How do i power recycle on SD card
I just read the 

USB2240 Part listing

and it looks really handy for interfacing a PC to the flash.  

However, I believe you are taking the wrong approach by trying to power recycle it yourself.  

To address your question about how to power recycle it:  If you are physically moving the connection cable then that should power recycle it automatically.  

If not, then you have some other problem with your software not tolerating the disappearance then reappearance of the SD card.  In other works, it is likely a software problem.  The SD card should always remain connected so the software does not get confused and require a reset.

It is like how you need to eject USB devices in Linux.  If you don't, then you can get file corruption because the buffers may not be fully flushed.  Back in the day we used sync; sync; sync to ensure buffers were written out to storage devices, even just to do a normal shutdown.  Fortunately, modern Linux takes care of that, with the exception of USB flash memory.  With that you need to actually go through the eject process to avoid damage or system confusion.

But a much better approach would be to just leave it on one or the other.
Then use some sort of communications (it doesn't have to be USB) between the two computers for memory access.