This work presents the design, construction and characterization of air-coupled piezoelectric transducers using 1-3 connectivity piezocomposite disks with a stack of matching layers being the outer one an active quarter wavelength layer made of polypropylene foam ferroelectret film. This kind of material has shown a stable piezoelectric response together with a very low acoustic impedance (<0.1...

Measurements and predictions have been made of the absorption coefficient and the surface acoustic impedance of poroelastic plates clamped in a large impedance tube and separated from the rigid termination by an air gap. The measured and predicted absorption coefficient and surface impedance spectra exhibit low frequency peaks. The peak frequencies observed in the absorption coefficient are clo...

Foam injection is a promising method to improve sweep efficiency for gas flooding in enhanced oil recovery (EOR). The effect of oil on foam is a complex phenomenon and for this reason three phase foam simulations have shown to be difficult in the past. Initially the objective of this simulation study was getting a better understanding of relating composition paths for foam displacements on the ...

OBJECTIVE Accurate ear-canal acoustic measurements, such as wideband acoustic admittance, absorbance, and otoacoustic emissions, require that the measurement probe be tightly sealed in the ear canal. Air leaks can compromise the validity of the measurements, interfere with calibrations, and increase variability. There are no established procedures for determining the presence of air leaks or cr...

foam injection is becoming a standard conditioning agent when tunnelling with an earth-pressure balanced shield, resulting in an increasing interest in this technique. the technique is mostly based on empirical rules and experience. to be able to determine what foam and how may foam has to be injected for different soils, it is necessary to know the mechanical parameters of the foam-water-soil ...

In the present study, we examined the role of different habitat components and their relationship with microhabitat use by three species of egret: Cocoi heron (Ardea cocoi), Great egret (Ardea alba), and Cattle egret (Bubulcus ibis), in wetlands of southern Brazil. Ardea alba and A. cocoi were not habitat-specific (e.g. vegetation cover and flooding level). Conversely, B. ibis was associated wi...

In May 2014, the Balkans were hit by a Vb-type cyclone that brought disastrous flooding and severe damage to Bosnia and Herzegovina, Serbia, and Croatia. Vb cyclones migrate from the Mediterranean, where they absorb warm and moist air, to the north, often causing flooding in central/eastern Europe. Extreme rainfall events are increasing on a global scale, and both thermodynamic and dynamical me...

We present a new model for diffuse material, i. e. water-air mixtures, that can be combined with particle-based fluids. Diffuse material is uniformly represented with particles which are classified into spray, foam and air bubbles. Physically-motivated rules are employed to generate, advect and dissipate diffuse material. The approach is realized as a post-processing step which enables efficien...