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Neutron generator power supply modeling in EMMA

Description: Sandia National Laboratories has prime responsibility for neutron generator design and manufacturing, and is committed to developing predictive tools for modeling neutron generator performance. An important aspect of understanding component performance is explosively driven ferroelectric power supply modeling. EMMA (ElectroMechanical Modeling in ALEGRA) is a three dimensional compile time version of Sandia`s ALEGRA code. The code is built on top of the general ALEGRA framework for parallel shoc… more
Date: December 1, 1996
Creator: Robinson, A. C.; Farnsworth, A. V.; Montgomery, S. T.; Peery, J. S & Merewether, K. O.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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Lamb waves from airborne explosion sources: Viscous effects and comparisons to ducted acoustic arrivals

Description: Observations of large explosions in the atmosphere at long range are dominated by a leading pulse of large amplitude and long period that is often followed by a series of higher frequency impulses usually of smaller amplitude. This description can be interpreted using linearized acoustic-gravity wave theory in terms of a Lamb wave arrival followed by ducted acoustic and/or gravity waves. This pattern of arrivals is not the same at all ranges nor is it independent of the source energy or of the … more
Date: December 31, 1996
Creator: Revelle, D.O. & Whitaker, R.W.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Response matrix transport calculations on parallel computers

Description: The response matrix method offers an excellent vehicle for adapting three-dimensional neutron transport methods to parallel computers. Our current thrust is in utilizing the three-dimensional Variational nodal code VARIANT as a point of departure for performing three- dimensional parallel computations on the IBM SPx at Argonne National Laboratory. The code employs a planar red-black iteration with a secondary red-black or four-color iteration within each plane. Speed- up and efficiency results … more
Date: December 1996
Creator: Hanebutte, U. R.; Palmiotti, G.; Khalil, H. S.; Tatsumi, M. & Lewis, E. E.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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DANTSYS/MPI: a system for 3-D deterministic transport on parallel architectures

Description: Since 1994, we have been using a data parallel form of our deterministic transport code DANTSYS to perform time-independent fixed source and eigenvalue calculations on the CM-200`s at Los Alamos National Laboratory (LANL). Parallelization of the transport sweep is obtained by using a 2-D spatial decomposition which retains the ability to invert the source iteration equation in a single iteration (i.e., the diagonal plane sweep). We have now implemented a message passing version of DANTSYS, refe… more
Date: December 31, 1996
Creator: Baker, R.S. & Alcouffe, R.E.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Hamiltonian models of quantum computers which evolve quantum ballistically

Description: Quantum computation is a subject of much recent interest. In much of the work in the literature quantum computers are described as built up from a sequence of unitary operators where each unitary operator carries out a stage of the overall quantum computation. The sequence and connection of the different unitary operators is provided presumably by some external agent which governs the overall process. However there is no description of a an overall Hamiltonian needed to give the actual quantum … more
Date: December 31, 1996
Creator: Benioff, P.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Tensor methods for large sparse systems of nonlinear equations

Description: This paper introduces censor methods for solving, large sparse systems of nonlinear equations. Tensor methods for nonlinear equations were developed in the context of solving small to medium- sized dense problems. They base each iteration on a quadratic model of the nonlinear equations. where the second-order term is selected so that the model requires no more derivative or function information per iteration than standard linear model-based methods, and hardly more storage or arithmetic operati… more
Date: December 1996
Creator: Bouaricha, A. & Schnabel, R. B.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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A parallel, volume-tracking algorithm for unstructured meshes

Description: Many diverse areas of industry benefit from the use of volume of fluid methods to predict the movement of materials. Casting is a common method of part fabrication. The accurate prediction of the casting process is pivotal to industry. Mold design and casting is currently considered an art by industry. It typically involves many trial mold designs, and the rejection of defective parts is costly. Failure of cast parts, because residual stresses reduce the part`s strength, can be catastrophic. Ca… more
Date: October 1, 1996
Creator: Mosso, S.J.; Swartz, B.K.; Kothe, D.B. & Ferrell, R.C.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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An implicit method for hyperbolic conservation laws on meshes with small cells in one dimension

Description: In this paper we study a new method for solving hyperbolic conservation laws on a Cartesian mesh with some small cells. Our main task here is to devise a stable algorithm in the small zones. An algorithm proposed by Berger and LeVeque combines the small zones with neighboring zones and solves rotated Riemann problems. This method is very geometrically oriented. It requires knowledge of the areas of the small cells, as well as the areas of cells contained in various {open_quote}boxes{close_quote… more
Date: August 14, 1996
Creator: Pao, K. & Saltzman, J.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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Partial least squares, conjugate gradient and the fisher discriminant

