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Integrated analysis of global lakes and reservoirs: Global reservoirs modeling database, climate-driven changes in thermal stratification, depth-area-volume relationships, dam operation, and downstream phosphorus export
No full textInland freshwater bodies, including lakes, reservoirs, and wetlands, are critical components of the global freshwater system. They play essential roles in water storage, flow regulation, biodiversity, nutrient cycling, and many other ecosystem services including food production and local climate regulation. However, human interventions such as dam construction, urbanization, intensive agriculture, and climate change significantly alter their hydrological and ecological functions. This underscores the importance of data integration and modeling tools to predictively understand and effectively manage these water bodies to ensure their sustainability and resilience under changing climate and environmental conditions.
With this thesis, I aim to contribute to the comprehensive, global-scale analysis of inland water bodies. I present a new global reservoir water modeling database, abbreviated GRM, that can be coupled with hydrodynamic and water quality simulations. The use of GRM is illustrated by computing temperature changes in nearly 7000 large reservoirs between 1980 and 2019. I also present a database of depth-area-volume (D-A-V) relationships for over 1.4 million lakes and reservoirs worldwide. These relationships provide easy access to essential bathymetric information to users interested in carrying out modeling studies. The D-A-V database is complemented by a Python package that generates bathymetric representations for multidimensional water quality modeling. Lastly, for a reservoir in southern Ontario, I analyze how controlling water level, and the positioning of dam outflow gates can be used to reduce the outflow of total and bioavailable phosphorus, which, more generally, opens the possibility of considering dam operation strategies that help protect downstream water bodies from eutrophication impacts.
Chapter 1 provides an overview of the significance of inland water bodies and the impacts of anthropogenic activities on their biogeochemical dynamics. The chapter reviews existing global databases on lakes and reservoirs, highlighting their strengths and limitations. I further argue that existing global-scale biogeochemical modeling studies of inland waters have primarily relied on simple box models and empirical relationships that lack the ability to capture the complex temporal and multidimensional physical-geochemical-biological interactions in these ecosystems. This gap sets the stage for developing the comprehensive global multidimensional model database presented in Chapter 2.
Chapter 2 describes the development of the Global Reservoir Modeling (GRM) database that integrates multiple existing global datasets to facilitate reservoir hydrodynamic and water quality modeling on a global scale. The current GRM database version brings together 40 years (1980-2019) of diverse data series for nearly 7,000 reservoirs worldwide. The corresponding data are extracted from the following datasets: GRanD for reservoir attributes, ReGeom for bathymetric data, WaterGAP for streamflow, and ERA5 for meteorological parameters. With these data, GRM can generate compatible input files for hydrodynamic and water quality simulations with the popular CE-QUAL-W2 model. Thus, GRM offers researchers a practical and readily usable tool to model changes in reservoir water temperature and mixing regimes and their impacts on water quality, whether for a single or a large selection of the GRanD reservoirs.
Chapter 3 offers an example of the type of global-scale assessments that can be performed with GRM by calculating the temporal trajectories of the thermal gradients in all the reservoirs included in GRM from 1980 to 2019. For each reservoir, a 30×30 depth-length bathymetry is generated by GRM, which is then used in the multithreaded, process-based CE-QUAL-W2 model to calculate the temperature distribution as a function of space and time. The results are illustrated globally by mapping both the surface-to-bottom temperature difference and the distributions of thermocline depth for 1980, 2000, and 2019. The findings confirm not only a widespread increase in surface-to-bottom temperature differences (on average by 0.39 ℃ per decade) but also a generalized deepening of the thermocline, on average by 1.2 m (around 0.3 m per decade) between 1980 and 2019. The results confirm that global reservoir thermal stratification has both intensified and migrated downward over the past four decades.
Chapter 4 compiles depth–area–volume (D-A-V) relationships for over 1.4 million lakes and reservoirs by merging HydroLAKES and GLOBathy. The resulting GLRDAV database contains > 17 million equations—five polynomial functions (orders 1–5) and one power function for both depth–area and depth–volume—evaluated at 0.1 m depth increments. Validation against ReGeom, GRDL, and in-situ Texas Water Development Board surveys show that 4th- and 5th-order polynomials deliver the highest accuracy. Lower-order polynomials and the power function perform adequately for small, simple basins but not for large waterbodies. A Python package, named “Global Waterbody Calculator”, provides streamlined access to all 17 million equations and coefficients, facilitating rapid bathymetric reconstruction for hydrodynamic and water-quality models. The tool rasterizes shoreline
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polygons at 1 arcsecond (~30 m) resolution and rapidly generates full 3-D GeoTIFF bathymetry on a standard desktop, enabling immediate visualization and 3-D model-ready inputs.
