Master of Science in Engineering (MSEgr), Wright State University, 2011, Electrical Engineering

Current-mode control is the most popular scheme used for the operation of SMPS (Switch Mode Power Supplies). Current-mode control, also known as current-programmed mode or current-injected control is a multi-loop control scheme that has an inner loop and an outer voltage loop. The current loop controls the inductor peak current while the voltage loop controls the output voltage. The inner loop follows a set program by the outer loop. Some of the most popular small-signal models that predict the small-signal characteristics of current-mode control scheme have been analyzed and compared in this thesis. A PWM dc-dc buck converter in CCM(Continuous Conduction Mode) has been chosen to explain the phenomenon of current-mode control in all these models. Small-signal characteristics are generated in MATLAB using the simplified analytical transfer functions. Some of the important small-signal characteristics include the current loop gain, control-to-output gain with the current-loop closed and outer loop open, audio susceptibility, and output impedance. The two most important models in consideration are: 1) Continuous-Time Model and 2) Peak Current-Mode control Model. Despite the fact that both these models predict the instability of current-mode control at a duty ratio of 0.5, these models differ significantly in deriving the expression for the sampling gain. As a result, their small-signal characteristics differ over a wide frequency range. Also, a very less explored average current mode control is compared with the peak-current mode control based on the similar small-signal characteristics.

Doctor of Philosophy, The Ohio State University, 2013, Mechanical Engineering

A series of high-fidelity, three-dimensional simulations has been performed to investigate hypersonic phenomena encountered in the HIFiRE Flight 1 and Flight 2 experiments. The investigation of HIFiRE-1highlights the performance of turbulence modeling in realistic hypersonic flight vehicles subject to laminar-to-turbulent boundary layer transition and geometry induced adverse pressure gradient separated shock boundary layer interactions (corner flows) influenced by three-dimensional effects. Comparisons with flight test data indicate that the performance of the turbulence model is dependent on the flow condition and the variable under examination. The surface pressure trends are reproduced in all cases, and predictions for the axial separation location is generally within 20% of the separated region length. For the lower Mach number cases, the surface pressure is predicted better at the lower Reynolds number case. Heat transfer predictions on the cone are good, although the use of empirically specified laminar-to-turbulent transition is necessary. The best comparison in heat transfer rates at the flare are observed at the highest Mach number. Overall, the results suggest that the K-ω turbulence model used in this study can be used for flight test prediction, though such uses must be done with care. The primary focus of this dissertation is on the HIFiRE-2 scramjet, specifically, the transient process of dual-to-scramjet mode-transition. For this geometry, the role of the primary fuel injectors in scramjet-mode operation is very important. The barrel shocks from the jet-in-crossflow interaction serves as a flameholder, allowing upstream propagation of pressure rise from the combustion in the cavity into the isolator. It is also shown that the presence of inlet shocks in theisolator can profoundly change the flow, a fact which must be considered in ground testing. A mode-transition event is present which demarcates dual-mode operation from scramjet-mode operation. (open full item for complete abstract)

Doctor of Philosophy (PhD), Wright State University, 2020, Electrical Engineering

The pulse-width modulated (PWM) dc-dc converters play a vital role in several industrial applications that include motor drives, electric vehicles, dc distribution systems, and consumer electronics. The switched-mode power converters step the input voltage up or down based on their typology and provide a regulated output voltage. The stability and regulation performance of a power converter can tremendously be improved via a suitable control design. However, due to the nonlinearity of the power converters and the presence of the line and load disturbances, the design of a robust and low-cost control circuit becomes a challenging task. The sliding-mode control of the dc-dc converters has been studied for decades because of its robustness, design simplicity, and suitability for variable structure systems. Despite the merits of the sliding-mode control method, the linear controllers are still dominant and attractive to the commercial applications since they require less design efforts and can be implemented using simple analogue circuits. This research aims to develop simplified sliding-mode control circuits for the classical PWM dc-dc converters in continuous-conduction mode (CCM). The control objectives are to maintain a constant switching frequency, enhance the transient response, provide wide operating range, and track the desired reference voltage under large disturbances. In order to design and test the control circuit, an accurate power converter model should be derived. Hence, large-signal non-ideal averaged models of dc-dc buck and boost converters in CCM are developed. The models are simulated in MATLAB/SIMULINK and compared with the corresponding circuits in SaberRD simulator for validation purpose. Next, PWM-based simplified sliding-mode voltage and current control schemes are designed for the dc-dc buck and boost converters in CCM, respectively. The design procedure and the analogue realization of the control equations are presented, where the control c (open full item for complete abstract)

