Artículos de revistas: "Plane-Wave transducer"

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Zennaro, Marco, Dan J. O’Boy, Premesh Shehan Lowe y Tat-Hean Gan. "Characterization and Design Improvement of a Thickness-Shear Lead Zirconate Titanate Transducer for Low Frequency Ultrasonic Guided Wave Applications". Sensors 19, n.º 8 (18 de abril de 2019): 1848. http://dx.doi.org/10.3390/s19081848.

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Thickness-shear transducers for guided wave testing have been used in industry for over two decades and much research has been conducted to improve the resolution and sensitivity. Due to a geometric feature of the current state-of-the art transducer, there is an out-of-plane component in the propagation direction of the fundamental shear horizontal mode which complicates the signal interpretation. In such case, complex signal processing techniques need to be used for mode discrimination to assess the structural health with higher precision. Therefore, it is important to revise the transducer design to eliminate the out-of-plane components in the propagation direction of fundamental shear horizontal mode. This will enhance the mode purity of fundamental shear horizontal mode for its application in guided wave inspection. A numerical investigation has been conducted on a 3 mm thick 2 m circular steel plate to understand the behaviour and the characteristics of the state-of-the-art thickness-shear transducer. Based on the results, it is noted that the redesigning the electrode arrangement will suppress the out-of-plane components on the propagation direction of the fundamental shear horizontal mode. With the aid of this information current state-of-the-art transducers were redesigned and tested in laboratory conditions using the 3D Laser Doppler Vibrometer. This information will aid future transducer designers improve the resolution of thickness-shear transducers for guided wave applications and reduce the weight and cost of transducer array by eliminating the need of additional transducers to suppress spurious modes.

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2

Go, Dooyoung, Jinbum Kang, Ilseob Song y Yangmo Yoo. "Efficient Transmit Delay Calculation in Ultrasound Coherent Plane-Wave Compound Imaging for Curved Array Transducers". Applied Sciences 9, n.º 13 (8 de julio de 2019): 2752. http://dx.doi.org/10.3390/app9132752.

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The recently introduced plane-wave compounding method based on multiple plane-wave excitation has enabled several new applications due to its high frame rate (>1000 Hz). In this paper, a new efficient transmit delay calculation method in plane-wave compound imaging for a curved array transducer is presented. In the proposed method, the transmit delay is only calculated for a steering angle of 0° and is shifted along the element of the transducer to obtain other transmit delays for different steering angles. To evaluate the performance of the proposed method, the computational complexity was measured for various transmission conditions. For the number of elements and plane-wave excitations of 128 and 65, respectively, the number of operations was substantially decreased in the proposed method compared with the conventional method (256 vs. 8320). The benefits of the proposed method were demonstrated with phantom and in vivo experiments, where coherent plane-wave compounding with 65 excitations provided larger CR and CNR values compared to nine excitations (−22.5 dB and 2.7 vs. −11.3 dB and 1.9, respectively). These results indicate the proposed method can effectively reduce the computational complexity for plane-wave compound imaging in curved array transducers.

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3

Berthelot, J.-M., Souda M. Ben y J. L. Robert. "Study of wave attenuation in concrete". Journal of Materials Research 8, n.º 9 (septiembre de 1993): 2344–53. http://dx.doi.org/10.1557/jmr.1993.2344.

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The experimental study of wave attenuation in concrete has been achieved in the case of the propagation of plane waves in concrete rods. Different mortars and concretes have been investigated. A transmitter transducer coupled to one of the ends of the concrete rod generates the propagation of a plane wave in the rod. The receiver transducer, similar to the previous one, is coupled to the other end of the rod. The experimental results lead to an analytical expression for wave attenuation as function of the concrete composition, the propagation distance, and the wave frequency.

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4

Theobald, Pete T. y F. Dar. "AE Sensor Calibration for Out-of-Plane and In-Plane Displacement Sensitivity". Advanced Materials Research 13-14 (febrero de 2006): 91–98. http://dx.doi.org/10.4028/www.scientific.net/amr.13-14.91.

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This paper proposes a method for both the out-of-plane and in-plane displacement sensitivity calibration of an acoustic emission (AE) sensor. In the method, a laser homodyne interferometer is used to measure the out-of-plane and in-plane displacement of the surface of a large test block excited by a repeatable source transducer. The out-of-plane displacement is measured by aligning the laser beam perpendicular to the surface with time gating of the receive waveform used to isolate only the direct arrival of the longitudinal wave produced by the piston source transducer. For the in-plane displacement measurement, the laser beam is aligned parallel to the surface to intersect a small optically reflective step with the time waveform being gated to measure only the direct shear arrival produced using a normal incidence shear wave source transducer. In each case, the interferometer measurement is followed by coupling the sensor under test to the measurement surface, which is then exposed to the same acoustic field and the sensor output signal measured. This substitution method allows the sensor sensitivity to be obtained in terms of volts per unit displacement for both the out-of-plane and in-plane surface displacement. The method allows a comprehensive description of an AE sensor response to different planes of displacement and offers the potential for a traceable sensor calibration to units of length.

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5

Liu, Zhi-Ying, Ping Zhang, Bi-Xing Zhang y Wen Wang. "Multi Spherical Wave Imaging Method Based on Ultrasonic Array". Sensors 22, n.º 18 (8 de septiembre de 2022): 6800. http://dx.doi.org/10.3390/s22186800.

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The imaging range of traditional plane wave imaging is usually limited by the directivity of the plane wave. In this paper, a multi spherical wave imaging method based on an ultrasonic array is proposed, which radiates both compression and shear waves in a solid medium to form the multi spherical wave. Firstly, excitation characteristics of the multi spherical wave are analyzed theoretically and the calculation method of echo delay of multi spherical wave imaging is derived. Multi spherical wave imaging is compared with conventional ultrasonic plane wave imaging by designing experiments. Compared with ultrasonic plane wave imaging, multi spherical wave imaging is not limited to the size of the transducer and can greatly improve the detection range. In addition, compared with the multi plane wave imaging method, the multi spherical wave imaging algorithm is relatively simple, fast, and has high application value.

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Tang, Yujia, Zhangjian Li, Yaoyao Cui, Chen Yang, Jiabing Lv y Yang Jiao. "Micro Non-Uniform Linear Array (MNULA) for Ultrasound Plane Wave Imaging". Sensors 21, n.º 2 (18 de enero de 2021): 640. http://dx.doi.org/10.3390/s21020640.

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Ultrasound plane wave imaging technology has been applied to more clinical situations than ever before because of its rapid imaging speed and stable imaging quality. Most transducers used in plane wave imaging are linear arrays, but their structures limit the application of plane wave imaging technology in some special clinical situations, especially in the endoscopic environment. In the endoscopic environment, the size of the linear array transducer is strictly miniaturized, and the imaging range is also limited to the near field. Meanwhile, the near field of a micro linear array has serious mutual interferences between elements, which is against the imaging quality of near field. Therefore, we propose a new structure of a micro ultrasound linear array for plane wave imaging. In this paper, a theoretical comparison is given through sound field and imaging simulations. On the basis of primary work and laboratory technology, micro uniform and non-uniform linear arrays were made and experimented with the phantom setting. We selected appropriate evaluation parameters to verify the imaging results. Finally, we concluded that the micro non-uniform linear array eliminated the artifacts better than the micro uniform linear array without the additional use of signal processing methods, especially for target points in the near-field. We believe this study provides a possible solution for plane wave imaging in cramped environments like endoscopy.

