Nonlinear energy harvesting Cottone, F; Vocca, H; Gammaitoni, L
Physical review letters,
02/2009, Letnik:
102, Številka:
8
Journal Article
Recenzirano
Ambient energy harvesting has been in recent years the recurring object of a number of research efforts aimed at providing an autonomous solution to the powering of small-scale electronic mobile ...devices. Among the different solutions, vibration energy harvesting has played a major role due to the almost universal presence of mechanical vibrations. Here we propose a new method based on the exploitation of the dynamical features of stochastic nonlinear oscillators. Such a method is shown to outperform standard linear oscillators and to overcome some of the most severe limitations of present approaches. We demonstrate the superior performances of this method by applying it to piezoelectric energy harvesting from ambient vibration.
Among the main vibration-to-electricity conversion systems, resonant harvesters suffer from a series of strong limits like their narrow frequency response and poor output power at small scale. Most ...of all, realistic vibration sources are variable in time and abundant at relatively low frequencies. Nonlinear vibration harvesters, on the other hand, are more attractive, thanks to their large bandwidth response and flexibility to convert kinetic energy of the natural frequency of the sources. In particular, bistable oscillators have been proven to show higher global performances when excited by random vibrations. In this paper, such an approach is investigated for piezoelectric beams by exerting an increasing axial compression. An advantage of this technique is the absence of magnetic forces to create bistable dynamics. A thin piezoelectric axially loaded beam is theoretically modelled and experimentally investigated under wideband random vibrations. In the buckled configuration, the device exhibits superior power generation over a large interval of resistive load, with gains up to more than a factor of ten compared to the unbuckled state. The numerical model and experimental results are in good qualitative agreement.
Multi-messenger astronomy is an emerging field of research aimed at unravelling the physics governing astrophysical transients. GW170817 stands out as the first multi-messenger observation of the ...coalescence of a binary system of neutron stars, detected by the LIGO and Virgo gravitational-wave interferometers, along with space- and ground-based electromagnetic telescopes. It is a striking example of how multi-messenger observations significantly enhance our understanding of the physics of compact objects, relativistic outflows, and nucleosynthesis. It shows a new way of making cosmology and has the potential to resolve the tension between different measurements of the expansion rate of the Universe. To optimise multi-messenger observational strategies, to evaluate the efficiency of the searches for counterparts, and to identify the host galaxy of the source in a large sky localisation, information about the volumes of galaxies within the gravitational-wave localisation is of paramount importance. This requires the use of galaxy catalogues and appropriate knowledge of their completeness. Here, we describe a new interactive web tool named GLADEnet that allows us to identify catalogued galaxies and to assess the incompleteness of the catalogue of galaxies in real time across the gravitational-wave sky localisation. This measure is of particular importance when using catalogues such as the GLADE catalogue (Galaxy List for the Advanced Detector Era), which includes a collection of various catalogues that make completeness differ across different regions of the sky. We discuss the analysis steps to defining a completeness coefficient and provide a comprehensive guide on how to use the web app, detailing its functionalities. The app is geared towards managing the vast collection of over 22 million objects in GLADE. The completeness coefficient and the GLADE galaxy list will be disseminated in real time via GLADEnet , powered by the Virtual Observatory (VO) standard and tools.
Nonlinear 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.
The Advanced Virgo monolithic fused silica suspension Aisa, D.; Aisa, S.; Campeggi, C. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
07/2016, Letnik:
824
Journal Article
Recenzirano
Odprti dostop
The detection of gravitational waves is one of the most challenging prospects faced by experimental physicists. Suspension thermal noise is an important noise source at operating frequencies between ...approximately 10 and 30Hz, and represents a limit to the sensitivity of the ground based interferometric gravitational wave detectors. Its effects can be reduced by minimizing the losses and by optimizing the geometry of the suspension fiber as well as its attachment system. In this proceeding we will describe the mirrors double stage monolithic suspension system to be used in the Advanced Virgo (AdV) detector. We also present the results of the thermal noise study, performed with the help of a finite elements model, taking into account the precise geometry of the fibers attachment systems on the suspension elements. We shall demonstrate the suitability of this suspension for installation in AdV.
•Suspension system design for the test masses of the gravitational wave detectors.•Finite element model studies.•Suspension thermal noise studies.
The realization of third-generation gravitational wave interferometric detectors is under way. An important improvement in detector sensitivity can be obtained with the reduction of thermal noise by ...reaching a cryogenic stage. Two materials have been identified to perform efficiently at low temperatures: silicon and sapphire. In this work the breaking strength of the silicate bonding that glues cylinders of silicon (Si) and sapphire (Al2O3) has been investigated. All material combinations, flatness quality and orientations have been tested over time. Breaking strength between Si--Si and Si--Al2O3 shows a value similar to that of fused silica, while Al2O3--Al2O3 does not seem to be a promising combination.
Precise low-frequency internal friction measurements on vitreous silica, taken over a wide temperature (4K < T < 300K) and frequency range (40 Hz < v < 14 kHz), show remarkable similarities, but also ...suggestive differences with recent light scattering experiments. In the interval 30K < T < 110K, the exponent a of the power law relaxational spectrum turns out to be proportional to T - Tk, with a minimum at around Tk = 13K. This phenomenon is interpreted as a manifestation of thermal activation in an asymmetric double well system, the asymmetry being associated to quenched spatial disorder. For T > 160 K the loss angle develops a distinct step-like structure followed by a plateau, both independent of v, thus signalling the onset of a competing relaxation mechanism with much higher an activation energy.
Low-frequency losses in silica glass at low temperature Travasso, F.; Bosi, L.; Dari, A. ...
Materials science & engineering. A, Structural materials : properties, microstructure and processing,
09/2009, Letnik:
521
Journal Article, Conference Proceeding
Recenzirano
Precise low-frequency internal friction measurements on vitreous silica, taken over a wide temperature (
4
K
<
T
<
300
K) and frequency range (40
Hz
<
ν
<
14
kHz), show remarkable similarities, but ...also suggestive differences with recent light-scattering experiments. In the interval
30
K
<
T
<
110
K, the exponent
α
(
T
)
of the power-law relaxational spectrum at low frequencies turns out to be proportional to
T
−
T
k
, with a minimum at around
T
k
=
13
K. This phenomenon is interpreted as a manifestation of quenched spatial disorder.
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