说明：  基于PCA和白化的数据预处理操作，PCA具有两个功能：维数约减和数据可视化；白化的目的是去掉数据之间的相关性。深度学习的一个主要工作就是数据的预处理
(Based on PCA and data pre-whitening operation, PCA has two functions: dimensionality reduction and data visualization whitening purpose is to remove the correlation between the data. One of the main work is to study the depth of pre-processed data)