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(29) MLR analysis of rice by means of extended derivatives of NIR spectra
¡¡¡¡¡¡Proceedings of Japan-Thailand Joint Symposium on Nondestructive Evaluation Technology, pp.103-110, 2004-5
In NIR analyses, first and second derivatives are sometimes used as important pretreatments of spectra. There are, however, some drawbacks in derivatives of spectra, such as deformation (shift or inversion) of peaks and noise enhancement. To reduce or avoid these problems, two types of extended derivatives, fractional derivative and fractional absolute derivative, are introduced on the basis of Fourier transform approach of numerical differentiation. The former extends the order of derivatives from an integer to any positive real number and the latter has an additional property of suppressing the shift and inversion of the peaks. Some fundamental properties of the extended derivatives are elucidated using simple Gaussian peaks and NIR spectra of rice. They are subsequently applied to MLR analysis of three major constituents, water, amylase and protein, of rice to show their effect on the performance of calibrations. It is shown that the multiple correlation coefficient and the standard error of calibration depend on the order as well as the type of derivatives, and that the best calibration result is mostly obtained at a fractional order. It is also shown that, in general, selected wavelengths in MLR are more stable in the FAD than in the FD, since the wavelength of each absorption peak remains almost constant in the former and shift with an increase in the latter.
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