Doctoral theses

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Adaptation of microalgae bioprospected from stressed environments in Northern Ontario for the production of lipids
(2020-12-16) Desjardins, Sabrina Marie
Photosynthetic green microalgae are a promising bio-feedstock that can be used to generate lipids for transesterification into biodiesel and/or various human health products such as polyunsaturated fatty acids. Unfortunately, due to their cultivation requirements, such as high energy requirements and carbon dioxide (CO2) as a carbon source, large-scale biomass production generally remains uneconomical. To address this issue, the use of industrial flue gas as a low-cost source of CO2 and a biorefinery approach to help mend the economic burden of microalgae-based products with an emphasis on creating co-products from lipid-extracted biomass (LEB) are assessed in this thesis. Microalgae’s ability to sequester CO2 through photosynthesis is also advantageous in mitigating harmful industrial emissions. While these flue gases can have high concentrations of CO2, they also can contain numerous contaminants (e.g., heavy metals, particulate matter) that discourage microalgae growth, and therefore their ability to fix CO2. But, the most significant issue can be high nitrous oxide (NOx) and sulphuric dioxide (SO2) concentrations within a flue gas that cause acidification when bubbled through liquid media. It is due to this acidification that finding the productive microalgae species to grow in those systems can be problematic. To address this, bioprospecting acid-tolerant microalgae from low pH environments in active and non-active mining sites was explored and the acidophilic species present identified through DNA sequence analysis. Bioprospected algal species were then grown in acidic conditions similar to those created by bubbling flue gas from a nickel smelter into water (pH 2.5). From this work, it was found that the acid-tolerant green microalgae in the genus Coccomyxa acclimated to the acidic conditions with suitable growth rates (0.136 day-1) and biomass production (25.71 mg L-1day-1). However, anabolic production of target biochemical molecules, such as lipids, is the key step in the bio-product process. It is known that microalgae have the ability to accumulate bioactive compounds when placed in stressed environments, such as high illumination and low nutrient availability, but little is known an about the impact of low pH and in particular the lipid composition of acidophilic microalgae. Research confirmed that the lipid compositions of bioprospected acid-tolerant microalgae was in the target range (13%). However, further work showed that an increased total lipid content (up to 27%), with a desirable rise in the relative level of health beneficial higher polyunsaturated fatty acid, could be achieved by applying dark stress at the end of the exponential growth phase. It is, therefore, proposed that this approach could be an easy, low-cost method to enhance lipid productivity
Air entrainment and air-water separation in hydraulic air compressors
(2018-08-16) Hutchison, Alex
A hydraulic air compressor (HAC) is an isothermal gas compressor that uses hydropower to compress air, originally developed by Charles Taylor in the 1890s to supply industry with compressed air. In the modern revival of this technology, the hydropower will be provided by pumps rather than natural sources. As such, energy efficiency is an important driver of component design; all of the hydropower is consumed either to overcome irreversibility or to compress air. The compressor relies on the increasing pressure of water flowing downward in a downcomer to compress air in the form of bubbles being dragged along with the flow. The air entrainment process at the top of the downcomer is facilitated by a mixing head. At the bottom of the downcomer, the bubbles are separated from the flow in a separator vessel. The objective of this thesis is to develop the design methodology for the air entrainment and air-water separation components on either end of the downcomer process. Several mixing heads were tested on a small (4.5 m height) prototype HAC. The test without a mixing head successfully entrained air, confirming that air entrainment is a system effect. Two heads with dissimilar geometry were associated with the lowest irreversibility, leading to the conclusion that the best design at that scale is a mixing head incorporating some form of vortex breaker. Air entrainment is driven by a system energy balance and not exclusively by a local Venturi geometry. The fraction of the air successfully captured in the plenum of the separator is called the separator effectiveness. Mechanistic models have been created to characterize both the irreversibility and separator effectiveness of two types of gravity separator (horizontal and vertical orientation) for iv the design of separators for future commercial-scale compressors. The separator effectiveness models require as input the flow field information from computational fluid dynamics analysis and the bubble size distribution at inlet. The bubble size distribution was measured on the small prototype and used to select a bubble size prediction model for testing on a much larger scale (29 m height) demonstrator HAC. The displacement model for horizontal separators matched the actual performance at the prototype scale well, particularly at high flow rate. The vertical velocity model produced a good match for the separator on the demonstrator HAC, but not for the same bubble size model identified on the small prototype.
Application of neuroergonomics in the industrial design of mining equipment.
(2015-06-26) Mach, Quoc Hao
Neuroergonomics is an interdisciplinary field merging neuroscience and ergonomics to optimize performance. In order to design an optimal user interface, we must understand the cognitive processing involved. Traditional methodology incorporates self-assessment from the user. This dissertation examines the use of neurophysiological techniques in quantifying the cognitive processing involved in allocating cognitive resources. Attentional resources, cognitive processing, memory and visual scanning are examined to test the ecological validity of theoretical laboratory settings and how they translate to real life settings. By incorporating a non-invasive measurement technique, such as the quantitative electroencephalogram (QEEG), we are able to examine connectivity patterns in the brain during operation and discern whether or not a user has obtained expert status. Understanding the activation patterns during each phase of design will allow us to gauge whether our design has balanced the cognitive requirements of the user.
