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<p>I want delay publication of my dissertation until April 30 2013. Thanks.</p> / <p>Strontium titanate (SrTiO₃) has a wide range of applications in the electronic industry and attracts growing world-widely interest recently because of novel discoveries at its surfaces, interfaces and with selected dopants. The understanding of some of the structural properties of SrTiO₃ and its optical properties have been lagging due to limited characterization techniques available to study single monolayers and dopants in this material.</p> <p>In the present thesis, pure SrTiO₃ single crystals with (2x1) and c(4x2) surface patterns were synthesized and samples (Pr, Al) doped SrTiO₃ were prepared through ion implantation. The atomic and electronic structures of these samples were investigated by various high-resolution imaging and spectroscopic techniques available in an aberration-corrected transmission electron microscope. Particularly, the direct imaging of individual light atoms and vacancies within a bulk material containing heavier elements was demonstrated for the first time via the STEM-annular dark-field (ADF)/annular bright-field (ABF) images. In addition, the first electron energy-loss spectroscopy (EELS) 2-dimensional maps of dopants located in a lattice were obtained. These results provided a solid foundation regarding the mechanism of red light emission in doped SrTiO₃. More importantly, a new experimental approach allowing the effective extraction of weak EELS signals from low-dimensional defects was developed and successfully applied to understand the chemical state and coordination of Ti cations within a single monolayer on a reconstructured SrTiO₃surface and the local defect configurations of injected Pr⁺ and Al⁺ ions within SrTiO₃ single crystals.</p> / Doctor of Philosophy (PhD)

Increasingly virtual worlds are being used to provide new and varied learning opportunities by various educational organizations such as universities, K-12 schools, and museums (Dembo, 2008; Ketelhut, Nelson, Clarke, & Dede, 2010; The Forbidden City: Beyond Space and Time, 2008). Simultaneously teacher preparation programs are increasingly being offered online (Minsun & Yoon-Joo, 2009; Saltmarsh & Sutherland-Smith, 2010; Sawchuk, 2009; Schrum, Burbank, & Capps, 2007). However, these more traditional online asynchronous learning experiences are often more challenging in several ways: (a) they require greater self-regulation (Artino & Stephens, 2009; Bol & Garner, 2011), (b) they have been reported as sometimes less effective than face-toace learning (Hudson, 2006; C. L. Peterson & Bond, 2004; Saltmarsh & Sutherland-Smith, 2010; Zirkle, 2002); and (c) they have sometimes been perceived as less effective (E. I. Allen & Seaman, 2011; Huss, 2007). Given the potential of virtual worlds for teaching and learning, it was believed that the use of a virtual world for middle level teacher preparation might provide a solution to some of these reported challenges of online learning. The purpose of this study was to describe and examine the experiences of online middle level teacher candidates using a multi-user virtual environment (MUVE) for teacher preparation. Case study methodology was employed, using multiple data sources including interviews, surveys, observations, snapshots, course artifacts, and the primary researcher’s journal. All data were coded and reviewed iteratively to inductively deduce the nature of the participants’ experiences. The data indicate middle level teacher preparation in the MUVE was more supportive and engaging than traditional online-learning experience, and was useful for learning about middle level education. Though the participants found the experiences to be positive, distractions including personal and technical issues played a role. This study offers insights on the use and implementation of MUVEs in online middle level teacher preparation.

The purpose of the present study was to determine whether or not the combination of normobaric hypoxia and exercise training would enhance adaptations in skeletal muscle over and above that which occurs with the same amount of training under normoxic conditions. Also investigated was the effect of such training conditions on performance as assessed by V0_2max and maximal aerobic capacity (MAC). Ten males performed unilateral cycle ergometry training 3 times per week for 8 weeks so that one leg was trained under normoxic conditions and the other while breathing an hypoxic gas mixture (FI0_2= 13.5%; equivalent to an altitude of 3,292 meters). Absolute power output was kept constant for both conditions and subjects performed both continuous (75% pre-training maximal power output) and interval (100% pre-training maximal power output) training. Needle biopsies were taken from the vastus lateralis of both legs to assess pre- and post-training differences in morphometric and biochemical data. Performance measures included V0_2max and MAC (time to fatigue at 95% pre-training maximal power output) for each leg. Significant increases in V0_2max (p <0.05) occurred in both legs with higher peak ventilation and blood lactate concentrations (p <0.05) post-training. Marked improvements (p <0.05) in MAC were also seen with an increase of 402% in the normoxically-trained leg and 513% in the hypoxically-trained leg. Citrate synthase (CS), succinate dehydrogenase, and phosphofructokinase activity was significantly (p <0.05) higher in both legs following training with a significantly greater (p <0.05) increase in CS in the hypoxically-trained leg. There were no differences in capillary/fiber ratio, capillary density, fiber area, fiber type, and mitochondrial volume density for either condition, pre- or post-training. It is concluded that hypoxia enhanced the muscle oxidative capacity (as marked by cs activity) but was unable to improve performance over and above that which occurs with the same training at sea level. / Thesis / Master of Science (MS)

