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Articles 421 - 450 of 654
Full-Text Articles in Mechanical Engineering
Advancements In Alternative Energy Applications For Space Conditioning., Brian S. Robinson
Advancements In Alternative Energy Applications For Space Conditioning., Brian S. Robinson
Electronic Theses and Dissertations
This dissertation documents advancements made in passive, renewable energy applications for building space conditioning (heating and cooling). Since, for most climates across the US, space heating requires a much larger annual energy demand than space cooling, the majority of this dissertation is focused on the heating season. The dissertation is divided into five chapters, primarily covering computer simulations and experimental studies pertaining to specific space conditioning technologies. Chapter One discusses the significance of supplanting fossil fuel based energy production with clean, renewable sources, and provides further detail on the organization of this dissertation. Chapter Two provides background on the heat …
Development And Evaluation Of A Calibration Free Exhaustive Coulometric Detection System For Remote Sensing., Thomas James Roussel
Development And Evaluation Of A Calibration Free Exhaustive Coulometric Detection System For Remote Sensing., Thomas James Roussel
Electronic Theses and Dissertations
Most quantitative analytical measurement techniques require calibration to correlate signal with the quantity of analyte. The purpose of this study was to employ exhaustive coulometry, an implementation of coulometric analysis in a stopped-flow, fixed-volume, thin-layer cell, to attain calibration-free measurements that would directly benefit intervention-free analysis systems designed for remote deployment. This technique capitalizes on the short diffusion lengths (< 100 µm) to dramatically reduce the time for analysis (< 30 sec). For this work, a thin-layer fluidic cell was designed in software, fabricated via CNC machining, and evaluated using Ferri/Ferrocyanide {Fe(CN)63-/4-} as a model analyte. The 2 µL fixed volume incorporated an oval, 8mm by 4 mm, thin-film gold electrode sensor with an integrated Ag|AgCl pseudo-reference electrode. The flow cell area matched the shape of the sensor, with a volume set by the thickness of a laser-cut silicone rubber gasket (~80 µm). A semi-permeable membrane isolated the working electrode and counter electrode chambers to prevent analyte diffusion. A miniaturized custom potentiostat was designed and built to measure reaction currents ranging from 10 mA to 0.1 nA. Software was developed to perform step voltammetry as well as cyclic voltammetry analysis for verifying electrode condition and optimal redox potential levels. Experimentally determined oxidation/reduction potentials of -100 mV and 400 mV, respectively, were applied to the working electrode for sample concentrations ranging from 50 µM to 10,000 µM. The current generated during the reactions was recorded and the total charge captured at each concentration was obtained by integrating the amperograms. When compared to the expected charge for a 2 µL sample, the total charge vs. concentration plots displayed a near perfect linearity over the full concentration range, and the expected charge (100 % converted) was reached within 20 seconds. The reaction currents ideally should have decayed to background levels, but exhibited constant offset values slightly larger than the background signal, a phenomenon assumed to be lingering residual flow from sample injection. After adding rigid tubing and external valves, the thin-layer cell was shown to remain within 6% of the theoretical charge after 200 seconds. Continued development of this system will offer the possibility of remote, calibration-free determinations of real-world analytes such mercury and lead.
