轴向位移
参考答案：
用来表证汽轮机转子在轴向推力作用下的位移情况。
超声波通过一定厚度的薄层介质时，如两边介质的声阻抗相等，则薄层厚度为1/2波长及其整数倍时，将有最大的声压通过率。
From the middle part to the end of the 18th century, in English literature （） flourished. They were mostly stories of mystery and horror which take place in some haunted or dilapidated middle age castles.
