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31
Nonmanifold Modeling: An Approach Based on Spatial Subdivision
, 1997
"... This paper deals with the problem of creating and maintaining a spatial ..."
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Cited by 22 (7 self)
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This paper deals with the problem of creating and maintaining a spatial
Stable Spectral Methods For Conservation Laws On Triangles With Unstructured Grids
, 1997
"... . This paper presents an asymptotically stable scheme for the spectral approximation of linear conservation laws defined on a triangle. Lagrange interpolation on a general two-dimensional nodal set is employed and, by imposing the boundary conditions weakly through a penalty term, the scheme is prov ..."
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Cited by 15 (3 self)
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. This paper presents an asymptotically stable scheme for the spectral approximation of linear conservation laws defined on a triangle. Lagrange interpolation on a general two-dimensional nodal set is employed and, by imposing the boundary conditions weakly through a penalty term, the scheme is proven stable in L 2 . This result is established for a general unstructured grid in the triangle. A special case, for which the nodes along the edges of the triangle are chosen as the Legendre Gauss-Lobatto quadrature points, is discussed in detail. The eigenvalue spectrum of the approximation to the advective operator is computed and is shown to result in an O(n \Gamma2 ) restriction on the time-step when considering explicit time-stepping. Key words. Spectral Methods, Asymptotic Stability, Penalty Methods, Triangular Elements. AMS subject classifications. 65L20, 65A70, 65A60, 41A10, 41A63 1. Introduction. The use of pseudospectral methods beyond one dimension has traditionally been conf...
Adaptive Methods for Non-linear Finite Element Analysis of Shell Structures
, 1994
"... This report is concerned with methods leading to automated adaptive numerical solutions to geometrically non-linear shell--type problems. In particular, procedures for improving the accuracy, the reliability as well as the computational efficiency of the finite element solution are of primary intere ..."
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Cited by 11 (11 self)
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This report is concerned with methods leading to automated adaptive numerical solutions to geometrically non-linear shell--type problems. In particular, procedures for improving the accuracy, the reliability as well as the computational efficiency of the finite element solution are of primary interest. This is addressed through use of h--adaptive mesh refinement based on a posteriori error estimation and self-adaptive methods in global incremental--iterative processes. Integration of h--adaptive finite element methods with non-linear solution algorithms makes it possible to maintain a prescribed solution accuracy efficiently without user intervention throughout the process of a non-linear analysis. The above objective is addressed by considering the four--noded shell element developed by Simo and co-workers, which has been implemented in the non-linear finite element code FENRIS. Error estimation by the Zienkiewicz--Zhu method is employed to provide guidance for an h--adaptive mesh re...
Sas , “Hybrid Finite Element - Wave Based Method for Acoustic
- Problems”, 2005 http: // www.ijesrt.com(C)International Journal of Engineering Sciences & Research Technology
"... The finite element method (FEM) is widely accepted for the steady-state dynamic response analysis of acoustic systems. It exhibits almost no restrictions with respect to the geometrical features of these systems. However, its application is practically limited to the low-frequency range. An alternat ..."
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Cited by 8 (6 self)
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The finite element method (FEM) is widely accepted for the steady-state dynamic response analysis of acoustic systems. It exhibits almost no restrictions with respect to the geometrical features of these systems. However, its application is practically limited to the low-frequency range. An alternative method is the wave based method, which is an indirect Trefftz method. It exhibits better convergence properties than the FEM and therefore allows accurate predictions at higher frequencies. However, the applicability is limited to systems of moderate geometrical complexity. The coupling between both methods is proposed. Only the parts of the problem domain with a complex geometry are modelled using the FEM, while the remaining parts are described with a wave based model. The proposed hybrid method has the potential to cover the mid-frequency range, where it is still difficult for currently existing (deterministic) techniques to provide satisfactory prediction results within a reasonable computational time. 1
Improved non-rigid registration of prostate MRI
- in Proc. of MICCAI, vol. LNCS 3216
, 2004
"... Abstract. This paper introduces a fast non-rigid registration method for aligning pre-operative 1.5 T MR images to intra-operative 0.5 T MR images for guidance in prostate biopsy. After the acquisition of both pre-operative 1.5 T and intra-operative 0.5 T, an intensity correction method is applied t ..."
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Cited by 5 (0 self)
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Abstract. This paper introduces a fast non-rigid registration method for aligning pre-operative 1.5 T MR images to intra-operative 0.5 T MR images for guidance in prostate biopsy. After the acquisition of both pre-operative 1.5 T and intra-operative 0.5 T, an intensity correction method is applied to the pre-operative images to reduce the significant artifacts in the signal intensities due to the presence of an endo-rectal coil. A fast manual segmentation of prostate in both modalities is carried out to enable conformal mapping of the surface of the pre-operative data to the intra-operative data. A displacement field is estimated with a linear elastic inhomogeneous material model using the surface displacements established by the conformal mapping. We then use this as an initialization for a mutual information based non-rigid registration algorithm to match the internal structures of the prostate. This non-rigid registration is based on a finite element method discretization using the mutual information metric with a linear elastic regularization constraint. The registration is accelerated while preserving accuracy by using an adaptive mesh based on the body-centered cubic lattice and a significantly improved registration is achieved. 1
Structural Design Optimization and Comparative Analysis of a New High-Performance Robot Arm via Finite Element Analysis
, 1997
"... This paper reports the structural design of a new high-performance robot arm. Design objectives for the new arm include large (1-2 meter) workspace, low weight, 5 kg payload capacity, high stiffness, high structural vibration frequencies, precise joint-level torque control, a total of three degrees- ..."