Design And Evaluation Of A Propulsion System For Small, Compact, Low-Speed Maneuvering Underwater Vehicles, Florence M. Mbithi
Design And Evaluation Of A Propulsion System For Small, Compact, Low-Speed Maneuvering Underwater Vehicles, Florence M. Mbithi
Electronic Theses and Dissertations
Underwater vehicles used to perform precision inspection and non-destructive evaluation in tightly constrained or delicate underwater environments must be small, have low-speed maneuverability and a smooth streamlined outer shape with no appendages. In this thesis, the design and analysis of a new propulsion system for such underwater vehicles is presented. It consists primarily of a syringe and a plunger driven by a linear actuator and uses different inflow and outflow nozzles to provide continuous propulsive force. A prototype of the proposed propulsion mechanism is built and tested. The practical utility and potential efficacy of the system is demonstrated and assessed …
Computational Fluid Dynamics Uncertainty Analysis For Payload Fairing Spacecraft Environmental Control Systems, Curtis Groves
Computational Fluid Dynamics Uncertainty Analysis For Payload Fairing Spacecraft Environmental Control Systems, Curtis Groves
Electronic Theses and Dissertations
Spacecraft thermal protection systems are at risk of being damaged due to airflow produced from Environmental Control Systems. There are inherent uncertainties and errors associated with using Computational Fluid Dynamics to predict the airflow field around a spacecraft from the Environmental Control System. This paper describes an approach to quantify the uncertainty in using Computational Fluid Dynamics to predict airflow speeds around an encapsulated spacecraft without the use of test data. Quantifying the uncertainty in analytical predictions is imperative to the success of any simulation-based product. The method could provide an alternative to traditional “validation by test only” mentality. This …
Computational Fluid Dynamics Simulation Of United Launch Alliance Delta Iv Hydrogen Plume Mitigation Strategies, Stephen Guimond
Computational Fluid Dynamics Simulation Of United Launch Alliance Delta Iv Hydrogen Plume Mitigation Strategies, Stephen Guimond
Electronic Theses and Dissertations
During the launch sequence of the United Launch Alliance Delta IV launch vehicle, large amounts of pure hydrogen are introduced into the launch table and ignited by Radial-Outward-Firing-Igniters (ROFIs). This ignition results in a significant flame, or plume, that rises upwards out of the launch table due to buoyancy. The presence of the plume causes increased and unwanted heat loads on the surface of the vehicle. A proposed solution is to add a series of fans and structures to the existing launch table configuration that are designed to inject ambient air in the immediate vicinity of the launch vehicle's nozzles …
Piezospectroscopic Calibration Of Alumina-Nanocomposites For The Development Of Stress-Sensing Structures, Daniela Fugon-Dessources
Piezospectroscopic Calibration Of Alumina-Nanocomposites For The Development Of Stress-Sensing Structures, Daniela Fugon-Dessources
Electronic Theses and Dissertations
Alpha-alumina is known to exhibit photo-luminescent (PL) properties, mainly characteristic R-lines that shift according to applied stress. In addition to showing excellent PL properties, polymers with embedded alumina nanoparticles have been shown to improve the overall composite mechanical properties. While the use of the PL properties to develop stress-sensing materials using an alumina-epoxy material has been success- fully shown in compression, the properties have not been developed for tension. In this study, the PL response of variable volume fraction alumina-epoxy composites will be determined under tensile conditions. It is expected that increasing the volume fraction of alumina nanoparticles will increase …
Response Of Electrified Micro-Jets To Electrohydrodynamic Perturbations, Weiwei Yang
Response Of Electrified Micro-Jets To Electrohydrodynamic Perturbations, Weiwei Yang
Electronic Theses and Dissertations
The breakup of liquid jets is ubiquitous with rich underpinning physics and widespread applications. The natural breakup of liquid jets originates from small ambient perturbations, which can grow exponentially until the amplitude as large as the jet radius is reached. For unelectrified inviscid jets, surface energy analysis shows that only the axisymmetric perturbation is possibly unstable, and this mode is referred as varicose instability. For electrified jets, the presence of surface charge enables additional unstable modes, among which the most common one is the whipping (or kink) instability that bends and stretches the charged jet that is responsible for the …
A Study Of Compressive Sensing For Application To Structural Health Monitoring, Vaahini Ganesan
A Study Of Compressive Sensing For Application To Structural Health Monitoring, Vaahini Ganesan
Electronic Theses and Dissertations
One of the key areas that have attracted attention in the construction industry today is Structural Health Monitoring, more commonly known as SHM. It is a concept developed to monitor the quality and longevity of various engineering structures. The incorporation of such a system would help to continuously track health of the structure, indicate the occurrence/presence of any damage in real time and give us an idea of the number of useful years for the same. Being a recently conceived idea, the state of the art technique in the field is straight forward - populating a given structure with sensors …
