( ( ( The energy ) ( received ( at ( the ( radar site ) ) ) ) ) ( ( is ( proportional ( to ( ( the concentration ) ( of ( particles ( in ( the ( irradiated volume ) ) ) ) ) ) ) ) ) . ) )
(ROOT (S (NP (NP (DT The) (NN energy)) (VP (VBN received) (PP (IN at) (NP (DT the) (NN radar) (NN site))))) (VP (VBZ is) (ADJP (JJ proportional) (PP (TO to) (NP (NP (DT the) (NN concentration)) (PP (IN of) (NP (NP (NNS particles)) (PP (IN in) (NP (DT the) (JJ irradiated) (NN volume))))))))) (. .)))
The energy received at the radar site is proportional to the concentration of particles in the irradiated volume.
(ROOT (S (NP (NP (DT The) (NN number)) (PP (IN of) (NP (NP (NNS particles)) (PP (IN of) (NP (NP (DT a) (NN substance)) (PP (IN in) (NP (DT a) (VBN given) (NN volume)))))))) (VP (VBZ is) (VP (VBN known) (PP (IN as) (NP (DT the) (NN concentration))))) (. .)))