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The effect of CO2(aq), Al(aq) and temperature on feldspar dissolution (open access)

The effect of CO2(aq), Al(aq) and temperature on feldspar dissolution

The authors measured labradorite (Ca{sub 0.6}Na{sub 0.4}Al{sub 1.6}Si{sub 2.4}O{sub 8}) dissolution rates using a mixed flow reactor from 30 to 130 C as a function of CO{sub 2} (3 x 10{sup -3} and 0.6 M), and aluminum (10{sup -6} to 10{sup -3}M) at pH 3.2. Over these conditions, labradorite dissolution can be described with a single rate expression that accounts for observed increases in dissolution rate with temperature and decreases in dissolution rate with dissolved aluminum: Rate{sub Si} (mol Labradorite cm{sup -2} s{sup -1}) = k{double_prime} x 10{sup -Ea/2.303RT} [(a{sub H{sup +}}{sup 3n}/a{sub Al{sup 3+}}{sup n})K{sub T}/(1+K{sub T} (a{sub H{sup +}}{sup 3n}/a{sub Al{sup 3+}}{sup n}))] where the apparent dissolution rate constant, k{double_prime} = 10{sup -5.69} (mol Labradorite cm{sup -2}s{sup -1}); the net activation energy, E{sub a} = 10.06 (kcal mol{sup -1}); H{sup +}-Al{sup 3+} exchange coefficient, n = 0.31; and silica rich surface complex formation constant K{sub T} = 4.5 to 5.6 from 30 to 130 C. The effect of CO{sub 2}(aq) on mineral dissolution is accounted for by changes in solution pH. At temperatures below 60 C, labradorite dissolves incongruently with preferential dissolution of Na, Ca and Al over Si.
Date: October 14, 2003
Creator: Carroll, S. & Knauss, K.
System: The UNT Digital Library
Simulations of rapid pressure-induced solidification in molten metals (open access)

Simulations of rapid pressure-induced solidification in molten metals

The process of interest in this study is the solidification of a molten metal subjected to rapid pressurization. Most details about solidification occurring when the liquid-solid coexistence line is suddenly transversed along the pressure axis remain unknown. We present preliminary results from an ongoing study of this process for both simple models of metals (Cu) and more sophisticated material models (MGPT potentials for Ta). Atomistic (molecular dynamics) simulations are used to extract details such as the time and length scales that govern these processes. Starting with relatively simple potential models, we demonstrate how molecular dynamics can be used to study solidification. Local and global order parameters that aid in characterizing the phase have been identified, and the dependence of the solidification time on the phase space distance between the final (P,T) state and the coexistence line has been characterized.
Date: October 14, 2003
Creator: Patel, M V & Streitz, F H
System: The UNT Digital Library
Measured energy savings from the application of reflective roofsin 2 small non-residential buildings (open access)

Measured energy savings from the application of reflective roofsin 2 small non-residential buildings

Energy use and environmental parameters were monitored in two small (14.9 m{sup 2}) non-residential buildings during the summer of 2000. The buildings were initially monitored for about 1 1/2 months to establish a base condition. The roofs of the buildings were then painted with a white coating and the monitoring was continued. The original solar reflectivities of the roofs were about 26%; after the application of roof coatings the reflectivities increased to about 72%. The monitored electricity savings were about 0.5kWh per day (33 Wh/m2 per day). The estimated annual savings are about 125kWh per year (8.4 kWh/m2); at a cost of $0.1/kWh, savings are about $0.86/m2 per year. Obviously, it costs significantly more than this amount to coat the roofs with reflective coating, particularly because of the remote locations of these buildings. However, since the prefabricated roofs are already painted green at the factory, painting them a white (reflective) color would bring no additional cost. Hence, a reflective roof saves energy at no incremental cost.
Date: January 14, 2003
Creator: Akbari, Hashem
System: The UNT Digital Library
Supporting Dynamic Ad hoc Collaboration Capabilities (open access)

