Rhodium Catalysts in the Oxidation of CO by O<sub>2</sub> and NO: Shape, Composition, and Hot Electron Generation (open access)

Rhodium Catalysts in the Oxidation of CO by O<sub>2</sub> and NO: Shape, Composition, and Hot Electron Generation

It is well known that the activity, selectivity, and deactivation behavior of heterogeneous catalysts are strongly affected by a wide variety of parameters, including but not limited to nanoparticle size, shape, composition, support, pretreatment conditions, oxidation state, and electronic state. Enormous effort has been expended in an attempt to understand the role of these factors on catalytic behavior, but much still remains to be discovered. In this work, we have focused on deepening the present understanding of the role of nanoparticle shape, nanoparticle composition, and hot electrons on heterogeneous catalysis in the oxidation of carbon monoxide by molecular oxygen and nitric oxide. These reactions were chosen because they are important for environmental applications, such as in the catalytic converter, and because there is a wide range of experimental and theoretical insight from previous single crystal work as well as experimental data on nanoparticles obtained using new state-of-the-art techniques that aid greatly in the interpretation of results on complex nanoparticle systems. In particular, the studies presented in this work involve three types of samples: ~ 6.5 nm Rh nanoparticles of different shapes, ~ 15 nm Rh<sub>1-x</sub>Pd<sub>x</sub> core-shell bimetallic polyhedra nanoparticles, and Rh ultra-thin film (~ 5 nm) catalytic nanodiodes. The colloidal …
Date: March 8, 2010
Creator: Renzas, James R.
System: The UNT Digital Library
Laser Intertial Fusion Energy: Neutronic Design Aspects of a Hybrid Fusion-Fission Nuclear Energy System (open access)

Laser Intertial Fusion Energy: Neutronic Design Aspects of a Hybrid Fusion-Fission Nuclear Energy System

This study investigates the neutronics design aspects of a hybrid fusion-fission energy system called the Laser Fusion-Fission Hybrid (LFFH). A LFFH combines current Laser Inertial Confinement fusion technology with that of advanced fission reactor technology to produce a system that eliminates many of the negative aspects of pure fusion or pure fission systems. When examining the LFFH energy mission, a significant portion of the United States and world energy production could be supplied by LFFH plants. The LFFH engine described utilizes a central fusion chamber surrounded by multiple layers of multiplying and moderating media. These layers, or blankets, include coolant plenums, a beryllium (Be) multiplier layer, a fertile fission blanket and a graphite-pebble reflector. Each layer is separated by perforated oxide dispersion strengthened (ODS) ferritic steel walls. The central fusion chamber is surrounded by an ODS ferritic steel first wall. The first wall is coated with 250-500 {micro}m of tungsten to mitigate x-ray damage. The first wall is cooled by Li{sub 17}Pb{sub 83} eutectic, chosen for its neutron multiplication and good heat transfer properties. The {sub 17}Pb{sub 83} flows in a jacket around the first wall to an extraction plenum. The main coolant injection plenum is immediately behind the Li{sub …
Date: April 8, 2010
Creator: Kramer, K
System: The UNT Digital Library
An investigation of exploitation versus exploration in GBEA optimization of PORS 15 and 16 Problems (open access)

An investigation of exploitation versus exploration in GBEA optimization of PORS 15 and 16 Problems

It was hypothesized that the variations in time to solution are driven by the competing mechanisms of exploration and exploitation.This thesis explores this hypothesis by examining two contrasting problems that embody the hypothesized tradeoff between exploration and exploitation. Plus one recall store (PORS) is an optimization problem based on the idea of a simple calculator with four buttons: plus, one, store, and recall. Integer addition and store are classified as operations, and one and memory recall are classified as terminals. The goal is to arrange a fixed number of keystrokes in a way that maximizes the numerical result. PORS 15 (15 keystrokes) represents the subset of difficult PORS problems and PORS 16 (16 keystrokes) represents the subset of PORS problems that are easiest to optimize. The goal of this work is to examine the tradeoff between exploitation and exploration in graph based evolutionary algorithm (GBEA) optimization. To do this, computational experiments are used to examine how solutions evolve in PORS 15 and 16 problems when solved using GBEAs. The experiment is comprised of three components; the graphs and the population, the evolutionary algorithm rule set, and the example problems. The complete, hypercube, and cycle graphs were used for this experiment. …
Date: May 8, 2012
Creator: Koch, Kaelynn
System: The UNT Digital Library
Wither the Whip, Strengthen the Sword: Colonial Legacy and Geno-/Politicide in the Post-Colonial World, 1945-2012 (open access)

Wither the Whip, Strengthen the Sword: Colonial Legacy and Geno-/Politicide in the Post-Colonial World, 1945-2012

Undergraduate thesis examining the causes of geno-/politicides and the potential correlation between colonial legacy and the increased likelihood of seeing geno-/politicide across all newly independent states post-WWII from 1945-2012. This study reviews colonialism through an anthropological and sociological lens and applies it to state-structure's impact on political violence.
Date: May 8, 2014
Creator: Wood, Colin
System: The UNT Digital Library
Lessons from the Past: Possible Courses of Action for the Conflict in Syria (open access)

Lessons from the Past: Possible Courses of Action for the Conflict in Syria

Undergraduate thesis examining the Syrian conflict and the international community's struggle to find an appropriate response. This thesis reviews the conflicts that occurred in Bosnia and Rwanda, the interventions that took place within these states, and how a resolution to these conflicts was created. From this information, the author determines what conflict management strategies had the most success and what types of outside interventions were failures and the similarities of these instances to the Syrian conflict. Further intervention strategies and reasonings are presented that could be applied in Syria.
Date: June 8, 2014
Creator: Carter, Rachel
System: The UNT Digital Library