title: A partial least squares and wavelet-transform hybrid model to analyze carbon content in coal using laser-induced breakdown spectroscopy.
abstract: A partial least squares (PLS) and wavelet transform hybrid model are proposed to analyze the carbon content of coal by using laser-induced breakdown spectroscopy (LIBS). The hybrid model is composed of two steps of wavelet analysis procedures, which include environmental denoising and background noise reduction, to pretreat the LIBS spectrum. The processed wavelet coefficients, which contain the discrete line information of the spectra, were taken as inputs for the PLS model for calibration and prediction of carbon element. A higher signal-to-noise ratio of carbon line was obtained after environmental denoising, and the best decomposition level was determined after background noise reduction. The hybrid model resulted in a significant improvement over the conventional PLS method under different ambient environments, which include air, argon, and helium. The average relative error of carbon decreased from 2.74 to 1.67% under an ambient helium environment, which indicated a significantly improved accuracy in the measurement of carbon in coal. The best results obtained under an ambient helium environment could be partly attributed to the smallest interference by noise after wavelet denoising. A similar improvement was observed in ambient air and argon environments, thereby proving the applicability of the hybrid model under different experimental conditions.
authors.affiliation: State Key Lab of Power Systems, Department of Thermal Engineering, Tsinghua-BP Clean Energy Center, Tsinghua University, Beijing, China; Guodian Science and Technology Research Institute, Nanjing, China.
authors.forename: Tingbi
authors.initials: T
authors.lastname: Yuan
authors.affiliation: State Key Lab of Power Systems, Department of Thermal Engineering, Tsinghua-BP Clean Energy Center, Tsinghua University, Beijing, China. Electronic address: zhewang@tsinghua.edu.cn.
authors.forename: Zhe
authors.initials: Z
authors.lastname: Wang
authors.affiliation: State Key Lab of Power Systems, Department of Thermal Engineering, Tsinghua-BP Clean Energy Center, Tsinghua University, Beijing, China.
authors.forename: Zheng
authors.initials: Z
authors.lastname: Li
authors.affiliation: State Key Lab of Power Systems, Department of Thermal Engineering, Tsinghua-BP Clean Energy Center, Tsinghua University, Beijing, China.
authors.forename: Weidou
authors.initials: W
authors.lastname: Ni
authors.affiliation: Guodian Science and Technology Research Institute, Nanjing, China.
authors.forename: Jianmin
authors.initials: J
authors.lastname: Liu
keywords: Coal; Laser-induced breakdown spectroscopy; Partial least square regression; Wavelet transform