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A high-order finite-volume method for hyperbolic conservation laws on locally-refined grids

Description: We present a fourth-order accurate finite-volume method for solving time-dependent hyperbolic systems of conservation laws on Cartesian grids with multiple levels of refinement. The underlying method is a generalization of that in [5] to nonlinear systems, and is based on using fourth-order accurate quadratures for computing fluxes on faces, combined with fourth-order accurate Runge?Kutta discretization in time. To interpolate boundary conditions at refinement boundaries, we interpolate in time… more
Date: January 28, 2011
Creator: McCorquodale, Peter & Colella, Phillip
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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NSLS-II: Nonlinear Model Calibration for Synchrotrons

Description: This tech note is essentially a summary of a lecture we delivered to the Acc. Phys. Journal Club Apr, 2010. However, since the estimated accuracy of these methods has been naive and misleading in the field of particle accelerators, i.e., ignores the impact of noise, we will elaborate on this in some detail. A prerequisite for a calibration of the nonlinear Hamiltonian is that the quadratic part has been understood, i.e., that the linear optics for the real accelerator has been calibrated. For s… more
Date: October 8, 2010
Creator: Bengtsson, J.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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Reduced order models for thermal analysis : final report : LDRD Project No. 137807.

Description: This LDRD Senior's Council Project is focused on the development, implementation and evaluation of Reduced Order Models (ROM) for application in the thermal analysis of complex engineering problems. Two basic approaches to developing a ROM for combined thermal conduction and enclosure radiation problems are considered. As a prerequisite to a ROM a fully coupled solution method for conduction/radiation models is required; a parallel implementation is explored for this class of problems. High-fid… more
Date: September 1, 2010
Creator: Hogan, Roy E., Jr. & Gartling, David K.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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Multiscale analysis of nonlinear systems using computational homology

Description: This is a collaborative project between the principal investigators. However, as is to be expected, different PIs have greater focus on different aspects of the project. This report lists these major directions of research which were pursued during the funding period: (1) Computational Homology in Fluids - For the computational homology effort in thermal convection, the focus of the work during the first two years of the funding period included: (1) A clear demonstration that homology can sensi… more
Date: May 24, 2010
Creator: Mischaikow, Konstantin; Schatz, Michael; Kalies, William & Wanner, Thomas
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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Multiscale analysis of nonlinear systems using computational homology

Description: This is a collaborative project between the principal investigators. However, as is to be expected, different PIs have greater focus on different aspects of the project. This report lists these major directions of research which were pursued during the funding period: (1) Computational Homology in Fluids - For the computational homology effort in thermal convection, the focus of the work during the first two years of the funding period included: (1) A clear demonstration that homology can sensi… more
Date: May 19, 2010
Creator: Mischaikow, Konstantin; Schatz, Michael; Kalies, William & Wanner, Thomas
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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Nonlinear accelerator lattices with one and two analytic invariants

Description: Integrable systems appeared in physics long ago at the onset of classical dynamics with examples being Kepler's and other famous problems. Unfortunately, the majority of nonlinear problems turned out to be nonintegrable. In accelerator terms, any 2D nonlinear nonintegrable mapping produces chaotic motion and a complex network of stable and unstable resonances. Nevertheless, in the proximity of an integrable system the full volume of such a chaotic network is small. Thus, the integrable nonlinea… more
Date: February 1, 2010
Creator: Danilov, V. & Nagaitsev, S.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Solving a Class of Nonlinear Eigenvalue Problems by Newton's Method

Description: We examine the possibility of using the standard Newton's method for solving a class of nonlinear eigenvalue problems arising from electronic structure calculation. We show that the Jacobian matrix associated with this nonlinear system has a special structure that can be exploited to reduce the computational complexity of the Newton's method. Preliminary numerical experiments indicate that the Newton's method can be more efficient for small problems in which a few smallest eigenpairs are needed. more
Date: July 2, 2009
Creator: Gao, Weiguo; Yang, Chao & Meza, Juan C.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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Simulations and model of the nonlinear Richtmyer-Meshkov instability (U)

Description: The nonlinear evolution of the Richtmyer-Meshkov (RM) instability is investigated using numerical simulations with the FLASH code in two-dimensions (20). The purpose of the simulations is to develop a nonlinear model of the RM instability that is accurate to the regime of inertial confinement fusion (ICF) and ejecta formation, namely, at large Atwood number A and initial amplitude kh{sub o} (k {triple_bond} wavenumber) of the perturbation. The FLASH code is first validated by obtaining excellen… more
Date: January 1, 2009
Creator: Dimonte, Guy
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Variational particle scheme for the porous medium equation and for the system of isentropic Euler equations

