Engineering Commons^™

Effect Of Sample Properties On Short-Circuited Waveguide Measurements For Materials Characterization, Alexander Hook, Jared Sinkey, Kristen M. Donnell

Electrical and Computer Engineering Faculty Research & Creative Works

Microwave materials characterization measurements can be performed using a number of well-established approaches. One such approach, the filled transmission line approach featuring a short-circuited rectangular waveguide (SC-RWG) sample holder, is known to have sample placement restrictions related to measurement viability. This work focuses on this approach and addresses the measurement restrictions within the context of sample length and dielectric properties. The complex reflection properties, S11, of a sample placed in a SC-RWG sample holder are studied to quantitively define when a sample must be offset from the SC-end. The impact of the sample holder is also studied from a measurement …

Decentralized Linear Solvers: Communication Cost And Privacy, Nelson G. Brasil, Vinay A. Vaishampayan

Publications and Research

We consider the problem of multiple parties iteratively solving a system of linear equations in a decentralized manner. Specifically, we solve for $\negr{x} \in \R^n$, the $n \times n$ system of linear equations $M\negr{x} = \negr{b}$ when each party only knows their row of the matrix $M$ and a single component of $\negr{b} \in \R^n$. Our objective is to determine the tradeoff between the accuracy of the solution and the total communication cost measured in bits. A fully connected, reliable mesh network is assumed to connect the different parties. We develop a general formulation that applies to a large class …

Voltage Stability Enhancement Of Large Load Interconnections Using Syncronous Condensers, Muhammad Ibrahim Abbas

Graduate Studies Theses and Dissertations 2026

The rapid integration of hyperscale data centers as large, concentrated loads presents a growing voltage stability challenge in grids weakened by synchronous generator retirement and increasing inverter-based resource penetration. This work proposes a Jacobian-based sensitivity framework for systematically identifying voltage-critical buses and optimally siting synchronous condensers as voltage support resources. A voltage-weighted sensitivity index, extracted from the full Jacobian inverse, is introduced to combine network-wide reactive coupling strength with observed voltage drops into a single deployable placement criterion. Validation on IEEE 14-bus and 30-bus test systems under multiple loading scenarios demonstrates that the proposed criterion consistently identifies the correct placement …

Detection And Discrimination Of Targets In Infrared Imagery, Adam T. Cuellar

Graduate Studies Theses and Dissertations 2026

Automated infrared (IR) imagery analysis is essential for persistent surveillance, defense, and security, yet it remains difficult when sensors move and when unknown objects appear. This dissertation addresses two fundamental problems: (1) detecting small moving targets amid platform-motion induced parallax and (2) distinguishing between known stationary targets and out-of-distribution (OOD) objects.   For detecting moving targets while the platform itself is in motion, auxiliary Global Positioning System and Inertial Navigation System data are combined with image analysis. Direction Cosine Matrices from calibrated inertial measurements enable sub-pixel frame alignment unattainable with purely image-based registration. The stabilized sequence is processed by a Reed–Xiaoli …

Predicting Safety And Mobility Parameters Based On Comprehensive Analytics Of Connected Vehicle Data, Lei Han

Graduate Studies Theses and Dissertations 2026

Traffic safety and mobility remain critical challenges for modern transportation systems. The emergence of connected vehicle (CV) data offers unprecedented opportunities to capture microscopic, non-aggregated driving dynamics to support precise and finer-grained traffic safety and mobility research. This dissertation develops a comprehensive CV data–driven analytical framework to advance traffic safety and mobility research across multiple roadway contexts, including intersections, segments, freeways, and urban arterial networks. For traffic safety, this research extracts both longitudinal and lateral risky driving behaviors from CV trajectories and integrates them with macro-level roadway, traffic, and visual environment features. A spatial machine learning framework is proposed for …

Evaluation Of Chromium-Crosslinked Amps-Hpam Copolymer Gels: Effects Of Key Parameters On Gelation Time And Strength, Maryam Sharifi Paroushi, Baojun Bai, Thomas P. Schuman, Yin Zhang, Mingzhen Wei

Geosciences and Geological and Petroleum Engineering Faculty Research & Creative Works

