压单：泛指一个股票术语，指在股票中当前积压了两个或者两个以上的订单，且订单数目已经导致暂时或者在将来的某一段时间内不能按时完成或者结束的动作。
它围绕船底的一个钉子旋转，放下时提供压载力，以抵抗由于单侧风导致的船只侧向摆动。
Pivoting on a pin inside the hull, it swings down to provide ballast and resistance against sideways motion of the boat caused by the wind blowing from one side.
单轴对称的角钢、T型钢压杆有必要做弯扭屈曲验算。
Struts of monosymmetric section built with angles and cut-Ts need to be checked on flexural-torsional buckling.
试验结果表明，串联吸气全压与单风机全压相比在小流量区域全压显著增大，改善了风机的性能；
The results show that the pressure in series is increased markedly in small flow-rate area, so performance of the fans is improved.
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