I was reading the research article: Demonstration of optimizing piezoelectric polarization in the design of a flextensional actuator, where I had confusion differentiating between poling angle, which is supposed to be the angle between the applied electric field and arbitrary reference axis, and the polarization angle which is the angle between the average direction of the electric dipoles in the absence of an external electric field and a reference axis. 
But in the figures, poling angle appears to be the angle between polarization vector and electric field, and the polarization angle is ok, seems to be the angle between the electric field and polarization vector (though taken arbitrary), but I didn't understand why only the electric field direction taken variable where as the arbitrary polarization vector taken fixed upon rotation.
I am very confused and mixing things together. I appreciate any clear explanation. Thank you.
