I hoe you're well today!

Just to confirm: by "alias" you mean that the domain "imems.gatech.edu" is mapped to "sites.gatech.edu/imems", so when you access "imems.gatech.edu" the actual site that's at "sites.gatech.edu/imems" is loaded under the "imems.gatech.edu" domain, right? 

If so, then yes - it is already set this way. 

For every site that you are an administrator of, you can always take a look at the "Tools -> Domain Mapping" page in that site's back-end/dashboard. 
You'll see there if there's any domain mapped and if it has "active" status. In case of doubt - if it shows that domain is already mapped and active but you're still not sure if it works correctly - you can also use the "DNS Record Lookup" tool of this service https://viewdens.info to check DNS settings. For example, if you put "imemes.gatech.edu" in the "Enter domain" box there and run "Lookup" it will show that the CNAME record for that domain is set to "imems.gatech.edu.c14750.campuspress.com." and a quick look at aforementioned "Tools -> Domain Mapping" page in "sites.gatech.edu/imems" back-end shows that this is correct record. 

I hope this helps but if I misunderstood your question or you need some additional assistance, let us know please. 

Kind regards,
Adam
Customer Support