TY JOUR TI MEASURING THE DEGREE BLACK SURFACE BY COMPARISON RADIATIVE FLUX KW comparison method KW thermal radiation KW radiation flow KW thermal stability KW emissivity KW experimental installation JO Problems of risk management in the technosphere AU Nekrasov, A.S. AU Kuzmin, A.A. AU Romanov, N.N. PY 2017 IS 2017 PB Saint-Petersburg University of State Fire Service of Emercom of Russia