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Comparison of Experimental and Model Data for the Evaporation of a Synthetic Topopah Spring Tuff Pore Water, Yucca Mountain, NV
The evaporation of a range of synthetic pore water solutions representative of the potential high-level-nuclear-waste repository at Yucca Mountain, NV is being investigated. The motivation of this work is to understand and predict the range of brine compositions that may contact the waste containers from evaporation of pore waters, because these brines could form corrosive thin films on the containers and impact their long-term integrity. A relatively complex synthetic Topopah Spring Tuff pore water was progressively concentrated by evaporation in a closed vessel, heated to 95 C in a series of sequential experiments. Periodic samples of the evaporating solution were taken to determine the evolving water chemistry. According to chemical divide theory at 25 C and 95 C our starting solution should evolve towards a high pH carbonate brine. Results at 95 C show that this solution evolves towards a complex brine that contains about 99 mol% Na{sup +} for the cations, and 71 mol% Cl{sup -}, 18 mol% {Sigma}CO{sub 2}(aq), 9 mol% SO{sub 4}{sup 2-} for the anions. Initial modeling of the evaporating solution indicates precipitation of aragonite, halite, silica, sulfate and fluoride phases. The experiments have been used to benchmark the use of the EQ3/6 geochemical code in …
Date:
October 14, 2003
Creator:
Alai, M; Sutton, M & Carroll, S
Object Type:
Article
System:
The UNT Digital Library
Oxygen Isotopes in Chondritic Interplanetary Dust: Parent-Bodies and Nebular Oxygen Reservoirs
Planetary objects have preserved various amounts of oxygen issued from isotopically different oxygen reservoirs reflecting their origin and physico-chemical history. An {sup 16}O-rich component is preserved in refractory inclusions (CAIs) whereas meteorites matrices are enriched in an {sup 16}O-poor component. The origin of these components is still unclear. The most recent models are based on isotope selective photodissociation of CO in a {sup 16}O-rich nebula/presolr cloud resulting in a {sup 16}O-poor gas in the outer part of the nebula. However because most meteorite components are thought to be formed in the inner 3AU of the solar nebula, the precise isotopic composition of outer solar system components is yet unknown. In that respect, the oxygen isotopic composition of cometary dust is a key to understand the origin of the solar system. The Stardust mission will bring back to the Earth dust samples from comet Wild2, a short period comet from the Jupiter family. A precise determination of the oxygen isotope composition of Wild2 dust grains is essential to decipher the oxygen reservoirs of the outer solar system. However, Stardust samples may be extremely fragmented upon impact in the collector. In addition, interplanetary dust particles (IDPs) collected in the stratosphere are likely …
Date:
February 14, 2006
Creator:
Aleon, J.; McKeegan, K. D. & Leshin, L.
Object Type:
Article
System:
The UNT Digital Library
Development of a CO2 Sequestration Module by Integrating Mineral Activation and Aqueous Carbonation
Mineral carbonation is a promising concept for permanent CO{sub 2} sequestration due to the vast natural abundance of the raw materials and the permanent storage of CO{sub 2} in solid form as carbonates. The sequestration of CO{sub 2} through the employment of magnesium silicates--olivine and serpentine--is beyond the proof of concept stage. For the work done in this project, serpentine was chosen as the feedstock mineral due to its abundance and availability. Although the reactivity of olivine is greater than that of serpentine, physical and chemical treatments have been shown to increase greatly the reactivity of serpentine. The primary drawback to mineral carbonation is reaction kinetics. To accelerate the carbonation, aqueous processes are preferred, where the minerals are first dissolved in solution. In aqueous carbonation, the key step is the dissolution rate of the mineral, where the mineral dissolution reaction is likely to be surface-controlled. The relatively low reactivity of serpentine has warranted research into physical and chemical treatments that have been shown to greatly increase its reactivity. The use of sulfuric acid as an accelerating medium for the removal of magnesium from serpentine has been investigated. To accelerate the dissolution process, the mineral can be ground to very fine …
Date:
August 14, 2006
Creator:
Alexander, George; Aksoy, Parvana; Andresen, John; Maroto-Valer, Mercedes & Schobert, Harold
Object Type:
Report
System:
The UNT Digital Library
Whales and Sonar: Environmental Exemptions for the Navy's Mid-Frequency Active Sonar Training
This report discusses laws related to the protection of marine mammals when using mid-frequency active sonar including the Marine Mammal Protection Act (MMPA), the Endangered Species Act (ESA), the National Environmental Policy Act (NEPA), and the Coastal Zone Management Act (CZMA). The report discusses each of the laws generally, and then reviews the litigation surrounding the Navy's compliance with these laws in the context of using the sonar for training purposes off California's coast.
