DSpace@RPI (Rensselaer Polytechnic Institute)
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Engineering cathode electrolyte interface for low co and co-free lithium ion batteries
No full textAugust2025School of EngineeringThe advancement of high-energy lithium-ion batteries and quest to lower cathode costs is critically limited by the interfacial instability of Ni-rich and high-voltage cathode materials under high cutoff voltages. This work addresses two key materials challenges - electrolytedriven surface degradation in Ni-rich layered oxides and in spinel-type cathodes - through targeted surface engineering strategies. Firstly, a magnetite (Fe₃O₄) nanoparticle coating was developed for NMC811 cathodes to suppress parasitic reactions and structural deterioration at high voltages (up to 4.6 V vs. Li/Li⁺). The iron-based coating acted as a chemically robust interface, mitigating electrolyte decomposition transition metal dissolution and surface oxygen loss, thereby enabling stable long-term cycling with enhanced energy density. Secondly, nearsurface oxygen vacancies were introduced on LiNi₀.₅Mn₁.₅O₄ (LNMO) cathodes via controlled ammonia solution treatment. This approach tailored the surface defect chemistry interfacial transport pathways. The resulting vacancy-rich surface not only improved Li⁺ diffusion kinetics but also imparted greater tolerance against electrolyte oxidation and Mn dissolution during operation above 4.6 V (vs Li/Li+). A suite of materials and electrochemical analysis has been carried out to reveal the improvements and substantiate proposed mechanisms. Together, these materials-centric strategies highlight the importance of interface design in overcoming intrinsic limitations of next-generation cathodes. This work provides a foundation for developing highvoltage, cobalt-free cathode systems with improved chemical stability and electrochemical performance.Ph
Efficient singularity-robust inverse kinematics and redundancy management for robotic systems
No full textAugust2025School of EngineeringA robot must control the position of its hand or end effector, but this requires understanding the complex relationship between the end effector pose and the joint angles. This thesis seeks to provide a unified, computationally efficient, and singularity-robust framework for the inverse kinematics (IK) and redundancy management of robotic systems. IK is the problem of finding which joint angles correspond to an end effector pose. There is a need for an IK solver which is efficient, robust, and precise, and which finds all solutions including singular solutions. We present new IK methods using geometric subproblem decomposition which apply to 6-DOF arms, 7-DOF arms, and parallel manipulators (also solving forward kinematics for parallel manipulators). Depending on intersecting or parallel joint axes, the methods are closed-form or use 1D or 2D search. Search methods may be converted to high-order polynomials. The open-source implementation, IK-Geo, is the fastest general IK solver in our testing, with >40x faster IK for the UR5 than IKFast. 7-DOF manipulators avoid singularities and obstacles better than 6-DOF manipulators because they have an extra internal degree of freedom. However, redundancy parameterizations create new algorithmic singularities. We propose a new parameterization called the Stereographic SEW angle that reduces the presence of algorithmic singularities in the workspace. We prove algorithmic singularities are unavoidable, but the stereographic SEW angle is ideal in that the robot pose is singular only when the wrist is on a half-line from the shoulder. We apply our 7-DOF analysis to the ABB YuMi and provide the first complete and validated definition of the SEW angle used by the ABB controllers. Cuspidal robots are a surprising and increasingly common class of manipulator. Classical path planners may fail for these robots because they can travel between IK solutions without encountering a singularity. We are the first to show the ABB GoFa and some 3-parallel-axis robots are cuspidal. We also propose a graph-based planner to find optimal joint paths for a given end effector path and an optimizer to adjust the workpiece placement. For the first time, we apply cuspidality analysis to 7-DOF arms. While redundant arms can usually travel between self-motion manifolds without encountering a singularity, certain 7-DOF arms may or may not be cuspidal once the redundancy is parameterized. We find the ABB YuMi is cuspidal after parameterization, while the KUKA iiwa is not.Ph
On changing computing: a case study of systemic change in a university department of computer science and engineering
No full textAugust2025School of Humanities, Arts, and Social SciencesInequity in computer science and engineering (CS&E) is greater than its disproportionately misrepresentative workforce. Inequities in its social organization, pedagogy, knowledge, and institutions come from CS&E’s knowledge culture that privileges masculinist and colonial forms of knowledge and action. As a result, the efficacy of equity-based change initiatives is limited by CS&E’s commitments to social/technical dualisms and deficit-based approaches to minoritized communities.In this dissertation, I analyze the discourses, dynamics, and socioemotional experiences of equity initiatives in CSE. I present a case study of “cultural change” in a CS&E department in a predominantly white university in the United States. In this action-oriented autoethnography, I spent two years working with a team of students, faculty, and alum to actualize their vision of systemic change through curriculum development, mentoring, and other research activities. Drawing on feminist grounded theory, I use situational analysis to analyze extensive field notes, team interviews, faculty interviews, documentation, and analytic memos.
