Engineering Commons^™

Synthesis And Reactivity Of Hy Zeolite-Supported Rhodium Complexes, Artem D. Vityuk

Theses and Dissertations

The growing interest in the design of heterogeneous analogs of highly active and selective homogeneous catalysts prompted researchers to invest significant efforts in understanding of synthetic pathways, structure, and reactivity of supported single-site metal complexes. Synthesis of catalytically active organometallic species on solid supports with properties resembling those of their homogeneous counterparts could offer the opportunities to perform efficiently the solution organic reactions by utilizing flow instead of batch reactors. In this regard, rhodium carbonyl complexes and their derivatives are viewed as very attractive candidates for heterogenization due to their extensive application as catalysts for variety of industrially important reactions. …

The Role Of Interface Effects And Minority Carriers In The Metal-Semiconductor Schottky Junction, Sabih Uddin Omar

Theses and Dissertations

The metal-semiconductor (MS) Schottky barrier junction, formed by putting a metal in contact with a semiconductor crystal, is the simplest form of electronic rectifier. Despite the simple structure, the MS junction shows a variety of anomalous electrical characteristics. The non-ideality is generally described as a linear bias-dependence of the energy barrier height at the MS junction, quantified by an ideality factor. As the physical origin of this bias-dependent barrier height, the presence of various interface effects, such as the Schottky barrier inhomogeneity, interface trap states and morphological defects, have been proposed. However, there is no consensus among the researchers about …

Electrochemical, Interfacial, And Surface Studies Of The Conversion Of Carbon Dioxide To Liquid Fuels On Tin Electrodes, Jingjie Wu

Theses and Dissertations

The electrochemical reduction of carbon dioxide (CO2) into liquid fuels especially coupling with the intermittent renewable electricity offers a promising means of storing electricity in chemical form, which reduces the dependence on fossil fuels and mitigates the negative impact of anthropogenic CO2 emissions on the planet. Although converting CO2 to fuels is not in itself a new concept, the field has not substantially advanced in the last 30 years primarily because of the challenge of discovery of structural electrocatalysts and the development of membrane architectures for efficient collection of reactants and separation of products. An efficient catalyst for the electrochemical …

Use Of In-Situ Tests To Identify Soil Behavior Type And Liquefaction Susceptibility Of Sccp Soils, Rajshekhar Sarkar

Theses and Dissertations

For many years, the Cone Penetrometer Test (CPT), Flat Plate Dilatometer Test (DMT) and Standard Penetration Test (SPT) have been used as in-situ tools to assess the liquefaction potential of soils. Given the importance of evaluating liquefaction potential in the South Carolina Coastal Plain (SCCP), research was conducted to study the soil behavior of soils prone to liquefaction, develop site specific correlations between SPT, DMT and CPT testing parameters and evaluate the liquefaction susceptibility of the soils in the SCCP. The SCCP sites studied in this thesis are Sampit (SAM), Gapway (GAP), Hollywood (HWD), Four Hole Swamp (FHS) and Fort …

Secure And Reliable Wireless Communication Through End-To-End-Based Solution, Hossen Asiful Mustafa

Theses and Dissertations

In the past few decades, network architectures and protocols are often designed to achieve a high throughput and a low latency. Security was rarely considered during the initial design phases. As a result, many network systems are insecure by design. Once they are widely deployed, the inherent vulnerabilities may be difficult to eliminate due to the prohibitive update cost. In this dissertation, we examine such types of vulnerabilities in various networks and design end-to-end-based solutions that allow end systems to address such loopholes.

The end-to-end argument was originally proposed to let end hosts implement application-specific functions rather than letting intermediate …

Bio-Inspired And Low-Content Polymer Cement Mortar For Structural Rehabilitation, Nima Zohhadi

Theses and Dissertations

Use of polymers as partial replacement for Portland cement in cement mortar and concrete can diminish several drawbacks of these composites such as low tensile strength and strain capacity, high permeability and low adhesion. Main reasons for the use of polymers are to improve damage tolerance, adhesion, and resistance to water permeation. Various polymers with a wide range of physical and mechanical properties have been used in fabrication of cementitious composites. Typical polymer content for such composites is 5% to 20% (by the weight of cement) for both mortar and concrete. There are also drawbacks associated with the use of …

