FGS - Electronic Theses and Practica
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This collection contains University of Manitoba electronic theses and practica.
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- ItemOpen AccessAn improved Cox proportional hazards model for reliability analysis of aviation gas turbines considering varying environmental conditions and operational settings(2025-02-18) Cui, Bo; Wang, Jay (Mechanical Engineering); Chen, Yuejian (Mechanical Engineering); Liang, XihuiAviation gas turbines are critical components in the aerospace industry, where reliability directly influences maintenance costs, operational efficiency, and safety. The Cox proportional hazards model (Cox model) is crucial in reliability analysis, traditionally employed to evaluate the impact of multiple covariates on the likelihood of failure. However, its application in aviation gas turbines has revealed limitations, particularly when working conditions and gas path parameters are used as direct covariates. These factors, while relevant, often fail to fully capture the degradation process due to their sensitivity to varying working conditions. In recent years, the integration of machine learning techniques with the Cox model has gained traction, offering a potential pathway to enhance the accuracy of reliability predictions. Despite this progress, existing approaches still predominantly rely on direct covariates that may not accurately reflect the underlying degradation of gas turbines. This thesis proposes a novel method that leverages machine learning to generate new, more robust covariates for the Cox model. By first modeling a healthy gas turbine, the method produces covariates that are less influenced by the variability in working conditions, leading to a more precise representation of turbine degradation over time. The thesis explores the theoretical foundations of this approach, detailing how machine learning algorithms can be employed to model a healthy gas turbine and subsequently generate new covariates that better align with the actual degradation process. This method addresses the inherent limitations of conventional covariates, providing a more comprehensive method for reliability analysis under varying operational scenarios. The effectiveness of the proposed method is validated through extensive experiments using the NASA C-MAPSS dataset, which includes data from turbofan engines operating under diverse conditions. Comparative analysis demonstrates that the improved Cox model, enhanced with machine learning-derived covariates, offers better accuracy in predicting gas turbine reliability compared to the traditional model. The results demonstrate the potential of this approach to significantly improve reliability assessments in the aerospace industry, ultimately contributing to safer and more efficient operations. This research not only advances the application of the Cox model in the context of aviation gas turbines but also opens new avenues for integrating machine learning to generate new covariates with traditional reliability analysis techniques. The findings have broader implications for the aerospace industry and could inform future developments in turbine maintenance strategies and operational practices.
- ItemEmbargoAssessment of the effect of smoke on discharge characteristics of air in positive and negative dc electric fields(2025-02-19) Ediriweera, Edirimuni Gevindu Pramod; Filizadeh, Shaahin (Electrical and Computer Engineering); Fernando, Namal (Electrical and Computer Engineering); Kordi, Behzad; Rajapakse, AthulaHVdc transmission lines extend over extensive landscapes, such as forests, prairies, and grasslands. The risk of wildfires has increased in these terrains due to the presence of combustible vegetation. One of the main issues associated with wildfires is the massive amount of smoke that typically spreads across thousands of square kilometers away from the wildfire area. Wildfire smoke is primarily composed of fine particulate matter (PM), with particle sizes dominated by PM2.5 (particulate diameter ≤ 2.5 μm) and/or PM10 (particulate diameter ≤ 10 μm). These particles can become charged and participate in gas discharge mechanisms under the high electric field around conductors of HVdc transmission lines. This thesis presents an experimental study conducted to evaluate the impact of smoke on corona discharge and breakdown characteristics of air under negative and positive dc voltage. An experimental setup in which test electrodes are placed inside a chamber, where the smoke density can be maintained at a desired level, is developed enabling the investigation of corona discharges and breakdown voltage under positive and negative dc voltages. Experiments on negative dc corona with various levels of smoke were conducted employing a needle-plane electrode configuration. The variation of characteristics of negative dc corona, with different levels of smoke in PM2.5 ranging from 0 to 6000 μg/m3) were determined and compared. It was concluded that the impact of smoke on the negative dc corona is negligible. Similarly, the effect of smoke on positive dc corona characteristics was also investigated. There is a greater particle deposition on the ground plane of the needle-plane electrode setup, caused by the positive dc corona. It was noticed that this particle deposition causes the termination of corona discharges. The particles introduced by smoke acts as a barrier to the generation of corona discharges under positive dc voltages. Additionally, the variations in the breakdown characteristics of air under various levels of smoke for positive and negative dc voltages were investigated. It was concluded that there is no significant effect of smoke on the breakdown voltage of air in a uniform electric field for the smoke density levels considered in this study.
- ItemOpen AccessExploring the essential elements of meaningful public participation in next generation impact assessment: the Colombian context(2025-02-17) Bayuelo Gonzalez, Mario Enrique; Mignone, Javier (Community Health Sciences); Stephen, Johny (Environment and Geography); Sinclair, JohnThe research explored the essential elements of meaningful public participation in next generation impact assessment (NGIA), in relation to the Colombian Environmental Impact Assessment (EIA) process. The goals of the research were to test and inform these elements further and identify approaches to achieving more meaningful public participation in Colombian EIAs. Qualitative methods were used in the research, with data collection including a document review and semi-structured one-on-one interviews with EIA participants in Colombia. Data showed that public participation in Colombian EIA is framed by laws and guidelines, especially Law 99 of 1993 and Decree 2076 of 2015. Guidelines require project proponents to conduct thematic sessions with communities covering preliminary information about the project, impact assessment and management measures workshops, and a presentation of results. Additional mechanisms for public participation include public environmental hearings, the intervening third party, and the right to petition. These practices are common ways for the public to participate in the EIA process in Colombia. Interview participants indicated that the strengths of this process include access to information, legislation and guidelines, and increasing community interest. Challenges include access to education, transparency issues, political violence, armed conflict, and infrastructure deficits in rural areas. These challenges hinder effective participation and lead to power imbalances and conflicts. Exploring the 10 essential elements of meaningful public participation in this context indicated that implementing these elements could enhance the public participation process in EIAs in Colombia – particularly early and ongoing participation, fair and open participation, and learning-oriented approaches. Overcoming challenges such as illiteracy in some communities, conflicts of interest, and public infrastructure deficits in rural areas is, however, also fundamental for achieving more meaningful public participation in the Colombian context.
