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The focusing of acoustic waves is used to study nucleation phenomena in liquids. At large amplitude , non-linear effects are important so that the magnitude of pressure or density oscillations is difficult to predict. We present a calculation of these oscillations in a spherical geometry. We show that the main source of non-linearities is the shape of the(More)
The article describes a new field sensor to monitor continuously in situ moisture and salinity of a porous medium via measurements of its dielectric permittivity, conductivity and temperature. It intends to overcome difficulties and biases encountered with sensors based on the same sensitivity principle. Permittivity and conductivity are determined(More)
By focusing a high-intensity acoustic wave in liquid helium, we have observed the nucleation of solid helium inside the wave above a certain threshold in amplitude. The nucleation is a stochastic phenomenon. Its probability increases continuously from 0 to 1 in a narrow pressure interval around P(m) + 4.7 bars ( P(m) = 25.3 bars is the melting pressure(More)
This paper describes a sensor dedicated to measuring the vertical profile of the complex permittivity and the temperature of any medium in which sensor electrodes are inserted. Potential applications are the estimate of the humidity and salinity in a porous medium, such as a soil. It consists of vertically-stacked capacitors along two conductive parallel(More)
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