DESCRIPTION:  Mira’s Model

The coordinates of the points on the Mira curve are generated iteratively through the following system of nonlinear difference equations:

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x(k+1) = by(k)+F(x(k))

y(k+1) = -x(k)+F(x(k+1))

where

F(x) = ax + (2(1-a)x*x)/(1+x*x)
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