The Experts below are selected from a list of 270 Experts worldwide ranked by ideXlab platform

Keke Zhang - One of the best experts on this subject based on the ideXlab platform.

  • Simulations of Fluid Motion in ellipsoidal planetary cores driven by longitudinal libration
    Physics of the Earth and Planetary Interiors, 2020
    Co-Authors: Kit H. Chan, Xinhao Liao, Keke Zhang
    Abstract:

    Deformed by tidal forces, the cavity of a planetary Fluid core may be in the shape of a biaxial ellipsoid x 2/a 2+y 2/b 2+z 2/a 2=1, where a and b are two different semi-axes and z is in the direction of rotation. Gravitational interaction between a planet and its parent star exerts an axial torque on the planet and forces its longitudinal libration, a periodic variation of its angular velocity around its rotating axis. Longitudinal libration drives Fluid Motion in the planetary core via both viscous and topographic coupling between the mantle and Fluid. For an arbitrary size of the equatorial eccentricity E=√a 2-b 2/a, direct numerical simulation of the fully nonlinear problem is carried out using an EBE (Element-By-Element) finite element method. It is shown that Fluid Motion driven by longitudinal libration vacillates between two different phases: a prograde phase when the planet's rotation speeds up and a retrograde phase when it slows down. For weak longitudinal libration, the Fluid Motion is laminar without exhibiting noticeable differences between the two phases and a multi-layered, time-independent, nearly geostrophic mean flow can be generated and maintained by longitudinal libration in a biaxial or triaxial ellipsoidal cavity. For strong slow libration, there are profound differences between the two different phases: the retrograde phase is usually marked by Fluid Motion with instabilities and complex spatial structure while in the prograde phase the flow is still largely laminar. © 2011 Elsevier B.V.link_to_subscribed_fulltex

  • Simulations of Fluid Motion in spheroidal planetary cores driven by latitudinal libration
    Physics of the Earth and Planetary Interiors, 2020
    Co-Authors: Kit H. Chan, Xinhao Liao, Keke Zhang
    Abstract:

    The Motion of a homogeneous viscous Fluid confined in a latitudinally librating, oblate spheroidal cavity with arbitrary eccentricity γ is investigated via direct three-dimensional numerical simulation using an EBE (Element-By-Element) finite element method. When the spheroidal cavity has moderate or large eccentricity with topographic coupling being dominant, an inviscid analytical solution describing the Fluid Motion driven by latitudinal libration is derived for the purpose of illustrating the nature of the Fluid Motion. It suggests that, in contrast to the Fluid Motion driven by longitudinal libration in ellipsoidal cavities, resonance of a spheroidal inertial wave mode with azimuthal wavenumber m=1 can occur when the non-dimensional frequency of forced latitudinal libration is close to ω resonance=2/(2-γ 2), as predicted by the inviscid analytical solution. Three-dimensional direct numerical simulation at non-resonant frequencies, which includes the full effect of viscosity and nonlinearity, is carried out, showing a satisfactory agreement between the inviscid analytical solution and the numerical simulation. Emphasis of the numerical simulation is then placed on the strongly nonlinear librating flow at the exact resonance. The simulation reveals the existence of strong retrograde mean zonal flow due to nonlinear effects in the viscous boundary layer and different profiles of the zonal flow dependent upon the size of the libration frequency. Implications of the result for planetary evolution are also discussed. © 2011 Elsevier B.V.link_to_subscribed_fulltex

  • simulations of Fluid Motion in spheroidal planetary cores driven by latitudinal libration
    Physics of the Earth and Planetary Interiors, 2011
    Co-Authors: Kit H. Chan, Xinhao Liao, Keke Zhang
    Abstract:

    The Motion of a homogeneous viscous Fluid confined in a latitudinally librating, oblate spheroidal cavity with arbitrary eccentricity gamma is investigated via direct three-dimensional numerical simulation using an EBE (Element-By-Element) finite element method. When the spheroidal cavity has moderate or large eccentricity with topographic coupling being dominant, an inviscid analytical solution describing the Fluid Motion driven by latitudinal libration is derived for the purpose of illustrating the nature of the Fluid Motion. It suggests that, in contrast to the Fluid Motion driven by longitudinal libration in ellipsoidal cavities, resonance of a spheroidal inertial wave mode with azimuthal wavenumber m = 1 can occur when the non-dimensional frequency of forced latitudinal libration is close to omega(resonance) = 2/(2 - gamma(2)), as predicted by the inviscid analytical solution. Three-dimensional direct numerical simulation at non-resonant frequencies, which includes the full effect of viscosity and nonlinearity, is carried out, showing a satisfactory agreement between the inviscid analytical solution and the numerical simulation. Emphasis of the numerical simulation is then placed on the strongly nonlinear librating flow at the exact resonance. The simulation reveals the existence of strong retrograde mean zonal flow due to nonlinear effects in the viscous boundary layer and different profiles of the zonal flow dependent upon the size of the libration frequency. Implications of the result for planetary evolution are also discussed. (C) 2011 Elsevier B.V. All rights reserved.

