以往在利用超音波檢測蔬果時，常會為了獲得較佳的穿透波特性而對探頭施以一固定的接觸力，蔬果可能會因此而受到傷害。本研究目的在於將超音波量測方式移至水中進行，並探討開發一部可連續檢測機器的可行性。本研究以馬鈴薯為樣本，以水面高度、探頭距離及輸送帶前進速度三種變因進行超音波水中測試，以找出最佳的水中量測方式。接著以此方式量測馬鈴薯的水中超音波穿透波與擷取波形時機之間的關係。結果指出超音波波形與擷取不同部位馬鈴薯通過受測區域的波形時機有關。
利用細鐵棒沿馬鈴薯的長軸穿入，製造不同的空心程度，再分析其超音波穿透波的衰減係數和能量頻譜矩。結果發現有穿孔的馬鈴薯其能量頻譜矩比無空心的馬鈴薯要小，所以水中超音波檢測馬鈴薯機械具有開發的可行性。

It is common to press the transducer against the surface of fruits and vegetables in the ultrasonic evaluation of produce quality. This testing method might induce some damage if the pressing force is beyond the limit. The objectives of this study was to evaluate produce quality non-destructively by employing underwater ultrasonic testing method and discuss the feasibility of developing a underwater ultrasonic detection machine for potato.
Potato samples were selected in this study. The treatments for studying influencing factors on ultrasonic measuring accuracy were water level, distance between transducers and speed of the conveyor belt. Relationships between the characters of underwater transmitting ultrasonic waves (attenuation and spectral moment) and the timing of measurement were also investigated. The results showed that the underwater ultrasonic transmitting waves were affected by timing of measurement.
Potatoes were penetrated by a steel bar along the major axis to create different degrees of hollowness. The spectral moment of transmitting ultrasonic wave was found smaller in hollow potato than in normal potato. It is feasible to develop a underwater ultrasonic detection machine for potato.

第一章 前言1
1.1 前言1
1.2 研究目的3
第二章 文獻探討4
2.1 超音波的起源4
2.2 超音波在農業上的應用5
2.3 超音波水中之應用23
2.4馬鈴薯的重要性及利用28
第三章 理論分析31
3.1超音波的定義32
3.2波速、頻率與波長34
3.3反射、折射與音阻抗35
3.4超音波的衰減37
3.5超音波的產生與接收39
3.6連續波與脈波41
第四章 實驗設備與方法43
4.1實驗設備43
4.2實驗步驟48
4.2.1水下輸送機測試方式（第一階段） 48
4.2.2擷取訊號時機之測試（第二階段） 48
4.2.3馬鈴薯外型與超音波波形關係試驗 50
4.2.4模擬空心試驗 52
4.3衰減性質測定 53
4.4能量頻譜矩測定 54
第五章 實驗結果 55
5.1波形分析 55
5.2水下輸送機測試結果 58
5.3擷取訊號時機試驗之結果 63
5.4馬鈴薯外型與超音波特性關係之結果 65
5.5模擬空心實驗之結果 68
第六章 結論71
第七章 建議72
參考文獻73
附表77

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