Mechanical Engineering

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https://hdl.handle.net/10315/34419

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Open Access
Theoretical and Experimental Investigation of Free-Floating Space Manipulator Motion Control Using Reinforcement Learning
(2024-11-07) Al Ali, Ahmad Ibrahim; Zhu, George
This doctoral research is motivated by the need to capture a non-cooperative target in Earth orbits by autonomous manipulators for debris removal. It investigates the critical motion planning problem for a 6DOF free-floating space manipulator using model-free Reinforcement Learning. This problem is caused by dynamic coupling between the spacecraft and robotic manipulator, which significantly affects control and precision in the space environment. This research addresses critical requirements for efficient and effective manipulation in space, including accurate pose alignment between the end-effector and target debris, collision avoidance with both the target and other links of the manipulator and external obstacles, smoothing of joint velocities using optimization terms integrated into the reward function, and adaptation to the high mass ratio between the manipulator and its base spacecraft. Recognizing the imperfection of real-world sensors, this research also incorporates observation noise in the training process to enhance the agent's resilience to noise. Additionally, the reinforcement learning agent is trained with varying initial conditions that are randomly set at the start of each episode, including the manipulator’s initial joint angles, target positions, and obstacle locations. The trained agent can find suitable paths for any target location and avoid obstacles regardless of the manipulator's initial position. The study provides a solid foundation for the application of reinforcement learning in complex free-floating space robotic operations and offers insights for future missions. In addition to numerical verification, ground experimental validation is essential. To overcome the difficulty in mimicking the 3D microgravity environment on Earth, this doctoral research has devoted efforts to designing and building a hardware-in-the-loop ground testbed with active gravity compensation in our lab. The testbed involves two industrial 6DOF robotic arms, one robotic finger gripper and various sensing equipment, including cameras and force/torque sensors, to mimic the 6DOF motion maneuvers that a free-floating robotic manipulator or tumbling satellite/target in microgravity. Initial experimental results in motion control, computer vision, and sensing capabilities are presented to show the potential of the testbed. This facility will be an invaluable tool for the future development and validation of space robotic manipulators, ultimately improving their effectiveness and reliability in space missions.
Open Access
Material Characterization and Development of Simulant Phantoms for a Biofidelic Head Model
(2024-11-07) Tenio, Tristan Virgilio; Boakye-Yiadom, Solomon
Traumatic Brain Injury (TBI) is a global health crisis, with concussions — classified as mild TBI — being particularly common in sports and daily activities. These non-penetrative injuries complicate diagnosis and analysis due to ethical and observational challenges. This thesis aims to develop a biofidelic head model for lab-based impact testing, bridging the gap of anatomical representation between computational models and physical validation. This research focuses on characterizing materials that mimic the mechanical properties of human brain and skull tissues under impact conditions. These materials are tested for their ability to simulate the brain’s compressive and shear responses and the skull’s flexural strength, using advanced manufacturing techniques. The research, structured across five chapters, reviews existing head impact methods and current practices for simulant characterization, selects and tests brain and skull simulants, and designs a comprehensive methodology for creating a full-scale biofidelic head model, proposing advancements for more accurate TBI analysis and prevention.
Open Access
Deformation Behavior and Microstructural Evolution of Armox 500T with Varying Strain Rates and Temperatures
(2024-11-07) Tak, Gurnek Singh; Boakye-Yiadom, Solomon
Armour steels have long been used for ballistic performance application purposes as they provide high hardness, toughness, and strength to resist penetration. However, literature lacks a complete understanding of failure mode analysis under various stress-loading conditions. This thesis explores the microstructure and evolution of Armox 500T as well as the correlated stress-strain data to characterize and gain a deeper understanding of its behaviour under compression, tension, and torsion with temperatures ranging from 0°C - 400°C. Results indicate that performance was increased in high strain rate compression at elevated temperatures up to 200°C, withstanding 2.0% more impact momentum and 3.7% higher toughness than room temperature samples. Temperatures above 200°C showed compromised microstructural properties and decreased performance. At 400°C high strain rate compression, the samples fractured at lower impact momentum and displayed increased brittleness and microhardness. In a reduced temperature of 0°C, low strain rate tensile test conditions decreased toughness by 11.8%.
