一、請將下列英文譯為中文：（25 分）Propeller excitation is far more difficult to quantify than the excitation from internalmachinery sources. This is because of the complexity of the unsteady hydrodynamics ofthe propeller operating in the non-uniform hull wake. In fact, the non-uniform hull wake isthe most complicated part; unfortunately it is also the most important part. Propeller-induced vibration would never be considered in ship design if the propeller disk inflow iscircumferentially uniform. Any treatment of propeller excitation must begin with considerationof the hull wake.