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Reactive Transport Modeling of Geologic CO{sub 2} Sequestration in Saline Aquifers: The Influence of Intra-Aquifer Shales and the Relative Effectiveness of Structural, Solubility, and Mineral Trapping During Prograde and Retrograde Sequestration (open access)

Reactive Transport Modeling of Geologic CO{sub 2} Sequestration in Saline Aquifers: The Influence of Intra-Aquifer Shales and the Relative Effectiveness of Structural, Solubility, and Mineral Trapping During Prograde and Retrograde Sequestration

In this study, we address a series of fundamental questions regarding the processes and effectiveness of geologic CO{sub 2} sequestration in saline aquifers. We begin with the broadest: what is the ultimate fate of CO{sub 2} injected into these environments? Once injected, it is immediately subject to two sets of competing processes: migration processes and sequestration processes. In terms of migration, the CO{sub 2} moves by volumetric displacement of formation waters, with which it is largely immiscible; by gravity segregation, which causes the immiscible CO{sub 2} plume to rise owing to its relatively low density; and by viscous fingering, owing to its relatively low viscosity. In terms of sequestration, some fraction of the rising plume will dissolve into formation waters (solubility trapping); some fraction may react with formation minerals to precipitate carbonates (mineral trapping); and the remaining portion eventually reaches the cap rock, where it migrates up-dip, potentially accumulating in local topographic highs (structural trapping). Although this concept of competing migration/sequestration processes is intuitively obvious, identifying those sub-processes that dominate the competition is by no means straightforward. Hence, at present there are large uncertainties associated with the ultimate fate of injected CO{sub 2} (Figure 1). Principal among these: can a …
Date: April 24, 2001
Creator: Johnson, J. W.; Nitao, J. J.; Steefel, C. I. & Knauss, K. G.
System: The UNT Digital Library
Physics and Applications of NIS Junctions (open access)

Physics and Applications of NIS Junctions

This paper reviews the physics and applications of Normal-Insulator-Superconductor (NIS) tunnel junctions. The current-voltage properties of NIS junctions are diode-like with a strong temperature dependence. Hence, these structures can be used as sensitive thermometers at temperatures well below the energy gap, {Delta}, of the superconducting electrode. For junction voltages comparable to {Delta}/q, current flow removes energy from the normal electrode. This property has been exploited to build refrigerators capable of cooling thin-film circuits from 0.3 K to 0.1 K. Calorimeters and bolometers for the detection of X-rays and millimeter-wave radiation, respectively, have successfully been built from NIS junctions. NIS junctions have also been used to probe the superconducting state. Finally, recent ideas for the use of NIS junctions as simple circuit elements are described.
Date: August 24, 2001
Creator: Ullom, J N
System: The UNT Digital Library
A Comparative experimental study of media access protocols for wireless radio networks (open access)

A Comparative experimental study of media access protocols for wireless radio networks

We conduct a comparative experimental analysis of three well known media access protocols: 802.11, CSMA, and MACA for wireless radio networks. Both fixed and ad-hoc networks are considered. The experimental analysis was carried out using GloMoSim: a tool for simulating wireless networks. The main focus of experiments was to study how (i) the size of the network, (ii) number of open connections, (iii) the spatial location of individual connections, (iv) speed with which individual nodes move and (v) protocols higher up in the protocol stack (e,g. routing layer) affect the performance of the media access sublayer protocols. The performance of the protocols was measured w.r.t. three important parameters: (1) number of received packets, (2) average latency of each packet, and (3) throughput. The following general qualitative conclusions were obtained; some of the conclusions reinforce the earlier claims by other researchers. (1) Although 802.11 performs better than the other two protocols with respect to fairness of transmission, packets dropped, and latency, its performance is found to (i) show a lot of variance with changing input parameters and (ii) the overall performance still leaves a lot of room for improvement. (2) CSMA does not perform too well under the fairness criteria, however, …
Date: May 24, 2001
Creator: Barrett, C. L. (Christopher L.); Drozda, M. (Martin) & Marathe, M. V. (Madhav V.)
System: The UNT Digital Library
Are the J/psi and chi_c A dependencies the same? (open access)

Are the J/psi and chi_c A dependencies the same?

