High-Performance Systems Biology and Associated Combinatorial Scientific Computing Problems

Presentation discussing a metabolomics study focused on a hydrogen-producing green alga and the problems encountered that are addressable using combinatorial scientific computing methods.
Date: June 1, 2008
Creator: Alber, D.
Object Type: Presentation
System: The UNT Digital Library
HIGH TEMPERATURE IRRADIATION RESISTANT THERMOCOUPLES – A LOW COST SENSOR FOR IN-PILE TESTING AT HIGH TEMPERATURES (open access)

HIGH TEMPERATURE IRRADIATION RESISTANT THERMOCOUPLES – A LOW COST SENSOR FOR IN-PILE TESTING AT HIGH TEMPERATURES

Several options have been identified to improve recently-developed Idaho National Laboratory (INL) High Temperature Irradiation Resistant ThermoCouples (HTIR-TCs) for in-pile testing. These options have the potential to reduce fabrication costs and allow HTIR-TC use in higher temperature applications (up to at least 1800 °C). The INL and the University of Idaho (UI) investigated these options with the ultimate objective of providing recommendations for alternate thermocouple designs that are optimized for various applications. This paper summarizes results from these INL/UI investigations. Specifically, results are reported about several options found to enhance HTIR-TC performance, such as improved heat treatments, alternate geometries, alternate fabrication techniques, and the use of copper/nickel alloys as soft extension cable.
Date: June 1, 2008
Creator: Rempe, Joy L.; Knudson, Darrell L.; Condie, Keith G.; Wilkins, S. Curtis & Daw, Joshua E.
Object Type: Article
System: The UNT Digital Library
HIGH TEMPERATURE THERMAL AND STRUCTURAL MATERIAL PROPERTIES FOR METALS USED IN LWR VESSELS (open access)

HIGH TEMPERATURE THERMAL AND STRUCTURAL MATERIAL PROPERTIES FOR METALS USED IN LWR VESSELS

Because of the impact that melt relocation and vessel failure may have on subsequent progression and associated consequences of a Light Water Reactor (LWR) accident, it is important to accurately predict heating and relocation of materials within the reactor vessel, heat transfer to and from the reactor vessel, and the potential for failure of the vessel and structures within it. Accurate predictions of such phenomena require high temperature thermal and structural properties. However, a review of vessel and structural steel material properties used in severe accident analysis codes reveals that the required high temperature material properties are extrapolated with little, if any, data above 1000 K. To reduce uncertainties in predictions relying upon extrapolated high temperature data, Idaho National Laboratory (INL) obtained high data for two metals used in LWR vessels: SA 533 Grade B, Class 1 (SA533B1) low alloy steel, which is used to fabricate most US LWR reactor vessels; and Type 304 Stainless Steel SS304, which is used in LWR vessel piping, penetration tubes, and internal structures. This paper summarizes the new data, and compares it to existing data.
Date: June 1, 2008
Creator: Rempe, J. L.; Knudson, D. L.; Daw, J. E. & Crepeau, J. C.
Object Type: Article
System: The UNT Digital Library
IceCube: A Cubic Kilometer Radiation Detector (open access)

IceCube: A Cubic Kilometer Radiation Detector

IceCube is a 1 km{sup 3} neutrino detector now being built at the Amudsen-Scott South Pole Station. It consists of 4800 Digital Optical Modules (DOMs) which detect Cherenkov radiation from the charged particles produced in neutrino interactions. IceCube will observe astrophysical neutrinos with energies above about 100 GeV. IceCube will be able to separate {nu}{sub {mu}}, {nu}{sub t}, and {nu}{sub {tau}} interactions because of their different topologies. IceCube construction is currently 50% complete.
Date: June 1, 2008
Creator: Collaboration, IceCube; Klein, Spencer R & Klein, S.R.
Object Type: Article
System: The UNT Digital Library
The Impact of Carbon Control on Low-Income Household Electricity and Gasoline Expenditures (open access)

The Impact of Carbon Control on Low-Income Household Electricity and Gasoline Expenditures

