TY JOUR TI Method for Operational Diagnostics of the Prepumping State of Gas Turbine Engines Based on Invariants of Acoustic Processes KW : invariant KW acoustic signal KW random process KW pre-surge state KW unstable operation of gas turbine engines KW surge KW failure KW hardware and software complex JO NDT World AU Popov, A.V. AU Romanov, A.A. PY 2021 IS 24 PB LLC SVEN