1,721,332 research outputs found
On the recovery of refractive-index profiles of ion-exchanged glass waveguides
No full textThe problem of determining the refractive-index profile of graded-index waveguides from the distribution of effective indices is analysed. The most common WKB-based methods appear to be rather poor in recovering smooth profiles in the case of waveguides supporting a low number of modes. A routine for the recovery of smooth refractive-index profiles of potassium-exchanged waveguides is described, which exploits accurate in-depth concentration measurements performed by secondary ion mass spectrometry. The method allows the separation of the compositional and the stress contributions to the index change of the analysed waveguides
Stress-induced birefringence in silver-diffused glass waveguides
No full textExperimental data on the stress-induced birefringence in Ag+-Na+ ion-exchanged monomode waveguides are presented. From accurate measurements of modal birefringence and in-depth silver distribution, it is possible to reconstruct the birefringence profile, and give an estimation of the stress built up in the exchanged layer. © 1992 Taylor and Francis Ltd
On the role of local field correlation effects on the ionic interdiffusion in soda-lime glass
No full textGoing 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
Refractive-index profiles of double-silver-exchanged glass systems
No full textExperimental data on silver ion-exchanged glass waveguides are presented. The waveguides are prepared by a three-step route consisting of two Ag+ – Na+ ion-exchanges alternated with a heat treatment, and exhibit peculiar refractive-index profiles. The reliability of two inverse Wentzel-Kramers-Brillouin reconstruction methods is also discussed for the systems at issue. © 1994 Taylor and Francis Ltd
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
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