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Two variants of minimum discarded fill ordering

Description: It is well known that the ordering of the unknowns can have a significant effect on the convergence of Preconditioned Conjugate Gradient (PCG) methods. There has been considerable experimental work on the effects of ordering for regular finite difference problems. In many cases, good results have been obtained with preconditioners based on diagonal, spiral or natural row orderings. However, for finite element problems having unstructured grids or grids generated by a local refinement approach, … more
Date: January 1, 1991
Creator: D'Azevedo, E.F. (Oak Ridge National Lab., TN (USA)); Forsyth, P.A. & Tang, Wei-Pai (Waterloo Univ., ON (Canada). Dept. of Computer Science)
Partner: UNT Libraries Government Documents Department
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Further Studies on Equal-Order Interpolation for Navier-Stokes

Description: The simplest quadrilateral element available for the incompressible Navier-Stokes equations is the mixed interpolation 4-node element with bilinear velocity and (piecewise) constant pressure - denoted herein by 4/1. The next simplest is the 4/4 element, in which (continuous) bilinear approximation is also employed for pressure - i.e., the simplest case of equal-order interpolation. The 4/4 element had been more or less rejected early-on, following the pioneering work of Hood and Taylor who firs… more
Date: October 1, 1983
Creator: Gresho, P. M.; Lee, R. L. & Sani, R. L.
Partner: UNT Libraries Government Documents Department
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Algorithms for sparse, symmetric, definite quadratic lambda-matrix eigenproblems

Description: Methods are presented for computing eigenpairs of the quadratic lambda-matrix, M lambda/sup 2/ + C lambda + K, where M, C, and K are large and sparse, and have special symmetry-type properties. These properties are sufficient to insure that all the eigenvalues are real and that theory analogous to the standard symmetric eigenproblem exists. The methods employ some standard techniques such as partial tri-diagonalization via the Lanczos Method and subsequent eigenpair calculation, shift-and- inve… more
Date: January 1, 1981
Creator: Scott, D. S. & Ward, R. C.
Partner: UNT Libraries Government Documents Department
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ML 3.0 smoothed aggregation user's guide.

Description: ML is a multigrid preconditioning package intended to solve linear systems of equations Az = b where A is a user supplied n x n sparse matrix, b is a user supplied vector of length n and x is a vector of length n to be computed. ML should be used on large sparse linear systems arising from partial differential equation (PDE) discretizations. While technically any linear system can be considered, ML should be used on linear systems that correspond to things that work well with multigrid methods … more
Date: May 1, 2004
Creator: Sala, Marzio; Hu, Jonathan Joseph & Tuminaro, Raymond Stephen
Partner: UNT Libraries Government Documents Department
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Hamiltonian structure of multi-species fluid electrodynamics

Description: The phase space for multi-species fluid electrodynamics is the function space of fluid variables and Maxwell field variables. The Poisson bracket on phase functionals is constructed as a Lie algebra product following general methods of infinite dimensional symplectic geometry.
Date: December 1, 1981
Creator: Spencer, R.G.
Partner: UNT Libraries Government Documents Department
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Second order particle motion equations and linear chromaticity calculation in accelerator rings

Description: The first part of this note presents a thorough study on the second order particle motion equations, both in continuous field and in hard edges, with emphasis put on the latter. Having quite general conditions and strict mathematical treatments, it provides a sound ground from which many problems can be solved without fear of being misled. Then the linear CHR calculation is inspected, the first step being a general analytical expression of the transverse oscillation phase increment due to a sma… more
Date: January 1, 1984
Creator: Liu, R.Z.
Partner: UNT Libraries Government Documents Department
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Remarks on the Kuramoto-Sivashinsky equation

Description: We report here a joint work in progress on the Kuramoto-Sivashinsky equation. The question we address is the analytical study of a fourth order nonlinear evolution equation. This equation has been obtained by Sivashinsky in the context of combustion and independently by Kuramoto in the context of reaction diffusion-systems. Both were motivated by (nonlinear) stability of travelling waves. Numerical calculations have been done on this equation. All the results seem to indicate a chaotic behavior… more
Date: January 1, 1983
Creator: Nicolaenko, B. & Scheurer, B.
Partner: UNT Libraries Government Documents Department
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Stochastic cooling: recent theoretical directions