Chapter 5 applies the CE-QUAL-W2 model to Fanshawe Reservoir (Ontario, Canada) to test how 33 dam operation scenarios—three dam withdrawal elevations crossed with eleven water-level elevations from 0 to +10 m relative to the current conditions—alter phosphorus retention by the reservoir. Under baseline operation (normal withdrawal, 0 m water level) the reservoir retains only 13% of incoming total phosphorus (TP) annually and can become a net TP and dissolved phosphorus (DRP) source in summer. Switching to surface withdrawal alone boosts the annual TP retention to 20 %, while combining surface withdrawal with a +10 m pool-raise pushes summer retention of TP above 78% and the annual retention to 52%. These gains stem from a four-fold lengthening of the water residence time (peaking at 149 days) and the hydraulic isolation of the P-rich hypolimnion. However, these dam operation and water level conditions also prolong bottom-water hypoxia (with dissolved oxygen < 2 mg/l for around 48 days). The modeling highlights the trade-off between maximizing phosphorus retention and avoiding in-reservoir deoxygenatiom, underscoring the need for seasonally targeted, adaptive dam management.
Finally, Chapter 6 synthesizes the thesis’s key insights and charts a path forward. It emphasizes how the new global datasets (GRM and GLRDAV) and the Fanshawe case study together advance our understanding of the links between hydrodynamics, nutrient cycling, and dam operation. Looking ahead, this chapter calls for coupling “big-data” archives with process-based and machine-learning models, building reservoir-scale digital twins, and incorporating sediment and groundwater interactions to assess long-term climate and management impacts. Strengthening this predictive framework will be instrumental in safeguarding lakes and reservoirs under accelerating environmental change
Efficient Algorithm with No-Regret Bound for Sleeping Expert Problem
No full textThe sleeping experts problem is a variant of decision-theoretic online learning (DTOL)
where the set of available experts may change over time. In this thesis, we study a special
case of the sleeping experts problem with constraints on how the set of available experts can
change. The benchmark we use is ranking regret, which is a common benchmark used in
sleeping experts problem. Previous research shows that achieving sub-linear ranking regret
bound in the general sleeping experts problem is NP-hard, so we relax the sleeping experts
problem by imposing constraints on how the set of available experts may change. Under
those constraints, we present an efficient algorithm which achieves a sub-linear ranking
regret bound
Full-scale Modeling of PEM Water Electrolyzer: Effect of Geometrical Parameters
No full textThe transition to a low-carbon energy system has intensified interest in green hydrogen as a clean energy carrier. Proton Exchange Membrane Water Electrolyzers (PEMWE), powered by renewable electricity, offer a promising pathway for hydrogen production. The performance of PEMWE is essentially affected by operating conditions and geometrical parameters. However, a full-scale model is seldomly considered for numerical simulations, which requires investigation for better performance of PEMWE. This study develops a 3D full-scale model of A numerical simulation that has been conducted in this study to analyze the effects of PEMWE geometrical parameters, including porous transport layer (PTL) thickness, channel width and cell length, on hydrogen production rate and temperature distribution. Cell length was analyzed as a sensitive factor for hydrogen production rate while all three parameters were sensitive factors for temperature distribution. The results reveal that longer cell lengths and thinner PTL contribute positively to hydrogen output. The channel width demonstrated parabolic trend across different ranges and can be optimized for maximum efficiency. Additionally, both the average temperature and the temperature variance within the catalyst layer rise with increasing PTL thickness, channel width and cell length. The model was further optimized with respect to three geometrical parameters, aiming to maximize the hydrogen production rate while minimizing the operating temperature. This study provides an evaluation of geometrical design of PEMWE in a full-scale numerical model, offering practical guidance for the design of advanced electrolyzer systems with improved performance
Design and Evaluation of Targeted mRNA Delivery Systems to the Retina
No full textGlaucoma is a neurodegenerative eye disease traditionally linked to elevated intraocular pressure (IOP). However, recent studies have revealed a complex pathogenic process involving the interplay of multiple factors, leading to the death of retinal ganglion cells (RGCs) and ultimately resulting in vision loss. Current treatments primarily aim to normalize IOP levels. Nonetheless, they are limited by issues and have often failed to prevent eventual vision loss. Neuroprotective gene therapy presents a promising approach to safeguarding RGCs and promoting their survival against potential damage from elevated IOP. This can be achieved by increasing neurotrophic factors (NTFs) and reducing the activation of apoptotic pathways.