Optimal Design Of Geothermal Power Plants, Joshua Clarke

Theses and Dissertations

The optimal design of geothermal power plants across the entire spectrum of meaningful geothermal brine temperatures and climates is investigated, while accounting for vital real-world constraints that are typically ignored in the existing literature. The constrained design space of both double-flash and binary geothermal power plants is visualized, and it is seen that inclusion of real-world constraints is vital to determining the optimal feasible design of a geothermal power plant. The effect of varying condenser temperature on optimum plant performance and optimal design specifications is analyzed. It is shown that condenser temperature has a significant effect on optimal plant design …

Experimental Development Of Advanced Air Filtration Media Based On Electrospun Polymer Fibers, Negar Ghochaghi

Theses and Dissertations

Electrospinning is a process by which polymer fibers can be produced using an electrostatically driven fluid jet. Electrospun fibers can be produced at the micro- or nano-scale and are, therefore, very promising for air filtration applications. However, because electrospun fibers are electrically charged, it is difficult to control the morphology of filtration media. Fiber size, alignment and uniformity are very important factors that affect filter performance. The focus of this project is to understand the relationship between filter morphology and performance and to develop new methods to create filtration media with optimum morphology.

This study is divided into three focus …

Electron – Phonon Interaction In Multiple Channel Gan Based Hfets: Heat Management Optimization, Romualdo A. Ferreyra

Theses and Dissertations

New power applications for managing increasingly higher power levels require that more heat be removed from the power transistor channel. Conventional treatments for heat dissipation do not take into account the conversion of excess electron energy into longitudinal optical (LO) phonons, whose associated heat is stored in the channel unless such LO phonons decay into longitudinal acoustic (LA) phonons via a Ridley path. A two dimensional electron gas (2DEG) density of ~5×10¹²cm^-2 in the channel results in a strong plasmon–LO phonon coupling (resonance) and a minimum LO phonon lifetime is experimentally observed, implying fast heat removal from …

Tissue Engineering Scaffold Fabrication And Processing Techniques To Improve Cellular Infiltration, Casey Grey

Theses and Dissertations

Electrospinning is a technique used to generate scaffolds composed of nano- to micron-sized fibers for use in tissue engineering. This technology possesses several key weaknesses that prevent it from adoption into the clinical treatment regime. One major weakness is the lack of porosity exhibited in most electrospun scaffolds, preventing cellular infiltration and thus hosts tissue integration. Another weakness seen in the field is the inability to physically cut electrospun scaffolds in the frontal plane for subsequent microscopic analysis (current electrospun scaffold analysis is limited to sectioning in the cross-sectional plane). Given this it becomes extremely difficult to associate spatial scaffold …

A Practical Tool For The Determination Of Surface Stresses In Railroad Bearings With Different Contact Geometries And Load Conditions Using Finite Element Analysis, Michael A. Mason

Theses and Dissertations

The connection between contact geometry and fatigue in tapered roller bearings utilized in the railroad environment is still of interest. Roller bearings for railroad applications are typically precision ground with crowned contact geometries to prevent edge loading of components. This normally results in completely elastic Hertzian contact stresses under standard railcar loads. However, under extreme load conditions, detrimental edge loading has been known to occur. It is proposed to develop a tool, using finite element analysis, that can be utilized to optimize complex raceway crown geometries for severe applications.

A successful implementation of this tool is presented and validated using …

Transient Stability Enhancement Of Wind Farms Using Power Electronics And Facts Controllers, Hossein A. Mohammadpour

Theses and Dissertations

Nowadays, it is well-understood that the burning of fossil fuels in electric power station has a significant influence on the global climate due to greenhouse gases. In many countries, the use of cost-effective and reliable low-carbon electricity energy sources is becoming an important energy policy. Among different kinds of clean energy resources- such as solar power, hydro-power, ocean wave power and so on, wind power is the fastest-growing form of renewable energy at the present time. Moreover, adjustable speed generator wind turbines (ASGWT) has key advantages over the fixed-speed generator wind turbines (FSGWT) in terms of less mechanical stress, improved …

