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Chromium ion implantation of In625 for in-situ tem molten chloride salt corrosion
No full textDecember 2022School of EngineeringConcentrated Solar Power plants (CSP) capture the Sun's thermal energy by concentrating sunlight to a central tower which transfers the heat to a thermal energy storage material (TES) such as molten salts. The TES containers can raise the temperature of water and create steam which powers a turbine generator to output electrical power. CSP is a renewable energy technology with flexible energy delivery for moments of high-energy demand, variable regional solar flux, and non-daylight hours. But for CSP to be utilized in a greater capacity, there remains the challenge to increase the overall efficiency and keep costs competitive. Use of chloride based salts could achieve this goal with their lower material cost, lower melting point (compared to other salt compositions), and stability at higher operating temperatures which increases efficiency being operated over a wider temperature range. However, chloride based salts have been found to be very corrosive when contaminated with water or oxygen, jeopardizing the lifetime of the container materials which use nickel (Ni) alloys.
This study investigated corrosion in a NaCl-MgCl2-KCl salt environment to observe the influence of chromium (Cr) on Ni-Cr based alloy Inconel 625 (In625) which was patterned with local Cr concentrations using ion implantation. Two different masking methods for ion implantation- one with PMMA resist and the other a FIB milled physical mask- were used to create discrete Cr-enhanced regions in the alloy. The physical mask approach was successful in achieving a patterned alloy surface which could be suitably prepared for Transmission Electron Microscope (TEM) imaging.
The implanted samples were then used in a recently developed in-situ technique using the TEM to study the corrosion at high-magnification and inert ambient of N2. The diffraction rings taken in each discrete region of implanted Cr (RI) and unaltered alloy (RU) both showed the formation of CrNiO4 with Ni(OH)2 found only in the non-implanted region. Also post-corrosion XPS analysis also confirmed the oxidation of Ni and Cr, which was to be expected based on the corrosion reactions reported in literature. This study demonstrates the advantages of in-situ TEM to study molten salt corrosion. Reduction of water and air contamination, as well as being able to simultaneously compare the influence of the alloy's composition on corrosion products will help in the understanding of the relationship between factors that cause severe corrosion. The possible contributions of this technique can lead to advancements which improve the lifetime and utility of CSPs.M
Applying temperature-dependent losses to high-fidelity electric motor analysis
No full textMay 2023School of EngineeringTurning to hybrid-electric and electric propulsion in the aviation industry brings about a new set of engineering design challenges. There has always been motivation to optimize existing propulsion technologies such as gas-turbine or turbo-prop engines. Electric motors are a more novel technology that has not been fully optimized to date. Engineers need to make geometric design decisions to make these motors as efficient, light, or powerful as possible. To date, there has been limited high-fidelity analysis and optimization performed for propulsive electric motors for aircraft. Previous aircraft motor analysis and optimization have not accounted for the fully coupled nature of the electromagnetic and thermal analyses needed for analysis and optimization. In addition, electromagnetic losses have been considered without regard to temperature. In order to optimize propulsive electric motors for aircraft, a multidisciplinary high-fidelity analysis model in the form of a software tool is needed that accounts for temperature-dependent losses and allows for both one-way and bi-directional electro-thermal coupling. Temperature-dependent loss models are adapted from the literature and applied to a motor model problem. These models provide the interface between the electromagnetic and thermal analyses that allow for both one-way and bi-directional electro-thermal coupling. The high-fidelity one-way and bi-directional electro-thermal coupled results validate the conservation of energy and demonstrate the importance of accounting for temperature in electric motor analyses. Furthermore, it is shown that bi-directional electro-thermal coupling allows for more accurate solutions in both disciplines.M
An exploration of the strong coupling regime of the su(2) georgi-glashow model
No full textAugust 2023School of ScienceIn this dissertation, we delve into an in-depth analysis of the Georgi-Glashow model in a four-dimensional space-time configuration, particularly emphasizing its strong coupling behavior. We systematically investigate several order parameters inherent to the model, unveiling hitherto unobserved critical phenomena within a distinct parameter range. Notably, the model has interesting topological phenomena such as monopoles. The scaling behavior of the model is juxtaposed with the pure model. Furthermore, we illuminate the phase diagram that illustrates the relationship between the magnitude of Higgs and center symmetry breaking. Our analysis reveals an interesting overlap between these phase transitions across an expansive portion of the strong coupling regime, establishing an unexpected correlation between two unrelated phase transitions. Complementing this, we extend our investigation to the -dimensional supersymmetric Yang-Mills model, identifying minimal -closed terms and establishing that the low-level Feynman integrals are . Studying this contributes to our long-term understanding of the Montonen-Olive duality in supersymmetric Yang-Mills.Ph
