663 Matching Results

Search Results

Advanced search parameters have been applied.

in subjects: "Statistical Models"

open access

Aspects of model selection in multivariate analyses

Analysis of data sets that involve large numbers of variables usually entails some type of model fitting and data reduction. In regression problems, a fitted model that is obtained by a selection process can be difficult to evaluate because of optimism induced by the choice mechanism. Problems in areas such as discriminant analysis, calibration, and the like often lead to similar difficulties. The preceeding sections reviewed some of the general ideas behind assessment of regression-type predic… more

Date: January 1, 1982

Creator: Picard, R.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Thermodynamics of natural and industrial waters

The most effective general formulations of thermodynamic equations for multicomponent aqueous solutions are discussed with respect to various ranges of temperature, pressure and composition with emphasis on solutes important in natural or industrial waters. A familiar equation in molality and in excess Gibbs energy is very successful up to 300{degree}C and ionic strength 6 mol{center dot}kg{sup {minus}1}, and can often be extended to 350{degree}C or above at high pressure and in favorable cases… more

Date: August 1, 1991

Creator: Pitzer, K.S.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

FY 1992 task plans for the Hanford Environmental Dose Reconstruction Project

Phase 1 of the HEDR Project was designed to develop and demonstrate a method for estimating radiation doses people may have received from Hanford Site operations since 1944. The method researchers developed relied on a variety of measured and reconstructed data as input to a modular computer model that generates dose estimates and their uncertainties. As part of Phase 1, researchers used the reconstructed data and computer model to calculate preliminary dose estimates for populations from limit… more

Date: October 1, 1991

Item Type: Report

Partner: UNT Libraries Government Documents Department

open access

0. 9 a Gev /sup 238/U on /sup 238/U collisions in the LBL streamer chamber. Appendix A

Charged particle exclusive data for high multiplicity U on U events are reported. Analyses are based on comparison with Cugnon's intranuclear cascade model, and the explosion-evaporation simulation of Fai and Randrup. The azimuthal structure of the observed events shows evidence of collective flow. The widely used flow angle methodology proves to be relatively insensitive to collective effects under the conditions of the present experiment. An isotropic pattern of ejectile emission is not reach… more

Date: January 1, 1984

Creator: Fung, S.Y.; Beavis, D.; Gorn, W.; Keane, D.; Liu, Y.M.; Poe, R.T. et al.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Nuclear-data evaluation based on direct and indirect measurements with general correlations

Optimum procedures for the statistical improvement, or updating, of an existing nuclear-data evaluation are reviewed and redeveloped from first principles, consistently employing a minimum-variance viewpoint. A set of equations is derived which provides improved values of the data and their covariances, taking into account information from supplementary measurements and allowing for general correlations among all measurements. The minimum-variance solutions thus obtained, which we call the meth… more

Date: January 1, 1988

Creator: Muir, D.W.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

CDFTBL: A statistical program for generating cumulative distribution functions from data

This document describes the theory underlying the CDFTBL code and gives details for using the code. The CDFTBL code provides an automated tool for generating a statistical cumulative distribution function that describes a set of field data. The cumulative distribution function is written in the form of a table of probabilities, which can be used in a Monte Carlo computer code. A a specific application, CDFTBL can be used to analyze field data collected for parameters required by the PORMC compu… more

Date: June 1, 1991

Creator: Eslinger, P.W. (Pacific Northwest Lab., Richland, WA (United States))

Item Type: Report

Partner: UNT Libraries Government Documents Department

open access

Some fundamental aspects of the optical potential for the interaction of fast neutrons with cobalt

Differential elastic- and inelastic-scattering cross sections, measured from approx.1.5 to 10.0 MeV, are interpreted in terms of spherical-optical-statistical (OM) and coupled-channels models. A successful description of the differential elastic scattering below 10 MeV and the total cross section to 20.0 MeV is achieved using the spherical OM with energy-dependent strengths and geometries. These energy dependencies are large below approx.7.0 MeV, but become smaller and similar to those reported… more

Date: January 1, 1988

Creator: Smith, A. B. & Lawson, R. D.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Type II successful supernovae, the anatomy of shocks: neutrino emission and the adiabatic index

Hydrodynamic calculations of stellar collapse in Type II Supernova are described using a variable stiffness and compressibility for the nuclear equation of state at high density. Initial models employing a relatively small mass core with low central entropy are necessary to achieve viable shocks; near success the models are sensitive to both neutrino emission and the high density equation of state. The treatment of neutrino production and transport is sketched and recent results reported.