Description: A kinetic-equation derivation of the stochastic-cooling Fokker-Planck equation of correlation is introduced to describe both the Schottky spectrum and signal suppression. Generalizations to nonlinear gain and coupling between degrees of freedom are presented. Analysis of bunch beam cooling is included.
Date: March 1, 1983
Creator: Bisognano, J.
Partner: UNT Libraries Government Documents Department
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Introduction to Hydrodynamics

Description: Various aspects of hydrodynamics and elastic--plastic flow are introduced for the purpose of defining hydrodynamic terms and explaining what some of the important hydrodynamic concepts are. The first part covers hydrodynamic theory; and discussed fundamental hydrodynamic equations, discontinuities, and shock, detonation, and elastic--plastic waves. The second part deals with applications of hydrodynamic theory to material equations of state, spall, Taylor instabilities, and detonation pressure … more
Date: January 9, 1979
Creator: Wilkins, M. L.
Partner: UNT Libraries Government Documents Department
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Particle energization

Description: A first-principles approach to the physics of particle energization is presented. The general physics of particle acceleration is then applied to a number of the classical astrophysical mechanisms for accelerating particles, with references to recent literature where these are used in specific circumstances. The solar flare is recommended as a microcosm for studying particle acceleration because many different processes seem to be occurring in close proximity, and there is abundant high time re… more
Date: January 1, 1990
Creator: Gisler, G.
Partner: UNT Libraries Government Documents Department
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Transverse mis-alignments in a driver

Description: The transverse errors of the beam lines are usually corrected by an appropriate feed back to bring the beam back on axis. In an induction linac, however, the head and tail of the bunch differ substantially in momentum at a given lens location. As a result, the correction has to be time dependent. Such a correction becomes increasingly difficult as the beam energy increases and the time duration of the bunch decreases. As a step towards an understanding of the problem, we have analyzed the extre… more
Date: June 1, 1988
Creator: Smith, L. & Hahn, K.
Partner: UNT Libraries Government Documents Department
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On the directional symmetry of the impedance

Description: The independence of the impedance on the beam direction is an important feature of an accelerator structure, in particular, for the electron-positron storage rings where bunches of opposite charges travel through the same vacuum chamber in opposite directions. Recently Gluckstern and Zotter considered a cylindrically symmetric but longitudinally asymmetric cavity with side pipes of equal radii. They were able to prove that for a relativistic particle the longitudinal impedance of the cavity wit… more
Date: March 1, 1990
Creator: Heifets, S.A.
Partner: UNT Libraries Government Documents Department
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Scaling laws for aberrations in magnetic quadrupole lens systems

Description: A comparison has been made of the third-order (spherical) abberrations in magnetic quadrupole lenses for use in conventional charged particle beam transport systems. An analytical description of the abberrations is presented and this is compared with the results of high order numerical integration. The dependence of the aberration strength on the system geometry and f number is given and a comparison of doublet and triplet systems made. The reduction of the aberrations in both doublet and tripl… more
Date: January 1, 1987
Creator: Moses, R. W.; Heighway, E. A.; Christian, R. S. & Dragt, A. J.
Partner: UNT Libraries Government Documents Department
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Polarizable media in classical gluodynamics and the SU/sub 2/ vacuum

Description: The description of a polarizable medium interacting with non-Abelian gauge fields can be formulated in a simple, gauge-invariant manner. Working with a Euclidean-space version of an SU/sub 2/ gauge-theory, we find a solution to the resulting field equations with vacuum-like properties: (1) E/sub i/sup a/Bsub i/sup a/ = 0; (2) E/sub i/sup a/E/sub i/sup a/ + B/sub i/sup a/B/sub i/sup a/ constant; (3) area law behavior for Wilson loops formed from the classical fields. It is possible to express th… more
Date: March 1, 1983
Creator: Ralston, J.P. & Sivers, D.
Partner: UNT Libraries Government Documents Department
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On the Operator Approach to the Problem of Stability of Difference Schemes and the Convergence of Certain Iteration Procedures

