永久作用 Permanent action 在结构使用期间，其量值不随时间而变化，或其变化值与平均值比较可忽略不计的作用。
本文通过大量的试验、调查分析，得到了组成铁路桥梁永久作用各分随机变量的统计特征值，并进一步分别得到了钢桥、混凝土桥桥上永久作用的概率分布。
In this paper the probability distribution curve of the dead Loads acting on railway Bridges is obtained through a great number of experiments, investigations and analyses.
与其他方法相比，生物防治的优点是它提供了一种成本相对较低、有害副作用最小的永久性防治系统。
The advantage of biological control in contrast to other methods is that it provides a relatively low-cost, perpetual control system with a minimum of detrimental side-effects.
最近的试验表明这些副作用在停药后消失，但可能存在永久的作用。
The current trial showed that the side effects disappeared after participants stopped the medication, but there may be more permanent effects to consider.
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