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He-ping Tan - One of the best experts on this subject based on the ideXlab platform.
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Discontinuous finite element method for vector Radiative Transfer
Journal of Quantitative Spectroscopy and Radiative Transfer, 2017Co-Authors: Cun-hai Wang, He-ping TanAbstract:Abstract The discontinuous finite element method (DFEM) is applied to solve the vector Radiative Transfer in participating media. The derivation in a discrete form of the vector radiation governing equations is presented, in which the angular space is discretized by the discrete-ordinates approach with a local refined modification, and the spatial domain is discretized into finite non-overlapped discontinuous elements. The elements in the whole solution domain are connected by modelling the boundary numerical flux between adjacent elements, which makes the DFEM numerically stable for solving Radiative Transfer equations. Several various problems of vector Radiative Transfer are tested to verify the performance of the developed DFEM, including vector Radiative Transfer in a one-dimensional parallel slab containing a Mie/Rayleigh/strong forward scattering medium and a two-dimensional square medium. The fact that DFEM results agree very well with the benchmark solutions in published references shows that the developed DFEM in this paper is accurate and effective for solving vector Radiative Transfer problems.
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Polarized Radiative Transfer in an arbitrary multilayer semitransparent medium
Applied Optics, 2014Co-Authors: Xun Ben, He-ping TanAbstract:Polarized Radiative Transfer in a multilayer system is an important problem and has wide applications in various fields. In this work, a Monte Carlo (MC) model is developed to simulate polarized Radiative Transfer in a semitransparent arbitrary multilayer medium with different refractive indices in each layer. Two kinds of polarization mechanisms are considered: scattering by particles and reflection and refraction at the Fresnel surfaces or interfaces. The MC method has an obvious superiority in that complex mathematical derivations can be avoided in solving the polarization by Fresnel reflection and refraction in an arbitrary multilayer system. We define the vector Radiative Transfer matrix (VRTM), which describes the polarization characteristics of Radiative Transfer, and obtain four elements of Stokes vector using the VRTM. The results for the two-layer model by MC method are compared against those for coupled atmosphere–ocean model by the discrete–ordinate method available in the literature, which validates the correctness of the MC multilayer model of polarized Radiative Transfer. Finally, the results for three-layer, five-layer, and ten-layer models are presented in graphical form. Results show that in the multilayer system, total reflections occurring at the surfaces/interfaces have significant effects on the polarized Radiative Transfer, which causes abrupt changes or fluctuations like waves in the curves of the Stokes vector.
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Transient Radiative Transfer in a scattering slab considering polarization.
Optics Express, 2013Co-Authors: Xun Ben, He-ping TanAbstract:The characteristics of the transient and polarization must be considered for a complete and correct description of short-pulse laser Transfer in a scattering medium. A Monte Carlo (MC) method combined with a time shift and superposition principle is developed to simulate transient vector (polarized) Radiative Transfer in a scattering medium. The transient vector Radiative Transfer matrix (TVRTM) is defined to describe the transient polarization behavior of short-pulse laser propagating in the scattering medium. According to the definition of reflectivity, a new criterion of reflection at Fresnel surface is presented. In order to improve the computational efficiency and accuracy, a time shift and superposition principle is applied to the MC model for transient vector Radiative Transfer. The results for transient scalar Radiative Transfer and steady-state vector Radiative Transfer are compared with those in published literatures, respectively, and an excellent agreement between them is observed, which validates the correctness of the present model. Finally, transient Radiative Transfer is simulated considering the polarization effect of short-pulse laser in a scattering medium, and the distributions of Stokes vector in angular and temporal space are presented.
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Recent progress in computational thermal Radiative Transfer
Chinese Science Bulletin, 2009Co-Authors: He-ping Tan, Linhua Liu, Junming Zhao, Jianyu TanAbstract:The equation describing the Transfer of radiant energy in semitransparent media is Radiative Transfer equation. In three-dimensional semitransparent media, Radiative intensity is a function of 7 dimensions, which can only be solved through the numerical method in most circumstances. Numerical simulation has become an important way in the study and application of the theory of thermal Radiative Transfer in semitransparent media. This paper reviews the recent progress of Chinese scholars in the field of computational thermal Radiative Transfer, and proposes some important subjects in this field for future study.
Jason Soderblom - One of the best experts on this subject based on the ideXlab platform.
