Simulation of Dimensional Changes and Hot Tears During Solidification of Steel Castings (open access)

Simulation of Dimensional Changes and Hot Tears During Solidification of Steel Castings

During solidification, contractions or distortions of the steel, known as “dimensional changes,” can cause the final product to vary significantly from the original pattern. Cracks in the casting that form during the late stages of solidification, called “hot tears,” occur when contractions can no longer be accommodated by residual liquid metal flow or solid metal displacement. Dimensional changes and hot tears are major problems in the steel casting industry. These occurrences are difficult to anticipate and correct using traditional foundry engineering methods. While dimensional changes are accommodated using pattern allowances, the desired dimensions are often inaccurate. Castings that form hot tears must then be scrapped or weld repaired, expending unnecessary energy. Correcting either of these problems requires a tedious trial-and-error process that may not necessarily yield accurate results. A model that predicts hot tears and dimensional changes during steel casting solidification has been successfully developed and implemented in commercial casting and stress analysis software. This model is based on a visco-plastic constitutive model with damage, where the damage begins to form when liquid feed metal is cut off to a solidifying region. The hot tear prediction is a locater for hot tear initiation sites, and not a full tear prediction: …
Date: July 22, 2011
Creator: Beckermann, Christoph & Carlson, Kent
Object Type: Report
System: The UNT Digital Library
Simulation of Distortion and Residual Stress Development During Heat Treatment of Steel Castings (open access)

Simulation of Distortion and Residual Stress Development During Heat Treatment of Steel Castings

Heat treatment and associated processing, such as quenching, are critical during high strength steel casting production. These processes must be managed closely to prevent thermal and residual stresses that may result in distortion, cracking (particularly after machining), re-work, and weld repair. The risk of casting distortion limits aggressive quenching that can be beneficial to the process and yield an improved outcome. As a result of these distortions, adjustments must be made to the casting or pattern design, or tie bars must be added. Straightening castings after heat treatments can be both time-consuming and expensive. Residual stresses may reduce a casting’s overall service performance, possibly resulting in catastrophic failure. Stress relieving may help, but expends additional energy in the process. Casting software is very limited in predicting distortions during heat treatment, so corrective measures most often involve a tedious trial-and-error procedure. An extensive review of existing heat treatment residual stress and distortion modeling revealed that it is vital to predict the phase transformations and microstructure of the steel along with the thermal stress development during heat treatment. After reviewing the state-of-the-art in heat treatment residual stress and distortion modeling, an existing commercial code was selected because of its advanced capabilities in …
Date: July 22, 2011
Creator: Beckermann, Christoph & Carlson, Kent
Object Type: Report
System: The UNT Digital Library
Time Lens Based Single-Shot Ultrafast Waveform Recording: From High Repetition Rate to High Dynamic Range (open access)

Time Lens Based Single-Shot Ultrafast Waveform Recording: From High Repetition Rate to High Dynamic Range

None
Date: July 22, 2011
Creator: Bennett, C. V.; Hernandez, V. J.; Moran, B. D.; Lowry, M. E.; Vernon, S. P.; Steele, P. T. et al.
Object Type: Article
System: The UNT Digital Library
Heuristic-based techniques for mapping irregular communication graphs to mesh topologies (open access)

Heuristic-based techniques for mapping irregular communication graphs to mesh topologies

None
Date: July 22, 2011
Creator: Bhatele, A & Kale, L V
Object Type: Article
System: The UNT Digital Library
Applicability of Transactional Memory to Modern Codes (open access)

Applicability of Transactional Memory to Modern Codes

None
Date: July 22, 2010
Creator: Bihari, B L
Object Type: Article
System: The UNT Digital Library
Experimental And Theoretical High Energy Physics Research At UCLA (open access)

Experimental And Theoretical High Energy Physics Research At UCLA

This is the final report of the UCLA High Energy Physics DOE Grant No. DE-FG02- 91ER40662. This report covers the last grant project period, namely the three years beginning January 15, 2010, plus extensions through April 30, 2013. The report describes the broad range of our experimental research spanning direct dark matter detection searches using both liquid xenon (XENON) and liquid argon (DARKSIDE); present (ICARUS) and R&D for future (LBNE) neutrino physics; ultra-high-energy neutrino and cosmic ray detection (ANITA); and the highest-energy accelerator-based physics with the CMS experiment and CERN’s Large Hadron Collider. For our theory group, the report describes frontier activities including particle astrophysics and cosmology; neutrino physics; LHC interaction cross section calculations now feasible due to breakthroughs in theoretical techniques; and advances in the formal theory of supergravity.
Date: July 22, 2013
Creator: Cousins, Robert D.
Object Type: Report
System: The UNT Digital Library
Global and Local Mechanical and Fabric Measurements of Sand Using DEM (open access)

