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Goddard rattler-jamming mechanism for quantifying pressure dependence of elastic moduli of grain packs

Description: An analysis is presented to show how it is possible for unconsolidated granular packings to obey overall non-Hertzian pressure dependence due to the imperfect and random spatial arrangements of the grains in these packs. With imperfect arrangement, some gaps that remain between grains can be closed by strains applied to the grain packing. As these gaps are closed, former rattler grains become jammed and new stress-bearing contacts are created that increase the elastic stiffness of the packing. By allowing for such a mechanism, detailed analytical expressions are obtained for increases in bulk modulus of a random packing of grains with increasing stress and strain. Only isotropic stress and strain are considered in this analysis. The model is shown to give a favorable fit to laboratory data on variations in bulk modulus due to variations in applied pressure for bead packs.
Date: January 5, 2009
Creator: Pride, Steven R. & Berryman, James G.
Partner: UNT Libraries Government Documents Department

Geometrical Aspects of a Hollow-cathode Magnetron (HCM)

Description: A hollow-cathode magnetron (HCM), built by surrounding a planar sputtering-magnetron cathode with a hollow-cathode structure (HCS), is operable at substantially lower pressures than its planar-magnetron counterpart. We have studied the dependence of magnetron operational parameters on the inner diameter D and length L of a cylindrical HCS. Only when L is greater than L sub zero, a critical length, is the HCM operable in the new low-pressure regime. The critical length varies with HCS inner diameter D. Explanations of the lower operational pressure regime, critical length, and plasma shape are proposed and compared with a one-dimension diffusion model for energetic or primary electron transport. At pressures above 1 mTorr, an electron-impact ionization model with Bohm diffusion at a temperature equivalent to one-half the primary electron energy and with an ambipolar constraint can explain the ion-electron pair creation required to sustain the discharge. The critical length L sub zero is determined by the magnetization length of the primary electrons.
Date: November 1, 1998
Creator: Cohen, Samuel, A. & Wang, Zhehui
Partner: UNT Libraries Government Documents Department

Thermal decomposition of UO{sub 3}-2H{sub 2}0

Description: The first part of the report summarizes the literature data regarding the uranium trioxide water system. In the second part, the experimental aspects are presented. An experimental program has been set up to determine the steps and species involved in decomposition of uranium oxide di-hydrate. Particular attention has been paid to determine both loss of free water (moisture in the fuel) and loss of chemically bound water (decomposition of hydrates). The influence of water pressure on decomposition has been taken into account.
Date: February 26, 1998
Creator: Flament, T.A.
Partner: UNT Libraries Government Documents Department

Pressure Fluctuations as a Diagnostic Tool for Fluidized Beds

Description: The purpose of this project was to investigate the origin of pressure fluctuations in fluidized bed systems. The study assessed the potential for using pressure fluctuations as an indicator of fluidized bed hydrodynamics in both laboratory scale cold-models and industrial scale boilers. Both bubbling fluidized beds and circulating fluidized beds were evaluated. Testing including both cold-flow models and laboratory and industrial-scale combustors operating at elevated temperatures. The study yielded several conclusions on the relationship of pressure fluctuations and hydrodynamic behavior in fluidized beds. The study revealed the importance of collecting sufficiently long data sets to capture low frequency (on the order of 1 Hz) pressure phenomena in fluidized beds. Past research has tended toward truncated data sets collected with high frequency response transducers, which miss much of the spectral structure of fluidized bed hydrodynamics. As a result, many previous studies have drawn conclusions concerning hydrodynamic similitude between model and prototype fluidized beds that is insupportable from the low resolution data presented.
Date: May 1, 1998
Creator: Bure, Ethan; Schroeder, Joel R.; Cruz, Ramon De La & Brown, Robert C.
Partner: UNT Libraries Government Documents Department

Pressure Fluctuations as a Diagnostic Tool for Fluidized Beds

Description: The purpose of this project is to investigate the origin of pressure fluctuations in fluidized bed systems. The study will asses the potential for using pressure fluctuations as an indicator of fluidized bed hydrodynamics in both laboratory scale cold-models and industrial scale boilers.
Date: April 23, 1998
Creator: Schroeder, Joel R. & Brown, Robert C.
Partner: UNT Libraries Government Documents Department

The lean oxidation of iso-octane at elevated pressures

Description: Both spark-ignition and compression-ignition engines burn large molecular-weight blended fuels, a class to which the primary reference fuels (PRF), n-heptane and iso-octane belong. In this study experiments were performed using iso-octane in a high pressure flow reactor at a temperature of 925 K, at 3, 6 and 9 atm pressure and with a fuel/air equivalence ratio of approximately 0.05. Many hydrocarbon and oxygenated hydrocarbon intermediates were identified and quantified as a function of time. These experimental results provide a strin- gent test of the low temperature chemistry portion of a kinetic model as they emphasise the importance of alkyl radical addition to molecular oxygen and internal H-atom isomerization reactions relative to alkyl radical decomposition reactions. A detailed chemical kinetic mechanism is used to simulate these experiments. We provide comparisons of model predictions with experimentally measured species profiles and describe how each species is formed as predicted by the detailed model.
Date: October 30, 1998
Creator: Chen, J S; Curran, H J & Litzinger, T A
Partner: UNT Libraries Government Documents Department

