Lakehead University Knowledge Commons

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A single-phase H-type five-level Current Source Inverter
(2026) Zhou, Zhiming; Wei, Qiang
Current Source Inverters (CSIs) have drawn growing attention in modern energy conversion systems due to their inherent voltage-boosting capability, reliable short-circuit protection, and smooth output current profiles. This dissertation investigates single-phase multilevel CSIs and systematically reviews the evolution of three-level, five-level, and seven-level topologies. The advantages and limitations of different five-level CSI configurations are further analyzed, and the trade-off between output current quality, circuit complexity, and efficiency indicates that the five-level CSI provides a suitable balance for practical applications. However, conventional five-level CSIs suffer from dc current imbalance, which necessitates complicated active balancing control schemes. Although a recently developed single-phase X-type five-level CSI successfully achieves inherent current balancing without complex external controllers, it requires significantly large DC inductors, which inevitably leads to increased system volume, higher manufacturing costs, and degraded efficiency. To overcome these limitations, this dissertation presents a novel single-phase H-type five-level CSI. The proposed topology retains the self-balancing capability for inductor currents while significantly reducing the required DC inductance across its full operating range. The operating principle, modulation scheme, passive component design, inductor current self-balancing, switch voltage stresses, and power losses of the proposed inverter are investigated. A comparative analysis is performed between the proposed H-type and X-type five-level CSIs in terms of required dc inductance, peak voltage of switches, semiconductor device count, and efficiency. Finally, the performance of the proposed inverter is verified through MATLAB/Simulink simulations and lab-scale experiments.
Forest harvesting generates attractive breeding habitat for male Eastern Gray Treefrogs (Dryophytes versicolor) at their poleward range edge
(2026) Sim, Abby; Algar, Adam; Dey, Cody; Lee-Yaw, Julie
Climate change and anthropogenic disturbance are changing many species' ranges. Anthropogenic habitat modification typically restricts species ranges, but at poleward range edges it could create warmer microclimates that offset marginal climatic conditions. I hypothesized that clearcutting is creating warmer, more favourable breeding habitat at the expanding, poleward range edge of the Eastern Gray Treefrog (Dryophytes versicolor). Using an autodetection tool and passive acoustic monitoring, I found higher calling activity at recently clearcut ponds compared to forested ponds. Structural equation modelling revealed significant direct effects of warmer air and pond surface temperatures on calling activity. Reduced canopy cover, leading to higher pond surface temperatures, were the key mediators between harvesting and increased calling activity. Clearcut ponds were 1.9±0.5 degrees warmer than forested ponds during the breeding season, which could facilitate faster tadpole development. However, I found no difference in tadpole food resources (periphyton production) between clearcut and forested ponds. These findings demonstrate how microclimate and anthropogenic disturbance influence breeding habitat at a poleward range edge. However, we still require crucial information on pond preference of females, tadpole development, and juvenile survival as a measure of fitness, and to determine whether anthropogenic habitat modification is facilitating this range expansion.
