Update README.md

README.md

@@ -13,4 +13,4 @@ Hi! 👋
 
 This is an ***unofficial*** organization of [Xi'an Jiaotong University](http://en.xjtu.edu.cn/), and all interested people are welcome to join! 😊
 
-<img src="https://vi.xjtu.edu.cn/images/a4-7sbzh.png" width="300" height="300" />
+<img src="http://vi.xjtu.edu.cn/images/a4-7sbzh.png" width="300" height="300" />