Open Access
Development of Advanced Adsorbent-beds for Storing Thermal Energy Derived from Solar and Waste Heat
(2024-11-07) Kapil Narwal; O'Brien, Paul; Kempers, Roger
Climate change is an undeniable reality. A pivotal focus in the battle against climate change is sustainability. One way to achieve this is through safeguarding the environment, optimizing natural resource usage, and minimizing waste. Solar energy has played a vital role in advancing sustainability efforts. This energy can be harnessed as electricity or heat. Emerging technologies, including flat plate and evacuated tube collectors, provide promising pathways for harvesting solar thermal energy. Thermal energy storage for short-distance mobile applications is an attractive research domain. The first objective of this research work evaluate the zeolite 13X for short-distance mobile thermal energy storage applications. The study investigates the feasibility of storing thermal energy in zeolite 13X charged externally to dedicated heat recovery units. Impressively, the research demonstrates that zeolite 13X charged at 200°C and stored external to the discharging unit can achieve remarkable energy storage densities (ESD) exceeding 110 kWh/m3 under specific conditions. This achievement aligns with previously reported ESD values in the literature. A particularly crucial aspect addressed in the research is the integration of adsorbents with solar thermal energy storage systems, a relatively underexplored avenue. The study explores diverse configurations, analyzing their impact on enhancing thermal energy storage performance. Through meticulous experimental analysis utilizing Zeolite 13X and water as the adsorbent-adsorbate pair, the research compares direct irradiation with a solar thermal collector. Moreover, the research dives into a critical aspect of adsorbent-based thermal energy storage (ATES) systems. While these systems boast high energy storage densities over long durations, these often face limitations in terms of the heat provided by prevalent sources such as industrial waste heat and solar energy. To bridge this gap, the study explores experiments that leverage both simulated solar radiation and waste heat concurrently to charge Zeolite 13X for ATES applications.
Open Access
Analysis of the Interface Properties of Multi-material 3D Printed Structures
(2024-11-07) Pahari, Shauvik; Melenka, Garrett
Multi-material 3D printed (MM3DP) samples offer enhanced mechanical performance with the added benefit of being customizable for specific applications. However, MM3DP structures have weak adhesion at the boundary interface. So, the interface characteristics in those structures are a critical factor in determining the strength of the structures and predicting failure. Digital image correlation (DIC) is a full-field strain measurement technique ideal for evaluating the non-uniform load response in anisotropic materials due to their heterogeneous composition. This thesis demonstrates the fabrication of MM3DP samples using two distinctly different printing methods. The multi-material samples were extensively compared with the homogenous samples of the same base material with a shear test to assess their mechanical performance. Strain variations on the samples were analyzed and post-processed with DIC software as different material combinations were explored. Additionally, statistical analysis was performed to validate the results and assess the feasibility of the methodology.
Open Access
Towards Optimal Grasping Of Unknown Objects Using Deep Reinforcement Learning
(2024-11-07) Jabarnejad, Behrad; Zhang, Dan
Smart manufacturing, which uses advanced technologies to optimize processes, has become increasingly popular. Improving the agility of robotic systems, including manipulation skills, is crucial in this field. Grasp synthesis, the process of developing grasping plans while manipulating objects, can be approached empirically. Deep reinforcement learning (DRL) is an empirical method that does not require a dataset and learns tasks by interacting with an environment. This study aims to utilize DRL algorithms to perform grasping by creating a novel grasping environment for a simulation model of a three-finger gripper and then validating this model to achieve optimal grasp on unknown objects. The results showed that the trained DRL model in the validated simulation environment successfully grasped unknown objects placed randomly. The agent identified optimal grasps using a grasp quality score in the DRL model’s reward function.
