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Ultrasonics, Ferroelectrics, and Frequency Control, IEEE Transactions on

Issue 8 • Date Aug. 2006

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  • IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control - Aug. 2006

    Publication Year: 2006 , Page(s): 0_1 - 0_2
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  • [Inside front cover]

    Publication Year: 2006 , Page(s): 3
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  • [Back inside cover]

    Publication Year: 2006 , Page(s): 0_4
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  • Table of contents - Vol. 53 No. 8

    Publication Year: 2006 , Page(s): 5 - 6
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  • Information for Contributors with Multimedia Addition

    Publication Year: 2006 , Page(s): 1393 - 1397
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  • A multimedia example

    Publication Year: 2006 , Page(s): 1398
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  • In Memoriam: Harry F. Tiersten, Professor and Ph.D. 1930-2006

    Publication Year: 2006 , Page(s): 1399
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  • Characterization of superhydrophobic materials using multiresonance acoustic shear wave sensors

    Publication Year: 2006 , Page(s): 1400 - 1403
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (971 KB) |  | HTML iconHTML  

    Various superhydrophobic (SH) surfaces, with enhanced superhydrophobicity achieved by the use of nanoparticles, were characterized by a new acoustic sensing technique using multiresonance thickness-shear mode (MTSM) sensors. The MTSM sensors were capable of differentiating SH properties created by nano-scale surface features for film, exhibiting similar macroscopic contact angles View full abstract»

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  • A simple viscoelastic model for soft tissues the frequency range 6-20 MHz

    Publication Year: 2006 , Page(s): 1404 - 1411
    Cited by:  Papers (1)
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    In this paper, we present measurements of the shear properties of porcine skeletal muscle, liver, and kidney and a novel model describing them. Following a previously used method, shear mechanical impedances are measured, and complex shear moduli are obtained in the frequency range 6-20 MHz. As indicated in previous results, negative storage moduli are obtained in some measurements, which yield negative shear moduli in traditional linear viscoelastic models such as the Maxwell model, the Voigt model, and the Kelvin model. To resolve this problem, we propose a simple extension of the Voigt model. A mass is introduced into the model to account for the extra phase shift that apparently produces the negative moduli, and the shear stress thereby is related to the inertia of the material. The observed negative storage moduli are predicted by the new model when the relaxation time of the material is large and the working frequency is high. The model is fitted to experimental data to obtain values for material constants View full abstract»

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  • A new strategy to enhance cavitational tissue erosion using a high-intensity, initiating sequence

    Publication Year: 2006 , Page(s): 1412 - 1424
    Cited by:  Papers (6)
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    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (682 KB) |  | HTML iconHTML  

    Our previous studies have shown that pulsed ultrasound can physically remove soft tissue through cavitation. A new strategy to enhance the cavitation-induced erosion is proposed wherein tissue erosion is initiated by a short, high-intensity sequence of pulses and sustained by lower intensity pulses. We investigated effects of the initiating sequence on erosion and cavitation sustained by lower intensity pulses. Multiple three-cycle pulses at a pulse repetition frequency of 20 kHz delivered by a 788-kHz focused transducer were used for tissue erosion. Fixing the initiating sequence at ISPPA of 9000 W/cm2, 16 combinations of different numbers of pulses within the initiating sequence and different sustaining pulse intensities were tested. Results showed: the initiating sequence increases the probability of erosion occurrence and the erosion rate with only slight overall increases in propagated energy; the initiating sequence containing more pulses does not increase the sustained cavitation period; and if extinguished and reinitiated, the sustained cavitation period becomes shorter after each initiation, although the waiting time between adjacent cavitation periods is random. The high-intensity, initiating sequence enhances cavitational tissue erosion and enables erosion at intensities significantly lower than what is required to initiate erosion View full abstract»

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  • Accurate Doppler angle estimation for vector flow measurements

    Publication Year: 2006 , Page(s): 1425 - 1431
    Cited by:  Papers (16)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1469 KB) |  | HTML iconHTML  

