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Recent Submissions
On the utility of a rotating swim bench as a freestyle swimming emulator
(University of Waterloo, 2024-08-30) Webster, Kathryn Frances
The swim bench is an isokinetic ergometer intended to aid competitive swimming training by replicating the underwater pull of the freestyle stroke. Yet limited literature addresses the biomechanical fidelity of the swim bench relative to in-water swimming (Olbrecht & Clarys, 1983; Piovezan et al., 2019). Further, the lack of body roll on the swim bench may limit simulation fidelity. Accordingly, the Kayak Pro SwimFast swim bench includes a rotating bench setting. Specific changes to a competitive swimmer’s kinematics and muscle activation patterns with a rotating setting is unknown. The purposes of this study were assessment of the influences of swim bench settings on kinematics and muscle recruitment, and exploration of the similarity of kinematic data between swim bench and in-water data sets.
Fifteen collegiate and/or national level, male, competitive swimmers completed 8 sets (4 rotating and 4 fixed) of 30 second continuous freestyle stroke pulling on a Kayak Pro SwimFast swim bench. Surface electromyography of 12 right upper limb muscles and bilateral upper limb and torso kinematics were collected. Time-series swim bench kinematic and electromyographic data were compared using statistical parametric mapping, enabling holistic evaluation. The swim bench kinematics were compared to existing in-water data from McCabe (2008).
Few kinematic and electromyographic differences existed between the rotating and fixed swim bench settings. Briefly, left shoulder elevation was higher on the rotating swim bench setting nearing the end of the push leading into the recovery phases of the freestyle swimming stroke (p = 0.08). The left shoulder axial rotation approached significance at during the push phase, with a higher internal rotation angle on the rotating setting. Right wrist radial deviation was greater on the fixed setting during the recovery phase (p = 0.024). Infraspinatus achieved greater activations on the fixed bench than the rotating during the late pull to early push phases (p = 0.012). Despite the device’s roll design, no differences existed in shoulder roll between the rotating or fixed setting and, regardless of bench setting, participants laterally flexed the torso, potentially as compensation for the overall lack of roll allowance. The similarities between settings indicated that the rotating setting may not substantially augment the realism of stroke mechanics on the swim bench.
Compared to in-water swimming, the swim bench produced similar elbow flexion angles and maximum vertical depth at the third distal phalanx. However, entry phase duration phase decreased on the swim bench, while the pull, push, and recovery phases increased (p < 0.0001). Additionally, the stroke length, mediolateral stroke width range, and vertical stroke depth range, and total shoulder roll decreased (p = 0.0002, p < 0.0001, p < 0.0001, p < 0.0001). The differences between the stroke mechanics, lack of entry phase, and addition of the lateral torso flexion on the swim bench are notable considerations for swim bench use in training and research. Swimmers could develop associated habits that reduce swimming economy, and the results suggest that using the swim bench in training may not extrapolate to in-water swimming.
Sex Differences in the Physiological Response to the Modern Fire Environment
(University of Waterloo, 2024-08-30) Pulford-Thorpe, Alexis
Due to recent changes in building design and materials, modern structural fires tend towards a ‘ventilation-limited’ fire environment, resulting in globally low levels of oxygen (O2) and increased amounts of carbon monoxide (CO) and smoke. It is unknown how the dynamic hypoxic and hypercapnic environment as a result of the fire impacts an occupant’s physiological and cognitive ability to evacuate. Moreover, it is unknown if physiological sex differences in males and females may further impact egress abilities. This work explored the effects of this dynamic hypoxic and hypercapnic environment on the ability to egress by exposing males and females to sub-incapacitating levels of hypoxic and hypercapnic gases measured in large-scale ventilation-limited fires. Thirty participants (n=15 females) completed three testing days. Day 1 was a familiarization day, intended for participants to familiarize themselves with the experimental protocol of the egress scenario in ambient conditions. Day 2 consisted of five trials of the simulated evacuation scenario wherein real-time changes to O2 and CO2 were administered with CO saturations (%COHb) of 4% and 7%. Day 3 consisted of four trials of the simulated egress scenario wherein changes to O2 and CO2 were carried out in tandem and in isolation. The egress scenario consisted of the following 12.5 minute sequence: 1 min seated pre-test baseline, 5 mins seated, 3.5 mins walking, 4 mins walking carrying a 20lb weight and 2.5 mins seated post-test baseline. This scenario was intended to simulate a realistic evacuation of an occupant from a residential structure, however did not include the more dangerous fire elements (increased temperature, smoke and particulate matter). End-tidal gases, ventilation, heart rate and oxygen saturation were measured continuously. Response (decision, answer and reaction) time was assessed by participants answering a prompt every 15s throughout each trial. The prompts consisted of a directional EXIT sign in which participants had to select the arrow corresponding to the direction of the EXIT sign, as well as a modified Stroop Colour Test. Results demonstrate that females elicited a greater percent change within a condition compared to males for heart rate (p=0.04), tidal volume (p=0.03) and fraction of hemoglobin bound to oxygen (p=0.02). Physiological changes in responses for all participants were significantly greater during the hypercapnia egressing trials compared to hypoxia and control trials (Ventilation: 72±20 L/min, 34±8.9 L/min, 33±6.4 L/min, p< 0.05; tidal volume: 2.3±0.6L, 1.5±0.4, 1.4±0.3, p <0.05). Physiological responses during 4% COHb and 7% COHb trials did not differ other than the fraction of hemoglobin bound to oxygen during pre and post baselines (p<0.05). Overall, the presence of CO2 resulted in the greatest physiological response and coincided with a decrement in ability to complete the egress protocol. Smaller females appeared to be more affected by fire conditions during egress than males. These results indicate that the modern ventilation-limited fire environment results in physiological responses that could negatively impact an occupant’s ability to effectively evacuate.
