Recherche uO, le dépôt numérique de l'Université d'Ottawa, réunit le matériel de recherche et d'enseignement créé par notre communauté universitaire et nos partenaires. Le savoir de l'Université est ainsi disponible à long terme et en accès libre, ce qui lui procure de la visibilité et facilite sa diffusion.

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    TRACE: A Multimodal Multi-Agent System for Transparent Chest X-Ray Assistance
    (Université d'Ottawa / University of Ottawa, 2026-09-02) Wang, Zhaoyu; El Saddik, Abdulmotaleb
    Chest X-ray (CXR) AI has shown strong progress in abnormality detection, report generation, and multimodal medical reasoning, yet many existing systems remain limited as user-facing assistive tools. In particular, report-centered or text-only systems often provide limited support for evidence inspection, follow-up interaction, and cross-study continuity. This thesis presents TRACE (Transparent Radiology Assistance for Chest X-ray Explanation), a multimodal multi-agent system for transparent CXR assistance. TRACE integrates detector-supported image analysis, multimodal report drafting, report refinement, transparency-oriented interaction, consultation support, and archive-assisted comparison within a unified workflow. TRACE was evaluated from four complementary perspectives: objective report quality, transparency-supported consultation preparation, archive-assisted cross-study comparison, and subjective usability and workload. Objective report quality was assessed on a 2,000-image frontal CXR benchmark constructed from MIMIC-CXR and the Indiana University Chest X-rays dataset, using external comparisons against LLaVA-Med and the MedRAX report-generation tool as well as an internal ablation of the TRACE reporting pipeline. TRACE achieved the best overall profile across most reported semantic and label-oriented metrics, indicating that detector-supported finding integration and report refinement can improve report quality within a broader assistive workflow. Two controlled user studies and a questionnaire-based human-factors assessment were also conducted with 48 participants. The transparency-oriented interface significantly improved users' ability to identify verification-worthy report conclusions, justify why they warranted clinician verification, and formulate more specific verification-oriented consultation questions. Archive support significantly improved report-level difference identification and reduced cross-study comparison time. In addition, the full TRACE interface was associated with higher perceived usability and lower subjective workload than the text-only interface, with the largest workload reductions observed in mental demand and frustration. Overall, this thesis shows that, within the controlled benchmark and user-study settings examined here, CXR AI can provide measurable assistive value when it is designed and evaluated not only for report generation, but also for evidence inspection, verification-oriented interaction, and continuity across encounters within a unified assistive workflow. Clinical usefulness remains to be established through further validation with patients and clinicians.
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    Experimental Modeling of Ice Cover Effects on the Secondary Flow Formation in Meander Bend
    (Université d'Ottawa / University of Ottawa, 2026-09-02) Ebrahimi, Samaneh; Mohammadian, Abdolmajid; Rennie, Colin D.
    When a river surfaces freezes, the ice cover introduces a rigid upper boundary that alters flow structure. In straight reaches, this results in a two-layer system governed by shear at both the bed and the ice-water interface. In bends, the combined effects of channel curvature and the ice boundary generate counter-rotating secondary circulation cells near the bed and the ice underside. These processes remain poorly understood due to limited observations under ice-covered conditions, and because many existing models assume an idealized open-channel condition with negligible surface shear, thereby neglecting ice-induced roughness and resistance. This study investigates the mechanisms governing secondary flow in ice-covered bends, hypothesizing that the observed flow structure arises from the interaction between channel curvature and the rigid ice boundary, although the underlying dynamics are not yet fully resolved. The central focus of this thesis is advancing the understanding of how these circulation cells form and develop under varying flow and roughness conditions. The effects of flow rate, flow depth, and the ice cover surface roughness on the flow structure in a simulated ice-covered bend are systematically examined. A comprehensive set of experimental investigations was conducted using uOttawa’s laboratory bend flume, where Particle Image Velocimetry (PIV) technology was applied to capture 3D velocity components. The data was used to carry a detailed examination of flow characteristics under ice-covered conditions. These measurements provided unique insights into the spatial variations of velocity, turbulence, and secondary flow circulations in ice-covered confined channel bends where the flow displays strong three-dimensional characteristics. In particular, it was found that variations in flow rate (i.e., Froude number) distinctly influenced turbulence distribution patterns beneath the ice cover in the channel bend. As discharge decreased, the normalized mean kinetic energy increased, indicating more structured flow and greater relative turbulence at lower flow rates. Results related to increasing ice-cover roughness revealed a reduction in total secondary circulation within the ice layer, while circulation near the bed was enhanced. The three-dimensional momentum response under varying roughness conditions was also examined, revealing directional sensitivity differences: vertical and cross-stream momentum exhibited greater sensitivity to ice roughness than streamwise momentum, leading to a reshaping of the secondary vortex structure under increased roughness. The aspect ratio variation under the ice cover additionally showed a marked change in the spatial configuration and strength of secondary circulation vortices. Clear variations in the height of maximum velocity were observed along the channel, a related but distinct trend driven by local turbulence as the aspect ratio changed. Such data are rare (if not entirely absent) in existing experimental studies, especially for meander bend river channels. These findings provide new insights into the influence of ice cover on turbulent flow fields in meandering rivers and offer valuable guidance for hydraulic engineers and researchers working in cold-region water systems.
