UWSpace
UWSpace is the University of Waterloo’s institutional repository for the free, secure, and long-term home of research produced by faculty, students, and staff.
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Recent Submissions
From the comfort of home: Examining consumer virtual reality use in the home
(Taylor and Francis, 2025-08-12) Tawfik, Reem; Harley, Daniel
Despite the hype that has driven mass-market consumer virtual reality (VR), research relating to the at-home use of these technologies is underexplored. The contexts, responses, and experiences of people who use VR offer insight into the ways that VR is becoming a domestic technology. Applying methods drawn from digital ethnography, our research asks how participants interpret their use of VR in the home, and how they integrate it into their social, personal, and material contexts. We examine data consisting of interviews, images, and videos from participants (n = 15) across 10 countries to begin to chart the complexities of the real-world conditions of VR. Our findings show that as these participants make efforts to creatively integrate VR into their everyday routines, the enjoyment that they describe is entwined with a variety of difficulties, demonstrating that consumer VR offloads a burden of adaptation onto the people who bring these technologies into their homes.
An alternative approach to address uncertainty in hub location
(Springer Nature, 2023) Janschekowitz, Marc; Taherkhani, Gita; Alumur, Sibel A.; Nickel, Stefan
In this paper, optimization and simulation techniques are integrated to address single and multiple allocation hub network design problems under uncertainty. Using a scenario-based iterative optimization–simulation approach, four sources of uncertainty are considered: the demand to be transported within the network, the associated transportation costs as well as the fixed costs for both opening hub facilities and establishing the connections between them. Additionally, flow-dependent economies of scale on all network connections are incorporated in the simulation phase. A value of simulation measure is introduced to evaluate the performance of the methodology. The computational tests conducted on the well-known CAB dataset with varying levels of uncertainty show that the approach can result in better solutions with up to 6.6% lower cost compared to its deterministic counterpart.
The Mediating Effect of Functional Social Support in the Pathway between Memory and Depressive Symptoms: A Longitudinal Mediation Analysis of the Canadian Longitudinal Study on Aging
(University of Waterloo, 2025-09-09) Modebelu, Ifunanya
Background: Cognitive function and emotional wellbeing are essential for healthy aging. Cognitive impairment and depressive symptoms can lead to severe morbidity and mortality in aging adults. Strong, positive associations exist between memory impairment – memory is a subdomain of cognition – and depressive symptoms. Evidence also suggests one’s perceived level of functional social support (FSS) may affect the emergence of depressive symptoms in aging adults with memory impairment. However, few studies have explored whether FSS mediates the association between memory and depressive symptoms.
Methods: This research utilized an analytical sample drawn from 21,241 participants between the ages of 45 and 85 years who were enrolled in the Tracking Cohort of the Canadian Longitudinal Study on Aging (CLSA) at baseline. The thesis examined three aims: the association between memory and depressive symptoms across three time points of data (baseline, three-year follow-up, and six-year follow-up), controlling for health, lifestyle, and sociodemographic covariates; the potential mediation effect of FSS on this association; and whether moderated mediation was present by age group and sex.
Results: Overall, memory function was inversely associated with depressive symptoms (β ̂ = -0.08; 95% confidence interval [CI]: -0.11, -0.04). The indirect (mediated) effect of memory on depressive symptoms through FSS was statistically significant, though minimal (β ̂ = -0.02; 95% CI: -0.02, -0.01), and most of the effect was direct (β ̂ = -0.07; 95% CI: -0.10, -0.04). No evidence existed for statistically significant moderated mediation by age group or sex.
Contribution: This novel research suggested that functional social support may mediate the association between memory and depressive symptoms. Further research is required to advise health practitioners who deal with memory-impaired individuals as to whether interventions promoting functional social support (e.g., social prescribing) can help minimize symptoms of depression.
Investigating the Impacts of Policy Stringency on the Public Perceptions of Pandemic Policies, Sentiment Analysis of Tweets During the Second and Third COVID-19 Pandemic Waves in Ontario
(University of Waterloo, 2025-09-09) Grigg, Bailey Marie
Background: Public sentiment plays a critical role in shaping compliance and trust during public health crises. The COVID-19 pandemic was the first example of an infodemic, and the significant amount of social media data from that time period can be useful for understanding public responses and experiences throughout the pandemic. This study explores emotional responses to COVID-19 policy interventions in Ontario, Canada, using Twitter data to assess how public sentiments varied across lockdowns, mask policies, and vaccine mandates. The research aims to understand how policy stringency and a regional context influenced public attitudes throughout the pandemic.
