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Davide Curreli - One of the best experts on this subject based on the ideXlab platform.
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density estimation techniques for multiscale coupling of kinetic models of the plasma Material Interface
Journal of Computational Physics, 2020Co-Authors: Shane Keniley, Davide CurreliAbstract:Abstract In this work we analyze two classes of Density-Estimation techniques which can be used to consistently couple different kinetic models of the plasma-Material Interface, intended as the region of plasma immediately interacting with the first surface layers of a Material wall. In particular, we handle the general problem of interfacing a continuum multi-species Vlasov-Poisson-BGK plasma model to discrete surface erosion models. The continuum model solves for the energy-angle distributions of the particles striking the surface, which are then driving the surface response. A modification to the classical Binary-Collision Approximation (BCA) method is here utilized as a prototype discrete model of the surface, to provide boundary conditions and impurity distributions representative of the Material behavior during plasma irradiation. The numerical tests revealed the superior convergence properties of Gaussian Mixture Models over Kernel Density Estimation methods, with Gaussian Mixtures and Epanechnikov-KDEs both being up to two orders of magnitude faster than Gaussian-KDEs. The methodology here presented allows a self-consistent treatment of the plasma-Material Interface in magnetic fusion devices, including both the near-surface plasma (plasma sheath and presheath) in magnetized conditions, and surface effects such as sputtering, back-scattering, and ion implantation. The same coupling techniques can also be utilized for other discrete Material models such as Molecular Dynamics.
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density estimation techniques for multiscale coupling of kinetic models of the plasma Material Interface
arXiv: Computational Physics, 2018Co-Authors: Shane Keniley, Davide CurreliAbstract:In this work we analyze two classes of Density-Estimation techniques which can be used to consistently couple different kinetic models of the plasma-Material Interface, intended as the region of plasma immediately interacting with the first surface layers of a Material wall. In particular, we handle the general problem of interfacing a continuum multi-species Vlasov-Poisson-BGK plasma model to discrete surface erosion models. The continuum model solves for the energy-angle distributions of the particles striking the surface, which are then driving the surface response. A modification to the classical Binary-Collision Approximation (BCA) method is here utilized as a prototype discrete model of the surface, to provide boundary conditions and impurity distributions representative of the Material behavior during plasma irradiation. The numerical tests revealed the superior convergence properties of Kernel Density Estimation methods over Gaussian Mixture Models, with Epanechnikov-KDEs being up to two orders of magnitude faster than Gaussian-KDEs. The methodology here presented allows a self-consistent treatment of the plasma-Material Interface in magnetic fusion devices, including both the near-surface plasma (plasma sheath and presheath) in magnetized conditions, and surface effects such as sputtering, back-scattering, and ion implantation. The same coupling techniques can also be utilized for other discrete Material models such as Molecular Dynamics.
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ion energy angle distribution functions at the plasma Material Interface in oblique magnetic fields
Physics of Plasmas, 2015Co-Authors: Rinat Khaziev, Davide CurreliAbstract:The ion energy-angle distribution (IEAD) at the wall of a magnetized plasma is of fundamental importance for the determination of the Material processes occurring at the plasma-Material Interface, comprising secondary emissions and Material sputtering. Here, we present a numerical characterization of the IEAD at the wall of a weakly collisional magnetized plasma with the magnetic field inclined at an arbitrary angle with respect to the wall. The analysis has been done using two different techniques: (1) a fluid-Monte Carlo method, and (2) particle-in-cell simulations, the former offering a fast but approximate method for the determination of the IEADs, the latter giving a computationally intensive but self-consistent treatment of the plasma behavior from the quasi-neutral region to the Material boundary. The two models predict similar IEADs, whose similarities and differences are discussed. Data are presented for magnetic fields inclined at angles from normal to grazing incidence (0°–85°). We show the scaling factors of the average and peak ion energy and trends of the pitch angle at the wall as a function of the magnetic angle, for use in the correlation of fluid plasma models to Material models.
Freddy Yin Chiang Boey - One of the best experts on this subject based on the ideXlab platform.
