Arbitrary Volume

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Y C Shiah - One of the best experts on this subject based on the ideXlab platform.

  • boundary element modeling of 3d anisotropic heat conduction involving Arbitrary Volume heat source
    Mathematical and Computer Modelling, 2011
    Co-Authors: Y C Shiah
    Abstract:

    Abstract This article presents a BIE (Boundary Integral Equation) modeling that applies the technique of domain mapping (Shiah and Tan (1998) [12] ) as well as MRM (Multiple Reciprocity Method (Nowak (1989) [10] )) to treat the problem of 3D anisotropic heat conduction involving Arbitrary Volume heat source. By the domain mapping technique, the original function of the Volume heat source is accordingly transformed to a new function defined in the mapped domain. As a result of applying MRM, the Volume integral arising from the transformed heat source is transformed into a series of boundary integrals. At the end of this paper, three numerical examples are presented to show the veracity and accuracy of the proposed algorithm. Also, the convergence of the transformed boundary integrals is also investigated for different types of Volume heat source functions.

  • anisotropic heat conduction involving internal Arbitrary Volume heat generation rate
    International Communications in Heat and Mass Transfer, 2002
    Co-Authors: Y C Shiah
    Abstract:

    In this article, the problem of anisotropic heat conduction involving internal Arbitrary Volume heat generation rate is solved by the boundary element method. In the direct formulation for the boundary element analysis ofheat conduction problems, the presence of a Volume heat source will give rise to a domain integral, which conventionally demands internal cell discretisation throughout the whole domain. However, this domain discretisation will destroy the distinctive feature of the boundary element method as a boundary solution technique. In this paper, the multiple reciprocity method in conjunction with the standard characteristics method is employed to exactly transform the domain integral into a series of boundary ones. The distribution of heat generation in a Volume heat source could be in an Arbitrary form of a continuous function. After the anisotropic heat conduction problem is iteratively solved in the mapped plane, the obtained numerical solution is thereafter interpolated and transformed back to the one in the physical domain.

Albert Macovski - One of the best experts on this subject based on the ideXlab platform.

  • rapid fully automatic Arbitrary Volume in vivo shimming
    Magnetic Resonance in Medicine, 1991
    Co-Authors: Peter Webb, Albert Macovski
    Abstract:

    MR spectroscopy and many MR imaging methods benefit from a well-shimmed magnet. We have developed a pulse sequence which enables fast and accurate measurement of three-dimensional field maps in vivo, and a data analysis package that allows calculation of shim currents to optimally shim Arbitrary selected Volumes. A data link to the shim power supply allows automatic update of currents. No intervention by the operator is required. Typical in vivo shimming time is less than 5 min. Performance analysis, phantom, and in vivo results are presented. © 1991 Academic Press, Inc.

  • Rapid, fully automatic, ArbitraryVolume in vivo shimming
    Magnetic Resonance in Medicine, 1991
    Co-Authors: Peter Webb, Albert Macovski
    Abstract:

    MR spectroscopy and many MR imaging methods benefit from a well-shimmed magnet. We have developed a pulse sequence which enables fast and accurate measurement of three-dimensional field maps in vivo, and a data analysis package that allows calculation of shim currents to optimally shim Arbitrary selected Volumes. A data link to the shim power supply allows automatic update of currents. No intervention by the operator is required. Typical in vivo shimming time is less than 5 min. Performance analysis, phantom, and in vivo results are presented. © 1991 Academic Press, Inc.

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

  • Bifurcation diagrams of axisymmetric liquid bridges subjected to axial electric fields
    Physics of Fluids, 1994
    Co-Authors: Antonio Ramos, H. González, A Castellanos
    Abstract:

    The stability of dielectric liquid bridges between plane parallel electrodes when an electric potential difference is applied between them is studied for an axisymmetric configuration regarding Arbitrary Volume, axial gravity, and unequal coaxial anchoring disks attached to the electrodes. The stability is determined from the bifurcation diagrams related to the static problem. Two mathematical approaches are presented which are different in scope. First, the Lyapunov–Schmidt projection technique is applied to give the liquid bridge bifurcation diagrams for the bridge considered as an imperfect cylindrical one. The imperfection parameters, i.e., the relative difference of radii to the mean diameter, the deviation from the cylindrical Volume, and the gravitational Bond number, are assumed to be small. Second, a Galerkin/finite element technique is used to obtain numerically bifurcation diagrams for Arbitrary values of all the parameters. Agreement between both methods is good for small enough values of the ...

