Resource Type

States

Characterization of Environmental Stability of Pulsed Laser Deposited Oxide Ceramic Coatings (open access)

Characterization of Environmental Stability of Pulsed Laser Deposited Oxide Ceramic Coatings

A systematic investigation of candidate hydrogen permeation materials applied to a substrate using Pulsed Laser Deposition has been performed. The investigation focused on application of leading permeation-resistant materials types (oxide, carbides, and metals) on a stainless steel substrate. and evaluation of the stability of the applied coatings. Type 304L stainless steel substrates were coated with aluminum oxide, chromium oxide, and aluminum. Characterization of the coating-substrate system adhesion was performed using scratch adhesion testing and microindentation. Coating stability and environmental susceptibility were evaluated for two conditions-air at 350 degrees Celsius and Ar-H2 at 350 degrees Celsius for up to 100 hours. Results from this study have shown the pulsed laser deposition process to be an extremely versatile technology that is capable of producing a sound coating/substrate system for a wide variety of coating materials.
Date: March 2, 2004
Creator: Adams, Thad M.
System: The UNT Digital Library
Direct Experimental Evidence of Back-Surface Acceleration from Laser-Irradiated Foils (open access)

Direct Experimental Evidence of Back-Surface Acceleration from Laser-Irradiated Foils

Au foils were irradiated with a 100-TW, 100-fs laser at intensities greater than 10{sup 20} W/cm{sup 2} producing proton beams with a total yield of {approx} 10{sup 11} and maximum proton energy of > 9 MeV. Removing contamination from the back surface of Au foils with an Ar-ion sputter gun reduced the total yield of accelerated protons to less than 1% of the yield observed without removing contamination. Removing contamination the front surface (laser-interaction side) of the target had no observable effect on the proton beam. We present a one-dimensional particle-in-cell simulation that models the experiment. Both experimental and simulation results are consistent with the back-surface acceleration mechanism described in the text.
Date: March 29, 2004
Creator: Allen, Matthew; Patel, Pravesh K.; Mackinnon, Andrew; Price, Dwight; Wilks, Scott & Morse, Edward
System: The UNT Digital Library
Complex Flows by Nanohydrodynamics (open access)

Complex Flows by Nanohydrodynamics

The study of complex flows by particle simulations is speeded up over molecular dynamics (MD) by more than two orders of magnitude by employing a stochastic collision dynamics method (DSMC) extended to high density (CBA). As a consequence, a picture generated on a single processor shows the typical features of the Rayleigh-Taylor instability and is in quantitative agreement with the experimentally found long time behavior.
Date: March 1, 2004
Creator: Alley, E; Covello, P & Alder, B
System: The UNT Digital Library
Design and Status of the Visa II Experiment. (open access)

Design and Status of the Visa II Experiment.

VISA II is the follow-up project to the successful Visible to Infrared SASE Amplifier (VISA) experiment at the Accelerator Test Facility (ATF) in Brookhaven National Lab (BNL). This paper will report the motivation for and status of the two main experiments associated with the VISA II program. One goal of VISA II is to perform an experimental study of the physics of a chirped beam SASE FEL at the upgraded facilities of the ATF. This requires a linearization of the transport line to preserve energy chirping of the electron beam at injection. The other planned project is a strong bunch compression experiment, where the electron bunch is compressed in the chicane, and the dispersive beamline transport, allowing studies of deep saturation.
Date: March 24, 2004
Creator: Andonian, G.
System: The UNT Digital Library
Quantifying Stratospheric Ozone in the Upper Troposphere Using in situ Measurements of HCl (open access)

Quantifying Stratospheric Ozone in the Upper Troposphere Using in situ Measurements of HCl

