The Experts below are selected from a list of 186 Experts worldwide ranked by ideXlab platform
F. Piazza - One of the best experts on this subject based on the ideXlab platform.
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ISCAS (5) - Neural blind separation of complex sources by extended Hebbian learning (EGHA)
ISCAS'99. Proceedings of the 1999 IEEE International Symposium on Circuits and Systems VLSI (Cat. No.99CH36349), 1999Co-Authors: S. Fiori, F. PiazzaAbstract:The aim of this paper is to present a nonlinear extension to Sanger's generalized Hebbian learning rule for complex-valued data neural processing. A possible choice of the involved nonlinearity is discussed recalling the Sudjianto-Hassoun interpretation of the nonlinear Hebbian learning. Extension of this interpretation to the complex case leads to a nonlinearity called Rayleigh Function, which allows for separation of mixed independent complex-valued source signals.
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Complex independent component analysis by nonlinear generalized Hebbian learning with Rayleigh nonlinearity
1999 IEEE International Conference on Acoustics Speech and Signal Processing. Proceedings. ICASSP99 (Cat. No.99CH36258), 1999Co-Authors: E. Pomponi, S. Fiori, F. PiazzaAbstract:This paper presents a non-linear extension of the Sanger's (1989) generalized Hebbian algorithm to the processing of complex-valued data. A possible choice of the involved nonlinearity is discussed recalling the Sudjianto-Hassoun (1994) interpretation of the nonlinear Hebbian learning. Extension of this interpretation to the complex case leads to a nonlinearity called the Rayleigh Function, which allows for separating mixed independent complex-valued source signals.
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ICASSP - Complex independent component analysis by nonlinear generalized Hebbian learning with Rayleigh nonlinearity
1999 IEEE International Conference on Acoustics Speech and Signal Processing. Proceedings. ICASSP99 (Cat. No.99CH36258), 1999Co-Authors: E. Pomponi, S. Fiori, F. PiazzaAbstract:This paper presents a non-linear extension of the Sanger's (1989) generalized Hebbian algorithm to the processing of complex-valued data. A possible choice of the involved nonlinearity is discussed recalling the Sudjianto-Hassoun (1994) interpretation of the nonlinear Hebbian learning. Extension of this interpretation to the complex case leads to a nonlinearity called the Rayleigh Function, which allows for separating mixed independent complex-valued source signals.
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Neural blind separation of complex sources by extended Hebbian learning (EGHA)
1999 IEEE International Symposium on Circuits and Systems (ISCAS), 1999Co-Authors: S. Fiori, F. PiazzaAbstract:The aim of this paper is to present a nonlinear extension to Sanger's generalized Hebbian learning rule for complex-valued data neural processing. A possible choice of the involved nonlinearity is discussed recalling the Sudjianto-Hassoun interpretation of the nonlinear Hebbian learning. Extension of this interpretation to the complex case leads to a nonlinearity called Rayleigh Function, which allows for separation of mixed independent complex-valued source signals.
S. Fiori - One of the best experts on this subject based on the ideXlab platform.
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ISCAS (5) - Neural blind separation of complex sources by extended Hebbian learning (EGHA)
ISCAS'99. Proceedings of the 1999 IEEE International Symposium on Circuits and Systems VLSI (Cat. No.99CH36349), 1999Co-Authors: S. Fiori, F. PiazzaAbstract:The aim of this paper is to present a nonlinear extension to Sanger's generalized Hebbian learning rule for complex-valued data neural processing. A possible choice of the involved nonlinearity is discussed recalling the Sudjianto-Hassoun interpretation of the nonlinear Hebbian learning. Extension of this interpretation to the complex case leads to a nonlinearity called Rayleigh Function, which allows for separation of mixed independent complex-valued source signals.
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Complex independent component analysis by nonlinear generalized Hebbian learning with Rayleigh nonlinearity
1999 IEEE International Conference on Acoustics Speech and Signal Processing. Proceedings. ICASSP99 (Cat. No.99CH36258), 1999Co-Authors: E. Pomponi, S. Fiori, F. PiazzaAbstract:This paper presents a non-linear extension of the Sanger's (1989) generalized Hebbian algorithm to the processing of complex-valued data. A possible choice of the involved nonlinearity is discussed recalling the Sudjianto-Hassoun (1994) interpretation of the nonlinear Hebbian learning. Extension of this interpretation to the complex case leads to a nonlinearity called the Rayleigh Function, which allows for separating mixed independent complex-valued source signals.
