Multi-traveling salesman problem(MTSP) is an extension of traveling salesman problem,which is a famous NP hard problem,and can be used to solve many real world problems,such as railway transportation,routing and pipeline laying.In this paper,we analyze the general properties of MTSP,and find that the multiple depots and closed paths in the graph is a big issue for MTSP.Thus,a novel method is presented to solve it.We transform a complicated graph into a simplified one firstly,then an effective algorithm is proposed to solve the MTSP based on the simplified results.In addition,we also propose a method to optimize the general results by using 2-OPT.Simulation results show that our method can find the global solution for MTSP efficiently.
In wireless sensor networks(WSNs),nodes are usually powered by batteries.Since the energy consumption directly impacts the network lifespan,energy saving is a vital issue in WSNs,especially in the designing phase of cryptographic algorithms.As a complementary mechanism,reputation has been applied to WSNs.Different from most reputation schemes that were based on beta distribution,negative multinomial distribution was deduced and its feasibility in the reputation modeling was proved.Through comparison tests with beta distribution based reputation in terms of the update computation,results show that the proposed method in this research is more energy-efficient for the reputation update and thus can better prolong the lifespan of WSNs.