Description: A number of considerations related to the stability of certain difference analogs of the differential equation of heat conduction and with the convergence of iteration procedures derived from implicit difference equations are presented. The operator approach is used in a manner which dispenses with the knowledge of eigenvalues. (J.R.D.)
Date: March 1, 1957
Creator: Lowan, A. N.
Partner: UNT Libraries Government Documents Department
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An Existence Theorem for an Integral Equation

Description: The principal theorem of this thesis is a theorem by Peano on the existence of a solution to a certain integral equation. The two primary notions underlying this theorem are uniform convergence and equi-continuity. Theorems related to these two topics are proved in Chapter II. In Chapter III we state and prove a classical existence and uniqueness theorem for an integral equation. In Chapter IV we consider the approximation on certain functions by means of elementary expressions involving "bent … more
Date: May 1985
Creator: Hunt, Cynthia Young
Partner: UNT Libraries
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Improved Method for Numerically Solving Multi-Group Reactor Equations

Description: "A method for solving multi-group reactor equations which arise in the diffusion approximation is outlined. Considerable work has been done on this problem at KAPL and ORNL. Their approach is to replace the differential equations by difference equations. Complications arise in this method where more than one slowing down medium is present since the fluxes are discontinuous at the interfaces. The primary purpose of this article is to develop an exact integral expression for the neutron flux w… more
Date: September 15, 1954
Creator: Lehman, G. W.
Partner: UNT Libraries Government Documents Department
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Implicit Plasma Simulation

Description: Implicit time integration methods have been used extensively in numerical modelling of slowly varying phenomena in systems that also support rapid variation. Examples include diffusion, hydrodynamics and reaction kinetics. This article discussed implementation of implicit time integration in plasma codes of the ''particle-in-cell'' family, and the benefits to be gained.
Date: March 3, 1985
Creator: Langdon, A. B.
Partner: UNT Libraries Government Documents Department
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Restoring force method and response estimation

Description: The restoring force method is briefly outlined. Signal modifications that are necessary to successfully determine restoring force functions are discussed and illustrated. Restoring force functions for a base and a force excited system were determined and their effectiveness demonstrated by comparing measured and predicted signals. Additional developments that would make the restoring force method more general are suggested. 5 refs., 12 figs.
Date: January 1, 1989
Creator: Endebrock, E.G.
Partner: UNT Libraries Government Documents Department
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Laser focusing of particle beams

Description: We propose a scheme using the Inverse Cerenkov effect to focus particle beams with the potential of high focusing gradients ({approximately}200 kG/cm) and rapid, accurate control of the focusing element. 6 refs.
Date: January 1, 1991
Creator: Channell, P.J.; Elliott, C.J. (Los Alamos National Lab., NM (United States)) & Fontana, J.R. (California Univ., Santa Barbara, CA (United States). Dept. of Electrical and Computer Engineering)
Partner: UNT Libraries Government Documents Department
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Hydrogen mixing study (HMS) in LWR type containments

Description: A numerical technique has been developed for calculating the full three-dimensional time-dependent Navier-Stokes equations with multiple speies transport. The method is a modified form of the Implicit Continuous-fluid Eulerian (ICE) technique to solve the governing equations for low Mach number flows where pressure waves and local variations in compression and expansion are not significant. Large density variations, due to thermal and species concentration gradients, are accounted for without t… more
Date: January 1, 1983
Creator: Travis, J.R.
Partner: UNT Libraries Government Documents Department
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Attractors for the Kuramoto-Sivashinsky equations

Description: In this paper, we address the question of constructing an upper bound of the Hausdorff and Fractal dimensions d/sub H/(x) and d/sub F/(x) for attractors X of the kuramoto-Sivanshinsky equation.
Date: January 1, 1985
Creator: Nicolaenko, B.; Scheurer, B. & Temam, R.
Partner: UNT Libraries Government Documents Department
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