Using clustering analysis method on the classification of Chinas urban air quality levels, gather into the city air quality in most similar category, analysis of causes, concluded.
运用聚类分析方法对我国城市空气质量等级进行分类，把空气质量状况最相似的城市聚成一类，分析原因、得出结论。
Causes for safety accidents were analysed, with summary on the method for its correct use and key points and evaluation analysis for the uncertainty of site voltage measurement.
分析了其安全事故发生的原因，总结了对其正确使用的方法和要点，并对现场电压测量的不确定度进行了评定分析。
Based on analysis of the causes, method for reducing heated length variation as well as simplified identifying approach are proposed aiming at its technological process.
分析了原因，提出了从工艺着手降低加热长度变化率的方法，以及加热长度变化率的简易鉴定方法。
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