TY JOUR TI Internal friction investigation of the natural and compressed birch (Betula pendula Roth) wood KW internal friction of wood KW natural and modified wood birch (Betula pendula Roth) KW Boltzmann superposition principle KW modification KW ultrasound KW magnetic field JO Forestry Engineering Journal AU Russu, A.V. AU Shamaev, V.A. AU Razinkov, E.M. AU Zimelis, A.. PY 2023 IS 13 PB FSBE Institution of Higher Education Voronezh State University of Forestry and Technologies named after G.F. Morozov