Ruled surfaces asymptotically normalized
We consider a skew ruled surface $Φ$ in the Euclidean space $E^{3}$ and relative normalizations of it, so that the relative normals at each point lie in the corresponding asymptotic plane of $Φ$. We call such relative normalizations and the resulting relative images of $Φ$ \emph{asymptotic}. We determine all ruled surfaces and the asymptotic normalizations of them, for which $Φ$ is a relative sphere (proper or inproper) or the asymptotic image degenerates into a curve. Moreover we study the sequence of the ruled surfaces ${Ψ_{i}}_{i\in \mathbb{N}}$, where $Ψ_{1}$ is an asymptotic image of $Φ$ and $Ψ_{i}$, for $i\geq2$, is an asymptotic image of $Ψ_{i-1}$. We conclude the paper by the study of various properties concerning some vector fields, which are related with $Φ$.