AC stray current can cause AC corrosion and destroy the safe operation of buried pipelines, which comes mainly from nearby high voltage transmission lines and AC electric railway. The research and evaluation lags far behind DC stray current at home and abroad, besides, the AC current density measuring procedures are complex. Through experimental study of different parameters on the impact of the AC current density established a mathematical model of damaged area, soil resistivity, pipe-to-soil potential and coating resistivity. With it can indirectly get the AC current density, which improve efficiency by simplifying the measuring procedures. Also, provide a basis for harmfulness evaluation of AC stray current by studying the impact of AC current density on the corrosion rate.

The position and application of hydraulic system on the engineering machinery are analyzed while the current situation and application of electric technology are discussed. A new idea is proposed in which the end effectors are driven by electric motors while the restriction of hydraulic system is taken over. Several key problems are analyzed during the refitting of engineering machinery such as the high-power, the distribution and focus of energy, the source of energy and the redesign of the control system. The detail is discussed with the Komatsu excavator PC200-8. The advantages of electric engineering machinery are also summarized.

Abstract. The problem of traversing obstacles for a six-wheeled rocker bogie lunar rover is presented. Based on the analysis of forces and rover movement track angle, a criterion to determine traversing obstacles ability for the rover is developed to predict whether the robot can overcome current obstacle. The concept of traversing obstacles ability index is presented, which can be used to describe the trafficability of the rover quantificationally. The caculated results of wheels driving torques by this method can be used as a reference for confirming appropriate driving torque with the wheels during they challenge the terrain. A numerical example is given to illustrate our method.