Combining concrete examples, the method to solve the difference equations of steady plane temperature field with programming in Mathcad Language is given, and the advantage of it is pointed out.

According to the fact that a universal coupling was constantly broken in a mine, the paper gave a common formula of the drive rate of a bi universal coupling on the basis of other people s work, and thus a universal conclusion was obtained that the drive rate can be kept constan

For eliminate redundant stress in spring unit brought by continuously variation of strain,in wind spring device,the adopt spiral output wheel with continuously variant radii was used and the variation of moment can be canceled out by variation of radii,the approximate constant output force can be obtained.