  Three groups of DAV star models are evolved with time-dependent element
diffusion by \texttt{WDEC}. The core compositions of these models are directly
from white dwarf models evolved by \texttt{MESA}, which are results of
thermonuclear burning. Based on these DAV star models, we try to study the
dispersion of period spacing. The thickness of hydrogen atmosphere can
seriously affect the deviation degree of minimal period spacings. The minimal
period spacings dominate the dispersion of period spacing. The thinner the
hydrogen atmosphere, basically, the more dispersive the period spacing.
Standard deviations are used to analyze the dispersion of period spacing.
Studying the dispersion of period spacing on a DAV star KUV03442+0719
preliminarily, we suggest that log($M_{\rm H}/M_{*}$) is from -8.5 to -5.5. In
addition, modes partly trapped in C/O core are found based on those DAV star
models. The identified modes and average period spacings indicate that
KUV03442+0719 may be the first star to 'observe' modes partly trapped in C/O
core.
