Master of Science (M.S.), University of Dayton, 2011, Electrical Engineering

In this thesis, the theory of coupled resonators for non-adiative wireless power transfer are explored from a lumped element circuit perspective. A basic circuit model is developed and standard circuit parameters are defined. A directly fed resonant shielded loop for wireless power transfer is presented. Basic lumped component values and circuit parameters are experimentally extracted for two resonant shielded loops. Optimal efficiency conditions are derived and used to design optimal matching networks. Matching networks are constructed and the system is tested for power transfer efficiency. Two means of producing a tunable system are explored: frequency tuned sources and dynamic matching networks. It is shown that frequency tuned systems cannot achieve maximum efficiencies. A tunable system is constructed and tested. Experimental results show excellent agreement with theory, and the ability to achieve maximum achievable efficiencies.

Committee: Robert Penno PhD (Committee Chair); Anthony Grbic PhD (Advisor); Monish Chatterjee PhD (Committee Member); Augustine Urbas PhD (Committee Member); John Weber PhD (Other); Tony Saliba PhD (Other) Subjects: Electrical Engineering; Electromagnetics; Electromagnetism; Energy; Engineering; Solid State Physics

Master of Science (MS), Bowling Green State University, 2024, Geology

Precise estimation of canopy chlorophyll content (CCC) and canopy nitrogen content (CNC) is essential for effective monitoring of crop growth conditions. The field of satellite imaging spectroscopy, known as hyperspectral imaging, offers a non-destructive, large-area, and real-time approach to monitoring of CCC and CNC over large areas. With the introduction of recent science-driven mission such as the Environmental Mapping and Analysis Program (EnMAP), imaging spectroscopy has emerged as a crucial component of empirical and physical modelling. This study introduces two approaches for retrieving CCC and CNC using EnMAP hyperspectral imagery acquired over Kellogg Biological Station, Michigan in the summer 2023: i) Machine learning regression algorithms (MLRAs), and ii) a hybrid model that combines a radiative transfer model with machine learning. We assessed the performances of six regression techniques including kernel ridge regression (KRR), least squares linear regression (LSLR), partial least squares regression (PLSR), Gaussian process regression (GPR), neural network (NN), and random forest (RF) for retrieving CCC and CNC. In the hybrid model workflow, each of the six techniques were integrated with PROSAIL, a widely known radiative transfer model. For both the approaches, the final CCC and CNC models were validated against field data. For CCC retrieval, KRR demonstrated the best performance in the MLRA approach (RMSE = 10.01, NRMSE = 9.81%, R2 = 0.93), while GPR exhibited the best performance in the hybrid approach (RMSE = 9.62, NRMSE = 9.43%, R2 = 0.93). Regarding CNC retrieval, KRR outperformed other models in both the MLRA (RMSE = 10.10, NRMSE = 8.13%, R2 = 0.94) and hybrid approach (RMSE = 16.98, NRMSE = 13.67%, R2 = 0.83). While the hybrid model outperformed the standalone MLRA approach for CCC retrieval, the MLRA approach surpassed the hybrid approach in CNC retrieval. In CCC retrieval, the most significant bands of EnMAP were identified in the visible to (open full item for complete abstract)

Committee: Anita Milas Ph.D. (Committee Chair); Qing Tian Ph.D. (Committee Member); Jochem Verrelst Ph.D. (Committee Member) Subjects: Geographic Information Science; Geography; Geology; Remote Sensing

Master of Science (M.S.), University of Dayton, 2023, Mechanical Engineering

Particle systems for concentrating solar applications present a non-trival challenge to adequately model with DEM software. A compiled modeling suite for radiative exchange, coined DEM+, is directly integrated into commercial software Aspherix®. A presentation of this modeling suite, advantages, and disadvantages is followed by an expanded look at the Distance Based Approximation (DBA) method for estimating particle-particle and particle-wall radiative exchange of more realistic particle size distributions and some simple binary mixtures. In addition, design, operation, and preliminary experimental results for a lab-scale multi-stage falling particle curtain are evaluated with particle image velocimetry (PIV) from two perspectives with discussion of the challenges therein. A room temperature DEM model of investigated particles is compared to experimental results with emphasis on future work for material calibration for DEM+.