A chemical ionization mass spectrometry (CIMS) technique has been developed for precise in situ measurements of hydrochloric acid (HCl) from a high-altitude aircraft. In measurements at subtropical latitudes, minimum HCl values found in the upper troposphere (UT) are often near or below the 0.005-ppbv detection limit of the measurements, indicating that background HCl values are much lower than a global mean estimate. However, significant abundances of HCl were observed in many UT air parcels as a result of stratosphere-to-troposphere transport events. A method for diagnosing the amount of stratospheric ozone in these UT parcels was developed using the compact linear correlation of HCl with ozone found throughout the lower stratosphere (LS). Expanded use of this method will lead to improved quantification of cross-tropopause transport events and validation of global chemical transport models.
Date: March 8, 2004
Creator: Atherton, C. S.; Bergmann, D. J.; Marcy, T. P.; Fahey, D. W.; Gao, R. S.; Popp, P. J. et al.
System: The UNT Digital Library
A technique for accelerating the convergence of restarted GMRES (open access)

A technique for accelerating the convergence of restarted GMRES

We have observed that the residual vectors at the end of each restart cycle of restarted GMRES often alternate direction in a cyclic fashion, thereby slowing convergence. We present a new technique for accelerating the convergence of restarted GMRES by disrupting this alternating pattern. The new algorithm resembles a full conjugate gradient method with polynomial preconditioning, and its implementation requires minimal changes to the standard restarted GMRES algorithm.
Date: March 9, 2004
Creator: Baker, A H; Jessup, E R & Manteuffel, T
System: The UNT Digital Library
High-speed horizontal-path atmospheric turbulence correction using a large actuator-number MEMS spatial light modulator in an interferometric phase conjugation engine (open access)

High-speed horizontal-path atmospheric turbulence correction using a large actuator-number MEMS spatial light modulator in an interferometric phase conjugation engine

Atmospheric propagation results for a high-speed, large-actuator-number, adaptive optics system are presented. The system uses a MEMS-based spatial light modulator correction device with 1024 actuators. Tests over a 1.35 km path achieved correction speeds in excess of 800 Hz and Strehl ratios close to 0.5. The wave-front sensor was based on a quadrature interferometer that directly measures phase. This technique does not require global wave-front reconstruction, making it relatively insensitive to scintillation and phase residues. The results demonstrate the potential of large actuator number MEMS-based spatial light modulators to replace conventional deformable mirrors.
Date: March 4, 2004
Creator: Baker, K.; Stappaerts, E.; Gavel, D.; Wilks, S.; Tucker, J.; Silva, D. et al.
System: The UNT Digital Library
Group Theoretical Analysis of Vibrational Modes, Rovibronic Levels and Nuclear Spin Statistics of extended aromatic C48N12 Azafullerene (open access)

Group Theoretical Analysis of Vibrational Modes, Rovibronic Levels and Nuclear Spin Statistics of extended aromatic C48N12 Azafullerene

We have presented a group theoretical analysis of the vibrational modes and rovibronic levels of a novel extended aromatic C{sub 48}N{sub 12} azafullerene. The nuclear spin multiplets and statistical weights of {sup 14}N spin-1 bosons, vibrational and rotational analysis and computed vibrational spectra are provided. We have also predicted the properties of the {sup 3}A{sub u}, {sup 3}E{sub g}, and {sup 3}E{sub u} excited states of C{sub 48}N{sub 12} that lie 1.9 eV above the {sup 1}A{sub g} ground state, and that the {sup 3}E{sub g} and {sup 3}E{sub u} states would undergo Jahn-Teller distortion into chiral structures with no symmetry and an achiral structure with C{sub i} symmetry.
Date: March 17, 2004
Creator: Balasubramanian, K
System: The UNT Digital Library
Spectroscopic Properties of Novel Aromatic Metal Clusters: NaM4 (M=Al, Ga, In) and their Cations and Anions (open access)

Spectroscopic Properties of Novel Aromatic Metal Clusters: NaM4 (M=Al, Ga, In) and their Cations and Anions

