what are the blue concentric circles in sch?
Please reference the Schematic and what page of the schematic this symbol is on.
http://www.zedboard.org/sites/default/files/documentations/Schematic_G-04-02.zip tin the page 3, left of DDR3_T_A14
That is a net tie. It has no electrical value, it is trictly used in the design tool to rename a signal. If you refer to the left and right side of the net tie you will notice the different naming conventions.
Thanks! (feed to 50 characters, if not enough, just duplicate 50 characters!)