Master of Science in Engineering, University of Akron, 2014, Electrical Engineering

This thesis develops a debris sensor interface to perform real-time continuous transmission of data from a sensor to monitor debris particles in oil. A test setup is created in which data from a single wear debris sensor is transmitted by the implemented debris sensor interface to a personal computer using a dedicated ethernet connection. The test setup is used to evaluate the requirements of processing time, memory and data communication associated with three operating modes that use three different levels of data compression. The results are analyzed to determine the capacity of the debris sensor interface and the ethernet channel to transmit data from a large number of sensor channels. The analysis shows the capacity of a single debris sensor interface is limited by the processing time needed to implement data compression; thus the mode with no data compression allows a single debris sensor interface communicating via a dedicated ethernet link to support the largest number of sensor channels. The number of sensor channels that can be monitored when multiple debris sensor interfaces are connected to a single dedicated ethernet channel is limited by the capacity of the ethernet channel; thus the mode that has the highest compression ratio supports the largest number of sensor channels. However, achieving a high compression ratio generally requires a significant computation time to process the debris signals; as a result, each individual debris sensor interface can process data from only a limited number of sensors, and more debris sensor interfaces are required.

Doctor of Philosophy, The Ohio State University, 2005, Electrical Engineering

The contributions of this Ph.D. research include the application of a modified space vector pulse width modulation (MSVPWM) scheme combined with robust servomechanism control in a three-phase four-wire split dc bus inverter and real-time implementation of Newton-Raphson Method on digital signal processors for on-line power system identification and power flow control of a distributed generation (DG) unit. This dissertation addresses digital control strategies of solid-state electric power converters for distributed generation applications in both island and grid-connected modes. Three major issues of DG, island operation, grid-connected operation, and front-end converter control, are discussed with proposed solutions and related analysis. In island mode, a control approach is developed for a three-phase four-wire transformerless inverter system to achieve voltage regulation with low steady state error and low total harmonic distortion (THD) and fast transient response under various load disturbances. The control algorithm combines robust servomechanism and discrete-time sliding mode control techniques. An MSVPWM scheme is proposed to implement the control under Clarke's reference frame. The robust stability of the closed-loop system is analyzed. In grid-connected mode, a real and reactive power control solution is proposed based on the proposed voltage control strategy for island operation. The power control solution takes advantage of a system parameter identification method and a nonlinear feedforward algorithm, both of which are based on Newton-Raphson iteration method. The proposed technique also performs grid-line current conditioning and yields harmonic free grid-line current. A phase locked loop (PLL) based algorithm is developed as a part of the solution to handle possible harmonic distorted grid-line voltage. In a DG unit with three-phase three-wire ac-dc-ac double conversion topology including a controlled power factor correction (PFC) front-end rectifier, (open full item for complete abstract)

Master of Science, Miami University, 2025, Mechanical and Manufacturing Engineering

Reduced order modeling (ROM) methods, such as those based upon Proper Orthogonal Decomposition (POD) and Dynamic Mode Decomposition (DMD), offer data-based turbulence modeling with potential applications for flow control. While these models are often cheaper than numerical approaches, their results require validation with source data. Within the literature, the metrics and standards used to validate these models are often inconsistent. Chabot (2014) produced a data-driven framework for validating these ROMs that used surrogate Markov models (SMMs) to compare how the system dynamics evolved rather than how any single metric evolved. These SMMs were constructed by clustering the flow data into different states of suitably similar flow fields, and the Markov model then mapped how likely each state was to transition into another. While this method was successful, there persisted an amount of uncertainty in how the outlier states within this clustering scheme were determined. Additionally, the study only examined the application of this procedure to POD-Galerkin ROMs. This study aims to tie the outlier state determination directly to the models' parent data. The study will also apply this procedure to ROMs generated from DMD to investigate how this framework's effectiveness carries over to different classes of ROMs.

