Tray for forming dental model comprises base wall forming floor upon which dental casting material is poured. Actuation of a motor causes the metering device to separate individual ice pieces and the sensing device detects ice pieces before, after, or during dispensing. One modular unit is a tractor unit configured to propel the system through the pipeline. At least a portion of the packets are unicast from the access node for reception by a new requesting decoder in response to receiving from the new requesting decoder a request for reception designating a media stream identifier corresponding to the media stream. An apparatus for refreshing the memory cells of the memory element is provided for refreshing the first number of memory cells when reaching the first retention time, and for refreshing the second number of memory cells when reaching the second retention time.