\begin{equation}
\left{
\begin{array}{lr}
x=\dfrac{3\pi}{2}(1+2t)\cos(\dfrac{3\pi}{2}(1+2t)), & \
y=s, & 0 \leq s \leq L,|t| \leq1. \
z=\dfrac{3\pi}{2}(1+2t)\sin(\dfrac{3\pi}{2}(1+2t)), &
\end{array}
\right.
\end{equation}
\begin{equation}
\left{
\begin{array}{lr}
x=\dfrac{3\pi}{2}(1+2t)\cos(\dfrac{3\pi}{2}(1+2t)), & \
y=s, & 0 \leq s \leq L,|t| \leq1. \
z=\dfrac{3\pi}{2}(1+2t)\sin(\dfrac{3\pi}{2}(1+2t)), &
\end{array}
\right.
\end{equation}