Date: January 1, 1983

Creator: Kahana, S.; Baron, E. & Cooperstein, J.

Item Type: Report

Partner: UNT Libraries Government Documents Department

open access

Random choice method for calculating fluid displacement in a porous medium

Multiphase fluid displacement in a porous medium gives rise naturally to the occurrence of steep fronts, for example between different fluids or between regions of differing chemical concentrations. Such fronts pose substantial difficulty for most numerical methods. However, the recently developed random choice numerical method has been found capable of following effectively even perfectly sharp fronts. An application to the calculation of immiscible displacement in a petroleum reservoir is dis… more

Date: June 1, 1980

Creator: Albright, N.; Anderson, C. & Concus, P.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Supersymmetric statistical models on the lattice

SUSY models in statistical mechanics involve spinless fermions and form an ideal laboratory for latticization. Extension of SUSY relations to the lattice may clarify, as well, the question of their validity beyond perturbation theory. A non-linear approach to lattice SUSY is introduced by the assignment of coupled commuting and anticommuting variables to each lattice site. As a typical example we demonstrate a SUSY dimer Hamiltonian which generates lattice branched-polymers configurations. We s… more

Date: January 1, 1983

Creator: Shapir, Y.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Fragmentation in rotating isothermal protostellar clouds

Results of an extensive set of 3-D hydrodynamic calculations that have been performed to investigate the susceptibility of rotating clouds to gravitational fragmentation are presented. (GHT)

Date: January 1, 1980

Creator: Bodenheimer, P.; Tohline, J.E. & Black, D.C.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Molecular dynamics simulations

The molecular dynamics computer simulation discovery of the slow decay of the velocity autocorrelation function in fluids is briefly reviewed in order to contrast that long time tail with those observed for the stress autocorrelation function in fluids and the velocity autocorrelation function in the Lorentz gas. For a non-localized particle in the Lorentz gas it is made plausible that even if it behaved quantum mechanically its long time tail would be the same as the classical one. The general… more

Date: July 1, 1985

Creator: Alder, B. J.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Systematics of gamma decay through low-lying vibrational levels of even--even nuclei excited by (p,p') and (n,n') reactions

A series of experiments was performed in which gamma-ray spectra were measured, using a Ge(Li) detector, for incident 7 to 26-MeV protons on the even-even vibrational nuclei /sup 56/Fe, /sup 62/Ni, /sup 64/Zn, /sup 108/Pd, /sup 110/Cd, /sup 114/Cd, /sup 116/Cd, /sup 116/Sn, /sup 120/Sn, and /sup 206/Pb, and for incident 14-MeV neutrons on natural Fe, Ni, Zn, Cd, Sn, and Pb. These measurements yielded gamma-ray cross sections from which it was inferred that almost all of the gamma cascades from … more

Date: June 30, 1977

Creator: Koopman, R. P.

Item Type: Report

Partner: UNT Libraries Government Documents Department

open access

ORNL ALICE: a statistical model computer code including fission competition. [In FORTRAN]

A listing of the computer code ORNL ALICE is given. This code is a modified version of computer codes ALICE and OVERLAID ALICE. It allows for higher excitation energies and for a greater number of evaporated particles than the earlier versions. The angular momentum removal option was made more general and more internally consistent. Certain roundoff errors are avoided by keeping a strict accounting of partial probabilities. Several output options were added.

Date: November 1, 1977

Creator: Plasil, F.

Item Type: Report

Partner: UNT Libraries Government Documents Department

open access

Curium-245 and curium-247 neutron cross sections between 10 keV and 10 MeV

The optical model code 2PLUS and the statistical model codes COMNUC and CASCADE were used to compute neutron cross sections for Cm-245 and Cm-247 between 10 keV and 10 MeV. Cross sections for elastic and inelastic scattering, radiative capture, fission, and the (n,2n) reactions were computed. The parameters for the fission model were selected to yield agreement with the cross sections from the Physics-8 bomb shot. Pu-239 cross sections were calculated and compared with existing cross section ev… more

Date: July 1, 1982

Creator: Clifford, L.R. & McCrosson, F.J.

Item Type: Report

Partner: UNT Libraries Government Documents Department

open access

Role of rotational degrees of freedom in heavy-ion collisions

The degrees of freedom affected by the angular momentum are identified. The relevance of the equilibrium fluctuations in a diffusive evolution of the system is discussed. The statistical limit is described and chosen as a reference for comparing with experiment. The rigid rotation regime is shown to be reached in a variety of reactions. The fragment spin alignment is measured from ..gamma..-ray multiplicities and anisotropies as well as from sequential fission angular distributions. Good agreem… more

Date: April 1, 1982

Creator: Moretto, Luciano G.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Search for extreme states in nuclear matter (or looking for collective phenomena)

After some introductory background material, the report discusses data from single-particle inclusive reactions with emission of nucleons and pions. The anomalous neutron-to-proton ratio is explained; pion data show a possible indication of a long-lived fireball. The other major topic is multiparticle correlations (noninclusive data). The energy dissipation in the target nucleus and the process of total disintegration (target explosion) leads over to pressure effects (bounce-off) in the heavy f… more

Date: March 1, 1980

Creator: Gutbrod, H.H.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Pion Condensation in a Field Theory Consistent with Bulk Properties of Nuclear Matter

No Description Available.

Date: May 1, 1980

Creator: Banerjee, B.; Glendenning, N.K. & Gyulassy, M.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Filling the strategic petroleum reserve: its price and economic effects

The estimated movements of the economic indicators under the 1989 target plan (with no OPEC retaliation) are small and could be considered almost negligible when viewed against the size of the economy and the error properties inherent in the macroeconomic model. Therefore, it cannot be firmly stated that a significant loss in real output and increases in inflation and unemployment occur in filling the Reserve. Accelerating the fill rate to meet the 1985 Target (without OPEC retaliation) could i… more

Date: March 1, 1980

Creator: Paul, E.S.

Item Type: Report

Partner: UNT Libraries Government Documents Department

open access

Three-dimensional free Lagrangian hydrodynamics

The purpose of the discussion is to describe the development of a 3-D free Lagrangian hyrodynamics algorithm. The 3-D algorithm is an outgrowth of an earlier 2-D free Lagrange model. Only the more pertinent issues of the free Lagrange algorithm are presented. A complete production code is being developed to support the free Lagrange algorithm described. 4 refs.

Date: January 1, 1985

Creator: Trease, H.E.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Comparison of models of high energy heavy ion collision. [0. 1 to 2. 0 GeV/nuo, review]

Some of the main theoretical developments on heavy ion collisions at energies (0.1 to 2.0) GeV/nuc are reviewed. The fireball, firestreak, hydrodynamic (1-fluid, 2-fluids), ''row on row'', hard sphere and intranuclear cascades, and classical equations of motion models are discussed in detail. Results are compared to each other and to measured Ne + U ..-->.. p + X reactions.

Date: October 1, 1977

Creator: Gyulassy, M.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Statistical fracture mechanics approach to the strength of brittle rock

Statistical fracture mechanics concepts used in the past for rock are critically reviewed and modifications are proposed which are warranted by (1) increased understanding of fracture provided by modern fracture mechanics and (2) laboratory test data both from the literature and from this research. Over 600 direct and indirect tension tests have been performed on three different rock types; Stripa Granite, Sierra White Granite and Carrara Marble. In several instances assumptions which are commo… more

Date: June 1, 1981

Creator: Ratigan, J.L.

Item Type: Report

Partner: UNT Libraries Government Documents Department

open access

Improvements to SOIL: An Eulerian hydrodynamics code

Possible improvements to SOIL, an Eulerian hydrodynamics code that can do coupled radiation diffusion and strength of materials, are presented in this report. Our research is based on the inspection of other Eulerian codes and theoretical reports on hydrodynamics. Several conclusions from the present study suggest that some improvements are in order, such as second-order advection, adaptive meshes, and speedup of the code by vectorization and/or multitasking. 29 refs., 2 figs.

Date: April 1, 1988

Creator: Davis, C.G.

Item Type: Report

Partner: UNT Libraries Government Documents Department

open access

Recent developments in nuclear reaction theories and calculations

A brief review is given of some recent developments in the fields of optical model potentials; level densities; and statistical model, precompound, and direct reaction codes and calculations. Significant developments have occurred in all of these fields since the 1977 Conference on Neutron Cross Sections, which will greatly enhance the ability to calculate high-energy neutron-induced reaction cross sections in the next few years. 11 figures, 3 tables.

Date: May 5, 1980

Creator: Gardner, D. G.

Item Type: Article

Partner: UNT Libraries Government Documents Department