Pedro Acevedo

KLM model for lossy piezoelectric transducers.

A KLM model has been developed using equivalent circuits to analyze the effects of different loss mechanisms on the transducer performance in the time and frequency domain. Transducers from two different piezoelectric materials (lead-zirconate-titanate (PZT) and polyvinylidene fluoride) were constructed to validate our model. Experimental results are in good agreement with the theoretical simulation.

Thickness measurement in composite materials using Lamb waves

Abstract Pulse propagation in plate elements is investigated with the identification of Lamb modes in the range 40–150 kHz. The possibilities of the application of this technique in the measurement of thickness in composites and coarse materials are evaluated, particularly in ferrocement materials.

Thickness measurement in composite materials using lamb waves: Viscoelastic effects

Pulse propagation in plates has been investigated with the identification of Lamb modes. The application of this technique to the measurement of thickness in composite and coarse materials was previously evaluated. As a sequel, results of the application of this technique taking into account the viscoelastic properties of PVC and ferrocement are presented.

The measurement of the spatial average temporal average intensity Isata and ultrasonic power W in composite ultrasonic transducers for medical application

Two possible methods to determine the spatial average temporal average intensity I(sata) and ultrasonic power W in composite ltrasonic transducers for medical application are described. Results showed that integrals using one method will yield accurate results but a vast amount of computational effort is required. On the other hand, using an alternative method these integrals may readily be solved at the expense of the accuracy of the results deduced.

Pulse propagation in plate elements

Abstract This paper describes a theoretical and experimental study of pulse propagation in plates. Specifically, this approach uses the Fourier–Laplace Transform (FLT), for the solution of the Lame equation with the boundary condition given by the transducer over one side of the plate. It is shown that a pulse in plates is formed by three fundamental components with its own dispertion relationship. Experiments were performed in elastic plates to validate the model.

The use of a novel acoustic matching material in the construction of an ultrasonic Doppler transducer for medical application

The design and construction of an ultrasonic Doppler transducer with a fixed angle for medical application using a novel acoustic matching material are described. This transducer was constructed using an 8 MHz commercial piezoelectric ceramic (PIC255) and REXOLITE which is an excellent acoustic matching material. The objective of the present work was the design and construction of an ultrasonic transducer using REXOLITE, this transducer will be part of a Doppler blood flow measurement system, the novelty of this transducer is that it includes an internal angle (45°). The resonance frequency is around 5 MHz. The transducer must work with the associated electronics using quadrature demodulation generated for the ultrasonic Doppler blood flow signal.

Pulse generator for ultrasonic PZT and PVDF transducer arrays based on a Programmable System-on-Chip (PSoC)

This paper describes the design of a pulse generator to excite PZT and PVDF ultrasonic transducer arrays, based on the Programmable System-on-Chip (PSoC) module. In this module, using programmable logic different pulses were implemented, these pulses are required in ultrasonic applications, for multiple channels to excite PZT and PVDF transducer arrays. This module can operate with programmable frequencies from 3-74 MHz; its programming may be versatile covering a wide range of ultrasonic applications. It is ideal for low-power ultrasonic applications.

Design of an angled ultrasonic transducer for blood flow measurement applications

This paper describes the design and construction of an angled ultrasonic transducer for blood flow measurement. The transducer was constructed using as sensing element, a commercial 8 MHz PIC255 piezoceramic, Insulcast 501 and Rexolite 4422 as backing and matching layer materials respectively. The objective of this work was to design and construct a single element transducer for pulsed wave Doppler blood flow measurement, with an angle of 60° resonating at approximately 8 MHz. Results show that the overall performance of the transducer fulfils the requirements of its design and it is possible to use it for blood flow measurement applications.

Simulation of a PVDF transducer array using the finite element method (FEM) to measure temperature gradients in a soft tissue

The objective of this work is to use the Finite Element Method (FEM) to simulate the performance of a PVDF transducer array to measure temperature gradients through the determination of phase shifts, i.e. time shifts of the waveform of the echo due to a change in the speed of propagation of ultrasound as a result of a change in temperature, they can be interpreted as phase shifts in the frequency domain. Making it possible to determine the change in temperature from the phase shifts; in a medium of propagation previously characterized.

Performance Improvement of Algorithms Based on the Synthetic Aperture Focusing Technique

An analysis to improve the performance of the ultrasonic synthetic aperture focusing technique (SAFT) on a PC platform is presented in this paper. Some useful processing techniques like apodization, dynamic focusing, envelope detection and image composition are used to improve the quality of the image. Finally, results of the algorithm implemented using MATLAB and C/C++ and the respective images are presented