Master of Science (MS), Ohio University, 2019, Civil Engineering (Engineering and Technology)

This thesis evaluates natural and chemically stabilized subgrade soils from five project sites throughout Ohio. Three of the five project sites were historically known to have moderate to high sulfate concentrations in the natural soils (DEF-24-2.67-W, LAK- 2-7.76-W, MRW-71-3.17-N), while the other two sites were known to have little to no sulfate levels (CLA-70-13.98-W, CLI-73-6.52-E), and were used as controls. The main objective of the study was to compare in-situ and laboratory test results to determine if there were formations of ettringite or thaumasite in the soil, which can lead to sulfate heave and premature failure of pavement. Several field tests were performed such as PSPA, FWD, LWD, DCP, and SPT. Standard soil tests were performed on natural and chemically stabilized samples, such as gran size analysis, Atterberg limits, organic content, moisture content, and pH, as well as a chemical analysis comprising of neutralization potential, sulfate concentration, and X-ray diffraction (XRD). Analysis showed no major differences of moduli for pavement or soil layers between control and non-control. Results showed that sites where sulfates were known to exist, the chemically stabilized layers had sulfate concentrations greater than 3000 ppm and the pH was just barely greater than 10, which is an indication of concern for ettringite and thaumasite formation. However, the chemical analysis did not indicate formation of either mineral, therefore all conditions were not met.

Committee: Issam Khoury (Advisor) Subjects: Civil Engineering; Geotechnology; Soil Sciences

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

Roadbeds are considered one of the most problematic components in pavement design and construction. Its engineering properties differ significantly in terms of soil composition, gradation, and strength parameters. Soil stabilization techniques have been widely used to improve the engineering properties of roadbed soils. Therefore, in order to study the effects of the stabilization of subgrade layers for pavement structures, theoretical and experimental work was carried out to study pavement responses constructed over stabilized subgrade with lime and cement. The theoretical study involved creating finite element models to study the nature of stresses and strains in the subgrade and asphalt layers when stabilized layer is used in the pavement structure. To study the durability and long term performance of chemically stabilized subgrade, FWD and DCP tests were performed on several pavement sections constructed with stabilized layer. The results from the theoretical study showed that the subgrade could be protected from being over-stressed during construction by providing a suitable stabilized layer. Results from field testing showed that the stiffness of chemically stabilized layers increases significantly over time. It also showed that it provides structural stability to the pavement constructed over stabilized subgrades. Based on these results, input parameters were recommended to MEPDG of flexible pavements.

Committee: Shad Sargand (Advisor) Subjects: Civil Engineering; Transportation

Master of Science, The Ohio State University, 2013, Electrical and Computer Engineering

In this thesis, we utilize the precession efect of the gyroscope to stabilize the bicycle both at zero forward velocity and varying velocities. Equations of motion of a bicycle with a wheel mounted on its bottom are derived and a first order sliding mode controller is designed to achieve the goal of stabilization. In order to verify the designed feedback controller, two experimental setups are built; an inverted pendulum setup and a bicycle setup. SMC design for the static bicycle model is tested on both the inverted pendulum and the bicycle setups. In order to judge the performance of the controller, a well-tuned PID controller is also tested on these setups. Then, in the light of the experimental results obtained on the inverted pendulum setup, a controller scheme for the stabilizing control of an autonomous bicycle is designed and tested on various road structures through simulation environment.

Committee: Umit Ozguner Professor (Advisor); Keith Redmill Professor (Committee Member) Subjects: Electrical Engineering; Engineering; Mechanical Engineering; Robotics; Robots

