s. The linear resonance of both subsystems is observed for m ¼ 1:0 and around this
value we find complex dynamics with many coexisting attractors, not only periodic but also quasiperiodic and chaotic
ones. In the principal resonance zone the pendulum oscillations decrease the oscillation amplitude of the Duffing oscillator
so we observe an energy transfer from the Duffing oscillator to the pendulum. These properties are observed only for 1 : 1
oscillatory resonance, for other locked solutions (oscillations or rotations) the pendulum oscillations increase the
oscillations amplitude of the Duffing oscillator (the control and the possible decrease of the amplitude for other
resonances will be considered in future work)