Vibration it can be very harmful – leading to eventual failure of the system. Consequently, one of the major reasons for vibration analysis is to predict when this type of resonance may occur and then to determine what steps to take to prevent it from occurring. As the amplitude plot shows, adding damping can significantly reduce the magnitude of the vibration. Also, the magnitude can be reduced if the natural frequency can be shifted away from the forcing frequency by changing the stiffness or mass of the system. If the system cannot be changed, perhaps the forcing frequency can be shifted
Unit of time lunation. Such calendars include the Sumerian, Egyptian, Chinese, Babylonian, ancient Athenian, Buddhist, Hindu, Islamic, Icelandic, Mayan, and French Republican calendars. The modern calendar has its origins in the Roman calendar, which evolved into the Julian calendar, and then the Gregorian. Note: The light-year is not a unit of time, but a unit of length of about 9.5 trillion kilometres (9,454,254,955,488 kilometres). All of the important units of time can be interrelated. The key units are the second, defined in terms of an atomic process; the day, an integral multiple of seconds; and the year, usually 365 days (more info HERE).