Methods: Data from the Twitter API was collected and analysed. Tweets posted between December 1st, 2020 and June 30th, 2021 from app users in Ontario were compiled and sorted using zero-shot classification into subgroups for relevant categories – vaccine mandates, mask policies, and lockdown measures. These tweets were then analyzed using sentiment analysis and the COVID-19 Stringency Index to identify trends in the sentiments expressed on Twitter over time, considering changes in the strictness of various pandemic measures.
Results: Initial temporal analysis identified key events that led to notable sentiment changes, such as sentiment spikes following the announcement of the CERB program in March, followed by lockdown sentiments declining sharply in April after the use of the “provincial emergency brake”. Lockdown sentiments remained consistently neutral to negative, with no significant threshold effects or time-based recovery. Vaccine mandates showed a positive shift in sentiment beyond identified stringency breakpoints, with further improvement over time. Mask mandates initially received positive sentiments but declined sharply after passing a stringency threshold. Ottawa Twitter users expressed more positive and emotionally reactive sentiment than Toronto users, particularly in response to lockdown and vaccine policies.
Conclusion: Social media data offers valuable insight into public sentiment dynamics during health emergencies. Findings suggest that policy framing and perceived intrusiveness significantly influence emotional responses, with vaccine mandates benefiting from proactive messaging and civic framing. Regional differences underscore the importance of localized communication strategies. These results can inform future public health interventions by emphasizing the role of timing, tone, and threshold sensitivity in shaping public trust and engagement.
Dry Extraction of Nickel from Mixed-Hydroxide Precipitates via Reduction and Carbonylation
(University of Waterloo, 2025-09-09) Dave, Param
The global transition towards electric vehicles (EVs) has prompted significant research into the sustainable and efficient production of battery-grade materials. Among the critical components of rechargeable batteries, nickel (Ni) is of particular importance due to its central role in cathode materials, specifically for Nickel Manganese Cobalt (NMC) and Nickel Cobalt Aluminum (NCA) batteries. Ni is conventionally extracted from primary sources such as laterite ores (containing 2-3% Ni by mass) through hydrometallurgy (with acid-intensive processing) or pyrometallurgy (with high-temperature, energy-intensive processing). Hydrometallurgical extraction produces an intermediate product called mixed-hydroxide precipitate (MHP), which can contain up to 50% Ni by mass on a dry basis, but still requires further processing to obtain high-purity nickel. This study explores an alternative, sustainable and selective extraction pathway for nickel from MHPs derived from laterite ores and spent battery materials (black mass). The explored vapour metallurgical approach is a two-step, dry process: 1) hydrogen reduction of nickel hydroxides with the MHP to metallic nickel at temperatures between 400°C to 500°C, and 2) selective nickel extraction via carbonylation and conditions of 100°C to 120°C and 150 psig to 450 psig. The carbonylation of metallic Ni using carbon monoxide (CO) produces a volatile molecule called nickel tetracarbonyl (Ni(CO)4), which selectively extracts Ni into the vapour phase. Rigorous safety protocols were employed in this research study to handle the toxic nature of the produced Ni(CO)4 molecules, including CO detectors to identify leaks, and an in-situ decomposition furnace downstream of the reactor to thermally decompose the carbonyls. Reduction and subsequent carbonylation experiments were conducted in a pressurized thermogravimetric analyzer (PTGA), allowing for real-time monitoring of mass changes associated with the reactions. Characterization techniques, including Fourier Transform Infrared (FTIR) spectroscopy, inductively coupled plasma–optical emission spectroscopy (ICP-OES), and Brunauer-Emmett-Teller (BET) analysis, were used to quantify Ni extraction, evaluate morphological changes from fresh samples to reaction residue, and confirm the formation of Ni(CO)4. Significant results demonstrated that the Ni extraction via carbonylation is strongly dependent on the precursor’s structural properties, specifically requiring high surface areas, adequate pore sizes, and minimal cobalt content to enhance transport of CO and Ni(CO)4. Optimal reduction conditions were identified at 450°C, producing residues with a balanced surface area and average pore size, favourable for the carbonylation reaction. Increased carbonylation pressure, at 450 psig, improved Ni extraction efficiency to 95% for a black mass-based MHP.