1,721,083 research outputs found
How to make large, void-free dust clusters in dusty plasma under micro-gravity
No full textCollections of micrometer-sized solid particles immersed in plasma
are used to mimic many systems from solid state and fluid physics, due to their
strong electrostatic interaction, their large inertia, and the fact that they are large
enough to be visualized with ordinary optics. On Earth, gravity restricts the
so-called dusty plasma systems to thin, two-dimensional (2D) layers, unless
special experimental geometries are used, involving heated or cooled electrons,
and/or the use of dielectric materials. In micro-gravity experiments, the
formation of a dust-free void breaks the isotropy of 3D dusty plasma systems.
In order to do real 3D experiments, this void has somehow to be closed. In this
paper, we use a fully self-consistent fluid model to study the closure of a void
in a micro-gravity experiment, by lowering the driving potential. The analysis
goes beyond the simple description of the ‘virtual void’, which describes the
formation of a void without taking the dust into account. We show that selforganization
plays an important role in void formation and void closure, which
also allows a reversed scheme, where a discharge is run at low driving potentials
and small batches of dust are added. No hysteresis is found this way. Finally, we
compare our results with recent experiments and find good agreement, but only
when we do not take charge-exchange collisions into account.Dusty plasmaNumerical simulationVoid closureMicrogravit
Hydrodynamic and kinetic modelling of complex radio-frequency plasmas
No full textIn this paper hydrodynamic and kinetic approaches to model low-pressure capacitively coupled complex radio-frequency discharges are discussed and applied to discharges under micro-gravity. Complex plasmas contain dust grains with a large negative charge and are characterized by a strong coupling between the properties of the plasma and those of the dust grains. After a discussion of the physics and methods involved, examples are presented from modelling of experiments under micro-gravity in the PKE-Nefedov reactor on board the International Space Station. These discharges are simulated with a 2D cylindrically symmetric hydrodynamic model. Kinetic effects are studied with a 1D particle-in-cell plus Monte Carlo model in which capture and scattering by dust grains is included. Since experiments are often performed at low pressures, the electron energy distribution function is no longer determined by the local plasma properties. This has consequences for the charging of the dust. Results of simulations with this model are compared with the hydrodynamic results. In addition, we address the behaviour of the dust charge in decaying plasmas
Modelling of Voids in Complex Radio Frequency Plasmas
Full text linkIn this paper hydrodynamic and kinetic approaches to model low pressure capacitively coupled complex radio-frequency discharges are discussed and applied to discharges under microgravity. Experiments in the PKE-Nefedov reactor on board the International Space Station, as well as discharges in which gravity is compensated by means of thermophoresis are simulated with a 2-D cylindrically symmetric hydrodynamic model. Kinetic effects are studied with a 1-D Particle-In-Cell plus Monte Carlo model in which capture and scattering by dust grains is included. Simulations with this model address non-local effects and modulated discharges. (C) WILEY-VCH Verlag GmbH & Co. KGaA, Weinhei
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
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
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