My findings elucidate the consequences and construction of equity-based change expertise in CS&E. Change expertise is the product of (1) perceived difference, where minoritized people are assumed to embody the difference and expertise needed for change, and (2) competency in care ethics, which facilitates the reflective activities of critical technical practice. However, CS&E’s dualistic culture and history frames change expertise as the mutually exclusive complement to technical expertise. This leads engineers to disqualify their relevant experiential knowledge and defer the responsibilities of action to change experts. I describe this effect, where change experts are responsible for the initiative and their colleagues’ critical consciousness, as the mammification of change expertise. The process and efficacy of equity-based change in CS&E is structured by the mammy, a longstanding controlling image of Black women as subservient, polite, undesirable, and caring maternal figures.
In addition to providing insights into the barriers for equity-based change in CSE, this dissertation contributes to knowledge on the politics of misogynoir, the social organization of knowledge, and the culture of computing.Ph
Improvement and functionalization of bacterial cell wall lytic enzymes for increased cell killing and reduction of bacteria on surfaces
No full textDecember 2024School of EngineeringAntibiotic resistant pathogenic bacteria are a rising global issue. Once successfully infecting an individual, these microbes are often extremely difficult to treat with commonly used antibiotics and may spread from person to person, especially in hospital settings. Clearly, new therapies are necessary to eliminate this threat. Enzymes are one alternative treatment that has proven efficacious to antibiotic susceptible as well as antibiotic resistant strains of bacteria. Many types of cell wall lytic enzymes have been studied for their antibacterial properties and have the advantage of being narrow-spectrum and possesses a lower chance of imparting resistance to their target. Lytic enzymes are naturally produced by bacteriophages, which perforate bacterial cell wall to infect and then escape a host bacterium, and by bacteria, which either employ lytic enzymes to help with cell growth and division or to eliminate competing bacteria. In my research, I have attempted to optimize the activity of two lytic enzymes, lysostaphin (Lst), whose target is Staphylococcus aureus, and PlyG, which targets Bacillus sp. Out of several optimization strategies, I have chosen to affect the electrostatic interactions between lytic enzyme and target cell wall by including a string of charged or neutral residues on the lytic enzymes. Because wall teichoic acids located on the bacterial cell surface render the cell wall largely negative in charge, I hypothesize that a lytic enzyme with a positively charged tag will be more drawn to the cell wall of bacteria, thus lysing a greater number of cells, while the opposite will hold true for a negatively charged construct. I have also sought to generate lytic enzymes that are especially active on various medical and non-medical surfaces, such as indwelling catheters and clothing. Peptide tags with affinity for silicone, polyethylene terephthalate (PET), polyvinyl chloride, and cellulose have been evaluated for their adherence to their respective surfaces. The surface binding peptides fused to Lst will provide a lytic enzyme that adheres to and inhibits bacterial growth on the surfaces. Because the lytic enzyme is not covalently attached, older enzymes can be removed and replaced by newer enzymes to enable efficient reuse of the surface. Finally, enzyme treatments for Corynebacteria species have been explored. Few lytic enzyme therapies exist to treat pathogenic species within this genus, most likely due to their unique cell wall architecture. Thus, Corynebacteria cell killing studies have been conducted in an attempt to further the literature.Ph
Investigation of transients important for heat pipes in microreactor applications
No full textDecember 2024School of EngineeringHeat pipes are two-phase heat transfer devices that employ the cyclicevaporation and condensation of a working fluid to transfer heat between two
interfaces. Due to their safety, efficiency, and passive operation, heat pipes
have found diverse applications that include electronics, aerospace, and nuclear
systems. In particular, the use of heat pipes with liquid metal working fluids
in nuclear microreactors is of interest due to unique advantages compared to
conventional, as well as other novel advanced reactor concepts. Heat pipes can
enable increased reliability in microreactors as they eliminate the need for
reactor coolant pumps and their associated auxiliary systems, which also results
in greatly reduced spatial footprint. Experimental work is needed to aid and
expedite the design and licensing of future heat pipe microreactors (HPMRs),
especially on the validation of heat pipe performance as key heat transfer
components. High operating temperatures and chemical reactivity of working fluids such as liquidmetals dictate stringent safety precautions and require high startup costs.
