Doctor of Philosophy (Ph.D.), University of Dayton, 2023, Electrical Engineering

Doping of metal oxide semiconductors with other metal oxides or metal ions is an effective way to improve the sensing performance of gas sensors. In this dissertation, In-doped SnO2 thin film is used in different gas sensing platforms, such as surface acoustic wave (SAW) transducers and impedance spectroscopy, for the detection of volatile organic vapors at room temperature. The properties of the piezoelectric materials play a critical role in determining the sensing response of the SAW based gas sensors. Recently, various ferroelectric materials have been used as piezoelectric materials in the manufacturing of SAW based gas sensors. Among them, Ba0.6Sr0.4TiO3 (BST) has emerged as a potential candidate due to its high acoustic velocity and electromechanical coupling coefficient. In the development of gas sensors, noble metals are extensively used as electrode or transducer materials. However, noble metals are expensive and scarce. On the basis of their favorable electrical conductivity, 2D metallic transition-metal dichalcogenides (VTe2, NbTe2, and TaTe2) are emerging as promising candidates for use in 2D electronic devices. In this dissertation, the design, fabrication, and validation of BST-based SAW and NbTe2- based impedance spectroscopy sensor platforms with the In-doped SnO2 sensing film were demonstrated. Different deposition and photolithography techniques were applied to fabricate the sensors. The morphology, structural, elemental compositions, and electrical properties of the as-deposited samples were characterized by HRSEM, XRD, EDS, and the four-point probe sheet resistance method. The samples exhibited excellent film adhesion. Furthermore, the sensing performances of the SAW and impedance spectroscopy-based gas sensors towards ethanol and humidity were evaluated at room temperature. The SAW sensors exhibited a significant negative frequency shift, which can be attributed to the mass and electric loading effects o (open full item for complete abstract)

Committee: Guru Subramanyam (Advisor) Subjects: Electrical Engineering; Materials Science; Nanotechnology

Doctor of Philosophy, The Ohio State University, 2006, Materials Science and Engineering

The objective of this study was to quantitatively study localized corrosion, especially exfoliation corrosion (EFC) of high strength aluminum alloys and to investigate the mechanism of exfoliation corrosion with a focus on the effects of alloy temper, microstructure, relative humidity (RH) and mechanical stress. A new technique, Exfoliation of Slices in Humidity (ESH), was developed for the determination of exfoliation corrosion (EFC) susceptibility and quantification of EFC kinetics. This technique involves in exposing properly oriented and unconstrained samples to high humidity following an electrochemical pretreatment. The EFC kinetics was determined by measuring the width of the central unattacked region of the samples. The ESH results show the capability of the ESH test to discriminate between plates of varying susceptibility and to determine EFC rates quantitatively. Optical microscopy and analytical TEM were used to investigate the effects of microstructure and local chemistry at grain boundary on EFC susceptibility. Alloys with more elongated grain shape are more susceptible to EFC and a high Zn content in grain boundary precipitate free zone relates to a high susceptibility. The effects of RH, temper and applied stress on EFC kinetics of AA7178 were investigated by ESH tests. The critical RH for EFC propagation in AA7178 was found to be about 56% and the EFC kinetics increased with RH. ESH tests provide a quantitative description of the temper effect on EFC kinetics. The effects of applied compressive and tensile stresses on EFC kinetics were studied using a four-point bending jig. Compression accelerated EFC significantly and tension reduced kinetics. An equation describing the effects of RH, stress and time on EFC kinetics was developed based on the ESH results using Eyring model. In situ X-ray radiography was used to characterize intergranular and exfoliation corrosion in high strength Al alloys. The samples were either exposed to sodium chloride solutio (open full item for complete abstract)

