1,720,988 research outputs found
Motion compensation and multi-resolution coding
No full textMultiresolution techniques have become more and more appealing in current image coding. Image multispectral representation produces many important features such as spectral shaping of coding noise according to human eye perception, good image energy compaction, coder tuning with respect to any band characteristics, and allows for multilevel layered transmission that is one of the main targets pursued by the broadcaster. Despite these appealing capabilities, multiresolution techniques have failed to give the expected results. One of the reasons for this failure is the difficulty of exploiting the temporal redudancy present in image sequences. This paper addresses the problem of motion compensation in a multiresolution environment, considering both QMF-SBC and wavelet transform approaches. Different motion compensation schemes are derived and their efficiency is considered with regard to scalability and to the lengths of subband analysis and synthesis filters. Simulation results are used to support relevant conclusions where needed
ASAR ScanSAR Modes: Quality Enhancement
No full textThis paper focuses on the optimization of the image quality for the ENVISAT ASAR ScanSAR modes. The best trade-off between Noise Equivalent σ (NEσ) and Equivalent Number of Looks (ENL) is achieved by optimizing both system and processing parameters within the instrument constraints. An end-to-end model to validate the study has been used. Thereafter a novel phase preserving focusing technique is presented. Conventional approaches (that exploit the SAR matched filter) introduce a space-variant distortion when focusing very law resolution ScanSAR data. The focusing technique here proposed uses a set of space-variant focusing kernels properly computed by means of Wiener pseudo-inversion. In this way focusing is achieved with no distortion, thus getting the finer resolution and the lower sidelobes
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
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
Flexible Dynamic Block Adaptive Quantization for Sentinel-1 SAR Missions
No full textThe letter introduces a novel quantizer suited for medium to high-resolution synthetic aperture radar (SAR) systems, like the forthcoming SENTINEL-1 SAR. The Flexible Dynamic Block Adaptive Quantization (FDBAQ) extends the concept of the Block Adaptive Quantization (BAQ), used in spaceborne SAR since the Magellan mission, by adaptively tuning the quantizer rate according to the local signal-to-noise-ratio (SNR). A design is presented aiming to optimize the average bit-rate, while constraining the minimum SNR. FDBAQ optimized performance is then evaluated using backscatter maps derived from ENVIronment SATellite (ENVISAT) data
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