Controlling CO₂ channeling in heterogeneous reservoirs remains a major challenge for both enhanced oil recovery (EOR) and secure geological storage. AMPS-HPAM copolymers exhibit high-temperature resistance and brine tolerance compared with conventional HPAM gels, making them well suited for the harsh environments associated with CO₂ injection. Chromium-based crosslinkers (CrAc and CrCl₃) were investigated because sulfonic acid groups in AMPS can coordinate with trivalent chromium ions, enabling dual ionic crosslinking and the formation of a robust gel network. While organic crosslinked AMPS-HPAM gels have been widely studied, the behavior of chromium-crosslinked AMPS-containing systems, particularly their gelation kinetics under …

Effect Of Ionic Strength On Gelation Time And Strength Of Amps-Based Polymer Gels, Maryam Sharifi Paroushi, Xuyang Tian, Baojun Bai, Thomas P. Schuman, Yin Zhang, Mingzhen Wei

Geosciences and Geological and Petroleum Engineering Faculty Research & Creative Works

Polymer gel treatment has been widely applied for improving sweep efficiency and controlling excessive water and gas production. Their performance depends on gelation time and final gel strength. In most studies, brine salinity is used to describe the effect of formation water on gel behavior. However, changing salinity also changes ionic strength and ion composition at the same time. Because of this coupling, it is difficult to identify the mechanisms controlling gelation, which has led to inconsistent trends in the literature. Increasing salinity has been reported to either slow or accelerate gelation and to weaken or strengthen gels depending on …

Solubility And Dissolution Mechanism Of Novel Multi-Ester Headgroup Surfactants In Supercritical Co2, Ning Xu, Yan Ling Wang, Baojun Bai, Shi Zhang Cui, Yu Zhang, Wen Jing Shi, Zhao Nian Zhang, Wen Hui Ding, Pei Xu Ma, Zan Gao

Geosciences and Geological and Petroleum Engineering Faculty Research & Creative Works

To address the limited solubility and applicability of conventional hydrocarbon surfactants in supercritical CO₂, a series of multi-ester headgroup surfactants were designed and synthesized by leveraging the CO₂-philic properties of ester groups. The molecular structures were characterized using Fourier transform infrared (FT-IR) spectroscopy and ¹H NMR. A custom-designed laser-based apparatus was developed to quantify surfactant solubility and systematically investigate phase behavior in CO2. Molecular dynamics (MD) simulations were employed to elucidate structure–solubility relationships across multiple scales, including solubility parameters, interaction energies, radial distribution functions (RDFs), and free volume fractions. Results indicate that, at 323.15 K, …

Renewable And Affordable Energy For Apartments. Inquiry Into Renewable And Affordable Energy For Apartments, Nishadi Ruwandima Weerasinghe Mudiyanselage, Asma Aziz

Research outputs 2022 to 2026

Recent literature identifies a persistent disparity between detached housing and apartments in accessing renewable and affordable electricity. While rooftop solar PV deployment in Australia  has expanded rapidly since 2017, access to these technologies in multi-unit dwellings (MUDs) remains limited, resulting in higher electricity costs for apartment residents compared with standalone houses. This inequity is increasingly significant given rising electricity prices and the growing share of Australians living in apartments.

Effect Of Molybdenum Content On The Microstructure And Tribological Properties Of Ti-Nb-Cu Alloys Produced By Lpbf Additive Manufacturing, Lei Qin, Shengfeng Zhou, Jianbo Jin, Huan Yang, Kunmao Li, Cheng Deng, Yujie Yuan, Seyed Reza Elmi Hosseini, Laichang Zhang

Research outputs 2022 to 2026

Obtaining excellent wear resistance is critical for titanium alloys used as orthopedic implants. In this study, the β-type Ti-35Nb-5Cu- x Mo alloys (Ti355 x , x = 0, 1, 2, and 4 wt%) were fabricated by the laser powder bed fusion (LPBF) method. In the meantime, the influence mechanism of Mo content on the microstructure and tribological properties was systematically investigated. The results show that all the LPBF-produced Ti355 x alloys exhibit a bimodal columnar-equiaxed grain structure, with Mo refining columnar grains and suppressing the α″ phase formation. Moreover, increasing the Mo content reduced the relative density, while enhancing the …

