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Claudio M. Rocco - One of the best experts on this subject based on the ideXlab platform.

  • Global Sensitivity Analysis in a Multi-State Physics Model of Component Degradation Based on a Hybrid State-Space Enrichment and Polynomial Chaos Expansion Approach
    IEEE Transactions on Reliability, 2013
    Co-Authors: Claudio M. Rocco
    Abstract:

    This paper extends previous works related to the assessment of component degradation, through Markov multi-State Physic models. The extension includes the evaluation of the effects of uncertain parameters in the model, and the definition of their importance with respect to their influence on the output of the model. Global Sensitivity Analysis (GSA) is selected as the technique because it enables us to 1) consider the simultaneous effects of parameters variations, and 2) to define importance indexes that allow a ranking of the components. GSA requires a large number of evaluations for specific points, identified by an appropriate design of experiment. To avoid the many costly evaluations, a meta-model is built based on polynomial chaos expansion (PCE). A PCE is a multi-dimensional polynomial approximation of the model with coefficients determined by evaluating the model in a reduced set of predetermined points. Importance index values are then derived directly from the PCE. Because, in the problem considered, the model provides the time-dependent behavior of the State probabilities, the importance indexes are also functions of time. An application is presented, related to the cracking process in an Alloy 82/182 dissimilar metal weld in the primary coolant system of a nuclear power plant.

Enrico Zio - One of the best experts on this subject based on the ideXlab platform.

  • Global sensitivity analysis in a Multi-State Physics Model of Component Degradation based on a hybrid State-Space Enrichment and Polynomial Chaos Expansion approach
    IEEE Transactions on Reliability, 2013
    Co-Authors: Claudio Rocco, Enrico Zio
    Abstract:

    This paper extends previous works related to the assessment of component degradation, through Markov multi-State Physic models. The extension includes the evaluation of the effects of uncertain parameters in the model and the definition of their importance with respect to their influence on the output of the model. Global Sensitivity Analysis (GSA) is selected as the technique because able to: 1) consider the simultaneous effects of parameters variations and 2) to define importance indexes that allow a ranking of the components. GSA requires a large number of evaluations for specific points, identified by an appropriate design of experiment. To avoid the many costly evaluations, a meta-model is built based on polynomial chaos expansion (PCE). A PCE is a multidimensional polynomial approximation ofthe model with coefficients determined by evaluating the model in a reduced set of predetermined points. Importance indexes values are then derived directly from the PCE. Since in the problem considered, the model provides the timedependent behavior of the State probabilities, the importance indexes are also functions of time. An application is presented, related to the cracking process in an Alloy 82/182 dissimilar metal weld in the primary coolant system of a nuclear power plant.

Claudio Rocco - One of the best experts on this subject based on the ideXlab platform.

  • Global sensitivity analysis in a Multi-State Physics Model of Component Degradation based on a hybrid State-Space Enrichment and Polynomial Chaos Expansion approach
    IEEE Transactions on Reliability, 2013
    Co-Authors: Claudio Rocco, Enrico Zio
    Abstract:

    This paper extends previous works related to the assessment of component degradation, through Markov multi-State Physic models. The extension includes the evaluation of the effects of uncertain parameters in the model and the definition of their importance with respect to their influence on the output of the model. Global Sensitivity Analysis (GSA) is selected as the technique because able to: 1) consider the simultaneous effects of parameters variations and 2) to define importance indexes that allow a ranking of the components. GSA requires a large number of evaluations for specific points, identified by an appropriate design of experiment. To avoid the many costly evaluations, a meta-model is built based on polynomial chaos expansion (PCE). A PCE is a multidimensional polynomial approximation ofthe model with coefficients determined by evaluating the model in a reduced set of predetermined points. Importance indexes values are then derived directly from the PCE. Since in the problem considered, the model provides the timedependent behavior of the State probabilities, the importance indexes are also functions of time. An application is presented, related to the cracking process in an Alloy 82/182 dissimilar metal weld in the primary coolant system of a nuclear power plant.