Committee: Andrew Schrader (Committee Chair); Kevin Hallinan (Committee Member); Andrew Chiasson (Committee Member); Rydge Mulford (Committee Member) Subjects: Alternative Energy; Energy; Experiments; Mechanical Engineering; Sustainability

Master of Science (MS), Ohio University, 2022, Chemical Engineering (Engineering and Technology)

Methane, the second largest greenhouse gas, is often released as a fugitive emission from natural gas drilling sites commonly located in rural, sparsely populated areas. At this level satellites lack the necessary spatial resolution to identify methane emissions, and site by site ground-based monitoring is economically unsustainable. To reconcile these issues, implementing aerial remote sensing platforms have recently been investigated. In this study a low altitude aircraft retrofitted with a shortwave infrared (SWIR), non-imaging spectrometer was used to locate methane leaks and estimate methane concentrations from active natural gas producing regions and natural gas infrastructures in Eastern Ohio. Three separate monitoring flights were completed on July 3rd, 2018, October 18th, 2018 and May 8th, 2019. Pairing flight data with MODTRAN6 radiative modeling, multiple concentration heat maps displaying flight path and estimated methane concentration were constructed. From these maps there was shown to be elevated methane concentrations in multiple regions: Proctor and Wheeling, West Virginia, Piedmont Lake, Ohio and an area of Eastern Ohio densely populated with actively producing horizontally drilled natural gas wells. There was also shown to be elevated methane concentrations at several specific locations: the Athens-Hocking Reclamation Center, a natural gas compressor station, a natural gas processing facility, and a surface mining site.

Committee: Kevin Crist (Advisor); Geoffrey Dabelko (Committee Member); Douglas Goetz (Committee Member); Valerie Young (Committee Member) Subjects: Atmosphere; Atmospheric Sciences; Chemical Engineering; Remote Sensing

Master of Science (M.S.), University of Dayton, 2021, Mechanical Engineering

Radiative fin technology is used in a wide variety of applications: automotive, electronics, and space. However, throughout history, radiative fin geometry is generally only analyzed along the thickness profile. This work analyzes radiative fin planar geometry and thickness profile in tandem. From there, the findings are used to investigate a novel dynamic spacecraft radiator system. Fins are analyzed to optimize for a variety of performance criteria, including maximum heat transfer, tip temperature, or fin efficiency. For analysis of both static and dynamic fins, a two-dimensional mathematical heat transfer model is developed. It is found that a triangular thickness profile is most critical for heat rate maximization. A fin with a triangular thickness profile increases heat rate by 38.8% when compared to a fin with identical planar geometry and volume, but with a uniform thickness profile. Planar shape is also found to influence fin performance. A fin with a rectangular planar geometry has a 6.8% increase in heat transfer as compared to a fin with a triangular planar geometry and identical thickness profile and volume. Additionally, it is also found that triangular thickness profiles produce the maximally efficient fins. Following these results, a novel design for a dynamic spacecraft radiator with annular geometry and varied thickness profiles is presented. It is found that turndown ratios of 3.33 are capable with the novel system. Furthermore, it was found that fins with tapered thickness profile have the highest efficiency and turndown ratio. Finally, it was shown that turndown ratio and fin efficiency decrease as operating temperature increases.

Committee: Rydge Mulford (Committee Chair); Andrew Schrader (Committee Member); Kevin Hallinan (Committee Member); Andrew Chiasson (Committee Member) Subjects: Aerospace Engineering; Applied Mathematics; Engineering; Mechanical Engineering; Radiation

Master of Science, University of Akron, 2018, Applied Mathematics

A mathematical model is developed to describe the light field in vertical line seaweed cultivation to determine the degree to which the seaweed shades itself and limits the amount of light available for photosynthesis. A probabilistic description of the spatial distribution of kelp is formulated using simplifying assumptions about frond geometry and orientation. An integro-partial differential equation called the radiative transfer equation is used to describe the light field as a function of position and angle. A finite difference solution is implemented, providing robustness and accuracy at the cost of large CPU and memory requirements, and a less computationally intensive asymptotic approximation is explored for the case of low scattering. Conditions for applicability of the asymptotic approximation are discussed, and depth-dependent light availability is compared to the predictions of simpler light models. The 3D model of this thesis is found to predict significantly lower light levels than the simpler 1D models, especially in regions of high kelp density where a precise description of self-shading is most important.