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7

Cowes, Diego A., Juan I. Mieza y Martín P. Gómez. "Polyvinylidene fluoride transducer shape optimization for the characterization of anisotropic materials". Journal of the Acoustical Society of America 156, n.º 6 (1 de diciembre de 2024): 3943–53. https://doi.org/10.1121/10.0034601.

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In the context of ultrasonic determination of mechanical properties, it is common to use oblique incident waves to characterize fluid-immersed anisotropic samples. The lateral displacement of the ultrasonic field owing to leaky guided wave phenomena poses a challenge for data inversion because beam spreading is rarely well represented by plane wave models. In this study, a finite beam model based on the angular spectrum method was developed to estimate the influence of the transducer shape and position on the transmitted signals. Additionally, anisotropic solids were considered so that the beam skewing effect was contemplated. A small-emitter large-receiver configuration was chosen, and the ideal shape and position of the receiving transducer were obtained through a meta-heuristic optimization approach with the goal of achieving a measurement system that sufficiently resembles plane wave propagation. A polyvinylidene fluoride receiver was fabricated based on the findings and tested in three cases: a single-crystal silicon wafer, a lightly anisotropic stainless-steel plate, and a highly anisotropic composite plate. Good agreement was found between the measurements and the plane wave model.

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8

Annenkov, Alexander Yu, Sergey V. Gerus y Edwin H. Lock. "Superdirected beam of the backward volume spin wave". EPJ Web of Conferences 185 (2018): 02006. http://dx.doi.org/10.1051/epjconf/201818502006.

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Visualized patterns of the backward volume spin wave (BVSW) excited by arbitrarily oriented linear transducer in tangentially magnetized ferrite film are investigated experimentally in the plane of ferrite film for the case where the transducer length D is much larger than the wavelength λ0. Superdirected BVSW beam having zero angular width and minimal smearing of the beam energy along the film surface is observed experimentally. Thus, it is proved that such phenomenon as “superdirected propagation of the wave” exists in the nature.

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9

Harris, John G. "The Wavefield Radiated Into an Elastic Half-Space by a Transducer of Large Aperture". Journal of Applied Mechanics 55, n.º 2 (1 de junio de 1988): 398–404. http://dx.doi.org/10.1115/1.3173689.

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The wavefield radiated into an elastic half-space by an ultrasonic transducer, as well as the radiation admittance of the transducer coupled to the half-space, are studied. Two models for the transducer are used. In one an axisymmetric, Gaussian distribution of normal traction is imposed upon the surface, while in the other a uniform distribution of normal traction is imposed upon a circular region of the surface, leaving the remainder free of traction. To calculate the wavefield, each wave emitted by the transducer is expressed as a plane wave multiplied by an asymptotic power series in inverse powers of the aperture’s (scaled) radius. This reduces the wave equations satisfied by the compressional and shear potentials to their parabolic approximations. The approximations to the radiated waves are accurate at a depth where the wavefield remains well collimated.

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10

Wei, Yanfei, Xin Yang, Yukai Chen, Zhihe Zhang y Haobin Zheng. "Modeling of High-Power Tonpilz Terfenol-D Transducer Using Complex Material Parameters". Sensors 22, n.º 10 (16 de mayo de 2022): 3781. http://dx.doi.org/10.3390/s22103781.

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The loss effect in smart materials, the active part of a transducer, is of significant importance to acoustic transducer designers, as it directly affects the important characteristics of the transducer, such as the impedance spectra, frequency response, and the amount of heat generated. It is therefore beneficial to be able to incorporate energy losses in the design phase. For high-power low-frequency transducers requiring more smart materials, losses become even more appreciable. In this paper, similar to piezoelectric materials, three losses in Terfenol-D are considered by introducing complex quantities, representing the elastic loss, piezomagnetic loss, and magnetic loss. The frequency-dependent eddy current loss is also considered and incorporated into the complex permeability of giant magnetostrictive materials. These complex material parameters are then successfully applied to improve the popular plane-wave method (PWM) circuit model and finite element method (FEM) model. To verify the accuracy and effectiveness of the proposed methods, a high-power Tonpilz Terfenol-D transducer with a resonance frequency of around 1 kHz and a maximum transmitting current response (TCR) of 187 dB/1A/μPa is manufactured and tested. The good agreement between the simulation and experimental results validates the improved PWM circuit model and FEA model, which may shed light on the more predictable design of high-power giant magnetostrictive transducers in the future.

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11

Li, Shichang, Yu Lan y Lianjin Hong. "A method to analyze the radiation characteristics of a liquid column resonance transducer based on fluid motion". Journal of the Acoustical Society of America 155, n.º 1 (1 de enero de 2024): 252–61. http://dx.doi.org/10.1121/10.0024339.

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Liquid column resonance (LCR) transducers have been widely used in deep-sea acoustic applications because of their fluid-filled structures. Until now, studies of pipe resonance have generally been based on the plane acoustic wave equation, but for a vibrating object, the velocity is the primary focus instead of the pressure. Thus, the motion equation of a pipe resonance mode can be deduced based on the Navier–Stokes (N–S) equations. In this work, the velocity of an LCR transducer is obtained using the finite element model, and the velocity distribution inside the liquid column is examined. In addition, the radiating surface of the LCR transducer is identified and a simplified model of the radiation that consists of concave pistons and ring sources is proposed and verified. The theory behind the high mechanical quality (Q) value of the LCR transducer is explained through the radiation of the LCR transducer and the low viscosity of the water. This is also verified through a finite element model and measurements. Due to the high mechanical Q value and the low frequency of the LCR transducer, such measurements should be carried out in open-field water and the pulse should be long enough to achieve a steady state.

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12

Elhady, Alaa y Eihab M. Abdel-Rahman. "Characterization of Shear Horizontal Waves Using a 1D Laser Doppler Vibrometer". Sensors 21, n.º 7 (2 de abril de 2021): 2467. http://dx.doi.org/10.3390/s21072467.

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We developed a new technique for the detection of shear horizontal surface acoustic waves (SH-SAW) using a one-dimensional laser-based Doppler vibrometer. It measures the out-of-plane surface deformation at the fingertip of an interdigitated transducer (the boundary of the wave aperture) and uses it to estimate the instantaneous in-plane displacement field given the substrate Poisson ratio. It can also estimate the degree of surface confinement (wave decay rate). The proposed approach was first verified using finite element analysis (FEA) and demonstrated experimentally using a Bleustein–Gulyaev resonator.

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13

Krokhmal, A. A., D. A. Nikolaev, S. A. Tsysar y O. A. Sapozhnikov. "Creating a Reference Plane Ultrasonic Wave in a Fluid Using a Plane Piezoelectric Transducer with a Large Wave Dimension". Acoustical Physics 66, n.º 5 (septiembre de 2020): 449–60. http://dx.doi.org/10.1134/s1063771020050061.

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14

Jia, Jiuhong, Zuoyu Liao, Xiaotao Cai, Yun Tu y Shan-Tung Tu. "Critical Excitation of the Fundamental Quasi-Shear Mode Wave in Waveguide Bars for Elevated Temperature Applications". Sensors 19, n.º 4 (15 de febrero de 2019): 793. http://dx.doi.org/10.3390/s19040793.

