慢阻肺是一种吸烟引起的肺部疾病，也包括肺气肿和慢性支气管炎。
COPD is a disease of the lungs caused by smoking and includes the conditions of emphysema and chronic bronchitis.
慢阻肺通常表现为肺气肿或慢性支气管炎，二者经常共存，其特征是气道扩张。
Chronic obstructive pulmonary disease (COPD), of which emphysema and chronic bronchitis are the most common form (and often co-exist), is characterized by swelling of the airways.
球阀在完全开启时，流阻很小，几乎等于零，因此等径球阀广泛应用于石油天然气管线中，因为容易清扫管线。
Ball valve fully open, the flow resistance is very small, almost zero, so the ball valve diameter is widely used in petroleum and natural gas pipelines because the pipeline cleaning easy.
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