    Traditional Doppler methods measure only the axial component of the velocity vector. The lack of information on the beam-flow angle creates an ambiguity that can lead to large errors in velocity magnitude estimates. Different triangulation techniques so far have been proposed, which basically perform multiple measurements of the Doppler frequency shift originating from the same region. In this work, an original approach is introduced, in which two ultrasound beams with known relative orientation are directed toward the same vessel, but only one of them is committed to perform a Doppler measurement; the second (reference) beam has the specific task of detecting the beam-flow angle. The latter goal is obtained by accurately identifying the achievement of the target 90deg reference-beam-to-flow angle through the inspection of the backscattered Doppler signal spectrum. In transverse flow conditions, in fact, such spectrum is expected to be centered on the zero frequency, and even small deviations from the desired 90deg orientation cause noticeable losses of spectral symmetry. Validation of the new method has been performed through experimental tests, which show that the beam-flow angle can be estimated with high accuracy (rms errors lower than 1deg), and repeatable velocity magnitude measurements are possible. A procedure for automatically tracking the desired orientation by the reference beam is also introduced and shown suitable for implementation in steerable linear array transducers View full abstract»

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  • Phase-aberration correction with a 3-D ultrasound scanner: feasibility study

    Publication Year: 2006 , Page(s): 1432 - 1439
    Cited by:  Papers (7)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (879 KB) |  | HTML iconHTML  

    We tested the feasibility of using adaptive imaging, namely phase-aberration correction, with two-dimensional (2-D) arrays and real-time, 3-D ultrasound. Because of the high spatial frequency content of aberrators, 2-D arrays, which generally have smaller pitch and thus higher spatial sampling frequency, and 3-D imaging show potential to improve the performance of adaptive imaging. Phase-correction algorithms improve image quality by compensating for tissue-induced errors in beamforming. Using the illustrative example of transcranial ultrasound, we have evaluated our ability to perform adaptive imaging with a real-time, 3-D scanner. We have used a polymer casting of a human temporal bone, root-mean-square (RMS) phase variation of 45.0 ns, full-width-half-maximum (FWHM) correlation length of 3.35 mm, and an electronic aberrator, 100 ns RMS, 3.76 mm correlation, with tissue phantoms as illustrative examples of near-field, phase-screen aberrators. Using the multilag, least-squares, cross-correlation method, we have shown the ability of 3-D adaptive imaging to increase anechoic cyst identification, image brightness, contrast-to-speckle ratio (CSR), and, in 3-D color Doppler experiments, the ability to visualize flow. For a physical aberrator skull casting we saw CSR increase by 13% from 1.01 to 1.14, while the number of detectable cysts increased from 4.3 to 7.7 View full abstract»

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  • High-resolution ultrasonic imaging using two-dimensional homomorphic filtering

    Publication Year: 2006 , Page(s): 1440 - 1448
    Cited by:  Papers (7)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (623 KB) |  | HTML iconHTML  

    A new method for two-dimensional deconvolution of medical ultrasonic images is presented. The spatial resolution of the deconvolved images is much higher compared to the common images of the fundamental and second harmonic. The deconvolution also results in a more distinct speckle pattern. Unlike the most published deconvolution algorithms for ultrasonic images, the presented technique can be implemented using currently available hardware in real-time imaging, with a rate up to 50 frames per second. This makes it attractive for application in the current ultrasound scanners. The algorithm is based on two-dimensional homomorphic deconvolution with simplified assumptions about the point spread function. Broadband radio frequency image data are deconvolved instead of common fundamental harmonic data. Thus, information of both the first and second harmonics is used. The method was validated on image data recorded from a tissue-mimicking phantom and on clinical image data View full abstract»

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  • Analysis of temperature rise for piezoelectric transformer using finite-element method

    Publication Year: 2006 , Page(s): 1449 - 1457
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (751 KB) |  | HTML iconHTML  

    Analysis of heat problem and temperature field of a piezoelectric transformer, operated at steady-state conditions, is described. The resonance frequency of the transformer is calculated from impedance and electrical gain analysis using a finite-element method. Mechanical displacement and electric potential of the transformer at the calculated resonance frequency are used to calculate the loss distribution of the transformer. Temperature distribution using discretized heat transfer equation is calculated from the obtained losses of the transformer. Properties of the piezoelectric material, dependent on the temperature field, are measured to recalculate the losses, temperature distribution, and new resonance characteristics of the transformer. Iterative method is adopted to recalculate the losses and resonance frequency due to the changes of the material constants from temperature increase. Computed temperature distributions and new resonance characteristics of the transformer at steady-state temperature are verified by comparison with experimental results View full abstract»