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The safety of critical pressure equipment in elevated temperature is increasingly important. Moreover, the on-line monitoring method is potentially useful to improve their safety. A waveguide bar system can enable monitoring of critical equipment working in elevated temperature using reliable ultrasonic technology. Among the waveguide bar system, the matching mechanism of the transducer and the waveguide bar is crucial to propagate the pure fundamental quasi-shear mode (shorten for SH0*) wave. In the present research, the loading line sources that can excite pure SH0* wave are investigated and the anti-plane shear loading source is selected. The critical values about the geometric dimensions of the junctions between the piezoelectric transducer and the waveguide bar are explored by simulation and experiments. On the condition that the excitation sources satisfy the critical values, the loading can be approximated to an anti-plane shear one to excite the pure SH0* wave. Some waveguide bar systems are designed based on the simulated critical values and some experiments at high temperature are carried out. The experimental results verify that the designed waveguide bar systems can excite the pure SH0* wave at elevated temperatures, which verify the reliability of the simulated critical results.

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15

Varadan, V. V., Jen Hwa Jeng, Liang Chi Chin, Xiao Qi Bao y V. K. Varadhan. "Eigenmode Approach for a Periodic Composite Transducer Subject to Fluid Loading". Journal of Vibration and Acoustics 120, n.º 2 (1 de abril de 1998): 313–23. http://dx.doi.org/10.1115/1.2893833.

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A hybrid finite element eigenmode—Floquet mode representation is formulated and numerically implemented to study the performance of composite transducers subject to fluid loading. The periodic distribution of the piezoelectric elements in the form of rods in a dielectric host material permits consideration of only one unit cell of the distribution in the finite element solution. Again, due to periodicity, the acoustic field in the infinite fluid is represented as superposition of plane wave Floquet modes. The finite element method is used to solve the eigenmodes of vibration of the transducer and an eigenmode superposition with unknown weighting coefficients is interfaced with the Floquet representation. Continuity at the boundary is used to solve for both sets of unknown coefficients. The effect of rod cross section, concentration, material damping are studied as a function of frequency. Useful transducer parameters such as transmission efficiency and the conductance spectrum as well as reflection and transmission spectrum of the array are simulated numerically.

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16

Derepa, A. V., A. G. Leiko y O. N. Pozdniakova. "PHYSICAL FIELDS OF CIRCULAR CYLINDRICAL PIEZOCERAMIC RECEIVER IN PRESENCE OF A FLAT ACOUSTIC SOFT SCREEN". Devices and Methods of Measurements 8, n.º 2 (9 de junio de 2017): 168–76. http://dx.doi.org/10.21122/2220-9506-2017-8-2-168-176.

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System in the form of a circular cylindrical piezoceramic transducer near a flat acoustic screen was analyzed. The aim of the work was to solve the problem of receiving plane sound waves by «cylindrical piezoceramic transducer – flat acoustically soft screen» system.Considered system was characterized by a violation of the radial symmetry of the radiation load of the transducer while maintaining the radial symmetry of the electric load. At the same time, the energy perceived by the system under consideration is distributed between all modes of oscillation of the transducer, while the conversion of mechanical energy into electric is realized only at zero mole of oscillations.Special attention was paid to the method of coupled fields in multiply connected domains using the imaging method. The design model of the «transducer–creen» system was formulated taking into account the interaction of acoustic, mechanical and electric fields in the process of energy conversion, the interaction of a cylindrical transducer with a flat screen and the interaction of a converter with elastic media outside and inside it. The physical fields of the system under consideration were determined by following solutions: the wave equation; equations of motion of thin piezoceramic cylindrical shells in displacements; equations of stimulated electrostatics for piezoceramics for given boundary conditions, conditions for coupling fields at interfaces and electrical conditions.A general conclusion was made concerning solving of an infinite system of linear algebraic equations with respect to the unknown coefficients of the expansion of the fields. As an example of the application of the obtained relations, a calculation was made and an analysis of the dependences of the electric fields of the system under consideration for various parameters of its construction on the direction of arrival on the plane wave system was conducted.

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CHRISTOPHER, P. TED. "A NONLINEAR PLANE-WAVE ALGORITHM FOR DIFFRACTIVE PROPAGATION INVOLVING SHOCKWAVES". Journal of Computational Acoustics 01, n.º 03 (septiembre de 1993): 371–93. http://dx.doi.org/10.1142/s0218396x93000202.

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A new algorithm for nonlinear plane-wave propagation is presented. The algorithm uses a novel time domain representation to account for nonlinearity, while accounting for absorption in the frequency domain. The new algorithm allows for accurate representations of diffractive shockwave propagation in the framework of an existing nonlinear beam propagation model using far fewer harmonics (and thus time) than alternative algorithms based on a frequency domain solution to Burgers' equation. The new algorithm is tested against the frequency domain solution to Burgers' equation in a variety of cases and then used to model a focused ultrasonic piston transducer operating at very high source intensities.

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Liu, Wentao, Longlong Shan, Zhongliang Lin, Binghua Wan, Bin Yang, Xiaomei Zeng, Bing Yang y Vasiliy Pelenovich. "Dual-Wave ZnO Film Ultrasonic Transducers for Temperature and Stress Measurements". Sensors 24, n.º 17 (1 de septiembre de 2024): 5691. http://dx.doi.org/10.3390/s24175691.

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ZnO film ultrasonic transducers for temperature and stress measurements with dual-mode wave excitation (longitudinal and shear) were deposited using the reactive RF magnetron sputtering technique on Si and stainless steel substrates and construction steel bolts. It was found that the position in the substrate plane had a significant effect on the structure and ultrasonic performance of the transducers. The transducers deposited at the center of the deposition zone demonstrated a straight columnar structure with a c-axis parallel to the substrate normal and the generation of longitudinal waves. The transducers deposited at the edge of the deposition zone demonstrated inclined columnar structures and the generation of dominant shear or longitudinal shear waves. Transducers deposited on the bolts with dual-wave excitation were used to study the effects of high temperatures in the range from 25 to 525 °C and tensile stress in the range from 0 to 268 MPa on ultrasonic response. Dependencies between changes in the relative time of flight and temperature or axial stress were obtained. The dependencies can be described by second-order functions of temperature and stress. An analysis of the contributions of thermal expansion, strain, and the speed of sound to changes in the time of flight was performed. At high temperatures, a decrease in the signal amplitude was observed due to the decreasing resistivity of the transducer. The ZnO ultrasonic transducers can be used up to temperatures of ~500 °C.

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Eastland, Grant C., Peter J. Curry y Laura C. Tolliver. "Investigations into acoustic dipole helical wave generation". Journal of the Acoustical Society of America 152, n.º 5 (noviembre de 2022): 2929–33. http://dx.doi.org/10.1121/10.0015137.

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Acoustic waves that transmit phase information spatially have recently been applied to navigation and communications systems. This paper will describe a helical wave, a type of wave that transmits phase information across a section of the plane linearly about the azimuth. The wave will be described from the ground up. First, a circular baffled transducer pressure field will be derived. Next, the field generated using two crossed circular transducers will be derived and approximations given for the far field. The general expression for the acoustic field from this arrangement is derived in the far field utilizing a paraxial ray approximation for ideal sources but applied to the more complex conceptualization of the monopole source being given by the circular piston source. In addition, the work presented was investigated numerically in comparison to a different approximation made in the field dependence on monopole separation of the two sources making up the dipole. Next, numerical examination of two crossed dipoles is examined with visualizations of the pressure and discussion of transients created when the direction of spiral changes. Finally, there is a discussion for the detection and estimation of helical waves and potential uses.

