LaserFest Celebration (open access)

LaserFest Celebration

LaserFest was the yearlong celebration, during 2010, of the 50th anniversary of the demonstration of the first working laser. The goals of LaserFest were: to highlight the impact of the laser in its manifold commercial, industrial and medical applications, and as a tool for ongoing scientific research; to use the laser as one example that illustrates, more generally, the route from scientific innovation to technological application; to use the laser as a vehicle for outreach, to stimulate interest among students and the public in aspects of physical science; to recognize and honor the pioneers who developed the laser and its many applications; to increase awareness among policymakers of the importance of R&D funding as evidenced by such technology as lasers. One way in which LaserFest sought to meet its goals was to encourage relevant activities at a local level all across the country -- and also abroad -- that would be identified with the larger purposes of the celebration and would carry the LaserFest name. Organizers were encouraged to record and advertise these events through a continually updated web-based calendar. Four projects were explicitly detailed in the proposals: 1) LaserFest on the Road; 2) Videos; 3) Educational material; and 4) …
Date: August 25, 2011
Creator: Chodos, Alan & Rogan, Elizabeth A.
Object Type: Text
System: The UNT Digital Library
Halo Formation And Emittance Growth of Positron Beams in Plasmas (open access)

Halo Formation And Emittance Growth of Positron Beams in Plasmas

An ultrarelativistic 28.5 GeV, 700-{micro}m-long positron bunch is focused near the entrance of a 1.4-m-long plasma with a density n{sub e} between {approx}10{sup 13} and {approx}5 x 10{sup 14} cm{sup -3}. Partial neutralization of the bunch space charge by the mobile plasma electrons results in a reduction in transverse size by a factor of {approx}3 in the high emittance plane of the beam {approx}1 m downstream from the plasma exit. As n{sub e} increases, the formation of a beam halo containing {approx}40% of the total charge is observed, indicating that the plasma focusing force is nonlinear. Numerical simulations confirm these observations. The bunch with an incoming transverse size ratio of {approx}3 and emittance ratio of {approx}5 suffers emittance growth and exits the plasma with approximately equal sizes and emittances.
Date: October 25, 2011
Creator: Muggli, P.; Blue, B. E.; Clayton, C. E.; Decker, F. J.; Hogan, M. J.; Huang, C. et al.
Object Type: Article
System: The UNT Digital Library
Performance Validation and Scaling of a Capillary Membrane Solid-Liquid Separation System (open access)

Performance Validation and Scaling of a Capillary Membrane Solid-Liquid Separation System

Algaeventure Systems (AVS) has previously demonstrated an innovative technology for dewatering algae slurries that dramatically reduces energy consumption by utilizing surface physics and capillary action. Funded by a $6M ARPA-E award, transforming the original Harvesting, Dewatering and Drying (HDD) prototype machine into a commercially viable technology has required significant attention to material performance, integration of sensors and control systems, and especially addressing scaling issues that would allow processing extreme volumes of algal cultivation media/slurry. Decoupling the harvesting, dewatering and drying processes, and addressing the rate limiting steps for each of the individual steps has allowed for the development individual technologies that may be tailored to the specific needs of various cultivation systems. The primary performance metric used by AVS to assess the economic viability of its Solid-Liquid Separation (SLS) dewatering technology is algae mass production rate as a function of power consumption (cost), cake solids/moisture content, and solids capture efficiency. An associated secondary performance metric is algae mass loading rate which is dependent on hydraulic loading rate, area-specific hydraulic processing capacity (gpm/in2), filter:capillary belt contact area, and influent algae concentration. The system is capable of dewatering 4 g/L (0.4%) algae streams to solids concentrations up to 30% with capture efficiencies …
Date: October 25, 2011
Creator: Rogers, S.; Cook, J.; Juratovac, J.; Goodwillie, J.; Burke, T. & Stuart, B., ed.
Object Type: Article
System: The UNT Digital Library
MWRRET Value-Added Product: The Retrieval of Liquid Water Path and Precipitable Water Vapor from Microwave Radiometer (MWR) Data Sets (Revision 2) (open access)

