Starting from the four concepts of orbit energy, energy class,shielding effect and infixing effect, the author uses the two commonly applied methods of caculation orbit energy to analyse and compare 4s orbit energy and 3d orbit energy.

In pipeline directional drilling crossing of Ji-Ning branch line of West to East Gas Transportation Pipeline, the radiation crosslinked polyethylene heat shrinking strips are used in the field joints.

A mud purification and recovery device used for non-open-cut directional drilling;