清扫枯叶,刈割杂草,约翰在自己的花园里整整忙碌了一天。然后他陷入了沉思:应该有一种更快更省力的方法。 实际上该项技术早就有了:真空吸尘器。然而作为一名工程师,约翰知道这项技术会产生两大问题:其一,吸尘器风扇会被潮湿的树叶阻塞;其二,吸尘袋会很快塞满而导致吸力减弱。约翰一边思索一边拿来吸尘器反复实验,但几小时过去 Sweeping dead leaves, cutting weeds, John spent a full day in his own garden. Then he fell in thought: there should be a faster and more efficient way. In fact the technology has long been: vacuum cleaners. However, as an engineer, John knew that the technology had two major problems: first, the vacuum cleaner fan was blocked by damp leaves; second, the suction bag would quickly become clogged and the suction weakened. John pondered over the vacuum while experimenting, but hours passed