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Nonlinear symmetric stability of planetary atmospheres

Description: The energy-Casimir method is applied to the problem of symmetric stability in the context of a compressible, hydrostatic planetary atmosphere with a general equation of state. Linear stability criteria for symmetric disturbances to a zonally symmetric baroclinic flow are obtained. In the special case of a perfect gas the results of Stevens (1983) are recovered. Nonlinear stability conditions are also obtained that, in addition to implying linear stability, provide an upper bound on a certain positive-definite measure of disturbance amplitude.
Date: November 1, 1994
Creator: Bowman, J.C. & Shepherd, T.G.
Partner: UNT Libraries Government Documents Department

Mesoscale Molecular Dynamics of Geomaterials: the Glass Transition, Long-Range Structure of Amorphous Silicates and Relation between Structure, Dynamics and Properties of geomaterials at elevated Temperature and Pressure

Description: Objectives: Our aims were (1) Large particle-number Molecular Dynamics (MD) simulations of molten silicate and aluminosilicate geomaterials (e.g., CaAl{sub 2}Si{sub 2}O{sub 8}, MgSiO{sub 3}, Mg{sub 2}SiO{sub 4}) with emphasis on understanding the connection between atomic structure and properties at temperatures and pressures characteristic of Earth's mantle (2) Study of the transport properties and equations of state for silicate liquids based on the MD results (3) Development of geochemical models for the evolution of crustal magma bodies undergoing simultaneous assimilation, fractional crystallization, periodic recharge and periodic eruption and application to magmatic systems (4) Study of current-day rates of generation and eruption of magma on earth.
Date: July 31, 2006
Creator: Spera, Frank
Partner: UNT Libraries Government Documents Department

A new global hydrogen equation of state model

Description: Simple statistical mechanics models have been assembled into a wide-range equation of state for the hydrogen isotopes. The solid is represented by an Einstein-Grtineisen model delimited by a Lindemann melting curve. The fluid is represented by an ideal gas plus a soft-sphere fluid configurational term. Dissociation and ionization are approximated by modifying the ideal gas chemical-equilibrium formulation. The T = 0 isotherm and dissociation models have been fitted to new diamond-anvil isotherm and laser-generated shock data. The main limitation of the model is in ionization at high compression.
Date: June 25, 1999
Creator: Young, D
Partner: UNT Libraries Government Documents Department

Shock-wave properties of soda-lime glass

Description: Planar impact experiments and wave profile measurements provided single and double shock equation of state data to 30 GPa. Both compression wave wave profile structure and release wave data were used to infer time-dependent strength and equation of state properties for soda-lime glass.
Date: November 1996
Creator: Grady, D. E. & Chhabildas, L. C.
Partner: UNT Libraries Government Documents Department

Equation of State Measurements of Materials Using a Three-Stage Gun to Impact Velocities of 11km/s

Description: Understanding high pressure behavior of homogeneous as well as heterogeneous materials is necessary in order to address the physical processes associated with hypervelocity impact events related to space science applications including orbital debris impact and impact lethality. At very high impact velocities, material properties will be subjugated to phase-changes, such as melting and vaporization. These phase states cannot be obtained through conventional gun technology. These processes need to be represented accurately in hydrodynamic codes to allow credible computational analysis of impact events resulting from hypervelocity impact. In this paper, techniques that are being developed and implemented to obtain the needed shock loading parameters (Hugoniot states) for material characterization studies, namely shock velocity and particle velocity, will be described at impact velocities up to 11 km/s. What is new in this report is that these techniques are being implemented for use at engagement velocities never before attained utilizing two-stage light-gas gun technology.
Date: September 26, 2000
Partner: UNT Libraries Government Documents Department

Modeling Initiation in Exploding Bridgewire Detonators

Description: One- and two-dimensional models of initiation in detonators are being developed for the purpose of evaluating the performance of aged and modified detonator designs. The models focus on accurate description of the initiator, whether it be an EBW (exploding bridgewire) that directly initiates a high explosive powder or an EBF (exploding bridgefoil) that sends an inert flyer into a dense HE pellet. The explosion of the initiator is simulated using detailed MHD equations of state as opposed to specific action-based phenomenological descriptions. The HE is modeled using the best available JWL equations of state. Results to date have been promising, however, work is still in progress.
Date: May 18, 2005
Creator: Hrousis, C A
Partner: UNT Libraries Government Documents Department

Three-Dimensional Magnetohydrodynamic Simulation of Slapper Initiation Systems

Description: Although useful information can be gleaned from 2D and even 1D simulations of slapper type initiation systems, these systems are inherently three-dimensional and therefore require full 3D representation to model all relevant details. Further, such representation provides additional insight into optimizing the design of such devices from a first-principles perspective and can thereby reduce experimental costs. We discuss in this paper several ongoing efforts in modeling these systems, our pursuit of validation, and extension of these methods to other systems. Our results show the substantial dependence upon highly accurate global equations of state and resistivity models in these analyses.
Date: March 9, 2010
Creator: Christensen, J S & Hrousis, C A
Partner: UNT Libraries Government Documents Department


Description: Compression wave analysis started nearly 50 years ago with Fowles. Coperthwaite and Williams gave a method that helps identify simple and steady waves. We have been developing a method that gives describes the non-isentropic character of compression waves, in general. One result of that work is a simple analysis tool. Our method helps clearly identify when a compression wave is a simple wave, a steady wave (shock), and when the compression wave is in transition. This affects the analysis of compression wave experiments and the resulting extraction of the high-pressure equation of state.
Date: August 1, 2011
Creator: Orlikowski, D & Minich, R
Partner: UNT Libraries Government Documents Department

Equations of state for titanium and Ti6A14V alloy.

