Engineering Commons^™

Effects Of Additions On The Microstructure, Macrostructure, And Mechanical Properties Of Gray Iron, Evan J. Carter

College of Graduate Studies: Theses & Dissertations

The iron matrix is a major component of the gray iron (GI) microstructure, which is the transformation product of austenite during solidification. It is generally accepted that the structure of the austenite will impact the final grain structure and thus the properties of GI. Refinement of the austenite grain structure has the potential to increase the strength of GI. Knowledge of controlling austenite grain size with common alloy additions in GI is very limited and is investigated in this research. Utilizing the DAAS heat treatment process, the austenite grain boundaries can be retained and observed directly. The observations were correlated …

Cross-Layer Performance Evaluation Of C-V2x, Dhruba Sunuwar

College of Graduate Studies: Theses & Dissertations

The evolution of connected vehicles from a distant futuristic concept to an integral part of daily life is indisputable. Vehicle-to-everything communication (V2X) serves as the cornerstone of this transformation, facilitating seamless interaction among vehicles, infrastructure, pedestrians, and networks. However, evaluating V2X system performance proves intricate due to the dynamic nature of vehicles influenced by mobility factors. To address this complexity, we have developed a specialized system-level simulator expressly for evaluating V2X communication performance. Notably, the simulator encompasses (i) intelligent transportation system (ITS) scenarios integrated into a geographical framework and (ii) the capability to assess cross-layer performance spanning physical (PHY) and …

Numerical Analysis Of A Novel Elastohydrodynamic Seal For Supercritical Co2 Power Cycles With Experimental Verification, Ali Akbor Topu

College of Graduate Studies: Theses & Dissertations

Supercritical carbon dioxide (sCO₂) power cycles outperform conventional thermodynamic cycles regarding the efficiency and equipment footprint because of its unique property of maintaining the density of liquid in the gaseous phase at supercritical state (304.13 K and 7.37 MPa). It has robust use in concentrated solar power, fossil fuel power plants, geothermal electricity, nuclear power, and ship propulsion. To fully utilize sCO2 power cycles, technology readiness must be demonstrated at 10-60 MWe scale, with a working temperature and pressure of 350-700°C, and 10-35 MPa respectively. A crucial obstacle to the full realization of this technology is the absence …

Self-Supervised Contrastive Learning Using Eeg Signals For Mental Stress Assessment, Ugochukwu Uraechu

College of Graduate Studies: Theses & Dissertations

A study is presented to investigate self-supervised contrastive learning (SSCL) models using physiological data obtained from non-invasive wearable sensors for mental stress assessment. The present work involved acquisition of electroencephalography (EEG) signals using wearable sensors, signal preprocessing, data augmentation, and investigation of self-supervised contrastive learning (SSCL) algorithms for multi-class mental stress assessment. Seven volunteers participated in this study executing various mental tasks while wearing an OpenBCI head cap to acquire EEG signals. The acquired EEG signals were preprocessed and utilized for data augmentation in time and frequency domains with different SSCL models. Optimal data augmentation combinations and SSCL models were …

Mathematical Modeling Of Coupled Heat And Mass Transfer In Metal-Hydride Hydrogen Storage Systems, Muhammad Hasnain

College of Graduate Studies: Theses & Dissertations

As a promising clean energy carrier hydrogen has recently gained significant interest, but its efficient and safe storage is a major challenge. Compared to the gaseous state and liquid state, metal hydrides (MH) offer a potentially more effective storage approach for hydrogen. However, the main challenge in this approach is the low thermal conductivity of the MH bed that leads to low heat transfer and ultimately to higher charging and discharging times. The purpose of this work is to develop an in-house comprehensive heat and mass transfer model for hydrogen sorption in MH reactors to simulate the dynamic behavior of …

Machine Learning Based Three-Limb Core-Type Transformer Core Aspect Ratios Identification, Ananta Bijoy Bhadra

College of Graduate Studies: Theses & Dissertations

Power transformers are considered one of the key elements of electric grids. Transient studies include transformer transient analysis which is required for the continuous power supply. However, to perform the transient analysis, the details of the internal structure of the transformer are required which are unobtainable and considered as confidential information. Therefore, the application of topological-based transformer models is limited although the models can accurately represent the transformers. To address this concern, a novel approach utilizing Machine Learning (ML) to identify the core aspect ratios of the three-limb core-type transformer is introduced. The proposed approach, using only the voltage and …

