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1,455 Matching Results
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Bill Viola: "The Crossing"
Catalog for the exhibition, "Bill Viola: 'The Crossing,'" November 12, 1998–February 1, 1999,held at the Dallas Museum of Art. Includes: essay and image.
Date:
1998
Creator:
Dallas Museum of Art
Object Type:
Pamphlet
System:
The Portal to Texas History
Geothermal regimes of the Clearlake region, northern California
The first commercial production of power from geothermal energy, at The Geysers steamfield in northern California in June 1960, was a triumph for the geothermal exploration industry. Before and since, there has been a search for further sources of commercial geothermal power in The Geysers--Clear Lake geothermal area surrounding The Geysers. As with all exploration programs, these were driven by models. The models in this case were of geothermal regimes, that is, the geometric distribution of temperature and permeability at depth, and estimates of the physical conditions in subsurface fluids. Studies in microseismicity and heat flow, did yield geophysical information relevant to active geothermal systems. Studies in stable-element geochemistry found hiatuses or divides at the Stoney Creek Fault and at the Collayomi Fault. In the region between the two faults, early speculation as to the presence of steamfields was disproved from the geochemical data, and the potential existence of hot-water systems was predicted. Studies in isotope geochemistry found the region was characterized by an isotope mixing trend. The combined geochemical data have negative implications for the existence of extensive hydrothermal systems and imply that fluids of deep origin are confined to small, localized systems adjacent to faults that act as …
Date:
June 1, 1998
Creator:
Amador, M.; Burns, K. L. & Potter, R. M.
Object Type:
Report
System:
The UNT Digital Library
U.S. Hydropower Resource Assessment - California
The U.S. Department of Energy is developing an estimate of the underdeveloped hydropower potential in the United States. For this purpose, the Idaho National Engineering and Environmental Laboratory developed a computer model called Hydropower Evaluation Software (HES). HES measures the undeveloped hydropower resources available in the United States, using uniform criteria for measurement. The software was developed and tested using hydropower information and data provided by the Southwestern Power Administration. It is a menu-driven program that allows the personal computer user to assign environmental attributes to potential hydropower sites, calculate development suitability factors for each site based on the environmental attributes present, and generate reports based on these suitability factors. This report describes the resource assessment results for the State of California.
Date:
October 1, 1998
Creator:
Conner, A. M.; Rinehart, B. N. & Francfort, J. E.
Object Type:
Report
System:
The UNT Digital Library
Increasing Heavy Oil Reserves in the Wilmington Oil Field Through Advanced Reservoir Characterization and Thermal Production Technologies
The project involves improving thermal recovery techniques in a slope and basin clastic (SBC) reservoir in the Wilmington field, Los Angeles Co., Calif. using advanced reservoir characterization and thermal production technologies. The existing steamflood in the Tar zone of Fault Block (FB) II-A has been relatively inefficient because of several producibility problems which are common in SBC reservoirs. Inadequate characterization of the heterogeneous turbidite sands, high permeability thief zones, low gravity oil, and nonuniform distribution of remaining oil have all contributed to poor sweep efficiency, high steam-oil ratios, and early steam breakthrough. Operational problems related to steam breakthrough, high reservoir pressure, and unconsolidated formation sands have caused premature well and downhole equipment failures. In aggregate, these reservoir and operational constraints have resulted in increased operating costs and decreased recoverable reserves. The advanced technologies to be applied include: (1) Develop three-dimensional (3-D) deterministic and stochastic geologic models. (2) Develop 3-D deterministic and stochastic thermal reservoir simulation models to aid in reservoir management and subsequent development work. (3) Develop computerized 3-D visualizations of the geologic and reservoir simulation models to aid in analysis. (4) Perform detailed study on the geochemical interactions between the steam and the formation rock and fluids. (5) Pilot …
Date:
March 3, 1998
Creator:
Hara, Scott
Object Type:
Report
System:
The UNT Digital Library
Electromagnetic induction tomography field experiment at Lost Hills, CA
We have collected borehole to surface electromagnetic induction field data for a shallow steam injection that is underway at Mobil Oil� s Lost Hills-3 field in San Joaquin Valley. Earlier work had been done at the same site by Wilt et al. (1996). This site is an interesting test for techniques under development for environmental engineering, because it can be viewed as an excellent analog of a shallow environmental remediation using steam injection. Surface magnetic field data (vertical and radial fields, magnitude and phase) were collected using 18 receiver stations along two profiles which ran radially from the EM transmitter well from 5 m to 120 m. The data at each surface station were collected while the EM transmitter was raised slowly from a depth of 120 m to a final depth of 20 m. As part of this experiment, a calibration of the EM transmitter was also performed. Magnetic field data from Lost Hills were successfully collected, including both vertical and horizontal (surface radial) magnitude and phase data along a northerly profile and along a westerly profile. We have observed that the radial receiver data appear to be better behaved than the vertical receiver data, suggesting that these data …
