1.读取第二个book元素的price元素值 2.给第一个book元素的price元素添加一个属性danwei,值为rmb 3.添加一个book元素，包括name子元素和price子元素，值分别为ppp和45.67-1. Read the second element of the price element of book value of 2. To the first element of the price element book to add an attribute dan

Using a large number of finite element method to solve partial differential equations, Matching Pursuit and orthogonal matching pursuit, Using weighted model nodes in the network strength and weight are power law distribution.