说明：  产生一512点的随机序列xe( u),并用xc(u)和 xe(u)作线性卷积，观察卷积前后xe( n)频谱的变化。要求将xe(n)分成8段，分别采用重叠相加法和重叠保留法.
(Generate a 512-point random sequence xe (u), and use xc (u) and xe (u) for linear convolution. Observe the change of xe (n) spectrum before and after convolution. It is required to divide xe (n) into 8 segments, and use overlapping addition method and overlapping retention method, respectively.)