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  2. Triangle wave - Wikipedia

    en.wikipedia.org/wiki/Triangle_wave

    Animation of the additive synthesis of a triangle wave with an increasing number of harmonics. See Fourier Analysis for a mathematical description.. It is possible to approximate a triangle wave with additive synthesis by summing odd harmonics of the fundamental while multiplying every other odd harmonic by −1 (or, equivalently, changing its phase by π) and multiplying the amplitude of the ...

  3. Slowly varying envelope approximation - Wikipedia

    en.wikipedia.org/wiki/Slowly_varying_envelope...

    The space and time scales over which E 0 varies are generally much longer than the spatial wavelength and temporal period of the carrier wave. A numerical solution of the envelope equation thus can use much larger space and time steps, resulting in significantly less computational effort.

  4. Dirichlet problem - Wikipedia

    en.wikipedia.org/wiki/Dirichlet_problem

    The next steps in the study of the Dirichlet's problem were taken by Karl Friedrich Gauss, William Thomson (Lord Kelvin) and Peter Gustav Lejeune Dirichlet, after whom the problem was named, and the solution to the problem (at least for the ball) using the Poisson kernel was known to Dirichlet (judging by his 1850 paper submitted to the ...

  5. Wave equation - Wikipedia

    en.wikipedia.org/wiki/Wave_equation

    The wave equation is a second-order linear partial differential equation for the description of waves or standing wave fields such as mechanical waves (e.g. water waves, sound waves and seismic waves) or electromagnetic waves (including light waves). It arises in fields like acoustics, electromagnetism, and fluid dynamics.

  6. Spectral density estimation - Wikipedia

    en.wikipedia.org/wiki/Spectral_density_estimation

    Example of voice waveform and its frequency spectrum A periodic waveform (triangle wave) and its frequency spectrum, showing a "fundamental" frequency at 220 Hz followed by multiples (harmonics) of 220 Hz The power spectral density of a segment of music is estimated by two different methods, for comparison

  7. Helmholtz equation - Wikipedia

    en.wikipedia.org/wiki/Helmholtz_equation

    The Helmholtz equation has a variety of applications in physics and other sciences, including the wave equation, the diffusion equation, and the Schrödinger equation for a free particle. In optics, the Helmholtz equation is the wave equation for the electric field. [1] The equation is named after Hermann von Helmholtz, who studied it in 1860. [2]

  8. List of equations in wave theory - Wikipedia

    en.wikipedia.org/wiki/List_of_equations_in_wave...

    The phase velocity is the rate at which the phase of the wave propagates in space. The group velocity is the rate at which the wave envelope, i.e. the changes in amplitude, propagates. The wave envelope is the profile of the wave amplitudes; all transverse displacements are bound by the envelope profile.

  9. List of numerical analysis topics - Wikipedia

    en.wikipedia.org/wiki/List_of_numerical_analysis...

    Finite difference methods for heat equation and related PDEs: FTCS scheme (forward-time central-space) — first-order explicit; Crank–Nicolson method — second-order implicit; Finite difference methods for hyperbolic PDEs like the wave equation: Lax–Friedrichs method — first-order explicit; Lax–Wendroff method — second-order explicit