The ground and several excited states of metal aromatic clusters, namely NaM4 and NaM{sub 4}{sup {+-}} (M=Al, Ga, In) clusters have been investigated by employing complete activespace self-consistent-field (CASSCF) followed by Multi-reference singles and doubles configuration interaction (MRSDCI) computations that included up to 10 million configurations and other methods. The ground states NaM{sub 4}{sup -} of aromatic anions are found to be symmetric C{sub 4v} ({sup 1}A{sub 1}) electronic states with ideal square pyramid geometries. While the ground state of NaIn4 is also predicted to be a symmetric C{sub 4v} ({sup 2}A{sub 1}) square pyramid, the ground state of the NaAl4 cluster is found to have a C{sub 2v} ({sup 2}A{sub 1}) pyramid with a rhombus base and the ground state of NaGa{sub 4} possesses a C{sub 2v} ({sup 2}A{sub 1}) pyramid with a rectangle base. In general these structures exhibit 2 competing geometries, viz., an ideal C{sub 4v} structure and a distorted rhomboidal or rectangular pyramid structure (C{sub 2v}). All of the ground states of the NaM{sub 4}{sup +} (M= Al, Ga, In) cations are computed to be C{sub 2v} ({sup 3}A{sub 2}) pyramids with rhombus bases. The equilibrium geometries, vibrational frequencies, dissociation energies, adiabatic ionization potentials, adiabatic electron …
Date: March 17, 2004
Creator: Balasubramanian, K & Zhao, C
System: The UNT Digital Library
Freeeze-Out Dynamics at RHIC. (open access)

Freeeze-Out Dynamics at RHIC.

Investigation of the final hadronic state properties of ultra-relativistics pp and Au+Au collisions supplies information on freeze-out conditions at RHIC and possible insights into early stages of these collisions. A variety of particle spectra measured by STAR are studied within the framework of chemical and local kinetic equilibrium models. Here we present the extracted chemical and final kinetic freeze-out temperatures, strangeness saturation factor, final collective flow velocity, and the inferred flow velocity at chemical freeze-out. In light of those measurements we discuss dynamical evolution of the collision system.
Date: March 15, 2004
Creator: Barannikova, O.
System: The UNT Digital Library
IFC HVAC Interface to EnergyPlus - A Case of Expanded Interoperability for Energy Simulation (open access)

IFC HVAC Interface to EnergyPlus - A Case of Expanded Interoperability for Energy Simulation

Tedious manual input of data that define a building, its systems and its expected pattern of use and operating schedules for building energy performance simulation has in the past diverted time and resources from productive simulation runs. In addition to its previously released IFCtoIDF utility that semiautomates the import of building geometry, the new IFC HVAC interface to EnergyPlus (released at the end of 2003) makes it possible to import and export most of the data that define HVAC equipment and systems in a building directly from and to other IFC compatible software tools. This reduces the manual input of other data needed for successful simulation with EnergyPlus to a minimum. The main purpose of this new interface is to enable import of HVAC equipment and systems definitions, generated by other IFC compatible software tools (such as HVAC systems design tools) and data bases, into EnergyPlus, and to write such definitions contained in EnergyPlus input files to the original IFC files from which building geometry was extracted for the particular EnergyPlus input. In addition, this interface sets an example for developers of other software tools how to import and/or export data other than building geometry from and/or into EnergyPlus. This …
Date: March 29, 2004
Creator: Bazjanac, Vladimir & Maile, Tobias
System: The UNT Digital Library
Soft Radiative Strength in Warm Nuclei (open access)

Soft Radiative Strength in Warm Nuclei

Unresolved transitions in the nuclear {gamma}-ray cascade produced in the decay of excited nuclei are best described by statistical concepts: a continuous radiative strength function (RSF) and level density yield mean values of transition matrix elements. Data on the soft (E{sub {gamma}} < 3-4 MeV) RSF for transitions between warm states (i.e. states several MeV above the yrast line) have, however, remained elusive.
Date: March 8, 2004
Creator: Becker, J. A.; Bernstein, L. A.; Garrett, P. E.; Nelson, R. O.; Schiller, A.; Voinov, A. et al.
System: The UNT Digital Library
Flat-Field Grating Spectrometer for High-Resolution Soft X-Ray and EUV Measurements on an Electron Beam Ion Trap (open access)

Flat-Field Grating Spectrometer for High-Resolution Soft X-Ray and EUV Measurements on an Electron Beam Ion Trap