Characterization of seismic sources using sequential spatial clustering and fractal dimension
(2018-07-30) Cortolezzis, Donna Marie
Despite years of research, unexpected seismic events in mines continue to cause damage and loss to people, equipment, infrastructure, and reserves. This research uses novel approaches to characterize the locations, times, and intensity of seismic events for four known seismic sources. The seismic source case studies are the development of a ramp, the abutments around a zone of stopes, a failing stope pillar, and a shear zone adjacent to an orebody. Each seismic source is characterized by sequential spatial clustering, and the fractal dimension of the seismic source parameters of location, time and intensity. The novel application of sequential spatial clustering preserves the sequence of events within a cluster. The method can be used at any point in time which means as a rock mass changes the seismic response is expressed and identified very early on. Once identified, it allows the opportunity for investigation and decision making to take place as the rock mass changes in an unexpected manner. The application of fractal dimension to seismic source parameters revealed that the fractal nature of a parameter is not infinite but exists within a range. The fractal range reflects the character of a seismic source. If some events occur outside the fractal range they also provide important information about the history of the seismic source that occur less often than the fractal range but are still possible. This research has expanded the knowledge of when, where, and how intense seismic events can be expected for four seismic sources using a new sequential spatial clustering method and fractal dimension characterization.
Cobalt-doped zinc oxide thin films as model Fischer-Tropsch nano-catalysts grown by pulsed electron beam ablation
(2017-12-05) Ali, Asghar
The production of materials in thin film form with unique properties is of growing scientific and technological interest. Zinc oxide is a low cost, and environmentally benign wide band gap semiconductor, which makes it an excellent supporting material for nanoparticles with a plethora of potential applications. Upon doping with Co and other transition metals, ZnO exhibits room temperature ferromagnetic properties with enhanced performance and new functionalities when used in thin film devices. Zinc oxide-supported cobalt nano-composites are promising materials with desirable catalytic properties making it an interesting material for use as an efficient nano-catalyst in many important reactive processes such as Fischer-Tropsch synthesis (FTS), photocatalysis, hydrogen production and steam reforming. Pulsed electron beam ablation (PEBA) has recently emerged as a potential technique for the fabrication of superior quality thin films. The production of well controlled nano-sized particulates is a characteristic feature of PEBA, which has a strong bearing on the surface morphology of the deposited films. In the current work, the potential of PEBA in the deposition of Co-doped ZnO thin films has been assessed and the critical process conditions that affect the growth of the thin films on different substrates have been thoroughly investigated. The main objective of the current work is to deposit Co-doped ZnO thin films via PEBA, and assess the potential of the deposited films as model nano-structured catalysts for the synthesis of green liquid fuels from syngas. PEBA has several advantages including modest requirements for vacuum, control of film thickness, easy set-up, low capital cost, reduced operation and maintenance costs, small footprint, enhanced efficiency, and relative safety (no toxic gases as in pulsed laser ablation or potential noxious by-products as in solvo-thermal routes) over other film preparation techniques. In this project, Co:ZnO thin films have been synthesized from a single target on various substrates. Numerous process parameters have been assessed such as substrate material, deposition temperature, electron beam voltage, beam pulse frequency. Targets of varying cobalt loads viz., 5 w%, 10 w%, and 20 w% have been investigated as well. The effects of pre and post annealing on the physico-chemical properties of the thin films have also been studied. The deposited films have been characterized using complementary analytical techniques such as xray diffraction (XRD), x-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), energy dispersive x-ray (EDX), visible reflectance spectroscopy (VRS), and atomic force microscopy (AFM). Such comprehensive analyses have helped in assessing the quality of the films and in guiding the experimental strategy in the quest to find the optimal process conditions. Finally, the films have been evaluated for their potential as model nano-catalysts for FischerTropsch synthesis in a 3-phase continuously-stirred tank slurry reactor (3-φ-CSTSR) using a Robinson-Mahoney stationary basket (RMSB). The results have been described in terms of activity and selectivity of the thin film nano-catalysts.
Design and optimization of a novel top-lit gas-lift bioreactor for industrial CO2 mitigation and microalgae-sourced biodiesel production
(2017-03-24) Seyed Hosseini, Nekoo
Mitigation of CO2 in industrial off-gasses by sparging the gas through photosynthetic microalgae bioreactors is an attractive concept. The goal is for the CO2 to be consumed by the microalgae as a nutrient, which in turn produces lipids suitable for conversion into biodiesel, as well as other value-added bioproducts such as Omega-3 fatty acids and antioxidants. Open systems are considered the most economic outdoor, large-scale cultivation option but have large land space requirements due to their shallow depths (15-35 cm). Consequently, finding sufficient space to locate them close to off-gas sources on industrial sites can be a significant challenge. Shallow depths are also likely to result in low uptake of CO2 and consequently reduced biomass productivity due to short gas residence times in the culture medium. In order to obtain longer gas/liquid transfer times, as well as greater per area productivity, the tanks through which the off-gas is sparged must be as deep as possible. However, to make the tanks deeper and avoid the costs associated with sub-surface artificial lighting, the issue is how to ensure the microalgae receive adequate light exposure. We have, therefore, looked for a novel method for increasing the depth of the tanks through which the off-gas is sparged. To achieve this, we have investigated the use of a gas-lift circulating system in a deep top-lit open bioreactor. In addition to providing CO2, the sparged gas also provides continual vertical circulation of the microalgae to ensure good mixing and an adequate light/dark cycle. Compared to existing shallow open systems, the results obtained showed comparable biomass productivity per unit volume, but importantly around three-times higher biomass productivity per unit area occupied by the bioreactor. The lipid productivity was also increased due to light and hydrodynamic stresses. In order to enhance further light utilization efficiency in the deep cultivation bioreactor, the use of a novel non-energy-consuming light column was also evaluated. The results of using the light column showed a 33% increase in areal biomass productivity and a 16% increase in areal lipid production. The proposed design and developed models can be easily translated into larger scale, onsite production facilities in industrial sectors emitting off-gas. The carbon capturing properties of microalgae can, therefore, help reduce industrial carbon dioxide emissions, whilst at the same time producing biodiesel from the resulting lipids.