Date:
November 3, 1998
Creator:
Berryman, J G & Buettner, H M
Object Type:
Article
System:
The UNT Digital Library
Scientific drilling into the San Andreas fault and site characterization research: Planning and coordination efforts. Final technical report
The fundamental scientific issue addressed in this proposal, obtaining an improved understanding of the physical and chemical processes responsible for earthquakes along major fault zones, is clearly of global scientific interest. By sampling the San Andreas fault zone and making direct measurements of fault zone properties to 4.0 km at Parkfield they will be studying an active plate-boundary fault at a depth where aseismic creep and small earthquakes occur and where a number of the scientific questions associated with deeper fault zone drilling can begin to be addressed. Also, the technological challenges associated with drilling, coring, downhole measurements and borehole instrumentation that may eventually have to be faced in deeper drilling can first be addressed at moderate depth and temperature in the Parkfield hole. Throughout the planning process leading to the development of this proposal they have invited participation by scientists from around the world. As a result, the workshops and meetings they have held for this project have involved about 350 scientists and engineers from about a dozen countries.
Date:
August 30, 1998
Creator:
Zoback, M. D.
Object Type:
Report
System:
The UNT Digital Library
Instrumentation for the absorbers in the low Beta* Insertions of the LHC
Concepts are examined for the measurement of luminosity, beam-beam separation and transverse beam shape and size using the high flux of forward neutral particles produced at the low {beta}* (high luminosity) interaction points (IP's) of the LHC. At design luminosity 10{sup 34} cm{sup -2}sec{sup -1} the flux of neutrals striking the neutral beam absorbers (TAN) in front of the D2 beam separation dipoles is high enough ({approx} 8 neutrons per bunch crossing with mean energy 2.3 TeV) to allow measurement of luminosity with 1% precision in {approx} 1.8 x 10{sup 3} bunch crossings and measurement of beam-beam separation at the collision point with 0.1{sigma}* precision in {approx} 3 x 10{sup 4} bunch crossings. An Argon ionization chamber placed near the shower maximum {approx} 22 cm inside the Cu neutral beam absorber is analyzed as a possible detector. Background effects due to beam-gas interactions, beam-halo scraping, beam crossing angle modulation and transverse drift of the IP are estimated and found to be small compared to the anticipated signals. Extending these concepts to the front quadrupole absorber (TAS) and segmenting the ionization chambers into four quadrants allows additional measurements of the beam-beam crossing angle and the transverse position of the IP.
Date:
August 1, 1998
Creator:
Turner, W.C.
Object Type:
Article
System:
The UNT Digital Library
Laser-plasma interactions relevant to Inertial Confinement Fusion
Research into laser-driven inertial confinement fusion is now entering a critical juncture with the construction of the National Ignition Facility (NIF) at Lawrence Livermore National Laboratory (LLNL). Many of the remaining unanswered questions concerning NIF involve interactions between lasers and plasmas. With the eventual goal of fusion power in mind, laser-plasma interactions relevant to laser fusion schemes is an important topic in need of further research. This work experimentally addresses some potential shortcuts and pitfalls on the road to laser-driven fusion power. Current plans on NIF have 192 laser beams directed into a small cylindrical cavity which will contain the fusion fuel; to accomplish this the beams must cross in the entrance holes, and this intersection will be in the presence of outward-flowing plasma. To investigate the physics involved, interactions of crossing laser beams in flowing plasmas are investigated with experiments on the Nova laser facility at LLNL. It was found that in a flowing plasma, energy is transferred between two crossing laser beams, and this may have deleterious consequences for energy balance and ignition in NIF. Possible solutions to this problem are presented. A recently-proposed alternative to standard laser-driven fusion, the ''fast ignitor'' concept, is also experimentally addressed in …
Date:
November 2, 1998
Creator:
Wharton, Kenneth Bradford
Object Type:
Thesis or Dissertation
System:
The UNT Digital Library
Observation of resonant energy transfer between identical-frequency laser beams
Enhanced transmission of a low intensity laser beam is observed when crossed with an identical-frequency beam in a plasma with a flow velocity near the ion sound speed. The time history of the enhancement and the dependence on the flow velocity strongly suggest that this is due to energy transfer between the beams via a resonant ion wave with zero frequency in the laboratory frame. The maximum energy transfer has been observed when the beams cross in a region with Mach 1 flow. The addition of frequency modulation on the crossing beams is seen to reduce the energy transfer by a factor of two. Implications for indirect-drive fusion schemes are discussed.
