Engineering Commons^™

Experimental Modal Analysis Of Distinguishing Microstructural Variations In Carbon Steel Sa516 By Applied Heat Treatments, Natural Frequencies, And Damping Coefficients, Mohammadreza Ahmadpar, Siamak Hoseinzadeh, Fardis Nakhaei, Saim Memon

Mining Engineering Faculty Research & Creative Works

The life assessment of materials that structurally shifts, creating mechanical corrosion and damage, during the operation at high temperatures is one of the most critical areas in the gas turbine power plants. This study investigates the widely used carbon steel grade 55 SA516 in the gas turbine blades at metallographic microscopic level and relating it to natural frequency and damping coefficients. In which heat treatments (aging tests) were applied and compared between multiple samples. The results show pearlite is broken up and converted into the ferrite and spherical carbides at grain boundaries. With an increase in microstructural variations in samples …

Evaluating Deep-Learning Models For Debris-Covered Glacier Mapping, Zhiyuan Xie, Vijayan K. Asari, Umesh K. Haritashya

Electrical and Computer Engineering Faculty Publications

In recent decades, mountain glaciers have experienced the impact of climate change in the form of accelerated glacier retreat and other glacier-related hazards such as mass wasting and glacier lake outburst floods. Since there are wide-ranging societal consequences of glacier retreat and hazards, monitoring these glaciers as accurately and repeatedly as possible is important. However, the accurate glacier boundary, especially the debriscovered glacier (DCG) boundary, which is one of the primary inputs in many glacier analyses, remains a challenge even after many years of research using conventional remote sensing methods or machine-learning methods. The GlacierNet, a deep-learning-based approach, utilized the …

Sigesn Light-Emitting Devices: From Optical To Electrical Injection, Yiyin Zhou

Graduate Theses and Dissertations

Si photonics is a fast-developing technology that impacts many applications such as data centers, 5G, Lidar, and biological/chemical sensing. One of the merits of Si photonics is to integrate electronic and photonic components on a single chip to form a complex functional system that features compact, low-cost, high-performance, and reliability. Among all building blocks, the monolithic integration of lasers on Si encountered substantial challenges. Si and Ge, conventional epitaxial material on Si, are incompetent for light emission due to the indirect bandgap. The current solution compromises the hybrid integration of III-V lasers, which requires growing on separate smaller size substrates …

Interplay Between The Lattice And Spin Degrees Of Freedom In Magnetoelectric And Magnetic Materials, Temuujin Bayaraa

Graduate Theses and Dissertations

This dissertation contains several investigations on the cross-coupling between structural and spin degrees of freedom in multiferroic and ferrimagnetic compounds by means of first-principles calculations and ab-initio-based Monte-Carlo simulations. We start with the reviews of magnetoelectricity, ferrimagnetism, strain engineering, followed by a brief introduction to first-principles computational methods, magnetic effective Hamiltonians, and other techniques that are utilized here. The results section of the dissertation can be divided into two parts. The first half focuses on magnetoelectric effects arising from different sources, while the second half is about the ferrimagnetic nature of materials. In the first part, we examine the epitaxial …

Study Of Thick Indium Gallium Nitride Graded Structures For Future Solar Cell Applications, Manal Abdullah Aldawsari

Graduate Theses and Dissertations

Indium gallium nitride (InxGa1-xN) materials have held great potential for the optoelectronic industry due to their electrical and optical properties. The tunable band gap that can span the solar spectrum was one of the most significant features that attracted researchers’ attention. The band gap can be varied continuously from 0.77 eV for InN to 3.42 eV for GaN, covering the solar spectrum from near infrared to near ultraviolet. Additionally, it has a high absorption coefficient on the order of ∼105 cm−1, a direct band gap, high radiation resistance, thermal stability, and so on. Nevertheless, the epitaxial growth of high quality …

Multi-Scale Hydrologic Evaluation Of The National Water Model Streamflow Data Assimilation, Bong Chul Seo, Witold F. Krajewski, Felipe Quintero

Civil, Architectural and Environmental Engineering Faculty Research & Creative Works

