D = 5 Maximally Supersymmetric Yang-Mills Theory Diverges at Six Loops (open access)

D = 5 Maximally Supersymmetric Yang-Mills Theory Diverges at Six Loops

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Date: October 31, 2012
Creator: Bern, Zvi; Carrasco, John Joseph; Dixon, Lance J.; Douglas, Michael R.; von Hippel, Matt & Johansson, Henrik
System: The UNT Digital Library
Advanced Electric Submersible Pump Design Tool for Geothermal Applications (open access)

Advanced Electric Submersible Pump Design Tool for Geothermal Applications

Electrical Submersible Pumps (ESPs) present higher efficiency, larger production rate, and can be operated in deeper wells than the other geothermal artificial lifting systems. Enhanced Geothermal Systems (EGS) applications recommend lifting 300 C geothermal water at 80kg/s flow rate in a maximum 10-5/8-inch diameter wellbore to improve the cost-effectiveness. In this paper, an advanced ESP design tool comprising a 1D theoretical model and a 3D CFD analysis has been developed to design ESPs for geothermal applications. Design of Experiments was also performed to optimize the geometry and performance. The designed mixed-flow type centrifugal impeller and diffuser exhibit high efficiency and head rise under simulated EGS conditions. The design tool has been validated by comparing the prediction to experimental data of an existing ESP product.
Date: May 31, 2012
Creator: Qi, Xuele; Turnquist, Norman & Ghasripoor, Farshad
System: The UNT Digital Library
Balance of Nanostructure and Bimetallic Interactions in Pt Model Fuel Cell Catalysts: An in Situ XAS and DFT Study (open access)

Balance of Nanostructure and Bimetallic Interactions in Pt Model Fuel Cell Catalysts: An in Situ XAS and DFT Study

We have studied the effect of nanostructuring in Pt monolayer model electrocatalysts on a Rh(111) single-crystal substrate on the adsorption strength of chemisorbed species. In situ high energy resolution fluorescence detection X-ray absorption spectroscopy at the Pt L(3) edge reveals characteristic changes of the shape and intensity of the 'white-line' due to chemisorption of atomic hydrogen (H(ad)) at low potentials and oxygen-containing species (O/OH(ad)) at high potentials. On a uniform, two-dimensional Pt monolayer grown by Pt evaporation in ultrahigh vacuum, we observe a significant destabilization of both H(ad) and O/OH(ad) due to strain and ligand effects induced by the underlying Rh(111) substrate. When Pt is deposited via a wet-chemical route, by contrast, three-dimensional Pt islands are formed. In this case, strain and Rh ligand effects are balanced with higher local thickness of the Pt islands as well as higher defect density, shifting H and OH adsorption energies back toward pure Pt. Using density functional theory, we calculate O adsorption energies and corresponding local ORR activities for fcc 3-fold hollow sites with various local geometries that are present in the three-dimensional Pt islands.
Date: May 31, 2012
Creator: Friebel, Daniel; Viswanathan, Venkatasubramanian; Miller, Daniel James; Anniyev, Toyli; Ogasawara, Hirohito; Larsen, Ask Hjorth et al.
System: The UNT Digital Library
Disposal Activities and the Unique Waste Streams at the Nevada National Security Site (NNSS) (open access)

Disposal Activities and the Unique Waste Streams at the Nevada National Security Site (NNSS)

This slide show documents waste disposal at the Nevada National Security Site. Topics covered include: radionuclide requirements for waste disposal; approved performance assessment (PA) for depleted uranium disposal; requirements; program approval; the Waste Acceptance Review Panel (WARP); description of the Radioactive Waste Acceptance Program (RWAP); facility evaluation; recent program accomplishments, nuclear facility safety changes; higher-activity waste stream disposal; and, large volume bulk waste streams.
Date: October 31, 2012
Creator: Arnold, P.
System: The UNT Digital Library
Efficient Theoretical Screening of Solid Sorbents for CO2 Capture Applications* (open access)

Efficient Theoretical Screening of Solid Sorbents for CO2 Capture Applications*

By combining thermodynamic database mining with first principles density functional theory and phonon lattice dynamics calculations, a theoretical screening methodology to identify the most promising CO2 sorbent candidates from the vast array of possible solid materials has been proposed and validated. The ab initio thermodynamic technique has the advantage of allowing identification of thermodynamic properties of CO2 capture reactions without any experimental input beyond crystallographic structural information of the solid phases involved. For a given solid, the first step is to attempt to extract thermodynamic properties from thermodynamic databases and the available literatures. If the thermodynamic properties of the compound of interest are unknown, an ab initio thermodynamic approach is used to calculate them. These properties expressed conveniently as chemical potentials and heat of reactions, which obtained either from databases or from calculations, are further used for computing the thermodynamic reaction equilibrium properties of the CO2 absorption/desorption cycles. Only those solid materials for which lower capture energy costs are predicted at the desired process conditions are selected as CO2 sorbent candidates and are further considered for experimental validations. Solid sorbents containing alkali and alkaline earth metals have been reported in several previous studies to be good candidates for CO2 sorbent …
Date: March 31, 2012
Creator: Duan, Yuhua; Luebke, David & Pennline, Henry
System: The UNT Digital Library
Governance of the International Linear Collider Project (open access)

