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    Continuous-Time Planning and Control Synthesis under Temporal Logic Specifications with Applications to Quadrotors
    (University of Waterloo, 2026-08-20) Yuan, Yating
    Modern robotic systems are increasingly required to perform complex, safety-critical tasks in which system behaviors must be achieved under specified conditions and temporal constraints. Temporal logic provides a formal language for specifying such requirements in a precise and interpretable manner. In this thesis, signal temporal logic (STL) is used for continuous-time trajectory planning with quantitative temporal constraints, while linear temporal logic (LTL) is considered for control synthesis with qualitative task requirements. This thesis focuses on continuous-time planning and control synthesis for robotic systems under temporal logic specifications, with the goal of generating dynamically feasible control strategies that satisfy high-level task requirements. The first aspect of this thesis considers continuous-time trajectory planning under STL specifications. We represent trajectories using Bézier curves so that the generated plans are continuous in time and possess inherent smoothness properties. Within this trajectory representation, we introduce a time-varying robustness formulation for STL specifications, which replaces the conventional use of a uniform robustness margin over the entire task horizon. The proposed formulation allows different portions of the trajectory to be associated with different robustness requirements, thereby reducing unnecessary conservatism while maintaining satisfaction of the STL specification. This framework connects continuous-time trajectory generation with STL robustness analysis and yields smooth trajectories that are suitable for control execution. The second aspect of this thesis studies control synthesis for executing trajectories that satisfy STL specifications. Since the closed-loop trajectory may deviate from the planned trajectory, the proposed framework integrates tracking-error bounds into the STL robustness analysis to ensure that specification satisfaction is preserved during execution. In this thesis, quadrotor systems are considered a representative class of high-dimensional nonlinear robotic systems. Geometric controllers on $\mathrm{SE}(3)$ with diagonal matrix gains are developed and analyzed to characterize tracking convergence and execution errors. Compared with controllers using scalar gains, the formulation with diagonal matrix gains yields tighter tracking error bounds, which can be incorporated into the robustness analysis. Building on this framework, the thesis further extends the approach to multi-quadrotor systems by deriving inter-agent safety conditions for STL planning using Bézier curves. For long-horizon task execution, this thesis develops an abstraction-free LTL control-synthesis framework for continuous-time systems by patching together locally certified control Lyapunov–barrier function (CLBF) solutions. By decomposing temporal-logic specifications into a sequence of safe-stabilization problems, the framework constructs switching feedback controllers that realize the required transitions over continuous-state regions. This enables efficient execution of long-horizon LTL tasks, without requiring the explicit construction of a global symbolic abstraction. Through numerical simulations and robotic case studies, we demonstrate the effectiveness of the proposed methods for reach-avoid planning, quadrotor trajectory execution, multi-agent coordination, and long-horizon temporal logic tasks. The proposed LTL control synthesis framework is further demonstrated on a Crazyflie platform.
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    The nutrient profile of the beverage market: associations with national-level sugar-sweetened beverage taxes and nutrition labelling policies
    (University of Waterloo, 2026-08-20) Hock, Karen
    Background A healthy diet across the lifespan is critical to help prevent malnutrition and non-communicable diseases. However, global dietary patterns have shifted in recent decades toward increased intake of less healthful foods and beverages, which are often energy-dense and nutrient-poor. An increasing number of countries have implemented nutrition policies aimed at improving the consumer nutrition environment, such as sugar-sweetened beverage (SSB) taxes, front-of-package nutrition labels (FOPLs), and serving size regulations. While these policies may be associated with reduced sugar consumption, product (re)formulation and/or consumer understanding of nutritional information, several evidence gaps remain on their real-world impact. First, most research on SSB taxes and FOPLs has focused on within-country changes in sales or nutrient content, with less cross-country evidence examining how different policy designs are associated with beverage composition. Second, existing literature on (re)formulation has focused on sugar reduction, with fewer studies examining the presence of low/no-calorie sweeteners (LNCS), which may influence beverage composition without reducing the level of processing. Third, there is limited cross-country evidence comparing serving size formats and amounts. Research Objectives The overall objective of this thesis was to examine how nutritional composition, sweetener use, and serving sizes of non-alcoholic pre-packaged beverages vary across countries with different sugar-related policies (i.e., SSB taxes, FOPLs, and serving size regulations). Study 1 examined differences in sugar concentrations across countries and