Research Article
Duffing-Type Oscillator with a Bounded from above Potential in the Presence of Saddle-Center Bifurcation and Singular Perturbation: Frequency Control
Figure 4
Phase portraits for (from top-left to bottom-right):2.5 2 ; 0 (heteroclinic connections between two saddles of associated system, ); 1; 2 (); 2.5 .