1 XL â or EXL, Exploration Licence (United Kingdom), a type of onshore licence issued between the First Onshore Licensing Round (1986) and the Sixth (1992). 2  Xln â Crystalline (minerals). 3  XLPE-Cross-linked Polyethylene. 4  XMAC â Cross-Multipole Array Acoustic log.
When the frequency approaches 120 CPM (2 Hz), occupants perceive the ride as harsh. Consequently, the suspension of the average family sedan will have a natural frequency of about 60 to 90 CPM. A high-performance sports car will have a stiffer suspension with a natural frequency of about 120 to 150 CPM (2 to 2.5 Hz). Originally, human sensitivity to ride frequency was believed to be associated with the natural oscillations of an adult human body during a walking gait.
Four or three marks can be seen at other flicker light frequency; for example, three fixed marks can be seen at a flicker frequency of 1650 rpm (real RPMs multiplied by 1.5), four marks at a flicker frequency of 1466 rpm (real RPMs multiplied by 1.333.) and five marks at a flicker frequency of 1375 rpm (real RPMs multiplied by 1.25).