Mechanical Engineering Commons^™

Investigation Of Transmission Loss Through Double Wall Structures With Varying Small Air Gaps Using Modal Analysis., Richard Michael Phillips 1988-

Electronic Theses and Dissertations

Noise reduction testing is completed for two single steel plate constructions with different thicknesses and for two double wall constructions with different air gap thicknesses that include the same two plates used in the single plate constructions. Results compare favorably with known theory and experimental results from previous literature. These favorable comparisons include the direct relationship between mass per unit area and transmission loss for single plate constructions, the presence of a noise reduction valley near the mass-air-mass frequency, the dependency of the mass-air-mass frequency on the air gap thickness, and the existence of a bridge frequency. Despite the similarities …

The Development Of A Laminated Copolyester Electric Guitar, Addison S. Karnes

Electronic Theses and Dissertations

This thesis is an investigation of the fabrication and assembly methodologies employed in the development of a proof-of-principle prototype electric guitar composed of laminated copolyester. The objective of the project was to develop the processes and procedures to create an optimized physical and visual bond between layers to minimize vibratory dissipation, thus maximizing sustain. A high speed CNC router, abrasive waterjet, laser engraver-cutter, as well as various manual fabrication and assembly methods were investigated in the construction of the guitar prototypes. The lamination processes explored include low-temperature, heat-assisted pressure bonding, solvent and chemical welding, and contact adhesives. The project concluded …

Transient Heat Transfer Between A Magnetocaloric Packed Particle Bed And Stagnant Interstitial Fluid., Michael G. Schroeder 1988-

Electronic Theses and Dissertations

In the field of magnetocaloric heat pumps, many system models have been made. What most of these models lack is heat transfer occurring while there is no fluid motion. It is the objective of this paper to analytically determine and experimentally verify heat transfer with no bulk fluid motion. The addition of a pure dwell period to the typical magnetocaloric cycle was shown to have a positive performance impact in specific conditions. These conditions correspond to regenerators that are heat transfer rate limited in operation. The heat transfer mechanism for this particular case was shown to be pure conduction via …

Cavitation In Vial Drop Subjected To Mechanical Shock, Houman Babazadehrokni

Electronic Theses and Dissertations

Cavitation is a phenomenon that occurs when the local pressure falls down below the critical pressure. Previous work from the Randolph lab demonstrated that protein aggregates can form when a vial of therapeutic solution is dropped onto a hard surface. The process by which this occurs is most likely shock induced cavitation. During this process, hot spots can be created with temperatures and pressures reaching thousands of Kelvin and hundreds of atmospheres, respectively, leading to degradation of protein therapeutics. This work will extend previous efforts by exploring differences generated by change in vial materials, solutions, drop methods and fill volumes. …

Photomechanical Actuation Of Liquid Crystal Nanotube Elastomers., Xiaoming Fan

Electronic Theses and Dissertations

Elastomeric composites based on nanotube liquid crystals (LCs) that preserve the internal orientation of nanotubes could lead to anisotropic physical properties and flexible energy conversion. Using simple vacuum filtration technique of fabricating nanotube LCs films and utilizing a transfer process to poly (dimethyl) siloxane wherein the LCs arrangement is preserved, in this thesis we demonstrate unique and reversible photomechanical response of this layered composite to excitation by near infra-red (NIR) light at ultra-low nanotube mass fractions. Schlieren textures were noted in these LCs composites confirming long range macroscopic nematic order of nanotubes within the composites. Maximum photomechanical stress of ~23kPa, …

Numerical Investigation Of Hydrodynamic Focusing And Coulter Principle In A Microfluidic Device, Muheng Zhang

