31.真空沸騰式造水機停用時，下列各項步驟的正確順序為何？①關斷給水並停海水泵 ②停止冷卻 ③關凝水閥，停凝水泵 ④停止加熱 (A)①→②→③→④ (B)③→①→②→④ (C)④→③→①→② (D)③→④→①→②

10.Longitudinal vibration of propulsion shafting systems is often excited by the variable thrust developed by the propeller due to the non-uniform wake pattern in which it operates. The predominant periodic component of the thrust developed by a propeller occurs at blade-rate frequency, i.e., the number of propeller blades times the rotational frequency of the shaft. For a four-blade propeller running at 60 rev/min, what is the predominant periodic frequency that excites the longitudinal vibration of the propulsion shafting systems? (A)1 Hz (B)2 Hz (C)3 Hz (D)4 Hz

31.真空沸騰式造水機停用時，下列各項步驟的正確順序為何？①關斷給水並停海水泵 ②停止冷卻 ③關凝水閥，停凝水泵 ④停止加熱
(A)①→②→③→④
(B)③→①→②→④
(C)④→③→①→②
(D)③→④→①→②

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