Thus, the present work develops fluid-to-fluid and geometric scaling laws for
heat pipes and two-phase closed thermosyphons that can be used to quantify
similarities between a model system that uses low-temperature working fluids and
a prototypical system using liquid metals. Similarity parameters which were
obtained from the non-dimensionalized governing equations and constitutive
relations were tabulated and discussed. A case study involving the scaling of a
microreactor heat pipe for the purpose of investigating the pressure and
temperature profiles was given. In addition, a parametric study was conducted on
the effects of the liquid and vapor Prandtl numbers on the steady state pressure
and temperature profiles. Furthermore, a Low-Temperature Heat Pipe Test Facility (LTHPF) was designed andconstructed according to the developed scaling laws to bypass the difficulties
of experimenting with liquid metal working fluids by using surrogate fluids. The
design, instrumentation, and experimental capabilities of the facility were
described. The testing conditions including various operating limits and the
ranges of the non-dimensional parameters used for scaling analysis were
reported. Due to the complex flow structures within heat pipes and thermosyphons, acomprehensive experimental database consisting of temperatures, pressures,
pressure drops, flow visuals, and film thicknesses, is needed for model
development and verification, along with the robust identification of
operational characteristics, potential instabilities, and oscillatory
phenomena. Thus, the present work develops an extensive heat pipe
experimental database using water working fluid under wickless (two-phase closed
thermosyphon), annulus-screen, and wrapped-screen configurations. The
investigated experimental cases include quasi-steady states, condenser heat
transfer coefficient transients, and power transients. Emphasis is placed on
describing oscillatory phenomena, disturbances, and other observed
irregularities and instabilities. From thermosyphon experiments, it was found that high fill ratios and condensercoolant flow rates diminish isothermal operation through liquid holdup in the
condenser in the form of increased subcooled liquid presence and the formation
of a liquid plug at the condenser endcap. The sustained liquid plug effectively
decouples that portion of the condenser from the rest of the thermosyphon.
Furthermore, intermittent or geyser boiling oscillations observed at low powers
were characterized based on their amplitudes and frequencies, which were found
to be strongly influenced by the fill ratio. Lastly, high frequency temperature
and pressure oscillations were identified at the onset of flooding, along with a
lower secondary frequency for higher fill ratios. Two sets of heat pipe tests were conducted using annulus-screen andwrapped-screen wicks. The quasi-steady state characteristics are described
through time series, axial temperature and pressure profiles, thermal
resistances, and operating parameters. The quasi-steady experiments allowed the
investigation of the effects of input power, condenser coolant flow rate, and
fill ratio on important operational parameters and limit conditions.
