Engineering Commons^™

A Framework For Miniaturized Mechanical Characterization Of Tensile, Creep, And Fatigue Properties Of Slm Alloys, Jonathan Torres-Caceres

Electronic Theses and Dissertations

With the heightened design complexity that may be achieved through additive manufacturing (AM) comes an equally complex set of distinct material characteristics. To properly characterize new materials for use in selective laser melting (SLM), extensive analysis is necessary. Traditional testing techniques, however, can be prohibitive in time and cost incurred. The small punch test (SPT) has been developed for such purposes, where material is scarce or costly. Although lacking standardization, SPT has been successfully employed with various materials to assess material properties such as the yield and ultimate strength and verified by traditional testing results. With the accompaniment of numerical …

Characterization, Classification, And Genesis Of Seismocardiographic Signals, Amirtaha Taebi

Electronic Theses and Dissertations

Seismocardiographic (SCG) signals are the acoustic and vibration induced by cardiac activity measured non-invasively at the chest surface. These signals may offer a method for diagnosing and monitoring heart function. Successful classification of SCG signals in health and disease depends on accurate signal characterization and feature extraction. In this study, SCG signal features were extracted in the time, frequency, and time-frequency domains. Different methods for estimating time-frequency features of SCG were investigated. Results suggested that the polynomial chirplet transform outperformed wavelet and short time Fourier transforms. Many factors may contribute to increasing intrasubject SCG variability including subject posture and respiratory …

Generation And Characterization Of Isolated Attosecond Pulse In The Soft X-Ray Regime, Jie Li

Electronic Theses and Dissertations

The observation of any atomic and molecular dynamics requires a probe that has a timescale comparable to the dynamics itself. Ever since the invention of laser, the temporal duration of the laser pulse has been incrementally reduced from several nanoseconds to just attoseconds. Picosecond and femtosecond laser pulses have been widely used to study molecular rotation and vibration. In 2001, the first single isolated attosecond pulse (1 attosecond = 10^-18 seconds.) was demonstrated. Since this breakthrough, "attoscience" has become a hot topic in ultrafast physics. Attosecond pulses typically have span between EUV to X-ray photon energies and sub-femtosecond pulse duration. …

Analyzing Destination Choices Of Tourists And Residents From Location Based Social Media Data, Md Mehedi Hasnat

Electronic Theses and Dissertations

Ubiquitous uses of social media platforms in smartphones have created an opportunity to gather digital traces of individual activities at a large scale. Traditional travel surveys fall short in collecting longitudinal travel behavior data for a large number of people in a cost effective way, especially for the transient population such as tourists. This study presents an innovating methodological framework, using machine learning and econometric approaches, to gather and analyze location-based social media (LBSM) data to understand individual destination choices. First, using Twitter's search interface, we have collected Twitter posts of nearly 156,000 users for the state of Florida. We …

Energy Efficient And Secure Wireless Sensor Networks Design, Afraa Attiah

Electronic Theses and Dissertations

Wireless Sensor Networks (WSNs) are emerging technologies that have the ability to sense, process, communicate, and transmit information to a destination, and they are expected to have significant impact on the efficiency of many applications in various fields. The resource constraint such as limited battery power, is the greatest challenge in WSNs design as it affects the lifetime and performance of the network. An energy efficient, secure, and trustworthy system is vital when a WSN involves highly sensitive information. Thus, it is critical to design mechanisms that are energy efficient and secure while at the same time maintaining the desired …

Masquerading Techniques In Ieee 802.11 Wireless Local Area Networks, Omar Nakhila

Electronic Theses and Dissertations

The airborne nature of wireless transmission offers a potential target for attackers to compromise IEEE 802.11 Wireless Local Area Network (WLAN). In this dissertation, we explore the current WLAN security threats and their corresponding defense solutions. In our study, we divide WLAN vulnerabilities into two aspects, client, and administrator. The client-side vulnerability investigation is based on examining the Evil Twin Attack (ETA) while our administrator side research targets Wi-Fi Protected Access II (WPA2). Three novel techniques have been presented to detect ETA. The detection methods are based on (1) creating a secure connection to a remote server to detect the …

