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- ItemGlobal bifurcation analysis of limit cycles for a generalized van der Pol system(Berlin : Weierstraß-Institut für Angewandte Analysis und Stochastik, 2019) Schneider, Klaus R.; Grin, AlexanderWe present a new approach for the global bifurcation analysis of limit cycles for a generalized van der Pol system. It is based on the existence of a Dulac-Cherkas function and on applying two topologically equivalent systems: one of them is a rotated vector field, the other one is a singularly perturbed system.
- ItemGlobal algebraic Poincaré--Bendixson annulus for van der Pol systems(Berlin : Weierstraß-Institut für Angewandte Analysis und Stochastik, 2021) Grin, Alexander; Schneider, Klaus R.By means of planar polynomial systems topologically equivalent to the van der Pol system we demonstrate an approach to construct algebraic transversal ovals forming a parameter depending Poincaré-Bendixson annulus which contains a unique limit cycle for the full parameter domain. The inner boundary consists of the zero-level set of a special Dulac-Cherkas function which implies the uniqueness of the limit cycle. For the construction of the outer boundary we present a corresponding procedure
- ItemLower and upper bounds for the number of limit cycles on a cylinder(Berlin : Weierstraß-Institut für Angewandte Analysis und Stochastik, 2019) Schneider, Klaus R.; Grin, AlexanderWe consider autonomous systems with cylindrical phase space. Lower and upper bounds for the number of limit cycles surrounding the cylinder can be obtained by means of an appropriate Dulac-Cherkas function. We present different possibilities to improve these bounds including the case that the exact number of limit cycles can be determined. These approaches are based on the use of several Dulac-Cherkas functions or on applying some factorized Dulac function.