data sink
2.Abstract By setting up a network model of data aggregation and using a bit-hop metric to quantify energy costs in wireless sensor networks, we formally analyze the problem of area-based data aggregation and obtain that data aggregation will definitely be energy efficient when the relative difference between the average lengths of the two shortest paths, which are from source sensor nodes to the sink and to the aggregation node respectively, is not less than the ratio of data correlation to the number of source sensor nodes.
3.In this paper,the author revolves round an exercise and apply Procedure-eliciatatian Teaching Method to piece together various kinds of data such as"the cause of produce buoyancy","Archimedean Law","the condition of body to float or sink"and so on,the author also points out the originality of this teaching method on the training of students ability to analyse and solve problems.