Hole Selective Tunneling Oxide Applications With Insight Into Sophisticated Characterization Techniques, Nizamettin Kortan Ogutman

Electronic Theses and Dissertations

Tunneling metal oxide layers combined with industrially applicable novel cleaning methods can boost the current efficiency limit, which corresponds to approximately %22 in production, of crystalline silicon (c-Si) solar cells. Within the scope of this dissertation, extremely thin tunneling layers (1-3nm) of aluminum oxide is studied in conjunction with the development of wet cleaning procedures that are feasible in production lines currently exist today. These tunneling stacks are deployed to serve as exceptional surface passivation layers due to the inherent built-in charge provided by aluminum oxide. This capability is further strengthened by the introduction of extremely well controlled wet chemical …

The Active Phase Of Gold Catalyst For Propylene Epoxidation, Manchhiben Patel

Summer Community of Scholars Posters (RCEU and HCR Combined Programs)

No abstract provided.

Control Of Thiol-Maleimide Reaction Kinetics In Peg Hydrogel Networks, Lauren E. Jansen, Lenny J. Negrón-Piñeiro, Sualyneth Galarza, Shelly Peyton

Chemical Engineering Faculty Publication Series

Michael-type addition reactions are widely used to polymerize biocompatible hydrogels. The thiol-maleimide modality achieves the highest macromer coupling efficiency of the reported Michael-type pairs, but the resulting hydrogel networks are heterogeneous, because polymerization is faster than the individual components can be manually mixed. The reactivity of the thiol dictates the overall reaction speed, which can be slowed in organic solvents and acidic buffers. Since these modifications also reduce the biocompatibility of resulting hydrogels, we investigated a series of biocompatible buff­ers and crosslinkers to decelerate gelation while maintaining high cell viability. We found that lowering the polymer weight percentage (wt%), buffer …

Anomalously Diffusing And Persistently Migrating Cells In 2d And 3d Culture Environments, Igor D. Luzhansky, Alyssa D. Schwartz, Joshua D. Cohen, John P. Macmunn, Lauren E. Barney, Lauren Jansen, Shelly Peyton

Chemical Engineering Faculty Publication Series

Appropriately chosen descriptive models of cell migration in biomaterials will allow researchers to characterize and ultimately predict the movement of cells in engineered systems for a variety of applications in tissue engineering. The persistent random walk (PRW) model accurately describes cell migration on two-dimensional (2D) substrates. However, this model inherently cannot describe subdiffusive cell movement, i.e. migration paths in which the root mean square displacement increases more slowly than the square root of the time interval. Subdiffusivity is a common characteristic of cells moving in confined environments, such as three-dimensional (3D) porous scaffolds, hydrogel networks, and in vivo tissues. We …

Two Essays On Whole Farm Modeling And Crop Marketing In Western Kentucky, Benjamin A. Martin

Theses and Dissertations--Agricultural Economics

This thesis is composed of two essays that investigate whole farm planning and crop marketing in western Kentucky. In the first essay, contracting decisions between food corn producers and a mill are analyzed to observe factors affecting the bushel amount farmers contract. Unbalanced panel data containing seven years’ worth of pricing and contract information are used with a fixed-effects model to generate parameter estimates and quantify their effect on bushels contracted. It was found that contract attributes, market condition, and relationship-specific assets had a significant effect on producers’ food corn contracting decisions. The second essay utilizes mixed-integer programming to optimize …

Mixture Models With Grouping Structure: Retail Analytics Applications, Haidar Almohri

Wayne State University Dissertations

Growing competitiveness and increasing availability of data is generating tremendous interest in data-driven analytics across industries. In the retail sector, stores need targeted guidance to improve both the efficiency and effectiveness of individual stores based on their specific location, demographics, and environment. We propose an effective data-driven framework for internal benchmarking that can lead to targeted guidance for individual stores. In particular, we propose an objective method for segmenting stores using a model-based clustering technique that accounts for similarity in store performance dynamics. It relies on effective Finite Mixture of Regression (FMR) techniques for carrying out the model-based clustering with …

