FGS - Electronic Theses and Practica

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http://hdl.handle.net/1993/6

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This collection contains University of Manitoba electronic theses and practica.

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The Faculty of Graduate Studies requires that all graduate students submit a copy of their thesis or practicum to this collection. Consult FGS Submitting your thesis or practicum to MSpace and Thesis/Practicum Deposit Step-by-Step for instructions and/or more information. Go to My MSpace to begin the submission process and, when prompted, choose the FGS - Electronic Theses and Practica collection. Unfinished or rejected submissions can be restarted by accessing My MSpace.

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Open Access
Frazil ice measurements using the four-frequency AQUAscat sonar in laboratory and field environments
(2024-04-30) Shoorangiz, Leila; Ehn, Jens (Environment and Geography); McFarlane, Vincent (University of Alberta); Clark, Shawn
This research describes laboratory experiments conducted to investigate the capability of a multifrequency Aquatec AQUAscat 1000R sonar in detecting and measuring frazil ice particles. A series of laboratory experiments were conducted at the University of Manitoba and the University of Alberta to measure the particle size and concentration of frazil ice particles using four transducers, including 0.3, 0.5, 2 and 4 MHz. Also, the AQUAscat Toolkit software was utilized to post-process the logged data using the sonar instrument. The results indicated that the 2 MHz transducer was the most sensitive to the presence of frazil ice particles, while the 0.3 MHz had the least sensitivity. The device started to detect the frazil ice particles when the maximum supercooling occurred. The concentration was determined to reach its maximum value of 0.65% and 0.45% in different setups at the University of Manitoba and the University of Alberta, respectively. The outcomes showed that the mean frazil particle size ranged from 100 to 300 µm at the University of Alberta in a supercooling event. In contrast, the findings based on experiments conducted at the University of Manitoba were unreliable due to the large number of bad cells within the particle size data. The multifrequency sonar instrument was deployed on the riverbed at Dauphin River for a one-day experiment on December 6, 2022. It was revealed that the apparatus was able to detect the frazil ice particles but not the frazil flocs and ice rafts. The results showed that the average concentration of frazil ice was 0.0066%. Although the particle size outcomes were not reliable in the first 25 cm above the transducers, the average particle size in the rest of the water column was found to be between 150 and 300 µm.
Open Access
Three essays on climate finance and international finance
(2024-05-01) Qi, Zhen; Fan, Zhenhen (Accounting and Finance); Liao, Chi (Accounting and Finance); Yuan, Wenlong (Business Administration); Shi, Jing (Zhongnan University); Lu, Lei
This thesis includes three essays. In the first essay, In the first essay, we employ machine learning techniques to predict corporate bond returns globally. Utilizing a unique dataset, we identify strong predictability in international corporate bond markets. Notably, factors influencing U.S. bond returns differ significantly from those impacting non-U.S. markets, where downside risk and illiquidity play a more prominent role. Additionally, we observe variations in the degree of bond cross-country integration and bond-stock integration, with developed markets generally exhibiting higher integration than emerging markets. The second essay investigates the impact of abnormal-temperature-related climate risk on bank loan pricing using syndicated loans from 35 countries. Our findings indicate that banks charge higher interest rates for borrowers with higher climate risk. We also find that climate risk affects loan spreads of both long-term and non-long-term loans, and this effect is more pronounced for non-long-term loans. Our cross-sectional analyses reveal that voluntary climate risk disclosures in conference calls by borrowers mitigate the impact of climate risk on loan spreads, especially when lead banks have less climate-risk-related lending experience. Furthermore, the U.S. borrowing cost for high-climate-risk borrowers decreases following SEC guidance on climate risk disclosure, while ESG disclosure requirements in 19 other countries do not alter climate risk's effect on bank loan pricing. In the third essay, we explore the influence of climate risk disclosures in earnings conference calls on analyst forecast errors and dispersion for U.S. firms. The disclosure of physical climate risk correlates with smaller forecast errors, particularly after the SEC issued guidance. However, disclosures of regulatory and opportunity shocks related to climate change show no significant impact. Subsample analyses reveal that physical climate risk disclosures enhance forecast accuracy for industries sensitive to climate change, firms in regions affected by extreme weather events, and states with stronger beliefs in climate change. Overall, our findings suggest that physical climate risk disclosures in earnings conference calls contribute to more accurate analyst forecasts.
