-
Prospective Students
-
Faculty and Staff
-
Current Students
-
Alumni and Friends
The SiC devices have been a strong competitor than the conventional Si devices due to the superior characteristics of high operating voltage, low forward voltage, fast switching speed, and high operating temperature. However, the maturity of SiC technology is still in the progress of catching up with the Si devices, the device cost for SiC MOSFET is still much higher than the Si devices. In addition, the maximum current rating of the available SiC devices are still lower than the Si devices, this also limits the utilization of SiC device in high-power applications. In order to combine the Si IGBT’s advantages of low cost and high overload capability and the SiC MOSFET’s advantages of low switching loss. The Si IGBT and SiC MOSFET are connected in parallel as a new switching unit. In this dissertation, the Si IGBT and SiC MOSFET hybrid switch (Si/SiC HyS) in the application of voltage source converters is investigated.
The United States trains have the highest energy demands in rail transport in the world. More than 90% of the trains are powered by diesel, which aggressively impacts climate change. In addition, the current procedure of charging an electric locomotive is more complicated compared with charging an electric vehicle. Thus, Inductive power transfer (IPT) technology has a huge potential for charging locomotives wirelessly. IPT technology has been extensively studied for EV application in the past decades. However, it has not drawn much attention to railway applications. Due to the unique requirements of the railway system, most of the EV coupler designs are not directly compatible with wireless charging applications for a train. To fill this technical gap, this dissertation discusses the design considerations for railway application and introduces a design of a modular 5-kW IPT system for rail locomotives. A novel W-I coupler is proposed for the 5-kW IPT system, and the system is optimized via ANSYS Maxwell, to achieve high power transfer capability and lower cost. The optimized LCL-S compensated IPT system is also proposed for the railway IPT system to improve the system efficiency. Besides, the factory manufacturing tolerance effect on the power transfer capability was also investigated. A 10% coil tolerance can lead to a power reduction of up to 61.3%. The dissertation proposed a frequency modulated maximum power point tracking method to adjust the inverter frequency to achieve its maximum power point. The simulation and experimental results are demonstrated and analyzed to validate the feasibility of the design.
Cnidarians are part of a complex clade of marine invertebrates that inhabit a variety of extreme environments. The conditions of these habitats are becoming more extreme with the progression of time. These organisms associate with bacteria, which are composed of a larger community, known as the microbiome. To better understand the interactions between individual bacterial isolates and the model cnidarian Nematostella vectensis, it is imperative to investigate and develop methodologies. Here, the impacts of antibiotics were quantified throughout the life stages with a variety of methods. Antibiotic treatment effectively eliminates the resident bacteria of N. vectensis, though the anemone experiences transcriptional changes, even after removal of the stressor. Additionally, two methods to vector bacteria to the terminal host were quantitatively compared: Prey Feeding Method (PFM), and Solution Uptake Method (SUM). The PFM resulted in higher sustained concentrations through two weeks, indicating its potential as a viable method to vector bacteria. Lastly, part of the culturable microbiome was assessed for viability through thermal and saline stressors. Investigation of these methods is imperative to quantifying the interactions between bacteria and the host organism. Together, the assessment of common methodologies in a common cnidarian model contributes directly to understanding individual bacteria from the microbiome of N. vectensis.
The quality and quantity of water in degraded watersheds (i.e.: watersheds undergoing changing land-use, urbanization, agricultural use) may be impaired compared to undisturbed forested watersheds. To enhance the ecosystem function of impaired watersheds, restoration projects have been implemented on a variety of land-use types and at a variety of spatial scales. The 6km2 Reedy Creek urban forested watershed located in Charlotte, North Carolina, has undergone extensive, whole-watershed stream restoration to offset ecosystem degradation caused by historical agricultural use and urban development within the watershed. Streams within the Reedy Creek watershed exhibited channel straightening, disconnection with surrounding floodplains, channel widening, channel incision, and reduced groundwater retention.