Design and verification of a Hydraulic Air Compressor as a CO2 capture and sequestration system.
(2023-08-17) Mahdavi, Maryam
As a result of human activities, the level of atmospheric carbon dioxide (CO2) has increased. Carbon capture and sequestration (CCS) technologies offer an effective approach for mitigating CO2 from various industrial process to reduce the global climate change effect. These technologies can be integrated into existing infrastructure with minimal disruption. This study reviews on post- combustion CO2 capture and sequestration techniques, with a specific focus on mineral carbonation process routes and their potential feedstocks. Mineral carbonation is an approach that mimics the natural weathering of rock, in which metal oxide-bearing materials, for instance natural silicate minerals (serpentinite, olivine) react with gaseous CO2 to form solid carbonates. This process takes place on geological time scales, but it can be accelerated by increasing the concentration of CO2 in a reactor through pressurization of the system. The purpose of this study was investigation of technical feasibility of a CCS process by means of a hydraulic air compressor (HAC). A series of experiments were conducted on the HAC pilot plant to investigate the potential of the system as a post-combustion CO2 capture system. Those experiences experimentally verified a one-dimensional steady-state model for two-phase bubbly flow. The verified bubbly flow model was used to compare the hydrodynamics and mass transfer characteristics of HAC downcomers and upward co-current flow bubble column reactors and to predict gas liquid mass transfer coefficients. The experimental results showed that the HAC is an effective technology for intensification of CCS processes due to its improved mass transfer performance compared to other mass transfer devices. While the high capital cost of HAC construction, following a general Millar (2014) design paradigm, limits applicability, the horizontal injector loop (HIL), developed in this thesis offers a new apparatus with similar gas compressor performance and reduced height, which would make the concept more accessible for capital restricted projects. A mathematical dynamic kinetic model is developed to simulate the kinetics of CO2 absorption into an alkaline solution in the HIL. This model makes a significant contribution in predicting the absorption rate under operating conditions beyond those achievable in experimental tests undertaken. In addition, this model can be used to guide the design of a new reactor and future experiments, making it a valuable tool for CO2 capture and sequestration activity. Carbon dioxide capture and sequestration by means of a HIL as a pressurized, continuous chemical reactor was also investigated experimentally. The experimental results demonstrated that the HIL has a credible potential for this purpose. These experiments were also simulated using the dynamic kinetic model, which showed good agreement with the experimental findings. However, some potential improvements to the dynamic kinetic model have been identified to enhance its compatibility with experimental conditions.
Dynamic modelling of catalytic SO2 converter in a sulfuric acid plant of an industrial smelter
(2018-04-16) He, Jianjun
In industrial nickel and copper production, sulfur dioxide (SO2) is generated from the combustion of sulfide ores. With increasingly tightened regulations on SO2 emissions, a sulfuric acid plant has become a crucial part of industrial smelters. It converts environmentally harmful SO2, which is generated in smelter furnaces, roasters, and Cu-reactors, into commercially beneficial sulfuric acid. This method is recognized as one of the most effective ways to ensure that smelters are able to satisfy the SO2 emission regulations. A sulfuric acid plant is primarily comprised of a central catalytic SO2 converter, SO3 (sulfur trioxide) absorption towers and a series of interconnected heat exchangers. The catalytic SO2 converter is the key component and the focus of this research. Both steady-state and dynamic models of the converter are developed in this thesis. A steady-state model of the converter is established in accordance with steady-state mass and energy balances. The developed model provides an explicit relation between SO2 conversion ratio and gas temperature, which is denoted as the heat-up path of the converter. By combining the heat-up path with the equilibrium curve of the SO2 oxidation reaction, an equilibrium state for every converter stage can be obtained. Using the developed steady-state model, simulations are performed to investigate the effect of inlet SO2 molar fraction and gas temperature on the equilibrium conversion ratio. In an industrial SO2 converter, the SO2 concentration and conversion ratio out of each bed are important variables but are not measured in real time. To monitor these unmeasured variables in industrial operations, a soft sensor is proposed by combining the derived steadystate model with dynamic data analysis. The obtained soft sensor provides a real-time estimation of outlet SO2 concentration and the conversion ratio from measured temperatures. For synchronization between the inlet SO2 concentration and outlet temperature, a first-order exponential data filter is applied to the feed SO2 data. With the filtered signal being used, the proposed soft sensors give a satisfactory estimation of both outlet SO2 concentration and conversion ratio in the converter stages. Dynamic modelling is carried out using two different model forms: ordinary differential equation (ODE) and partial differential equation (PDE) models. The ODE model is obtained by applying dynamic mass and energy conservation to the SO2 converter. The resulting model can be used in industrial applications and describes the converter performance even if information of reaction kinetics is not available. A good fit with collected industrial data verifies the validity of the developed ODE model. The effect of process input variables is studied using simulations with the ODE model. Dynamic modelling is performed by implementing mass and energy balances on both fluid and solid-phase gas flows. The proposed two-phase dynamic model, which takes the PDE form, is able to generate detailed profiles of the SO2 converter within time and space. With the estimated parameters, this two-phase dynamic model generates a good fit between the simulated and measured outlet temperatures. Based on the PDE model, simulations are run to investigate the detailed mechanistic performance of the converter. The detailed PDE model provides useful explanation of, and prediction for the converter behaviour.