Committee: Kevin Kreider Ph.D (Advisor); Curtis Clemons Ph.D (Advisor); Gerald Young Ph.D (Advisor) Subjects: Applied Mathematics; Aquaculture; Aquatic Sciences; Ocean Engineering; Optics

Doctor of Philosophy, The Ohio State University, 1975, Graduate School

Committee: Not Provided (Other) Subjects: Physics

Doctor of Philosophy, The Ohio State University, 2016, Nuclear Engineering

Molten salts, such as the fluoride salt eutectic LiF-NaF-KF (FLiNaK) or the transition metal fluoride salt KF-ZrF4, have been proposed as coolants for numerous advanced reactor concepts. These reactors are designed to operate at high temperatures where radiative heat transfer may play a significant role. If this is the case, the radiative heat transfer properties of the salt coolants are required to be known for heat transfer calculations to be performed accurately. Chapter 1 describes the existing literature and experimental efforts pertaining to radiative heat transfer in molten salts. The physics governing photon absorption by halide salts is discussed first, followed by a more specific description of experimental results pertaining to salts of interest. The phonon absorption edge in LiF-based salts such as FLiNaK is estimated and the technique described for potential use in other salts. A description is given of various spectral measurement techniques which might plausibly be employed in the present effort, as well as an argument for the use of integral techniques. Chapter 2 discusses the mathematical treatments required to approximate and solve for the radiative flux in participating materials. The differential approximation and the exact solutions to the radiative flux are examined, and methods are given to solve radiative and energy equations simultaneously. A coupled solution is used to examine radiative heat transfer to molten salt coolants. A map is generated of pipe diameters, wall temperatures, and average absorption coefficients where radiative heat transfer will increase expected heat transfer by more than 10% compared to convective methods alone. Chapter 3 presents the design and analysis of the Integral Radiative Absorption Chamber (IRAC). The IRAC employs an integral technique for the measurement of the entire electromagnetic spectrum, negating some of the challenges associated with the methods discussed in Chapter 1 at the loss of spectral informat (open full item for complete abstract)

Committee: Thomas Blue PhD (Advisor); Wolfgang Windl PhD (Committee Member); Xiaodong Sun PhD (Committee Member); Merat Khafizov PhD (Committee Member) Subjects: Nuclear Engineering

PhD, University of Cincinnati, 2015, Arts and Sciences: Physics

We present the results of a complete Monte Carlo radiative transfer modeling effort to investigate the structure of and reproduce published observational results for a group of transitional proto- planetary disks: V1247 Orionis, Ophiuchus IRS 48, GM Aurigae, and SAO 206462. The modeling contained herein attempts to reproduce spectral energy distributions formed from decades of pho- tometry and spectroscopy, tightly constrained by more recent interferometric and near-infrared scattered light imagery to compare our synthetic best fit model images to. Our results place con- straints on aspects of the disks' structure, such as scale height, disk mass, and dust composition while reproducing the bulk of known observational data from a variety of techniques.

Committee: Michael Sitko Ph.D. (Committee Chair); Philip Argyres Ph.D. (Committee Member); F. Paul Esposito Ph.D. (Committee Member); Kay Kinoshita Ph.D. (Committee Member) Subjects: Astrophysics

Master of Science, University of Toledo, 2010, Physics

We have modeled the circumstellar disk of the B0.5 IVe star Gamma Cassiopeiae using a 3-D non-local thermodynamic equilibrium Monte Carlo radiative transfer code. The code produces a self-consistent determination of the electron temperature, hydrogen level population, and gas density for hot star disks. We have found that a viscous decretion disk model is consistent with the overall spectral energy distribution, optical and infrared line profiles, and polarization observations. Our model's predicted inclination is 25 degrees less than current interferometric observations (Tycner et al. 2006), and we find inconsistencies in the Brackett 15 line profile fit. This may be indicative of some physical mechanism not included in the model which is responsible for additional heating in the inner disk, or there may be some peculiarity in the Be star Gamma Cas.

