In order to prevent deterioration in performance of an oil-free screw compressor and scuffing caused by rust, surfaces of both male and female rotors are coated with heat-resistance coatings containing a solid lubricant. In one particular embodiment, a Lyapunov exponent calculating method includes obtaining a value indicative of a condition of a chaotic system and assigning the value to first and second precision levels, the second precision level having a higher level of precision than the first precision level. The flexibility of the system is owed in part to payload data being carried within payload-carrying regions of so-called ZCell signals as the payload data moves between the line card layer and the switch fabric layer. Alternatively, a conduit having multiple channels may be placed in a pathway. A reporting module 9 sends the user status to the channel on which the keyword was sent.