1,720,966 research outputs found
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
Fluid modeling of pressure anisotropy effects in a magnetized plasma
No full textIt is well known that in many cases the dynamics of a magnetized plasma involve a very large number of scale lengths and frequencies which, even if separated by several orders of magnitudes, are intrinsically connected one each other. Such a system cannot be studied by solving numerically the whole dynamics, but it is necessary to make appropriate approximations in order to simplify the analysis and work out a model able to capture the main features that characterize the evolution
of the system. Therefore, a suitable fluid modeling, capable of including the main kinetic effects, is of primary importance for the description of space and laboratory plasmas. Moreover, space and laboratory plasma are characterized by the presence of a background magnetic field which introduces conditions for a more complex dynamics, globally modifying the symmetry of the system. From a theoretical point of view, the set of fluid equations cannot be closed by means of the usual adiabatic relation on the pressure term, because of the different behaviour along or perpendicular to the magnetic field. Therefore, the pressure tensor cannot be longer assumed as isotropic.
An appropriate alternative is to adopt a model based on the double adiabatic invariants of particle motion. This theory, proposed by Chew, Goldberger and Low (CGL), gives two conservative equations for the parallel and the perpendicular pressures, allowing the system to follow a different evolution for each component. Depending if the level of pressure anisotropy overcomes some given threshold, the
magnetized plasma becomes unstable under two important anisotropy instabilities: the firehose instability (FHI) and the mirror instability (MI). These instabilities tend to compensate the pressure unbalance changing the equilibrium configuration of the system.
The development of a pressure anisotropy is a relevant process which may be involved in many problems of space and laboratory plasmas. The phenomenon analysed in this work is the non-linear evolution of vortices generated by the Kelvin-Helmholtz instability (KHI), which occurs in the solar wind-magnetosphere interaction. Multi-spacecraft measurements have provided unambiguous evidence for rolled-up vortices as well as observed boundary layer features resulting from the suggested KH instability. This important mechanism is supposed to be the best candidate for the formation of a mixing layer along the low latitude flanks of the magnetosphere during the northwards conditions (when the solar-wind field and geomagnetic field are parallel), providing an efficient way for the solar wind plasma to enter the magnetospheric region. Indeed, the magnetic field line reconnection, which is the dominant process in the southwards conditions, cannot explain experimental data in the opposite northwards configuration, when the mixing process is larger than expected. The vortex motion is in turn the source of secondary magneto-fluid instabilities, e.g. magnetic reconnection, KH, Rayleigh-Taylor. The characteristic time scales of these secondary instabilities have a crucial role in the competition with the vortex pairing hydrodynamic process, driving a disruptive process inside and outside the vortices. During this non-linear dynamics, the firehose instability may have an important role in the evolution of the magnetic field configuration, considerably increasing the small in-plane component and bringing the system in a more complex turbolent state.
The present work has the purpose to study the development of the pressure anisotropy during the formation of vortex structures driven by an initial shear velocity configuration and their non-linear evolution. The simplified 2D dynamics is defined by the velocity field and the perpendicular inhomogeneous direction. The shear velocity length and the magnetofast Mach number characterize the vortex motion. Several initial configurations, concerning the subsonic and supersonic regimes and the presence of a density gradient, have been investigated during the linear KHI development and during the evolution of its non-linear stage. More attention has been given to the compressibility property connected to the pressure anisotropy evolution. In particular, it has been observed that in the supersonic regime the pressure anisotropy is large enough to be able to drive the FH instability. Moreover, its linear growth can occur on a much smaller time-scale compared to the vortex dynamics, competiting with the pairing and the secondary instabilities processes. Finally, in this work we have also started to consider the full 3D system. In particular, we have focused our attention on the development of the FH instability. The preliminary work is limited to the analysis of the linear growth rate of the FH instability assuming as initial state several anisotropy conditions
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
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
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