Doctor of Philosophy (Ph.D.), University of Dayton, 2021, Electro-Optics

Mode-locked oscillators are the building blocks to generate ultrafast pulses which can then be used for many applications, including optical communication, metrology, spectroscopy, microscopy, material processing, as well as many applications in the healthcare industry. Mode-locked fiber oscillators are especially popular for their compactness, efficiency, and beam quality compared to their solid-state counterparts such as Ti: Sapphire lasers. Apart from their practicality, the mode-locked fiber lasers are an interesting object for studies, as they represent dynamically rich nonlinear systems. For ultrafast fiber oscillators at normal dispersion, a spectral filter is the utmost important optical component that determines the behavior of these systems in terms of the spectral bandwidth, pulse duration, central wavelength of the output spectra, multipulse dynamics, pulse structure as well as pulse velocity. Recently, there is a growing interest in fiber based spectral filters as they facilitate the construction of all-fiber laser cavities. This dissertation investigates the laser performance parameters by developing an all-fiber spectral filter and exploiting its characteristics. Especially, this dissertation reports the first experimental observation of dissipative solitons of the complex Swift Hohenberg equation. This is very important as it births multiple future projects related to implementing higher order spectral filtering in mode-locked fiber lasers. Although most of the ultrafast oscillators in this dissertation are built at 1 μm, ideas to build mode-locked lasers at visible wavelengths are also presented along with primary numerical simulation and experimental results. Finally, all the upcoming research directions are discussed in detail.

MS, University of Cincinnati, 2021, Engineering and Applied Science: Mechanical Engineering

Vibration-based damage detection methods have been extensively used in structural health monitoring as these are response-based techniques and can be applied to experimental/operational data. The conventional methods of obtaining full-field vibration measurements are limited due to the location and number of sensors. Advancements in imaging technology have enabled the use of the digital image correlation (DIC) technique to measure the full-field deformation of a vibrating structure. In this study, the DIC technique was used to obtain vibration measurements from an impact test of a cantilever beam for damage identification. The application of curvature mode shapes (CMSs) developed from the mode shapes (MSs) of the beam is studied to detect and locate the damage. The CMSs of the undamaged state of the beam are determined only from the damaged state of the beam, without prior information about the associated undamaged beam, provided the beam is geometrically smooth. It is shown that the polynomial fit of the appropriate order of measured MS is equivalent to the associated MS of the undamaged beam. The objective of this study was to investigate the use of DIC technique and CMSs to locate and detect damage in the form of a machined area with reduced thickness in a cantilever beam. The modal parameter estimation (MPE) was done using X-Modal software, based on the unified matrix polynomial approach (UMPA), to obtain mode shapes and natural frequencies from the vibration measurements. It is shown that the proposed method can successfully detect and locate damage in the beam, for the data obtained from a single-input impact test. The work focuses on understanding how the parameters used in the DIC technique and MPE influence the damage detection. The influences of parameters such as subset size and step size used in the DIC technique are studied. The influences of parameters such as type of MPE algorithm, frequency band selection and model order during MPE are studied. (open full item for complete abstract)

