| 1. |
- Carlson, Johan, et al.
(författare)
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Echo-cancellation in a single-transducer ultrasonic imaging system
- 2002
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Ingår i: NORSIG 2002. - Trondheim : The Institute of Electrical and Electronics Engineers. - 8299315840
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Konferensbidrag (refereegranskat)abstract
- During the last ten years, time-reversal of acoustic fields have been shown to be a very useful technique in ultrasonic imaging and testing. With the use of transducer arrays, it is possible to steer the sound beam to an arbitrary position within the medium, even if the medium is inhomogeneous or contains scatterers. The major drawback with traditional beamforming and time-reversal techniques is that they require the use of transducer arrays. Recently a new technique was presented that, with the use of a waveguide, makes it possible to focus sound arbitrarily, with only one transducer elements. A problem with the setup is that the signal-to-noise ratio (SNR) is degraded because of interfering echoes from the waveguide. In this paper, we present an echo-cancellation scheme that results in an SNR gain of approximately 33 dB. This enables the new technique to be used in pulse-echo mode, where this was not previously possible.
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| 2. |
- Carlson, Johan, et al.
(författare)
-
Ultrasonic particle velocimetry in multiphase flows
- 2002
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Ingår i: Proceedings. - Piscataway, NJ : IEEE Communications Society. - 0780375823 ; , s. 761-764
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Konferensbidrag (refereegranskat)abstract
- Two-dimensional ultrasonic speckle correlation velocimetry (USV) is a new technique that allows to image moving scattering media, at a high frame-rate. In this paper we apply the. technique to determine two-dimensional particle velocity profiles of multiphase flows. Experiments are realized with suspensions of Sonazoid (medical contrast agent) and Magnetite (Fe/sub 3/O/sub 4/) in water. All measurements are performed in a vertical pipe with the flow moving downwards. The two-dimensional particle velocity profiles are then compared with a reference liquid volume flow velocity. As expected from theory, the heavier Magnetite particles have slightly higher velocity than the liquid whereas the contrast agent simply follows the liquid motion. The proposed technique can be used in combination with other techniques to measure the mass flow of the solid phase, in solid/liquid multiphase flow. This is generally more interesting than-measuring the bulk mass or volume flow.
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| 3. |
- Carlson, Johan, et al.
(författare)
-
Ultrasonic speckle correlation imaging of 2D particle velocity profiles in multiphase flows
- 2003
-
Ingår i: Flow Measurement and Instrumentation. - 0955-5986 .- 1873-6998. ; 14:4-5, s. 193-200
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Tidskriftsartikel (refereegranskat)abstract
- Two-dimensional ultrasonic speckle correlation velocimetry (USV) is a new technique that allows imaging of moving scattering media, at a high frame-rate. In this paper we apply the technique to determine two-dimensional particle velocity profiles of multiphase flows. Experiments are realized with suspensions of Sonazoid (medical contrast agent) and Magnetite (Fe3O4) in water. All measurements are performed in a vertical pipe with the flow moving downwards. The two-dimensional particle velocity profiles are then compared with a reference liquid volume flow velocity. As expected from theory, the heavier Magnetite particles have slightly higher velocity than the liquid, whereas the contrast agent simply follows the liquid motion. The proposed technique can be used in combination with other techniques to measure the mass flow of the solid phase, in solid/liquid multiphase flow. This is generally more interesting than measuring the bulk mass or volume flow.
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