  • bifurcation diagrams of axisymmetric liquid bridges of Arbitrary Volume in electric and gravitational axial fields
    Journal of Fluid Mechanics, 1993
    Co-Authors: Antonio Ramos, A Castellanos
    Abstract:

    Finite-amplitude bifurcation diagrams of axisymmetric liquid bridges anchored between two plane parallel electrodes subjected to a potential difference and in the presence of an axial gravity field are found by solving simultaneously the Laplace equation for the electric potential and the Young–Laplace equation for the interface by means of the Galerkin/finite element method. Results show the strong stabilizing effect of the electric field, which plays a role somewhat similar to the inverse of the slenderness. It is also shown that the electric field may determine whether the breaking of the liquid bridge leads to two equal or unequal drops. Finally, the sensitivity of liquid bridges to an axial gravity in the presence of the electric field is studied.

Jiseong Barg - One of the best experts on this subject based on the ideXlab platform.

  • rapid theoretically artifact free calculation of static magnetic field induced by voxelated susceptibility distribution in an Arbitrary Volume of interest
    Magnetic Resonance in Medicine, 2018
    Co-Authors: Seonha Hwang, Jiseong Barg
    Abstract:

    PURPOSE: To demonstrate a computationally efficient and theoretically artifact-free method to calculate static field (B0 ) inhomogeneity in a Volume of interest induced by an Arbitrary voxelated susceptibility distribution. METHODS: Our method computes B0 by circular convolution between a zero-filled susceptibility matrix and a shifted, voxel-integrated dipolar field kernel on a grid of size NS +NT - 1 in each dimension, where NS and NT are the sizes of the susceptibility source and B0 target grids, respectively. The computational resource requirement is independent of source-target separation. The method, called generalized susceptibility voxel convolution, is demonstrated on three susceptibility models: an ellipsoid, MR-compatible screws, and a dynamic human heartbeat model. RESULTS: B0 in an ellipsoid calculated by generalized susceptibility voxel convolution matched an analytical solution nearly exactly. The method also calculated screw-induced B0 in agreement with experimental data. Dynamic simulation demonstrated its computational efficiency for repeated B0 calculations on time-varying susceptibility. On the contrary, conventional and alias-subtracted k-space-discretized Fourier convolution methods showed nonnegligible aliasing and Gibbs ringing artifacts in the tested models. CONCLUSION: Generalized susceptibility voxel convolution can be a fast and reliable way to compute susceptibility-induced B0 when the susceptibility source is not colocated with the B0 target Volume of interest, as in modeling B0 variations from motion and foreign objects.

  • Rapid, theoretically artifact‐free calculation of static magnetic field induced by voxelated susceptibility distribution in an Arbitrary Volume of interest
    Magnetic Resonance in Medicine, 2018
    Co-Authors: Seonha Hwang, Jiseong Barg
    Abstract:

    To demonstrate a computationally efficient and theoretically artifact-free method to calculate static field (B0 ) inhomogeneity in a Volume of interest induced by an Arbitrary voxelated susceptibility distribution. Our method computes B0 by circular convolution between a zero-filled susceptibility matrix and a shifted, voxel-integrated dipolar field kernel on a grid of size NS +NT - 1 in each dimension, where NS and NT are the sizes of the susceptibility source and B0 target grids, respectively. The computational resource requirement is independent of source-target separation. The method, called generalized susceptibility voxel convolution, is demonstrated on three susceptibility models: an ellipsoid, MR-compatible screws, and a dynamic human heartbeat model. B0 in an ellipsoid calculated by generalized susceptibility voxel convolution matched an analytical solution nearly exactly. The method also calculated screw-induced B0 in agreement with experimental data. Dynamic simulation demonstrated its computational efficiency for repeated B0 calculations on time-varying susceptibility. On the contrary, conventional and alias-subtracted k-space-discretized Fourier convolution methods showed nonnegligible aliasing and Gibbs ringing artifacts in the tested models. Generalized susceptibility voxel convolution can be a fast and reliable way to compute susceptibility-induced B0 when the susceptibility source is not colocated with the B0 target Volume of interest, as in modeling B0 variations from motion and foreign objects. © 2018 International Society for Magnetic Resonance in Medicine.

O Polit - One of the best experts on this subject based on the ideXlab platform.

  • thermal and thermo mechanical solution of laminated composite beam based on a variables separation for Arbitrary Volume heat source locations
    Applied Mathematical Modelling, 2017
    Co-Authors: P Vidal, L Gallimard, Isabelle Ranc, O Polit
    Abstract:

    In this work, a method to compute explicit thermal solutions for laminated and sandwich beams with Arbitrary heat source location is developed. The temperature is written as a sum of separated functions of the axial coordinate x , the transverse coordinate z and the Volumetric heat source location x 0. The derived non-linear problem implies an iterative process in which three 1D problems are solved successively at each iteration. In the thickness direction, a fourth-order expansion in each layer is considered. For the axial description , classical Finite Element method is used. The presented approach is assessed on various laminated and sandwich beams and comparisons with reference solutions with a fixed heat source location are proposed. Based on the accurate results of the thermal analysis , thermo-mechanical response is also addressed using also a separated representation.