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Normandin, Benjamin y Martin Veidt. "Single Transducer Pair Lamb Wave Time Reversal for Damage Detection in Composite Laminates". Key Engineering Materials 558 (junio de 2013): 205–17. http://dx.doi.org/10.4028/www.scientific.net/kem.558.205.

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This paper investigates the potential of single transducer pair guided waves time reversal to detect damage in composite laminates. According to dynamic reciprocity of Lamb waves propagation in linear media, the time reversal process should reconstruct the original signal. The similarity of original and reconstructed time signals is calculated for different damage types using numerical and experimental studies with the aim to investigate, if the interaction of the wave pulse with inhomogeneities introduces any nonlinearity that time reversibility breaks down and single transducer pair time reversal could be used as damage diagnostics tool. 3D explicit finite element analysis is used for the numerical simulation and laser Doppler vibrometry is used to capture out-of-plane displacement time histories excited by an adhesively bonded piezoceramic transducer disc in the experimental time reversal process. In the case of an undamaged composite laminate the similarity index used to quantify the similarity of the original and reconstructed wave pulses is better than 95%. The similarity index is smaller for laminates with artificial damages including embedded fluoro polymer films to simulate delamination damage, through holes and bonded mass inhomogeneities. Although numerical and experimental similarity indices are smaller at higher frequencies, there is no clear evidence that single transducer pair time reversibility breaks down and represents a reliable damage diagnostics tool.

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21

Yu-rim, Kang, Lee Su-hyeon, Seo Im-mee, Ko Jae-un, Kim Jae-hwan y Eom Ki-dong. "Comparison of shear-wave velocities obtained with shear-wave elastography of various peripheral lymph nodes in healthy Beagles". American Journal of Veterinary Research 82, n.º 12 (diciembre de 2021): 981–87. http://dx.doi.org/10.2460/ajvr.82.12.981.

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Abstract OBJECTIVE To compare shear-wave velocities (SWVs) with shear-wave elastography of various peripheral lymph nodes (LNs). ANIMALS 11 healthy Beagles. PROCEDURES For each dog, bilateral mandibular, medial retropharyngeal, superficial cervical, axillary, superficial inguinal, and popliteal LNs were evaluated with shear-wave elastography in sagittal and transverse scanning planes. Depth of each lymph node was recorded, and intra- and interobserver reliability was determined. RESULTS SWVs for all LNs were significantly higher in the sagittal scanning plane, compared with those in the transverse scanning plane. The SWV of the most superficial LN, the mandibular LN, was significantly higher, compared with that for the other LNs, except for the medial retropharyngeal LN. The SWV of the deepest LN, the medial retropharyngeal LN, was as high as that for the mandibular LN. Intra- and interobserver reliability was excellent. CONCLUSIONS AND CLINICAL RELEVANCE SWVs for normal peripheral LNs of Beagles may serve as a reference to compare with those for other breeds and diseased LNs. Scanning plane, LN depth, and interfering tissues between the LN and the transducer may affect SWV. Shear-wave elastography may not be operator dependent.

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Wang, Congzhi, Yang Xiao, Jingjing Xia, Weibao Qiu y Hairong Zheng. "Effects of Non-Elevation-Focalized Linear Array Transducer on Ultrasound Plane-Wave Imaging". Sensors 16, n.º 11 (12 de noviembre de 2016): 1906. http://dx.doi.org/10.3390/s16111906.

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23

Bae, Sua, Pilsu Kim y Tai-kyong Song. "Ultrasonic sector imaging using plane wave synthetic focusing with a convex array transducer". Journal of the Acoustical Society of America 144, n.º 5 (noviembre de 2018): 2627–44. http://dx.doi.org/10.1121/1.5065391.

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24

Kwon, Young Seok, Hae Youn Kim, Dong-Hyun Kang, Dong Hun Kim, Jae-Woong Jeong y Byung Chul Lee. "Real-time 3D plane-wave imaging using annular capacitive micromachined ultrasonic transducer array". Sensors and Actuators A: Physical 359 (septiembre de 2023): 114475. http://dx.doi.org/10.1016/j.sna.2023.114475.

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25

ORR, LEIGH-ANN, ANTHONY J. MULHOLLAND, RICHARD L. O'LEARY y GORDON HAYWARD. "ANALYSIS OF ULTRASONIC TRANSDUCERS WITH FRACTAL ARCHITECTURE". Fractals 16, n.º 04 (diciembre de 2008): 333–49. http://dx.doi.org/10.1142/s0218348x08004101.

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Ultrasonic transducers composed of a periodic piezoelectric composite are generally accepted as the design of choice in many applications. Their architecture is normally very regular and this is due to manufacturing constraints rather than performance optimization. Many of these manufacturing restrictions no longer hold due to new production methods such as computer controlled, laser cutting, and so there is now freedom to investigate new types of geometry. In this paper, the plane wave expansion model is utilized to investigate the behavior of a transducer with a self-similar architecture. The Cantor set is utilized to design a 2-2 configuration, and a 1-3 configuration is investigated with a Sierpinski carpet geometry. Ideally a single longitudinal mode in the thickness direction will drive the transducer in a piston-like fashion. In this paper it was found that by increasing the fractal generation level, the bandwidth surrounding the main thickness mode will increase, but there will be a corresponding reduction in the amplitude of the electrical conductance. It is also shown that a shift in the frequency of operation of the device can be achieved by altering the spatial periodicity of the electrical excitation.

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Xu, Chunguang, Joseph L. Rose y Xiang Zhao. "Detection Principle of Shape and Orientation of Corrosive Defects Using Lamb Waves". Journal of Robotics and Mechatronics 21, n.º 5 (20 de octubre de 2009): 568–73. http://dx.doi.org/10.20965/jrm.2009.p0568.

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The shape and orientation of corrosive defects are critical in the evaluation of the reliability and durability of plate-like structures. And Lamb wave is considered as an effective tool for inspections of this kind corrosive plates. In this paper, the shape and orientation of plane defects are detected and presented using a circular transducer array with Lamb wave tomography approach. Here, considering a special shape defect with two-dimensions elliptical contour in the plate, the various ratios for both defect shape and orientation, individually representing different classifications of defects, is identified and investigated using Lamb wave tomography approach. And the validity of this approach has been proved through simulation experiments.

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Raghavan, Ajay y Carlos E. S. Cesnik. "3-D Elasticity-Based Modeling of Anisotropic Piezocomposite Transducers for Guided Wave Structural Health Monitoring". Journal of Vibration and Acoustics 129, n.º 6 (8 de febrero de 2007): 739–51. http://dx.doi.org/10.1115/1.2748776.

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Anisotropic piezocomposite transducers (APTs), such as macro fiber composites and active fiber composites, have great potential to be used as structurally integrated transducers for guided-wave (GW) structural health monitoring. Their main advantages over conventional monolithic piezoceramic wafer transducers are mechanical flexibility, curved surface conformability, power efficiency, their ability to excite focused GW fields, and their unidirectional sensing capability as a GW sensor. In this paper, models are developed to describe excitation of GW fields by APTs in isotropic structures. The configurations explored are plane Lamb-wave fields in beams with rectangular cross-section, axisymmetric GW fields in cylinders, and 3-D GW fields in plates. The dynamics of the substrate and transducer are assumed uncoupled. The actuator is modeled as causing shear traction at the edges of the actuator’s active area along the fiber direction. The sensor is modeled as sensing the average extensional strain over the active area along the fiber direction. The work is unique in that the formulation is based on 3-D elasticity, and no reduced-order structural assumptions are used. This is crucial to model multimodal GW propagation, especially at high frequencies. A formulation is also proposed to model the behavior of APTs as GW sensors. Finally, results from experimental tests to examine the validity of the models are discussed and the possible sources of error are examined in detail.