M. Da Cunha Belo - One of the best experts on this subject based on the ideXlab platform.

  • Photoelectrochemistry : Theoretical Basis
    Electrochemical and Optical Techniques for the Study and Monitoring of Metallic Corrosion, 1991
    Co-Authors: M. Da Cunha Belo
    Abstract:

    An attempt is made to present the essential features specific to photoelectrochemical processes on semiconductors. Thus, some basic notions on solid State Physic (band structure and electron distribution) are first introduced. Then the kinetics of electrochemical reactions is described taking into account the contribution of the two types of charge carriers and the influence of a space charge near the semiconductor-electrolyte interface. Finally, two approaches for describing electrochemical processes based on photoexcitation of the semiconductor are discussed: a kinetic approach, and a thermodynamic approach which introduces the concept of the quasi-Fermi levels. The influence of the mutual position of the different energy levels on the conditions of stability and corrosion of a semiconductor is examined.

A. Piasecka Belkhayat - One of the best experts on this subject based on the ideXlab platform.

  • The interval lattice Boltzmann method for transient heat transport
    2009
    Co-Authors: A. Piasecka Belkhayat
    Abstract:

    In this paper an application of the interval lattice Boltzmann method for solving one-dimensional problems is presented. The Boltzmann transport equation transformed in the phonon energy density equation is considered. Such approach in which the parameters appearing in the problem analyzed are treated as the constant values is widely used. Here, the model with interval value of relaxation time is analyzed. In the final part of the paper, results of numerical computations are shown. Introduction Heat transport in dielectric materials and semiconductors is mainly realized by quanta of crystal vibrational energy called phonons. The study of phonons is an important part of solid State Physic, because phonons play a major role in many of the Physical properties of solids, especially a material's thermal conductivity. The crystal can be considered as a container filled with a gas of phonons. Phonons always “move” from the part with the higher temperature to the part with the lower temperature. During this move phonons carry energy. This kind of phenomena can be described by the Boltzmann transport equation in which the relaxation time appears. The relaxation time is estimated experimentally and its actual value is still a subject of discussion [3, 4]. In such conditions it seems natural to define the relaxation time as an interval value. In the paper the heat transport proceeding in a thin silicon film is considered. 1. Boltzmann transport equation The Boltzmann transport equation (BTE) is one of the fundamental equations of solid State Physic and takes the following form [1, 2] 0 ef r f f f f g t ∂ − + ⋅∇ = + ∂ τ v (1) A. Piasecka Belkhayat 156 where f is the phonon distribution function, 0 f is the equilibrium distribution function given by the Bose-Einstein statistic, v is the phonon group velocity, r τ is the relaxation time and ef g is the phonon generation rate due to electron-phonon scattering. In order to take advantage of the simplifying assumption of the Debye model, the BTE can be transformed in a phonon energy density equation of the form [1] 0 v r e e e e q t ∂ − + ⋅∇ = − + ∂ τ v (2) where e is the phonon energy density, 0 e is the equilibrium phonon energy density and v q is the internal heat generation rate related to an unit of volume. The equation (2) must be supplemented by the boundary initial conditions. Using the Debye model the relation between phonon energy and lattice temperature can be calculated using the formula / 3 4 3 0 9 ( ) d exp( ) 1 D T b D k z e T z T z Θ   η =     Θ −   ∫ (3) where D Θ is the Debye temperature of the solid, b k is the Boltzmann constant, T is the lattice temperature while η is the number density of oscillators and is defined using the formula 3 2 1 6 b D k   Θ η =   π ω   h (4) where h is the Planck constant divided by 2π and ω is the phonon frequency. 2. The Interval Lattice Boltzmann Method The interval lattice Boltzmann method (ILBM) is a discrete representation of the Boltzmann transport equation. For one dimensional problems the interval Boltzmann transport equation can be written as