Additionally, heat transfer coefficient and evaporator input power transients
are investigated, and important parameters are discussed along with the response
times of liquid film temperatures and operating pressures. Overall, it was found
that the performance of the annulus-screen wick was seriously limited due to
perceived vapor generation within the annulus in the evaporator, whereas a
relatively coarse wrapped-screen wick yielded a considerably larger operating
envelop. Important phenomena observed includes subcooled liquid presence near
the condenser endcap and distinct behavior of heat pipes with different fill
ratios near limit conditions.Ph
Characterizing rural resident acceptance of drone delivery: a large language model (llm) empowered approach
No full textDecember 2024School of EngineeringWith the increasing demand for rural logistics services and the notable disparities in service provision between urban and rural areas, there arises a compelling need to explore innovative drone-based delivery solutions. This thesis aims to uncover the challenges hindering the adoption of drone-based delivery, due to technological and physical barriers, which consequently affect service quality for rural residents. Such disparities amplify concerns regarding delivery equity and residents' acceptance of potential drone delivery services. Our research presents an inaugural investigation into residents' direct willingness and sentiment toward drone delivery services in rural areas using a Large Language Model (LLM)-empowered machine learning framework. Leveraging the LLM-driven Light Gradient-Boosting Machine (LightGBM) method, our prediction model mitigates cognitive bias and enhances the predictive accuracy of residents' acceptance categories compared to traditional ordinal logistic regression models. This thesis advances the understanding of rural residents' acceptance of drone delivery services, uncovering pertinent challenges within the rural logistic landscape and the evolution of the drone delivery market. Moreover, it reveals the gap between the supply of rural drone delivery services and the demand from the rural consumer base, exploring the intricate interplay between socioeconomic factors and delivery preferences. This approach fosters a drone-based delivery ecosystem that inclusively benefits all rural residents, irrespective of their geographical location.M
Abiotic amino acid polymerization in simulated hydrothermal environments on early earth and ocean worlds
No full textDecember 2024School of ScienceThe abiotic polymerization of amino acids has been a topic of interest within origin of life studies, as amino acids provide the basic building blocks for proteins and therefore plays a substantial role in the emergence of life’s biochemistry. This study investigates the polymerization of glycine, β-alanine, and γ-aminobutyric acid (GABA) under simulated hydrothermal conditions representative of Early Earth, Enceladus, and Europa by using high-temperature (80 °C) and high-pressure (500 bar) environments in varying saline compositions. The experimental design included simulates brines modeled after the hypothesized ocean compositions of each environment, including FeCl₂-rich Early Earth oceans, NH₄Cl-dominated Enceladus brines, and MgSO₄-rich Europa oceans. The presence or absence of olivine was tested on each condition to see the ultramafic mineral’s influence on amino acid polymerization under these conditions. Results demonstrate that Early Earth conditions were most favorable for polymerization, particularly for glycine, while Enceladus showed moderate polymerization and Europa displayed minimal yields. The study underscores the importance of planetary conditions in the abiotic synthesis of complex organic molecules and provides a comparative framework for understanding chemical processes on Earth and other ocean worlds.M
Analytic and numerical investigations of lattice-based statistical mechanical models
No full textDecember 2024School of ScienceWe study the canonical ensembles of two lattice models which work with vorticity. In a 2D setting vorticity can be treated as a scalar quantity. Certain functions of vorticity, most notably its first moment, are conserved. By choosing a set of conserved quantities appropriate to the problem being studied, and an inverse temperature which allows one to specify whether a high energy or low energy regime is of interest, one can construct a statistical ensemble. An ensemble encodes certain long-term behaviors of the system, but does not require solving the underlying differential equations which govern the dynamics. The first system is studied is based off the Helmholtz-Onsager point vortex gas, and studies the low positive temperature/low energy regime in a multiply-connected domain. In this regime vorticity particles have high probability to be near the domain walls, as the system energy has a self-interaction term for each vortex which is negative in this neighborhood. This behavior was observed in the canonical ensemble. Due to the simplicity of the point vortex dynamics, the results were supplemented with a microcanonical analysis based on simulating the system and analytically solving a mean field equation which gives its long-term density average. The second system studied is the Kac-Berlin spherical model, which conserves the second moment of the site strengths. The low negative temperature/high energy regime of the spherical model has been used to depict wave systems which undergo inverse energy cascade. We approach the model with new analytical techniques and find evidence for a phase transition, as well as an equation for the expectation of energy after the phase transition. These predictions are then examined and verified with numerical simulations on several lattices which encode a particular instance of the spherical model.Ph
