How can I implement to view a logo by pulling a UITableView down or up

[Behnam Izadi]

The practical example is implemented in many application such as Clear or Dayone... 

Its like once you pull down/up TableView a logo appears like the picture below shows:

If you look closely down the picture is the Dayone logo which appears once you pull up the table view

I only want to know the concept but if you can introduce me similar sample codes or the practical codes It would really appreciated.

Thank you