Finding Extremal Periodic Orbits with Polynomial Optimization, with Application to a Nine-Mode Model of Shear Flow. - Mayur V. Lakshmi; Giovanni Fantuzzi; Jesús D. Fernández-Caballero; Yongyun Hwang; Sergei Ivanovich Chernyshenko (SIAM J. Appl. Dyn. Syst., 2020)