A new power conditioning system (PCS) for superconductive magnetic energy storage (SMES) is developed and its prototype test system is built and tested. The PCS uses IGBTs for high-speed PWM operation and has a multi-level chopper-VSC structure. The prototype test system has three-level that can handle up to 250-kVA with a 1800-V DC link, a 200-A maximum load current , and a switching frequency reaching 20-kHz with the help of zero-current-transition (ZCT) soft-switching. This PCS has a great number of advantages over conventional ones in terms of size, speed, and cost. Conventional PCSs use thyristors, due to the power capacity of the SMES system. The speed limit of the thyristor uses a six-pulse operation that generates a high harmonic. To reduce the harmonic, multiple PCSs are connected together with phase-matching transformers that need to be precise to be effective in reducing the harmonics. So, the system becomes large and expensive. In addition, the dynamic range of the PCSs are also limited by the six-pulse operation, because it limits the useful area of the PCS applications. By employing a high-speed PWM, the new PCS can reduce the harmonics without using the transformers reducing size and cost, and has wide dynamic range. However, the speed of a switching device is generally inversely proportional to its power handling capacity. Therefore, employing a multi-level structure is one method of extending the power-handling capability of the high-speed device. Switching loss is another factor that limits the speed of the switch, but it can be reduced by soft-switching techniques. The 20-kHz switching frequency can be obtained with the help of the ZCT soft-switching technique, which can reduce about 90% of switching losses from the IGBT during both turn-on and turn-off transients. There are two different topologies of the PCS; the current source converter (CSC) type and the chopper and voltage source converter (VSC) type. In terms of the SMES system efficiency, the chopper-VSC type shows a less volt-ampere requirement of the power device. Therefore, the new PCS system has a chopper-VSC structure. Since the chopper-VSC structure consists of multiple legs that can be modularized, a power electronics building block (PEBB) leg is a good choice; all of the system problems caused by the high frequency can be solved within the PEBB leg. The VSC is built with three of the PEBB legs. Three-phase AC is implemented with a three-level space vector modulation (SVM) that can reduce the number of switching and harmonic contents from the output current. A closed-loop control system is also implemented for the VSC, and shows 600-Hz control bandwidth. The multi-level structure used requires too many high-speed switches. However, not all of them are used at the same time during normal multi-level operation. A new multi-level topology is suggested that requires only two high-speed switches, regardless of the number of levels. Other switches can be replaced with slow-speed switches that can allow additional cost savings. / Ph. D.

Community college transfer students may have to repeat one or more courses at the four-year institution or may have to take more than the required number of courses to obtain a baccalaureate degree. This uncertainty about the transfer of credits and the extra cost in higher education that goes along with it, has come about mainly due to the lack of a working definition for college-level course work. Community colleges need to insure that every course designated as a transfer course will be transferable to a receiving institution. Four-year colleges and universities should expect the courses they accept in transfer to meet the same standards required within their own curricula. The defining characteristics of "college-level" should be identified to facilitate equitable transfer of course credit and insure that transfer students are prepared academically to continue their baccalaureate studies. This study explored the defining characteristics of lower-level college course work in two North Carolina community college and universities, specifically in the areas of study in accounting and business management. Simultaneously, the characteristics of community college-level course work were compared with those of the university. The data gathering methodology utilized the qualitative research method of semi-structured elite-interviewing which allowed for in-dept exploration of the opinions of the knowledgeable individuals involved in the issue being studied. A set of broad, open-ended interview questions were designed to gather information from community college and university professors of accounting and business management. A total of 16 professors were interviewed. The analysis of the interviews included organizing the data into domains; generating categories, themes, and patterns; and comparing and contrasting the two-year analysis with the four-year analysis and the areas of study against each other. There are more similarities than differences in the comments among and between the groups, and the analysis resulted in the identification of ten categories of characteristics defining college-level course work. They include (a) Problem solving using higher level thinking skills, (b) Mastery of the subject matter, (c) Connections within and across disciplines, (d) Student maturity, (e) Essential knowledge base from high school, (f) Course content/professor expectations, (g) Pedagogical issues which include writing, reading, mathematics, student evaluation and textbook, (h) Rigor, (i) Application of the subject matter, and (j) Interpersonal skills. / Ph. D.

