The key of background subtraction is to extract and update the background image adaptively in changeable road environment affected by all kinds of factors such as weather and illumination condition.

由于实际交通道路状况受气候、光照等多种因素的影响，变化非常复杂，因此如何设计一种自适应的背景提取与更新算法以适应实际环境的变化，是背景差法的关键所在。

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We all feel our mood lift in this weather, too, including those who suffer from seasonal affective disorder (SAD), a depressive condition thought to be caused by the lack of sunshine in winter.

即便是那些患有季节性情感障碍症(SAD，一种由于在冬天缺乏阳光而引起季节性抑郁症)的人，也变得开朗起来。

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In saving time, high-speed railway reduced the travel time and improves the traveling condition by using the high speed, high density and all-weather running programs.

在节约时间方面，高速铁路采用高速度、高密度、全天候运行方案，借助市内交通的有机衔接，大幅缩短了点到点旅行时间，改善了人们出行方式的选择。

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