Toward Polymer Coating With Easy Ice Release, Chenyu Wang

Theses and Dissertations

Minimizing adhesion of ice has been the subject of extensive studies for applications such aircraft wings, wind turbine blades spacecraft, power transmission wires, while a growing interest concerns coatings for aerospace applications. The work described here describes progress for coatings and ice release test method development over the last few years. Major achievements include: (1) New Rigid Adherent-Resistant Elastomers (RARE), (2) A new Epoxied Cylinder (EC) adhesion test, (3) Validation of an ice release test, and (4) Study of ice adhesion strength on coating thickness for a PDMS elastomer. Rigid Adhesion-Resistance Elastomers (RARE) are comprised of 3F 1 terminated with …

Multiferroic Nanomagnetic Logic: Hybrid Spintronics-Straintronic Paradigm For Ultra-Low Energy Computing, Mohammad Salehi Fashami

Theses and Dissertations

Excessive energy dissipation in CMOS devices during switching is the primary threat to continued downscaling of computing devices in accordance with Moore’s law. In the quest for alternatives to traditional transistor based electronics, nanomagnet-based computing [1, 2] is emerging as an attractive alternative since: (i) nanomagnets are intrinsically more energy-efficient than transistors due to the correlated switching of spins [3], and (ii) unlike transistors, magnets have no leakage and hence have no standby power dissipation. However, large energy dissipation in the clocking circuit appears to be a barrier to the realization of ultra low power logic devices with such nanomagnets. …

Computational Study Of Protein-Protein Interactions In Misfolded States, Oscar Bastidas

Theses and Dissertations

Protein-protein interactions (PPI’s) play important roles in biological systems. In particular, intra-protein interactions help create and maintain correctly folded protein states and mutations that result in misfolded states may be associated with significant changes in PPI behavior. Six unrelated protein systems with known structure files, each consisting of a wild-type and mutant strain, were studied using the computational algorithm OpenContact©. OpenContact© is a simple tool that can be used to rapidly identify or map interactions “hot-spots” in a protein and was, consequently, used in this study as a starting point to examine the potential or possible role of PPI’s on …

The Effect Of Simultaneous, Irrelevant Auditory And Visual Stimuli On A Forced-Attention Dichotic Listening Test, Keri Davis

Theses and Dissertations

Many of the studies examining cognitive control during selective attention across different sensory modalities conflict. This study was designed to study the effect of an irrelevant visual stimulus and an auditory distraction of backward speech on a forced attention dichotic listening test. I predicted that the visual stimulus and backward speech would not have a significant effect on the ear advantage. The results showed that all subjects were able to force their attention to the ear regardless of the visual or auditory distracters. In addition, I found that an irrelevant visual stimulus affects auditory attention more so in the left …

Applications Of 4-State Nanomagnetic Logic Using Multiferroic Nanomagnets Possessing Biaxial Magnetocrystalline Anisotropy And Experiments On 2-State Multiferroic Nanomagnetic Logic, Noel D'Souza

Theses and Dissertations

Nanomagnetic logic, incorporating logic bits in the magnetization orientations of single-domain nanomagnets, has garnered attention as an alternative to transistor-based logic due to its non-volatility and unprecedented energy-efficiency. The energy efficiency of this scheme is determined by the method used to flip the magnetization orientations of the nanomagnets in response to one or more inputs and produce the desired output. Unfortunately, the large dissipative losses that occur when nanomagnets are switched with a magnetic field or spin-transfer-torque inhibit the promised energy-efficiency. Another technique offering superior energy efficiency, “straintronics”, involves the application of a voltage to a piezoelectric layer to generate …

Early Prediction Of Fracture In Bodies Bounded By Random Rough Surfaces, Hector Medina

Theses and Dissertations

Under certain loading conditions, surfaces topography coupled with materials degree of brittleness can significantly compromise the mechanical performance of structures. The foregoing remains valid even if roughness is intentionally introduced for engineering reasons. In either case, stress can concentrate. The case of the stress concentration in surfaces having randomly distributed pits is a problem that, although being very practical, yet it remains unsolved. The complexity of a random configuration renders difficult the problem of analytically finding relationships between surface parameters and markers indicative of mechanical failure. Another difficulty is the reproducibility of replicates of specimens possessing random rough surfaces, for …