It has been empirically observed that the dependence of J/{psi} and {psi}{prime} production on nuclear mass number A is very similar. This has been postulated to be due to the predominance of color octet pre-resonant states in charmonium production and absorption. Two new experiments, NA60 at CERN and HERA-B at DESY, will measure the {chi}{sub c} A dependence for the first time. These measurements should shed new light on the charmonium production and absorption mechanisms.
Date: September 24, 2001
Creator: Vogt, R.
System: The UNT Digital Library
Integrated simulation environment for lighting design (open access)

Integrated simulation environment for lighting design

Lighting design involves the consideration of multiple performance criteria, from the earliest stages of conceptual design, through various stages of controls and operation in a project's life cycle. These criteria include: (1) the quantitative analysis of illuminance and luminance distribution due to daylighting and electric lighting; (2) qualitative analysis of the lighting design with photometrically accurate renderings of the designed environment; (3) analysis of energy implications of daylighting and electric lighting design and operation;, and (4) analysis of control strategies and sensor placement for maximizing energy savings from lighting control while providing visual comfort. In this paper we describe the development of an integrated decision-making environment that brings together several different tools, and provides the data management and process control required for a multi-criterion support of the design and operation of daylighting and electric lighting systems. The result is a powerful design and decision-making environment to meet the diverse and evolving needs of lighting designers and operators.
Date: May 24, 2001
Creator: Pal, Vineeta & Papamichael, Konstantinos
System: The UNT Digital Library
INTERACTION REGION MAGNETS FOR VLHC. (open access)

INTERACTION REGION MAGNETS FOR VLHC.

The interaction region (IR) magnets for the proposed very large hadron collider (VLHC) require high gradient quadrupoles and high field dipoles for high luminosity performance. Moreover, the IR magnets for high energy colliders and storage rings must operate in an environment where the amount of energy deposited on superconducting coils is rather large. In the case of doublet IR optics with flat beams, the design of the first 2-in-1 quadrupole defines the geometry and pole tip field in this and other IR magnets. This paper will present a novel design of this magnet that allows a very small separation between the two apertures. A brief discussion of the conceptual magnetic design of this and other magnets for interaction regions is given. The influence of critical current density in superconductor (a higher value of which is most beneficial to high performance IR magnet design) is also discussed. Since High Temperature Superconductors (HTS) retain most of their critical current density at high fields and at elevated temperatures, they offer an attractive possibility for the IR magnet designs of future colliders or upgrades of present colliders.
Date: September 24, 2001
Creator: Gupta, R. & Harrison, M.
System: The UNT Digital Library
Underground Corrosion of Activated Metals in an Arid Vadose Zone Environment (open access)

Underground Corrosion of Activated Metals in an Arid Vadose Zone Environment

The subsurface radioactive disposal site located at the Idaho National Engineering and Environmental Laboratory contains neutron-activated metals from nonfuel nuclear-reactor- core components. A long-term corrosion test is being conducted to obtain site-specific corrosion rates to support efforts to more accurately estimate the transfer of activated elements in an arid vadose zone environment. The tests use nonradioactive metal coupons representing the prominent neutron-activated material buried at the disposal location, namely, Type 304L stainless steel, Type 315L stainless steel, nickel-chromium alloy (UNS NO7718), beryllium, aluminum 6061-T6, and a zirconium alloy, (UNS R60804). In addition, carbon steel (the material presently used in the cask disposal liners and other disposal containers) and a duplex stainless steel (UNS S32550) (the proposed material for the high- integrity disposal containers) are also included in the test program. This paper briefly describes the test program and presents the early corrosion rate results after 1 year and 3 years of underground exposure.
Date: October 24, 2001
Creator: Adler Flitton, M. K.; Mizia, R. E. & Bishop, C. W.
System: The UNT Digital Library
Conceptual Design of Pion Capture Magnets of Up to 15 Cm Bore and 20 T Peak Field. (open access)

Conceptual Design of Pion Capture Magnets of Up to 15 Cm Bore and 20 T Peak Field.