Description: The theory of multivariate regression has been extensively studied and is commonly used in many diverse scientific areas. A wide variety of techniques are currently available for solving the problem of multivariate calibration. The volume of literature on this subject is so extensive that understanding which technique to apply can often be very confusing. A common class of techniques for solving linear systems, and consequently applications of linear systems to multivariate analysis, are iterat… more
Date: December 1996
Creator: Faber, V.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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Parallel supercomputing: Advanced methods, algorithms, and software for large-scale linear and nonlinear problems. Final report, August 15, 1993--February 28, 1996

Description: This report gives a quick description of progress on methods, algorithms and software for large-scale parallel supercomputer applications. Focus is on large-scale applications of interest to DOE such as coupled viscous flow and heat or mass transport, and energy-related applications such as 3D petroleum and gas reservoir simulations on massively parallel systems. The interdisciplinary collaboration has been effective since it enhances the development of new iterative schemes for complex problem… more
Date: July 1, 1996
Creator: Carey, G.F. & Young, D.M.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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Three-dimensional finite element simulation of viscoelastic fluid flow using the EVSS-G

Description: An implementation of the EVSS-G method in a finite element framework is presented for modeling three-dimensional viscoelastic flows. The extension from two to three dimensions is discussed, along with the use of the Picard and Newton-Raphson iterative techniques. A selection of benchmark problems, with known analytical solutions are presented as validation of the implementation as well as results for secondary flows in rectangular ducts. 7 refs.
Date: October 1, 1996
Creator: Benard, A.; Lovalenti, P. M.; Tullock, D. L.; Montalbano, E. D. & Guell, D. C.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Second SIAM conference on sparse matrices: Abstracts. Final technical report

Description: This report contains abstracts on the following topics: invited and long presentations (IP1 & LP1); sparse matrix reordering & graph theory I; sparse matrix tools & environments I; eigenvalue computations I; iterative methods & acceleration techniques I; applications I; parallel algorithms I; sparse matrix reordering & graphy theory II; sparse matrix tool & environments II; least squares & optimization I; iterative methods & acceleration techniques II; applications II; eigenvalue computations I… more
Date: December 31, 1996
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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An analytical model of the HINT performance metric

Description: The HINT benchmark was developed to provide a broad-spectrum metric for computers and to measure performance over the full range of memory sizes and time scales. We have extended our understanding of why HINT performance curves look the way they do and can now predict the curves using an analytical model based on simple hardware specifications as input parameters. Conversely, by fitting the experimental curves with the analytical model, hardware specifications such as memory performance can be … more
Date: October 1, 1996
Creator: Snell, Q.O. & Gustafson, J.L.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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A superlinear infeasible-interior-point algorithm for monotone complementarity problems

Description: We use the globally convergent framework proposed by Kojima, Noma, and Yoshise to construct an infeasible-interior-point algorithm for monotone nonlinear complementary problems. Superlinear convergence is attained when the solution is nondegenerate and also when the problem is linear. Numerical experiments confirm the efficacy of the proposed approach.
Date: November 1, 1996
Creator: Wright, S. & Ralph, D.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
open access

Adjacent-cell preconditioners for accelerating multidimensional neutron transport methods

Description: The Adjacent-cell Preconditioner (AP) is derived for accelerating generic fixed-weight, Weighted Diamond Difference (WDD) neutron transport methods in multidimensional Cartesian geometry. The AP is determined by requiring: (a) the eigenvalue of the combined mesh sweep-AP iterations to vanish in the vicinity of the origin in Fourier space; and (b) the diagonal and off-diagonal elements of the preconditioner to satisfy a diffusion-like condition. The spectra of the resulting iterations for a wide… more
Date: April 1, 1996
Creator: Azmy, Y.Y.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Preconditioning a product of matrices arising in trust region subproblems

Description: In solving large scale optimization problems, we find it advantageous to use iterative methods to solve the sparse linear systems that arise. In the ETR software for solving equality constrained optimization problems, we use a conjugate gradient method to approximately solve the trust region subproblems. To speed up the convergence of the conjugate gradient routine, we need to precondition matrices of the form Z{sup T} W Z, which are not explicitly stored. Four preconditioners were implemented … more
Date: March 1, 1996
Creator: Hribar, M. E. & Plantenga, T. D.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
open access