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  • Position and time-delay calibration of transducer elements in a sparse array for underwater ultrasound imaging

    Publication Year: 2006 , Page(s): 1458 - 1467
    Cited by:  Papers (5)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (740 KB) |  | HTML iconHTML  

    This paper describes a novel method for the calibration of the position and time delay of transducer elements in a large, sparse array used for underwater, high-resolution ultrasound imaging. This method is based on the principles used in the global positioning system (GPS). However, unlike GPS, in which the wave propagation speed is generally assumed known, the sound propagation speed in the water usually is unknown and it is calibrated simultaneously in this method to achieve high calibration accuracy. In this method, a high-precision positioning system is used to scan a single hydrophone (used for transmission) in the imaging field of the array. The hydrophone transmits pulses at selected positions, and the transducer elements in the sparse array receive the transmitted signals. Time of flight (TOF) values between transducer elements and hydrophone positions then are measured. From a series of measured TOF values, the position and time delay values for each transducer element as well as the propagation speed can be calibrated. The performances of the calibration algorithm are theoretically analyzed and evaluated with numerical calculations and simulation studies. It is found that this method is capable of calibrating the positions and time delays of transducer elements with high accuracy View full abstract»

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  • A torque estimator for a traveling wave ultrasonic motor - application to an active claw

    Publication Year: 2006 , Page(s): 1468 - 1477
    Cited by:  Papers (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (984 KB) |  | HTML iconHTML  

    Depending on its electrical-to-mechanical energy conversion process, the torque on a traveling wave ultrasonic motor (TWUM) 's shaft is not directly proportional to a measurable electrical variable, such as current or voltage. But it is derived from a complicated process at the stator/rotor interface. The load torque is thus quite unknown, and this can be a disadvantage in applications in which a torque limitation is required or a torque measurement is needed. The aim of this article is to come up with a straightforward torque estimator on a TWUM. For that purpose, the motor is modeled; this modeling leads to different estimator strategies. More specifically, we chose a strategy for which a speed sensor is useless, relying only on the stator's resonant behavior. The parameters of the motor needed for the estimator are measured afterward, and some nonlinearities are identified and taken into account. Several experimental trials then are carried out to check the performance of the estimator. A claw actuated by a TWUM is presented because this is a typical application in which the knowledge of the torque helps guarantee the safety of the device View full abstract»

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  • Flexible ultrasonic transducers

    Publication Year: 2006 , Page(s): 1478 - 1486
    Cited by:  Papers (5)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1018 KB) |  | HTML iconHTML  

    Flexible ultrasonic transducers (UTs) consisting of a metal foil, a piezoelectric ceramic film, and a top electrode have been developed. The flexibility is realized owing to the porosity of piezoelectric film and the thinness of metal foil. In this paper, the stainless steel (SS), lead-zirconate-titanate (PZT)/PZT composite and silver paste were chosen as metal foil, piezoelectric film, and top electrode materials, respectively. The SS foil serves as both substrate and bottom electrode. The PZT/PZT piezoelectric composite film is made by the sol-gel spray technique. PZT/PZT films of thicknesses from 40 to 70 mum were fabricated onto SS foils. The capability of these flexible sensors operated in the pulse-echo mode for nondestructive testing on flat and curved surfaces of different materials at room temperature and 160degC has been demonstrated. Numerical simulations of the effects of the metal foil thickness on the ultrasonic performance of flexible UTs also were carried out, and the results are in reasonable agreement with experimental data. In addition, a PZT/PZT flexible transducer showed a signal strength comparable with that obtained by a commercial room temperature broad bandwidth transducer View full abstract»

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  • Attenuation of acoustic normal modes in piezoelectric plates loaded by viscous liquids

    Publication Year: 2006 , Page(s): 1487 - 1492
    Cited by:  Papers (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (368 KB) |  | HTML iconHTML  