In July of 2007 The Department of Energy's (DOE's) Energy Information Administration (EIA) released its impact analysis of 'The Climate Stewardship And Innovation Act of 2007,' known as S.280. This legislation, cosponsored by Senators Joseph Lieberman and John McCain, was designed to significantly cut U.S. greenhouse gas emissions over time through a 'cap-and-trade' system, briefly described below, that would gradually but extensively reduce such emissions over many decades. S.280 is one of several proposals that have emerged in recent years to come to grips with the nation's role in causing human-induced global climate change. EIA produced an analysis of this proposal using the National Energy Modeling System (NEMS) to generate price projections for electricity and gasoline under the proposed cap-and-trade system. Oak Ridge National Laboratory integrated those price projections into a data base derived from the EIA Residential Energy Consumption Survey (RECS) for 2001 and the EIA public use files from the National Household Transportation Survey (NHTS) for 2001 to develop a preliminary assessment of impact of these types of policies on low-income consumers. ORNL will analyze the impacts of other specific proposals as EIA makes its projections for them available. The EIA price projections for electricity and gasoline under …
Date: June 1, 2008
Creator: Eisenberg, Joel Fred
Object Type: Report
System: The UNT Digital Library
Impacts of Large Amounts of Wind Power on Design and Operation of Power Systems; Results of IEA Collaboration (open access)

Impacts of Large Amounts of Wind Power on Design and Operation of Power Systems; Results of IEA Collaboration

This paper summarizes the results from 18 case studies, with discussion on differences in methodology as well as issues that have been identified to impact the cost of wind integration.
Date: June 1, 2008
Creator: Ela, E.; Parsons, B.; Holttinen, H.; Meibom, P.; Orths, A.; O'Malley, M. et al.
Object Type: Article
System: The UNT Digital Library
Implications of Air Ingress Induced by Density-Difference Driven Stratified Flow (open access)

Implications of Air Ingress Induced by Density-Difference Driven Stratified Flow

One of the design basis accidents for the Next Generation Nuclear Plant (NGNP), a high temperature gas-cooled reactor, is air ingress subsequent to a pipe break. Following a postulated double-ended guillotine break in the hot duct, and the subsequent depressurization to nearly reactor cavity pressure levels, air present in the reactor cavity will enter the reactor vessel via density-gradient-driven-stratified flow. Because of the significantly higher molecular weight and lower initial temperature of the reactor cavity air-helium mixture, in contrast to the helium in the reactor vessel, the air-helium mixture in the cavity always has a larger density than the helium discharging from the reactor vessel through the break into the reactor cavity. In the later stages of the helium blowdown, the momentum of the helium flow decreases sufficiently for the heavier cavity air-helium mixture to intrude into the reactor vessel lower plenum through the lower portion of the break. Once it has entered, the heavier gas will pool at the bottom of the lower plenum. From there it will move upwards into the core via diffusion and density-gradient effects that stem from heating the air-helium mixture and from the pressure differences between the reactor cavity and the reactor vessel. This …
Date: June 1, 2008
Creator: Oh, Chang; Kim, Eung Soo; Schultz, Richard; Petti, David & Liou, C. P.
Object Type: Article
System: The UNT Digital Library
Improving SFR Economics through Innovations from Thermal Design and Analysis Aspects (open access)

Improving SFR Economics through Innovations from Thermal Design and Analysis Aspects

Achieving economic competitiveness as compared to LWRs and other Generation IV (Gen-IV) reactors is one of the major requirements for large-scale investment in commercial sodium cooled fast reactor (SFR) power plants. Advances in R&D for advanced SFR fuel and structural materials provide key long-term opportunities to improve SFR economics. In addition, other new opportunities are emerging to further improve SFR economics. This paper provides an overview on potential ideas from the perspective of thermal hydraulics to improve SFR economics. These include a new hybrid loop-pool reactor design to further optimize economics, safety, and reliability of SFRs with more flexibility, a multiple reheat and intercooling helium Brayton cycle to improve plant thermal efficiency and reduce safety related overnight and operation costs, and modern multi-physics thermal analysis methods to reduce analysis uncertainties and associated requirements for over-conservatism in reactor design. This paper reviews advances in all three of these areas and their potential beneficial impacts on SFR economics.
Date: June 1, 2008
Creator: Zhao, Haihua; Zhang, Hongbin; Mousseau, Vincent & Peterson, Per F.
Object Type: Article
System: The UNT Digital Library
Indoor Thermal Factors and Symptoms in Office Workers: Findings from the U.S. EPA BASE Study (open access)

