question: In between Nikolay Mitrofanovich Krylov and Valery Goppa who is known for works on interpolation, non-linear mechanics, and numerical methods?
answer: Nikolay Mitrofanovich Krylov
context: Title: Nikolay Mitrofanovich Krylov
  Passage: Nikolay Mitrofanovich Krylov (Russian: Никола́й Митрофа́нович Крыло́в , Ukrainian: Микола Митрофанович Крилов ) (29 November [O.S. 17 November] 1879 – May 11, 1955) was a Russian and Soviet mathematician known for works on interpolation, non-linear mechanics, and numerical methods for solving equations of mathematical physics.
  Title: Newton–Krylov method
  Passage: Newton–Krylov methods are numerical methods for solving non-linear problems using Krylov subspace linear solvers.
  Title: Describing function
  Passage: In control systems theory, the describing function (DF) method, developed by Nikolay Mitrofanovich Krylov and Nikolay Bogoliubov in the 1930s, and extended by Ralph Kochenburger is an approximate procedure for analyzing certain nonlinear control problems.  It is based on quasi-linearization, which is the approximation of the non-linear system under investigation by a linear time-invariant (LTI) transfer function that depends on the amplitude of the input waveform.  By definition, a transfer function of a true LTI system cannot depend on the amplitude of the input function because an LTI system is linear.  Thus, this dependence on amplitude generates a family of linear systems that are combined in an attempt to capture salient features of the non-linear system behavior.  The describing function is one of the few widely applicable methods for designing nonlinear systems, and is very widely used as a standard mathematical tool for analyzing limit cycles in closed-loop controllers, such as industrial process controls, servomechanisms, and electronic oscillators.
  Title: Valery Goppa
  Passage: Valery Denisovich Goppa (Russian: Вале́рий Дени́сович Го́ппа ; born 1939) is a Soviet and Russian mathematician.
citations: Valery Goppa Nikolay Mitrofanovich Krylov