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Spherical Radiative Transfer in C++ (SRTC++): A Parallel Monte Carlo Radiative Transfer Model for Titan
Astronomical Journal, 2018Co-Authors: Jason Barnes, Shannon Mackenzie, Eliot Young, Laura Trouille, Sébastien Rodriguez, Thomas Cornet, Brian Jackson, Máté Ádámkovics, Christophe Sotin, Jason SoderblomAbstract:We present a new computer program, SRTC++, to solve spatial problems associated with explorations of Saturn's moon Titan. The program implements a three-dimensional structure well-suited to addressing shortcomings arising from plane-parallel Radiative Transfer approaches. SRTC++ʼs design uses parallel processing in an object-oriented, compiled computer language (C++) leading to a flexible and fast architecture. We validate SRTC++ using analytical results, semianalytical Radiative Transfer expressions, and an existing Titan plane-parallel model. SRTC+ + complements existing approaches, addressing spatial problems like near-limb and near-terminator geometries, non-Lambertian surface phase functions (including specular reflections), and surface albedo nonuniformity.
Jason Barnes - One of the best experts on this subject based on the ideXlab platform.
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Spherical Radiative Transfer in C++ (SRTC++): A Parallel Monte Carlo Radiative Transfer Model for Titan
Astronomical Journal, 2018Co-Authors: Jason Barnes, Shannon Mackenzie, Eliot Young, Laura Trouille, Sébastien Rodriguez, Thomas Cornet, Brian Jackson, Máté Ádámkovics, Christophe Sotin, Jason SoderblomAbstract:We present a new computer program, SRTC++, to solve spatial problems associated with explorations of Saturn's moon Titan. The program implements a three-dimensional structure well-suited to addressing shortcomings arising from plane-parallel Radiative Transfer approaches. SRTC++ʼs design uses parallel processing in an object-oriented, compiled computer language (C++) leading to a flexible and fast architecture. We validate SRTC++ using analytical results, semianalytical Radiative Transfer expressions, and an existing Titan plane-parallel model. SRTC+ + complements existing approaches, addressing spatial problems like near-limb and near-terminator geometries, non-Lambertian surface phase functions (including specular reflections), and surface albedo nonuniformity.
Jp Kaipio - One of the best experts on this subject based on the ideXlab platform.
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Utilising the coupled Radiative Transfer - diffusion model in diffuse optical tomography
Diffuse Optical Imaging IV, 2013Co-Authors: Tanja Tarvainen, Jp Kaipio, Ville Kolehmainen, Ossi Lehtikangas, Simon R. ArridgeAbstract:The coupled Radiative Transfer - diffusion model can be used as light transport model in turbid media with non-diffusive regions. In the coupled Radiative Transfer - diffusion model, light propagation is modelled with the Radiative Transfer equation in sub-domains in which the approximations of the diffusion equation are not valid and the diffusion approximation is used elsewhere in the domain. In this work, the image reconstruction problem of diffuse optical tomography utilising the coupled Radiative Transfer - diffusion model is considered. Absorption and scattering distributions are estimated using the coupled Radiative Transfer - diffusion model as a forward model for light propagation. The results are compared to reconstructions obtained using other light transport models. The results show that the coupled Radiative Transfer - diffusion model can produce as good estimates for absorption and scattering as the full Radiative Transfer equation also in situations in which the approximations of the diffusion equation are not valid.
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Utilizing the Radiative Transfer equation in optical tomography
PIERS Online, 2008Co-Authors: Tanja Tarvainen, Jp Kaipio, Marko Vauhkonen, Ville Kolehmainen, Simon R. ArridgeAbstract:We propose a method which utilizes the Radiative Transfer equation in optical tomography. In this approach, the Radiative Transfer equation is used as light propagation model in those regions in which the assumptions of the diffusion theory are not valid and the diffusion approximation is used elsewhere. Both the Radiative Transfer equation and the diffusion approximation are numerically solved with a finite element method. In the finite element solution of the Radiative Transfer equation, both the spatial and angular discretizations are implemented in piecewise linear bases.
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Coupled Radiative Transfer Equation and Diffusion Approximation
Photon Migration and Diffuse-Light Imaging II, 2005Co-Authors: Tanja Tarvainen, Marko Vauhkonen, Ville Kolehmainen, Jp KaipioAbstract:A coupled Radiative Transfer equation and diffusion approximation model for photon migration in tissues is proposed. The light propagation is modeled with the Radiative Transfer equation in sub-domains in which the assumptions of the diffusion approximation are not valid and the diffusion approximation is used elsewhere in the domain. The coupled equations are solved using the finite element method. The proposed method is tested with simulations. The results of the coupled Radiative Transfer equation and diffusion approximation model are compared with the finite element solutions of the Radiative Transfer equation and the diffusion approximation. The results show that the coupled Radiative Transfer equation and diffusion approximation model can be used to describe photon migration in tissues more accurately than the conventional diffusion model.
