A cartridge type HDD unit 20 is mounted on the outside of a back plate panel 2 of an exterior cover rear portion in an image forming apparatus 1. A transparent substrate is disposed between the first and second screens. Systems and methods employing the substantially V-shaped plow blade extension and dual directional rotating flailing assemblies are also disclosed. Responsive to a determination that the second location is within a predetermined distance of the first location, the meeting server transmits a command to mute the second device. In another embodiment, the method may include determining correction terms for parameter of the lithography system, which if applied to the parameter, the correctable errors would be eliminated resulting in approximately optimal imaging performance of the lithography system.