Engineering Commons^™

Analytical And Experimental Investigation Of Microstructural Alterations In Bearing Steel In Rolling Contact Fatigue, Sina Mobasher Moghaddam

Open Access Dissertations

Rolling Contact Fatigue (RCF) is one the most common failure modes in bearings. RCF is usually associated with particular microstructural alterations. Such alterations (i.e. white etching cracks, butterflies, etc.) which lead to RCF failure are known to be among the most concerning matters to bearing industry.

In the current work, an analytical as well as experimental approaches are used to investigate “butterfly wing” formation, crack initiation and propagation from inclusions. A new damage evolution equation coupled with a FE model is employed to account for the effect of mean stresses and alternating stresses simultaneously to investigate butterfly formation. The proposed …

Enhancing A Flight Dispatcher Display For Safer Flight Operations, Jeongjoon Boo

Open Access Theses

This study assesses capability of flight dispatchers to adopt enhancements on their display that enables detection of flights in abnormal activities and investigation of the causes. Three approaches were used. First, the expected function for enhancements was designed by collecting information from different places about what technologies are available for consideration. Second, hierarchical task analysis was conducted based on data collected by interviewing a former flight dispatcher in order to assess operational capability to handle the enhancement. Third, based on the results of first two approaches, a display prototype that includes the enhancement was developed and evaluated for usability and …

Modernizing The Current Afghan Engineering Education System: Challenges And Opportunities, Khalilullah Mayar

Open Access Theses

Having an effective engineering education system in place can play a crucial role in the development and reconstruction process of a war-ravaged country, such as Afghanistan, where tens of billions of dollars of international aid has been spent in the past 14 years for that process, including higher education. Unfortunately, at this point, the Afghan engineering education system is not yet financially self-sufficient nor can it address the education requirements of today’s job market. This thesis aimed to identify the major challenges still faced by Afghanistan and to provide a comprehensive list of recommendations and priorities that can make the …

Learning The Language Of Academic Engineering: Sociocognitive Writing In Graduate Students, Catherine G. P. Berdanier

Open Access Dissertations

Although engineering graduate programs rarely require academic writing courses, the indicators of merit in academic engineering, such as journal publications, successful grants, and doctoral milestones (e.g. theses, dissertations) are based in effective written argumentation and disciplinary discourse. Further, graduate student attrition averages 57% across all disciplines, with some studies classifying up to 50% of these students as “ABD” (All But Dissertation.) In engineering disciplines specifically, graduate attrition rates across the U.S. average 36% (both Master’s and PhD students), according to the Council of Graduate Schools. The lack of socialization is generally noted as a main reason for graduate attrition, one …

Hydrologic And Water Quality Impacts From Perennial Crop Production On Marginal Lands, Qingyu Feng

Open Access Dissertations

Marginal lands are proposed as a viable option for producing biofeedstocks as these lands are not heavily engaged in agricultural production or may not be suitable for intensive row-crop food/feed production. However, meeting biofeedstock production goals will require large amount of marginal lands and the unintended consequences of producing biofeedstocks on marginal lands are not fully clear. The overall goal of this study was to evaluate the productivity of biofeedstocks on marginal lands and the potential impacts on hydrologic and water quality processes from the land use conversion.

This study was conducted in the Upper Mississippi River Basin (UMRB). First, …

Analytical Investigation Of Fretting Wear With Special Emphasis On Stress Based Models, Arnab Jyoti Ghosh

Open Access Dissertations

Fretting refers to the minute oscillatory motion between two surfaces in contact under an applied normal load. It can cause either surface or subsurface initiated failure resulting in either fatigue or wear or both. Two distinct regimes – partial slip and gross slip are typically observed in fretting contacts. Due to the nature of contact, various factors such as wear debris, oxidation, surface roughness, humidity etc. effect failures caused due to fretting. A number of different techniques have been developed to quantify fretting damage and several numerical models are proposed to predict damage due to fretting. Fretting wear also depends …

