Master of Science, Miami University, 2023, Mechanical Engineering

Radial pulses are crucial for assessing health and serve as a surrogate marker for arterial compliance and cardiovascular disease. They aid in diagnosing internal diseases in Eastern Medicine and monitoring activities and vital signs. Reproducing accurate human radial pulses is vital for the development of wearable healthcare devices and training healthcare providers for various healthcare applications. As a result, pulse generators are of high importance as they can play an important role in advancing many fields. To this end, a pulse generator is proposed which is comprised of MR fluids to shape a base pulse into a variety of pulses. The study presents the experimental set-up and successful results of replicating a range of radial pulses continuously. Moreover, analysis of the Windkessel Model (WM) is presented which verifies the theory of continuous pulse shaping. A six element WM was studied which used a single input to generate a range of age-related pulses. Finally, the project introduces a model which predicts the inputs required to generate the desired pulse waveform. Overall, the study achieved its goal of creating a pulse generator capable of continuously reproducing a wide variety of radial pulse waveforms.

Committee: Jeong-Hoi Koo (Advisor); Yingbin Hu (Committee Member); Tae-Heon Yang (Committee Member) Subjects: Biomedical Engineering; Engineering; Mechanical Engineering

Master of Science (M.S.), University of Dayton, 2019, Electrical Engineering

Electroporation is a process that uses high voltage pulsed electric field to permeate cell membrane for drug infusion or cell death. Changing the voltage level, pulse period, or pulse width modifies the effect of the treatment. The purpose of this paper is to present a new alternative to high power pulsed field electric generators that, for the first time, reduces the system to a single custom complementary metal-oxide semiconductor (CMOS) chip, as well as allows various customizations in terms of frequency or duty cycle. A 206 kHz, 500V square wave was obtained from our chip design. The chip schematic simulation showed a duty cycle variation from 12.5% to 34.9%.

Committee: Vamsy Chodavarapu P.E., Ph.D (Advisor); Guru Subramanyam Ph.D (Committee Member); Amy Neidhard-Doll Ph.D (Committee Member) Subjects: Electrical Engineering

Doctor of Philosophy (PhD), Ohio University, 2014, Electrical Engineering (Engineering and Technology)

Next Generation aviation, in short “NextGen,” requires an Alternate Positioning Navigation and Timing (APNT) system to back up the Global Navigation Satellite Systems (GNSS). Distance Measuring Equipment (DME) is a favorable APNT candidate but likely needs to be upgraded to enhanced Distance Measuring Equipment (eDME) to support the stringent NextGen aeronautical navigation requirements. This dissertation proposes, researches, and demonstrates eDME carrier phase, a key enabling technology that can dramatically improve the eDME system performance. eDME carrier phase provides line-of-sight displacement measurements with mm-level accuracy. After introducing the eDME carrier phase concept, this dissertation discusses the required changes for airborne and ground equipment. A novel flight test methodology is presented that allows evaluation of the eDME carrier phase performance without requiring changes to existing equipment. A spectrum-based carrier phase acquisition algorithm is presented next. Combined with several interference-mitigation techniques, this acquisition method demonstrates fault-free acquisition. Furthermore, a phase-locked loop (PLL) is designed for eDME carrier phase. A correction term is first proposed to modify the conventional PLL design to reduce the undesired loop stability and bandwidth changes when the loop noise equivalent bandwidth is close to the Nyquist frequency of the loop. This modified PLL is then further adapted to accommodate eDME's random pulse timing. The carrier phase tracking results show dm-level errors for 110-km straight and level flights and for various banking maneuvers up to 60 degrees. These errors are further characterized and quantified. eDME carrier phase can be used in combination with the eDME pulse range to significantly improve the accuracy and integrity of the DME system. Several algorithms are introduced and the resulting improvement of the eDME accuracy and integrity performance are illustrated. Finally, DM (open full item for complete abstract)

Committee: Wouter Pelgrum Dr. (Advisor); Frank van Graas Dr. (Committee Member); Maarten Uijt de Haag Dr. (Committee Member); Sanjeev Gunawardena Dr. (Committee Member) Subjects: Aerospace Engineering; Electrical Engineering