Joining And Hermetic Sealing Of Silicon Carbide Using Iron, Chromium, And Aluminum Alloys, Andrew Morgan

Theses and Dissertations

Silicon Carbide (SiC) is increasingly gaining attention as a potential fuel cladding material, on account of its favorable thermo-mechanical and neutronic properties. The major limitations of such a cladding is currently associated with joining and hermetic sealing. The work presented here investigated the use of Al, Cr and Fe metals and a specialized alloy (FeCrAl) to achieve hermetic sealing of SiC tubes as well as a joining technology of SiC. Major part of solving this issue requires addressing joining of ceramic and metallic components, which are largely dissimilar in both thermal and mechanical properties. Preliminary experiments to bond SiC with …

A Low Cost Implementation Of Autonomous Takeoff And Landing For A Fixed Wing Uav, Thomas Carnes

Theses and Dissertations

The take-off and landing of an Unmanned Aerial Vehicle (UAV) is often the most critical and accident prone portion of its mission. This potential hazard coupled with the time and resources necessary to train a remote UAV pilot makes it desirable to have autonomous take-off and landing capabilities for UAVs. However, a robust, reliable, and accurate autonomous takeoff and landing capability for fixed-wing aircraft is not an available feature in many low-cost UAV flight control systems. This thesis describes the design of an autonomous take-off and landing algorithm implemented on an existing low-cost flight control system for a small fixed …

Fabrication Of Micropatterns For The Spatial Control Of Cell Propagation And Differentiation, Mahmoud Moustafa

Theses and Dissertations

Challenges in the development of successful cell therapies involve engineering and control of cues to regulate the balance between differentiation and self-renewal. However, the complexity of architecture and function make this an intriguing problem in the context of forming functional connections. Here we present the design and fabrication of microstructured scaffolds that present a biomimetic framework along which neural cell lines can organize into oriented constructs. Specifically, we show microfabricated non-linear architectures that promote cellular fate related to propagation of human neuroblastoma cells and directed differentiation towards neurons. By mimicking biological networks that allow for spreading of the cells instead …

Development Of A Compact, Low-Cost Wireless Device For Biopotential Acquisition, Graham Kelly

Theses and Dissertations

A low-cost circuit board design is presented, which in one embodiment is smaller than a credit card, for biopotential (EMG, ECG, or EEG) data acquisition, with a focus on EEG for brain-computer interface applications. The device combines signal conditioning, low-noise and high-resolution analog-to-digital conversion of biopotentials, user motion detection via accelerometer and gyroscope, user-programmable digital pre-processing, and data transmission via Bluetooth communications. The full development of the device to date is presented, spanning three embodiments. The device is presented both as a functional data acquisition system and as a template for further development based on its publicly-available schematics and computer-aided …

Novel 3d Head And Neck Cancer Model To Evaluate Chemotherapeutic Efficacy, Kelly Morgan

Theses and Dissertations

HNSCC accounts for 7 percent of all new cancer occurrences. Despite currently available treatments, there continues to be a high mortality and recurrence rate in HNSCC. Well over 50 percent of all cancer patients receive chemotherapy as a standard treatment. However, only 5 percent of these cases have been shown to help with treatment of the disease. Formerly, two options were available for drug testing: in vivo animal models, and in vitro two-dimensional models. While in vivo models remain the most representative, their use is burdened by high costs, time constraints, and ethical concerns. 2D models are simple to use …

Effect Of Leg Geometries, Configurations, And Dimensions On Thermo-Mechanical And Power-Generation Performance Of Thermoelectric Devices, Ugur Erturun

Theses and Dissertations

Environmental challenges, such as global warming, growing demand on energy, and diminishing oil sources have accelerated research on alternative energy conversion methods. Thermoelectric power generation is a promising method to convert wasted heat energy into useful electrical energy form. A temperature gradient imposed on a thermoelectric device produces a Seebeck potential. However, this temperature gradient causes thermal stresses due to differential thermal expansions and mismatching of the bonded components of the device. Thermal stresses are critical for thermoelectric devices since they can generate failures, including dislocations, cracks, fatigue fractures, and even breakdown of the entire device. Decreases in power-generation performance …

Quantum Efficiency Enhancement For Gan Based Light-Emitting Diodes And Vertical Cavity Surface-Emitting Lasers, Fan Zhang