Dynamic Transverse Debondong Of A Single S-2 Fiber, Stephen E. Levine

Open Access Theses

Fiber reinforced composites are becoming increasingly common due to their high strength to weight ratios as compared to more conventional materials. Along with this increased used comes the need to have a higher level of understanding of the material characteristics. Specifically, the interface between the fiber and matrix is of particular interest. Loss of adhesion at this interface, known as debonding, can greatly decrease material strength. There has been significant research into debdonding phenomena at low strain rates. However, there is still a need for further insight at higher strain rates. In addition, given the opacity of many epoxy resins, …

Supervised Learning-Based Explicit Nonlinear Model Predictive Control And Unknown Input Estimation In Biomedical Systems, Ankush Chakrabarty

Open Access Dissertations

Application of nonlinear control theory to biomedical systems involves tackling some unique and challenging problems. The mathematical models that describe biomedical systems are typically large and nonlinear. In addition, biological systems exhibit dynamics which are not reflected in the model (so-called 'un-modeled dynamics') and hard constraints on the states and control actions, which exacerbate the difficulties in designing model-based controllers or observers.

This thesis investigates the design of scalable fast explicit nonlinear model predictive controllers (ENMPCs). The design involves (i) the estimation of a feasible region using Lyapunov stability methods and support vector machines; and (ii) within the estimated feasible …

Analysis And Simulation Of Small Scale Microwave Interferometer Experiments On Non-Ideal Explosives, David E. Kittell

Open Access Dissertations

Small scale experiments for non-ideal and homemade explosives (HMEs) were investigated, analyzed, and subsequently modeled in an attempt to develop more predictive capabilities for the threat assessment of improvised explosive devices (IEDs), as well as to provide new analysis capabilities for other investigators in the field. Non-ideal explosives and HMEs are challenging to characterize because of the nearly limitless parameter space (e.g. sample composition, density, particle morphology, etc.) which gives rise to a broad range of explosive sensitivity and performance. Large scale tests, such as rate stick and gap tests, are not feasible for characterizing every HME of interest due …

Kinetic Energy Harvesting Mechanism For Vortex Drop Structures, Mungtra Chusilp

Doctoral Dissertations

Energy recovery from wastewater is gaining significance as utilities work toward achieving energy neutrality and sustainability in their wastewater collection and treatment systems. In this dissertation, kinetic energy harvesting mechanism for vortex drop structures found within the municipal waste and storm water conveyance systems is presented. There are thousands of sewer drop structures installed across the U.S. carrying billions of gallons of sewage each year. A custom micro water turbine is developed in this research which could be retrofitted within the existing drop shafts to harvest the excessive kinetic energy available. This dissertation presents the conceptual design and analysis of …

Tailoring Optical And Plasmon Resonances In Core-Shell And Core-Multishell Nanowires, Sarath Ramadurgam

Open Access Dissertations

Semiconductor nanowires (NWs) are sub-wavelength structures which exhibit strong optical (Mie) resonances in the visible range. In addition to such optical resonances, the localized surface plasmon resonances (LSPR) in metal and semiconductor (or dielectric) based core-shell (CS) and core-multishell (CMS) NWs can be tailored to achieve novel negative-index metamaterials (NIM), extreme absorbers, invisibility cloaks and sensors. Particularly, in this dissertation, the versatility of CS and CMS NWs for the design of negative-index metamaterials in the visible range and, plasmonic light harvesting in ultrathin photocatalyst layers for water splitting are studied.

Utilizing the LSPR in the metal layer and the magnetic …

Impedance Characterization Of Ysz Based Nox Sensors, Ling Cui

Doctoral Dissertations

Yttria-stabilized zirconia has been utilized as an electrolyte of SOFC (Solid Oxide Fuel Cell) studies for years. It is also preferred as the electrolyte for solid state electrochemical sensor which is able to measure nitrogen oxides in the exhaust system. Electrochemical Impedance Spectroscopy method yields the change in impedance which is caused by an electron exchange of NO x gases at the sensing electrodes. From the EIS data, the fractional change in the phase angle is calculated for detecting sensor sensitivity.