Global and Local Mechanical and Fabric Measurements of Sand Using DEM

None
Date: July 22, 2011
Creator: Fu, P & Dafalias, Y F
Object Type: Article
System: The UNT Digital Library
Final Report for Enhancing the MPI Programming Model for PetaScale Systems (open access)

Final Report for Enhancing the MPI Programming Model for PetaScale Systems

This project performed research into enhancing the MPI programming model in two ways: developing improved algorithms and implementation strategies, tested and realized in the MPICH implementation, and exploring extensions to the MPI standard to better support PetaScale and ExaScale systems.
Date: July 22, 2013
Creator: Gropp, William Douglas
Object Type: Report
System: The UNT Digital Library
RECENT ADVANCES IN THE DEVELOPMENT OF THE HYBRID SULFUR PROCESS FOR HYDROGEN PRODUCTION (open access)

RECENT ADVANCES IN THE DEVELOPMENT OF THE HYBRID SULFUR PROCESS FOR HYDROGEN PRODUCTION

Thermochemical processes are being developed to provide global-scale quantities of hydrogen. A variant on sulfur-based thermochemical cycles is the Hybrid Sulfur (HyS) Process, which uses a sulfur dioxide depolarized electrolyzer (SDE) to produce the hydrogen. In the HyS Process, sulfur dioxide is oxidized in the presence of water at the electrolyzer anode to produce sulfuric acid and protons. The protons are transported through a cation-exchange membrane electrolyte to the cathode and are reduced to form hydrogen. In the second stage of the process, the sulfuric acid by-product from the electrolyzer is thermally decomposed at high temperature to produce sulfur dioxide and oxygen. The two gases are separated and the sulfur dioxide recycled to the electrolyzer for oxidation. The Savannah River National Laboratory (SRNL) has been exploring a fuel-cell design concept for the SDE using an anolyte feed comprised of concentrated sulfuric acid saturated with sulfur dioxide. The advantages of this design concept include high electrochemical efficiency and small footprint compared to a parallel-plate electrolyzer design. This paper will provide a summary of recent advances in the development of the SDE for the HyS process.
Date: July 22, 2010
Creator: Hobbs, D.
Object Type: Book
System: The UNT Digital Library
LULESH 2.0 Updates and Changes (open access)

LULESH 2.0 Updates and Changes

None
Date: July 22, 2013
Creator: Karlin, I; Keasler, J & Neely, J R
Object Type: Report
System: The UNT Digital Library
FLUX MEASUREMENTS FROM A TALL TOWER IN A COMPLEX LANDSCAPE (open access)

FLUX MEASUREMENTS FROM A TALL TOWER IN A COMPLEX LANDSCAPE

The accuracy and representativeness of flux measurements from a tall tower in a complex landscape was assessed by examining the vertical and sector variability of the ratio of wind speed to momentum flux and the ratio of vertical advective to eddy flux of heat. The 30-60 m ratios were consistent with theoretical predictions which indicate well mixed flux footprints. Some variation with sector was observed that were consistent with upstream roughness. Vertical advection was negligible compared with vertical flux except for a few sectors at night. This implies minor influence from internal boundary layers. Flux accuracy is a function of sector and stability but 30-60 m fluxes were found to be generally representative of the surrounding landscape. This paper will study flux data from a 300 m tower, with 4 levels of instruments, in a complex landscape. The surrounding landscape will be characterized in terms of the variation in the ratio of mean wind speed to momentum flux as a function of height and wind direction. The importance of local advection will be assessed by comparing vertical advection with eddy fluxes for momentum and heat.
Date: July 22, 2010
Creator: Kurzeja, R.; Weber, A.; Chiswell, S. & Parker, M.
Object Type: Article
System: The UNT Digital Library
DISSOLUTION OF IRRADIATED MURR FUEL ASSEMBLIES EFFECT OF INCREASED PURGE RATE AND CATALYST CONCENTRATION ON THE BATCH SIZE (open access)

DISSOLUTION OF IRRADIATED MURR FUEL ASSEMBLIES EFFECT OF INCREASED PURGE RATE AND CATALYST CONCENTRATION ON THE BATCH SIZE