Super:Lightness: Lightweight High Performance Northern Architecture
(University of Waterloo, 2024-08-30) Gordon, Landers
Super:Lightness proposes lightweighting as a means of providing high
performance residential architecture in the Canadian North. The North faces
severe challenges relating to buildings and infrastructure, as goods and fuel
resupply must be shipped at great expense from southern Canada. These
challenges compound each other, as the climate of the region and the cost
of resupply necessitates highly efficient buildings, while the construction of
these projects is complicated by the remoteness and lack of infrastructure.
Lightweighting presents a means of moving through these problems,
simplifying transportation and construction in remote communities, allowing
for the construction of high performance architecture.
Through study of the challenges in the North, from climatic to
socioeconomic, and studying past and current building practices in the
region, three key elements of transportability, constructability, and building
energy performance are identified, with lightweighting as an important means
of addressing these. Considering this, precedents from alternative disciplines,
and architecture in other settings, are studied as they relate to lightweightness
and these key elements, informing building design in the North.
Drawing on research of the northern context and the study of precedents,
two prototypes of lightweight high performance residential architecture are
proposed, Super:Light Architecture and Northern Lightweight Architecture.
These proposals improve on key elements of transportability, constructability,
and energy performance, addressing the needs of the North through
lightweight design. The design process of these proposals is highly analytical,
quantifying component weights and modelling energy consumption to
develop an optimized design. This process can inform architecture at large,
as the challenges of the North become relevant worldwide due to climate
change, fossil fuel depletion, and economic limitations, making lightweight
high performance architecture an increasingly impactful design methodology.
Low Power TFT Logic Implementation on Display Backplane, Using Unipolar TFTs
(University of Waterloo, 2024-08-30) Kapar, Sparsh
Active-Matrix (AM) displays are key components in devices such as computer monitors, smartphones, laptops, portable gaming consoles, and wearable devices. These displays are trending towards becoming the primary display technology in today’s market. The demand for current displays has surpassed 4K (4096 rows by 2160 columns) and have even reached 8K Ultra-High-Definition (UHD, 7680 rows by 4320 columns). The display panel is generally fabricated on low-cost thin-film transistors (TFT), while the driver and control circuits are built using conventional Complementary-Metal-Oxide-Semiconductor (CMOS) circuits. A bonding pad serves as interface between CMOS circuits and TFT display panel. For each row and column of pixels added to the display backplane, an additional bonding pad needs to be added to properly interface the off-panel peripheral row and column control circuit with TFT and OLED pixel array. As the pixel density of the display increases, the bonding pad pitch must decrease, to accommodate. However, the pitch can only reduce finitely, and this imposes a bottleneck on achieving high-density large-scale displays. Additionally, with each row-line connected to a gate of thousands of pixels, there is a high capacitive load, which contributes to a high dynamic power consumption. Recent research has been investigating the use of TFTs to change the off-panel integrated-circuit (IC) and integrate it onto the display backplane, eliminating the need for bonding pads, while also reducing the overall power consumption. Amorphous silicon (a-Si:H) TFTs have good uniformity and low mask count fabrication process, making it suitable for large-scale displays, in comparison to Low-Temperature-Polysilicon (LTPS) TFTs. However, a-Si:H TFTs are naturally unipolar, which make it hard to replicate the CMOS like logic that the off-panel ICs have. This thesis aims at tackling the bottlenecks of large-scale displays, that is, the high dynamic power consumption, and the limited space from the bonding pads. The proposed row driver circuit presented in this thesis can be used to eliminate the off-panel row IC, and be integrated into the display backplane, while reducing the dynamic power consumption, with a-Si:H TFT technology.
The Descent to Water: Revitalization of the Ashapura Mata Stepwell in India
(University of Waterloo, 2024-08-30) Varikuti, Likhitha
This thesis explores the restoration of a historical water architectural typology indigenous to the Indian subcontinent in its pre-colonial past. Stepwells or Vavs are ancient subterranean structures designed with complex engineering and utmost precision to harvest groundwater. As the name suggests, Stepwells or stepped wells are a series of steps that lead down to a water well. They were vital in providing a water source and acted as a communal gathering space.
Stepwells prevailed for centuries and were shut down during colonial rule as the British considered the water in the wells unsanitary and introduced new water harvesting techniques. The wells, once vital for the communities, are deteriorating to a state of disrepair and are now used as dumping grounds. Considering how the stepwells have played a crucial role in shaping the water architecture typology in India, it becomes essential to revive these wells so that their historical and cultural values are preserved for generations to come. On a parallel tangent, with the growing population and rapid urbanization in India, there has been a significant drop in water tables leading to groundwater depletion. This water crisis issue calls for conservation and effective groundwater management. While the stepwells provided an infrastructure for harvesting groundwater in the past, restoring them would help with groundwater recharge and contribute to reviving the lost heritage.
Along with the restoration of the stepwell as an artifact, this thesis project proposes small-scale, architectural interventions to help with creating a resilient and self-sustaining community around the stepwell and working with and improving both public space and water infrastructure. The revitalization of the Ashapura Mata Stepwell and its surrounding neighbourhood proposes to act as an urban catalyst model for providing restoration strategies for other stepwells in the country.