Unlike the industrial hydrogen used to make ammonia fertiliser , or for converting heavy oil fractions into petrol , the hydrogen needed for fuel cells must be 99.999 % pure .
与制造氨肥或将重油馏分转化为汽油用的工业氢气不同,燃料电池所用氢气纯度须达到99.999%。
Fractions let you divide up a measure of music into notes of varying length .
从分数的概念来看,一段音乐可分成几串长短不一的音符。
Measuring ingredients teaches kids about fractions .
称量食材能教他们学习分数。
Baking in the kitchen , ms. cameron explains fractions while having each of her children crack half the eggs .