1,720,962 research outputs found
Maritime moving target detection and localisation technique for Global Navigation Satellite Signals-based passive multistatic radar
No full textThis article puts forward a ship target detection and localisation technique for GNSS-based passive multistatic radar. The approach capitalises on the large spatial diversity offered by navigation satellite constellations to provide maritime awareness using short integration time windows, thus bypassing the shortcomings suffered by approaches relying on long dwells typically considered in satellite-based passive radar systems. The proposed approach entirely operates on the Cartesian plane and it is able to provide in a single stage the detection and localisation of the target in the surveyed area. Theoretical and simulated performance analysis are provided to illustrate as the proposed approach can outperform conventional two-stages (i.e. bistatic detection then localisation) procedures, with particular regard to the case of significant radar cross section scintillation, likely experienced in the system under consideration. The effectiveness of the approach has been verified via experimental data acquired in a few scenarios of interest comprising opportunistic targets belonging to different types
A Centralized Approach for Ship Target Detection and Localization with Multitransmitters Gnss-Based Passive Radar
No full textThis work focuses on ship target detection and localization with a passive radar system exploiting multiple navigation satellites. Particularly, a centralized approach, entirely working on the Cartesian plane, is proposed to achieve a joint detection and localization of the targets. The approach can outperform conventional decentralized approaches, where individual decisions are taken at each bistatic link and, in a second stage, localization is implemented via bistatic ranges intersection. Theoretical formulations of the probability of detection and localization for both the centralized and decentralized techniques are derived in the case of target radar cross section variation among the different links, likely occurring in the system under consideration. The effectiveness of the proposed approach is tested by means of simulated analysis. Experimental results are also provided, verifying its potentiality in practical applications
Maritime targets velocity estimation in space-based passive multistatic radar using long integration times
Full text linkTarget detection by means of space-based passive radar sensors generally requires the adoption of long integration time strategies to reinforce sufficiently the signal strength. These are usually based on the recovery of the target Doppler-rate to cope with the range and Doppler migration experienced over the long dwell considered. In this work, we put forward a Taylor-series approach that capitalizes on the set of bistatic Doppler-rates estimated in Global Navigation Satellite Systems (GNSS)-based multistatic radar configurations to estimate the velocity of ship targets with increased accuracy with respect to conventional Doppler-based procedures. Both the cases of single-element and array receiver configurations have been considered. Theoretical and numerical results under different use cases show as leveraging on the long integration times adopted at the detection stage could significantly increase the accuracy of the estimated ship velocity components. Few experimental results are also provided, verifying the potentialities of the proposed approach in operative scenarios of practical interest for this technology. The proposed approach is not limited at the GNSS case, but it could be potentially applied to any multistatic passive radar system
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
LA SCALA DI VALUTAZIONE DEGLI STATI DEPRESSIVI (SVSD): ANALISI FATTORIALE SUI RISULTATI OTTENUTI DA UNA SOMMINISTRAZIONE A 601 ADOLESCENTI IN AMBITO SCOLASTICO
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