Air pollution is often identified with major stationary sources, but the greatest source of emissions is mobile sources, mainly automobiles.
空气污染通常是与主要的固定污染源，但排放的最大来源是移动来源主要是汽车。
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Keep positional tracking in mind with audio design; for example, sounds should get louder as the user leans towards their source, even if the avatar is otherwise stationary.
In the paper, it is discussed the whole process of quality control in waste gas (stationary pollution source) monitoring, which includes the preparation, monitoring, and data processing, etc.