The precessing jet-nozzle scenario previously proposed was applied to
interpret the VLBI-measured kinematics of five superluminal components
(C4,C5,C9,C10 and C22) and their flux density evolution in blazar 3C345. It is
shown that in the inner-trajectory sections their kinematic properties,
including trajectory,coordinates, core separation and apparent velocity can be
well model-simulated by using the scenario with a precession period of 7.30yr
(4.58yr in the source frame) and a precessing common trajectory, which produces
the individual knot-trajectories at their corresponding precession phases.
Through the model-simulation of their kinematic behavior their bulk Lorentz
factor ,viewing angle and Doppler factor were derived as functions of time.
These anticipatively-determined Lorentz/Doppler factors were used to
investigate the knots' Doppler-boosting effect and interpret their flux
evolution. It was found that the light-curves of the five superluminal
components observed at 15, 22 and 43GHz were extraordinarily well coincident
with their Doppler boosting profiles. Additionally, some flux fluctuations on
shorter time-scales could be due to variations in knots' intrinsic flux and
spectral index. The close relation between the flux evolution and the Doppler
boosting effect not only firmly validates the precessing jet-nozzle scenario
being fully appropriate to explain the kinematic and emission properties of
superluminal components in QSO 3C345, but also strongly supports the traditioal
common point-view: superluminal components are physical entities (shocks or
plasmoids) participating relativistic motion toward us with
acceleration/deceleration along helical trajectories.