Ab-initio calculation of optical properties of wurtzitic In_x Ga_1x N and In_x Al_1x N alloys including excitonic effects (open access)

Ab-initio calculation of optical properties of wurtzitic In_x Ga_1x N and In_x Al_1x N alloys including excitonic effects

None
Date: September 5, 2012
Creator: de Carvalho, L C; Schleife, A; Furthmueller, J & Bechstedt, F
Object Type: Article
System: The UNT Digital Library
Brute Force Modeling of the Kessler Syndrome (open access)

Brute Force Modeling of the Kessler Syndrome

None
Date: September 5, 2012
Creator: Nikolaev, S.; Phillion, D.; Springer, H. K.; deVries, W.; Jiang, M.; Pertica, A. et al.
Object Type: Article
System: The UNT Digital Library
Coexistence of the Alpha and Delta Phases in As-Cast Uranium-Rich U-Zr Alloys (open access)

Coexistence of the Alpha and Delta Phases in As-Cast Uranium-Rich U-Zr Alloys

None
Date: September 5, 2012
Creator: McKeown, J T; Irukuvarghula, S; Ahn, S; Wall, M; Hsiung, L L; McDeavitt, S et al.
Object Type: Article
System: The UNT Digital Library
Design & Fabrication of a High-Voltage Photovoltaic Cell (open access)

Design & Fabrication of a High-Voltage Photovoltaic Cell

Silicon photovoltaic (PV) cells are alternative energy sources that are important in sustainable power generation. Currently, applications of PV cells are limited by the low output voltage and somewhat low efficiency of such devices. In light of this fact, this project investigates the possibility of fabricating high-voltage PV cells on float-zone silicon wafers having output voltages ranging from 50 V to 2000 V. Three designs with different geometries of diffusion layers were simulated and compared in terms of metal coverage, recombination, built-in potential, and conduction current density. One design was then chosen and optimized to be implemented in the final device design. The results of the simulation serve as a feasibility test for the design concept and provide supportive evidence of the effectiveness of silicon PV cells as high-voltage power supplies.
Date: September 5, 2012
Creator: Felder, Jennifer & /SLAC, /North Carolina State U.
Object Type: Report
System: The UNT Digital Library
Effect of SOFC Interconnect-Coating Interactions on Coating Properties and Performance (open access)

Effect of SOFC Interconnect-Coating Interactions on Coating Properties and Performance

The high operating temperature of solid oxide fuel cells (SOFCs) provides good fuel flexibility which expands potential applications, but also creates materials challenges. One such challenge is the interconnect material, which was the focus of this project. In particular, the objective of the project was to understand the interaction between the interconnect alloy and ceramic coatings which are needed to minimize chromium volatilization and the associated chromium poisoning of the SOFC cathode. This project focused on coatings based on manganese cobalt oxide spinel phases (Mn,Co)3O4, which have been shown to be effective as coatings for ferritic stainless steel alloys. Analysis of diffusion couples was used to develop a model to describe the interaction between (Mn,Co)3O4 and Cr2O3 in which a two-layer reaction zone is formed. Both layers form the spinel structure, but the concentration gradients at the interface appear like a two-phase boundary suggesting that a miscibility gap is present in the spinel solid solution. A high-chromium spinel layer forms in contact with Cr2O3 and grows by diffusion of manganese and cobalt from the coating material to the Cr2O3. The effect of coating composition, including the addition of dopants, was evaluated and indicated that the reaction rate could be decreased …
Date: September 5, 2012
Creator: Fergus, Jeffrey W.
Object Type: Report
System: The UNT Digital Library
Experimental Neutrino Physics: Final Report (open access)

Experimental Neutrino Physics: Final Report

Experimental studies of neutrino properties, with particular emphasis on neutrino oscillation, mass and mixing parameters. This research was pursued by means of underground detectors for reactor anti-neutrinos, measuring the flux and energy spectra of the neutrinos. More recent investigations have been aimed and developing detector technologies for a long-baseline neutrino experiment (LBNE) using a neutrino beam from Fermilab.
Date: September 5, 2012
Creator: Lane, Charles E. & Maricic, Jelena
Object Type: Report
System: The UNT Digital Library
Fusion Simulation Program Definition. Final report (open access)

Fusion Simulation Program Definition. Final report

We have completed our contributions to the Fusion Simulation Program Definition Project. Our contributions were in the overall planning with concentration in the definition of the area of Software Integration and Support. We contributed to the planning of multiple meetings, and we contributed to multiple planning documents.
Date: September 5, 2012
Creator: Cary, John R.
Object Type: Report
System: The UNT Digital Library
High-Average Power Facilities (open access)

High-Average Power Facilities

There has been significant progress in the development of high-power facilities in recent years yet major challenges remain. The task of WG4 was to identify which facilities were capable of addressing the outstanding R&D issues presently preventing high-power operation. To this end, information from each of the facilities represented at the workshop was tabulated and the results are presented herein. A brief description of the major challenges is given, but the detailed elaboration can be found in the other three working group summaries.
Date: September 5, 2012
Creator: Dowell, David H. & Power, John G.
Object Type: Article
System: The UNT Digital Library
Improving Conservation for First-Order System Least Squares Finite-Element Methods (open access)

