The choice of land gradation factors is a basic job in land gradation,the reasonability of which is directly related to objectivity and practicability of the gradation results.

With the example of farmland grading in Shanhaiguan district under Qinhuangdao City, Hebei Province, this paper illustrates processes and methods of factors on farmland grading in terms of factor selection, classification of grading units, point-giving to factors, calculation of total points and classification of grades.

The choice of land gradation factors is closely related to the objectivity and practical results.

Effect of atomic size factor and electron factor on the formation of quasicrystalline have been studied.

The effect of atomic size factors and electron factors on the formation of quasicrystalline was studied.

aswell as the carbonyi's electron factor and space factor.

To investigate the constitution of prime factors of binomial coefficients by utilizing divisibility theory,two theorems on searching the prime factors of {2n n} are given.

It is proved that such finite groups with 4pm maximal order elements are solvable by making use of corresponding results on K3-simple group and K4-simple group, as well as the prime factor of the order of a group and the length of the conjugate class of cyclic subgroups with order k.

In this paper,we get all of unitary perfect number that has less than 6 prime factors,apart from 6,60,90,87360.