{TAIL ~ Two or more vibration generators} may introduce vibrations with different frequencies into {HEAD ~ the chemical bath liquid} and at different angles 
{ TAIL ~ Two or more vibration generators } may introduce vibrations with different frequencies into { HEAD ~ the chemical bath liquid } and at different angles
TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH