1,720,956 research outputs found
Harmonics of the AC susceptibility for the study of I-V curves in melt grown YBCO
No full textThe measurements of the first and the third harmonics of the AC magnetic susceptibility, performed on melt grown YBCO samples as a function of the temperature and the external parameters (frequency and amplitude of AC magnetic field, intensity of a DC field) were studied by using the Cole–Cole plot analysis. By considering the AC field dependence of the third harmonics Cole–Cole plots, we have extracted information about the peculiar behaviour of the I–V characteristics and, therefore, about the dissipative phenomena in the sample. The experimental results have been analysed with the help of both analytical and numerical curves. In particular, the use of a phenomenological expression for the resistivity allowed us to reproduce the main experimental features, including the observed invariance of the area inside the Cole–Cole plots and their behaviour as a function of the AC field
Additional Non Equilibrium Processes in the Dynamic Interaction between Flux Quanta and Defects
No full textDetection of the flux creep regime in the AC susceptibility curves by using higher harmonic response
No full textIn order to investigate dynamic properties of the flux line lattice, the temperature dependencies of the basic and higher harmonic complex AC susceptibilities have been analyzed. In particular, the first (i.e., fundamental) and the third harmonic χ1,3(T) = χ′1,3(T)+iχ′′1,3(T), have been measured at different frequencies, and the measurements have been compared with both analytical and numerical results. In this way, by using a combined analysis of the first and the third harmonics, it is possible to affirm that the experimental behaviour of the χ′3(T) curves is due only to flux creep and flux flow dynamical processes for each temperature T lower than the temperature T* close to the peak temperature of the first harmonic imaginary part, Tp(χ′′1). In fact, in this temperature region, the χ′3(T) Bean critical state prediction does not agree with the experimentally detected magnetic response. Moreover, the experimental curves show that, when the frequency is increased, the flux dynamics always gets more relevant as compared to the critical state. Finally, the superposition of a DC field, HDC, much higher than the AC field amplitude, allows to evidence the contribution which is due only to flux creep events in the harmonic respons
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
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