Optimizing The Size And Siting Of Distributed Generation In Unbalanced Distribution Systems With Multi-Objective Reptile Search Algorithm, Pema Dorji, Chimi Pelden Dorji, Stefan Lachowicz, Octavian Bass

Research outputs 2022 to 2026

This paper presents the Multi-Objective Reptile Search algorithm for identifying ideal rating and location of distributed generation in unbalanced grids, focusing on minimizing power losses, total costs, and carbon emissions. The proposed methodology integrates DIgSILENT PowerFactory and Python platforms to evaluate unbalanced IEEE distribution feeders under varying power factor conditions. The results demonstrate that optimal DG configurations involve strategically positioning multiple units to enable both active and reactive power injection, significantly improving overall system performance across multiple objectives and voltage deviation index. The analysis identifies an optimal PF range between 0.75 and 0.89, with unity power factor operations yielding suboptimal …

Numerically Evaluating The Effect Of Extrusion Angle On Material Flow And Thermal Behaviour During Additive Friction Extrusion Deposition (Afed), Numan Habib, Ferdinando Guzzomi, Ana Vafadar

Research outputs 2022 to 2026

Additive Friction Extrusion Deposition (AFED), also known as “SoftTouch”, is an emerging friction-based Additive Manufacturing (AM) technology allowing material to soften before the deposition, increasing the printing speed and reducing cost [1]. However, high power is required during the process, as excessive force is needed to extrude enough material through the printing head. This study investigates how extrusion angle and tool rotational speed affect thermal distribution and material flow in AFED to minimise power consumption. A three-dimensional computational fluid dynamics (CFD) model is proposed, and ANSYS ^® Workbench CFD code (Fluent) is used to discretise the CFD model. A User-Defined …

A Critical Perspective On The Society Of Environmental Toxicology And Chemistry's Adherence To Founding Principles— Opportunities For The Future, Barnett A. Rattner, Annegaaike Leopold, Carys L. Mitchelmore, Glenn W. Suter, Mark S. Johnson, Adriana C. Bejarano, Lawrence A. Kapustka, Niranjana Krishnan, Derek C. G. Muir, Beatrice O. Opeolu, Martha Georgina Orozco-Medina, April Reed, Bruce W. Vigon, Adam R. Wronski

Epidemiology, Biostatistics, & Environmental Health Faculty Publications

The Society of Environmental Toxicology and Chemistry (SETAC) is a global organization whose mission is the advancement of environmental science and management through collaboration, leadership, communication and education. On SETAC's 45th anniversary, the following question was raised: Are the 1979 founding principles of SETAC, multidisciplinary approaches to solving environmental problems, multisector engagement and scientific objectivity, still useful, adequate and effective in fulfilling its mission? In a special session held at the 45th Annual Meeting in Fort Worth, Texas, United States, a critical evaluation of the founding principles was initiated by reviewing SETAC's history and ongoing activities, and recommendations were made …

Explaining The Unseen: Multimodal Vision-Language Reasoning For Situational Awareness In Underground Mining Disasters, Mizanur Rahman Jewel, Mohamed Elmahallawy, Sanjay Kumar Madria, Samuel Frimpong

Computer Science Faculty Research & Creative Works

Underground mining disasters produce pervasive darkness, dust, and collapses that obscure vision and make situational awareness difficult for humans and conventional systems. To address this, we propose MDSE, Multimodal Disaster Situation Explainer, a novel vision-language framework that automatically generates detailed textual explanations of post-disaster underground scenes. MDSE has three-fold innovations: (i) Context-Aware Cross-Attention for robust alignment of visual and textual features even under severe degradation; (ii) Segmentation-aware dual pathway visual encoding that fuses global and region-specific embeddings; and (iii) Resource-Efficient Transformer-Based Language Model for expressive caption generation with minimal compute cost. To support this task, we present the Underground Mine …

Long Short-Term Memory (Lstm) -Based Neural Network Model For Optimizing Composite Manufacturing Process Using Autoclave, Sourav Bolar, Steven Corns, Nayan Pundhir, Kumbla Chandrashekhara

