本文提出了基于网络层和数据链路层的移动自组织网络层次安全通信机制,既避免多重安全机制的过大开销,也避免单一安全机制的安全隐患

K-means clustering algorithm is reviewed.K-means clustering algorithm is a NP hard optimal problem and global optimal result cannot be reached.The goal,main steps and example of K-means clustering algorithm are introduced.K-means algorithm requires three user-specified parameters:number of clusters K,cluster initialization,and distance metric.Problems and improvement of K-means clustering algorithm are summarized then.Further study directions of K-means clustering algorithm are pointed at last.