Fundamental study on a drift-controlled stiffening and supplemental damping system for seismic protection of buildings
No full textMay 2020School of EngineeringSeismic protection systems are typically designed to limit loss of life in the event of a high-magnitude seismic event. This objective is achieved by preventing collapse of the structure. The objective of some other seismic protection systems is to limit the damage to buildings; however, they often do not adequately prevent collapse of buildings. This research develops a seismic protection system that achieves the collapse prevention objective or the damage prevention objective, depending on the magnitude of the applied loading. The seismic protection system developed consists of three distinct components. The first component developed is referred to as drift-controlled stiffening. This component supplements the lateral stiffness of a building when high-intensity loads are applied to the building, thereby preventing collapse of the building and when subjected to low-intensity loads the lateral stiffness of the building is not supplemented. The next components are vehicle shock absorbers that supplement the damping in a building to prevent damage to the building. The last component is a mast damper connection, which provides an efficient method for transferring inter-story motion to motion across supplemental damping devices. Combining these components resulted in a seismic protection system that achieves collapse prevention under high-magnitude loads, and damage prevention under low-magnitude loads. Investigations of the effect of drift-controlled stiffening and a mast damper connection on simple systems showed the ability for drift-controlled stiffening to prevent collapse of buildings and a mast damper connection to effectively transfer inter-story motion to motion across a damper. A preliminary investigation of vehicle shock absorbers suggested similarities between shock absorbers and viscous fluid dampers currently used in seismic protection systems, however research has not determined the behavior of vehicle shock absorbers subjected to motion that is commonly seen in structures. The aforementioned investigations motivated experimental testing of vehicle shock absorbers and a scale building model. The experimental testing of vehicle shock absorbers confirmed that their force output can be predicted using a generalized viscous dashpot model. The experimental testing of a scale building model shows that the seismic protection system has the ability to meet different objectives dependent on the intensity of the applied seismic ground motions. The scale building model was constructed with drift-controlled stiffening and vehicle shock absorbers installed using a mast damper connection. The addition of vehicle shock absorbers was shown to increase the damping of the scale building model by a factor of twenty five, and the mast damper connection was shown to transfer eighty percent of roof displacement to displacement across the vehicle shock absorbers. Drift-controlled stiffening was shown to have a minimal effect on the response of the scale building model to low intensity seismic loads. Meanwhile, when subjected to high intensity seismic loads, drift-controlled stiffening reduced the displacement of the roof of the scale building model by over twelve percent.Ph
Social optimal disaster relief distribution with mobile beneficiaries
No full textDecember 2022School of EngineeringIn post-disaster scenarios, where there are not enough critical relief supplies to satisfy the needs of individuals, the allocation of supplies available is a complex process. This dissertation proposes mathematical formulations that determine the optimal location of points of distribution (PODs) of relief supplies and the optimal allocation of these supplies to those points. This dissertation enhances the analytical formulations in disaster response logistics by incorporating a frequently overlooked feature of disaster conditions: the movements of the impacted population along the disaster area. These formulations explicitly consider the mobility of beneficiaries searching for aid by incorporating their walking trajectories towards their most preferred PODs. Mixed-integer non-linear discrete-time optimization models, these formulations consider other characteristics, such as the beneficiaries' vulnerability and availability of prepositioned relief supplies. The formulations minimize social costs, which include logistics and suffering costs. The latter comprise deprivation costs, an economic valuation of the lack of access to critical supplies in the aftermath of a disaster, and walking costs, associated with the walking trajectory of the beneficiaries. The proposed formulations differ in the composition of the populations. The first formulation assumes that the populations have the same vulnerability characteristics and deprivation cost function parameters. The second formulation considers a heterogeneous composition of the populations in which there are two groups of individuals in each population. One group comprises less vulnerable individuals who can walk, while the other comprises more vulnerable individuals who cannot walk and require the supplies to be delivered to them directly. This dissertation also provides extensive numerical experiments that serve as proof of concept for the proposed formulations and provide a starting point to understanding disaster response logistics dynamics. Last, this dissertation examines the impact of varying such variables on the formulation's social cost function and other critical outputs by investigating the heterogeneous formulation's properties. This dissertation makes a theoretical contribution to the field of disaster response logistics by providing the first analytical formulations for disaster relief distribution decisions that take into account beneficiaries' behavior in the decision-making process and their preferences and walking movements while being comprehensive and maintaining consistency and theoretical adequacy within the latest theoretical developments.Ph
