Time-Dependent Two-Dimensional Radiation Hydrodynamics of Accreting Matter Onto Highly Magnetized Neutron Stars (open access)

Time-Dependent Two-Dimensional Radiation Hydrodynamics of Accreting Matter Onto Highly Magnetized Neutron Stars

We present for the first time, the self-consistent solution of the two-dimensional, time-dependent equations of radiation-hydrodynamics governing the accretion of matter onto the highly magnetized polar caps of luminous x-ray pulsars. The calculations show a structure in the accretion column very different from previous one-zone uniform models. We have included all the relevant magnetic field corrections to both the hydrodynamics and the radiative transport. We include a new theory for the diffusion and advection of both radiation energy density and photon number density. For initially uniformly accreting models with super-Eddington flows, we have uncovered evidence of strong radiation-driven outflowing optically thin radiation filled regions of the accretion column embedded in optically-thick inflowing plasma. The development of these photon bubbles'' have growth times on the order of a millisecond and show fluctuations on sub-millisecond timescales. The photon bubbles are likely to be a consequence of convective over-stability and may result in observable fluctuations in the emitted luminosity leading to luminosity dependent changes in the pulse profile. This may provide important new diagnostics for conditions in accreting x-ray pulsars. 13 refs., 18 figs.
Date: November 24, 1989
Creator: Klein, R.I. (California Univ., Los Angeles, CA (USA). Dept. of Astronomy Lawrence Livermore National Lab., CA (USA) California Univ., Los Angeles, CA (USA). Inst. of Geophysics and Planetary Physics) & Arons, J. (California Univ., Berkeley, CA (USA). Dept. of Astronomy California Univ., Los Angeles, CA (USA). Inst. of Geophysics and Planetary Physics CEA Centre d'Etudes Nucleaires de Saclay, 91 -
Object Type: Article
System: The UNT Digital Library
Hadron masses in lattice gauge theories: The inclusions of dynamical fermions (open access)

Hadron masses in lattice gauge theories: The inclusions of dynamical fermions

Hadron masses are calculated on an 8/sup 3/ /times/ 16 lattice using four flavors of staggered fermion to generate the gauge configurations, but using Wilson fermions to calculate the hadron propagators. The identification of a value of the Wilson hopping parameter with the value of the bare quark mass used in the simulations is discussed.
Date: November 24, 1987
Creator: Richards, D.G.
Object Type: Article
System: The UNT Digital Library
Safety assessment document for the dynamic test complex (Building 836) (open access)

Safety assessment document for the dynamic test complex (Building 836)

A safety assessment was performed to determine if potential accidents at the 836 Complex at Site 300 could present undue hazards to the general public, personnel at Site 300, or have an adverse effect on the environment. The credible accidents that might have an effect on these facilities or have off-site consequences were considered. These were earthquake, extreme wind (including missiles), lightning, flood, criticality, high explosive (H) detonation that disperses uranium and beryllium, spontaneous oxidation of plutonium, explosions due to finely divided particles, and a fire.
Date: November 24, 1981
Creator: Odell, B.N. & Pfeifer, H.E.
Object Type: Report
System: The UNT Digital Library
Goose River, Maine, demonstration project, January 1978-October 1978. Final report (open access)

Goose River, Maine, demonstration project, January 1978-October 1978. Final report

The proposed Goose River Project is a commercial power development consisting of 4 power dams and one storage dam. All available energy is to be wholesaled to the Central Maine Power Company, the utility holding the franchise for the area. A description of the economic feasibility of the proposed project is presented.
Date: November 24, 1978
Creator: unknown
Object Type: Report
System: The UNT Digital Library
Potential impacts of artificial intelligence expert systems on geothermal well drilling costs: (open access)

Potential impacts of artificial intelligence expert systems on geothermal well drilling costs:

The Geothermal research Program of the US Department of Energy (DOE) has as one of its goals to reduce the cost of drilling geothermal wells by 25 percent. To attain this goal, DOE continuously evaluates new technologies to determine their potential in contributing to the Program. One such technology is artifical intelligence (AI), a branch of computer science that, in recent years, has begun to impact the marketplace in a number of fields. Expert systems techniques can (and in some cases, already have) been applied to develop computer-based ''advisors'' to assist drilling personnel in areas such as designing mud systems, casing plans, and cement programs, optimizing drill bit selection and bottom hole asssembly (BHA) design, and alleviating lost circulation, stuck pipe, fishing, and cement problems. Intelligent machines with sensor and/or robotic directly linked to AI systems, have potential applications in areas of bit control, rig hydraulics, pipe handling, and pipe inspection. Using a well costing spreadsheet, the potential savings that could be attributed to each of these systems was calculated for three base cases: a dry steam well at The Geysers, a medium-depth Imerial Valley well, and a deep Imperial Valley well. Based on the average potential savings to be …
Date: November 24, 1987
Creator: Satrape, J.V.
Object Type: Report
System: The UNT Digital Library
Long-range and head-on beam-beam compensation studies in RHIC with lessons for the LHC (open access)

Long-range and head-on beam-beam compensation studies in RHIC with lessons for the LHC

Long-range as well as head-on beam-beam effects are expected to limit the LHC performance with design parameters. They are also important consideration for the LHC upgrades. To mitigate long-range effects current carrying wires parallel to the beam were proposed. Two such wires are installed in RHIC where they allow studying the effect of strong long-range beam-beam effects, as well as the compensation of a single long-range interaction. The tests provide benchmark data for simulations and analytical treatments. To reduce the head-on beam-beam effect electron lenses were proposed for both RIDC and the LHC. We present the experimental long-range beam-beam program at RHIC and report on head-on compensations studies based on simulations.
Date: November 24, 2008
Creator: Fischer, W.; Luo, Y.; Abreu, N.; Calaga, R.; Montag, C.; Robert-Demolaize, G. et al.
Object Type: Article
System: The UNT Digital Library
Depth-resolved soft x-ray photoelectron emission microscopy in nanostructures via standing-wave excited photoemission (open access)

Depth-resolved soft x-ray photoelectron emission microscopy in nanostructures via standing-wave excited photoemission

We present an extension of conventional laterally resolved soft x-ray photoelectron emission microscopy. A depth resolution along the surface normal down to a few {angstrom} can be achieved by setting up standing x-ray wave fields in a multilayer substrate. The sample is an Ag/Co/Au trilayer, whose first layer has a wedge profile, grown on a Si/MoSi2 multilayer mirror. Tuning the incident x-ray to the mirror Bragg angle we set up standing x-ray wave fields. We demonstrate the resulting depth resolution by imaging the standing wave fields as they move through the trilayer wedge structure.
Date: November 24, 2008
Creator: Kronast, F.; Ovsyannikov, R.; Kaiser, A.; Wiemann, C.; Yang, S. -H.; Locatelli, A. et al.
Object Type: Article
System: The UNT Digital Library
Evaluation of near field rock treatment during constructions (LADSfeature #22) (open access)

Evaluation of near field rock treatment during constructions (LADSfeature #22)

The purpose of this report is to evaluate the effect of near-field rock treatment by injection of reactive material (calcite) above the drift for the purpose of decreasing postclosure drift seepage. The method used for the calculation was a coupled reaction-transport numerical model for gas-water-rock interaction. This includes the mass conservation of heat, liquid and gas for thermohydrological calculations, of aqueous and gaseous species for advective and diffusive transport, and the kinetics of mineral-water reactions.
Date: November 24, 1998
Creator: Sonnenthal, Eric & Spycher, Nicolas
Object Type: Report
System: The UNT Digital Library
Formic Acid Dehydrogenation on Au-Based Catalysts at Near-Ambient Temperatures (open access)

Formic Acid Dehydrogenation on Au-Based Catalysts at Near-Ambient Temperatures

Formic acid (HCOOH) is a convenient hydrogen carrier in fuel cells designed for portable use. Recent studies have shown that HCOOH decomposition is catalyzed with Ru-based complexes in the aqueous phase at near-ambient temperatures. HCOOH decomposition reactions are used frequently to probe the effects of alloying and cluster size and of geometric and electronic factors in catalysis. These studies have concluded that Pt is the most active metal for HCOOH decomposition, at least as large crystallites and extended surfaces. The identity and oxidation state of surface metal atoms influence the relative rates of dehydrogenation (HCOOH {yields} H{sub 2} + CO{sub 2}) and dehydration (HCOOH {yields} H{sub 2}O + CO) routes, a selectivity requirement for the synthesis of CO-free H{sub 2} streams for low-temperature fuel cells. Group Ib and Group VIII noble metals catalyze dehydrogenation selectively, while base metals and metal oxides catalyze both routes, either directly or indirectly via subsequent water-gas shift (WGS) reactions.
Date: November 24, 2008
Creator: Ojeda, Manuel & Iglesia, Enrique
Object Type: Article
System: The UNT Digital Library
Oxide Ferromagnetic Semiconductors for Spin-Electronic Transprt (open access)

