Assessing the Radiation Tolerance of 3C Silicon Carbide and Silicon Carbide Composites

The radiation response of 3C CVD SiC and two SiC/SiC composites have been assessed in nuclear reactor relevant conditions in order to find their suitability as nuclear materials for current Generation 2, and fusion power reactors. The MIAMI facilities have been used to irradiate 3C CVD SiC and SiC/SiC composites using ion beam systems with in-situ TEM so that the microstructural evolution of these proposed nuclear materials could be analysed whilst under irradiation to help understand the underlying mechanisms involved. This work shows for the first time, the nucleation of highly pressurised helium platelets forming within stacking faults in 3C CVD SiC, a defect that could potentially lead to crack formation in a reactor scenario. Two SiC/SiC composites, the first comprising of Tyranno SA3 fibres coated in PyC with a CVI SiC interface, and the second comprising of Hi-Nicalon Type S fibres with a C particle reinforced SiC matrix, were irradiated for the first time with a He ion beam capable of implanting He into the samples at the same rate per dpa as calculated for a pressurised water reactor. High radiation resistance was found for both composites at the PWR relevant temperature of 350oC as no microstructural changes were observed. At the fusion relevant temperature of 1000oC, the ORNL composite was also found to have high radiation tolerance up to the proposed upper limit of 200 dpa. With ahigh He implantation rate induced by a 15 keV He ion beam, the PyC interface within the ORNL sample was found to lose its crystallinity at 2 dpa, 400oC with a He concentration of 24,000 appm, a third of the concentration to be found in SiC during a PWI in a fusion reactor although no delamination of the PyC between the fibre or matrix occurred. SRIM calculations regarding the I-NERI Project PERSEUS have highlighted the low damage level of approximately 0.02 dpa where SiC has been seen to corrode in LWR relevant conditions suggesting that radiolysis products may have a bigger impact on corrosion than the direct damage induced in SiC via radiation

Effects of Leg Girth and Leg Strength on Division I Track Athletes Race Performance

Thesis presented to the faculty of the College of Science, Morehead State University in partial fulfillment of the requirements for the degree of Master of Arts by Benjamin Clay Dixon on December 7, 2017

Development and application of a rational water quality planning model

Ph.D.William W. Hine

How Explanation Adequacy of Security Policy Changes Decreases Organizational Computer Abuse

We use Fairness Theory to help explain why sometimes security policy sometimes backfire and increase security violations. Explanation adequacy—a key component of Fairness Theory—is expected to increase employees’ trust in their organization. This trust should decrease internal computer abuse incidents following the implementation of security changes. The results of our analysis provide support for Fairness Theory as applied to our context of computer abuse. First, the simple act of giving employees advance notification for future information security changes positively influences employees’ perceptions of organizational communication efforts. The adequacy of these explanations is also buoyed by SETA programs. Second, explanation adequacy and SETA programs work in unison to foster organizational trust. Finally, organizational trust significantly decreases internal computer abuse incidents. Our findings show how organizational communication can influence the overall effectiveness of information security changes among employees and how organizations can avoid becoming victim to their own efforts

The Hall of Mirrors Perceptions and Misperceptions in the Congressional Foreign Policy Process

Explores several factors related to an inconsistency in the voting record by the U.S. Congress on foreign policy issues, compared with the position taken by the public, administration officials, and leaders in business, labor, media, and education

Multiple Indicators and Multiple Causes (MIMIC) Models as a Mixed-Modeling Technique: A Tutorial and an Annotated Example

Formative modeling of latent constructs has produced great interest and discussion among scholars in recent years. However, confusion exists surrounding researchers’ ability to validate these models, especially with covariance-based structural equation modeling (CB-SEM) techniques. With this paper, we help to clarify these issues and explain how formatively modeled constructs can be assessed rigorously by researchers using CB-SEM capabilities. In particular, we explain and provide an applied example of a mixed-modeling technique termed multiple indicators and multiple causes (MIMIC) models. Using this approach, researchers can assess formatively modeled constructs as the final, distal dependent variable in CB-SEM structural models—something previously impossible because of CB-SEM’s mathematical identification rules. Moreover, we assert that researchers can use MIMIC models to assess the content validity of a set of formative indicators quantitatively—something considered conventionally only from a qualitative standpoint. The research example we use in this manuscript involving protection-motivated behaviors (PMBs) details the entire process of MIMIC modeling and provides a set of detailed guidelines for researchers to follow when developing new constructs modeled as MIMIC structures

INVESTIGATING CATALYST DESIGN STRATEGIES FOR SELECTIVE REACTION OF CYCLIC C4 OXYGENATES FROM BIOMASS

Numerous studies have shown that the properties of metal catalysts can in principle be fine-tuned by controlling the composition of the metal surface with high precision. The ability to design catalysts capable of high selectivity towards the conversion of a single functional group in a multifunctional molecule is a major objective for heterogeneous catalysis research. This need for high selectivity toward a single functional group is of growing importance in efforts to improve biorefining operations, where biomass-derived multifunctional carbohydrates are key building block intermediates that must be converted to a vast range of commodity chemical products such as fuels, pharmaceuticals, food products, and more. This work focuses on results from high resolution electron energy loss spectroscopy (HREELS) and temperature programmed desorption (TPD) experiments combined with selective use of density functional theory (DFT) calculations on single-crystal surfaces under ultrahigh vacuum conditions to study structure-property relations for a series of C4 cyclic oxygenates on catalytic metal surfaces. The objective of this work is to identify methods to tailor surfaces that are able to selectively catalyze conversions of one functional group in the multifunctional molecule. Two types of cyclic probe molecules have been studied in particular: 3-membered epoxide rings (in which ring-strain is high and the character of the oxygenate function is therefore more reactive) and 5-membered furanone rings (in which the ring is relatively stable). Both the epoxides and furanones contain an unsaturated C=C bond; for many biorefining applications it is desirable to selectively hydrogenate the olefin while keeping the oxygenate functionality intact. In this contribution, we explore the role of surface structure and composition in dictating the reaction pathways for multifunctional C4 cyclic oxygenates on key transition metal and bimetallic surfaces. Results for the epoxide probe molecule studies indicate differing modes of interaction with different metal surfaces. On a platinum or palladium surface, the epoxide ring opens irreversibly while the C=C functional group has a strong interaction with the surface. However, on a silver surface, the epoxide ring also opens, but can be made to close reversibly. An effective catalyst design strategy, then, is to combine silver on a predominantly platinum or palladium surface in order to create a bimetallic catalyst with high selectivity toward reaction of the olefin while keeping the epoxide ring intact. Recent studies of the chemistry of furanone species indicate that the olefin group interacts strongly with a platinum or palladium metal surface, and therefore is very likely to also determine how the molecule reacts. In this presentation, relationships between catalyst design strategies for epoxides versus furanones will be discussed, as will the likely biorefining reactions that such strategies can impact

Validation of Measured Damping Trends for Flight-Like Vehicle Panel/Equipment including a Range of Cable Harness Assemblies

This validation study examines the effect on vibroacoustic response resulting from the installation of cable bundles on a curved orthogrid panel. Of interest is the level of damping provided by the installation of the cable bundles and whether this damping could be potentially leveraged in launch vehicle design. The results of this test are compared with baseline acoustic response tests without cables. Damping estimates from the measured response data are made using a new software tool that leverages a finite element model of the panel in conjunction with advanced optimization techniques. While the full test series is not yet complete, the first configuration of cable bundles that was assessed effectively increased the viscous critical damping fraction of the system by as much as 0.02 in certain frequency ranges