MWRRET Value-Added Product: The Retrieval of Liquid Water Path and Precipitable Water Vapor from Microwave Radiometer (MWR) Data Sets (Revision 2)

This report provides a short description of the Atmospheric Radiation Measurement (ARM) Climate Research Facility microwave radiometer (MWR) Retrieval (MWRRET) value-added product (VAP) algorithm. This algorithm utilizes a complementary physical retrieval method and applies brightness temperature offsets to reduce spurious liquid water path (LWP) bias in clear skies resulting in significantly improved precipitable water vapor (PWV) and LWP retrievals. We present a general overview of the technique, input parameters, output products, and describe data quality checks. A more complete discussion of the theory and results is given in Turner et al. (2007b).
Date: July 25, 2011
Creator: Gaustad, K. L.; Turner, D. D. & McFarlane, S. A.
Object Type: Report
System: The UNT Digital Library
IMPROVEMENT OF CdMnTe DETECTOR PERFORMANCE BY MnTe PURIFICATION (open access)

IMPROVEMENT OF CdMnTe DETECTOR PERFORMANCE BY MnTe PURIFICATION

Residual impurities in manganese (Mn) are a big obstacle to obtaining high-performance CdMnTe (CMT) X-ray and gamma-ray detectors. Generally, the zone-refining method is an effective way to improve the material's purity. In this work, we purified the MnTe compounds combining the zone-refining method with molten Te, which has a very high solubility for most impurities. We confirmed the improved purity of the material by glow-discharge mass spectrometry (GDMS). We also found that CMT crystals from a multiply-refined MnTe source, grown by the vertical Bridgman method, yielded better performing detectors.
Date: April 25, 2011
Creator: Kim, K. H.; Bolotnikov, A. E.; Camarda, G. S.; Tappero, R.; Hossain, A.; Cui, Y. et al.
Object Type: Article
System: The UNT Digital Library
Nonlinear pulse propagation and phase velocity of laser-driven plasma waves (open access)

Nonlinear pulse propagation and phase velocity of laser-driven plasma waves

Laser evolution and plasma wave excitation by a relativistically-intense short-pulse laser in underdense plasma are investigated in the broad pulse limit, including the effects of pulse steepening, frequency red-shifting, and energy depletion. The nonlinear plasma wave phase velocity is shown to be significantly lower than the laser group velocity and further decreases as the pulse propagates owing to laser evolution. This lowers the thresholds for trapping and wavebreaking, and reduces the energy gain and efficiency of laser-plasma accelerators that use a uniform plasma profile.
Date: March 25, 2011
Creator: Schroeder, Carl B.; Benedetti, Carlo; Esarey, Eric & Leemans, Wim
Object Type: Article
System: The UNT Digital Library
MPO B593110 - Final Report (open access)

MPO B593110 - Final Report

National Security Technologies, LLC (NSTec) shall provide one (1) Mechanical Engineer to support the Linear Collider Subsystem Development Program at Lawrence Livermore National Security, LLC (LLNS). The NSTec Mechanical Engineer's efforts will include engineering, design, and drawing support for the Vacuum Seal Test. NSTec will also provide a final report of the setup and input to LLNL's project management on project status. The NSTec Mechanical Engineer's efforts will also include engineering, design, and drawing support to the conceptual design for manufacturing of the Flux Concentrator Magnet. NSTec will also contribute to LLNS's final report on the Flux Concentrator Magnet. The deliverables are drawings, sketches, engineering documents, and final reports delivered to the LLNS Technical Representative.
Date: July 25, 2011
Creator: Brooksby, C
Object Type: Report
System: The UNT Digital Library
Costilla County Biodiesel Pilot Project (open access)