Open Access
Modelling Tubular Braided Composites Using Geometrical, Micro-Computed Tomography and Finite Element Analysis Methods
(2024-11-07) Gholami, Ali; Melenka, Garrett
This thesis investigates various modelling approaches for two-dimensional Tubular Braided Composite (TBC) structures. Because of TBCs' flexible nature, modelling them properly is challenging and usually involves some assumptions. However, having an accurate modelling procedure would help researchers and industries obtain more accurate simulation results before manufacturing or using TBCs. In this research, the gap in the modelling of TBCs will be addressed. Some equations are available in the literature to generate geometrical models of TBCs. However, the intricate nature of the equations involved makes creating accurate geometrical models challenging. This research introduces a user-friendly and open-source software, TBC-Gen, which streamlines the modelling process, eliminating the need for extensive knowledge of the underlying equations. Moreover, some modifications have been applied to the equations to enhance the precision of TBC simulations. Comparative analyses are conducted between TBC-Gen outputs, results from other software, and physical TBC samples to investigate the accuracy of the TBC-Gen results. Micro-computed tomography (µCT) proves to be a precise method for scanning TBCs. This study employs µCT to scan various TBCs with different patterns, dimensions, and materials. Different image processing techniques have been developed to extract essential parameters (minor and major yarn and mandrel diameter, center point, orientation, and cross-sectional area of yarns) from the scanned models. Also, an innovative segmentation and splitting algorithm is implemented for overlapping yarns. Subsequently, two yarns from the scanned TBCs are extracted, and their paths are plotted. A simulated yarn path is fitted to the extracted path, and a new parameter is introduced to the geometrical model to enhance the fitness of the yarn paths. The error between the fitted geometrical model and the segmented yarn path is less than 1%. The TBC-Gen program is then utilized to design different geometrical models, and Finite Element Simulations (FEM) are developed to analyze their behaviour under tensile tests. Periodic Boundary Conditions (PBC) are applied to optimize computational efficiency. The impact of braid angle on TBC displacement during tensile testing is investigated by simulating seven models with similar geometries but varying braid angles (30°-70°). Additionally, three TBCs with similar geometries but different patterns are simulated, and their displacements are reported. The result shows that the displacement of simulated TBCs increases as the braid angle increases. Also, the Hercules pattern shows the most displacement and the Diamond pattern shows the least displacement under a similar tensile test. The FEM results are further validated by simulating the setup of an experimental test and comparing the outcomes against both experimental and Classical Laminate Plate Theory (CLPT) results. The FEM results are closer than the CLPT results to the experimental results. This comprehensive research not only advances TBC modelling methodologies but also validates their accuracy through a combination of advanced imaging techniques, innovative algorithms, and rigorous simulations, contributing valuable insights to the field of composite materials. The TBC-Gen program developed in this study can help other researchers and industries generate geometrical models without a deep understanding of the details of the equations. It can also be used for educational and visualization purposes.
