Plasticity performance of Al0.5CoCrCuFeNi high-entropy alloys under nanoindentation

The statistical and dynamic behaviors of the displacement-load curves of a high-entropy alloy Al0.3CoCrCuFeNi were analyzed for the nanoindentation performed at two temperatures. Critical behavior of serrations at room temperature and chaotic flows at 200 degrees C were detected. These results are attributed to the interaction among a large number of slip hands. For the nanoindentation at room temperature recurrent partial events between slip hands introduce a hierarchy of length scales leading to a critical state. For the nanoindentation at 200 degrees C there is no spatial interference between two slip hands which is corresponding to the evolution of separated trajectory of chaotic behavior

Bifurcations of a periodically forced microbial continuous culture model with restrained growth rate

A three dimensional microbial continuous culture model with a restrained microbial growth rate is studied in this paper. Two types of dilution rates are considered to investigate the dynamic behaviors of the model. For the unforced system, fold bifurcation and Hopf bifurcation are detected, and numerical simulations reveal that the system undergoes degenerate Hopf bifurcation. When the system is periodically forced, bifurcation diagrams for periodic solutions of period-one and period-two are given by researching the Poincare map, corresponding to different bifurcation cases in the unforced system. Stable and unstable quasiperiodic solutions are obtained by Neimark-Sacker bifurcation with different parameter values. Periodic solutions of various periods can occur or disappear and even change their stability, when the Poincare map of the forced system undergoes Neimark-Sacker bifurcation, flip bifurcation, and fold bifurcation. Chaotic attractors generated by a cascade of period doublings and some phase portraits are given at last. Published by AIP Publishing