For the Neutrino Factory and Muon Collider Collaboration, BNL has considered solenoidal magnet systems of several types to capture pions generated by bombarding a mercury jet with multi-GeV protons. The magnet systems generate up to 20 T, uniform to 5% throughout a cylindrical volume 0.15 m in diameter and 0.6 m long. Axially downstream the field ramps gradually downward by a factor of sixteen, while the bore increases fourfold. The steady-state system needed for an accelerator has many superconducting coils and a radiation-resistant insert of mineral-insulated hollow conductor. Less costly, pulsed systems suffice to study pion capture and the effect of a magnetic field on a jet hit by a proton beam. BNL has explored three types of magnets, each with its principal coils precooled by liquid nitrogen. One type employs two sets of coils energized sequentially. Charged in 23 s by a power supply of 5 MVA, the 16ton outer set generates 10 T and stores 28 MJ, from which, in 1/3 s, to charge a half-ton inner coil that adds 12 1/2 T to the 7 1/2 T remaining from the outer set. An alternative design uses 25 MVA to energize, in 1.4 s, a single 3-ton set …
Date: September 24, 2001
Creator: Weggel, R. J.
System: The UNT Digital Library
R AND D FOR ACCELERATOR MAGNETS WITH REACT AND WIND HIGH TEMPERATURE SUPERCONDUCTORS. (open access)

R AND D FOR ACCELERATOR MAGNETS WITH REACT AND WIND HIGH TEMPERATURE SUPERCONDUCTORS.

High Temperature Superconductors (HTS) have the potential to change the design and operation of future particle accelerators beginning with the design of high performance interaction regions. HTS offers two distinct advantages over conventional Low Temperature Superconductors (LTS)--they retain a large fraction of their current carrying capacity (a) at high fields and (b) at elevated temperatures. The Superconducting Magnet Division at Brookhaven National Laboratory (BNL) has embarked on a new R&D program for developing technology needed for building accelerator magnets with HTS. We have adopted a ''React & Wind'' approach to deal with the challenges associated with the demanding requirements of the reaction process. We have developed several ''conductor friendly'' designs to deal with the challenges associated with the brittle nature of HTS. We have instituted a rapid turn around program to understand and to develop this new technology in an experimental fashion. Several R&D coils and magnets with HTS tapes and ''Rutherford'' cables have been built and tested. We have recently performed field quality measurements to investigate issues related to the persistent currents. In this paper, we report the results to date and plans and possibilities for the future.
Date: September 24, 2001
Creator: Gupta, R.; Anerella, M.; Cozzolino, J.; Escallier, J.; Ganetis, G.; Ghosh, A. et al.
System: The UNT Digital Library
Applications of Crystal Plasticity in Multiscale Modeling (open access)

Applications of Crystal Plasticity in Multiscale Modeling

Multiscale modeling with crystal plasticity constitutive relations is used to determine the average response of a polycrystal. The measured crystallographic texture of a copper shaped charge liner is used in a crystal plasticity model to construct a yield surface that exhibits normal-shear coupling. Simulations with this yield surface model demonstrate the spinning behavior observed in the spin formed copper shaped charges.
Date: September 24, 2001
Creator: Becker, R.; Busche, M.; Schwartz, A. J. & Kumar, M.
System: The UNT Digital Library
US NEUTRINO FACTORY STUDIES. (open access)

US NEUTRINO FACTORY STUDIES.

