This dissertation describes methods of mitigating radio frequency interference (RFI) in the frequency range 10-100 MHz, developing and evaluating coherent methods with which RFI is subtracted from the afflicted data, nominally resulting in no distortion of the underlying signals. This approach is of interest in weak signal applications such as radio astronomy, where the signal of interest may have interference-to-noise ratio much less than one, and so can be easily distorted by other methods. Environmental noise in this band is strong and non-white, so a realistic noise model is developed, with which we characterize the performance of signal parameter estimation, a key component of the proposed algorithms. Two classes of methods are considered: "generic" parameter estimation/subtraction (PE/S) and a modulation-specific form known as demodulation-remodulation ("demod--remod") PE/S. It is demonstrated for RFI in the form of narrowband FM and Broadcast FM that generic PE/S has the problem of severely distorting underlying signals of interest and demod-remod PE/S is less prone to this problem. Demod-remod PE/S is also applied and evaluated for RFI in the form of Digital TV signals. In both cases, we compare the performance of the demod-remod PE/S with that of a traditional adaptive canceling method employing a reference antenna, and propose a hybrid method to further improve performance. A new metric for "toxicity" is defined and employed to determine the degree to which RFI mitigation damages the underlying signal of interest. / Ph. D.

Irreversible electroporation (IRE) is an energy directed focal ablation technique. This procedure typically involves the placement of two or more electrodes into, or around, a region of interest within the tissue and administering a sequence of short, intense, pulsed electric fields (PEFs). The application of these PEFs results in an increase in the transmembrane potential of all cells within the electric field above a critical value, destabilizing the lipid bilayer of the cellular membrane and increasing the cell-tissue permeability. For years, many have used this phenomenon to assist the transport of macromolecules typically unable to penetrate the cell membrane with the intent of avoiding cell necrosis or irreversible electroporation. More recently, however, irreversible electroporation has proven to be a successful alternative for the treatment of cancer. Proper tuning of the pulse parameters has allowed for a targeted treatment of localized tumors, and has shown immense value in the treatment of surgically inoperable tumors located near major blood vessels and nerves. While it is critical to ensure sufficient treatment of the target tissue, it can be equally vital to the treatment and patients overall outcome that the pulsing conditions are set to moderate the associated thermal effects with the electroporation of biological tissue. The development of thermal mitigation strategies for IRE treatment is the focus of this dissertation. Herein, the underlying theory and thermal considerations of tissue electroporation in various scenarios are described. Additionally, new thermal mitigation approaches with the intention of maintaining tissue temperature below a thermally damaging threshold, while also preserving or improving IRE lesion volume are detailed. Further, numerical models were developed and ex vivo tissue experiments performed using a perfused organ model to examine three thermal mitigation strategies in their ability to moderate temperature. Tests conducted using thermally mitigating treatment delivery on live tissue confirm the capacity to deliver more energy to the tissue at a thermally acceptable temperature, and provide the potential for a replete IRE lesion. / Doctor of Philosophy / Irreversible electroporation (IRE) is a minimally invasive therapy utilized to treat a variety of cancers. This procedure involves the delivery energy in the form of pulsed electric fields (PEFs) through two or more needle electrodes. These PEFs destabilize the cell membrane, increase the cell-tissue permeability, and ultimately induce cell death for any given cell within the targeted treatment region. Over the years, this treatment modality has shown a great deal of promise in the treatment of unresectable tumors in which the tumor is positioned near or around sensitive regions making the surgical removal of the tumor impossible and thermal ablation techniques limited in their ability to treat without irrevocably damaging the underlying tissue architecture and other critical surrounding structures. Thus, it can be vital to the treatment and patients overall outcome that the IRE therapy is set to moderate any associated thermal effects with the electroporation of biological tissue. However, the design of an electric field that simultaneously maps the entire region of interest for a single treatment and avoids undesirable thermal effects can be challenging when treating larger or irregularly shaped volumes of tissue. Thus, in this dissertation, we demonstrate various treatment delivery methods/ enhancements to reduce temperature rise during IRE therapy. The underlying theory of tissue electroporation and associated thermal considerations are described to provide a foundation and general context. Additionally, novel approaches to tissue electroporation therapy with the intention of maintaining tissue temperature below a thermally damaging threshold throughout treatment are detailed.