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Nguyen, Thi Huong Ly y Suhyun Park. "Multi-Angle Liquid Flow Measurement Using Ultrasonic Linear Array Transducer". Sensors 20, n.º 2 (10 de enero de 2020): 388. http://dx.doi.org/10.3390/s20020388.

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Most ultrasonic flowmeters utilize several wedge sensors for transmission and reception. Thus, the location and alignment of the sensors are critical factors that determine the performance of the ultrasonic flowmeter. In this study, we proposed an ultrasound liquid flowmeter utilizing a 128-element linear array transducer with a transmit delay control for varying the incidence angles of ultrasound wave transmission. The performance of the flowmeter was evaluated at flow rates of 0–50 L/min in a specially designed pipe system. Flow estimation was performed with the transit-time method using cross-correlation with phase zero-crossing for sub-sample estimation. While a single plane wave approach performed invasive electromagnetic measurements with only 74% accuracy as a reference, a multiple angular compensation method with 24 angles was proposed to increase the accuracy of measurements up to 93%. This study demonstrated the capability of the non-invasive single-sided ultrasonic flowmeter with a linear array transducer for liquid flow measurements in the metal pipe system.

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29

Fillinger, Laurent, Lars Hörchens, Laurens C. J. M. Peters, Roy G. F. A. Verbeek, Bart Peeters, Thijs Schrama, Egon J. W. Merks-Swolfs et al. "Demonstration of medical imaging using flexible polymer ultrasound technology". Journal of the Acoustical Society of America 154, n.º 4_supplement (1 de octubre de 2023): A140. http://dx.doi.org/10.1121/10.0023052.

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We present a novel ultrasound transducer technology based on piezo polymers. Its fabrication process (PillarWaveTM), based on creating hexagonal micro-structured PVDF-TrFE pillars. This makes it fully flexible and allows scaling to large apertures (>15 × 15 cm2). Large area flexible transducers enable to select relevant field of view in automated post-processing. This can alleviate the need for a skilled sonographer and enable applications of echography outside clinics. To demonstrate its performance, a 128 element 8 MHz linear array is designed and manufactured. Its total thickness is 0.1 mm. Its acoustic characteristics are determined demonstrating 5.2 kPa/V transmit efficiency and 150 mV/Pa sensitivity. The receive bandwidth at -6dB is larger than 100%. A peak pressure in excess of 1 MPa at 4 cm from the array is measured in water. The transducer array is connected to a Verasonics Vantage research medical ultrasound system. The imaging performance of the array is demonstrated experimentally. Real-time imaging of an in vitro- medical phantom using plane wave compounding and delay-and-sum beamforming is demonstrated at 15 frames per second, with point spread functions at -20 dB of 1.3 and 0.92 mm in the lateral and depth directions, respectively. Finally, imaging of a human carotid in vivo is demonstrated.

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30

Griffin, Connor, Hanfei Mei, Sivaji Karna, Tianyu Zhang, Victor Giurgiutiu y Lang Yuan. "Exploring Piezoelectric Actuation towards Its Applications in Laser Powder Bed Fusion Additive Manufacturing". Sensors 24, n.º 12 (7 de junio de 2024): 3704. http://dx.doi.org/10.3390/s24123704.

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Piezoelectric materials, which exhibit a charge distribution across the surfaces in reaction to mechanical strain, find significant utility in actuation and sensing applications. Apart from actuation applications like acoustic devices, motors, and vibration damping, an emerging domain for ultrasonic actuators lies in additive manufacturing processes. Ultrasonic waves applied during solidification aim to modulate grain structure and minimize defects. This research focuses on a fixture designed to facilitate and optimize ultrasonic wave propagation through the build plate in laser powder bed fusion additive manufacturing by utilizing a piezoelectric transducer. Three implementations of piezoelectric transducers were evaluated based on their out-of-plane ultrasonic velocity transmissions. It was determined that a thin plate adhered to the surface of the piezoelectric transducer yielded the most favorable outcomes for implementation, achieving 100% transmission of velocity and energy. Preliminary analysis of melt pool morphology and defects in single-track laser scanning experiments demonstrated the impact of ultrasound on solidification, hinting at a novel approach to enhancing the printability of alloys in laser powder bed fusion additive manufacturing processes. The optimal fixture and the explored transducing efficiency could further guide advanced ultrasound testing to enable in situ defect and texture detection during the additive manufacturing processes.

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31

Bae, Sua, Jintae Jang, Moon Hyung Choi y Tai-Kyong Song. "In Vivo Evaluation of Plane Wave Imaging for Abdominal Ultrasonography". Sensors 20, n.º 19 (5 de octubre de 2020): 5675. http://dx.doi.org/10.3390/s20195675.

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Although plane wave imaging (PWI) has been extensively employed for ultrafast ultrasound imaging, its potential for sectorial B-mode imaging with a convex array transducer has not yet been widely recognized. Recently, we reported an optimized PWI approach for sector scanning that exploits the dynamic transmit focusing capability. In this paper, we first report the clinical applicability of the optimized PWI for abdominal ultrasonography by in vivo image and video evaluations and compare it with conventional focusing (CF) and diverging wave imaging (DWI), which is another dynamic transmit focusing technique generally used for sectorial imaging. In vivo images and videos of the liver, kidney, and gallbladder were obtained from 30 healthy volunteers using PWI, DWI, and CF. Three radiologists assessed the phantom images, 156 in vivo images, and 66 in vivo videos. PWI showed significantly enhanced (p < 0.05) spatial resolution, contrast, and noise and artifact reduction, and a 4-fold higher acquisition rate compared to CF and provided similar performances compared to DWI. Because the computations required for PWI are considerably lower than that for DWI, PWI may represent a promising technique for sectorial imaging in abdominal ultrasonography that provides better image quality and eliminates the need for focal depth adjustment.

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32

Yan, Li y Peter M. Byrne. "Simulation of downhole and crosshole seismic tests on sand using the hydraulic gradient similitude method". Canadian Geotechnical Journal 27, n.º 4 (1 de agosto de 1990): 441–60. http://dx.doi.org/10.1139/t90-060.

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A method of simulating downhole and crosshole seismic shear-wave tests in a model under controlled stress conditionsis described. The downhole and shear wave in horizontal plane (SH) crosshole shear waves are generated and received along the principal stress axes using piezoceramic bender elements. The K0in situ stress conditions, including loading and unloading stress paths, are simulated by the hydraulic gradient similitude method, which allows high stresses simulating field conditions to be obtained. The horizontal stress during the tests is directly measured by a lateral total-stress transducer. The test data are used to evaluate various published empirical equations that relate shear-wave velocity and soil stress state. It is found that although the various empirical equations can predict the in situ shear-wave velocity profile reasonably well, only the equation that relates the shear-wave velocity to the individual principal stresses in the directions of wave propagation and particle motion can predict the variation of the velocity ratio between the downhole and SH crosshole tests. It was also found that the stress ratio has some effects on the downhole (or shear wave in vertical plane (SV) crosshole) shear-wave velocity, but not on the SH crosshole shear-wave velocity. This indicates that it is only the stress ratio in the plane of wave propagation that is important to the shear-wave velocity. Comparison between the downhole and SH crosshole shows that structure anisotropy is in the order of 10%. In addjtion, K0 values are predicted from shear-wave measurement and compared with measured ones. The difficulties in obtaining K0 values from shear-wave measurement are also discussed. Key words: hydraulic gradient, model tests, downhole and crosshole shear-wave tests, sand.