Committee: Gerald Frankel (Advisor) Subjects: Engineering, Materials Science

Doctor of Philosophy, The Ohio State University, 2024, Environmental Science

Every occupied indoor environment, including spacecraft, has its own unique microbiome. This composition and quantity of the microbiome present in these environments is dependent on many factors including building materials, occupants cleaning habits, presence of pets, and environmental conditions inside. Indoor microbes can be found in dust, which is generated in both Earth- and space-based built environments, a unique nutrient rich substrate that can act as both a source and sink especially in Earth-based buildings with carpet. Unintended microbial growth indoors can affect the health of the occupants and cause premature failure of building materials via biodegradation. Water is the limiting factor for growth, with moisture in the indoor air sufficient to support microbial growth indoors, especially for fungi. However, we need an improved understanding of microbes and their growth in indoor spaces to ensure healthier environments. The goal of this paper is to provide these examples and show how they fit into the concepts of One Space and bioastronautics. One Space is the idea that the built environment and human health are interconnected based on the One Health principles. Bioastronautics is the study of living organisms in spaceflight conditions. These two ideas complement each other and provide ample opportunity for interdisciplinary collaborations that can lead to innovative solutions to making healthier, safer, and more comfortable built environments on Earth and in space. In these studies, we focus on the intersection between microbiology and the built environment, by looking at the indoor dust microbiome in Earth- and space-based built environments like the International Space Station (ISS). We show that bacteriophages in common Earth-based building materials such as carpet and house dust can remain viable and infectious for up to several days making it a potential source of exposure. We also found the viral genetic material (RNA) remained stable for weeks t (open full item for complete abstract)

Committee: Karen Dannemiller (Advisor); John Horack (Committee Member); Michael Bisesi (Committee Member); Natalie Hull (Committee Member) Subjects: Environmental Health; Environmental Science; Microbiology

Doctor of Philosophy, The Ohio State University, 2023, Materials Science and Engineering

7xxx series aluminum alloys are exposed to complex atmospheric environments when they are used in airframe components. If contaminant salts are deposited onto these components, humid air can lead to surface electrolyte droplets that accelerate crack growth. When coupled with a cyclic load, these environments can lead to corrosion fatigue (CF), a major failure mode for aircraft components. Conventional test environments consisting of room temperature moist air exposures or full immersion in aqueous chloride solutions may not fully capture the effect of the environment on fatigue crack growth for these alloys and better estimation of fatigue lifetimes may be achieved through CF testing in more realistic environments. In this work, complex atmospheric environments consisting of moist air ranging from 25 to 85% RH and varied temperature from -10 to 25°C were examined in samples with surface NaCl deposited in the range of 10 to 1000 µg/cm². The effects of these atmospheric environments on the CF performance of AA7085-T7451 were evaluated and compared to conventional testing environments. Corrosion fatigue crack growth kinetics were measured as function of loading frequency using fracture mechanics specimens loaded with 300 µg/cm² of NaCl and exposed to 80% RH air. These atmospheric tests demonstrated crack growth rates up to five times higher than equivalent testing in 40% RH air. Atmospheric testing was at least as aggressive as full immersion testing in aqueous chloride environments with crack growth proceeding approximately twice as fast in an equivalent chloride solution of 23.1 wt.% NaCl when loading frequency exceeded 3 Hz. After this, the effects of RH were evaluated by measuring crack growth kinetics while subjecting samples to wet-dry cycling. These tests showed the humidity needed to cause crack growth acceleration was typically in the range of 78–85% RH. The humidity needed to cause crack growth deceleration was dependent on humidity ramp (open full item for complete abstract)

Committee: Jenifer Locke (Advisor); Eric Schindelholz (Committee Member); Gerald Frankel (Committee Member) Subjects: Aerospace Materials; Materials Science

Master of Science in Polymer Engineering, University of Akron, 2021, Polymer Science

Torsional shape memory property of spider Major Ampullate (MA) silk is a fascinating, yet less well-established property in spider's behavioral ecology. A MA silk that first oscillates near the twist angle and form a new equilibrium, over a long period of time, followed by returning to the starting twist angle without using any other external factors is defined as torsional shape memory. Because the mechanical properties of MA spider silk are a strong function of humidity (change in diameter and length in humidity; supercontraction), our hypothesis is that the torsional shape memory for the MA silk will depend on humidity. Here, MA silk of Larinoides cornutus was twisted in different strain twist angles and different humidity using a magnetic field and allowed for free oscillation. We found that the MA silk of Larinoides cornutus does not exhibit shape memory properties for small twists angles (30˚ and 90˚) for humidity at 30%, 60% and 90%, which is different from the published result of Araneus diadematus. For a large twist angle of 270˚, the MA silk undergoes plastic deformation for all values of humidity studied here. This study provides the evidence of how humidity and twist angle affect the torsional modulus of MA silk of Larinoides cornutus.

