I make use of [alpha/Fe] ratios derived from SEGUE spectra of 17,277
G-type dwarfs to separate them into likely thin- and thick-disk
subsamples, and investigate the rotational velocity and eccentricity
gradients with metallicity, [Fe/H], distance from the plane, |Z|, and
Galactocentric distance, R. Some of the notable findings are that
there is a rather strong rotational velocity gradient of -20 to -30 km/s/dex
with [Fe/H] for the thin-disk population, and +40 to +50 km/s/dex for the
thick-disk population. The rotational velocity decreases with |Z| for both
disk components, with similar slopes (-9.0 +\- 1.0 km/s/kpc). A relatively
strong gradient of orbital eccentricity with [Fe/H] (about -0.2/dex) is
observed for the thick-disk stars, whereas the eccentricity is independent
of [Fe/H] for the thin-disk subsample. The shapes of the eccentricity
distributions for the thin- and thick-disk populations remain roughly
unchanged with |Z|. Comparison with several contemporary models of disk
evolution indicates that radial migration seems to have played a vital role
in the evolution of the thin-disk population, but probably less so for the
thick disk, relative to the gas-rich merger or disk
heating scenarios. I emphasize that more physically realistic
models and simulations are required to perform detailed quantitative
comparisons.