The Experts below are selected from a list of 3060 Experts worldwide ranked by ideXlab platform
Jin Hai - One of the best experts on this subject based on the ideXlab platform.
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Numerical Simulation of Conformal PML Based on Orthogonal Trajectory Method
Computer Simulation, 2009Co-Authors: Jin HaiAbstract:As viewed from the material,the perfectly matched layer(PML) is an anisotropic media,and the fields in the PML obey Maxell' equations.Progress in metamaterial design and fabrication has provided further impetus to study such constitutive tensor blueprints.This paper presents an application of a two-dimensional Orthogonal Trajectory grid generation scheme for the numerical implementation of a conformal PML in conjunction with FDTD method.Numerical results show that Orthogonal Trajectory grid-based conformal PML implementation provides an efficient absorbing boundary condition for a body-conformal FDTD or FEM simulation involving complex geometries.
X.-l. Luo - One of the best experts on this subject based on the ideXlab platform.
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Numerical simulation of Weissenberg phenomena – the rod-climbing of viscoelastic fluids
Computer Methods in Applied Mechanics and Engineering, 1999Co-Authors: X.-l. LuoAbstract:Abstract A finite element simulation of the Weissenberg effect, i.e., the rod-climbing of viscoelastic fluids, is presented. The flow features axisymmetric swirling, free surface, gravity, surface tension, centrifugal force and all six viscoelastic stresses. An operator splitting algorithm is employed to solve the highly non-linear system of equations governing the upper-convected Maxwell (UCM) or the Phan-Thien–Tanner (PTT) fluid. Normal displacement of free surface is tracked explicitly in time and an elaborate Orthogonal Trajectory scheme applicable to unstructured as well as structured grids is developed to update the mesh. Comparison of numerical and experimental results shows good agreement.
Reijo Kouhia - One of the best experts on this subject based on the ideXlab platform.
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On kinematical relations of spatial framed structures
Computers & Structures, 1991Co-Authors: Reijo KouhiaAbstract:Abstract In three-dimensional space the non-commutative nature of finite rotations complicates the formulation of incremental equilibrium equations, capable for handling large rotational increments. The rotation matrix can be expressed in concise and elegant form as an exponential of a skew-symmetric matrix, a result which can be deduced by arguments based on Lie's theory of groups as is done in quantum mechanics. Keeping in mind that the kinematical relations for an updated incremental finite element formulation are sought, the rotation matrix can be expressed as a series expansion in which higher order terms than quadratic can be omitted, if small incremental rotations are assumed. In this paper the shortcomings of using a linear rotation matrix in deriving the equilibrium equations of spatial beam structures are discussed. Stability problems are considered especially. The resulting discretized non-linear equilibrium equations are solved using Fried's Orthogonal Trajectory method, which allows easy handling of bifurcation and snap-through instability points. Numerical examples of lateral buckling analyses of beams are presented
Clough Shelton - One of the best experts on this subject based on the ideXlab platform.
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Transtemporal approach to the removal of a lateral pontine tumor
Neurosurgical Focus, 2014Co-Authors: William T. Couldwell, Clough SheltonAbstract:This video demonstrates a very useful Trajectory to a pontine lesion. A 68-year-old man presented with tongue numbness and weakness. The approach used was a transtemporal presigmoid retrolabyrinthine approach to enable an Orthogonal Trajectory to the lateral pons. Following the transtemporal opening, the root entry zone of the trigeminal nerve and the root exit zone of the facial nerve are identified. The lateral pons is incised to access the tumor, which upon histological analysis was found to be a metastasis. Excellent visualization of the lateral pons is achieved. The opening, relevant anatomy, and closure are illustrated. The video can be found here: http://youtu.be/vS5fCOY6vp8.
Jun‐qiang Sun - One of the best experts on this subject based on the ideXlab platform.
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Gradient fields of potential energy surfaces
The Journal of Chemical Physics, 1994Co-Authors: Klaus Ruedenberg, Jun‐qiang SunAbstract:While contour plots provide conceptual pictures of potential energy surfaces and exhibit their critical points, quantitative determinations of critical points and reaction paths as well as dynamical calculations require a knowledge of the gradient fields. The corresponding Orthogonal Trajectory maps are more complex than contour maps, but they provide additional insights. They are found to contain certain frequently occurring structural elements and these patterns are here examined. It is shown that many of them result from local confluences of Orthogonal Trajectory bundles with gradient extremals. The analysis leads to the distinction between eight different kinds of such gradient extremal channels. The most important ones are the streambeds and ridges, the former being typical conceptual prototypes of reaction channels, the latter being prototypes of reaction barriers. Gradient extremal channels emanate from second order critical points in the directions of all normal modes, but they do not necessarily follow along the entire reaction path of any one reaction. They can also exist unrelated to critical points. The conclusions are exemplified on a number of model potential energy surfaces.
