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Recent Submissions
Exploring the use of the RCRA equation as an MSD risk assessment tool to evaluate electrical harness installation tasks.
(University of Waterloo, 2025-08-29) Nestor, Hailey Michelle
Intro: Electrical wire harnessing on an automotive line consists of routing a harness through a car’s engine, securing electrical connections, and successfully securing retention clips to keep the harness in place. The wire harnessing task is complex in nature and installation involves many hand forces and repetitive motions. Additionally, wire harnessing is highly repetitive, with workers having to install up to 500 engine harnesses per shift. Anecdotal evidence is emerging that some wiring harnessing work can lead to workplace musculoskeletal disorders of the hand and wrist. Due to the complex nature of the task, and difficultly in measuring internal exposures in-field by using tools such as electromyography, there is a lack of quantification and analysis of biomechanical demands of the task. The Recommended Cumulative Rest Allowance (RCRA) tool, developed by Potvin & Gibson (2016), aims to characterize exposures by assessing isolated subtasks in conjunction with other subtasks to assess the risk of a complete job. The RCRA is informed by percent efforts (%Efforts) that can vary and result in different outcomes based on inputs. Thus, there is a need to quantify and analyze biomechanical demands of wire harnessing using both high-fidelity in-laboratory equipment and potential lower-fidelity in- field equipment to compare and validate a cumulative tool to be used on the line. This study aimed to evaluate the usability of the RCRA tool for estimating required rest necessary to prevent undue fatigue during harness installation.
Methods: Using a mock-engine setup in a controlled laboratory environment, 26 participants completed repeated installations of two harness types while surface electromyography (EMG) and force data were collected for wrist flexors, extensors, and applied hand force. RCRA ratios were calculated across subtasks and input types including muscle activity as a percent of maximum voluntary contraction of the wrist flexors and extensors and applied force as a percent maximum voluntary force to assess fatigue accumulation.
Results: Findings revealed that input selection significantly influenced RCRA outputs, with applied force and wrist flexor EMG producing consistent and interpretable estimates of required rest allowances. In contrast, peak wrist extensor inputs often resulted in unrealistically high RCRA ratios due to the extensor muscle’s sustained activation patterns and the equation’s sensitivity to frequency and duration. No significant differences were found between the two harness types, likely due to their similar physical characteristics.
Conclusion: Overall, this study supports that the RCRA tool yields similar outputs when driven with peak force or peak wrist flexor EMG, but not when driven with peak extensor EMG. It also underlines the need for careful input selection and complementary assessment strategies when evaluating different muscles. These insights provide a foundation for developing validated, in-field fatigue assessment protocols to help prevent overuse injuries in automotive manufacturing.
The Effects of Partisan Political Stripe on Provincial Labour Policy Orientation in Canada
(University of Waterloo, 2025-08-29) Cesnik, Clare
This paper aims to answer the question of how partisan political stripe affects provincial labour policy. It does so by examining labour policy legislation passed from 1997 to 2024 in British Columbia and Saskatchewan. These cases were chosen on the basis of differences in the partisan stripe of their governing parties both across the two cases and over time within each. Over the period of study, British Columbia transitioned from right-wing governments with labour-negative policy to left-wing governments with labour-positive policy. Saskatchewan instead began with left-wing governments with labour-positive policy, while right-wing governments with labour-negative policy followed.
If parties adhere to different ideological orientations regarding labour policy, one should expect differences in labour policy orientation under governments of different partisan political stripes. If these policy differences are significant, they should manifest themselves in differences in unionization rates. However, as provincial governments are both regulators of collective union bargaining and employers themselves, it seems crucial to examine their behaviour in both roles and to consider unionization rates in both the public and private sectors.
Unionization rates in each province, as an indicator of labour power, have varied in the public sector, but consistently decreased in the private sector, providing an example of the effects of change in labour policy orientation. These patterns can be connected to those of government party. However, the conclusion speculates that this effect is limited in the private sector realm given similarities in the patterns of private sector unionization rates in both provinces over time which might be explained by the adherence of both left- and right-wing provincial governments in their roles as labour policymakers to neoliberal economic principles following a belief in the efficacy of the free market which is distinctive from their behaviour in their roles as public sector employers where partisan political stripe does seem to correspond to distinctive policy approaches.
