把各阶导函数的ESD作为a的函数，确定其峰值频率的数值。该函数把以下变量作为输入：a的最小值alphamin，其增量步长alphastep；-various derivative function of the ESD as a function of its peak frequency values. The function of the following variables as input : a minimum of alphamin. its incremental step alphastep;