Streamflow predictions derived from a hydrologic model are subjected to many sources of errors, including uncertainties in meteorological inputs, representation of physical processes, and model parameters. To reduce the effects of these uncertainties and thus improve the accuracy of model prediction, the United States (U.S.) National Water Model (NWM) incorporates streamflow observations in the modeling framework and updates model-simulated values using the observed ones. This updating procedure is called streamflow data assimilation (DA). This study evaluates the prediction performance of streamflow DA realized in the NWM. We implemented the model using WRF-Hydro® with the NWM modeling elements and assimilated 15-min …

A New Dead-Time Determination Method For Gamma-Ray Detectors Using Attenuation Law, T. Akyurek

Nuclear Engineering and Radiation Science Faculty Research & Creative Works

This study presents a new dead-time measurement method using the gamma attenuation law and generalized dead-time models for nuclear gamma-ray detectors. The dead-time of the NaI(Tl) detection system was obtained to validate the new dead-time determination method using very thin lead and polyethylene absorbers. Non-paralyzing dead-time was found to be 8.39 μs, and paralyzing dead-time was found to be 8.35 μs using lead absorber for NaI(Tl) scintillator detection system. These dead-time values are consistent with the previously reported dead-time values for scintillator detection systems. The gamma build-up factor's contribution to the dead-time was neglected because a very thin material was …

Development And Validation Of An Analytical Modeling Tool For Solar Borehole Heat Exchangers, Adam Ornelles

All Theses

Current numerical modeling solutions used for subsurface heat flow, such as the Berkeley TOUGH codes, are often difficult to use and time-consuming compared to analytical modeling methods. However, current analytical modeling methods for subsurface heat flow and groundwater cannot accurately model the subsurface in 3 dimensions, a feature paramount to the planning and installation of thermal borehole heat exchangers used in environmental remediation.

This research developed a novel 3-dimensional analytical modeling tool for solar-powered borehole heat exchangers. The analytical modeling tool can plan thermal remediation systems while being more straightforward to operate than current numerical modeling software. By creating a …

Rational Design Of Multifunctional Nanocatalysts For Environmental Remediation And Energy Conversion Technologies, Md Ariful Ahsan

Open Access Theses & Dissertations

The discovery of efficient and sustainable carbon-based nanotechnologies to solve both the scarcity of drinking water and global energy crisis has become a paramount task in the last decades. Owed to the fast population growth and industrialization of the modern society, access to potable water and clean energy technologies is becoming very hard around the globe. Water pollutants have become a serious threat to the environment and ecology because of their toxic nature. Parallelly, the current hydrocarbon-based fuel industries are generating high levels of contamination across the planet, making imperative the development of cleaner energy technologies. In this regard, the …

Goes-16 Level 2 Land Surface Temperature Product-Filling For Cloud Masked Data, Guadalupe Ortega

Open Access Theses & Dissertations

The GOES-16 satellite ground segment team develops different levels of environmental products and makes them readily available to the public. The level 2 Land Surface Temperature (LST) product aims to provide a remote measurement of the Earth’s surface temperature every hour. LST is of fundamental importance to many aspects of the geosciences, for example, to study the Urban Heat Islands (UHI) effect. The product however, does not provide values for pixels where the satellite imager’s view is obstructed by clouds, as determined by a cloud mask intermediate product. The objective of this thesis is to estimate LST in the cloud …

Supercritical Co2 Recompression Closed Brayton Cycle Analysis, Andres Eduardo Gutierrez Hernandez

Open Access Theses & Dissertations

On this research, the results of an analysis made of a Supercritical Carbon Dioxide (sCO2) Recuperated Closed Brayton Cycle (RCBC) done by performing theorical calculations and comparing it to the results obtained with the use of the software ASPEN Plus will be presented. To demonstrate and determine that this software is a useful tool for modeling the proposed type of cycle, a preliminary comparison was made to verify with previous studies found in literature. A comparison and analysis between the possible working fluids and thermal energy sources was also performed to emphasize the decision of using CO2 as the cycle …

Best Practices For Performance Measurement In Transportation Operations And Maintenance, Bryan Gibson, Rachel Catchings, Chris Van Dyke, Steve Waddle, Doug Kreis

Kentucky Transportation Center Research Report

Public agencies benefit from measuring their performance as it helps to focus employee and organizational activities. State departments of transportation have become more performance-oriented over the past two decades and routinely collect data on highway safety, infrastructure condition, system operations, project delivery, winter maintenance, transit, bicycle and pedestrian facilities, and customer service. While the Kentucky Transportation Cabinet (KYTC) use performance measures in a variety of areas, the agency wants to adopt new metrics related to mobility and the responsiveness of maintenance operations. This report documents performance measurement strategies used at state transportation agencies throughout the country and proposes new performance …

Genome Annotation Using Average Mutual Information, Garin P. Newcomb

Department of Electrical and Computer Engineering: Dissertations, Theses, and Student Research

Advancements in high-throughput DNA sequencing technologies and ambitious goals for their use are resulting in the generation of a deluge of unannotated sequenced genomes. This makes computational tools that can aid in annotation increasingly valuable.