Costilla County Biodiesel Pilot Project

The Costilla County Biodiesel Pilot Project has demonstrated the compatibility of biodiesel technology and economics on a local scale. The project has been committed to making homegrown biodiesel a viable form of community economic development. The project has benefited by reducing risks by building the facility gradually and avoiding large initial outlays of money for facilities and technologies. A primary advantage of this type of community-scale biodiesel production is that it allows for a relatively independent, local solution to fuel production. Successfully using locally sourced feedstocks and putting the fuel into local use emphasizes the feasibility of different business models under the biodiesel tent and that there is more than just a one size fits all template for successful biodiesel production.
Date: August 25, 2011
Creator: Doon, Ben & Quintana, Dan
Object Type: Report
System: The UNT Digital Library
Real-time Studies of Shocked Polycrystalline Materials with Single-Pulse X-ray Diffraction (open access)

Real-time Studies of Shocked Polycrystalline Materials with Single-Pulse X-ray Diffraction

Characteristic K-α x-rays used for single-pulse XRD are conventionally produced by a 37-stage high-voltage Marx pulse generator coupled to a vacuum needle-and-washer x-ray diode via coaxial transmission line. A large field-of-view x-ray image plate detection system typically enables observation of several Debye-Scherrer rings. Recently, we have developed a fiber-optic reducer, coupled to a CCD camera, to obtain low-noise, large field-of-view images. The direct beam spot is produced by bremsstrahlung radiation attenuated by a twomillimeter tungsten beam stop. Determination of the direct beam position is necessary to perform the ring integration.
Date: May 25, 2011
Creator: Morgan, Dane V.
Object Type: Article
System: The UNT Digital Library
Electronic Structure of CeFeAsO1-xFx (x=0, 0.11/x=0.12) compounds (open access)

Electronic Structure of CeFeAsO1-xFx (x=0, 0.11/x=0.12) compounds

We report an extensive study on the intrinsic bulk electronic structure of the high-temperature superconductor CeFeAsO{sub 0.89}F{sub 0.11} and its parent compound CeFeAsO by soft and hard x-ray photoemission, x-ray absorption and soft-x-ray emission spectroscopies. The complementary surface/bulk probing depth, and the elemental and chemical sensitivity of these techniques allows resolving the intrinsic electronic structure of each element and correlating it with the local structure, which has been probed by extended-x-ray absorption fine structure spectroscopy. The measurements indicate a predominant 4f{sup 1} (i.e. Ce{sup 3+}) initial state configuration for Cerium and an effective valence-band-to-4f charge-transfer screening of the core hole. The spectra also reveal the presence of a small Ce f{sup 0} initial state configuration, which we assign to the occurrence of an intermediate valence state. The data reveal a reasonably good agreement with the partial density of states as obtained in standard density functional calculations over a large energy range. Implications for the electronic structure of these materials are discussed.
Date: January 25, 2011
Creator: Bondino, F.; Magnano, E.; Booth, C. H.; Offi, F.; Panaccione, G.; Malvestuto, M. et al.
Object Type: Article
System: The UNT Digital Library
Novel deflecting cavity design for eRHIC (open access)

Novel deflecting cavity design for eRHIC

To prevent significant loss of the luminosity due to large crossing angle in the future ERL based Electron Ion Collider at BNL (eRHIC), there is a demand for crab cavities. In this article, we will present a novel design of the deflecting/crabbing 181 MHz superconducting RF cavity that will fulfil the requirements of eRHIC. The quarter-wave resonator structure of the new cavity possesses many advantages, such as compact size, high R{sub t}/Q, the absence of the same order mode and lower order mode, and easy higher order mode damping. We will present the properties and characteristics of the new cavity in detail. As the accelerator systems grow in complexity, developing compact and efficient deflecting cavities is of great interest. Such cavities will benefit situations where the beam line space is limited. The future linac-ring type electron-ion collider requires implementation of a crab-crossing scheme for both beams at the interaction region. The ion beam has a long bunches and high rigidity. Therefore, it requires a low frequency, large kicking angle deflector. The frequency of the deflecting mode for the current collider design is 181 MHz, and the deflecting angle is {approx}5 mrad for each beam. At such low frequency, the previous …
Date: July 25, 2011
Creator: Wu, Q.; Belomestnykh, S. & Ben-Zvi, Ilan
Object Type: Article
System: The UNT Digital Library
RESULTS FOR THE SECOND QUARTER 2011 TANK 50 WAC SLURRY SAMPLE: CHEMICAL AND RADIONUCLIDE CONTAMINANT RESULTS (open access)