Supporting Dynamic Ad hoc Collaboration Capabilities

Modern HENP experiments such as CMS and Atlas involve as many as 2000 collaborators around the world. Collaborations this large will be unable to meet often enough to support working closely together. Many of the tools currently available for collaboration focus on heavy-weight applications such as videoconferencing tools. While these are important, there is a more basic need for tools that support connecting physicists to work together on an ad hoc or continuous basis. Tools that support the day-to-day connectivity and underlying needs of a group of collaborators are important for providing light-weight, non-intrusive, and flexible ways to work collaboratively. Some example tools include messaging, file-sharing, and shared plot viewers. An important component of the environment is a scalable underlying communication framework. In this paper we will describe our current progress on building a dynamic and ad hoc collaboration environment and our vision for its evolution into a HENP collaboration environment.
Date: July 14, 2003
Creator: Agarwal, Deborah A. & Berket, Karlo
System: The UNT Digital Library
Tracking down the origin of Arc plasma science. II. Early continuous discharges (open access)

Tracking down the origin of Arc plasma science. II. Early continuous discharges

None
Date: January 14, 2003
Creator: Anders, Andre
System: The UNT Digital Library
Tracking down the origin of Arc plasma science. I. Early pulsed and oscillating discharges (open access)

Tracking down the origin of Arc plasma science. I. Early pulsed and oscillating discharges

None
Date: January 14, 2003
Creator: Anders, Andre
System: The UNT Digital Library
Historical background: Why is it important to improve automated particle selection methods? (open access)

Historical background: Why is it important to improve automated particle selection methods?

A current trend in single-particle electron microscopy is to compute three-dimensional reconstructions with ever-increasing numbers of particles in the data sets. Since manual--or even semi-automated--selection of particles represents a major bottleneck when the data set exceeds several thousand particles, there is growing interest in developing automatic methods for selecting images of individual particles. Except in special cases, however, it has proven difficult to achieve the degree of efficiency and reliability that would make fully automated particle selection a useful tool. The simplest methods such as cross correlation (i.e., matched filtering) do not perform well enough to be used for fully automated particle selection. Geometric properties (area, perimeter-to-area ratio, etc.) and the integrated ''mass'' of candidate particles are additional factors that could improve automated particle selection if suitable methods of contouring particles could be developed. Another suggestion is that data be always collected as pairs of images, the first taken at low defocus (to capture information at the highest possible resolution) and the second at very high defocus (to improve the visibility of the particle). Finally, it is emphasized that well-annotated, open-access data sets need to be established in order to encourage the further development and validation of methods for automated …
Date: August 14, 2003
Creator: Glaeser, Robert M.
System: The UNT Digital Library
A New Tall-Tower Meteorological Monitoring System (open access)

A New Tall-Tower Meteorological Monitoring System

The Atmospheric Technologies Group of the Savannah River Technology Center operates an extensive meteorological monitoring network of 13 tower in and near the Savannah River Site near Aiken, South Carolina. The data from this system are available in ''real-time'' for emergency response atmospheric release modeling and operational weather forecasting.
Date: January 14, 2003
Creator: Parker, M. J.
System: The UNT Digital Library
Optimal use of information for measuring M(t) in lepton + jets t anti-t events (open access)

Optimal use of information for measuring M(t) in lepton + jets t anti-t events

The observation of the top (t) quark served as one of the major confirmations of the validity of the standard model (SM) of particle interactions. Through radiative corrections of the SM, the mass of the top quark, along with that of the W boson, provide the best indication for the value of the mass of the hypothesized Higgs boson. The mass of the W is known to a precision of < 0.1%, while the uncertainty on the mass of the top quark is at the 4% level. Improvements in both measurements are required to limit the range of mass that the Higgs boson can assume in the SM, and, of course, to check whether that agrees with expectation. It is therefore important to develop techniques for extracting the mass of the top quark that can provide the sharpest values possible.
Date: October 14, 2003
Creator: Estrada, Juan
System: The UNT Digital Library
Investigation of layered intergrowth Li{sub x}M{sub y}Mn{sub 1-y}O{sub 2+z} (M=Ni,Co,Al) compounds as positive electrodes for Li-ion batteries (open access)

Investigation of layered intergrowth Li{sub x}M{sub y}Mn{sub 1-y}O{sub 2+z} (M=Ni,Co,Al) compounds as positive electrodes for Li-ion batteries

