Shear and longitudinal attenuations and quality factors of poly(methyl metacrylate) (PMMA) from 20 kHz to 12 MHz investigation with ultrasonic spectroscopy.

PMMA is often considered as a calibration material for experimental benches dedicated to viscoelasticity investigation. Nevertheless, regarding literature, data concerning attenuation coefficients and quality factors are essentially available in the MHz frequency range and results in the low-frequency range are scarce and scattered. In this communication, thanks to the use of high-frequency ultrasonic spectroscopy between 2 and 8 MHz in the range 6 °C - 45 °C, Time-Temperature Superposition principle and Resonant Ultrasonic Spectroscopy (RUS), we show that both longitudinal and shear quality factors of PMMA decrease considerably for low frequencies ( View Article and Find Full Text PDF

Particulate Metal Composites as Backing for Ultrasonic Transducers for Continuous Nondestructive Measurements at Moderate and High Temperatures.

There is an increasing need for ultrasonic transducers able to operate continuously at high temperatures in many industrial sectors. Operating temperatures may be 600 °C and higher. There is not any commercial solution to deal with such applications, and only a few ultrasonic prototype probes exist.

1550 nm modulating retroreflector based on coated nanoparticles for free-space optical communication.

Nowadays, there is a renaissance in the field of space exploration. Current and future missions depend on astronauts and a swarm of robots for reconnaissance. In order to reduce the power consumption, weight, and size of the robots, an asymmetric communication system may be used.

Tunable electro-optic filter based on metal-ferroelectric nanocomposite for VLC.

The emerging technology of visible light communications (VLC) will provide a new modality of communication. This technology uses illumination lighting to carry information. We propose to add a smart capability to mitigate interferences from unwanted light sources.