Committee: Dr. Jon E. Bjorkman (Committee Chair); Dr. J. D. Smith (Committee Member); Dr. Rupali Chandar (Committee Member) Subjects: Astronomy; Astrophysics

Doctor of Philosophy, University of Toledo, 2010, Physics

Gravitational instability provides a means of rapidly forming giant planets with large orbital radii. For protoplanetary disks to be unstable to gravitational fragmentation, they must 1) have a Toomre Q ≤ 1 and 2) be able to cool the excess energy from a collapsing perturbation in less than the dynamical time (Ω tcool ≤ 1). We present an analytical technique for calculating this perturbation cooling time for externally illuminated disks and/or disks with internal heating. We compare our analytical technique with a numerical Monte Carlo code, and find good agreement. We use our analytical technique to test the ability of the gravitational instability to re-create the observed planetary systems of Fomalhaut, HR 8799, and HL Tau. We find that the required disk mass interior to the planet's orbital radius is ∼0.1 Msun for Fomalhaut b, the protoplanet orbiting HL Tau, and the outermost planet of HR 8799. The two inner planets of HR 8799 probably could not have formed in situ by disk fragmentation. The perturbation cooling time can be reduced significantly through the inclusion of geometrical effects, specifically fragmentation originating at a location other than the disk mid-plane, and/or dust settling. In particular, dust settling to one-tenth of the gas scale height can reduce the perturbation cooling below the fragmentation threshold for all surface densities Σ ≤ 103 g/cm2. We study the fragmentation criteria and fragment masses produced for a grid of parameters covering pre-main sequence masses ranging from 0.1–5 Msun, ages ranging from 0.5–10 Myr, and differing degrees of dust settling. We find that the instability criteria and fragment mass scales with pre-main sequence mass (as expected), while the pre-main sequence age (i.e., luminosity) provides only a modest effect—indicating that disk fragmentation is equally likely at all stages of pre-main sequence evolution, given sufficiently high disk mass. Dust settling can lead to disk fragmentation at orbital radii th (open full item for complete abstract)

Committee: Jon Bjorkman PhD (Committee Chair); Lawrence Anderson-Huang PhD (Committee Member); Lee Hartmann PhD (Committee Member); Victor Karpov PhD (Committee Member); S. Thomas Megeath PhD (Committee Member); Adolf Witt PhD (Committee Member) Subjects: Astrophysics

Doctor of Philosophy, The Ohio State University, 2010, Geological Sciences

Continuous monitoring of changes in the Greenland ice sheet from both space and air borne sensors has been conducted since the early 1970's. Since the mid-1990's dramatic changes occurring on the Greenland ice sheet have been observed both from space borne sensors and field work. These changes, primarily mass loss from the ice sheet, are related to the observed trend of earth's warmer climate in recent decades both in peer reviewed journals and in popular media. This dissertation addresses two parameters that contribute to Greenland ice sheet mass balance estimates. The first factor is characterization of surface melting of the Greenland ice sheet from satellite-based passive and active microwave sensors. We use a wavelet based edge detection technique to delineate surface melt from brightness temperature measured by passive microwave sensors. Along with brightness temperature data, we also use normalized backscatter data from the Quick Scatterometer (QuikSCAT) as an independent sensor for comparison with the radiometer derived results. We use a semi-empirical threshold based method for surface melt detection from QuikSCAT. Our results show a step-like, consistent increase in melt area of the Greenland ice sheet since 1995. This step-like increase is also observed in the mean summer air temperature along portions of the Greenland coast. The 1995 step-like increase of melt area (and melt index, a measure of melt intensity) is correlated with a distinct change of the North Atlantic Oscillation (NAO) index (from positive to negative) after 1995. The second factor is mass accumulation in the upper reaches of the ice-sheet. We use an empirical model that correlates mean annual brightness temperature to annual accumulation rate. We apply a microwave emission model for the dry snow region of Greenland to show that 37 GHz vertically polarized brightness temperature data are better suited to capture the inter-annual variability of snow accumulation. Using our model we esti (open full item for complete abstract)