The effects of automation on the environmental impact of deep underground metal ore mining operations
(2020-10-27) Moreau, Kyle Steven
The growing demand for increased production has resulted in the need to develop deeper underground mines to extract more resources. However, the mining process becomes less economically attractive as the ventilation and ore transportation costs drastically increase when operating at large depths. This has led to the industry investigating automated battery-electric and biodiesel fueled machinery instead of diesel machines to reduce emissions, and hence ventilation costs, as well improve productivity and thereby, the economic viability of deep mine projects. A life cycle assessment (LCA) approach has been developed to evaluate the environmental impact from introducing automated equipment in underground copper mines. This is a novel application for an LCA, and as a gauge of model accuracy, it was found that calculated greenhouse gas (GHG) emissions for an underground mine site in Canada were within 5.6% of their reported emissions. The model was then expanded using data collected from automation trials at a Canadian mine to predict changes due to the introduction of various levels of automation with regards to the impact potentials of global warming, acidification, eutrophication and human toxicity. All impact levels were quantified and found to decrease due to automation. Data from this site study was then used to further develop the LCA model to predict changes in environmental impacts for underground copper mine sites in Australia, Canada, Poland, USA and Zambia. Site specific parameters and processes that contribute to their overall environmental impacts were identified, and the calculated CO2 emissions were within 4.2-5.6% of the reported values. The mining industry is moving toward introducing significantly more technology to enhance both productivity and safety. This thesis investigates using an LCA approach to add a third dimension; improved environmental impacts that contribute to more sustainable mining
Estimation of confined peak strength for highly interlocked jointed rockmasses
(Laurentian University of Sudbury, 2015-07-20) Bahrani, Navid
The determination of rockmass strength for mining has become critically important in recent years due to the increase in the number of projects at depths exceeding 1500 m. The commonly used empirical approaches for the estimation of rockmass strength are primarily based on experiences at shallow depths (< 1500 m) and from observations of rockmass behaviours at low confinement (e.g., tunnel wall failure). Therefore, the application of these techniques for estimating the strength of rockmasses when highly interlocked and confined (e.g., pillar cores) is hypothesized to be flawed. The goal of this research is to develop reliable means of estimating the confined strength of highly interlocked jointed rockmasses. A two-dimensional code based on the Distinct Element Method (DEM) and its embedded Grainbased Model (GBM) is used to simulate the behaviour of a highly interlocked jointed rockmass to better understand its Strength Degradation (SD) from intact rock with increasing confinement. The GBM is first calibrated to the laboratory response of intact and granulated marble. The term "granulated" refers to a heat-treated marble where the cohesion at grain boundaries has been destroyed. The granulated marble represents an analogue for a highly interlocked jointed rockmass. The calibrated GBMs are then used to simulate micro-defected and defected rocks and jointed rockmasses. The results of triaxial test simulations on the calibrated synthetic rockmass specimens are used to develop two semi-empirical approaches. In the first approach, called the SD approach, equations that relate the strength degradation of a jointed rockmass from intact rock to the confinement are developed. The second approach is based on adjusting the strength parameters of the Hoek-Brown failure criterion to extend its applicability to highly interlocked jointed rockmassess. It is demonstrated that these two approaches can be used to estimate the confined strength of such rockmasses in a situation where the unconfined and confined strengths of the intact rock and the unconfined strength of the rockmass are known. The findings of this research provides the foundation for a better characterization of the strength for highly interlocked jointed rockmasses, and increases our understanding of the influence of confinement on rockmass strength.
Flexible floating thin film photovoltaic (PV) array concept for marine and lacustrine environments
(Laurentian University of Sudbury, 2014-05-16) Trapani, Kim
The focus of the research is on the development of the concept of floating flexible thin film arrays for renewable electricity generation, in marine and lacustrine application areas. This research was motivated by reliability issues from wave energy converters which are prone to large loads due to the environment which they are exposed in; a flexible system would not need to withstand these loads but simply yield to them. The solid state power take off is an advantage of photovoltaic (PV) technology which removes failure risks associated with mechanical machinery, and also potential environmental hazards such as hydraulic oil spillage. The novelty of this technology requires some development before it could even be considered feasible for large scale installation. Techno-economics are a big issue in electricity developments and need to be scoped in order to ensure that they would be cost-competitive in the market and with other technologies. Other more technical issues relate to the change in expected electrical yield due to the modulation of the PV array according to the waves and the electrical performance of the PVs when in wet conditions. Results from numerical modelling of the modulating arrays show that there is not expected variation in electrical yield at central latitudes (slightly positive), although at higher latitudes there could be considerable depreciation. With regards to the electrical performance a notable improvement was measured due to the cooling effect, slight decrease in performance was also estimated due to water absorption (of ~ 1.4%) within the panels. Overall results from both economic and technical analysis show the feasibility of the concept and that it is a possibility for future commercialisation.
