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Interval neural networks

Description: Traditional neural networks like multi-layered perceptrons (MLP) use example patterns, i.e., pairs of real-valued observation vectors, ({rvec x},{rvec y}), to approximate function {cflx f}({rvec x}) = {rvec y}. To determine the parameters of the approximation, a special version of the gradient descent method called back-propagation is widely used. In many situations, observations of the input and output variables are not precise; instead, we usually have intervals of possible values. The imprec… more
Date: May 1, 1995
Creator: Patil, R. B.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Parallel spatial direct numerical simulation of boundary-layer flow transition on IBM SP1

Description: The spatially evolving disturbances that are associated with laminar-to-turbulent transition in three-dimensional boundary-layer flows are computed with the PSDNS code on an IBM SP1 parallel supercomputer. By remapping the distributed data structure during the course of the calculation, optimized serial library routines can be utilized that substantially increase the computational performance. Although the remapping incurs a high communication penalty, the parallel efficiency of the code remain… more
Date: July 1, 1995
Creator: Hanebutte, U.R.; Joslin, R.D. & Zubair, M.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Performance of a fully parallel dense real symmetric eigensolver in quantum chemistry applications

Description: The parallel performance of a dense, standard and generalized, real, symmetric eigensolver based on bisection for eigenvalues and repeated inverse iteration and reorthogonalization for eigenvectors is described. The performance of this solver, called PeIGS, is given for two test problems and for three ``real-world`` quantum chemistry applications: SCF-Hartree-Fock, density functional theory,and Moeller-Plesset theory. The distinguishing feature of the repeated inverse iteration and orthogonaliz… more
Date: April 1, 1995
Creator: Fann, G.I.; Littlefield, R.J. & Elwood, D.M.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Mixed direct-iterative methods for boundary integral formulations of continuum dielectric solvation models

Description: This paper develops and characterizes mixed direct-iterative methods for boundary integral formulations of continuum dielectric solvation models. We give an example, the Ca{sup ++}{hor_ellipsis}Cl{sup {minus}} pair potential of mean force in aqueous solution, for which a direct solution at thermal accuracy is difficult and, thus for which mixed direct-iterative methods seem necessary to obtain the required high resolution. For the simplest such formulations, Gauss-Seidel iteration diverges in r… more
Date: August 7, 1995
Creator: Corcelli, S. A.; Kress, J. D. & Pratt, L. R.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Robust controller design of four wheel steering systems using mu synthesis techniques

Description: In this paper, a linearized four wheel steering (4WS) system model is deduced and then modified into a form which is appropriate for applying Matlab {mu} Toolbox to design robust controller. Several important topics are discussed in detail, such as (1) how to make system set-up match Matlab {mu} Toolbox requirement, (2) how to select weights based on plant`s uncertainty, (3) how to solve controller discretization problem, and (4) how to adjust the system so that the conditions necessary for usi… more
Date: February 27, 1995
Creator: Gao, X.; McVey, B. D. & Tokar, R. L.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Interatomic potentials for covalent materials from a local approximation to tight binding

Description: We present a local approximation to total energy tight binding (TB) designed to be suitable as a semiempirical potential form for covalent and metallic-covalent materials. Chebyshev polynomial moments of the Hamiltonian matrix are generated in a stable and efficient manner through recursive matrix-vector multiplies. The electronic density of states is approximated by a Chebyshev polynomial expansion with Gibbs damping which maintains positivity. The scaling of the computational work is made lin… more
Date: August 1, 1995
Creator: Voter, A. F.; Kress, J. D. & Silver, R. N.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Continuous contour phase plates for tailoring the focal plane irradiance profile

Description: We present fully continuous phase screens for producing super-Gaussian focal-plane irradiance profiles. Such phase screens are constructed with the assumption of either circular symmetric near-field and far-field profiles or a separable phase screen in Cartesian co-ordinates. In each case, the phase screen is only a few waves deep. Under illumination by coherent light, such phase screens produce high order super-Gaussian profiles in the focal plane with high energy content effects of beam aberr… more
Date: August 9, 1995
Creator: Dixit, S. N.; Rushford, M. C.; Thomas, I. M. & Perry, M. D.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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A diffusion accelerated solution method for the nonlinear characteristic scheme

Description: Recently the nonlinear characteristic scheme for spatially discretizing the discrete-ordinate equations was introduced. This scheme is accurate for both optically thin and optically thick spatial meshes and produces strictly positive angular and scalar fluxes. The nonlinear characteristic discrete-ordinate equations can be solved using the source iteration method; however, it is well known that the this method converges prohibitively slowly for optically thick problems with scattering ratios at… more
Date: February 1, 1995
Creator: Wareing, T. A.; Walters, W. F. & Morel, J. E.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
open access

