Search results for "ACOUSTIC"

Semiconductor optical waveguide devices modulated by surface acoustic waves

2019

Surface waves on cylindrical solids: numerical and experimental study.

2013

The use of Rayleigh waves enables the solution of several important inspection problems. Propagation of surface waves along straight boundaries has been properly studied but investigations about their propagation on cylindrical surfaces are not sufficient, despite they can be still of interest for NDE applications. It has been proved experimentally that a surface wave pulse suffers a phase shift during its propagation along a cylindrical surface. A numerical approach has been developed to efficiently study these effects for different materials, curvatures and frequencies. This study can help the scientific community to better understand the phenomenon, quite complex and not yet fully explor…

Dynamic carrier distribution in quantum wells modulated by surface acoustic waves

2001

We have investigated the dynamics of photogenerated carriers under surface acoustic wave (SAW) fields in GaAs quantum wells using spatially and time-resolved photoluminescence (PL). The frequency and phase of the PL oscillations under a SAW yield information about the carrier distribution and the band-gap modulation induced by the SAW. We directly prove that the transport properties of the carriers ultimately control their distribution, storage and, subsequent recombination in the modulated potential.

Perception and replication of planar sonic gestures

2012

As tables, boards, and walls become surfaces where interaction can be supported by auditory displays, it becomes important to know how accurately and effectively a spatial gesture can be rendered by means of an array of loudspeakers embedded in the surface. Two experiments were designed and performed to assess: (i) how sequences of sound pulses are perceived as gestures when the pulses are distributed in space and time along a line; (ii) how the timing of pulses affects the perceived and reproduced continuity of sequences; and (iii) how effectively a second parallel row of speakers can extend sonic gestures to a two-dimensional space. Results show that azimuthal trajectories can be effectiv…

Improving surface detection on nanoindentation of compliant materials

2010

Nanoindentation is a versatile tool for monitoring mechanical properties on a local scale. Accurate knowledge of a contact area, and therefore an initial contact, is however necessary for translating the force curve into sample mechanical properties. It is shown that methods for sensing an initial contact by depth sensing instruments (DSI) may be severely in error for compliant materials. With the hardware adopted in this work, the threshold is determined by the elastic modulus; hence the error potentially increases if the material becomes more compliant. A simple method is therefore suggested to determine with accuracy the initial contact on compliant materials whereby the surface contact …

Integrated photonic routers driven by surface acoustic waves

2016

Durante la segunda mitad del siglo XX se produjo un desarrollo excepcional de la capacidad de transmitir y procesar información electrónicamente. Esto fue debido en parte a la capacidad de integrar en un único substrato una gran cantidad de transistores, que son las unidades fundamentales de procesamiento de datos. Este comportamiento quedó resumido en la ley de Moore, que predecía que el número de transistores integrados se duplicaría cada 24 meses. Esta tendencia, que se ha mantenido hasta la actualidad con transistores de tamaño nanométrico, no puede continuar indefinidamente. Uno de los problemas fundamentales reside en la capacidad limitada para disipar el calor que generan los disposi…

Remote monitoring of building oscillation modes by means of real-time Mid Infrared Digital Holography

2016

AbstractNon-destructive measurements of deformations are a quite common application of holography but due to the intrinsic limits in the interferometric technique, those are generally confined only to small targets and in controlled environment. Here we present an advanced technique, based on Mid Infrared Digital Holography (MIR DH), which works in outdoor conditions and provides remote and real-time information on the oscillation modes of large engineering structures. Thanks to the long wavelength of the laser radiation, large areas of buildings can be simultaneously mapped with sub-micrometric resolution in terms of their amplitude and frequency oscillation modes providing all the modal p…

Design & Optimization of Large Cylindrical Radomes with Subcell and Non-Orthogonal FDTD Meshes Combined with Genetic Algorithms

2021

The word radome is a contraction of radar and dome. The function of radomes is to protect antennas from atmospheric agents. Radomes are closed structures that protect the antennas from environmental factors such as wind, rain, ice, sand, and ultraviolet rays, among others. The radomes are passive structures that introduce return losses, and whose proper design would relax the requirement of complex front-end elements such as amplifiers. The radome consists mostly in a thin dielectric curved shape cover and sometimes needs to be tuned using metal inserts to cancel the capacitive performance of the dielectric. Radomes are in the near field region of the antennas and a full wave analysis of th…

A linear generator for a waveroller power device

2017

In this paper experimental tests on a small scale tubular linear generator to be applied to wave rollers device are presented. A reduced scale of gnerator is presented and experimental results obtained in on test bench are shown. Experimental waveforms of current and voltage are recorded. Simulation results are compared to the experimental ones in order to validate the mathematical models used.

Integrazione di celle fotovoltaiche ibride nel vetromattone

2012

L’invenzione riguarda l’integrazione del vetromattone con celle solari ibride (organiche/inorganiche), conosciute come Dye-sensitized Solar Cell (DSC). La combinazione del vetromattone con le DSC consente di migliorare le prestazioni del prodotto originario rendendolo in grado di produrre energia pulita. Le caratteristiche di trasparenza e isolamento termo-acustico del prodotto possono essere regolate agendo sulla configurazione delle DSC. Il prodotto può essere assemblato a formare pannelli fotovoltaici per la realizzazione di facciate traslucide energeticamente “attive” in varie condizioni luminose (condizioni di luce diffusa o artificiale) e indipendentemente dall’angolo di radiazione so…