Description: We introduce variational particle schemes for the porous medium equation and the system of isentropic Euler equations in one space dimension. The methods are motivated by the interpretation of each of these partial differential equations as a 'steepest descent' on a suitable abstract manifold. We show that our methods capture very well the nonlinear features of the flows.
Date: December 10, 2008
Creator: Westdickenberg, Michael & Wilkening, Jon
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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A Numerical Algorithm for the Solution of a Phase-Field Model of Polycrystalline Materials

Description: We describe an algorithm for the numerical solution of a phase-field model (PFM) of microstructure evolution in polycrystalline materials. The PFM system of equations includes a local order parameter, a quaternion representation of local orientation and a species composition parameter. The algorithm is based on the implicit integration of a semidiscretization of the PFM system using a backward difference formula (BDF) temporal discretization combined with a Newton-Krylov algorithm to solve the … more
Date: December 4, 2008
Creator: Dorr, M R; Fattebert, J; Wickett, M E; Belak, J F & Turchi, P A
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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NSLS-II Control of Dynamic Aperture

Description: We have outlined how, by an intuitive approach, the on- and off-momentum dynamic aperture for a synchrotron light source can be estimated from a nonlinear system of algebraic equations for the sextupole/multipole strengths. The approach has only two free parameters: the relative weight for resonance vs. tune shift terms and the tune footprint for stable trajectories in a modern third generation synchrotron light source. In other words, we have established a control theory approach for the mediu… more
Date: October 31, 2008
Creator: Bengtsson,J.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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Development of a High Fidelity System Analysis Code for Generation IV Reactors

Description: Traditional nuclear reactor system analysis codes such as RELAP and TRAC employ an operator split methodology. In this approach, each of the physics (fluid flow, heat conduction and neutron diffusion) is solved separately and the coupling terms are done explicitly. This approach limits accuracy (first order in time at best) and makes the codes slow in running since the explicit coupling imposes stability restrictions on the time step size. These codes have been extensively tested and validated … more
Date: June 1, 2008
Creator: Zhang, Hongbin; Mousseau, Vincent & Zhao, Haihua
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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User's Guide for TOUGH2-MP - A Massively Parallel Version of the TOUGH2 Code

Description: TOUGH2-MP is a massively parallel (MP) version of the TOUGH2 code, designed for computationally efficient parallel simulation of isothermal and nonisothermal flows of multicomponent, multiphase fluids in one, two, and three-dimensional porous and fractured media. In recent years, computational requirements have become increasingly intensive in large or highly nonlinear problems for applications in areas such as radioactive waste disposal, CO2 geological sequestration, environmental assessment a… more
Date: May 27, 2008
Creator: Zhang, Keni; Zhang, Keni; Wu, Yu-Shu & Pruess, Karsten
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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Adagio 2.9 user's guide.

Description: Adagio is a Lagrangian, three-dimensional, implicit code for the analysis of solids and structures. It uses a multi-level iterative solver, which enables it to solve problems with large deformations, nonlinear material behavior, and contact. It also has a versatile library of continuum and structural elements, and an extensive library of material models. Adagio is written for parallel computing environments, and its solvers allow for scalable solutions of very large problems. Adagio uses the SI… more
Date: May 1, 2008
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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Center for Extended Magnetohydrodynamic Modeling Cooperative Agreement

Description: The Center for Extended Magnetohydrodynamic Modeling (CEMM) is developing computer simulation models for predicting the behavior of magnetically confined plasmas. Over the first phase of support from the Department of Energy’s Scientific Discovery through Advanced Computing (SciDAC) initiative, the focus has been on macroscopic dynamics that alter the confinement properties of magnetic field configurations. The ultimate objective is to provide computational capabilities to predict plasma behavi… more
Date: February 15, 2008
Creator: Sovinec, Carl R.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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Technical Report --Final Work Accomplishment

Description: The main goal of this project was to understand the solution structure of nonlinear boundary value problems arising in self-similar solutions of nonlinear systems of multidimensional conservation laws. This project further extended to study on biocomplex systems including Morphogen gradients systems (reaction-diffusion systems) and tumor growth and its treatment model problems (free boundary, conservation of mass and reaction-diffusion systems). The list of publications and the summary of those… more
Date: November 19, 2007
Creator: Kim, Eun Heui
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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Accuracy and Efficiency of a Coupled Neutronics and Thermal Hydraulics Model

Description: The accuracy requirements for modern nuclear reactor simulation are steadily increasing due to the cost and regulation of relevant experimental facilities. Because of the increase in the cost of experiments and the decrease in the cost of simulation, simulation will play a much larger role in the design and licensing of new nuclear reactors. Fortunately as the work load of simulation increases, there are better physics models, new numerical techniques, and more powerful computer hardware that w… more
Date: September 1, 2007
Creator: Mousseau, Vincent A. & Pope, Michael A.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Realistic Non-Linear Model and Field Quality Analysis in Rhic Interaction Regions.