The design and simulated performance of a second feasibility study are presented. The efficiency of producing muons is {approx} 0.17 {micro}/p with 24 GeV protons. This study was sponsored by the BNL Director, with BNL site specific driver and layout. It was a follow on to the First Study sponsored by the Fermilab Director, with Fermilab site specific driver and layout, and was the main US collaboration conceptual effort during the past year. Other studies, and technical work by the collaboration is reported in other papers.
Date: May 24, 2001
Creator: OZAKI,S. PALMER,R. B. ZISMAN,M. S.
System: The UNT Digital Library
Predicting and Evaluating the Effectiveness of Ocean Carbon Sequestration by Direct Injection (open access)

Predicting and Evaluating the Effectiveness of Ocean Carbon Sequestration by Direct Injection

Direct injection of CO{sub 2} into the ocean is a potentially effective carbon sequestration strategy. Therefore, we want to understand the effectiveness of oceanic injection and develop the appropriate analytic framework to allow us to compare the effectiveness of this strategy with other carbon management options. Here, after a brief review of direct oceanic injection, we estimate the effectiveness of ocean carbon sequestration using one dimensional and three dimensional ocean models. We discuss a new measure of effectiveness of carbon sequestration in a leaky reservoir, which we denote sequestration potential. The sequestration potential is the fraction of global warning cost avoided by sequestration in a reservoir. We show how these measures apply to permanent sequestration and sequestration in leaky reservoirs, such as the oceans, terrestrial biosphere, and some geologic formations. Under the assumptions of a constant cost of carbon emission and a 4% discount rate, injecting 900 m deep in the ocean avoids {approx}90% of the global warming cost associated with atmospheric emission; an injection 1700 m deep would avoid > 99 % of the global warming cost. Hence, for discount rates in the range commonly used by commercial enterprises, oceanic direct injection may be nearly as economically effective as …
Date: April 24, 2001
Creator: Caldeira, K; Herzog, H J & Wickett, M E
System: The UNT Digital Library
Uranyl-Fluoride (233U) Solutions in Spherical Stainless Steel Vessels with Reflectors of Be, CH2, and Be-CH2 Composites (open access)
COMPLETION OF SUPERCONDUCTING MAGNET PRODUCTION AT BNL FOR THE HERA LUMINOSITY UPGRADE (open access)

COMPLETION OF SUPERCONDUCTING MAGNET PRODUCTION AT BNL FOR THE HERA LUMINOSITY UPGRADE

Brookhaven National Laboratory (BNL) has completed production of the superconducting multi-function magnets that are now installed as part of the HERA luminosity upgrade at DESY. The magnets, cryostats, and lead assemblies were designed and built at BNL. To fit inside the existing detectors, the coils plus cryostat structure had to meet a challenging radial budget (e.g., 39 mm horizontally). Two types of magnets were needed and three of each type were built. Each magnet contained normal and skew quadrupole, normal and skew dipole, and sextupole coils. The magnets operate in the {approx}1.5 T solenoid field of a detector. The quadrupole coils produce gradients up to 13 T/m. The dipole coils generate fields up to 0.3 T. Coils were wound under computer control using either seven-strand round cable or a single strand. To simultaneously avoid excessive synchrotron radiation background scattered from the beam pipe and yet have a small cryostat, one type of magnet used a tapered coil structure. The cryogenic system incorporates cooling with both 40 K helium and supercritical helium. All of the coils were tested in liquid helium in a vertical dewar. Quench test results have been excellent. The field quality of the magnets has met the stringent …
Date: September 24, 2001
Creator: WANDERER,P. ANERELLA,M. ESCALLIER,J. GHOSH,A. JAIN,A. MARONE,A. MURATORE,J. PARKER,A. PRODELL,A. THOMPSON,P. WU,K. C.
System: The UNT Digital Library
Magnet Performance and Rhic Commissioning. (open access)

Magnet Performance and Rhic Commissioning.

