Lyapunov Exponents of Simulated and Measured Quasi-Periodic Flows

摘要

Lyapunov exponents are calculated from numerically simulated and measured signals. The existing algorithms for their estimation have free parameters and their impact and the impact of noise are analysed on quasi-periodic simulated signals. Furthermore, calculation of the exponents of the blood flow signal, measured on a healthy subject, is presented. Two typical patterns of both the global and the local Lyapunov exponents are obtained over a wide range of parameter values. Either we have four paired and one zero exponent, or five paired exponents. This may indicate the deterministic and almost conservative nature of the system governing blood circulation on the time-scale of minutes.