1,721,003 research outputs found
"Multi-frequency approach to the inverse scattering problem: the linear and the quadratic models"
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"Dielectric profiles reconstruction via the quadratic approach in 2-D geometry from multifrequency and multifrequency/multiview data"
No full textDielectric profiles reconstruction via the quadratic approach in 2-D geometry from multifrequency and multifrequency/multiview data
No full textDeals with the reconstruction of the contrast function of a dielectric cylinder with rectangular cross section starting from the knowledge of the electric scattered far field produced under the incidence of plane waves. We analyze the set of the reconstructable Fourier harmonics of the unknown permittivity contrast function with linear and quadratic approaches. This set depends on the ranges of the wavenumbers β, of the angles of incidence θi of the impinging plane waves, and of the observation angles θo. We discuss a simple way to describe such a dependence, which allows us to find out that the set of the retrievable harmonics for the quadratic approach contains that for the linear one. Moreover, our investigation points out how increasing the amount of independent data through a multifrequency/multiview measurement scheme allows us to enlarge the set of the retrievable unknown harmonics with respect to a multifrequency/single-view one. Our analysis is confirmed by numerical results. Memory storage requirements and processing time consumption for the quadratic approach are greatly reduced thanks to the massive use of the fast Fourier transform algorithm
Peculiar morphologies of coastal and subaqueous landslides deposits and their relationship to flow dynamics.
No full textThe Acheron dorsum on Mars. A novel interpretation of its linear depressions and a model for its evolution
No full textThe Acheron Dorsum north of Olympus Mons on Mars is a unique 800 km-long arcuate ridge apparently unrelated to other adjacent morphologies. Acheron Dorsum is crossed by deep and wide fractures (“fossae”, here referred to also as Linear Depressions or “LDs”), commonly interpreted as grabens formed by local lithosphere stress in response to endogenous mantle upwelling. We suggest an alternate view that the linear depressions may result from gravitational self-adjustment of a loose deposit similar to the Deep-Seated Gravitational Slope Deformations (DSGSD or Sackung), akind of slow mass movement well documented on Earth. Numerical simulations based on a finite difference numerical model devised for terrestrial DSGSDs reproduce the timing and position of LDs reasonably well provided that the viscosity of the viscoplastic layer is between ≈7 1015and ≈1017Pas. While rock masses typically exhibit much higher values, based on comparison with glacial examples, we find that these viscosities could be compatible to a rock–ice mixture.
This leads to the hypothesis that the rock underneath Acheron Dorsum may be highly fragmented and that ice might have been involved in its deformation. Our hypothesis could shed light on the puzzling stress pattern on Acheron Dorsum, which follows approximately the ridge, without requiring the presence of hypothetical small-scale, endogenous currents
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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