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Developing a Multiscale Modeling Approach Using Lumped Kinetics for Pyrolysis of Plastic Waste
No full textPlastic waste poses a global environmental problem and one day the State of Qatar needs to address it in line with its 2030 vision. The pyrolysis of plastic waste is a thermochemical conversion process that has recently gained considerable attention for its potential to convert plastic waste while generating valuable chemicals. Despite extensive research on plastic waste pyrolysis, there is a notable gap in the literature regarding the exploration of connections between different scales���experimental, kinetic, reactor, and process scales. This thesis aims to address this gap by establishing a multiscale approach, bridging the transition from laboratory-scale experiments to process models for plastic waste pyrolysis by utilizing lumped kinetic models, demonstrated for the cases of polyolefins.
A methodology is developed to link the scales, followed by the creation of a sequence chart representing all the necessary steps to complete each stage. This approach is explored through three case studies that vary either in lumped kinetics, plastic feedstock, or component selection. For each case, a lump kinetic model is integrated into 1D pseudo-homogeneous tubular reactor model, that is developed using MATLAB. Parametric studies were conducted for residence time (0-2 hours), wall temperature (650-950 K), and overall heat transfer coefficients (300, 500, and 1000 W/m����K) within the reactor. With the insights gained from these parametric studies, selected scenarios based on the minimum reactor energy and maximum plastic consumption were integrated into Aspen Plus to construct process models for determining mass and energy requirements. Additionally, the fourth case was subjected to techno-economic analysis, where the total annualized cost, profit, and circularity indicators were calculated and compared with other thermochemical plastic waste routes.
Through this research, the gaps associated with multi-scale modeling aspects in literature are aimed to be addressed, and a framework is sought to be established that seamlessly connects information from each scale. By achieving this goal, a holistic understanding of the entire plastic waste pyrolysis chain is aimed to be provided to decision-makers, empowering them to be informed about implementing plastic waste pyrolysis as an effective and sustainable solution for waste management. The results are within the range of other plastic waste management processes, showcasing the practical implementation and gap-bridging capabilities of the approach
Multi Agent-Based Model for Residential Households Trading Market of Renewable Energy in Qatar
No full textPeer-to-peer energy trading (P2P) is a new paradigm for operating energy systems. You can generate energy from renewable energy sources (RES) in your home or office and share it locally. RES is crucial for the transition to sustainable development. The integration of distributed energy resources (DER) and energy storage systems (ESS) has several advantages, such as reduced Greenhouse gas (GHG) emissions, loss reduction, and reduced dependency on the grid.
An architectural energy market model was proposed and simulated to represent the design and interoperability aspects of components for P2P energy trading between nano-grids. An equitable marketplace is simulated using agent-based modeling (ABM) and game theory to enable owners of photovoltaic (PV) systems to sell their electricity to neighbors and the grid. The transacting entities include decentralized energy producers, consumers, or both, such as residential entities. Each residential entity is a villa simulated as a nano-grid having a battery and solar PV panels. This model was developed as a case study for Qatar.
Solar energy is traded at a rate local energy producers and consumers determine. The energy price is dynamic and depends on changes in the generation-to-demand ratio throughout the day. The amount of excess energy produced can be purchased by anyone and is listed in the market by all available sellers, along with the generation type, price, and location. Buyers place orders for energy, and the trading market framework matches prospective buyers with sellers. Game theoretical
modeling is used for the decision-making between the agents. A novel method integrating game theory and agent-based modeling to simulate the P2P market is developed and validated.
The market framework was tested using various scenarios, including battery storage, reduction of subsidies for non-renewable energy, introduction of a carbon tax, and increasing PV capacity to study plausible outcomes of solar PV trading. The results suggest that when greater PV capacity is assumed, the benefits of trading increase, and a larger proportion of household demand is met locally without the need to buy energy from the grid. Adding battery storage to the system enhances trading, provides more energy for sale, and reduces the amount of energy purchased from the grid.
