As ships gradually getting larger, more special, tug assisted operation of the ship in and out of Port , berthing and unberthing becomes increasingly prominent, Tug-related training and safety assessment is increasingly important, increasing the tug unit for marine simulator is urgent.In tug unit, the cable is an important part, to establish the mathematical model of cable is key. Mooring strain satisfy Hooke's law, using the catenary equation and Hooke's Law deduces mooring unstressed length formula, according to the Department to calculate the cable unstressed length and the corresponding relations of the actual length of the mooring to calculate the tension of the mooring; Otherwise, ignoring the weight of the mooring by mooring strain curve fitting polynomial to calculate the tension of the mooring, and calculated the level of tension and vertical tension of the mooring. calculating example to verify the correctness and practicability of the model.

In order to meet the requirement of high voltage transmission lines monitoring system, this paper presents a heterogeneous integrated network which contains Optical Ethernet, broadband wireless communication networks and wireless sensor networks in high voltage transmission line monitoring system. Moreover, considering the characteristics of the heterogeneous integrated communication network and analyzing the features of service security mechanism in communication network, this paper proposes an authentication and encryption security system, which has certain value in the authentication and encryption aspects to electric power system communication.

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