Embodiments include a method for halftoning a source image. Specifically, as a preferred aspect of the invention the implant includes a tapered portion and the implant may be inserted from multiple approaches to the spine with the orientation and taper properly oriented in the disc space regardless of the approach. It can be used on food pans that are full of food, partially full of food or empty. On the other hand, when the spark ignition combustion is performed, a normal feedback control of air-fuel ratio activates a three-way catalyst to reduce HC, CO and NOx simultaneously. The second differential stage includes a gear mechanism which applies a rotational torque to the output drive shaft when a difference occurs between the rotational speeds for the shafts.