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KJ Lee

Publications and source records attributed to KJ Lee.

14 recordsLinked to original sources
PubMed2000

Superlattice, rhombus, square, and hexagonal standing waves in magnetically driven ferrofluid surface

Standing wave patterns that arise on the surface of ferrofluids by (single frequency) parametric forcing with an ac magnetic field are investigated experimentally. Depending on the frequency and amplitude of the forcing, the system exhibits various patterns including a superlattice and subharmonic rhombuses as well as conventional harmonic hexagons and subharmonic squares. The superlattice arises in a bicritical situation where harmonic and subharmonic modes collide. The rhombic pattern arises due to the nonmonotonic dispersion relation of a ferrofluid.

Journal Article↗
PubMed2000

Complex dynamics of a spiral tip in the presence of an extrinsic local modulation

With a generic model excitable system, we have investigated the spatio-temporal dynamics of a spiral tip in the presence of an extrinsic localized periodic modulation. The tip of a modulated spiral does exhibit a variety of different trajectories depending on the strength and the frequency of the modulation. Its motion can be quasiperiodic on a 2-torus, quasiperiodic or mode locked on a 3-torus, or fully chaotic. Various bifurcations, including hard Hopf bifurcations and saddle-node bifurcations at strong resonances and period-doubling bifurcations of a mode-locked 3-torus, are revealed. In particular, the phenomenon of the period-doubling cascade of a resonant spiral tip trajectory is reported.

Journal Article↗