| Summary: | 碩士 === 國立成功大學 === 系統及船舶機電工程學系碩博士班 === 98 === This paper discusses the application of acoustic waves in water. The first part is the underwater acoustic imaging, and the second part is the non-linear loads combining underwater acoustic waves. The first part acquires much more scattering data mainly by utilizing acoustic wave diversity techniques, including frequency diversity and angle diversity. Followed by adopting the concept of Ewald sphere to fill Fourier space, and then apply bi-linear interpolation, calibration and two-dimensional inverse Fourier transformation to reconstruct the image of objects. During the experiment, we image one metal cylinder and two metal cylinders respectively. The second part is about non-linear loads applied to underwater acoustic waves. This part applies the characteristics of non-linear loads that produce multiple frequencies component signal, which is used to disguise cheating. Experiment applies acoustic waves as the signal source to launch a base frequency signal passing the hydrophone and amplifier, and then transmit signal to data acquisition card through the non-linear loads. Lastly, send it back to the computer to perform fast Fourier transformation and then analyze harmonic acoustic waves. In this part, we experiment on the four different non-linear loads. This study has certain contribution in underwater acoustic imaging, underwater archeology, non-destructive testing and underwater submarine electronic warfare.
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