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Development of an Atmospheric Climate Model with Self-Adapting Grid and Physics

Description: This project was targeting the development of a computational approach that would allow resolving cloud processes on small-scales within the framework of the most recent version of the NASA/NCAR Finite-Volume Community Atmospheric Model (FVCAM). The FVCAM is based on the multidimensional Flux-Form Semi-Lagrangian (FFSL) dynamical core and uses a ?vertically Lagrangian? finite-volume (FV) representation of the model equations with a mass-conserving re-mapping algorithm. The Lagrangian coordinate requires a remapping of the Lagrangian volume back to Eulerian coordinates to restore the original resolution and keep the mesh from developing distortions such as layers with overlapping interfaces. The main objectives of the project were, first, to develop the 3D library which allows refinement and coarsening of the model domain in spherical coordinates, and second, to develop a non-hydrostatic code for calculation of the model variables within the refined areas that could be seamlessly incorporated with the hydrostatic finite volume dynamical core when higher resolution is wanted. We also updated the aerosol simulation model in CAM in order to ready the model for the treatment of aerosol/cloud interactions.
Date: August 10, 2013
Creator: Penner, Joyce E.
Partner: UNT Libraries Government Documents Department

Advanced Variance Reduction for Global k-Eigenvalue Simulations in MCNP

Description: The "criticality" or k-eigenvalue of a nuclear system determines whether the system is critical (k=1), or the extent to which it is subcritical (k<1) or supercritical (k>1). Calculations of k are frequently performed at nuclear facilities to determine the criticality of nuclear reactor cores, spent nuclear fuel storage casks, and other fissile systems. These calculations can be expensive, and current Monte Carlo methods have certain well-known deficiencies. In this project, we have developed and tested a new "functional Monte Carlo" (FMC) method that overcomes several of these deficiencies. The current state-of-the-art Monte Carlo k-eigenvalue method estimates the fission source for a sequence of fission generations (cycles), during each of which M particles per cycle are processed. After a series of "inactive" cycles during which the fission source "converges," a series of "active" cycles are performed. For each active cycle, the eigenvalue and eigenfunction are estimated; after N >> 1 active cycles are performed, the results are averaged to obtain estimates of the eigenvalue and eigenfunction and their standard deviations. This method has several disadvantages: (i) the estimate of k depends on the number M of particles per cycle, (iii) for optically thick systems, the eigenfunction estimate may not converge due to undersampling of the fission source, and (iii) since the fission source in any cycle depends on the estimated fission source from the previous cycle (the fission sources in different cycles are correlated), the estimated variance in k is smaller than the real variance. For an acceptably large number M of particles per cycle, the estimate of k is nearly independent of M; this essentially takes care of item (i). Item (ii) can be addressed by taking M sufficiently large, but for optically thick systems a sufficiently large M can easily be unrealistic. Item (iii) cannot be accounted for by ...
Date: June 1, 2008
Creator: Larsen, Edward W.
Partner: UNT Libraries Government Documents Department

Annual Report 2006 for Hydrodynamics and Radiation Hydrodynamics with Astrophysical Applications

Description: We report the ongoing work of our group in hydrodynamics and radiation hydrodynamics with astrophysical applications. During the period of the existing grant, we have carried out two types of experiments at the Omega laser. One set of experiments has studied radiatively collapsing shocks, obtaining data using a backlit pinhole with a 100 ps backlighter and beginning to develop the ability to look into the shock tube with optical or x-ray diagnostics. Other experiments have studied the deeply nonlinear development of the Rayleigh-Taylor (RT) instability from complex initial conditions, using dual-axis radiographic data with backlit pinholes and ungated detectors to complete the data set for a Ph.D. student. We lead a team that is developing a proposal for experiments at the National Ignition Facility and are involved in experiments at NIKE and LIL. All these experiments have applications to astrophysics, discussed in the corresponding papers. We assemble the targets for the experiments at Michigan, where we also prepare many of the simple components. We also have several projects underway in our laboratory involving our x-ray source. The above activities, in addition to a variety of data analysis and design projects, provide good experience for graduate and undergraduates students. In the process of doing this research we have built a research group that uses such work to train junior scientists.
Date: April 5, 2007
Creator: Drake, R. Paul
Partner: UNT Libraries Government Documents Department