Investigations Of Performance And Emissions Of A Fischer-Tropsch Gtl Sustainable Aerospace Fuel With Lubricity Improver In A Compression Ignition Engine With Butanol Port Fuel Injection, James B. Willis

College of Graduate Studies: Theses & Dissertations

As there is increasing concern over emissions of traditional fossil fuels, as well as the future of continued reliance on this dwindling resource, it is becoming increasingly evident that alternative fuels are a necessity. This research investigates the use of a Fischer-Tropsch fuel from natural gas feedstocks, S8, in an internal combustion research engine with a common rail fuel injection system. This synthetic kerosene fuel has a high DCN of 62, indicating high affinity to autoignition compared to conventional pump diesel (ULSD) at 48 DCN. However, due to the process by which it is produced, this fuel lacks the necessary …

Investigation Of Mechanically Fatigue Low-Frequency Energy Harvesting Effects On Isotropic Materials, Daniel J. Meade

College of Graduate Studies: Theses & Dissertations

This research project reports an exploratory investigation of energy harvesting effect on isotropic material that goes through low frequency mechanical fatigue. Energy harvesting is a growing field of study that can recycle ambient energy back into a system that would otherwise be lost. This is a significantly useful method for the ongoing energy crisis and provides an alternate route to design and upgrade systems to be more efficient and last longer than current system designs. However, it is time to investigate if there is any effect vibration-based energy harvesting has on the structure from which energy is being harvested. To …

Computational Analysis Of A Naca 0012 Straight Wing At Various Reynolds Numbers Approaching Stall, John E. Crowe Iii

College of Graduate Studies: Theses & Dissertations

As the capabilities and power of computational resources improve with each passing year, the implementation of simulation in the field of aerospace engineering also increases due to its increased efficiency, as it allows for reducing both time and resources. In this study, a computational method is created and tested for determining and visualizing the effect of increasing flow velocity on a NACA 0012 3D wing as it approaches and reaches stall. For this study, the flow over a NACA 0012 3D wing is simulated using a Reynolds-averaged Navier Stokes simulation at angles of attack of 6, 8, 10, 12, and …

Resonant Ultrasound Spectroscopy(Rus) For Material Characterization Of Metal Am Parts, Malik Marks

College of Graduate Studies: Theses & Dissertations

Additive manufacturing (AM) has revolutionized the manufacturing industry by offering flexibility, customization, and rapid prototyping capabilities. However, ensuring the quality and reliability of AM parts remains a significant challenge due to variations in material properties and process parameters. The NDE method used in this study is Resonant Ultrasound Spectroscopy (RUS). This method was used to evaluate and understand its ability to detect internal voids and defects. Dog-bone samples were made using the 316L stainless steel alloy which were fabricated by powder bed fusion (PBF) AM technique at different processing conditions and post processing conditions. These samples were tested to find …

Closing Dichloramine Decomposition Nitrogen And Oxygen Mass Balances: Relative Importance Of End-Products From The Reactive Nitrogen Species Pathway, Huong T. Pham, David G. Wahman, Julian L. Fairey

Civil Engineering Faculty Publications and Presentations

In drinking water chloramination, monochloramine autodecomposition occurs in the presence of excess free ammonia through dichloramine, the decay of which was implicated in N-nitrosodimethylamine (NDMA) formation by (i) dichloramine hydrolysis to nitroxyl which reacts with itself to nitrous oxide (N₂O), (ii) nitroxyl reaction with dissolved oxygen (DO) to peroxynitrite or mono/dichloramine to nitrogen gas (N₂), and (iii) peroxynitrite reaction with total dimethylamine (TOTDMA) to NDMA or decomposition to nitrite/nitrate. Here, the yields of nitrogen and oxygen-containing end-products were quantified at pH 9 from NHCl₂ decomposition at 200, 400, or 800 μeq Cl₂·L …

The Surrogate Fold Catalog: A Design Tool For Origami-Inspired Mechanical Systems, Larry L. Howell, Ivy Running, Phebe Ramsdell, Carolina Wright, Spencer P. Magleby

Faculty Publications

Origami has inspired work in many fields of science and engineering. However, it can be difficult to transfer the motion of an origami design from folded paper to thicker, stiffer materials. When using engineering materials, creases from an origami fold pattern are usually replaced with “surrogate folds”. While many different surrogate folds have been developed, it is challenging for a designer to quickly survey and compare potential surrogate folds. Surrogate folds can improve many origami-inspired designs and applications by changing how the designs are manufactured and how they behave. This work categorizes compliant mechanisms that may be effective as surrogate …

