| 1. |
- Aitomäki, Yvonne, et al.
(författare)
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Estimating material properties of solid and hollow fibers in suspension using ultrasonic attenuation
- 2013
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Ingår i: IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control. - 0885-3010 .- 1525-8955. ; 60:7, s. 1424-1434
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Tidskriftsartikel (refereegranskat)abstract
- Estimates of the material properties of hollow fibers suspended in a fluid using ultrasound measurements and a simple, computationally efficient analytical model are made. The industrial application is to evaluate the properties of wood fibers in paper pulp. The necessity of using a layered cylindrical model (LCM) as opposed to a solid cylindrical model (SCM) for modeling ultrasound attenuation in a suspension of hollow fibers is evaluated. The two models are described and used to solve the inverse problem of estimating material properties from attenuation in suspensions of solid and hollow polyester fibers. The results show that the measured attenuation of hollow fibers differs from that of solid fibers. Elastic properties estimates using LCM with hollow-fiber suspension measurements are similar to those using SCM with solid-fiber suspension measurements and compare well to block polyester values for elastic moduli. However, using the SCM with the hollow-fiber suspension did not produce realistic estimations. In conclusion, the LCM gives reasonable estimations of hollow fiber properties and the SCM is not sufficiently complex to model hollow fibers. The results also indicate that the use of a distributed radius in the model is important in estimating material properties from fiber suspensions.
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| 2. |
- Almqvist, Monica, et al.
(författare)
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Characterization of micromachined ultrasonic transducers using light diffraction tomography
- 2005
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Ingår i: IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control. - 0885-3010. ; 52:12, s. 2298-2302
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Tidskriftsartikel (refereegranskat)abstract
- This paper demonstrates that light diffraction tomography can be used to measure the acoustic field of micromachined ultrasonic transducers (MUT) in cases in which standard methods like hydrophone and microphone measurements fail. Two types of MUTs have been characterized with the method, one air-coupled capacitive MUT (cMUT) and one waterloaded continuous wave (CW) miniature multilayer lead zirconate titanate (PZT) transducer. Light diffraction tomography is an ultrasound measurement method with some special characteristics. Based on the interaction of light and ultrasound, it combines light intensity measurements with tomography algorithms to produce a measurement system. The method offers nonperturbing pressure measurements with high spatial resolution. It has been shown that, under certain circumstances, light diffraction tomography can be used as an absolute pressure measurement method with accuracy in the order of 10% in water and 13% in air. The results show that air-coupled cMUTs in the frequency range of about 1 MHz as well as the extreme near field of a miniaturized CW 10 MHz waterloaded transducer were successfully characterized with light diffraction tomography.
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| 3. |
- Berge, John, et al.
(författare)
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Tunable bulk acoustic wave resonators based on Ba0.25Sr0.75TiO3 thin films and a HfO2/SiO2 Bragg reflector
- 2011
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Ingår i: IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control. - 0885-3010 .- 1525-8955. ; 58:12, s. 2768-2771
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Tidskriftsartikel (refereegranskat)abstract
- A switchable and tunable bulk acoustic wave resonator based on a paraelectric phase Ba0.25Sr0.75TiO3 thin film and an all-dielectric HfO2/SiO2 Bragg reflector is presented. The achieved tuning range (3.8%) and effective electromechanical coupling coefficient (7.1%) are the highest reported for solidly mounted tunable bulk acoustic wave resonators. The non-conductive Bragg reflector stack provides excellent integration possibilities.
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| 4. |
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| 5. |
- Bjurström, Johan, et al.
(författare)
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Synthesis of textured thin piezoelectric AlN films with a nonzero C-axis mean tilt for the fabrication of shear mode resonators
- 2006
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Ingår i: IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control. - 0885-3010 .- 1525-8955. ; 53:11, s. 2095-2100
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Tidskriftsartikel (refereegranskat)abstract
- A method for the deposition of thin piezoelectric aluminum nitride (AlN) films with a nonzero c-axis mean tilt has been developed. The deposition is done in a standard reactive magnetron sputter deposition system without any hardware modifications. In essence, the method consists of a two-stage deposition process. The resulting film has a distinct tilted texture with the mean tilt of the c-axis varying roughly in the interval 28 to 32 degrees over the radius of the wafer excluding a small exclusion zone at the center of the latter. The mean tilt angle distribution over the wafer has a circular symmetry. A membrane-type shear mode thickness-excited thin film bulk acoustic resonator together with a micro-fluidic transport system has been subsequently fabricated using the two stage AIN deposition as well as standard bulk micro machining of Si. The resonator consisted of a 2-mu m-thick AlN film with 200-nm-thick A1 top and bottom electrodes. The resonator was characterized with a network analyzer when operating in both air and water. The shear mode resonance frequency was about 1.6 GHz, the extracted device Q around 350, and the electromechanical coupling k(t)(2) 2% when the resonator was operated in air, whereas the latter two dropped down to 150 and 1.8%, respectively, when the resonator was operated in pure water.
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| 6. |
- Boström, Anders E, 1951, et al.