Synchrotron Studies of Quantum Emergence in Non-Low Dimensional Materials Final Report

Description: This document is the final report of research performed under U.S. DOE Award Number DE-FG02-07ER46379, entitled Synchrotron Studies of Quantum Emergence in Non-Low Dimensional Materials. It covers the full period of the award, from June 1, 2007 through May 31, 2011.
Date: August 26, 2011
Creator: Allen, James W.
Partner: UNT Libraries Government Documents Department

Radiation-Induced Segregation and Phase Stability in Candidate Alloys for the Advanced Burner Reactor

Description: Major accomplishments of this project were the following: 1) Radiation induced depletion of Cr occurs in alloy D9, in agreement with that observed in austenitic alloys. 2) In F-M alloys, Cr enriches at PAG grain boundaries at low dose (<7 dpa) and at intermediate temperature (400°C) and the magnitude of the enrichment decreases with temperature. 3) Cr enrichment decreases with dose, remaining enriched in alloy T91 up to 10 dpa, but changing to depletion above 3 dpa in HT9 and HCM12A. 4) Cr has a higher diffusivity than Fe by a vacancy mechanism and the corresponding atomic flux of Cr is larger than Fe in the opposite direction to the vacancy flux. 5) Cr concentration at grain boundaries decreases as a result of vacancy transport during electron or proton irradiation, consistent with Inverse Kirkendall models. 6) Inclusion of other point defect sinks into the KLMC simulation of vacancy-mediated diffusion only influences the results in the low temperature, recombination dominated regime, but does not change the conclusion that Cr depletes as a result of vacancy transport to the sink. 7) Cr segregation behavior is independent of Frenkel pair versus cascade production, as simulated for electron versus proton irradiation conditions, for the temperatures investigated. 8) The amount of Cr depletion at a simulated planar boundary with vacancy-mediated diffusion reaches an apparent saturation value by about 1 dpa, with the precise saturation concentration dependent on the ratio of Cr to Fe diffusivity. 9) Cr diffuses faster than Fe by an interstitial transport mechanism, and the corresponding atomic flux of Cr is much larger than Fe in the same direction as the interstitial flux. 10) Observed experimental and computational results show that the radiation induced segregation behavior of Cr is consistent with an Inverse Kirkendall mechanism.
Date: May 29, 2011
Creator: Was, Gary S. & Wirth, Brian D.
Partner: UNT Libraries Government Documents Department

Final Report for Integrated Multiscale Modeling of Molecular Computing Devices

Description: In collaboration with researchers at Vanderbilt University, North Carolina State University, Princeton and Oakridge National Laboratory we developed multiscale modeling and simulation methods capable of modeling the synthesis, assembly, and operation of molecular electronics devices. Our role in this project included the development of coarse-grained molecular and mesoscale models and simulation methods capable of simulating the assembly of millions of organic conducting molecules and other molecular components into nanowires, crossbars, and other organized patterns.
Date: August 28, 2013
Creator: Glotzer, Sharon C.
Partner: UNT Libraries Government Documents Department

Fast Neutron Imaging Systems

Description: 3-dimensional position-sensitive solid state detectors. In particular, extensive investigation had been carried out on 3-D CdZnTe detectors for detection of fission neutrons.
Date: October 11, 2006
Creator: He, Zhong
Partner: UNT Libraries Government Documents Department

An Advanced Neutronic Analysis Toolkit with Inline Monte Carlo capability for BHTR Analysis