This dissertation explores three research topics with the aim of understanding the efficacy of using restoration to reestablish ecological and hydrological functioning within the watershed. I investigated: 1) if whole-watershed stream restoration was successful at increasing recharge to the thick unsaturated zone and ultimately raising groundwater levels by increasing the elevation of stream channels; 2) if the whole-watershed stream restoration approach used in the Reedy Creek watershed in which stream channel morphology and characteristics were altered has changed N retention and seasonal flux; and 3) whether stream restoration has influenced TSS flux within the watershed at both baseflow and stormflow. Findings indicate that 1) restoration was successful at increasing groundwater levels and groundwater retention throughout the watershed; 2) that restoration was successful at decreasing growing season N flux but lead to an increase in N flux during the dormant season; and 3) that restoration was successful at reducing TSS flux at both baseflow and stormflow.
The new era of next-generation intelligent systems is leveraging the usage of smart sensing technology to perform intelligent sensing tasks and collect useful information for different applications. This dissertation discusses secure smart sensing and applications based on the non-intrusive Photoplethysmographic (PPG) sensor, which is commonly available in current wearable devices.
In this dissertation, we first study how to authenticate a user's offline/online signature with data from the PPG sensor. We propose a novel method for offline and online signature authentication, leveraging the widely deployed PPG sensors in wrist-worn wearable devices. The unique blood flow changes in the supplicant's hand movement are being exploited in this system to validate the signature. Our experiments with real-life data sets verify the feasibility and efficiency of the proposed solutions.
In our final work, we focus on a system that can classify a user's lifted weighted object into its corresponding weight label. It leverages the change in the blood volume in the wrist region that occurred due to the strain caused by the different weights being lifted to classify the labels. We believe the importance of PPG sensing in secure smart sensing and applications during this technology era is immense.
Antibiotic resistance (AR) is an ongoing pandemic that is unnoticed by many. Predictably, the environment has been implicated in the widespread of AR in clinical settings. Wastewater treatment plants (WWTPs) are considered major sources for the release of antibiotic-resistant bacteria (ARB) and antibiotic resistance genes (ARGs) into the environment. In this regard, effective wastewater treatment can serve as a barrier against the release of ARB and ARGs into the environment. Moreover, addressing AR threats involves eliminating the development of new resistant bacterial traits by developing alternative antimicrobials. This study presents advanced oxidation processes (AOPs) that utilize the strong oxidizing power of hydroxyl radical and sulphate radical as promising technologies for ARG degradation. Also, we presented antimicrobial nanoparticles (NPs) as alternatives to conventional antibiotics. The reaction kinetics study investigated the degradation of intracellular (i-) and extracellular (e-) plasmid-encoded tetA, ampR and sul1 ARGs using UV254, hydroxyl radical and sulphate radical UV-based AOP (UV254/H2O2 and UV254/S2O82-, respectively). The degradation of tetA, ampR and sul1 was quantified using quantitative polymerase chain reaction (qPCR). Culture-based horizontal gene transformation experiments were used to estimate the deactivation kinetics of pCR™2.1-TOPO AR plasmid. Furthermore, we investigated the antibacterial synergy of photosensitizer (PS)-AgNP conjugates using protoporphyrin IX (PpIX) as PS. The last objective assessed the use of nanoscale monocaprin (NMC) as a first line of defense antimicrobials against the entrance of intracellular pathogens like E. coli and SARS-CoV-2 using phi6 as a virus surrogate.