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β phase poly vinylidene fluoride films encouraged more homogeneous cell distribution and more significant deposition of fibronectin towards the cell Material Interface compared to α phase poly vinylidene fluoride films
Materials Science and Engineering: C, 2014Co-Authors: Yuen Kei Adarina Low, Xi Zou, Yuming Fang, Junling Wang, Weisi Lin, Freddy Yin Chiang BoeyAbstract:Abstract The piezoelectric response from β-phase poly(vinylidene fluoride) (PVDF) can potentially be exploited for biomedical application. We hypothesized that α and β-phase PVDF exert direct but different influence on cellular behavior. α- and β-phase PVDF films were synthesized through solution casting and characterized with FT-IR, XRD, AFM and PFM to ensure successful fabrication of α and β-phase PVDF films. Cellular evaluation with L929 mouse fibroblasts over one-week was conducted with AlamarBlue® metabolic assay and PicoGreen® proliferation assay. Immunostaining of fibronectin investigated the extent and distribution of extracellular matrix deposition. Image saliency analysis quantified differences in cellular distribution on the PVDF films. Our results showed that β-phase PVDF films with the largest area expressing piezoelectric effect elicited highest cell metabolic activity at day 3 of culture. Increased fibronectin adsorption towards the cell–Material Interface was shown on β-phase PVDF films. Image saliency analysis showed that fibroblasts on β-phase PVDF films were more homogeneously distributed than on α-phase PVDF films. Taken collectively, the different molecular packing of α and β-phase PVDF resulted in differing physical properties of films, which in turn induced differences in cellular behaviors. Further analysis of how α and β-phase PVDF may evoke specific cellular behavior to suit particular application will be intriguing.
Shane Keniley - One of the best experts on this subject based on the ideXlab platform.
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density estimation techniques for multiscale coupling of kinetic models of the plasma Material Interface
Journal of Computational Physics, 2020Co-Authors: Shane Keniley, Davide CurreliAbstract:Abstract In this work we analyze two classes of Density-Estimation techniques which can be used to consistently couple different kinetic models of the plasma-Material Interface, intended as the region of plasma immediately interacting with the first surface layers of a Material wall. In particular, we handle the general problem of interfacing a continuum multi-species Vlasov-Poisson-BGK plasma model to discrete surface erosion models. The continuum model solves for the energy-angle distributions of the particles striking the surface, which are then driving the surface response. A modification to the classical Binary-Collision Approximation (BCA) method is here utilized as a prototype discrete model of the surface, to provide boundary conditions and impurity distributions representative of the Material behavior during plasma irradiation. The numerical tests revealed the superior convergence properties of Gaussian Mixture Models over Kernel Density Estimation methods, with Gaussian Mixtures and Epanechnikov-KDEs both being up to two orders of magnitude faster than Gaussian-KDEs. The methodology here presented allows a self-consistent treatment of the plasma-Material Interface in magnetic fusion devices, including both the near-surface plasma (plasma sheath and presheath) in magnetized conditions, and surface effects such as sputtering, back-scattering, and ion implantation. The same coupling techniques can also be utilized for other discrete Material models such as Molecular Dynamics.
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density estimation techniques for multiscale coupling of kinetic models of the plasma Material Interface
arXiv: Computational Physics, 2018Co-Authors: Shane Keniley, Davide CurreliAbstract:In this work we analyze two classes of Density-Estimation techniques which can be used to consistently couple different kinetic models of the plasma-Material Interface, intended as the region of plasma immediately interacting with the first surface layers of a Material wall. In particular, we handle the general problem of interfacing a continuum multi-species Vlasov-Poisson-BGK plasma model to discrete surface erosion models. The continuum model solves for the energy-angle distributions of the particles striking the surface, which are then driving the surface response. A modification to the classical Binary-Collision Approximation (BCA) method is here utilized as a prototype discrete model of the surface, to provide boundary conditions and impurity distributions representative of the Material behavior during plasma irradiation. The numerical tests revealed the superior convergence properties of Kernel Density Estimation methods over Gaussian Mixture Models, with Epanechnikov-KDEs being up to two orders of magnitude faster than Gaussian-KDEs. The methodology here presented allows a self-consistent treatment of the plasma-Material Interface in magnetic fusion devices, including both the near-surface plasma (plasma sheath and presheath) in magnetized conditions, and surface effects such as sputtering, back-scattering, and ion implantation. The same coupling techniques can also be utilized for other discrete Material models such as Molecular Dynamics.
M A K Chowdhuri - One of the best experts on this subject based on the ideXlab platform.