Efficient Algorithm with No-Regret Bound for Sleeping Expert Problem
(University of Waterloo, 2025-08-29) Lin, Junhao
The sleeping experts problem is a variant of decision-theoretic online learning (DTOL)
where the set of available experts may change over time. In this thesis, we study a special
case of the sleeping experts problem with constraints on how the set of available experts can
change. The benchmark we use is ranking regret, which is a common benchmark used in
sleeping experts problem. Previous research shows that achieving sub-linear ranking regret
bound in the general sleeping experts problem is NP-hard, so we relax the sleeping experts
problem by imposing constraints on how the set of available experts may change. Under
those constraints, we present an efficient algorithm which achieves a sub-linear ranking
regret bound.
Looking Back or Looking Ahead: Metamotivational Beliefs About Progress Framing in Goal Pursuit
(University of Waterloo, 2025-08-29) Ross, Jessica
We are often told that if we keep our eyes on the prize, we will achieve our goals. However, research on the dynamics of self-regulation has established that whether it helps to focus on the starting line or the finish line depends on how committed people are to their goals: if commitment is strong, focusing on remaining progress (“to-go” information) is more motivating, whereas if commitment is weak, focusing on accumulated progress (“to-date” information) is more motivating. Yet research has not systematically examined whether people recognize and leverage these progress framing strategies based on their commitment strength. Across seven studies (N = 2,792), I applied a metamotivational approach to examine the nature and normative accuracy of people’s beliefs about progress framing and whether these beliefs manifest in or are related to behavioural and self-regulatory outcomes. Studies 1 and 2 found that people’s beliefs about progress framing aligned with normative effects observed in the literature on average, though with substantial variability. Studies 3-5 explored whether beliefs manifest in consequential choices. Study 3 found that people made differential progress framing choices as a function of their own commitment levels for personal goals. However, Studies 4 and 5 failed to replicate this pattern when commitment was experimentally manipulated in lab contexts or when making recommendations for others. Studies 6 and 7 investigated links between beliefs and outcomes, finding no relationship with goal progress (Studies 6 and 7) or life satisfaction (Study 6), though more normatively accurate beliefs were associated with experiencing less distress and difficulty during goal pursuit (Study 7). These findings demonstrate that while people possess a nuanced understanding of progress framing strategies, translating this knowledge into improved self-regulatory outcomes remains complex. By examining the nature and implications of people’s progress framing beliefs, this research offers novel contributions to the field of motivation science with valuable insights for goal pursuit and motivation regulation.
Additive engineering and interface engineering for high-quality perovskite films toward efficient and stable perovskite solar cells
(University of Waterloo, 2025-08-29) Chen, Qiaoyun
Perovskite solar cells (Pero-SCs) have emerged as one of the research hotspots due to the rapidly increasing power conversion efficiency (PCE) from 3.8% to 27.3%, a simple and environmentally friendly preparation process and great commercialization potential. Despite significant progress, Pero-SCs still face considerable challenges in achieving commercialization, particularly in further enhancing their efficiency and long-term stability. Perovskite layers play critical roles in determining device performance, governing exciton absorption, charge transport and recombination dynamics, and overall device stability. However, during the fabrication of perovskite layers, it is challenging to completely suppress the formation of defects and non-radiative recombination centers, which significantly impact charge carrier dynamics. Moreover, the inherent soft-lattice nature of perovskite materials renders them highly sensitive to environmental factors, accelerating degradation and ultimately compromising device performance and long-term stability. To obtain stable high-quality perovskites, additive engineering has emerged as a highly effective strategy. Furthermore, the growth substrates underlying the perovskite layers play a critical role in governing perovskite crystallization kinetics and film morphology, such that interface engineering is also receiving significant attention. Among various modification materials, inorganic compounds are widely adopted due to their superior stability and semiconducting properties, zwitterionic molecules offer additional advantages owing to their multifunctional groups, and perovskite A-site cation halides can facilitate structural modulation of the perovskite lattice. Consequently, these three categories of additives have been investigated for performance enhancement in Pero-SCs. In this thesis, inorganic copper sulfide (CuS) nanomaterials, the zwitterionic molecule soybean lecithin (SL), guanidium iodide (GAI) and cesium iodide (CsI) are selected as additives for the hole transport layer or perovskite layers to improve the PCE and stability. The research is presented as four studies：
1) Although poly[bis(4-phenyl) (2,4,6-trimethylphenyl) amine] (PTAA) is a widely used hole transport layer (HTL) in Pero-SCs, its poor conductivity and the mismatched energy levels between PTAA and formamidinium-based perovskites increase interfacial carrier recombination and charge-transport resistance. To solve these problems, inorganic CuS nanosheets were synthesized and applied as additives in PTAA for the first time. After the addition of CuS, the conductivity of the HTL improves, and the energy levels are better aligned. In addition, perovskite growth is controlled through the interaction between CuS and PbI2, thus improving the quality of the perovskite films, which reduces nonradiative recombination. The addition of CuS into PTAA improved the PCE from 21.99 % to 22.92 %. Moreover, both the thermal and humidity stability improved.
