下图为2014 年11月以来的美元对人民币汇率走势图。据此回答下列小题。

    I'm Alan. The weekend just ended. Yesterday I went to visit the museum. It is about 3 kilometers away from my home. So I decided to go there by bike, I set off at half past eight. At the museum I saw many photos and other things. I learned a lot. There were also a lot of children with their parents，students with their teachers and soldiers. At eleven o'clock, I left the museum for home. I had a wonderful time yesterday.

阅读短文，回答下列问题。

定义运算“⊗”x⊗y=$\frac{x^2+2y^2}{2xy}$（x，y∈R，xy≠0）．当x＞0，y＞0时，x⊗y+（2y）⊗x的最小值为____