A R = 44.3 m grazing-incidence grating spectrometer has been implemented on the Livermore electron beam ion traps for high-resolution measurements in the soft x-ray and extreme ultraviolet region spanning from below 10 Angstrom up to 50 Angstrom. The instrument uses a grating with variable line spacing (about 2400 l/mm) for a flat field of view. Spectra are recorded with a back-illuminated charge-coupled device detector. The new instrument greatly improves upon the resolution achieved with existing grating spectrometers and complements crystal spectrometers at the shorter wavelengths both in terms of wavelength coverage and polarization independent reflectivity response.
Date: March 27, 2004
Creator: Beiersdorfer, P.; Magee, E.; Trabert, E.; Chen, H.; Lepson, J. K.; Gu, M. F. et al.
System: The UNT Digital Library
Wavelengths of the 4s1/2 - 4p3/2 resonance lines in Cu- and Zn-like heavy ions (open access)

Wavelengths of the 4s1/2 - 4p3/2 resonance lines in Cu- and Zn-like heavy ions

Using an electron beam ion trap and a high-resolution flat-field spectrometer, the EUV resonance lines 4s{sub 1/2} - 4p{sub 3/2} of the Cu- and Zn-like ions of Os, Bi, Th, and U (Z = 76-92) have been observed and their wavelengths measured. Our experiments remove systematic errors from line blends encountered in earlier work. Our results on Cu-like ions are in good agreement with recent ab initio calculations for all ions that include QED. Our results for Zn-like ions corroborate and extend our earlier findings, but consistently good theoretical values for comparison are lacking.
Date: March 1, 2004
Creator: Beiersdorfer, P; Chen, H & Trabert, E
System: The UNT Digital Library
X-ray Polarization Measurements at Relativistic Laser Intensities (open access)

X-ray Polarization Measurements at Relativistic Laser Intensities

An effort has been started to measure the short pulse laser absorption and energy partition at relativistic laser intensities up to 10{sup 21} W/cm{sup 2}. Plasma polarization spectroscopy is expected to play an important role in determining fast electron generation and measuring the electron distribution function.
Date: March 20, 2004
Creator: Beiersdorfer, P; Shepherd, R; Mancini, R C; Chen, H; Dunn, J; Keenan, R et al.
System: The UNT Digital Library
Active control for turbulent premixed flame simulations (open access)

Active control for turbulent premixed flame simulations

Many turbulent premixed flames of practical interest are statistically stationary. They occur in combustors that have anchoring mechanisms to prevent blow-off and flashback. The stabilization devices often introduce a level of geometric complexity that is prohibitive for detailed computational studies of turbulent flame dynamics. As a result, typical detailed simulations are performed in simplified model configurations such as decaying isotropic turbulence or inflowing turbulence. In these configurations, the turbulence seen by the flame either decays or, in the latter case, increases as the flame accelerates toward the turbulent inflow. This limits the duration of the eddy evolutions experienced by the flame at a given level of turbulent intensity, so that statistically valid observations cannot be made. In this paper, we apply a feedback control to computationally stabilize an otherwise unstable turbulent premixed flame in two dimensions. For the simulations, we specify turbulent in flow conditions and dynamically adjust the integrated fueling rate to control the mean location of the flame in the domain. We outline the numerical procedure, and illustrate the behavior of the control algorithm. We use the simulations to study the propagation and the local chemical variability of turbulent flame chemistry.
Date: March 26, 2004
Creator: Bell, John B.; Day, Marcus S.; Grcar, Joseph F. & Lijewski, Michael J.
System: The UNT Digital Library
Comparison of two up-scaling methods in poroelasticity and its generalizations (open access)