Master of Science, Miami University, 2024, Mechanical and Manufacturing Engineering

Wire electrical discharge machining (WEDM) enables production of complex parts with tight tolerances, although maintaining dimensional accuracy in corners and tapers remains challenging due to wire deflection and vibration. This study optimizes WEDM parameters for achieving high-accuracy in machining complex geometrical parts and taper cuts in 6061 Aluminum alloy using Excetek W350G WEDM machine with a copper wire electrode. Parameters including Wire Tension, Pulse On-Time, Pulse Off-Time, Wire Feed Rate, Open Circuit Voltage, and Flashing Pressure were varied using L18 Taguchi Orthogonal Array and response graph method to identify optimal cutting conditions. Results indicated feature-specific optimization is crucial, as different geometrical features (rectangular fins, triangular fins, gears) exhibited varying critical parameters. Key findings highlighted the importance of Wire Tension and Pulse On-Time in maintaining cutting accuracy, although at varying levels for specific features. Response graphs demonstrated effects of major WEDM parameters on corner and profile accuracies, whereas Taguchi analysis provided optimum settings of parameters for each feature and taper cutting. Validation experiments for rectangular fins showed significant improvement in the dimensional error for the fin length and taper angle. These advancements will enhance precision, efficiency, and versatility of WEDM processes in machining complex profiles, and corners, contributing to precision manufacturing.

Committee: Muhammad Jahan (Advisor); Carter Hamilton (Committee Member); Jinjuan She (Committee Member) Subjects: Aerospace Engineering; Biomedical Engineering; Industrial Engineering; Mechanical Engineering

Master of Science, The Ohio State University, 2017, Mechanical Engineering

Perovskite crystals have been widely researched and applied in the field of solar cell engineering, and recently in the field of high energy photon detection. Within the nuclear detection industry, there is a desire for new, cost-effective materials for the use of gamma spectroscopy. This thesis sets out to produce a new hybrid inorganic – organic metal halide perovskite based, low-cost gamma spectroscopy detector. With the aid of Professor Haung's group from the University of Nebraska-Lincoln, various perovskite device structures are fabricated and tested. To assist in the verification of the experimental results, the energy spectrum for the nuclear decay of the 137Cs isotope is generated through modeling of real-time pulse height analysis with simulation software Geant4. A well-defined 137Cs energy spectrum is acquired by using a CH3NH3PbBr2.94Cl0.06 single crystal at room temperature. The energy spectrum obtained, along with supporting data, provides evidence of how perovskite single crystal can successfully detect high energy photons. The low cost, simple synthesis, and excellent radiation hardness of the hybrid perovskites make them ideal candidates for radiation detector materials.

Committee: Lei Cao Ph.D (Advisor); Vaibhav Sinha Ph.D (Committee Member) Subjects: Electrical Engineering; Mechanical Engineering; Nuclear Engineering

Doctor of Philosophy, University of Akron, 2014, Mechanical Engineering

The response of single-curvature composite panels under external blast was studied. For the single-curvature composite shells under external pressure pulse loading, Lagrange’s equations of motion were established to determine the shell response and the Budiansky-Roth criterion was used to examine the instability. The predicted transient shell response compared very well with FEA results from ABAQUS Implicit, and the predicted buckling loads also agreed with experiments on steel arches. Under various load durations, buckling was impulsive, dynamic and quasi-dynamic. Thicker composite shells were more likely to fail by first-ply failure rather than buckling. It was shown that the composite lay-up could be adjusted to increase the buckling resistance of the shell. For the single-curvature composite sandwich panels under external pressure pulse loading, a multi-layered approach was used to distinguish facesheets and core deformations. Core compressibility and transverse shear through the thickness were accounted for using linear displacement fields through the thickness. Equations of motion for the facesheet transient deformations were again derived from Lagrange’s equations of motion, and predicted solutions using this approach compared very well with FEA results from ABAQUS Implicit. In the case of core undergoing elastic deformations only, both facesheet fracture during stable deformation response and local dynamic pulse buckling of facesheets were considered as possible modes of failure in the curved sandwich panel. It was found that local facesheets buckling is more likely to occur than facesheet fracture in thin and deeply curved sandwich panels. The facesheet laminate lay-up could also be adjusted to improve the local buckling resistance of the curved sandwich panel. In the case of the core undergoing elastic-plastic deformations, a parametric study showed that blast resistance of the curved sandwich panel can be increased by allowing cores to un (open full item for complete abstract)