Theses and Dissertations

This thesis explores the improvement of quantum efficiencies for InGaN/GaN heterostructures and their applications in light-emitting diodes (LEDs) and vertical cavity surface-emitting lasers (VCSELs). Different growth approaches and structural designs were investigated to identify and address the major factors limiting the efficiency. (1) Hot electron overflow and asymmetrical electron/hole injection were found to be the dominant reasons for efficiency degradation in nitride LEDs at high injection; (2) delta p-doped InGaN quantum barriers were employed to improve hole concentration inside the active region and therefore improve hole injection without sacrificing the layer quality; (3) InGaN active regions based on InGaN multiple …

System Analysis With Improved Thermo-Mechanical Fuel Rod Models For Modeling Current And Advanced Lwr Materials In Accident Scenarios, Ian Edward Porter

Theses and Dissertations

A nuclear reactor systems code has the ability to model the system response in an accident scenario based on known initial conditions at the onset of the transient. However, there has been a tendency for these codes to lack the detailed thermo-mechanical fuel rod response models needed for accurate prediction of fuel rod failure. This proposed work will couple today's most widely used steady-state (FRAPCON) and transient (FRAPTRAN) fuel rod models with a systems code TRACE for best-estimate modeling of system response in accident scenarios such as a loss of coolant accident (LOCA). In doing so, code modifications will be …

Implementation And Evaluation Of Fuel Creep Using Advanced Light-Water Reactor Materials In Frapcon 3.5, Spencer Carroll

Theses and Dissertations

As current reactors approach the end of their operable lifetime, new reactors are needed if nuclear power is to continue being generated in the United States. Some utilities have already began construction on newer, more advanced LWR reactors, which use the same fuel as current reactors and have a similar but updated design. Others are researching next generation (GEN-IV) reactors which have new designs that utilize alternative fuel, coolants and other reactor materials. Many of these alternative fuels are capable of achieving higher burnups and are designed to be more accident tolerant than the currently used UO2 fuel. However, before …

High Throughput Multi-Solution Genetic Algorithm (Htmga) For Identification Of Alternate Solutions In A Structural Model Updating Context, Muslum Kilinc

Theses and Dissertations

Model updating techniques seek to improve numerical models of existing structure by integrating experimental data from the structure. Many techniques use an error function that describes the differences between the numerical model and the experimental data. For example, if dynamic data is available, the error between experimental and numerical modal parameters can be used. Optimization techniques are used to identify the structural parameters that minimize this function. Most model updating techniques are interested in finding the global minima of the error function. However, one could argue that due to a number of factors, such as modeling errors and low sensor …

Modeling Of Chemical-Mechanical Couplings In Solid Oxide Cells And Reliability Analysis, Xinfang Jin

Theses and Dissertations

Solid oxide fuel cell (SOFC) has been well demonstrated as a promising clean energy conversion technology. For practical applications, the SOFC systems should have both good electrochemical performance and high reliability. The SOFCs are usually operated under very aggressive conditions, e.g., high temperatures (600-1000oC) and extremely low oxygen partial pressures (anode electrode). These aggressive operating conditions could lead to a variety of material system degradations, imposing great challenges on meeting lifetime requirement of SOFC commercial applications. It is therefore essential to increase the understanding of fundamental SOFC degradation mechanisms.

The basic structure of SOFCs is a positive electrode-electrolyte-negative electrode (PEN) …

Identifying Performance Criteria Of Fully Bioresorbable Scaffolds For Endovascular Applications, Jahid Ferdous

Theses and Dissertations

Background: Bioresorbable scaffolds (BRS) have revolutionized percutaneous coronary intervention in clinical cardiovascular medicine. As opposed to permanent alternatives such as metallic stents, BRS have an inherent potential to reduce the occurrence of untoward events such as vessel re-narrowing or thrombosis by virtue of undergoing complete and controlled resorption post- implantation. While BRS platforms demonstrate a clear potential to mitigate risk stemming from incomplete vessel healing, they introduce a new set of considerations to clinical safety and efficacy. Foremost among these issues is the fate of and biological response to material by-products that evolve throughout the scaffold degradation and erosion processes, …