In an optical engine for a projection system, a fan unit is mounted on an upper surface of a housing, and has an inlet port facing toward light modulators within the housing for drawing air upwardly so as to dissipate heat generated by the light modulators, and an outlet port that is transverse to the inlet port for discharging the air drawn into the inlet port. The invention will improve the work efficiency for wheel balance adjustment and manufacturing of tirewheel assembly. A device for arranging the sleeve around the container will arrange the sleeve in a position with respect to the container. A controller detects, during transmission of the data packets, a counter associated with a buffer for a particular COS has risen to be greater than or equal to the XOFF threshold level of congestion. This computational approach uses the fact that the autocorrelation is the weighted sum of shifted copies of an image, where the shifts are obtained by sequentially placing each individual scattering cell of the object at the origin of the autocorrelation space.