Falls from heights are a major concern in the occupational setting, and are often the result of a loss of balance. Lumbar extensor fatigue (LEF) increases postural sway which has been associated with degradations in balance. Study one focuses on the effects of fatiguing time and fatigue level on the duration of these increases in postural sway. Measures of postural sway were collected before fatigue and at 3 minute intervals for 30 minutes following fatigue. LEF had a significant effect on postural sway immediately following fatigue but this effect had only minor dependence on fatigue condition. During the 30 minutes following fatigue, the effects of fatiguing time and fatigue level became more apparent. Longer fatiguing time and higher fatigue levels resulted in significantly greater prolonged effects. While it is important to understand the immediate effect of LEF on sway, this study has demonstrated that the prolonged effect of such fatigue should be considered when addressing falls from heights. Study two attempts to explain the increases in postural sway associated with LEF. The ankle plays a major role in upright standing and degradations in proprioception could contribute to increases in sway, thus the effect of LEF on ankle proprioception was studied. Additionally, the effect of circumferential ankle pressure (CAP) on ankle proprioception was assessed to evaluate it as a potential intervention to improve proprioception. Results showed that both LEF and CAP impaired proprioception. These results may help to explain observed increases in postural sway subsequent to LEF. / Master of Science

Coastal communities face threats of flooding associated with episodic storm events and high tides that are increasing in severity and frequency due to climate change and sea level rise (SLR). The Mid-Atlantic U.S. is experiencing SLR at rates faster than the global average, especially in Hampton Roads, Virginia where the rate of SLR is accelerating due to land subsidence. Adaptation plans for coastal flooding are mostly made at the municipality level, ignoring the propagation of water across its administrative boundaries. Impact assessment at the watershed scale identifies areas where municipalities will need to collaborate to mitigate the flood impact. The main purpose of this project was to evaluate the impact of flooding among watersheds in Hampton Roads and identify those most at risk that overlap one or more municipal boundary. Additionally, this research assessed the impact on land use/cover and population throughout the Hampton Roads region and within a case study watershed. To meet these objectives, we used U.S. Army Corps of Engineers 50-year floodplain and NOAA intermediate SLR scenarios for 2030, 2060, and 2090 to calculate the percent land area inundated for each watershed in Hampton Roads. Further, we assessed the flood impact on populations and specific land use/covers throughout the region for each SLR scenario, as well as within the Elizabeth River watershed. Key findings show that five watersheds will see a greater increase in inundated area than the surrounding watersheds, with two that overlap multiple municipalities. The anticipated land use impacts indicate significant inundation of land occupied by military, followed by commercial, industrial, and wetland covers both in Hampton Roads and within the Elizabeth River watershed. These findings not only highlight the need for more synchronized collaboration on adaptation between municipalities in Hampton Roads, but also provide a framework for the impact assessments in similar settings globally. / Master of Science / Coastal communities face numerous threats of flooding due to storm events and high tides. These events are becoming more frequent due to climate change and sea level rise (SLR). The Mid-Atlantic U.S. is experiencing SLR at rates faster than the global average, especially in Hampton Roads, Virginia where the rate of SLR is accelerating due to sinking land. Water movement does not recognize administrative boundaries but rather reflects physical features of the land. At the same time most plans to combat rising water levels are often made within administrative boundaries. The main objective of this research is to evaluate the flood impacts at the watershed scale and identify areas where localities will need to collaborate to reduce flood impact. This research further explores answers the following questions: 1.)Which watersheds in Hampton Roads are most prone to flooding?; and 2.) How many people will be impacted by flooding, and what kinds of land uses will be impacted? To answer these questions, we used floodplain data and SLR scenarios for 2030, 2060, and 2090 to determine land area inundated for each watershed in Hampton Roads. Further, we summarized population and land use impacts within the floodplain for the entire region, as well as within a case study of the Elizabeth River watershed in Norfolk and Portsmouth. Key findings include five watersheds that will see a greater increase in inundated area with SLR than surrounding watersheds, two of which contain multiple municipalities. Finally, we identified significant impacts for military, commercial, industrial, and wetland land covers both in Hampton Roads and within the Elizabeth River watershed.

