$U$	The average extrusion velocity inside the nozzle
$V$	Moving speed of nozzle relative to substrate
$\delta$	The gap between nozzle tip and substrate
$a_0$	Inner radius of the nozzle tip
$W$	Strand width
$H$	Strand height
$A$	Cross-sectional area of strand
$X$	Spacing of strand
$C$	Layer height
$P$	Air pressure
$Q$	Flow rate