Stochastic Processes

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Jun 13, 2016 - Michael D. Shields. Assistant Professor. Dept. of Civil Engineering. Dept. of Materials Science and Engineering. Johns Hopkins University.
Meccanica Stocastica, Capri, Italy

Simulation of Higher-Order Stochastic Processes by Spectral Representation: Asymmetrically Nonlinear Processes Hwanpyo Kim Graduate Student Dept. of Civil Engineering Johns Hopkins University

Michael D. Shields Assistant Professor Dept. of Civil Engineering Dept. of Materials Science and Engineering Johns Hopkins University 13 June 2016

Simulation of Stochastic Processes Generation of Stochastic Processes (typically 2nd order) ,

𝑥 𝑡, 𝜃 = & 𝐶( (𝜃)𝜉( (𝑡) (-.

- Spectral representation method - K-L expansion 𝐶( 𝜃 ≡ R. V. - etc.

Generation of Non-Gaussian Stochastic Processes - Translation process [Grigoriu 1998, Shields et al. 2011, Kim and Shields 2015]

- Update K-L random variables [Phoon et al. 2005]

- etc.

𝜉( 𝑡 ≡ Basis Fun.

To match marginal PDF & 2nd order moments

Higher-order Properties of Non-Gaussian process?? • We aim to derive an inherently higher-order expansion from which stochastic processes can be simulated directly from polyspectra (bispectrum and power spectrum).

Polyspectra and Cumulants •

Polyspectrum – The nth order polyspectrum is given by the Fourier transform of the nth order cumulant [Wiener-Khinchine theorem]. ,

,

1 C ⋯ C 𝑐;< 𝜏. , ⋯ , 𝜏;?. 𝑒 ?((GHIHJ⋯JGKLHIKLH) 𝑑𝜏. ⋯ 𝑑𝜏;?. ;?. (2𝜋) ?, ?, 3 rd order cumulant and bispectrum (complex value) , , 1 𝐶N< 𝜔. , 𝜔O = 𝐵 𝜔. , 𝜔O = C C 𝑐N< 𝜏. , 𝜏O 𝑒 ?((GHIHJGQIQ) 𝑑𝜏. 𝑑𝜏O O (2𝜋)

𝐶;< 𝜔. , ⋯ , 𝜔; ?. = –

?, ?,

– For zero mean process, 3 rd order cumulant and 3 rd order moment function are identical. 𝑐N< 𝜏. , 𝜏O = 𝑚