MS, University of Cincinnati, 2006, Engineering : Mechanical Engineering

Hydrofoils are used in maritime applications; such as ships and submarines, for stabilization, maneuvering, etc. In many of these applications, the hydrofoil may experience dynamic motion; an example would be an active-fin ship stabilization system where the hydrofoil oscillates periodically at large angles of attack. Computational Fluid Dynamics (CFD) is used for simulating the flow over an oscillating hydrofoil used in such systems. The CFD simulations for oscillating-hydrofoil flow are used in analysis of performance of the active-fin ship stabilization system. A system model has been created in MATLAB for this purpose. A Proportional Integral Derivative (PID) control system has also been developed to control the fin motion. Simulation of the active-fin ship-stabilization system in MATLAB provides the typical motion experienced by a hydrofoil used in ship stabilization. This motion is fed back to a CFD solver to determine the effect of non-sinusoidal oscillation on Lift, Drag and Moment of the hydrofoil. The aerodynamics of the non-sinusoidally oscillating hydrofoil is analyzed so as to find an optimum pitching motion for the hydrofoil so as to produce higher lift forces and thus provide better performance. Another important aspect which affects the performance of an active-fin ship stabilization system is cavitation occurring in the flow over oscillating hydrofoils. Cavitation occurs because the pressure on the suction side of the hydrofoil falls below the vapor pressure of water. Numerical simulations using Reynolds-averaged Navier-Stokes equations are carried out to analyze the effect of cavitation on the dynamic stall of an oscillating hydrofoil. It was found that the flow physics changes considerably with cavitation. The dynamic stall vortex (DSV) was formed at an angle of attack much smaller than that for the non-cavitating case. The vortical structures were found to be distorted as compared to the non-cavitating case. Cavitation led to large oscillations i (open full item for complete abstract)

Committee: Dr. Urmila Ghia (Advisor) Subjects:

Master of Science, University of Toledo, 2010, Bioengineering

Dynamic stabilization devices such as the Stabilimax (Applied Spine Technologies Inc.) are being considered as a viable alternative to fusion for patients suffering from low back pain. As opposed to fusion, the Stabilimax provides controlled range of motion in patients undergoing decompression procedures for central or lateral lumbar spinal stenosis at one or two adjacent levels. This pedicle screw based system features an internal dual spring mechanism which combined with a ball and socket joint provides stability by allowing controlled motion to the treated level(s) of the lumbar region. In the recent times, efforts are being made to have the motion preserving devices stabilize the segments, like the rigid instrumentation, if needed. The Stabilimax could be made to achieve this goal by limiting the range of motion of the treated segment with different spring travel lengths (interpedicular travel). More recently, hybrid stabilization has been proposed with an intention to treat patients with segmental lumbar degenerative pathologies. If needed, Stabilimax could also be modified to achieve this goal by using it in conjunction with rigid rod instrumentation. The aim of this study was to evaluate the biomechanics of the decompressed segment (s) implanted with single, multilevel, and hybrid Stabilimax devices with three different spring travel distances. The hypotheses here are 1) the overall stabilization of the decompressed segment implanted with Stabilimax devices does not change with variations in interpedicular travel. 2) A dynamic system in conjunction to a fusion system reduces the risk of adjacent level degeneration as seen in lumbar arthrodesis. A validated 3-D nonlinear finite element model of the intact L3-S1 lumbar spine was used to evaluate the biomechanics of the following devices: a) L4-L5 Single level Stabilimax b) L3-L4-L5 Multilevel Stabilimax c) L4-L5-S1 Multilevel Stabilimax d) L4-L5 Stabilimax + L5-S1 Fusion The intact model was modified to simulat (open full item for complete abstract)

Committee: Vijay Goel PhD (Advisor); Constantine Demetropoulos PhD (Committee Member); Molitor Scott PhD (Committee Member) Subjects: Biomechanics

Master of Science, The Ohio State University, 2009, Civil Engineering

As part of the Ohio Department of Transportation's (ODOT's) ongoing effort to solve engineering problems for the Ohio transportation system through research, The Ohio State University has undertaken a study entitled “Bioengineering for Land Stabilization” under the direction of Professor Patrick J. Fox and Professor Emeritus T. H. Wu. A large number of slopes and embankments throughout Ohio are experiencing shallow slope failures and/or erosion problems. The aim of this study is to identify bioengineering methods to address ODOT's slope stabilization needs in response to these occurrences. Bioengineering is an ecologically, and often economically, attractive alternative to conventional slope stabilization techniques. The objectives of this research are: 1) to identify important factors that control success or failure of bioengineering methods, 2) to develop installation techniques and designs for successful application of bioengineering methods, and 3) to provide thorough documentation to aid in the development of future design guides for bioengineering work for ODOT. Three field installations were conducted and monitored at demonstration sites located in Muskingum, Logan and Union Counties. Results indicate that biostabilization methods can be effective for the stabilization of shallow (less than 3 – 4 ft.) slides if vegetation can be established. Establishment of vegetation is dependent on local soil and climate conditions, especially during the first growing season after installation. The use of instrumentation (tensiometers, piezometers) can be effective in predicting vegetation survivability. Side-by-side panel comparisons indicated that varying installation techniques do not affect the survivability of live willow poles. The cost of bioengineering stabilization is expected to be approximately 25% less than that of conventional methods.

