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An optimized algorithm for solving the nodal diffusion method on shared memory multiprocessors

Description: Nodal methods play a special role in reactor physics calculations. In recent papers the high computational efficiency of nodal methods has been established and the development of more efficient algorithms tailored to the advanced architectures of modern day computers proposed. The rapidly changing architectures of today's computer influence the way codes have to be programmed so that reasonable speed up and efficiency are attained. We have applied these concepts in solving the one-group neutron… more
Date: January 1, 1990
Creator: Kirk, B.L. & Azmy, Y.Y.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Thermally Induced Structural Changes in Coal Combustion

Description: The effect of particle shape on char burnout is investigated in the limit of shrinking core combustion. As a first step, the particle temperature is assumed to proceed in the shrinking core regime and under conditions of negligible Stefan flow. The problem then reduces to calculating the oxygen concentration field around a non-spherical particle with the oxidation reaction taking place on the external surface. This problem has been addressed by an analytical technique and a numerical technique.… more
Date: January 17, 1990
Creator: Gavalas, G. R. & Flagan, R. C.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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Neoclassical transport of energetic minority tail ions generated by ion-cyclotron resonance heating in tokamak geometry

Description: Neoclassical transport of energetic minority tail ions, which are generated by high powered electromagnetic waves of the Ion Cyclotron Range of Frequencies (ICRF) at the fundamental harmonic resonance, is studied analytically in tokamak geometry. The effect of Coulomb collisions on the tail ion transport is investigated in the present work. The total tail ion transport will be the sum of the present collision-driven transport and the wave-driven transport, which is due to the ICRF-wave scatteri… more
Date: January 1, 1990
Creator: Chang, C.S. (New York Univ., NY (USA). Courant Inst. of Mathematical Sciences); Hammett, G.W. & Goldston, R.J. (Princeton Univ., NJ (USA). Plasma Physics Lab.)
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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Nonadiabatic geometric phases of multiphoton transitions in dissipative systems and spin-j systems

Description: We present new developments in nonadiabatic geometric phases along two lines for systems undergoing changes of quantum state in intense fields. We first present a geometric representation of the non-Hermitian Schrodinger equation and introduce the notion of a complex multiphoton Aharonov-Anandan (AA) phase associated with dissipative two-level systems driven by periodic fields. The concept is further extended to include field modulation effects. We then develop the AA phase for spin-j systems i… more
Date: January 1, 1990
Creator: Layton, E.G. & Chu, Shih-I.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Control of energetic ion confinement by ion cyclotron range of frequency waves

Description: It is shown that ICRF waves can induce fast convective radial transport of energetic ions in a tokamak geometry without affecting the background ion transport. Spatially inhomogeneous ICRF waves with directional parallel wave vectors are needed; otherwise, a net parallel flow of the energetic ions has to be present. 8 refs.
Date: February 1, 1990
Creator: Chang, C.S. (New York Univ., NY (USA). Courant Inst. of Mathematical Sciences)
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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Validation and verification summary report for GRIMHX and TRIMHX

Description: As part of the code Certification process, codes used by Reactor Physics to calculate values in Technical Specifications or Safety Analyses must undergo formal Validation and Verification. GRIMHX and TRIMHX are codes used in such a manner. This report summarizes and consolidates the work done to date on the Validation and Verification of these two codes. GRIMHX is a 3-D static reactor code which uses finite difference algorithms to solve the neutron diffusion equation in hex-z geometry. TRIMHX … more
Date: December 1, 1990
Creator: Trumble, E.F.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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A Tutorial on the Construction of High-Performance Resolution/Paramodulation Systems

Description: Over the past 25 years, researchers have written numerous deduction systems based on resolution and paramodulation. Of these systems, a very few have been capable of generating and maintaining a formula database "containing more than just a few thousand clauses. These few systems were used to explore mechanisms for rapidly extracting limited subsets of relevant" clauses. We have written this tutorial to reflect some of the best ideas that have emerged and to cast them in a form that makes them … more
Date: September 1990
Creator: Butler, R. & Overbeek, R.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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A Theory for Fluidelastic Instability of Tube-Support-Plate Inactive Modes

