碩士 / 國立成功大學 / 系統及船舶機電工程學系碩博士班 / 101 / The purpose of this paper is developing a procedure to distinguish target characteristics such as material and size by observing convergence frequency through iterative time reversal process. The proposed procedure is verified from designed simulations and experiments by using slim shell circular tubes as targets. These slim shell structures produce lamb waves that contain energy within corresponding frequency bandwidth. The iterative time reversal process is then performed to enhance energy of responding lamb waves and makes it possible to distinguish target characteristics. In addition, target distance can be determined from wave propagation time. In experiments, interrogating signals are controlled by LabVIEW and emitted from an unfocused broadband underwater transducer. Specular echo and responding lamb wave signals are then received by another same type transducer and recorded by a digital oscilloscope. Due to the enhancing effect of iterative time reversal, energy of iterative receiving signals converges to certain frequencies. After comparing these frequencies from varying target material and target size, the result proves that the proposed procedure is capable to distinguish properties of different targets. The simulation of a thin and fluid-loaded elastic shell is computed using the classical theoretical formulation of Goodman and Stern to create shell model and find convergence frequency
| Identifer | oai:union.ndltd.org:TW/101NCKU5345007 |
| Date | January 2013 |
| Creators | Yu-ChenKo, 柯昱辰 |
| Contributors | Gee-Pin Too, 涂季平 |
| Source Sets | National Digital Library of Theses and Dissertations in Taiwan |
| Language | zh-TW |
| Detected Language | English |
| Type | 學位論文 ; thesis |
| Format | 72 |
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