Modular Product Architecture’S Decisions Support For Remanufacturing-Product Service System Synergy, Johnson Adebayo Fadeyi

Wayne State University Dissertations

Remanufacturing is identified as the most viable product end-of-life (EOL) management strategy. However, about 80% of manufactured products currently end up as wastes. Besides other benefits, the product service system (PSS) could curtail the main bottlenecks to remanufacturing namely quantity, quality, recovery time of used product, and negative perception of remanufactured products. Therefore, the integration of PSS and remanufacturing has been increasingly recommended as an enhanced product offering. However, an integration that is informed by mathematical analysis is missing. Meanwhile, the variables that bolster the performance of PSS and remanufacturing are substantially influenced by product development (PD) decisions. Among the …

Study Of Probabilistic Characteristics Of Local Field Fluctuations In Isotropic Two Phase Composites: Conductivity Type Problems, David Ostberg

Wayne State University Dissertations

Probability distributions of electric …field and electric potential in two-phase particulate composite materials with spherical inclusions are found in the limit of small particle concentration. Additionally a method for the approximation of local fields within random statistically isotropic composites with a …finite number of …field ‡fluctuations which retain potentiality is presented and an approximate solution with the

variational principal for homogenization in statistical terms for three ‡fluctuations within one phase and a homogeneous second phase is found.

Ethanol Autoignition Modeling And Validation At Wide Ranges Of Mixture Temperatures, Pressures, And Equivalence Ratios, Antowan Zyada

Wayne State University Dissertations

A new ethanol detailed kinetic model with 107 species and 1795 reactions was developed by using the reaction mechanism generator (RMG) and a thorough reaction path analysis. The mechanism model was extensively evaluated against measured ignition delay times, laminar flame speeds, and time-resolved species concentrations. The ignition delay experiments were conducted at pressures of 15, 20, and 30 bar, a temperature range of 850 to 1000 K, and equivalence ratios of 0.5, 1.0 and 2.0 using an optically accessible rapid compression machine (RCM). The effect of oxygen concentration on the ignition delay at a fixed equivalence ratio was also measured …

Multiple Factors Drive Variation Of Forest Root Biomass In Southwestern China, Hao Zhang, Kelin Wang, Zhaoxia Zeng, Zhigang Zou, Yanfang Xu, Fuping Zeng

Nebraska Center for Biotechnology: Faculty and Staff Publications

The roots linking the above-ground organs and soil are key components for estimating net primary productivity and carbon sequestration of forests. The patterns and drivers of root biomass in forest have not been examined well at the regional scale, especially for the widely distributed forest ecosystems in southwestern China. We attempted to determine the spatial patterns of root biomass (RB, Mg/ha), annual increment root biomass (AIRB, Mg/ha/year), ratio of root and above-ground (RRA), and the relative contributions of abiotic and biotic factors that drive the variation of root biomass. Forest biomass and multiple factors (climate, soil, forest types, and stand …

Non-Targeted Colonization By The Endomycorrhizal Fungus, Serendipita Vermifera, In Three Weeds Typically Co-Occurring With Switchgrass, Prasun Ray, Yingqing Guo, Jaydeep Kolape

Nebraska Center for Biotechnology: Faculty and Staff Publications

Serendipita vermifera (=Sebacina vermifera; isolate MAFF305830) is a mycorrhizal fungus originally isolated from the roots of an Australian orchid that we have previously shown to be beneficial in enhancing biomass yield and drought tolerance in switchgrass, an important bioenergy crop for cellulosic ethanol production in the United States. However, almost nothing is known about how this root-associated fungus proliferates and grows through the soil matrix. Such information is critical to evaluate the possibility of non-target effects, such as unintended spread to weedy plants growing near a colonized switchgrass plant in a field environment. A microcosm experiment was conducted …