Description: The PANDA code is used to build tabular equations of state (EOS) for titanium and the alloy Ti4Al6V. Each EOS includes solid-solid phase transitions, melting, vaporization, and thermal electronic excitation. Separate EOS tables are constructed for the solid and fluid phases, and the PANDA phase transition model is used to construct a single multiphase table. The model explains a number of interesting features seen in the Hugoniot data, including an anomalous increase in shock velocity, recently observed near 200 GPa in Ti6Al4V. These new EOS tables are available for use with the CTH code and other hydrocodes that access the CTH database.
Date: October 1, 2003
Creator: Kerley, Gerald Irwin (Kerley Technical Services, Appomattox, VA)
Partner: UNT Libraries Government Documents Department

Equations of state for hydrogen and deuterium.

Description: This report describes the complete revision of a deuterium equation of state (EOS) model published in 1972. It uses the same general approach as the 1972 EOS, i.e., the so-called 'chemical model,' but incorporates a number of theoretical advances that have taken place during the past thirty years. Three phases are included: a molecular solid, an atomic solid, and a fluid phase consisting of both molecular and atomic species. Ionization and the insulator-metal transition are also included. The most important improvements are in the liquid perturbation theory, the treatment of molecular vibrations and rotations, and the ionization equilibrium and mixture models. In addition, new experimental data and theoretical calculations are used to calibrate certain model parameters, notably the zero-Kelvin isotherms for the molecular and atomic solids, and the quantum corrections to the liquid phase. The report gives a general overview of the model, followed by detailed discussions of the most important theoretical issues and extensive comparisons with the many experimental data that have been obtained during the last thirty years. Questions about the validity of the chemical model are also considered. Implications for modeling the 'giant planets' are also discussed.
Date: December 1, 2003
Creator: Kerley, Gerald Irwin (Kerley Technical Services, Appomattox, VA)
Partner: UNT Libraries Government Documents Department

Changes to the LANL gas-driven two-stage gun: Magnetic gauge instrumentation, etc.

Description: Our gas-driven two-stage gun was designed and built to do initiation studies on insensitive high explosives as well as other equation of state experiments on inert materials. Our preferred method of measuring initiation phenomena involves the use of magnetic particle velocity gauges. In order to accommodate this type of gauging in our two-stage gun, projectile velocity was sacrificed in favor of a larger experimental target area (obtained by using a 50 mm diameter launch tube). We have used magnetic gauging on our 72-mm bore diameter single-stage gun for over 15 years and it has proven a very effective technique to monitor reactive shock wave evolution. This technique has now been adapted to our gas-driven two-stage gun. We describe the method used, as well as some of the difficulties that arose while installing this technique. Several magnetic gauge experiments have been completed on plastic materials. Waveforms obtained in one experiment are given, along with the Hugoniot information that was obtained. This new technique is now working quite well, as is evidenced by the data. To our knowledge, this is the first time magnetic gauging has been used on a two-stage gun. We have also made changes to the burst diaphragm package in the transition section to ensure that the petals do not break off during the opening process and to increase the burst pressure. This will also be discussed briefly.
Date: December 31, 1996
Creator: Sheffield, S.A.; Gustavsen, R.L.; Martinez, A.R. & Alcon, R.R.
Partner: UNT Libraries Government Documents Department

Estimate for the maximum compression of single shocks

Description: The authors derive that the maximum compression for any single-shock Hugoniot has an upper bound of 7. For the principal Hugoniot, they present a simple analytic estimate for the maximum compression as a function of {rho}{sub o} (initial density), A (atomic weight), Z (atomic number), and {Delta}E (the sum of cohesion, dissociation, and total ionization energies).
Date: February 1, 1998
Creator: Johnson, J.D.
Partner: UNT Libraries Government Documents Department

Phase change in uranium: Discrepancy between experiment and theory

Description: Using a diamond-anvil cell (DAC) phase transformation and room temperature Equation of State (EOS) for some actinides and lanthanides were studied to multimegabar (megabar = 100 GPa) pressures. Experimental data are compared with the theoretically predicted crystal structural changes and the pressure-volume relationships. There is a general agreement between theory and experiment for the structural changes in the lighter actinides, however in detail there are some discrepancies still. A generalized trend for the phase transformations in the lanthanides can be seen, which again has broad agreement with theory. We conclude that an accurate and robust theoretical base for predicting the phase transformations in the f-electron metals can be developed by incorporating the DAC data.
Date: July 22, 1996
Creator: Akella, J.
Partner: UNT Libraries Government Documents Department

Joint Actinide Shock Physics Experimental Research (JASPER) Facility Update

Description: The JASPER Facility utilizes a Two-Stage Light Gas Gun to conduct equation-of-state(EOS) experiments on plutonium and other special nuclear materials. The overall facility will be discussed with emphasis on the Two-Stage Light Gas Gun characteristics and control interfaces and containment. The containment systems that were developed for this project will be presented.
Date: October 1, 2003
Creator: Conrad, C. H.; Miller, J.; Cowan, M.; Martinez, M. & Whitcomb, B.
Partner: UNT Libraries Government Documents Department