In this project, the main objective was to develop an effective non-viral lipid nanoparticle (LNP) system for mRNA for intravitreal (IVT) delivery in the eye using a second-generation parent 18-7NH-18 gemini surfactant (GS) and three derived cell-adhesive-peptide (CAP p1, p3 and p5) conjugated GSs: 18-7Np1-18, 18-7Np3-18, and 18-7Np5-18, along with other lipids. The goal was to enable effective mRNA delivery to the retina as an initial step towards developing a non-viral neuroprotective gene therapy for glaucoma.
Gem++ION hybrid lipid nanoparticle (LNP) system was developed and prepared using Ultrasonication Method 1-3h (USM1-3). The parent Gem++ION Supra formulation and two peptide-conjugated Gem++ION (pGem++ION) Supra formulations were evaluated in vitro in two retinal cell lines and in vivo in CD-1 mouse model. The results demonstrated >90% transfection efficiency (TE) in vitro for all three formulations in both cell lines. In the in vivo study, the two pGem++ION Supra formulations, after 48 hours of intravitreal administration, showed GFP expression in various retinal layers, consistent with the Cy5-labelled LNP biodistribution results by confocal microscopy. Additionally, the three Gem++ION Supra LNP formulations exhibited GFP expression in the anterior eye segment, including the ciliary body, iris, and cornea.
Overall, in this project, a novel hybrid dicationic+ionizable lipid LNP system with CAP targeting ligands, termed Gem++ION Supra, and pGem++ION Supra formulations, with high efficiency to deliver and transfect retinal cells, particularly the RGCs, both in vitro and in vivo, were developed, paving the way for further development in neuroprotective gene therapy for glaucoma
Optimizing Weld Quality in High Stacking Ratio Automotive Joints: Integrated Experimental Design and Machine Learning Benchmarking with Limited Datasets
No full textEnsuring crashworthiness in automotive body-in-white (BIW) structures requires reliable resistance spot welds meeting AWS D8.1 guidelines, which mandate minimum 20% nugget penetration into thin sheets. However, this conventional criterion based solely on nugget penetration is inadequate for high stacking ratio (HSR) joints increasingly used with advanced high-strength steels (AHSS). This research quantifies the relationship between nugget penetration and mechanical strength in dissimilar multi-sheet AHSS joints with thickness ratios ≥5:1 and develops machine learning (ML) based parameter optimization models to predict the process parameters for optimal weld joints.
Systematic experimentation investigated three-sheet lap joints with thicknesses ranging from 0.65 to 2.0 mm and tensile strengths varying from 280 to 2100 MPa. A comprehensive design of experiments approach combining Box-Behnken Design (BBD) and Latin Hypercube Sampling (LHS) was implemented to optimize six welding process parameters across 80 conditions. Mechanical testing, including tensile shear strength (TSS) and cross tension strength (CTS), alongside microstructural characterization, revealed that joints without visible nugget penetration into the thin top sheet could achieve high mechanical strengths compared to fully penetrated joints. Interrupted welding experiments confirmed that bonding between sheets with high joint strength and no nugget penetration was due to either diffusion bonding or localized brazing. SEM and EDS analysis distinguished two distinct fusion interfaces: complete fusion zones with full nugget penetration and brazed interfaces, each exhibiting unique diffusion mechanisms.
To extend these experimental insights, six supervised machine learning algorithms were developed and trained to predict nugget dimensions using process parameters and engineered features based on physical process relationships. Gradient boosting provided the highest predictive accuracy with R² values of 0.948 for maximum nugget width and 0.903 for nugget penetration, reducing prediction errors to 13% compared to 30% from Minitab statistical tool. Shapley additive explanation (SHAP) analysis identified welding current as the dominant process parameter, while interactions among current, weld time per pulse and electrode force proved critical for joint formation. Model-guided inverse prediction enabled dual-objective parameter optimization with experimental validation confirming predicted outcomes within target tolerances.