Date:
December 9, 1998
Creator:
Afeyan, B. B.; Cohen, B. I.; Estabrook, K. G.; Glenzer, S. H.; Joshi, C.; Kirkwood, R. K. et al.
Object Type:
Article
System:
The UNT Digital Library
Bigplate: an oblique angle explosive EOS test
Bigplate is an advanced explosive equation of state (EOS) test. It consists of a point detonator driving a large disc (100 mm radius) of explosive, which pushes a 0.5 mm thick copper or tantalum plate. The plate is observed by a five-beam Fabry-Perot interferometer, which has beams at 0, 10, 20,40 and 80 mm on the plate. A short Fabry gives the jump-off to high accuracy; a long Fabry runs out to I0-15 microsec. A detailed error analysis is given, with the final velocity measurements considered good to ±0.066 mm/microsec. Jump-offs are measured to 0.01-0.02 microsec. Spall is seen in all shots, which creates a time delay on both the first and second velocity plateaus. A 0.1 microsec delay in jump-off of unknown origin is also seen at 80 mm. In order of decreasing explosive ideality, the explosives tired have been LX-14, LX-04 and LX-17. To partially negate the time delays, the data and code runs are overlaid at each radial position between the first and second plateaus. Traditional JWL's model LX-14 and LX-04 within accuracy, but not so for LX-17. The spall may be partly modeled using the pmin model but high resolution zoning is required. At longer times, …
Date:
April 16, 1998
Creator:
Anderson, S; Avara, R; Fried, L; Janzen, J; McGuire, E; Souers, P C et al.
Object Type:
Report
System:
The UNT Digital Library
Modeling anomalous surface - wave propagation across the Southern Caspian basin
The crust of the south Caspian basin consists of 15-25 km of low velocity, highly attenuating sediment overlying high velocity crystalline crust. The Moho depth beneath the basin is about 30 km as compared to about 50 km in the surrounding region. Preliminary modeling of the phase velocity curves shows that this thick sediments of the south Caspian basin are also under-lain by a 30-35 km thick crystalline crust and not by typical oceanic crust. This analysis also suggest that if the effect of the over-pressuring of the sediments is to reduce Poissons` ratio, the over-pressured sediments observed to approximately 5 km do not persist to great depths. It has been shown since 1960`s that the south Caspian basin blocks the regional phase Lg. Intermediate frequency (0.02-0.04 Hz) fundamental mode Raleigh waves propagating across the basin are also severely attenuated, but the low frequency surface waves are largely unaffected. This attenuation is observed along the both east-to-west and west-to-east great circle paths across the basin, and therefore it cannot be related to a seismograph site effect. We have modeled the response of surface waves in an idealized rendition of the south Caspian basin model using a hybrid normal mode / …
Date:
January 9, 1998
Creator:
Priestly, K. F.; Patton, H. J. & Schultz, C. A.
Object Type:
Report
System:
The UNT Digital Library
The impact of ELMs on the ITER divertor
Edge-Localized-Modes (ELMs) are expected to present a significant transient flux of energy and particles to the ITER divertor. The threshold for ablation of the graphite target will be reached if the ELM transient exceeds Q/t{sup 1/2} {approximately} 45 MJ-m{sup {minus}2}-s{sup {minus}1/2} where Q is the ELM deposition energy density and t is the ELM deposition time. The ablation parameter in ITER can be determined by scaling four factors from present experiments: the ELM energy loss from the core plasma, the fraction of ELM energy deposited on the divertor target, the area of the ELM profile onto the target, and finally the time for the ELM deposition. Review of the ELM energy loss of Type 1 ELM data suggests an ITER ELM energy loss of 2--6% of the stored energy or 25--80 MJ. The fraction of heating power crossing the separatrix due to ELMs is nearly constant (20--40%) resulting in an inverse relationship between ELM amplitude and frequency. Measurements on DIII-D and ASDEX-Upgrade indicate that 50--80% of the ELM energy is deposited on the target. There is currently no evidence for a large fraction of the ELM energy being dissipated through radiation. Profiles of the ELM heat flux are typically 1--2 …
Date:
July 1, 1998
Creator:
Leonard, A.W.; Osborne, T.H.; Suttrop, W.; Hermann, A.; Itami, K.; Lingertat, J. et al.