Doctor of Philosophy (Ph.D.), University of Dayton, 2018, Mechanical Engineering

This research presents engineering models that simulate steady-state and transient operations of air-cooled condensing units and an automatic commercial ice making machines ACIM, respectively. The models use easily-obtainable inputs and strategies that promote quick computations. Packaged, air-cooled condensing units include a compressor, condensing coil, tubing, and fans, fastened to a base or installed within an enclosure. A steady-state standard condensing unit system simulation model is assembled from conventional, physics-based component equations. Specifically, a four-section, lumped-parameter approach is used to represent the condenser, while well-established equations model compressor mass flow and power. To increase capacity and efficiency, enhanced condensing units include an economizer loop, configured in either upstream or downstream extraction schemes. The economizer loop uses an injection valve, brazed-plate heat exchanger (BPHE) and scroll compressor adapted for vapor injection. An artificial neural network is used to simulate the performance of the BPHE, as physics-based equations provided insufficient accuracy. The capacity and power results from the condensing unit model are generally within 5% when compared to the experimental data. A transient ice machine model calculates time-varying changes in the system properties and aggregates performance results as a function of machine capacity and environmental conditions. Rapid "what if" analyses can be readily completed, enabling engineers to quickly evaluate the impact of a variety of system design options, including the size of the air-cooled heat exchanger, finned surfaces, air flow rate, ambient air and inlet water temperatures, compressor capacity and/or efficiency for freeze and harvest modes, refrigerants, suction/liquid line heat exchanger and thermal expansion valve properties. Simulation results from the ACIM model were compared with the experimental data of a fully instrumented, standar (open full item for complete abstract)

Doctor of Philosophy (PhD), Wright State University, 2018, Electrical Engineering

Energy efficient, wide-bandwidth, and well-regulated dc-dc power converters are in great demand in today's emerging technologies in areas such as medical, communication, aerospace, and automotive industries. In addition to design and selection of the converter components, a robust closed-loop modeling is very essential for reliable power-electronic systems. Two closed-loop control techniques for power converters exist: voltage-mode control and current-mode control. The principles of voltage-mode control have been explored in great depths by researchers over the last two decades. However, the dynamic modeling of current-mode controlled dc-dc power converters has many uncharted areas that needs careful attention. Two main methods exist under the category of current-mode control: peak current-mode control and average current-mode control. Both of these control strategies are very attractive in applications that require fast control speeds, improved voltage regulation, and improved power supply noise rejection ratio. In recent technological advancements, where high noise immunity and tight regulation are desired, the average current-mode control has proven to be a superior choice, when compared to other control techniques for power converters. In this dissertation, a complete systematic theoretical framework for analysis, design, characterization, and measurements of the dc-dc converters with average current-mode control is introduced. To overcome the drawbacks of the traditional average current-mode control method, a new, true-averaged current-mode control technique is proposed. The new technique is implemented on the basic converter topologies namely, buck, boost, and buck-boost. The dynamic small-signal models of the converter power-stages are developed using the circuit-averaging technique. The inner-current loop of the power converters is designed and their frequency-domain, time-domain, and pole-zero domain characteristics are exploited. Subseque (open full item for complete abstract)

Doctor of Philosophy, The Ohio State University, 2017, Aero/Astro Engineering

Shock-boundary layer interactions (SBLIs) are ubiquitous occurrences in supersonic and hypersonic vehicles and have the tendency to inhibit their structural and aerodynamic performance. For example, in the inlets and isolators of such vehicles, the shock wave generated by one surface interacts with the boundary layer on an adjacent one. They are also present on the exterior of the vehicles, e.g. at the fuselage/vertical stabilizer junctions. These interactions cause unsteady separation, resulting in reduced air in-take efficiency, or unstart in extreme cases; unsteady vortex shedding which yields undesirable broadband noise; and significant pressure fluctuations which compromise the structural integrity of the vehicle and which can lead to loss of control authority. Mitigating these issues is therefore an important part of optimizing aerodynamic and structural design of high speed vehicles. The first step in this respect is obtaining a better understanding of the interaction unsteadiness. Nominally 2-D interactions have been studied extensively and have identified low-frequency shock motions which lead to undesirable pressure loads. The particular frequencies associated with the motions have been characterized using time resolved experiments and computations, and shown to depend on the mean size of the separation. The physical processes responsible for these frequencies are however still under investigation and the physical relationship between the shock motions and pulsations of the separation bubble remains obscure. For flow fields where the shock is swept, a complex 3-D interaction is encountered whose unsteady features are even less well understood. The mean structure of these 3-D interactions has been obtained experimentally and using RANS simulations, and shown to be profoundly different from the 2-D flow field indicating that progress in understanding 2-D interactions cannot be directly translated to 3-D. Specifically, there is no reci (open full item for complete abstract)

