APFT 1 Aliasing 1 Almost periodic 1 Almost periodic Fourier transform 1 Almost periodic fourier transform 1 Condition number 1 Condition numbers 1 Discrete Fourier transforms 1 Duffing oscillator 1 Duffing's oscillator 1 Fourier analysis 1 Harmonic Balance method 1 Harmonic analysis 1 Harmonic balance Multiple frequency 1 Nonlinear equations 1 Number theory 1 Ordinary differential equations 1 Oscillators (mechanical) 1 Periodic Fourier transform 1