The findings demonstrated that conventional acceptance criteria based solely on nugget penetration were inadequate for evaluating joint quality in complex dissimilar multi-sheet RSW assemblies and highlighted the need of quantitatively assessing interfacial bonding mechanisms. The validated machine learning framework provided accurate, interpretable parameter optimization, and offered a scalable pathway for broader industrial applications
Mapping Absence, Making Presence: Hydrosocial Repair Along Proctor Creek in West Atlanta
No full textMapping Absence, Making Presence, analyses how ecological restoration can serve as a reparative framework for landscapes shaped by systemic neglect and forms of erasure. The Proctor Creek Watershed in Atlanta, Georgia, woven into the everyday life of Westside neighbourhoods was buried and reduced to a piped conduit, essentially severing both its ecological function and its role in community life. Its absence is materially expressed through recurrent flash flooding, water quality decline, and widespread vacancy and blight, material presence of symptoms drawn from redlining, disinvestment, and environmental injustice. This thesis argues that restoration must go beyond ecological metrics to confront histories of displacement and spatial inequalities. Through layered mapping of water, race, and land, tracing buried hydrology, redlined neighbourhoods, and demographic shifts leading to patterns of vacancy, the project indicates how systemic absences are embedded in the urban landscape. By analyzing and mapping eight past plans and visions for these neighbourhoods including the Proctor North Avenue Vision, it identifies recurring goals such as flood control, green infrastructure implementation, and community revitalization, alongside gaps in implementation, concerns about community displacement, and missed opportunities to integrate ecological restoration with neighbourhood redevelopment. This analysis informs a delicate incremental approach which is grounded in exisiting conditions and community priorities. Methodologically it brings together watershed-scale analysis, story mapping, and ecological sectioning to locate opportunities for intervention that balance hydrological performance with cultural and spatial sensitivity.
Daylighting Proctor Creek is reimagined not as a scale of infrastructural reconditioning but as a series of non-invasive, almost surgical acts that are targeted exposures of the buried creek that stitch water back into the redlined neighbourhoods of English Avenue, Vine City, and Bankhead. These interventions are not confined to vacant or blighted parcels of land but function across a range of conditions within these marginalized areas. Daylighted stream sections, bioswales, rain gardens, and micro-wetlands across the area form a distributed network of living infrastructure that performs both ecologically and socially. By making present what has long been absent, this thesis positions Proctor Creek as more than a piped stream flowing beneath but as a conduit of memory, resistance, and renewal. Through this action, based on community-identified needs, the design offers a model for reparative urbanism, advancing the role of water as a medium for justice and resilience of the Proctor Creek Watershed Community, which is grounded in care.
Keywords: reclamation, ecological time, environmental justice, belonging, creek daylighting, urban voids, community identity, ecological design, public space, urban hydrology
The Racialization of Land: An Ontological Investigation into 'Settler-Becoming' and Land Racialization
No full textThis thesis is concerned with an ontological premise about the genesis of the settler, and what settler-being implies for the development and dispossession of land. It argues that the racialization of land produces what is known as the settler-being, a distinct ontology developed by the archetypal Settler within the settler colony. This Settler views capitalist private property and elimination as fundamental characteristics that produce the subject as the Settler and is thus the consequence of varying colonial phenomena. Private property and capital accumulation in the context of North American settler colonialism reveal a tendency within the settler-colonial project to ap-ply the characteristics of racialized capitalism towards the land, which settlers seek to colonize and ‘settle,’ thus revealing the subsequent process of racializing the land that they seek to control. Understanding the land as racialized helps make sense of tendencies within settler-colonial society, as the role that private property plays within the continent reveals the role that white supremacy plays in colonization, in capitalism, and settler-colonial ontology
Multimetallic Complexes Supported by an Unsymmetrical Imidazopyrimidine-Based Ligand: Synthesis, Characterization, and Catalytic Studies
No full textBimetallic catalysts containing two metals in close proximity harness cooperative effects that enable enhanced or unique reactivity in comparison to traditional monometallic catalysts. The development of such catalysts relies on the development of binucleating ligands that support their assembly and modulate key parameters, synthetic routes to access bimetallic complexes, and continued exploration of their catalytic properties. In this regard, heterobimetallic catalysts are particularly underdeveloped due to synthetic challenges associated with incorporating two different metal centers selectively. This thesis explores the synthesis of heterobimetallic complexes using a novel unsymmetrical ligand design.
In Chapter 2, imidazopyrimidine-based ligands are introduced as a novel motif for binucleating ligand design. The imidazopyrimidine motif was selected for its ease of synthesis and inherently unsymmetrical nature. A representative ligand was synthesized in high yield from readily available starting materials, and the route was successfully extended to multigram scale.
