1,720,955 research outputs found
Comparing phase-locked and non-phase-locked architectures for dual-channel DVB-S passive radar
No full textThis paper addresses the possibility to obtain low-cost passive radar that exploits DVB-S satellite transmissions as signals of opportunity using Commercial-Off The Shelf (COTS) hardware. In particular, low-noise down-conversion blocks (LNB) are typically available on the market, which include the Local Oscillator. Their use does not guarantee the fully coherent acquisition of surveillance and reference signal, required for passive radar operation. However, we estimate the frequency drift between the two channels, from the collected signals, and operate effectively for short-range surveillance applications. Using an ad-hoc experimental setup with 'less commercial' LNBs that can be locked to a reference, we compare two different types of receiver architectures: The non-phase-locked and a phase-locked architecture where the two LNBs are locked to the same 10 MHz oscillator. It is found that for small coherent integration times, the two schemes have very similar performance, whereas the phase-locked architecture is required to allow longer integration times and thus greater correlation gains. However, the lower-cost prototype is shown to be effective to detect and follow cars at least in the short ranges of typical parking-lots
Non-Coherent DVB-S Passive Radar Demonstrator
No full textIn recent years passive radar systems research has been increasingly focused on the use of satellite opportunity signals, and DVB-S signals in particular, since these offer virtually global coverage. Several papers have been published recently proving the effectiveness of very simple demonstrators based on COTS. However, conventional architectures struggle to employ coherent channels on the receiver impacting directly in their cost. In this work we show preliminary results for ground targets obtained using a very low-cost non-coherent COTS architecture
Multiband passive radar for drones detection and localization
No full textFor many surveillance systems, a multisensory architecture is essential when aiming
at providing accurate and reliable surveillance of critical infrastructures and
protected areas. This is certainly the case for airports, harbours, prisons and chemical
facilities as well as for public places such as parking areas, train stations or
stadiums, especially due to the new and emerging threat represented by commercial
drones and unmanned aerial vehicles (UAVs). In particular, their small size,
low radar reflectivity and flexibility of manoeuvre make them especially difficult to
detect, localize and classify. The potentials of passive radar (PR) in counter drone
operations, by exploiting different illuminators of opportunity (IOs), such as DVB-T,
DAB, GSM, WiFi, GNSS (Global Navigation Satellite Systems) and DVB-S that
were introduced in previous chapters, have been recently investigated in several
works. The reported results demonstrate that such sensors could be effectively
employed for detecting and localizing small and medium drones up to a few
kilometres from the PR receiver when DVB-T transmissions are exploited.
However, in urban areas and highly populated environments, where the use of the
non-invasive and green PR technology represents an attractive solution for enhancing
the security level, it is important to consider the possibility to exploit a
multisensory system by integrating PR with multiple operational frequency bands.
The integration of PRs operating at different frequency bands can be obtained
using two approaches:
1. A hardware integration can be conceived that provides a single multiband
sensor, which exploits a common multichannel receiver, common data
memory and common processing techniques for different signals of opportunity
and therefore greater frequency bandwidth.
2. At functional level, where each sensor operates with independent receiving
structures but the outputs of the multiple sensors are combined to provide
improved performance.
In the following sections, we proceed as follows. First, in Section 7.2, we
briefly review the most attractive sources of opportunity for an anti-drone PR
with their characteristics and signal processing requirements. Three specific
sources of opportunity are identified that appear to be well suited for a multiband
operation due to the complementarity of their characteristics. Therefore, we
illustrate the concept of the multisensory system on the basis of the parasitic
exploitation of such signals and discuss possible implementations and benefits.
The different components of the multisensory system are then separately
addressed in Sections 7.3–7.5 which are devoted respectively to anti-drone PR
based on DVB-S satellite broadcast signals, DVB-T terrestrial TV and WiFi, in
order to analyse the specific characteristics of their sensors as well as their performance.
This analysis also allows to identify hardware and signal processing
requirements for an effective implementation of the integrated multiband PR
system
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
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
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
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
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