Indoor Thermal Factors and Symptoms in Office Workers: Findings from the U.S. EPA BASE Study

Some prior research in office buildings has associated higher indoor temperatures even within the recommended thermal comfort range with increased worker symptoms. We reexamined this relationship in data from 95 office buildings in the U.S. Environmental Protection Agency's Building Assessment Survey and Evaluation (BASE) Study. We investigated relationships between building-related symptoms and thermal metrics constructed from real-time measurements. We estimated odds ratios (ORs) and 95percent confidence intervals in adjusted logistic regression models with general estimating equations, overall and by season. Winter indoor temperatures spanned the recommended winter comfort range; summer temperatures were mostly colder than the recommended summer range. Increasing indoor temperatures, overall, were associated with increases in few symptoms. Higher winter indoor temperatures, however, were associated with increases in all symptoms analyzed. Higher summer temperatures, above 23oC, were associated with decreases in most symptoms. Humidity ratio, a metric of absolute humidity, showed few clear associations. Thus, increased symptoms with higher temperatures within the thermal comfort range were found only in winter. In summer, buildings were overcooled, and only the higher observed temperatures were within the comfort range; these were associated with decreased symptoms. Confirmation of these findings would suggest that thermal management guidelines consider health effects as well as …
Date: June 1, 2008
Creator: Mendell, Mark & Mirer, Anna
Object Type: Article
System: The UNT Digital Library
Influence of base and PAG on deprotection blur in EUV photoresists and some thoughts on shot noise (open access)

Influence of base and PAG on deprotection blur in EUV photoresists and some thoughts on shot noise

A contact-hole deprotection blur metric has been used to monitor the deprotection blur of an experimental open platform resist (EH27) as the weight percent of base and photo acid generator (PAG) were varied. Patterning ability in 1:1 line-space patterns is shown to improve at smaller pitches as base/PAG are increased however no significant change in deprotection blur was observed. Isolated (or intrinsic) line-edge-roughness (LER) is shown to improve with increased base loading while remaining fixed through PAG loading. A discussion of improved patterning performance as related to shot noise and deprotection blur concludes with a speculation that the spatial distribution of PAG molecules has been playing some role, perhaps a dominant one, in determining the uniformity of photo generated acids in the resists that have been studied.
Date: June 1, 2008
Creator: Jones, Juanita; Anderson, Christopher; Naulleau, Patrick; Niakoula, Demitra; Hassanein, Elsayed; Brainard, Robert et al.
Object Type: Article
System: The UNT Digital Library
Influence of base and PAG on deprotection blur in EUV photoresists and some thoughts on shot noise (open access)

Influence of base and PAG on deprotection blur in EUV photoresists and some thoughts on shot noise

A contact-hole deprotection blur metric has been used to monitor the deprotection blur of an experimental open platform resist (EH27) as the weight percent of base and photo acid generator (PAG) were varied. A 6x increase in base weight percent is shown to reduce the size of successfully patterned 1:1 line-space features from 52 nm to 39 nm without changing deprotection blur. Corresponding isolated line-edge-roughness is reduced from 6.9 nm to 4.1 nm. A 2x increase in PAG weight percent is shown to improve 1:1 line-space patterning from 47 nm to 40 nm without changing deprotection blur or isolated LER. A discussion of improved patterning performance as related to shot noise and deprotection blur concludes with a speculation that the spatial distribution of PAG molecules has been playing some role, perhaps a dominant one, in determining the uniformity of photo generated acids in the resists that have been studied.
Date: June 1, 2008
Creator: Anderson, Christopher N.; Naulleau, Patrick P.; Niakoula, Dimitra; Hassanein, Elsayed; Brainard, Robert; Gallatin, Gregg et al.
Object Type: Article
System: The UNT Digital Library
Initial Operation of the High Temperature Electrolysis Integrated Laboratory Scale Experiment at INL (open access)

Initial Operation of the High Temperature Electrolysis Integrated Laboratory Scale Experiment at INL