The universality of this market framework is confirmed through comprehensive validation exercises involving data from Qatar and Europe (Germany), representing distinct regions. The proposed model exhibits scalability, offering the potential to extend its application to entire neighborhoods or even entire cities in various geographical locations. This adaptable framework can address diverse energy trading needs and preferences across different regions
Posttraumatic Stress, Alcohol Use, and Alcohol Use Motives Among Latina Survivors of Interpersonal Trauma: Examining Associations with Anxiety Sensitivity and Distress Tolerance
No full textHazardous alcohol use, interpersonal trauma, and posttraumatic stress disorder (PTSD) symptomatology are prevalent among college students, especially women who identify as Hispanic/Latinx. However, a dearth of literature has focused on alcohol use and PTSD relations among Hispanic/Latinx college student women, specifically. Thus, research is needed to investigate malleable transdiagnostic psychological factors involved in PTSD symptoms and alcohol use and motivations for alcohol use among Hispanic/Latinx students to inform culturally-tailored, evidence-based interventions. A growing body of literature has demonstrated that anxiety sensitivity (i.e., fear of anxiety-related bodily sensations) and distress tolerance (i.e., ability to tolerate negative emotional states) are two malleable transdiagnostic mechanisms with relevance to both alcohol use and PTSD. The current project examined, among 288 Hispanic/Latina college students (Mage = 23.3, SD = 5.4) with interpersonal trauma histories, the indirect effects of PTSD symptom severity on (1) alcohol use and (2) alcohol use motives (i.e., coping, conformity, enhancement, social) through distress tolerance and anxiety sensitivity, evaluated as parallel statistical mediators. Covariates included subjective social status, country of origin, and trauma load. Results revealed anxiety sensitivity, but not distress tolerance, mediated the link between PTSD symptom severity and a) alcohol use severity; b) conformity motives for alcohol use; and c) social motives for alcohol use. Further, PTSD symptom severity was associated with coping motives for alcohol use via both anxiety sensitivity and distress tolerance. This line of research has the potential to inform and advance culturally-informed literature focused on factors that may impact co-occurring PTSD symptoms and alcohol use among an understudied population
Unveiling the Myth Within: The Role of Narrative Perspective in C.S. Lewis' "Till We Have Faces"
No full textThis thesis explores the embodiment and performance of myth through the first-person viewpoint in C.S. Lewis��� Till We Have Faces (Faces). In this novel, Lewis moves away from his previous rationalist approach and uses myth and a first-person narrator to write an intimate story unlike what he had accomplished before. It is a shift in narrative methodology that signifies a corresponding evolution in Lewis��� theology. I study the potential cause of this shift through a study of Lewis��� Christian conversion and an impactful philosophical debate. The result is a particular and unique utilization of myth as a vehicle of conflict, as the protagonist, Orual, is shrouded from reality and must reckon with her own mythology to gain an accurate interpretation of herself and of the divine. I compare the original myth of Cupid and Psyche in The Golden Asse with Faces in order to understand Lewis��� purposes in changing the original story and glimpse the result. Ultimately, he seeks to reveal the importance of coming ���face to face��� with one���s self and holding on to one���s identity. I investigate the theme of identity, as highlighted by the first-person perspective, through the embodiment and performance of myth to argue how Faces is unique among Lewis��� literature
Sequential Decision-Making Under Uncertainty in Multi-Robot Target Tracking Application
No full textA significant advance in robotics and automation is making robots handle uncertainty, a prerequisite to deploying robots outside the lab. To interact with a stochastic environment, the significant effort of evaluating possible conditions challenges the robotic system���s reaction and functionality. For example, how to meet the typical 1 Hz decision frequency with online planning to accommodate uncertainties in a multi-robot system, combined by robots maintaining multiple robotic layers in a single-board computer.
This thesis focuses on such trade-offs between computation and optimality in the world of uncertainty. We formalize planning tasks as Partial Observation Markov Decision Process (POMDP) as it models uncertainties in a horizon-based mathematical model.
The first topic is to plan under time-dependent stochastic constraints, specifically traffic signals. The vehicle���s pass at the intersection depends on the stochastic fixed-pattern traffic signal, introducing the time dimension to the planning space. We propose a spatial horizon-based search to avoid such a curse of additional dimensionality in the planning. Furthermore, the uncertainty of the future signal is overcome by the event of an initial signal change, after which the problem is no longer stochastic. With probabilistic modeling of traffic signal dynamics, we define such planning as an MDP and obtain the solution.
Uncertainty needs tackling in partially observable environments and multi-agent systems. Our second topic, multi-sensor active target tracking, involves interacting with objects of interest (OOI) in a multi-robot system. The objective is to deploy multiple robots with a limited field of view (FoV) to maximize the system-wise target tracking performance. We formulate the problem as a POMDP and apply the approximate dynamic programming (ADP) method to generate the receding horizon control policy for the POMDP. Planning horizon incorporates the estimation of OOIs to handle tricky target-tracking scenarios such as divergent OOI trajectories. On the other hand, extending the horizon increases resilience to the uncertainty of the world model, such as the unknown object of occlusion to the sensing.
The multi-agent aspect injects other robots��� actions, which become a consideration in the uncertainty of the ego agent. Agent-by-agent planning reduces the complexity of planning, and we found the performance boundary of such sequential decision-making based on the locally Greedy algorithm. Since the original locally Greedy algorithm does not consider agents��� policies, which are not updated, adding the intention of those agents shows improvement based on our empirical studies. From implementing multi-agent planning based on receding horizon and objective optimization, we observe the emergent behaviors of cooperation. We show the consistency between planning algorithms��� optimality and the frequency of cooperative behavior in active target-tracking scenarios.