Engineering Management and Systems Engineering Faculty Research & Creative Works

Producing high-quality fiber-reinforced composites requires precise temperature control during autoclave curing, as even small variations can lead to defects that compromise strength and reliability. At the same time, manufacturers aim to reduce energy use and shorten curing cycles without sacrificing material performance. To address these challenges, this study develops a data-driven Long Short-Term Memory (LSTM) neural network model capable of forecasting temperature evolution inside the autoclave throughout the curing cycle. The model is trained on time-series temperature data collected from multiple sensing locations, enabling it to learn the spatial and temporal trends that govern heat flow during curing. Data augmentation …

Work-In-Progress: Evaluating Feasibility Of Band Matrix Solvers For Scaling Up Extreme Learning Machine Method, Anton Akusok, Kaj Mikael Björk, Amaury Lendasse, Leonardo Espinosa Leal

Engineering Management and Systems Engineering Faculty Research & Creative Works

This work presents the results of the potential of band linear system solvers for improving the scalability of the Extreme Learning Machine (ELM) method at large model sizes. The model is tested on the standard MNIST dataset with a range of solvers provided by the SciPy Python library. The results are analyzed taking into consideration the overall performance and the performance impact of band solvers across different matrix bandwidths, as well as the performance versus runtime analysis. The findings show potential in applying the proposed method to very large ELM models with narrow band matrices.

Evaluating The Use Of Machine Learning For Road Maintenance Cost Estimation, Shahla Shirinzad, David Enke

Engineering Management and Systems Engineering Faculty Research & Creative Works

Accurate estimation of highway maintenance costs is essential for efficient resource allocation and long-term infrastructure sustainability. This study evaluates the effectiveness of advanced machine learning models, including ResNet, Transformer, and other neural network architectures, for forecasting maintenance costs using historical data from the Highway Maintenance Improvement Program (HMIP) provided by the North Carolina Department of Transportation (NC DOT). A comprehensive comparative analysis is conducted across multiple models using standard performance metrics, including R², MAE, RMSE, and MSE. The results demonstrate that advanced architectures, particularly ResNet and Transformer, consistently outperform traditional statistical approaches and baseline machine learning models, achieving …

A Four-Step Thermocatalytic Route For Converting Co2 Into High-Purity Oxalic Acid, Hao Feng, Muhammad Kashif Khan, Lei Li, Hongyan Ma, Xinhua Liang

Civil, Architectural and Environmental Engineering Faculty Research & Creative Works

This research outlines a four-step methodology for transforming CO₂ into high-purity oxalic acid. CO2 was first sequestered as KHCO₃ through its reaction with aqueous KOH, followed by hydrogenation using a supported AgPd/CNT catalyst in a batch reactor at an initial H₂ pressure of 60 bar and a temperature of 150°C. The formate yield reached 91.8% at optimum conditions. Potassium formate in the solid state was thermally coupled in the presence of KOH at 400°C under N2 flow, yielding potassium oxalate of up to 76% yield. The final step was the selective precipitation of potassium oxalate with ferrous …

Flow Regime-Independent Two-Group Interfacial Area Concentration Model For Dispersed Gas-Liquid Flows In Large-Diameter Pipes, Hossein Barati, Takashi Hibiki, Joshua P. Schlegel, Naofumi Tsukamoto

Nuclear Engineering and Radiation Science Faculty Research & Creative Works

In many power plants, boiling can result in two-phase flows during normal and accident conditions. Heat and mass transfers through the gas-liquid interface in a two-phase flow process are proportional to the interfacial area concentration (IAC). These calculations for nuclear systems are typically performed using advanced system analysis codes such as TRACE. TRACE uses a two-group (2G) model, where bubbles are divided into two groups according to their drag coefficients. Correlations are used to calculate the group-wise void fractions (VFs) and IACs. This study evaluates the accuracy of the TRACE 2G VF and IAC models for vertically upward dispersed flows …

Implementation Of Tritium Transport In A Gas-Liquid Contactor Cfd Simulation Of Tritium Extraction From Lead-Lithium In Ansys Fluent, Anthony G. Bowers, Subash L. Sharma, Thomas F. Fuerst

