Good separation of co-ions and counter ions cannot be achieved by a single type of the singly charged NF membranes.

采用单一的荷电纳滤膜是不能实现同名离子和反荷离子之间的高效分离的。

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Normally, variables are best named by their use (like firstName or title), but as this variable is essentially a loop counter, using single letters is also fine.

变量一般最好根据用途命名（如 firstName 或r title），不过由于这个变量基本上是一个循环计数器，也可使用单个字母。

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Imagine that you were only allowed to fly on one airline, or take a single route to work, or use one designated checkout counter at the grocery store.

想象一下，你只能使用一家航空公司，或者只走一条路去工作，或者在杂货店只能使用一个指定的收银台。

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An employee at the special share-sale counter took not a single order in the first three days of the offering.

ECONOMIST: Special delivery

If I were to reduce our counter-productive speaking to a single motivation, it would be this: We often speak to make ourselves feel better in the short-term.

FORBES: How to Speak More Strategically

There is not a single bed, couch, lab counter, library desk, football end zone, university founder's statue, Henry Moore sculpture or monkey research cage on top of which you, the outstanding class of 2013, haven't copulated.

WSJ: Rob LaZebnik's Message for the Class of 2013 | Saturday Essay