Description: Monte Carlo capability has been combined with a production LWR lattice physics code to allow analysis of high temperature gas reactor configurations, accounting for the double heterogeneity due to the TRISO fuel. The Monte Carlo code MCNP5 has been used in conjunction with CPM3, which was the testbench lattice physics code for this project. MCNP5 is used to perform two calculations for the geometry of interest, one with homogenized fuel compacts and the other with heterogeneous fuel compacts, where the TRISO fuel kernels are resolved by MCNP5.
Date: December 30, 2009
Creator: Martin, William R. & Lee, John C.
Partner: UNT Libraries Government Documents Department

Final Report for the NERI Project

Description: This final report summarizes the research activities during the entire performance period of the NERI grant, including the extra 9 months granted under a no-cost time extension. Building up on the 14 quarterly reports submitted through October 2008, we present here an overview of the research accomplishments under the five tasks originally proposed in July 2004, together with citations for publications resulting from the project. The AFCI-NERI project provided excellent support for two undergraduate and 10 graduates students at the University of Michigan during a period of three years and nine months. Significant developments were achieved in three areas: (1) Efficient deterministic fuel cycle optimization algorithms both for PWR and SFR configurations, (2) Efficient search algorithm for PWR equilibrium cycles, and (3) Simplified Excel-based script for dynamic fuel cycle analysis of diverse cycles. The project resulted in a total of 8 conference papers and three journal papers, including two that will be submitted shortly. Three pending publications are attached to the report.
Date: March 31, 2009
Creator: Lee, John C.
Partner: UNT Libraries Government Documents Department

Unconventional Magnetism in Low Carrier Density Systems and Nanoparticle Composites

Description: Under the auspices of this funding, we have developed a program to synthesize and characterize highly monodispersed magnetic nanoparticles. We have been particularly interested in the origin of the exchange bias effect, which occurs in compound nanoparticles with a ferromagnetic core and an antiferromagnetic shell, and have mostly focused on Co/CoO core-shell nanoparticles. The exchange bias effect involves exchange coupling between the core moment and the antiferromagnetic shell which stabilizes the core moment, which would otherwise be quickly reorienting in ferromagnetic particles of this size.
Date: June 14, 2008
Creator: Aronson, Meigan C
Partner: UNT Libraries Government Documents Department

Final Report 2007: DOE-FG02-87ER60561

Description: This project involved a multi-faceted approach to the improvement of techniques used in Positron Emission Tomography (PET), from radiochemistry to image processing and data analysis. New methods for radiochemical syntheses were examined, new radiochemicals prepared for evaluation and eventual use in human PET studies, and new pre-clinical methods examined for validation of biochemical parameters in animal studies. The value of small animal PET imaging in measuring small changes of in vivo biochemistry was examined and directly compared to traditional tissue sampling techniques. In human imaging studies, the ability to perform single experimental sessions utilizing two overlapping injections of radiopharmaceuticals was tested, and it was shown that valid biochemical measures for both radiotracers can be obtained through careful pharmacokinetic modeling of the PET emission data. Finally, improvements in reconstruction algorithms for PET data from small animal PET scanners was realized and these have been implemented in commercial releases. Together, the project represented an integrated effort to improve and extend all basic science aspects of PET imaging at both the animal and human level.
Date: April 26, 2007
Creator: Kilbourn, Michael R
Partner: UNT Libraries Government Documents Department

Final Report: "Large-Eddy Simulation of Anisotropic MHD Turbulence"

Description: To acquire better understanding of turbulence in flows of liquid metals and other electrically conducting fluids in the presence of steady magnetic fields and to develop an accurate and physically adequate LES (large-eddy simulation) model for such flows. The scientific objectives formulated in the project proposal have been fully completed. Several new directions were initiated and advanced in the course of work. Particular achievements include a detailed study of transformation of turbulence caused by the imposed magnetic field, development of an LES model that accurately reproduces this transformation, and solution of several fundamental questions of the interaction between the magnetic field and fluid flows. Eight papers have been published in respected peer-reviewed journals, with two more papers currently undergoing review, and one in preparation for submission. A post-doctoral researcher and a graduate student have been trained in the areas of MHD, turbulence research, and computational methods. Close collaboration ties have been established with the MHD research centers in Germany and Belgium.
Date: June 23, 2008
Creator: Zikanov, Oleg
Partner: UNT Libraries Government Documents Department