Description: The existence of multipole components in the dipole and quadrupole magnets is one of the factors limiting the beam stability in the RHIC operations. So, a realistic non-linear model is crucial for understanding the beam behavior and to achieve the ultimate performance in RHIC. A procedure is developed to build a non-linear model using the available multipole component data obtained from measurements of RHIC magnets. We first discuss the measurements performed at different stages of manufacturin… more
Date: June 25, 2007
Creator: Beebe-Wang, J. & Jain, A.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Nonlinear Bayesian Algorithms for Gas Plume Detection and Estimation from Hyper-spectral Thermal Image Data

Description: This paper presents a nonlinear Bayesian regression algorithm for the purpose of detecting and estimating gas plume content from hyper-spectral data. Remote sensing data, by its very nature, is collected under less controlled conditions than laboratory data. As a result, the physics-based model that is used to describe the relationship between the observed remotesensing spectra, and the terrestrial (or atmospheric) parameters that we desire to estimate, is typically littered with many unknown "… more
Date: June 13, 2007
Creator: Heasler, Patrick G.; Posse, Christian; Hylden, Jeff L. & Anderson, Kevin K.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Asymptotic Behavior of the Electron Cloud Instability

Description: The fast beam-ion instability and the single bunch electron-cloud instability are substantially nonlinear phenomena and can be analyzed in a similar way. The initial exponential growth of the amplitudes known for both instabilities takes place only in the linear approximation. Later, in the nonlinear regime, amplitudes grow according to a power law or even decrease. We analyze the nonlinear regime describing the growth of amplitudes in time and along the train of bunches. Analytic analysis is c… more
Date: June 6, 2007
Creator: Heifets, Samuel
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Nonlinearly-constrained optimization using asynchronous parallel generating set search.

Description: Many optimization problems in computational science and engineering (CS&E) are characterized by expensive objective and/or constraint function evaluations paired with a lack of derivative information. Direct search methods such as generating set search (GSS) are well understood and efficient for derivative-free optimization of unconstrained and linearly-constrained problems. This paper addresses the more difficult problem of general nonlinear programming where derivatives for objective or c… more
Date: May 1, 2007
Creator: Griffin, Joshua D. & Kolda, Tamara Gibson
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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Aria 1.5 : user manual.

Description: Aria is a Galerkin finite element based program for solving coupled-physics problems described by systems of PDEs and is capable of solving nonlinear, implicit, transient and direct-to-steady state problems in two and three dimensions on parallel architectures. The suite of physics currently supported by Aria includes the incompressible Navier-Stokes equations, energy transport equation, species transport equations, nonlinear elastic solid mechanics, and electrostatics as well as generalized sc… more
Date: April 1, 2007
Creator: Hopkins, Matthew Morgan; Moffat, Harry K.; Noble, David R.; Notz, Patrick K. & Subia, Samuel Ramirez
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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Quadratic eigenvalue problems.

Description: In this report we will describe some nonlinear eigenvalue problems that arise in the areas of solid mechanics, acoustics, and coupled structural acoustics. We will focus mostly on quadratic eigenvalue problems, which are a special case of nonlinear eigenvalue problems. Algorithms for solving the quadratic eigenvalue problem will be presented, along with some example calculations.
Date: April 1, 2007
Creator: Walsh, Timothy Francis & Day, David Minot
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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Finite element calculations illustrating a method of model reduction for the dynamics of structures with localized nonlinearities.

Description: A technique published in SAND Report 2006-1789 ''Model Reduction of Systems with Localized Nonlinearities'' is illustrated in two problems of finite element structural dynamics. That technique, called here the Method of Locally Discontinuous Basis Vectors (LDBV), was devised to address the peculiar difficulties of model reduction of systems having spatially localized nonlinearities. It's illustration here is on two problems of different geometric and dynamic complexity, but each containing loca… more
Date: October 1, 2006
Creator: Griffith, Daniel Todd & Segalman, Daniel Joseph
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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