A framework to develop a hybrid methodology for modeling of diesel particulate matter concentration in underground mine ventilation systems
(2019-10-15) Zhang, Hongbin
The purpose of this research is to develop a hybrid methodology for diesel particulate matter (DPM) modeling for underground mine ventilation systems. The hybrid methodology, which is an enhanced and complementary tool, is proposed to provide improved diesel input to a ventilation network solver by using a computational fluid dynamics (CFD) solver. The hybrid methodology uses the DPM results from a calibrated CFD model to update those from a network model at shared locations. A CFD approach for simulating DPM over an extended period has been proposed to make the hybrid methodology more adaptable to large ventilation systems. With the proposed CFD modeling approach, contaminants like DPM can be modeled accurately in a timely manner over an extended period of time. The results from this approach are then used to update the network model results at the shared outlets. The workflow to update DPM results from the network model using the calibrated CFD model is presented. Two field studies were conducted in an underground mine in the western United States. Due to the low quality airflow and DPM data collected from the field, this study should be viewed as a qualitative study rather than a quantitative study. Corresponding CFD models, ventilation network models, and updated ventilation models were also established, and results from these models were compared with the experimental data. The limitations for both the instruments and the methodology were defined as well.
An improved energy management methodology for the mining industry.
(2015-09-10) Levesque, Michelle
The focus for this work was the development of an improved energy management methodology tailored for the mining sector. Motivation for this research was driven by perception of slow progress in adoption of energy management practices to improve energy performance within the mining sector. Energy audits conducted for an underground mine, a mineral processing facility, and a pyrometallurgical process were reviewed and recommendations for improved data gathering, reporting and interpretation were identified. An obstacle for conducting energy audits in mines without extensive sub-metering is a lack of disaggregated data indicating end use. Thus a novel method was developed using signal processing techniques to disaggregate the end-use electricity consumption, exemplified through isolation of a mine hoist signal from the main electricity meter data. Further refinements to the method may lead to its widespread adoption, which may lower energy auditing costs via a reduced number of meters and infrastructure, as well as lower data storage requirements. Mine ventilation systems correspond to the largest energy demand center for underground mines. Thus a detailed analysis ensued with the development of a techno-economic model that could be used to assess various fan and duct options. Furthermore, the need for a standardized methodology for determination of duct friction factors from ventilation surveys was proposed, which included a method to verify the validity of the resulting value from asperity height measurements. A method was also suggested for determination of leakage and duct friction factor values from ventilation survey data. Dissemination of best practice is a strategy that could be employed to improve energy performance throughout the mining sector, thus a Best Practice database was developed to iv improve communication and provide a standardized reporting framework for sharing of energy conservation initiatives. Demonstration of continuous improvement is an underpinning element of the ISO 50001 energy management standard but as mines extract ore from deeper levels energy use increases. Thus ensued the development of a benchmarking metric, with the use of appropriate support variables that included mine depth, production, and climate data, that demonstrated the benefit of implemented energy conservation measures for an underground mine. The development of an ultimate energy management methodology for all stages of mineral processing from ‘Mine to Bullion’ is beyond the scope of this work. However, this research has resulted in several recommendations for improvement and identified areas for further improvements.
Influence of test conditions on post-peak deformation behavior of rock
(2017-04-10) Xu, Yuhang
Understanding the post-peak deformation behavior of rock is important for underground rock engineering. Laboratory property testing is commonly employed to investigate the post-peak deformation behavior. However, the test conditions of laboratory testing, especially the Loading System Stiffness (LSS) of stiff test machines, are usually varied and the influence of this variation on the test results has not been fully elucidated. In addition, studying the influence of test conditions on the post-peak deformation behavior of rock is crucial for interpreting test results and subsequently applying the results to rock engineering design. The goal of this dissertation is to identify how the post-peak deformation behavior of a rock specimen is affected by three major aspects of test conditions––the specimen geometry, the contact conditions, and the LSS. To achieve this goal, an FEM/Explicit tool was employed to carry out numerical experiments, in which the same material property was assumed for the rock specimens and each wanted test condition was isolated for analysis. The well-observed slenderness effect and the recently-observed cross-sectional shape effect on the Uniaxial Compressive Strength (UCS) of rocks were studied. The modeling results suggest that the numerical tool and models are suitable for investigating the problem and the hoop tension theory could be flawed. Next, the cross-sectional shape effect on the post-peak deformation behavior was investigated. The modeling results reveal that although the influence of the cross-sectional shape on the UCS of rocks is small, the cross-sectional shape affects the post-peak deformation behavior considerably. The actual contact condition and the end effect in true triaxial compression tests were simulated while the legitimate intermediate principal stress (2) effect was excluded from the rock material contacts are frictional and the specimen in the 2 loading direction is squat. Thus, existing 3D empirical failure criteria based on previous true triaxial compression test results may overestimate the rock strength. The influence of LSS on the post-peak stress–strain relations of stable rock failure was examined. Key loading components of stiff test machines were considered in the numerical model. The modeling results clarify that LSS affects the post-peak stress–strain curves of rocks even when the failure process is stable. Unless LSS is either perfectly rigid or equivalent to the critical LSS (), the post-peak stress–strain curves obtained under various LSS (with LSS >  ) are varied and all steeper than the one under an ideal loading condition. This dissertation demonstrates the cross-sectional shape effect in the post-peak deformation stage, the long overlooked 2 effect caused by the end effect, and the variation of post-peak stress– strain curves due to the LSS. This dissertation also makes a contribution to examining the hoop tension theory and recognizing the correct choice of cross-sectional shape for test specimens, offers insights into improving 3D empirical failure criteria and true triaxial test settings, and suggests new requirements for developing stiff test machines in the future.
