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  2. Decimal time - Wikipedia

    en.wikipedia.org/wiki/Decimal_time

    Units were either written out in full, or abbreviated. Thus, five hours eighty three minutes decimal might be written as 5 h. 83 m. Even today, "h" is commonly used in France to separate hours and minutes of 24-hour time, instead of a colon, such as 14h00. Midnight was represented in civil records as "ten hours".

  3. Carnegie Unit and Student Hour - Wikipedia

    en.wikipedia.org/wiki/Carnegie_Unit_and_Student_Hour

    The Student Hour is approximately 12 hours of class or contact time, approximately 1/10 of the Carnegie Unit (as explained below). As it is used today, a Student Hour is the equivalent of one hour (50 minutes) of lecture time for a single student per week over the course of a semester, usually 14 to 16 weeks.

  4. Naismith's rule - Wikipedia

    en.wikipedia.org/wiki/Naismith's_rule

    Pace [6] in minutes per kilometre or mile vs. slope angle resulting from Naismith's rule [7] for basal speeds of 5 and 4 km / h. [n 1] The original Naismith's rule from 1892 says that one should allow one hour per three miles on the map and an additional hour per 2000 feet of ascent. [1] [4] It is included in the last sentence of his report ...

  5. Flight-time equivalent dose - Wikipedia

    en.wikipedia.org/wiki/Flight-time_equivalent_dose

    Flight-time equivalent dose (FED) is an informal unit of measurement of ionizing radiation exposure. Expressed in units of flight-time (i.e., flight-seconds, flight-minutes, flight-hours), one unit of flight-time is approximately equivalent to the radiological dose received during the same unit of time spent in an airliner at cruising altitude.

  6. ΔT (timekeeping) - Wikipedia

    en.wikipedia.org/wiki/ΔT_(timekeeping)

    Analysis of layering in fossil mollusc shells from 70 million years ago, in the Late Cretaceous period, shows that there were 372 days a year, and thus that the day was about 23.5 hours long then. [ 20 ] [ 21 ] Based on geological studies of tidal rhythmites , the day was 21.9±0.4 hours long 620 million years ago and there were 13.1±0.1 ...

  7. Leap second - Wikipedia

    en.wikipedia.org/wiki/Leap_second

    Screenshot of the UTC clock from time.gov during the leap second on 31 December 2016.. A leap second is a one-second adjustment that is occasionally applied to Coordinated Universal Time (UTC), to accommodate the difference between precise time (International Atomic Time (TAI), as measured by atomic clocks) and imprecise observed solar time (), which varies due to irregularities and long-term ...

  8. Air changes per hour - Wikipedia

    en.wikipedia.org/wiki/Air_changes_per_hour

    Air changes per hour, abbreviated ACPH or ACH, or air change rate is the number of times that the total air volume in a room or space is completely removed and replaced in an hour. If the air in the space is either uniform or perfectly mixed, air changes per hour is a measure of how many times the air within a defined space is replaced each hour.

  9. Revolutions per minute - Wikipedia

    en.wikipedia.org/wiki/Revolutions_per_minute

    ISO 80000-3:2019 defines a physical quantity called rotation (or number of revolutions), dimensionless, whose instantaneous rate of change is called rotational frequency (or rate of rotation), with units of reciprocal seconds (s −1).