They went ahead to clear the road of obstructions .

他们先走了一步以清除路上的障碍。

But they can be obstructions to the treatment of an unhealthy one .

但对一个患者来说，这些屏障成了他们的治疗过程中的壁垒。

The obstructions of construction quality cost management practice .

建筑业企业实施质量成本管理的阻碍与对策。

Many patients experience dramatic improvements when their doctors prescribe nighttime breathing masks , which gently force air past obstructions .

有些病人使用了医生建议的夜间呼吸面罩，情况有了极大改善，这种面罩温和而有力地迫使空气通过呼吸障碍。

But to date , all that 's traveled through its circular beam pipe are ping-pong balls to test for obstructions .

但直至今天，科学家们只完成了将乒乓球注入圆形粒子束管道中以测试是否存在障碍。