Open Access
High Throughput Centrifuge Microfluidic Device for Simultaneous Particle Separation and Solution Exchange
(2024-11-07) Norouzy, Nima; Rezai, Pouya
Microfluidic centrifuge devices have gained increasing attention for point-of-need (PoN) sample preparation processes, e.g., in separation or solution exchange of various microparticles, bacteria, and mammalian cells. Yet, those devices capable of simultaneous solution exchange and particle separation are low in throughput (can operate at up to 2 mL/min), hindering their applicability to real-world settings. This thesis introduces a multilayer microfluidic device designed for high-throughput solution exchange and efficient microparticle separation, addressing the need for processing large sample volumes at elevated flow rates. The device integrates Dean flow recirculation and selective inertial focusing of microparticles within 24 curved microchannels assembled in a compact three-layer configuration via in-plane and out-of-plane parallelization. Exploring substrate materials (glass or PDMS) and operational flow rates, we studied solution exchange and particle migration using singleplex and duplex samples across devices with varying curve numbers (2-curve, 8-curve, and 24-curve). Transitioning from glass to PDMS enhanced solution exchange efficiency in curved channels. Processing 5 µm and 10 µm microparticles at flow rates up to 16.8 mL/min (33.6 mL/min total in the multilayer device) achieved a solution exchange efficiency of 96.7%. In singleplex suspensions, 10 µm and 5 µm particles selectively migrated to different outlets of the device, demonstrating separation efficiencies of 99.7% and 90.3%, respectively. With duplex samples, sample purity was measured to be 93.4% and 98.6% for 10 µm and 5 µm particles collected from different outlets, respectively. Application of our device in biological assays was shown by performing duplex experiments where 10 µm particles were isolated from Salmonella bacterial suspension with purity of 97.8%. This parallelization enabled desirable combinations of high throughput, low-cost, and scalability, without compromising efficiency and purity, advancing the technology towards sample preparation.
Open Access
Biofabrication of a Heart Wall Section using the FRESH Bioprinting Method
(2024-10-28) Horvath, Victoria Bianca; Czekanski, Aleksander
This dissertation addresses the challenge of bioprinting cardiac wall tissues. It focuses on three different aspects. The first is around materials that mimic the different cardiac wall tissue layers by testing the different materials pre- and post-crosslinked for their characteristics and behaviour. Secondly, it explores the adaptation of a 3D printer for bioprinting using the FRESH bioprinting method, which utilizes a single extrusion point for multi-material printing. This printer came with a unique printhead design, allowing multiple materials to enter the chamber to print continuously. Lastly, it explores the 3D printing of hybrid tissue and the optimization of the printing process. The hybrid tissue creation started with two materials before moving to three materials for the cardiac wall. The outcomes of this study The outcomes of the study such as the bioprinter that can print multiple material without leaving the print site and the materials which work as the anatomical heart wall layers, represent a significant step forward in the field of tissue and organ engineering, offering promising new directions for personalized medical treatments and advances for organ transplants by bridging the research gap between hybrid tissue bioprinting with specialized materials and a unique bioprinter that specializes in multi-material printing with better precision and material structure. This research lays the foundation for future advancements in the field of regenerative medicine.
Open Access
Stress-State and Strain-Rate Dependent Multiscale Characterization of ARMOX 500T
(2024-08-28) Mateos, Diego; Boakye-Yiadom, Solomon
A strain-rate and stress-state dependent experimental characterization is conducted for the parameterization of a triaxiality and lode angle parameter (LAP) dependent Generalized Incremental Stress-State Dependent Damage Model (GISSMO) for ARMOX 500T (AX500) armour steel. 100+ mechanical tests have been conducted which differentiate the effects of triaxiality, LAP, and strain-rate on instability and fracture strains. Quasistatic characterization tests have been conducted at 18 different stress-states abiding by previous GISSMO literature and ASTM standards. LaVision’s Digital Image Correlation (DIC) system is employed in 2D & stereo 3D configurations to acquire high resolution full-field strain measurements. The stain-paths are quantified in the fracture regions of all specimens, from which in-situ equivalent plastic strains are derived. A novel and low-cost Tensile Hopkinson bar has been designed and constructed for dynamic characterization of ductile metals at intermediate to high strain rates (500-1500 /s). High strain rate mechanical tests coupled with high-speed 2D-DIC have been conducted to provide a strain-rate dependent GISSMO extension to the model. Two Hopkinson bars (direct compression, split-tension) have been used to provide lode angle dependent strain-rate hardening data on stress-states of axisymmetric compression and tension covering the lode angle parameter values of -1 and 1, respectively. In addition, two cylindrical