- ItemOpen AccessTransnational circuits of precarity: a qualitative examination of temporary worker wellbeing in Manitoba(2025-02-11) Huynh, Anthony; Chase, Robert (Community Health Sciences); Varley, Emma (Community Health Sciences); Sethi, Bharati (Trent University); Marcelino, Diwa (Migrante Manitoba); Lorway, Robert; Hatala, AndrewABSTRACT Background In western Canada, Manitoba is a critical hub for a large population of migrant workers. Usually with limited English or French language ability and possessing limited rights and protections under the current TFWP, Temporary foreign workers (TFWs) are often tied to a single employer, leaving them vulnerable to employer abuse and the under-reporting of workplace injuries and illnesses due to the threat of deportation. Within the context of the COVID-19 pandemic, when my dissertation research began, the many cases seen among TFWs in Manitoba raises additional important public health questions on the health and wellbeing of migrant workers in Manitoba that I discuss in this dissertation. Methodology In close collaboration with Migrante Manitoba (MB), I conducted a qualitative study to explore the precarious lives of migrant workers during the COVID-19 pandemic. I virtually interviewed 20 migrant workers who entered Canada through the TFWP, employed either as seasonal agricultural workers (n=7) or TFWs (n=13). Thirteen TFWs came from Philippines and seven farmworkers from Mexico (n=6) and Jamaica (n=1). Theoretical contribution I developed the notion of transnational circuits of precarity to understand the multiple temporal-spatial layers of precarity that migrant workers encounter along their journeys to Manitoba. This multivalent concept is comprised of the following interconnected pieces: 1) a broader political economic “force-field” that compels the movement of human labour resources from the global South to the global North; 2) the rigid and regulated pathway put in place to ensure workers arrival at their work destinations; 3) the process of making “model minorities” through training programs that ensure the “smooth” transition of workers in their host country; and 4) the affective economy that is fueled by workers’ hopes, dreams, and desires. All together, these seemingly disparate processes articulate to produce complex temporal and spatial realities that shape the precarious trajectories of migrant workers. Such a paradigm shift away from the narrow temporal and spatial limits of a focus on “occupational health hazards” will be critical if workers are to realize any meaningful and substantive changes to their overall physical and mental well-being.
- ItemOpen AccessOptimization of in vitro RNA interference assays to reduce variability in target gene knockdown in the phytopathogen Sclerotinia sclerotiorum(2025-01-16) Fatema, Reemana; Gerstein, Aleeza (Microbiology); Marcus, Jeffrey (Biological Sciences); Whyard, SteveSclerotinia sclerotiorum is a broad host range fungal phytopathogen that is the causal agent of Sclerotinia stem rot in many crop plants, causing devastating yield losses worldwide. Sclerotinia is partially controlled using broad-spectrum chemical fungicides, but new, more species-specific fungicides, such as double-stranded RNAs, are being considered as safer alternatives. This study evaluated the effectiveness of long double-stranded RNAs (dsRNAs) and paperclip RNAs (pcRNAs) to induce gene silencing in two different fungal inoculants of S. sclerotiorum. The three different genes that were targeted in this study, SS1G_01703, SS1G_00005, SS1G_14116, are all involved in different aspects of S. sclerotiorum’s infection process i.e. pathogenicity, encoding 60S ribosomal unit and mycelial growth respectively. Initial dsRNA experiments using small fungal plugs collected from solid media generally resulted in highly variable levels of transcript knockdown, potentially arising from unequal hyphal amounts in treatment tubes. This led to the development of fungal slurries as the inoculum to provide a more uniform distribution of hyphae across all the samples. The slurry method resulted in significant transcript knockdowns using all three long dsRNAs at different doses, although some variability persisted. The variability using the slurry method was linked to potential differences in hyphal developmental stages, age of hyphae and differences in expression levels of each target gene. In contrast, structurally different and shorter in length pcRNAs failed to induce consistent transcript knockdown in both plug and slurry assays, despite earlier reports of their efficacy in reducing lesion sizes on canola leaves. This inefficacy may stem from pcRNAs' reliance on a single siRNA for gene targeting, potentially insufficient to overcome the structural complexity of target mRNAs. These findings highlighted the potential of long dsRNAs for gene knockdown in S. sclerotiorum using optimized slurry-based assays, while suggesting that pcRNAs require further modifications. Future work can explore alternative siRNA designs, increased pcRNA doses, and identifying accessible mRNA regions to improve knockdown efficiency. Additionally, optimizing the methods to assess hyphal developmental stages and minimizing variability during sample preparation are crucial for reproducibility and accuracy in RNAi-based studies.