617 research outputs found
Thermal noise study of a radiation pressure noise limited optical cavity with fused silica mirror suspensions
No full textIn this work we study the thermal noise of two monolithically suspended mirrors in a tabletop high-finesse optical cavity. We show that, given suitable seismic filters, such a cavity can be designed to be sensitive to quantum radiation pressure fluctuations in the audio band of gravitational wave interferometric detectors below 1 kHz. Indeed, the thermal noise of the suspensions and of the coatings constitutes the main limit to the observation of quantum radiation pressure fluctuations. This limit can be overcome with an adequate choice of mirror suspension and coating parameters. Finally, we propose to combine two optical cavities, like those modeled in this work, to obtain a tabletop quantum radiation pressure-limited interferometer
Nonlinear Kinetic Energy Harvesting
No full textAbstractHarvesting of kinetic energy present in the form of random vibrations is an interesting option due to the almost universal presence of this kind of motion. Traditional generators based on piezoelectric effect are built with linear oscillators made by a piezoelectric beam and a mass used to tune the resonance frequency on the predominant frequency of the vibrations spectrum. However, in most cases the ambient random vibrations have their energy distributed over a wide spectrum of frequencies, being rich especially at low frequency. Furthermore frequency tuning is not always possible due to geometrical/dynamical constraints. In this work we present a different method based on the exploitation of the nonlinear dynamical features of bistable oscillator. The experimental results and the digital simulations show that nonlinear harvester (e.g. bistable oscillators) can overcome some of the most severe limitations of generators based on linear dynamics
Mechanical quality factor mirror substrates for VIRGO
No full textThermal noise in the mirror substrates is expected to be the main limit to the VIRGO sensitivity in the 50-500 Hz frequency range. The mechanical quality of the mirror substrates and the geometry of their suspension are expected to affect the noise level of the detector output. High mechanical Q have been obtained for different large fused silica substrates under VIRGO suspension conditions. Moreover, calcium fluoride substrates are shown to provide a more promising option for the design of future cryogenic, low thermal noise interferometers
El Tlacuache Núm. 365 (2009). 365 Año 9 (2009) mayo. El Tlacuache
No full textRubén Jaramillo: las intenciones del crimen por Aura Hernández. - Jaramillo y la disputa el sentido de la vida por Flavio Barbosa. - De campesinos a obreros: una comunidad surgida entre las flores por Rafael Gutiérrez
Personnalisation et leadership Le cas du Mouvement Cinq Étoiles
No full textThe article draws a characterisation of the late comer among the Italian populist parties, the Five Star’ Movement, led by the ancient comedian Beppe Grillo. Starting with a definition of what he means by “political personalisation”, the Author first describe this party as a political organisation in which the leader masters all the key areas – notably, communication, rules setting, and resolution of internal conflicts. Then, he argue that the Five Star Movement is a “personalist party”, in which Beppe Grillo embodies a powerful but non-charismatic leader. In the closing section, the Author tries to shed light above the probable evolutions of the party, particularly dealing with its institutionalisation process
Monolithic fused silica suspension for the Virgo gravitational waves detector
No full textThermal noise in mirror suspension wires is the most severe limit to the low frequency sensitivity of interferometric gravitational wave detectors presently under construction. The pendulum mode mechanical quality factor of the suspension last stage significantly affects the noise level of the detector output. The monolithic design for this suspension stage, using a low dissipation material, is proposed for Virgo. High mechanical Q(s) and high breaking strengths have been obtained for monolithic fused silica fibers. A low dissipation and high strength bonding technique using potassium silicate bonding is proposed. (C) 2002 American Institute of Physics
Mechanical quality factor of large mirror substrates for gravitational waves detectors
No full textThermal noise in the mirror substrates sets a most severe limit to the low-frequency sensitivity of the interferometric gravitational wave detectors presently under construction. The mechanical quality of the mirror substrates and the geometry of their suspension are shown to affect markedly the noise level of the detector output. High mechanical Q have been obtained for different large fused silica substrates under Virgo suspension conditions. Moreover, calcium fluoride substrates are shown to provide a more promising option for the design of future cryogenic, low thermal noise interferometers. (C) 2002 American Institute of Physics
Un capitolo della fortuna delle "Decades" di Biondo Flavio: da Pio II a Giovanni Albino
No full textL’articolo concentra l’attenzione sul contenuto del ms. München, Bayerische Staatsbibliothek, Clm 11 324, descritto dal catalogo come «Albini Lucani excerpta ex Blondi decadibus». Ma il codice non contiene gli excerpta delle Historiae ab inclinatione Romano rum imperii di Biondo Flavio, bensí una sintesi della Abbreviatio supra Decades Blondi di papa Pio II. L’autore Giovanni Albino Lucano, storiografo e curatore della biblioteca dei re aragonesi di Napoli, nella dedica al re Alfonso II non fa alcuna menzione del testo di Pio II da lui usato. L’epitome offre una curiosa attestazione indiretta della fortuna di Biondo Flavio, il quale intrattenne diverse relazioni con la corte napoletana di Alfonso il Magnanimo.This article focuses on the contents of MS Munich Bayerische Staatsbibliothek, Clm 11324, described in the catalogue as «Albini Lucani excerpta ex Blondi decadibus». But the MS does not contain the excerpts of the ‘Historiae ab inclinatione Romanorum imperii’ of Biondo Flavio, but a summary of the ‘Abbreviatio supra Decades Blondi’ by Pope Pius II. The author, Giovanni Albino Lucano, historian and librarian for the Aragonese kings of Naples, makes no mention in his preface of the work by Pius II which he had used. The epitome is a curious indirect proof of the influence of Biondo Flavio, who had various contacts with the Neapolitan court of Alfonso il Magnanimo
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