Committee: Tianbo Liu (Committee Member); Ali Dhinojwala (Advisor); Nita Sahai (Committee Member) Subjects: Biophysics; Polymers

Master of Science (MS), Bowling Green State University, 2019, Biological Sciences

Understanding responses of food webs to climate change is vital, especially when those food webs influence important ecosystem services, like pollination, valued at over $3 billion globally. Historically the focus has been on single factors (e.g. temperature) and mechanisms (e.g. change in mortality). However, global climate change is predicted to alter temperature and moisture simultaneously. Additionally, thermal and hygric physiological performance and species interactions are both likely mechanisms underlying food web responses to changing climate. The current lack of a synergistic, mechanistic understanding of how food webs respond to key aspects of global climate change is a major research gap. Here we questioned how changes in temperature and moisture may alter food web composition through filtering of sensitive taxa (physiological limits) or by modifying consumption (trophic interactions). We placed bumblebees (Bombus impatiens) and tomato plants (Solanum lycopersicum) in 32 mesocosms within a greenhouse in Bowling Green, OH in July 2018. We explored differences in fruit set and tomato quality by excluding half of the flowers from buzz-pollination via bags. Additionally, all mesocosms were categorized in four abiotic treatments (cool/dry, cool/moist, hot/dry, hot/moist), and were paired based on predator presence (with or without Green Lynx spiders (Peucetia viridans)). We found that predatory spider body temperature was significantly higher when more moisture was available in the environment (SE=0.779, df=28.0, t-ratio=-3.661, p=0.005). Our findings also indicate that if predatory spiders are more hydrated, they change their behavior and expose themselves more to heat (χ2=4.028, df=1, p= 0.045). Furthermore, this behavioral change influences spider consumption of bumblebees. When more moisture was available in the environment, spiders ate significantly more bumblebees (χ2=8.924, df=1, p=0.003). However, there were no significant differences between the h (open full item for complete abstract)

Committee: Kevin McCluney Dr. (Advisor); Helen Michaels Dr. (Committee Member); Daniel Wiegmann Dr. (Committee Member) Subjects: Behavioral Sciences; Biology; Climate Change; Conservation; Ecology; Entomology

Doctor of Philosophy, University of Akron, 2019, Polymer Engineering

Alkyds, one of the most commonly used binders for coating systems, are modified polyesters derived from seed oils. They find utility in several coating applications, including architectural, industrial and wood coatings. Formulation involves the use of reactive diluents to decrease the viscosity and trigger the autoxidative curing mechanism of the alkyds to avoid the use of volatile organic compounds (VOCs). This work studies the modification of alkyds and reactive diluents and the differences between the coating performance of these additives. Two differently functionalized alkyds and reactive diluents were synthesized and formulated into high solids alkyds coatings. Alkoxysilane and fluorine functionalities were chosen to improve adhesion, hardness, and chemical and corrosion resistance of the coating system. The resulting coatings were analyzed for performance, tensile properties, corrosion resistance and weatherability. ESEM-EDX was used to observe the distribution of the fluorine and alkoxysilane in the cross-section of the coating. Stratification was observed for the modified reactive diluents at high concentrations, and these coatings showed improved adhesion and corrosion resistance. The modified alkyds performed better in terms of mechanical properties, but stratification was not observed. Next, the moisture sensitivity of alkoxysilanes was studied by looking into the effect of various relative humidity conditions on the curing and performance of alkoxysilane functionalized alkyd coatings. These coatings were evaluated for drying time, adhesion, hardness and mechanical properties. At high humidity, the alkoxysilane functional reactive diluents dried more quickly and formed harder coatings than the unmodified control. The functionalized alkyds showed enhanced adhesion and tensile strength at high humidity. Thirdly, fluorinated alkyds and reactive diluents were compared to understand the effects of molecular weight and viscosity on the stratification (open full item for complete abstract)

Committee: Mark Soucek PhD (Advisor); Thein Kyu PhD (Committee Chair); Younjin Min PhD (Committee Member); Tianbo Liu PhD (Committee Member); Chelsea Monty-Bromer PhD (Committee Member) Subjects: Chemistry; Materials Science; Polymer Chemistry; Polymers

