1,721,013 research outputs found
Optical Second-Harmonic Generation from Metals Viewed in Terms of Inter- and Intraband Effects
No full textA Nonlocal Description Relation and the Energy Flow Associated with Surface Electromagnetic Waves on Metals
No full textUse of the Wigner distribution function in optical problems
No full textThe paper presents a review of the Wigner distribution function (WDF) and of some of its applications to optical problems. The WDF describes a signal in space and spatial frequency simultaneously, and can be considered as the local spatial-frequency spectrum of the signal. Although derived in terms of Fourier optics, the description of a signal by means of its WDF closely resembles the ray concept in geometrical optics. The concept of the WDF is not restricted to deterministic signals; it can be applied to stochastic signals as well, thus presenting a link between partial coherence and radiometry. Properties of the WDF and its propagation through linear systems are considered; again, the description of systems by WDFs can be interpreted directly in geometric-optical terms. Three main categories of optical problems are considered, in which the concept of the WDF can be applied usefully. First, the application to geometric-optical systems, i.e., systems where a single ray remains a single ray. Second, the application to problems in which the signal appears quadratically, like in the case of partial coherence. Third, the application to problems where properties of the signal are discussed in space and spatial frequency simultaneously; the uncertainty principle in Fourier optics might be an example. The WDF approach is extremely useful when two or more categories are combined: for instance, the propagation of partially coherent light through geometric-optical systems, or the formulation of uncertainty relations for partially coherent light
Measurement Of Reflectivity And Color Of Translucent Materials
No full textThis paper discusses the error made when measuring the color of translucent materials, using the same window for illumination and light collection. Two methods, based on large-window illumination and small-window collection are described
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
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
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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