Linked to the application of electric propulsion system in spacecraft,the effects of various factors on the optimum specific impulse and the selecting of the specific impulse of electric thruster are discussed.

,using orthogonal experiments,we can get the best ratio of its components of the surface mortar,which can improve heat preservation,heat insulation performances,and economize the energy.

5 (the level of over-fertilization), plus zinc sulfate treatment, calculated by the regression equation analysis to identify high,medium, low-level production structure in different fields of nitrogen, phosphorus and potassium the best ratio of performance to maximize production.

The optimum proportion was 0.

In this paper, we work out a forecast equation for aim-yield of rice, an equal-product-curve equation under different application rates of N and K2O, and the optimum proportion equation for N and K2O.

The results showed that the optimum proportions of compound phosphates(sodium hexametaphosphate:sodium polyphosphate:sodium pyrophosphate) are 20:28:13 for the minimum cooking loss and 10:30:19 for the maximum yield of sausage,respectively.

The optimum compositions of several refrigerant mixtures as substitutes of R22 are obtained,and comparisons with other available substitutes are made.

However there are different thermodynamic performances of J-T cryocooler using mixtures withsame components but different compositions, so there must be an optimum composition for mixture with givencomponents.