Solution of problems with material nonlinearities with a coupled finite element/boundary element scheme using an iterative solver. Yucca Mountain Site Characterization Project

Description: The prediction of stresses and displacements around tunnels buried deep within the earth is an important class of geomechanics problems. The material behavior immediately surrounding the tunnel is typically nonlinear. The surrounding mass, even if it is nonlinear, can usually be characterized by a simple linear elastic model. The finite element method is best suited for modeling nonlinear materials of limited volume, while the boundary element method is well suited for modeling large volumes of… more
Date: January 1, 1996
Creator: Koteras, J.R.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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TENSOLVE: A software package for solving systems of nonlinear equations and nonlinear least squares problems using tensor methods

Description: This paper describes a modular software package for solving systems of nonlinear equations and nonlinear least squares problems, using a new class of methods called tensor methods. It is intended for small to medium-sized problems, say with up to 100 equations and unknowns, in cases where it is reasonable to calculate the Jacobian matrix or approximate it by finite differences at each iteration. The software allows the user to select between a tensor method and a standard method based upon a li… more
Date: December 1996
Creator: Bouaricha, A. & Schnabel, R. B.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
open access

DANTSYS: a system for deterministic, neutral particle transport calculations

Description: The THREEDANT code is the latest addition to our system of codes, DANTSYS, which perform neutral particle transport computations on a given system of interest. The system of codes is distinguished by geometrical or symmetry considerations. For example, ONEDANT and TWODANT are designed for one and two dimensional geometries respectively. We have TWOHEX for hexagonal geometries, TWODANT/GQ for arbitrary quadrilaterals in XY and RZ geometry, and THREEDANT for three-dimensional geometries. The desi… more
Date: December 31, 1996
Creator: Alcouffe, R.E. & Baker, R.S.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Analysis and performance of adjacent-cell preconditioners for accelerating multidimensional transport calculations

Description: The formal development of the Adjacent-cell Preconditioner (AP) and its implementation in the TORT code are briefly reviewed. Based on earlier experience with diffusion type acceleration, and excellent results in slab geometry the reciprocal averaging formula is used to mix the preconditioner elements across material and mesh discontinuities. Numerical testing of the method employing the Burre Suite of Test Problems (BSTeP), a collection of 144 cases covering a wide range in parameter space, us… more
Date: December 31, 1996
Creator: Azmy, Y.Y.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Gamma-ray imaging of the Quinby sources

Description: The Quinby sources are alumina cylinders 7 inches in diameter and 8 inches high doped with weapons grade plutonium. We describe a computer tomography system for reconstructing three-dimensional images of these sources. Each reconstruction maps the spatial distribution of the internal [sup 241]Am gamma ray activity and is computed using an iterative, expectation-maximization algorithm with detection efficiencies based both on geometric model of the experimental setup and attenuation corrections.… more
Date: December 31, 1996
Creator: Gregor, J. & Hensley, D.C.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Iterative prediction of chaotic time series using a recurrent neural network

Description: Chaotic systems are known for their unpredictability due to their sensitive dependence on initial conditions. When only time series measurements from such systems are available, neural network based models are preferred due to their simplicity, availability, and robustness. However, the type of neutral network used should be capable of modeling the highly non-linear behavior and the multi-attractor nature of such systems. In this paper the authors use a special type of recurrent neural network … more
Date: December 31, 1996
Creator: Essawy, M.A.; Bodruzzaman, M.; Shamsi, A. & Noel, S.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
open access

Time-dependent 3-D dterministic transport on parallel architectures using Dantsys/MPI

Description: In addition to the ability to solve the static transport equation, we have also incorporated time dependence into our parallel 3-D S{sub {ital N}} code DANTSYS/MPI. Using a semi-implicit scheme, DANTSYS/MPI is capable of performing time-dependent calculations for both fissioning and pure source driven problems. We have applied this to various types of problems such as nuclear well logging and prompt fission experiments. This paper describes the form of the time- dependent equations implemented,… more
Date: December 31, 1996
Creator: Baker, R.S. & Alcouffe, R.E.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
open access

An improved algorithm for geocentric to geodetic coordinate conversion

Description: The problem of performing transformations from geocentric to geodetic coordinates has received an inordinate amount of attention in the literature. Numerous approximate methods have been published. Almost none of the publications address the issue of efficiency and in most cases there is a paucity of error analysis. Recently there has been a surge of interest in this problem aimed at developing more efficient methods for real time applications such as DIS. Iterative algorithms have been propose… more
Date: February 1, 1996
Creator: Toms, R.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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