Master of Mathematical Sciences, The Ohio State University, 2017, Mathematical Sciences

Partial Differential Equation simulations can produce large amounts of data that are very slow to transfer. There have been many model reduction techniques that have been proposed and utilized over the past three decades. Two popular techniques Proper Orthogonal Decomposition and Dynamic Mode Decomposition have some hindrances. Non-Uniform Dynamic Mode Decomposition (NU-DMD), which was introduced in 2015 by Gueniat et al., that overcomes some of these hindrances. In this thesis, the NU-DMD's mathematics are explained in detail, and three versions of the NU-DMD's algorithm are outlined. Furthermore, different numerical experiments were performed on the NU-DMD to ascertain its behavior with repect to errors, memory usage, and computational efficiency. It was shown that the NU-DMD could reduce an advection-diffusion simulation to 6.0075% of its original memory storage size. The NU-DMD was also applied to a computational fluid dynamics simulation of a NASA single-stage compressor rotor, which resulted in a reduced model of the simulation (using only three of the five simulation variables) that used only about 4.67% of the full simulation's storage with an overall average percent error of 8.90%. It was concluded that the NU-DMD, if used appropriately, could be used to possibly reduce a model that uses 400GB of memory to a model that uses as little as 18.67GB with less than 9% error. Further conclusions were made about how to best implement the NU-DMD.

Master of Science, University of Akron, 2016, Physics

In this thesis, I investigated c-axis optical properties of a family of high temperature superconductors La2-xSrxCuO4. Eight samples with different dopings, from x = 0.04 to x = 0.20 were studied at temperatures 32 K, 80 K, and 300 K, all in the normal (non-superconducting) state. I used the Fano model to fit their infrared spectra and from the best fits I extracted the parameters of the phonons: oscillator frequency, plasma frequency, scattering rate and Fano frequency. I then compared these results with the results obtained previously on the same data set using the Drude-Lorentz model. The fits obtained using the Fano fit are better, which indicates that electron-phonon coupling in La2-xSrxCuO4 is strong and must be taken into account during band-structure and phonon calculations. I also found that stripe instability in La2-xSrxCuO4, which is known to be strongest at 1/8 doping, has a significant effect on phonon line-shapes.

Doctor of Philosophy (Ph.D.), University of Dayton, 2016, Electro-Optics

This dissertation reports on the research to design and build a pulsed fiber laser with the Er doped fiber based on a new mode locking technique. The numerical simulations begin by launching an optical wave in a fiber which will be amplified during propagation. The device to mode-lock the waves is outside the fiber, but connecting to fibers at both ends; it is a nonlinear optical material that can reshape the beam as it propagates using a nonlinear change of the refractive index, which is called a Kerr effect. The device is made with a nonlinear material sandwiched between two fiber ends; it takes an optical field from one end of the fiber and propagates it to the other fiber end. In between the two ends, a nonlinear medium will be used to balance the diffraction through Kerr effect (which can lead to Self-focusing of the optical beam). With the second fiber end working as a soft aperture, the combination of the self-focusing effect through the nonlinear medium and the aperture will act as an intensity dependent coupling loss; this effect is referred to as a fast saturable absorber which means that higher intensity corresponds to higher coupling efficiency and thus the cavity modes will be gradually phase locked together to form pulses. The saturable absorber action is calculated using different nonlinear mediums (CS2, As2S2 and As40Se60) and the fibers used are assumed to be of the same size. Whole cavity simulation is then conducted using the proposed SA design and the pulse energy produced from the laser cavity is generally below 1 nJ. In those simulations the pulse peak power is weak and the saturable absorber action is not strong. Experiments are designed to test the mode locking idea with the chalcogenide glass plate (As40Se60). Firstly, a mode locked laser is constructed from a ring fiber laser cavity with an Er doped fiber as the gain fiber. Three modes from this cavity are routinely generated. Two modes have pulse durations of 220 fs and 160 fs with s (open full item for complete abstract)