Date:
November 14, 2008
Creator:
Alexander, Kristina
Object Type:
Report
System:
The UNT Digital Library
THE SECOND STAGE OF FERMI@ELETTRA: A SEEDED FEL IN THE SOFT X-RAY SPECTRAL RANGE
The second stage of the FERMI FEL, named FEL-2, is based on the principle of high-gain harmonic generation and relies on a double-seeded cascade. Recent developments stimulated a revision of the original setup, which was designed to cover the spectral range between 40 and 10 nm. The numerical simulations we present here show that the nominal (expected) electron-beam performance allows extension of the FEL spectral range down to 4 nm. A significant amount of third harmonic power can be also expected. We also show that the proposed setup is flexible enough for exploiting future developments of new seed sources, e.g., high harmonic generation in gases.
Date:
August 14, 2009
Creator:
Allaria, E.; DeNinno, G. & Fawley, W. M.
Object Type:
Article
System:
The UNT Digital Library
Studies of vibrational properties in Ga stabilized delta-Pu by extended X-ray absorption fine structure
Temperature dependent extended x-ray absorption fine structure (EXAFS) spectra were measured for a 3.3 at. % Ga stabilized Pu alloy over the range T= 20 - 300 K. EXAFS data were acquired at both the Ga K-edge and the Pu L{sub III} edge. Curve-fits were performed to the first shell interactions to obtain pair-distance distribution widths, {sigma}, as a function of temperature. The temperature dependence of {sigma}(T) was accurately modeled using a correlated-Debye model for the lattice vibrational properties, suggesting Debye-like behavior in this material. Using this formalism, we obtain pair-specific correlated-Debye temperatures, {Theta}{sub cD}, of 110.7 {+-} 1.7 K and 202.6 {+-} 3.7 K, for the Pu-Pu and Ga-Pu pairs, respectively. The result for the Pu-{Theta}{sub cD} value compares well with previous vibrational studies on {delta}-Pu. In addition, our results represent the first unambiguous determination of Ga-specific vibrational properties in Pu-Ga alloys, i.e, {Theta}{sub cD} for the Ga-Pu pair. Because the Debye temperature can be related to a measure of the lattice stiffness, these results indicate the Ga-Pu bonds are significantly stronger than the Pu-Pu bonds. This effect has important implications for lattice stabilization mechanisms in these alloys.
Date:
February 14, 2002
Creator:
Allen, P. G.; Henderson, A. L.; Sylwester, E. R.; Turchi, P. E. A.; Shen, T. H.; Gallegos, G. F. et al.
Object Type:
Article
System:
The UNT Digital Library
Water and Energy Savings using Demand Hot Water Recirculating Systems in Residential Homes: A Case Study of Five Homes in Palo Alto, California
This report summarizes a preliminary study aimed at estimating the potential of saving potable water, (and the electrical energy used to heat it), that is presently lost directly to the drain while occupants wait for hot water to arrive at the faucet (point of use). Data were collected from five single-family homes in Palo Alto, California. Despite the small sample size in this study, the results make a compelling case for retrofitting homes with hot water recirculation systems to eliminate unnecessary wastage of water at the point of use. Technical as well as behavioral and attitudinal changes towards water conservation are necessary for a fulfilling and successful conservation effort. This report focuses on the technical issues, but behavioral issues are also noted, which may be factored into future studies involving local and state governments and utility companies.
Date:
November 14, 2002
Creator:
Ally, M.R.
Object Type:
Report
System:
The UNT Digital Library
Handling Pyrophoric Reagents
Pyrophoric reagents are extremely hazardous. Special handling techniques are required to prevent contact with air and the resulting fire. This document provides several methods for working with pyrophoric reagents outside of an inert atmosphere.