Nuclear Engineering and Radiation Science Faculty Research & Creative Works

Modifications to the Computational Fluid Dynamic (CFD) software ANSYS Fluent were done to quantify and characterize tritium transport in gas-liquid contactors (GLCs). A double-slit, Ergun-like equation was employed for the porous media model, with Ergun coefficients validated with Sulzer's Sulcol software. Tritium transport from PbLi within the GLC was verified against analytical models. The geometry of the CFD model was based on the MELODIE GLC experiment. The hydrodynamic CFD pressure drop results align well with Sulcol estimations and fall between the predictions of the analytical Delft-Olujić and Billet and Schultes models. In terms of mass transfer efficiency, traditional mass transfer …

Synthesis Of Nickel Nanoparticles By Gamma Irradiation And Femtosecond Laser Ablation, V. M. Rao, Y. Han, H. Tsai, C. H.C. Giraldo, T. Akyurek

Nuclear Engineering and Radiation Science Faculty Research & Creative Works

Nickel nanoparticles were synthesized by (i) gamma irradiation of aqueous nickel chloride precursors and (ii) double scan femtosecond laser (FSL) ablation of a pure nickel foil in water. The nanoparticles produced by FSL ablation were further stabilized in acetone. Gamma radiolysis yielded nickel nanoparticles in the 2–22 nm range, with the average particle diameter governed by the total absorbed dose. Nickel nanoparticles produced by double scan FSL ablation were in the 2–17 nm range but less monodispersed than the nanoparticles produced via gamma radiolysis. FSL ablation proved to be superior in terms of yielding a higher number of smaller nanoparticles …

Injectable Borate/Borosilicate Bioactive Glass Systems For The Regeneration Of Hard Tissue – A Critical Review Of The Literature, S. Sina Mohammadi, Sunjeev S. Phull, Ryan J. Gilbert, Mark R. Towler

Chemical and Biochemical Engineering Faculty Research & Creative Works

Bone defects caused by trauma, infection, or tumor resection remain difficult to treat because successful repair requires both structural restoration and control of the local pathological microenvironment. Osteolysis, defined as pathological bone resorption, is central to many of these conditions and is commonly driven by excessive osteoclast activity. Clinically translated injectable products such as NovaBone® Putty demonstrate the value of moldable bioactiveglass grafts for defect filling; however, conventional silicate bioactive glasses are permanent and provide limited therapeutic ion release. This limitation has motivated the development of injectable borate bioactive glass (B-BGs) and injectable borosilicate bioactive glass (BS-BG) systems as more …

Effect Of Complex Alloying Elements On Oxide Scale Formation And Water-Jet Descaling Performance On Continuously Cast Low-Carbon Steels, Tochukwu P. Ojiako, Tsvetkov Dmitry, Mario Buchely, Haiming Wen, Simon N. Lekakh, Ronald J. O'Malley

Materials Science and Engineering Faculty Research & Creative Works

The formation and evolution of oxide scale in contact with mold flux during continuous casting, subsequent reheating, and hydraulic descaling are strongly governed by steel chemistry. To elucidate the effect of complex alloying elements (Si, Mn, and Cr), two industrially produced continuously cast low-carbon steel grades for manufacturing stamped parts (a base and alloyed steel grade) were investigated. The objective was to determine how alloying elements influence oxidation behavior, scale morphology, interfacial adhesion, and water-jet descaling efficiency. Continuously cast slab specimens were subjected to controlled thermal and atmospheric oxidation cycles simulating multistage industrial practice. Three initial surface conditions (industrial as-cast, …

Processing, Characterization And Performance Of Ceramic Liners For Hydrogen Gas Turbine Engines, Fahim Faysal

Graduate Studies Theses and Dissertations 2026

Advanced ceramics and ceramic matrix composites (CMCs) are known for their endurance at high temperatures. This study investigated the fabrication and testing of two material systems: silicon carbide nitride (SiCN) reinforced with yttria-stabilized zirconia (YSZ) fiber manufactured through polymer infiltration and pyrolysis (PIP), and 3D-printed alumina (Al₂O₃) ceramics. The CMC thermal stability at high temperatures was explored through a hydrogen torch test. The CMC surface could withstand a temperature of 1,400°C for 10 minutes during the torch test. Furthermore, the internal surface of a hydrogen combustion chamber was coated with CMC to assess its applicability as a protective barrier against …