Comparison of two up-scaling methods in poroelasticity and its generalizations

Two methods of up-scaling coupled equations at the microscale to equations valid at the mesoscale and/or macroscale for fluid-saturated and partially saturated porous media are discussed, compared, and contrasted. The two methods are: (1) two-scale and multiscale homogenization, and (2) volume averaging. Both these methods have advantages for some applications and disadvantages for others. For example, homogenization methods can give formulas for coefficients in the up-scaled equations, whereas volume averaging methods give the form of the up-scaled equations but generally must be supplemented with physical arguments and/or data in order to determine the coefficients. Homogenization theory requires a great deal of mathematical insight from the user in order to choose appropriate scalings for use in the resulting power-law expansions, while volume averaging requires more physical insight to motivate the steps needed to find coefficients. Homogenization often is performed on periodic models, while volume averaging does not require any assumption of periodicity and can therefore be related very directly to laboratory and/or field measurements. Validity of the homogenization process is often limited to specific ranges of frequency - in order to justify the scaling hypotheses that must be made - and therefore cannot be used easily over wide ranges of frequency. …
Date: March 16, 2004
Creator: Berger, E. L.
System: The UNT Digital Library
Pore Fluid Effects on Shear Modulus for Sandstones with Soft Anisotropy (open access)

Pore Fluid Effects on Shear Modulus for Sandstones with Soft Anisotropy

None
Date: March 25, 2004
Creator: Berger, E. L.
System: The UNT Digital Library
Development of a Real-Time Radiological Area Monitoring Network for Emergency Response at Lawrence Livermore National Laboratory (open access)

Development of a Real-Time Radiological Area Monitoring Network for Emergency Response at Lawrence Livermore National Laboratory

A real-time radiological sensor network for emergency response was developed and deployed at the Lawrence Livermore National Laboratory (LLNL). The Real-Time Radiological Area Monitoring (RTRAM) network is comprised of 16 Geiger-Mueller (GM) sensors positioned on the LLNL Livermore site perimeter to continuously monitor for a radiological condition resulting from a terrorist threat to site security and the health and safety of LLNL personnel. The RTRAM network sensor locations coincide with wind sector directions to provide thorough coverage of the one square mile site. These low-power sensors are supported by a central command center (CCC) and transmit measurement data back to the CCC computer through the LLNL telecommunications infrastructure. Alarm conditions are identified by comparing current data to predetermined threshold parameters and are validated by comparison with plausible dispersion modeling scenarios and prevailing meteorological conditions. Emergency response personnel are notified of alarm conditions by automatic radio and computer based notifications. A secure intranet provides emergency response personnel with current condition assessment data that enable them to direct field response efforts remotely. The RTRAM network has proven to be a reliable system since initial deployment in August 2001 and maintains stability during inclement weather conditions.
Date: March 8, 2004
Creator: Bertoldo, N; Hunter, S; Fertig, R; Laguna, G & MacQueen, D
System: The UNT Digital Library
Community-Owned wind power development: The challenge of applying the European model in the United States, and how states are addressing that challenge (open access)

Community-Owned wind power development: The challenge of applying the European model in the United States, and how states are addressing that challenge

Local farmers, towns, schools, and individual investors are, however, beginning to invest in wind power. With the help of state policy and clean energy fund support, new federal incentives, and creative local wind developers who have devised ownership structures that maximize the value of both state and federal support, community wind power is beginning to take a foothold in parts of the US, in particular the upper Midwest. The purpose of this report is to describe that foothold, as well as the state support that helped to create it. There are a number of reasons why states are becoming increasingly interested in community wind power. In rural Midwestern states such as Minnesota, Wisconsin, Iowa, and Illinois, community wind is seen as a way to help supplement and stabilize farmer income, and thereby contribute to the preservation of farming communities and the rural landscapes and values they create. In the Northeast, densely populated states such as Massachusetts are turning to community-scale wind development to increase not only the amount of wind power on the grid, but also the public's knowledge, perception, and acceptance of wind power. In still other areas--such as the Pacific Northwest, which is already home to several large …
Date: March 28, 2004
Creator: Bolinger, Mark
System: The UNT Digital Library
An Evaluation of Savings and Measure Persistence Fromretrocommissioning of Large Commercial Buildings (open access)

An Evaluation of Savings and Measure Persistence Fromretrocommissioning of Large Commercial Buildings