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    Temperature-Dependent Transport and Mechanical Properties of Frozen Soils: Physics-Based Parameterization and Data-Driven Modeling
    (Université d'Ottawa / University of Ottawa, 2026-09-02) Song, Xinye; Vanapalli, Sai K.; Ren, Junping
    Frozen soils behavior is governed by strongly coupled thermal, hydraulic, and mechanical processes driven by temperature-dependent phase changes and unfrozen water redistribution, which collectively control transport properties, mechanical response, and the performance of infrastructure in cold regions. Despite extensive experimental and theoretical studies, reliable determination of thermo-hydro-mechanical (THM) properties remains challenging, as experimental investigations are time-consuming, require specialized facilities, and are often prohibitively expensive. Recent advances in machine learning (ML) offer a complementary and cost-effective strategy for parameterizing frozen soil properties by utilizing existing experimental data reported in the literature. The primary objective of this thesis is to develop an integrated and scalable modeling framework for frozen soils by combining physics-based formulations with data-driven methods to predict temperature-dependent transport and mechanical properties and their coupled behavior. The first goal of this thesis is to establish a transferable predictive framework for temperature-dependent transport properties that include thermal conductivity and hydraulic conductivity. To this end, physics-informed and data-driven models are developed to capture the nonlinear dependence of transport properties on temperature, unfrozen water distribution, and pore-scale liquid connectivity across a wide range of soil textures. The results demonstrate that transport behavior in frozen soils is jointly governed by phase-change-controlled liquid distribution and pore-scale connectivity, indicating that neither thermal conductivity nor hydraulic conductivity can be uniquely characterized by unfrozen water content alone. The soil texture and pore-scale ice-water configuration play a critical role in controlling heat transfer and liquid-phase connectivity and help explain to a greater extent the observed variability of traditional models. In addition, the evolution of liquid connectivity during freezing, together with freezing pattern within pores, governs the temperature sensitivity of hydraulic conductivity, leading to markedly different hydraulic transport capacities under identical unfrozen water contents. In parallel, the second goal of this thesis is to develop a high-dimensional and generalizable data-driven framework for modeling the mechanical response of frozen soils. A hybrid modeling strategy is proposed to describe the highly nonlinear stress-strain behavior of frozen sands under varying temperature, confining pressure, and loading conditions. The results reveal that although frozen soil behavior exhibits high-dimensional characteristics, its mechanical response is strongly influenced by a limited number of key state variables, while remaining inherently path- and temperature-dependent. These findings highlight the necessity of modeling approaches that explicitly account for loading history and uncertainty to achieve robust and transferable predictions. The third and final goal of this thesis is to integrate the developed transport and mechanical models into a unified THM numerical framework for engineering-scale applications. The coupled framework enables simulation of freezing-induced processes, including freezing front evolution, ice accumulation, and soil deformation under transient thermal and hydraulic conditions. Coupled THM simulations further demonstrate that consistent parameterization of temperature-dependent transport and mechanical properties is essential for capturing the coupled evolution of thermal, hydraulic, and mechanical responses in frozen soils. In summary, this study demonstrates that accurate prediction of frozen soil behavior requires a modeling framework that explicitly represents pore-scale freezing geometry and liquid-phase connectivity, rather than relying on unfrozen water content as a sole state variable. The proposed framework provides a robust basis for coupled THM modeling of frozen soils, offering practical potential for improving the design and analysis of cold-region infrastructure while reducing reliance on time-consuming and costly experimental testing.