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33

LIAUH, CHIHNG-TSUNG. "INTENSITY DISTRIBUTION AND TEMPERATURE RISE FOR TRANSCRANIAL BRAIN ULTRASOUND HYPERTHERMIA". Biomedical Engineering: Applications, Basis and Communications 16, n.º 02 (25 de abril de 2004): 87–100. http://dx.doi.org/10.4015/s1016237204000141.

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The main purpose of this paper is to investigate the intensity distribution and the temperature responses when ultrasound beams are used for the intact brain tumor hyperthermia. A search method is developed to search for the appropriate transducer diameter and the input power level that induce a well focused high intensity region and an effective thermal dose region to enhance the goodness of the brain ultrasound hyperthermia treatments. This work employs a simplified model of a scanned ultrasound transducer power deposition (a cone with convergent/divergent shape). Multiple reflections and transmissions occurring at the interfaces are taken into consideration of calculating the intensity distribution as an ultrasound plane wave propagates through skull bone into brain tissue. The distributions of ultrasound intensity, specific absorption rate ratio, and temperature are used to determine the appropriateness of the transducer diameter and the input power level for a yielded set of tumor conditions. Simulation results demonstrate that (1) the maximum intensity ratio in the tumor region is larger than that in the bone region for all frequencies; (2) the treatments for larger tumors become more difficult to solve if the ratio of the diameter of transducer to the tumor diameter is less than 10 when one tries to use only high intensity ultrasound exposure to cause small lesions due to the cavitation effects. Results demonstrate the feasibility of inducing both a well focused high intensity region to produce local cavitation lesions and an effective thermal dose region to enhance the goodness of the intact brain ultrasound hyperthermia treatments. The results of this study can be a guideline for designing an optimal ultrasound heating system, arranging the transducers, and implementing further treatment planning for the transcranial brain tumor hyperthermia.

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34

Larin, Kirill. "Quantitative biomechanics using reverberant optical coherence elastography". Journal of the Acoustical Society of America 153, n.º 3_supplement (1 de marzo de 2023): A264. http://dx.doi.org/10.1121/10.0018792.

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In this presentation, I will introduce and discuss recent developments in our effort for quantitative biomechanics of tissues and organs using a multifocal acoustic radiation force source (that combines an ultrasound transducer and a 3D-printed acoustic lens) in reverberant optical coherence elastography (Rev-OCE). An array of plano-concave acoustic lenses, each with an 11.8 mm aperture diameter, were used to spatially distribute the acoustic energy generated by a 1 MHz planar ultrasound transducer, producing multiple focal spots on a target plane. These focal spots generate reverberant shear wave fields detected by the Optical Coherence Tomography (OCT) system. The effectiveness of the multifocal Rev-OCE system in probing mechanical properties with high resolution is demonstrated in layered gelatin phantoms, tissues ex vivo, and whole mouse embryos in vivo.

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35

Park, Hwijin, Yeong Bae Won, Sehyeong Jeong, Joo Young Pyun, Kwan Kyu Park, Jeong-Min Lee, Hee-Seon Seo y Hak Yi. "Reflected Wave Reduction Based on Time-Delay Separation for the Plane Array of Multilayer Acoustic Absorbers". Sensors 21, n.º 24 (17 de diciembre de 2021): 8432. http://dx.doi.org/10.3390/s21248432.

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This paper presents a control technique for reducing the reflection of acoustic signals for the plane array of multilayer acoustic absorbers underwater. In order to achieve this, a plane array of multilayer acoustic absorbers is proposed to attenuate low-frequency noise, with each unit consisting of a piezoelectric transducer, two layers of polyvinylidene fluorides and three layers of the acoustic window. Time-delay separation is used to find the incident and reflected acoustic signals to achieve reflected sound reduction. Experimental comparison of the attenuation rate of the reflected acoustic signal when performing passive and active controls is considered to verify the effectiveness of the time-delay separation technique applied plane array absorbers. Experiments on the plane array of smart skin absorbers confirmed that the reduction of reflected acoustic signals makes it suitable for a wide range of underwater applications.

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36

Wang, Wentao y Yongchao Yang. "Generation of selective single-mode guided waves by d₃₆ type piezoelectric wafer". Applied Physics Letters 120, n.º 21 (23 de mayo de 2022): 214101. http://dx.doi.org/10.1063/5.0091284.

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In general, mixed modes and dispersion of guided wave occur at any excitation frequency, while single modes are needed for effective nondestructive evaluation of structures. In this work, we present an approach to generate a selective single-mode guided wave in plate-like structures by exploiting the unique directionality of the d36 type piezoelectric wafer and the symmetry of fundamental guided wave modes. Specifically, we devise a unified fundamental shear horizontal (SH0) wave/fundamental antisymmetric mode (A0) wave directional transducer pair by attaching the d36 type piezoelectric wafers back to back on the opposite sides of the plate to provide selective, directional single-mode guided waves for actuation and sensing. Originally, the d36-type piezoelectric wafer, poled and cut from the lead magnesium niobate-lead titanate crystal, produces a mixture of the in-plane SH0 (symmetric) mode and out-of-plane A0 (asymmetric) and S0 (symmetric) modes. By applying the in-phase or out-of-phase applied electrical field to the coupled d36-type piezoelectric wafer pair, our devised approach generates selective single modes, SH0 or A0, respectively, to propagate in the structure. We describe the theoretical development of our approach and conduct both numerical simulations and laboratory experiments for validations.

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37

Nohara, Takuya, Takahiko Yanagitani, Mami Matsukawa y Yoshiaki Watanabe. "Conversion Characteristics of the Shear Wave Transducer Made of Unidirectionally Aligned ZnO Film in Plane". Japanese Journal of Applied Physics 45, n.º 5A (9 de mayo de 2006): 4201–3. http://dx.doi.org/10.1143/jjap.45.4201.

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38

Kadota, Michio y Toshinori Miura. "Shear Bulk Wave Transducer Made of (11\bar20)-Plane Epitaxial ZnO Film on R-Sapphire". Japanese Journal of Applied Physics 41, Part 1, No. 5B (30 de mayo de 2002): 3281–84. http://dx.doi.org/10.1143/jjap.41.3281.

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39

Choi, Kook Hyun, Hyeong Joon, Su Jin Chung, Jin Yong Kim, Tae Kun Lee y Young Jin Kim. "Experimental and theoretical characterization of the surface acoustic wave propagation properties of GaN epitaxial layers on c-plane sapphire". Journal of Materials Research 18, n.º 5 (mayo de 2003): 1157–61. http://dx.doi.org/10.1557/jmr.2003.0158.

