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A return period, also known as a recurrence interval or repeat interval, is an average time or an estimated average time between events such as earthquakes, floods, [1] landslides, [2] or river discharge flows to occur. It is a statistical measurement typically based on historic data over an extended period, and is used usually for risk analysis.
The counter implementation's accuracy is limited by the clock frequency. If time is measured by whole counts, then the resolution is limited to the clock period. For example, a 10 MHz clock has a resolution of 100 ns. To get resolution finer than a clock period, there are time interpolation circuits. [6]
The image sampling frequency is the repetition rate of the sensor integration period. Since the integration period may be significantly shorter than the time between repetitions, the sampling frequency can be different from the inverse of the sample time: 50 Hz – PAL video; 60 / 1.001 Hz ~= 59.94 Hz – NTSC video
The TU (for time unit) is a unit of time defined as 1024 μs for use in engineering. The svedberg is a time unit used for sedimentation rates (usually of proteins). It is defined as 10 −13 seconds (100 fs). The galactic year, based on the rotation of the galaxy and usually measured in million years. [2]
The period (symbol T) is the interval of time between events, so the period is the reciprocal of the frequency: T = 1/f. [ 2 ] Frequency is an important parameter used in science and engineering to specify the rate of oscillatory and vibratory phenomena, such as mechanical vibrations, audio signals ( sound ), radio waves , and light .
where Δt is the time interval between two co-local events (i.e. happening at the same place) for an observer in some inertial frame (e.g. ticks on their clock), known as the proper time, Δt′ is the time interval between those same events, as measured by another observer, inertially moving with velocity v with respect to the former observer ...
The RMS wave height, which is defined as square root of the average of the squares of all wave heights, is approximately equal to H s divided by 1.4. [2] [8] For example, according to the Irish Marine Institute: [9] "… at midnight on 9/12/2007 a record significant wave height was recorded of 17.2m at with [sic] a period of 14 seconds."
The spatial frequency is a measure of how often sinusoidal components (as determined by the Fourier transform) of the structure repeat per unit of distance. The SI unit of spatial frequency is the reciprocal metre (m −1 ), [ 1 ] although cycles per meter (c/m) is also common.