Open Access
Investigating the role of ADORA2B receptors in pyroptosis of inflammatory macrophages through gene knockdown and overexpression
(2024-04-30) Deuna, Fatima Almira; Pascoe, Christopher (Physiology and Pathophysiology); Thompson, Peter (Physiology and Pathophysiology); da Silva, Robin
Adenosine receptors (ARs) regulate the immune response by activating pro- and anti- inflammatory cascades through mechanisms that are not completely defined. Macrophages also play a central role in the regulation of inflammation from initiation to resolution. ARs on macrophages have been shown to direct major functions including macrophage cell death. Pyroptosis is a highly immunogenic cell death induced by inflammasomes that cause cleavage of caspases and gasdermins. This process leads to the release of inflammatory cytokines Interleukin 18 (IL-18) and Interleukin -1β (IL-1β). The canonical pathway that leads to pyroptosis involves the NLRP3 (nucleotide-binding domain, leucine-rich–containing family, pyrin domain–containing-3) inflammasome, caspase-1 and gasdermin-D (GSDMD), though other pathways exist. Recently, our lab found that knocking down the Adenosine 2B (A2B) receptor renders macrophages susceptible to pyroptosis. In this thesis, we seek to confirm the role of the NLRP3 inflammasome specifically in pyroptosis observed after A2B receptor knockdown, and whether lost receptor-protein interactions promote this pathway. Results show that in A2B receptor deficient macrophages, NLRP3 inhibition was able to prevent IL-1β secretion and GSDMD cleavage. However, addition of adenosine to macrophages induced GSDMD cleavage that was not sensitive to NLRP3 inhibition. Furthermore, preliminary experiments showed that caspase-4 was activated by adenosine. Proteomic analysis was used to study receptor-protein interactions and pyroptotic proteins were identified in immunoprecipitation assays. A2B coimmunoprecipitation in epithelial cells and macrophages show that A2B receptors enrich and interact with cellular communication, calcium signaling and gap-junction proteins as well as Toll-like receptor signaling, and serine proteases. Results from proteomics and gene ontology analysis have identified possible alternative pathways through which the A2B receptor might influence macrophage pyroptosis.
Open Access
Joint beamforming optimization in RIS-aided MIMO wireless systems under mutual coupling and multiple reflections
(2024-04-25) Wijekoon, Dilki; Mezghani, Amine (Electrical and Computer Engineering); Yahampath, Pradeepa (Electrical and Computer Engineering); Hossain, Ekram
In a Reconfigurable Intelligent Surface (RIS), Mutual Coupling (MC) is unavoidable as a result of the sub-wavelength structure of its unit elements. In addition, MC inherently leads to multiple reflection effects that are ignored in conventional (approximative) RIS models. In this thesis, we examine the problem of joint active and passive beamforming in a controllable multi-user reconfigurable intelligent surface (RIS)-assisted downlink and uplink wireless communication system, considering the MC among RIS elements. We formulate a problem to optimize active and passive beamforming jointly under the MMSE criterion. Given the non-convex nature of the problem, we use alternating optimization to decompose the problem into two sub-problems for downlink and uplink transmissions separately. In both transmissions, one sub-problem involves optimizing the phase-shift matrix of RIS. In downlink, the other sub-problem is the optimization of active precoding for the base station (BS), while the equivalent sub-problem in uplink is the optimization of the linear receiver matrix. We optimize the phase shift matrix under a physically-consistent model using the gradient descent algorithm for both transmissions. We use the Lagrange multiplier method to optimize active precoding in the downlink and apply the First Order Necessary Condition (FONC) to optimize the linear receiver in the uplink. Simulation results are represented for both lossless and lossy RIS scenarios under perfect and imperfect channel state information. We discuss the impact of changing the number of RIS elements and the RIS element spacing on system performance. The results show that, with optimized phase shifts and active precoding, the inherent multiple reflection effect can improve the performance of RIS-aided wireless communications systems. In our previous analysis, we focused on optimizing joint beamforming within a physically consistent environment by incorporating MC effects. However, we did not explicitly address the optimization of MC itself. This represents a critical