In Chapter 3, the coordination chemistry of this ligand was investigated through the synthesis of homobimetallic complexes. Dinickel(II), dicopper(II), and dipalladium(II) complexes were prepared and characterized to assess the structural influence of the imidazopyrimidine motif. Serendipitously, trinickel(II) and tricobalt(II) complexes were also prepared and characterized, demonstrating the ability of imidazopyrimidine-based ligands to potentially accommodate variable nuclearities. Key structural features, such as the metal-metal distances, were evaluated and compared with literature complexes.
Chapter 4 focuses on the synthesis of heterobimetallic complexes supported by an imidazopyrimidine-based ligand. One-step syntheses of nickel(II)/copper(II) and cobalt(II)/copper(II) complexes were achieved, including both binuclear and trinuclear complexes. NMR studies revealed that the heterometallic complexes were thermodynamically favoured. Competition reactions analyzed by ESI-MS demonstrated that the selective formation of heterometallic complexes was driven in part by the preferential binding of copper(II) to one of the coordination sites on the ligand. Attempts to access other heterobimetallic combinations, including nickel(II)/palladium(II) or copper(II)/palladium(II), were unsuccessful.
In Chapter 5, the Glaser-Hay coupling is explored using a dicopper complex supported by an imidazopyrimidine-based ligand. Compared to related monometallic catalysts, the dicopper complex exhibited a consistently reduced reaction rate, as determined by NMR studies
Quantum Error Correction and Quantum Metrology with Non-Markovian Noise
No full textQuantum technologies have the potential to solve many important problems across science and industry. An important example is quantum computation. Quantum simulators promise to better model chemistry. Further, Shor’s factoring algorithm solves a problem in exponentially less time than what it would take now on our classical computers. This has led many to believe that quantum computers could bring exponential speedups to other difficult, real-world problems, such as optimization. Another example is quantum sensing, where quantum mechanical effects can be leveraged to increase measurement precision beyond the classical state of the art. This has many applications in both fundamental science, such as the LIGO experiment, and in industry, such as Nitrogen vacancy magnetometers. For these quantum technologies to reach their full potential, however, the barrier of noise must be overcome. Quantum effects usually live at very small system sizes or very cold temperatures, making them extra sensitive to thermal noise or small perturbations of the environment. A proposed solution to this problem, for both computation and sensing, is to use quantum error correction. Quantum error correction encodes a few quantum degrees of freedom into many physical degrees of freedom, building in redundancy. This redundancy allows for the detection and correction of unwanted errors in our protocol. Most of the literature on quantum error correction focuses on Markovian noise models, i.e., models where the noise is not temporally correlated. The temporally correlated, or non-Markovian, regime remains relatively unexplored. In this thesis, we explore quantum error correction for non-Markovian noise models. We first present a few of the many definitions and models for quantum non-Markovian phenomena present in the literature. We then generalize the Knill-Laflamme quantum error conditions to the hidden Markov model, an experimentally motivated model of non-Markovian noise. These conditions allow one to guarantee that a quantum error-correcting code will still do its job for more realistic noise models. Finally, we apply our notion of non-Markovian error correction to quantum sensing. We generalize previous Markovian results and derive conditions for guaranteeing Heisenberg limited precision scaling in the presence of temporally correlated noise using quantum error correction. The Heisenberg limit is the fundamental precision limit allowed by quantum mechanics for parameter estimation in a physical system. We also study the next-best achievable precision scaling when the Heisenberg limit is unattainable
Reflected and nonsymmetric crystal graphs
No full textThis thesis is comprised of two projects. The first studies a certain composition of crystal operators on semistandard Young tableaux, which we term raised reflection operators, and are related to a sign-reversing involution used to prove the Littlewood--Richardson rule. In particular, we investigate the graph defined by these crystal operators. Our main result is that this graph is balanced bipartite, giving another proof of the Littlewood--Richardson rule. We do so by giving a set of local rules that this graph satisfies and showing that any graph satisfying these rules is balanced bipartite.
The second studies crystal operators on multiline queues. Certain multiline queues, called non-wrapping multiline queues, are in bijection with semistandard Young tableaux but are better equipped to study nonsymmetric polynomials called Demazure atoms. Indeed, each multiline queue comes equipped with a weak composition, called the type, and summing over all multiline queues of a fixed type yields a Demazure atom. Crystal operators on multiline queues do not preserve type. Our main result characterizes how crystal operators interact with the type of a multiline queue. In particular, we show that these operators may only change the type by a simple transposition and that the type changes if and only if the multiline queue is in a specific configuration