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Surface acoustic wave (SAW) propagation properties of gallium nitride (GaN) epitaxial layers on sapphire were theoretically and experimentally characterized. GaN thin films were grown on a c-plane sapphire substrate using a metalorganic chemical vapor deposition system. The experimental characterization of SAW propagation properties was performed with a linear array of interdigital transducer structures, while SAW velocities were calculated by matrix methods. Experimentally, we found pseudo-SAW and high-velocity pseudo-SAW modes in the GaN/sapphire structure, which had a good agreement with calculated velocities.

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40

Qian, Fu, Zhen Feng Pan y Jia Mei Jin. "Optimal Design of an in-Plane Traveling Wave Rotary Ultrasonic Motor Excited by Single Composite Transducer". Advanced Materials Research 338 (septiembre de 2011): 499–504. http://dx.doi.org/10.4028/www.scientific.net/amr.338.499.

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This paper presents an optimal design for an in-plane traveling wave rotary ultrasonic motor with a composite transducer. The structure of the stator was improved to minimize negative influence on vibration modes from the supporter, and a new stator based on it was designed and fabricated. Two operating modal frequencies of new stator have been adjusted to equality by reducing one structural parameter according to sensitivity analysis. The performance experiments of the prototype motor shows that maximum no-load speed is 450rpm and maximum torque achieves 0.04Nm at an exciting voltage of 200Vrms.

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41

Hedayatrasa, Saeid y Mathias Kersemans. "3D intra-cellular wave dynamics in a phononic plate with ultra-wide bandgap: attenuation, resonance and mode conversion". Smart Materials and Structures 31, n.º 3 (2 de febrero de 2022): 035010. http://dx.doi.org/10.1088/1361-665x/ac4d65.

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Abstract The intra-cellular wave dynamics of a water jetted phononic plate are experimentally investigated by means of high-resolution three-dimensional (3D) scanning laser Doppler vibrometry. The study is focused on the vibrational behavior around the ultra-wide bandgap of the plate (with a relative bandgap width of 0.89), as the critical frequency range of its phononic functionality. Broadband vibrational excitations are applied using a piezoelectric transducer and both in-plane and out-of-plane operational deflection shapes of the unit-cells are analyzed with respect to mode shapes calculated by finite element (FE) simulation. Attenuation and resonance of both symmetric and antisymmetric wave modes are validated, and it is shown that despite the absence of in-plane wave energy actuation, the symmetric modes are effectively excited in the phononic lattice, due to mode conversion from co-existing antisymmetric modes. Supported by FE modal analysis, this mode conversion observation is explained by the slight through-the-thickness asymmetry introduced during manufacturing of the phononic plate which leads to coupling of modes with different symmetry. The results confirm the potential of such detailed 3D inspection of phononic crystals (and in general acoustic metamaterials) in gaining full insight about their intracellular dynamics, which can also illuminate discrepancies with respect to idealized numerical models that might be due to manufacturing imperfections.

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42

Lionetto, Francesca, Francesco Montagna y Alfonso Maffezzoli. "Out-Of-Plane Permeability Evaluation of Carbon Fiber Preforms by Ultrasonic Wave Propagation". Materials 13, n.º 12 (12 de junio de 2020): 2684. http://dx.doi.org/10.3390/ma13122684.

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Out-of-plane permeability of reinforcement preforms is of crucial importance in the infusion of large and thick composite panels, but so far, there are no standard experimental methods for its determination. In this work, an experimental set-up for the measurement of unsaturated through thickness permeability based on the ultrasonic wave propagation in pulse echo mode is presented. A single ultrasonic transducer, working both as emitter and receiver of ultrasonic waves, was used to monitor the through thickness flow front during a vacuum assisted resin infusion experiment. The set-up was tested on three thick carbon fiber preforms, obtained by stacking thermal bonding of balanced or unidirectional plies either by automated fiber placement either by hand lay-up of unidirectional plies. The ultrasonic data were used to calculate unsaturated out-of-plane permeability using Darcy’s law. The permeability results were compared with saturated out-of-plane permeability, determined by a traditional gravimetric method, and validated by some analytical models. The results demonstrated the feasibility and potential of the proposed set-up for permeability measurements thanks to its noninvasive character and the one-side access.

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43

Lu, Jian-yu. "A phase-shifting method for computation reduction for high-frame-rate imaging". Journal of the Acoustical Society of America 152, n.º 4 (octubre de 2022): A245. http://dx.doi.org/10.1121/10.0016153.

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High-frame rate (HFR) imaging using steered plane wave (SPW) or limited-diffraction beam has a high-temporal resolution and thus has found many applications. To further study the HFR imaging methods, computer simulations were performed. However, the simulations require a large number of computations, especially for 3D imaging with 2D array transducers for a large imaging volume. In this paper, a phase-shifting method was developed to reduce the number of computations. In the method, the grid points of the transmit and receive beams were calculated at 1-mm interval in the depth direction that is perpendicular to the transducer surface. The interval is much larger than the 1/4 of the 0.58-mm wavelength required for an accurate interpolation for millions of random scatterers in pulse-echo response without aliasing. Since the HFR imaging uses either SPW or LDB, the wave vectors of these beams are fixed at each frequency. Due to the fact that the amplitude of ultrasound beams changes very little over a couple of wavelengths, the interpolation in the depth direction was replaced with a phase shift. Results show that images reconstructed with the phase-shifting method removed the artifacts caused by aliasing when conventional tri-linear interpolations were used for 3D imaging.

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44

Gautam, Ambuj Kumar, Ching-Chung Yin y Bishakh Bhattacharya. "Design of orthogonal directional shear horizontal electromagnetic acoustic transducer". Proceedings of the Annual British Conference on Non-Destructive Testing 2023, n.º 1 (1 de enero de 2023): 1–11. http://dx.doi.org/10.1784/ndt2023.1b4.

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This research proposed an electromagnetic acoustic transducer (EMAT) for generating and receiving orthogonal directional shear horizontal (ODSH) guided waves in the metal plate-like structure. The proposed EMAT generates the fundamental mode of SH wave in the horizontal and vertical direction in the plane of the test sample. The ODSHEMAT combines a new Chevron-like coil design which generates an eddy current effect in the skin depth of the plate surface, and a periodic permanent magnet that applies a static magnetic field vertically with a periodicity equal to its wavelength. The direction of the resultant Lorentz force acting on the test surface-controlled PPM underneath a specific chevron angle of the coil wire. The constructive interference of propagated waves has been developed in the orthogonal directions, enhancing the ultrasonic signals and improving the signal-to-noise ratio. A finite element simulation has been carried out with a thin aluminum plate, keeping the proposed EMAT at the center of the sample. Further, the simulation results show good agreement with the proposed design.

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45

Schiefler, Nivaldo, Joaquim Maia, Fabio Schneider, Acácio Zimbico, Amauri Assef y Eduardo Costa. "Generation and Analysis of Ultrasound Images Using Plane Wave and Sparse Arrays Techniques". Sensors 18, n.º 11 (28 de octubre de 2018): 3660. http://dx.doi.org/10.3390/s18113660.

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Ultrasonic imaging is one of the most important techniques to help medical diagnosis. However, obtaining high quality images requires the acquisition, processing, and storage of a large amount of data. In this work, we evaluated a new ultrasound imaging technique based on plane wave and sparse arrays to increase the scan rate and reduce the amount of data amount to be stored. The performance of the proposed method was tested using simulated echo data (from Field II) and phantom data acquired using a Verasonics system equipped with a L11-4v linear array transducer. The tests were done using 128 elements for transmission and 128, 65, 44, and 23 elements sparsely distributed for reception. The simulated data were compared with images obtained with the Delay and Sum (DAS) method and the experimental data were compared with those acquired from Verasonics. The obtained results using the Full Width at Half Maximum (FWHM) criteria at −6 dB showed that the images generated by the proposed method were similar in terms of resolutions (axial and lateral) and contrast to the simulated and the Verasonics commercial ones, indicating that the sparse reception proposed method is suitable for ultrasound imaging.