inclined compression-shear specimens with varied angles have been impacted at high strain rate to quantify the effect of stress-state on the formation and evolution of Adiabatic Shear Bands (ASBs) and their consequential effect on ductility. This innovative dynamic characterization procedure is conducted to stipulate diligent test matrices and enable improved multiscale terminal ballistics simulations on novel combat vehicle development, with the purpose to increase the predictability of shear plugging. High strain rate axisymmetric compression, compression-shear and tension specimens have been investigated using a combination of optical (OM) and electron microscopy (SEM/TEM) to elucidate their microstructural evolution. Ductile fracture is observed under all stress-states, with changes from mode I to mode II crack formation from positive to negative lode angles. Under axisymmetric dynamic tension, enhanced damage tolerance in comparison to quasistatic loading is found attributed to increased dislocation pileups (work hardening) and subsequent ductile void growth responsible for enhanced plastic flow during necking. Axisymmetric dynamic compression reveals a severe loss of global ductility and strengthening not observed under quasistatic loading, with continuous work hardening until premature fracture and localized hardening in the ASB regions. Compression-shear specimens reveal higher susceptibility to ASB initiation with increasing angle of inclination (shear stress) and corresponding ductility loss due to increased strain localization along the plane of maximum shear. Lastly, ASB multisite microcrack initiation and coalescence, multi-directional cracking, secondary ASBs and bifurcation, nanosized grain refinement, nanoscale twinning, and dislocation cell networks are found within triaxial ASB regions revealing that AX500 has various energy absorbing mechanisms to delay crack propagation and fracture after the onset of ASB initiation.
Open Access
Investigation of the Repairability of Thermoplastic Composite Structures Through Conduction Welding
(2024-07-18) Bijl, Calvin Zachary; Melenka, Garrett
Thermoplastic composites are gaining prominence in various industries for their recyclability and superior mechanical properties. This thesis investigates the use of thermoplastic composites, emphasizing their notable capability for repair and joining through conduction welding, a cost-effective fusion bonding technique that eliminates the necessity for adhesives or mechanical fasteners in the assembly of composite materials. By applying this method, the repairability of thermoplastic composite samples is assessed through the application of variously sized repair patches welded to open hole tensile samples. Furthermore, this research investigates the optimization of welding parameters, such as temperature and compaction pressure, aiming to produce high shear strength joints produced by this technique. The findings of these studies highlight the potential of conduction welding as an effective and economical approach for the assembly and repair of thermoplastic composites, suggesting its promise for wider adoption in composite manufacturing and repair processes.
Open 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.
Open 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.
Open Access
Low-Cost and High-Throughput Optofluidic Add-on Device for Light Sheet Imaging of Larval and Adult C. Elegans
(2024-03-16) Rahimpouresfahani, Faraz; Tabatabaei, Nima; Rezai, Pouya
In this research, we have made modifications to our low-cost light sheet platform, allowing us to capture high-content cross-sectional images of nematodes' nervous systems at earlier stages of development and with higher throughputs. Our platform was put to the test in imaging larval and adult pan neural worms, as well as in analyzing control and neurotoxin-exposed worms. Additionally, we utilized a new transgenic worm model for Parkinson's disease and were able to detect a fluorescence difference between larval and adult stages. The result is a vast dataset of high-content images that will be invaluable in future research.
Open Access
Optimization of Thermophotovoltaic Systems Using One Dimensional Photonic Crystal Optical Filters with a Graded Index of Refraction Profile
(2024-03-16) Mansoor, Mehran Sepah; O'Brien, Paul
This thesis investigates the enhancement of thermophotovoltaic (TPV) systems using one-dimensional photonic crystals (1DPC) with a graded index of refraction as optical filters. It compares three 1DPC configurations: graded index, traditional quarter-wave, and modified quarter-wave stacks, to improve TPV performance. Designed for TPV applications, these filters aim to increase in-band transparency and minimize absorption while ensuring high out-of-band reflection. Graded index 1DPCs, made of porous silicon dioxide and solid zirconium dioxide, exhibit low absorbance across a broad spectrum, offering a novel approach in TPV applications. Significantly, a double-stack graded filter at an emitter temperature of 2000 K achieved 74% in-band transmittance and 55% out-of-band reflectance. Highlighting a design trade-off, the study presents an optimal filter configuration that yields a 24% system efficiency and a power density of 6.9 W/cm^2. The analysis focuses on system efficiency and power output, emphasizing the advancement in TPV efficiency through the application of graded index 1DPC filters.
