到那时纯镁可用作燃料(其能量密度大约是氢的十倍)。
The pure magnesium can then be used as a fuel (its energy density is about ten times that of hydrogen).
龙舌兰花蜜的热量密度比食糖高，但因为它具有大于40倍的甜度，更可用于实现同一水平的甜度。
Agave nectar is more calorie dense than sugar but because it is about forty times sweeter much less can be used to achieve the same level of sweetness.
Skyhook将所有近年来使用其服务的应用程序的信息收集了起来，并用来预测特定城区的人口密度——随时，随地可用。
Drawing on all the data it has collected in recent years from apps using its services, the firm can predict the density of people in specific urban areas-anywhere, any day and at any hour.
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