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Hybrid Radiative-Transfer-diffusion model for optical tomography.
Applied Optics, 2005Co-Authors: Tanja Tarvainen, Marko Vauhkonen, Ville Kolehmainen, Jp KaipioAbstract:A hybrid Radiative-Transfer–diffusion model for optical tomography is proposed. The light propagation is modeled with the Radiative-Transfer equation in the vicinity of the laser sources, and the diffusion approximation is used elsewhere in the domain. The solution of the Radiative-Transfer equation is used to construct a Dirichlet boundary condition for the diffusion approximation on a fictitious interface within the object. This boundary condition constitutes an approximative distributed source model for the diffusion approximation in the remaining area. The results from the proposed approach are compared with finite-element solutions of the Radiative-Transfer equation and the diffusion approximation and Monte Carlo simulation. The results show that the method improves the accuracy of the forward model compared with the conventional diffusion model.
Tanja Tarvainen - One of the best experts on this subject based on the ideXlab platform.
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Utilising the coupled Radiative Transfer - diffusion model in diffuse optical tomography
Diffuse Optical Imaging IV, 2013Co-Authors: Tanja Tarvainen, Jp Kaipio, Ville Kolehmainen, Ossi Lehtikangas, Simon R. ArridgeAbstract:The coupled Radiative Transfer - diffusion model can be used as light transport model in turbid media with non-diffusive regions. In the coupled Radiative Transfer - diffusion model, light propagation is modelled with the Radiative Transfer equation in sub-domains in which the approximations of the diffusion equation are not valid and the diffusion approximation is used elsewhere in the domain. In this work, the image reconstruction problem of diffuse optical tomography utilising the coupled Radiative Transfer - diffusion model is considered. Absorption and scattering distributions are estimated using the coupled Radiative Transfer - diffusion model as a forward model for light propagation. The results are compared to reconstructions obtained using other light transport models. The results show that the coupled Radiative Transfer - diffusion model can produce as good estimates for absorption and scattering as the full Radiative Transfer equation also in situations in which the approximations of the diffusion equation are not valid.
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Utilizing the Radiative Transfer equation in optical tomography
PIERS Online, 2008Co-Authors: Tanja Tarvainen, Jp Kaipio, Marko Vauhkonen, Ville Kolehmainen, Simon R. ArridgeAbstract:We propose a method which utilizes the Radiative Transfer equation in optical tomography. In this approach, the Radiative Transfer equation is used as light propagation model in those regions in which the assumptions of the diffusion theory are not valid and the diffusion approximation is used elsewhere. Both the Radiative Transfer equation and the diffusion approximation are numerically solved with a finite element method. In the finite element solution of the Radiative Transfer equation, both the spatial and angular discretizations are implemented in piecewise linear bases.
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Coupled Radiative Transfer Equation and Diffusion Approximation
Photon Migration and Diffuse-Light Imaging II, 2005Co-Authors: Tanja Tarvainen, Marko Vauhkonen, Ville Kolehmainen, Jp KaipioAbstract:A coupled Radiative Transfer equation and diffusion approximation model for photon migration in tissues is proposed. The light propagation is modeled with the Radiative Transfer equation in sub-domains in which the assumptions of the diffusion approximation are not valid and the diffusion approximation is used elsewhere in the domain. The coupled equations are solved using the finite element method. The proposed method is tested with simulations. The results of the coupled Radiative Transfer equation and diffusion approximation model are compared with the finite element solutions of the Radiative Transfer equation and the diffusion approximation. The results show that the coupled Radiative Transfer equation and diffusion approximation model can be used to describe photon migration in tissues more accurately than the conventional diffusion model.
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Hybrid Radiative-Transfer-diffusion model for optical tomography.
Applied Optics, 2005Co-Authors: Tanja Tarvainen, Marko Vauhkonen, Ville Kolehmainen, Jp KaipioAbstract:A hybrid Radiative-Transfer–diffusion model for optical tomography is proposed. The light propagation is modeled with the Radiative-Transfer equation in the vicinity of the laser sources, and the diffusion approximation is used elsewhere in the domain. The solution of the Radiative-Transfer equation is used to construct a Dirichlet boundary condition for the diffusion approximation on a fictitious interface within the object. This boundary condition constitutes an approximative distributed source model for the diffusion approximation in the remaining area. The results from the proposed approach are compared with finite-element solutions of the Radiative-Transfer equation and the diffusion approximation and Monte Carlo simulation. The results show that the method improves the accuracy of the forward model compared with the conventional diffusion model.
