Open AccessBook
Fourier Transform: Applications
Reads0
Chats0
TLDR
The Fourier transform is very useful in solving a variety of linear constant coefficient ordinary and partial differential equations describing processes which take place over an infinite interval, −∞ < x < ∞.Abstract:
The Fourier transform is very useful in solving a variety of linear constant coefficient ordinary and partial differential equations describing processes which take place over an infinite interval, −∞ < x < ∞. We will provide a number of examples of this sort of application in the present section. Our first example involves a simple, time independent, equilibrium process. Example 1 We consider a stretched string, or cord, with small transverse displacement y(x), subject to an external transverse force f (x) and a transverse restoring force −κ y(x), maintained at tension τ > 0 over the interval −∞ < x < ∞ and constrained so that lim |x| → ∞ y(x) = 0. It can then be shown that y(x) satisfies τ d 2 y dx 2 − κ y(x) + f (x) = 0. Taking a 2 = κ/τ and applying the Fourier transform to both sides of this equation, using the differentiation property (twice) we have − ξ 2 + a 2 ˆ y(ξ) + 1 τ ˆ f (ξ) = 0 ⇒ ˆ y(ξ) = 1 τ ˆ f (ξ) ξ 2 + a 2. Using the convolution property of the Fourier transform we obtain y(x) = 1 τ ∞ −∞ F −1 1 ξ 2 + a 2 (r) f (x − r) dr as the solution. To make any further progress on this we need to find the function K(x) such thatˆK(ξ) ≡ (F K) (ξ) = 1 ξ 2 +a 2. It turns out that this function is K(x) = e −ax 2a , x > 0, e ax 2a , x < 0.read more
Citations
More filters
Journal ArticleDOI
Real-time observation of interfering crystal electrons in high-harmonic generation
Matthias Hohenleutner,F. Langer,Olaf Schubert,Matthias Knorr,U. Huttner,Stephan W. Koch,Mackillo Kira,Rupert Huber +7 more
TL;DR: This work studies high-harmonic generation in a bulk solid directly in the time domain, and reveals a new kind of strong-field excitation in the crystal that justifies the hope for all-optical band-structure reconstruction and lays the foundation for possible quantum logic operations at optical clock rates.
Journal ArticleDOI
Longitudinal sound velocities, elastic anisotropy, and phase transition of high-pressure cubic H2O ice to 82 GPa
Maju Kuriakose,Samuel Raetz,Qing-Miao Hu,Sergey M. Nikitin,Nikolay Chigarev,Vincent Tournat,Alain Bulou,Alexey M. Lomonosov,Philippe Djemia,Vitalyi Gusev,Andreas Zerr +10 more
TL;DR: In this article, the authors used the time-domain Brillouin scattering (TDBS) technique to measure longitudinal sound velocities (V L) in polycrystalline ice samples compressed in a diamond anvil cell.
Journal ArticleDOI
Pulvinar Modulates Synchrony across Visual Cortical Areas.
TL;DR: Findings indicate that the pulvinar is involved in the mechanisms underlying oscillatory communication along the visual cortex, and modulated the oscillatory information between areas 17 and 21a in gamma and alpha bands for the feedforward and feedback processing, respectively.
Proceedings Article
Dictionary Learning Using EMD and Hilbert Transform for Sparse Modeling of Environmental Sounds
TL;DR: A new dictionary learning method for reconstruction tasks based on Empirical Mode Decomposition and Hilbert Transformation that has a good reconstructive sparse over complete encoding and is largely competitive against KSVD and MOD algorithms.
Distribution of Electrical Conductivity in Mammalian Muscle Tissue Model on Exposed to a Pulsed Electric Field
TL;DR: In this paper, the authors used a finite element method to compute conductivity distribution on a specific biological tissue (e.g. mammalian muscle tissue) that being electrically pulsed.