Electronic Theses and Dissertations

Particle information such as particle size and amount is significant to many fields such as chemical engineering, biological research, medical analysis, and environment detection. Microfluidic Coulter counter is suitable for this task because it can get fast and accurate analysis. However, the fundamental principle and several design strategies details are still needed to be analyzed and modeled in order to improve its performance. This dissertation focused on several challenges from the numerical simulation aspects. First one is the analysis for the hydrodynamic focusing in microfluidic Coulter Counter. In recent years, many microfluidic Coulter Counter designs have utilized a technique termed …

Hydraulic Switch For Dishwashers With Bottle Blaster System., Lazaro Galban

Electronic Theses and Dissertations

A dishwasher works by using water pressure to operate the Spray Arms. There are different types of wash systems with the most common being two spray arms, a lower and middle arm. These two spray arms operate independently from each other and can be powered individually. In this particular wash system, the subsystem of interest is the Mid Spray Arm which is connected with the Bottle Blaster where both operate simultaneously. The Mid Spray Arm is used to clean the upper dishwasher rack while the Bottle Blaster is used to clean bottles, also in the upper rack. In order to …

The Second Generation Of The Cccm System For In-Vitro Cardiac Tissue Engineering., Mai-Dung Thi Nguyen

Electronic Theses and Dissertations

Cardiovascular disease is the leading cause of death worldwide. When a myocardial infarction occurs, scar tissue compensates the damaged myocardial tissue. This scar tissue increases the stiffness of the heart tissue, reduces the heart’s function, and finally leads to the heart failure (HF) disease. To have the tissue engraftment, in-vitro cardiac tissue should have the same properties as the native mature cardiac tissue. However, current in-vitro cell culture technologies fail to accurately recreate the in-vivo like mechanically physiological environment for in-vitro cardiac tissue culture, and therefore, fail to regenerate the in-vivo like mature cardiac tissue. Hence, a microfluidic cardiac cell …

Nanoporous Bi2te3 Thermoelectric Based Knudsen Gas Pump., Abderrazzak Faiz

Electronic Theses and Dissertations

This dissertation reports on the fabrication of a bi-directional Knudsen gas pump using a multifunctional nanoporous thermoelectric material. The integration of the channels into the thermoelectric material has the advantages of reducing heat losses and power consumption, improving the pump efficiency, and reducing the overall pump size. The Knudsen pump operates on the thermal transpiration principle, the phenomenon that gas molecules drift from the cold end to the hot end of a narrow channel. The gas pumping is realized in the transition or free molecular regime. The Knudsen pump is needed in a great number of applications such as gas …

Numerical Study Of Leading Edge Vortex Circulation Development On Finite Aspect Ratio Perching Wings., Kyle Hord

Electronic Theses and Dissertations

The perching maneuver of natural fliers is a complex motion involving fast change of angle of attack, complicated wing kinematics, large wing deformation and agile body motion control, but the prominent aerodynamic features can be revealed using a simple pitch-up wing motion coupled with a stream wise deceleration. In this dissertation the aerodynamic forces, the leading edge vorterx (LEV) development, and LEV circulation of pitch-up and perching wings are extensively studied at low Reynolds number conditions. 2D and 3D wings of different aspect ratios were linearly pitched up from 0 to 90 at three reduced pitch rates. The numerical investigation …

Stress Corrosion Cracking In Polymer Matrix Glass Fiber Composites, Jonathan Kosak

Electronic Theses and Dissertations

With the use of Polymer Matrix Glass Fiber Composites ever expanding, understanding conditions that lead to failure before expected service life is of increasing importance. Stress Corrosion Cracking (SCC) has proven to be one such example of conditions found in use in high voltage transmission line applications that leads to brittle fracture of polymer matrix composites.

SCC has been proven to be the result of acid buildup on the lines due to corona discharges and water buildup. This acid leaches minerals from the fibers, leading to fracture at low loads and service life. In order to combat this problem, efforts …

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.

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 …

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 …

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

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 …

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 …

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 …

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 …

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 …

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 …

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 …

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

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. …

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 …

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 …

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 …

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. …

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 …

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 …