Amin Ghadami

Forecasting Subcritical and Supercritical Flutter Using Gust Responses

This work presents a unique method to forecast flutter (Hopf) bifurcations based on observations of the system only in the pre-bifurcation regime. New techniques are introduced in to enhance prediction accuracy for both low-frequency oscillations and large-dimensional dynamical systems. The method is applied to an aeroelastic system using its response to gust loads. Numerical results demonstrate that the method can predict the post-bifurcation regime accurately for both supercritical and subcritical flutter.Copyright

Rate of recovery from perturbations as a means to forecast future stability of living systems

Anticipating critical transitions in complex ecological and living systems is an important need because it is often difficult to restore a system to its pre-transition state once the transition occurs. Recent studies demonstrate that several indicators based on changes in ecological time series can indicate that the system is approaching an impending transition. An exciting question is, however, whether we can predict more characteristics of the future system stability using measurements taken away from the transition. We address this question by introducing a model-less forecasting method to forecast catastrophic transition of an experimental ecological system. The experiment is based on the dynamics of a yeast population, which is known to exhibit a catastrophic transition as the environment deteriorates. By measuring the system’s response to perturbations prior to transition, we forecast the distance to the upcoming transition, the type of the transition (i.e., catastrophic/non-catastrophic) and the future equilibrium points within a range near the transition. Experimental results suggest a strong potential for practical applicability of this approach for ecological systems which are at risk of catastrophic transitions, where there is a pressing need for information about upcoming thresholds.