Characterization Of Magnetically Stabilized Hinges For Origami-Inspired Mechanisms, Larry L. Howell, H T. Pruett, Philip Klocke, Spencer Magleby

Faculty Publications

Origami-inspired mechanisms provide opportunities for deployable systems, including reflectarray antennas. There is a need for approaches to deploy and stabilize such arrays. Magnetic mechanisms show promise for meeting those needs and methods for modeling their behavior would facilitate their design and analysis. We demonstrate the existence of bistability in select configurations of magnetically stabilized hinges and characterize their equilibrium positions as a function of parameters estimated from simulation data for these mechanisms. Other relevant information such as potential energy, axial force data, angular position of unstable equilibria, and transition values from bistability to monostability are also modeled. The results are …

Draft Makerspace Optimization And Procedure For The University Of Northern Iowa And Cedar Falls, Andrew Nii Anang

Graduate Research Papers

The University of Northern Iowa (UNI) Makcrspace is a dynamic, communal setting created to encourage members of the community at large to be creative, innovative and engage in hands-on learning. Access to a variety of hand and power tools as well as state-of-the-art technologies is available at this cutting-edge facility. The Makerspace promotes a culture of experimentation and entrepreneurship while offering assistance for multidisciplinary initiatives. The Makerspace incorporates real-world, project-based learning experience, greatly improving UNI's educational environment. It enhances the university's reputation for encouraging innovation and research by drawing in potential students and community members who are interested in cutting-edge …

Experimental Investigation And Performance Analysis Of The Transformational Challenge Reactor (Tcr) System Under Various Temperature And Pressure Conditions, Ahmed Mohamed Ali Soliman

Dissertations and Theses

The Transformational Challenge Reactor (TCR) represents a significant advancement in nuclear reactor technology, taking into consideration modularity, efficiency, and safety. This study explores the coupling between thermal behavior and the coolant gas flow behavior of the TCR’s 3D-printed ceramic core under various operating conditions. Using nitrogen as a coolant, experiments were performed at pressures ranging from 20.4 bar to 40.8 bar (300 to 600 psi) and temperatures from 100°C to 300°C. The main parameters including gas inlet and outlet temperatures, the TCR wall temperature at the inlet and outlet, and flow rates, were analyzed to evaluate heat transfer efficiency and …

An Optical Aptamer-Based Carbon Nanosensor For Cortisol Detection, Jessica Kretli Zanetti

Dissertations and Theses

Cortisol is a hormone related to numerous biological functions. This hormone is primarily associated with regulating the body’s stress response, including its effects on metabolism, immune function, and energy balance. Additionally, it plays a critical role in maintaining physiological homeostasis during periods of physical or psychological stress. Consequently, it is critical to monitor levels of this hormone to understand different vital processes it can impact. This work presents the development of an optical aptamer-based carbon nanosensor for the detection of cortisol. The sensor utilizes single-walled carbon nanotubes (SWCNTs) functionalized with a specific DNA aptamer to achieve high specificity and sensitivity. …

Change Of Metal Oxidation State At High Temperature, Impact Of Temperature And Reactive Gases, Yegor Nikitin

Dissertations and Theses

The fundamental understanding of gas-solid reactions enables a wide range of applications to be developed and improved. Specifically, the use of metal-based materials is critical to ensuring robust, safe, and long-term operations. For example, in power systems where boilers are used to generate steam for heat or electricity generation the use of stainless metal alloys is critical to allow high quality steam to be produced in a very harsh environment. Alternatively, in catalysis, the use of metal doped heterogeneous catalysts are essential in achieving selectivity and conversion performance for chemical synthesis to emissions abatement. Typically, these metal alloys must withstand …

Blockchain Based Framework For Secure And Decentralized Energy Trading - Transforming Local Energy Markets For Sustainable Communities, Saurabh Sachdeva

Dissertations and Theses

The emergence of prosumers provides an opportunity for the setup of a local energy market (LEM) where individual households with distributed energy resources (DERs) can produce, store, and trade energy. Peer-to-peer(P2P) and decentralized energy trading (ET) can be implemented between the participants within or across microgrids. Several solutions based on the existing technologies have been proposed worldwide for the integration of prosumers in the existing energy setup and to enable and support ET, but these solutions present the issues of centralization, data integrity, and confidentiality, user and anonymity, and transparency. The applications of blockchain technology have recently become fascinating for …

