Hydrogen Storage in Metal-Organic Frameworks (open access)

Hydrogen Storage in Metal-Organic Frameworks

Conventional storage of large amounts of hydrogen in its molecular form is difficult and expensive because it requires employing either extremely high pressure gas or very low temperature liquid. Because of the importance of hydrogen as a fuel, the DOE has set system targets for hydrogen storage of gravimetric (5.5 wt%) and volumetric (40 g L-1) densities to be achieved by 2015. Given that these are system goals, a practical material will need to have higher capacity when the weight of the tank and associated cooling or regeneration system is considered. The size and weight of these components will vary substantially depending on whether the material operates by a chemisorption or physisorption mechanism. In the latter case, metal-organic frameworks (MOFs) have recently been identified as promising adsorbents for hydrogen storage, although little data is available for their sorption behavior. This grant was focused on the study of MOFs with these specific objectives. (1) To examine the effects of functionalization, catenation, and variation of the metal oxide and organic linkers on the low-pressure hydrogen adsorption properties of MOFs. (2) To develop a strategy for producing MOFs with high surface area and porosity to reduce the dead space and increase the hydrogen …
Date: April 26, 2012
Creator: Yaghi, Omar M.
Object Type: Report
System: The UNT Digital Library
Event-by-event study of photon observables in spontaneous and thermal fission (open access)

Event-by-event study of photon observables in spontaneous and thermal fission

None
Date: September 26, 2012
Creator: Vogt, R & Randrup, J
Object Type: Article
System: The UNT Digital Library
Performance Characteristics of Hardware Transactional Memory for Molecular Dynamics Application on BlueGene/Q: Toward Efficient Multithreading Strategies for Large-Scale Scientific Applications (open access)

Performance Characteristics of Hardware Transactional Memory for Molecular Dynamics Application on BlueGene/Q: Toward Efficient Multithreading Strategies for Large-Scale Scientific Applications

None
Date: September 26, 2012
Creator: Kunaseth, M.; Kalia, R. K.; Nakano, A.; Vashishta, P.; Richards, D. F. & Glosli, J. N.
Object Type: Article
System: The UNT Digital Library
Washoe Wisk'e'em Project (open access)

Washoe Wisk'e'em Project

The Washoe Tribe Wiskem Project (Project) was a Congressionally Directed Project identified for funding in the Energy and Water Development and Related Agencies Appropriations Act, 2010. The Project focused on installing up to four small vertical wind turbines at designated locations on Tribal lands to offset energy costs for the Tribe. The Washoe Tribe will use and analyze data collected from the wind turbines to better understand the wind resource.
Date: March 26, 2012
Creator: Hess-McGeown, Tara
Object Type: Report
System: The UNT Digital Library
High efficiency multilayer blazed gratings for EUV and soft X-rays: Recent developments (open access)

High efficiency multilayer blazed gratings for EUV and soft X-rays: Recent developments

Multilayer coated blazed gratings with high groove density are the best candidates for use in high resolution EUV and soft x-ray spectroscopy. Theoretical analysis shows that such a grating can be potentially optimized for high dispersion and spectral resolution in a desired high diffraction order without significant loss of diffraction efficiency. In order to realize this potential, the grating fabrication process should provide a perfect triangular groove profile and an extremely smooth surface of the blazed facets. Here we report on recent progress achieved at the Advanced Light Source (ALS) in fabrication of high quality multilayer coated blazed gratings. The blazed gratings were fabricated using scanning beam interference lithography followed by wet anisotropic etching of silicon. A 200 nm period grating coated with a Mo/Si multilayer composed with 30 bi-layers demonstrated an absolute efficiency of 37.6percent in the 3rd diffraction order at 13.6 nm wavelength. The groove profile of the grating was thoroughly characterized with atomic force microscopy before and after the multilayer deposition. The obtained metrology data were used for simulation of the grating efficiency with the vector electromagnetic PCGrate-6.1 code. The simulations showed that smoothing of the grating profile during the multilayer deposition is the main reason for …
Date: July 26, 2011
Creator: Voronov, Dmitriy; Ahn, Minseung; Anderson, Erik; Cambie, Rossana; Chang, Chih-Hao; Goray, Leonid et al.
Object Type: Article
System: The UNT Digital Library
RF Test Results from Cryomodule 1 at the Fermilab SRF Beam Test Facility (open access)

