The calculation of spot welding current is determined by the way of point-by-point integration,the software and hardware system is constituted based on 80C196KC single chip computer.

a method of spot welding constant current control is explored which may solve the problem of too much time spent in calculating the virtual value of welding current adopting integral point by point.

Throush the interlace series type linear differential equation,coefficient containing three negative number of times,power function and arrangement number can be changed into the linear differential equation of successive integral.

Pass linear differential equation xy~((n))+ny~((n-1))=f(x) change into the linear differential equation of successive integral has been found witty the form that untied,have gicen strict proof,and to popularize it gets to know xy~((n))+(x+n)y~((n-1))+(n-1)y~((n)-2)=f(x) to untie.

By transforming the interlace series type linear differential equation with coefficients containing negative second order power function and arrangement number into the linear differential equation of successive integral,the theory and method for the general solution of this kind of equation are determined.

Using HITRAN 2004,the updated molecular spectroscopic database,and an exact line-by-line integration,we take CO2 15absorption bands as an example to discuss the temperature dependence of half width,the line intensity and absorption coefficient.

Based on HITRAN2004 database, the infrared absorption properties of dissolved gases in transformer oil including CH4, C2H6, C2H4, C2H2, CO, CO2 and H2O, were researched by the line-by-line integration method.

In this paper, the theorems of term-by-term integration have been studied further.