IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control

To overcome the inherent low frame rate of conventional ultrasound, we have previously presented a system that can be implemented on conventional ultrasound scanners for high-frame-rate imaging of monochromatic tissue motion. The system employs a sector subdivision technique in the sequencer to increase the acquisition rate. To eliminate the delays introduced during data acquisition, a motion phas... View full abstract»

The electro-mechanical coupling and resonance characteristics of a piezoelectric modulated thin film bulk acoustic wave resonator (PMBAR) is described quantitatively. The derived 1-D analytical model is in agreement with 2-D finite element modeling (FEM). The modeling shows that a pure shear mode excitation can be achieved and that coupling of parasitic Lamb waves is reduced in this design. View full abstract»

We present a linearization circuit based on a capacitive Wheatstone bridge that is able to set a desired polarization in a piezoactuator. The system is meant to be used for dynamic actuation in a broad frequency range. A general nonlinear model for piezoactuators is presented in which two nonlinear sub-systems are cascaded: the electric-field-to-polarization (E-P) and the polarization-to-strain (P... View full abstract»

A piezoelectric transducer for harvesting energy from ambient mechanical vibrations/strains under pressure condition was developed. The proposed transducer was made of two ring-type piezoelectric stacks, one pair of bow-shaped elastic plates, and one shaft that pre-compresses them. This transducer works in flex-compressive (F-C) mode, which is different from a conventional flex-tensional (F-T) one... View full abstract»

A novel drive system is described which improves the operational characteristics of piezoelectric actuators. Electronic controls to increase the range of movement across a wide temperature range usually need a temperature sensor for maximum effect. This paper describes a novel system that uses the polarization characteristics of the piezoelectric ceramic to reverse polarize the ceramic without a t... View full abstract»

We propose a method for direct digital frequency synthesis (DDS) using a cubic spline piecewise-polynomial model for a phase-to-sinusoid amplitude converter (PSAC). This method offers maximum smoothness of the output signal. Closed-form expressions for the cubic polynomial coefficients are derived in the spectral domain and the performance analysis of the model is given in the time and frequency d... View full abstract»

A hybrid approach that inherits both the robustness of the regularized motion tracking approach and the efficiency of the predictive search approach is reported. The basic idea is to use regularized speckle tracking to obtain high-quality seeds in an explorative search that can be used in the subsequent intelligent predictive search. The performance of the hybrid speckle-tracking algorithm was com... View full abstract»

Observation techniques for measuring the small vibration of a single microcapsule of tens of nanometers in an acoustic standing wave field are discussed. First, simultaneous optical observation of a microbubble vibration by two methods is investigated, using a high-speed video camera, which permits two-dimensional observation of the bubble vibration, and a laser Doppler vibrometer (LDV), which can... View full abstract»

Although quantitative ultrasound imaging based on backscattering coefficients has proven potential for tissue characterization, the scattering models used in most studies assume distributions of identical scatterers. However, actual tissues may exhibit multiple levels of spatial scales. Therefore, the objective of the present study is to analyze the effects of scatterer size distributions when usi... View full abstract»

A full-wave equation that describes nonlinear propagation in a heterogeneous attenuating medium is solved numerically with finite differences in the time domain (FDTD). This numerical method is used to simulate propagation of a diagnostic ultrasound pulse through a measured representation of the human abdomen with heterogeneities in speed of sound, attenuation, density, and nonlinearity. Conventio... View full abstract»

This report describes a system that utilizes a single high-intensity focused ultrasound (HIFU) transducer for both the localization and ablation of arteries with internal diameters of 0.5 and 1.3 mm. In vitro and in vivo tests were performed to demonstrate both the imaging and ablation functionalities of this system. For imaging mode, pulsed acoustic waves (3 cycles for in vitro and 10 cycles for ... View full abstract»

The wavelet transform (WT) is widely used in ultrasonic flaw detection (UFD) systems because of its property of multiresolution time-frequency analysis. Those traditional WT-based methods for UFD use a wavelet basis with limited types to match various echo signals (called wavelet matching signals), so it is difficult for those methods to achieve the optimal match between echo signal and wavelet ba... View full abstract»

In this work we propose a novel circuit design: a double-resonance oscillator. Its oscillation shows two oscillation modes: frequency locking to the quartz crystal resonance and LC resonance oscillation. Transition of the oscillation mode and the strength of oscillation are analyzed and reviewed for the fundamental mode in comparison with a Colpitts oscillator. The experimental results support the... View full abstract»

Lithium niobate has recently been used for SAW tags and temperature sensors because of its high coupling coefficient and high reflectivity. To increase the device operating frequency for a given electrode line resolution, harmonic operation of the reflector is a very attractive option. When used in conjunction with harmonically operated transducers, the device operating frequency can be increased ... View full abstract»

High-power ultrasound has many diverse uses in process applications in industries ranging from food to pharmaceutical. Because cavitation is frequently a desirable effect within many high-power, low-frequency systems, these systems are commonly expected to feature highly nonlinear acoustic propagation because of the high input levels employed. This generation of harmonics significantly alters the ... View full abstract»

Potential NASA optical missions such as the Space Interferometer Mission require actuators for precision positioning to accuracies of the order of nanometers. Commercially available multilayer piezoelectric stack actuators are being considered for driving these precision mirror positioning mechanisms. These mechanisms have potential mission operational requirements that exceed 5 years for one miss... View full abstract»

The vibration characteristics of a piezoelectric fiber actuator with helical electrodes are studied theoretically and experimentally. Its working principle indicates that the torsional, longitudinal, and tangential deformations of the fiber are coupled. A simplified dynamic model is deduced to investigate the properties of the coupled vibrations and their corresponding equivalent circuits are also... View full abstract»

In ultrasound strain and elasticity imaging, an accurate and cost-effective sub-pixel displacement estimator is required because strain/elasticity imaging quality relies on the displacement SNR, which can often be higher if more computational resources are provided. In this paper, we introduce an autocorrelation-based method to cost-effectively improve subpixel displacement estimation quality. To ... View full abstract»

Cubic design of a stator in a rotary-linear piezoelectric actuator is sophisticated and interesting, but the vibration theory of the cubic stator remains unclear when using the finite element method (FEM). In this paper, we analyze the vibration behavior of the cubic stator by applying the energy method, which distinguishes the component of mechanical energy. By changing the design of the stator (... View full abstract»