Governance of the International Linear Collider Project

Governance models for the International Linear Collider Project are examined in the light of experience from similar international projects around the world. Recommendations for one path which could be followed to realize the ILC successfully are outlined. The International Linear Collider (ILC) is a unique endeavour in particle physics; fully international from the outset, it has no 'host laboratory' to provide infrastructure and support. The realization of this project therefore presents unique challenges, in scientific, technical and political arenas. This document outlines the main questions that need to be answered if the ILC is to become a reality. It describes the methodology used to harness the wisdom displayed and lessons learned from current and previous large international projects. From this basis, it suggests both general principles and outlines a specific model to realize the ILC. It recognizes that there is no unique model for such a laboratory and that there are often several solutions to a particular problem. Nevertheless it proposes concrete solutions that the authors believe are currently the best choices in order to stimulate discussion and catalyze proposals as to how to bring the ILC project to fruition. The ILC Laboratory would be set up by international treaty …
Date: May 31, 2012
Creator: Foster, B.; U., /Oxford; Barish, B.; /Caltech; Delahaye, J. P.; /CERN et al.
System: The UNT Digital Library
Grafting AMR Capability Into the Diffusion Package of an Existing ALE Code (open access)

Grafting AMR Capability Into the Diffusion Package of an Existing ALE Code

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Date: December 31, 2012
Creator: Howell, Louis
System: The UNT Digital Library
A Historical Profile of the Higgs Boson (open access)

A Historical Profile of the Higgs Boson

The Higgs boson was postulated in 1964, and phenomenological studies of its possible production and decays started in the early 1970s, followed by studies of its possible productionin e{sup +} e{sup -}, {anti p}p and pp collisions, in particular. Until recently, the most sensitive searches for the Higgs boson were at LEP between 1989 and 2000, which have been complemented bysearches at the Fermilab Tevatron. The LHC has recently entered the hunt, excluding a Higgs boson over a large range of masses and revealing a tantalizing hint in the range 119 to125 GeV, and there are good prospects that the existence or otherwise of the Higgs boson will soon be established. One of the most attractive possibilities is that the Higgs bosonis accompanied by supersymmetry, though composite options have yet to be excluded. This article reviews some of the key historical developments in Higgs physics over the past half-century.
Date: January 31, 2012
Creator: Ellis, John; Gaillard, Mary K. & Nanopoulos, Dimitri V.
System: The UNT Digital Library
Multi-core and Many-core Shared-memory Parallel Raycasting Volume Rendering Optimization and Tuning (open access)

Multi-core and Many-core Shared-memory Parallel Raycasting Volume Rendering Optimization and Tuning

Given the computing industry trend of increasing processing capacity by adding more cores to a chip, the focus of this work is tuning the performance of a staple visualization algorithm, raycasting volume rendering, for shared-memory parallelism on multi-core CPUs and many-core GPUs. Our approach is to vary tunable algorithmic settings, along with known algorithmic optimizations and two different memory layouts, and measure performance in terms of absolute runtime and L2 memory cache misses. Our results indicate there is a wide variation in runtime performance on all platforms, as much as 254% for the tunable parameters we test on multi-core CPUs and 265% on many-core GPUs, and the optimal configurations vary across platforms, often in a non-obvious way. For example, our results indicate the optimal configurations on the GPU occur at a crossover point between those that maintain good cache utilization and those that saturate computational throughput. This result is likely to be extremely difficult to predict with an empirical performance model for this particular algorithm because it has an unstructured memory access pattern that varies locally for individual rays and globally for the selected viewpoint. Our results also show that optimal parameters on modern architectures are markedly different from those …
Date: January 31, 2012
Creator: Howison, Mark
System: The UNT Digital Library
Narrowing the uncertainty on the total charm cross section and itseffect on the J/psi cross section (open access)

Narrowing the uncertainty on the total charm cross section and itseffect on the J/psi cross section

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Date: August 31, 2012
Creator: Nelson, R; Vogt, R & Frawley, A D
System: The UNT Digital Library
Neutron Production Using a Pyroelectric Driven Target Coupled with a Gated Field Ionization Source (open access)

Neutron Production Using a Pyroelectric Driven Target Coupled with a Gated Field Ionization Source

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Date: July 31, 2012
Creator: Ellsworth, J L; Tang, V; Falabella, S; Naranjo, B & Putterman, S
System: The UNT Digital Library
Overview of Phase Space Manipulations of Relativistic Electron Beams (open access)

Overview of Phase Space Manipulations of Relativistic Electron Beams

Phase space manipulation is a process to rearrange beam's distribution in 6-D phase space. In this paper, we give an overview of the techniques for tailoring beam distribution in 2D, 4D, and 6D phase space to meet the requirements of various applications. These techniques become a new focus of accelerator physics R&D and very likely these advanced concepts will open up new opportunities in advanced accelerators and the science enabled by them.
Date: August 31, 2012
Creator: Xiang, Dao
System: The UNT Digital Library
A Staged Muon-Based Neutrino and Collider Physics Program (open access)

A Staged Muon-Based Neutrino and Collider Physics Program

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Date: July 31, 2012
Creator: Kaplan, Daniel M.
System: The UNT Digital Library
Transport and Installation of the Dark Energy Survey CCD Imager (open access)

Transport and Installation of the Dark Energy Survey CCD Imager

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Date: July 31, 2012
Creator: Derylo, Greg; Chi, Edward; Diehl, H.Thomas; Estrada, Juan; Flaugher, Brenna & Schultz, Ken
System: The UNT Digital Library
Web-based Testing for an Environmental Information Management System (open access)

Web-based Testing for an Environmental Information Management System

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Date: August 31, 2012
Creator: Barbosa, E & Laguna, G W
System: The UNT Digital Library