137091 research outputs found
Sort by
Applying Optimization Methods to Wildfire: A Simulation Study
No full textPresented at AIAA SciTech 2026 Forum in Orlando, FL on January 15th, 2026.Wildfire response is a wide field that spans many disciplines, from first response and fire thermodynamics to aircraft operations and system-of-systems analysis. While many fires can be addressed with only ground crews, fires in high-risk conditions (high temperature, low humidity, high wind, etc.) can be difficult to tame even for high-cost air-tankers. In such situations, aerial retardant drops are a critical tool, yet their effectiveness depends strongly on where and when they are deployed. Quantifying the quality of a retardant drop is therefore essential for guiding operational decisions and improving suppression outcomes. Wildfire growth, however, is inherently a multi-objective problem. It involves tradeoffs between minimizing burned area, reducing risk to human populations, limiting emissions, and slowing fire spread. This complexity makes it difficult to define a single measure of success and to apply optimization techniques directly. To address this challenge, this work compares multiple novel cost functions to compress one or more spatial variables related to wildfire growth into a single scalar variable representing the “level of undesirability” of future fire growth. The cost functions integrate metrics of area burned, fire progression, population exposure, or emissions, thereby capturing both local and global impacts of suppression strategies. Using these cost functions, an optimization of retardant drop locations for aircraft operations was conducted using brute force search, Bayesian optimization, and differential evolution. Results demonstrate that the proposed framework can systematically evaluate tradeoffs between competing objectives and provide actionable guidance for aerial firefighting operations. Beyond immediate tactical applications, this approach offers a foundation for integrating ecological, social, and environmental priorities into wildfire management, supporting more resilient and sustainable suppression strategies
Impact of Total-Ionizing Dose on Injection-Locked Voltage-Controlled Oscillators
No full textVoltage-controlled oscillators (VCOs) are key components in providing periodic signals that are used in RF communications systems for time synchronization and signal processing. However, standalone VCOs can have poor phase noise performance and experience frequency drift; therefore, injection locking can be implemented in a VCO to stabilize these performance metrics. Injection-locked VCOs (ILVCOs) in satellite communications or radar systems can be subject to total- ionizing dose (TID) effects, which could alter the performance of the oscillator. The present work analyzes the effects of TID in a 5 GHz ILVCO using an X-ray source, and demonstrates that the locking range increases and phase noise of the ILVCO improves with total dose. This unexpected result was analyzed using circuit simulations and shows that the threshold voltage shifts induced by TID raises the ratio of injection signal current to oscillator signal current, which equates to extending the locking range. Consequently, the increase in locking range may also lead to the decrease of phase noise. These improvements suggest that use of ILVCOs in satellite systems may provide performance benefits and is TID radiation tolerant compared to standalone oscillators.M.S.Electrical and Computer Engineerin
Tumor-Localized Control of CAR T Cells to Potentiate Solid Tumor Immunotherapy
No full textChimeric antigen receptor (CAR) T cell therapy has revolutionized the treatment of several hematological malignancies, achieving durable remissions in patients with B cell cancers. However, its efficacy against solid tumors remains limited due to challenges such as antigen heterogeneity, an immunosuppressive tumor microenvironment (TME), and the scarcity of tumor-specific antigens (TSAs). These obstacles not only impede T cell infiltration, activation, and persistence within tumors but also increase the risk of off-tumor toxicity due to the expression of tumor-associated antigens (TAAs) by healthy tissues. Addressing these barriers is crucial to unlock the full potential of CAR T cell therapy for solid tumor treatment. This thesis focuses on developing tumor-localized strategies to potentiate CAR T cell-mediated immunity against solid tumors.