An integrated laboratory scale, 15 kW high-temperature electrolysis facility has been developed at the Idaho National Laboratory under the U.S. Department of Energy Nuclear Hydrogen Initiative. Initial operation of this facility resulted in over 400 hours of operation with an average hydrogen production rate of approximately 0.9 Nm3/hr. The integrated laboratory scale facility is designed to address larger-scale issues such as thermal management (feed-stock heating, high-temperature gas handling), multiple-stack hot-zone design, multiple-stack electrical configurations, and other “integral” issues. This paper documents the initial operation of the ILS, with experimental details about heat-up, initial stack performance, as well as long-term operation and stack degradation.
Date: June 1, 2008
Creator: Stoots, C. M.; O'Brien, J. E.; Condie, K. G.; Herring, J. S. & Hartvigsen, J. J.
Object Type: Article
System: The UNT Digital Library
Internal electric-field-lines distribution in CdZnTe detectors measured using X-ray mapping (open access)

Internal electric-field-lines distribution in CdZnTe detectors measured using X-ray mapping

The ideal operation of CdZnTe devices entails having a uniformly distributed internal electric field. Such uniformity especially is critical for thick long-drift-length detectors, such as large-volume CPG and 3-D multi-pixel devices. Using a high-spatial resolution X-ray mapping technique, we investigated the distribution of the electric field in real devices. Our measurements demonstrate that in thin detectors, <5 mm, the electric field-lines tend to bend away from the side surfaces (i.e., a focusing effect). In thick detectors, 21 cm, with a large aspect ratio (thickness-to-width ratio), we observed two effects: the electric field lines bending away from or towards the side surfaces, which we called, respectively, the focusing field-line distribution and the defocusing field-line distribution. In addition to these large-scale variations, the field-line distributions were locally perturbed by the presence of extended defects and residual strains existing inside the crystals. We present our data clearly demonstrating the non-uniformity of the internal electric field.
Date: June 1, 2008
Creator: Bolotnikov, A. E.; Camarda, G. S.; Cui, Y.; Hossain, A.; Yang, G.; Yao, H. W. et al.
Object Type: Article
System: The UNT Digital Library
Investigation into Interface Lifting Within FSW Lap Welds (open access)

Investigation into Interface Lifting Within FSW Lap Welds

Friction stir welding (FSW) is rapidly penetrating the welding market in many materials and applications, particularly in aluminum alloys for transportation applications. As this expansion outside the research laboratory continues, fitness for service issues will arise, and process control and NDE methods will become important determinants of continued growth. The present paper describes research into FSW weld nugget flaw detection within aluminum alloy lap welds. We present results for two types of FSW tool designs: a smooth pin tool and a threaded pin tool. We show that under certain process parameters (as monitored during welding with a rotating dynamometer that measures x, y, z, and torque forces) and tooling designs, FSW lap welds allow significant nonbonded interface lifting of the lap joint, while forming a metallurgical bond only within the pin region of the weld nugget. These lifted joints are often held very tightly together even though unbonded, and might be expected to pass cursory NDE while representing a substantial compromise in joint mechanical properties. The phenomenon is investigated here via radiographic and ultrasonic NDE techniques, with a copper foil marking insert (as described elsewhere) and by the tensile testing of joints. As one would expect, these results show that …
Date: June 1, 2008
Creator: Miller, K. S.; Tolle, C. R.; Clark, D. E.; Nichol, C. I.; McJunkin, T. R. & Smartt, H. B.
Object Type: Article
System: The UNT Digital Library
Investigation of key parameters influencing the efficient photocatalytic oxidation of indoor volatile organic compounds (VOCs) (open access)

Investigation of key parameters influencing the efficient photocatalytic oxidation of indoor volatile organic compounds (VOCs)

Photocatalytic oxidation of indoor VOCs has the potential to eliminate pollutants from indoor environments, thus effectively improving and/or maintaining indoor air quality while reducing ventilation energy costs. Design and operation of UV photocatalytic oxidation (UVPCO) air cleaners requires optimization of various parameters to achieve highest pollutant removal efficiencies while avoiding the formation of harmful secondary byproducts and maximizing catalyst lifetime.
Date: June 1, 2008
Creator: Quici, Natalia; Kibanova, Daria; Vera, Maria Laura; Choi, Hyeok; Dionysiou, Dionysios D.; Litter, Marta I. et al.
Object Type: Article
System: The UNT Digital Library
Investigation of possible csr induced energy spread effects with the A0 photoinjector bunch compressor (open access)

Investigation of possible csr induced energy spread effects with the A0 photoinjector bunch compressor