Using Mechanical Interventions To Enhance Drug Transport To Bone Tumors, Michelle Gelbs

Dissertations and Theses

Bone metastasis occurs when cancer cells spread from a primary site to a secondary location in bone. Current treatments for metastatic bone tumors typically involve systemic chemotherapy, bisphosphonates, radiotherapy, or surgery; however, due to morphological changes in the tumor microenvironment and elevated interstitial fluid pressure, tissue penetration of therapeutic agents is often more limited in cancerous tumors compared to normal tissue. Weight-bearing mechanical loading applied to bone, as well as other mechanical stimulations such as vibration, have been shown to cause loading-induced bone deformations that increase convective transport via interstitial fluid flow. We hypothesize that mechanical loading can increase the …

Optimizing Transcranial Focused Ultrasound: Calibration, Neuro Navigation, And Bold Fmri Evidence Of Neuromodulation, Amilcar J. Malave

Dissertations and Theses

This thesis presents the development, calibration, and initial implementation of transcranial focused ultrasound (tFUS) for neuromodulation in a human study. The primary objectives were to design a system capable of delivering precise and safe ultrasound stimulation to targeted brain regions and to conduct preliminary trials to assess its effects on brain activity. A custom calibration device was developed to ensure accurate measurement of acoustic pressure, addressing challenges such as voltage alterations caused by changes in system impedance. Additionally, a neuro-navigation tool was created to facilitate precise targeting of the right subgenual anterior cingulate cortex (right sgACC), enabling accurate placement of …

Nanoparticle Stabilized Interfaces And Their Effect On Foam Stability, Nicole T. Donovan

Dissertations and Theses

No abstract provided.

On The Understanding Of The Coastal-Urban Nexus Of Weather, Air Quality And Energy, Harold Gamarro

Dissertations and Theses

Urban environments exhibit complex interactions between atmospheric processes, building energy consumption, and air quality, particularly during periods of seasonal extremes such as summer ozone peaks and winter heating. Accurate representation of these interactions in urban modeling is crucial for understanding and addressing air pollution and energy management challenges in cities. This research presents a comprehensive study that advances urban atmosphere simulations by integrating building energy dynamics, air quality, and robust multi-source observational evaluation. Leveraging the Weather Research and Forecasting (WRF) model, coupled with a multilayer building environment parameterization (BEP) and a building energy model (BEM), with an improved boundary layer …

Analysis Of Energy Savings And Feasibility Of Retrofitting New York City Midrise Multifamily Buildings With Air Source Heat Pump Technology, Samuel Chussid

Dissertations and Theses

Motivated by reducing impacts of climate change due to greenhouse gas emissions, many dense urban cites throughout the United States have set into law ambitions decarbonization policies that will require buildings to replace fossil fuel space and water heating systems with electric powered alternatives. In many cities, especially in the northeast, fossil fuel space and water heating systems are used in a vast majority of buildings and significantly contribute to citywide carbon emissions. In New York City (NYC), it is estimated that over 40 percent of citywide emissions come from space heating and water heating systems that run on fossil …

Implementation Of Acid/Gas Digestion Approach To Maximize Volatile Fatty Acids Production From Municipal Sludge And A Techno-Economic Feasibility Study, Aykut Sayin

Dissertations and Theses

Acid digestion, which is the first step of two-phase acid/gas anaerobic digestion process, was studied to identify the optimum operating conditions that would maximize the production of volatile fatty acids (VFAs). Batch and semi-continuous acid digesters were operated using combined primary sludge and waste-activated sludge as the feedstock from New York City (NYC)’s Wards Island water resource recovery facility (WRRF). Operating conditions tested in batch acid digesters for maximizing VFAs production included temperature (35-70°C), inoculum-to-substrate ratio (0.0-0.5 mgVS/mgVS), thickening (3-13%TS), and contact time (0-10 days), while simultaneously inhibition mechanisms on VFAs production were investigated. Once the optimum operating conditions for …

Modulation Of Motor Learning With High-Intensity Transcranial Electric Stimulation, Gavin Hsu

Dissertations and Theses

Research thus far on noninvasive, transcranial electric stimulation have produced mixed results from in vivo human experiments. This work tests the hypothesis that applying higher stimulation intensities would induce intracranial electric fields that more closely match the higher magnitudes used in animal and in vitro studies and subsequently yield more robust effects. As done commonly in the literature, we targeted the motor cortex (M1), specifically in the context of neuroplastic changes taking place during motor learning in healthy adult humans. This work also seeks a better understanding of the neural correlates underlying motor skill learning.

