1,721,018 research outputs found
Vuoti e scarti di democrazia
No full textLa democrazia è un oggetto teorico e storico sfuggente e mutevole, che eccede qualsiasi tentativo di definirla. Non è un caso, infatti, se proprio nell’epoca in cui maggiormente si afferma il discorso democratico, si assiste a uno scontro acceso volto all’appropriazione dell’uso stesso del termine “democrazia”.
Mai come oggi, l’espressione democrazia riesce a definire ambiti e contingenze politiche diametralmente opposte: da un lato, la democrazia significa pratiche volte alla stabilizzazione e conservazione delle ineguaglianze; dall'altro, essa è utilizzata per legittimare insorgenze popolari tendenti a una più piena trasformazione politico-istituzionale.
I contributi presenti in questo volume indagano e discutono alcune delle possibili declinazioni della democrazia. Tale sforzo è compiuto assumendo i nodi problematici principali che segnano oggi questa forma di governo: mancanza di partecipazione; tensione tra le pratiche, gli esiti e i residui (i vuoti e gli scarti) dei tentativi d’insorgenze democratiche; l’eccesso e l’accumulo di identità definite e statiche; l'attivazione di politiche emergenziali e/o conservative
Improved Coherent Processing of Synthetic Aperture Radar Data through Speckle Whitening of Single-Look Complex Images
No full textIn this study, we investigate the usefulness of the spectral whitening procedure, devised by one of the authors as a preprocessing stage of envelope-detected single-look synthetic aperture radar (SAR) images, in application contexts where phase information is relevant. In the first experiment, each of the raw datasets of an interferometric pair of COSMO-SkyMed images, representing industrial buildings amidst vegetated areas, was individually (1) synthesized by the SAR processor without Fourier-domain Hamming windowing; (2) synthesized with Hamming windowing, used to improve the focalization of targets, with the drawback of spatially correlating speckle; and (3) processed for the whitening of complex speckle, using the data obtained in (2). The interferograms were produced in the three cases, and interferometric coherence and phase maps were calculated through 3 × 3 boxcar filtering. In (1), coherence is low on vegetation; the presence of high sidelobes in the system’s point-spread function (PSF) causes the spread of areas featuring high backscattering. In (2), point targets and buildings are better defined, thanks to the sidelobe suppression achieved by the frequency windowing, but the background coherence is abnormally increased because of the spatial correlation introduced by the Hamming window. Case (3) is the most favorable because the whitening operation results in low coherence in vegetation and high coherence in buildings, where the effects of windowing are preserved. An analysis of the phase map reveals that (3) is likely to be facilitated also in terms of unwrapping. Results are presented on a TerraSAR-X/TanDEM-X (TSX-TDX) image pair by processing the interferograms of original and whitened data using a non-local filter. The main results are as follows: (1) with autocorrelated speckle, the estimation error of coherence may attain 16% and inversely depends on the heterogeneity of the scene; and (2) the cleanness and accuracy of the phase are increased by the preliminary whitening stage, as witnessed by the number of residues, reduced by 24%. Benefits are also expected not only for differential InSAR (DInSAR) but also for any coherent analysis and processing carried out performed on SLC data
Recovery and characterization of the metal polymeric organic fraction (polymerin) from olive oil mill waste waters
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Recovery and characterization of the metal polymeric organic fraction (polymerin) from olive oil mill waste waters
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