Open Access
Investigation and Characterization of Composite Silica Aerogel Nanostructures Obtained Via Magnetron Sputtering
(2024-03-16) Capacchione, Amanda; Freire-Gormaly, Marina; O'Brien, Paul
This study explores the deposition of Copper (Cu) onto hydrophilic Silica Aerogel (SA) monoliths using magnetron sputtering, with Cu thicknesses of 20 nm, 50 nm, and 100 nm. Leveraging the mesoporous nanostructure of SA, a Cu-sputtered SA nanocomposite was fabricated, creating a non-homogeneous nanocomposite material. Trace amounts of Cu penetrate up to 10 µm into the SA structure, as revealed by SEM-EDS analysis. The resulting nanocomposite, characterized by spectrophotometric examination, exhibited UV scattering, high transmittance, and absorption in the visible range. FTIR spectra revealed reduced transmission in the near-infrared (NIR) and mid-infrared (MIR) regions with increasing Cu thickness. Infrared imaging showed a photothermal effect. The temperatures of samples comprising 100 nm of Cu sputtered onto Silica aerogels reached 94.8°C under solar-simulated irradiation at an intensity of 100 mW/cm^2. These findings provide fundamental context to an under explored area, laying the groundwork for alternative thin-film deposition techniques like magnetron sputtering deposition for the fabrication of metallic, nanocomposite Silica aerogel supports.
Open Access
Development, Processing and Characterization of Advanced Alumina Matrix Multi-material Nanocomposites Reinforced with Zirconia, Graphene and Carbon Nanotubes
(2023-12-08) Duntu, Solomon Hanson; Boakye-Yiadom, Solomon
The demand for tough materials in extreme conditions has grown due advanced technology requirements, such as high pressures (> 90GPa), elevated temperatures (> 2000°C), and radiation exposure, has grown substantially. Advanced ceramics, particularly alumina (Al2O3), with their low weight, hardness, and chemical resistance, are promising candidates. However, their inherent brittleness (low fracture toughness) has limited their applications. To address this, researchers have incorporated sub-micron and nano-scale reinforcements like zirconia (ZrO2), graphene (GN), and carbon nanotubes (CNTs) into alumina to create composite materials. However, challenges remain in achieving consistent mechanical properties and minimizing trade-offs between fracture toughness (KIC) and strength. This study investigates the impact of single and combined nano-scale reinforcements (ZrO2, GN, and CNTs) on the microstructure, mechanical properties, toughening mechanisms, tribological performance, and functional attributes of monolithic alumina. The nanocomposites were fabricated by uniformly dispersing selected optimal amounts of ZrO2 (4wt% and 10wt%), GN (0.5wt%), and CNTs (2wt%) through a colloidal mixing process, followed by hot-press sintering. The results revealed a uniform distribution of additives within the alumina matrix, leading to significant matrix grain size reduction (up to 80%) in the Al2O3-10wt%ZrO2-0.5wt%GN-2wt%CNTs multi-material nanocomposite compared to pure alumina. Microhardness increased by up to 48% in the Al2O3-10wt%ZrO2-0.5wt%GN-2wt%CNTs multi-material nanocomposites due to refined grain structures and effective load transfer capabilities. Furthermore, fracture toughness (KIC) improved by up to 160%, and bending strength increased by up to 46% in Al2O3-10wt%ZrO2-0.5wt%GN-2wt%CNTs multi-material nanocomposite, due to synergistic toughening and strengthening mechanisms involving pull-outs, crack arrest, and crack bridging by GN and CNTs. This nanocomposite also exhibited up to a 93% reduction in wear rate compared to pure alumina, attributed to wear resistance mechanisms such as micro-crack bridging and intergranular fracture restriction during sliding. Further, the incorporation of GN and CNTs improved the electrical conductivity of monolithic alumina from 10-13 S/m up to 102 S/m (increase up to 15 orders of magnitude), with the Al2O3-10wt%ZrO2-2wt%CNTs nanocomposite registering the highest conductivity value. This was ascribed to the intrinsic electrical properties of carbon nanostructures, percolation effect and the refined grain structure of the nanocomposite which enhances electron mobility by forming continuous networks and pathways.