Mechanical And Thermal Characterization Of Continuous Fiber-Reinforced Pyrolysis-Derived Carbon-Matrix Composites, Donovan Lui
Mechanical And Thermal Characterization Of Continuous Fiber-Reinforced Pyrolysis-Derived Carbon-Matrix Composites, Donovan Lui
Electronic Theses and Dissertations
Maturity of high-temperature polymer-reinforced composites defer to conventionally expensive and intensive methods in both material and manufacturing aspects. Even traditional carbon-carbon, aerogel, and ceramic approaches are highly limited by difficult manufacturing techniques and are subject to sensitive handling throughout their processing and lifetime. Despite their utility in extreme environments, the high costs of existing high-temperature composites find limited practical applicability under high-performance applications. The development of continuous fiber-reinforced pyrolysis-derived carbon-matrix composites aim to circumvent the issues surrounding the manufacturing and handling of conventional high-temperature composites. Polymer matrix composites (PMCs) have a number of attractive properties including light weight, high stiffness-to-weight …
Using Acoustic Emission Monitoring For Energy-Based Fatigue Life Prediction, Sepehr Nesaei
Using Acoustic Emission Monitoring For Energy-Based Fatigue Life Prediction, Sepehr Nesaei
Electronic Theses and Dissertations
The study of fatigue and fracture mechanics is crucial to the health monitoring and overall safety of aerospace and civil structures. The materials used to manufacture these industry parts have inherent anomalies that eventually grow under cyclic loadings during regular operation. The ASTM and/or military testing guidelines used to analyze and qualify structures and materials for use are costly and time consuming. Therefore, any additional methods or knowledge that can be used to reduce the number of tests will be useful to the industry to avoid unnecessary costs. Acoustic emission (AE) monitoring is currently used in many applications to assess …
Assessment Of Corn Stover Torrefaction For On-Farm Biochar Production, Christina M. Gerometta
Assessment Of Corn Stover Torrefaction For On-Farm Biochar Production, Christina M. Gerometta
Electronic Theses and Dissertations
Torrefaction is a thermochemical pretreatment process that is typically achieved by slowly heating biomass (<50°C/min) within the temperature range of 200 – 300°C under an inert atmosphere. This process yields a storable solid product with enhanced fuel characteristics that are influenced by the ligno-cellulosic composition of the original feedstock and the imposed torrefaction conditions (time and temperature). This study is an assessment of corn stover properties that are relevant for designing an on-farm torrefaction system. The first portion of this study compared the thermal decomposition behaviors of corn stover fractions (leaf, stalk, cob) to the respective ligno-cellulosic composition using thermo-gravimetric analysis. It was found that the thermal decomposition pattern correlates to the structure and ratio of ligno-cellulosic polymers and provides design guidelines for an on-farm torrefaction system capable of handling large quantities of mixed fraction stover. The second part of this study investigated the effects of torrefaction time and temperature on the mass and energy yield of mixed fraction corn stover using a 46.3 L batch style reactor. It was found that longer reaction times and higher temperatures were required to obtain mass and energy yields similar to those found using lab-scale reactors and finely milled samples. Non-uniform torrefaction occurred between fractions due to chemical composition of each fraction and proximity to the heating elements.
Microstructure, Quasi-Static, And High-Strain Rate Dynamic Characterization Of Metakaolin And Fly Ash Based Geopolymers For Structural Applications, Damian Lee Stoddard
Microstructure, Quasi-Static, And High-Strain Rate Dynamic Characterization Of Metakaolin And Fly Ash Based Geopolymers For Structural Applications, Damian Lee Stoddard
Electronic Theses and Dissertations
Geopolymers are a class of rapid setting cementing systems that have been used as mortar or additives in concrete mixes to improve properties. Several types of geopolymer systems such as metakaolin and fly ash based geopolymers are widely used, and are available in different mixture proportions [1, 2]. Metakaolin (Al2Si2O7), a dehydroxylated form of Kaolinite (Al2Si2O5(OH)4) clay readily available from many sources, provides several benefits whenadded to a concrete mix design or used as a mortar system, including durability, freeze/thaw, acid resistance, and high temperature resistance [3]. Class F fly ash-based mortar geopolymers provide added fire retardation, reduces crack formation, …
Bio-Inspired Attitude Control Of Micro Air Vehicles Using Rich Information From Airflow Sensors, He Shen
Bio-Inspired Attitude Control Of Micro Air Vehicles Using Rich Information From Airflow Sensors, He Shen
Electronic Theses and Dissertations