Commercial building retrocommissioning activity has increased in recent years. LBNL recently conducted a study of 8 participants in Sacramento Municipal Utility District's (SMUD) retrocommissioning program. We evaluated the persistence of energy savings and measure implementation, in an effort to identify and understand factors that affect the longevity of retrocommissioning benefits. The LBNL analysis looked at whole-building energy and the retrocommissioning measure implementation status, incorporating elements from previous work by Texas A&M University and Portland Energy Conservation Inc. When possible, adjustments due to newly discovered major end uses, occupancy patterns and 2001 energy crisis responses were included in the whole-building energy analysis. The measure implementation analysis categorized each recommended measure and tracked the measures to their current operational status. Results showed a 59% implementation rate of recommended measures. The whole-building energy analysis showed an aggregate electricity savings of approximately 10.5% in the second post-retrocommissioning year, diminishing to approximately 8% in the fourth year. Results also showed the 2001 energy crisis played a significant role in the post-retrocommissioning energy use at the candidate sites. When natural gas consumption was included in the analysis, savings were reduced slightly, showing the importance in considering interactive effects between cooling and heating systems. The cost effectiveness …
Date: March 10, 2004
Creator: Bourassa, Norman J.; Piette, Mary Ann & Motegi, Naoya
System: The UNT Digital Library
Mechanism of GEMS formation (open access)

Mechanism of GEMS formation

GEMS (glass with embedded metal and sulfides) in interplanetary dust particles (IDPs) were examined using 200 keV analytical transmission electron microscopy. The morphologies and crystallography of embedded relict grains reveal that GEMS are pseudomorphs formed by irradiation processing of crystals free-floating in space. Some GEMS retain a compositional and morphological ''memory'' of the crystal from which they formed. Pseudomorphism rules out condensation, annealing, flash heating, or shock melting as alternative mechanisms of GEMS formation. A significant and often dominant fraction of the atoms in GEMS were sputtered deposited from other grains. Therefore, a normal (solar) isotopic composition is not a reliable indicator of whether GEMS formed in the solar system or in presolar interstellar or circumstellar environments.
Date: March 10, 2004
Creator: Bradley, J P & Dai, Z R
System: The UNT Digital Library
Computational investigation of unusual behavior in certain capillary tubes (open access)

Computational investigation of unusual behavior in certain capillary tubes

We investigate computationally two recent mathematical findings involving unusual behavior of solutions of the Young-Laplace capillary equation in cylindrical tubes of particular sections. The first concerns a configuration for which smoothing of the boundary curve at a sharp corner leads from existence to non-existence of a solution over the container section in zero gravity. The second describes a discontinuous behavior of relative rise height in nesting tubes placed vertically in an infinite reservoir. The numerical results support and quantify the mathematical predictions.
Date: March 12, 2004
Creator: Brady, Victor; Concus, Paul & Finn, Robert
System: The UNT Digital Library
Evolution of Safety Basis Documentation for the Fernald Site (open access)

Evolution of Safety Basis Documentation for the Fernald Site

The objective of the Department of Energy's (DOE) Fernald Closure Project (FCP), in suburban Cincinnati, Ohio, is to safely complete the environmental restoration of the Fernald site by 2006. Over 200 out of 220 total structures, at this DOE plant site which processed uranium ore concentrates into high-purity uranium metal products, have been safely demolished, including eight of the nine major production plants. Documented Safety Analyses (DSAs) for these facilities have gone through a process of simplification, from individual operating Safety Analysis Reports (SARs) to a single site-wide Authorization Basis containing nuclear facility Bases for Interim Operations (BIOs) to individual project Auditable Safety Records (ASRs). The final stage in DSA simplification consists of project-specific Integrated Health and Safety Plans (I-HASPs) and Nuclear Health and Safety Plans (N-HASPs) that address all aspects of safety, from the worker in the field to the safety basis requirements preserving the facility/activity hazard categorization. This paper addresses the evolution of Safety Basis Documentation (SBD), as DSAs, from production through site closure.
Date: March 1, 2004
Creator: Brown, T.; Kohler, S.; Fisk, P.; Krach, F. & Klein, B.
System: The UNT Digital Library