Committee: Michelle Hoo Fatt Dr. (Advisor); Xiaosheng Gao Dr. (Committee Member); Gregory Morscher Dr. (Committee Member); Ernian Pan Dr. (Committee Member); Kevin Kreider Dr. (Committee Member) Subjects: Mechanical Engineering

PhD, University of Cincinnati, 2002, Engineering : Aerospace Engineering

Highly sophisticated and extensively tested computational fluid dynamics codes are available to simulate the operation of inlet and compressor systems in high-speed air-breathing propulsion devices. In contrast, the methods used to couple these codes during the simulation of an unsteady flow transient are in a significantly less advanced state. In engineering practice the computations are typically performed separately for each device, while representing the adjacent component through a boundary condition. Unfortunately, the lack of experimentally validated compressor face boundary conditions leaves the accuracy of these models open to doubt. From the viewpoint of inlet computations, the compressor face boundary condition amounts to an approximate description of the manner in which upstream moving acoustic waves are induced by the arrival of downstream moving acoustic and entropy (temperature) disturbances to the compressor. This dissertation presents the results of an experimental investigation involving such rapid flow transients in a facility that combined a constant area circular inlet with a single-stage axial-flow compressor. Inlet Mach numbers ranged from 0.15 to 0.45. The experiment employed an impulse method, in which short-duration, large amplitude acoustic and entropy pulses were generated within the inlet utilizing an exploding wire technique. The incident acoustic pulse, its reflection from the compressor and the acoustic wave transmitted across the compressor were tracked by fast response pressure transducers, while entropy pulses were detected by dual-element hotfilm probes. Frequency domain analysis of the data yielded transfer functions that may be thought of as non-dimensional frequency-resolved reflection, transmission and induction coefficients. Transfer functions have been demonstrated to be suitable for the prediction of transients induced by small amplitude, incident acoustic and entropy pulses, thereby representing a powerful method for exten (open full item for complete abstract)

Committee: Dr. Miklos Sajben (Advisor) Subjects: Engineering, Aerospace

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

This dissertation reports findings on three different but related topics. Determination of cathodic kinetics for Al-containing phases is essential to characterize the corrosion behavior of high strength Al alloys. However, the current density measured from a potentiostat can be different than the true cathodic current because anodic dissolution occurs during cathodic polarization of Al alloys and a potentiostat only senses the net current. Therefore, it is necessary to use a nonelectrochemical measurement, such as Eletrochemical Quartz Crystal Microbalance (EQCM) technique. EQCM was used on thin film compositional analogs of S phase (Al2CuMg) particle, which is an important intermetallic particle commonly found in Al alloys, to evaluate the true cathodic current density. In principle, it should be possible to apply the EQCM technique to determine kinetic parameters, e.g., diffusivity of water. However, little research has been performed to relate this information to delamination and subsequent corrosion of the substrate under the coatings. Therefore, it is interesting to use EQCM for investigating water uptake in organic coatings, delamination, and corrosion on coated Al electrode. Electrochemical Impedance Spectroscopy (EIS) cannot accurately sense the initial degradation of protective coatings as they are just starting to fail because the low frequency impedance is typically higher than the input impedance of the EIS system for reasonably-sized samples. Changes in corrosion resistance of these good coatings cannot be sensed until a significant degradation occurs. Therefore, it is interesting to investigate other evaluation techniques to assess the early stage of organic coating failure. Potentiostatic Pulse Testing (PPT), which involves the application of potential steps instead of sine waves, holds promise for the evaluation of these protective coatings.

