1,721,061 research outputs found
Laser pulse compression by coherent control in a Doppler broadened medium: Analytical and numerical studies
No full textWe have studied the temporal compression of laser pulses occurring in a scheme based on the coherent control peculiarities of electromagnetically induced transparency. This work extends earlier model studies, including the effect of Doppler broadening in a real hot medium. For definiteness and consistency of the atomic parameters employed, we have treated a scheme in argon. In this way, we establish a realistic model that enables us to predict quantitatively the performance of laser pulse compression experiments
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
Temporal pulse compression and retardation by incoherent all-optical control
No full textWe present a theoretical analysis of a new scheme for temporal retardation combined with temporal compression of weak laser pulses, optically controlled by the presence of one additional light pulse. A realistic realization of this scheme in hot Rb is discussed, showing that a large range of values of the optically controllable delay-bandwidth product can be obtained with a limited pulse distortion
Enhancement of harmonic generation by Fresnel-lensing effects
No full textWe present experimental results of enhanced second- and third-harmonic generation efficiency from Fresnel-lensing effects. We obtained enhancement by a factor of 6 in the third-harmonic yield by simply limiting the laser beam with an iris. Higher enhancement factors (up to 16) were obtained with a Fresnel zone plate. The experimental findings are in good agreement with the results of a simple theoretical analysis
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
Sali e Tabacchi. Voyages et paysages biographiques en Italie
No full textThe article is a round trip between memories and personal impressions of rail travel in Italy, and geographical or literary scientific references on the theme of Italian landscape. It focuses more generally on the notions of ordinary landscape versus tourist or prestige landscape in Italy, adopting the approaches of cultural and humanistic geography.L'article est un aller-retour entre des souvenirs et des impressions personnelles de voyages ferroviaires en Italie, et des références scientifiques géographiques ou littéraires sur le thème du paysage italien. Il se penche plus globalement sur les notions de paysage ordinaire (ordinary landscape) versus paysage touristique ou de prestige en Italie, en adoptant les approches de la géographie culturelle et humaniste.Scariati Renato. Sali e Tabacchi. Voyages et paysages biographiques en Italie. In: Le Globe. Revue genevoise de géographie, tome 156, 2016. Italie. Paysage et identité, sous la direction de Gianni Hochkofler et Renato Scariati. pp. 19-48
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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