Through multiple large-sample studies, this …

The Racial Disparities Of The Gamma-Secretase/Notch Pathway And Inhibition In Triple Negative Breast Cancer, Jobin Joseph

Dissertations and Theses

Triple Negative Breast Cancer (TNBC) continues to be a formidable challenge in oncology, characterized by its aggressive phenotype and limited treatment options. Alarming racial disparities in TNBC outcomes persist, with underrepresented populations experiencing disproportionately higher rates of mortality and poorer prognoses. This master's thesis aims to delve into the molecular intricacies that contribute to these disparities, with a specific focus on gamma secretase activity, a key regulator of cellular processes.

The research methodology encompasses a multi-faceted approach, amalgamating clinical data analysis with extensive in vitro and in vivo experimentation. The study employs cutting-edge molecular profiling techniques and gene expression analysis …

Ring Resonators Intergrating With Dichoric Materials And In Spin-Valley Controlled Photonic Topological System, Yuma Kawaguchi

Dissertations and Theses

Photonic technology plays an important role in the development of diverse applications, ranging from optical telecommunications to sensing and imaging. The utilization of photonic circuits emerges as a promising platform for the establishment of advanced communication systems characterized by high speed and large capacity. This advancement is crucial to facilitate fast and efficient data transfer while concurrently managing multiple devices. It is imperative that essential components such as lasers, modulators, and isolators exhibit compactness without incurring significant losses.

Non-reciprocal devices represent a valuable addition to photonic circuits, enabling the creation of unidirectional waveguides that function as optical isolators, preventing signals …

Alkaline Potassium Polyacrylate Electrolytes For Rechargeable Zinc-Manganese Dioxide Batteries, Jungsang Cho

Dissertations and Theses

Zinc (Zn)–manganese dioxide (MnO₂) rechargeable batteries have high specific theoretical capacity as well as being environmentally friendly, intrinsically safe and low-cost. Liquid electrolytes, such as potassium hydroxide (KOH), are historically used in these batteries; however, many failure mechanisms of the Zn–MnO₂ battery chemistry result from the use of liquid electrolytes, including the formation of electrochemically inactive compounds and shape change of Zn electrodes during charge and discharge cycling. This led to incorporation of an alkaline polymer electrolyte as an alternative to the liquid KOH electrolyte in Zn-MnO₂ rechargeable batteries, with the aim of making them non-spillable …

Surface Activity At The Air-Water Interface And Self-Stratification Of Silica Nanoparticles Functionalized With Tri-Methoxy Poly(Ethylene Glycol) Silane, Hyeongoo Jung

Dissertations and Theses

Aggregated silica nanoparticles (SNPs) have been functionalized with tri-methoxy poly(ethylene glycol) silane (mPEG silane), end-capped with a methyl group. This functionalization imparts surface activity at the air-water interface due to the hydrophobic nature of the end-capped methyl group. To determine the surface coverage of silane on the particle surface, solution-state ¹H-NMR spectroscopy was utilized for characterization, and surface tension measurements were conducted to assess their tension-lowering ability. Solutions containing 10 wt% of the functionalized SNPs reduced the quasi-static surface tension to approximately 53 mN/m, regardless of the amount of reacted mPEG silane. However, the quantification of mPEG silane influenced …

Hydrodynamics Of Drops And Particles Driven By Marangoni And Diffusiophoretic Forces, Subramaniam Chembai Ganesh

Dissertations and Theses

This study investigates the hydrodynamics of particles and drops driven by forces generated by an asymmetrical physical and chemical surrounding environment. In the first part, a novel colloidal motor design driven by surface tension forces is proposed, utilizing an active Janus particle encapsulated in an immiscible liquid drop to form a compound drop/particle. Marangoni forces induced by asymmetric solute adsorption at the liquid-liquid interface of the drop propels the compound system. The propulsion speeds of the motor are analyzed for various relative sizes and configurations of the Janus particle and the encapsulating drop and the effects of varying the transport …