1,721,547 research outputs found
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
Image processing for the analysis and conservation of paintings: opportunities and challenges
No full textOver the past few decades, analytical methods developed in the physical sciences started to contribute to the analysis, conservation, and dissemination of works of art. By focusing on the visual arts, this paper sketches the main applications that could benefit from the introduction of ad hoc image processing tools, outlines the state-of-the-art, describes the main peculiarities of this field, and discusses the main obstacles impeding a more fruitful cooperation between the image processing community and art historians, restorers, and artists in general
Multichannel watermarking of color images
No full textIn the field of image watermarking, research has been mainly focused on grayscale image watermarking, whereas the extension to the color case is usually accomplished by marking the image luminance, or by processing each color channel separately. A DCT domain watermarking technique expressly designed to exploit the peculiarities of color images is presented. The watermark is hidden within the data by modifying a subset of full-frame DCT coefficients of each color channel. Detection is based on a global correlation measure which is computed by taking into account the information conveyed by the three color channels as well as their interdependency. To ultimately decide whether or not the image contains the watermark, the correlation value is compared to a threshold. With respect to existing grayscale algorithms, a new approach to threshold selection is proposed, which permits reducing the probability of missed detection to a minimum, while ensuring a given false detection probability. Experimental results, as well as theoretical analysis, are presented to demonstrate the validity of the new approach with respect to algorithms operating on image luminance onl
Performance analysis of ST-DM watermarking in presence of non-additive attacks
No full textThe performance of spread-transform dither modulation (ST-DM) watermarking in the presence of two important classes of non additive attacks, such as the gain attack plus noise addition, and the quantization attack are evaluated. The analysis is developed under the assumption that the host features are independent and identically distributed Gaussian random variables, and that a minimum distance criterion is used to decode the hidden information. The theoretical bit-error probabilities are derived in closed form, thus permitting to evaluate the impact of the considered attacks on the watermark at a theoretical level. The analysis is validated by means of extensive Monte Carlo simulations. In addition to the validation of the theoretical analysis, Monte Carlo simulations permitted to abandon the hypothesis of normally distributed host features, in favor of more realistic models adopting a Laplacian or a generalized Gaussian probability density function. The general result of our analysis is that the excellent performance of ST-DM are confirmed in all cases with the only noticeable exception of the gain attack
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