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a new test method for the measurement of normal shear bonding strength at bi Material Interface
Mechanics of Advanced Materials and Structures, 2013Co-Authors: Zihui Xia, M A K ChowdhuriAbstract:This article presents a new test method, including specimen design, test procedure, and calculation algorithm, for more accurate and complete characterization of bonding strength property of bi-Material Interfaces. With the proposed method, the stress singularity at the free edge of the bi-Material Interface is effectively eliminated and the same specimen design can be used for tension, torsion, or combined tension-torsion tests. An iterative algorithm for computing the normal-shear bonding strength envelope from the test results is also developed. As an example, the epoxy-aluminum Interface strength envelope is determined by the proposed test method.
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Interface bonding strength measurement of a joint between elastic and viscoelastic Materials
Composites Part B-engineering, 2013Co-Authors: M A K ChowdhuriAbstract:Abstract Measurement of bi-Materials Interface bonding strength is crucial for the design and application of structures with two or more Materials since bi-Material Interface debonding is one of the major modes of failures for these structures. However, accurate determination of the Interface bonding strength is not an easy task due to the discontinuity of Material properties at the Interface. There may exist a stress singularity at the edges of bi-Material Interface, where the debonding usually initiates from. A new specimen design that can eliminate the stress singularity is proposed. In practical applications, the Interface failure often occurs under the actions of combined Interface normal and shear stresses. Therefore, a biaxial normal-shear bonding strength envelope is required for practical applications. This paper presents a new experimental method integrated with finite element analysis and an iterative algorithm to determine the Interface strength envelope between aluminum and epoxy polymer Materials, in which the former is considered as an elastic isotropic Material and the latter as a linear viscoelastic Material.
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an innovative method to determine bonding strength envelope based on theory of bi Material Interface mechanics
Procedia Engineering, 2011Co-Authors: M A K ChowdhuriAbstract:Abstract Bi-Material Interfaces exist in many advanced Materials and structures. Measurement of Interface bonding strength is more diffucult than measurement of strengths of homogeneous Materials because of the presence of stress singularity at the Interface corner, non uniform stress distribution along the Interface and co-existence of normal and shear stress components. The order of the stress singularity depends on the Interface geometry and Material combination. Besides pure tensile and pure shear strength, a general biaxial normal-shear bonding strength criterion, for example, in the form of a strength envelope in normal-shear stress plane, is prefered to more realistically and adequately characterize the strength property of bi-Material Interface. This paper presents a new test method to determine the Interface bonding strength envelope. The design of specimen geometry is based on an axi-symmetric asymptotic analysis on the stress field near the free edge of the bi-Material Interface, through which appropriate Interface bonding angle is chosen to eliminate the stress singularity. As an example, the epoxy-aluminum Interface strength envelope is determined by the new proposed method.
Yuen Kei Adarina Low - One of the best experts on this subject based on the ideXlab platform.
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β phase poly vinylidene fluoride films encouraged more homogeneous cell distribution and more significant deposition of fibronectin towards the cell Material Interface compared to α phase poly vinylidene fluoride films
Materials Science and Engineering: C, 2014Co-Authors: Yuen Kei Adarina Low, Xi Zou, Yuming Fang, Junling Wang, Weisi Lin, Freddy Yin Chiang BoeyAbstract:Abstract The piezoelectric response from β-phase poly(vinylidene fluoride) (PVDF) can potentially be exploited for biomedical application. We hypothesized that α and β-phase PVDF exert direct but different influence on cellular behavior. α- and β-phase PVDF films were synthesized through solution casting and characterized with FT-IR, XRD, AFM and PFM to ensure successful fabrication of α and β-phase PVDF films. Cellular evaluation with L929 mouse fibroblasts over one-week was conducted with AlamarBlue® metabolic assay and PicoGreen® proliferation assay. Immunostaining of fibronectin investigated the extent and distribution of extracellular matrix deposition. Image saliency analysis quantified differences in cellular distribution on the PVDF films. Our results showed that β-phase PVDF films with the largest area expressing piezoelectric effect elicited highest cell metabolic activity at day 3 of culture. Increased fibronectin adsorption towards the cell–Material Interface was shown on β-phase PVDF films. Image saliency analysis showed that fibroblasts on β-phase PVDF films were more homogeneously distributed than on α-phase PVDF films. Taken collectively, the different molecular packing of α and β-phase PVDF resulted in differing physical properties of films, which in turn induced differences in cellular behaviors. Further analysis of how α and β-phase PVDF may evoke specific cellular behavior to suit particular application will be intriguing.