    Attenuation alphan versus viscosity eta of adjacent liquid is measured for each normal mode n generated in 30 different plates of commercially available, piezoelectric crystals with thickness-to-wavelength ratio in the range h/lambda = 0.6-2.5. Two modes with an optimal combination of sensitivity (0.1 dB/mmmiddotcP), insertion loss (<35 dB), and stop-band rejection (>15 dB) are found in liquid-loaded 128degY, X + 90deg-LiNbO3 with h/lambda = 1.67. Both modes are suited for viscosity measurements and other sensing tasks in viscous liquids. They have predominantly longitudinal displacement and large propagation velocity vn about 15,000 m/s View full abstract»

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  • Recognition of organic solvents molecules by simultaneous detection using SAW oscillator sensors and optical fiber devices coated by Langmuir-Blodgett cadmium arachidate films

    Publication Year: 2006 , Page(s): 1493 - 1502
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1105 KB) |  | HTML iconHTML  

    Surface acoustic waves (SAW) 433 and 315 MHz, two-port resonator-based oscillators coated with a Langmuir-Blodgett (LB) thin layer of chemosensitive cadmium arachidate (CdA) provide highly sensitive chemical acoustic sensors for detection and monitoring of organic vapors, at room temperature. LB CdA film-coated silica optical fibers (SOF) have been successfully fabricated and studied for organic solvents molecules sensing applications. The sensing performance of both types of acoustic and optical transducers has been compared for detecting six molecular species. Simultaneous measurements of frequency changes (Deltaf) and optoelectronic signal changes (DeltaV) of the LB CdA film assembled onto SAW sensors and SOF devices have been realized for organic vapors recognition purposes. Six molecular species such as ethanol, methanol, isopropanol, ethylacetate, acetone, and toluene have been identified and recognized by a specific index (Deltaf/DeltaV), which can be considered a characteristic property of the chemosensitive material. The discrimination of the six molecular species examined also has been obtained by chemical patterns using a couple of specific index (Deltaf433/DeltaV;Deltaf315/DeltaV) measured by combining SAW 433 or 315 MHz oscillators and SOF sensing devices. Transient responses, calibration curves, intertransducer relationships, and chemical patterns are presented and discussed View full abstract»

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  • Comparison of the frequency and physical nature of the lowest order parasitic mode in single crystal and ceramic 2-2 and 1-3 piezoelectric composite transducers

    Publication Year: 2006 , Page(s): 1503 - 1512
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (2220 KB) |  | HTML iconHTML  

    This work describes an investigation into the first order parasitic mode (i.e., that closest to the fundamental thickness mode) that can occur in 2-2 and 1-3 thickness drive piezoelectric composite transducers. Specifically, the authors compare the performance of piezoceramic and piezocrystal composites with a common passive phase. A local Lamb wave approach is used to describe the generation of such modes, and the validity of this theory is investigated over the entire volume fraction range. It is shown that, when the parasitic mode is primarily generated by Lamb wave activity in the passive phase, both active materials demonstrate similar behavior. However, at higher volume fractions, the first order mode is related to the lateral resonance of the active material, and quite different behavior may be observed between the two sets of devices. The phase velocity of the parasitic modes in each device configuration was investigated by a combination of experimental measurement on a number of transducers along with simulations using the finite-element code PZFlex. Both 2-2 and 1-3 composites made from the single crystal materials pzn-4.5%pt, pzn-8%pt, and pmn-30%pt were investigated along with composites made from pzt5h ceramic. The PZFlex results are compared with experimental impedance analysis and laser scanning of surface displacement, with good agreement demonstrated. By comparing two very different active materials, additional insight into parasitic resonant activity within composite devices is demonstrated View full abstract»

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  • Experimental characterization of collapse-mode CMUT operation

    Publication Year: 2006 , Page(s): 1513 - 1523
    Cited by:  Papers (7)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (736 KB) |  | HTML iconHTML  