Here, we provide a detailed exploration of the utility as well as the limitations of average mutual information (AMI) in several steps of genome annotation. For a genomic sequence, AMI is a measure of the information a base contains about the base separated by a fixed lag. A profile is constructed by calculating AMI at multiple lags. In addition to traditional AMI, we employ two …

Risk-Based Machine Learning Approaches For Probabilistic Transient Stability, Umair Shahzad

Department of Electrical and Computer Engineering: Dissertations, Theses, and Student Research

Power systems are getting more complex than ever and are consequently operating close to their limit of stability. Moreover, with the increasing demand of renewable wind generation, and the requirement to maintain a secure power system, the importance of transient stability cannot be overestimated. Considering its significance in power system security, it is important to propose a different approach for enhancing the transient stability, considering uncertainties. Current deterministic industry practices of transient stability assessment ignore the probabilistic nature of variables (fault type, fault location, fault clearing time, etc.). These approaches typically provide a conservative criterion and can result in expensive …

Detecting And Evaluating Cracks On Aging Concrete Members With Deep Convolutional Neural Networks, Brendan Barnes

Department of Civil and Environmental Engineering: Dissertations, Theses, and Student Research

Cracks in concrete structures are evaluated through a timely and subjective manual inspection. The location of cracks is often recorded in an inspection report where some cracks are measured. Although measurements or locations may not be necessary for all cracks observed in concrete members, if quantitative data can be gathered in an autonomous way, allowing measurement data to be used in tracking changes in spatial and temporal scales, this quantitative data can provide useful information not yet captured in the manual inspection process. This thesis aims to construct an image-based crack detection and evaluation pipeline that can assist health monitoring …

Comparative Analysis Of Kmer Counting And Estimation Tools, Ankitha Vejandla

School of Computing: Dissertations, Theses, and Student Research

The rapid development of next-generation sequencing (NGS) technologies for determining the sequence of DNA has revolutionized genome research in recent years. De novo assemblers are the most commonly used tools to perform genome assembly. Most of the assemblers use de Bruijn graphs that break the sequenced reads into smaller sequences (sub-strings), called kmers, where k denotes the length of the sub-strings. The kmer counting and analysis of kmer frequency distribution are important in genome assembly. The main goal of this research is to provide a detailed analysis of the performance of different kmer counting and estimation tools that are currently …

Augmented Communications : A Solution For Overcoming High Spatial Correlation Of The Massive-Miso Vlc Channel, Monette Khadr

Legacy Theses & Dissertations (2009 - 2024)

A key challenge for future wireless networks is to come upon a riveting compromise between spectral efficiency, complexity, and energy efficiency. The challenge is also intensified due to the pace at which the Internet-of-Things (IoT) technology is arriving, causing an upheaval to pre-existing network infrastructures in terms of elevating spectrum scarcity. To keep pace with the exploding data demand forecasts, a circumvention is required. One realization is by utilizing the high-band spectrum and the rich body of knowledge on multiple-input multiple-output (MIMO) technologies. One of the prominent high frequency technologies is visible light communications (VLC). VLC provide a large unregulated …

Reliability Characterization Of A Low-K Dielectric Using Its Magnetoresistance As A Diagnostic Tool, Philip Alister Williams

Legacy Theses & Dissertations (2009 - 2024)

The introduction of low dielectric constant materials within the integrated circuit (IC) chip technology industry was a concerted effort to decrease the resistance-capacitance (RC) time delay inherent within the dielectric materials used as insulators. This stems from a demand for greater device density per IC chip and decreased feature sizes but is fast becoming a reliability issue. Concomitant with the demand for decreased feature sizes, also in adherence with Moore’s Law (which states that the number of devices on a die doubles every two years), is a reduction in device speed and performance due to device intra-level interconnection signal delays. …

