Valve opening area ratio
at-the-opening (opening only) order
fire area opening and closing
opening area of the Yangtze River to sea
Opening ratio
开松比
开口率
开孔率
开洞面积
井中压力与打开防喷器心子的操作液压比
Opening Ratio of the Infiltration Well
air to surface area ratio
anode-to-cathode area ratio