Turbine Exhaust Cylinder And Manifold Wake Interactions At High Swirl Angle, Christian A. Anzalotta

Graduate Studies Theses and Dissertations 2026

A commonly observed flow interaction in industrial gas turbine (IGT) exhaust diffuser configurations is investigated, where upstream structural wakes interact with downstream airfoil-like components, potentially leading to unsteady loading. To better understand the mechanisms contributing to this behavior, a scale-model is designed. Dynamic similarity is achieved by matching the Strouhal number (St) of the vortex shedding from the strut. A bell-mouth followed by a swirler is installed in front of the strut to mimic the flow angles at the inlet section of the turbine exhaust. Experiments are conducted for three swirl angles, namely, 30°, 45°, and 60°. Power spectra computed …

Machine Learning Acceleration Of Micro-Credentialing, Knowledge Gap Remediation, And Micro-Recruiting Of Stem Assessments: From Learner Data To Hardware, Paul Amoruso

Graduate Studies Theses and Dissertations 2026

The growing demand for a skilled STEM workforce calls for adaptive, data-driven education that personalizes learning while aligning competencies with industry needs. This work introduces a multi-layered framework that integrates artificial intelligence (AI), data mining and hardware-aware optimization to support this goal. At its core, the AchieveUp system applies generative AI-assisted skill tagging to digitized assessments, enabling multi-semester tracking of student progress. Analysis across 14 semesters shows that underperforming students were found to benefit most from attending score clarification sessions, a relationship validated by an R² value of 0.83, indicating strong predictive validity between attendance and skill acquisition. To remediate …

Development Of A 3d-Printed Hemodynamic Model To Characterize Doppler Signatures Of Obstructed Tapvr, Michael R. Turner, Maher R. Saadeh, Holly D. Bauser-Heaton, Vahid Serpooshan

Summer Research Program Abstracts

No abstract provided.

Experimental Investigation Into The Effects Of Air Staging On Fouling In A Fixed-Bed Biomass Combustor, Akram Elsebaie

Theses: Doctorates and Masters

Biomass offers significant potential as a sustainable and renewable substitute for fossil fuels in energy generation, playing a critical role in the reduction of global warming. However, despite its environmental benefits, biomass combustion faces persistent operational challenges, particularly fouling, which reduces efficiency and increases maintenance costs. Although fouling mechanisms have been studied in various combustion systems, there is limited research which addresses its formation and behaviour in fixed-bed biomass combustors under different air staging conditions. This research investigates fouling behaviour in a counter-current combustor, focusing on the influence of design (secondary air location), operational (air staging flowrates between the primary …

Synergistic Removal Of Microplastic Fibres: Integrating Chitosan Coagulation In Hybrid Water Pre-Treatment Systems, Jayasuriya Arachchilage Nimesha Thathsarani

Theses: Doctorates and Masters

Microplastic fibres (MPFs) are the most prevalent form of microplastics detected in the influents of water and wastewater treatment plants. Owing to their elongated shape and low density, MPFs frequently evade removal even during tertiary processes such as membrane filtration. Enhancing pretreatment, particularly through cost-effective coagulation-flocculation can reduce the treatment burden on downstream systems. However, conventional inorganic coagulants often necessitate high dosages and can leave residual ions, posing environmental concerns.

As a sustainable alternative, the use of environmentally friendly coagulants such as Chitosan has gained attention for MPF removal. While Chitosan exhibits favourable qualities, its practical application is hindered by …

Enhancing Deep Reinforcement Learning With Expert Demonstrations For Mobile Robot Navigation In Unstructured Off-Road Environments, Dulitha Dabare

Theses: Doctorates and Masters

Advancements in the field of Deep Learning has ushered in a boom in autonomous navigation research. Most of the work being conducted in this space, however, has focused on on-road urban navigation scenarios, with unstructured outdoor terrain navigation receiving much more limited attention. Given the wide range of applications that exist for legged and wheeled ground robots in off-road environments in areas such as agriculture, mining and disaster recovery, there is a growing need for research work to improve the navigational capabilities of mobile robots deployed in these challenging environments.

A promising candidate for application to these navigation challenges in …