both models involve inhomogeneous winds. This makes interpretation of the optical depths of NACs in terms of $\dot{M}$ more complex. For a homogeneous wind, one can argue that for some combination of stellar parameters, the ion fraction of a specific element, $q$, must approach 1. For an inhomogeneous wind, this is no longer the case. Different ions of the same element may attain their largest ion fractions in different constituents of the wind for different stellar parameters. For example, it is possible that when $q($Si$^{2+}) \sim 1$ in the denser wind structures, $q($Si$^{3+}) 
\sim 1$ in the surrounding medium, and that when $q($Si$^{3+}) \sim 1$ in the structures, $q($Si$^{4+}) \sim 1$ (which lacks an observable wind line) in the surrounding medium. As a result, the maximum value of $q$ for a given ion may only be $\sim 1/2$ or less. However, constraints can be applied to the possible ion stages present. For example, if a wind lacks strong C [iv]{} and N [v]{} lines, then most of the silicon must be in stages Si$^{3+}$ and below, all of which have observable resonance lines.

Returning to HD 13866 and HD 47240, their effective temperatures approximately correspond to the regime where $q($Si$^{3+}$) 