Biological phenomena found in nature can be learned and customized to obtain innovative engineering solutions. In recent years, biologists found that birds and bats use their mechanoreceptors to sense the airflow information and use this information directly to achieve their agile flight performance. Inspired by this phenomenon, an attitude control system for micro air vehicles using rich amount of airflow sensor information is proposed, designed and tested. The dissertation discusses our research findings on this topic. First, we quantified the errors between the calculated and measured lift and moment profiles using a limited number of micro pressure sensors over a …
Design And Development Of Heterogenous Combustion Systems For Lean Burn Applications, Anthony Terracciano
Design And Development Of Heterogenous Combustion Systems For Lean Burn Applications, Anthony Terracciano
Electronic Theses and Dissertations
Combustion with a high surface area continuous solid immersed within the flame, referred to as combustion in porous media, is an innovative approach to combustion as the solid within the flame acts as an internal regenerator distributing heat from the combustion byproducts to the upstream reactants. By including the solid structure, radiative energy extraction becomes viable, while the solid enables a vast extension of flammability limits compared to conventional flames, while offering dramatically reduced emissions of NOx and CO, and dramatically increased burning velocities. Efforts documented within are used for the development of a streamlined set of design principles, and …
A Lab-Scale Experimental Framework For Studying The Phenomenon Of Autorotation, Sigitas Rimkus
A Lab-Scale Experimental Framework For Studying The Phenomenon Of Autorotation, Sigitas Rimkus
Electronic Theses and Dissertations
While wind energy has emerged as a popular source of renewable energy, the traditional wind turbine has an inherent limitation, namely that it only generates power in the presence of sufficiently high and consistent wind speeds. As a result, wind farms are typically built in areas with a high probability of the required wind speeds, which are geographically sparse. One way of overcoming this drawback is to tap into the energy available in winds at high altitudes which are not only consistent and of high magnitude, but also globally pervasive. An airborne wind energy device based upon the phenomenon of …
Modeling Repair Patches Of Ship Hull And Studying The Effect Of Their Orientation On Stresses, Halima Enwegy
Modeling Repair Patches Of Ship Hull And Studying The Effect Of Their Orientation On Stresses, Halima Enwegy
Electronic Theses and Dissertations
The hull is the most important structural part of any maritime vessel. It must be adequately designed to withstand the harsh sailing environmental conditions and associated forces. In the past, the basic material used to manufacture the ship hull was wood, where the hull was usually shaped as cylindrical wooden shanks. In the present, hull designs have developed to steel columns or stiffened panels that are made of different types of materials. Panels that are stiffened orthogonally in two or more directions and have nine independent material constants are defined as orthotropic panels, and they achieve high specific strength. This …
Perovskite Catalysts Enhanced Combustion On Porous Media And Thermoelectric Power Conversion, Manuel Robayo
Perovskite Catalysts Enhanced Combustion On Porous Media And Thermoelectric Power Conversion, Manuel Robayo
Electronic Theses and Dissertations
A combustion chamber incorporating a high temperature porous matrix was design and tested. The effects and merits of combining combustion on porous media and catalytic enhancement were explored, in addition to the proof of concept of integrating these technologies with simple heat engines, such as thermoelectric generators, to generate efficient and reliable power. The direct observation of the flame during the combustion becomes possible due to a specially designed stainless steel chamber incorporating a quartz window where the initiation and propagation of the combustion reaction/flame was directly visible. The simple design of the combustion chamber allowed for a series of …
Modeling And Contour Control Of Multi-Axis Linear Driven Machine Tools, Ran Zhao
Modeling And Contour Control Of Multi-Axis Linear Driven Machine Tools, Ran Zhao
Electronic Theses and Dissertations
In modern manufacturing industries, many applications require precision motion control of multi-agent systems, like multi-joint robot arms and multi-axis machine tools. Cutter (end effector) should stay as close as possible to the reference trajectory to ensure the quality of the final products. In conventional computer numerical control (CNC), the control unit of each axis is independently designed to achieve the best individual tracking performance. However, this becomes less effective when dealing with multi-axis contour following tasks because of the lack of coordination among axes. This dissertation studies the control of multi-axis machine tools with focus on reducing the contour error. …
Decentralized Power Management And Transient Control In Hybrid Fuel Cell Ultra-Capacitor System, Seyed Omid Madani
Decentralized Power Management And Transient Control In Hybrid Fuel Cell Ultra-Capacitor System, Seyed Omid Madani
Electronic Theses and Dissertations
