Bifurcating limit cycles in quadratic polynomial differential systems

We conducted a study on the plane quadratic polynomial differential systems with two or three parameters. Bifurcation curves were drawn in the cross-s ection of parameter space, dividing the section into several regions. Diffe rent number of limit cycles can be identified in different regions. Diagram s of variation of amplitude of limit cycles versus parameters are shown and realistic examples of systems having different number of limit cycles are constructed. As an example, a quadratic equation with limit cycles in (1,3) distribution is shown. (C) 2000 Elsevier Science B.V. All rights reserved.