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Cited by 5 (3 self)
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This paper reports the structural design of a new high-performance robot arm. Design objectives for the new arm include large (1-2 meter) workspace, low weight, 5 kg payload capacity, high stiffness, high structural vibration frequencies, precise joint-level torque control, a total of three degrees-offreedom, and mechanical simplicity. A comparative analysis is reported for four very different two degree-of-freedom linkage candidates using the finite element method. The authors gratefully acknowledge the support of the National Science Foundation under CAREER grant BES9625143 awarded to the last author. Correspondence Address: 123 Latrobe Hall, 3400 North Charles Street, Baltimore, Maryland, 21218, email addresses: roy@jhu.edu, llw@jhu.edu. A preliminary version of this paper was presented at the 1997 IEEE International Conference on Robotics and Automation, Albuquerque,New Mexico. 1 Introduction Our goal is to design and build a robot arm for high performance tracking and force c...
Laboratory Determination of Anisotropic Aggregate Resilient Moduli Using A New Innovative Test Device
, 1999
"... The important aspect of anisotropic aggregate behavior is presently not considered in material characterization for pavement design due to the lack of proper laboratory equipment and testing capabilities. A newly acquired, innovative triaxial testing machine, referred to as University of Illinois Fa ..."
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Cited by 5 (2 self)
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The important aspect of anisotropic aggregate behavior is presently not considered in material characterization for pavement design due to the lack of proper laboratory equipment and testing capabilities. A newly acquired, innovative triaxial testing machine, referred to as University of Illinois FastCell (UI-FC), was used in this study for determining in the laboratory the anisotropic resilient properties of granular materials. Since stresses can be cycled independently in the vertical and horizontal directions, UI-FC is ideally suited for simulating dynamic stresses on the sample and for studying the effects of anisotropic, stress path dependent aggregate behavior. Preliminary results obtained from four aggregates tested using UI-FC indicated definite directional dependency (anisotropy) of aggregate moduli. The resilient moduli computed in the vertical and radial directions varied pronouncedly with the applied stress states. When the same testing procedure was applied for testing a s...
High Performance, Process Oriented, Weld Spot Approach
"... Simulation of automotive vehicles has become a more important step in car development in the last few years. Rapid prototyping, which o ers a close-to-market product, with less hardware, requires a fast and accurate computer simulation to guarantee a quality product. Generation of body-in-white nite ..."
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Simulation of automotive vehicles has become a more important step in car development in the last few years. Rapid prototyping, which o ers a close-to-market product, with less hardware, requires a fast and accurate computer simulation to guarantee a quality product. Generation of body-in-white nite element models for full vehicle simulation of Linear Statics, Normal Modes, NVH, and Crash is one of the most critical items. This is due to the need to connect various body-in-white components which requires: a signi cant amount of manpower because of di cult automation possibilities a "physically correct " representation of part-connectors such as weld spots, screws, etc., which cannot be easily automated and requires more manpower resulting in delays and a potentially large source of error In the past, a number of methods were developed for joining these parts together, such as ho-mogenous models and various other weld spot approaches. In the generation of FE-models, each part depended on its connected parts, which made it di cult to shorten the modeling process. Bene ts of faster hardware, and some improvements in preprocessors, were diminished by the need for bigger models. Despite the above improvements, a signi cant amount of time was still required to generate FE models. CDH and BMW developed a spot welding approach, linchweld, which simultane-ously reduced the modeling time, invested manpower, and increased the quality of simulation (compared to test). The program containing the linchweld approach is called CDH/SPOT. 2 Requirements for Spot Weld Modeling
A p-adaptive scheme for overcoming volumetric locking during plastic flow
- Computer Methods in Applied Mechanics and Engineering 191
, 2002
"... Abstract. A p-adaptive scheme is developed in order to overcome volumetric locking in low order finite elements. A special adaptive scheme is used which is based on the partition of unity concept. This allows higher order polynomial terms to be added locally to the underlying finite element interpol ..."
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Abstract. A p-adaptive scheme is developed in order to overcome volumetric locking in low order finite elements. A special adaptive scheme is used which is based on the partition of unity concept. This allows higher order polynomial terms to be added locally to the underlying finite element interpolations basis through the addition of extra degrees of freedom at existing nodes. During the adaptive process, no new nodes are added to the mesh. Volumetric locking is overcome by introducing higher order polynomial terms in regions where plastic flow occurs. The model is able to overcome volumetric locking for plane strain, axisymmetric and three-dimensional problems.
