1,720,993 research outputs found
Visualizing the Intellectual Structure of Iranian Physicists in Scisearch during 1990-2009: An Author Co-Citation Analysis (ACA)
Full text linkThe purpose of this paper was to study and map the intellectual structure of Iranian physicists using author co-citation technique during 1990-2009. The results of the study showed that Iranian physicists have produced 6290 documents indexed in Science Citation Index (SciSearch) during the studied period. Publication counts have grown at an approximate rate of 24/70 % per year. Setare M.R. with 121 documents was the most productive Iranian author in this study. Applied Physics, with1564 documents was the most interesting subject area for the Iranian physicists. We identified 42 Iranian and international physicists who were highly co-cited in 6290 documents during the studied period. Using principal components analysis, 8 subject factors were extracted. The subject areas of factors were in: "Physics, Particles & Fields", "Astronomy & Astrophysics", “Physics, Mathematical", “Physics, Multidisciplinary", "Physics, Nuclear", "Cosmology", "Physics, Atomic, Molecular & Chemical", and "Physics, Fluids & Plasmas". The PFNet map of the intellectual structure of Iranian physicists in SciSearch during 1990-2009 showed a central subject area in "Physics, Particles & Field" with Witten E. as its focal author. The other clusters were rooted in this essential cluster
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
Surface vacuum energy and stresses for a brane in de Sitter spacetime
No full textAbstractVacuum expectation values of the surface energy–momentum tensor is investigated for a massless scalar field obeying mixed boundary condition on a brane in de Sitter bulk. To generate the corresponding vacuum surface densities we use the conformal relation between de Sitter and Rindler spacetimes
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
Generalized second law of thermodynamics in quintom dominated universe
No full textAbstractIn this Letter we will investigate the validity of the generalized second law of thermodynamics for the quintom model of dark energy. Reviewing briefly the quintom scenario of dark energy, we will study the conditions of validity of the generalized second law of thermodynamics in three cases: quintessence dominated, phantom dominated and transition from quintessence to phantom will be discussed
Holographic Chaplygin gas model
No full textAbstractIn this Letter we consider a correspondence between the holographic dark energy density and Chaplygin gas energy density in FRW universe. Then we reconstruct the potential and the dynamics of the scalar field which describe the Chaplygin cosmology
The self-gravitational corrections as the source for stiff matter on the brane in SAdS5 bulk
No full textAbstractA D3-brane with non-zero energy density is considered as the boundary of a five-dimensional Schwarzschild–anti-de Sitter bulk background. Taking into account the semi-classical corrections to the black hole entropy that arise as a result of the self-gravitational effect, and employing the AdS/CFT correspondence, we obtain the self-gravitational correction to the first Friedmann-like equation. The additional term in the Hubble equation due to the self-gravitational effect goes as a−6. Thus, the self-gravitational corrections act as a source of stiff matter contrary to standard FRW cosmology where the charge of the black hole plays this role
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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