Oxide Ferromagnetic Semiconductors for Spin-Electronic Transprt

The objective of this research was to investigate the viability of oxide magnetic semiconductors as potential materials for spintronics. We identified some members of the solid solution series of ilmenite (FeTiO3) and hematite (Fe2O3), abbreviated as (IH) for simplicity, for our investigations based on their ferromagnetic and semiconducting properties. With this objective in focus we limited our investigations to the following members of the modified Fe-titanates: IH33 (ilmenitehematite with 33 atomic percent hematite), IH45 (ilmenite-hematite with 45 atomic percent hematite), Mn-substituted ilmenite (Mn-FeTiO3), and Mn-substituted pseudobrookite (Mn- Fe2TiO5). All of them are: 1. wide bandgap semiconductors with band gaps ranging in values between 2.5 to 3.5 eV; 2. n-type semiconductors; 3.they exhibit well defined magnetic hysteresis loops and 4. their magnetic Curie points are greater than 400K. Ceramic, film and single crystal samples were studied and based on their properties we produced varistors (also known as voltage dependent resistors) for microelectronic circuit protection from power surges, three-terminal microelectronic devices capable of generating bipolar currents, and an integrated structured device with controlled magnetic switching of spins. Eleven refereed journal papers, three refereed conference papers and three invention disclosures resulted from our investigations. We also presented invited papers in three international conferences …
Date: November 24, 2008
Creator: Dr. R. K. Pandey, Cudworth Endowed Professor (Professor Emeritus of The Unviersity of Alabama) Ingram Endowed Professor, Ingram School of Engineering and Physics Department, Texas State University, San Marocs, TX78666
Object Type: Report
System: The UNT Digital Library
Search for a permanent electric dipole moment using liquid 129Xe (open access)

Search for a permanent electric dipole moment using liquid 129Xe

Search for an electric dipole moment is one of the best motivated low-energy approaches for investigating physics beyond the Standard Model. Our experimental effort is focused on improving the limit on EDM in liquid 129Xe to put constraints on nuclear CP-violating interactions. High nuclear spin density and high electrical breakdown strength make 129Xe a promising medium for EDM searches. At the time the project started, the transverse nuclear spin relaxation time T2 of 129Xe was unknown. We made measurements of T2 using NMR spin-echo techniques and found that it is exceeds 1300 sec, the longest relaxation time ever measured in a liquid [1]. We also began to investigate non-linear dipolar interaction effects in a high-density spin-polarized liquid Xe. In the second iteration of the experiment we setup a high-Tc SQUID system in magnetic shields and performed detailed studies of Xe spin precession. We developed a model for non-linear dipolar interactions and found that for one set of conditions non-linear interactions can delay spin dephasing due to magnetic field gradients, while for another set of conditions they can lead to exponential amplification of the spin precession signals [2]. Our experimental data were in good quantitative agreement with predictions of the model. …
Date: November 24, 2008
Creator: ROMALIS, PROFESSOR MICHAEL
Object Type: Report
System: The UNT Digital Library
EMSL Quarterly Highlights Report: 4th Quarter, FY08 (open access)

EMSL Quarterly Highlights Report: 4th Quarter, FY08

This report outlines the science highlights, publications, and other happenings at EMSL in 4th quarter of FY08.
Date: November 24, 2008
Creator: Showalter, Mary Ann
Object Type: Report
System: The UNT Digital Library
Fastbus backplane impedance (open access)

Fastbus backplane impedance

None
Date: November 24, 1982
Creator: Haldeman, M.
Object Type: Report
System: The UNT Digital Library
High-frequency microinstabilities in hot-electron plasmas (open access)

