flow unit characterization plays an important role in heterogeneity analysis and reservoir simulation studies. usually, a correct description of the lateral variations of reservoir is associated with uncertainties. from this point of view, the well data alone does not cover reservoir properties. because of large well distances, it is difficult to build the model of a heterogenic reservoir, but ...

In a previous study [J. Acoust. Soc. Am. 108, 1290 (2000)] the acoustic impedance difference between intercostal tissue and lung was evaluated as a possible explanation for the enhanced lung damage with increased hydrostatic pressure, but the hydrostatic-pressure-dependent impedance difference alone could not explain the enhanced occurrence of hemorrhage. In that study, it was hypothesized that...

This paper presents the effects of a wall impedance on the propagation of higher-order modes in a three-dimensional vocal-tract model. This model is constructed using an asymmetrically connected structure of rectangular acoustic tubes, and can parametrically represent acoustic characteristics in higher frequencies where the assumption of the plane wave propagation does not hold. The propagation...

in exploration seismology, estimation of elastic parameters of rocks using seismic amplitudes is considered as inverse problems. nowadays, model-based and more generally optimization-based algorithms are of the most common methods of seismic inversion. these algorithms which are known as deterministic methods, are suffering from two main problems; first, vertical resolution of outputs is very l...

measurement of the stroke volume and its changes over time can be very helpful for diagnosis of dysfunctions in the blood circulatory system and monitoring their treatments. impedance cardiography (icg) is a simple method of measuring the stroke volume based on changes in the instantaneous mean impedanceof the thorax. this method has received much attention in the last two decades because it is...

The input acoustic impedance of musical wind instruments necessarily has a dramatic variation with frequency. Our technique uses an acoustic current source whose output is calibrated on a purely resistive load, provided by a ‘semi-infinite’ cylindrical pipe. The frequencies, amplitudes and phases of the sinusoidal components in the stimulus are chosen explicitly to provide the desired frequency...

Variations in the acoustic impedance throughout cells and tissue can be used to gain insight into cellular microstructures and the physiologic state of the cell. Ultrasound imaging can be used to create a map of the acoustic impedance, on which fluctuations can be used to help identify the dominant ultrasound scattering source in cells, providing information for ultrasound tissue characterizati...

We describe a simple and inexpensive method for monitoring nasal air flow resistance using measurement of the small-signal acoustic input impedance of the nasal passage, similar to the audiological measurement of ear drum compliance with acoustic tympanometry. The method requires generation of a fixed sinusoidal volume-velocity stimulus using ear-bud speakers, and an electret microphone to moni...

refractor ambiguities are big problem in seismic refraction method especially in seismic engineering. there can be hidden subsurface geological phenomena such as hidden faults and shear zones which are not simply predicted by the travel-time graph or some geophysical methods. head wave amplitudes are used to show the resolution of refractor ambiguities and the existence of anisotropy in complex...

In (3) φ is an arbitrary test function and ρ the density of the fluid. In consequence, to calculate the acoustic field and thus, to solve the acoustic wave equation, the impedance Za on the surface Γ has to be known. Hence, a measurement technique to determine the acoustic impedance is of great importance, because a realistic sound field can only be calculated, if the real acoustic impedance at...