  The energy cascade rate of turbulence can be measured with the structure
function. In practice, the 3D velocity of the gas in molecular cloud is hard to
measure, which makes the measurement of structure function difficult. In the
case of thin molecular clouds perpendicular to the line of sight, the structure
function $S^2_{ tt}$ can be measured with core velocity dispersion (CVD), ${\rm
CVD}^2=\frac{1}{2}S^2_{ tt}$. This method was extended to the case when the
thin molecular cloud is not perpendicular to the line of sight, with
intersection angle $\theta$, ${\rm CVD}^2=\frac{1}{2}S^2_{
tt}\left(1-\frac{1}{8}\cos^2\theta\right)R^{2/3}$, where $R$ can be expressed
with elliptic integrals of the second kind $E(k,\varphi)$ as
$R=\frac{2}{\pi}E(\cos\theta,\frac{\pi}{2})$.
