Analysis and Optimization of a Piezoelectric Harvester on a Car Damper

AbstractLow power levels obtained from piezoelectric conversion of ambient vibrations appear to be a promising solution to supply wireless sensors embedded inside automotive suspension. However such a solution requires overall an optimum power extraction from the piezoelectric power harvester. This leads to the use of a sufficiently accurate and flexible modelling method to find the optimal characterics and configuration of the harvester. To this end, an innovative bond graph model of the piezoelectric harvester embedded in the quarter vehicle system is proposed for providing the harvested power when a car travels a road with a speed bump at 30km/h. Results show that around of 0.5 milliwatt electrical power is harvested when varying key parameters like the location and characteristics of the piezoelectric device

Non destructive evaluation of heterogeneous media using cepstrum analysis

A new direction for the non destructive evaluation of heterogeneous materials is presented, which relies on the cepstrum of the backwards diffused signal for the characterization of the internat structure of the medium under study . The spectrum of the reflected signal is correlated to the sample structure . By using the cepstrum transform, informations about the mean spacing between the scatterers and the volume percent of heterogeneites may be obtained for biphase media . A set of simulations make the advantages of the cepstrum analysis over the spectral analysis clear . The theoretical results are compared with experiments.Approche nouvelle du contrôle non destructif par ultrasons des milieux hétérogènes. Elle permet, à l'aide de l'analyse cepstrale du signal rétrodiffusé, une caractérisation de la structure du milieu étudi

Recent advances in the prevention and management of infections in children undergoing treatment for cancer

A major consequence of the intensive multi-modal chemotherapy commonly used to treat malignancies in childhood is life-threatening infection, frequently during periods of profound neutropenia. Recent advances have been made in all areas of management, from trying to prevent infection to getting patients off antimicrobials and home again in the shortest, safest way. Potential avenues of further research are outlined for readers to be aware of in the next few years

Mesure quantitative de la porosité résiduelle des ciments chirurgicaux par ultrasons de haute fréquence

A high frequency ultrasonic quantitative characterization of the porosity of biological cements for the fixation of prosthetic components has been realised. The images were acquired with a C-Scan system using a focused 50 MHz transducer. The images were treated by a histogram processing technique associated with a segmentation algorithm. The use of this system has allowed us to demonstrate that a decrease in porosity could be obtained by a polymerization under a high power insonification at 500 kHz

Etude de la cavitation par caractérisation dynamique impulsionnelle

La cavitation ultrasonore haute fréquence est aujourd'hui de plus en plus étudiée car elle fournit un outil efficace à la synthèse chimique. Le transducteur ultrasonore étant un émetteur récepteur, il est utilisé en mode réflexion. Notre but est d'obtenir des mesures quantitatives de paramètres physiques des bulles en étudiant la propagation d'impulsions ultrasonores dans le milieu de cavitation. L'intérêt majeur de cette méthode réside dans son caractère non perturbant.As it provides a more efficient tool for some typical chemical reactions, the high frequency ultrasonic cavitation is nowadays increasingly studied. The ultrasonic transducer is a reciprocal sensor, so it is used in this work in a pulse reflection mode. Our purpose is to obtain quantitative measurements of physical parameters of the bubbles , studying the propagation of ultrasonic pulses in the cavitating medium

Transport and accumulation of particles in a granular bed : application to the injection of pulverized coal in a blast furnace

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