The RHIC accelerator complex completed commissioning activities in 2000 and is presently operating for the first physics run. The complete ensemble of magnets was thus operating over an extended period for the first time. We review the magnet performance as well as relate machine performance characteristics and accelerator physics results to the various magnetic measurements made during the construction phase. The conclusions may be useful for the LHC Project.
Date: September 24, 2001
Creator: Harrison, M.
System: The UNT Digital Library
Supervised and unsupervised discretization methods for evolutionary algorithms (open access)

Supervised and unsupervised discretization methods for evolutionary algorithms

This paper introduces simple model-building evolutionary algorithms (EAs) that operate on continuous domains. The algorithms are based on supervised and unsupervised discretization methods that have been used as preprocessing steps in machine learning. The basic idea is to discretize the continuous variables and use the discretization as a simple model of the solutions under consideration. The model is then used to generate new solutions directly, instead of using the usual operators based on sexual recombination and mutation. The algorithms presented here have fewer parameters than traditional and other model-building EAs. They expect that the proposed algorithms that use multivariate models scale up better to the dimensionality of the problem than existing EAs.
Date: January 24, 2001
Creator: Cantú-Paz, Erick
System: The UNT Digital Library
Stepwise Reduction of Dinitrogen Bond Order by a Low-Coordinate Iron Complex (open access)

Stepwise Reduction of Dinitrogen Bond Order by a Low-Coordinate Iron Complex

This article discusses stepwise reduction of dinitrogen bond order by a low-coordinate iron complex.
Date: August 24, 2001
Creator: Smith, Jeremy M.; Lachicotte, Rene J.; Pittard, Karl A.; Cundari, Thomas R., 1964-; Lukat-Rodgers, Gudrun; Rodgers, Kenton R. et al.
System: The UNT Digital Library
Neutrino Observations From the Sudbury Neutrino Observatory (open access)

Neutrino Observations From the Sudbury Neutrino Observatory

The Sudbury Neutrino Observatory (SNO) is a water imaging Cherenkov detector. Its usage of 1000 metric tons of D{sub 2}O as target allows the SNO detector to make a solar-model independent test of the neutrino oscillation hypothesis by simultaneously measuring the solar {nu}{sub e} flux and the total flux of all active neutrino species. Solar neutrinos from the decay of {sup 8}B have been detected at SNO by the charged-current (CC) interaction on the deuteron and by the elastic scattering (ES) of electrons. While the CC reaction is sensitive exclusively to {nu}{sub e}, the ES reaction also has a small sensitivity to {nu}{sub {mu}} and {nu}{sub {tau}}. In this paper, recent solar neutrino results from the SNO experiment are presented. It is demonstrated that the solar flux from {sup 8}B decay as measured from the ES reaction rate under the no-oscillation assumption is consistent with the high precision ES measurement by the Super-Kamiokande experiment. The {nu}{sub e} flux deduced from the CC reaction rate in SNO differs from the Super-Kamiokande ES results by 3.3{sigma}. This is evidence for an active neutrino component, in additional to {nu}{sub e}, in the solar neutrino flux. These results also allow the first experimental determination …
Date: September 24, 2001
Creator: Ahmad, Q. R.; Allen, R. C.; Andersen, T. C.; Anglin, J. D.; Barton, J. C.; Beier, E. W. et al.
System: The UNT Digital Library
DISTRIBUTED CONTAINER FAILURE MODELS FOR THE DUST-MS COMPUTER CODE. (open access)

DISTRIBUTED CONTAINER FAILURE MODELS FOR THE DUST-MS COMPUTER CODE.

Improvements to the DUST-MS computer code have been made that permit simulation of distributed container failure rates. The new models permit instant failure of all containers within a computational volume, uniform failure of these containers over time, or a normal distribution in container failures. Incorporation of a distributed failure model requires wasteform releases to be calculated using a convolution integral. In addition, the models permit a unique time of emplacement for each modeled container and allow a fraction of the containers to fail at emplacement. Implementation of these models, verification testing, and an example problem comparing releases from a wasteform with a two-species decay chain as a function of failure distribution are presented in the paper.
Date: February 24, 2001
Creator: Sullivan,Terry & de Lemos, Francisco
System: The UNT Digital Library
Kaon Condensation in Neutron Stars. (open access)

Kaon Condensation in Neutron Stars.