RESULTS FOR THE SECOND QUARTER 2011 TANK 50 WAC SLURRY SAMPLE: CHEMICAL AND RADIONUCLIDE CONTAMINANT RESULTS

The Saltstone Facility is designed and permitted to immobilize and dispose of low-level radioactive and hazardous liquid waste (salt solution) remaining from the processing of radioactive material at the Savannah River Site. Low-level waste (LLW) streams from the Effluent Treatment Project (ETP), H-Canyon, the DDA (Deliquification, Dissolution, and Adjustment) process, and the decontaminated salt solution product from the Actinide Removal Process/Modular Caustic Side Solvent Extraction (CSSX) Unit (ARP/MCU) process are stored in Tank 50 until the LLW can be transferred to the Saltstone Facility for treatment and disposal. The LLW must meet the specified waste acceptance criteria (WAC) before it is processed into saltstone. The specific chemical and radionuclide contaminants and their respective WAC limits are listed in the current Saltstone WAC. Waste Solidification Engineering (WSE) requested that Savannah River National Laboratory (SRNL) perform quarterly analysis on saltstone samples. The concentrations of chemical and radionuclide contaminants are measured to ensure the saltstone produced during each quarter is in compliance with the current WAC. This report documents the concentrations of chemical and radionuclide contaminants for the 2011 Second Quarter samples collected from Tank 50 on April 4, 2011 and discusses those results in further detail than the previously issued results report. …
Date: August 25, 2011
Creator: Eibling, R.
Object Type: Report
System: The UNT Digital Library
Annual Report of Monitoring at Barnes, Kansas, in 2010 (open access)

Annual Report of Monitoring at Barnes, Kansas, in 2010

The Commodity Credit Corporation of the U.S. Department of Agriculture (CCC/USDA) operated a grain storage facility at Barnes, Kansas, in 1949-1974. Carbon tetrachloride contamination was initially detected in 1986 in the town's public water supply wells. In 2006-2007, the CCC/USDA conducted a comprehensive targeted investigation at and near its former property in Barnes to characterize this contamination. Those results were reported previously (Argonne 2008a). The results of that investigation indicated that carbon tetrachloride contamination is present in groundwater at low to moderate levels in the vicinity of the former CCC/USDA grain storage facility. Information obtained during the 2006-2007 investigation also indicated that at least one other potential source might have contributed to the groundwater contaminant plume (Argonne 2008a). The former agriculture building owned by the local school district, located immediately east of well PWS3, is also a potential source of the contamination. In November 2007, the CCC/USDA began periodic groundwater monitoring at Barnes. The monitoring is being conducted on behalf of the CCC/USDA by Argonne National Laboratory, under the direction of the Kansas Department of Health and Environment (KDHE). The objective is to monitor the carbon tetrachloride contamination identified in the groundwater at Barnes. Through 2010, sampling was conducted in …
Date: May 25, 2011
Creator: LaFreniere, L. M.
Object Type: Report
System: The UNT Digital Library
PILOT SCALE TESTING OF MONOSODIUM TITANATE MIXING FOR THE SRS SMALL COLUMN ION EXCHANGE PROCESS - 11224 (open access)