Improving Conservation for First-Order System Least Squares Finite-Element Methods

None
Date: September 5, 2012
Creator: Adler, J H & Vassilevski, P S
Object Type: Article
System: The UNT Digital Library
Infrared Spectroscope for Electron Bunch-length Measurement: Heat Sensor Parameters Analysis (open access)

Infrared Spectroscope for Electron Bunch-length Measurement: Heat Sensor Parameters Analysis

The Linac Coherent Light Source (LCLS) is used for many experiments. Taking advantage of the free electron laser (FEL) process, scientists of various fields perform experiments of all kind. Some for example study protein folding; other experiments are more interested in the way electrons interact with the molecules before they are destroyed. These experiments among many others have very little information about the electrons x-ray produced by the FEL, except that the FEL is using bunches less than 10 femtoseconds long. To be able to interpret the data collected from those experiments, more accurate information is needed about the electron's bunch-length. Existing bunch length measurement techniques are not suitable for the measurement of such small time scales. Hence the need to design a device that will provide more precise information about the electron bunch length. This paper investigates the use of a pyreoelectric heat sensor that has a sensitivity of about 1.34 micro amps per watt for the single cell detector. Such sensitivity, added to the fact that the detector is an array sensor, makes the detector studied the primary candidate to be integrated to an infrared spectrometer designed to better measure the LCLS electron bunch length.
Date: September 5, 2012
Creator: Domgmo-Momo, Gilles & /SLAC, /Towson U.
Object Type: Report
System: The UNT Digital Library
Lead Research and Development Activity for DOE's High Temperature, Low Relative Humidity Membrane Program (Topic 2) (open access)

Lead Research and Development Activity for DOE's High Temperature, Low Relative Humidity Membrane Program (Topic 2)

The Department of Energy’s High Temperature, Low Relative Humidity Membrane Program was begun in 2006 with the Florida Solar Energy Center (FSEC) as the lead organization. During the first three years of the program, FSEC was tasked with developing non-Nafion® proton exchange membranes with improved conductivity for fuel cells. Additionally, FSEC was responsible for developing protocols for the measurement of in-plane conductivity, providing conductivity measurements for the other funded teams, developing a method for through-plane conductivity and organizing and holding semiannual meetings of the High Temperature Membrane Working Group (HTMWG). The FSEC membrane research focused on the development of supported poly[perfluorosulfonic acid] (PFSA) – Teflon membranes and a hydrocarbon membrane, sulfonated poly(ether ether ketone). The fourth generation of the PFSA membrane (designated FSEC-4) came close to, but did not meet, the Go/No-Go milestone of 0.1 S/cm at 50% relative humidity at 120 °C. In-plane conductivity of membranes provided by the funded teams was measured and reported to the teams and DOE. Late in the third year of the program, DOE used this data and other factors to decide upon the teams to continue in the program. The teams that continued provided promising membranes to FSEC for development of membrane electrode …
Date: September 5, 2012
Creator: Fenton, James; Slattery, Darlene & Mohajeri, Nahid
Object Type: Report
System: The UNT Digital Library
RAPID METHOD FOR DETERMINATION OF {sup 228}Ra IN WATER SAMPLES (open access)

RAPID METHOD FOR DETERMINATION OF {sup 228}Ra IN WATER SAMPLES

A new rapid method for the determination of {sup 228}Ra in natural water samples has been developed at the SRNL/EBL (Savannah River National Lab/ Environmental Bioassay Laboratory) that can be used for emergency response or routine samples. While gamma spectrometry can be employed with sufficient detection limits to determine {sup 228}Ra in solid samples (via {sup 228}Ac) , radiochemical methods that employ gas flow proportional counting techniques typically provide lower MDA (Minimal Detectable Activity) levels for the determination of {sup 228}Ra in water samples. Most radiochemical methods for {sup 228}Ra collect and purify {sup 228}Ra and allow for {sup 228}Ac daughter ingrowth for ~36 hours. In this new SRNL/EBL approach, {sup 228}Ac is collected and purified from the water sample without waiting to eliminate this delay. The sample preparation requires only about 4 hours so that {sup 228}Ra assay results on water samples can be achieved in < 6 hours. The method uses a rapid calcium carbonate precipitation enhanced with a small amount of phosphate added to enhance chemical yields (typically >90%), followed by rapid cation exchange removal of calcium. Lead, bismuth, uranium, thorium and protactinium isotopes are also removed by the cation exchange separation. {sup 228}Ac is eluted from …
Date: September 5, 2012
Creator: Maxwell, S.
Object Type: Article
System: The UNT Digital Library
Re-architecting TEIMS Web-based Legacy Applications Using the Model View Controller Paradigm (open access)

Re-architecting TEIMS Web-based Legacy Applications Using the Model View Controller Paradigm

None
Date: September 5, 2012
Creator: Barbosa, E & Laguna, G W
Object Type: Article
System: The UNT Digital Library