Efficient deep learning frameworks for LiDAR point cloud analysis: from classification to 3D object detection
(2026) Rahman, Fahim Ur; Akilan, Thangarajah; Yassine, Abdulsalam; Deng, Yong; Alkhateeb, Abedalrhman; Zhou, Yushi
Reliable three-dimensional (3D) perception from Light Detection and Ranging (LiDAR) point clouds is essential for autonomous driving, where vehicles must recognize and localize traffic participants from sparse, irregular, and range-dependent point returns to plan and act safely. Existing methods struggle to meet this need efficiently: many high-accuracy classifiers and detectors rely on heavy transformers or deep attention stacks that are poorly matched to real-time or resource-constrained deployment, pillar-based Bird’s-Eye-View (BEV) detectors apply a uniform receptive field regardless of local point density—so sparse, far-range objects receive no more context than dense, near-range ones—and single-resolution BEV grids force a trade-off in which fine cells preserve localization precision but lack scene context, while coarse cells capture context but destroy sub-meter precision in the process. This thesis addresses these limitations through a phased research built around a single key idea: adaptive gating and multi-resolution fusion, rather than uniformly heavier computation to let LiDAR perception be both accurate and efficient. In the first phase, SiGF-Net performs point cloud object classification using a dual-stream architecture in which semantic-derived sigmoid gating adaptively fuses multi-scale geometric features with semantic context (Chapter 3). In the second phase, AG-DPE extends this principle to scene-level LiDAR 3D object detection, using a lightweight density estimator to guide continuous gating across fine, mid, and coarse BEV scales and to condition attention on local point sparsity within a pillar-based pipeline (Chapter 4). In the third phase, DPCA-Net resolves the single-grid detail–context trade-off by encoding each LiDAR sweep into complementary fine and coarse BEV grids and fusing them through bidirectional cross-stream attention at mid-level, followed by semantic-gated injection (Chapter 5). Experiments on standard benchmarks validate each phase. SiGF-Net reaches 94.17% accuracy on ModelNet40 and 81.49% on ScanObjectNN with only 0.15M parameters and 0.52 GFLOPs, giving an efficiency score of 9.56 that exceeds competing methods. AG-DPE improves KITTI validation mAP over a PointPillars baseline from 63.05% to 66.53% on 3D and from 64.08% to 68.81% on BEV with only 24.5K additional parameters (+0.5%), and remains competitive on nuScenes with 0.696 mAP / 0.737 NDS and Waymo with 0.8320 AP/L2 / 0.8170 APH/L2. DPCANet achieves the highest overall Moderate mAP among compared methods on the KITTI validation set holding 75.58% 3D, 73.26% BEV, +11.33 over PointPillars, with the largest gains on Pedestrian and Cyclist, and remains competitive on the Waymo while scoring 88.05 AP L1 / 82.52 APH L2 and nuScenes by 70.0% mAP / 73.9 NDS test leaderboards. Collectively, these results demonstrate that explicit density- and context-aware gating provides an effective, generalizable alternative to uniformly heavy architectures for LiDAR perception, delivering competitive or state-of-the-art accuracy from object-level classification through scene-level 3D detection while remaining efficient enough.
The reliability of ultrasound assessment of muscle mass in end-stage renal disease patients receiving hemodialysis
(2026) Adri, Delight; Sanzo, Paolo; Zerpa, Carlos; Freill, Holly
Introduction: Muscle wasting is a major complication of end-stage renal disease (ESRD) particularly for patients undergoing hemodialysis. Muscle wasting is associated with morbidity, increased hospitalization, and mortality in ESRD patients. With the increasing prevalence of ESRD disease, it is important to routinely assess and monitor changes in muscle size to guide interventions and monitor disease progression in this population. Ultrasound is a reliable tool for muscle thickness assessment, however, its routine application in ESRD population undergoing hemodialysis is limited by the higher rate lower limb amputation. This often makes the rectus femoris muscle, which is commonly used as a surrogate for overall muscle mass inaccessible. Therefore, there was a need to explore different muscle sites for potential ultrasound muscle thickness assessment in this population. This study aimed to explore upper limb muscles including the biceps brachii and the triceps brachii muscles as potential and reliable alternative ultrasound muscle thickness assessment sites to the rectus femoris muscle and further explore the perception of healthcare professionals and patients on the integration of ultrasound assessment of muscle thickness into routine renal care. Methods: This study was a convergent parallel design. The quantitative aspect was a longitudinal design with 50 ESRD patients (30 males and 20 females) recruited for baseline ultrasound muscle