Immersed interface methods. Progress report

Description: Considerable progress has been made on several problems mentioned in the original proposal and in last year`s progress report. Our work is also going in some new directions. The primary focus is still on Immersed Interface Methods (IIM`s) for high order accuracy of interface problems on Cartesian grids, but the investigators have also been involved in other projects. In particular, LeVeque`s work on clawpack described below has been supported in part by these grants and has been used in direct … more
Date: April 1, 1995
Creator: LeVeque, Randall J.; Adams, Loyce M. & Bube, Kenneth P.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
open access

Numerical simulation via parallel-distributed computing of energy absorption by metal deformation

Description: Collapsible steering column designs are credited with saving tens-of-thousands of lives since their introduction in the late 1960`s. The collapsible steering column is a safety feature designed to absorb energy and protect-the driver in a head-on collision. One of the most frequently used design concepts employs two telescoping metal tubes that slide over one another as the occupant impacts the steering wheel. Hardened steel ball bearings are embedded in a plastic sleeve located between the two… more
Date: July 1, 1995
Creator: Plaskacz, E.J. & Kulak, R.F.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Heterogeneous domain decomposition for singularly perturbed elliptic boundary value problems

Description: A heterogeneous domain-decomposition method is presented for the numerical solution of singularly perturbed elliptic boundary value problem. The method, which is parallelizable at various levels, uses several ideas of asymptotic analysis. The sub-domains match the domains of validity of the local ({open_quotes}inner{close_quotes} and {open_quotes}outer{close_quotes}) asymptotic expansions, and cut-off functions are used to match solutions in neighboring subdomains. The positions of the interfac… more
Date: April 14, 1995
Creator: Garbey, M. & Kaper, H.G.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
open access

The workshop on iterative methods for large scale nonlinear problems

Description: The aim of the workshop was to bring together researchers working on large scale applications with numerical specialists of various kinds. Applications that were addressed included reactive flows (combustion and other chemically reacting flows, tokamak modeling), porous media flows, cardiac modeling, chemical vapor deposition, image restoration, macromolecular modeling, and population dynamics. Numerical areas included Newton iterative (truncated Newton) methods, Krylov subspace methods, domain… more
Date: December 1, 1995
Creator: Walker, H.F. & Pernice, M.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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PCG reference manual: A package for the iterative solution of large sparse linear systems on parallel computers. Version 1.0

Description: PCG (Preconditioned Conjugate Gradient package) is a system for solving linear equations of the form Au = b, for A a given matrix and b and u vectors. PCG, employing various gradient-type iterative methods coupled with preconditioners, is designed for general linear systems, with emphasis on sparse systems such as these arising from discretization of partial differential equations arising from physical applications. It can be used to solve linear equations efficiently on parallel computer archi… more
Date: January 1, 1995
Creator: Joubert, W. D.; Carey, G. F.; Kohli, H.; Lorber, A.; McLay, R. T.; Shen, Y. et al.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
open access

Massively parallel fast elliptic equation solver for three dimensional hydrodynamics and relativity

Description: Through the work proposed in this document we expect to advance the forefront of large scale computational efforts on massively parallel distributed-memory multiprocessors. We will develop tools for effective conversion to a parallel implementation of sequential numerical methods used to solve large systems of partial differential equations. The research supported by this work will involve conversion of a program which does state of the art modeling of multi-dimensional hydrodynamics, general r… more
Date: January 1, 1995
Creator: Sholl, P. L.; Wilson, J. R.; Mathews, G. J. & Avila, J. H.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
open access

A Novel Iterative Optimizing Quantization Technique for Three-Dimensional Reconstruction from a Limited Number of Views

Description: The Iterative Optimizing Quantization Technique (IOQT) is a novel method in reconstructing three-dimensional images from a limited number of two-dimensional projections. IOQT reduces the artifacts and image distortion due to a limited number of projections and limited range of viewing angles. IOQT, which reduces the number of projections required for reconstruction, can simplify the complexity of an experimental set-up and support the development of techniques to nondestructively image microstr… more
Date: June 14, 1995
Creator: Lee, H.-R.; DaSilva, L.; Haddad, L.; Trebes, J.; Yeh, Y. & Ford, G.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
open access

New techniques for the scientific visualization of three-dimensional multi-variate and vector fields

