tokens: The effect of different thicknesses of H atmosphere is discussed in Section 3.1 . The effect of different values of effective temperature and He layer mass is discussed in Section 3.2 . The effect of different values of total stellar mass are discussed in Section 3.3 . The average period spacing for DAV star models is analysed in Section 4 . In Section 5 , we preliminarily study the dispersion of period spacing for a DAV star KUV03442+0719. In Section 6 , discussion and conclusions are summarized. 2 INPUT PHYSICS AND MODEL CALCULATIONS In this section, we discuss the input physics and model calculations. In Paxton et al. ( 2011 ) reported modules for experiments in stellar astrophysics ( mesa ) which can evolve a star from main sequence (MS) stage to WD stage. mesa is updated quickly on the web site of ‘ http://mesa.sourceforge.net/ ’. The core compositions of a WD star are results of thermonuclear burning. The thermonuclear reaction rates are from Caughlan Fowler ( 1988 ) and Angulo et al. ( 1999 ) for mesa . With mesa version 4298, we evolve a group of MS stars, as shown in the first column in Table 1 , to WD stage by a module named make_co_wd. The input settings in the module are default by mesa . When these progenitor stars evolve to the WD cooling curve on the Hertzsprung-Russell ( H − R ) diagram, the WD models are took out. The core composition structures of these WD models, including mass, radius, luminosity, pressure, temperature, entropy, and carbon profile, are took out together. The location of maximal carbon profile is used as the boundary of the core for approximate calculations. The evolved WD masses in mesa and their core masses are showed in Table 1 . Using the module make_co_wd to evolve WDs is quick but a little rough. In the future work, we will try to evolve WDs in the module named 1M_pre_ms_to_wd and refine the input settings. Table 1. Masses of MS stars, WD stars evolved by mesa , corresponding cores, and corresponding WD stars evolved by wdec . The structure parameters are inserted into white dwarf evolution code ( wdec ). wdec was first written by Schwarzschild and subsequently modified by Kutter Savedoff ( 1969 ) ( wdec 1.0), Lamb van Horn ( 1975 ) ( wdec 2.0), Winget ( wdec 3.0), Kawaler ( wdec 4.0), Wood 1990 ( wdec 5.0), and Bradley ( wdec 6.0). The program is from White Dwarf Research Corporation ( http://whitedwarf.org/ ). wdec can evolve groups of DAV star models. The model parameters are adopted as total stellar mass, effective temperature, He layer mass fraction, and H atmosphere mass fraction. With the core composition structures from WD models evolved by mesa , groups of WD models are evolved by wdec . The He layer and the H atmosphere are very thin for a DAV star. Therefore, we take the total stellar mass of WD models in wdec the same as the WD core masses in mesa , as shown in Table 1 . The carbon profiles of those WD models are results of thermonuclear burning. The element diffusion scheme of Thoul,
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