Flowsheets for the dissolution of aluminum-clad spent nuclear fuel have been proposed using 0.002 M mercuric nitrate catalyst in 5 to 6 M nitric acid. Previous calculations for flammable gas control during the dissolution of spent nuclear fuel have been extended to cover a range of dissolver purge rates from 40 to 55 scfm. A range of dissolver solution volumes from 12000 to 15000 liters were considered for the large H-Canyon dissolver (6.4D). Depending on the purge rate, anywhere from four to six bundles of MURR fuel can be initially charged to the dissolver (6.4D). For successive charges where the dissolver solution already contains 0.002 M mercury catalyst and the dissolved aluminum from five bundles of MURR fuel, five to nine bundles of additional fuel can be charged depending on the purge rate and the dissolver solution volume. Similar calculations have been performed for the small H-Canyon dissolver (6.1D) for solution volumes that ranged from 6000 to 7500 liters and purge rates from 40 to 55 scfm. The limitations on the initial charge are four to six bundles depending on the purge rate. The aluminum from four bundles of fuel in an initial charge will allow nine to ten bundles …
Date: July 22, 2010
Creator: Kyser, E.
Object Type: Report
System: The UNT Digital Library
MIX and Instability Growth from Oblique Shock (open access)

MIX and Instability Growth from Oblique Shock

We have studied the formation and evolution of shock-induced mix resulting from interface features in a divergent cylindrical geometry. In this research a cylindrical core of high-explosive was detonated to create an oblique shock wave and accelerate the interface. The interfaces studied were between the high-explosive/aluminum, aluminum/plastic, and finally plastic/air. Pre-emplaced surface features added to the aluminum were used to modify this interface. Time sequence radiographic imaging quantified the resulting instability formation from the growth phase to over 60 {micro}s post-detonation. Thus allowing the study of the onset of mix and evolution to turbulence. The plastic used here was porous polyethylene. Radiographic image data are compared with numerical simulations of the experiments.
Date: July 22, 2011
Creator: Molitoris, J D; Batteux, J D; Garza, R G; Tringe, J W; Souers, P C & Forbes, J W
Object Type: Article
System: The UNT Digital Library
Human Factors Engineering Program Review Model (NUREG-0711)Revision 3: Update Methodology and Key Revisions (open access)

Human Factors Engineering Program Review Model (NUREG-0711)Revision 3: Update Methodology and Key Revisions

The U.S. Nuclear Regulatory Commission (NRC) reviews the human factors engineering (HFE) programs of applicants for nuclear power plant construction permits, operating licenses, standard design certifications, and combined operating licenses. The purpose of these safety reviews is to help ensure that personnel performance and reliability are appropriately supported. Detailed design review procedures and guidance for the evaluations is provided in three key documents: the Standard Review Plan (NUREG-0800), the HFE Program Review Model (NUREG-0711), and the Human-System Interface Design Review Guidelines (NUREG-0700). These documents were last revised in 2007, 2004 and 2002, respectively. The NRC is committed to the periodic update and improvement of the guidance to ensure that it remains a state-of-the-art design evaluation tool. To this end, the NRC is updating its guidance to stay current with recent research on human performance, advances in HFE methods and tools, and new technology being employed in plant and control room design. NUREG-0711 is the first document to be addressed. We present the methodology used to update NUREG-0711 and summarize the main changes made. Finally, we discuss the current status of the update program and the future plans.
Date: July 22, 2012
Creator: Ohara J. M.; Higgins, J. & Fleger, S.
Object Type: Article
System: The UNT Digital Library
Comparative assessment of status and opportunities for carbon Dioxide Capture and storage and Radioactive Waste Disposal In North America (open access)

Comparative assessment of status and opportunities for carbon Dioxide Capture and storage and Radioactive Waste Disposal In North America

Aside from the target storage regions being underground, geologic carbon sequestration (GCS) and radioactive waste disposal (RWD) share little in common in North America. The large volume of carbon dioxide (CO{sub 2}) needed to be sequestered along with its relatively benign health effects present a sharp contrast to the limited volumes and hazardous nature of high-level radioactive waste (RW). There is well-documented capacity in North America for 100 years or more of sequestration of CO{sub 2} from coal-fired power plants. Aside from economics, the challenges of GCS include lack of fully established legal and regulatory framework for ownership of injected CO{sub 2}, the need for an expanded pipeline infrastructure, and public acceptance of the technology. As for RW, the USA had proposed the unsaturated tuffs of Yucca Mountain, Nevada, as the region's first high-level RWD site before removing it from consideration in early 2009. The Canadian RW program is currently evolving with options that range from geologic disposal to both decentralized and centralized permanent storage in surface facilities. Both the USA and Canada have established legal and regulatory frameworks for RWD. The most challenging technical issue for RWD is the need to predict repository performance on extremely long time scales …
Date: July 22, 2011
Creator: Oldenburg, C. & Birkholzer, J.T.
Object Type: Book
System: The UNT Digital Library
Demonstration of a Plasma Mirror Based on a Laminar Flow Water Film (open access)