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

Master of Science (MS), Ohio University, 1999, Electrical Engineering & Computer Science (Engineering and Technology)

The purpose of this thesis is to investigate and implement an optimal firing strategy for harmonic distortion minimization in variable frequency control of three-phase inverters. Optimal techniques for the minimization of harmonic distortion previously developed at Ohio University were adapted to calculate firing strategies for variable frequency applications. A control program was developed to execute the variable frequency control. A lab inverter was configured to demonstrate the minimization technique. Lab data was collected and compared with calculated values. In conclusion, harmonic distortion is effectively minimized for variable frequency control applications using the optimal technique.

Committee: Herman Hill (Advisor) Subjects:

Doctor of Philosophy, Case Western Reserve University, 2011, Chemical Engineering

Kinetic parameters that describe the operating efficiency and rate of a reaction are revealed in situ by applying normal pulse voltammetry to normally operating proton exchange membrane fuel cells. The Tafel slope for the oxygen reduction reaction is directly extracted from the steady state chronoamperometric response. Conditioning potential, temperature, and relative humidity are varied independently to observe their effect on the Tafel slope. Aqueous ex situ techniques commonly used to collect kinetic data only mimic the conditions within fuel cell and are unable to capture true operating processes, especially the effects of relative humidity. The observed Tafel slopes are 47-62 mV/decade for oxide covered platinum indicating a smaller activation overpotential than that for oxide free platinum with Tafel slopes of 91-119 mV/decade in initial studies. High temperature operation at 120°C showed no kinetic or mechanistic benefit compared to fuel cell operation at 80°C. If high efficiency is desired, the fuel cell should be operated in a potential range where oxide is present on the platinum surface. A novel technique is presented using pulse voltammetry measure platinum oxide coverage in situ on PEMFC electrodes. A linear logarithmic rate was noticed for oxide conditioning times longer than 1 second. Extended testing of relative humidity effects at 80 °C, combined with electrochemical active surface area measurements to normalize the oxide growth, showed a growth rate of 28 μC cm-2 (log s)-1 and also provided the ability to monitor platinum dissolution from the electrode. Concepts from both these projects are assimilated to develop novel pulse voltammetry waveforms that are applied in situ on normally operating proton exchange membrane fuel cells to reveal Tafel kinetics with control of adsorbed oxide on platinum. The results show that the Tafel slope decreases with increasing platinum oxide coverage on the electrode. The oxidation of higher order polyols such as gl (open full item for complete abstract)

Committee: Thomas Zawodzinski Jr. (Advisor); Jay Mann Jr. (Committee Chair); Mohan Sankaran (Committee Member); David Schiraldi (Committee Member) Subjects: Alternative Energy; Analytical Chemistry; Chemical Engineering; Energy; Engineering; Mechanical Engineering

Doctor of Philosophy, Case Western Reserve University, 2005, Physics

Short pulse tunable sources in the mid-infrared optical region have been an indispensible tool of research for several years. Yet the complexity of these systems limits their usefulness in many applications. In this study, pulse compression in a synchronously pumped optical parametric oscillator (SPOPO) is investigated as an alternative to these systems. Although pulse compression has been known for several years, a full understanding of the process has not been developed. This has inhibited its full exploitation. In this work, a search of the input parameter space is conducted in order to illucidate the mechanisms involved in pulse compression. The experiments conducted correlated compression to the input energy, optical parametric oscillator (OPO) wavelengths, and OPO cavity length detuning. The 10 ps pump pulses from a pulsed Nd:YAG laser interact in the parametric oscillator to generate infrared output pulses as short as 400 fs—a 20 fold compression. Experiments indicate that the compression varies directly with the input energy and inversely with the signal-idler group velocity mismatch (GVM) across the 2.5 – 4.0μm spectral range. It is also found that the cavity detuning length affected the dynamics of the nonlinear interaction. To gain physical insight into the experimental findings, numerical modeling is employed. Using nominal values for the input parameters, it is found that the model predicts the compression within about 30% and accurately predicts the input energy and signal-idler GVM trends. This agreement is then the basis for employing the model to extract physical insight into the compression mechanism. The dependence of compression on the signal-idler GVM is found to be more than an order of magnitude stronger than the signal-pump GVM usually thought to be responsible for the pulse compression. The model further predicts that using a 1 ps pump source should yield pulses on the order of 50 fs and that strong pulse compression could also be observed i (open full item for complete abstract)

