Killing disconnected sessions on server

Does anyone know of a way to automatically end disconnected windows sessions on a server? I have users in the company I work at that are not good about logging off their remote session and instead just close out of it where it shows in task manager that there session is still live. Therefore it is eating up our memory usage on our server. It would be nice to know if there is something you can set up to automatically close those sessions. Any feed back would be most appreciated. Thanks