TY JOUR TI Express Assessment of Coal Quality using Domestic X-ray Spectral Analyzer KW сoal quality KW ash content KW at-line analysis KW X-ray fluorescence JO NDT World AU Kudryashov, V.I. AU Moroz, A.P. AU Serebryakov, A.S. AU Mashovets, Y.I. PY 2019 IS 22 PB LLC SVEN