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Recent Submissions

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    Novel Class Discovery for 3D Point Cloud Semantic Segmentation in Large-Scale Environments
    (University of Waterloo, 2026-01-23) Du, Jing
    Modern urban environments undergo continuous transformation as emerging infrastructure appears worldwide. Traditional semantic segmentation methods for 3D point clouds operate on fixed taxonomies, producing static representations that cannot adapt to novel categories. This dissertation addresses novel class discovery (NCD) in large-scale 3D point cloud segmentation through geometry-aware mechanisms, adaptive multi-source fusion, and hybrid supervision frameworks. The first study establishes geometric foundations through voxel-geometry integration with region-centric organization, termed CHNCD. The framework couples voxel representations with original spatial coordinates via index mapping, identifies semantically informative points within clusters, accelerates neighbor retrieval through proximity hash mapping, and consolidates localized features with global context via spatial attention. Experiments on S3DIS, Toronto-3D, SemanticSTF, and SemanticPOSS demonstrate consistent improvements over discovery baselines. The second study deepens representation through adaptive geometric sequence modeling, dynamic Gaussian embeddings, and gated multi-source fusion, termed AGDNet. Adaptive geometric sequence modeling employs learnable dimension weighting and dynamic grouping adjusted to local point density. Dynamic Gaussian embeddings represent point clouds as 3D Gaussians and compute Mahalanobis distances to generate multi-scale spatial embeddings. Gated multi-source fusion intelligently weights features through context-aware mechanisms. Three knowledge-transfer objectives operate at category, instance, and distribution levels to bridge semantic gaps. Evaluation on Toronto-3D, SemanticSTF, and SemanticPOSS demonstrates substantial improvements. The third study integrates discovery with operational land cover mapping, termed 3DLCDM. The framework processes features through a supervised head for established categories and a dual unsupervised head comprising a primary branch with fixed prototypes and an over-segmentation branch with progressive scheduling. Temporal Sinkhorn-Knopp normalization with adaptive temperature scheduling stabilizes pseudo-labels, while dynamic weighting combines per-batch and global frequency statistics to address class imbalance. Evaluation on DALES and H3D datasets demonstrates substantial improvements for continuous land cover discovery mapping. Taken together, the three studies advance a progressive research agenda unifying discovery and 3D segmentation for large-scale point cloud scenes. The dissertation demonstrates consistent gains across six benchmark datasets, exhibits generalization across sensors and acquisition geometries, and provides a principled route to maintain updated urban maps as new structures emerge.
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    Signals of Legitimacy or Tools of Strategy? Investigating ESG Score Drivers in the Age of Sustainability Accounting Standardization, an Analysis of Canadian Firms
    (University of Waterloo, 2026-01-23) Scarfone, Joseph
    ESG scores non-financial reporting sustainability reporting legitimacy theory TSX firms positive accounting
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    How Gender Shapes Youth Perspectives on the Health Impacts of Urban Design in High-Rise Environments
    (University of Waterloo, 2026-01-23) Asafo-Agyei, James Kusi
    This thesis investigates how urban design in high-rise neighborhoods shapes adolescent health, with a particular focus on gendered experiences. Guided by an adapted framework from the CIP Healthy Communities guide and using the Gender-Based Analysis Plus (GBA+) lens, the study identified neighborhood spaces where youth engage in health-related activities and examined how gender influences youth perceptions of urban design and its impact on physical, mental, and social well-being. A participatory qualitative methodology was employed, involving 22 adolescents also described as youth or teens aged 13–18, from two Ontario cities using ‘go-along’ interviews and participant-directed photography. Thematic and content analysis revealed that parks, recreational centers, and urban public spaces serve as key sites for youth health engagement. Boys reported greater ease accessing sports and outdoor spaces, often taking safety and mobility for granted, while girls expressed heightened concern over sanitation, environmental stressors, and personal safety. These findings demonstrate how gender and spatial design intersect to create unequal health experiences for adolescents. The study calls for gender-responsive urban planning that centers youth voices and promotes inclusive, safe, and accessible high-rise environments that support holistic adolescent well-being.
