Abstract— This work investigates the improvement of the active reflection coefficient of waveguide-fed phased-array antenna using liquid crystal layers. The anisotropy properties of liquid crystal layer can be employed to eliminate blind scan angle and improve the wide angle impedance matching of the waveguide-fed phased array antennas. The authors have expressed the modal analysis of the waveg...

For understanding the physics of sound and the biophysics of acoustic sensors in animals, the concepts of impedance and admittance, impedance matching, transducer, transformer, passive and active, bidirectional coupling, and resonance are widely used. They all arise from the circuit-theory metamodel, which has been applied extensively in acoustics. As the name suggests, the circuit-theory metam...

The process by which sound is propagated in the head of a toothed whale is still a subject of discussion. Investigating the distribution of acoustic impedance calculated by density and Young's modulus is effective for quantitative comprehension because acoustic impedance determines the reflection coefficient of a sound wave. However, the sound propagation process of the toothed whale has been m...

In this paper, the contact motion between rigid body systems floating in space is formulated and dynamic conditions are investigated in order to capture a non-cooperative satellite. As for the theoretical investigation, impedance matching is discussed for the case in which the robot hand under impedance control approaches and collides with a passive target, and a specific impedance value is def...

Noise pollution has become one of the most serious problems of our society. Considerable part of unpleasant noise is transmitted into the interior of buildings through large vibrating planar structures windows with poor noise-isolation properties caused by their low flexural rigidity. In this Paper, we demonstrate and analyze a noise shielding using an active acoustic metamaterial (AAMM) with e...

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...

The acoustic impedance at the diaphragm of an electroacoustic transducer can be modified using a range of active control strategies, amongst which is “direct impedance control”. This technique employs a combination of feedbacks, one on the acoustic pressure and the other on the diaphragm velocity, to the loudspeaker electric terminals, allowing significant modifications of the acoustic resonato...

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 this work we present a new hybrid imaging technique that combines electrical impedance tomography (EIT) with acoustic tomography. The novel technique makes use of the fact that the absorbed electrical energy inside the body raises its temperature, thus leading to expansion effects. The expansion then induces an acoustic wave which can be recorded outside the body and consequently be used to ...

PURPOSE The aim of this study is to correlate the intraocular pressure (IOP) change with the acoustic impedance of the cornea, in order to propose a noncontact and noninvasive method for IOP monitoring. METHODS AND MATERIALS A highly focused transducer (frequency 47-MHz; bandwidth 62%) was made to measure the echo from the anterior and posterior surfaces of intact porcine eyes, respectively. ...