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ICASSP - Complex independent component analysis by nonlinear generalized Hebbian learning with Rayleigh nonlinearity
1999 IEEE International Conference on Acoustics Speech and Signal Processing. Proceedings. ICASSP99 (Cat. No.99CH36258), 1999Co-Authors: E. Pomponi, S. Fiori, F. PiazzaAbstract:This paper presents a non-linear extension of the Sanger's (1989) generalized Hebbian algorithm to the processing of complex-valued data. A possible choice of the involved nonlinearity is discussed recalling the Sudjianto-Hassoun (1994) interpretation of the nonlinear Hebbian learning. Extension of this interpretation to the complex case leads to a nonlinearity called the Rayleigh Function, which allows for separating mixed independent complex-valued source signals.
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Neural blind separation of complex sources by extended Hebbian learning (EGHA)
1999 IEEE International Symposium on Circuits and Systems (ISCAS), 1999Co-Authors: S. Fiori, F. PiazzaAbstract:The aim of this paper is to present a nonlinear extension to Sanger's generalized Hebbian learning rule for complex-valued data neural processing. A possible choice of the involved nonlinearity is discussed recalling the Sudjianto-Hassoun interpretation of the nonlinear Hebbian learning. Extension of this interpretation to the complex case leads to a nonlinearity called Rayleigh Function, which allows for separation of mixed independent complex-valued source signals.
Tõnu Viik - One of the best experts on this subject based on the ideXlab platform.
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Average photon path-length of radiation emerging from finite atmospheres
Astrophysics and Space Science, 1995Co-Authors: Tõnu ViikAbstract:The determination of the average path-length of photons emerging from a finite planeparallel atmosphere with molecular scattering is discussed. We examine the effects of polarisation on the average path-length of the emergent radiation by comparing the results with those obtained for the atmosphere where the scattering obeys the scalar Rayleigh Function. Only the axial radiation field is considered for both cases.
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Average photon path-length of radiation emerging from finite atmospheres
Astrophysics and Space Science, 1995Co-Authors: Tõnu ViikAbstract:The determination of the average path-length of photons emerging from a finite planeparallel atmosphere with molecular scattering is discussed. We examine the effects of polarisation on the average path-length of the emergent radiation by comparing the results with those obtained for the atmosphere where the scattering obeys the scalar Rayleigh Function. Only the axial radiation field is considered for both cases. To solve this problem we have used the integro-differential equations of Chandrasekhar for the diffuse scattering and transmission Functions (or matrices). By differentiation of these equations with respect to the albedo of single scattering we obtain new equations the solution of which gives us the derivatives of the intensities of the emergent radiation at the boundaries. As in the case of scalar transfer the principles of invariance by Chandrasekhar may be used to find an adding scheme to obtain both the scattering and transmission matrices and their derivatives with respect to the albedo of single scattering. These derivatives are crucial in determining the average path length. The numerical experiments have shown that the impact of the polarisation on the average pathlength of the emergent radiation is the largest in the atmospheres with optical thickness less than, or equal to, three, reaching ≈ 6.9% in the reflected radiation.
M Spies - One of the best experts on this subject based on the ideXlab platform.
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Green’s Function for Lamb’s Problem and Rayleigh Wave Propagation in General Transversely Isotropic Materials1
Review of Progress in Quantitative Nondestructive Evaluation, 1996Co-Authors: M Spies, Michael KröningAbstract:Composite materials have gained considerable industrial importance, being widely applied e.g. in aerospace industries. The need for their proper testing in view of delaminations, inclusions and other defects has correspondingly stimulated the interest in describing wave propagation in such anisotropic media. In this study, Lamb’s problem of determining the disturbance resulting from a point source in a half-space [1] is investigated for the case of transversely isotropic (TI) symmetry, which is characteristic for unidirectional fiber composites and extruded metal-matrix composites, but also for fiber-textured columnar-grained steels. Using the dyadic and triadic full-space Green’s Functions obtained previously in their 2d-space-time spectral representations [2], a corresponding representation of Green’s dyad for the half-space has been derived exploiting the boundary condition of the stress-free surface. The resulting dyadic Function is the solution of the elastic wave equation with point forces applied at the surface or within the uniform half-space, the fiber orientation being variable. First numerical evaluations have been performed with respect to Rayleigh-surface wave propagation by determining the zeroes of the corresponding Rayleigh Function, which is included in the analytical expressions. Resulting slowness and wave curves are presented for several materials. The work presented can be further applied, e.g., to determine Rayleigh wave directivity patterns for point sources on the half-space as well as to model laser-generated wave propagation in composites. Application in the field of seismic wave propagation is also possible.