Master of Science in Electrical Engineering (MSEE), Wright State University, 2015, Electrical Engineering

In this thesis, an average current-mode controller is analyzed for controlling power electronic converters. This controller consists of two loops. An inner loop, which senses and controls the inductor current and an outer loop, which is used to control the output voltage and provide reference voltage for the inner current loop. An average current-mode controller averages out high frequency harmonics it senses from the inductor current to provide a smooth DC component. This can be used as a control voltage for a pulse width modulator and produce switching pulses for the power electronic converters. An average current-mode controller can also be designed for a good bandwidth, which helps in accurate tracking of the sensed inductor current. For a better understanding of the operation of an average current-mode controller analytical equations are derived. Many transfer functions, which help analyze the properties of an open loop system, the controller transfer functions and a block diagram representing the converter along with current and voltage-control loops are presented. The block diagram and the transfer functions were used to derive the required controller parameters on MATLAB. The designed converter along with the controller is implemented on SABER circuit simulator. Waveforms representing the analytical equations along with the dynamic properties of the converter with the controller were plotted. The plotted SABER simulations were in agreement with the analytical equations. The designed controller was able to produce a controlled output voltage for step change in input voltage and load resistance, when simulated on SABER. Ripples could be observed in the control voltage of the controller, when designed for a good bandwidth. This was also represented by the derived analytical equations.

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

A Cryogenic Irradiation Facility (CRIF) has been designed, fabricated, and tested for use in the pool of the Ohio State University Research Reactor (OSURR). This CRIF has supported in situ radiation induced damage experiments in optical and electronic materials at cryogenic temperatures and temperature controlled low temperature annealing experiments from cryogenic temperatures to above room temperature. The facility has been tested with liquid nitrogen and liquid helium out of the reactor pool. Temperature control has been demonstrated in the experimental volume of the CRIF from 4.2 K to above room temperature. The 10" Dry Tube, which will house the CRIF in the OSURR pool, has been inserted into OSURR pool and tested. The empty 10" Dry Tube and the CRIF have been simulated in a model of the OSURR using MCNP6 to understand the predicted radiation fields and total energy deposition in the empty 10" Dry Tube and in typical optical and electronic materials in the experimental volume of the CRIF. The radiation fields and the total radiation energy deposition have been used to predict experimental operating parameters for CRIF experiments, based upon desired dose calculations and time to boil-off for the liquid helium inside the CRIF. The CRIF has been used for four sets of experiments on single-mode and multi-mode silica optical fibers, in conjunction with a Luna Optics Optical Backscatter Reflectometer and an optical transmission measurement system, and on GaN High Electron Mobility Transistors, in conjunction with an integrated NI PXI Electronics Measurements System. These four experiments included (1) cryogenic materials characterization experiments without radiation, (2) gamma-only cryogenic irradiation experiments and low temperature annealing experiments, (3) reactor-on mixed field cryogenic irradiation experiments and low temperature annealing experiments, and (4) reactor-on mixed field room temperature irradiation experiments. These experiments were all compl (open full item for complete abstract)

Doctor of Philosophy, The Ohio State University, 2014, Physics

The emergent field of spintronics, which utilizes the spin of the electron rather than the charge for information processing, relies on an understanding of interfaces and surfaces of ferromagnetic thin films. An interface between a ferromagnetic thin film and a neighboring material can be engineered to provide tuneable static and dynamic couplings, which manifest as effective fields on the ferromagnet. Ferromagnetic resonance (FMR) is a powerful spectroscopic technique for studying these effective fields and couplings. In addition, FMR has been used to generate a pure spin current at these interfaces, which allows for the transfer of angular momentum without an accompanying charge current. The technique of magnetic resonance force microscopy (MRFM) has allowed the study of spin dynamics at the nanometer scale and with sensitivity down to single electron spins in paramagnetic materials and it would be illuminating to use this technique to study the spin transport behavior near an interface. MRFM uses the field from a magnetic probe to define a sensitive slice in which the resonance condition is met. The combination of MRFM techniques with FMR spectroscopy has, until recently, been limited to the measurement of global properties of a sample due to strong spin-spin exchange interactions that lead to collective spin wave modes that are defined by the sample and not sensitive to the probe field. Recently, the negative dipole field from a high coercivity probe magnet has been used to strongly perturb the spin wave spectrum of metallic ferromagnetic films, resulting in the localization of precessing magnetization in the `field well' of the probe magnet into discrete modes, analogous to the discrete modes of a particle in a quantum well. The localized nature of these modes enables their use as a local probe of magnetic properties, and this has been utilized in the demonstration of FMR imaging of a ferromagnetic thin film using ferromagnetic resonance force microscopy (FMRF (open full item for complete abstract)