Date:
August 14, 2009
Creator:
Alnajjar, Mikhail S. & Haynie, Todd O.
Object Type:
Report
System:
The UNT Digital Library
Criticality Model
The ''Disposal Criticality Analysis Methodology Topical Report'' (YMP 2003) presents the methodology for evaluating potential criticality situations in the monitored geologic repository. As stated in the referenced Topical Report, the detailed methodology for performing the disposal criticality analyses will be documented in model reports. Many of the models developed in support of the Topical Report differ from the definition of models as given in the Office of Civilian Radioactive Waste Management procedure AP-SIII.10Q, ''Models'', in that they are procedural, rather than mathematical. These model reports document the detailed methodology necessary to implement the approach presented in the Disposal Criticality Analysis Methodology Topical Report and provide calculations utilizing the methodology. Thus, the governing procedure for this type of report is AP-3.12Q, ''Design Calculations and Analyses''. The ''Criticality Model'' is of this latter type, providing a process evaluating the criticality potential of in-package and external configurations. The purpose of this analysis is to layout the process for calculating the criticality potential for various in-package and external configurations and to calculate lower-bound tolerance limit (LBTL) values and determine range of applicability (ROA) parameters. The LBTL calculations and the ROA determinations are performed using selected benchmark experiments that are applicable to various waste forms …
Date:
September 14, 2004
Creator:
Alsaed, A.
Object Type:
Report
System:
The UNT Digital Library
Searching for Gluinos at the Tevatron
This letter describes how to perform model-independent searches for new pair-produced color octet particles that each subsequently decay into two jets plus missing energy at the Tevatron. Current searches are not sensitive to all regions of parameter space because they employ CMSSM-motivated cuts. Optimizing the H{sub T} and E{sub T} cuts expands the sensitivity of searches for all kinematically allowed decays.
Date:
March 14, 2008
Creator:
Alwall, Johan; Le, My-Phuong; Lisanti, Mariangela; Wacker, Jay G. & /SLAC /Stanford U., Phys. Dept.
Object Type:
Article
System:
The UNT Digital Library
Top-of-Rail lubricant
Analysis of the volatile and semivolatile fractions collected after use of the TOR lubricant indicated that other than contaminants in the collection laboratory, no compounds on the EPA's Target Compound Lists (Tables 2 and 5) were detected in these fractions. The data of these qualitative analyses, given in the various tables in the text, indicate only the relative amounts of the tentatively identified compounds. The authors recommend that quantitative analysis be performed on the volatile and semivolatile fractions to allow confirmation of the tentatively identified compounds and to obtain absolute amounts of the detected compounds. Additionally, the semivolatile fraction should be analyzed by liquid chromatography/mass spectrometry to identify compounds that are not chromatographable under the temperature program used for determination of semivolatile compounds. Introducing the top-of-rail (TOR) lubricant into the wheel/rail interface results in a reduction of almost 60% of lateral friction force over the forces encountered under dry conditions. This reveals good potential for energy savings, as well as wear reduction, for railroad companies. In TOR lubrication, an increase in the angle of attack and axle load results in increased lateral friction and rate of lubricant consumption. The most efficient TOR lubricant quantity to be used in the wheel/rail …
Date:
July 14, 2000
Creator:
Alzoubi, M. F.; Fenske, G. R.; Erck, R. A. & Boparai, A. S.
Object Type:
Report
System:
The UNT Digital Library
Hands-free operation of a small mobile robot
The Intelligent Systems and Robotics Center of Sandia National laboratories has an ongoing research program in advanced user interfaces. As part of this research, promising new transduction devices, particularly hands-free devices, are being explored for the control of mobile and floor-mounted robotic systems. Brainwave control has been successfully demonstrated by other researchers in a variety of fields. In the research described here, Sandia developed and demonstrated a proof-of-concept brainwave-controlled mobile robot system. Preliminary results were encouraging. Additional work required to turn this into a reliable. fieldable system for mobile robotic control is identified. Used in conjunction with other controls, brainwave control could be an effective control method in certain circumstances.
Date:
March 14, 2000
Creator:
Amai, Wendy A.; Fahrenholtz,Jill C. & Leger, Chris L.