beverage categories. Study 2 examined the proportion of beverages containing sweeteners across countries and beverage categories. Study 3 examined differences in serving size formats (‘per 100mL’, ‘per serving’, or both) and voluntary serving sizes on labels selected by brands across countries and beverage categories, when applicable. Methods Data for the three studies were based on a market scan of non-alcoholic, pre-packaged beverages across six countries: Australia, Canada, Chile, Mexico, the United Kingdom (UK), and the United States (US). Data were collected by web scraping websites of grocery stores, food delivery platforms, and brands between October 2023 and February 2025. Data collection involved two approaches: manual web scraping (i.e., copying data from brand websites) and automatic web scraping (i.e., applying Python 3.13 scripts to grocery store and food delivery websites). Study 1 included 15,640 beverages from Australia (n=1,728), Canada (n=2,643), Chile (n=1,242), Mexico (n=1,588), the UK (n=2,598), and the US (n=5,841). Linear regression examined cross-country differences in sugar concentrations, adjusting for beverage category and retail source. Proportions of beverages within 1.0g/100mL below (or at) versus above country-specific sugar concentration thresholds from SSB tax or sugar FOPL policies were also examined. Study 2 included 15,994 beverages from Australia (n=2,105), Canada (n=2,672), Chile (n=1,229), Mexico (n=1,564), the UK (n=2,587), and the US (n=5,837). Binary regression models examined differences in sweetener presence between countries and beverage categories, adjusting for beverage category and retail source. Study 3 included 26,552 beverages from Australia (n=4,589), Canada (n=4,907), Chile (n=1,816), Mexico (n=3,430), the UK (n=3,554), and the US (n=8,256). Linear regression examined cross-country differences in serving sizes, adjusting for beverage category and retail source. Proportions examined cross-country differences in serving size formats and containers with multiple servings. Results Study 1: Sugar concentrations differed across countries and by policy design. Adjusted mean sugar concentrations were lowest in countries with SSB tax or sugar FOPL policies triggered by sugar-concentration thresholds (the UK: 4.3g/100mL; Chile: 4.3g/100mL) versus other countries (the US: 5.2g/100mL; Mexico: 5.5g/100mL; Australia: 5.5g/100mL; Canada: 6.0g/100mL; all pairwise contrasts p<0.05, except Chile versus the UK). The proportion of beverages with sugar concentrations that were 1.0g below (or at) the 5.0g/100mL threshold used by the UK tax and Chile FOPL (versus above) was greatest in the UK (21.6-23.7%) and Chile (23.8-31.7%) versus other countries (≤12.0-15.2%). Sugar concentrations were lower in countries with threshold-based sugar-related taxes and FOPLs, with greater proportions just below (or at) thresholds. Study 2: The percentage of beverages with LNCS was highest in countries with mandatory SSB taxes and/or sugar FOPLs (Chile: 64.7%; UK: 48.8%; Mexico: 45.3%) versus countries without mandatory policies (US: 36.1%; Australia: 24.4%; Canada: 17.5%; p<0.001). Similar patterns were observed for combined presence of LNCS and added sugars (Chile: 31.7%; UK: 27.1%; Mexico: 26.5% vs US: 17.4%; Australia: 8.4%; Canada: 7.5%; p<0.001). Patterns were less consistent for added sugars without LNCS (Chile: 45.2%; UK: 59.2%; Mexico: 58.9% vs US: 56.3%; Australia: 46.8%; Canada: 56.4%; p=0.002). Across all countries, LNCS presence was highest in energy drinks (75.2% vs ≤49.5% in other categories) and added sugars presence was lowest in water drinks (36.7% vs ≥52.9% in other categories). Study 3: Results: Over 60% of beverages in Australia, Chile, and the UK used both ‘per 100mL’ and ‘per serving’ sizes, while nearly half in Mexico used ‘per 100mL’ only, and virtually all in Canada and the US used ‘per serving’ only. Adjusted mean serving sizes were highest in Canada (327.4mL) and the US (340.1mL) versus other countries (≤304.3mL; all contrasts p<0.001). The proportion of small containers (<355mL) with multiple servings was highest in the UK (7.9%) and Mexico (16.1%) versus other countries (≤5.6%), while proportions among moderate containers >355-600mL were highest in the UK (40.1%), Chile (67.5%), and Mexico (79.8%) versus other countries (≤20.1%). Contribution/Significance The findings of this thesis add to the growing body of evidence on the complexity of the consumer nutrition environment. Specifically, this thesis highlighted that nutrition policies can shape how beverages are formulated across countries: mandatory policies involving sugar thresholds may incentivize (re)formulation to lower-sugar options and greater LNCS use, suggesting that these approaches do not necessarily improve overall product healthfulness. While these observed patterns are consistent with policy-related differences in product composition, the cross-sectional design does not allow causal conclusions to be drawn, and other factors may have contributed to differences across countries. Additionally, the findings suggest opportunities to standardize the use of ‘per 100mL’ and ‘per serving’ formats, as well as serving size labelling requirements for smaller and larger beverage containers, which may improve the comparability and interpretability of nutrition information across beverages. The branded beverage composition database developed as part of this thesis provides a baseline for ongoing monitoring of beverages across countries, supporting the examination of sugar-related policies aimed at promoting healthier intakes and reducing the burden of diet-related disease worldwide.