    This paper reports on the experimental characterization of collapse-mode operation of capacitive micromachined ultrasonic transducers (CMUTs). CMUTs are conventionally operated by applying a direct current (DC) bias voltage less than the collapse voltage of the membrane, so that the membrane is deflected toward the bottom electrode. In the conventional regime, there is no contact between the membrane and the substrate; the maximum alternating current (AC) displacement occurs at the center of the membrane. In collapse-mode operation, the DC bias voltage is first increased beyond the collapse voltage, then reduced without releasing the collapsed membrane. In collapse-mode operation, the center of the membrane is always in contact with the substrate. In the case of a circular membrane, the maximum AC displacement occurs along the ring formed between the center and the edge of the membrane. The experimental characterization presented in this paper includes impedance measurements in air, pulse-echo experiments in immersion, and one-way optical displacement measurements in immersion for both conventional and collapse-mode operations. A 205-mum times 205-mum 2-D CMUT array element composed of circular silicon nitride membranes is used in the experiments. In pulse-echo experiments, a custom integrated circuit (IC) comprising a pulse driver, a transmit/receive switch, a wideband low-noise preamplifier, and a line driver is used. By reducing the parasitic capacitance, the use of a custom IC enables pulse-echo measurements at high frequencies with a very small transducer. By comparing frequency response and efficiency of the transducer in conventional and collapse regimes, experimental results show that a collapsed membrane can be used to generate and detect ultrasound more efficiently than a membrane operated in the conventional mode. Furthermore, the center frequency of the collapsed membrane can be changed by varying the applied DC voltage. In this study, the center frequen- - cy of a collapsed transducer in immersion is shown to vary from 20 MHz to 28 MHz with applied DC bias; the same transducer operates at 10 MHz in the conventional mode. In conventional mode, the maximum peak-to-peak pressure is 370 kPa on the transducer surface for a 40-ns, 25-V unipolar pulse excitation. In collapse mode, a 25-ns, 25-V unipolar pulse generates 590 kPa pressure at the surface of the transducer View full abstract»

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  • High-frequency transducers based on integrated piezoelectric thick films for medical imaging

    Publication Year: 2006 , Page(s): 1524 - 1533
    Cited by:  Papers (6)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (750 KB) |  | HTML iconHTML  

    A screen-printed PZT thick film with a final thickness of about 40 mum was deposited on a porous PZT substrate to obtain an integrated structure for ultrasonic transducer applications. This process makes it possible to decrease the number of steps in the fabrication of high-frequency, single-element transducers. The porous PZT substrates allow high acoustic impedance and attenuation to be obtained, satisfying transducer backing requirements for medical imaging. The piezoelectric thick films deliver high electromechanical performance, comparable to that of standard bulk ceramics (thickness coupling factor over 45%). Based on these structures, high-frequency transducers with a center frequency of about 25 MHz were produced and characterized. As a result, good sensitivity and axial resolution were obtained in comparison with similar transducers integrating a lead titanate (PT) disk as active material. The two transducers were integrated into a high-frequency imaging system, and comparative skin images are shown View full abstract»

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  • The stiffening of arteries by the tissue-mimicking gelatin

    Publication Year: 2006 , Page(s): 1534 - 1539
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (764 KB) |  | HTML iconHTML  

    Pulse wave velocity (PWV) is widely used for estimating the stiffness of an artery. PWV is measured by the time of travel of the "foot" of the pressure wave over a known distance. This technique has a low time resolution and is an average measurement of artery stiffness between the two measuring sites. The elastic modulus of the artery can be estimated with PWV, but the surrounding tissue effects are not considered. In this paper an external short pulse wave is generated noninvasively in the arterial wall by the radiation force of ultrasound. The pulse wave velocity in the artery is measured by a scanning technique with high-time resolution. The effect of tissue-mimicking gelatin on the artery is analyzed by measuring the wave velocity of the artery without and embedded in gelatin. It is found that the tissue-mimicking gelatin significantly stiffens the rubber tube and the artery if they are embedded in gelatin View full abstract»

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  • Complex notation for the dielectric response of ferroelectric materials beyond the small sinusoidal fields

    Publication Year: 2006 , Page(s): 1540 - 1543
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (330 KB) |  | HTML iconHTML  

    For the polarization response beyond the small field range, Rayleigh's law has been introduced in the past to describe the field-dependent behavior (with loss) of ferroelectric materials with some success. We examine the relationship between Rayleigh's law and the complex dielectric constant notation that has been used widely in the scientific and engineering community; and we show that a modified complex notation can describe the field-dependent dielectric response with loss in the small and medium field range quite well. In addition, the modified complex notation easily can include a field independent dielectric loss that is, in fact, present in all the dielectric materials. The results also show that the alternating current (AC) field response is still predominantly linear with the amplitude and phase of the complex coefficient changing with the applied field amplitude 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