1,721,008 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
ANALYTIC RELATIONS BETWEEN CLASSICAL ORBITS IN CHAOTIC SYSTEMS, AND THEIR IMPLICATIONS FOR QUANTUM CHAOS
Get PDFThesis (Ph.D.), Physics, Washington State UniversityRare sets of classical orbits, such as the heteroclinic and periodic orbits, play central roles in various semiclassical sum rules, in which they sum up in interference-like ways to determine spectral quantities of quantum systems. The interferences between them are governed by the orbits’ classical actions and Maslov indices. In particular, the classical actions as the phase factors, are scaled by h. Therefore, even small errors in the actions will significantly compromise the accuracy of semiclassical calculations. Due to the “butterfly effect”, numerical determinations of orbits (thus their actions) become exponentially difficult with increasing orbit lengths, hindering the calculation of the system’s spectra on finer scales. In this study, we present new approaches for determining the classical actions of heteroclinic and periodic orbits using phase-space invariant structures, such as the stable and unstable manifolds, and the areas they enclose. These manifolds can be grown in fast and numerically stable ways, which completely bypass the exponential divergence inherent in chaotic systems. By relating orbits to phase-space areas, we also provide analytic expressions for universal action relations between classical orbits, which lead to corrections of the cycle expansion, and a novel scheme of expressing the exponentially proliferating set of homoclinic orbit actions in terms of a sub-algebraically growing set of phase-space areas, which represents a major reduction on the information input for semiclassical methods.Washington State University, Physic
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
Comment on "Ehrenfest times for classically chaotic systems"
No full textIn a recent Phys. Rev. E Rapid Communication, the authors, Silvestrov and
Beenakker, introduce a way to lengthen the Ehrenfest time, , for fully
chaotic systems. We disagree with several statements made in their paper, and
address the following points essential to their conclusions: 1) it is not true
that all semiclassical approximations for chaotic systems fail at a so-called
`logtime', , differing only by a numerical
coefficient; and 2) the limitation of the semiclassical approximation as
expressed in the authors' Eq. (8) is not limited by their argument leading to
Eq. (12)
Charge States of Thorium-229m: Path to Finding the Half-Life
Get PDFThis thesis was completed at the Washington State University Honors College. It received a ranking of "passed with distinction."After conducting my experiment, I was able to determine that the thorium-229 nuclei were indeed positively charged, which means that the isomers should decay to the ground state by bound internal conversion, emitting light in the process. By observing the emitted light, we should be able to measure the half-life of the isomer, which is the next step. After the half-life is observed, a nuclear clock can be built, and when compared with the atomic clock, we will know whether the fine structure constant is, indeed, a constant. Knowing the half-life of thorium-229m will also allow scientists to probe relationships between electrons and their nuclei, an area of physics that is typically difficult to do because of the large differences in energy between electrons and nuclei. This research could potentially open up an area of physics that is not well understood, and could also eventually show whether some fundamental constants are indeed constant.Honors College, Washington State Universit
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
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A reduced dimensional Monte Carlo method Preliminary integrations
Get PDFA technique for reducing the number of integrals in a Monte Carlo simulation is presented. For multidimensional integrals relying on classical equations of motions with localized weight functions, it is possible to integrate at least half of the variables prior to running a Monte Carlo simulation. An analysis of classical phase space structures shows the dynamics of nonlinear systems is reducible into composite subspaces that are either stable or unstable respectively. The subspaces that are stable leads to a local action-angle-like coordinate system corresponding to each constant of the motion. The techniques necessary for identifying the proper canonical coordinate transformations that decouple the local degrees of freedom are developed and shown to block diagonalize the stability matrix. The simple structure of these degrees of freedom allow them to bepre-integrated prior to the Monte Carlo simulation. With regards to the unstable subspaces, the technique takes advantage of universal properties of chaotic degrees of freedom to integrate over directions that exponentially contract in phase space. The method is demonstrated by calculating expectation values and return probabilities for a chaotic two dimensional coupled quartic oscillator within a classical Wigner method framework
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