In summary, this dissertation mainly includes algorithmic research in robotic planning in an environment with various uncertainties: sensing, world model, and other agents��� decisions. It also contributes to the eco-driving and multi-robot sensing system application in the problem statement, algorithm design, behavior analysis, and simulation
Second-hand Illegality: Bureaucratic Exclusion and Resource Inequality in College Financial Aid for U.S.-born Latina/o Children of Undocumented Parents
No full textThis study presents a systematic analysis of the bureaucratic obstacles confronted by U.S.-born Latina/o children of undocumented parents when seeking financial aid for college. It delves into the unique challenges these students face during the financial aid application process, where parental information is a pivotal factor. Methods: Employing a semi-structured interview approach, I engaged with 15 participants who shared their experiences with bureaucratic barriers when parental information was requested. The study unveils the concept of "Second-hand illegality," where participants found their own access to resources for education obstructed due to their parents' undocumented status. This phenomenon became most pronounced at three key junctures within the Free Application for Federal Student Aid (FAFSA) form: (1) when the application necessitated parental social security numbers, (2) when it required parent income details, and (3) when it demanded parent signatures for submission. Consulting these points compelled participants to employ innovative strategies to surmount the obstacles. This research underscores a fundamental structural issue within the higher education system, focusing on a demographic often overlooked in immigration literature. The strategies devised to overcome the bureaucratic hurdles posed by the FAFSA lead to outcomes mirroring those experienced by their undocumented parents, including rejection, denial, or limitations on access to crucial resources, services, and benefits. In a broader context, this study highlights the need for systemic changes and policy reform to ensure equitable access to higher education for all U.S. students, regardless of their parental immigration status
Nuclear Safeguards Feasibility Study for a Molten Salt Reactor Using MCNP Modeling and Simulations
No full textThe technological developments within the last couple of decades have exponentially increased the demand for reliable and sustainable energy. The successful fulfillment of this energy demand shows a strong correlation with the Human Development Index, which is based on health, education, and income parameters. Among other energy sources, nuclear energy has become prominent in providing clean energy by protecting air quality, having a small footprint with high energy density, and being a reliable and stable option. However, considering the dual nature (peaceful and non-peaceful uses) of nuclear energy, nuclear safeguards are an important international instrument to prevent nuclear material diversion for non-peaceful purposes. This work focused on developing a nuclear safeguards monitoring approach for a generic Molten Salt Reactor (MSR) designed at Texas A&M University.
This thesis includes a comprehensive neutronics modeling of the MSR using the Monte Carlo radiation transport code, MCNP��6.2. The modeled MSR has a 300 MWth power and operates in a thermal neutron spectrum at 900 K. It uses molten fluoride salt (2LiF:BeF2) as a coolant with UF4 fuel mixture with 3.5% low-enriched uranium (LEU). The reactor core design used graphite as the neutron moderator and reflector. Non-soluble fission products (FP) were extracted through gaseous extraction, and FP removal was conducted to improve the performance. A High-Purity Germanium (HPGe) detector, a widely used Non-Destructive Assay (NDA) equipment was modeled for Special Nuclear Material (SNM) mass quantification. In this methodology, the first step was determining the relationship between the Pu amount and fuel burnup. In the second step, the fuel burnup relationships with the radioactivity of 137Cs, the radioactivity ratios of 134Cs/137Cs, and 154Eu/137Cs were established. In the last step, these relationships were used to estimate SNM mass.