Adherent microbial communities, known as biofilms, are a major contributing factor in the incidence of healthcare-associated infections (HCAIs). HCAIs are responsible for annually causing 100,000 deaths and medical expenses estimated to be $35-45 billion. Physical and chemical surface modification techniques are thought to be critical in the fight against biofilm formation within medical settings. Nanoscale structural features have been found to have significant effects on bacterial adhesion and biofilm formation, but their effects on fungal pathogens are less explored. This thesis systematically explores the effect of surface topography in the form of nano and microscale polymeric fibers (~0.4-1.2 µm in diameter) on biofilm formation and virulence of a common HCAI-causing fungal pathogen, Candida albicans. We show that both C. albicans attachment density and differentiation to its virulent phenotype significantly vary with fiber diameter and spacing on polymeric fiber-coated surfaces. We further show that high throughput and high content techniques, such as Raman spectroscopy, can be used to track environmental and physical effects on the organism's resulting morphology and associated virulence. Findings from this thesis will inform the design of antifouling surfaces including implantable medical devices. In a prototypical example, we demonstrate the use of fiber coating to modulate C. albicans attachment on polyurethane, silicone, and latex catheters. / Master of Science / Microbial communities that adhere to surfaces, known as biofilms, are largely associated with incidence of healthcare-associated infections (HCAIs). HCAIs are responsible for annually causing 100,000 deaths and medical expenses estimated to be $35-45 billion. Modification of surfaces using physical and chemical techniques is believed to be critical in the fight against biofilm formation on surfaces within medical settings. Nanoscale structural features have been found to have significant effects on bacterial adhesion and biofilm formation, but their effects on fungal pathogens have not been extensively studied. This thesis focuses on the effect of surface topography, or textures, in the form of nano and microscale polymeric fibers (~0.4-1.2 µm in diameter) on biofilm formation and disease-causing ability, or virulence, of a common HCAI-causing fungal pathogen, Candida albicans. We show that both C. albicans attachment density and differentiation to its virulent form significantly vary with fiber diameter and spacing on polymeric fiber-coated surfaces. We also show that high throughput and detailed imaging techniques, such as Raman spectroscopy, can be used to track environmental and physical effects on the organism's resulting morphology and associated virulence. Findings from this thesis can be used to aid in the design of surfaces that discourage biofilm formation, including implantable medical devices. We demonstrate the use of fiber coating to vary C. albicans attachment on polyurethane, silicone, and latex catheters in one of our studies.

A cost effective method of rollover mitigation in vehicles is presented. The method was designed so that some of the system states were measured by sensors that are already available on most vehicles and so that other states could be measured with relatively low cost sensors. Also, the control algorithm was designed to be implementable using a series of look up tables and computationally efficient equations to enable the use of low-cost controller platforms. These look up tables and equations can be modified to change the conservativeness of the method as well as to configure the method for use on almost any 4-wheeled vehicle. Lastly, the proposed mitigation technique was designed to be directly implementable with existing vehicle hardware. To develop this method, a vehicle model was created using several advanced computer packages including SolidWorks 2008™, MATLAB ®, Simulink®, and SimMechanics™. Once created, the model was outfitted with virtual sensors that represent data from realistic sensor types. A detection algorithm was designed around the hypothesis of a stability boundary utilizing the sensor data to detect impending rollover. Finally, a mitigation algorithm was designed to limit throttle and braking upon impending rollover. This algorithm was defined using the basic principles of end-stop control, but was adapted to work appropriately with this scenario. To conclude this research, two simple maneuvers were used to verify the effectiveness of this system to mitigate vehicle rollover. This research was government sponsored and in some instances utilized secured data. Due to the nature of this material, some data has been omitted from this document. / Master of Science