2) Although excess PbI2 can passivate perovskite boundaries and improve the PCE, under continuous illumination, the decomposition of PbI2 will introduce non-radiative recombination centers and destroy the device stability. To mitigate the side effects of PbI2, CuS nanoparticles were synthesized and incorporated into the PbI2 solution. The interaction between PbI2 and the CuS nanoparticles inhibited the PbI2 crystallization and decreased the PbI2 particle size. With the addition of CuS nanoparticles, more porous PbI2 films were obtained and the reaction between PbI2 and ammonium salts was facilitated due to smoother diffusion of formamidinium iodide (FAI). In addition, CuS nanoparticles can replace PbI2 to prevent defects. As a result, the PCE of Pero-SCs increased from 23.21% to 24.31% with improved N2, humidity and light stability.
3) The low affinity caused by the mismatched surface energies of the perovskite precursor solution and the underlayer is the main reason for the poor coverage of perovskite films, which is also responsible for the pinholes in the perovskite films. To solve this problem, amphiphilic SL, which has two long aliphatic chains, is applied as an additive in the perovskite precursor solution. The amphiphilic nature of SL improves the coverage of perovskite films on hydrophobic PTAA, which is conducive to the fabrication of large-scale devices. In addition, the C=O, P=O, and quaternary ammonium groups in the zwitterion segment can passivate charged defects, thus decreasing the defect density of perovskite films. Notably, the PCE of the corresponding Pero-SCs with an active area of 0.1 cm2 increased from 20.11% to 22.93%. Furthermore, the SL-modified devices with an active area of 1.1 cm2 demonstrated a PCE of 18.32%. The SL-modified Pero-SCs also showed better humidity stability than the pristine Pero-SCs.
4) GAI and CsI have been demonstrated as effective functional additives to FAI and PbI2, respectively, significantly enhancing the PCE and stability of perovskite solar cells. It has been observed that the introduction of GAI into the PbI2 lattice forms a long-range hydrogen-bonding network within the [PbI6]4- octahedra. However, the large GA⁺ induces lattice distortion. To address this, this study innovatively introduces Cs⁺ ions, which have smaller atomic radii, to synergistically regulate crystal growth kinetics and successfully achieve lattice stress balance. Experimental results show that the synergistic effect of GAI and CsI significantly reduces the defect-state density in the perovskite thin film (from 3.0 ×1016 to 2.3 ×1016 cm-3). A n-i-p structured device based on this approach achieves an efficiency of 24.29% (compared to 22.66% for the control group) and exhibits excellent operational stability under 80 ± 5% relative humidity at room temperature — retaining 86% of its initial efficiency after 1000 hours of storage. This study provides a new technological pathway for improving perovskite crystal quality and device performance through cation-size-engineering strategies.
In summary, in order to solve various problems existing in perovskite films, SL, CuS nanomaterials, GAI and CsI with different properties and functions were utilized in additive engineering and interface engineering. These strategies passivated the defects in perovskite, regulate the growth of perovskite, adjust the content of PbI2, thereby reducing non-radiative recombination, promoting charge transfer, and improving device efficiency and stability.