TY JOUR TI Mathematical model for determining the volume of birch bark at woodworking enterprises when organizing the production of composite materials KW wood waste KW birch bark KW birch bark paper KW spline function KW volume KW composite material KW recycling JO Forestry Engineering Journal AU Chernykh, A.S. AU Rublev, I.Y. PY 2025 IS 15 PB FSBE Institution of Higher Education Voronezh State University of Forestry and Technologies named after G.F. Morozov