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    Mine Tailings as Sources of Greenhouse Gas Emissions: A Multi-Site Investigation Incorporating Isotopic Signatures
    (University of Waterloo, 2026-01-23) Wang, Jiahe
    Tailings are the slurry waste product from mining operations deposited in impoundments in large quantities and are associated with challenging environmental issues such as acid mine drainage. Sulfide-rich tailings can be oxidized due to O2 ingress and water infiltration, producing H+ that dissolves surrounding carbonate minerals, leading to CO2 production. To characterize the seasonal CO2 emissions from tailings impoundments with various cover systems and explore the geochemical and physical controls on the emissions, field studies were conducted at five mine tailings sites in Canada. The sites included tailings that are uncovered (Giant Mine, NT), sand/gravel-covered (South Bay Mine, Long Lake Mine, and Nickel Rim North Tailings, ON), and multi-layer-covered with O2-consuming-organic material and desulfurized tailings (Strathcona Tailings Management Area, ON). Physical properties were measured and analyzed including tailings water content, soil temperature, particle density, and porosity. Tailings solid and pore water samples were collected via manual coring and squeezing extraction from core samples. Gas depth profile sampling and gas flux chambers were used to quantify subsurface gas concentrations and CO2 fluxes in the subsurface and to the atmosphere. To characterize the stable carbon isotope signatures across phases and source-trace CO2 transport, the δ13C values of solid, aqueous, and gaseous phases in the investigated tailings systems were determined. At uncovered and sand/gravel covered sites with high sulfide content, acidic conditions (pH <2), rapid O2 depletion, high subsurface CO2 concentrations (>20 vol.%), and substantial surface fluxes (up to 140 kg ha-1 day-1) to the atmosphere were measured. Effective covers (composite desulfurized tailings/organic materials) suppressed acid generation but still sustained considerable CO₂ fluxes to the atmosphere (~100-120 kg ha⁻¹ day⁻¹). Sites rehabilitated with different cover systems showed CO2 fluxes in June and July that were twice as high compared to September and October. δ13C values (-4‰ to +3‰) of pore-gas CO2 samples suggest that CO2 originated from geogenic carbonate mineral dissolution at the sand/gravel-covered site. At the multi-layer-covered site, the δ13C-CO2 values of <-20‰ in the organic material cover and -10‰ to -5‰ in the deeper desulfurized tailings, suggest mixed sources of CO2 production. This study demonstrates that tailings emit CO2 at rates exceeding or comparable to wetlands, forests, and farmland sites. A large portion of the CO2 is derived from primary carbonate minerals contained within the mine wastes. Integrating CO2 emissions into global C budgets is critical, and future cover designs must balance remediation control with C management to mitigate climate impacts.
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    Atomistic Modelling and ReaxFF Parameter Optimization for Ionic Liquid Electrolyte
    (University of Waterloo, 2026-01-23) Birgili, Bugra
    The optimization of organic carbonate-based electrolytes, such as ethylene carbonate (EC) and propylene carbonate (PC), was a pivotal enabler for graphite anode materials in the mid-1990s and remains at the heart of modern Li-ion battery (LIB) technology. With battery R&D publications growing 4.5 times faster than general literature between 2010 and 2017 (Li et al., 2018), current research prioritizes electrode and electrolyte improvements to enhance energy capacity, cycling rates, and safety. However, future advancements rely heavily on the digitalization of materials science. Recent industry roadmaps indicate a critical global need for integrating multi-sourced, multi-fidelity data streams—combining experimental and computational data—to holistically analyze cell performance and safety (Batteries Europe Secretariat, 2023). In this framework, this thesis investigates an organic liquid electrolyte with an ionic liquid additive using atomistic and molecular simulations. Initial molecular topology, equilibration, and thermalization were established using Generalized Amber Force Field (GAFF) parameters. Subsequently, the Reactive Force Field (ReaxFF) was employed to simulate the reactive electrolyte environment. To optimize ReaxFF parameters for this specific system, Plane-wave Density Functional Theory (DFT) electronic calculations were performed to derive energy baselines. A custom-developed Python library was created to generate a comprehensive training dataset, comprising bond lengths, 3-body angles, 4-body dihedrals, partial atomic charges, interatomic forces, and reaction enthalpies. Molecular dynamics simulations revealed that the ionic liquid additive improves electrolyte properties by altering the solvation structure and acting as a Li-salt stabilizer. Furthermore, the weak cation-anion ligand interactions introduced by the additive were found to enhance Li-ion diffusion.