1,721,063 research outputs found
GNSS-based multistatic passive radar imaging of ship targets
No full textThis work brings forward a framework for passive radar imaging of ship targets by exploiting the reflections of navigation satellite signals. The specific objective is taking advantage of the inherent multistatic nature of the system for the ship passive imagery. To this aim, a bistatic image formation stage is first defined. Then, the bistatic images obtained over multiple baselines are mapped in a domain independent on the particular satellite viewing angle. Finally, different combination rules of the multiple images are defined in order to enable multistatic imagery with enhanced quality, potentially enabling finer feature extraction procedures for ship classification. The proposed approaches are validated and compared via an experimental campaign comprising multiple Galileo satellites and a commercial ferry undergoing different types of motion
Effect of Volume Distributed Clutter in PSK Modulated Automotive Radar
No full textDue to rapid progress in silicon technology, a number of companies have developed automotive radars which use Phase Shift Keying modulated signals. The effect of Volume Distributed Clutter (VDC), e.g. rain, hail, etc. on the radar performance is considered in this paper. It is shown that the sidelobe levels of the signal Ambiguity Function dramatically affects the radar performance, and modulation codes should be selected taking into account the presence of VDC. The methodology of the system performance evaluation is presented and accompanied with practical examples
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
Passive radar imagery of ship targets by using navigation satellites transmitters of opportunity
Full text linkThis paper considers the possibility to extract features of vessels at sea with a GNSS-based passive radar system. To this purpose, a passive imaging mode has been defined to form bistatic ISAR images of the detected ship. Then, proper range and cross-range scaling factors have been derived, so that relevant features of the target such as its length can be obtained, potentially enabling target recognition procedures. Experimental results obtained with Galileo satellites demonstrate the effective possibility of the proposed approach to extract relevant features of ship targets of interest, thus providing advanced capabilities to the GNSS-based radar for maritime surveillance applications
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
Passive multistatic SAR with GNSS transmitters and using joint bi/multi-static CLEAN technique
Full text linkThis paper explores the capability of GNSS as opportunity transmitters for passive multistatic SAR. The large number of navigation satellites illuminating the same area from multiple view angles enables a single ground-based stationary receiver to combine the individual bistatic images thus achieving multistatic imagery capability with improved spatial resolution. Nevertheless, such a technique introduces artifacts corrupting the quality of the image information space. In this paper, a joint bi/multi-static CLEAN algorithm is exploited in order to correctly recovering the information of the scene. An experimental study is therefore presented, demonstrating the potential of this technology to extract detailed information of an area for persistent monitoring purposes
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