D.b. Goldgof - One of the best experts on this subject based on the ideXlab platform.

  • Structure and semi-Fluid Motion analysis of stereoscopic satellite images for cloud tracking
    Proceedings of IEEE International Conference on Computer Vision, 1995
    Co-Authors: K. Palaniappan, C. Kambhamettu, A.f. Hasler, D.b. Goldgof
    Abstract:

    Time-varying multispectral observations of clouds from meteorological satellites are used to estimate cloud-top heights (structure) and cloud winds (semi-Fluid Motion). Stereo image pairs over several time steps were acquired by two geostationary satellites with synchronized scanning instruments. Cloud-top height estimation from these image pairs is performed using an improved automatic stereo analysis algorithm on a massively parallel Maspar computer with 16 K processors. A new category of Motion behavior known as semi-Fluid Motion is described for modeling cloud Motions and an automatic algorithm for extracting semi-Fluid Motion is developed to track cloud winds. The time sequential dense estimates of cloud-top height depth maps in conjunction with intensity data are used to estimate local semi-Fluid Motion parameters for cloud tracking. Both stereo disparities and Motion correspondences are estimated to sub-pixel accuracy. The Interactive Image SpreadSheet (IISS) is a new versatile visualization tool that was enhanced to analyze and visualize the results of the stereo analysis and semi-Fluid Motion estimation algorithms. Experimental results using time-varying data of the visible channel from two satellites in geosynchronous orbit is presented for the Hurricane Frederic.

  • ICCV - Structure and semi-Fluid Motion analysis of stereoscopic satellite images for cloud tracking
    Proceedings of IEEE International Conference on Computer Vision, 1995
    Co-Authors: K. Palaniappan, C. Kambhamettu, A.f. Hasler, D.b. Goldgof
    Abstract:

    Time-varying multispectral observations of clouds from meteorological satellites are used to estimate cloud-top heights (structure) and cloud winds (semi-Fluid Motion). Stereo image pairs over several time steps were acquired by two geostationary satellites with synchronized scanning instruments. Cloud-top height estimation from these image pairs is performed using an improved automatic stereo analysis algorithm on a massively parallel Maspar computer with 16 K processors. A new category of Motion behavior known as semi-Fluid Motion is described for modeling cloud Motions and an automatic algorithm for extracting semi-Fluid Motion is developed to track cloud winds. The time sequential dense estimates of cloud-top height depth maps in conjunction with intensity data are used to estimate local semi-Fluid Motion parameters for cloud tracking. Both stereo disparities and Motion correspondences are estimated to sub-pixel accuracy. The Interactive Image SpreadSheet (IISS) is a new versatile visualization tool that was enhanced to analyze and visualize the results of the stereo analysis and semi-Fluid Motion estimation algorithms. Experimental results using time-varying data of the visible channel from two satellites in geosynchronous orbit is presented for the Hurricane Frederic. >

K. Palaniappan - One of the best experts on this subject based on the ideXlab platform.

  • IPPS - Implementation of an automatic semi-Fluid Motion analysis algorithm on a massively parallel computer
    Proceedings of International Conference on Parallel Processing, 1996
    Co-Authors: K. Palaniappan, C. Kambhamettu, M. Faisal, A.f. Hasler
    Abstract:

    The implementation of a parallel algorithm for estimating non-rigid Motion vectors using a semi-Fluid Motion model applied to time-varying satellite imagery is described. Deformable Motion tracking of non-rigid biological objects and remotely-sensed objects, such as clouds, atmospheric aerosols and gases, polar sea ice or ocean currents, are important application domains for the semi-Fluid Motion analysis (SMA) algorithm. The focus of this paper is on the parallelization of the SMA algorithm for the MasPar MP-2 architecture. Implementation issues that were evaluated in order to make it feasible to explore dense semi-Fluid Motion estimates of rapid-scan time-varying geostationary satellite imagery of clouds and weather patterns are described. Cloud Motion vectors from the SMA algorithm can be used to estimate the wind field that would be useful in a variety of meteorological applications. Comparisons between the parallel and sequential implementations of the SMA algorithm and with manual results are briefly discussed.