Demonstration of a Plasma Mirror Based on a Laminar Flow Water Film

A plasma mirror based on a laminar water film with low flow speed 0.5-2 cm/s has been developed and characterized, for use as an ultrahigh intensity optical reflector. The use of flowing water as atarget surface automatically results in each laser pulse seeing a new interaction surface and avoids the need for mechanical scanning of the target surface. In addition, the breakdown of water does notproduce contaminating debris that can be deleterious to vacuum chamber conditions and optics, such as is the case when using conventional solid targets. The mirror exhibits 70percent reflectivity, whilemaintaining high-quality of the reflected spot.
Date: July 22, 2011
Creator: Panasenko, Dmitriy; Shu, Anthony J.; Gonsalves, Anthony; Nakamura, Kei; Matlis, Nicholas H.; Toth, Csaba et al.
Object Type: Article
System: The UNT Digital Library
Swift Wind Turbine Testing (open access)

Swift Wind Turbine Testing

Swift wind turbine testing to AWEA small wind turbine test standards.
Date: July 22, 2013
Creator: Peek, Richard T.
Object Type: Report
System: The UNT Digital Library
AN EXPERIMENTAL STUDY OF THE EFFECT OF OPERATOR HANDS ON THE REACTIVITY OF A FAST METAL SYSTEM (open access)

AN EXPERIMENTAL STUDY OF THE EFFECT OF OPERATOR HANDS ON THE REACTIVITY OF A FAST METAL SYSTEM

None
Date: July 22, 2011
Creator: Percher, C & Heinrichs, D
Object Type: Article
System: The UNT Digital Library
OXALATE MASS BALANCE DURING CHEMICAL CLEANING IN TANK 6F (open access)

OXALATE MASS BALANCE DURING CHEMICAL CLEANING IN TANK 6F

The Savannah River Remediation (SRR) is preparing Tank 6F for closure. The first step in preparing the tank for closure is mechanical sludge removal. Following mechanical sludge removal, SRS performed chemical cleaning with oxalic acid to remove the sludge heel. Personnel are currently assessing the effectiveness of the chemical cleaning to determine whether the tank is ready for closure. SRR personnel collected liquid samples during chemical cleaning and submitted them to Savannah River National Laboratory (SRNL) for analysis. Following chemical cleaning, they collected a solid sample (also known as 'process sample') and submitted it to SRNL for analysis. The authors analyzed these samples to assess the effectiveness of the chemical cleaning process. Analysis of the anions showed the measured oxalate removed from Tank 6F to be approximately 50% of the amount added in the oxalic acid. To close the oxalate mass balance, the author collected solid samples, leached them with nitric acid, and measured the concentration of cations and anions in the leachate. Some conclusions from this work are: (1) Approximately 65% of the oxalate added as oxalic acid was removed with the decanted liquid. (2) Approximately 1% of the oxalate (added to the tank as oxalic acid) formed precipitates …
Date: July 22, 2011
Creator: Poirier, M. & Fink, S.
Object Type: Report
System: The UNT Digital Library
Deep Eutectic Salt Formulations Suitable as Advanced Heat Transfer Fluids (open access)

Deep Eutectic Salt Formulations Suitable as Advanced Heat Transfer Fluids

Concentrating solar power (CSP) facilities are comprised of many miles of fluid-filled pipes arranged in large grids with reflective mirrors used to capture radiation from the sun. Solar radiation heats the fluid which is used to produce steam necessary to power large electricity generation turbines. Currently, organic, oil-based fluid in the pipes has a maximum temperature threshold of 400 °C, allowing for the production of electricity at approximately 15 cents per kilowatt hour. The DOE hopes to foster the development of an advanced heat transfer fluid that can operate within higher temperature ranges. The new heat transfer fluid, when used with other advanced technologies, could significantly decrease solar electricity cost. Lower costs would make solar thermal electricity competitive with gas and coal and would offer a clean, renewable source of energy. Molten salts exhibit many desirable heat transfer qualities within the range of the project objectives. Halotechnics developed advanced heat transfer fluids (HTFs) for application in solar thermal power generation. This project focused on complex mixtures of inorganic salts that exhibited a high thermal stability, a low melting point, and other favorable characteristics. A high-throughput combinatorial research and development program was conducted in order to achieve the project objective. Over …
Date: July 22, 2013
Creator: Raade, Justin; Roark, Thomas; Vaughn, John & Bradshaw, Robert
Object Type: Report
System: The UNT Digital Library
Final Technical Report for Collaborative Research: Regional climate-change projections through next-generation empirical and dynamical models, DE-FG02-07ER64429 (open access)