Object Type:
Article
System:
The UNT Digital Library
CALCULATION: PRECIPITATION CHARACTERISITICS FOR STORM WATER MANAGEMENT
This Calculation is intended to satisfy engineering requirements for maximum 60-minute precipitation amounts for 50 and 100-year return periods at and near Yucca Mountain. This data requirement is documented in the ''Interface Control Document for Support Operations to Surface Facilities Operations Functional and Organizational Interfaces'' (CRWMS M&O 1998a). These developed data will supplement the information on 0.1 hour to 6-hour (in 0.1-hour increments) probable maximum precipitation (PMP) presented in the report, ''Precipitation Design Criteria for Storm Water Management'' (CRWMS M&O 1998b). The Reference Information Base (RIB) item, Precipitation ''Characteristics for Storm Water Management'' (M09902RIB00045 .OOO), was developed based on CRWMS M&O (1998b) and will be supplemented (via revision) with the information developed in this Calculation. The ''Development Plan for the Calculation: Precipitation Characteristics for Storm Water Management'' (CRWMS M&O 2000) was prepared in accordance with AP-2.l3Q, ''Technical Product Development Planning''. This calculation was developed in accordance with AP-3.12Q, Rev. O/ICN 2.
Date:
August 14, 2000
Creator:
Ambos, D.
Object Type:
Report
System:
The UNT Digital Library
House Committee on Standards of Official Conduct: A Brief History of Its Evolution and Jurisdiction
This report provides a history of the creation and evolution of the House Committee on Standards of Official Conduct. Also known as the House Ethics Committee and the Committee on Standards, it was first established as a select committee in 1966. It became a standing committee in 1967. Since that time, it has undergone two major reorganizations, first in 1989, and again in 1997.
Date:
July 14, 2004
Creator:
Amer, Mildred
Object Type:
Report
System:
The UNT Digital Library
Selected Privileges and Courtesies Extended to Departing and Former Senators
This report provides information on selected privileges and courtesies (with the exception of federal health insurance, life insurance, and retirement benefits) extended to departing and former Senators. Some are derived from law and Senate Rules, but most are courtesies that have been extended as a matter of custom.
Date:
September 14, 2004
Creator:
Amer, Mildred
Object Type:
Report
System:
The UNT Digital Library
Major Leadership Election Contests in the Senate: A 27-Year Survey
None
Date:
November 14, 2001
Creator:
Amer, Mildred L.
Object Type:
Report
System:
The UNT Digital Library
Temperature Study of CdZnTe Coplanar-Grid Detectors
The coplanar-grid (CPG) and other electron only detection techniques have made possible the use of CdZnTe-based detectors for gamma-ray spectroscopy when high efficiency, good energy resolution, and near room temperature operation are required. Despite the demonstrated potential of the technologies, widespread use remains hampered in part by the limited availability of the highly uniform CdZnTe material required for high-resolution spectroscopy. However, it has been recently shown that mild cooling of CdZnTe CPG detectors can result in a significant improvement in the energy resolution of the detectors thereby allowing a wider range of material to be used for high-resolution applications. In this paper, we show that improved spectroscopic performance can consistently be achieved through a combination of detector cooling and increased detector bias. Energy resolutions of about 1 % FWHM at 662 keV for detector volumes up to 2.3 cm{sup 3} have been obtained at -20 C. With the electronic noise subtracted, this amounts to an intrinsic resolution of 0.76 %. We also show that further cooling of the detectors to -30 C leads to field polarization and a loss of spectroscopic performance.
Date:
February 14, 2006
Creator:
Amman, Mark; Lee, Julie S. & Luke, Paul N.
Object Type:
Article
System:
The UNT Digital Library
From plasma immersion ion implantation to deposition: A historical perspective on principles and trends
Plasma immersion techniques of surface modification are known under a myriad of names. The family of techniques reaches from pure plasma ion implantation, to ion implantation and deposition hybrid modes, to modes that are essentially plasma film deposition with substrate bias. In the most general sense, all plasma immersion techniques have in common that the surface of a substrate (target) is exposed to plasma and that relatively high substrate bias is applied. The bias is usually pulsed. In this review, the roots of immersion techniques are explored, some going back to the 1800s, followed by a discussion of the groundbreaking works of Adler and Conrad in the 1980s. In the 1990s, plasma immersion techniques matured in theoretical understanding, scaling, and the range of applications. First commercial facilities are now operational. Various immersion concepts are compiled and explained in this review. While gas (often nitrogen) ion implantation dominated the early years, film-forming immersion techniques and semiconductor processing gained importance. In the 1980s and 1990s we have seen exponential growth of the field but signs of slowdown are clear since 1998. Nevertheless, plasma immersion techniques have found, and will continue to have, an important place among surface modification techniques.