Committee: Patrick Fox (Advisor); Tien Wu (Committee Member); Halil Sezen (Committee Member) Subjects: Civil Engineering; Engineering

PHD, Kent State University, 2011, College of Arts and Sciences / Chemical Physics

Blue phases (BP) are phases of chiral liquid crystals formed by lattices of double-twist cylinders with corresponding lattices of disclination lines. The conditions under which such an arrangement is energetically favorable generally occur in only a narrow band of temperature ranges, commonly less than 2C. Several methods have been devised to expand this range, notably polymer stabilization or nanoparticle stabilization. In addition, there is interest in using unconventionally shaped liquid crystals to form blue phases as molecular biaxiality is expected to help stabilize the phase. Here, we explore the potential of bent-core liquid crystals in creating stable blue phase materials with broad temperature ranges. It is known that the presence of achiral bent-core molecules in a chiral nematic material can induce blue phases where none were previously observed, and that liquid crystal dimers with a flexible center can create broad-temperature blue phases. Here we develop broad-temperature blue phase materials using bent-core nematic liquid crystals and chiral dopants, resulting in the first known example of a broad-range BPIII. Additional methods of phase stabilization are utilized in an attempt to increase the temperature range of the phase to encompass room temperatures.

Committee: Antal Jakli PhD (Advisor); Hiroshi Yokoyama PhD (Committee Member); Liang-Chy Chien PhD (Committee Member); Robert Twieg PhD (Committee Member); E.C. Gartland PhD (Committee Member) Subjects: Materials Science

Doctor of Philosophy, University of Akron, 2024, Polymer Science

Atactic-poly(acrylonitrile) (PAN) is an industrially important polymer material because it is used as a significant precursor for carbon fiber (CF).In CF production, three important heating steps are involved: stabilization, carbonization, and graphitization of wet-spun fiber under tension and different atmospheres. Among them, the initial stabilization process is the most important, as it sets a further high-temperature tolerable structure and thus significantly influences the final mechanical properties of CFs. Therefore, many characterization techniques, including thermal, spectroscopic, scattering, and morphological analyses, have been used to understand complex chemical reactions and stabilized structures of PAN. Even nowadays, the stabilization process is not sufficiently understood due to the difficulty of characterization in solid products which are insoluble in solvents. Our group has recently improved spectral resolution and sensitivity in the solid-state NMR spectrum by combining 13C selective and multiple isotope labeling with state-of-the-art solid-state (ss) NMR techniques. In this dissertation, ssNMR spectroscopy combined with the 13C selective isotope labeling method is used to quantitatively analyze the chemical structures and reactions of PAN and polyacrylonitrile-co-itaconic acid (PAI) with 1mol% itaconic acid (IA) and PAI with 3mol% IA during the stabilization process. First, we investigate the spatial heterogeneity of the chemical reactions in PAN. It is found that both 13C direct polarization magic angle spinning NMR spectra and 1H spin-lattice relaxation time in the laboratory frame (T1H) of the stabilized 13C labeled aPAN films highly depend on the film thickness, which is attributed to different chemical reaction mechanisms at the surface and inner cores due to a limited oxygen diffusivity. For the first time, tunable T1H filtered 2D 13C–13C INADEQUATE NMR selectively observed either the well-stabilized aPAN at the surface or poorly st (open full item for complete abstract)

Committee: Toshikazu Miyoshi (Advisor); Tianbo Liu (Committee Chair); Chunming Liu (Committee Member); Yu Zhu (Committee Member); Mesfin Tsige (Committee Member) Subjects: Chemistry; Materials Science; Physics

Master of Science, The Ohio State University, 1982, Graduate School

Committee: Not Provided (Other) Subjects:

Master of Science, The Ohio State University, 1987, Graduate School

Committee: Not Provided (Other) Subjects:

Master of Science, The Ohio State University, 1960, Graduate School

Committee: Not Provided (Other) Subjects:

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

Given a set of video imagery from unknown device provenance, video-based source camera identification (V-SCI) refers to a task of identifying which device collected the imagery. V-SCI techniques predominantly leverage photo response non-uniformity (PRNU) patterns extracted from digital video for device identification decisions. PRNU patterns function as device fingerprints and SCI methods using PRNU from digital still imagery (I-SCI) are relatively mature; however, advancements in video processing, namely electronic image stabilization (EIS) algorithms, degrade video extracted PRNU distinctiveness yielding a significant obstacle toward extending I-SCI performance to EIS processed video datasets. We provide a new, more relevant PRNU dataset, UDAYTON23VSCI, for V-SCI benchmarking in contrast to current publicly available datasets. To address the EIS V-SCI challenge, we present a data-driven approach to exploit PRNU signals derived from EIS video via ``device-specific'' neural networks implemented with a novel PRNU image training and transfer learning strategy. Results implementing our device-specific network approach on UDAYTON23VSCI and a leading publicly available dataset confirm the advantages of our approach over state of the art SCI methods. We provide a new PRNU computation approach via Log-noise PRNU estimation which overcomes multiplicative noise constraints inherent to PRNU patterns in imagery. We show our Log-noise PRNU estimation approach outperforms the current widely accepted PRNU estimation approach based on maximum likelihood estimation (MLE) in V-SCI task thus eliminating the need for MLE in computing PRNU. Lastly, by removing MLE PRNU computation requirement, we show our Log-noise PRNU estimation approach is a key contribution toward realizing a fully data driven end-to-end (E2E) network design for tackling EIS V-SCI.

Committee: Keigo Hirakawa (Advisor); Barath Narayanan (Committee Member); Partha Banerjee (Committee Member); Vijayan Asari (Committee Member) Subjects: Artificial Intelligence; Electrical Engineering

Doctor of Philosophy, University of Akron, 2022, Psychology-Industrial/Organizational

This dissertation studies the emergence of Transactive Memory Systems (TMS), specifically the shared knowledge structure component of TMS. To this end, the first part of the project provides in-depth discussions around the theoretical and methodological integration of the TMS and broader teams literatures, the alignment of theoretical and empirical TMS definitions, and the need to study communication in depth as the mechanism through which TMS develops. In the second part of the dissertation, the principles of these discussions were applied to build a computational model of TMS shared knowledge structure emergence in R. Each simulation ran for 100 iterations to study whether communication between agents regarding their areas of expertise resulted in the emergence of the TMS shared knowledge structure. Decision-making and deep learning theories were drawn on to predict that when agents did not have overlap in areas of expertise (had some overlap in areas of expertise), selecting to communicate with the team member thought most likely to be an expert in an information area led to more favorable (less favorable) outcomes than selecting which team member to communicate with randomly. The simulation was repeated for seven learning rates representing how readily agents changed their perceptions about their team members. Results indicated that query and response regarding expertise areas of agents consistently led to the emergence of a TMS shared knowledge structure across conditions. In most instances the pattern of emergence was marked by an initial period of rapid emergence followed by a decrease in the emergence rate. The results supported the hypotheses that when there is no expertise overlap, selecting maximally would lead to a more emerged shared knowledge structure than searching randomly, while the opposite would be the found when there was some expertise overlap. The latter finding challenges the assumption present in the TMS literature that searching for inf (open full item for complete abstract)

Committee: Joelle Elicker (Advisor); Andrea Snell (Committee Co-Chair); Matthew Juravich (Committee Member); James Diefendorff (Committee Member); Paul Levy (Committee Member) Subjects: Psychology

Master of Science, The Ohio State University, 2022, Environmental Science

Agricultural soils have considerable potential to mitigate climate change by sequestering substantial amounts of atmospheric carbon as soil organic carbon (SOC). This research hypothesized that adding winter wheat to corn-soybean crop rotations increases fungal abundance and diversity and the amount of more stabilized SOC. Corn-soybean (CS) and corn-soybean-wheat (CSW) treatments were established in 2012 under a no-till system with a randomized block design at two separate locations, the Northwest and Western Agricultural Research Stations (NWARS and WARS, respectively). Soil samples were collected in fall 2020 after corn harvest at a depth of 0-10 cm. Total fungal biomass and enzyme activity were measured in conjunction with long-read genetic sequencing of the mycobiome to provide fungal taxonomic abundance and diversity. Soil carbon (C) was examined using a modified Walkley-Black method along with total C analysis after size and density separation and chemical oxidation. Total fungal biomass was higher under CSW than the CS rotation (26% at NWARS, 9% at NWARS) with greater diversity at WARS but not NWARS. Concentrations of oxidatively resistant SOC were higher under CSW than the CS rotation (0.68% at NWARS, 13.1% at WARS). This study showed that diversifying crops can impact soil fungi and potentially increase the amount of stable SOC, but farmers should be aware of how rotations affect their operations. As methods to monitor and increase SOC improve, C farming programs and markets will expand allowing yield uncertainty to be countered by generating sellable C credits.