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Elastic wave propagation in transversely isotropic media. II. The generalized Rayleigh Function and an integral representation for the transducer field. Theory
Journal of the Acoustical Society of America, 1995Co-Authors: M SpiesAbstract:The basis for the derivation of elastodynamic holography for arbitrarily oriented transversely isotropic materials, given in Part I of this presentation [M. Spies, J. Acoust. Soc. Am. 96, 1144–1157 (1994)], is Huygens’ principle and a resulting relationship which links the spatial spectra of surface traction and displacement distribution. Similar to deriving the plane‐wave spectral decomposition of elastic wavefields for given displacement, this relationship yields a corresponding decomposition for the case of given surface traction, which can be applied to model the problem of transducer radiation as significant to nondestructive testing. For a physically reasonable distribution of surface traction within the transducer aperture, an integral representation for the resulting transducer field is obtained. The main problem in this approach is the inversion of the 2‐D space‐time spectral representation of Green’s triadic Function. A specifically interesting result of this inversion is the Rayleigh Function f...
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theory of transducer radiation in transversely isotropic media introducing the generalized Rayleigh Function
1995Co-Authors: M SpiesAbstract:Progress in materials’ science and engineering has lead to the development of low-density composite materials exhibiting high strength and toughness. Those structural materials like fiber composites and metal-matrix composites (MMC) have gained an important industrial role, being widely applicated e.g. in aerospace industries. The need for their proper testing in view of delaminations, inclusions and other defects has correspondingly stimulated the interest in studying wave propagation in such anisotropic media. In this study, the fundamental mathematical formulation of Huygens’ principle is employed to derive an integral representation for transducer-generated wavefields. Use is made of the dyadic and triadic Green’s Functions, which have been derived recently in form of their 2d-space-time spectral representations for the case of transversely isotropic symmetry [1], which is characteristic for unidirectional fiber composites and extruded MMCs, but also for ideally fiber-textured columnar-grained steels. A particularly interesting outcome of this analysis is the generalized formulation of the transversely isotropic Rayleigh-Function describing the Rayleigh-wavefronts propagating at the free surface. Since the material’s spatial orientation is included as an additional parameter, a coordinate-free approach is used to reduce the inherent complexity of this analysis as far as possible. The use of the derived relationships for modeling transducer radiation into these media, possible ways of evaluation and the significance of the generalized Rayleigh-Function are discussed.
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elastic wave propagation in transversely isotropic media ii the generalized Rayleigh Function and an integral representation for the transducer field theory
Journal of the Acoustical Society of America, 1995Co-Authors: M SpiesAbstract:The basis for the derivation of elastodynamic holography for arbitrarily oriented transversely isotropic materials, given in Part I of this presentation [M. Spies, J. Acoust. Soc. Am. 96, 1144–1157 (1994)], is Huygens’ principle and a resulting relationship which links the spatial spectra of surface traction and displacement distribution. Similar to deriving the plane‐wave spectral decomposition of elastic wavefields for given displacement, this relationship yields a corresponding decomposition for the case of given surface traction, which can be applied to model the problem of transducer radiation as significant to nondestructive testing. For a physically reasonable distribution of surface traction within the transducer aperture, an integral representation for the resulting transducer field is obtained. The main problem in this approach is the inversion of the 2‐D space‐time spectral representation of Green’s triadic Function. A specifically interesting result of this inversion is the Rayleigh Function for arbitrarily oriented transversely isotropic media, which characterizes the propagation of the respective Rayleigh wavefronts. Since the resulting expressions are explicitly dependent on the orientation of the material’s axis of rotational symmetry, their numerical evaluation will be much more complicated than in the isotropic case.
E. Pomponi - One of the best experts on this subject based on the ideXlab platform.
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Complex independent component analysis by nonlinear generalized Hebbian learning with Rayleigh nonlinearity
1999 IEEE International Conference on Acoustics Speech and Signal Processing. Proceedings. ICASSP99 (Cat. No.99CH36258), 1999Co-Authors: E. Pomponi, S. Fiori, F. PiazzaAbstract:This paper presents a non-linear extension of the Sanger's (1989) generalized Hebbian algorithm to the processing of complex-valued data. A possible choice of the involved nonlinearity is discussed recalling the Sudjianto-Hassoun (1994) interpretation of the nonlinear Hebbian learning. Extension of this interpretation to the complex case leads to a nonlinearity called the Rayleigh Function, which allows for separating mixed independent complex-valued source signals.
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ICASSP - Complex independent component analysis by nonlinear generalized Hebbian learning with Rayleigh nonlinearity
1999 IEEE International Conference on Acoustics Speech and Signal Processing. Proceedings. ICASSP99 (Cat. No.99CH36258), 1999Co-Authors: E. Pomponi, S. Fiori, F. PiazzaAbstract:This paper presents a non-linear extension of the Sanger's (1989) generalized Hebbian algorithm to the processing of complex-valued data. A possible choice of the involved nonlinearity is discussed recalling the Sudjianto-Hassoun (1994) interpretation of the nonlinear Hebbian learning. Extension of this interpretation to the complex case leads to a nonlinearity called the Rayleigh Function, which allows for separating mixed independent complex-valued source signals.