Layered substituted lithium manganese oxides suitable for use as lithium ion battery electrodes may be prepared from the corresponding sodium manganese metal oxide compounds by ion-exchange. Stacking arrangements (O2, O3, or O2/O3 intergrowths) in the lithiated materials are dependent upon the Na/transition metal ratio in the sodium-containing precursors, the degree of substitution, and the identity of the substituting metal. O3 layered materials deliver up to 200 mAh/g at moderate current densities in lithium cell configurations, but convert rapidly to spinels upon cell cycling, while O2 compounds are more stable but deliver less capacity. Intergrowths show intermediate behavior, with higher capacities than pure O2 materials and better phase stability than O3 compounds. Some intergrowth structures do not appear to convert to spinel during normal cycling, suggesting it may be possible to tailor high energy density, phase stable layered manganese oxide electrodes for lithium batteries.
Date: July 14, 2003
Creator: Dolle, M.; Hollingsworth, J.; Richardson, T. J. & Doeff, M. M.
System: The UNT Digital Library
Organometallic Chemistry. Final Progress Report (open access)

Organometallic Chemistry. Final Progress Report

The Gordon Research Conference (GRC) on Organometallic Chemistry was held at Salve Regina, Newport, Rhode Island, 7/21-26/02. Emphasis was placed on current unpublished research and discussion of the future target areas in this field.
Date: July 14, 2003
Creator: unknown
System: The UNT Digital Library
Far-infrared absorption in GaAs:Te liquid phase epitaxial films (open access)

Far-infrared absorption in GaAs:Te liquid phase epitaxial films

None
Date: May 14, 2003
Creator: Cardozo, B. L.; Haller, E. E.; Reichertz, L. A. & Beeman, J. W.
System: The UNT Digital Library
Scanning x-ray microdiffraction with submicron white beam for strain and orientation mapping in thin films (open access)

Scanning x-ray microdiffraction with submicron white beam for strain and orientation mapping in thin films

Scanning X-ray Microdiffraction (m-SXRD) combines the use of high brilliance synchrotron sources with the latest achromatic X-ray focusing optics and fast large area 2D-detector technology. Using white beams or a combination of white and monochromatic beams, it allows for orientation and strain/stress mapping of polycrystalline thin films with submicron spatial resolution. The technique is described in detail as applied to the study of thin aluminium and copper blanket films and lines following electromigration testing and/or thermal cycling experiments. It is shown that there are significant orientation and strain/stress variations between grains and inside individual grains. A polycrystalline film when investigated at the granular (micron) level shows a highly mechanically inhomogeneous medium that allows insight into its mesoscopic properties. If the m-SXRD data are averaged over a macroscopic range, results show good agreement with direct macroscopic texture and stress measurements .
Date: January 14, 2003
Creator: Tamura, N.; MacDowell, A. A.; Spolenak, R.; Valek, B. C.; Bravman, J. C.; Brown, W. L. et al.
System: The UNT Digital Library
'Mini'-Roadmapping - Ensuring Timely Sites' Cleanup/Closure by Resolving Science & Technology Issues (open access)

'Mini'-Roadmapping - Ensuring Timely Sites' Cleanup/Closure by Resolving Science & Technology Issues

Roadmapping is a powerful tool to manage technical risks and opportunities associated with complex problems. Roadmapping identifies technical capabilities required for both project- and program-level efforts and provides the basis for plans that ensure the necessary enabling activities will be done when needed. Roadmapping reveals where to focus further development of the path forward by evaluating uncertainties for levels of complexity, impacts, and/or the potential for large payback. Roadmaps can be customized to the application, a ''graded approach'' if you will. Some roadmaps are less detailed. We have called these less detailed, top-level roadmaps ''mini-roadmaps''. These mini roadmaps are created to tie the needed enablers (e.g., technologies, decisions, etc.) to the functions. If it is found during the mini-roadmapping that areas of significant risk exist, then those can be roadmapped further to a lower level of detail. Otherwise, the mini-roadmap may be sufficient to manage the project/program risk. Applying a graded approach to the roadmapping can help keep the costs down. Experience has indicated that it is best to do mini-roadmapping first and then evaluate the risky areas to determine whether to further evaluate those areas. Roadmapping can be especially useful for programs/projects that have participants from multiple sites, programs, …
Date: January 14, 2003
Creator: Luke, D. E.; Dixon, B. W. & Murphy, J. A.
System: The UNT Digital Library
Booster's coupled bunch damper upgrade (open access)

