The Nyquist frequency is equal to one-half the sampling rate.

Shannon’s sampling theorem states that a sampled time signal must not contain components at frequencies above the Nyquist frequency. Otherwise, an aliasing error will occur.

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Here are some papers:

Notes on sample rate and aliasing:aliasing_notes.pdf

The Need for Analog Anti-aliasing Filters in the Pyrotechnic Shock Testing of Avionics Components:

AA_Filter_Pyro.pdf

Potential Aliasing in Pyrotechnic Shock Data: Numerical Experiments: aliasing_numerical_experiments.pdf

NASA Letter: NTS_Pyroshock_NASA_KSC_Letter.pdf

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Ceiling fan, optical aliasing video: fan_aliased.avi

The ceiling fan appears to change rotational direction several times. In reality, the fan always rotates in the same direction. The optical illusion is due to aliasing.

The frame rate of the video camera was too low to accurately capture the motion. Note that the video footage was decimate to enhance this effect.

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– Tom Irvine

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