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Figure 1: Spectra of different spectral preprocessing methods for PLS and ANN. (a) Raw specta; (b) constant offset elimination; (c) Min/max normalization; (d) MSC; (e) Straight line subtraction; (f) Standard normal variate transformation; (g) 1^{st} D; (h) 2^{nd} D; (i) 1^{st} D + MSC; (j) 1^{st} D + SLS; (k) 1^{st} D + SNV. 1^{st} D: Fist derivative; 2^{nd} D: Second derivative; MSC: Multiplicative scatter correction; SLS: Straight line subtraction; SNV: Standard normal variate transformation; PLS: Partial least square; ANN: Artificial neural network 