Master of Science, University of Toledo, 2018, Mechanical Engineering

This thesis work elaborates a facile technique for fabrication of functionally graded all graphene films using a one-step film coating process. The film coating consists of inter-facial reduction and self-assembly of a graphene oxide (GO) precursor on an active metal substrate. Processing parameters such as the underlying substrate metal and the film drying environment are controlled in order to tailor the internal architecture of the films and to achieve functionally graded structure during the reduction of GO. The self-assembly and functional grading of the films, where one side is electrically conductive reduced GO (rGO) and the opposite side is insulating GO, was confirmed by SEM, Raman, XRD, FTIR, and XPS characterization studies. All graphene based free standing films with selectively reduced GO were used in transient electronics application as flexible circuitry and RFID tag antenna where their decommissioning was easily achieved by capitalizing on GO's ability to readily dissociate and create a stable suspension in water. Furthermore, the functionally graded structure was found to exhibit differential swelling behavior and its potential applications in graphene-based actuators were outlined.

Committee: Reza Rizvi (Committee Chair); Hossein Sojoudi (Committee Member); Ahalapitiya Jayatissa (Committee Member) Subjects: Chemistry; Materials Science; Mechanical Engineering; Nanotechnology

Doctor of Philosophy, University of Akron, 2018, Polymer Science

Interfaces play a crucial role in phenomena such as wetting, adsorption, adhesion, friction, heterogenous ice-nucleation, and biocompatibility. The interfacial molecules exhibit unique behavior due to missing interactions at the surface (or differing interactions across an interface). Designing molecules for targeted applications demands a thorough understanding of the connection between molecular-level interfacial interactions and macroscopic observables, which is currently limited due to the difficulties in accessing the buried solid/liquid and solid/solid interfaces in situ. In this dissertation, we employ interface-sensitive infrared-visible sum frequency generation (SFG) spectroscopy to probe the interfacial structure of simple liquids (or liquid mixtures) as well as complex proteins next to a sapphire substrate and discuss the ramifications for macroscopic phenomena such as adsorption, solidification, and adhesion. SFG, being a second order non-linear optical technique, provides insights into the interfacial structure, orientation, and concentration of molecules. First, the competitive adsorption to sapphire from three binary liquid mixtures, acetone-chloroform, tetrahydrofuran (THF)-benzene, and N,N-dimethylformamide (DMF)-benzene, has been investigated using SFG. The preferential adsorption of one component over another forms the basis for a variety of applications such as separation or purification using membranes or column chromatography, as well as biological implant acceptance or rejection. The relative interfacial concentrations of the two components from binary mixtures are determined by analyzing the shape of the sapphire hydroxyl peak. By fitting the adsorption isotherm with the thermodynamic Everett model, the differences in interfacial energies (Δγ) of the two components with the sapphire substrate are determined. These are then compared with the Δγ values calculated using the Dupre-Fowkes approach. The calculated Δγ values are consistent with the (open full item for complete abstract)

Committee: Ali Dhinojwala (Advisor); Mesfin Tsige (Committee Chair); Mark Foster (Committee Member); Toshikazu Miyoshi (Committee Member); Jutta Luettmer-Strathmann (Committee Member) Subjects: Materials Science; Polymers

Doctor of Philosophy, The Ohio State University, 2018, Plant Pathology

Salmonellosis cases caused by Salmonella enterica through pre-harvest contamination of fresh produce represent a risk to human health worldwide; however, little is known about the interactions between Salmonella, phytopathogens, environment, and the plant host contributing to this food safety issue. Furthermore, the control of Salmonella from “farm to fork” is challenging due to the development of resistance mechanisms towards current control methods and restrictions on use of antimicrobials imposed by regulatory agencies. We investigated the effects of specific environmental conditions on the persistence and dissemination of Salmonella enterica subsp. enterica serotype Typhimurium (S. Typhimurium) following artificial contamination of `Tiny Tim' tomato plants. We found that higher temperatures (30°C day/25°C night) reduced the persistence of S. Typhimurium in the phyllosphere compared to lower temperatures (20°C day/15°C night) when plants were sprayed on the leaves with a S. Typhimurium -contaminated solution. Wounding cotyledons with contaminated tools increased S. Typhimurium persistence and internalization in planta compared to spray inoculation. Low relative humidity enhanced the dissemination of Salmonella into non-inoculated plant tissues. S. Typhimurium was detected in the root systems for at least 98 days-post inoculation. Further, we showed that splice-grafting (`Celebrity' with 'MaxiFort') is a major risk for the internalization and long-term survival of S. Typhimurium inside the tomato plant. S. Typhimurium was detected in the root system for over 137 days if at least 5 x 10^3 colony-forming units were introduced during grafting. The survival of S. Typhimurium in tomato foliage was also affected by the presence of phytopathogens, the genotype of S. Typhimurium and tomato variety used. We found that rfbV, involved in O antigen synthesis, might be essential for S. Typhimurium persistence in inoculated tomato plants and especially in `Tiny Tim' plants (open full item for complete abstract)