The results indicate that the Pu amount relationships with 137Cs radioactivity and the ratio of 134Cs/137Cs can be utilized to quantify SNM mass at all fuel burnup levels. The ratio of 154Eu/137Cs is applicable even for very-high fuel burnup levels. However, it does not provide accurate results at ultra-high fuel burnup levels due to its saturation. The proposed safeguards monitoring approach in this thesis provides a method for estimating the Pu mass in the MSR at different fuel burnup levels so that any diversion of Pu for non-peaceful purposes can be prevented through early detection and deterrence
Centering Cemeteries in Environmental Justice: Observing Community Connectivity in Historic Texas Black Cemeteries
No full textThis research seeks to create new knowledge on Black cemeteries by employing methodologies that are innovative within the field of urban planning. Drawing from concepts borrowed from Black Geographies and Anthropology, particularly Participatory Geographic Information Systems (PGIS) methods, this study aims to delve into the intricate dynamics and significance of Black cemeteries within their respective communities. The significance of Black cemeteries transcends their role as mere burial sites; they serve as crucial spaces for memorialization, historic preservation, and community cohesion. Over generations, these cemeteries have acted as repositories of collective memory, fostering a sense of continuity, and belonging among community members. Moreover, they function as dynamic hubs of activity, where rituals, events, and ongoing preservation efforts contribute to the creation of a shared sense of space and identity. Furthermore, the interconnectedness of Black cemeteries unveils a broader network of stewards and community members dedicated to place-making and heritage preservation. These networks facilitate land-use planning and address environmental justice issues by promoting resource sharing and skill exchange among communities. This research highlights the relevance of local histories and the engagement of local stewards in the preservation and management of Black cemeteries. However, the primary contribution lies in the incorporation of local knowledge into urban planning practices related to cemetery management. It emphasizes the importance of recognizing and valuing the intrinsic significance of these cemeteries within the context of environmental justice movements. In conclusion, safeguarding and advocating for the preservation of Black cemeteries is not merely an act of historical conservation but a fundamental aspect of social and environmental justice efforts. The utilization of geo-humanities as a tool in this research allows for a nuanced understanding of memorialization, place-making, visibility, accessibility, and vulnerability at the granular level, as evidenced through two case studies
Development of a Constant-Volume Bomb Experiment for the Study of Lithium-Ion Battery Thermal Runaway and Its Associated Hazards
No full textLithium-ion battery (LIB) thermal runaway (TR) has increasingly become a serious concern for consumer safety. As a result, many different LIB TR experiments have been developed to study this phenomenon. The present study outlines the development of a LIB TR experiment that seeks to improve upon the preexisting methodologies. The experiment centers around a constant-volume vessel with a programmable heating controller and external gas system to allow for complete control of testing parameters. The results for representative tests of a single cell are presented to illustrate the experiment���s fidelity. Two different LIBs were utilized for these tests which were performed in air at standard ambient conditions and heated at a rate of ~5 ��C /min. The first test was an LG INR18650 cell at 100% state-of-charge (SoC) which had a TR onset temperature of 142 ��C to 175 ��C and produced 0.18 �� 0.004 moles of gas. These values and the composition of the gas were consistent with literature.
The next three tests were performed with Panasonic NCR 18650b cells at 0%, 50%, and 100% SoC. It was found that increasing the SoC of the battery led to increased reactivity and agreed with relevant literature. Particles ejected from these batteries were also characterized using scanning electron microscopy (SEM), energy-dispersive x-ray spectroscopy (EDS), x-ray diffraction (XRD), and x-ray photoelectron spectroscopy (XPS). The 0% SoC battery produced no ejected particles, so the debris was collected from the 50% and 100% tests. Additionally, the particles collected from the 50% test were sieved into the following size ranges: (1) > 212 ��m; (2) 75-212 ��m; (3) 25-75 ��m; and (4) ��� 25 ��m. Qualitative and quantitative sizing of SEM images taken from these samples found particles ranging from the microscale to nanoscale. It was found that approximately 75% of the particles in the ��� 25 ��m were less than 8 ��m. The EDS, XRD, and XPS techniques identified various compounds created from reactions which took place between the different battery components. Future testing efforts seek to further validate the processes developed for this experiment and continue investigating the hazards associated with LIB TR
High-Temperature Ignition of HTPB-Based Mixtures in a Shock Tube
No full textHydroxyl-terminated polybutadiene (HTPB) is a molecule of continued interest within the aerospace community due to its excellent mechanical characteristics and combustibility as a rocket propellant ingredient. Recent developments in the defense and space industry such as the development of solid-fuel ramjets and solid rocket propellants depend on the characterization of HTPB as a fuel. However, much of the transport and thermodynamic data available for HTPB are relatively unknown due to the pyrolysis of HTPB to ethylene and butadiene occurring near the vaporization temperature of HTPB. The time scale of this pyrolysis is on the order of seconds and, therefore, a characterization of HTPB using timescales under one second is necessary. To achieve the sub-second characterization, the High-Pressure Shock Tube (HPST) at the TEES Turbomachinery Laboratory was utilized. A recent development for the HPST is the endwall injector system which utilizes the increase in temperature and pressure of the incident wave of the shock tube to vaporize the liquid fuel prior to the arrival of the post-reflected-shock conditions. The fuel is placed into the barrel of the injector, and the injector is actuated when the incident shock wave arrives at the location of a pressure transducer 2 m upstream from the endwall. The injector subsequently opens and allows 40 psia of air to blow through the fuel meniscus, sending it into the shock tube where it vaporizes upon interacting with the hot gas behind the incident wave. This thesis utilized the endwall injector system to test HTPB in sub-second time frames and record combustion at 2.5- and 4.25-atm conditions over a temperature range of 1230 to 1400 K. Additionally, in-situ additives were synthesized in the HTPB by collaborators at the University of Central Florida to produce HTPB-based mixtures without affecting the mechanical behavior of the fuel. This thesis studied a titania-infused HTPB mixture at a pressure of 4.25 atm and a temperature range of 1230 to 1400 K. Following the experiments of the HTPB based mixtures is a brief overview of the chemical kinetics data currently available on HTPB and current issues in modeling the molecule