RF Test Results from Cryomodule 1 at the Fermilab SRF Beam Test Facility

Powered operation of Cryomodule 1 (CM-1) at the Fermilab SRF Beam Test Facility began in late 2010. Since then a series of tests first on the eight individual cavities and then the full cryomodule have been performed. We report on the results of these tests and lessons learned which will have an impact on future module testing at Fermilab. Since November 2010 Cryomodule 1 has been operating at 2 Kelvin. After evaluating each of the eight cavities while individually powered, the entire module has recently been powered and peak operation determined as shown in Figure 4. Several more weeks of measurements are planned before the module is warmed up, removed and replaced with Cryomodule 2 now under assembly at Fermilab.
Date: July 26, 2011
Creator: Harms, E.; Carlson, K.; Chase, B.; Cullerton, E.; Hocker, A.; Jensen, C. et al.
Object Type: Article
System: The UNT Digital Library
LESSONS LEARNED FROM A RECENT LASER ACCIDENT (open access)

LESSONS LEARNED FROM A RECENT LASER ACCIDENT

A graduate student received a laser eye injury from a femtosecond Ti:sapphire laser beam while adjusting a polarizing beam splitter optic. The direct causes for the accident included failure to follow safe alignment practices and failure to wear the required laser eyewear protection. Underlying root causes included inadequate on-the-job training and supervision, inadequate adherence to requirements, and inadequate appreciation for dimly visible beams outside the range of 400-700nm. This paper describes how the accident occurred, discusses causes and lessons learned, and describes corrective actions being taken.
Date: January 26, 2011
Creator: Woods, Michael
Object Type: Article
System: The UNT Digital Library
Laser Safety: A Laser Alignment Practical Training Course (open access)

Laser Safety: A Laser Alignment Practical Training Course

SLAC National Accelerator Laboratory has developed a Laser Alignment Practical Training Course as one of its core laser safety classes. The course is taught to small groups of up to three students and takes 1-3 hours to complete. This practical course is not a substitute for site-specific On-the-Job Training; it does, however, provide a good introduction in core laser safety practices that can be broadly applied. Alignment and diagnostic tasks are performed with low power lasers. Students learn safe alignment and diagnostic techniques and how to avoid common mistakes that might lead to an accident. The class is taught by laser supervisors, enabling them to assess the skill level of new laser personnel and determine the subsequent level of supervision needed. The course has six alignment tasks. For each task, discussion points are given for the instructor to review with the students. The optics setup includes different wavelength lasers, a beam expander, mirrors, irises, a periscope, a beam-splitting polarizer and a diffraction grating. Diagnostic tools include viewing cards, an IR viewer and a ccd camera. Laser eyewear is available to block some laser wavelengths in the setup.
Date: January 26, 2011
Creator: Woods, Michael & Edstrom, Steve
Object Type: Article
System: The UNT Digital Library
All auto shredding: evaluation of automotive shredder residue generated by shredding only vehicles. (open access)

All auto shredding: evaluation of automotive shredder residue generated by shredding only vehicles.

A well developed infrastructure exists for the reuse and recycling of automotive parts and materials. At the end of a vehicle's useful life many parts are removed and sold for reuse and fluids are recovered for recycling or proper disposal. What remains is shredded, along with other metal bearing scrap such as home appliances, demolition debris and process equipment, and the metals are separated out and recycled. The remainder of the vehicle materials is call shredder residue which ends up in the landfill. As energy and natural resources becomes more treasured, increased effort has been afforded to find ways to reduce energy consumption and minimize the use of our limited resources. Many of the materials found in shredder residue could be recovered and help offset the use of energy and material consumption. For example, the energy content of the plastics and rubbers currently landfilled with the shredder residue is equivalent to 16 million barrels of oil per year. However, in the United States, the recovered materials, primarily polymers, cannot be recycled due to current regulatory barriers which preclude the re-introduction into commerce of certain materials because of residual contamination with substances of concern (SOCs) such as polychlorinated biphenyls (PCBs). The …
Date: September 26, 2011
Creator: Duranceau, C. M. & Spangenberger, J. S.
Object Type: Report
System: The UNT Digital Library
Post-Closure Report for Closed Resource Conservation and Recovery Act Corrective Action Units, Nevada National Security Site, Nevada, For Fiscal Year 2010 (open access)

