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Ultrasonics, Ferroelectrics, and Frequency Control, IEEE Transactions on

Issue 8 • Date August 2008

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Displaying Results 1 - 25 of 27
  • IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control

    Publication Year: 2008 , Page(s): c1
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  • IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control - Staff

    Publication Year: 2008 , Page(s): c2
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  • IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control - Committee

    Publication Year: 2008 , Page(s): i
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  • Table of contents

    Publication Year: 2008 , Page(s): ii - iv
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  • Information for Contributors - Table of Contents

    Publication Year: 2008 , Page(s): 1671 - 1675
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  • A Multimedia Example

    Publication Year: 2008 , Page(s): 1676
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  • Call for front-cover images for the Transactions on Ultrasonics, Ferroelectrics, and Frequency Control

    Publication Year: 2008 , Page(s): 1677
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  • A thickness mode acoustic wave sensor for measuring interface stiffness between two elastic materials

    Publication Year: 2008 , Page(s): 1678 - 1681
    Cited by:  Papers (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (259 KB) |  | HTML iconHTML  

    We studied thickness vibration of 2 elastic layers with an elastic interface mounted on a plate piezoelectric resonator. The effect of the interface elasticity on resonant frequencies was examined. The result obtained suggests an acoustic wave sensor for measuring the elastic property of an interface between 2 materials. View full abstract»

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  • Lead-free piezoelectric-metal-cavity (PMC) actuators

    Publication Year: 2008 , Page(s): 1682 - 1685
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (420 KB) |  | HTML iconHTML  

    A piezoelectric piezoelectric-metal-cavity (PMC) actuator was reported previously that can exhibit a large flexural displacement. In this paper, a lead-free piezoelectric ceramic was used as a driving element of the PMC actuator. Bi0.5(Na0.725K0.175Li0.1)0.5TiO3 (abbreviated as BNKLT) is a soft-type piezoelectric ceramic with good piezoelectric properties at room temperature. Both the electrical and mechanical properties of the BNKLT PMC actuator were measured. With good piezoelectric coefficients and low density, the BNKLT ceramic has the potential to be used as the driving element of the lead-free actuator. View full abstract»

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  • Dedicated finite elements for electrode thin films on quartz resonators

    Publication Year: 2008 , Page(s): 1686 - 1697
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1365 KB) |  | HTML iconHTML  

    The accuracy of the finite element analysis for thickness shear quartz resonators is a function of the mesh resolution; the finer the mesh resolution, the more accurate the finite element solution. A certain minimum number of elements are required in each direction for the solution to converge. This places a high demand on memory for computation, and often the available memory is insufficient. Typically the thickness of the electrode films is very small compared with the thickness of the resonator itself; as a result, electrode elements have very poor aspect ratios, and this is detrimental to the accuracy of the result. In this paper, we propose special methods to model the electrodes at the crystal interface of an AT cut crystal. This reduces the overall problem size and eliminates electrode elements having poor aspect ratios. First, experimental data are presented to demonstrate the effects of electrode film boundary conditions on the frequency-temperature curves of an AT cut plate. Finite element analysis is performed on a mesh representing the resonator, and the results are compared for testing the accuracy of the analysis itself and thus validating the results of analysis. Approximations such as lumping and Guyan reduction are then used to model the electrode thin films at the electrode interface and their results are studied. In addition, a new approximation called merging is proposed to model electrodes at the electrode interface. View full abstract»

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  • Up-converted 1/f PM and AM noise in linear HBT amplifiers

    Publication Year: 2008 , Page(s): 1698 - 1704
    Cited by:  Papers (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (839 KB) |  | HTML iconHTML  

    In this paper we describe a technique to predict the 1/f phase modulation (PM) and 1/f amplitude modulation (AM) noise due to up-conversion of 1/f baseband current noise in microwave heterojunction bipolar transistor (HBT) amplifiers. We obtain an accurate model for the amplifier and find the expression for voltage gain in terms of DC bias, transistor parameters, and circuit components. Theoretical 1/f PM and AM noise sensitivities to 1/f baseband current noise are then found by applying the definitions of PM and AM noise to the gain expression of the amplifier. Measurements of PM and AM sensitivities at 500 MHz and 1 GHz were in good agreement with the values predicted by theory, verifying the validity of this technique. This method can be used to optimize amplifier design for low PM and AM noise. We show that the amplifier PM noise can be reduced by 9 dB by adjusting the value of the input coupling capacitor. View full abstract»

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  • Imaging with concave large-aperture therapeutic ultrasound arrays using conventional synthetic-aperture beamforming

