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Ultrasonics, Ferroelectrics, and Frequency Control, IEEE Transactions on

Issue 5 • Date May 2003

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Displaying Results 1 - 17 of 17
  • A nonlinear electromechanical model for ferroelectric materials: application to soft-PZT thick films screen-printed on alumina substrate

    Publication Year: 2003 , Page(s): 471 - 480
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1497 KB) |  | HTML iconHTML  

    Motivated by experimental observations made on soft-PZT/alumina cantilever bimorphs, a nonlinear electromechanical model is presented describing the characteristic phenomena of ferroelectricity: the dielectric hysteresis, the butterfly loop, and the ferroelastic hysteresis. This model uses a phenomenological formulation, written within the general framework of thermodynamics of irreversible processes. The one-dimensional formulation of the model is successfully validated using experimental data from the literature. The model is used to predict the electromechanical behavior of a PZT/alumina cantilever bimorph. The results of the simulations are very promising. View full abstract»

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  • Growth of PZN crystals with improved optical quality using the BSFT technique

    Publication Year: 2003 , Page(s): 481 - 486
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1261 KB) |  | HTML iconHTML  

    The bottom seeded fluxothermal (BSFT) high-temperature solution growth technique was used to grow Pb(Zn/sub 1/3/Nb/sub 2/3/)O/sub 3/ (PZN) relaxor crystals. During the process, the seed was held in a cold spot of a Pt crucible having a relatively high temperature gradient. The method can separate the perovskite and pyrochlore phases, decrease the spontaneous nucleation, and increase the thermodynamic driving force resulting in larger crystals than those obtained by conventional slow-cooling techniques. The BSFT technique also can improve the quality of the structural and morphological characteristics, which has been demonstrated by visual observation, x-ray diffraction, Raman, ultraviolet-visible (UV-VIS), and IR absorption measurements. These PZN crystals have less distortion in the unit cell, high optical transparency in the 390 nm-5700 nm range, and improved Pb-related stoichiometry. View full abstract»

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  • Modeling of quartz crystal oscillators by using nonlinear dipolar method

    Publication Year: 2003 , Page(s): 487 - 495
    Cited by:  Papers (2)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1217 KB) |  | HTML iconHTML  

    A quartz crystal oscillator can be thought of as a resonator connected across an amplifier considered as a nonlinear dipole the impedance of which depends on the amplitude of the current that flows through it. The nonlinear amplifier resistance and reactance are obtained by using a time domain electrical simulator like SPICE (Simulation Program with Integrated Circuit Emphasis): the resonator is replaced with a sinusoidal current source of the same frequency and a set of transient analyses is performed by giving the current source a larger amplitude. A Fourier analysis of the steady-state voltage across the dipolar amplifier is performed to calculate both real and imaginary parts of the dipolar impedance as a function of the current amplitude. From these curves, it is then possible to accurately calculate the oscillation amplitude and frequency without having to perform unacceptably long transient analyses needed by a direct oscillator closed loop simulation. This method implemented in the Analyse Dipolaire des Oscillateurs a Quartz or Quartz Crystal Oscillators Dipolar Analysis (ADOQ) program calculates the oscillation start-up condition, the oscillation steady-state features (oscillation amplitude and frequency), and the oscillator sensitivity to various parameters. The oscillation nonlinear differential equation is solved by using the slowly varying function method so that the program quickly and accurately calculates the current amplitude and frequency transients. Measurements performed on an actual amplifier show a very good agreement with the results obtained by the simulation program. View full abstract»

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  • Native tissue imaging at superharmonic frequencies

    Publication Year: 2003 , Page(s): 496 - 506
    Cited by:  Papers (28)  |  Patents (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1302 KB) |  | HTML iconHTML  

    The second harmonic imaging mode has been adapted to image tissue and shown considerable improvements in image quality in several applications compared to the fundamental mode. The improvements were attributed to the effects of wave distortion due to nonlinear propagation in tissue. However, imaging tissue at the second harmonic frequency only has various drawbacks. Because the energy in the second harmonic frequency band is much lower than that in the fundamental frequency band, there must be excellent sensitivity and dynamic range in the receiving system to achieve an acceptable amount of signal-to-noise ratio. To increase the sensitivity, the spectral overlap between the fundamental and the second harmonic has to be diminished, which in return deteriorates the imaging resolution. Consequently, a trade-off is mandatory between resolution and sensitivity. Using simulations and measurements, we show that, at appropriate scanning acoustic settings, higher harmonics are generated in tissue. The higher harmonics represent additional, relevant information for tissue imaging and characterization. An elegant way to take advantage of the higher harmonics and to bring all the information together is to combine and incorporate all the multiple higher harmonics into a single component that we call the superharmonic component. Using a newly developed array transducer having a wide frequency band, B-mode images of a phantom were made in the superharmonic mode transmitting at 1.2 MHz. These images have exceptionally improved clarity and yield a dramatically cleaner and sharper contrast between the different structures being imaged. In addition to increased signal-to-noise ratio, superharmonic imaging shows better contrast and axial resolution as well as acceptable penetration depth. View full abstract»