Alloys for 1000 degree C service in the Next Generation Nuclear Plant NERI 05-0191

Description: The objective of the proposed research is to define strategies for the improvement of alloys for structural components, such as the intermediate heat exchanger and primary-to-secondary piping, for service at 1000 degree C in the He environment of the NGNP. Specifically, we will investigate the oxidation/carburization behavior and microstructure stability and how these processes affect creep. While generating this data, the project will also develop a fundamental understanding of how impurities in the He environment affect these degradation processes and how this understanding can be used to develop more useful life prediction methodologies.
Date: January 15, 2009
Creator: Was, Gary S.; Jones, J.W. & Pollock, T.
Partner: UNT Libraries Government Documents Department

Localized Deformation as a Primary Cause of Irradiation Assisted Stress Corrosion Cracking

Description: The objective of this project is to determine whether deformation mode is a primary factor in the mechanism of irradiation assisted intergranular stress corrosion cracking of austenitic alloys in light watert reactor core components. Deformation mode will be controlled by both the stacking fault energy of the alloy and the degree of irradiation. In order to establish that localized deformation is a major factor in IASCC, the stacking fault energies of the alloys selected for study must be measured. Second, it is completely unknown how dose and SFE trade-off in terms of promoting localized deformation. Finally, it must be established that it is the localized deformation, and not some other factor that drives IASCC.
Date: March 31, 2009
Creator: Was, Gary S.
Partner: UNT Libraries Government Documents Department

Accelerator-Based Irradiation Creep of Pyrolytic Carbon Used in TRISO Fuel Particles for the (VHTR) Very Hight Temperature Reactors

Description: Pyrolytic carbon (PyC) is one of the important structural materials in the TRISO fuel particles which will be used in the next generation of gas-cooled very-high-temperature reactors (VHTR). When the TRISO particles are under irradiation at high temperatures, creep of the PyC layers may cause radial cracking leading to catastrophic particle failure. Therefore, a fundamental understanding of the creep behavior of PyC during irradiation is required to predict the overall fuel performance.
Date: July 30, 2010
Creator: Wang, Lumin & Was, Gary
Partner: UNT Libraries Government Documents Department

Thermodynamic Properties of Nonstoichiometric Nickel Tellurides and of Tellurium

Description: As part of a thermodynamic study of NiTe and NiTe/sub 2/, an attempt was made to gather data which would determine zero-point entropies as a function of composition. Part of the necessary data have been gathered, and in addition a number of other pertinent or interesting properties of the nickel tellurides, and of Te, have been investigated. Specific heats from 4 to 350 deg K have been measured on NiTe/sub 1.1/ NiTe/sub 1.5/, and NiTe/sub 2.0/, and the thermodynamic functions of these and all intermediate compositions may be considered accurately known over this temperature range. The method employed was conventional precise adiabatic calorimetry in an existing apparatus. The melting point of Te has been redetermined and the highly discordant literature critically reexamined; the triple point may now be stated with some confidence to be 449.7 plus or minus 0.2 deg C. The dissociation pressures of compositions from NiTe/sub 1.5/ to NiTe/ sub 2.0/ have been accurately measured at temperatures up to 780 deg C in order to determine the partial molal free energies and entropies of Te in these compounds. These measurements have incidentally elucidated the phase behavior in the Te-rich region, showing a high solubility of Ni in liquid Te at elevated temperatures, and incongruent melting of the solid solutions such that Te-rich solid solutions are unstable at elevated temperatures. By extrapolation, the boiling point of Te is computed to be 993.6 plus or minus 2 deg C. and the heat of vaporization to be 33,850-908 t cal/mole (one mole equals two gram-atoms). with an accuracy of plus or minus several hundred calories, from the triple point to t = 850 deg , or perhaps 950 deg C. This figure may be considered more accurate, though stated with less precision, than those of previous investigators. (auth)
Date: January 1, 1957
Creator: Machol, R. E.
Partner: UNT Libraries Government Documents Department