Committee: Laura Lindsey (Advisor); Scott Demyan (Committee Member); Soledad Benitez-Ponce (Committee Member) Subjects: Agronomy; Environmental Science; Soil Sciences

Doctor of Philosophy (PhD), Ohio University, 2022, Civil Engineering (Engineering and Technology)

Perpetual pavement can be defined as a flexible pavement that lasts longer than 50 years by maintaining strain at the bottom of the Asphalt Concrete (AC) layer below a specified threshold called fatigue endurance limit. This goal can be achieved by designing a proper pavement thickness and underlying layers that resist pavement distresses. In this research, U.S. route 23 project in Delaware County, Ohio, was considered, which is one of the Strategic Highway Research Test roads (SHRP). This study aims to optimize the thickness of pavement layers to achieve the acceptance criterion of perpetual pavements in Ohio. A three-dimensional viscoelastic finite element model was developed to simulate perpetual pavement response under a different truck and tire configurations, pavement temperature, AC layer thicknesses, soil stabilization, traffic speed and tire pressures. The viscoelastic model was calibrated and validated using field-measured pavement responses using dynamic instrumentation gages embedded in the pavement layers during construction. The viscoelastic behavior of asphalt material was determined by following interconversion procedures using dynamic modulus test results to estimate Prony series where 9 terms of Prony series were used. The results showed that the developed viscoelastic model accurately captures and predicts pavement response in comparison to measured values. Six cases of thickness variation incorporated with five cases of temperature variation with and without subgrade stabilization were studied to optimize the thickness of perpetual pavement under loading and environmental conditions. The results showed that changing the AC base thickness has a higher impact on reducing tensile strain at the bottom of the AC layer despite changing aggregate base thickness due to stiffness difference. In addition, utilizing stabilized subgrade allows thinner pavement design by reducing tensile strain at the bottom of AC l (open full item for complete abstract)

Committee: Shad Sargand (Advisor); Issam Khoury (Committee Member); Adam Fuller (Committee Member); Bahaven Naik (Committee Member); Tao Yuan (Committee Member); Teruhisa Masada (Committee Member) Subjects: Civil Engineering

Doctor of Philosophy, The Ohio State University, 2022, Chemistry

The objective of this dissertation is to physically and chemically characterize a hydrophobic paper-based microsampling platform and to apply it to various applications including drug testing and the development of a three-dimensional (3D)-embossed hydrophobic paper platform that enables field collection, storage, and direct analysis of biological samples through ambient ionization mass spectrometry (MS). Conventional microsampling platforms have several advantages when compared to traditional collection methods; however, several notable disadvantages are commonly associated with these platforms, such as cold storage requirements and laborious sample pre-treatment and clean-up steps prior to analysis. Ambient ionization techniques have been developed to overcome these challenges to enable rapid, direct analysis of samples in situ by coupling the microsampling platform (e.g., paper spray, PS) to MS, a powerful analytical tool that allows for quantitative and qualitative studies to be performed. Chapter 2 describes the process by which a protective barrier forms on the exterior surface of dried blood spheroids on hydrophobic paper substrate. This was achieved through chemical characterization of cocaine spiked in blood using PS-MS and physical characterization of red blood cell (RBC) morphology through scanning electron microscopy (SEM). It was determined that the self-assembly of RBCs during the initial evaporation stages of drying ultimately leads to an external protective barrier that passivates the interior bulk, protecting it from environmental stressors. Chapter 3 describes the utilization of an exogenous polymer, xanthan gum, to help stabilize dried blood spheroids that dry under non-optimal drying conditions which leads to severe cracking and cratering, subjecting the interior bulk to potential degradation due to exposure to the environmental elements. This insight led to the fortification of a less viscous b (open full item for complete abstract)

Committee: Abraham K. Badu-Tawiah (Advisor); L. Robert Baker (Committee Member); Bern Kohler (Committee Member); Vicki H. Wysocki (Committee Member) Subjects: Chemistry

Master of Science, The Ohio State University, 2021, Mechanical Engineering

This work presents a neural network (NN) based adaptive feedback regulator to ensure the lateral and longitudinal stability and regulate the desired walking velocity of a lower-limb exoskeleton under model uncertainty. The traditional model-based controllers for lower-limb exoskeletons often fail to stabilize the robot or accurately track the desired behaviors under model uncertainties or external disturbances. This paper proposes a neural network (NN) based online adaptive regulator that compensates for the unknown changes in model parameters and external disturbances by modifying the nominal joint trajectory. A gradient descent-based delta rule is implemented to update the weights of a single layer NN, which can be efficiently performed online by design. We demonstrate the performance of the presented regulator on ATALANTE, a fully actuated lower limb exoskeleton designed for paraplegic patients. The simulation results show that the proposed approach noticeably improves stability and the tracking performance of the system, despite significant changes in model parameters and large adversarial pushes.