Committee: Gireesh Rajashekara (Advisor); Sally Miller (Advisor); Laurence Madden (Committee Member); Christopher Taylor (Committee Member); Corey Nislow (Committee Member) Subjects: Agriculture; Bioinformatics; Biology; Environmental Health; Molecular Biology; Plant Pathology; Public Health

Master of Science, University of Toledo, 0, Mechanical Engineering

The development of effective gas sensors for the detection of hazardous gases is important because of elevated concentrations of hazardous gases in the ambient. Gas sensors can be fabricated using different electronic materials such as metal oxides, carbon nanotubes, organic compounds, and ceramic compounds. Among them, metal oxides are considered as the potential materials for gas sensor application because of their high stability, high sensitivity, and ability to detect a wide range of target gases. There are some limitations associated with metal-oxide gas sensors such as low response, low conductivity, high operating temperature, and slow recovery speed. However, these limitations can be eliminated by the modification of metal oxides with impurity doping, mixing with other metal oxides, surface modification with catalytic metals. In this study, possible improvement of gas sensors by doping of impurities and addition of graphene to enhance carrier transport phenomena was investigated. Graphene was mixed with nickel oxide to produce composite films that can be used in gas sensor filament. The sensing characteristics of graphene added nickel oxide were studied as a function of graphene concentration. The samples were tested for NH3, CH4, and H2 at different operating temperatures. The response time, recovery time, cross-sensitivity, selectivity and repeatability of the test specimens were studied in details. It was found that the response, response time, recovery time, and conductivity of the films were improved after mixing of nickel oxide with graphene. The electrical properties, optical properties, and the crystal structures of the samples were studied with UV spectrophotometry and X-ray diffraction measurements. Also, zinc oxide was doped with aluminum and graphene oxide and deposited using the sol-gel method. The samples were tested for some gases and humidity. The ZnO films doped with graphene oxide and aluminum showe (open full item for complete abstract)

Committee: Ahalapitiya Jayatissa (Committee Chair); Matthew Franchetti (Committee Member); Sanjay V. Khare (Committee Member) Subjects: Materials Science; Mechanical Engineering; Nanoscience; Nanotechnology

Doctor of Philosophy (PhD), Ohio University, 2018, Biological Sciences (Arts and Sciences)

My study presents information on summer use of terrestrial habitat by IUCN “endangered” North American Wood Turtles (Glyptemys insculpta), sampled over four years at two forested montane sites on the southern periphery of the species' range in the central Appalachians of Virginia (VA) and West Virginia (WV) USA. The two sites differ in topography, stream size, elevation, and forest composition and structure. I obtained location points for individual turtles during the summer, the period of their most extensive terrestrial roaming. Structural, compositional, and topographical habitat features were measured, counted, or characterized on the ground (e.g., number of canopy trees and identification of herbaceous taxa present) at Wood Turtle locations as well as at paired random points located 23-300m away from each particular turtle location. First, I report and discuss basic morphometric and activity area data of the VA and WV turtles. Chapter two uses a nine-year dataset of adult WV Wood Turtles to estimate population size, population growth rate (lambda), and survivorship with open population Cormack-Jolly-Seber and Pradel models in program MARK. My third chapter assess Wood Turtle thermal ecology by examining three data sets of environmental and turtle temperatures: 1) temperatures in three different microhabitat types (unshaded by ground cover [exposed], under vegetation [UV], under litter [UL]) recorded by iButtons at arrays throughout the two study sites; 2) ground temperatures at the locations of radio-tracked individuals and their paired random points measured within 300 meters and 30 minutes of each other; 3) body temperatures estimated with iButtons attached to the shell bridges of adult Wood Turtles. In the fourth chapter, I examine highly localized conditions resulting from short-term weather patterns and fine-scale microhabitat characteristics by comparing ground-level relative humidity at the locations of radio-tracked Wood Turtles to those at paired ra (open full item for complete abstract)

