The Experts below are selected from a list of 19959 Experts worldwide ranked by ideXlab platform

Jean-françois Colonna - One of the best experts on this subject based on the ideXlab platform.

Boris Rubinsky - One of the best experts on this subject based on the ideXlab platform.

  • Linear Superposition electrical impedance tomography imaging with multiple electrical biopsy probes
    IEEE Transactions on Biomedical Engineering, 2009
    Co-Authors: Antoni Ivorra, M. Shini, Boris Rubinsky
    Abstract:

    In medical diagnostics, tissue is often examined with multiple discrete biopsies taken under ultrasound placement. In a previous theoretical study, we have suggested that the Linear nature of the equations used in electrical impedance tomography (EIT) can be employed with the conventional practice of biopsy sampling to produce an image of the tissue between the biopsy samplings. Specifically, the biopsy probes can be used to record EIT-type electrical data during the discrete tissue sampling. The location of the discrete biopsy needle insertions available from the ultrasound placement of the probes can be combined with the electrical measurement data and used with Linear Superposition to produce a complete EIT image of the tissue between the sampled sites. In this study, we explore the concept experimentally using gel phantoms to simulate tissue and heterogeneities in the tissue. The experiments are performed in 2-D and 3-D configurations, and data are taken discretely, one at a time, through single electrical probe insertions. In the 2-D configuration, we were able to produce images of reasonable quality for heterogeneities with a diameter larger than 3 mm (conductivity ratio 1:5) and with relative conductivity differences above 50% (diameter 5 mm).

  • Linear Superposition Electrical Impedance Tomography Imaging With Multiple Electrical/Biopsy Probes
    IEEE Transactions on Biomedical Engineering, 2009
    Co-Authors: Antoni Ivorra, M. Shini, Boris Rubinsky
    Abstract:

    In medical diagnostics, tissue is often examined with multiple discrete biopsies taken under ultrasound placement. In a previous theoretical study, we have suggested that the Linear nature of the equations used in electrical impedance tomography (EIT) can be employed with the conventional practice of biopsy sampling to produce an image of the tissue between the biopsy samplings. Specifically, the biopsy probes can be used to record EIT-type electrical data during the discrete tissue sampling. The location of the discrete biopsy needle insertions available from the ultrasound placement of the probes can be combined with the electrical measurement data and used with Linear Superposition to produce a complete EIT image of the tissue between the sampled sites. In this study, we explore the concept experimentally using gel phantoms to simulate tissue and heterogeneities in the tissue. The experiments are performed in 2-D and 3-D configurations, and data are taken discretely, one at a time, through single electrical probe insertions. In the 2-D configuration, we were able to produce images of reasonable quality for heterogeneities with a diameter larger than 3 mm (conductivity ratio 1:5) and with relative conductivity differences above 50% (diameter 5 mm).

Ruud Weijermars - One of the best experts on this subject based on the ideXlab platform.

  • Linear Superposition method (LSM) for solving stress tensor fields and displacement vector fields: Application to multiple pressure-loaded circular holes in an elastic plate with far-field stress
    Applied Mathematics and Computation, 2020
    Co-Authors: Ruud Weijermars, Tri Pham, Mahmood Ettehad
    Abstract:

    Abstract This study presents a novel, Linear Superposition method (LSM) to compute the stress tensor field and displacement vector field in a homogeneous elastic medium with an unlimited (but finite) number of circular cylindrical holes. The displacement field and the associated stress concentrations are due to a far-field stress. The method allows for the hole-centers to occur in arbitrary locations, and the hole-radii may vary over a wide range (but holes may not overlap). The holes may also induce additional elastic displacement due to internal pressure loading that will affect the local stress field, which is fully accounted for in the method. Each hole may be loaded by either equal or individual pressure loads. The underlying algorithms and solution methodology are explained and examples are given for a variety of cases. Selected case study examples show excellent matches with results obtained via independent methods (photo-elastics, complex analysis, and discrete volume solution methods). The LSM provides several advantages over alternative methods: (1) Being closed-form solutions, infinite resolution is preserved throughout, (2) Being grid-less, no time is lost on gridding, and (3) fast computation times. The specific examples of LSM applications to the multi-hole problem developed here, allow for an unlimited number of holes, with either equal or varying radii, in arbitrary constellations. The solutions further account for variable combinations of far-field stress and pressure loads on individual holes. The method can be applied for either plane strain or plane stress boundary conditions. A constitutive equation for Linear elasticity controls the stress field solutions, which can be scaled for the full range of Poisson's ratios and Young moduli possible in Linear elastic materials.

