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The application of laser reflective tomography in near-field measurements of ultrasonic transducers 被引量:4
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作者 WANG Yuebing WANG Shiquan 《Chinese Journal of Acoustics》 2014年第3期257-266,共10页
With Laser Reflective Tomography(LRT),the near fields of ultrasonic transducers were measured and analyzed.The principle of LRT measurement of ultrasonic field distribution was introduced and an experimental system ... With Laser Reflective Tomography(LRT),the near fields of ultrasonic transducers were measured and analyzed.The principle of LRT measurement of ultrasonic field distribution was introduced and an experimental system was set up.Acoustic pressure of a multiple element piston transducer was measured by using of a laser vibrometer.Its distribution in amplitude and phase was obtained.The acoustic pressure in the same region was measured with a needle hydrophone to validate the LRT method.Furthermore,through reconstruction of acoustic fields,it indicated that LRT method is suitable for predicting the distribution on transducers'surface and conditions of active elements. 展开更多
关键词 The application of laser reflective tomography in near-field measurements of ultrasonic transducers LRT
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Data-Domain Wave Equation Reflection Traveltime Tomography 被引量:4
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作者 Bo Feng Huazhong Wang 《Journal of Earth Science》 SCIE CAS CSCD 2015年第4期487-494,共8页
Estimation of an accurate macro velocity model plays an important role in seismic imag- ing and model parameter inversion. Full waveform inversion (FWI) is the classical data-domain inver- sion method. However, the ... Estimation of an accurate macro velocity model plays an important role in seismic imag- ing and model parameter inversion. Full waveform inversion (FWI) is the classical data-domain inver- sion method. However, the misfit function of FWI is highly nonlinear, and the local optimization cannot prevent convergence of the misfit function toward local minima. To converge to the global minimum, FWI needs a good initial model or reliable low frequency component and long offset data. In this article, we present a wave-equation-based reflection traveltime tomography (WERTT) method, which can pro- vide a good background model (initial model) for FWI and (least-square) pre-stack depth migration (LS-PSDM). First, the velocity model is decomposed into a low-wavenumber component (background velocity) and a high-wavenumber component (reflectivity). Second, the primary reflection wave is pre- dicted by wave-equation demigration, and the reflection traveltime is calculated by an automatic picking method. Finally, the misfit function of the 12-norm of the reflection traveltime residuals is mini- mized by a gradient-based method. Numerical tests show that the proposed method can invert a good background model, which can be used as an initial model for LS-PSDM or FWI. 展开更多
关键词 reflection traveltime tomography primary reflection wave wave equation demigration background velocity building rough reflectivity.
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Research on algorithms for ultrasonic reflection mode tomography
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作者 CHEN Yanhua, LAN Congqin XU Keke (Wuhan Institute of Physics. Academia Sinics, Wuhan 430071) 《Chinese Journal of Acoustics》 1992年第3期229-236,共8页
In this paper, mathematical analysis shows that the reconstruction of ultrasonic reflection mode tomography using a single transducer acting as both source and receiver far from the object can be obtained by employing... In this paper, mathematical analysis shows that the reconstruction of ultrasonic reflection mode tomography using a single transducer acting as both source and receiver far from the object can be obtained by employing filtered-backprojection algorithm which is widely used in X-ray tomography; but when the transducer is near to the object, this algorithm will result in image distortion. On the basis of mathematical analysis, we propose a new algorithm. Computer simulation demonstrates an obvious improvement in the reconstructed images employing this algorithm over the conventional filtered-backprojection method of X-ray tomography. 展开更多
关键词 MODE Research on algorithms for ultrasonic reflection mode tomography exp
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