在国家游径系统法案的指导下，美国已建成了世界上最完善的国家游径系统。
With the guidance of the national trails system Act, America has currently developed the most mature national trails system in the world.
双变径轮式抽油机是在继承常规游梁式抽油机优点的基础上设计而成的大载荷、长冲程、低冲次节能型抽油机。
A dual variable-diameter wheel pumping unit, which has long stroke and low pumping speed and large load capacity, is designed based on conventional beam pumping units.
可丰富该类型的灌木层的物种，增添指示牌以提高专类园的科普教育功能和游步径的知识趣味性。
Enriching the specie of shrub and adding signs are helpful to enhance science educational function of special class garden and fun of tour path.
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