Committee: Willem Roosenburg Professor (Advisor) Subjects: Animals; Ecology; Environmental Science; Forestry; Wildlife Conservation; Wildlife Management; Zoology

Doctor of Philosophy, University of Akron, 2017, Polymer Science

Orb web spiders are carnivores that use sticky capture silk to catch and retain prey their web. Prey capture is an essential part of their survival. Remarkably, the sticky capture silk needs to be sticky in diverse spider habitats that can range from dry and arid to wet and humid. This is in contrast to most synthetic adhesives which fail above a critical humidity. In this study, I used spider glue as a model system to conduct a detailed investigation of its humidity responsive adhesion at multiple length scales. On a macro scale, I found that spiders use a combination of capillary instability and environmental humidity to control the spacing and size of glue droplets on their capture silk. Modulation of BOAS morphology results in non-linear scaling of capture silk adhesion with glue volume, and can be used to catch different sized prey in their habitats. Investigating further, I found that spider glue adhesion changes with humidity such that adhesion is maximum at the humidity resembling the habitat humidity of the spider species. Using the fundamental droplet spreading power law, I measured the viscosity of glue droplets as a function of humidity. The glue viscosity varies over five orders of magnitude with humidity, but is very similar at the humidity of maximum adhesion, which can be very different, 30\%-90\% relative humidity (RH) for different species. Moreover, droplet spreading contributes significantly to adhesion modulation. Both overspreading and underspreading of glue droplets leads to reduced adhesion. Maximum adhesion is observed under optimal spreading of the glue droplet such that crack initiation is delayed and high peeling forces are required to initiate the crack. Spider glue is an aqueous mix of glycoproteins, and small molecules that include both organic and inorganic compounds. The optically heterogeneous structure of spider glue droplet was hypothesized because of phase-separation betweem proteins and small molecules. I (open full item for complete abstract)

Committee: Ali Dhinojwala (Advisor) Subjects: Biophysics; Materials Science; Polymer Chemistry; Polymers

Doctor of Philosophy, Case Western Reserve University, 2017, Macromolecular Science and Engineering

Since CH3NH3PbI3 based perovskites were discovered as viable active materials for the next generation photovoltaic devices, their instability in different environmental conditions has been a constant challenge. In pursuit of a better understanding of the degradation mechanisms, perovskite solar cells have been fabricated and investigated by scientists in order to find correlations between the solar cell characteristics/performance and the interface variation. In this thesis, the perovskite reactivity to humidity is studied by exposing samples to D2O environment for different durations. The degradation process of CH3NH3PbI3 perovskite is examined in-situ by using time-of-flight secondary ion mass spectrometry (ToF-SIMS). 3D images are constructed through the layer-by-layer spatially resolved elemental distribution analysis and the D2O moisture penetration through the sample. The intermediate products of interaction with moisture are analyzed by ToF-SIMS and X-ray photoelectron spectroscopy (XPS). We also investigated the electrical operation-induced degradation on CH3NH3PbI3 perovskite solar cells. Upon exposure to electrical current, the structure and composition were examined by combining depth-resolved imaging with ToF-SIMS, XPS and field-emission scanning electron microscopy (FE-SEM). The results show that the interface of the perovskite and the meso-porous TiO2 intermix into each other during the initial operations of solar cell. This intermixing turns the efficiency upward and improves the power conversion efficiency (PCE) up to ~50%. Both depth profiles and SEM images proved that operating devices undergo irreversible changes in thickness, which results in a dramatic performance loss eventually. In addition to studying the degradation process of the perovskite, a new formation method was developed to achieve complete conversion of PbI2 to CH3NH3I3 on FTO/Compact TiO2 substrate by employing a quaternary ammonium salt as an additive in the PbI2 solution. Thi (open full item for complete abstract)

Committee: Clemens Burda (Advisor); David Schiraldi (Committee Chair); Alex Jamieson (Committee Member); Chung-Chiun Liu (Committee Member); Xuan Gao (Committee Member) Subjects: Chemistry; Materials Science; Molecular Chemistry; Organic Chemistry; Polymer Chemistry