Airframe And Systems Design, Analysis, And Testing Of The Horizon Morphing-Wing Aircraft, Sabrina A. Snow

All Graduate Plan B and other Reports, Spring 1920 to Spring 2023

Morphing trailing edge technology can provide the ability to dynamically alter the twist distribution, and therefore lift distribution, of an aircraft during flight. There are certain optimal lift distributions which can be chosen to create proverse yawing effects and eliminate the need for vertical control surfaces. The purpose of this project is to support the design and testing of a morphing, crescent flying wing airframe which will be used to evaluate yaw control in an aircraft without vertical control surfaces. There are three main objectives of this project, which are to perform static and dynamic analysis on the crescent wing …

Toward Lignin Valorization: Development Of Rhodococcus Opacus Pd630 As A Chassis For Triacylglycerol (Tag) Production From Recalcitrant Aromatic Feedstocks, Rhiannon R. Carr

McKelvey School of Engineering Graduate Student Theses & Dissertations

The advent of the industrial era was precipitated by the discovery of fossil fuels, and ushered in unprecedented changes for humanity included but not limited to the development of rapid transit and communications, improvements to food distribution and preservation, the mass production of goods, and a radical rearrangement of communities from relatively small enclaves to metropolises. With all the benefits, however, come considerable costs, especially to the global environment. Greenhouse gas emissions, built up over centuries of unregulated combustion, have precipitated a rate of global temperature change unparalleled in the 4.5 billion-year history of this planet. In order to preserve …

Measuring Foundation Course Modulus Using Falling Weight Deflectometer, Light Weight Deflectometer, And Dynamic Cone Penetration, Bruce Barrett, Kellie Troxel, Brady Dresselhaus, David Hansen

Nebraska Department of Transportation: Research Reports

Phase I results showed that FWD, LWD, and DCP provided valid results and trended with each other at the stations all three tests were run. This gives confidence that any test method is reliable when used on an exposed bituminous foundation course.

The results of Phase I and Phase II indicate that using FWD testing after concrete is built does not provide an accurate modulus of the foundation course. As demonstrated through the statistical analysis, foundation course moduli cannot be reliably calculated by using FWD on top of doweled concrete pavements and back-calculated using Darwin software or ME Design. Additionally, …

Gasification Based Waste Tire Integrated Energy Conversion Systems, Karah Powell

Honors Theses

The objective of this study was to evaluate the operating parameters impacts on the performance of a gasification-based waste tire integrated energy conversion system. In this system, the waste tires are put into a downdraft gasifier that is providing fuel for a solid oxide fuel cell (SOFC). The system is evaluated by the syngas production, power generation, and overall efficiency under various operating conditions. A hybrid 1-D model was adopted to perform a parametric study of the tire gasification and calculations were done to estimate the integrated system power generation and overall efficiency using MATLAB. Three parameters were studied: the …

Second-Order Reliability Methods: A Review And Comparative Study, Zhangli Hu, Rami Mansour, Mårten Olsson, Xiaoping Du

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Second-order reliability methods are commonly used for the computation of reliability, defined as the probability of satisfying an intended function in the presence of uncertainties. These methods can achieve highly accurate reliability predictions owing to a second-order approximation of the limit-state function around the Most Probable Point of failure. Although numerous formulations have been developed, the lack of full-scale comparative studies has led to a dubiety regarding the selection of a suitable method for a specific reliability analysis problem. In this study, the performance of commonly used second-order reliability methods is assessed based on the problem scale, curvatures at the …

Formation Of B Horizons In Engineered Putting Green Soils, Glen R. Obear

Department of Agronomy and Horticulture: Dissertations, Theses, and Student Research

Engineered turfgrass putting green soils are designed to drain quickly, while maintaining adequate water- and nutrient-holding capacity to sustain plant growth. These soils are designed to meet specific performance characteristics when they are constructed, but the process of soil formation changes these characteristics over time. Chapter 1 of this dissertation is a literature review of soil formation in engineered putting green soils. Pedogenesis of putting greens is such that A horizons form as organic matter accumulates near the surface, and B horizons form as particles and solutes are translocated to textural or pH boundaries in soil profiles. In the engineered …

