1,721,153 research outputs found
Instability of a quasi-neutral plasma soliton-like perturbation in the presence of an oscillating electric field
No full textThe stability of a quasi-neutral envelope soliton perturbation is investigated in the presence of a time-varying oscillating electric field is an unmagnetized plasma. It is shown that in the early time of the slow plasma response, the envelope perturbation is unstable, resulting in a purely growing mode on account of the driver energy. © 1989
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
Constants of motion in the dynamics of a 2N-junction SQUID
No full textWe show that a 2N-junction SQUID (superconducting quantum interference device) made of 2N overdamped, shunted, identical junctions may be described as a system having only six degrees of freedom for any N ≥ 3. This is achieved by means of the reduction introduced by Watanabe and Strogatz [Physica D 74 (1994) 197] for series biased arrays. In our case six rather than three degrees of freedom are necessary to describe the system, due to the requirement of phase quantization along the superconducting loop constituting the device. Generalization to multijunction parallel arrays is straightforward
Modification of the ion background profile in the nonlinear electron-plasma oscillations
No full textWe give an approximate analytical solution, correct to the first order in m\M, the electron to ion mass ratio, for the ion background modification under the influence of the free non linear electron plasma oscillations driven by the initial unbalance between electron and ion density distribution, n(e)(x,0) = n0 and n(i)(x, 0) = n0(1 + alpha cos kx). When the electron plasma oscillations grow starting from a very small perturbation (alpha less-than-or-similar-to 0.02), we find a remarkable modification in the ion background profile before the electron oscillation wavebreaking takes place
X-RAY ENERGY SPECTRUM MEASUREMENTS BY AN ANNULAR SUPERCONDUCTING TUNNEL JUNCTION WITH TRAPPED MAGNETIC FLUX QUANTA
No full textVariations 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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