PILOT SCALE TESTING OF MONOSODIUM TITANATE MIXING FOR THE SRS SMALL COLUMN ION EXCHANGE PROCESS - 11224

The Small Column Ion Exchange (SCIX) process is being developed to remove cesium, strontium, and select actinides from Savannah River Site (SRS) Liquid Waste using an existing waste tank (i.e., Tank 41H) to house the process. Savannah River National Laboratory (SRNL) is conducting pilot-scale mixing tests to determine the pump requirements for suspending monosodium titanate (MST), crystalline silicotitanate (CST), and simulated sludge. The purpose of this pilot scale testing is to determine the requirements for the pumps to suspend the MST particles so that they can contact the strontium and actinides in the liquid and be removed from the tank. The pilot-scale tank is a 1/10.85 linear scaled model of SRS Tank 41H. The tank diameter, tank liquid level, pump nozzle diameter, pump elevation, and cooling coil diameter are all 1/10.85 of their dimensions in Tank 41H. The pump locations correspond to the proposed locations in Tank 41H by the SCIX program (Risers B5 and B2 for two pump configurations and Risers B5, B3, and B1 for three pump configurations). The conclusions from this work follow: (i) Neither two standard slurry pumps nor two quad volute slurry pumps will provide sufficient power to initially suspend MST in an SRS waste …
Date: January 25, 2011
Creator: Poirier, M.; Restivo, M.; Williams, M.; Herman, D. & Steeper, T.
Object Type: Article
System: The UNT Digital Library
Case Study of the Failure of two 13.8kV Control & Metering Transformers that caused significant Equipment Damage (open access)

Case Study of the Failure of two 13.8kV Control & Metering Transformers that caused significant Equipment Damage

The degradation and failure of cast-coil epoxy windings within 13.8kV control power transformers and metering potential transformers has been shown to be dangerous to both equipment and personnel, even though best industrial design practices were followed. Accident scenes will be examined for two events at a U.S. Department of Energy laboratory. Failure modes will be explained and current design practices discussed with changes suggested to prevent a recurrence and to minimize future risk. New maintenance philosophies utilizing partial discharge testing of the transformers as a prediction of end-of-life will be examined.
Date: August 25, 2011
Creator: Dreifuerst, G R; Chew, D B; Mangonon, H L & Swyers, P W
Object Type: Article
System: The UNT Digital Library
Design Calculations For NIF Convergent Ablator Experiments (open access)

Design Calculations For NIF Convergent Ablator Experiments

The NIF convergent ablation tuning effort is underway. In the early experiments, we have discovered that the design code simulations over-predict the capsule implosion velocity and shock flash rhor, but under-predict the hohlraum x-ray flux measurements. The apparent inconsistency between the x-ray flux and radiography data implies that there are important unexplained aspects of the hohlraum and/or capsule behavior.
Date: October 25, 2011
Creator: Olson, R E; Hicks, D G; Meezan, N B; Callahan, D A; Landen, O L; Jones, O S et al.
Object Type: Article
System: The UNT Digital Library
Validation of Numerical Two-Fluid and Kinetic Plasma Models (open access)

Validation of Numerical Two-Fluid and Kinetic Plasma Models

This was a four year grant commencing October 1, 2003 and finishing September 30, 2007. The funding was primarily used to support the work of the Principal Investigator, who collaborated with Profs. Scott Parker and John Cary at U. Colorado, and with two students, N. Xiang and J. Cheng also of U. Colorado. The technical accomplishments of this grant can be found in the publications listed in the final Section here. The main accomplishments of the grant work were: (1) Development and implementation of time-implicit two-fluid simulation methods in collaboration with the NIMROD team; and (2) Development and testing of a new time-implicit delta-f, energy-conserving method The basic two-fluid method, with many improvements is used in present NIMROD calculations. The energy-conserving delta-f method is under continuing development under contract between Coronado Consulting, a New Mexico sole proprietorship and the Oak Ridge National Laboratory.
Date: March 25, 2011
Creator: Barnes, Daniel
Object Type: Report
System: The UNT Digital Library
Neutron Compound Refractive Prisms - DOE SBIR Phase II Final Report (open access)