Solid Oxide Fuel Cells (SOFCs) are considered suitable for alternative energy solutions due to advantages such as high efficiency, fuel flexibility, tolerance to impurities, and potential for combined cycle operations. One of the main operating constraints of SOFCs is fuel starvation, which can occur under fluctuating power demands. It leads to voltage loss and detrimental effects on cell integrity and longevity. In addition, reformer based SOFCs require sufficient steam for fuel reforming to avoid carbon deposition and catalyst degradation. Steam to carbon ratio (STCR) is an index indicating availability of the steam in the reformer. This work takes a holistic …
Combustion Instability Mechanism Of A Reacting Jet In Cross Flow At Gas Turbine Operating Conditions, Jared Pent
Combustion Instability Mechanism Of A Reacting Jet In Cross Flow At Gas Turbine Operating Conditions, Jared Pent
Electronic Theses and Dissertations
Modern gas turbine designs often include lean premixed combustion for its emissions benefits; however, this type of combustion process is susceptible to self-excited combustion instabilities that can lead to damaging heat loads and system vibrations. This study focuses on identifying a mechanism of combustion instability of a reacting jet in cross flow, a flow feature that is widely used in the design of gas turbine combustion systems. Experimental results from a related study are used to validate and complement three numerical tools that are applied in this study – self-excited Large Eddy Simulations, 3D thermoacoustic modeling, and 1D instability modeling. …
In-Situ Synchrotron Studies Of Turbine Blade Thermal Barrier Coatings Under Extreme Environments, Kevin Knipe
In-Situ Synchrotron Studies Of Turbine Blade Thermal Barrier Coatings Under Extreme Environments, Kevin Knipe
Electronic Theses and Dissertations
Thermal Barrier Coatings have been used for decades to impose a thermal gradient between the hot combustion gases and the underlying superalloy substrate in engine turbine blades. Yttria Stabilized Zirconia (YSZ) is an industry standard high temperature ceramic for turbine applications. The protective coating is adhered to the substrate using a nickel based alloy bond coat. Through exposure to high temperature, a Thermally Grown Oxide (TGO) layer develops at the bond coat-YSZ interface. Large residual stresses develop in these layers due to thermal expansion mismatch that occurs during cool down from high temperature spraying and cyclic operating conditions. Despite their …
Synchrotron X-Ray Diffraction And Piezospectroscopy Used For The Investigation Of Individual Mechanical Effects From Environmental Contaminants And Oxide Layer Undulations In Thermal Barrier Coatings, Sanna Siddiqui
Electronic Theses and Dissertations
The durability of Thermal Barrier Coatings (TBCs) used on the turbine blades of aircraft and power generation engines has been known to be affected by sand particle ingression comprised of Calcium-Magnesium-Alumina-Silicate (CMAS). Previous studies have shown that these effects present themselves through variations in the thermomechanical and thermochemical properties of the coating. This study investigated the impact of CMAS ingression on the Yttria Stabilized Zirconia Topcoat (YSZ) and Thermally Grown Oxide (TGO) strain in sprayed Thermal Barrier Coating (TBC) samples of varying porosity with and without CMAS ingression. In-Situ Synchrotron X-ray Diffraction measurements were taken on the sample under thermal …
Nanocomposite Coating Mechanics Via Piezospectroscopy, Gregory Freihofer
Nanocomposite Coating Mechanics Via Piezospectroscopy, Gregory Freihofer
Electronic Theses and Dissertations
Coatings utilizing the piezospectroscopic (PS) effect of alpha alumina could enable on the fly stress sensing for structural health monitoring applications. While the PS effect has been historically utilized in several applications, here by distributing the photo-luminescent material in nanoparticle form within a matrix, a stress sensing coating is created. Parallel to developing PS coatings for stress sensing, the multi-scale mechanics associated with the observed PS response of nanocomposites and their coatings has been applied to give material property measurements, providing an understanding of particle reinforced composite behavior. Understanding the nanoparticle-coating-substrate mechanics is essential to interpreting the spectral shifts for …
An Introductory Study Of The Dynamics Of Autorotation For Wind Energy Harvesting, Bilal Salih
An Introductory Study Of The Dynamics Of Autorotation For Wind Energy Harvesting, Bilal Salih
Electronic Theses and Dissertations
Wind turbines have been used for decades to harvest wind energy. They are suitable only to work on close to ground, and have several drawbacks that are related to the availability of the wind and the amount of extracted power compared with the cost of construction. On the other hand, there is an abundant wind power that is available at high altitudes. The wind jet streams at high elevations 8 - 12 kms are pervasive and persistent, and can potentially produce immense wind energy. Even at moderate elevations of 4 - 5 kms, wind power densities are much higher than …
Optimization Of Wind Fence Enclosures For Infrasonic Wind Noise Reduction, Johnpaul Russell Abbott
