1,721,166 research outputs found
On the Equivalence Between Jensen-Shannon Divergence and Michelson Contrast
No full textThis paper focuses on the link between a visible linear and local distortion in a pictorial scene and its cost in terms of information theory quantities. In particular, a formal relation between the Michelson visual contrast and the Jensen-Shannon divergence (JSD) will be provided. A universal just noticeable threshold is also derived by maximizing JSD constrained to the greatest Michelson contrast of an invisible distortion. Such a threshold is independent of both distortion parameters and the probability density function of the degraded image. It is then able to measure the bits budget to be spent for leaving the distortion invisible. Some tests on both synthetic and real distorted images validate the theoretical findings. They confirm that the proposed universal threshold is really able to get the lower bound of human perception and then it may be useful for many applications, such as bit allocation in coding procedures and automatic parameters setting in restoration algorithms
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
A Model for the Restoration of Semi-transparent Defects Based on Lie Groups and Human Visual System
No full textThis paper presents a new model for the restoration of semi-transparent blotches on archived sepia-toned images. Its main feature is the combination of Human Visual System mechanism and Lie groups transformations properties. The former allows to define restoration as a gradual reduction of the visual perception of the defect. The latter allows to easily select the transformation that better performs this reduction exploiting Lie groups properties. Extensive experimental results on original photographs of the Alinari Archive affected by semi-transparent blotches show the potential of the proposed approach. © Springer-Verlag Berlin Heidelberg 2013
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
Jensen-Shannon divergence for visual quality assessment
No full textThis paper focuses on some theoretical properties of the Jensen-Shannon divergence (JSD) that well match human visual system (HVS) features. In particular, it is firstly shown that JSD between the probability density function (pdf) of the reference (original) image and the test (distorted) one can be reformulated as a mathematical expansion, independently of the image subject and the distortion kind. Such expansion contains a component of the well-known structural similarity measure (SSIM), some powers of the Weber's law, and an additional component tied to the skewness of the involved pdfs. This theoretical link with some HVS-based quantities is further stressed by some experimental results showing that JSD has a trend similar to other popular quality assessment measures like SSIM, VIF, and MSE on frequent degradation kinds like JPEG, Additive Gaussian Noise, Gaussian Blur, and JPEG2K. Experimental tests on several images from LIVE database show that the proposed approach can be a valid theoretical and objective support for modeling HVS behavior. © 2013 Springer-Verlag London
Perceptual object tracking
No full textThis paper presents an improved kernel-based target tracking that uses new and effective features able to describe the target appearance. The key idea consists of adopting features that are related to the visual perception of the target in place of its color histogram. The change of the feature space is twofold advantageous. It allows us to faithfully follow the target and to considerably reduce the computational cost of the whole tracking algorithm thanks to the reduced dimension of the perceptual feature space. Preliminary tests on some video sequences are encouraging. The proposed tracker is able to follow the target even in case of complete occlusion for some consecutive frames. Moreover, it is more stable than the algorithm that uses just the luminance histogram as target feature. Finally, it is robust to the presence of other moving targets. © 2012 IEEE
Optimal image restoration using HVS-based rate-distortion curves
No full textThis paper proves that the Jensen-Shannon Divergence (JSD) is a good information theory measure of the visibility cost of a degraded region in a pictorial scene. Hence, it can be combined with Michelson contrast for building a visual rate-distortion curve. The latter allows to optimize parameters of restoration algorithms. Some results on both synthetic and real data show the potential of the proposed approach. © 2011 Springer-Verlag
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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