Considering the fabrication of a sensor, several variables have been investigated which include the choice of electrolyte processing, sensing …

Improving Nano-Drug Delivery By Using Near-Real Time Sensing And Feedback, Pratik Adhikari

Doctoral Dissertations

Personalized medicine, seen as the solution to address the variability among the individuals, is the movement which proposes customization of medical procedures based on the need of the patient during the stages of prevention, diagnosis, treatment, and follow up. As the technology in medicine expands and newer methods of diagnosis and treatment are introduced in the clinic, real time data from the procedures is critical to assess the performance at point of care. Real time feedback, through collection of data at point of care would help make informed clinical decisions, potentially improving the efficacy of the treatment. In this dissertation, …

Size Specific Transfection To Mammalian Cells By Micropillar Array Electroporation, Yingbo Zu

Doctoral Dissertations

Electroporation serves as a promising non-viral gene delivery approach, while its current configurations carry drawbacks associated with high-voltage electrical pulses and heterogeneous treatment on individual cells. Here, we developed a new micropillar array electroporation (MAE) platform to advance the delivery of plasmid DNA and RNA to mammalian cells. By introducing well-patterned micropillar array on the electrode surface, the number of pillars each cell faces varies with its cell membrane surface area, despite their large population and random locations. In this way, cell size specific electroporation is conveniently done and contributed to a 2.5~3 fold increase on plasmid DNA transfection and …

A Standards-Based Grading Model To Predict Students' Success In A First-Year Engineering Course, Farshid Marbouti

Open Access Dissertations

Using predictive modeling methods, it is possible to identify at-risk students early in the semester and inform both the instructors and the students. While some universities have started to use standards-based grading, which has educational advantages over common score-based grading, at–risk prediction models have not been adapted to reap the benefits of standards-based grading. In this study, seven prediction models were compared to identify at-risk students in a course that used standards-based grading. When identifying at-risk students, it is important to minimize false negative (i.e., type II) errors while not increasing false positive (i.e., type I) errors significantly. To increase …

Estimating The Water Quality Condition Of River And Lake Water In The Midwestern United States From Its Spectral Characteristics, Jing Tan

Open Access Dissertations

This study focuses on developing/calibrating remote sensing algorithms for water quality retrieval in Midwestern rivers and lakes. In the first part of this study, the spectral measurements collected using a hand-held spectrometer as well as water quality observations for the Wabash River and its tributary the Tippecanoe River in Indiana were used to develop empirical models for the retrieval of chlorophyll (chl) and total suspended solids (TSS). A method for removing sky and sun glint from field spectra for turbid inland waters was developed and tested. Empirical models were then developed using a subset of the field measurements with the …

Development Of A Design Tool For Biologically Inspired Fault Adaptive Design By Strategy Mapping, Nicholas Steven Huisman

Graduate Theses and Dissertations

A design tool for Biologically Inspired Fault Adaption that utilizes the concept of strategy mapping was developed and the development process and testing is presented in this paper. The concept of strategy mapping is derived primarily from the field of military theory and supposes that for any given specific problem, that there exists a specific solution for, a single strategy can be identified for that solution/problem combination. This strategy, when applied to the specific problem yields the specific solution. This specific solution is referred to as the “tactics” of the strategy. The strategy can also be directly applied to a …

The Aerodynamic And Dynamic Loading Of A Slender Structure By An Impacting Tornado-Like Vortex: The Influence Of Relative Vortex-To-Structure Size On Structural Loading, Matthew Nicholas Strasser

Graduate Theses and Dissertations

Structural loading produced by an impacting vortex is a hazardous phenomenon that is encountered in numerous applications ranging from the destruction of residences by tornados to the chopping of tip vortices by rotors. Adequate design of structures to resist vortex-induced structural loading necessitates study of the phenomenon that control the structural loading produced by an impacting vortex. This body of work extends the current knowledge base of vortex-structure interaction by evaluating the influence of the relative vortex-to-structure size on the structural loading that the vortex produces. A computer model is utilized to directly simulate the two-dimensional impact of an impinging …

Development Of Pre-Stressed Cfrp Fatigue Retrofits For Common Steel Bridge Connections, Korey Albert Pough