Booster's coupled bunch damper upgrade

A new narrowband active damping system for longitudinal coupled bunch (CB) modes in the Fermilab Booster has recently been installed and tested. In the past, the Booster active damper system consisted of four independent front-ends. The summed output was distributed to the 18, h=84 RF accelerating cavities via the RF fan-out system. There were several problems using the normal fan-out system to deliver the longitudinal feedback RF. The high power RF amplifiers normally operate from 37 MHz to 53 MHz whereas the dampers operate around 83MHz. Daily variations in the tuning of the RF stations created tuning problems for the longitudinal damper system. The solution was to build a dedicated narrowband, Q {approx} 10, 83MHz cavity powered with a new 3.5kW solid-state amplifier. The cavity was installed in June 2002 and testing of the amplifier and damper front-end began in August 2002. A significant improvement has been made in both operational stability and high intensity beam damping. At present there are five CB modes being damped and a sixth mode module is being built. The new damper hardware is described and data showing the suppression of the coupled-bunch motion at high intensity is presented.
Date: August 14, 2003
Creator: Wildman, William A. Pellico and D. W.
System: The UNT Digital Library
Assessment of Ivanpah Playa as a Site for Thermal Vicarious Calibration for the MTI Satellite (open access)

Assessment of Ivanpah Playa as a Site for Thermal Vicarious Calibration for the MTI Satellite

The Savannah River Technology Center conducted four vicarious reflectance calibrations at Ivanpah Playa, California since July 2000 in support of the MTI satellite. The potential of the playa as a thermal calibration site was also investigated in the campaigns with a mobile Fourier transform infrared spectrometer. The multi-year study shows time and spatial variability in the spectral emissivity. The ground truth temperature and emissivity correlate quite well with the data from the MTI satellite imagery. The research paper will show the time-dependent emissivities measured during our ground truth campaigns and the corresponding satellite imagery.
Date: March 14, 2003
Creator: Villa-Aleman, E.
System: The UNT Digital Library
Modeling water seepage into heated waste emplacement drifts at Yucca Mountain (open access)

Modeling water seepage into heated waste emplacement drifts at Yucca Mountain

This paper describes numerical prediction of the coupled thermal-hydrological processes (TH) in the vicinity of waste emplacement drifts during the heating phase of the proposed geologic repository for nuclear waste at Yucca Mountain, Nevada. Heating of rock water to above-boiling conditions induces water saturation changes and perturbed water fluxes that affect the potential of water seepage into drifts. In addition to the capillary barrier at the rock-drift interface--independent of the thermal conditions--a second barrier exists to downward percolation at above-boiling conditions. This barrier is caused by vaporization of water in the fractured rock overlying the repository. A TOUGH2 simulation model was developed to analyze the combined effect of these two barriers; it accounts for all relevant TH processes in response to heating, while incorporating the capillary barrier condition at the drift wall. Model results are presented for a variety of simulation cases.
Date: April 14, 2003
Creator: Birkholzer, Jens; Mukhophadhyay, Sumit & Tsang, Yvonne
System: The UNT Digital Library
Neutrino physics, superbeams and the neutrino factory (open access)

Neutrino physics, superbeams and the neutrino factory

We summarize what has been learned about the neutrino mass spectrum and neutrino mixing, identify interesting open questions that can be answered by accelerator neutrino facilities of the future, and discuss the importance and physics of answering them.
Date: October 14, 2003
Creator: Kayser, Boris
System: The UNT Digital Library
SLOPE PROFILOMETRY OF GRAZING INCIDENCE OPTICS. (open access)

SLOPE PROFILOMETRY OF GRAZING INCIDENCE OPTICS.

Profiling instruments are well-suited to the measurement of grazing incidence optics, such as those found in synchrotron radiation beam lines. Slope measuring profilers, based upon the principle of the pencil beam interferometer, have proven to be especially useful in measuring the figure and slope errors on cylindrical aspheres. The Long Trace Profiler, in various configurations, is the most widely used of this class of profiler. Current performance provides slope measurement accuracy at the microradian level and height measurements accurate to 25 nm over 1 meter trace lengths.
Date: January 14, 2003
Creator: TAKACS,P.Z.
System: The UNT Digital Library
Radiological Characterization Methodology for INEEL-Stored Remote-Handled Transuranic (RH TRU) Waste from Argonne National Laboratory-East (open access)

Radiological Characterization Methodology for INEEL-Stored Remote-Handled Transuranic (RH TRU) Waste from Argonne National Laboratory-East