High-frequency microinstabilities in hot-electron plasmas

Instabilities with frequencies in the neighborhood of the electron cyclotron frequency are of interest in determining stable operating regimes of hot-electron plasmas in EBT devices and in tandem mirrors. Previous work used model distributions significantly different than those suggested by recent Fokker-Planck studies. We use much more realistic model distributions in a computer code that solves the full electromagnetic dispersion relation governing longitudinal and transverse waves in a uniform plasma. We allow for an arbitrary direction of wave propagation. Results for the whistler and upper-hybrid loss-cone instabilities are presented.
Date: November 24, 1981
Creator: Chen, Y. J.; Nevins, W. M. & Smith, G. R.
Object Type: Article
System: The UNT Digital Library
Transmission-corrected x-ray fluorescence analysis of uranium and plutonium solutions using a dual transmission source (open access)

Transmission-corrected x-ray fluorescence analysis of uranium and plutonium solutions using a dual transmission source

The energy-dispersive x-ray fluorescence analysis (XRFA) technique has been implemented at several spent nuclear fuel reprocessing facilities for nondestructive measurements of uranium and/or plutonium concentrations in process streams and product storage tanks. An important factor in these quantitative measurements is the absorption of the fluoresced x-rays by the solution matrix, which must be taken into account to accurately quantify the U or Pu concentrations. We describe a new, accurate method using a dual transmission source of Gd-153 and Co-57 to correct for matrix effects. Results of measurements on uranium and plutonium solution standards show the methodology to be better than 0.5%, which includes statistical precision, over the concentration range from 1 to 250 g/l. 5 refs., 4 figs., 3 tabs.
Date: November 24, 1987
Creator: Ruhter, W. D. & Camp, D. C.
Object Type: Article
System: The UNT Digital Library
Measurement of radiation dose using radiochromic film (open access)

Measurement of radiation dose using radiochromic film

We have irradiated samples of radiochromic film to doses between 0.005 and lMrad in a Co[sup 60] facility at ANL. The doses computed using the manufacturer's calibration curves for the absorption at 600 and 510 nm have been compared with the dose obtained from ion chamber measurements. Excellent agreement is obtained and high precision can be maintained by baseline measurement of the films prior to irradiation, appropriate choice of film and wavelength used.
Date: November 24, 1992
Creator: Jankowski, D. J. & Proudfoot, J.
Object Type: Report
System: The UNT Digital Library
Corrosion evaluation of cooling-water treatments for gas centrifuge facilities (open access)

Corrosion evaluation of cooling-water treatments for gas centrifuge facilities

The corrosion resistance of six different types of weighted metal coupons was evaluated at 29/sup 0/C (84/sup 0/F) in flowing water containing nitrite-borate-silicate corrosion inhibitors. The question for evaluation was whether it would be more advantageous: (1) to drain the treated cooling water from the centrifuge machine and to expose them to moisture-laden air over an assumed shop downtime and repair perid of 1 month; or (2) to let the treated cooling water remain stagnant in the machines during this downtime. The moisture-laden-air exposure was more detrimental.
Date: November 24, 1980
Creator: Schmidt, C. R. & Meredith, P. F.
Object Type: Report
System: The UNT Digital Library
Acid rain: the impact of local sources (open access)

Acid rain: the impact of local sources

It has been assumed that acid rain is predominantly a problem of long-range transport of pollutants from large fossil fuel combustion sources, namely coal-fired utilities. However, close examination of fuel use information and source emission characteristics in the Adirondacks, Florida, and California suggests that local oil burning and automotive sources may be major contributors to the occurrence of acid rain in these areas. This report describes the possible role of local combustion sources in the production of acid rain, discusses the implications of the findings, and their relevance to alternative control strategies for acid rain. Oil-fired boilers, especially the smaller commercial, industrial, and residential units, produce at least 3 to 10 times as much primary sulfate per unit of sulfur content as coal-fired units. Moreover, oil-fired units emit comparatively large quantities of catalytic compounds capable of rapidly converting still more sulfur oxide to sulfate in the atmosphere. Thus, in areas where large quantities of oil are burned, the direct impact from locally generated sulfates may equal or even exceed that produced by imported sulfates derived from distant coal-burning sources. Fuel consumption data show that large quantities of oil are being consumed in areas experiencing acid rain. Forty percent of the …
Date: November 24, 1980
Creator: Spaite, P.; Esposito, M.P.; Szabo, M.F. & Devitt, T.W.
Object Type: Report
System: The UNT Digital Library
Interactive fundamental physics. [THE REAL STUFF: The New Expanded Media Physics Course for secondary school students] (open access)

