206 research outputs found
Solar Physics with LISA
No full textGalactic cosmic rays and solar energetic particles (SEPs) with energies larger than 100 MeV/n are able to penetrate and charge the test masses of the LISA experiment. As this process constitutes one of the major sources of noise for the experiment, a small telescope of silicon detectors will be located on board the LISA PathFinder and, possibly, the three LISA spacecraft. This device will allow us to monitor real-time galactic and solar cosmic-ray incident proton fluxes above 100 MeV. Moreover, spectral information will be provided up to an energy of 500 MeV. We propose to use the above instrument for the evaluation of the test mass charging process and the study of SEPs accelerated by coronal mass ejection (CME) propagation. Because of the peculiar orbit of the LISA spacecraft around the Sun, this experiment offers a unique chance to monitor an evolving CME contemporary at 2 degrees (among spacecraft) and 20 degrees (between LISA and Earth) intervals in longitude at once. These observations are of particular interest for both solar physics and space weather investigations. SEP event occurrence is not predictable and these events are particularly dangerous to astronauts and space equipment
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
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
ACERCA DE LA ESTÉTICA DE ANTENOR ORREGO
No full textRESUMENEste artículo tiene el propósito de alcanzar un análisis panorámico de los aportes de Antenor Orrego acerca de la estética. Es el producto de nuestras reflexiones y de la investigación cualitativa realizada en torno al pensamiento del mencionado autor, para quien el hombre es un ser estético, por encima de su condición de ser pensante, ser afectivo, ser ético y ser social. Afirma que no hay una sola estética, sino varias estéticas. Y en su condición de ser estético, el hombre es creador de cultura. Sostiene que la estética mantiene con la ciencia lazos indesligables, y la compatibilidad de ambas con la afectividad. En tales relaciones, la educación juega papel fundamental. Lo último que acaba en el hombre, dice, es su manifestación de la belleza. Y no acepta parámetros en la obra del artista. Hemos consultado, para nuestro trabajo, principalmente los libros del citado autor.Palabras clave: estética, arte, belleza, ciencia y educación.ABSTRACTThe purpose of this present article is to provide an analytical overview of Antenor Orrego’s contributions on a esthetics. It is the product of our reflections and of the qualitative research concerning the thought of the aforementioned author, who associates the man to an esthetic being, over his condition as a thinking intelligent, affective, ethical and social being. He claims that there is not only one a esthetics, if not several ones. In his status as an esthetical being, the man is culture creator. He states that a esthetics main tains close ties to science together with the compatibility of affectivity. In such relationships, education plays a fundamental role. The last thing a man likes to part with is his manifestation of beauty. This does not accept parameter sin the artist’s work. In our investigation, the books of the mentioned author were main ly consulted.Key words: aesthetics, art, beauty, science and education
A comparison between nonlinear cantilever and buckled beam for energy harvesting
No full textNonlinear dynamics has become one of the key aspect to improve the efficiency of kinetic energy harvesters working in the real environment. Different methods based on the exploitation of the dynamical features of stochastic nonlinear oscillators using bi-stable piezoelectric cantilevers or buckled beams have been proposed in the past years. Such methods are shown to outperform standard linear oscillators and to overcome some of the most severe limitations of present approaches once applied to ambient vibrations. This work presents simulation results comparing the two methods. The same piezoelectric element subjected to a fixed vibrating body in a cantilever or bridge configuration has been simulated. The kinetic excitation considered is a zero mean exponentially correlated gaussian noise with different amplitudes. The piezoelectric oscillator output response has been obtained as a function of a nonlinear parameter. This work is intended to help designing the most performing energy harvester for real world applications starting from the same piezoelectric element
Effect of boundary conditions on piezoelectric buckled beams for vibrational noise harvesting
No full textNonlinear bistable systems have proven to be advantageous for energy harvesting of random and real ambient vibrations. One simple way of implementing a bistable transducer is setting a piezoelectric beam in a post-buckled configuration by axial compression. Besides, hinged or clamped-clamped type of boundary conditions correspond to two different post-buckled shape functions. Here we study, through theoretical analysis and numerical simulations, the efficiency of a hinged and clamped-clamped piezoelectric bridge under band-limited random noise with progressive axial load. Clamped configuration results to harvest 26% more power than hinged around an optimal axial load of 0.05%, while, in the intra-well trapped situation, above 0.1%, the two configurations present no substantial difference. Nevertheless, simulations confirm the advantage of exploiting inter-well oscillations in bistable regime
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