Description: Fluid-elastic instability of loosely supported tubes, vibrating in a tube-support-plate (TSP) inactive mode, is suspected to be one of the main causes of tube failure in some operating steam generators and heat exchangers. This report presents a mathematical model for fluid-elastic instability of loosely supported tubes exposed to non-uniform cross-flow. The model incorporates all motion-dependent fluid forces based on the unsteady flow theory. In the unstable region associated with a TSP-inact… more
Date: September 1990
Creator: Cai, Y.; Chen, Shoei-Sheng & Chandra, S.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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Thermalhydraulic Aspects of Decay Heat Removal by Natural Circulation in Fast Reactor Systems

Description: Natural convection in enclosures have been studied numerically to provide insight into the scaling laws existing for removal of decay heat in Liquid Metal Fast Reactors (LMFR). Specifically, 3-D simulations have been carried out for natural circulation in a cylinder with small aspect ratio (of the order of 0.5). These results have been compared to the results of an experiment conducted by UCSB, in collaboration with GE, to provide benchmark data for code validation. Parametric studies have been… more
Date: January 1, 1990
Creator: Roy, C. M.; Hetsroni, G. & Banerjee, S.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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Non-local kinetic transport studies of a field reversed configuration

Description: During this past period a computer code was developed to determine the global kinetic linear stability for a 1-D Field-Reversed Configuration (FRC). This report will describe the physical assumptions used to model the plasma, the equations solved by the code, the numerical analysis for certain aspects of the code, and some preliminary results from the code.
Date: January 1, 1990
Creator: Choi, Chan K.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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Nuclear and particle astrophysics

Description: We discuss the physics of matter that is relevant to the structure of compact stars. This includes nuclear, neutron star matter and quark matter and phase transitions between them. Many aspects of neutron star structure and its dependance on a number of physical assumptions about nuclear matter properties and hyperon couplings are investigated. We also discuss the prospects for obtaining constraints on the equation of state from astrophysical sources. Neuron star masses although few are known a… more
Date: October 31, 1990
Creator: Glendenning, N.K.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Lattice Boltzmann Methods for Some 2-D Nonlinear Diffusion Equations:Computational Results

Description: In this paper we examine two lattice Boltzmann methods (that are a derivative of lattice gas methods) for computing solutions to two two-dimensional nonlinear diffusion equations of the form {partial derivative}/{partial derivative}t u = v ({partial derivative}/{partial derivative}x D(u){partial derivative}/{partial derivative}x u + {partial derivative}/{partial derivative}y D(u){partial derivative}/{partial derivative}y u), where u = u({rvec x},t), {rvec x} {element of} R{sup 2}, v is a consta… more
Date: January 1, 1990
Creator: Elton, B.H.; Rodrigue, G.H. (California Univ., Davis, CA (USA). Dept. of Applied Science Lawrence Livermore National Lab., CA (USA)) & Levermore, C.D. (Arizona Univ., Tucson, AZ (USA). Dept. of Mathematics)
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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Iterative methods for nonsymmetric systems on MIMD machines

Description: A wide variety of physical phenomena arising within many scientific disciplines can be described by systems of coupled partial differential equations (PDEs). The numerical approximation of these PDEs often involves the solution of a system of algebraic equations (possibly nonlinear) which are typically large, sparse and nonsymmetric. The increasing computational demands required by the solution of such complex scientific applications has motivated the current direction toward large-scale parall… more
Date: October 16, 1990
Creator: Shadid, J.N. & Tuminaro, R.S.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Numerical modeling of HF skywave radiation from antennas in irregular terrain

Description: The problem of computing the radiation pattern of an HF antenna sited in irregular terrain was investigated. The primary interest is in antennas for skywave communication, however ionospheric models were not considered. Several methods for modeling terrain effects are briefly reviewed. A geometrical optics model for arbitrary terrain is developed and results are compared with published results from solution of a Volterra integral equation for scattering by a Gaussian ridge. This report covers w… more
Date: November 1, 1990
Creator: Burke, G. J.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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3 Dimensional radiation transport in dispersive media

Description: In plasmas the collective motion of free electrons affects the propagation of radiation by bending the light ray trajectory. The closer the light wave frequency is to the electron plasma frequency in value, the more pronounced the effect. We will present the results of radiation transport calculations in 3 spatial dimensions in the refractive plasma environment and compare the calculation to one done where the ray bending has been neglected (straight line ray paths). We also present the numeric… more
Date: November 1, 1990
Creator: Mayle, R.W.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Bayesian approximation of solutions to linear ordinary differential equations