An Acceptable Knowledge (AK)-based radiological characterization methodology is being developed for RH TRU waste generated from ANL-E hot cell operations performed on fuel elements irradiated in the EBR-II reactor. The methodology relies on AK for composition of the fresh fuel elements, their irradiation history, and the waste generation and collection processes. Radiological characterization of the waste involves the estimates of the quantities of significant fission products and transuranic isotopes in the waste. Methods based on reactor and physics principles are used to achieve these estimates. Because of the availability of AK and the robustness of the calculation methods, the AK-based characterization methodology offers a superior alternative to traditional waste assay techniques. Using the methodology, it is shown that the radiological parameters of a test batch of ANL-E waste is well within the proposed WIPP Waste Acceptance Criteria limits.
Date: January 14, 2003
Creator: Kuan, P. & Bhatt, R. N.
System: The UNT Digital Library
Comparison of Experimental and Model Data for the Evaporation of a Synthetic Topopah Spring Tuff Pore Water, Yucca Mountain, NV (open access)

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
System: The UNT Digital Library
Observation of anomalous Iron Ion Charge Distribution in FTU (open access)

Observation of anomalous Iron Ion Charge Distribution in FTU

Iron coming from the poloidal limiter or the stainless steel vessel is an important intrinsic impurity in the FTU tokamak discharges, and X-ray and VUV spectroscopy provide useful information about the impurity behavior. The iron ion charge state distribution, as usual for tokamaks, is analyzed assuming a collisional radiative model and an anomalous perpendicular diffusion. In our experiment the iron ionization level depends, as it is expected, on central electron temperature (fig. 1), but the ion charge state distribution shows a different behavior when the first wall material or the iron source are changed.
Date: November 14, 2003
Creator: Finkenthal, M.; May, M.; Pacella, D.; Leigheb, M.; Zagorski, R.; Mattioli, M. et al.
System: The UNT Digital Library
The Interaction of Dislocations and Radiation-Induced Obstacles at High-Strain Rate (open access)

The Interaction of Dislocations and Radiation-Induced Obstacles at High-Strain Rate

Improved understanding of the plastic deformation of metals during high strain rate shock loading is key to predicting their resulting material properties. This paper presents the results of molecular dynamics simulations that identify the deformation modes of aluminum over a range of applied shear stresses and examines the interaction between dislocations and irradiation induced obstacles. These simulations show that while super-sonic dislocation motion can occur during impact loading, the finite dimensions of the materials render this motion transient. Larger applied loads do not stabilize supersonic dislocations, but instead lead an alternate deformation mode, namely twinning. Finally, the atomistic mechanisms that underlie the observed changes in the mechanical properties of metals as a function of irradiation are examined. Specifically, simulations of the interactions between moving edge dislocations and nanometer-sized helium bubbles provide insight into increases of the critical shear stresses but also reveal the effect of internal gas pressure on the deformation mode. The information gained in these studies provides fundamental insight into materials behavior, as well as important inputs for multi-scale models of materials deformation.
Date: July 14, 2003
Creator: Young, J. A.; Wirth, B. D.; Robach, J. & Robertson, I.
System: The UNT Digital Library
Radiocarbon in otoliths of yelloweye rockfish (Sebastes ruberrimus): a reference time series for the coastal waters of southeast Alaska (open access)

Radiocarbon in otoliths of yelloweye rockfish (Sebastes ruberrimus): a reference time series for the coastal waters of southeast Alaska

Atmospheric testing of thermonuclear devices during the 1950s and 1960s created a global radiocarbon ({sup 14}C) signal in the environment that has provided a useful tracer and chronological marker in oceanic systems and organisms. The bomb-generated {sup 14}C signal retained in fish otoliths can be used as a permanent, time-specific recorder of the 14C present in ambient seawater, making it a useful tool in age validation of fishes. The goal of this study was to determine {sup 14}C levels in otoliths of the age-validated yelloweye rockfish (Sebastes ruberrimus) to establish a reference time series for the coastal waters of southeast Alaska. Radiocarbon values from the first year's growth of 43 yelloweye rockfish otoliths were plotted against estimated birth year to produce a 14C time series for these waters spanning 1940 to 1990. The time series shows the initial rise of bomb 14C occurred in 1958 in coastal southeast Alaskan waters and {sup 14}C levels rose relatively rapidly to peak {Delta}{sup 14}C values (60-70%) between 1966 and 1971, with a subsequent declining trend through the end of the record in 1990 (-3.2%). In addition, the radiocarbon data, independent of the radiometric study, confirms the longevity of the yelloweye rockfish up to …
Date: October 14, 2003
Creator: Kerr-Ferrey, L A; Andrews, A H; Frantz, B R; Coale, K H; Brown, T A & Cailliet, G M
System: The UNT Digital Library