Constraining prebiotic rna oligomerization in the context of hadean-archaean environments
No full textMay 2019School of ScienceN/APh
Non-intrusive coupling of codes for multi-physics simulations using the immersed approach
No full textMay 2023School of EngineeringComplex systems encountered in almost all modern-day engineering applications involve multiple distinct physical processes. Traditional ways of simulating multi-physics interactions, e.g., fluid-structure interactions, often involve a single but adaptable mesh with monolithic sets of coupled equations or involve intrusive ways of coupling two or more simulation codes. Immersed approach, such as the modified Immersed Finite Element Method (mIFEM) is a volume-based method that can efficiently and effectively couple multiple physics-based solvers with independent meshes where each representing a physics model. The mIFEM algorithm is modularly implemented as an open-source software called OpenIFEM. It is well-suited for coupling two solvers non-intrusively, mitigating the implementation cost and the computational cost involving mesh updates, thus offering the versatility of keeping the codes’ original formulation and implementation. This study focuses on developing a framework to couple pre-existing codes and expand their capabilities to perform multi-physics simulations. For this work, the immersed approach, specifically OpenIFEM, an open-source implementation of mIFEM, is considered the most suitable option. The contributions of this work can be divided into two steps. The first step involves creating a method to couple an external code with OpenIFEM, and the second step involves redesigning the existing mIFEM algorithm to produce more precise outcomes for the specific application chosen. Based on the accessibility of external codes, two different coupling strategies are developed. The first coupling strategy involves building OpenIFEM with the external code as a shared library. An alternative unique coupling strategy, which utilizes MPI communications, is also developed. Here, the two codes are built and launched independently. Separate communicators are maintained for each code to retain the independent MPI communications within each code. Different codes involved in the simulation interact only by exchanging necessary quantities. These key quantities are exchanged at each time step via synchronized MPI communications. Both of the proposed strategies facilitate a non-intrusive coupling, i.e., a coupling without any changes to the governing equations or data structures of the individual codes involved. The effectiveness of the proposed framework is demonstrated through two distinct multi-physics applications. The first coupling demonstrates interactions of thin shells with the surrounding fluids. A shell solver which represents thin solids using its mid-surface is coupled with an Eulerian fluid solver from OpenIFEM. To address fluid-shell interaction, a new extension of the mIFEM algorithm is proposed. This procedure facilitates robust, accurate, and realistic interfacial loading as well as immersed geometry representation during the interaction with the surrounding fluid. For the second multi-physics coupling, a Lagrangian solid solver from OpenIFEM is coupled with SABLE (Eulerian solid mechanics shock physics code provided by Sandia National Laboratories). The second application in this work provides a novel approach to simulate high-velocity impacts. Compared to the existing coupled Eulerian-Lagrangian techniques, this approach is more straightforward to implement since it only requires the exchange of forces and boundary conditions between the two domains. The ``immersed'' aspect of the method simplifies the utilization of a computational domain that consists of multiple materials, including a combination of solids and fluids. Several numerical tests demonstrate the validity and effectiveness of the immersed approach for the chosen applications. The techniques developed for the two multi-physics applications exhibit novelty and address certain limitations of the current methods. Furthermore, the proposed framework is extremely flexible and can be conveniently employed to couple diverse codes in the future, accelerating the advancement of different multi-physics simulations.Ph
Accountable Bench-to-Bedside Data-Sharing Mechanism for Researchers
No full textWe present a trustworthy mechanism for sharing, reusing, and repurposing data to address the challenge of the costly and time-consuming effort needed to bring an innovative idea from the bench (basic research) to the bedside (clinical level). Even though researchers may generate a solution on their own, other aspects of research, including peer review and dissemination of data/results, have an inherent social component. Compared with the centralized mechanisms of data-sharing (and the subsequent reuse and repurposing), many, if not all, aspects of these processes can be decentralized by using blockchain (for full decentralized and autonomous control), coupled with provenance (to ascertain how and where the resources have been leveraged) and incentive semantics (for characterizing how researchers would be rewarded for their contributions). By capturing metadata details at each step of the workflow, data will be easier to audit, verify, and merge with related datasets. It is common in settings where data is either sensitive or valuable (or both) to have formal data use agreements or sometimes less formal rules for reuse, which we have captured in smart contracts. A key innovative aspect of this work is