@article {NEUKIRCH2013,
	title = {{NONSTATIONARY TIME SERIES CONVOLUTION: ON THE RELATION BETWEEN THE HILBERT{\textendash}HUANG AND FOURIER TRANSFORM}},
	journal = {Advances in Adaptive Data Analysis},
	volume = {05},
	number = {01},
	year = {2013},
	month = {jan},
	pages = {1350004},
	publisher = {World Scientific Publishing Company},
	abstract = {The Hilbert{\textendash}Huang Transform (HHT) decomposes time series into intrinsic mode functions (IMF) in time-frequency domain. We show that time slices of IMFs equal time slices of Fourier series, where the instantaneous parameters of the IMF define the parameters amplitude and phase of the Fourier series. This leads to the formulation of the theorem that nonstationary convolution of an IMF with a general time domain response function translates into a multiplication of the IMF with the respective spectral domain response function which is explicitly permitted to vary over time. We conclude and show on a real world application that a de-trended signal{\textquoteright}s IMFs can be convolved independently and then be used for further time-frequency analysis. Finally, a discussion is opened on parallels in HHT and the Fourier transform with respect to the time-frequency domain.},
	keywords = {convolution, Fourier transform, Hilbert{\textendash}Huang transform, nonstationary, Time series},
	issn = {1793-5369},
	doi = {10.1142/S1793536913500040},
	url = {http://www.worldscientific.com/doi/abs/10.1142/S1793536913500040},
	author = {NEUKIRCH, MAIK and Garcia, Xavier}
}
@article {Garcia2009,
	title = {{Numerical study of the effects of particle shape and polydispersity on permeability}},
	journal = {Physical Review E},
	volume = {80},
	number = {2},
	year = {2009},
	month = {aug},
	pages = {021304},
	abstract = {We study through numerical simulations the dependence of the hydraulic permeability of granular materials on the particle shape and the grain size distribution. Several models of sand are constructed by simulating the settling under gravity of the grains; the friction coefficient is varied to construct packs of different porosity. The size distribution and shapes of the grains mimic real sands. Fluid flow is simulated in the resulting packs using a finite element method and the permeability of the packs is successfully compared with available experimental data. Packs of nonspherical particles are less permeable than sphere packs of the same porosity. Our results indicate that the details of grain shape and size distribution have only a small effect on the permeabilty of the systems studied. {\textcopyright} 2009 The American Physical Society.},
	issn = {1539-3755},
	doi = {10.1103/PhysRevE.80.021304},
	url = {http://www.scopus.com/inward/record.url?eid=2-s2.0-70349241904\&partnerID=tZOtx3y1},
	author = {Garcia, Xavier and Akanji, Lateef and Blunt, Martin and Matthai, Stephan and Latham, John}
}
