Usually, ionospheric Total Electron Conten (TEC) variation with time can be viewed as a stationary random process under quiet conditions.
平静状态下电离层总电子含量(TEC)随时间的变化通常可以视为平稳随机过程。
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The steel with low oxygen content is the main new product of iron and steel factories, especially gear wheel and gas vase steel which demand oxygen conten relatively.