I first develop thermal gene switches that enable remote control of gene expression in primary human and murine T cells in response to mild hyperthermia. By integrating these thermal switches with CAR T cells engineered to produce immunomodulators such as interleukin-15 superagonist (IL-15 SA) and bispecific T cell engagers (BTEs), I demonstrate that localized photothermal heating triggers the expression of therapeutic proteins within the TME to enhance intratumoral activity of CAR T cells. I then demonstrate that surface conjugation anisotropic gold nanoassemblies (GNAs) to thermal sensitive CAR T cells enables multimodal photoacoustic imaging and photothermal therapy to non-invasively monitor trafficking of CAR T cells and enhance antitumor activity against heterogeneous solid tumors. Next, to combat the immunosuppressive effects of the TME, I demonstrate that focused ultrasound-mediated hyperthermia locally triggers the expression of BTEs to redirect CAR T cell cytotoxicity towards the immunosuppressive brain tumors by depleting myeloid derived suppressor cells (MDSCs), leading to significant tumor regression in glioblastoma. Finally, I engineer synthetic antigens to sensitize solid tumors to CAR T cell therapy and bypass the need for tumor antigen discovery. I deliver VHH as an mRNA-encoded synthetic antigen using lipid nanoparticles (LNPs) which can be targeted by αVHH CAR T cells to significantly reduce tumor burden, mitigate antigen escape, and improve survival. Collectively, this thesis provides a foundation for tumor-localized control of CAR T cells to improve therapeutic responses against solid tumors.Ph.D.Biomedical Engineerin
Design and Formulation Optimization of Lipid Nanoparticles Carrying MRNA to the Heart and the Pancreas
No full textNucleic acid therapies are a field that has slowly been developing over time as a method that helps target the source cause of many diseases and provide a more natural and lasting treatment. In order for these therapies to be effective, they need to overcome various barriers such as an organism’s immune system, the cellular membrane and the lysosome process that cells go through to get rid of foreign molecules. Lipid nanoparticles (LNPs) are one of the vehicle types that have been developed to overcome some of these barriers. However, their full potential to target non-liver, organ-specific types of diseases while minimizing their off-target effects to the liver and other organs is yet to be fully explored. Additionally, another challenge is understanding how scaling up their production can influence how they perform in the clinic. The pancreas and the heart are examples of organs known for their hard-to-treat diseases and therefore a potential appealing opportunity for RNA-LNP drugs. The data presented here demonstrates how combining already existing LNP screening systems and testing production conditions can affect how these particles behave in vivo. By testing different chemical and mechanical factors, we were able to identify patterns that affect the performance of LNPs when targeting the heart and the pancreas. This works helps bridge the gap between LNPs that are effective at the benchside but are unable to make it to the clinic due to differences in formulation and preparation. Getting a better understanding of all the different factors that can affect LNP behavior in vivo can help direct earlier research and hopefully accelerate the work of further LNP-nucleic acid therapies for diseases such as atherosclerosis, pancreatic cancer or diabetes mellitus.Ph.D.Biomedical Engineerin
GridFormer - A New Approach to Stabilize and Manage a Higher IBR Penetration Grid
No full textAs the integration of intermittent renewable energy sources (IBRs), such as wind and solar, increases, the challenges of transmission line congestion, voltage instability, and power system frequency fluctuations intensify. IBRs, especially those based on grid-following (GFL) control, exacerbate grid stability issues, including overloading of critical components, voltage instability, and the inability to re-establish grid synchronization during faults. While Flexible AC Transmission Systems (FACTS) devices have been used for grid management, their high installation costs, limited fault current tolerance, and reliance on GFL control reduce their effectiveness in dynamic grid support. This thesis introduces a novel solution: the GridFormer, a utility-owned grid-enhancing shunt-series compensator designed to enhance both steady-state and dynamic grid operations. The GridFormer consists of a shunt transformer, a back-to-back (BTB) converter, a small energy storage unit, and a protection relay capable of handling high fault currents. It provides both series voltage and shunt current to stabilize frequency and voltage during grid events, offering improved reliability compared to traditional FACTS devices. A prototype of the GridFormer was tested at Clemson University's eGrid facility, successfully demonstrating its steady-state power flow control up to 800kVA at 24kV. This thesis highlights the GridFormer's design, operational modes, and control strategies, positioning it as a cost-effective, scalable solution to address the grid challenges posed by high IBR penetration in the near term.Ph.D.Electrical and Computer Engineerin
The Influence of Permeability and Melt Rate on Melt Extraction Times in Europa’s Ice Shell