Measuring and modelling human response to foot-transmitted vibration exposure
(2019-07-16) Goggins, Katie Anne
Foot-transmitted vibration (FTV) occurs when a worker is exposed to vibration through the feet and can occur when operating vibrating equipment such as bolters, jumbo drills, or crushers, or standing to operate mobile equipment such as locomotives and forklifts. Exposure to FTV has been linked to the development of vibration-induced white feet, a vascular disorder with reduced circulation to the toes causing blanching. Vibration research has been focused on whole-body vibration (WBV) and hand-arm vibration, with FTV being lumped in to standing WBV. This research includes, but is not limited to, resonant frequency identification, development of international standards governing safe exposure limits, personal protective equipment design, and model development. It is the intention of this research to initiate research specifically for FTV. The first step to preventing harmful exposure is to identify the resonant frequencies at different anatomical locations on the foot (Objective 1). The resonance of 24 anatomical locations on the foot was identified for 21 participants, where the most notable differences in the average peak frequency occurred between the toes (range: 99-147Hz), midfoot (range: 51-84Hz), and ankle (range: 16-39Hz). As workers do not normally stand in a completely natural position, it was equally important to measure how altering the location of the centre of pressure (COP) changes resonance and the transmissibility of vibration through the foot (Objective 2). The resonance at the same 24 anatomical locations was identified when the COP was pushed forward (towards toes) and backward (towards heels). Generally, resonance at the measurement location increased when the COP was concentrated to a particular portion of the foot. The third objective of this research was to reduce the measurements at 24 anatomical locations, from the first two objectives, down to a representative subset (Objective 3). Multiple correspondence analysis was conducted on the peak transmissibility magnitude in order to assess structure displacement leading to increases in potential injury risk. Transmissibility results were analysed based on two magnitude thresholds: at 2.0 indicating 100% amplification of the input signal, and at 2.5 indicating 150% amplification. Results indicate that transmissibility measurements at the nail bed of first phalange, head of first metatarsal, head of second metatarsal, and the lateral malleolus may be sufficient to effectively measure foot-transmitted vibration when participants changed their COP location from natural, forward and backward. Then a K-means analysis was conducted to minimize the anatomical locations necessary to capture the transmissibility response from 10 to 200 Hz, and using the reduced locations, a lumped-parameter model was designed and validated (Objective 4). Three locations (the nail of the big toe, the third metatarsal, and the lateral malleolus) were found to be sufficient for summarizing FTV transmissibility modulus. A three segment, four degrees-of-freedom lumpedparameter model of the foot-ankle system (FAS) was designed to model the transmissibility response at three locations when exposed to vertical vibration from 10 to 60 Hz. Reasonable results were found at the ankle, midfoot, and toes in the natural standing position and forward COP. However, when the COP is backward, the model does not sufficiently capture the transmissibility response at the ankle. Determining the resonant frequencies of the FAS is important for the prevention of vibration-induced injury. Resonance needs to be incorporated into the design of equipment, tools (e.g. anti-vibration drills, isolated platforms), and personal protective equipment (e.g. antivibration insoles or boots) can be modified to reduce vibration at the frequencies where tissue resonance occurs. These findings could also inform the development of new international standards for measuring/reducing exposure to FTV.
Model based fault detection for two-dimensional systems
(Laurentian University of Sudbury, 2014-05-05) Wang, Zhenheng
Fault detection and isolation (FDI) are essential in ensuring safe and reliable operations in industrial systems. Extensive research has been carried out on FDI for one dimensional (1-D) systems, where variables vary only with time. The existing FDI strategies are mainly focussed on 1-D systems and can generally be classified as model based and process history data based methods. In many industrial systems, the state variables change with space and time (e.g., sheet forming, fixed bed reactors, and furnaces). These systems are termed as distributed parameter systems (DPS) or two dimensional (2-D) systems. 2-D systems have been commonly represented by the Roesser Model and the F-M model. Fault detection and isolation for 2-D systems represent a great challenge in both theoretical development and applications and only limited research results are available. In this thesis, model based fault detection strategies for 2-D systems have been investigated based on the F-M and the Roesser models. A dead-beat observer based fault detection has been available for the F-M model. In this work, an observer based fault detection strategy is investigated for systems modelled by the Roesser model. Using the 2-D polynomial matrix technique, a dead-beat observer is developed and the state estimate from the observer is then input to a residual generator to monitor occurrence of faults. An enhanced realization technique is combined to achieve efficient fault detection with reduced computations. Simulation results indicate that the proposed method is effective in detecting faults for systems without disturbances as well as those affected by unknown disturbances.The dead-beat observer based fault detection has been shown to be effective for 2-D systems but strict conditions are required in order for an observer and a residual generator to exist. These strict conditions may not be satisfied for some systems. The effect of process noises are also not considered in the observer based fault detection approaches for 2-D systems. To overcome the disadvantages, 2-D Kalman filter based fault detection algorithms are proposed in the thesis. A recursive 2-D Kalman filter is applied to obtain state estimate minimizing the estimation error variances. Based on the state estimate from the Kalman filter, a residual is generated reflecting fault information. A model is formulated for the relation of the residual with faults over a moving evaluation window. Simulations are performed on two F-M models and results indicate that faults can be detected effectively and efficiently using the Kalman filter based fault detection. In the observer based and Kalman filter based fault detection approaches, the residual signals are used to determine whether a fault occurs. For systems with complicated fault information and/or noises, it is necessary to evaluate the residual signals using statistical techniques. Fault detection of 2-D systems is proposed with the residuals evaluated using dynamic principal component analysis (DPCA). Based on historical data, the reference residuals are first generated using either the observer or the Kalman filter based approach. Based on the residual time-lagged data matrices for the reference data, the principal components are calculated and the threshold value obtained. In online applications, the T2 value of the residual signals are compared with the threshold value to determine fault occurrence. Simulation results show that applying DPCA to evaluation of 2-D residuals is effective.