    Publication Year: 2008 , Page(s): 1705 - 1718
    Cited by:  Papers (5)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1351 KB) |  | HTML iconHTML  

    Several dual-mode ultrasound array (DMUA) systems are being investigated for potential use in image- guided surgery. In therapeutic mode, DMUAs generate pulsed or continuous-wave (CW) high-intensity focused ultrasound (HIFU) beams capable of generating localized therapeutic effects within the focal volume. In imaging mode, pulse-echo data can be collected from the DMUA elements to obtain B-mode images or other forms of feedback on the state of the target tissue before, during, and after the application of the therapeutic HIFU beam. Therapeutic and technological constraints give rise to special characteristics of therapeutic arrays. Specifically, DMUAs have concave apertures with low f-number values and are typically coarsely sampled using directive elements. These characteristics necessitate pre- and post-beamforming signal processing of echo data to improve the spatial and contrast resolution and maximize the image uniformity within the imaging field of view (IxFOV). We have recently developed and experimentally validated beamforming algorithms for concave large-aperture DMUAs with directive elements. Experimental validation was performed using a 1 MHz, 64- element, concave spherical aperture with 100 mm radius of curvature. The aperture was sampled in the lateral direction using elongated elements 1 - lambda times 33.3macr - lambda with 1.333macr - lambda center-to-center spacing (lambda is the wavelength). This resulted in f-number values of 0.8 and 2 in the azimuth and elevation directions, respectively. In this paper, we present a new DMUA design approach based on different sampling of the shared concave aperture to improve image quality while maintaining therapeutic performance. A pulse-wave (PW) simulation model using a modified version of the Field II program is used in this study. The model is used in generating pulse-echo data for synthetic-aperture (SA) beamforming for forming images of a variety of targets, e.g., wire arrays and speckle-generating cyst - hantoms. To provide validation for the simulation model and illustrate the improvements in image quality, we show SA images of similar targets using pulse-echo data acquired experimentally using our existing 64-element prototype. The PW simulation model is used to investigate the effect of transducer bandwidth as well as finer sampling of the concave DMUA aperture on the image quality. The results show that modest increases in the sampling density and transducer bandwidth result in significant improvement in spatial and contrast resolutions in addition to extending the DMUA IxFOV. View full abstract»

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  • Distortion-free delta-sigma beamforming

    Publication Year: 2008 , Page(s): 1719 - 1728
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (656 KB) |  | HTML iconHTML  

    We have analyzed a compact, digital delay- and-sum beamformer using 1-bit delta-sigma A/D converters, where dynamic delays are applied directly to the delta-sigma modulated bitstream. It has previously been shown that the introduction of this time-variant operation into the time-invariant delta-sigma demodulator distorts the output signal, and several methods for minimizing this effect have been suggested. We have described the effect using standard system terminology. Based on this description, a new method for removing the distortion without any significant increase in system complexity is introduced. Its advantages, performance-wise, are supported by theoretical assessments and simulations. View full abstract»

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  • High frame-rate blood vector velocity imaging using plane waves: Simulations and preliminary experiments

    Publication Year: 2008 , Page(s): 1729 - 1743
    Cited by:  Papers (33)
    Multimedia
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (2239 KB) |  | HTML iconHTML  

    Conventional ultrasound methods for acquiring color images of blood velocity are limited by a relatively low frame-rate and are restricted to give velocity estimates along the ultrasound beam direction only. To circumvent these limitations, the method presented in this paper uses 3 techniques: 1) The ultrasound is not focused during the transmissions of the ultrasound signals; 2) A 13 -bit Barker code is transmitted simultaneously from each transducer element; and 3) The 2-D vector velocity of the blood is estimated using 2-D cross-correlation. A parameter study was performed using the Field II program, and performance of the method was investigated when a virtual blood vessel was scanned by a linear array transducer. An improved parameter set for the method was identified from the parameter study, and a flow rig measurement was performed using the same improved setup as in the simulations. Finally, the common carotid artery of a healthy male was scanned with a scan sequence that satisfies the limits set by the Food and Drug Administration. Vector velocity images were obtained with a frame-rate of 100 Hz where 40 speckle images are used for each vector velocity image. It was found that the blood flow approximately followed the vessel wall, and that maximum velocity was approximately 1 m/s, which is a normal value for a healthy person. To further evaluate the method, the test person was scanned with magnetic resonance (MR) angiography. The volume flow derived from the MR scanning was compared with that from the ultrasound scanning. A deviation of 9% between the 2 volume flow estimates was found. View full abstract»

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  • Estimating 2-D vector velocities using multidimensional spectrum analysis

    Publication Year: 2008 , Page(s): 1744 - 1754
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (3517 KB) |  | HTML iconHTML  

