Revolving door. A revolving door typically consists of three or four doors that hang on a central shaft and rotate around a vertical axis within a cylindrical enclosure. Revolving doors are energy efficient as they (acting as an airlock) prevent drafts, thus decreasing the loss of heating or cooling for the building. 
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The nozzle of a cold gas thruster is generally a convergent-divergent nozzle that provides the required thrust in flight. The nozzle is shaped such that the high-pressure, low-velocity gas that enters the nozzle is accelerated as it approaches the throat (the narrowest part of the nozzle), where the gas velocity matches the speed of sound.[citation...
Cold gas thrusters benefit from their simplicity; however, they do fall short in other respects. The following list summarizes the advantages and disadvantages of a cold gas system.
Cold gas systems can use either a solid, liquid or gaseous propellant storage system; but the propellant needs to exit the nozzle in gaseous form. Storing liquid propellant may pose attitude control issues due to the sloshing of fuel in its tank. When deciding which propellant to use, a high specific impulse and a high specific impulse per unit vol...
Cold gas thrusters are especially well suited for astronaut propulsion unitsdue to the inert and non-toxic nature of their propellants.
Main article: Vernier Engines Larger cold gas thrusters are employed to help in the attitude control of the first stage of the SpaceX Falcon 9rocket as it returns to land.
In a tweet in June 2018, Elon Muskproposed the use of air-based cold gas thrusters to improve car performance. In September 2018, Boschsuccessfully tested its proof-of-concept safety system for righting a slipping motorcycle using cold gas thrusters. The system senses a sideways wheel slip and uses a lateral cold gas thruster to keep the motorcycle from slipping further.
The main focus of current research is miniaturization of cold gas thrusters using microelectromechanical systems.