Open Access
Aerosol Transmission of COVID-19 and other Airborne Diseases in office environments using Computational Fluid Dynamic Modeling and Machine Learning
(2023-12-08) Webb, Kishon Winston; Freire-Gormaly, Marina
The COVID-19 pandemic has shown the world how quickly airborne diseases can spread and the lasting impact they can have. Computational fluid dynamic (CFD) models and simulations and machine learning (ML) are powerful tools that allow engineers to create models to predict and advance tools to fight these airborne diseases. The research in this thesis studied the effects of heating, air conditioning and ventilation (HVAC) strategies in small office spaces. A novel methodology was developed to utilize ML, CFD and parallel computing by utilizing the user defined function (UDF) tool of ANSYS Fluent. It was shown that the resulting risk models were quick and effective at predicting high risk areas using spatial data or predicting regions of high risk over time. Future research will refine this method by creating higher fidelity ML models and investigating a wider range of input and output parameters.
Open Access
Optothermal Characterization of Nanoparticle Infused Aerogels
(2023-12-08) Nagi, Mubariz Ahmad; Cooper, Thomas; Freire-Gormaly, Marina
Here, custom fabricated nanoparticle infused aerogels are presented as a potential material to achieve super insulating and transparent opto-thermal properties. By incorporating nanoparticle solutions within the silicon dioxide (SiO₂) aerogel during the sol-gel process, unique monolithic samples were fabricated and opto-thermally characterized. The pure silica and nanoparticle infused (Zinc Oxide, Antimony doped Tin Oxide, Zirconia Dioxide) silica aerogel samples, through UV-Vis and FTIR measurements, spectrophotometrically demonstrated a solar weighted transmittance of 86, 86, 55 and 78% with measured effective thermal conductivity values of 0.035, 0.050, 0.045, 0.045 W/(m∙K) with an error threshold of ± 0.005 W/(m∙K) using a modified guarded hot-plate technique respectively. The inclusion of nanoparticles within SiO2 aerogels results in reduced transmission (heat loss) in the mid-infrared (MIR) while maintaining high transmission in the visible wavelength region. Importantly, the results show that nanoparticle infusion can be used as a flexible method to tailor the opto-thermal properties of aerogels.
Open Access
Optical performance of a seasonally adaptive asymmetric compound parabolic concentrator
(2023-12-08) Lenarduzzi Perez, Gianpaolo; Cooper, Thomas
Stationary concentrators have the capabilities to supply power in residential and commercial applications, where typical required temperatures range between 20° and 400°. To advance the performance and possible applications of these devices, this work presents an innovative asymmetric stationary concentrator, called Seasonally Adaptive ACPC, which maximizes concentration by semi-annual solar pseudo-tracking. The concentrator is described, and its performance is analyzed using theoretical, numerical, and experimental methods. The former includes the adaptation of the source-acceptance map matching method for ACPCs and the theoretical performance of possible designs; and numerical studies used Monte Carlo ray tracing to investigate optical performance parameters. Experimental efforts involved measuring the optical performance of a practically relevant prototype (ϑin,1=0°, ϑin,2=90°, and a Cg=2×) in Toronto, Canada, using an innovative flux mapping procedure. Through this work, the Seasonally Adaptive ACPC was found to be a low-cost alternative to meet low to medium temperature heating demands at high latitudes.