We discuss the kaon-nucleon interaction and its consequences for the change of the properties of the kaon in the medium. The onset of kaon condensation in neutron stars under various scenarios as well its effects for neutron star properties are reviewed.
Date: April 24, 2001
Creator: Ramos, A.; Schaffner-Bielich, J. & Wambach, J.
System: The UNT Digital Library
Long Term Oxidation of Model and Engineering TiAl Alloys (open access)

Long Term Oxidation of Model and Engineering TiAl Alloys

The purpose of this research was to characterize the oxidation behavior of several model (TiAl, TiAl-Nb, TiAl-Cr, TiAl-Cr-Nb) and engineering alloys (XD, K5, Alloy 7, WMS) after long-term isothermal exposure ({approx}7000 h) at 704 C, and after shorter time exposure ({approx}1000 h) at 800 C in air. High-resolution field emission and microprobe scanning electron microscopy were used to characterize the scales formed on these alloys. Similarities and differences observed in the scales are correlated with the various ternary and quaternary microalloying additions.
Date: August 24, 2001
Creator: Locci, IE
System: The UNT Digital Library
Nucleation of YBa{sub 2}Cu{sub 3}O{sub 7{minus}{delta}} in the BaF{sub 2} Process. (open access)

Nucleation of YBa{sub 2}Cu{sub 3}O{sub 7{minus}{delta}} in the BaF{sub 2} Process.

The nucleation of the c-axis aligned and non-c-axis YBa{sub 2}Cu{sub 3}O{sub {approximately}6.1} (YBCO) from precursor films on [001]-cut SrTiO{sub 3} was investigated for the so-called BaF{sub 2} process. Specimens with different thickness were quenched from 735 C, then studied by transmission electron microscopy and x-ray diffraction techniques. Preceding the formation of YBCO nuclei, three intermediate phases of (Y,Ba) oxy-fluoride and a transition phase without F were found in the precursor films. These were structurally and chemically related to the nuclei of YBCO which was found to be deficient in Cu relative to its stoichiometric composition.
Date: June 24, 2001
Creator: Wu, L.; Solovyov, V. F.; Wiesmann, H. J.; Zhu, Y. & Suenaga, M.
System: The UNT Digital Library
Intense Electron Beam Disruption Due to Ion Release From Surface (open access)

Intense Electron Beam Disruption Due to Ion Release From Surface

None
Date: July 24, 2001
Creator: Vermare, C.; Davis, H. A. & Al, Et
System: The UNT Digital Library
A Monte Carlo Approach to Calculate Probability Tables for the Unresolved-Resonance Region Using the AMPX Cross-Section Processing System (open access)

A Monte Carlo Approach to Calculate Probability Tables for the Unresolved-Resonance Region Using the AMPX Cross-Section Processing System

A new module, PURM (Probability tables for the Unresolved Region using Monte Carlo), has been developed for the AMPX-2000 cross-section processing system. PURM uses a Monte Carlo approach to calculate probability tables on an evaluator-defined energy grid in the unresolved-resonance region. For each probability table, PURM samples a Wigner spacing distribution for pairs of resonances surrounding the reference energy. The resonance distribution is sampled for each spin sequence (i.e., {ell}-J pair), and PURM uses the {Delta}{sub 3}-statistics test to determine the number of resonances to sample for each spin sequence. For each resonance, PURM samples the resonance widths from a Chi-square distribution for a specified number of degrees of freedom. Once the resonance parameters are sampled, PURM calculates the total, capture, fission and scatter cross sections at the reference energy using the single-level Breit-Wigner formalism with appropriate treatment for temperature effects. Probability tables have been calculated and compared with NJOY. The probability tables and cross-section values that are calculated by PURM and NJOY are in agreement, and the verification studies with NJOY establish the computational capability for generating probability tables using the new AMPX module PURM.
Date: August 24, 2001
Creator: Dunn, M. E.
System: The UNT Digital Library