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    Exploring the Amplification of Nature-Based Climate Solutions in Urban Canada: A Comparative Case Study
    (University of Waterloo, 2026-08-20) Boyall, Kayne
    As cities navigate increasingly severe impacts from interrelated climate, biodiversity and socioeconomic crises, nature-based climate solutions (NBCS) are increasingly promoted across research, policy and practice as compelling multi-solving approaches that conserve, restore, and steward natural places and processes for social-ecological benefit. Yet their implementation is often limited to small-scale pilots and short-lived programs. While scholarship has examined how to accelerate and scale urban NBCS, less is known about the conditions through which their impacts are amplified within and across urban contexts, particularly in Canada. This thesis investigates the pathways and governance conditions of urban NBCS amplification through a comparative case study of Vancouver and Halifax. In abductively analyzing 20 key informant interviews alongside policy and planning documents, I developed two manuscripts which: 1) map the pathways of how NBCS initiatives are amplified beyond their initial scope; and 2) identify what are the structural governance conditions that determine if and how these initiatives are amplified. The first manuscript shows that amplification follows non-linear, multidimensional, and recursive pathways involving multiple actors over time. It also introduces enriching as a new type of amplification to capture how initiatives increase their impact through a broader diversity of co-benefits. The second manuscript highlights that the context sensitivity of NBCS includes where in the organizational structure they are operated from. Structural barriers are identified as products of how complexes of governance conditions interact, as well as strategies that can catalyze how these complexes are reconfigured for advancing amplification. By empirically analyzing how urban NBCS are governed and amplified across scales and contexts, this study advances theoretical and practical understanding of how NBCS can shape and are shaped by urban regimes, and how they can contribute to transforming urban Canada towards positive futures.
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    Interface Behaviour and Mechanical Anisotropy in Layered Concrete Applicable to 3D Concrete Printing: Experimental and Numerical Investigations
    (University of Waterloo, 2026-08-20) Miri, Zahra Sadat
    Layered concrete systems are widely encountered in modern construction applications, including repair and strengthening of existing structures, precast-to-cast-in-place connections, and, more recently, 3-Dimensional Concrete Printing (3DCP). In such systems, structural performance is governed not only by the properties of the bulk material but also by the behaviour of interfaces formed between the layers. Among these applications, 3DCP has emerged as a rapidly developing construction technology in which cementitious material is deposited layer by layer to fabricate structural components without the need for conventional formwork. Although this technology offers several advantages, including reduced construction time, lower labor demand, material savings, and greater geometric freedom, several technical challenges still remain. One of the most important challenges is the formation of interfaces between adjacent filaments and successive deposited layers during the fabrication process. These interfaces act as critical weak links, degrading the hardened mechanical properties of the printed component and inducing pronounced mechanical anisotropy, in which the structural response depends on the loading direction relative to the layer orientation. Consequently, accurate characterization and modelling of interfacial behaviour are essential for the reliable structural assessment and design of layered concrete systems, especially 3D-printed components. This thesis uses destructive and non-destructive testing, along with Finite Element (FE) analysis, to characterize interfaces and investigate their influence on the mechanical response of layered concrete components fabricated with printable concrete materials. The first stage of this research investigates the flexural anisotropy of 3D-printed concrete beams using an interface-based finite element (FE) modeling approach. A Cohesive Zone Modeling (CZM) framework is used to explicitly simulate interfaces. The framework is calibrated and validated using experimental data from the literature and subsequently employed to evaluate the influence of loading direction, interface properties, and nozzle geometry on the flexural performance of 3D-printed concrete beams. The second stage of this research focuses on the experimental characterization and finite element modeling of concrete interfaces representative of those found in 3D-printed concrete. The primary objective was to determine the interface properties required for cohesive zone modeling through a comprehensive experimental program involving tensile, shear, and compression testing of monolithic and layered concrete specimens. Particular emphasis was placed on the use of Digital Image Correlation (DIC) to vi quantify interface deformation and obtain interface failure displacements, providing key input parameters for the finite element models that are difficult to measure using