本文研究了底空间为实射影空间时上协边类纤维丛表示的若干性质。
In this paper we deal with some properties of cobordism classes of fiber bundles over the real projective space.
协羽蝶阀是设计用于管路系统连接，两个法兰间的连接或一个法兰间的连接或一个法兰间的连接用于一边已经固定的管路系统。
Hsieh Yu butterfly valve is designed for pipeline system connection between two flanges or with one flange for connection with the pipeline system of which one side has been fixed.
协羽蝶阀是设计用于管路系统连接，两个法兰间的连接或一个法兰间的连接或一个法兰间的连接用于一边已经固定的管路系统。
Hsieh Yu butterfly valve is designed for pipeline system connection between two flanges or with one flange for connection with the pipeline system of which one side has been fixed.
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