TY JOUR TI MATHEMATICAL MODEL OF SEED SORTING PROCESS ON THE MULTI-STEP ROLLING SEPARATOR KW multi-step rolling separator KW technological process differential equation KW separator rolls KW conifer seeds JO Bulletin of KSAU AU Knyazev, A.V. AU Vakhnina, G.N. PY 2013 IS PB Krasnoyarsk State Agrarian University