Optimization Of Wind Fence Enclosures For Infrasonic Wind Noise Reduction, Johnpaul Russell Abbott
Electronic Theses and Dissertations
A large porous wind barrier enclosure has been built and tested to optimize wind noise reduction at infrasonic frequencies between 0.01-10 Hz in order to develop a technology that is simple, cost effective, and improves upon the limitations of pipe and porous hose arrays. The effects of varying the fence's porosity, modifying its top condition and bottom gap, doubling the height and diameter, and adding a secondary wind barrier were investigated. A simple mathematical model which estimates the wind noise measured at the center of the enclosure was derived based on the measured turbulence and velocity profiles measure outside the …
Development Of Full Surface Transient Thermochromic Liquid Crystal Technique For Internal Cooling Channels, Lucky Tran
Development Of Full Surface Transient Thermochromic Liquid Crystal Technique For Internal Cooling Channels, Lucky Tran
Electronic Theses and Dissertations
Proper design of high performance industrial heat transfer equipment relies on accurate knowledge and prediction of the thermal boundary conditions. In order to enhance the overall gas turbine efficiency, advancements in cooling technology for gas turbines and related applications are continuously investigated to increase the turbine inlet temperature without compromising the durability of the materials used. For detailed design, local distributions are needed in addition to bulk quantities. Detailed local distributions require advanced experimental techniques whereas they are readily available using numerical tools. Numerical predictions using a computational fluid dynamics approach with popular turbulence models are benchmarked against a semi-empirical …
Synthesis, Processing And Characterization Of Polymer Derived Ceramic Nanocomposite Coating Reinforced With Carbon Nanotube Preforms, Hongjiang Yang
Synthesis, Processing And Characterization Of Polymer Derived Ceramic Nanocomposite Coating Reinforced With Carbon Nanotube Preforms, Hongjiang Yang
Electronic Theses and Dissertations
Ceramics have a number of applications as coating material due to their high hardness, wear and corrosion resistance, and the ability to withstand high temperatures. Critical to the success of these materials is the effective heat transfer through a material to allow for heat diffusion or effective cooling, which is often limited by the low thermal conductivity of many ceramic materials. To meet the challenge of improving the thermal conductivity of ceramics without lowering their performance envelope, carbon nanotubes were selected to improve the mechanical properties and thermal dispersion ability due to its excellent mechanical properties and high thermal conductivity …
Decentralized Power Management In Microgrids, Amit Bhattacharjee
Decentralized Power Management In Microgrids, Amit Bhattacharjee
Electronic Theses and Dissertations
A large number of power sources, operational in a microgrid, optimum power sharing and accordingly controlling the power sources along with scheduling loads are the biggest challenges in modern power system. In the era of smart grid, the solution is certainly not simple paralleling. Hence it is required to develop a control scheme that delivers the overall power requirements while also adhering to the power limitations of each source. As the penetration of distributed generators increase and are diversifi ed, the choice of decentralized control becomes preferable. In this work, a decentralized control framework is conceived. The primary approach is …
Finite Element Analysis Of Shear Resistant Mechanisms For Biolaminate Interfaces, Matthew Nelms
Finite Element Analysis Of Shear Resistant Mechanisms For Biolaminate Interfaces, Matthew Nelms
Electronic Theses and Dissertations
The Alligator gar possesses a flexible dermal armor consisting of overlapping ganoid scales. Each scale is a bilayer hydroxyapatite and collagen-based bio-laminate for protection against predation. The exoskeleton fish scale is comprised of a stiff outer ganoine layer, a characteristic "sawtooth" pattern at the interface and a compliant bone inner layer with all materials exhibiting a decreasing elastic modulus, yield strength and density through the thickness. Experiments on ganoid scales revealed properties such as damage mitigation and energy dissipation that are unique to biological dermal armor. The objective of this investigation is to develop a fundamental understanding of the stress …
Multi-Physical Study Of Mems Resonators And Oscillators, Xiaobo Guo
Multi-Physical Study Of Mems Resonators And Oscillators, Xiaobo Guo
Electronic Theses and Dissertations
First, this research presents experimental and theoretical investigation of the response of micro scale dual-plate thermal-piezoresistive resonators (TPR) and self-sustained oscillators (TPO) to different gases and pressures. It is demonstrated that the resonant frequency of such devices follows particular trends in response to the changes in the surrounding gas and its pressure. A mathematical model has been derived to explain the damping dependent frequency shift characteristic of TPO. The solution of the model indicates that the stiffness of the actuator beam decreases as the value of damping coefficient drops at lower gas density caused by the change in the gas …