Committee: Kenneth Jezek (Advisor); Joel Johnson (Committee Member); Ralph von Frese (Committee Member) Subjects: Geophysics

Doctor of Philosophy (PhD), Ohio University, 2007, Physics (Arts and Sciences)

A time-dependent two-dimensional Monte Carlo/Fokker-Planck (MC/FP) code, which uses a Monte Carlo technique for Compton scattering and radiative transport, and a Fokker-Planck technique for electron evolution, has been fully parallelized with the Message Passing Interface (MPI) to take advantage of computers with multiple processors and decrease running time. This code has been successfully applied to the following astrophysically relevant scenario: it was coupled with the line transfer program XSTAR to simulate multiple Compton reflections within photon bubbles, making predictions for their X-ray spectral features. Predictions include a spectral feature at ~9 keV and hard power-law tails similar to those observed in X-ray binaries in the very high state. This dissertation also includes the results of an observational project to determine the redshifts of six BL Lac objects, (i.e., galaxies dominated by radiation from the jets emerging from their central black holes) with the 2.4 m Hiltner telescope at the MDM observatory on Kitt Peak, Arizona. The redshifts of these objects have been constrained in agreement with previous estimates in most cases; however, in one case (W Comae) the constraints and previous estimates were not in agreement.

Committee: Boettcher Markus (Advisor) Subjects: Physics, Astronomy and Astrophysics

BA, Oberlin College, 2009, Physics and Astronomy

This thesis discusses research being done to understand the inner parts of the Milky Way Galaxy. We already know that there are dense star clouds, a supermassive black hole, and a large bar structure, but much of the inner galaxy is shrouded in mystery. Dust absorption, for one thing, prevents us from seeing the galactic center directly with our eyes. To help understand the elusive inner Milky Way, we examine radio telescope data taken in Antarctica by Oberlin College Professor Chris Martin. His gigahertz radio observations were already analyzed to help understand how gas funnels into the Milky Way's supermassive black hole. We study this data further to characterize turbulence and predict how hot or cold the gas is. The analysis of this data will also help prepare for the next thing: Herschel Space Observatory. This European telescope is scheduled to be launched in late April and will begin taking data in the fall of 2009. Chris Martin was granted 125 hours of observation time on the telescope to study the Inner Milky Way.

Committee: Chris Martin PhD (Advisor) Subjects: Astrophysics

Master of Science, University of Akron, 2010, Applied Mathematics

Thermophotovoltaic (TPV) energy conversion is the conversion of heat energy to electrical energy via light. When a TPV material is heated, it emits ultraviolet light. This light is then collected by TPV diode cells and converted into electrical energy. In order to be used commercially, TPV energy conversion must become more efficient. A majority of the current research focuses on increasing the efficiency of the TPV diode cells. This thesis focuses on how to design the emitter, so the optimal amount of light reaches the TPV diode cells. This system is modeled inside an exhaust tube, which could be a smokestack of a factory or an exhaust pipe of a car. This model uses the diffusion approximation of the radiative transfer equation and homogenization. It shows how to optimize the geometry of the emitter and homogenize it with another material to maximize emission, while using the least amount of TPV material. This model is presented in axisymmetric coordinates. Different light sources include a ring source, a pancake source, a cylinder source, and a solid sphere source. It is shown that a light source composed of a mixture of a TPV material and a more optically transparent material could be more efficient than using a source of pure TPV material. This mixture is always more efficient if it is arranged in alternating layers on a small scale in the radial direction.

Committee: Dr. Gerald Young Dr. (Advisor) Subjects: Chemical Engineering; Mathematics