Interactive fundamental physics. [THE REAL STUFF: The New Expanded Media Physics Course for secondary school students]

THE REAL STUFF is an Expanded Media Physics Course aimed at students still in the formative early years of secondary school. Its consists of a working script for an interactive multimedia study unit in basic concepts of physics. The unit begins with a prologue on the Big Bang that sets the stage, and concludes with a lesson on Newton's first law of motion. The format is interactive, placing the individual student in control of a layered hypermedia'' structure that enables him or her to find a level of detail and difficulty that is comfortable and meaningful. The intent is to make physics relevant, intellectually accessible and fun. On-screen presenters and demonstrators will be females and males of various ages, ethnicities and backgrounds, and will include celebrities and physicists of note. A lean, layered design encourages repeated, cumulative study and makes the material useful for self-directed Teaming even by college students. THE REAL STUFF introduces a new science teaching paradigm, a way to teach science that will engage even students who have declined'' to be interested in science in the past. Increased participation in science by women, African-Americans and Spanish-speaking students is a particular goal.
Date: November 24, 1992
Creator: Rubin, E.L.
Object Type: Report
System: The UNT Digital Library
High Temperature Alkali Corrosion of Ceramics in Coal Gas (open access)

High Temperature Alkali Corrosion of Ceramics in Coal Gas

Calcia-stabilized cubic zirconia was mixed with soda, then fired at 840-1100 C. SiC was also reacted with alkali-containing atmosphere at 1000 C.
Date: November 24, 1992
Creator: Pickrell, G. R.; Sun, T. & Brown, J. J.
Object Type: Report
System: The UNT Digital Library
Advanced gas cooled nuclear reactor materials evaluation and development program. Progress report, July 1--September 30, 1978 (open access)

Advanced gas cooled nuclear reactor materials evaluation and development program. Progress report, July 1--September 30, 1978

Results of work performed from July 1, 1978 through September 30, 1978 on the Advanced Gas Cooled Nuclear Reactor Materials Evaluation and Development Program are presented. Candidate alloys were evaluated for Very High Temperature Reactor Nuclear Process Heat (NPH) and Direct Cycle Helium Turbine (DCHT) applications, in terms of the affect of simulated reactor primary coolant (Helium containing small amounts of various other gases), the high temperatures, and long time exposures, on the mechanical properties and structural and surface stability of selected candidate alloys. The activities associated with the characterization of the materials for the screening test program are reported, i.e., test specimen preparation, information from the materials characterization tests performed by General Electric, and the status of the simulated reactor helium supply system, testing equipment, and gas chemistry analysis instrumentation and equipment. The status of the data management system is presented.
Date: November 24, 1978
Creator: unknown
Object Type: Report
System: The UNT Digital Library
Improved optics for automatic stored-seam tracking on an electron-beam welder (open access)

Improved optics for automatic stored-seam tracking on an electron-beam welder

A commercial 7.5-kW electron-beam welder has been optically upgraded. The viewing system has been replaced by high-resolution optics (36 line pairs per millimeter (36l/mm) with video option. A high-intensity arc lamp provides illumination of the weld region. The upgraded optical system provides the capability for making accurate and repeatable welds with computer-automated seam tracking.
Date: November 24, 1978
Creator: Kitzke, K. A.
Object Type: Report
System: The UNT Digital Library
Monthly energy review, November 1993 (open access)

Monthly energy review, November 1993

The Monthly Energy Review gives information on production, distribution, and consumption for various energy sources, e.g. petroleum, natural gas, oil, coal, electricity, and nuclear energy. Some data is also included on international energy sources and supplies, the import of petroleum products into the US and pricing and reserves data (as applicable) for the various sources of energy listed above.
Date: November 24, 1993
Creator: unknown
Object Type: Report
System: The UNT Digital Library
High temperature alkali corrosion of ceramics in coal gas. Quarterly progress report No. 5, September 1, 1992--December 1, 1992 (open access)

High temperature alkali corrosion of ceramics in coal gas. Quarterly progress report No. 5, September 1, 1992--December 1, 1992

Calcia-stabilized cubic zirconia was mixed with soda, then fired at 840-1100 C. SiC was also reacted with alkali-containing atmosphere at 1000 C.
Date: November 24, 1992
Creator: Pickrell, G. R.; Sun, T. & Brown, J. J
Object Type: Report
System: The UNT Digital Library