Graduate Theses and Dissertations

Aging or deterioration of the nation’s bridge infrastructure is a significant issue that requires attention. Causes for much of this deterioration can be attributed to two main factors, 1) corrosion, and 2) metallic fatigue, both of which work together to reduce the strength and serviceability of bridge components over time. In many instances, strengthening of bridge components using localized retrofits offers an economical and fast solution for increasing the longevity of existing steel bridges; however, such retrofits must be resilient to further corrosion and fatigue damage. In this study, a localized retrofit is developed using pre-stressed Carbon Fiber Reinforced Polymer …

Investigation Of A Numerical Algorithm For A Discretized Rubber-Belt Continuously Variable Transmission Dynamic Model And Techniques For The Measurement Of Belt Material Properties., Brian Gene Ballew

Graduate Theses and Dissertations

A numerical algorithm for modeling the dynamic response of a rubber-belt Continuously Variable Transmission (CVT) belt is recreated. The numerical attributes applied to the algorithm and difficulties with numerical stability are discussed in detail. The degrees of freedom of the system have been expanded to include the dynamics of the engine torque output and vehicle loads such as rolling resistance and aerodynamic drag. This was done to emphasize the use of the model as an analysis tool for simulating CVT/engine/vehicle response. The increased degrees of freedom require the addition of a linear dampening element between belt nodes to dampen resonance …

Application Of Polyacrylamide-Based Floc Logs For Turbidity Control At Highway Construction Sites, Kien Ngo

Graduate Theses and Dissertations

Runoff waters generated on highway construction sites can have turbidities in excess of the proposed EPA regulatory standard of 280 NTU due to large areas of exposed soil. The objective of this research was to develop best management practices (BMPs) for the use of anionic polyacrylamide (PAM) based Floc Logs, for turbidity control. Five commercially available types of PAM-based Floc Logs were evaluated in jar tests, using soil excavated from Cato Springs Research Center (CSRC, Fayetteville AR) and six types of clay from the Clay Minerals Society (Chantilly, VA). These results show that no single Floc Log type was suitable …

Investigation Of The Inherent Chemical, Structural, And Mechanical Attributes Of Bio-Engineered Composites Found In Nature: Alligator Gar’S Exoskeleton Fish Scales, Wayne Derald Hodo

Graduate Theses and Dissertations

The U.S. Army has determined a huge cost savings of up to 51% can be accomplished by reducing the gross vehicle weight, for their personnel carrier, by 33%. To cut cost, composite materials are needed. Man-made composites can have superior material properties (high-strength, high-fracture toughness, and lightweight), but they are prone to delamination at the glued-layered interface. In contrast, fish scale is a natural composite that has the same material properties and, additionally, tend not to delaminate.

The focus of this study was to learn how nature integrates hard and soft materials at each length scale to form a layered …

Epitaxial Growth Of Si-Ge-Sn Alloys For Optoelectronic Device Application, Aboozar Mosleh

Graduate Theses and Dissertations

Microelectronics industry has experienced a tremendous change over the last few decades and has shown that Moore’s law has been followed by doubling the number of transistors on the chip every 18 months. However, continuous scaling down of the transistors size is reaching the physical limits and data transfer through metal interconnects will not be able to catch up with the increasing data processing speed in the future. Therefore, optical data transfer between chips and on-chip has been widely investigated. Silicon based optoelectronics has received phenomenal attention since Si has been the core material on which microelectronic industry has been …

Image Processing And Visualization Of Terahertz Pulsed Imaging Of Breast Cancer Tumors, Yuhao Wu

Graduate Theses and Dissertations

Terahertz imaging technology has grown substantially in recent years. With new advances made in the generation, manipulation, and detection of terahertz radiation, terahertz imaging has found its application as inspection tools in a wide range of areas including biomedicine, materials science, and aerospace industries. In the field of medical imaging, terahertz (THz) has emerged as a new imaging modality due to some fundamental physical properties of the THz wave. THz imaging has been used to examine various biological structures, and THz tomography has been developed to probe the 3D structures of those samples.