Description: An approach to numerically solving linear ordinary differential equations, based on statistical Bayesian prediction, is described. Preliminary results on the details of choice of correlation parameters and experimental design are given, using first- and second-order example problems. 6 refs., 7 figs.
Date: November 1, 1990
Creator: Herzog, K. J.; Morris, M. D. & Mitchell, T. J.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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An alternative approach to disturbances in boundary layers

Description: By modelling the boundary layer on a flat plate as a piece-wise linear velocity profile it is possible to analyze disturbances in the flow in a systematic manner. The approach is that of an initial-value, boundary-value problem but, unlike classical normal modes employed in stability theory, the solutions here can be obtained in closed form and they are non separable. A specific example is treated where the vertical component of the perturbation velocity is prescribed as a localized pulse initi… more
Date: January 1, 1990
Creator: Easthope, P.F. & Criminale, W.O.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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First-order inflation

Description: In the original proposal, inflation occurred in the process of a strongly first-order phase transition. This model was soon demonstrated to be fatally flawed. Subsequent models for inflation involved phase transitions that were second-order, or perhaps weakly first-order; some even involved no phase transition at all. Recently the possibility of inflation during a strongly first-order phase transition has been revived. In this talk I will discuss some models for first-order inflation, and empha… more
Date: September 1, 1990
Creator: Kolb, E.W. (Fermi National Accelerator Lab., Batavia, IL (USA) Chicago Univ., IL (USA). Enrico Fermi Inst.)
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Estimation of fracture toughness of cast stainless steels in LWR (light water reactor) systems

Description: A procedure and correlations are presented for predicting fracture toughness J-R curves and impact strength of aged cast stainless steels from known material information. The saturation'' fracture toughness of a specific cast stainless steel, i.e., the minimum fracture toughness that would ever be achieved for the material after long-term service, is estimated from the degree of embrittlement at saturation. Degree of embrittlement is characterized in terms of room-temperature Charpy-impact ener… more
Date: October 1, 1990
Creator: Chopra, O. K.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Cyclone performance and optimization

Description: The objectives of this project are: to characterize the gas flow pattern within cyclones, to revise the theory for cyclone performance on the basis of these findings, and to design and test cyclones whose dimensions have been optimized using revised performance theory. This work is important because its successful completion will aid in the technology for combustion of coal in pressurized, fluidized beds. This quarter, an empirical model for predicting pressure drop across a cyclone was develop… more
Date: September 15, 1990
Creator: Leith, D.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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Electron trapping in amorphous silicon: A quantum molecular dynamics study

Description: Quantum molecular dynamics (QMD) simulations provide the real-time dynamics of electrons and ions through numerical solutions of the time-dependent Schrodinger and Newton equations, respectively. Using the QMD approach we have investigated the localization behavior of an excess electron in amorphous silicon at finite temperatures. For time scales on the order of a few picoseconds, we find the excess electron is localized inside a void of radius {approximately}3 {Angstrom} at finite temperatures… more
Date: December 1, 1990
Creator: Yang, Lin H.; Kalia, R.K. & Vashishta, P.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Coherent-state description of free-electron lasers

Description: Free-electron lasers (FEL) have great advantages over traditional lasers because they have proved to be by far the most efficient way to generate coherent radiations which are also tunable over the widest range of frequencies. This is made possible by eliminating the middle-man,'' i.e., the atoms, molecules, or crystals in the traditional laser systems. Using quantum mechanical analysis, Maydey first explained the gain mechanism in propagating relativistic electrons through a static periodic ma… more
Date: January 1990
Creator: Lee, Ching Tsung (Alabama A and M Univ., Normal, AL (United States))
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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Response Matrix Monte Carlo for electron transport

Description: A Response Matrix Monte Carol (RMMC) method has been developed for solving electron transport problems. This method was born of the need to have a reliable, computationally efficient transport method for low energy electrons (below a few hundred keV) in all materials. Today, condensed history methods are used which reduce the computation time by modeling the combined effect of many collisions but fail at low energy because of the assumptions required to characterize the electron scattering. Ana… more
Date: November 1, 1990
Creator: Ballinger, C.T.; Nielsen, D.E. Jr. & Rathkopf, J.A.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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