  • Structure and semi-Fluid Motion analysis of stereoscopic satellite images for cloud tracking
    Proceedings of IEEE International Conference on Computer Vision, 1995
    Co-Authors: K. Palaniappan, C. Kambhamettu, A.f. Hasler, D.b. Goldgof
    Abstract:

    Time-varying multispectral observations of clouds from meteorological satellites are used to estimate cloud-top heights (structure) and cloud winds (semi-Fluid Motion). Stereo image pairs over several time steps were acquired by two geostationary satellites with synchronized scanning instruments. Cloud-top height estimation from these image pairs is performed using an improved automatic stereo analysis algorithm on a massively parallel Maspar computer with 16 K processors. A new category of Motion behavior known as semi-Fluid Motion is described for modeling cloud Motions and an automatic algorithm for extracting semi-Fluid Motion is developed to track cloud winds. The time sequential dense estimates of cloud-top height depth maps in conjunction with intensity data are used to estimate local semi-Fluid Motion parameters for cloud tracking. Both stereo disparities and Motion correspondences are estimated to sub-pixel accuracy. The Interactive Image SpreadSheet (IISS) is a new versatile visualization tool that was enhanced to analyze and visualize the results of the stereo analysis and semi-Fluid Motion estimation algorithms. Experimental results using time-varying data of the visible channel from two satellites in geosynchronous orbit is presented for the Hurricane Frederic.

  • ICCV - Structure and semi-Fluid Motion analysis of stereoscopic satellite images for cloud tracking
    Proceedings of IEEE International Conference on Computer Vision, 1995
    Co-Authors: K. Palaniappan, C. Kambhamettu, A.f. Hasler, D.b. Goldgof
    Abstract:

    Time-varying multispectral observations of clouds from meteorological satellites are used to estimate cloud-top heights (structure) and cloud winds (semi-Fluid Motion). Stereo image pairs over several time steps were acquired by two geostationary satellites with synchronized scanning instruments. Cloud-top height estimation from these image pairs is performed using an improved automatic stereo analysis algorithm on a massively parallel Maspar computer with 16 K processors. A new category of Motion behavior known as semi-Fluid Motion is described for modeling cloud Motions and an automatic algorithm for extracting semi-Fluid Motion is developed to track cloud winds. The time sequential dense estimates of cloud-top height depth maps in conjunction with intensity data are used to estimate local semi-Fluid Motion parameters for cloud tracking. Both stereo disparities and Motion correspondences are estimated to sub-pixel accuracy. The Interactive Image SpreadSheet (IISS) is a new versatile visualization tool that was enhanced to analyze and visualize the results of the stereo analysis and semi-Fluid Motion estimation algorithms. Experimental results using time-varying data of the visible channel from two satellites in geosynchronous orbit is presented for the Hurricane Frederic. >

A.f. Hasler - One of the best experts on this subject based on the ideXlab platform.

  • Implementation of an automatic semi-Fluid Motion analysis algorithm on a massively parallel computer
    Proceedings of International Conference on Parallel Processing, 1996
    Co-Authors: K. Palaniappan, M. Faisal, C. Kambhamettu, A.f. Hasler
    Abstract:

    The implementation of a parallel algorithm for estimating non-rigid Motion vectors using a semi-Fluid Motion model applied to time-varying satellite imagery is described. Deformable Motion tracking of non-rigid biological objects and remotely-sensed objects, such as clouds, atmospheric aerosols and gases, polar sea ice or ocean currents, are important application domains for the semi-Fluid Motion analysis (SMA) algorithm. The focus of this paper is on the parallelization of the SMA algorithm for the MasPar MP-2 architecture. Implementation issues that were evaluated in order to make it feasible to explore dense semi-Fluid Motion estimates of rapid-scan time-varying geostationary satellite imagery of clouds and weather patterns are described. Cloud Motion vectors from the SMA algorithm can be used to estimate the wind field that would be useful in a variety of meteorological applications. Comparisons between the parallel and sequential implementations of the SMA algorithm and with manual results are briefly discussed.

