This paper discusses the prime decomposition of recurring period of rational decimals,and provides the necessary and sufficient condition of pn|c1…ch(recurring period of a/b),for any prime pz7,any integer n and any decimal a/b.

The second problem of the three unsolved problems by mathematicians in mathemacics were discussed in the paper [1],this paper has improved some conditions about(b,3)=1 in the paper [1],and obtained the necessary and sufficient condition for 9|c_1…c_h(recurring period),generalized and proved the results of the second problem and the paper [1].

The new energy-saving cycle combined with the refrigeration cycle using mechanical compressor (RAC/MC) and the ejector-cooling system using ejector (EJC) is called CCRS.

Results show that the monsoon at low levels passes through a seasonal cycle of four phases: 1) the northeasterly prevailing in winter; 2) the southeasterly blowing as the transition from late January to mid April; 3) the vigorous SW wind in summer; and 4) again, the transitional southeasterly spanning early October to early November.

Both the observational data and the theoritical model are used to study the seasonal cycle of sea-surface height in the Bay of Bengal(BOB).

Based on the two instances,a new method of cyclic adjusting is developed to solve this difficult problem,which proves to be easy and effective.