Abstract: User engagement is detected and used to control operation of a computing device. User engagement is detected by a sensor such as a camera that identifies if a user's face is oriented towards a display device. If the user is not facing the display device, the sensor determines that the user is unengaged. The computing device is thus able to perform a power-saving operation, such as dimming the display device, when the user is unengaged. The computing device includes an API that abstracts sensor data into a user engagement signal indicating that the user is either engaged or unengaged. The OS and applications running on the computing device act on the user engagement signal provided by the API without communicating directly with the sensor. The user engagement signal may be provided as an input to a state machine.

Abstract: An apparatus and method for the production of small, uniform sized droplets. The apparatus is a droplet generator including a housing defining a chamber for holding a material to be ejected therefrom, an inlet and a droplet outlet communicating with the chamber. The housing is coupled to a pressurizing system connected to the inlet for applying pressure pulses to the chamber. The housing includes a vent in communication with the chamber for relieving pressure in the chamber. The vent has an effective size so that during application of the pressure pulse the chamber is pressurized to a pressure effective to eject a droplet of the material therefrom and thereafter the chamber is vented through the vent at a rate sufficient to prevent further discharge of droplets. The droplet generator produces molten metal or alloy droplets and is particularly suitable for generating single droplets on demand in manufacturing techniques using droplet deposition.