Reservoir level and discharge data were collected for three Tennessee Valley Authority (TVA) dams (Chickamauga, Watts Bar and Douglas) on the Tennessee river in the Eastern Tennessee Seismic Zone (ETSZ). Earthquake catalog data was also collected for the ETSZ from 1980-2018. Well levels from 2 U.S. Geological Survey groundwater monitoring wells were also collected. Rainfall data were collected for the ETSZ. Reservoir, well and rainfall data were examined for correlation with earthquake occurrence rates. High Pearson correlation and anti-correlation coefficients (.7-.9) were obtained for the reservoir level and dam discharge volume rates vs monthly earthquake counts. Pearson correlation coefficients for rainfall and well level vs. monthly earthquake counts were small (.0-.2). A large difference in earthquake rates between the months of February (low rate) and April (high rate) over the 39 year study period was observed. The difference in earthquakes rates for February and April are statistically significant at the 95% confidence interval using the two sample Poisson rate test. The high correlations for the reservoir level and flow discharge vs. earthquake counts provides strong evidence of hydro-seismicity occurring in the ETSZ from seasonal fluctuations in reservoir level and discharge flow. / Master of Science / Reservoir level and discharge data were collected for three Tennessee Valley Authority (TVA) dams (Chickamauga, Watts Bar and Douglas) on the Tennessee river in the Eastern Tennessee Seismic Zone (ETSZ). Reservoir discharge and level data was collected for the three reservoirs. Also collected were rainfall data for the study area. This was provided by the TVA. Earthquake and well level data was collected from the USGS. High Pearson correlations for dam discharge and reservoir level vs. earthquake counts provided strong evidence of hydro-seismicity in the ETSZ.

The purpose of this thesis was to assess the repeatability and reproducibility of two high-speed macrotexture measuring systems. The first portion of the study collected macrotexture measurements using the two high-speed systems on the Virginia Smart Road facility and validated the reproducibility of the mean profile depth (MPD) measurements with reference CT Meter measurements. The various data sets were then compared with each other. The objective was to determine whether the two systems are collecting repeatable and reproducible data. The analysis showed that the two high-speed systems investigated have good repeatability (0.105 mm for the Ames and 0.113 mm for the SCRIM) when measuring the average MPD of the sections investigated. The two systems produce measurements that are highly-correlated (Ames R2 = 0.9591 and SCRIM R2 = 0.9157) with the reference ones obtained with the CT Meter. While the Ames systems, with the data processed using the Virginia Tech filter, measures MPD values that are very close to those of the CT Meter, with a virtually zero systematic bias. The SCRIM obtains slightly lower readings. The differences are thought to be due to the filtering of the raw pavement elevation measurements used by the SCRIM processing software to eliminate dropout and spikes in the laser measurements. / Master of Science / The researched compared two different devices used to record data for a surface property of pavement, macrotexture. The macrotexture is a measure of the spaces in between the particles making up the surface of the asphalt. This property is linked to the level of friction on the roadways affecting safety. The readings from each of the devices were validated through a reference device in order to insure they were obtaining reliable results on the Virginia Smart Road. The repeatability and reproducibility of each of the devices was examined to determine whether the two systems were collecting repeatable and reproducible data. It was determined the two devices had good repeatability and were highly correlated with the reference device. The first device called the Ames system obtained measurements very close to those of the reference device, with a virtually zero systematic bias. The second device called the SCRIM system obtained measurements close to the reference device but slightly lower. Through the comparisons and data analysis, an equation permitting users to convert readings from the SCRIM to Ames system and vice versa was computed. Because one device obtains slightly higher readings than the other, this equation is very important in order to have comparable results.