The study on the relationship of the urban traffic and urban spatial structure is not limited to a certain point in time, and is conducted from time lapse's angle.

对城市交通与城市空间结构关系的研究不仅仅局限于某一时点，而且从时间推移的角度对两者关系进行了动态研究。

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Income is a flow of earnings per unit of time. Money, by contrast, is a stock: it is a certain amount at a given point in time.

收入是某一单位时间内收益的流量，而货币是一个存量，即某一时间点上一个特定的金额。

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"In order to know who has actually sent an email or made a Skype call the police need to know who has used a certain IP address at a given point in time, " it says.

BBC: 'Fresh proposals' planned over cyber-monitoring