The accuracy of the growing season used by regulators in hydric soil and wetland hydrology and the validity of ignoring land use in these definitions is questionable. This study compared measured air and soil temperature with various growing season dates and indicators, and determined the relationships between the hydrology, air and soil temperature. Water table depths, air temperature at 1-m height, soil temperature at 15-, 30-, and 50-cm depths, and CO₂ efflux were measured at 12 plots representing three landuse treatments (forest, field, and bare ground) at two restored wet flats in the thermic Great Dismal Swamp ecosystem. The forest was driest treatment. The forest air was the warmest in winter and coldest in summer, opposite of the bare ground. The forest soil at 50 cm was the warmest in winter and coolest in summer, opposite of the bare ground. Land use affected hydrology, air, and soil temperatures through the presence of surface litter and differences in shading, albedo, and ET. The regulatory frost-free period fell in between the measured frost-free period and the measured 5°C soil temperature period. Based on CO₂ efflux and soil temperature at 50 cm, the biological growing season of native plants and microbes should be year-round for forested areas, one week shorter for early-successional fields, and two weeks shorter for active cropland rather than March to November for all land uses. Changing the growing season definition of forested, thermic wet flats to year-round designation must be considered and studied carefully to avoid jeopardizing wetland hydrology qualifications. / Master of Science

[pt] Riscos geológicos, tais como os escorregamentos, são os maiores causadores dos desastres naturais em ambientes urbanos. Além dos impactos ambientais negativos, este fenômeno implica em consequências socioeconômicas, uma vez que existe a necessidade de reparos imediatos da área degradada. A avaliação de risco, principalmente em áreas urbanizadas, é necessária para se evitar os possíveis desastres e assegurar a qualidade de vida da população no entorno. No presente trabalho, a avaliação de risco foi realizada em três seções da encosta do Morro Dois Irmãos, localizada na Gávea, Rio de Janeiro, que sofreram sucessivas rupturas após intensas precipitações. A avaliação e classificação do risco pela abordagem qualitativa foi determinada utilizando a metodologia proposta pelo Ministério das Cidades e IPT e do GIDES-CPRM através da realização da vistoria em campo. A encosta foi classificada como de risco alto a muito alto ao escorregamento. Os resultados da abordagem quantitativa, obtidos pelas análises determinísticas de estabilidade com base no método de Morgenstern-Price, evidenciaram que as superfícies de ruptura crítica das seções apresentam fator de segurança menor que 1,5. Já nas análises probabilísticas de estabilidade FOSM, foram obtidas probabilidades de ruptura de 0,19, 0,14 e 0,08 sendo as seções classificadas como Perigoso no que diz respeito ao nível de desempenho esperado. Com isso, o índice de vulnerabilidade local encontra-se na faixa de 0,7 a 0,8. Para as seções analisadas, são necessárias ações como forma de mitigar e recuperar a área ambiental e socialmente. / [en] Geological hazards, such as landslides, are the biggest cause of natural disasters in urban environments. In addition to the negative environmental impacts, this phenomenon implies socioeconomic consequences, since there is a need for immediate repairs to the degraded area. Risk assessment, especially in urbanized areas, is necessary to avoid possible disasters and ensure the quality of life of the surrounding population. In the present work, the risk assessment was carried out in three sections of the slope of Morro Dois Irmãos, located in Gávea, Rio de Janeiro, which suffered successive ruptures after intense rainfall. The assessment and classification of risk by the qualitative approach was determined using the methodology proposed by the Ministry of Cities and IPT and GIDES-CPRM through field inspection. The slope was classified as high to very high slip risk. The results of the quantitative approach, obtained by deterministic stability analysis based on the Morgenstern-Price method, showed that the critical rupture surfaces of the sections have a safety factor lower than 1.5. In the FOSM stability probabilistic analyses, rupture probabilities of 0.19, 0.14 and 0.08 were obtained, with the sections classified as Dangerous with regard to the expected performance level. As a result, the local vulnerability index is in the range of 0.7 to 0.8. For the analyzed sections, actions are needed as a way to mitigate and recover the area environmentally and socially.