Post-Closure Report for Closed Resource Conservation and Recovery Act Corrective Action Units, Nevada National Security Site, Nevada, For Fiscal Year 2010

This report serves as the combined annual report for post-closure activities for the following closed Corrective Action Units (CAUs): (1) CAU 90, Area 2 Bitcutter Containment; (2) CAU 91, Area 3 U-3fi Injection Well; (3) CAU 92, Area 6 Decon Pond Facility; (4) CAU 110, Area 3 WMD U-3ax/bl Crater; and (5) CAU 112, Area 23 Hazardous Waste Trenches. The locations of the sites are shown in Figure 1. This report covers fiscal year 2010 (October 2009-September 2010). The post-closure requirements for these sites are described in Resource Conservation and Recovery Act Permit Number NEV HW0021 and summarized in each CAU-specific section in Section 1.0 of this report. Site inspections are conducted semiannually at CAUs 90 and 91 and quarterly at CAUs 92, 110, and 112. Additional inspections are conducted at CAU 92 if precipitation occurs in excess of 0.50 inches in a 24-hour period. Inspections include an evaluation of the condition of the units and identification of any deficiencies that may compromise the integrity of the units. The condition of covers, fencing, signs, gates, and locks is documented. In addition, soil moisture monitoring and subsidence surveys are conducted at CAU 110. The results of the inspections, summary of maintenance …
Date: January 26, 2011
Creator: National Security Technologies, LLC
Object Type: Report
System: The UNT Digital Library
Position Stability Monitoring of THEthe LCLS Undulator Quadrupoles (open access)

Position Stability Monitoring of THEthe LCLS Undulator Quadrupoles

X-ray FELs demand that the positions of undulator components be stable to less than 1 {mu}m per day. Simultaneously, the undulator length increases significantly in order to saturate at x-ray wavelengths. To minimize the impact of the outside environment, the Linac Coherent Light Source (LCLS) undulator is placed underground, but reliable data about ground motion inside such a tunnel was not available in the required stability range during the planning phase. Therefore, a new position monitor system had been developed and installed with the LCLS undulator. This system is capable of measuring x, y, roll, pitch and yaw of each of the 33 undulator quadrupoles with respect to stretched wires. Instrument resolution is about 10 nm and instrument drift is negligible. Position data of individual quadrupoles can be correlated along the entire 132-m long undulator. The system has been under continuous operation since 2009. This report describes long term experiences with the running system and the observed positional stability of the undulator quadrupoles.
Date: March 26, 2012
Creator: Nuhn, Heinz Dieter; Gassner, Georg & Peters, Franz
Object Type: Article
System: The UNT Digital Library
Results of applying a non-evaporative mitigation technique to laser-initiated surface damage on fused-silica (open access)

Results of applying a non-evaporative mitigation technique to laser-initiated surface damage on fused-silica

We present results from a study to determine an acceptable CO{sub 2} laser-based non-evaporative mitigation protocol for use on surface damage sites in fused-silica optics. A promising protocol is identified and evaluated on a set of surface damage sites created under ICF-type laser conditions. Mitigation protocol acceptability criteria for damage re-initiation and growth, downstream intensification, and residual stress are discussed. In previous work, we found that a power ramp at the end of the protocol effectively minimizes the residual stress (<25 MPa) left in the substrate. However, the biggest difficulty in determining an acceptable protocol was balancing between low re-initiation and problematic downstream intensification. Typical growing surface damage sites mitigated with a candidate CO{sub 2} laser-based mitigation protocol all survived 351 nm, 5 ns damage testing to fluences >12.5 J/cm{sup 2}. The downstream intensification arising from the mitigated sites is evaluated, and all but one of the sites has 100% passing downstream damage expectation values. We demonstrate, for the first time, a successful non-evaporative 10.6 {micro}m CO{sub 2} laser mitigation protocol applicable to fused-silica optics used on fusion-class lasers like the National Ignition Facility (NIF).
Date: October 26, 2010
Creator: Adams, J. J.; Bolourchi, M.; Bude, J. D.; Guss, G. M.; Matthews, M. J. & Nostrand, M. C.
Object Type: Article
System: The UNT Digital Library
Metallic Membrane Materials Development for Hydrogen Production from Coal Derived Syngas (open access)

