Hong-mei LIN, Qiu-hong CAO, Tong-jun ZHANG, Zhao-xin LI, Hai-qing HUANG, Xue-min LI, Bin WU, Qing-jian ZHANG, Xin-min LÜ, De-hua LI. Identification of Nephrite and Imitations Based on Terahertz Time-Domain Spectroscopy and Pattern Recognition[J]. Spectroscopy and Spectral Analysis, 2021, 41(11): 3352
- Spectroscopy and Spectral Analysis
- Vol. 41, Issue 11, 3352 (2021)
Fig. 1. Experimental schematic diagram of THz-TDS
Fig. 2. (a) Terahertz frequency spectrum, (b) refractive index of glass, marble, raw gemstone and Jades from Afghanistan, China’s Qinghai, Pakistan and China’s Xinjiang
Fig. 3. Scores of the first and second principal components of jade samples from Afghanistan, China’s Qinghai, Pakistan and China’s Xinjiang and imitations
Fig. 4. Result of GridSearch-SVM parameter selection(optimal parameter c= 2.828 4, g= 2)
Fig. 5. Fitness curve of GA(optimal parameter c =1.740 1, g =4.544 6)
Fig. 6. Fitness curve of PSO(optimal parameter c =11.287 2, g =1.833 1)
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Table 1. Variance contribution index and cumulative variance contribution index of each principal component of refractive index
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Table 2. Comparison of three optimization methods of SVM combined with Gridsearch, GA and PSO
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