1,720,997 research outputs found
Distortion of the ULF wave spatial structure upon transmission through the ionosphere
No full textDistortion of the ground-based spatial structure of ULF waves is described in detail using analytical and numerical models of the resonant Alfven wave transmission through the “thin” ionosphere. The numerical calculations have been done for geophysical conditions corresponding to the midlatitude Borok Observatory and the low-latitude L'Aquila Observatory. As compared with a resonant field-aligned oscillation above the ionosphere, the ground spatial structure has the following additional features which have not been described by existing models: the amplitude peak is shifted northward, the width of it is changed, and amplitude and phase are modified. The effect is most evident when the resonant frequency and ionospheric conductivity are high. From a physical point of view the effect is caused by two reasons: (1) excitation of a diffusive-like surface-type mode in the ionosphere and (2) finite Earth's conductivity. The possible influence of the predicted distortion of the ULF field on various ground-based methods for the determination of the magnetospheric resonant frequency is discussed
Magnetotelluric sounding of the crust and hydromagnetic monitoring of the magnetosphere with the use of ULF waves
No full textJCR Journalope
Magnetic effects due to earthquakes and underground explosions: a review
No full textThe physical nature of quasi-static and transient anomalies in the geomagnetic field induced by underground explosions or earthquakes is reviewed. New theoretical results obtained recently and so far little known to general circles of geophysicists are presented. The physical nature of residual magnetic and electrotelluric fields at the explosion point are considered. The seismic waves from explosions or distant earthquakes are suggested to be used as a tool for the preliminary probing of the Earth's crust sensitivity to various seismo-electromagnetic effects. The use of magnetic induction effects for tsunami detection and for crust sounding is outlined. The nature of ULF magnetic impulses related with earthquakes is discussed.JCR 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
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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