Physical modeling of a liquefiable soil-sheet pile retaining wall system
No full textDecember 2024School of EngineeringSheet-pile walls are retaining structures that are prone to liquefaction-induced lateral spreading in waterfront areas. This dissertation explores the dynamic behavior of soil-sheet pile retaining wall systems under seismic loading, focusing on the effects of various parameters such as peak ground acceleration (PGA), number of peak cycles, Arias Intensity, soil density, and embedment ratio. The Liquefaction Experiments and Analysis Projects (LEAP) is a global research collaboration aimed at producing reliable test data to advance and verify numerical models for soil liquefaction studies. The study employs a series of dynamic centrifuge tests performed at the Rensselaer Polytechnic Institute (RPI) as part of the LEAP 2020 and LEAP 2022 projects. The LEAP 2020 experiments simulated the seismic response of retaining wall systems in saturated granular soil to understand the soil-structure interaction and liquefaction phenomena. The problem involved a floating sheet pile wall supporting a deposit of liquefiable soil. The experimental setup of the LEAP 2020 models featured a backfill height to embedment support ratio of 2:1. These experiments investigated the impact of varying mass density and input motions on soil-structural interaction. As part of the LEAP 2020 research campaign, test RPI-LEAP 20-E was conducted at the RPI centrifuge facility by Dr. Evangelia Korre to assess the seismic behavior of the sheet pile wall. Subsequently, the author of this thesis performed the RPI-LEAP 20-S test at the same facility as a repeat experiment, achieving results that were highly consistent with the initial test.
Within the framework of LEAP 2022, a series of six centrifuge experiments, RPI-LEAP 22-5, RPI-LEAP 22-10-1, RPI-LEAP 22-10-2, RPI-LEAP 22-10-3, RPI-LEAP 22-19, and RPI-LEAP 22-36 were conducted at RPI to investigate the impact of varied input motion parameters (Number of peak cycles, motion duration and PGA) on the retaining wall models. LEAP 22 models had an increased embedment depth with an embedment ratio of 1:1.
The key findings from the LEAP 22 experiments indicated that higher PGAs lead to increased soil-structure interaction, manifesting in higher accelerations, pore water pressures, and lateral displacements of the retaining walls. An increase in Arias Intensity, while maintaining a comparable number of peak cycles, resulted in greater lateral displacement of the retaining wall. The settlement of the backfill surface away from the wall was found to increase with a higher number of peak cycles. The experiments also highlighted the significant role of soil density in mitigating seismic impacts, with denser soil models showing lower displacements. Additionally, varying the embedment ratio of the sheet-pile walls significantly influences their seismic performance, with deeper embedment reducing wall displacements and rotations. The study underscores the importance of considering PGA, number of cycles, Arias Intensity, and soil properties in designing resilient geotechnical structures.
The experimental results contribute to a better understanding of the complex dynamic behavior of retaining wall systems and provide valuable data for validating numerical models used in predicting soil liquefaction and seismic responses. This research highlights the critical factors influencing the stability of geotechnical structures in seismic-prone areas and offers insights for improving design and risk assessment practices.Ph
Accelerating architectural workflows through automated code compliance
No full textAugust2025School of ArchitectureAs cities become more interconnected, the government plays an increasingly vital role in shaping the relationship between clients and architects. This thesis explores how data and workflows are shared across these three key stakeholders, emphasizing the city’s impact through zoning laws, building codes, and regulatory processes. To address the challenges at these intersections, a set of digital tools was developed. Among them, CodeCheck—a Grasshopper plugin that addresses the legal and administrative setbacks caused by non-compliant designs— stands out for enabling real-time compliance checks directly within architectural design software. By automating zoning and code validation, it helps architects stay focused on design while ensuring projects meet legal requirements. CodeCheck also aims to incorporate generative design capabilities that respond to site boundary conditions, enabling more context-sensitive spatial solutions. To support this functionality, the system introduces mMake, a generative tool that produces compliant building models in real time. Future improvements include expanding the platform beyond New York City to support a wider range of building codes and jurisdictions. Ultimately, this research shows that compliance is not just about rules—it’s key to building better cities. By closing the gap between design and regulation, CodeCheck improves efficiency, supports accountability, and contributes to smarter, more sustainable urban development.M