Isolation And Onboarding: Gender Bias In Aviation Training Documents, William Hart

Technical Communication Capstone Course

There is a growing interest in male-dominated industries and the challenges women face finding their place within the workplace community. Yet, there seems to be little research on how training documents, generally created by technical communicators, may isolate and limit women who seek to pursue careers in these fields. Technical communication and gender scholars have examined women in the technical communication field and gender bias in male-dominated industries but have not yet examined gender stereotypes in training documents. Training documents are designed to provide written instructions and a reference guide for job functions, workplace rules, orientation, and company policies. This …

University Of Nebraska At Omaha 2018-2019 Course Catalog, University Of Nebraska At Omaha

Undergraduate Catalogs

Located in one of America’s best cities to live, work and learn, the University of Nebraska at Omaha (UNO) is Nebraska’s premier metropolitan university. With more than 15,000 students enrolled in 200-plus programs of study, UNO is recognized nationally for its online education, graduate education, military friendliness, and community engagement efforts.Founded in 1908, UNO has served learners of all backgrounds for more than 100 years and is dedicated to another century of excellence both in the classroom and in the community.

Aviation Outreach Model And Gap Analysis: Examining Solutions To Address Workforce Shortages, Rebecca K. Lutte

Aviation Institute Faculty Publications

The purpose of this research is to examine aviation outreach programs to identify best practices and areas for improvement in the endeavor to recruit youth to the aviation industry. The research includes creation of a model of aviation outreach and development and application of an aviation outreach gap analysis design. Three programs are analyzed, Women in Aviation Girls in Aviation Day, Experimental Aviation Association Young Eagles, and Aircraft Owners and Pilots Association High School Aviation Initiative. Each program takes a unique approach to recruiting youth and the strengths and weaknesses, based on the aviation outreach model, are discussed. Results of …

Investigation Of Temperature Dependence Of Microfibre Coil Resonators, Yu Yin, Jibo Yu, Yuxuan Jiang, Shi Li, Jing Ren, Gerald Farrell, Elfed Lewis, Pengfei Wang

Articles

The temperature-sensitive performance of a microfiber coil resonator (MCR) is thoroughly investigated. The MCR is fabricated by wrapping a microfiber on a PMMA rod coated with a UV-curable low refractive index epoxy. The temperature sensitivity is measured by investigating the correlation between the shift of the resonant wavelength and the surrounding temperature. It is determined that a range of parameters of the MCRs, including the gap between two adjacent rings, the diameter of the supporting rod, the number of rings, and the diameter of the microfiber, have a great influence on the temperature sensitivity of the MCRs. By optimizing the …

Analyzing The Spectral Energy Cascade In Turbulent Channel Flow, João Rodrigo Andrade, Ramon Silva Martins, Gilmar Mompean, Laurent Thais, Thomas B. Gatski

CCPO Publications

An analysis of the spectral turbulent kinetic energy budget in a fully developed turbulent plane channel flow is performed. Direct numerical simulation data are evaluated at friction Reynolds numbers Re_τ of 180 and 1000. The analysis is focused on the influence of the Reynolds number on the spectral cascade of energy and the corresponding energy cascade in physical space in the presence of inhomogeneity and anisotropy. The turbulent kinetic energy distribution is compared for both Reynolds numbers, and the relevant characteristics of the energy transfer process in a wall-bounded turbulent flow are described. Differences in energy cascade are noted …

Mental Workload Assessment: Knowledge-Bases Based Upon The Features Of The Original Nasa Task Load Index, Lucas Rizzo, Luca Longo

Other resources

No abstract provided.