Metallic Membrane Materials Development for Hydrogen Production from Coal Derived Syngas

The goals of Office of Clean Coal are: (1) Improved energy security; (2) Reduced green house gas emissions; (3) High tech job creation; and (4) Reduced energy costs. The goals of the Hydrogen from Coal Program are: (1) Prove the feasibility of a 40% efficient, near zero emissions IGCC plant that uses membrane separation technology and other advanced technologies to reduce the cost of electricity by at least 35%; and (2) Develop H{sub 2} production and processing technologies that will contribute {approx}3% in improved efficiency and 12% reduction in cost of electricity.
Date: February 26, 2012
Creator: Dogan, O. N.; Howard, B. H. & Alman, D. E.
Object Type: Article
System: The UNT Digital Library
Oxygen-Fired CO{sub 2} Recycle for Application to Direct CO{sub 2} Capture form Coal-Fired Power Plants (open access)

Oxygen-Fired CO{sub 2} Recycle for Application to Direct CO{sub 2} Capture form Coal-Fired Power Plants

The Southern Research/Southern Company 1 MWth Pilot-Scale Coal-Fired Test Facility was successfully retrofit to fire in either the traditional air-fired mode or with 100% oxygen and recycled flue gas, with a fully integrated feedback and control system, including oxygen and recycled flue gas modulation during startup, transfer, and shutdown, safety and operational interlocks, and data acquisition. A MAXON Staged Oxygen Burner for Oxy-Coal Applications produced a stable flame over a significant range of firing turn-down, staging, and while firing five different U.S. coal types. The MAXON burner design produces lower flame temperatures than for air firing, which will enable (A) Safe operation, (B) Reduction of recycle flow without concern about furnace flame temperatures, and (C) May likely be affective at reducing slagging and fouling in the boiler and super heater at full-scale Power Plants. A CFD model of the Oxy-fired Combustion Research Facility (OCRF) was used to predict the flame geometry and temperatures in the OCRF and make a comparison with the air-fired case. The model predictions were consistent with the experimental data in showing that the MAXON burner fired with oxygen produced lower flame temperatures than the air-fired burner while firing with air.
Date: September 26, 2010
Creator: Gale, Thomas
Object Type: Report
System: The UNT Digital Library
Gamma discrimination in pillar structured thermal neutron detectors (open access)

Gamma discrimination in pillar structured thermal neutron detectors

Solid-state thermal neutron detectors are desired to replace {sup 3}He tube based technology for the detection of special nuclear materials. {sup 3}He tubes have some issues with stability, sensitivity to microphonics and very recently, a shortage of {sup 3}He. There are numerous solid-state approaches being investigated that utilize various architectures and material combinations. By using the combination of high-aspect-ratio silicon PIN pillars, which are 2 {micro}m wide with a 2 {micro}m separation, arranged in a square matrix, and surrounded by {sup 10}B, the neutron converter material, a high efficiency thermal neutron detector is possible. Besides intrinsic neutron detection efficiency, neutron to gamma discrimination is an important figure of merit for unambiguous signal identification. In this work, theoretical calculations and experimental measurements are conducted to determine the effect of structure design of pillar structured thermal neutron detectors including: intrinsic layer thickness, pillar height, substrate doping and incident gamma energy on neutron to gamma discrimination.
Date: March 26, 2012
Creator: Shao, Q.; Radev, R. P.; Conway, A. M.; Voss, L. F.; Wang, T. F.; Nikolic, R. J. et al.
Object Type: Article
System: The UNT Digital Library
Non-linear Dynamics Of Toroidicity-induced Alfven Eigenmodes On The National Spherical Torus Experiment (open access)

