00546naa#a2200169#i#450# EN\\bibl\43348 20240911182723.3 1609-3178 20210514b2021####ek#y0engy0150####ca RU Method for Operational Diagnostics of the Prepumping State of Gas Turbine Engines Based on Invariants of Acoustic Processes Journal article Saint-Petersburg LLC SVEN 2021 3 с. Journal article local Popov Aleksey V. Romanov Aleksandr A. naukaru.ru