Nuclear Chemical Research Radiochemical Separations and Activation Analysis. Progress Report No. 6 for November 1956-October 1957. Dept. Of Chemistry

Description: The present facilities at the University of Michigan for research in nuclear chemistry are described. The determination of the cross sections of various (d, alpha ) reactions induced by thc 7.78 plus or minus 0.05 Mev deuterons from the Unlversity of Michigan cyclotron is presented. The work on the absolute (d, alpha ) reaction cross sections has been simed at surveying the reaction yields as a function of atomic number with the hope of establishlng the presence or absence of closed shell effects in these values. Methods are presented for the separation of carrier free P, Se, Mn, Co, Y, and Nb. Work continued on the development and evaluation of radiochemical separatlon procedures for Ba, Sr, Ca, Ag. and In. A series of small-scale laboratory tests was conducted to determine the feasibility of the decontamination of I/sup 131/ from air by means of adsorption on a highly efflcient solid adsorber molecular sieve. Graphs are presented of atomic cross sections for thermal neutron activation of isotopes not found in nature vs. half life of daughter radioisotopes produced. (For preceding period see AECU-5575.) (W.L.H.)
Date: November 1, 1957
Partner: UNT Libraries Government Documents Department

Correlation of Polarographic Walf-Wave Potentials With Nuclear Magnetic Resonance "Chemical Shifts." Parallel Correlation With Chemical Reactivity Parameters. Report No. 35

Description: Since nuclear magnetic resonance ''chemical shifts'' are considered to be good measures of electron densities in molecules, the extent to which they can be correlated with the polarographic half-wave potentials of organic compounds has been surveyed. To extend the applicability and interpretation of the proposed correlation, parallel correlatioan of E, with Hammett's sigma and Taft's sigma parameters were made, since both of the latter are also regarded as indication of electronic distrinution at the reactive center. The data in general support the view that changes in half-wave potential with structure are due to both electronic and steric effects, as well as perhaps to adsorption phenomena. Significantly, NMR data obtained with one type of substituent could be correlated with E/sub 1/2 data for a similar type of substituent. New NMR data for aliphatic nitro and halogen compounds are reported. (auth)
Date: July 14, 1958
Creator: Bennett, C. E. & Elving, P. J.
Partner: UNT Libraries Government Documents Department

Enrichment of Isotopes by the Difference in Rates of Isotopic Reactions

Description: The difference in rates of reaction of isotopic molecules may be utilized to produce appreciable isotope enrichments. When a competitive irreversible isotopic reaction is carried out to a high extent of completion, the residual unconverted substrate becomes exponentlally enriched in the heavier isotope. In deuterium systems, a substantial function of the D inventory is retained in the enriched residual substrate, so that conversion of the depleted product is unnecessary. For isotopes of heavier elements such as C/sup 13/, N/ sup 15/, and O/sup 18/ the retention is low, so that product conversion and recycling is desirable unless the starting material is of negligible value. Experiments are described in which enrichments of C/sup 13/ have been obtained using the reaction rate principle in dehydration of formic acid and hydrolysis of urea. Procedures are given for the preparation of decimolar barium carbonate at the level of 1.6% C/sup 13/, and molar barium carbonate at the 1.4% level starting with commercial materials. (J.R.D.)
Date: April 15, 1957
Creator: Bernstein, R. B.
Partner: UNT Libraries Government Documents Department

Alpha Ferric Oxide: Low Temperature Heat Capacity and Thermodynamic Functions

Description: ABS>The heat capacity of synthetic alpha ferric oxide was determined at 5 to 350 K. The experimental technique is described, and the heat capacity and molal thermodyamic functions are tabulated. The heat capacity vs. temperature is shown graphically. (J.R.D.)
Date: January 1, 1957
Creator: Gronvold, F. & Westrum, E. F., Jr.
Partner: UNT Libraries Government Documents Department