1,721,244 research outputs found
Radar environment experimental analysis for optimal siting
No full textSite selection for a new surveillance radar for various purposes as the surveillance of the airports and of urban and suburban areas, includes the optimal choice for minimization of clutter due to land, vegetation and man-made infrastructures. In the frame of measurement and modelling of clutter echoes, this paper is aimed to contribute with a practical procedure using lightweight, cheap and small radar after its calibration. Real-world Radar Cross Section measurements in a typical suburban area are shown and analyzed. Buildings, streets, highways, car parking areas with different coatings, large and medium size lampposts, bare soil, soil with vegetation of various types, trees, all in a radius of a very few kilometres, makes the Tor Vergata area interesting as far as land clutter characterization is concerned, as a test-bed for optimal siting procedures
High Resolution Measurements and Characterization of Urban, Suburban and Country Clutter at X-Band and Related Radar Calibration
No full textAt Tor Vergata University we are working on measurements and phenomenological characterization of urban, suburban and country radar clutter at X-band (3 cm wavelength, range resolution 8 to 10 m, azimuth resolution @ 1 km about 23.5 m) and on the related radar calibration problems. Measurements are “high resolution” when compared to most surveillance radars, and the related applications are in the frame of clutter maps for cognitive radar, drones detection, radar ornithology, and more. After calibration, done using opportunity targets with known radar cross section and a clutter fence, we carry on an analysis and a comparison of land clutter, considering different weather conditions: dry and wet soil, as well as the rare event of snow. Using fixed opportunity targets, such as lamppost and/or a large cylindrical steel tanker, we describe the attenuation effects due to the natural clutter fence (in this case due to cane thicket near to the target position) and its mitigation when the natural fence is gradually removed. Finally, but importantly, we analyze the multipath phenomenon due to reflection/scattering on ground, and propose a procedure to estimate the multipath factor and to correct for it
A soundscape assessment of the Sasso Fratino Integral Nature Reserve in the Central Apennines, Italy
No full textThis study, based on data collected in 2017, describes for the first time the soundscape of the Sasso Fratino Integral Nature Reserve (INR) in Italy, an area characterised by the almost absence of anthropogenic noise, where we selected three recording sites within and adjacent the reserve. We adopted a double approach: one qualitative, based on visual screening of compact daily spectrograms; the other quantitative, by generating acoustic indices. In general, all sites are characterised by quiet nights and very acoustically dense daylight hours, with a composite biophony occupying the range 1500–9000 Hz. Moreover, the principal component analysis shows that the sites inside and outside the reserve are well differentiated and distinctly clustered, which could be due to their spatial heterogeneity and to the biophony’s different contributions. In this case, our results agree with the recognition of sonic patterns, or sonotopes, related to the different overlapping of biotic and abiotic sonic agents
Computer simulation of weather radar signals
No full textComputer simulation is largely used in radar signal analysis. The present work treats the simulation of precipitation echoes in weather radar applications. Such simulated signals are very useful when different processing techniques have to be tested and compared. Modern weather radar has both Doppler and polarimetric capabilities; from the simulation point of view, this implies the generation of two pseudorandom sequences with an assigned autocorrelation function (ACF) and an assigned cross correlation. A new generator of pseudorandom sequences is proposed and compared with an old one. The results show that the novel technique represents correctly both the ACF and the cross correlation, even when a limited number of samples (e.g. 8 or 16 typical of Air Traffic Control applications) is considered. Finally, the computer time needed to generate one sequence is evaluated and compared for both generators
Calibration of an X-band commercial radar and reflectivity measurements in suburban areas
No full textCalibrating a radar system, i.e., establishing a precise relationship
between the radar observable (the power level of the received signal)
and the radar cross section (RCS, the equivalent echoing area)
of the object, or surface, of interest is not a trivial task. Concerning
radar observables, in this work, we are mostly interested in land
clutter (bare soil and soil with vegetation of different types) and
manmade objects such as buildings, lampposts, and tankers. Our
aim is to calibrate a simple, lightweight X-band radar to create
a map of the land clutter of a suburban and rural area, using the
one around Tor Vergata University, Rome
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
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