非负约束最小二乘法丰度反演 NCLS 矩阵运算 EA=X 参考文献：[1]R. Bro, S. D. Jong,"A FAST NON-NEGATIVITY-CONSTRAINED LEAST SQUARES algorithm" [2]Charles L. Lawson, Richard J. Hanson ,Solving Least Squares Problems (Classics in Applied Mathematics) (Society for Industri