aspect that warrants further investigation and consideration for a comprehensive and refined analysis. As mentioned earlier, MC emerges as an inherent feature in RIS particularly with sub-wavelength inter-element spacing. Alongside, the presence of electromagnetic (EM) transmit/receive radiation patterns is also inevitable. The simultaneous presence of these two factors naturally leads to the emergence of non-local RIS structures, which can be effectively described via non-diagonal phase shift matrices. As the second analysis, we focus on optimizing MC and radiation patterns in RIS-assisted multi-user MIMO wireless communication systems. We particularly formulate a novel problem to jointly optimize active and passive beamforming as well as MC and radiation patterns in a physically consistent manner considering reflective and transmissive RIS setups separately. To characterize the physically consistent model, we deploy scattering parameters and propose a novel approach to optimize MC and radiation patterns through an offline optimization method, rather than optimizing on the fly, using two distinct solution approaches for reflective and transmissive models. We present simulation results using both parametric and geometric channel modeling approaches. Our numerical results showcase that the system performance increases with the proposed MC and radiation patterns optimization, and this improvement is achievable without the need for optimizing them on the fly, which can be rather cumbersome.
Open Access
Rationalization of the empirical design method for reinforced bridge deck slab
(2024-04-30) Kheiri, Roksana; Bakht, Baidar (Civil Engineering); Fiorillo, Graziano (Civil Engineering); Mufti, Aftab
Abstract The empirical design of reinforced concrete bridge deck slabs of girder bridges, referred to as only ‘deck slabs,’ is the most efficient design method because it recognizes the inherent arching action that exists in these slabs. Because of the arching action, the deck slabs fail in a punching shear mode under much higher wheel loads than the loads that would make them fail in bending; it is noted that failure in bending assumes the absence of the arching action. The Canadian Highway Bridge Design Code provides specifications for the empirical design of deck slabs. As the term ‘empirical design’ implies, this method is based on experimental evidence rather than analytical methods. A computer program, PUNCH, based on an analytical method, was developed to analyze the failure loads of externally restrained deck slabs, also referred to as ‘steel-free deck slabs,’ which do not contain embedded reinforcement for strength. In this program, it is assumed that the transverse confinement to deck slabs is provided by steel straps lying outside the deck slabs. Thus, this program only models the behavior of externally reinforced bridge deck slabs accurately. For internally reinforced bridge deck slabs, the stress-deformation behavior of steel in concrete is investigated in experimental evidence on concrete prisms, each with an embedded central steel bar, which has confirmed that when these prisms are subjected to tensile forces through the steel bars, the axial stiffness of the composite prisms is initially much larger than that of the bare steel bar, and decreases nonlinearly with the increase in the magnitude of tensile force. A reinforced concrete prism can thus be conceptually replaced by a hypothetical equivalent steel bar, the diameter of which is larger than that of the bare steel bar and decreases with the increase in the magnitude of the tensile force. This thesis attempts to modify the program PUNCH to analyze deck slabs with embedded steel bars by replacing the bars with hypothetical equivalent steel bars that lie outside the concrete. The first part of the research work involves the establishment of the changing equivalent diameter of the composite concrete prisms under gradually increasing tensile forces. This research was conducted through non-linear finite element analysis, the results of which were compared favorably with available experimental results. The second part of the research was first to modify the PUNCH program to include variable axial stiffness of the external restraint and then to use the modified program to analyze a large number of deck slabs with variable external stiffness represented by hypothetical steel bars of varying equivalent diameters. The accuracy of the results has been established by comparing its results with those from available experimental tests, some of which were failure tests. Predictions from the modified PUNCH have confirmed that most reinforced concrete deck slabs never fail under wheel loads of even the heaviest commercial trucks traveling on highways. The modified PUNCH program is now called PUNCH.ED, can be used with confidence for predicting not only the failure loads of deck slabs but also their load-deflection behavior under smaller; loads.

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