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    A Deployment-Oriented Evaluation of Hybrid Deep Learning and Traditional Signal Processing for Acoustic Echo Cancellation and Speech Enhancement
    (Université d'Ottawa / University of Ottawa, 2026-09-02) Charles, Aidan; Bouchard, Martin
    Acoustic Echo Cancellation (AEC) is a key component of hands-free communication systems, enabling full-duplex operation by suppressing acoustic feedback between loudspeakers and microphones. Traditional adaptive filtering-based AEC systems remain widely used due to their efficiency and robustness but are limited by residual echo, nonlinear distortions, and background noise. Although hybrid deep learning-based enhancement methods have shown strong performance, they are often evaluated using idealized front-end configurations, making it difficult to isolate their contribution in real-time systems. This thesis presents a hybrid AEC framework that combines a production-oriented frequency-domain adaptive filter with a deep learning post-filter. The proposed model is derived from a convolutional recurrent architecture and redesigned for deployment using a Complex Ratio Mask (CRM)-based enhancement strategy, a simplified decoder, and Frequency-Temporal Long Short-Term Memory (F-T-LSTM) layers for temporal modelling. An identical linear echo cancellation front-end is used for both a traditional cascaded residual echo and noise suppression pipeline and the proposed neural system, enabling a controlled comparison. Evaluation is conducted using standardized ICASSP benchmark scenarios, including near-end single-talk, far-end single-talk, and double-talk conditions. Performance is assessed using perceptual metrics for echo suppression, speech distortion, and noise reduction, while Echo Return Loss Enhancement is used to evaluate suppression dynamics. Results show that the proposed system achieves comparable echo suppression to the traditional pipeline while improving speech preservation and overall perceptual quality. It also adapts more rapidly to changing acoustic conditions, whereas the baseline exhibits slower recovery. The proposed model achieved the highest perceptual evaluation scores, including an Echo Mean Opinion Score (MOS) of 4.53, a Degradation MOS of 3.55, and an overall perceptual MOS of 3.90. The system operates with 30 ms latency and a real-time factor of 0.68, demonstrating near real-time performance suitable for deployment.
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    Advancing the Care Experience for Patients Receiving Palliative Care as They Transition from Hospital to Home (ACEPATH): A Mixed Methods Approach on Evaluating the Readiness for Hospital Discharge of Palliative Care Patients and Caregivers
    (Université d'Ottawa | University of Ottawa, 2026-09-01) Rasaputra, Prabasha; Isenberg, Sarina
    Objective: To examine the association between receipt of the ACEPATH intervention and readiness for hospital discharge, comparing readiness scores pre- and post- intervention administration, as well as integrating RHDS scores with qualitative open-text responses to better understand the “how” of the effectiveness of ACEPATH in improving readiness for hospital discharge. Methods: We conducted a single-arm pilot intervention study, where palliative care patients and their caregivers received the ACEPATH intervention in the form of a guidebook and the delivery of the guidebook by a healthcare provider. We evaluated readiness for hospital discharge using an adapted RHDS for this context, and collected reflection question responses once participants were at home. Results: 13 participants completed the RHDS before and after the ACEPATH intervention was administered, with a median overall increase from 7.20 before the intervention to 7.87 after the intervention (p=0.002). Participants also experienced increased scores among the Knowledge, Personal status, and Coping ability domains, which may be partly attributable to the intervention. Mixed-methods integration suggested that the intervention impacted participants by providing information and reassurance through the guidebook and discussions with the facilitators, although medical complexity and limited social supports constrained benefits for some participants. Conclusions: This pilot study provides preliminary evidence that the ACEPATH intervention may increase participant readiness to be discharged, with the adapted RHDS showing good internal consistency in assessing readiness. Improvements in the knowledge and coping ability domains suggest that structured information sharing, and facilitator-guided discussions may be valuable components of supporting a hospital-to-home transition.