{HEAD ~ A fuel cell} adopting the liquid tank maintains {TAIL ~ the liquid level} in the tank near 50% of the full level even when the fuel cell is rotated 
maintains
{ HEAD ~ A fuel cell } adopting the liquid tank maintains { TAIL ~ the liquid level } in the tank near 50 % of the full level even when the fuel cell is rotated
HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH