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Aspects of model selection in multivariate analyses

Description: 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.
Partner: UNT Libraries Government Documents Department
open access

Thermodynamics of natural and industrial waters

Description: 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.
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

Description: 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.
Partner: UNT Libraries Government Documents Department
open access

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

Description: 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.
Partner: UNT Libraries Government Documents Department
open access

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

Description: 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.
Partner: UNT Libraries Government Documents Department
open access

Random choice method for calculating fluid displacement in a porous medium

Description: 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.
Partner: UNT Libraries Government Documents Department
open access

Supersymmetric statistical models on the lattice

Description: 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.
Partner: UNT Libraries Government Documents Department
open access

Fragmentation in rotating isothermal protostellar clouds

Description: 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.
Partner: UNT Libraries Government Documents Department
open access

Molecular dynamics simulations

Description: 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.
Partner: UNT Libraries Government Documents Department
open access

Role of rotational degrees of freedom in heavy-ion collisions

Description: 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.
Partner: UNT Libraries Government Documents Department
open access

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

Description: 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.
Partner: UNT Libraries Government Documents Department
open access

Three-dimensional free Lagrangian hydrodynamics

Description: 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.
Partner: UNT Libraries Government Documents Department
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Comparison of models of high energy heavy ion collision. [0. 1 to 2. 0 GeV/nuo, review]

Description: 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.
Partner: UNT Libraries Government Documents Department
open access

Recent developments in nuclear reaction theories and calculations

Description: 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.
Partner: UNT Libraries Government Documents Department
open access

Bump masses for BL Her stars

Description: The masses of classical Cepheids can be determined by using the phase of the Hertzsprung bump on the light or velocity curve, Cox-Stewart opacities, and nonlinear pulsation theory. The fact that these bump masses are some 60% lower than the evolutionary masses raises some questions about this approach. In support of our method, we calculate the light curve for BL Her, a population II Cepheid, with an observed bump on the declining portion of its light curve. The nonlinear hydrodynamic model we … more
Date: January 1, 1982
Creator: Davis, C.G.
Partner: UNT Libraries Government Documents Department
open access

Particle angular distributions and gamma-ray multiplicities as experimental probes for angular-momentum fluctuations

Description: The sequential emission of /sup 4/He is demonstrated in the reaction Ho + Ta and the /sup 4/He angular distribution is used to test the rigid rotation limit in the reaction Ho + Ag. A more refined analysis of the dependence of continuum ..gamma..-ray multiplicities upon Q-value and gamma ray energy shows that reasonable agreement with the statistical model is obtained if one assumes the presence of low energy aligned dipole transitions in the reactions Ho, Yb, Sm, Ag + Ho. Sequential fission an… more
Date: March 1, 1982
Creator: Moretto, Luciano G.
Partner: UNT Libraries Government Documents Department
open access

Theoretical models for Type I and Type II supernova

Description: Recent theoretical progress in understanding the origin and nature of Type I and Type II supernovae is discussed. New Type II presupernova models characterized by a variety of iron core masses at the time of collapse are presented and the sensitivity to the reaction rate /sup 12/C(..cap alpha..,..gamma..)/sup 16/O explained. Stars heavier than about 20 M/sub solar/ must explode by a ''delayed'' mechanism not directly related to the hydrodynamical core bounce and a subset is likely to leave blac… more
Date: January 1, 1985
Creator: Woosley, S. E. & Weaver, T. A.
Partner: UNT Libraries Government Documents Department
open access

Pulsations of delta Scuti stars

Description: A general review of the pulsating {delta} Scuti variables is given including the observed light curves and positions of the stars in the Hertzsprung-Russell diagram. Theoretical interpretations from evolution and pulsation calculations give their masses, radii, luminosities, and even their approximate internal compositions. Three models of these stars are discussed and used to study the nonlinear hydrodynamic behavior of these stars. The hydrodynamic equations and the Stellingwerf method for ob… more
Date: January 1, 1989
Creator: Cox, A. N.
Partner: UNT Libraries Government Documents Department
open access

Review of the fundamentals of the neutron-capture reaction

Description: Fifty years of research into the nature of the radiative capture reaction mechanisms is briefly summarized. A variety of such mechanisms is exploited to explain neutron capture over nine decades of neutron energy.
Date: January 1, 1982
Creator: Chrien, R. E.
Partner: UNT Libraries Government Documents Department
open access

Core helium flash

Description: The role of convection in the core helium flash is simulated by two-dimensional eddies interacting with the thermonuclear runaway. These eddies are followed by the explicit solution of the 2D conservation laws with a 2D finite difference hydrodynamics code. Thus, no phenomenological theory of convection such as the local mixing length theory is required. The core helium flash is violent, producing a deflagration wave. This differs from the detonation wave (and subsequent disruption of the entir… more
Date: January 1, 1980
Creator: Cole, P.W. & Deupree, R.G.
Partner: UNT Libraries Government Documents Department
open access

Risk-Based Plant Performance Indicators

Description: Tasked by the 1979 President's Commission on the Accident at Three Mile Island, the US nuclear power industry has put into place a performance indicator program as one means for showing a demonstrable record of achievement.'' Largely through the efforts of the Institute of Nuclear Power Operations (INPO), plant performance data has, since 1983, been collected and analyzed to aid utility management in measuring their plants' performance progress. The US Nuclear Regulatory Commission (NRC) has al… more
Date: January 1, 1989
Creator: Boccio, J. L.; Azarm, M. A.; Vesely, W. E. & Hall, R. E.
Partner: UNT Libraries Government Documents Department
open access

Results from the SPEAR magnetic detector with the lead-glass-addition

Description: Results from the SP-26 experiment at SPEAR are reported. The parameters of the psi (3772), recently discovered in this experiment, are discussed first. This resonance is just above threshold for D production; therefore the D masses could be measured with high precision. Measurements of D branching fractions into hadronic and semileptonic modes are reported; the hadronic branching fractions are reported here for the first time, and include a number of decay modes not observed before. At higher e… more
Date: October 1, 1977
Creator: Barbaro-Galtieri, A.
Partner: UNT Libraries Government Documents Department
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