Description: Volume rendering allows us to represent a density cloud with ideal properties (single scattering, no self-shadowing, etc.). Scientific visualization utilizes this technique by mapping an abstract variable or property in a computer simulation to a synthetic density cloud. This thesis extends volume rendering from its limitation of isotropic density clouds to anisotropic and/or noisy density clouds. Design aspects of these techniques are discussed that aid in the comprehension of scientific infor… more
Date: October 1, 1995
Creator: Crawfis, R.A.
Item Type: Refine your search to only Thesis or Dissertation
Partner: UNT Libraries Government Documents Department
open access

Premature saturation in backpropagation networks: Mechanism and necessary conditions

Description: The mechanism that gives rise to the phenomenon of premature saturation of the output units of feedforward multilayer neural networks during training with the standard backpropagation algorithm is described. The entire process of premature saturation is characterized by three distinct stages and it is concluded that the momentum term plays the leading role in the occurrence of the phenomenon. The necessary conditions for the occurrence of premature saturation are presented and their validity is… more
Date: December 31, 1995
Creator: Vitela, J. E. & Reifman, J.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
open access

Particle motion in the stable region near the edge of a linear sum resonance stopband

Description: This paper studies the particle motion when the tune is in the stable region close to the edge of linear sum resonance stopband. Results are found for the tune and the beta functions. Results are also found for the two solutions of the equations of motion. The results found are shown to be also valid for small accelerators where the large accelerator approximation may not be used.
Date: December 1, 1995
Creator: Parzen, G.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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Heteroscedasticity generated by errors in predictors

Description: The heteroscedasticity or changing variance observed ``raw`` data may be the result of randomness or uncertainty in the predictor variables. As an example we consider ``Charpy Test`` experiments widely used to characterize the ductile-brittle toughness of steels such as those used for nuclear pressure vessels. While this type of experiment is of interest in itself, our main objective is to show that the use of a proper statistical technique may help to avoid the use of more complicated physical… more
Date: November 1, 1995
Creator: Downing, D. J.; Fedorov, V. V. & Nanstad, R. K.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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Numerical construction of the Poincare map, with application to accelerators

Description: We show how to construct a symplectic approximation to the Poincar{prime}e map, using data from a symplectic integrator. We illustrate by producing a full-turn map for a realistic model of the Large Hadron Collider. Mapping of one turn is typically faster by a factor of 60 than direct integration. This allows one to follow orbits over times comparable to the required storage time of the beam, on a workstation computer. Fast mapping also allows the construction of quasi-invariant actions, which … more
Date: October 1, 1995
Creator: Warnock, R. L. & Berg, J. S.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
open access

Aztec user`s guide. Version 1

Description: Aztec is an iterative library that greatly simplifies the parallelization process when solving the linear systems of equations Ax = 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. Aztec is intended as a software tool for users who want to avoid cumbersome parallel programming details but who have large sparse linear systems which require an efficiently utilized parallel processing system. A collection of dat… more
Date: October 1, 1995
Creator: Hutchinson, S.A.; Shadid, J.N. & Tuminaro, R.S.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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Development of operator requested control system applications: Experience with the SLC control system at SLAC

Description: The SLC Control system at SLAC has evolved into a powerful tool for operation of the accelerator and for troubleshooting the unique problems encountered in extracting maximum performance from the SLC. The evolution has included the development of many custom applications and user interface features generated from accelerator operator and accelerator physicist requests. These applications are written and maintained primarily by the Controls Software Engineering group, and not by the users themse… more
Date: December 1, 1995
Creator: Stanek, M.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Crystalline beams

Description: A beam of confined charged particles, that are cooled to the extreme of the space-charge dominated regime, where the relative motion of particles within the beam is small compared to their Coulomb potential energies, will crystallize in a unique form of condensed matter. Such a system of particles can be simulated using the method of Molecular Dynamics, which explicitly includes the interaction between all pairs of particles and uses repeating cells to simulate the effects of a long beam. Withi… more
Date: June 1, 1995
Creator: Schiffer, J.P.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Iterative acceleration methods for Monte Carlo and deterministic criticality calculations

Description: If you have ever given up on a nuclear criticality calculation and terminated it because it took so long to converge, you might find this thesis of interest. The author develops three methods for improving the fission source convergence in nuclear criticality calculations for physical systems with high dominance ratios for which convergence is slow. The Fission Matrix Acceleration Method and the Fission Diffusion Synthetic Acceleration (FDSA) Method are acceleration methods that speed fission s… more
Date: November 1, 1995
Creator: Urbatsch, T.J.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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