    Wilson (1991) presented an ultrasonic wideband estimator for axial blood flow velocity estimation through the use of the 2-D Fourier transform. It was shown how a single velocity component was concentrated along a line in the 2-D Fourier space, where the slope was given by the axial velocity. Later, it was shown that this approach could also be used for finding the lateral velocity component by also including a lateral sampling. A single velocity component would then be concentrated along a plane in the 3-D Fourier space, tilted according to the 2 velocity components. This paper presents 2 new velocity estimators for finding both the axial and lateral velocity components. The estimators essentially search for the plane in the 3- D Fourier space, where the integrated power spectrum is largest. The first uses the 3-D Fourier transform to find the power spectrum, while the second uses a minimum variance approach. Based on this plane, the axial and lateral velocity components are estimated. Several phantom measurements, for flow-to-depth angles of 60, 75, and 90 degrees, were performed. Multiple parallel lines were beamformed simultaneously, and 2 different receive apodization schemes were tried. The 2 estimators were then applied to the data. The axial velocity component was estimated with an average standard deviation below 2.8% of the peak velocity, while the average standard deviation of the lateral velocity estimates was between 2.0% and 16.4%. The 2 estimators were also tested on in vivo data from a transverse scan of the common carotid artery, showing the potential of the vector velocity estimation method under in vivo conditions. View full abstract»

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  • Fast parametric beamformer for synthetic aperture imaging

    Publication Year: 2008 , Page(s): 1755 - 1767
    Cited by:  Papers (11)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1080 KB) |  | HTML iconHTML  

    This paper describes the design and implementation of a real-time delay-and-sum synthetic aperture beamformer. The beamforming delays and apodization coefficients are described parametrically. The image is viewed as a set of independent lines that are defined in 3D by their origin, direction, and inter-sample distance. The delay calculation is recursive and inspired by the coordinate rotation digital computer (CORDIC) algorithm. Only 3 parameters per channel and line are needed for their generation. The calculation of apodization coefficients is based on a piece- wise linear approximation. The implementation of the beamformer is optimized with respect to the architecture of a novel synthetic aperture real-time ultrasound scanner (SARUS), in which 4 channels are processed by the same set of field-programmable gate arrays (FPGA). In synthetic transmit aperture imaging, low-resolution images are formed after every emission. Summing all low-resolution images produces a perfectly focused high-resolution image. The design of the beamformer is modular, and a single beamformation unit can produce 4600 low-resolution images per second, each consisting of 32 lines and 1024 complex samples per line. In its present incarnation, 3 such modules fit in a single device. The summation of low-resolution images is performed internally in the FPGA to reduce the required bandwidth. The delays are calculated with a precision of 1/16th of a sample, and the apodization coefficients with 7-bit precision. The accumulation of low-resolution images is performed with 24-bit precision. The level of the side- and grating lobes, introduced by the use of integer numbers in the calculations and truncation of intermediate results, is below -86 dB from the peak. View full abstract»

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  • Wave equation-based imaging of mode converted waves in ultrasonic NDI, with suppressed leakage from nonmode converted waves

    Publication Year: 2008 , Page(s): 1768 - 1780
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1958 KB) |  | HTML iconHTML  

    The value of imaging techniques in ultrasonic nondestructive inspection (NDI) to find and characterize defects in steel components has already been demonstrated. The imaging techniques based on the integral representation of the wave equation, the Rayleigh integrals for wave field extrapolation, are becoming feasible and attractive due to advances in array technology and due to faster computers. Known implementations are the total focusing method (TFM), the synthetic aperture focusing method (SAFT), and the inverse wave field extrapolation method (IWEX). In principle, these techniques compensate propagation effects from sources to a scatterer such as a defect and propagation effects from the scatterer to receivers. Currently, this approach is applied to wave fronts of single modes (pure longitudinal or pure transversal). In practice, multiple wave fronts from the scatterer will be received as a result of mode conversion. These arrivals will not have the same arrival time because of the difference in sound velocity between longitudinal and transversal waves. Images of mode converted waves are obtained by choosing the appropriate sound velocity that corresponds with the mode-converted scattered wave in the imaging process. Therefore, the nonmode converted waves will image as leakage artifacts in the mode-converted images, and vice versa. This may lead to false interpretations. In this paper, such artifacts will be identified and explained with the help of an analytical example. Measurements from steel test pieces with a 4 MHz linear array transducer with 64 elements will be used to demonstrate the artifacts. Furthermore, a procedure to predict the artifacts and the subsequent suppression from the input measurements will be presented and demonstrated. View full abstract»