Date:
June 14, 2001
Creator:
Anders, Andre
Object Type:
Article
System:
The UNT Digital Library
A structure zone diagram including plasma based deposition and ion etching
An extended structure zone diagram is proposed that includes energetic deposition, characterized by a large flux of ions typical for deposition by filtered cathodic arcs and high power impulse magnetron sputtering. The axes are comprised of a generalized homologous temperature, the normalized kinetic energy flux, and the net film thickness, which can be negative due to ion etching. It is stressed that the number of primary physical parameters affecting growth by far exceeds the number of available axes in such a diagram and therefore it can only provide an approximate and simplified illustration of the growth condition?structure relationships.
Date:
October 14, 2009
Creator:
Anders, Andre
Object Type:
Article
System:
The UNT Digital Library
Tracking down the origin of Arc plasma science. I. Early pulsed and oscillating discharges
None
Date:
January 14, 2003
Creator:
Anders, Andre
Object Type:
Article
System:
The UNT Digital Library
Tracking down the origin of Arc plasma science. II. Early continuous discharges
None
Date:
January 14, 2003
Creator:
Anders, Andre
Object Type:
Article
System:
The UNT Digital Library
Ultrathin ta-C films on heads depositied by twist-filteredcathodic arc carbon plasmas
It is known that filtered cathodic-arc-deposited ta-C films have outstanding properties even within the family of diamondlike materials. However, filtering of macroparticles is usually incomplete or accompanied by significant plasma losses. Ongoing research effort is directed towards the following goals: (1) complete elimination of macro- and nanoparticles from the vacuum arc plasma, (2) increase of plasma utilization in the cathodic-arc and macroparticle-filter system, (3) precise control and reproducibility of film deposition, and (4) synthesis of ultrathin films (< 5 nm) that meet requirements of the magnetic storage industry. The development of new filters, in particular the ''Twist Filter'', enables cathodic arc plasma deposition to synthesize ultrathin ta-C films of 3 nm on heads that pass corrosion and other relevant tests. We describe the Twist Filter system and report about recent ta-C tests results. In light of these results, even thinner films seem to be possible.
Date:
July 14, 2000
Creator:
Anders, Andre & Ryan, Francis W.
Object Type:
Article
System:
The UNT Digital Library
Erratum: High power impulse magnetron sputtering:Current-voltage-time characteristics indicate the onset of sustainedself-sputtering
None
Date:
December 14, 2007
Creator:
Anders, Andre; Andersson, Joakim & Ehiasarian, Arutiun
Object Type:
Article
System:
The UNT Digital Library
Ion charge state fluctuations in vacuum arcs
Ion charge state distributions of cathodic vacuum arcs have been investigated using a modified time-of-flight method. Experiments have been done in double gate and burst gate mode, allowing us to study both systematic and stochastic changes of ion charge state distributions with a time resolution down to 100 ns. In the double gate method, two ion charge spectra are recorded with a well-defined time between measurements. The elements Mg, Bi, and Cu were selected for tests, representing metals of very different properties. For all elements it was found that large stochastic changes occur even at the limit of resolution. This is in agreement with fast changing arc properties observed elsewhere. Correlation of results for short times between measurements was found but it is argued that this is due to velocity mixing rather than due to cathode processes. The burst mode of time-of-flight measurements revealed the systematic time evolution of ion charge states within a single arc discharge, as opposed to previous measurements that relied on data averaged over many pulses. The technique shows the decay of the mean ion charge state as well as the level of material-dependent fluctuations.
Date:
December 14, 2004
Creator:
Anders, Andre; Fukuda, Kentaro & Yushkov, Georgy Yu
Object Type:
Article
System:
The UNT Digital Library