The nation's Section 404 permitting program, of the Clean Water Act (CWA), represents one of the longest regulatory histories of designing and implementing credit trading programs to satisfy regulatory requirements. The role and the function of in-lieu fee (ILF) programs in supporting this regulatory structure have undergone a substantial change. For the first time in the history of the Sec. 404 program, 33 CFR Part 332 and 40 CFR Part 230, Subpart J (the "2008 mitigation rule" or "rule"), prioritizes the use of off-site mitigation over on-site-mitigation. Additionally, the rule prioritizes advanced, third-party mitigation; especially as achieved through mitigation banks; over any off-site compensatory mitigation provided by ILF programs (33 CFR 332.3(b)(1)). This new regulatory environment favors the use of commercial mitigation bank credits while acknowledging that the limited permittee demand of off-site mitigation credits, in particular areas, justifies the continuing need for ILF programs (Corps and EPA 2008, p.19606,19611). This research examines how regulatory officials use ILF programs under the 2008 mitigation rule, and, it determines the extent to which ILF programs are capable of fulfilling the role envisioned for them under the 2008 mitigation rule. Simulation results indicate that commercial mitigation banks cannot meet risk adjusted returns under limited credit demand conditions. ILF programs offer some additional financial capacity to fill the void in commercial bank coverage; but, this potential is limited in low demand conditions. Furthermore, empirical case studies of a Virginia and Georgia provide evidence that regulatory officials rely on ILF programs to provide off-site compensatory mitigation almost exclusively in the absence of private credit supply, as intended in the 2008 rule. Evidence in Georgia and Virginia also indicate that, in some situations, ILF programs face difficulties in providing mitigation under the constraints of limited demand and more stringent regulatory requirements. / Master of Science / National permitting programs require people that impact wetlands or streams to offset unavoidable, adverse impacts by improving wetlands or streams elsewhere, a process called compensatory mitigation. A new regulatory rule, approved in 2008 (33 CFR Part 332 and 40 CFR Part 230, Subpart J), prioritizes that mitigation is provided at larger projects off-site of the impact. Key policy questions of “who should provide the mitigation?” and “when the mitigation should be provided” were an important part of the debate during the rule’s development. Wetland and stream mitigation may be provided by commercial (for profit) businesses, called mitigation banks. Commercial banks make wetland/stream improvement projects before permitted (adverse) impacts occur in anticipation of selling wetland/stream “credits” (quantified levels of improvement). Off-site mitigation may also be provided by in-lieu fee (ILF) programs operated by the government or nonprofit organizations. ILF programs first accept funds from permittees and then construct mitigation projects once sufficient funds have been collected, thus creating a lag between adverse impact and compensatory mitigation. The 2008 regulatory rule favors the use of commercial mitigation bank credits over ILF credits, but allows regulatory officials, under certain circumstances, to use ILF credits when commercial bank credits of the appropriate type are unavailable. This research examines how regulatory officials use ILF programs, and it investigates the extent to which ILF programs are financially capable of providing off-site mitigation in situations where the appropriate commercial credits are unavailable. A financial simulation model is developed to examine the feasibility of mitigation projects under different costs and credit demand conditions. Results indicate that commercial mitigation banks cannot meet financial objectives under limited credit demand conditions. ILF programs offer some additional financial capacity to fill the void in commercial bank coverage, but ILF programs also face financial limitations under conditions with low demand for credits. Empirical case studies of Virginia and Georgia provide evidence that regulatory officials rely on ILF programs to provide off-site compensatory mitigation almost exclusively in the absence of a private credit supply, as intended in the 2008 rule. However, evidence in Virginia and Georgia also affirm that ILF programs face difficulties in providing mitigation in some situations of limited demand and stringent regulatory requirements.

Vehicle modeling and simulation have fast become the easiest and cheapest method for vehicle testing. No longer do multiple, intensive, physical tests need be performed to analyze the performance parameters that one wishes to validate. One component of the vehicle simulation that is crucial to the correctness of the result is the tire. Simulations that are run by a computer can be run many times faster than a real test could be performed, so the cost and complexity of the testing is reduced. A computer simulation is also less likely to have human errors introduced with the caveat that the data input into the model and simulation is accurate, or as accurate as one would like their results to be. Simulation can lead to real tests, or back up tests already performed. The repeatability of testing is a non-issue as well. Tire models are the groundwork for vehicle simulations and accurate results cannot be conceived without an accurate model. The reason is that all of the forces transmitted to and from the vehicle to the ground must occur at the tire contact patches. This presents the problem of obtaining a tire model. Tire companies do not readily give out tire data since the tire industry is still as much "black art" as it is science. For tire data one must begin with a testing apparatus. The test rig must be accurate and must have been validated before results can be used. This thesis presents the process of the design and construction of a portable tire test rig. It then will discuss tire testing procedures and validation techniques. The resulting data shows good correlation between test data and known tire test data from flat track testing provided by a tire manufacturer. Then, a simple rollover study of a military truck will be compiled in TruckSim. Lastly, a control method for the rollover case will be designed and implemented. The results of the roll control simulation are positive. The study shows an increase in dynamic roll stability due to the implementation of the control algorithm. / Master of Science