Non-linear Dynamics Of Toroidicity-induced Alfven Eigenmodes On The National Spherical Torus Experiment

The National Spherical Torus Experiment (NSTX, [M. Ono et al., Nucl. Fusion 40, 557 (2000)]) routinely operates with neutral beam injection as the primary system for heating and current drive. The resulting fast ion population is super-Alfv#19;enic, with velocities 1 < vfast=vAlfven < 5. This provides a strong drive for toroidicity-induced Alfv#19;en eigenmodes (TAEs). As the discharge evolves, the fast ion population builds up and TAEs exhibit increasing bursts in amplitude and down-chirps in frequency, which eventually lead to a so-called TAE avalanche. Avalanches cause large (≤ 30%) fast ion losses over ~ 1 ms, as inferred from the neutron rate. The increased fast ion losses correlate with a stronger activity in the TAE band. In addition, it is shown that a n = 1 mode with frequency well below the TAE gap appears in the Fourier spectrum of magnetic fluctuations as a result of non-linear mode coupling between TAEs during avalanche events. The non-linear coupling between modes, which leads to enhanced fast ion transport during avalanches, is investigated.
Date: April 26, 2011
Creator: Podesta, M.; Crocker, N. A.; Fredrickson, E. D.; Gorelenkov, N. N.; Heidbrink, W. W.; Kubota, S. et al.
Object Type: Report
System: The UNT Digital Library
General Relativistic Magnetohydrodynamic Simulations of Magnetically Choked Accretion Flows around Black Holes (open access)

General Relativistic Magnetohydrodynamic Simulations of Magnetically Choked Accretion Flows around Black Holes

Black hole (BH) accretion flows and jets are qualitatively affected by the presence of ordered magnetic fields. We study fully three-dimensional global general relativistic magnetohydrodynamic (MHD) simulations of radially extended and thick (height H to cylindrical radius R ratio of |H/R| {approx} 0.2-1) accretion flows around BHs with various dimensionless spins (a/M, with BH mass M) and with initially toroidally-dominated ({phi}-directed) and poloidally-dominated (R-z directed) magnetic fields. Firstly, for toroidal field models and BHs with high enough |a/M|, coherent large-scale (i.e. >> H) dipolar poloidal magnetic flux patches emerge, thread the BH, and generate transient relativistic jets. Secondly, for poloidal field models, poloidal magnetic flux readily accretes through the disk from large radii and builds-up to a natural saturation point near the BH. While models with |H/R| {approx} 1 and |a/M| {le} 0.5 do not launch jets due to quenching by mass infall, for sufficiently high |a/M| or low |H/R| the polar magnetic field compresses the inflow into a geometrically thin highly non-axisymmetric 'magnetically choked accretion flow' (MCAF) within which the standard linear magneto-rotational instability is suppressed. The condition of a highly-magnetized state over most of the horizon is optimal for the Blandford-Znajek mechanism that generates persistent relativistic jets with …
Date: April 26, 2012
Creator: McKinney, Jonathan C.; Tchekhovskoy, Alexander & Blandford, Roger D.
Object Type: Article
System: The UNT Digital Library
Primer on Use of Multi-Spectral and Infra Red Imaging for On-Site Inspections (open access)

Primer on Use of Multi-Spectral and Infra Red Imaging for On-Site Inspections

The purpose of an On-Site Inspection (OSI) is to determine whether a nuclear explosion has occurred in violation of the Comprehensive Nuclear Test Ban Treaty (CTBT), and to gather information which might assist in identifying the violator (CTBT, Article IV, Paragraph 35) Multi-Spectral and Infra Red Imaging (MSIR) is allowed by the treaty to detect observables which might help reduce the search area and thus expedite an OSI and make it more effective. MSIR is permitted from airborne measurements, and at and below the surface to search for anomalies and artifacts (CTBT, Protocol, Part II, Paragraph 69b). The three broad types of anomalies and artifacts MSIR is expected to be capable of observing are surface disturbances (disturbed earth, plant stress or anomalous surface materials), human artifacts (man-made roads, buildings and features), and thermal anomalies. The purpose of this Primer is to provide technical information on MSIR relevant to its use for OSI. It is expected that this information may be used for general background information, to inform decisions about the selection and testing of MSIR equipment, to develop operational guidance for MSIR use during an OSI, and to support the development of a training program for OSI Inspectors. References are …
Date: October 26, 2010
Creator: Henderson, J. R.
Object Type: Report
System: The UNT Digital Library
Quantum Monte Carlo Endstation for Petascale Computing (open access)

