姓名 |
黄俊諺(Jiun-Yan
Huang) |
電子郵件信箱 |
E-mail 資料不公開 |
畢業系所 |
營建工程系碩士班(Department
and Graduate Institute of Constrction Engineering) |
畢業學位 |
碩士(Master) |
畢業時期 |
91學年第2學期 |
論文名稱(中) |
運用小波轉換改善超音波法檢測混凝土訊號判讀 |
論文名稱(英) |
Improving the Signal
Detection of Ultrasonic Pulse Velocity Method Based on Wavelet
Transform |
檔案 |
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|
論文使用權限 |
校內外完全公開 |
論文語文/頁數 |
中文/107 |
摘要(中) |
傳統的訊號分析是建立在傅立葉轉換的基礎之上,但由於傅立葉轉換無法表達訊號的時頻局部性質,因此有了小波轉換的發展,小波轉換相較於傅立葉轉換最大的不同,便是小波轉換是一種時間窗與頻率窗都可改變的時頻局部化分析方法,即在低頻部分具有較高的頻率分辨率和較低的時間分辨率,而在高頻部分具有較高的時間分辨率和較低的頻率分辨率。 以超音波檢測混凝土,會因為混凝土本身非均質材料的特性及不同邊界所造成複雜的波傳路徑影響,而使得超音波訊號出現難以解讀之訊號波形,本文利用小波轉換將超音波訊號進行時頻分析,發現小波轉換在提取特徵訊號及展示其時間成分具有良好的效果。 |
摘要(英) |
Fourier transform is
frequently used in analyzing the frequency content of a transient
signal. The drawback of Fourier transform is that the time-domain
characteristic cannot be shown simultaneously. Wavelet transform is one
of the time-frequency dual transforms that provide the transient
frequency content of a signal. The length of both time window and
frequency window can be varied in wavelet transform. As a result, the
time resolution is better in high frequency band while the frequency
resolution is better in low frequency band. This makes wavelet transform
a very attractive tool for analyzing the ultrasonic wave through
concrete. Current study focuses on the time dependence of spectral
characteristics of ultrasonic waves propagating in concrete. Wavelet
transform is applied to simulated signals as well as real signals.
Sources of excitation are compared and features of corresponding wavelet
transforms are identified. The peaks of signals obtained from heated
concrete appear to be delayed in time and the associated scales shift to
lower frequencies. |
關鍵字(中) |
小波轉換
超音波 |
關鍵字(英) |
ultrasonic
wavelet transform |
指導教授 |
江支弘
|