  • IPPS - Implementation of an automatic semi-Fluid Motion analysis algorithm on a massively parallel computer
    Proceedings of International Conference on Parallel Processing, 1996
    Co-Authors: K. Palaniappan, C. Kambhamettu, M. Faisal, A.f. Hasler
    Abstract:

    The implementation of a parallel algorithm for estimating non-rigid Motion vectors using a semi-Fluid Motion model applied to time-varying satellite imagery is described. Deformable Motion tracking of non-rigid biological objects and remotely-sensed objects, such as clouds, atmospheric aerosols and gases, polar sea ice or ocean currents, are important application domains for the semi-Fluid Motion analysis (SMA) algorithm. The focus of this paper is on the parallelization of the SMA algorithm for the MasPar MP-2 architecture. Implementation issues that were evaluated in order to make it feasible to explore dense semi-Fluid Motion estimates of rapid-scan time-varying geostationary satellite imagery of clouds and weather patterns are described. Cloud Motion vectors from the SMA algorithm can be used to estimate the wind field that would be useful in a variety of meteorological applications. Comparisons between the parallel and sequential implementations of the SMA algorithm and with manual results are briefly discussed.

  • Structure and semi-Fluid Motion analysis of stereoscopic satellite images for cloud tracking
    Proceedings of IEEE International Conference on Computer Vision, 1995
    Co-Authors: K. Palaniappan, C. Kambhamettu, A.f. Hasler, D.b. Goldgof
    Abstract:

    Time-varying multispectral observations of clouds from meteorological satellites are used to estimate cloud-top heights (structure) and cloud winds (semi-Fluid Motion). Stereo image pairs over several time steps were acquired by two geostationary satellites with synchronized scanning instruments. Cloud-top height estimation from these image pairs is performed using an improved automatic stereo analysis algorithm on a massively parallel Maspar computer with 16 K processors. A new category of Motion behavior known as semi-Fluid Motion is described for modeling cloud Motions and an automatic algorithm for extracting semi-Fluid Motion is developed to track cloud winds. The time sequential dense estimates of cloud-top height depth maps in conjunction with intensity data are used to estimate local semi-Fluid Motion parameters for cloud tracking. Both stereo disparities and Motion correspondences are estimated to sub-pixel accuracy. The Interactive Image SpreadSheet (IISS) is a new versatile visualization tool that was enhanced to analyze and visualize the results of the stereo analysis and semi-Fluid Motion estimation algorithms. Experimental results using time-varying data of the visible channel from two satellites in geosynchronous orbit is presented for the Hurricane Frederic.

  • ICCV - Structure and semi-Fluid Motion analysis of stereoscopic satellite images for cloud tracking
    Proceedings of IEEE International Conference on Computer Vision, 1995
    Co-Authors: K. Palaniappan, C. Kambhamettu, A.f. Hasler, D.b. Goldgof
    Abstract:

    Time-varying multispectral observations of clouds from meteorological satellites are used to estimate cloud-top heights (structure) and cloud winds (semi-Fluid Motion). Stereo image pairs over several time steps were acquired by two geostationary satellites with synchronized scanning instruments. Cloud-top height estimation from these image pairs is performed using an improved automatic stereo analysis algorithm on a massively parallel Maspar computer with 16 K processors. A new category of Motion behavior known as semi-Fluid Motion is described for modeling cloud Motions and an automatic algorithm for extracting semi-Fluid Motion is developed to track cloud winds. The time sequential dense estimates of cloud-top height depth maps in conjunction with intensity data are used to estimate local semi-Fluid Motion parameters for cloud tracking. Both stereo disparities and Motion correspondences are estimated to sub-pixel accuracy. The Interactive Image SpreadSheet (IISS) is a new versatile visualization tool that was enhanced to analyze and visualize the results of the stereo analysis and semi-Fluid Motion estimation algorithms. Experimental results using time-varying data of the visible channel from two satellites in geosynchronous orbit is presented for the Hurricane Frederic. >

Kit H. Chan - One of the best experts on this subject based on the ideXlab platform.