Catamarans provide vast deck space, high thrust efficiency, and excellent transverse stability, however, in rough conditions they can be susceptible to deck slamming from head seas or bow diving in following seas and a pitch-roll coupling effect that can lead to uncomfortable corkscrew motion under bow-quartering seas. A new class of catamaran called Wave-Adaptive Modular Vessels (WAM-V™) aims to help mitigate oceanic input from the cabin by allowing for the relative motion of components not common to classic catamaran design. This thesis presents a set of multi-body dynamics simulation models created for two active WAM-Vs™ along with analysis on their suspension characteristics. Both models provide conclusive and realistic results, with the final model being validated against on-water testing data from a 12-ft unmanned prototype WAM-V. The first of these simulations serves primarily as a tool to evaluate WAM-V™ response characteristics with respect to a variety of parametric variations. The modeling environment is highlighted along with details of the parametric simulation and how it was created. The results fall in line with our expectations and are presented along with analysis of the sensitivity of each parameter at three longitudinal locations. The final simulation attempts to model the response of a 12-ft unmanned surface vessel (USV) prototype of the WAM-V™ configuration. Testing data is collected, processed, and applied to the model for validation of its prediction accuracy. The results of the sea tests indicate that the simulation model performs well in predicting USV motions at sea. Future considerations for testing WAM-Vs™ can include changes in suspension and mass parameters as well as limiting particular degrees-of-freedom by making their joints rigid. / Master of Science

This thesis examines the relationships between rising water levels, vulnerable land, and sedimentation within the Chesapeake Bay watershed. Climate induced sea level rise threatens low lying coastal land, especially in regions of continuing subsidence such as the Chesapeake Bay. Alterations to shorelines over time have impacted the ability of coastal landscapes to capture and build up sediment, exposing them to continual erosion. The low lying neighborhood of Belle View along the Potomac River is the focus of the investigation due to its vulnerability to flooding and its cultural and ecological connections to the adjacent landscapes of Dyke Marsh and the George Washington Memorial Parkway. Through careful placement of breakwater infrastructure, sediment will build over time as the water rises, mitigating the effects of coastal flooding in this region. Alterations to the landscapes of the marsh and parkway allow for their cultural and recreational values to be strengthened over time as the landscape adjusts to the rising sea level. / Master of Landscape Architecture / Climate change, or the belief that human activity is altering the earth's climate, is projected to increase the occurrence of flood events due to water levels rising over time from glaciers melting. Previously, shorelines have been hardened with levee or seawall infrastructure to creates a barrier between the water and developed land. Hardened shorelines may increase water velocity and reflect wave energy in riverine landscapes, consequentially disturbing natural shorelines. This disturbance leads to the gradual loss of sediment over time and therefore a loss of ground elevation. When landscapes lose elevation, they become more vulnerable to rising water levels and flooding. This relationships between shoreline types, sedimentation, rising water, and vulnerability inspired me to discover and design a threatened landscape that would capture sediment within the river's water column to build elevation over time and protect the adjacent development from rising water. The area encompassing the low lying neighborhood of Belle View, Dyke Marsh, and the George Washington Memorial Parkway along the Potomac River is the focus of the investigation due to its vulnerability to flooding. With a careful understanding of sediment capture infrastructure dynamics, the design introduces breakwaters on the site to allow sediment to build over time as the water rises. This research and design thesis demonstrates a strategy to create landscapes that will evolve over time to mitigate future flooding events and create more resilient landscapes.