Committee: Kenneth Singer (Advisor) Subjects:

Master of Science in Engineering, Youngstown State University, 2012, Department of Electrical and Computer Engineering

Two different three-phase inverters are introduced and compared showing the differences and similarities between them in terms of output power, implementation, challenges and efficiency. Both inverters use the same feedback controller and both have the same input voltage and the same load levels. The first inverter is a three-phase sinusoidal pulse width modulation (PWM) inverter that generates gate-control signals using a sinusoidal wave source. It is shown that pulse width modulation utilizes a simpler approach to convert DC power into AC. The second inverter is a three-phase space vector pulse width modulation (SVPWM) inverter. SVPWM inverters utilize a space vector (reference vector) to create the desired sinusoidal waves. SVPWM proved to have less total harmonic distortion (THD% = 1.15%) and faster response time (114ms) with an output error of 0.13V. this compares with a sinusoidal PWM (THD% = 3.73%, response time = 136ms and output error = 0.23V). SVPWM proves to have better overall performance. MATLAB's Simulink is used to build and test the performances of each inverter and then compare the inverters with a pre-existing three-phase grid.

Committee: Jalal Jalali PhD (Advisor); Philip Munro PhD (Committee Member); Frank Li PhD (Committee Member) Subjects: Electrical Engineering; Engineering

Master of Science, The Ohio State University, 1970, Graduate School

Committee: Not Provided (Other) Subjects:

Master of Science, The Ohio State University, 1969, Graduate School

Committee: Not Provided (Other) Subjects:

Master of Science, The Ohio State University, 1967, Graduate School

Committee: Not Provided (Other) Subjects:

Master of Science, The Ohio State University, 1967, Graduate School

Committee: Not Provided (Other) Subjects:

Master of Science, The Ohio State University, 1971, Graduate School

Committee: Not Provided (Other) Subjects:

Master of Science, The Ohio State University, 1965, Graduate School

Committee: Not Provided (Other) Subjects:

Master of Science, The Ohio State University, 1966, Graduate School

Committee: Not Provided (Other) Subjects:

Doctor of Philosophy, The Ohio State University, 2024, Mechanical Engineering

In this dissertation, a series of experiments were carried out to investigate the auto-ignition process of transient fuel jets and sprays issuing into high-temperature, environments. Novel high-speed imaging and laser diagnostic techniques were developed and applied to characterize mixing and turbulent flow conditions prior to and at the onset of ignition. In addition, this research examines the topology and dynamics of ignition kernels as they grow and transition into a stable flame. Research was carried out primarily in canonical atmospheric pressure experiments, but a new high-pressure spray test facility is developed in this work with preliminary measurements presented, demonstrating new experimental capabilities. Specific contributions of this dissertation include: (1) characterization of the transient mixing processes of variable-density atmospheric pressure jets both before and after ignition, (2) determination of the most probable mixing and turbulent flow conditions leading to local auto-ignition, (3) statistical evaluation of the dynamic growth and transport of ignition kernels, (4) construction and characterization of a novel high-pressure, high temperature spray and combustion facility, and (5) demonstration of high-speed mixture fraction measurements in non-reacting and reacting sprays at realistic thermodynamic conditions. First, a series of transient gas-phase fuel jets issuing into a high-temperature, vitiated environment at atmospheric pressure was investigated. A well-known jet-into-hot coflow configuration was utilized with the addition of a fast-acting solenoid valves to achieve pulsed fuel injection in an environment with well-defined boundary conditions. Four test conditions were studied to examine the effects of variations in jet Reynolds number, the fuel mixture composition, and coflow temperature. High-speed laser Rayleigh scattering (LRS) was performed at 10 kHz to measure the mixture fraction and temperature fields from fuel injection (open full item for complete abstract)

Committee: Jeffrey Sutton (Advisor); Seung Hyun Kim (Committee Member); Datta Gaitonde (Committee Member); Igor Adamovich (Committee Member) Subjects: Aerospace Engineering; Fluid Dynamics; Mechanical Engineering