Committee: Ayonga Hereid Dr. (Advisor); Haijun Su Professor (Committee Member) Subjects: Mechanical Engineering

Master of City and Regional Planning, The Ohio State University, 2021, City and Regional Planning

The Neighborhood Stabilization Program helped to fund housing rehabilitation across the U.S. Columbus provides an interesting case study to help affirm previous research on the externality of rehabilitation. The application of a hedonic housing price model finds a 2% increase in the sale price for each completed rehabilitation project within 0.1-mile. Racial and class disparities in housing sale prices are also seen in the model results. Additional analysis shows the benefits of spatial regression for hedonic models. This research is framed by theories of displacement and revitalization such as disinvestment displacement, reinvestment displacement, and incumbent upgrading. In the field of planning, displacement is an important issue and a possible harmful outcome from government programs.

Committee: Zhenhua Chen (Advisor); Bernadette Hanlon (Committee Member) Subjects: Urban Planning

Master of Science, Miami University, 2020, Chemistry and Biochemistry

This thesis describes changes in structure and activity of lactate dehydrogenase in solution containing the Pluronic F127 polymer. The LDH structural study in Pluronic solutions is carried out by fluorescence and circular dichroism spectroscopy, and compared to that with polyethylene glycol. The LDH structure is more stabilized by the Pluronic F127 polymer than PEG against 20% acetonitrile in the aqueous solution. The change in LDH activity with Pluronic F127 is studied by flow injection analysis in conjunction with fluorescence. The LDH will denature and significantly lose its activity under room temperature over time. The presence of 5% Pluronic F127 in the solution will stabilize LDH for at least 96 hours with only a 3-8% loss in activity, comparable to polyethylene glycol. This thesis also provides a study of electrophoresis of low molar mass peptides (< 2 kDa) using the Pluronic F127 gel as the supporting medium, followed by matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) detection. Pluronic polymers suppress MALDI-MS signals of peptides but can be removed using ultrafiltration with a 10 kDa membrane filter. Separation of a four-peptide mixture pre-stained by Remazol Brilliant Blue was unsatisfactory. Further gel modifications should be carried out for electrophoresis separation of peptides.

Committee: Neil Danielson (Advisor); Hang Ren (Committee Chair); Benjamin Gung (Committee Member); Ann Hagerman (Committee Member) Subjects: Chemistry

Master of Science, The Ohio State University, 2020, Mechanical Engineering

Significant development of micro-electromechanical systems (MEMS) has led to various technologies for sensing, timing, signal processing, and energy harvesting. Owing to their compact size and ultra-low damping, micro-electro-mechanical (MEM) resonators can operate at high resonant frequencies with high-quality factors. However, the relatively large oscillation amplitudes compared to their characteristic dimension make their dynamics easily transfer from linear to nonlinear domain. Thus, there has been a growing interest in exploiting nonlinear dynamics to improve the performance of MEMS/NEMS. This thesis focuses on investigating one interesting type of nonlinear resonance that involves multiple resonance modes through an effective intermodal coupling: internal resonance (IR). IR occurs in a nonlinear system in which two or more resonant mode frequencies are commensurate or nearly commensurate to be in an m:n ratio where m and n are integers. This research aims to provide a better understanding of the mechanism of IR when it is exploited in MEMS oscillators to mitigate their critical issue of frequency fluctuation. In this regard, the detailed dynamic characteristics were theoretically investigated based on an analytical model that had been experimentally validated. This IR model was modified to include a second harmonic term in the excitation force because it naturally arises in the practical electrostatic actuation of MEM oscillators. A numerical analysis based on the Runge-Kutta method and the Newton-Raphson method was also performed to further validate the analytical model and obtain theoretical results. Finally, to understand the mechanism of frequency stabilization through IR, a stochastic process was employed by imposing random variations in the drive amplitude and frequency. Based on the analytical model, it was confirmed that the internally resonated mode is directly actuated by the externally driven mode within the range of IR. The (open full item for complete abstract)

Committee: Hanna Cho (Advisor); Manoj Srinivasan (Committee Member); David Talbot (Committee Member) Subjects: Mechanical Engineering