Study on the Noise Reduction of Vehicle Exhaust NO_X Spectra Based on Adaptive EEMD Algorithm

Table 2

Absorbance and inverted concentrations of NO_X before and after noise reduction.

Gas	Absorption wavelength & length	Sample gas concentration	Theoretical absorbance	Absorbance before denoising	Concentration before denoising	Absorbance after denoising	Concentration after denoising
NO	215.3 nm-40 cm	16 ppm	0.0269	0.0356	21.17 ppm	0.0221	13.15 ppm
NO	215.3 nm-40 cm	1572 ppm	2.6429	2.6587	1581.4 ppm	2.6407	1570.7 ppm
NO	215.3 nm-100 cm	16 ppm	0.0673	0.0798	18.76 ppm	0.0691	16.43 ppm
NO	215.3 nm-100 cm	1310 ppm	5.5102	5.5363	1318.2 ppm	5.5099	1309.9 ppm
NO2	430.7 nm-40 cm	25 ppm	0.0031	0.0123	99.01 ppm	0.0057	45.97 ppm
NO2	430.7 nm-40 cm	500 ppm	0.0616	0.0805	653.4 ppm	0.0569	461.9 ppm
NO2	430.7 nm-100 cm	25 ppm	0.0077	0.0136	44.16 ppm	0.0085	27.59 ppm
NO2	430.7 nm-100 cm	300 ppm	0.0924	0.1243	400.6 ppm	0.0956	310.4 ppm
NO2/NO	226.5 nm-100 cm	100/1310 ppm	0.9841	0.9997	101.6/1330.8 ppm	0.9912	100.7/1319.4 ppm
NO2/NO	226.5 nm-100 cm	200/1048 ppm	0.8243	0.8339	202.4/1060.2 ppm	0.8217	199.4/1044.7 ppm
NO2/NO	226.5 nm-100 cm	300/786 ppm	0.6028	0.6329	314.9/825.5 ppm	0.5988	298/780.8 ppm
NO2/NO	226.5 nm-100 cm	500/262 ppm	0.3446	0.3621	525.4/275.4 ppm	0.3399	493.2/259.4 ppm