Kriging method, generates maps of these indices which are then used to update the IRI output in terms of foF2 and hmF2. The height and electron density values of both top and bottom anchor points are used to obtain the H value, by means of a minimization procedure, making use of each of the aforementioned four topside analytical functions. The reliability of this approach is based on the hypothesis that H at heights around the F2 layer peak and for the first hundreds kilometers above is nearly constant, being this region dominated by O+ ions and with a temperature nearly constant. H values are statistically evaluated to look for any relevant relation with foF2 and hmF2. Moreover, a statistical comparison with COSMIC radio occulation profiles is carried out to asses which analytical profile function is the best one to represent the topside ionospheric profile, making use of the modelled H values
Effective solar indices for ionospheric modeling: a proposal for a real time regional IRI
Full text linkRadiation Explorer in the Far Infrared BreadBoard (REFIR/BB) for the atmospheric emission measurement in the 100- to 1100-cm-1 spectral range
No full textProceedings of SPIE Reprin
Effective solar indices for ionospheric modeling: a proposal for a real time IRI
Full text linkThe knowledge of accurate solar indices is essential to reliably forecast the conditions of the near-Earth space environment. The International
Reference Ionosphere (IRI) model, based on R12 and IG12 solar indices, provides a climatological depiction of the ionospheric plasma that can be
different from the real one, especially at solar terminator and for disturbed conditions. Assimilating data from a grid of ionosondes is possible to
obtain effective values of R12 and IG12 that can significantly improve the electron density representation made by the IRI model. Universal Kriging
interpolation method is employed for spatial mapping these indices
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
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