The nominal head was presented for preliminary selection of hydraulic models, with consideration of the efficiency and reliability at all operation conditions.
为了兼顾各种特征扬程工况下的运行效率和可靠性，在水力模型初选阶段提出了选型名义扬程的概念。
Jeff: I was told that with the increasing Numbers of the participants, they started to undertake preliminary selection contest in each continent, the winners could take part in the final.
杰夫：我听说过，此后随着参赛国家数量的不断增多，便开始在各大洲进行分区预选赛，优胜者参加最后的决赛。
Usually some hypothesis is a necessary preliminary to the collection of facts, since the selection of facts demands some way of determining relevance.
通常，有某种的假说是收集事实的必要先决条件，因为在对事实的选择上，要求有某种方法确定事实是否与题有关。
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