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1

An Approach to Design Broadband Air Backed Piezoelectric Sensor

Ali M. G. S., Elsayed N. Z., Eid E. A.

Archives of Acoustics

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2015

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Vol. 40, No. 1

3--10

EN

In this work, an approach to the design of broadband thickness-mode piezoelectric transducer is presented. In this approach, simulation of discrete time model of the impulse response of matched and backed piezoelectric transducer is used to design high sensitivity, broad bandwidth, and short-duration impulse response transducers. The effect of matching the performance of transmitting and receiving air backed PZT-5A transducer working into water load is studied. The optimum acoustical characteristics of the quarter wavelength matching layers are determined by a compromise between sensitivity and pulse duration. The thickness of bonding layers is smaller than that of the quarter wavelength matching layers so that they do not change the resonance peak significantly. Our calculations show that the −3 dB air backed transducer bandwidth can be improved considerably by using quarter wavelength matching layers. The computer model developed in this work to predict the behavior of multilayer structures driven by a transient waveform agrees well with measured results. Furthermore, the advantage of this this model over other approaches is that the time signal for optimum set of matching layers can be predicted rapidly.

2

A Simulation for Detecting Nonlinear Echoes from Microbubbles Packets

Ali M. G. S., Elsayed N. Z., Eid E. A.

Archives of Acoustics

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2015

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Vol. 40, No. 2

151--157

EN

This work presents a simulation of the response of packets of microbubbles in an ultrasonic pulse-echo scan line. Rayleigh-Plesset equation has been used to predict the echo from numerically obtained radial dynamics of microbubbles. Varying the number of scattering microbubbles on the pulse wave form has been discussed. To improve microbubble-specific imaging at high frequencies, the subharmonic and second harmonic signals from individual microbubbles as well as microbubbles packets were simulated as a function of size and pressure. Two different modes of harmonic generation have been distinguished. The strength and bandwidth of the subharmonic component in the scattering spectrum of microbubbles is greater than that of the second harmonic. The pressure spectra provide quantitative and detailed information on the dynamic behaviour of ultrasound contrast agent microbubbles packet.

3

Ultrasonic propagation for measuring the activation energy and volume of a hole in liquids

Ali M. G. S., Ebeid M. R., Mohamed E. A.

Archives of Acoustics

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2002

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Vol. 27, no. 4

351-360

EN

Mathematical expressions are introduced in this paper in order to measure the compressional relaxation time by the propagation of ultrasonic waves in associated and nonassociated liquids. The expressions are based on the concept of complex and frequency-dependent compressibility represented as a function of ultrasonic velocity and absorption in liquids. The available experimental data reported earlier in the literature are used in these mathematical expressions to calculate the molecular activation energy and the volume of a hole for some liquids. The introduced expressions concern the relations between the liquid compressional relaxation time and Frenkel's intermolecular relaxation time at different values of temperature and pressure. The effect of vibrational relaxation, bulk viscosity and structural rearrangement on ultrasonic absorption in liquids has been investigated.