  • Solving stress tensor fields around multiple pressure-loaded fractures using a Linear Superposition method (LSM)
    Applied Mathematical Modelling, 1
    Co-Authors: Tri Pham, Ruud Weijermars
    Abstract:

    Abstract The present paper presents the key steps to model internally pressurized fractures in a homogeneous elastic medium. Internal pressure in the cracks transforms the displacement field, which alters the associated stress concentration. The displacements are solved analytically using a Linear Superposition Method (LSM), and stresses are solved under the assumption of Linear elasticity. The method allows for the fractures to have any location, geometry, and orientation. Additionally, each crack may be pressurized by either equal or individual pressure loads. Solution methodology are explained, and results are generated for several cases. Selected LSM model results show excellent matches against other independent methods (photo-elastics for multiple crack problems, and prior analytical solutions for single crack problems). The grid-less, closed-form LSM solution is able to achieve fast computation times by side-stepping adaptive grid-refinement, while achieving high target resolution.

Sung Kyu Lim - One of the best experts on this subject based on the ideXlab platform.

  • tsv stress aware full chip mechanical reliability analysis and optimization for 3d ic
    Design Automation Conference, 2011
    Co-Authors: Moongon Jung, Joydeep Mitra, David Z Pan, Sung Kyu Lim
    Abstract:

    In this work, we propose an efficient and accurate full-chip thermo-mechanical stress and reliability analysis tool and design optimization methodology to alleviate mechanical reliability issues in 3D ICs. First, we analyze detailed thermo-mechanical stress induced by TSVs in conjunction with various associated structures such as landing pad and dielectric liner. Then, we explore and validate the use of the Linear Superposition principle of stress tensors and demonstrate the accuracy of this method against detailed finite element analysis (FEA) simulations. Next, we apply this Linear Superposition method to full-chip stress simulation and a reliability metric named the von Mises yield criterion. Finally, we propose a design optimization methodology to mitigate the mechanical reliability problems in 3D ICs. Our experimental results demonstrate the effectiveness of our methodology.

Wim Magnus - One of the best experts on this subject based on the ideXlab platform.

  • on the path integral representation of the wigner function and the barker murray ansatz
    Physics Letters A, 2012
    Co-Authors: Dries Sels, Wim Magnus, Fons Brosens
    Abstract:

    Abstract The propagator of the Wigner function is constructed from the Wigner–Liouville equation as a phase space path integral over a new effective Lagrangian. In contrast to a paper by Barker and Murray (1983) [1] , we show that the path integral can in general not be written as a Linear Superposition of classical phase space trajectories over a family of non-local forces. Instead, we adopt a saddle point expansion to show that the semiclassical Wigner function is a Linear Superposition of classical solutions for a different set of non-local time dependent forces. As shown by a simple example the specific form of the path integral makes the formulation ideal for Monte Carlo simulation.

  • On the path integral representation of the Wigner function and the Barker–Murray ansatz
    Physics Letters A, 2012
    Co-Authors: Dries Sels, Fons Brosens, Wim Magnus
    Abstract:

    Abstract The propagator of the Wigner function is constructed from the Wigner–Liouville equation as a phase space path integral over a new effective Lagrangian. In contrast to a paper by Barker and Murray (1983) [1] , we show that the path integral can in general not be written as a Linear Superposition of classical phase space trajectories over a family of non-local forces. Instead, we adopt a saddle point expansion to show that the semiclassical Wigner function is a Linear Superposition of classical solutions for a different set of non-local time dependent forces. As shown by a simple example the specific form of the path integral makes the formulation ideal for Monte Carlo simulation.