The bunch compressor of the A0 Photoinjector at Fermilab was removed this past spring to install a transverse to longitudinal emittance exchange experiment. Prior to its removal questions arose about the possibility of observing the effects of Coherent Synchrotron Radiation on the compressed beam. The energy spread of the beam with and without compression was measured to observe any changes. Various beam charges were used to look for square law effects associated with CSR. No direct observation of CSR in the compressor was attempted because the design of the vacuum chamber did not allow it. In this paper we report the results of these experiments and comparison with simulations using ASTRA and CSRTrack. The results are also compared with analytical approximations.
Date: June 1, 2008
Creator: Edwards, H.; Kazakevich, G.; Thurman-Keup, R. M. & Ruan, J.
Object Type: Article
System: The UNT Digital Library
Irradiation Test Plan for the ATR National Scientific User Facility - University of Wisconsin Pilot Project (open access)

Irradiation Test Plan for the ATR National Scientific User Facility - University of Wisconsin Pilot Project

The performance of advanced nuclear systems critically relies on the performance of the materials used for cladding, duct, and other structural components. In many proposed advanced systems, the reactor design pushes the temperature and the total radiation dose higher than typically seen in a light water reactor. Understanding the stability of these materials under radiation is critical. There are a large number of materials or material systems that have been developed for greater high temperature or high dose performance for which little or no information on radiation response exists. The goal of this experiment is to provide initial data on the radiation response of these materials. The objective of the UW experiment is to irradiate materials of interest for advanced reactor applications at a variety of temperatures (nominally 300°C, 400°C, 500°C, and 700°C) and total dose accumulations (nominally 3 dpa and 6 dpa). Insertion of this irradiation test is proposed for September 2008 (ATR Cycle 143A).
Date: June 1, 2008
Creator: MacLean, Heather J.; Sridharan, Kumar & Hyde, Timothy A.
Object Type: Report
System: The UNT Digital Library
Isochronous pion decay channel for enhanced muon capture (open access)

Isochronous pion decay channel for enhanced muon capture

Intense muon beams have many potential applications, including neutrino factories and muon colliders. However, muons are produced in tertiary beams into a diffuse phase space. To make useful beams, the muons must be rapidly cooled before they decay. A promising new concept for the collection and cooling of muon beams is being investigated, namely, the use of a nearly Isochronous Helical Transport Channel (IHTC) to facilitate capture of muons into RF bunches. Such a distribution could be cooled quickly and coalesced into a single bunch to optimize the luminosity of a muon collider. We describe the IHTC and provide simulations demonstrating isochronicity, even in the absence of RF and absorber.
Date: June 1, 2008
Creator: Yoshikawa, C.; Ankenbrandt, C.; Neuffer, D.; Popovic, M.; Yonehara, K.; Derbenev, Y. et al.
Object Type: Article
System: The UNT Digital Library
A kinetic approach to cosmic ray induced streaming instability at supernova shocks (open access)

A kinetic approach to cosmic ray induced streaming instability at supernova shocks

We show here that a purely kinetic approach to the excitation of waves by cosmic rays in the vicinity of a shock front leads to predict the appearance of a non-alfvenic fastly growing mode which has the same dispersion relation as that previously found by Bell (2004) by treating the plasma in the MHD approximation. The kinetic approach allows us to investigate the dependence of the dispersion relation of these waves on the microphysics of the current which compensates the cosmic ray flow. We also show that a resonant and a non-resonant mode may appear at the same time and one of the two may become dominant on the other depending on the conditions in the acceleration region. We discuss the role of the unstable modes for magnetic field amplification and particle acceleration in supernova remnants at different stages of the remnant evolution.
Date: June 1, 2008
Creator: Amato, Elena; Observ., /Arcetri; Blasi, Pasquale & Sasso, /Arcetri Observ. /Fermilab /Gran
Object Type: Article
System: The UNT Digital Library
LARP Long Nb3Sn Quadrupole Design (open access)

