Abstract: 10 A fluorescence system is developed by using several light emitting diodes (LEDs) with different 11 wavelengths as excitation light sources. The fluorescence detection head consists of multi LED light 12 sources and a multimode fiber for fluorescence collection, where the LEDs and the corresponding 13 filters can be easily chosen to get appropriate excitation wavelengths for different applications. By 14 analyzing fluorescence spectra with the principal component analysis method, the system is utilized in 15 the classification of four types of green tea beverages and two types of black tea beverages. Qualities of 16 the Xihu Longjing tea leaves of different grades, as well as the corresponding liquid tea samples, are 17 studied to further investigate the ability and application of the system in the evaluation of 18 classification/quality of tea and other foods.19
Abstract. In this paper we prove the existence of Hall's ray for the quadratic Lagrange spectrums of all real quadratic numbers. For a large class of real quadratic numbers, we compute the Hurwitz constants of their quadratic Lagrange spectrums.
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