conventional testing techniques. The experimentally derived interface properties were subsequently incorporated into finite element models. Following validation, the modeling framework was employed to conduct a parametric study investigating the influence of the number and arrangement of interfaces on the compressive behaviour of layered concrete representative of 3D-printed concrete. The third stage of this research investigates the use of Ultrasonic Pulse Testing (UPT) combined with advanced signal-processing techniques for the non-destructive characterization of early-age interfacial bond development in layered concrete applicable to 3D-printed concrete. The primary objective was to evaluate the ability of ultrasonic parameters to identify weak interlayers and monitor changes in interface quality with curing age. To provide reference measurements and assess the influence of surface moisture on bond development, mechanical testing and ultrasonic measurements were performed on monolithic specimens and layered specimens with dry and wet interface conditions. The recorded ultrasonic signals were subsequently analysed using velocity-, attenuation-, frequency-, and time-frequency-based parameters to determine their sensitivity to weak interfaces and their potential for non-destructive assessment of interlayer bond quality. Overall, this research advances the understanding of interfacial behaviour in layered concrete systems applicable to 3DCP through the integration of experimental testing, finite element modelling, digital image correlation, and ultrasonic evaluation. The research provides validated interface-based numerical modelling approaches for investigating mechanical anisotropy, experimentally derived interface properties and failure parameters for cohesive zone modelling, and insights into the potential of ultrasonic techniques for the non-destructive assessment of early-age interlayer bond quality. Collectively, these contributions support the characterization, modelling, and quality assessment of interfaces in 3D-printed concrete and contribute toward the future development of reliable design methodologies, inspection strategies, and codification efforts for structural 3DCP.
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    "Nothing Can Make Device Sharing Feel Safer..." Privacy and Security Challenges in Collectivist Immigrant Families
    (University of Waterloo, 2026-08-20) Shanza, Shanza
    In collectivist households, sharing digital devices is both a cultural norm and often a material necessity. After migration to more individualistic cultures such as Canada, these sharing practices persist but become entangled with new cultural norms, unfamiliar institutional infrastructures, and highly digitized systems. Immigrant families must adapt to host-country digital life expectations around privacy, safety, schooling, and online services while continuing to uphold home-country norms around family values, moral and collective responsibilities. Devices, in this context become channels through which trust, supervision, autonomy, and cultural expectations are continuously managed and negotiated. To understand how this negotiation actually plays out, we report findings from a qualitative study of 18 nuclear families, comprising 19 parents and 22 children and young adults, mainly from South Asia. The study examines three intertwined questions: how migration and sociocultural factors shape the security and privacy risks that shared-device households face, how well current devices support or hinder safe sharing once those risks appear, and how can we better design these devices to support safer device sharing. Our findings show that shared-device use exposed families to data breaches, reputational harms, cultural and religious boundary violations, and intergenerational tensions. Moreover, these risks were naturally amplified to household-level concerns because one person’s online activity, account access, or device use could affect any or all other family members. We find that families often approached shared devices with different goals. Parents sought visibility and control to protect children, preserve cultural and religious values, and manage safety in an unfamiliar digital environment. Children, in contrast, sought autonomy and ways to keep parts of their digital lives separate while still participating in device sharing household practices. Families used ad hoc and reactive strategies to manage these tensions, including monitoring, informal rules, parental control tools, activity concealment, and self censorship practices like keeping devices in a “morally clean” state. However, these strategies were often fragile, easy to workaround, difficult to sustain, or abandoned when they threatened family harmony. Our findings reveal a mismatch between single-user device assumptions and collectivist immigrants’ household realities of device sharing. Current devices offer limited support for shared use that can balance parental assurance, child privacy, cultural expectations, and everyday usability. Designing for shared-device contexts is therefore essential for building more inclusive digital infrastructures that not only support multicultural families but also others who rely on device sharing. Like curb cuts designed for wheelchair users that ultimately benefit many others, designing from the marginalized can produce more inclusive technologies for everyone.