No full textJupiter's moon Europa is a promising candidate for studying habitable environments in our solar system. Sustained chemical disequilibrium created by a combination of reactants in the ocean and oxidants sourced from the surface may be a key ingredient for habitable conditions on Europa. However, there needs to be a way to transport those oxidants through the ice shell to the ocean. Previous researchers have suggested that Darcy-like two-phase flow may be able to transport materials through the ice shell, but assumptions made about the permeability laws governing fluid transport make the results of these models difficult to compare. This masters thesis examines two-phase flow as a potential transport mechanism for oxidants, and investigates the effects of different permeability models on melt extraction times to assess the efficiency of this method. The results of this thesis show that permeability laws depending on different grain sizes/geometries and different power law relationships with porosity result in melt extraction times ranging from several hundreds of years to several millions of years. These uncertainties make assessing the viability of two-phase flow difficult. Additionally, simulations varying melting and freezing rates in the ice shell were run to explore how sensitive ice shells of different permeability are to changes in melt volume over time. While simulations with high permeability always resulted in significantly faster extraction times than those with low permeability regardless of the melting or freezing rate, low-permeability simulations were far more sensitive to melting and freezing rates than high-permeability simulations. Even very low rates of phase change ( kg//yr) were able to substantially shorten or lengthen the extraction timescale by thousands of years. This suggests that the effect of an emplaced plume or other heating scenario may promote very efficient transport of surface materials even with low melt generation. A lack of information about the permeability of Europa's ice shell creates substantial uncertainty about the possible timescales involved in melt extraction. In the future, this may be improved by more measurements from NASA's Europa Clipper mission and further modeling of Europa's ice shell that incorporates more complex processes such as solid-state ice convection and the inclusion of salts
Assessing Potency of Mesenchymal Stromal Cells By Profiling Sphingolipids
No full textThe cell therapeutic industry is expected to significantly grow over the next few decades and is projected to be worth $11 billion USD by 2030. With the expected growth of cell therapies, scaling methods, standardized process parameters, and cell manufacturing strategies are being expanded to meet clinical demand. Mesenchymal stromal cells (MSCs) have gained traction as a potential cell therapy due to their multipotent differentiation capacity, immunomodulation, and tissue regenerative capabilities via paracrine signaling. Despite their therapeutic potential, discrepancies in MSC characterization have limited further clinical application. Currently, the minimal criteria for MSC characterization are adherence to plastic, expression of specific surface antigens, and multipotent differential potential in vitro, however the International Society of Cell & Gene Therapy has more recently called for improvements to MSC characterization, suggesting omic characterization with functional tests to better explain MSCs’ potency. Lipidomics, a sub-branch of metabolomics, is a powerful technique that combines high-throughput analytical methods and informatics to quantify and characterize lipids in a biological system. This technique can be used for cell characterization as it provides a scope of a cell’s entire lipid profile to understand their role in complex cell signaling. Sphingolipids (SLs) are a class of bioactive lipids that participate in signaling processes involving proliferation, cell differentiation, immune cell trafficking, and extracellular vesicle (EV) biogenesis. However, their role in MSC behavior and potency remains largely unknown. This work aims to understand how bioactive SLs are involved in MSC therapeutic properties. In Aim 1, liquid chromatography-tandem mass spectrometry was utilized to target and characterize MSCs SL profile from multiple tissue sources and after stimulation with a pro-inflammatory cytokine. In Aim 2, MSC SL metabolic network was modulated by an exogenous SL enzyme. We conducted multi-omic characterization after enzyme treatment on MSCs and their EVs. The findings of this work can help develop an understanding of SL’s role in MSCs’ potency and offer a novel approach by modulating the SL pathway to enhance MSC pro- regenerative properties. This can lead to high-quality, therapeutic MSC cell therapies and improved MSC characterization techniques.Ph.D.Biomedical Engineerin
Development of Soft Substrate-Based In Vitro Muscle Models for Myokine Therapeutic Studies
No full textThough exercise is known to reduce the risks of various diseases, the underlying mechanism is largely unknown. In the last few decades, researchers have identified protein factors secreted by contracting skeletal muscle, termed myokines, that exert biological functions in the whole-body. Of all known myokines, however, only a small fraction has been studied and the majority of current in vitro myokine studies are conducted on hard plastic dishes, which limits the physiological relevance of the studies. Here, we utilized soft substrate-based muscle models to better understand the mechanisms underlying the protective effects of exercise and myokine. Frist, we developed soft in vitro muscle models and exercised the models to compare them with an in vivo mice exercise model. Then, as case studies, we investigated the protective effects of exercise and myokine on engineered muscles challenged with cancer cachexia or dexamethasone, a synthetic glucocorticoid commonly used as potent anti-inflammatory and immunosuppressive drugs but often leads to side effects, such as muscle atrophy. In vitro exercise models that better mimic in vivo exercise will serve as an important platform for future novel myokine-based drug discovery and studies.Ph.D.Biomedical Engineerin
Evaluation of Repairs Conducted on Full-Scale, Non-Conforming/Defective Prestressed Concrete Girders (PCI BT-54)
No full textThe research involved a synthesis of national guidelines, interviews with GDOT personnel and industry stakeholders, and full-scale experimental testing of BT-54 girders with simulated nonconformance issues. Results showed that top flange repairs consistently exceeded original girder strength, while bottom flange repairs were generally effective except in bearing zones and transfer regions, where re-tensioning methods failed due to poor strand-concrete bonding. Reinforced repair surfaces demonstrated strong adhesion and structural performance, reaching at least 95% of nominal moment capacity and 90% of nominal shear capacity. Recommendations include simplifying top flange repair procedures, reconsidering the use of epoxy bonding agents, and ensuring adequate exposure of steel reinforcement for proper bond of bottom flange repairs