- ItemOpen AccessSecure Smart Contract-based Computation (Verifiable computation, Fair two-party protocols, and Resource sharing)(2024-02-15) Avizheh, Sepideh; Safavi-Naini, Reihaneh; Jacobson Jr., Michael John; Henry, Ryan; Far, Behrouz; Pieprzyk, JosefA smart contract is a trusted computer program that runs on the decentralized computer that underlies a blockchain. Smart contracts are part of Web3 technology, the next generation of the Internet, and they enable distributed applications over the Internet. Smart contracts can remove intermediaries in real-world systems and have the promise of revolutionizing industries and processes in healthcare, retail, banking, government, and many more. Because of their trusted execution, smart contracts have been used as a trusted third party/referee in cryptographic protocols. They have also been used to automate processes and seamlessly incorporate cryptocurrency in payments. In this thesis, we consider the application of the smart contract as a trusted (semi-honest) third party/referee in the following problems: verifiable computation using refereed delegation of computation, fair two-party protocols that include fair private set intersection and fair exchange, and resource sharing. We show that the direct replacement of the trusted third party/referee with the smart contract can expose the protocols to new threats and attacks. We model the security of each protocol, analyze the security of the existing ones, propose new protocols that can achieve the required security guarantee in the smart contract setting, provide a proof-of-concept implementation, and evaluate their performance. Our results incorporate both secure smart contract-based cryptographic protocols and systems. We mainly propose formal models and descriptions in the real-world/ideal-world paradigm for the cryptographic protocols. We also look into the privacy in the smart contract setting. The smart contract is transparent and interactions with the smart contract are through public communication channels, thus ensuring the privacy of the parties' input and messages becomes a significant challenge in designing the protocols. We lay the foundations to define and capture privacy for a smart contract and use it to show the privacy of our cryptographic protocols.
- ItemOpen AccessStudying Network Variants With Electroencephalography(2024-02-15) McCarthy, Michael; Protzner, Andrea; Bray, Signe; Goodyear, Bradley; Pexman, PennyFunctional MRI (fMRI) studies have shown that the human functional connectome exhibits reliable and substantial variability in organization across individuals, so-called network variants. However, it is unclear whether neuroimaging modalities that measure different aspects of brain function show similar evidence of such individual differences. Here we explored the feasibility of using electroencephalography (EEG) to study network variants using repeated measures eyes-closed and eyes-open resting state data from 14 participants taken across three sessions over the course of three months—estimating how much and in which ways band-limited phase coupling and amplitude coupling functional connectomes differed in similarity within and between individuals across contexts. For each coupling mode and frequency band, we hypothesized that if functional connectome organization was influenced by stable individual- dependent factors in our sample, then functional connectomes would be more similar within than between individuals across all contexts, on average, with smaller variations in similarity related to session or state. Overall, our results were inconclusive. Although we generally found consistently positive differences in functional connectome similarity across coupling modes, frequency bands, and contexts on average—depending on the comparison, these differences were either negligible or at most small, and were inconsistent across participants. We discuss several factors that may explain the differences between our results and the larger, more consistent effects reported in fMRI network variant studies, such as the spatial and temporal resolution of EEG and fMRI, and the methods used to estimate functional connectivity. We then offer suggestions for future EEG research that might address some shortcomings of our study.
- ItemOpen AccessExamination of Shallow Structure in Geothermal Sites of Western Canada Using Microtremor Measurements: Mount Meager and Burwash Landing Case Studies(2024-02-15) Berumen Borrego, Fernando; Gilbert, Hersh Joseph; Dettmer, Jan; Eaton, David W. S.Canada has enormous geothermal potential, a sustainable alternative energy in the form of heat. Despite its significant role in moving Canada closer to net-zero CO2 goals, geothermal resource production faces numerous exploration challenges, notably the risks associated with drilling. However, with the emergence of new technologies, e.g., closed-loop systems and declining costs, geothermal energy is increasingly competing with conventional resources like coal. This thesis investigates the use of the Horizontal-to-Vertical Spectral Ratio (HVSR) method, also known as Nakamura’s method or microtremor HVSR (mHVSR), in two geothermal exploration projects. Commonly referred to as HVSR in the geophysical community, this method analyzes microtremors and is effective in determining seismic structures up to 200 meters deep at Mount Meager and 500 meters at Burwash Landing. HVSR complements other geophysical methods that focus on deeper structures and overcomes the limitations of surface geology. At Mount Meager, British Columbia, HVSR has been instrumental in identifying resonance frequencies and understanding the subsurface structure. It has revealed the variability in the shallow subsurface, aiding in the estimation of volcanic unit thicknesses and expanding upon existing geological and seismic data. This has enhanced the understanding of subsurface geology and associated risks. In Burwash Landing, Yukon Territory, where geothermal energy is crucial for local energy needs, the application of a trans-dimensional Bayesian inversion algorithm on HVSR curves has provided detailed insights into seismic structures. This method has offered accurate estimations of bedrock depth and sediment compaction, refining previous interpretations. Notably, it helped correct overestimated sediment layer thicknesses encountered during a drilling operation in November 2022. The trans-dimensional approach avoids the use of predefined models, quantifies uncertainty, and adds objectivity to interpretations. Overall, these studies highlight the importance of HVSR in geothermal exploration, especially in areas with complex topography and geology. HVSR is crucial for understanding shallow structures, assessing associated hazards, and informing studies on deeper geothermal resources. The findings significantly contribute to the understanding of seismic structures in these regions, with broader implications for global sustainability, energy self-sufficiency, and environmental objectives.
- ItemOpen AccessFault-Sketch: A Framework for Modeling Geological Faults and Displacements(2024-02-15) Banaeizadeh, Arya; Costa Sousa, Mario; Samavati, Faramarz; Costa Sousa, Mario; Samavati, Faramarz; Eaton, David; Yanushkevich, SvetlanaGeological faults, which result from rock fracturing and displacement in the subsurface, play an important role in shaping the Earth's crust. Modeling fault surfaces and their impact on rock formations is, thus, useful for various geological applications. However, due to the complex configurations of faults, the modeling process can become difficult, requiring a framework with a specialized modeling toolkit. The primary challenge in fault modeling lies in properly correlating the geometry of faults with their effects on rock layers and other fault surfaces during displacement. The final models also have to satisfy certain properties to be reusable for further geological analysis. A factor that even if users who have both modeling and geology expertise cannot guarantee to have. To address this, we have developed a series of operators designed for fault modeling. In this manner, we present Fault-Sketch, a Sketch-Based Interface and Modeling (SBIM) framework that tackles the task of fault modeling and captures their influence on various geological structures. This framework enables the creation of surfaces as a result of rock configurations that have previously been largely overlooked in the existing literature. The collection of operators presented in Fault-Sketch are built upon a data structure fit for the purpose of consistently representing fault surfaces and their boundaries together with the influence they cause both on other surfaces and on the volumes they bound. Moreover, the operators are designed to mimic the geologic processes relevant to fault creation and displacement to facilitate their use by domain experts.
- ItemOpen AccessCognitive-Executive Processes and Social Adjustment in Survivors of Pediatric Acute Lymphoblastic Leukemia(2024-02-14) McDonald, Kaelyn Anjali; Schulte, Fiona; Guilcher, Gregory; Yeates, KeithBackground: Survivors of pediatric acute lymphoblastic leukemia (ALL) have historically faced serious neurological and social difficulties as a consequence of their treatment with cranial radiation therapy (CRT). However, such difficulties are poorly understood among survivors treated with modern chemotherapy-only protocols. This study aimed to investigate cognitive-executive functioning and social adjustment, as well as factors relating to these outcomes, in this new wave of survivors as compared to survivors of pediatric non-central nervous system (CNS) solid tumours and healthy children. Methods: This cross-sectional study assessed survivors aged 8-17 and their caregivers at least two years after finishing treatment. Survivors of pediatric ALL (n=25) and non-CNS solid tumours (n=18) were recruited to the current study, and healthy children (n=33) were included from a previous study. Cognitive-executive outcome measures included the Wechsler Intelligence Scale for Children Fifth Edition (WISC-V) Working Memory Index (WMI) and Processing Speed Index (PSI), and social adjustment was measured through the Adaptive Behaviors Assessment System Third Edition (ABAS-3) Social Adaptive Domain. Group comparisons were made using Analysis of Variance (ANOVA) tests, and hierarchical regression analyses were conducted to explore potential predictors of these outcomes. Results: Survivors of pediatric ALL scored significantly worse than healthy children on the WMI (ANOVA post hoc p<.001) and a subscale of the Social Adaptive Domain (ANOVA post hoc p=.002). Survivors of pediatric non-CNS solid tumours scored significantly worse than healthy children on the WMI (ANOVA post hoc p=.028) and PSI (ANOVA post hoc p<.001). No significant differences were observed between the two survivor groups. WMI and PSI scores did not significantly predict Social Adaptive Domain scores. Conclusions: These findings highlight difficulties faced by both survivors of pediatric ALL and non-CNS solid tumours which have the potential to cause substantial, ongoing negative impacts on their lives. Future research should investigate the underlying causes of these difficulties in order to inform screening and intervention protocols aimed at improving these children’s quality of life.