Neutron Compound Refractive Prisms - DOE SBIR Phase II Final Report

The results of the research led to a pulsed electromagnetic periodic magnetic field array (PMF), which coupled with a pair of collimation slits, and a mechanical chopper slit, were able to deflect spin-up neutrons to a band of line-fused neutrons a focal plane heights that correspond to the time-varying magnetic field amplitude. The electromagnetic field PMF produced 5.4 pulses per minute in which each pulse was 50 msec in duration with a full width half maximum (FWHM) of 7.5 msec. The calculated 7.7 mm vertical height of the band of focused spin-up neutrons corresponded closely to the measured 7.5 mm height of the center line of the imaged band of neutrons. The band of deflected spin-up neutrons was 5 mm in vertical width and the bottom of the band was 5 mm above the surface of the PMF pole. The limited exposure time of 3 hours and the smaller 0.78 T magnetic field allowed focused and near focused neutrons of 1.8 àto 2.6 àneutrons, which were in the tails of the McClellan Nuclear Radiation Center Bay 4 Maxwell Boltzmann distribution of neutrons with peak flux at 1.1-1.2 à. The electromagnetic PMF was expected to produces a 2.0 …
Date: June 25, 2011
Creator: Dr. Jay Theodore Cremer, Jr
Object Type: Report
System: The UNT Digital Library
Final Scientific Report (open access)

Final Scientific Report

Hackensack University Medical Center's major initiative to create a cleaner healthier and safer environment for patients, employees and the community served by the medical center is built on its commitment to protect the environment and conserve precious energy resources. Since 2004 the Medical Center launched a long term campaign to temper the negative environmental impact of proposed and existing new construction at the medical center and to improve campus wide overall energy efficiency. The plan was to begin by implementing a number of innovative and eco-friendly enhancements to the Gabrellian Women's and Children's Pavilion, in construction at the time, which would lead to Certification by the US Green Building Councils Leadership & Environmental Design (LEED) program. In addition the medical center would evaluate the feasibility of implementing a photovoltaic system in the new construction (in development and planned) to provide clean pollution free electricity. The steps taken to achieve this included conducting a feasibility study complete with architectural and engineering assessments to determine the potential for implementation of a photovoltaic system on the campus and also to conduct an energy survey that would focus on determining specific opportunities and upgrades that would lead to a healthier energy efficient interior environment …
Date: May 25, 2011
Creator: Lutwick, Suzanne & Cunning, Helen
Object Type: Report
System: The UNT Digital Library
Optimization of Operating Parameters for Minimum Mechanical Specific Energy in Drilling (open access)

Optimization of Operating Parameters for Minimum Mechanical Specific Energy in Drilling

Efficiency in drilling is measured by Mechanical Specific Energy (MSE). MSE is the measure of the amount of energy input required to remove a unit volume of rock, expressed in units of energy input divided by volume removed. It can be expressed mathematically in terms of controllable parameters; Weight on Bit, Torque, Rate of Penetration, and RPM. It is well documented that minimizing MSE by optimizing controllable factors results in maximum Rate of Penetration. Current methods for computing MSE make it possible to minimize MSE in the field only through a trial-and-error process. This work makes it possible to compute the optimum drilling parameters that result in minimum MSE. The parameters that have been traditionally used to compute MSE are interdependent. Mathematical relationships between the parameters were established, and the conventional MSE equation was rewritten in terms of a single parameter, Weight on Bit, establishing a form that can be minimized mathematically. Once the optimum Weight on Bit was determined, the interdependent relationship that Weight on Bit has with Torque and Penetration per Revolution was used to determine optimum values for those parameters for a given drilling situation. The improved method was validated through laboratory experimentation and analysis of published …
Date: May 25, 2011
Creator: Hamrick, Todd
Object Type: Thesis or Dissertation
System: The UNT Digital Library
FINAL REPORT FOR TRITIUM WATER MONITOR (open access)