Every student deserves the opportunity to access and make progress in the general curriculum. Teachers have reported difficulties in meeting this goal for students with extensive support needs (ESN) who do not yet demonstrate foundational academic skills, such as in the areas of literacy and numeracy. It becomes even more difficult once students enter high school and the gap between their instructional and grade-level widens. Researchers have evaluated different interventions to teach both foundational and grade-level skills to students with ESN in the area of mathematics. This study builds on that research by evaluating the effects of an intervention package combining modified schema-based instruction (MSBI) and embedded simultaneous prompting (SP) to teach secondary students with ESN who do not demonstrate numeracy skills to solve simple linear equations (e.g., 3+x=9) and to identify numerals 1–9 concurrently. The experimental design was a single-case multiple probe across numeral sets replicated across participants, who were two high school males with ESN and their instructors, a paraeducator and a special education teacher who implemented the intervention. The intervention was not effective to teach numeral identification or solving simple linear equations, nor did the students generalize numeral identification to real-world settings. However, the instructors did find the study procedures to be socially acceptable and hypothesized that the students would eventually reach mastery criterion, given additional time in the intervention. The findings from this study can be used to guide future research designed to support the needs of secondary students with ESN who do not yet demonstrate foundational academic skills.
Green burial places are cemeteries and funeral homes that embrace green burial practices by providing green burial funeral services and educating their clients about green burial options. A green burial place within a cemetery may be a part or whole cemetery that is dedicated to following green burial protocol. Green burial involves the use of biodegradable containers rather than steel or hardwood caskets. The decedent is not embalmed and is buried directly in the ground instead of within a burial vault. The grave is typically more shallow than contemporary burials; this encourages natural decomposition of the body. Green burial places within cemeteries are designated areas where green burials can happen and can contribute to the overall ecological well-being of the land.
Although not new in concept, green burial places are not as abundant or accessible as green burial advocates such as the Green Burial Council, International 501(c)(3) non-profit would like. Compared to contemporary burial in the United States, green burial has greater ecological and social benefits, as it reduces resource consumption standard to contemporary burial and supports regulatory and social ecosystem services. However, there are many funeral homes and cemeteries who do not currently provide green burial. Therefore, this dissertation asks and answers the overarching question: What are the opportunities for successful green burial placemaking that address the obstacles faced and anticipated by death care professionals?
This dissertation uses qualitative methods, specifically grounded theory methods, to answer the overarching question. I do this via three lines of inquiry: 1) examining obstacles to green burial placemaking that are presented by a sample of funeral directors from across the United States (§5.1 - §5.3), 2) Analyzing current death care consumers’ awareness of and attitudes towards green burial (§5.3 - §5.4), and 3) Uncovering the opportunities that successful green burial placemakers employed to successful create green burial places (§5.5 - §5.7).
The key methods used in this study are semi-structured interviews and online surveys, which have produced robust qualitative data. Semi-structured interviews were used to ascertain the perspectives and experiences of funeral industry professionals who have successfully started and continue to operate a green cemetery. The purpose of these interviews is to provide an understanding of the local and regional obstacles to green burial provision that death care providers anticipated, faced, and overcame. A total of nine interviews were conducted, and ten people were interviewed. In one case, the semi-structured interview involved two interviewees. The interviewees represented green burial cemeteries across the Mid-Atlantic States of North Carolina, Tennessee, and Virginia.
Two questionnaires were developed to understand obstacles at a national level. The first questionnaire was targeted towards funeral directors; the questions were targeted to understand funeral directors’ level of knowledge about green burial, their willingness to provide green burial to their families, and the obstacles that they anticipate or currently face when considering whether to provide green burial. The second questionnaire, informed by both the interviews and the responses from the funeral directors, was directed at death care consumers—adults in the United States, eighteen years or older. The purpose of this survey was to explore one specific obstacle that death care providers have identified: there is not a market for green burial, i.e. no one knows about green burial and therefore no one asks for green burial. The consumer survey in the proposed research asks consumers to explain what they would like to have happen to their body after death. Consumers are then presented with the definition of green burial and asked if this is something that they would be interested in. Responses are again analyzed using grounded theory methods.
The grounded theory that emerges from the proposed research will make contributions on two fronts. First, the knowledge will directly benefit the Green Burial Council International 501(c)3, a non-profit whose mission is to make green burial more accessible via educational outreach to both death care providers and consumers. As a member of the board of directors, I am committed to making practical use of the knowledge uncovered in this research. Second, this research will contribute to the scholarly pursuit present and legitimized by Palko (2021) to understand the relationships between death care decision-making and ecological and social consciousness.
