1,721,259 research outputs found
Time-evolution of phonon spectra during decomposition in AgxNa1-xBr ionic crystals
No full textReal-time inelastic neutron scattering has been used to characterise the mechanism of decomposition in AgxNa1-xBr mixed single crystals well below the critical temperature on a microscopic scale. The chemical demixing process is associated with a splitting of acoustic phonon branches, which is observed to take place within some 100 s. Interestingly, the Bragg reflections exhibit a completely different time behaviour: the adaptation of the equilibrium lattice parameters occurs on a much longer time scale. Hence, decomposition is governed by large coherency strains which persist over a long period of time. Only in a second stage does the crystal lattice relax into the final equilibrium state
Kinetics of decomposition in ionic solids: III. Time evolution of phonons during spinodal decomposition in AgCl-NaCl
No full textReal-time inelastic neutron scattering has been used to study the kinetics of the demixing process in AgCl-NaCl mixed single crystals. The variation of transverse acoustic phonon spectra provides the most direct information about the microscopic non-equilibrium behaviour. It is shown that a well defined splitting of phonon peaks corresponding to the formation of the product phases takes place on a timescale of seconds. Along with the observation of satellite reflections these findings clearly demonstrate that the phase separation is governed by the mechanism of spinodal decomposition in this ionic system. During the entire process the lattice parameter keeps almost unchanged, thus leading to a metastable state characterized by large coherency strains
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
Time-resolved phonons as a microscopic probe for demixing processes
No full textTime-resolved inelastic neutron scattering from acoustic phonons has been used to characterise the mechanism of demixing in ionic crystals of the silver alkali halide type. Stroboscopic techniques allow to study the time-evolution of phonon spectra during the phase separation in AgBr-NaBr and AgCl-NaCl single crystals on a time scale of seconds. These data provide the most direct information about changes of interatomic interactions. Characteristic differences are observed for ageing temperatures above and below the spinodal temperature which allow to distinguish between different mechanisms based on nucleation on the one hand and concentration fluctuations on the other. (C) 2004 Elsevier B.V. All rights reserved
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
Kinetics of decomposition in ionic solids: IV: Transition between nucleation and spinodal decomposition observed by time-resolved phonon spectroscopy
No full textReal-time inelastic neutron scattering has been used to study the kinetics of the demixing process in AgBr-NaBr mixed single crystals. The variation of transverse acoustic phonon spectra provides most direct information about the microscopic non-equilibrium behaviour. The phase separation is monitored by a well defined splitting of phonon peaks that reflects the different dynamical behaviours of the constituents. As a function of temperature, time evolution of the phonon spectra changes drastically, thus proving unambiguously that the demixing process is dominated by nucleation in the high-temperature regime and by concentration fluctuations at low temperatures
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
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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