Quantum Monte Carlo Endstation for Petascale Computing

NCSU research group has been focused on accomplising the key goals of this initiative: establishing new generation of quantum Monte Carlo (QMC) computational tools as a part of Endstation petaflop initiative for use at the DOE ORNL computational facilities and for use by computational electronic structure community at large; carrying out high accuracy quantum Monte Carlo demonstration projects in application of these tools to the forefront electronic structure problems in molecular and solid systems; expanding the impact of QMC methods and approaches; explaining and enhancing the impact of these advanced computational approaches. In particular, we have developed quantum Monte Carlo code (QWalk, www.qwalk.org) which was significantly expanded and optimized using funds from this support and at present became an actively used tool in the petascale regime by ORNL researchers and beyond. These developments have been built upon efforts undertaken by the PI's group and collaborators over the period of the last decade. The code was optimized and tested extensively on a number of parallel architectures including petaflop ORNL Jaguar machine. We have developed and redesigned a number of code modules such as evaluation of wave functions and orbitals, calculations of pfaffians and introduction of backflow coordinates together with overall organization …
Date: January 26, 2011
Creator: Mitas, Lubos
Object Type: Report
System: The UNT Digital Library
Post-Closure Evaluation of the Area 3 and Area 5 Radioactive Waste Management Sites at the Nevada National Security Site in Support of the Site-Wide Environmental Impact Statement (open access)

Post-Closure Evaluation of the Area 3 and Area 5 Radioactive Waste Management Sites at the Nevada National Security Site in Support of the Site-Wide Environmental Impact Statement

The post-closure performance of the Area 3 Radioactive Waste Management Site (RWMS) and Area 5 RWMS are evaluated for the Site-Wide Environmental Impact Statement using current performance assessment and composite analysis methods and models. Two alternatives with different future waste volumes and inventories are evaluated. The No Action Alternative evaluates the inventory disposed through fiscal year (FY) 2010 plus an additional 4.5E5 cubic meters (m3) (1.59E7 cubic feet [ft3]) of waste disposed at the Area 5 RWMS. The Expanded Operations Alternative evaluates the FY 2010 inventory plus an additional 1.42E6 m3 (5.03E7 ft3) of waste disposed at the Area 5 RWMS and 4.93E4 m3 (1.74E6 ft3) disposed at the Area 3 RWMS. Both the No Action and Expanded Operations Alternatives have a reasonable expectation of meeting all performance objectives of U.S. Department of Energy Order DOE O 435.1, “Radioactive Waste Management.” No significant difference between the two alternatives was found because the waste concentrations are similar. The performance assessment model assesses radiological risk for residents at the RWMS boundary where risk is more closely related to waste concentration than total waste inventory. Results for the composite analysis also indicate that the dose constraint and dose limit can be met for …
Date: April 26, 2011
Creator: National Security Technologies, LLC
Object Type: Report
System: The UNT Digital Library
Options for Production Staging for a Low Energy Neutrino Factory (open access)

Options for Production Staging for a Low Energy Neutrino Factory

A low energy neutrino factory (LENF) is defined, for the purpose of this report, to accelerate a muon beam to a total energy in the range of 10-14 GeV, and store it in a decay ring directing a resulting neutrino beam to a detector 2200-2300 km distant. The machine should be ultimately capable of producing 10{sup 21} decays toward that detector per year of 10{sup 7} s. We consider such a neutrino factory to be the accelerator defined in the Interim Design Report (IDR) of the International Design Study for the Neutrino Factory (IDS-NF), modified to remove the final stage of acceleration, possibly modifying the remaining acceleration stages to adjust the final energy, and replacing the decay ring with one designed for the lower energy and shorter baseline. We discuss modifications to that design which would reduce the cost of the machine at the price of a reduction in neutrino production, down to as low as 10{sup 20} decays per year. These modifications will not preclude eventually upgrading the machine to the full production of 10{sup 21} decays per year. The eventual cost of a machine which achieves the full production through a series of lower-production stages should not exceed …
Date: October 26, 2011
Creator: Berg, J. S.
Object Type: Report
System: The UNT Digital Library
Integrated Nucleosynthesis in Neutrino Driven Winds (open access)

