1,721,368 research outputs found
Calibration of SIMO Formations with Azimuth Ambiguities
No full textFormations of small satellites are gaining momentum as an alternative to single synthetic aperture radar (SAR) systems, allowing them to improve performance and reduce costs. Each sensor operates with a low pulse repetition frequency (PRF), so swath size can be kept large, and the strong azimuth ambiguities are later resolved by combining acquisitions from multiple satellites. For proper imaging to be successful, careful calibration of the system and geometric parameters is performed based on the single-channel images. However, ambiguities jeopardize the retrieval of parameters from data; therefore, it is crucial to identify those areas that are inherently ambiguity-free. This article handles acquisitions that are highly affected by azimuth ambiguities, as in the case of the formation. First, we model the replica's structure in the focused image and then propose an effective yet simple method to detect such disturbances. Finally, we demonstrate an improved approach for estimating the along-track baseline by incorporating the aforementioned ambiguity detection scheme. The proposed analysis is validated with simulated data, considering a realistic reflectivity map derived from a COSMO-SkyMed stack
Along Track Slope Compensation In A SIMO Formation
Full text linkCompact single-input-multiple-output (SIMO) formations are a promising option for performance improvement in future Synthetic Aperture Radar (SAR) missions. A high-resolution unambiguous imaging is obtained by utilizing several satellites with small antennas. The across-track baseline between the satellites poses a significant issue for known signal reconstruction algorithms due to the dependency on the topography, which may vary along-track. Proposed here is a method to compensate for height variations along the azimuth direction using a simplified but powerful 1-D model. A theoretical derivation of a forward model is provided, and performance analysis in terms of signal to noise is demonstrated
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
Aspetti costruttivi
No full textLa scarsità di fonti archivistiche e iconografiche, ma anche l'esigua letteratura sull'organizzazione del cantiere tradizionale, hanno orientato lo studio che qui si presenta verso l'analisi diretta di un numero di chiese con cupole in asse, intrapresa attraverso rilievi architettonici allo scopo di identificare le soluzioni tecniche riconosciute come emblematiche della tradizione locale dell'arte del costruire. L'indagine si è soffermata su quattro tipi di copertura: le pseudocupole, le cupole, le volte e i catini absidali
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
Incidenza dell'handicap cerebrale perinatale a Parma dal 1972 al 1983: verifica delle reali possibilità di prevenzione.
No full textAspects of treatment of non-calculous acute cholecystitis [Nostro orientamento sulla terapia delle colecisti acute alitisiache]
No full textAppropriate 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
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