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  • Acoustic methods for obtaining the pressure reflection coefficient from a buffer rod based measurement cell

    Publication Year: 2008 , Page(s): 1781 - 1793
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (721 KB) |  | HTML iconHTML  

    The known acoustic methods for obtaining the pressure reflection coefficient from a buffer rod based measurement cell are presented, along with 2 new generic approaches for measuring the pressure reflection coefficient using 2 buffer rods enclosing the liquid to be characterized in a symmetrical arrangement. An acoustic transducer is connected to each of the buffer rods. The generic approaches are divided into a relative amplitude approach and a mixed amplitude approach. For the relative amplitude approach, families of 4, 5, or 6 echo signals can be used to obtain the pressure reflection coefficient. The mixed amplitude approach uses specific information about the transducers and/or the electronics sensitivities in receive mode to obtain the pressure reflection coefficient using families of 3, 4, 5, or 6 echo signals. Some of the new methods from the relative amplitude approach imply a reduced uncertainty relative to the previously known ABC method. The effect of the liquid attenuation, digitizer bit resolution, and the signal-to-noise ratio on the uncertainty characteristics of the pressure reflection coefficient are discussed, along with a discussion of the suitability of the various methods for different buffer materials. View full abstract»

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  • A novel approach to acoustic liquid density measurements using a buffer rod based measuring cell

    Publication Year: 2008 , Page(s): 1794 - 1808
    Cited by:  Papers (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1052 KB) |  | HTML iconHTML  

    A new method for measuring the pressure reflection coefficient in a buffer rod configuration is presented, together with experimental results for acoustic measurements of the liquid density, based on the measurement of the liquid's acoustic impedance. The method consists of using 2 buffers enclosing the liquid in a symmetrical arrangement with a transducer fixed to each buffer. One of the transducers is used in a pulse-echo mode while the other transducer operates as a receiver. The echo amplitudes leading to the pressure reflection coefficient as found by this method possess advantages such as reduced attenuation due to a shorter liquid transmission path and reduced interference, as compared with the ABC method. Measurements with distilled water and with special density calibration oil qualities have been performed using both the new method and the ABC method and are shown for the new method to give a density span within plusmn0.15% of the reference values. A comparison of the measured densities based on both a time-domain and a l2-norm frequency domain integration signal processing approach is given, along with a recommendation as to how the signal processing should be performed. View full abstract»

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  • Toward a reference ultrasonic cavitation vessel: Part 2-investigating the spatial variation and acoustic pressure threshold of inertial cavitation in a 25 kHz ultrasound field

    Publication Year: 2008 , Page(s): 1809 - 1822
    Cited by:  Papers (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (2965 KB) |  | HTML iconHTML  

    As part of an ongoing project to establish a reference facility for acoustic cavitation at the National Physical Laboratory (NPL), carefully controlled studies on a 25 kHz, 1.8 kW cylindrical vessel are described. Using a patented high-frequency acoustic emission detection method and a sonar hydrophone, results are presented of the spatial variation of inertial acoustic cavitation with increasing peak-negative pressure. Results show that at low operating levels, inertial acoustic cavitation is restricted to, and is strongly localized on, the vessel axis. At intermediate power settings, inertial acoustic cavitation also occurs close to the vessel walls, and at higher settings, a complex spatial variation is seen that is not apparent in measurements of the 25 kHz driving field alone. At selected vessel locations, a systematic investigation of the inertial cavitation threshold is described. This was carried out by making simultaneous measurements of the peak-negative pressures leading to inertial cavitation and the resultant MHz-frequency emissions, and indicates an inertial cavitation threshold of 101 kPa plusmn 14% (estimated expanded uncertainty). However, an intermediate threshold at 84 kPa plusmn 14% (estimated expanded uncertainty) is also seen. The results are discussed alongside theoretical predictions and recent experimental findings. View full abstract»

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  • A self-running standing wave-type bidirectional slider for the ultrasonically levitated thin linear stage

    Publication Year: 2008 , Page(s): 1823 - 1830
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (990 KB) |  | HTML iconHTML  