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  • Multilayer analysis: quantitative scanning acoustic microscopy for tissue characterization at a microscopic scale

    Publication Year: 2003 , Page(s): 507 - 516
    Cited by:  Papers (6)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (2435 KB) |  | HTML iconHTML  

    An in vitro acoustic microscopy method for the quantitative characterization of biological hard tissues at a microscopic scale is described. At a frequency of 900 MHz, the acoustic impedance is measured as a tissue parameter, which is closely related to its elastomechanical properties. Contrast influences caused by defocus, edges, and surface inclinations, respectively, are either compensated or excluded from the measurement by a special data acquisition and analysis concept. A raster grid was used to validate the capabilities and limitations of the method, and results obtained from human cortical bone are shown. The comparison of different evaluation methods demonstrate the significance of a sophisticated analysis under consideration of topographical and system parameters. Cortical bone impedance maps showed a strong dependence on the anatomical structures, and the mean values were found to be in the range from 3.5 to 6.5 Mrayl within one single osteon. View full abstract»

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  • Acoustic characterization of microbubble dynamics in laser-induced optical breakdown

    Publication Year: 2003 , Page(s): 517 - 522
    Cited by:  Papers (6)  |  Patents (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1449 KB) |  | HTML iconHTML  

    A real-time acoustic technique to characterize microbubbles produced by laser-induced optical breakdown (LIOB) in water was developed. Femtosecond laser pulses are focused just inside the surface of a small liquid tank. A tightly focused, high frequency, single-element ultrasonic transducer is positioned so its focus coincides axially and laterally with this laser focus. When optical breakdown occurs, a bubble forms and a pressure wave is emitted (i.e., acoustic emission). In addition to this acoustic signal, the microbubble is actively probed with pulse-echo measurements from the same transducer. After the bubble forms, received pulse-echo signals have an extra pulse, describing the bubble location and providing a measure of axial bubble size. Wavefield plots of successive recordings illustrate the generation, growth, and collapse of cavitation bubbles due to optical breakdown. These same plots also can be used to quantify LIOB thresholds. View full abstract»

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  • Simulations and measurements of optical images of insonified ultrasound contrast microbubbles

    Publication Year: 2003 , Page(s): 523 - 536
    Cited by:  Papers (11)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (2818 KB) |  | HTML iconHTML  

    Ultrasound contrast agents (UCAs) are used in a clinical setting to enhance the backscattered signal from the blood pool to estimate perfusion and blood flow. The UCAs consist of encapsulated microbubbles, measuring 1-10 /spl mu/m in diameter. Acoustic characterization of UCAs is generally carried out from an ensemble of bubbles. The measured signal is a complicated summation of all signals from the individual microbubbles. Hence, characterization of a single bubble from acoustic measurements is complex. In this study, 583 optical observations of freely flowing, oscillating, individual microbubbles from an experimental UCA were analyzed. The excursions during ultrasound exposure were observed through a microscope. Images were recorded with a high frame rate camera operating at 3 MHz. Microbubbles on these images were measured offline, and maximal excursions were determined. A technique is described to determine the diameters of the bubbles observed. We compared the maximal excursions of microbubbles of the same initial size in an ultrasound field with a 500 kHz center frequency at acoustic amplitudes ranging from 0.06 MPa to 0.85 MPa. It was concluded that maximal excursions of identical bubbles can differ by 150% at low acoustic pressures (mechanical index or MI<0.2). At a high acoustic pressure (MI=1.2) an image sequence was recorded on which a bubble collapsed, but an apparently identical bubble survived. View full abstract»

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  • Mg/sub x/Zn/sub 1-x/O: a new piezoelectric material

    Publication Year: 2003 , Page(s): 537 - 543
    Cited by:  Papers (3)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1318 KB) |  | HTML iconHTML  

    Piezoelectric ZnO thin films have been successfully used for multilayer surface acoustic wave (SAW) and bulk acoustic wave (BAW) devices. Magnesium zinc oxide (Mg/sub x/Zn/sub 1-x/O) is a new piezoelectric material, which is formed by alloying ZnO and MgO. Mg/sub x/Zn/sub 1-x/O allows for flexibility in thin film SAW device design, as its piezoelectric properties can be tailored by controlling the Mg composition, as well as by using Mg/sub x/Zn/sub 1-x/O/ZnO multilayer structures. We report the metal-organic chemical vapor deposition (MOCVD) growth, structural characterization and SAW evaluation of piezoelectric Mg/sub x/Zn/sub 1-x/O (x<0.35) thin films grown on (011~2) r-plane sapphire substrates. The primary axis of symmetry, the c-axis, lies on the Mg/sub x/Zn/sub 1-x/O growth plane, resulting in the in-plane anisotropy of piezoelectric properties. SAW test devices for Rayleigh and Love wave modes, propagating parallel and perpendicular to the c-axis, were designed and fabricated. Their SAW properties, including velocity dispersion and piezoelectric coupling, were characterized. It has been found that the acoustic velocity increases, whereas the piezoelectric coupling decreases with increasing Mg composition in piezoelectric Mg/sub x/Zn/sub 1-x/O films. View full abstract»