Object Type:
Article
System:
The UNT Digital Library
Symmetry breaking at magnetic surfaces and interfaces
Examples represented of how symmetry breaking enters into consideration of the physical properties of magnetic surfaces and ultrathin films. The role of magnetic anisotropy is discussed to understand: (i) the existence of two-dimensional (2D) magnetic long-ranged order at finite temperature, (ii) magnetization scaling behavior at the Curie transition, (iii) the 2D spin reorientation transition, and (iv) step-induced magnetic behavior. Experimental examples cited include ultrathin magnetic Fe and Co overlayer and wedge structures grown onto single crystal substrates that are either flat or curved to produce vicinal surfaces with a continuous gradient in the step density. Also included is an example of an atomically flat manganite intergrowth that appears as a stacking fault in a bulk single crystal of a naturally layered structure.
Date:
November 20, 1998
Creator:
Qiu, Z. Q.
Object Type:
Article
System:
The UNT Digital Library
Plasma flow in the DIII-D divertor
Indications that flows in the divertor can exhibit complex behavior have been obtained from 2-D modeling but so far remain mostly unconfirmed by experiment. An important feature of flow physics is that of flow reversal. Flow reversal has been predicted analytically and it is expected when the ionization source arising from neutral or impurity ionization in the divertor region is large, creating a high pressure zone. Plasma flows arise to equilibrate the pressure. A radiative divertor regime has been proposed in order to reduce the heat and particle fluxes to the divertor target plates. In this regime, the energy and momentum of the plasma are dissipated into neutral gas introduced in the divertor region, cooling the plasma by collisional, radiative and other atomic processes so that the plasma becomes detached from the target plates. These regimes have been the subject of extensive studies in DIII-D to evaluate their energy and particle transport properties, but only recently it has been proposed that the energy transport over large regions of the divertor must be dominated by convection instead of conduction. It is therefore important to understand the role of the plasma conditions and geometry on determining the region of convection-dominated plasma in …
Date:
July 1998
Creator:
Boedo, J. A.; Porter, G. D. & Schaffer, M. J.
Object Type:
Article
System:
The UNT Digital Library
Behavior of electron and ion transport in discharges with an internal transport barrier in the DIII-D tokamak
The authors report results of experiments to further determine the underlying physics behind the formation and development of internal transport barriers (ITB) in the DIII-D tokamak. The initial ITB formation occurs when the neutral beam heating power exceeds a threshold value during the early stages of the current ramp in low-density discharges. This region of reduced transport, made accessible by suppression of long-wavelength turbulence by sheared flows, is most evident in the ion temperature and impurity rotation profiles. In some cases, reduced transport is also observed in the electron temperature and density profiles. If the power is near the threshold, the barrier remains stationary and enclosed only a small fraction of the plasma volume. If, however, the power is increased, the transport barrier expands to encompass a larger fraction of the plasma volume. The dynamic behavior of the transport barrier during the growth phase exhibits rapid transport events that are associated with both broadening of the profiles and reductions in turbulence and associated transport. In some, but not all, cases, these events are correlated with the safety factor q passing through integer values. The final state following this evolution is a plasma exhibiting ion thermal transport at or below neoclassical …
Date:
December 1, 1998
Creator:
Greenfield, C. M.; Staebler, G. M. & Rettig, C. L.
Object Type:
Article
System:
The UNT Digital Library
Oral History Interview with Jack Browder, January 15, 1998
Access:
Use of this item is restricted to the UNT Community
Interview with Jack Browder, a Army WWII veteran from Duncan, Oklahoma. Browder was a staff officer with the 741st Tank Battalion in Europe; he recounts his education and entry to active duty in 1941, transfer to the new 741st, armor training and exercises, duties as a supply officer, preparations for the Normandy invasion, DD tanks, D-Day, attachment to the 2nd Infantry Division and advances through northern France, the M4 Sherman, his thoughts on General George S. Patton, the Battle of Saint Lô, souvenirs and trading, the Battle of the Bulge, crossing Germany into Czechoslovakia, returning to the States, and postwar service.