MS, University of Cincinnati, 2013, Engineering and Applied Science: Computer Engineering

The need to keep up with Moore's law calls for high packing density in chips. Due to this very reason, IC fabrication industry is transforming from using conventional planar transistors to using 3D transistors, of which FinFET proves to be most viable because of its good short channel characteristics and ease of fabrication. Leakage power consumption has been a major concern considering the CMOS technology and it proves vital to reduce it. FinFETs, especially in LP mode provide design flexibility by controlling Vth to reduce leakage by trading off delay. In this research, we design an LP mode SRAM array and compare it with a similar SG mode design for performance, power and reliability. We then model all possible spot defects in HSPICE. We also discuss how leakage current could drastically increase due to resistive opens at back gates. In our results, we find one new fault model and we propose a march algorithm to detect all the fault behaviors found in our simulations.

Master of Science in Engineering (MSEgr), Wright State University, 2009, Mechanical Engineering

Numerical analysis was performed on a Dual-Mode Scramjet isolator-combustor. Preliminary analysis was performed to form a baseline geometry. Another study validated the results of a 2D model compared to a 3D model. Stable combustion was shown at two different flight conditions, M=3.0 and M=2.5. A marginal 5% decrease in stream thrust was shown by introducing a 50/50 mix of methane and ethylene. Based on the results of the preliminary analysis, detailed geometry analysis was performed on the 3D baseline geometry. Adding a new set of cavity feeding injectors increased the overall stream thrust and the equivalence ratio in the cavity. Using less fuel than the baseline configuration, revealed a 6.4% increase in stream thrust and an 11% increase in combustion efficiency by placing the second stage injector further upstream. Future analysis includes combining the cavity feeding with closer injector placement, which is expected to yield even better results.

Doctor of Philosophy in Engineering, University of Toledo, 2009, Mechanical Engineering

In recent years, the higher price of fossil fuels and green house effects has been the motivating factors for the automotive industry to introduce more efficient vehicles. Today evolution in automobiles is mostly to reduce fuel consumption and emissions. Variable cylinder management has been employed in V6 & V8 engines to allow the vehicles to operate with only 3 or 4 active cylinders. Hybrid technologies including hybrid electric and emerging hydraulic hybrid equip the vehicles with additional power sources which work at higher efficiency than that of internal combustion engines. The proven advantages of the hybrid vehicles or variable cylinder management also come with challenging problem of noise, vibration and harshness (NVH). This issue has to be properly addressed in order for the technologies to find consumer acceptance. The NVH in modern vehicles is mainly due to the involvement of multiple power sources working in different modes and the switching among them. This feature can lead to shock and vibration over a wide range of frequencies. It has been proven that passive vibration isolators, e.g. elastomeric and hydraulic, are not sufficient to deal with this problem. Active mounts are effective, but they are expensive and can lead to stability problems. Research has shown that semi-active vibration isolators are as effective as active mounts while being significantly less expensive In this study, a novel shock and vibration isolator in the form of a magnetorheological (MR) mount is introduced. MR fluids are smart fluids which respond to magnetic fields. Using these fluids it is possible to transform a passive hydraulic vibration isolator to a semi-active device one. The semi-active MR mount presented in this dissertation is unique because it utilizes the MR fluid in two configurations flow (or valve) and squeeze modes to mitigate shock and vibration over a wide range of frequencies. The new mount was designed following a thorough literature review of the s (open full item for complete abstract)