Modeling of plasma dynamics during pulsed electron beam ablation of graphite.
(2017-07-26) Ali, Muddassir
Recent advances in the field of plasma nanofabrication suggest that plasma-based technologies may replace many of the conventional chemical and thermal routes in the synthesis of nanomaterials (with at least one dimension below 100 nm) and thin films. In contrast to the conventional processing routes, where only neutral species are involved, a plasma is made up of energetic species including ions, electrons, and excited molecules in addition to neutrals. Due to the highly energetic nature of interactions among these species and with other surfaces (substrates), a plasma allows for the formation of materials at higher rates even though their concentrations might be low as compared with those of neutral species in non-plasma based methods. While the mechanisms of the various interactions in a plasma are undoubtedly complex and require a fundamental understanding, they offer new opportunities for material nanofabrication. Pulsed electron beam ablation (PEBA) has recently emerged as a novel and promising technique for high quality thin films growth. Pulsed electron beam film deposition consists of many physical processes including target material heating, target ablation, plasma plume expansion, and film growth on a substrate. Electron beam ablation is a complex process, which comprises heating, phase change, and removal of a fine fraction from the target surface. Ablation strongly affects the space distribution, composition, mass transfer processes, which in turn has a critical bearing on the structure, stoichiometry and properties of thin films. Plasma plume expansion into an ambient gas is a fundamental issue in PEBA as the quality of thin films deposited onto the substrate depends on the composition, energy and density of particles ejected from the target. A one-dimensional heat conduction model is presented to investigate the heating and ablation of a graphite target upon interaction with a polyenergetic electron beam. The effect of electron beam efficiency, power density, accelerating voltage, and Knudsen layer just above the target surface during ablation are taken into account in the model. Phase transition induced during ablation is considered through the temperature dependent thermodynamic properties of graphite. The temperature distribution, surface receding velocity, melting depth, ablation depth, and ablated mass per unit area are numerically simulated. Upon ablation, plasma expansion, induced by interaction of a nanosecond electron beam pulse (~100 ns) with a graphite target in an argon atmosphere at reduced pressure, was investigated by solving gas-dynamics equations. The spatiotemporal profiles of the temperature, pressure, velocity, and density of the plasma plume are numerically simulated for a beam efficiency of 0.6 and accelerating voltage of 15 kV. Each model is validated by comparing some of the obtained simulation results with experimental data available in the literature.
Modeling time-dependent deformation behavior of jointed rock mass
(2022-07-04) Wang, Mingzheng
Long-term stability analysis and stand-up time prediction of underground excavations are important in engineering design and construction. In this thesis, a numerical study of the time-dependent deformation behavior of jointed rock mass is presented. Firstly, creep deformation behavior of intact rock is studied numerically using the grainbased modeling (GBM) approach based on the Distinct Element Method (DEM). A grainbased time-to-failure (GBM-TtoF) creep model for intact brittle rocks is proposed to simulate creep deformations in the first two creep stages and time-dependent failure at the tertiary creep stage. Parameters of the TtoF model are calibrated using experimental data of Lac du Bonnet (LdB) granite. Simulations of the time-dependent deformation of rock pillars using the GBM-TtoF model are conducted. The influence of pillar shape (width to height ratio) and loading ratio (stress / strength) on the time-dependent spalling on pillar walls is investigated. Secondly, creep deformation of rock joints is simulated by using the grain-based joint models that are established using the GBM-TtoF model. The influences of joint roughness and loading conditions (normal and shear stresses) on the long-term shear strength and creep sliding velocity of joints are investigated. A new creep model is proposed, which can be used to control the creep deformation behavior of flat joints in the DEM. The model is validated using experimental data of joints. Thirdly, a creep model for jointed rock masses, which can consider time-dependent deformations of both rock and joints, is proposed. Creep deformations of jointed rock masses are simulated using a few jointed rock mass models, i.e., a rock mass model with a single joint, a jointed pillar model and a high rock slope model. The creep deformation characteristics of the jointed rock mass models are analyzed. Finally, time-dependent deformation behaviors of tunnels excavated in jointed rock masses are simulated using the creep model for jointed rock masses. The weakening of face-effect due to creep deformation of the rock mass is modeled using the internal pressure reduction method and the convergence-confinement method. The stand-up time of unsupported tunnels is simulated considering the influence of rock mass quality and the unsupported roof span. The simulated result is validated using Bieniawski’s stand-up time chart. The models developed in this thesis provide novel numerical approaches to simulating creep deformations of rock, joints and jointed rock masses, and are important for improving the understanding of the time-dependent deformation behavior of jointed rock masses.
