TY CONF TI SIMULATION MODEL OF THE WORK OF THE RETURN DEPARTMENT OF A LARGE ONLINE STORE KW simulation modeling KW refund department KW e-commerce KW discrete event model KW business process optimization KW refund logistics JO MODELING INFORMATION SYSTEMS AND TECHNOLOGIES – 2026 AU Kosykh, V.D. PY 2026 PB FSBE Institution of Higher Education Voronezh State University of Forestry and Technologies named after G.F. Morozov