Doctor of Philosophy, The Ohio State University, 1960, Graduate School

Committee: Not Provided (Other) Subjects: Biology

Master of Science, The Ohio State University, 2016, Atmospheric Sciences

In this study, four key lake effect parameters were examined for 22 lake effect snowfall event case studies to the lee of Lake Erie from the period of 2007-2008 to 2015-2016. In addition, case study summaries were created to provide relevant background information. The case studies were broken down into that of 11 from Type I lake effect events and the remaining 11 from Type II lake effect events. The parameters studied include: lake induced instability, mean low-level wind flow, low-level relative humidity, and lake induced equilibrium level. Data for the parameters was extracted from the Penn State THREDDS Data Server in the form of RUC/RAP reanalysis data and then processed using a forecast profile visualization and analysis tool kit called BUFKIT. Reanalysis for the parameters was calculated on 3-hour intervals for the duration of the case studies and chosen for specific point locations across the surface of Lake Erie through the BUFKIT Data Distribution System. Type I case studies had three point locations or station identifications examined- LE1, LE2, and LE3, while Type II case studies had two point locations examined- LE1, LE2. The lake effect parameter data collected was then averaged over 6-hour intervals for each event and put in a table format. Complete event averages were also computed, charted, and put into table format. By doing so, an archive of key lake effect parameter values for past Type I and Type II events and the resulting snowfall amounts is available with the goal being to have created an analog system that can be used to help in the making of future lake effect snowfall forecasts. Type I and Type II complete event averages were then compiled and averaged for their corresponding band type. Once completed, trends in the lake effect parameters were observed and analyzed for statistical significance. Lake induced equilibrium level values as well as the height to which low-level relative humidity greater than or equal to 70% was (open full item for complete abstract)

Committee: Jay Hobgood (Advisor); Jialin Lin (Committee Member); Alvaro Montenegro (Committee Member) Subjects: Atmospheric Sciences; Meteorology

Doctor of Philosophy, University of Toledo, 2016, Physics

Photovoltaics (PV) is increasingly recognized as an important component of renewable energy sources after the rapid progress in the last decade due to increasing energy demand and reducing manufacturing costs. Despite the enormous growth of the PV market, the present solar technologies that are dominated by crystalline silicon are still limited by the relatively more expensive cost of electricity compared with power generation in the conventional fossil fuel plants. Consequently, there is an urgent need to increase the performance and reduce the manufacturing costs of solar cells. While the commercial thin film solar cells (CdTe and CuInGaSe2) have already demonstrated high efficiencies, the current fabrication processes heavily rely on intensive capital investment on expensive vacuum-based techniques. To reduce solar module costs, solution-processing techniques have been proposed as a promising route towards low cost, high throughput, large scale manufacturing of high efficiency thin film solar cells. In this thesis, we investigate the solution-processing of copper indium chalcogenides and methylammonium lead halides materials and their applications as high efficiency photovoltaic cells. In the first approach, we develop an ultrasonic spray deposition system to prepare the CuIn(S,Se)2 thin films. Spray deposition is a controllable, scalable, and high throughput process that is suitable for industrial manufacturing. Here we first explore the Cu-In-S films prepared by an aqueous precursor ink. By controlling the precursor composition, we fabricate PV devices consisting of the n-type In2S3 window and p-type CuInS2 absorber layers and demonstrate 2% efficiency in the preliminary devices. After replacing the aqueous ink by a hydrazine-based precursor solution and incorporating a selenization process, we are able to fabricate high quality CuIn(S,Se)2 thin film solar cells in both conventional substrate and the backwall superstrate configurations. The efficiency of 7.2 (open full item for complete abstract)

Committee: Michael J. Heben Ph.D. (Committee Chair); Robert W. Collins Ph.D. (Committee Member); Randy J. Ellingson Ph.D. (Committee Member); Terry P. Bigioni Ph.D. (Committee Member); Lawrence S. Anderson-Huang Ph.D. (Committee Member) Subjects: Chemical Engineering; Materials Science; Physics

