1,720,957 research outputs found
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
Discrete auroral arcs and nonlinear dispersive field line resonances
No full textDispersive effects in field line resonances (FLRs) are discussed in the context of potential structures, parallel currents, and auroral density cavities observed by the FAST satellite. Our model includes the Earth's dipole magnetic field, and accounts for electron inertia, electron thermal pressure, finite ion gyroradius effects, and field aligned variations of the plasma density and ambient electron and ion temperatures. For realistic backgound parameters, we show that finite plasma temperature effects determine the dynamics of FLRs and that solitary wave structures evolve out of the resonance region, producing deep density cavities above the polar ionospheres. Results are shown to be in reasonable agreement with ground and satellite observations, with the exception of the magnitude of low altitude electric fields
Self‐consistent wave‐particle interactions in dispersive scale long‐period field‐line‐resonances
No full textUsing 1D Vlasov drift-kinetic computer simulations, it is shown that electron trapping in long period standing shear Alfvén waves (SAWs) provides an efficient energy sink for wave energy that is much more effective than Landau damping. It is also suggested that the plasma environment of low altitude auroral-zone geomagnetic field lines is more suited to electron acceleration by inertial or kinetic scale Alfvén waves. This is due to the self-consistent response of the electron distribution function to SAWs, which must accommodate the low altitude large-scale current system in standing waves. We characterize these effects in terms of the relative magnitude of the wave phase and electron thermal velocities. While particle trapping is shown to be significant across a wide range of plasma temperatures and wave frequencies, we find that electron beam formation in long period waves is more effective in relatively cold plasma
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
Ponderomotive saturation of magnetospheric field line resonances
No full textCompressional Alfvén waves in the terrestrial magnetospheric cavity constitute a discrete spectrum of global modes which can resonate with specific components of the continuum spectrum of shear Alfvén wave (SAW) field line resonant frequencies. We investigate the effect of the ponderomotive force (PF) of excited standing SAWs on the nonlinear saturation of field line resonances (FLRs). In low β plasmas FLR saturation occurs due to a nonlinear phase slip between the fast mode driver and SAW field. Ponderomotive forces also lead to density depletions at the ionospheres, nonlinear narrowing of the FLR and meridional scales comparable to those embedded within temporally modulated discrete auroral arcs. Observational features relating to these effects are discussed
Parallel electric fields in dispersive shear Alfvén waves in the dipolar magnetosphere
No full textExisting theories do not explain large parallel electric fields that are associated with keV electron precipitation in auroral arcs. The MHD electron response results in an electrical conductivity in the low altitude magnetosphere that is two orders of magnitude greater than is required. We suggest a new mechanism for forming parallel electric fields based on a nonlocal electron response to standing shear Alfvén waves on dipole magnetic fields. Electron trapping is the primary cause of a significant reduction in the collisionless electron conductivity and consequent enhancement of parallel electric fields in the 1–4 mHz frequency range
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