Because of the great disturbance of boiler burning system, on the spot, we don't find absolute excess air coefficient but its optimum interval.

This article discusses the optimum interval estimation and fully proves the existence of the optimum interval estimation, simultaneously proposes a method to seek the optimum interval estimation.

For influence factors and rules of machined surface roughness, we studied on the influence factors of machined surface roughness such as scallop-height, path interval, feed rate and optimum tool path.