LARP Long Nb3Sn Quadrupole Design

A major milestone for the LHC Accelerator Research Program (LARP) is the test, by the end of 2009, of two 4m-long quadrupole magnets (LQ) wound with Nb{sub 3}Sn conductor. The goal of these magnets is to be a proof of principle that Nb{sub 3}Sn is a viable technology for a possible LHC luminosity upgrade. The design of the LQ is based on the design of the LARP Technological Quadrupoles, presently under development at FNAL and LBNL, with 90-mm aperture and gradient higher than 200 T/m. The design of the first LQ model will be completed by the end of 2007 with the selection of a mechanical design. In this paper we present the coil design addressing some fabrication technology issues, the quench protection study, and three designs of the support structure.
Date: June 1, 2008
Creator: Ambrosio, G.; Andreev, N.; Anerella, M.; Barzi, E.; Bossert, R.; Caspi, S. et al.
Object Type: Article
System: The UNT Digital Library
LHC Particle Collimation With Hollow Electron Beams (open access)

LHC Particle Collimation With Hollow Electron Beams

Electron lenses built and installed in the Tevatron have proven themselves as safe and very reliable instruments which can be effectively used in hadron collider operation for a number of applications, including compensation of beam-beam effects [1], a DC beam removal from abort gaps [2], and as a versatile diagnostic tool. In this article, we--following the original proposal [3,4]--consider in more detail a possibility of using electron lenses with hollow electron beam for ion and proton collimation in LHC and the Tevatron.
Date: June 1, 2008
Creator: Shiltsev, V.; Drozhdin, A.; Kamerdzhiev, V.; Kuznetsov, G. & Vorobiev, L.
Object Type: Article
System: The UNT Digital Library
Long Beach Transit: Two-Year Evaluation of Gasoline-Electric Hybrid Transit Buses (open access)

Long Beach Transit: Two-Year Evaluation of Gasoline-Electric Hybrid Transit Buses

This report focuses on a gasoline-electric hybrid transit bus propulsion system. The propulsion system is an alternative to standard diesel buses and allows for reductions in emissions (usually focused on reductions of particulate matter and oxides of nitrogen) and petroleum use. Gasoline propulsion is an alternative to diesel fuel and hybrid propulsion allows for increased fuel economy, which ultimately results in reduced petroleum use.
Date: June 1, 2008
Creator: Lammert, M.
Object Type: Report
System: The UNT Digital Library
Long Plasma Source for Heavy Ion Beam Charge Neutralization (open access)

Long Plasma Source for Heavy Ion Beam Charge Neutralization

Plasmas are a source of unbound electrons for charge neutralizing intense heavy ion beams to focus them to a small spot size and compress their axial length. The plasma source should operate at low neutral pressures and without strong externally-applied fields. To produce long plasma columns, sources based upon ferroelectric ceramics with large dielectric coefficients have been developed. The source utilizes the ferroelectric ceramic BaTiO{sub 3} to form metal plasma. The drift tube inner surface of the Neutralized Drift Compression Experiment (NDCX) is covered with ceramic material. High voltage ({approx} 8 kV) is applied between the drift tube and the front surface of the ceramics. A BaTiO{sub 3} source comprised of five 20-cm-long sources has been tested and characterized, producing relatively uniform plasma in the 5 x 10{sup 10} cm{sup -3} density range. The source was integrated into the NDCX device for charge neutralization and beam compression experiments, and yielded current compression ratios {approx} 120. Present research is developing multi-meter-long and higher density sources to support beam compression experiments for high energy density physics applications.
Date: June 1, 2008
Creator: Efthimion, P. C.; Gilson, E. P.; Grisham, L.; Davidson, R. C.; Logan, B. G.; Seidl, P. A. et al.
Object Type: Article
System: The UNT Digital Library
Lunar Wireless Power Transfer Feasibility Study (open access)

Lunar Wireless Power Transfer Feasibility Study

This study examines the feasibility of a multi-kilowatt wireless radio frequency (RF) power system to transfer power between lunar base facilities. Initial analyses, show that wireless power transfer (WPT) systems can be more efficient and less expensive than traditional wired approaches for certain lunar and terrestrial applications. The study includes evaluations of the fundamental limitations of lunar WPT systems, the interrelationships of possible operational parameters, and a baseline design approach for a notionial system that could be used in the near future to power remote facilities at a lunar base. Our notional system includes state-of-the-art photovoltaics (PVs), high-efficiency microwave transmitters, low-mass large-aperture high-power transmit antennas, high-efficiency large-area rectenna receiving arrays, and reconfigurable DC combining circuitry.
Date: June 1, 2008
Creator: Sheldon Freid, et al.
Object Type: Report
System: The UNT Digital Library