The Logout link is available in your personal menu on the minibar at the top of all pages. The personal menu opens when you click your name on the minibar. You can open the personal menu using an assistive technology's links list, or by tabbing through the minibar links at the top of the page.
Your institution might have a policy to automatically log you out of the system if you are inactive for an extended period of time. Your administrator can determine the amount of inactive time before you are automatically logged out. A JavaScript warning provides an option to remain logged in before your time expires.