THz pulsed imaging (TPI) is one of …

Evaluation Of Conservation Practices Through Simulation Modeling And Tool Development, Gurdeep Singh

Graduate Theses and Dissertations

For the first objective, predicted impacts of selected Mississippi River Basin Initiative (MRBI) conservation practices (CPs) on sediment and nutrient loss were assessed. The study area was L’Anguille River Watershed (LRW), a priority focus watershed of the MRBI program and the simulated CPs were filter strip, critical area planting, grade stabilization structure, irrigation land leveling, irrigation pipeline, irrigation water management, and nutrient management. The Soil and Water Assessment Tool (SWAT) model was calibrated (1998 – 2005) and validated (2006 – 2012) for flow, sediment, total phosphorus (TP), and nitrate-nitrogen (NO3-N) at the Colt site (503 sq. km. drainage area) and …

Swat Model Simulation Of Bioenergy Crop Impacts On Water Quality In Cache River Watershed, Eeshan Kumar

Graduate Theses and Dissertations

Energy security through increased biofuel production is one of the components of the Energy Independence and Security Act (EISA) 2007. As per EISA 2007 mandate, appropriate independent research institutes are required to assess concerns to natural biodiversity due to biofuel production and report it to the Congress through the Environment Protection Agency (EPA). Planners, researchers, and agencies concerned with environmental regulations, ideally, would like to have location-specific information about the impacts for developing appropriate management interventions. This study examines long-term impacts on water quality in response to targeted (i.e. marginal lands) production of biofuel crops by setting up two SWAT …

Storage Of Round And Square Switchgrass Bales: Effect Of Storage Time And Fungal Inoculation On Saccharification Efficiency, Noaa Frederick

Graduate Theses and Dissertations

To produce fermentable sugars from lignocellulosic biomass feedstock, severe pretreatment conditions are needed (either high acid concentration, temperature, or retention times). High severities can produce toxic byproducts which inhibit enzymatic hydrolysis or fermentation. In order to reduce pretreatment severities (and thus increase enzyme and fermentation efficiency), the white-rot fungus Pleurotus ostreastus was seeded into square and round bales of Kanlow switchgrass (Panicum virgastum L.) and left in the field over a period of 9 month. The laccase producing fungus is believed to selectively degrade lignin, a common plant structural polymer, which can function as an enzymatic inhibitor. Samples were taken …

Design Of Elastic Metamaterials, Yu-Chi Su

Open Access Dissertations

This study focused on the design and fabrication of a double negativity and three broadband single negativity elastic metamaterials using a 3D printer. We investigated dispersion curves and dynamic material properties of the metamaterials. Negative phase velocity in the double negativity metamaterial was also demonstrated.

For metamaterials with single negativity, three types of broadband metamaterials were designed from parametric studies. A comparison showed that using frame bending/stretching mode is more effective than applying beam bending mode to broaden bandgap. Furthermore, it is found that adding internal resonant components could enlarge the bandgap. The single negativity metamaterials were validated by numerical …

Generalized Techniques For Using System Execution Traces To Support Software Performance Analysis, Thelge Manjula Peiris

Open Access Dissertations

This dissertation proposes generalized techniques to support software performance analysis using system execution traces in the absence of software development artifacts such as source code. The proposed techniques do not require modifications to the source code, or to the software binaries, for the purpose of software analysis (non-intrusive). The proposed techniques are also not tightly coupled to the architecture specific details of the system being analyzed. This dissertation extends the current techniques of using system execution traces to evaluate software performance properties, such as response times, service times. The dissertation also proposes a novel technique to auto-construct a dataflow model …

Modeling The Residual Useful Life Of Railroad Bearing Grease, Thania Alejandra Martinez

Theses and Dissertations

Railroad bearing performance is often constrained by the life of its lubricant. The lubricant life is determined by tribomechanical processes that are present during bearing operation. No known physical models exist to predict the railroad bearing lubricant life. This thesis summarizes the efforts undertaken in the development of empirical models that can accurately predict the residual useful life of railroad bearing grease. Modeling techniques to be employed include regression, regression trees, and split plots. The grease samples used to populate this model come from healthy and faulty bearings that were run under different loads, speeds, and ambient conditions in a …