A novel method of detecting galling and other forms of catastrophic adhesion in tribotests
(Laurentian University of Sudbury, 2014-10-01) Dalton, Gregory Michael
Tribotests are used to evaluate the performance of lubricants and surface treatments intended for use in industrial applications. They are invaluable tools for lubricant development since many lubricant parameters can be screened in the laboratory with only the best going on to production trials. Friction force or coefficient of friction is often used as an indicator of lubricant performance with sudden increases in friction coefficient indicating failure through catastrophic adhesion. Under some conditions the identification of the point of failure can be a subjective process. This raises the question: Are there better methods for identifying lubricant failure due to catastrophic adhesion that would be beneficial in the evaluation of lubricants? The hypothesis of this research states that a combination of data from various sensors measuring the real-time response of a tribotest provides better detection of adhesive wear than the coefficient of friction alone. In this investigation an industrial tribotester (the Twist Compression Test) was instrumented with a variety of sensors to record: vibrations along two axes, acoustic emissions, electrical resistance, as well as transmitted torsional force and normal force. The signals were collected at 10 kHz for the duration of the tests. In the main study D2 tool steel annular specimens were tested on coldrolled sheet steel at 100 MPa contact pressure in flat sliding at 0.01 m/s. The effects of lubricant viscosity and lubricant chemistry on the adhesive properties of the surface were examined. Tests results were analyzed to establish the apparent point of failure based on the traditional friction criteria. Extended tests of one condition were run to various points up to and after this point and the results analyzed to correlate sensor data with the test specimen surfaces. Sensor data features were used to identify adhesive wear as a continuous process. In particular an increase “friction amplitude” related to a form of stick-slip was used as a key indicator of the occurrence of galling. The findings of this research forms a knowledge base for the development of a decision support system (DSS) to identify lubricant failure based on industrial application requirements.
Numerical modeling of seismic wave propagation in underground mines.
(2015-11-04) Wang, Xin
The phenomenon of rockburst damage localization, which is not well understood, has been observed in deep underground mines. Analysis of seismic wave propagation in underground mines is of great interest for improved understanding of the dynamic rock failure problem. This thesis aims at making a contribution for improving understanding of the seismic wave propagation in deep underground mines. Advanced numerical modeling tools are used and new modeling techniques are developed to attain this goal. In this thesis, research is emphasized on the ground motion around excavations due to seismic wave propagation that results from a fault-slip seismic event in the far-field and the near-field. It is found that moment tensor point source model seems to be suitable for the source representation in the far-field and the non-point source model (such as kinematic rupture source model) seems to be suitable for the source representation in the near-field. The modeling results confirm that ground motion is influenced by many factors such as target-source distance, slip direction, spatial location, and geometrical and geological conditions. Influence of wavelength-to-excavation span (/D) ratio on the wavefield is investigated to gain insights of ground motion behavior under both quasi-static and dynamic loading conditions. It is revealed that PPV (peak particle velocity) values increase as the /D ratio increases and the amplification effect increases as the /D ratio decreases. The loading condition maybe changed from the dynamic loading to the quasi-static condition when the /D is larger than 30. Strong dynamic loading should be considered when the /D ratio is small (less than 10, with a shear wavelength less than 50 m and an excavation span greater than 5 m) for most underground excavations. A method is proposed to estimate the quality factor (a measure of energy loss per oscillation cycle) for shear waves propagating in underground hard rocks so as to gain insight into the influence of internal attenuation on seismic wave propagation. A proper shear wave quality factor can be obtained by comparing modeling results with that from a scaling law, even if there are no high quality data for quality factor back analysis. Furthermore, the influence of different geological structures on seismic wave propagation is studied. It is shown that wave propagation patterns around an excavation can be altered and PPV amplification and shielding effect can occur near the excavation boundaries amongst other reasons due to heterogeneities such as tunnels, open and backfilled stopes, and dykes in underground mines. Finally, a coupled numerical procedure, which couples FLAC and SPECFEM2D, is developed to consider the excavation effect on ground motion. The FLAC model considers the excavationinduced stress change and rock mass failure, and passes the input data to SPECFEM2D by invoking FISH scripts. In addition, a new nonlinear velocity model that considers the influence of confinement and rock mass failure on wave velocity is presented. This nonlinear velocity model and the coupled numerical technique are used to model a simple stope excavation problem. It is found that there is a large difference in the wavefields and ground motions between the results from the uniform and non-uniform velocity models. A relatively stronger amplification is observed in the low confinement zones and on the excavation surface in the non-uniform velocity models. Because stress redistribution and rock mass failure around an excavation are considered, a realistic non-uniform velocity field can be obtained. The proposed coupled numerical procedure offers a method to improve the understanding of the site amplification effect and ground motion near excavation boundaries. This thesis presents some insights with regard to seismic wave propagation due to fault-slip seismic events in underground mines. If seismic wave propagation in underground mines can be modeled properly using techniques such as these presented in this thesis, then it is possible to conduct forensic analysis after a large seismic event so as to explain one of many factors that caused rockburst damage localization. Alternatively, the modeling approach may provide valuable inputs for decision-making with regard to strengthening high risk areas to prevent rockburst, thus improving mine safety.

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