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46

Nishizawa, Osamu, Takashi Satoh, Xinglin Lei y Yasuto Kuwahara. "Laboratory studies of seismic wave propagation in inhomogeneous media using a laser doppler vibrometer". Bulletin of the Seismological Society of America 87, n.º 4 (1 de agosto de 1997): 809–23. http://dx.doi.org/10.1785/bssa0870040809.

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Abstract We performed physical model experiments by utilizing a laser doppler vibrometer (LDV). Because LDV converts velocity of vibration to the Doppler shift frequency, it enables very precise measurements of ultrasonic waves without any resonating element that conventional transducers usually include. A piezoelectric transducer (PZT) was used as a source of elastic waves, and the waveform was measured in a very small area of about 400 μm in diameter by focusing the beam. We can easily perform very precise measurements of wave field in a physical model, and thus physical model experiments of wave propagation can simulate realistic seismic field observations. For models of inhomogeneous material, we used three granitic rocks with different grain sizes: Westerly granite (fine grained), Oshima granite (medium grained), and Inada granite (coarse grained). Large rock prisms, 300 × 300 × 80 to 90 mm, were used to prevent contamination by multiple reflections from the side ends in the earlier portion of waveforms. The direct P and S waves and reflected waves were identified by their travel times. Observations were made by long in-line, circular, and small-aperture arrays. When the rock grain size becomes comparable to the wavelength, transmitted waves are strongly attenuated by backward scattering, and a large amount of wave energy is transferred to the coda portion. Semblance plots in the time-slowness plane obtained from the small-aperture array suggest that incoherent waves become dominant as the grain size becomes large and comparable to the wavelength.

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47

Asfandiyarov, S. A., S. A. Tsysar y O. A. Sapozhnikov. "A Multi-Element Low-Frequency Ultrasonic Transducer as a Source of High-Intensity Focused Ultrasound in Air". Akustičeskij žurnal 70, n.º 4 (15 de julio de 2024): 622–35. https://doi.org/10.31857/s0320791924040143.

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The acoustic and electrical properties of a 128-element ultrasonic transducer designed to generate high-intensity focused ultrasound in air in the low-frequency ultrasonic range are investigated. To reduce parasitic grating maxima of the acoustic field, a spiral arrangement of piezoelectric elements on a spherical base was used. The operating frequency of the transducer was 35.5 kHz, and the diameter of the source and focal length were approximately 50 cm, significantly exceeding the wavelength (approximately 1 cm). This selection of parameters allowed for effective focusing, with localization of wave energy in a small focal region, thereby achieving extremely high levels of ultrasonic intensity. The parameters of the ultrasonic field were studied using a combined approach that included microphone recording of the acoustic pressure and measuring the acoustic radiation force acting on a conical reflector. Acoustic source parameters were determined from the two-dimensional spatial distribution of the acoustic pressure waveform, which was measured by scanning the microphone in a transverse plane in front of the source. Numerical modeling of nonlinear wave propagation was also used based on the Westervelt equation to simulate the behavior of intense waves. The acoustic pressure level reached 173 dB, with a focal spot size comparable to the wavelength.

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48

Asfandiyarov, S. A., S. A. Tsysar y O. A. Sapozhnikov. "A Multielement Low-Frequency Ultrasonic Transducer as a Source of High-Intensity Focused Ultrasound in Air". Acoustical Physics 70, n.º 4 (agosto de 2024): 759–68. http://dx.doi.org/10.1134/s1063771024601936.

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Abstract The acoustic and electrical properties of a 128-element ultrasonic transducer designed to generate high-intensity focused ultrasound in air in the low-frequency ultrasonic range are investigated. To reduce parasitic grating maxima of the acoustic field, a spiral arrangement of piezoelectric elements on a spherical base was used. The operating frequency of the transducer was 35.5 kHz, and the diameter of the source and focal length were approximately 50 cm, significantly exceeding the wavelength (approximately 1 cm). This selection of parameters allowed for effective focusing, with localization of wave energy in a small focal region, thereby achieving extremely high levels of ultrasonic intensity. The parameters of the ultrasonic field were studied using a combined approach that included microphone recording of the acoustic pressure and measuring the acoustic radiation force acting on a conical reflector. Acoustic source parameters were determined from the two-dimensional spatial distribution of the acoustic pressure waveform, which was measured by scanning the microphone in a transverse plane in front of the source. Numerical modeling of nonlinear wave propagation was also used based on the Westervelt equation to simulate the behavior of intense waves. The acoustic pressure level reached 173 dB, with a focal spot size comparable to the wavelength.

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49

Miranda, Edson, Clodualdo Aranas, Samuel Rodrigues, Hélio Silva, Gedeon Reis, Antônio Paiva y José Dos Santos. "Dispersion Diagram of Trigonal Piezoelectric Phononic Structures with Langasite Inclusions". Crystals 11, n.º 5 (28 de abril de 2021): 491. http://dx.doi.org/10.3390/cryst11050491.

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The dispersion relation of elastic Bloch waves in 1-3 piezoelectric phononic structures (PPnSs) with Langasite (La3Ga5SiO14) inclusions in a polymeric matrix is reported. Langasite presents promising material properties, for instance good temperature behaviour, high piezoelectric coupling, low acoustic loss and high quality factor. Furthermore, Langasite belongs to the point group 32 and has a trigonal structure. Thus, the 2-D bulk wave propagation in periodic systems with Langasite inclusions cannot be decoupled into XY and Z modes. The improved plane wave expansion (IPWE) is used to obtain the dispersion diagram of the bulk Bloch waves in 1-3 PPnSs considering the classical elasticity theory and D3 symmetry. Full band gaps are obtained for a broad range of frequency. The piezoelectricity enhances significantly the band gap widths and opens up a narrow band gap in lower frequencies for a filling fraction of 0.5. This study should be useful for surface acoustic wave (SAW) filter and 1-3 piezocomposite transducer design using PPnSs with Langasite.

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50

Sodagar, Sina y Reza Pourshab. "Evaluation of interfacial disbonding using finite element-based resonance ultrasonic spectroscopy". Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science 233, n.º 2 (19 de marzo de 2018): 675–84. http://dx.doi.org/10.1177/0954406218760060.

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In this paper, application of resonance scattering theory for nondestructive evaluation of embedded elastic cylindrical targets is investigated. For this purpose, an FE-based short-pulse method of isolation and identification of resonances is used to investigate the effects of cylinder-matrix interfacial disbonding involving the frequency effects of measurement system. Insonification of ultrasonic plane wave from an emitting transducer and the resulting scattered wave field from the embedded cylinder is simulated using commercial software ABAQUS/Explicit. The proposed FE-based method of isolation and identification of resonances is employed to investigate the effects of cylinder-matrix interfacial disbonding on the resonance modes using far-field backscattered frequency spectrum. It is observed that, compared to the whispering gallery resonance modes, the Rayleigh modes have higher sensitivity to the presence of side-wall interfacial disbonding which significantly decreases for back-wall defects.

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