Final Technical Report for Collaborative Research: Regional climate-change projections through next-generation empirical and dynamical models, DE-FG02-07ER64429

This is the final report for a DOE-funded research project describing the outcome of research on non-homogeneous hidden Markov models (NHMMs) and coupled ocean-atmosphere (O-A) intermediate-complexity models (ICMs) to identify the potentially predictable modes of climate variability, and to investigate their impacts on the regional-scale. The main results consist of extensive development of the hidden Markov models for rainfall simulation and downscaling specifically within the non-stationary climate change context together with the development of parallelized software; application of NHMMs to downscaling of rainfall projections over India; identification and analysis of decadal climate signals in data and models; and, studies of climate variability in terms of the dynamics of atmospheric flow regimes.
Date: July 22, 2013
Creator: Smyth, Padhraic
Object Type: Report
System: The UNT Digital Library
A HIGH REPETITION PLASMA MIRROR FOR STAGED ELECTRON ACCELERATION (open access)

A HIGH REPETITION PLASMA MIRROR FOR STAGED ELECTRON ACCELERATION

In order to build a compact, staged laser plasma accelerator the in-coupling of the laser beam to the different stages represents one of the key issues. To limit the spatial foot print and thus to realize a high overall acceleration gradient, a concept has to be found which realizes this in-coupling within a few centimeters. We present experiments on a tape-drive based plasma mirror which could be used to reflect the focused laser beam into the acceleration stage.
Date: July 22, 2011
Creator: Sokollik, Thomas; Shiraishi, Satomi; Osterhoff, Jens; Evans, Eugene; Gonsalves, Anthony; Nakamura, Kei et al.
Object Type: Article
System: The UNT Digital Library
Tape-Drive Based Plasma Mirror (open access)

Tape-Drive Based Plasma Mirror

We present experimental results on a tape-drive based plasma mirror which could be used for a compact coupling of a laser beam into a staged laser driven electron accelerator. This novel kind of plasma mirror is suitable for high repetition rates and for high number of laser shots. In order to design a compact, staged laser plasma based accelerator or collider [1], the coupling of the laser beam into the different stages represents one of the key issues. To limit the spatial foot print and thus to realize a high overall acceleration gradient, a concept has to be found which realizes this in-coupling within a few centimeters (cf. Fig 1). The fluence of the laser pulse several centimeters away from the acceleration stage (focus) exceeds the damage threshold of any available mirror coating. Therefore, in reference [2] a plasma mirror was suggested for this purpose. We present experiments on a tape-drive based plasma mirror which could be used to reflect the focused laser beam into the acceleration stage. Plasma mirrors composed of antireflection coated glass substrates are usually used to improve the temporal laser contrast of laser pulses by several orders of magnitudes [3,4]. This is particularly important for laser …
Date: July 22, 2011
Creator: Sokollik, Thomas; Shiraishi, Satomi; Osterhoff, Jens; Evans, Eugene; Gonsalves, Anthony; Nakamura, Kei et al.
Object Type: Article
System: The UNT Digital Library
A molecularly defined duplication set for the X chromosome of Drosophila melanogaster (open access)

A molecularly defined duplication set for the X chromosome of Drosophila melanogaster

We describe a molecularly defined duplication kit for the X chromosome of Drosophila melanogaster. A set of 408 overlapping P[acman] BAC clones was used to create small duplications (average length 88 kb) covering the 22-Mb sequenced portion of the chromosome. The BAC clones were inserted into an attP docking site on chromosome 3L using C31 integrase, allowing direct comparison of different transgenes. The insertions complement 92% of the essential and viable mutations and deletions tested, demonstrating that almost all Drosophila genes are compact and that the current annotations of the genome are reasonably accurate. Moreover, almost all genes are tolerated at twice the normal dosage. Finally, we more precisely mapped two regions at which duplications cause diplo-lethality in males. This collection comprises the first molecularly defined duplication set to cover a whole chromosome in a multicellular organism. The work presented removes a long-standing barrier to genetic analysis of the Drosophila X chromosome, will greatly facilitate functional assays of X-linked genes in vivo, and provides a model for functional analyses of entire chromosomes in other species.
Date: July 22, 2010
Creator: Venken, Koen J. T.; Popodi, Ellen; Holtzman, Stacy L.; Schulze, Karen L.; Park, Soo; Carlson, Joseph W. et al.
Object Type: Article
System: The UNT Digital Library