    A slider for a self-running standing wave-type, ultrasonically levitated, thin linear stage is discussed. The slider can be levitated and moved using acoustic radiation force and acoustic streaming. The slider has a simple configuration and consists of an aluminum vibrating plate and a piezoelectric zirconate titanate (PZT) element. The large asymmetric vibration distribution for the high thrust and levitation performance was obtained by adjusting the configuration determined by finite elemental analysis (FEA). As a preliminary step, the computed results of the sound pressure distribution in the 1-mm air gap by FEA was com pared with experimental results obtained using a fiber optic probe. The direction of the total driving force for the acoustic streaming in the small air gap was estimated by the sound pressure distribution calculated by FEA, and it was found that the direction of the acoustic streaming could be altered by controlling the vibration mode of the slider. The flexural standing wave could be generated along the vibrating plate near the frequencies predicted based on the FEA results. The slider could be levitated by the acoustic radiation force radiated from its own vibrating plate at several frequencies. The slider could be moved in the negative and positive directions at 68 kHz and 69 kHz, which correspond to the results computed by FEA, with the asymmetric vibration distribution of the slider's vibrating plate. Larger thrust could be obtained with the smaller levitation distance, and the maximum thrust was 19 mN. View full abstract»

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  • Elastic wave propagation in a microstructured acoustic fiber

    Publication Year: 2008 , Page(s): 1831 - 1839
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (660 KB) |  | HTML iconHTML  

    Elastic wave propagation along the structure of hollow cylinders in a linear isotropic medium is investigated. The multipole method for modeling elastic waves propagation in such structures is formulated and implemented. Using the multipole method, dispersion dependencies of the structures (microstructured fibers) containing 3, 6, and 7 hollow cylinders are calculated. Comparison with wave dispersion properties along one cylinder is made. Also, an approximate physical model based on an equivalent coaxial waveguide and multipole method is proposed. Exploiting this model, wave dispersion of the wave propagating along a structure with 18 hollow cylinders is calculated. Validation of the model is also proposed. View full abstract»

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  • Inline SAW RFID tag using time position and phase encoding

    Publication Year: 2008 , Page(s): 1840 - 1846
    Cited by:  Papers (23)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (963 KB) |  | HTML iconHTML  

    Surface acoustic wave (SAW) radio-frequency identification (RFID) tags are encoded according to partial reflections of an interrogation signal by short metal reflectors. The standard encryption method involves time position encoding that uses time delays of response signals. However, the data capacity of a SAW RFID tag can be significantly enhanced by extracting additional phase information from the tag responses. In this work, we have designed, using FEM-BEM simulations, and fabricated, on 128deg-LiNbO3, inline 2.44-GHz SAW RFID tag samples that combine time position and phase encoding. Each reflective echo has 4 possible time positions and a phase of 0deg, -90deg, -180deg, or -270deg. This corresponds to 16 different states, i.e., 4 bits of data, per code reflector. In addition to the enhanced data capacity, our samples also exhibit a low loss level of -38 dB for code reflections. View full abstract»

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  • A coupled analytical model for hydrostatic response of 1-3 piezocomposites

    Publication Year: 2008 , Page(s): 1847 - 1858
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (826 KB) |  | HTML iconHTML  

    This study presents a fully coupled analysis of a unit cell of a 1-3 piezocomposite under hydrostatic loading. The governing equations for coupled axisymmetric electroelastic field of a transversely isotropic piezoelectric medium and a transversely isotropic elastic medium are used. A reduced form of the analytical general solutions expressed in terms of series of modified Bessel functions of the first and second kind are used. The solution of the boundary-value problem corresponding to a unit cell is presented. The effective properties of a 1-3 piezocomposite are obtained for different fiber volume fractions, polymer and piezoceramic properties, and fiber aspect ratios. Comparisons with previously reported simplified and uncoupled models are made. View full abstract»

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  • Sound shielding by a piezoelectric membrane and a negative capacitor with feedback control

    Publication Year: 2008 , Page(s): 1859 - 1866
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (567 KB) |  | HTML iconHTML  

    The design and realization of an adaptive sound-shielding system based on a method to control the effective elastic stiffness of piezoelectric materials are presented in this paper. In this system, the sound-shielding effect is achieved by a sound reflection from the piezoelectric curved membrane fixed in rigid frame and connected to an active analog circuit that behaves as a negative capacitor. The acoustic transmission loss through the curved membrane was measured for the incident sound of frequency 1.6 kHz and of acoustic pressure level 80 dB. When the negative capacitor in the system was properly adjusted, the acoustic pressure level of the transmitted sound was reduced from the initial 60 dB to 15 dB by the action of the negative capacitor. Then the system was exposed to naturally changing operational conditions, and their effect on sound-shielding efficiency was studied. It is shown that the acoustic transmission loss of the system dropped by 35 dB within 30 min from the moment of negative capacitor adjustment. Therefore, a self-adjustment of the system has been implemented by appending an additional digital control circuit to the negative capacitor. It is shown that the aforementioned deteriorating effect has been eliminated by the adjusting action of the control circuit. The long-time sustainable value of 60 dB in the acoustic transmission loss of the adaptive sound shielding system has been achieved. View full abstract»

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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
s.freear@leeds.ac.uk