Integrated Nucleosynthesis in Neutrino Driven Winds

Although they are but a small fraction of the mass ejected in core-collapse supernovae, neutrino-driven winds (NDWs) from nascent proto-neutron stars (PNSs) have the potential to contribute significantly to supernova nucleosynthesis. In previous works, the NDW has been implicated as a possible source of r-process and light p-process isotopes. In this paper we present time-dependent hydrodynamic calculations of nucleosynthesis in the NDW which include accurate weak interaction physics coupled to a full nuclear reaction network. Using two published models of PNS neutrino luminosities, we predict the contribution of the NDW to the integrated nucleosynthetic yield of the entire supernova. For the neutrino luminosity histories considered, no true r-process occurs in the most basic scenario. The wind driven from an older 1.4M{sub {circle_dot}} model for a PNS is moderately neutron-rich at late times however, and produces {sup 87}Rb, {sup 88}Sr, {sup 89}Y, and {sup 90}Zr in near solar proportions relative to oxygen. The wind from a more recently studied 1.27M{sub {circle_dot}} PNS is proton-rich throughout its entire evolution and does not contribute significantly to the abundance of any element. It thus seems very unlikely that the simplest model of the NDW can produce the r-process. At most, it contributes to the …
Date: March 26, 2010
Creator: Roberts, L F; Woosley, S E & Hoffman, R D
Object Type: Article
System: The UNT Digital Library
SELECTIVE REMOVAL OF STRONTIUM AND CESIUM FROM SIMULATED WASTE SOLUTION WITH TITANATE ION EXCHANGERS IN A FILTER CARTRIDGE CONFIGURATION (open access)

SELECTIVE REMOVAL OF STRONTIUM AND CESIUM FROM SIMULATED WASTE SOLUTION WITH TITANATE ION EXCHANGERS IN A FILTER CARTRIDGE CONFIGURATION

This report describes experimental results for the selective removal of strontium and cesium from simulated waste solutions using monosodium titanate (MST) and crystalline silicotitanate (CST)-laden filter cartridges. Four types of ion exchange cartridge media (CST and MST designed by both 3M and POROX{reg_sign}) were evaluated. In these proof-of-principle tests effective uptake of both Sr-85 and Cs-137 was observed. However, the experiments were not performed long enough to determine the saturation levels or breakthrough curve for each filter cartridge. POREX{reg_sign} MST cartridges, which by design were based on co-sintering of the active titanates with polyethylene particles, seem to perform as well as the 3M-designed MST cartridges (impregnated filter membrane design) in the uptake of strontium. At low salt simulant conditions (0.29 M Na{sup +}), the instantaneous decontamination factor (D{sub F}) for Sr-85 with the 3M-design MST cartridge measured 26, representing the removal of 96% of the Sr-85. On the other hand, the Sr-85 instantaneous D{sub F} with the POREX{reg_sign} design MST cartridge measured 40 or 98% removal of the Sr-85. Strontium removal with the 3M-design MST and CST cartridges placed in series filter arrangement produced an instantaneous decontamination factor of 41 or 97.6% removal compared to an instantaneous decontamination factor of …
Date: May 26, 2011
Creator: Oji, L.; Martin, K. & Hobbs, D.
Object Type: Report
System: The UNT Digital Library
Measurement of the Cosmic Ray Energy Spectrum Using Hybrid Events of the Pierre Auger Observatory (open access)

Measurement of the Cosmic Ray Energy Spectrum Using Hybrid Events of the Pierre Auger Observatory

None
Date: June 26, 2012
Creator: Settimo, Mariangela & U., /Siegen u. /Salento
Object Type: Article
System: The UNT Digital Library