A low profile actuator assembly for controlling PCI card removal from the chassis bay of a hot pluggable computer. Each session includes a number of games. The aluminum phosphonate catalyst preferably has a general structure of RPO2, wherein O represents oxygen, P represents pentavalent phosphorous, Al represents aluminum, R comprises a hydrogen, a methyl group, an alkyl group, or an aryl group, and R and R independently comprise a halide, an alkyl group, an alkoxy group, an aryl group, or an aryloxy group. The movable part includes a movable arc contact selectively making contact with the fixed arc contact, a cylinder in which the movable arc contact is disposed, and a second fixed contact maker guiding a movement of the cylinder. Angle-domain sensitivity kernels are used to convert the depth residuals into velocity errors, which are then used to refine the velocity model.