Fig. 1. Flow chart of mid-infrared detection model for determining methanol content of methanol gasoline

Fig. 2. Original mid-infrared spectra of gasoline and absolute methanol. (a) Mid-infrared spectrum of gasoline; (b) mid-infrared spectrum of absolute methanol

Fig. 3. Original mid-infrared spectra of methanol gasoline with different methanol volume fractions

Fig. 4. Band selected by UVE method. (a) Band selection in full spectrum; (b) band points selected in full spectrum

Fig. 5. Wavelength variable screening based on CARS algorithm. (a) Number of variables versus sampling times; (b) RMSECV value versus sampling times; (c) regression coefficient versus sampling times

Fig. 6. Band points selected by CARS method within full spectrum

Fig. 7. Frequency of each wavelength being selected

Fig. 8. RMSECV varying with number of variables

Fig. 9. Scatter plots of methanol content in methanol gasoline predicted by CARS-PLS model. (a) Calibration set; (b) prediction set