Pressure dependence of donor excitation spectra in AlSb

Description: We have investigated the behavior of ground to bound excited-state electronic transitions of Se and Te donors in AlSb as a function of hydrostatic pressure. Using broadband far-infrared Fourier transform spectroscopy, we observe qualitatively different behaviors of the electronic transition energies of the two donors. While the pressure derivative of the Te transition energy is small and constant, as might be expected for a shallow donor, the pressure derivatives of the Se transition energies are quadratic and large at low pressures, indicating that Se is actually a deep donor. In addition, at pressures between 30 and 50 kbar, we observe evidence of an anti-crossing between one of the selenium electronic transitions and a two-phonon mode.
Date: January 16, 2002
Creator: Hsu, L.; McCluskey, M.D. & Haller, E.E.
Partner: UNT Libraries Government Documents Department

Pressure Dependence of Line Widths of Microwave Spectra of Sulphur Dioxide

Description: Measurements of line width parameters for eleven rotational transitions of type (J -- J + 1) of SO2 were made and are reported herein. The line width quantum number (J) trend was obtained. The microwave spectrograph used for these measurements of line width is described. Operational methods to operate the spectrograph are presented and discussed, with particular attention given to how to measure the line width. Suggestions for future avenues of probing this molecule to ascertain the non-uniform behavior of the line width parameter over the quantum number and frequency range are given.
Date: December 1972
Creator: Yang, Wei Han
Partner: UNT Libraries

Topical Report: Task 2.2 "Pressure Transmissibility"

Description: The rate and amplitude of pressure transmission of various drilling fluids--particularly aphron drilling fluids--are measured in a long conduit and in sand packs to determine how pressure transmissibility can affect fluid invasion.
Date: July 30, 2004
Creator: Belkin, Arkadiy & Growcock, Fred
Partner: UNT Libraries Government Documents Department

Investigation of internal cavity pressure and thickness response for injection-molded polycarbonates

Description: The internal cavity pressure of an injection mold was evaluated as a controlling variable for the thickness of typical polycarbonate moldings. Mold temperature, melt temperature, and mold-fill mode were evaluated for their effects on molding thickness and thickness runout, designated as the total indicator reading. (TIR). (auth)
Date: November 1, 1973
Creator: Black, P.C.
Partner: UNT Libraries Government Documents Department

Modeling flow in a pressure-sensitive, heterogeneous medium

Description: Using an asymptotic methodology, including an expansion in inverse powers of {radical}{omega}, where {omega} is the frequency, we derive a solution for flow in a medium with pressure dependent properties. The solution is valid for a heterogeneous medium with smoothly varying properties. That is, the scale length of the heterogeneity must be significantly larger then the scale length over which the pressure increases from it initial value to its peak value. The resulting asymptotic expression is similar in form to the solution for pressure in a medium in which the flow properties are not functions of pressure. Both the expression for pseudo-phase, which is related to the 'travel time' of the transient pressure disturbance, and the expression for pressure amplitude contain modifications due to the pressure dependence of the medium. We apply the method to synthetic and observed pressure variations in a deforming medium. In the synthetic test we model one-dimensional propagation in a pressure-dependent medium. Comparisons with both an analytic self-similar solution and the results of a numerical simulation indicate general agreement. Furthermore, we are able to match pressure variations observed during a pulse test at the Coaraze Laboratory site in France.
Date: June 1, 2009
Creator: Vasco, Donald W. & Minkoff, Susan E.
Partner: UNT Libraries Government Documents Department


Description: Sensitive (0.15 ppm) and unambiguous detection of carbon monoxide is reported and a comparison of acoustically resonant and nonresonant detectors is given. The pressure dependence of the optoacoustic signal is discussed in the context of atmospheric absorption.
Date: October 1, 1977
Creator: Gerlach, R. & Amer, N.M.
Partner: UNT Libraries Government Documents Department

Materials Performance in USC Steam

Description: Materials Performance in USC Steam: (1) pressure effects on steam oxidation - unique capability coming on-line; (2) hydrogen evolution - hydrogen permeability apparatus to determine where hydrogen goes during steam oxidation; and (3) NETL materials development - steam oxidation resource for NETL developed materials.
Date: September 7, 2011
Creator: Holcomb, G. R.; Tylczak, J.; Meier, G. H. & Yanar, N. M.
Partner: UNT Libraries Government Documents Department

Method and Apparatus for Atomizing Fluids with a Multi-Fluid Nozzle

Description: The invention relates to a method and apparatus for atomizing liquids. In particular, the present invention relates to a method and apparatus for atomizing heavy hydrocarbon fuels such as diesel, as part of a fuel reforming process. During normal operating conditions the fuel is atomized by a high pressure fluid. Under start-up conditions when only a low pressure gas is available the fuel films across part of the nozzle and is subsequently atomized by a radially directed low pressure dispersion gas.
Date: December 7, 2004
Creator: Novick, Vincent J. & Ahluwalia, Rajesh K.
Partner: UNT Libraries Government Documents Department

Nonlinear elastic properties of the piezoelectric crystal: GaPO{sub 4}

Description: These properties were investigated at high pressure/ordinary temperature and low temperature/ordinary pressure. Pressure dependence of the elastic constants (nonlinear behavior) shows that the GaPO{sub 4} crystal undergoes a structural phase transition around 14 GPa. This is tentatively correlated with a potential instability observed at low temperature (50 K).
Date: 1996-23~
Creator: Zarembowitch, A.; Palmier, D.; Polian, A. & Grimsditch, M.
Partner: UNT Libraries Government Documents Department