the departure from the traditional natural language–based data use agreements to make these agreements more computable, resulting in enhanced usability and interoperability by a broader community. We have developed the Data Sharing Ontology, a structured vocabulary to guide various incentive mechanisms and criteria used in the decentralized protocol we introduced with smart contracts. Our solution can track data reuse, provide peer reviews on accountable data reuse, and report any violations, thus providing metrics for measuring data producers’ impact on reward structures and research measures. We introduce the SCIENCE-index designed to incentivize data-sharing in scientific research, which builds upon prior indices used in academic research, such as the h-index and the data-index. The SCIENCE-index is publicly available and automatically calculated by a smart contract based on an individual’s data sharing, reuse, and responsible stewardship activities. By incentivizing fair and honest data-related activities, the SCIENCE-index can help improve the speed, cost, and quality of scientific research. As an example application of this decentralized data-sharing framework, we demonstrate how this approach could radically improve the quality and the efficiency of scientific output in the setting of COVID-19 research data-sharing from the National COVID Cohort Collaborative (N3C)
Angles only initial orbit determination and navigation for space debris capture applications
No full textDecember 2022School of EngineeringA major, long-term problem facing space exploration and utilization today is the increase in space debris. As has been highlighted increasingly in both peer-reviewed literature and national media, space debris poses an active hazard to satellites in orbit and to the space environment as a whole. One commonly discussed solution is active debris removal. Active debris removal entails removing space debris from orbit quickly, therefore preventing it from impacting satellites and other space debris in orbit.
This dissertation examines strategies to carry out active debris identification and removal using an inexpensive cube satellite platform. Primarily, the focus is navigation based on images collected by the satellite. This includes initial orbit determination, refinement of the orbit estimates, and rendezvous strategies. Matlab was used extensively to simulate the spacecraft and orbit environment.
Findings include a novel strategy for initializing satellite position and an algorithm for performing more robust initial orbit determination on space debris from a space-based platform. Strategies for successfully completing a rendezvous with a piece of space debris using only an inexpensive camera were also examined.
More broadly, the topics discussed in this dissertation show that vision-based navigation for space debris removal applications is a viable option, even when very inexpensive satellites are used. Further, much of the work done here is applicable to Space Situational Awareness (SSA), which is critical to understanding the environment in Earth orbit.Ph
Human-building collaboration: a case study on lighting enabled collaborative system design
No full textAugust 2023School of ArchitectureBuilding automation systems have gained increased attention by means of their ability to improve building performance. They increasingly rely on cutting-edge technologies, sensors, and the Internet of Things to autonomously detect changes and adapt to their surroundings. Consequently, contemporary lighting systems have similarly evolved into context-aware entities that react to occupant motion or changes in ambient lighting, acknowledge user preferences, and personalize lighting solutions. This trend requires that lighting designers incorporate into their design logic ideas of automation, dynamic controls, and user-system interaction. Previous investigations have explored the design of interactive, adaptive, and self-optimizable lighting systems. They have also addressed matters of spectrally tuning lighting using numerical optimization techniques and have formulated design considerations for interactive lighting. Nonetheless, holistic methodologies for designing intelligent systems and comprehensive guidelines for assembling system components are scarce. In an attempt to further the profession of lighting design and help designers navigate the shift from conventional to interactive lighting design practices, in this doctoral dissertation a holistic computational framework is proposed that cohesively addresses the design and evaluation of digitally programmable lighting systems. Specifically, this dissertation establishes: (a) a computational framework for designing systems that sculpt light, delivering activity tailored illumination where and when needed, (b) the levels of user-system interaction that may be attained as well as the minimum hardware requirements to accommodate them, (c) a method for evaluating the resulting systems virtually (real-time & offline simulations) and physically (hardware, testbed), and (d) a simulation platform developed in a gaming engine to accommodate real-time lighting simulations. In addition, it presents (e) three implementations that demonstrate how the framework may be applied to synthesize systems that comply with each of the discussed levels of interaction and (f) two additional implementations that demonstrate how the framework may be universally applied in any space and with any digitally programmable lighting hardware. The results of the study suggest significant potential for improving system performance and autonomy as well as user experience and wellbeing in scenarios requiring task-specific and context-adaptive lighting. The associated affordances and limitations are discussed considering existing interactive and autonomous system design frameworks.Ph