Doctor of Philosophy, The Ohio State University, 2015, Plant Pathology

Tomato is an economically important segment of agricultural production in the United States. Bacterial leaf spot (BLS) causes serious losses in tomato and pepper in the Midwest. Four Xanthomonas species cause BLS on these crops. In a four-year survey covering 16 counties in Ohio and one county in Michigan focused on the causal bacteria of BLS in processing tomatoes, fresh market tomatoes and peppers, a total of 240 strains were isolated, containing 169, 45, and 26 strains of X. gardneri, X. perforans, and X. euvesicatoria, respectively. The predominant species in processing and fresh market tomatoes was X. gardneri. Xanthomonas euvesicatoria was the most abundant species in peppers. Of all strains collected in this survey, 98%, 68% and 4% were insensitive to 30, 100, and 200 µg/ml copper sulfate, respectively. Bactericides and a plant resistance activator were evaluated for efficacy in reducing BLS disease intensity in the greenhouse and field. In a greenhouse simulating a commercial seedling production environment, both acibenzolar-S-methyl and aluminum Tris O-ethyl phosphate reduced bacterial populations relative to the negative control in one of the two trials. In the second trial, lower seedling density contributed to reduced BLS severity compared to higher seedling density. In field trials, both acibenzolar-S-methyl and isothiazolone in combination with the surfactant (Activator 90) significantly reduced the yield of fruits with BLS symptoms compared to the non-treated control in one of the two years of the study. The addition of Activator 90 improved the efficacy of acibenzolar-S-methyl and copper sulfate in reducing BLS on fruit in one of two years. However, fruits from plants treated with isothiazolone plus Activator 90 exhibited more large BLS lesions in one of the years than the non-treated control. The percentage of fruits with BLS symptoms, foliar BLS severity at the end of field experiment, and area under the disease progression curve for foliar BLS we (open full item for complete abstract)

Committee: Sally Miller (Advisor); Pierce Paul (Committee Member); Chris Taylor (Committee Member); David Francis (Committee Member); Peter Ling (Committee Member) Subjects: Agricultural Chemicals; Agriculture; Microbiology; Plant Pathology

Master of Science, University of Akron, 2015, Polymer Science

The use of adhesives, especially pressure sensitive adhesives (PSA), has relevance in many industrial, medical and commercial applications such as automotive, aerospace, biomedical and electronics. A number of characterization techniques have been used with the main purpose of understanding the performance of PSA by quantifying material properties, such as peeling strength. The peeling strength is dependent on the composition, viscoelastic properties of the adhesive, and its measurement provides information regarding stickiness and reversibility on different substrates. The work of Kendall and Gent explained the dependence of peeling force on peeling angle, work of adhesion and the modulus of the adhesive tape. Although the measurement of peeling strength has been widely studied, few experiments have explored the effect of humidity and temperature on peel strength. In this work we have used the Kendall approach to evaluate the effect of humidity on the peel strength of PSA at constant temperature (23°C). Our results confirm the expected angle dependence of the peel strength, being considerably superior when small angles were tested. Furthermore, our results indicate that the peel strength is reduced with increased humidity. Understanding the influence of humidity on adhesion will help provide insight to the humidity response of biological adhesives used by spiders and geckos

Committee: Ali Dhinojwala Dr. (Advisor); Abraham Joy Dr. (Committee Member) Subjects: Chemical Engineering; Materials Science; Mechanical Engineering; Physics; Political Science; Polymers

Master of Science (MS), Ohio University, 2014, Civil Engineering (Engineering and Technology)

Air moisture quality is of interest in the Ohio River Valley where coal-fired power plants are densely located. Air moisture was captured using a dehumidifier at 24 locations throughout the Ohio River Basin. The area, characterized by poor air quality due to coal-fired power plant and industrial emissions, exhibits air quality characteristics similar to urbanized areas. The water was analyzed, based on Standard Methods, for compliance with US Environmental Protection Agency (USEPA) drinking water standards including: total heterotrophic plate count (THPC), total and dissolved lead, total and dissolved mercury, pH, total solids (TS), total suspended solids (TSS), total dissolved solids (TDS), and conductivity. Based on the results of analyzed data, It was discovered that the air moisture collected contained levels of THPC higher than USEPA limits, lead concentrations were higher around power plants (but met USEPA standards), mercury was not present within condensate samples, and pH was slightly acidic (pH: 5.49-7.86), conductivity increased as distance from point sources diminished, and TDS was higher near point source locations.

Committee: Tiao Chang PhD (Advisor); Deborah McAvoy PhD (Committee Member); Guy Riefler PhD (Committee Member); Sinha Gaurav PhD (Committee Member); Sargand Shad PhD (Committee Chair) Subjects: Civil Engineering; Condensation; Environmental Engineering