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  2. Spectrum continuation analysis - Wikipedia

    en.wikipedia.org/wiki/Spectrum_continuation_analysis

    Spectrum continuation analysis (SCA) is a generalization of the concept of Fourier series to non-periodic functions of which only a fragment has been sampled in the time domain. Recall that a Fourier series is only suitable to the analysis of periodic (or finite-domain) functions f ( x ) with period 2π.

  3. Quasicrystal - Wikipedia

    en.wikipedia.org/wiki/Quasicrystal

    There are several ways to mathematically define quasicrystalline patterns. One definition, the "cut and project" construction, is based on the work of Harald Bohr (mathematician brother of Niels Bohr). The concept of an almost periodic function (also called a quasiperiodic function) was studied by Bohr, including work of Bohl and Escanglon. [47]

  4. Periodic function - Wikipedia

    en.wikipedia.org/wiki/Periodic_function

    A periodic function, also called a periodic waveform (or simply periodic wave), is a function that repeats its values at regular intervals or periods. The repeatable part of the function or waveform is called a cycle . [ 1 ]

  5. Chaos theory - Wikipedia

    en.wikipedia.org/wiki/Chaos_theory

    Although no universally accepted mathematical definition of chaos exists, a commonly used definition, originally formulated by Robert L. Devaney, says that to classify a dynamical system as chaotic, it must have these properties: [23] it must be sensitive to initial conditions, it must be topologically transitive, it must have dense periodic ...

  6. Spectral density estimation - Wikipedia

    en.wikipedia.org/wiki/Spectral_density_estimation

    General mathematical techniques for analyzing non-periodic functions fall into the category of Fourier analysis. The Fourier transform of a function produces a frequency spectrum which contains all of the information about the original signal, but in a different form.

  7. Quasiperiodicity - Wikipedia

    en.wikipedia.org/wiki/Quasiperiodicity

    Quasiperiodic behavior is almost but not quite periodic. [2] The term used to denote oscillations that appear to follow a regular pattern but which do not have a fixed period. The term thus used does not have a precise definition and should not be confused with more strictly defined mathematical concepts such as an almost periodic function or a ...

  8. Waveform - Wikipedia

    en.wikipedia.org/wiki/Waveform

    In electronics, acoustics, and related fields, the waveform of a signal is the shape of its graph as a function of time, independent of its time and magnitude scales and of any displacement in time. [1] [2] Periodic waveforms repeat regularly at a constant period. The term can also be used for non-periodic or aperiodic signals, like chirps and ...

  9. Einstein problem - Wikipedia

    en.wikipedia.org/wiki/Einstein_problem

    The presence of the screw symmetry resulted in a reevaluation of the requirements for non-periodicity. [4] Chaim Goodman-Strauss suggested that a tiling be considered strongly aperiodic if it admits no infinite cyclic group of Euclidean motions as symmetries, and that only tile sets which enforce strong aperiodicity be called strongly aperiodic ...