背相
背相-
吸气弯曲肘关节同时上提手臂直到上臂与背相平，如图所示。
Inhale and bend elbows while lifting arms until upper arms are parallel with back as shown .
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采用背散射电子相观察钎料与Ni润湿后的界面组织。
The interface structure of the brazing filler metal with Ni after its spreading was observed by backscattered electron images .
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班长用头盔内的吸管吸了几口水，这根管子与悬挂在他背上的水袋相连接。
The squad leader sucks from a tube inside his helmet that connects to a water pack hanging from his back .