Electric Vehicle Battery Charging Infrastructure, Javan Paul Luce Tanner

Industrial Technology Master's Projects

The progression away from internal combustion engines has been slowly gaining momentum over the last ten years. This project investigated the pathway forward regarding the charging of electric vehicles. As governments have begun enacting legislative initiatives in support of a greener and more sustainable future, we are now witnessing more rapid progress toward widespread adoption of fully electric and hybrid vehicles. This study focused directly on battery electric vehicles (BEVs). Some automotive manufacturers (each with their own timeframe) have committed to producing only these BEVs, and eliminating traditional combustion engine vehicles. This investigation was designed to examine the current state …

Fabrication Of Alloy 625 Through Electron Beam Powder Bed Fusion Additive Manufacturing, Characterization And Mechanical Performance, Aldo Rubio Hidalgo

Open Access Theses & Dissertations

Electron Beam Powder Bed Fusion (EB-PBF) is an additive manufacturing process that allows for the fabrication of nearly fully dense Alloy 625 parts. In this study EB-PBF Alloy 625 samples were fabricated in an Arcam A2X, heat-treated, then machined and tensile tested. Preliminary process tests varying focus offset, and speed function were conducted to establish baseline process parameter conditions to fabricate Alloy 625 parts based on surface finish and structural defects. The microstructure observed in EB-PBF Alloy 625 parts along the build direction in the as-built state consists of irregularly sized columnar grains averaging 105 μm in width that have …

Radio Direction Finding Implementing Music Algorithm With Usrp Node Arrays, Kevin Valdez

Open Access Theses & Dissertations

Direction Finding techniques are widely used across the fields of radar, telecommunications, geolocation systems, sonar, among many others to estimate the reference position of the incoming signal source. For this, the implementation of antenna arrays is essential as it allows the use of more advanced techniques in signal processing called spatial spectrum estimation [1]. This method of estimation is performed based on the antenna or sensor array response to the signal spatial parameters in every direction and estimate the location of the incoming signals. Algorithms have been developed for the purpose of spatial spectrum analysis, the most popular are MUSIC …

Thermodynamic Modeling Of Aqueous Fe-Cu-As-Sb-Bi-H2so4 Solutions And Its Application For Redox Potential Determination In Copper Electrorefining From 25°C To 70°C, Yongteng Dong

Open Access Theses & Dissertations

Impurity elements in copper electrorefining (ER) electrolyte have been becoming a crucial issue on purity of copper cathode. The objective of this doctoral research is to develop a speciation model to understand impurity behavior in aqueous ER solutions.

A thermodynamic model of Fe(II)-Fe(III)-Cu(II)-H2SO4-H2O system is developed and shown to reliably simulate the species distribution in industrial copper electrorefining electrolyte from 25°C to 70°C. The previously developed model of Fe(II)-Fe(III)-H2SO4-H2O system under leaching conditions was first evaluated. It has proved that its applicability can be extended to much higher acid concentration (185 g/L) and high amount of copper (40-50 g/L). Cu(II) …

Microstructure And Hardness Comparison Of Inconel 625 Alloy Of Various Additive Manufacturing Processes Following Heat Treatments, Ariel Gamon

Open Access Theses & Dissertations

This research study presents experimental examples of as-built microstructures and associated microindentation hardnesses (HV) for a variety of metal additive manufacturing (AM) methods for Inconel 625 alloy. Cold spray (CS), laser powder bed fusion (L-PBF), wire arc additive manufacturing (WAAM), electron beam directed energy deposition (EB-DED), laser hot wire (LHW), binder jetting (BJT), and laser power directed energy deposition (LP-DED), laser wire directed energy deposition (LW-DED) and electron beam melting (EBM) were among the techniques employed. Microstructures varied from impact-bonded, flattened grains containing microdendrites and dislocations with a microindentation hardness of HV 590 for cold spray to large, equiaxed grains …

Environmental Justice Issues And Sea Level Rise In Frontline Communties Along The Gulf Coast, Karla Michel Lopez

Open Access Theses & Dissertations

Sea level rise poses a great threat to coastal areas and our way of life. As flooding increases in frequency and intensity across the country, vulnerable populations become a target to its impacts. The U.S. dedicates much research to risk communication and climate change adaptation strategies; however, these coastal areas are home to a large percentage of underserved and underrepresented communities that can be challenging to meaningfully engage. The impacts of short-term sea level rise combined with long-term sea level rise will not only cause flooding, erosion, and intrusion of saltwater into freshwater resources but also increased financial consequences, such …