(författare)
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In-plane P-SV waves from a piezoelectric strip actuator: exact versus effective boundary condition solutions
- 2005
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Ingår i: IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control. - 0885-3010. ; 52:9, s. 1594-1600
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Tidskriftsartikel (refereegranskat)abstract
- A piezoelectric strip of finite width and thickness is placed on top of anisotropic elastic half-space. It operates in actuator mode and a timeharmonic voltage is thus applied across it. The piezoelectric material isof type $6mm$ oriented so that a 2D inplane (P-SV) problem results.By Fourier series expansions the problem is solved exactly and thisresult is compared to the case when the piezoelectric strip is replaced byan effective boundary condition, which is derived by series expansionsin the thickness coordinate in the piezoelectric strip. At low frequenciesthe results agree very well and this corresponds to the situation oftenmet in practice. In general, the effective boundary condition should bemuch easier to apply, for example when a FEM program is used.
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| 7. |
- Carlson, Johan, et al.
(författare)
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Prediction of molar fractions in two-component gas mixtures using pulse-echo ultrasound and PLS regression
- 2006
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Ingår i: IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control. - 0885-3010 .- 1525-8955. ; 53:3, s. 606-613
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Tidskriftsartikel (refereegranskat)abstract
- The composition, and thus the energy content and monetary value of natural gas and biogas, vary considerably depending on the source. Present energy measurement techniques are riot suitable for online use. We show with experiments on mixtures of ethane (C/sub 2/H/sub 6/) and oxygen (O/sub 2/) how partial least squares regression (PLSR) can be used to predict the molar fraction of ethane in the mixtures, given spectral data from ultrasonic pulse-echo measurements. The PLSR technique is compared with the standard principal component regression (PCR), and we show that PLSR yields better predictive performance.
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| 8. |
- Chen, Hongjian, et al.
(författare)
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On the Development of a Novel Contrast Pulse Sequence for Polymer-Shelled Microbubbles
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Ingår i: IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control. - 0885-3010 .- 1525-8955.
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Tidskriftsartikel (refereegranskat)abstract
- Contrast agents are routinely used in ultrasound examinations. Nonlinear ultrasound imaging techniques have been developed over decades to enhance the contrast between the tissue and the blood pool after the injection of ultrasound contrast agents. In this study, we introduce a new contrast pulse sequence, CPS4. The CPS4 combines pulse inversion, sub-harmonic, and ultra-harmonic techniques to remove propagation distortion while capturing the unique sub-harmonic, and ultra-harmonic responses from ultrasound contrast agents. The novel CPS4 and conventional pulse inversion, sub-harmonic, and ultra-harmonic techniques were used to detect the presence of a research-grade, thick shell, polymer microbubble in a tissue-mimicking flow phantom. The contrast-to-tissue ratio (CTR) obtained from the applications of all techniques were compared. The results show that the highest CTR of approximately 16 dB was obtained using CPS4, which was superior to the individual reference techniques: pulse inversion, sub-harmonic, and ultra-harmonic techniques, at all scenarios considered in this study.
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| 9. |
- Chen, Hongjian, et al.
(författare)
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On the Development of a Novel Contrast Pulse Sequence for Polymer-Shelled Microbubbles
- 2021
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Ingår i: IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control. - : Institute of Electrical and Electronics Engineers (IEEE). - 0885-3010 .- 1525-8955. ; 68:5, s. 1569-1579
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Tidskriftsartikel (refereegranskat)abstract
- Contrast agents are routinely used in ultrasound examinations. Nonlinear ultrasound imaging techniques have been developed over decades to enhance the contrast between the tissue and the blood pool after the injection of ultrasound contrast agents (UCAs). In this study, we introduce a new contrast pulse sequence, CPS4. The CPS4 combines pulse inversion (PI), subharmonic (SH), and ultraharmonic (UH) techniques to remove propagation distortion while capturing the unique SH and UH responses from UCAs. The novel CPS4 and conventional PI, SH, and UH techniques were used to detect the presence of a research-grade, thick-shell, polymer microbubble in a tissue-mimicking flow phantom. The contrast-to-tissue ratios (CTRs) obtained from the applications of all techniques were compared. The results show that the highest CTR of approximately 16 dB was obtained using CPS4, which was superior to the individual reference techniques: PI, SH, and UH techniques, in all scenarios considered in this study.
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| 10. |
- Cinthio, M., et al.
(författare)
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Evaluation of an ultrasonic echo-tracking method for measurements of arterial wall movements in two dimensions
- 2005
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Ingår i: IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control. - 0885-3010 .- 1525-8955. ; 52:8, s. 1300-1311
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Tidskriftsartikel (refereegranskat)abstract
- The longitudinal movement of blood vessel walls has so far gained little or no attention, as it has been presumed that these movements are of a negligible magnitude. However, modern high-resolution ultrasound scanners can demonstrate that the inner layers of the arterial wall exhibit considerable movements in the longitudinal direction. This paper evaluates a new, noninvasive, echo-tracking technique, which simultaneously can track both the radial and the longitudinal movements of the arterial wall with high resolution in vivo. Initially, the method is evaluated in vitro using a specially designed ultrasound phantom, which is attached to and moved by an X-Y system, the movement of which was compared with two high-resolution triangulation lasers. The results show an inaccuracy of 2.5% full scale deflection (fsd), reproducibility of 12 µm and a resolution of 5 µm, which should be more than sufficient for in vivo studies. The ability of the method is also demonstrated in a limited in vivo study in which a preselected part of the inner vessel wall of the right common carotid artery of a healthy volunteer is tracked in two dimensions over many cardiac cycles. The results show well reproducible x-y movement loops in which the recorded radial and longitudinal movements both are of the magnitude millimetre. © 2005 IEEE.
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