Date:
January 15, 1998
Creator:
Marcello, Ronald E. & Browder, Jack
Object Type:
Book
System:
The UNT Digital Library
Meeting the Challenge of International Peace Operations: Assessing the Contribution of Technology
This report contains the proceedings of a conference held in Livermore, California September 9-10, 1996.
Date:
June 1, 1998
Creator:
Gliksman, A
Object Type:
Article
System:
The UNT Digital Library
Measurements of flows in the DIII-D divertor by Mach probes
First measurements of Mach number of background plasma in the DIII-D divertor are presented in conjunction with temperature T{sub e} and density n{sub e} using a fast scanning probe array. To validate the probe measurements, the authors compared the T{sub e}, n{sub e} and J{sub sat} data to Thomson scattering data and find good overall agreement in attached discharges and some discrepancy for T{sub e} and n{sub e} in detached discharges. The discrepancy is mostly due to the effect of large fluctuations present during detached plasmas on the probe characteristic; the particle flux is accurately measured in every case. A composite 2-D map of measured flows is presented for an ELMing H-mode discharge and they focus on some of the details. They have also documented the temperature, density and Mach number in the private flux region of the divertor and the vicinity of the X-point, which are important transition regions that have been little studied or modeled. Background parallel plasma flows and electric fields in the divertor region show a complex structure.
Date:
June 1, 1998
Creator:
Boedo, J. A.; Lehmer, R.; Moyer, R. A.; Watkins, J. G.; Porter, G. D.; Evans, T. E. et al.
Object Type:
Article
System:
The UNT Digital Library
Generation of Subpicosecond X-ray Pulses Using RF OrbitDeflection
None
Date:
July 1, 1998
Creator:
Zholents, A.; Heimann, P.; Zolotorev, M. & Byrd, J.
Object Type:
Article
System:
The UNT Digital Library
DC SQUID Spectrometers for Nuclear Quadrupole and Low-Field Nuclear Magnetic Resonance Spectroscopy
None
Date:
April 1, 1998
Creator:
TonThat, Dinh M.
Object Type:
Thesis or Dissertation
System:
The UNT Digital Library
[Studies of the repair of radiation-induced genetic damage in Drosophila]. Annual progress report, February 1, 1993--November 1, 1994
This research focuses on two repair deficient mutations in Drosophila melanogaster, namely mei-9, mei-41. In addition, the authors propose to extend this study to include the mus-312 mutation. They expect these studies to provide substantial insights into both the molecular mechanisms of DNA repair in Drosophila and the role these genes play in normal biological processes.
Date:
September 1998
Creator:
Hawley, R. S.
Object Type:
Report
System:
The UNT Digital Library
Time-and-state resolved spectroscopy, diffraction, and circular dichroism in core photoelectron emission from clean and oxygen-covered W(110)
None
Date:
October 1998
Creator:
Ynzunza, Ramon Xavier
Object Type:
Thesis or Dissertation
System:
The UNT Digital Library
Study of Pair and many-body interactions in rare-gas halide atom clusters using negative ion zero electron kinetic energy (ZEKE) and threshold photodetachment spectroscopy
None
Date:
July 9, 1998
Creator:
Yourshaw, Ivan
Object Type:
Thesis or Dissertation
System:
The UNT Digital Library
Plasma pressure and flows during divertor detachment
MHD theory applied to tokamak plasma scrape-off layer (SOL) equilibria requires Pfirsch-Schlueter current, which, because the magnetic lines are open, normally closes through electrically conducting divertor or limiter components. During detached divertor operation the Pfirsch-Schlueter current path to the divertor target is sometimes blocked, in which case theory predicts that the plasma develops a poloidal pressure gradient around the upstream SOL and a corresponding parallel flow, in order to satisfy all the conditions of MHD equilibrium. This paper reports the only known examples of detached diverted plasma in the DIII-D tokamak with blocked Pfirsch-Schlueter current, and they show no clear SOL poloidal pressure differences. However, the predicted pressure differences are small, near the limit of detectability with the available diagnostics. In the more usual DIII-D partially detached divertor operation mode, the Pfirsch-Schlueter current appears to never be blocked, and no unusual poloidal pressure differences are observed, as expected. Finally, a local overpressure is observed just inside the magnetic separatrix near the X-point in both attached and detached Ohmically heated plasmas.
Date:
August 1, 1998
Creator:
Schaffer, M. J.; Brooks, N. H.; Boedo, J. A.; Isler, R. C. & Moyer, R. A.
Object Type:
Article
System:
The UNT Digital Library