FINAL REPORT FOR TRITIUM WATER MONITOR

The objective of this Plant Directed Research and Demonstration (PDRD) task was to develop a system to safetly analyze tritium in moisture collected from glovebox atmospheres in the Savannah River Site (SRS) Tritium Facility. In order to minimize potential radiation exposures that could occur in handling and diluting high-tritium-content water, SRS sought alternatives to liquid-scintillation counting. The proposed system determines tritium concentrations by measuring Bremsstrahlung radiation induced by low-energy beta interactions in liquid samples. Results show that, after a short counting period (30 seconds), detection limits are three orders of magnitude below the described concentration of tritiated water in the zeolite beds. Additionally, this report covers the analysis of process samples and the investigation of several cell window materials including beryllium, aluminum, and copper. Final tests reveal that alternate window materials and thicknesses can be used to obtain useful results. In particular, a window of stainless steel of moderate thickness (0.3 cm) can be used for counting relatively high levels of tritium.
Date: April 25, 2011
Creator: Sigg, R.; Ferguson, B. & DiPrete, D.
Object Type: Report
System: The UNT Digital Library
Evaluation of Ultrasonic Time-of-Flight Diffraction Data for Selected Control Rod Drive Nozzles from Davis Besse Nuclear Power Plant (open access)

Evaluation of Ultrasonic Time-of-Flight Diffraction Data for Selected Control Rod Drive Nozzles from Davis Besse Nuclear Power Plant

Pacific Northwest National Laboratory (PNNL) examined ultrasonic (UT) time-of-flight diffraction (TOFD) data from ten (10) nozzles in the Davis Besse Nuclear Power Plant reactor closure head. The TOFD data was acquired by AREVA after a bare metal visual examination of the pressure vessel head indicated potential leakage in at least one nozzle. A detailed analysis of the UT data shows that Nozzle 4 has three indications consistent with cracking in the penetration tube. One of the indications starts at the wetted side of the weld and progresses to the annulus. In addition, examination of UT data from the annulus region of Nozzle 4 displays an irregular pattern that could be associated with boric acid deposits and leakage/wastage in the interference fit. The review of TOFD data for the other nine nozzles resulted in several indications being detected in the weld region and near the inner diameter (ID) and outer diameter (OD) surfaces of the penetration tube, but no other indications that are consistent with cracking that may have resulted in leakage were observed. A review of the back-wall reflections in the other nine nozzles also did not show strong indications of leakage, although Nozzle 67 displayed an irregularly-shaped region of …
Date: April 25, 2011
Creator: Cumblidge, Stephen E.; Cinson, Anthony D. & Anderson, Michael T.
Object Type: Report
System: The UNT Digital Library
Evaluation of Simple Causal Message Logging for Large-Scale Fault Tolerant HPC Systems (open access)

Evaluation of Simple Causal Message Logging for Large-Scale Fault Tolerant HPC Systems

The era of petascale computing brought machines with hundreds of thousands of processors. The next generation of exascale supercomputers will make available clusters with millions of processors. In those machines, mean time between failures will range from a few minutes to few tens of minutes, making the crash of a processor the common case, instead of a rarity. Parallel applications running on those large machines will need to simultaneously survive crashes and maintain high productivity. To achieve that, fault tolerance techniques will have to go beyond checkpoint/restart, which requires all processors to roll back in case of a failure. Incorporating some form of message logging will provide a framework where only a subset of processors are rolled back after a crash. In this paper, we discuss why a simple causal message logging protocol seems a promising alternative to provide fault tolerance in large supercomputers. As opposed to pessimistic message logging, it has low latency overhead, especially in collective communication operations. Besides, it saves messages when more than one thread is running per processor. Finally, we demonstrate that a simple causal message logging protocol has a faster recovery and a low performance penalty when compared to checkpoint/restart. Running NAS Parallel Benchmarks …
Date: February 25, 2011
Creator: Bronevetsky, G.; Meneses, E. & Kale, L. V.
Object Type: Article
System: The UNT Digital Library
Cognitive Foundations for Visual Analytics (open access)

Cognitive Foundations for Visual Analytics

In this report, we provide an overview of scientific/technical literature on information visualization and VA. Topics discussed include an update and overview of the extensive literature search conducted for this study, the nature and purpose of the field, major research thrusts, and scientific foundations. We review methodologies for evaluating and measuring the impact of VA technologies as well as taxonomies that have been proposed for various purposes to support the VA community. A cognitive science perspective underlies each of these discussions.
Date: February 25, 2011
Creator: Greitzer, Frank L.; Noonan, Christine F. & Franklin, Lyndsey
Object Type: Report
System: The UNT Digital Library