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  • Calibration of Curie temperatures for LiTaO/sub 3/ single crystals by the LFB ultrasonic material characterization system

    Publication Year: 2003 , Page(s): 544 - 552
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (744 KB) |  | HTML iconHTML  

    The line-focus-beam ultrasonic material characterization (LFB-UMC) system is applied to a standardized comparison and evaluation of the Curie temperatures, T/sub C/, exclusively used in evaluating the chemical compositions of commercial LiTaO/sub 3/ crystals by measuring the velocities of Rayleigh-type leaky surface acoustic waves (LSAWs), V/sub LSAW/. We measured V/sub LSAW/ and T/sub C/ (standardized) under the same T/sub C/ measurement conditions for 36/spl deg/Y X-LiTaO/sub 3/ single-crystal wafers produced by four manufacturers and related the results to the T/sub C/ (individual) measured by the individual manufacturers. The relationships between V/sub LSAW/ and T/sub C/ (individual) varied from one company to another, and a single straight line of the proportional relationship between V/sub LSAW/ and T/sub C/ (standardized) was obtained for all wafers regardless of the manufacturer. These experimental results clarify that the problem associated with T/sub C/ measurements lies in the measurement conditions and the absolute accuracy of the measurement instruments. Measurements of the center frequencies of SH-type surface acoustic wave (SAW) filter devices are compared with V/sub LSAW/ measurements. A method of calibrating T/sub C/ using this ultrasonic system is proposed to establish standardized specifications of SAW-device crystal wafers. View full abstract»

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  • Elastic, anelastic, and piezoelectric coefficients of langasite: resonance ultrasound spectroscopy with laser-Doppler interferometry

    Publication Year: 2003 , Page(s): 553 - 560
    Cited by:  Papers (13)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (965 KB) |  | HTML iconHTML  

    This paper presents advanced techniques to determine all independent elastic-stiffness coefficients C/sub ij/, the associated internal friction Q/sub ij//sup -1/, and piezoelectric coefficients e/sub ij/ of monocrystal langasite (La/sub 3/Ga/sub 5/SiO/sub 14/) using a single rectangular parallelepiped specimen. Langasite's crystal structure belongs to the trigonal system with point group 32, and thus possesses six independent C/sub ij/, two e/sub ij/, and two dielectric coefficients /spl epsiv//sub ij/. All of the elastic and piezoelectric coefficients affect the mechanical resonance frequencies of the solid specimen, and measuring them very accurately permits one to determine the C/sub ij/ and e/sub ij/ with known density, dimensions, and e/sub ij/. We developed a piezoelectric tripod to support the specimen upward and measured the free-vibration resonance frequencies with minimum load from its own weight. This weak and stable acoustic coupling ensures accuracy of the frequency measurement better than 10/sup -5/, enough to determine the coefficients reliably. Our C/sub ij/ fall in the range of results measured with previous (conventional) methods. Our e/sub 11/ is smaller than the reported values by 1.2-13%, and e/sub 14/ is larger by 44-97%. For the internal friction measurement, we used a solenoid coil to vibrate the specimen without any contact. The longitudinal-wave internal friction considerably exceeds the shear-wave internal friction, which can be explained by phonon-phonon interactions. View full abstract»

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  • Denoising quadrature Doppler signals from bi-directional flow using the wavelet frame

    Publication Year: 2003 , Page(s): 561 - 564
    Cited by:  Papers (8)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (740 KB) |  | HTML iconHTML  

    A novel approach was proposed to denoise quadrature Doppler signals from bi-directional blood flow using the wavelet frame and a soft-thresholding algorithm. A direction separation step was carried out first to avoid the phase distortion of quadrature Doppler signals, which is induced from the nonlinear, soft-thresholding processing. Then real parts of separated complex signals from the unidirectional flow were denoised independently. The quadrature Doppler signals from the bi-directional flow were reconstructed from the denoised separated signals. The approach has been applied to the simulated Doppler signals from a femoral artery. It is concluded from the experimental results that this method is practical for denoising quadrature Doppler signals. View full abstract»

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  • [Front cover]

    Publication Year: 2003 , Page(s): i
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    Freely Available from IEEE
  • [Inside front cover]

    Publication Year: 2003 , Page(s): ii
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    Freely Available from IEEE
  • [Inside back cover]

    Publication Year: 2003 , Page(s): iii
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  • Table of contents

    Publication Year: 2003 , Page(s): iv
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  • Information for contributors

    Publication Year: 2003 , Page(s): 467 - 470
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    Freely Available from IEEE
  • Final Call for Papers for the 2003 IEEE Ultrasonics Symposium

    Publication Year: 2003 , Page(s): 565
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    Freely Available from IEEE

Aims & Scope

IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control focuses on the theory, design, and application on generation, transmission, and detection of bulk and surface mechanical waves.

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Editor-in-Chief
Steven Freear
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