thickness measurement with recruited patients reducing to 45 (27 males and 18 females) at 3 months follow up measurements. Muscle thickness, measured in centimeters (cm) of the rectus femoris muscle, biceps brachii muscle, and triceps brachii muscle A and B were performed by two dietitians. Measurements were performed during patients’ hemodialysis session by the first dietitian and immediately by the second dietitian blinded to the results of the first rater. Interclass correlation coefficient (ICC) was conducted to assess the inter-rater reliability of ultrasound-derived muscle thickness between the raters (dietitians) across timepoint. Pearson’s correlation and Spearman’s correlation were conducted to assess the association between the thickness of the rectus femoris muscle and the biceps brachii muscle thickness and the triceps brachii muscle A and B thickness. The qualitative aspect was conducted through a semi-structured interview. Nine participants (three dietitians, two nurses, a nephrologist, and three patients) were recruited and interviewed with guided interview scripts. Interviews were analysed using the Braun and Clarke (2006) approach to thematic analysis. Results: At baseline, inter-rater reliability of rectus femoris muscle thickness was excellent (ICC (2,1)=.91, 95% CI [.83, .96], n=33), good for biceps brachii muscle thickness (ICC (2,1)=.87, 95% CI [.76, .93], n=38), moderate for triceps brachii muscle A thickness (ICC (2,1)=.53, 95% CI [.27, .73], n=38), and moderate for triceps brachii muscle B thickness (ICC (2,1)=.66, 95% CI [.44, .81], n=38). At 3 months, the biceps brachii muscle thickness retained good inter-rater reliability (ICC (2,1)=.84, 95% CI [.68, .92], n=30), and the rectus femoris muscle thickness declined to good inter-rater reliability (ICC (2,1)=.75, 95% CI [.27, .91], n=21). Both triceps brachii muscle A thickness and triceps brachii muscle B thickness declined to poor inter-rater reliability (ICC (2,1)=.32, 95% CI [-.02, .60], n=30); and (ICC =.41, 95% CI [.05, .67], n=30) respectively. There was a moderate, positive, and significant association between the rectus femoris muscle and the biceps brachii muscle thickness for rater 1 at baseline (r=.44, 95% CI [.16, .66], n=42, p=.004), at 3 months (ρ=.42, 95% CI [.10, .67], n=36, p=.01). There was a moderate, positive, and significant association between the rectus femoris muscle and the biceps brachii muscle thickness for rater 2 (r=.53, 95% CI [.12, .77], n=22, p=.01) and triceps brachii muscle B thickness (r =.45, 95% CI [-.06, .67], n=22, p=.04) at 3 months. The themes identified in the interviews included (1) current assessment of muscle status, (2) ultrasound as a valuable clinical instrument, (3) competency, (4) application of ultrasound in hemodialysis care, (5) patients’ experience and acceptance, and (6) ultrasound data as potential motivational evidence. Conclusion: The biceps brachii muscle is a potential alternative muscle site for muscle thickness assessment but future validation with gold standard criterion is warranted for the hemodialysis population. Also, healthcare professionals and patients are receptive to the integration of ultrasound muscle thickness assessment into routine care as they perceive it to improve education, communication, and motivation.
Exploring pathways to blue justice: the theory and practice of blue justice in the St. Marys River Area of Concern
(2026) Hambleton, Julia; Levkoe, Charles; Lowitt, Kristen; Nguyen, Vivian
Unchecked growth of marine-based economies risks increasing displacement of coastal peoples, environmental degradation, loss of livelihood and access to marine resources, and exclusion from decision-making and governance. In response, blue justice is an organizing framework rooted in social and environmental justice that recognizes the meaningful involvement and fair treatment of small-scale fisheries and allied coastal groups in how marine resources are used, managed and enjoyed. The scholarship and practice of blue justice, while established in ocean fisheries, is underdeveloped in freshwater fisheries. This study applies the theory and practice of blue justice to the Lake Superior watershed through a case study of the St. Marys River, a 125 km connecting river situated between Lake Superior and Lake Huron by way of several different channels currently listed as a Great Lakes Area of Concern. Included in this study is a literature review and data collected through semi-structured interviews with key stakeholders and rights holders in the St. Marys River using a blue justice framework that highlights three analytical areas - recognitional, procedural and distributive justices. Findings reveal challenges that constrain social and environmental health in this Area of Concern and inform actions towards more equitable and sustainable decision-making. This research contributes to blue justice scholarship and offers a potential model for further exploration of blue justice in the Great Lakes basin.