1,354,513 research outputs found
A study of the interaction between the new C line of Roma underground and the Aurelian wall
No full textA study of the effects of the construction of the C Line of Roma Underground on the Aurelian Wall has been carried out as a research project sponsored by the municipality of Roma through STA S.p.A. This paper summarises the results of the study for a section where the two closed-shield (10m in diameter) running tunnels pass directly beneath the Wall, with a skew of about 45 degrees. At first, ground movements induced from construction of the tunnels, for different positions of the excavation face, were estimated in greenfield conditions using empirical methods. In a second stage, three dimensional finite difference analyses were carried out to simulate the interaction between the Wall and the construction of the tunnels. A distinctive feature of the research was the extended investigation aimed at an adequate definition of a model of the subsoil and of the geometry and quality of the foundations of the Wall
Studio dell’interazione tra le opere della nuova linea C della metropolitana di Roma e le mura aureliane
No full textA phase-center study of Fabry-Pérot cavity antennas
No full textThe phase center is studied for Fabry-Pérot cavity antennas viewed as two-dimensional leaky-wave radiators, adopting both local and global definitions. Closed-form expressions are obtained for the phase-center location of broadside pencil beams, as a function of the attenuation constant of the leaky mode responsible for radiation and of the extension of the angular sector of interest. Numerical results that validate the proposed formulas are given for specific antenna structures
Phase centre of Fabry-Pérot Cavity antennas: Leaky-wave model and analytical formulas
No full textThe phase centre of Fabry-Pérot Cavity antennas radiating broadside pencil beams is studied adopting a leaky-wave model of their radiation mechanism. Different definitions are considered for the phase centre, both local, based on curvature properties of the equiphase surfaces in the far field, and global, based on the minimization of suitable functionals of the antenna phase pattern. Analytical formulas are derived for the phase-center location as a function of the relevant leaky-mode attenuation constant and are validated on specific examples of antennas. © 2012 IEEE
Studio preliminare sulle caratteristiche di elementi riscaldanti etc.
No full textRapporto preliminare ENEA. Atti Istituto di Scienza delle Costruzioni Univ. di Roma La Sapienz
Geotechnics for the preservation of historic cities and monuments:Component of a multidisciplinary approach.
No full textGrant NSF, Student Paper Contest IEEE 2000 AP-S International Symposium
No full textGrant di 700 $ per la presentazione di una memoria finalista nello Student Paper Contest tenutosi in occasione dell'IEEE 2000 AP-S International Symposiu
A comparative analysis of Bessel and Gaussian beams beyond the paraxial approximation
No full textThe use of Bessel and Gaussian beams for focusing applications has long been debated. The former are attractive for their diffraction-resistant and self-healing character, whereas the latter notably exhibit higher efficiency. In previous works, efforts have been made to clarify whether Bessel or Gaussian beams are more suitable for wireless power transfer. However, the theoretical discussions proposed so far did not attract a general consensus from the community, the arguments often being based on restrictive, arbitrary hypotheses under the frame of the ray-optics and paraxial approximations. On the other hand, especially at microwaves, nonparaxial Bessel beams have found important applications. This work aims at providing an engineering perspective on the focusing properties of both Bessel and Gaussian beams by introducing significant figures of merit. The latter are defined taking into account the beam features that are of greatest interest in focusing applications, namely the beam efficiency, the maximum cover distance, and the beam resolution. Analytical expressions are provided, and results are shown for comparing the Bessel and Gaussian beam features when their beam waists are allowed to freely vary in a range of physical realizability
A leaky-wave analysis of the phase center in Fabry-Pérot cavity antennas
No full textPhase centers are studied for Fabry-Perot cavity antennas viewed as two-dimensional uniform leaky-wave antennas radiating pencil beams pointing at broadside. Alternative definitions for the phase center are considered and compared, as a function of the wavenumber of the relevant leaky waves and of the extension of the angular region of interest in the far field around the direction of maximum radiation amplitude. Analytical formulas are derived and numerical simulations of antennas constituted by planar grounded substrates covered with dielectric or metal partially-reflecting surfaces are provided to validate the analysis
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