1,721,473 research outputs found
Simplified seismic analysis of straight integral frame-abutment bridges
Full text linkSince the second post-war period, Integral Abutment Bridges (IABs) have become widespread in the construction of overpasses in America and Europe, as they allow to save on the costs of inspection and maintenance of the bearings and deck joints. They are characterized by having an internal continuity constraint between abutments and deck. Their static and dynamic behavior is thus characterized by the strong interaction between structure and soil. Due to these structural characteristics, the analysis models cannot disregard the contribution of the surrounding soil non-linear behavior. While the latter can be modeled by means of a continuous medium with a non-linear constitutive law, such models are very complex and require specialized knowledge and skills beyond those of the average structural designer. The aim of this thesis is therefore the study of simplified two- and three-dimensional models for practice-oriented seismic analysis of integral abutment bridges. The study focused first on a non-linear dynamic model where soil-structure interaction is modeled with non-linear Winkler springs. A comparison with a higher-order three-dimensional finite element model was performed, which allowed calibration and fine-tuning. The same non-linear dynamic model has been implemented both in OpenSEES and in SAP2000, in order to evaluate the sensitivity of the assessed system response to the limitations of commercial softwares and thus to highlight the practical applicability of the model for design. As a further step toward design, even more simplified static models, both non-linear and linear, were established and calibrated against the non-linear dynamic one. Finally the dynamic model was used to carry out a seismic risk analysis of archetypical overpasses with integral abutment on the Italian territory to quantify in probabilistic terms the better performance of these bridges with respect to bridges with traditional seat-type abutments
Risonatore cilindrico a microonde
Full text linkThe present invention relates in general to microwave resonators, in particular for the manufacture of oscillators. More specifically the invention relates to a cylindrical resonator, of the type comprising: a cylindrical tubular member made of metal material, and closure means likewise made of metal material and associated with the tubular member so as to define in the inside thereof a cylindrical cavity resonating at a predetermined frequency; and in which said closure means have a thermal elongation coefficient different from that of the tubular member so as to reduce the variation in the resonance frequency of the cavity upon variation of the temperature, including not only the linear variation term but also the nonlinear ter
Struttura tubolare con diametro interno termicamente stabilizzato, in particolare per un risonatore a microonde
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Frequency domain method and device to measure series resistance and figure of merit of thermoelectric devices
No full textSolutions and ultimate limits in temperature compensation of metallic cylindrical microwave resonators
No full textIn trying to implement temperature compensation of high-Q metallic microwave cavities with the two-metal technique, crippling problems arise from the exceedingly high uncertainty with which the Coefficients of Thermal Expansion (CTE) of the two metals are known, and from their non linearity with temperature. A novel approach is here proposed, following which both problems can be separately addressed, opening the way for improvement of the resonance frequency temp-co into the 10^-10/K and possibly the 10^-11/K regio
'Stachanovista' e 'pasticheur' della pittura fiorentina: lo 'Pseudo Pier Francesco Fiorentino'
No full textVittorio Cini collezionista di pittura: una splendida avventura, dal Castello di Monselice alla dimora veneziana, da Nino Barbantini a Federico Zeri
No full textIl saggio ricostruisce gli straordinari acquisti di pittura compiuti da Vittorio Cini mettendo in luce il ruolo di alcuni fra i suoi più importanti consulenti da Bernard Berenson a Federico Zer
Spatial variations of field polarization and phase in microwave cavities: application to the cesium fountain cavity
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