1,721,025 research outputs found
Closed-form evaluation of the second-order statistical distribution of the interferometric phases in dual-baseline SAR systems
No full textMultichannel inteferometric synthetic aperture radar (InSAR) systems allow to improve the accuracy of the estimation of the height profiles of the observed scenes. Multichannel images can be acquired by using different sensors operating at different frequencies (multifrequency InSAR) or acquiring multiple images with slightly different view angles (multibaseline InSAR). The enhanced accuracy height estimation is obtained exploiting the multichannel interferometric phases and an a priori inaccurate ground profile and requires the knowledge of the joint probability distribution of the multichannel interferometric phases, whose evaluation in a closed form is very complicated and is not found in literature. In this paper, we evaluate the analytical form of the second-order probability density function (pdf) of dual-baseline InSAR phase interferograms, obtained from three mutually correlated interferometric images. The evaluation exploits the Gaussian model for the complex SAR images, takes into account the mutual correlation of all the images, and does not use any approximation. The closed form of the second-order joint pdf can be usefully adopted in statistical digital elevation model (DEM) estimation methods using dual-baseline SAR systems, which commonly use an approximate expression of the joint pdf of measured interferometric phases, given by the product of the marginal pdfs of each phase interferogram, obtained in the assumption of independent interferograms. The effect of this approximation is evaluated by computing the Cramer-Rao lower bounds and the mean square estimation errors obtained using the exact and the approximate model. Presented results represent the basis for the generalization to the case of more than two interferograms. © 2010 IEEE
Closed-Form Evaluation of the Second-Order Statistical Distribution of the Interferometric Phases in Dual-Baseline SAR Systems
No full text
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
Finite group with Hall coverings
No full textIn this paper we describe the groups admitting a covering with Hall subgroups. We also determine the
groups with a \pi-Hall subgroup, where \pi is the connected component of the prime graph, containing the prime 2
C55-groups
Full text linkWe classify the C55-groups, i.e., finite groups in which the centralizer of every 5-element is a 5-group
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
A characterization of the sporadic group of Lyons
No full textWe show that Lyons' sporadic simple group is the unique finite simple group that is simultaneously of weak characteristic -type and characteristic -type for odd and with and
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
La mobilità quotidiana: economia ed ecologia nell’uso dello spazio in un’indagine empirica nel comune di Pisa
No full textA fronte di una crescente domanda di mobilità quotidiana che caratterizza i sistemi economici e urbani contemporanei, lo spostamento, in termini di mezzi di trasporto e tempi impiegati, può essere un elemento interpretativo dei mutamenti sociali. Sia sul piano individuale (familiare) che su quello sociale, la razionalità e l'ottimizzazione nell'uso dello spazio sono questioni importanti da indagare. Obiettivo del contributo è lo studio della mobilità quotidiana in una prospettiva di ecologia/economia degli spostamenti, e questo tema si può discutere esaminando l'importanza degli spostamenti multipli (economia dello spazio utilizzato) e di quelli collettivi (economia di mezzi di trasporto), nonché la diffusione di mezzi di trasporto "ecologicamente corretti". I dati alla base dello studio sono stati raccolti attraverso un'indagine campionaria sulla mobilità dei residenti del comune di Pisa, indagine che ha interessato 392 famiglie cui è stato sottoposto un qestionario, per un totale di 941 persone coivolte. Sono stati registrati gli spostamenti giornalieri, noché le caratteristiche socio-demografiche dei soggetti e le informazioni relative ai singoli spostamenti
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