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YorkSpace is York University's Institutional Repository. It supports York University's Senate Policy on Open Access by providing York community members with a place to preserve their research online in an institutional context.

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ItemOpen Access
Subjective and objective spatial memory and navigation abilities in aging and amnesia
(2024-03-16) Pishdadian, Sara; Rosenbaum, R. Shayna
Compared to the extensive research on how older adults evaluate their memory abilities, the evaluation of subjective spatial navigation abilities is understudied. This dissertation was guided by four research objectives: 1) Investigate the psychometric properties of a subjective spatial navigation questionnaire to assess the nature and extent of self-reported changes to spatial navigation in neurotypical aging; 2) Determine the relationship among subjective assessments of spatial navigation and of memory and how they relate to psychological distress and objective memory performance; 3) Understand the impact of hippocampal damage on subjective awareness of areas of spared and impaired episodic and spatial memory; and 4) Identify more precisely the conditions in which spatial memory and navigation depend on hippocampal integrity. In study 1, multidimensional item response theory was used to evaluate the factor structure and item reliability of the novel Changes in Navigation Questionnaire (CNQ) in a community sample of older adults. Results showed that the CNQ has a reliable factor structure, with items falling under typical and atypical changes. In study 2, the relationship between subjective spatial navigation and metamemory in aging was investigated using structural equation modeling. Findings showed that the subjective spatial navigation and metamemory constructs had a positive, weak correlation. Objective episodic memory performance did not load onto metamemory, and allocentric spatial memory performance had a weak loading onto spatial navigation abilities. Psychological distress symptoms had stronger loadings on metamemory than spatial navigation abilities. In study 3, two individuals with hippocampal amnesia completed questionnaires assessing metamemory and spatial navigation abilities and were compared to age-, gender-, and education-matched controls. The individuals with amnesia reported sound awareness of metamemory and spatial navigation difficulties. Lastly, in study 4, these individuals’ performance on a videogame wayfinding measure was compared with that of thousands of well-matched controls. The individuals showed distinct patterns of impairment and preservation on the tasks. These dissertation results show that subjective spatial navigation abilities can be reliably captured with questionnaires, are weakly related to metamemory, and that accurate self-evaluation is not contingent on intact episodic memory. The findings also highlight specific aspects of navigation that are hippocampal dependent.
ItemOpen Access
A Numerical Modelling Approach to Study the Impact of Ventilation Configurations on Airborne Transmission in Indoor Environments
(2024-03-16) Khan, Arma Mantissa; Freire-Gormaly, Marina
The airborne transmission of COVID-19 has been a topic of significant controversy since the pandemic began. Research was needed to demonstrate the importance of airborne transmission and develop tools to recommend appropriate control measures. This study aimed to analyze the factors that impact airborne transmission, find techniques for infection risk minimization, and develop methods to compare different control measures on infection risk. Computational Fluid Dynamics (CFD) studies were conducted to analyze the impact of ventilation layout and infection source location in indoor spaces. A novel spatio-temporal risk model was further developed to quantify the risk in indoor spaces based on different control measures. Conclusions have been made that the ventilation layout and infection source locations can significantly impact the risk of airborne transmitted infection. Further research into building design and airborne transmission minimization techniques is urgently needed to prepare for airborne infectious diseases that may emerge in the future.
ItemOpen Access
Design of Intermittently Operated Reverse Osmosis System and Membrane Coatings for Enhanced Fouling Mitigation
(2024-03-16) Truong, Brandon; Freire-Gormaly, Marina
Access to potable water is becoming an increasingly important issue, especially in communities residing in remote, off-grid locations. The use of solar powered reverse osmosis systems has been shown to be a viable solution to delivering clean drinking water. There is a need to improve the fouling resistance of the membranes to reduce costs, maintain water quality, and keep water output reliable. Membrane coatings have been shown to enhance antifouling properties, but more research is required. A lab-scale reverse osmosis (RO) system is developed to enable testing and monitoring of intermittent water treatment processes. Multiple sensors used to measure water quality and permeate flow were incorporated inline to gather data in real time. Membrane coating technology used to improve treatment performance through enhanced antifouling properties was studied. Several coating possibilities were considered for criteria such as: cost, antifouling & anti-scaling properties, and water output quality.
ItemOpen Access
Laser-Induced Graphene Electrodes for Organic Electrochemical Transistors (OECTs)
(2024-03-16) Nazeri, Mohammad; Grau, Gerd
Organic electrochemical transistors (OECTs) have drawn a lot of interest because of their low cost, biocompatibility, and ease of fabrication, allowing them to be utilized in various applications including flexible displays, electrochemical sensing, and biosensing. Key components of OECTs are the gate, source, and drain electrodes. Here, OECTs with laser-induced graphene (LIG) electrodes are presented. The electrode patterns for the source, drain, and gate are created by lasing the polymer substrate polyimide (PI). The entire process is simple and inexpensive without complicated chemical synthesis routines or expensive materials such as gold. Patterns can be customized quickly and digitally. Different laser parameters play an important role in changing the conductivity and porosity of the graphene leading to its use in different applications. The low-cost and porous LIG electrodes with low contact resistance, good electrical stability, and adhesion to the polymeric substrate play an essential role in device performance. Due to the flexibility of the laser process, source, drain, and gate can potentially have different properties even though they are fabricated together in a co-planar architecture. The minimum sheet resistance achieved with this laser method for the square patterned electrodes is 7.86 Ω/sq. The LIG-based OECTs demonstrate good electrical modulation and high on-current. The LIG-based OECT shows low OFF current in the order of 0.035 mA.
ItemOpen Access
Vulnerability Assessment of Power Transformers and Power Systems to Geomagnetic Disturbances
(2024-03-16) Ariannik, Mohamadreza; Rezaei Zare, Afshin
Powerful solar storms emit plasma that may travel towards the earth. Interactions between the plasma and the earth magnetic field cause geomagnetic disturbances (GMDs), which in turn induce quasi-dc voltage along long conductors in power systems. Assessing the power system resiliency against GMDs requires accurately calculating the induced electric fields and the resultant geomagnetically induced currents (GICs). Offline and online wide-area geomagnetic field monitoring systems are established in this research to estimate GIC flows in power systems accurately. The proposed monitoring systems process the magnetic field signals that are measured at several observatories worldwide. In the offline monitoring system, the magnetic field signals are denoised, and spikes are detected and replaced. The time derivative of the signal is taken by a continuous wavelet transform to prevent amplification of the noises. GICs in a modified IEEE 118-bus benchmark power system are calculated concerning a realistic geomagnetic storm to demonstrate the effectiveness of the proposed signal processing methods. A sliding window is applied in the online monitoring system, and its size is optimized to lower processing time while increasing the signal-to-noise ratio. High amplitude GICs can cause a sharp increase in the hottest-spot temperature of the power transformers. The high temperature allows the formation of gaseous bubbles in the oil-paper insulation and endangers the integrity of the transformer's insulation system. The bubbles include mainly water vapor and emerge in the cavities on the surface of the paper insulation. In the experimental phase of this research, a test setup is created to detect bubbling inception temperature (BIT) for Kraft and thermally upgraded papers (TUPs). The paper samples are dried, prepared at six different moisture levels, and immersed in synthetic ester oil for the experiments. The paper strips are wound around a cartridge heater, and a controller unit raises its temperature at 3 ºC/min and 20 ºC/min rates to detect BIT. The BITs are considered the operational limit on the hottest-spot temperature of the transformers.