Fractionation Of Lignin Derived Compounds From Thermochemically Processed Lignin Towards Antimicrobial Properties, Luke A. Dodge

Theses and Dissertations--Biosystems and Agricultural Engineering

The overuse of antibiotics in agriculture is an emerging concern, due to their potential detrimental impact to the environment. This study focuses on exploring antimicrobial properties of lignin derived compounds. Lignin is of interest as a feedstock to replacing some petroleum-based chemicals and products because it is the most abundant source of renewable aromatic compounds on the planet. Two lignin rich streams, residues from the enzymatic hydrolysis of dilute acid and alkaline pretreated corn stover, were decomposed via pyrolysis and hydrogenolysis, respectively. The resulting liquid oils were subjected to sequential extractions using a series of solvents with different polarities. Chemical …

Development Of Sorption Technology For Extracting Rare Earth Elements From Coal Fly Ash, Bilal Syed

Research Opportunities for Engineering Undergraduates (ROEU) Program 2017-18

Rare Earth Elements (REEs) are elements with many high tech uses (e.g., smartphones, electric cars, advanced weaponry) and have been identified by the DOE to be critical to the US economy. Currently, China supplies over 85% of REEs resulting in an undiversified market and susceptibility to supply shock and economic insecurity. To address this susceptibility, this research aims to develop an economic and environmentally-friendly method of extracting REEs from nascent, plentiful sources such as coal and coal by-products like fly ash.

Optical Coherence Tomography Application To Alopecia In The Scalp, Elizabeth Melcher

Research Opportunities for Engineering Undergraduates (ROEU) Program 2017-18

Alopecia is the loss of hair, whether it be from the scalp or other regions of the body. Current techniques used to best diagnose and track alopecia are often invasive, requiring a biopsy for results. The use of the OCT, or optical coherence tomography, could drastically improve a patient’s experience in undergoing a diagnosis while proving accurate results. The objective of this study is to develop diagnostic algorithms for the rapid, non-invasive diagnosis of alopecia with OCT. The first step is collecting OCT images of a healthy scalp to understand the anatomical structures with the imaging technique.

Low Cost Waist Line Circumference Health Management Belt, Raghav Talreja

Research Opportunities for Engineering Undergraduates (ROEU) Program 2017-18

One third of the American population is obese or near obese, and $150 billion is spent in weight management. Current devices to monitor weight are expensive, and niche products are designed for health enthusiasts. This project investigates user needs, development and commercialization steps for a low cost health management belt.

Cfd/Fea Of A Steam Methane Reforming Tube, Matthew Wegener

Research Opportunities for Engineering Undergraduates (ROEU) Program 2017-18

Steam methane reforming is the primary method by which hydrogen is produced; increased efficiency in hydrogen production could enable hydrogen’s usage as an alternative fuel. The objectives of this project are to construct a robust CFD/FEA model of a steam methane reforming tube, and to perform CFD/FEA analysis in both steady and transient operational states, comparing thermal stresses/strains in the tube wall in the two states and relating tube stresses/strains to properties of the process controller.

Design And Development Of An Emergency System For Children In A Hot Car At Risk Of Heatstroke, Nathan Kisha

Research Opportunities for Engineering Undergraduates (ROEU) Program 2017-18

Since 1998, an average of 37 children have died every year due to heat-related deaths after being stuck in a vehicle, making it the leading cause of non-crash-related fatalities among children. This creates an opportunity to create a system which will be able to detect this danger and do something in order to prevent it. There are 4 main objectives for the system to be able to accomplish: 1) determine if the temperature in the car poses a risk, 2) use an alarm to provide a warning and wake up a sleeping child, 3) determine if someone is in the …

Developing Vascular Graft From Adipose-Derived Stem Cells, Ashley C. Apil

Research Opportunities for Engineering Undergraduates (ROEU) Program 2017-18

This project aims to differentiate adipose-derived stem cells into fibroblasts through the addition of platelet-derived growth factor (PDGF) into the culture media. Differentiation protocol will be optimized, then successful differentiation will be verified through PCR analysis. The ASC-fibroblasts will then be seeded into a ring construct as outlined by the protocol by Lam et al. The ring constructs will be tensile tested and analyzed through histology to characterize their strength and cellularity.