  • Simulations of Fluid Motion in ellipsoidal planetary cores driven by longitudinal libration
    Physics of the Earth and Planetary Interiors, 2020
    Co-Authors: Kit H. Chan, Xinhao Liao, Keke Zhang
    Abstract:

    Deformed by tidal forces, the cavity of a planetary Fluid core may be in the shape of a biaxial ellipsoid x 2/a 2+y 2/b 2+z 2/a 2=1, where a and b are two different semi-axes and z is in the direction of rotation. Gravitational interaction between a planet and its parent star exerts an axial torque on the planet and forces its longitudinal libration, a periodic variation of its angular velocity around its rotating axis. Longitudinal libration drives Fluid Motion in the planetary core via both viscous and topographic coupling between the mantle and Fluid. For an arbitrary size of the equatorial eccentricity E=√a 2-b 2/a, direct numerical simulation of the fully nonlinear problem is carried out using an EBE (Element-By-Element) finite element method. It is shown that Fluid Motion driven by longitudinal libration vacillates between two different phases: a prograde phase when the planet's rotation speeds up and a retrograde phase when it slows down. For weak longitudinal libration, the Fluid Motion is laminar without exhibiting noticeable differences between the two phases and a multi-layered, time-independent, nearly geostrophic mean flow can be generated and maintained by longitudinal libration in a biaxial or triaxial ellipsoidal cavity. For strong slow libration, there are profound differences between the two different phases: the retrograde phase is usually marked by Fluid Motion with instabilities and complex spatial structure while in the prograde phase the flow is still largely laminar. © 2011 Elsevier B.V.link_to_subscribed_fulltex

  • Simulations of Fluid Motion in spheroidal planetary cores driven by latitudinal libration
    Physics of the Earth and Planetary Interiors, 2020
    Co-Authors: Kit H. Chan, Xinhao Liao, Keke Zhang
    Abstract:

    The Motion of a homogeneous viscous Fluid confined in a latitudinally librating, oblate spheroidal cavity with arbitrary eccentricity γ is investigated via direct three-dimensional numerical simulation using an EBE (Element-By-Element) finite element method. When the spheroidal cavity has moderate or large eccentricity with topographic coupling being dominant, an inviscid analytical solution describing the Fluid Motion driven by latitudinal libration is derived for the purpose of illustrating the nature of the Fluid Motion. It suggests that, in contrast to the Fluid Motion driven by longitudinal libration in ellipsoidal cavities, resonance of a spheroidal inertial wave mode with azimuthal wavenumber m=1 can occur when the non-dimensional frequency of forced latitudinal libration is close to ω resonance=2/(2-γ 2), as predicted by the inviscid analytical solution. Three-dimensional direct numerical simulation at non-resonant frequencies, which includes the full effect of viscosity and nonlinearity, is carried out, showing a satisfactory agreement between the inviscid analytical solution and the numerical simulation. Emphasis of the numerical simulation is then placed on the strongly nonlinear librating flow at the exact resonance. The simulation reveals the existence of strong retrograde mean zonal flow due to nonlinear effects in the viscous boundary layer and different profiles of the zonal flow dependent upon the size of the libration frequency. Implications of the result for planetary evolution are also discussed. © 2011 Elsevier B.V.link_to_subscribed_fulltex

  • simulations of Fluid Motion in spheroidal planetary cores driven by latitudinal libration
    Physics of the Earth and Planetary Interiors, 2011
    Co-Authors: Kit H. Chan, Xinhao Liao, Keke Zhang
    Abstract:

    The Motion of a homogeneous viscous Fluid confined in a latitudinally librating, oblate spheroidal cavity with arbitrary eccentricity gamma is investigated via direct three-dimensional numerical simulation using an EBE (Element-By-Element) finite element method. When the spheroidal cavity has moderate or large eccentricity with topographic coupling being dominant, an inviscid analytical solution describing the Fluid Motion driven by latitudinal libration is derived for the purpose of illustrating the nature of the Fluid Motion. It suggests that, in contrast to the Fluid Motion driven by longitudinal libration in ellipsoidal cavities, resonance of a spheroidal inertial wave mode with azimuthal wavenumber m = 1 can occur when the non-dimensional frequency of forced latitudinal libration is close to omega(resonance) = 2/(2 - gamma(2)), as predicted by the inviscid analytical solution. Three-dimensional direct numerical simulation at non-resonant frequencies, which includes the full effect of viscosity and nonlinearity, is carried out, showing a satisfactory agreement between the inviscid analytical solution and the numerical simulation. Emphasis of the numerical simulation is then placed on the strongly nonlinear librating flow at the exact resonance. The simulation reveals the existence of strong retrograde mean zonal flow due to nonlinear effects in the viscous boundary layer and different profiles of the zonal flow dependent upon the size of the libration frequency. Implications of the result for planetary evolution are also discussed. (C) 2011 Elsevier B.V. All rights reserved.