push方法观察当前最顶的节点，构建一个新节点放在堆栈上，然后，如果最顶端的节点在初始观察之后没有变化，那么就安装新节点。
The push method observes the current top node, constructs a new node to be pushed on the stack, and then, if the topmost node has not changed since the initial observation, installs the new node.
在bloggers . rdf模型中，contributor会和图1顶部的空节点foaf： Agent匹配。
In the bloggers.rdf model, contributor will match the foaf: Agent blank-node at the top of Figure 1.
为此对双腹板、顶底角钢半刚性节点的试验数据进行分析，绘出试件各组合件关键点的荷载-应变关系曲线。
Then the experimental data of joints of top and seat angle with double web angle are analyzed and load-strain curves of member subassemblages key points are drawn.
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