Engineering

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Ultra-small carbon nanospheres (< 50 nm) of uniform tunable sizes by a convenient catalytic emulsion polymerization strategy: superior supercapacitive and sorption performances
(2013-01-01) Ye, Zhibin; Tiwari, Vimal K.; Chen, Zhe; Gao, Fan; Gu, Zhiyong; Sun, Xueliang
Porous carbon nanospheres have received enormous attention for various applications. Though there are several elegant strategies existing for the synthesis of relatively large carbon nanospheres (> ca. 100 nm), the synthesis of carbon nanospheres with well-defined tunable ultra-small sizes (< 50 nm) has often been challenging while such ultra-small nanospheres are much more valuable. A novel, convenient, and scalable catalytic emulsion polymerization technique is demonstrated in this paper for highly efficient synthesis of ultra-small carbon nanospheres with uniform tunable sizes in the range of 11–38 nm. In this strategy, a simple change of the emulsion polymerization recipe renders a convenient yet efficient tuning of the size of the carbon nanospheres. In particular, activated carbon nanospheres (A-CNS21 of average size of 21 nm) obtained by carbonization in the presence of KOH as the chemical activation agent is featured with very high surface area (2,360 m2/g) and the desired hierarchical macro-/meso-/micropore structures resulting from nanosphere packing/aggregation. A-CNS21 is demonstrated to have superior high-rate supercapacitive performances and outstanding sorption capacities towards volatile organic compounds (VOCs), H2, and CO2, which are comparable to or even better than the best results reported to date in these applications. To the best of our knowledge, this is the first synthesis of ultrasmall carbon nanospheres with uniform tunable sizes and superior performances for these applications by the emulsion polymerization strategy.
Imaging, characterization and processing with axicon derivatives.
(Laurentian University of Sudbury, 2013-08-06) Saikaley, Andrew Grey
Axicons have been proposed for imaging applications since they offer the advantage of extended depth of field (DOF). This enhanced DOF comes at the cost of degraded image quality. Image processing has been proposed to improve the image quality. Initial efforts were focused on the use of an axicon in a borescope thereby extending depth of focus and eliminating the need for a focusing mechanism. Though promising, it is clear that image processing would lead to improved image quality. This would also eliminate the need, in certain applications, for a fiber optic imaging bundle as many modern day video borescopes use an imaging sensor coupled directly to the front end optics. In the present work, three types of refractive axicons are examined: a linear axicon, a logarithmic axicon and a Fresnel axicon. The linear axicon offers the advantage of simplicity and a significant amount of scientific literature including the application of image restoration techniques. The Fresnel axicon has the advantage of compactness and potential low cost of production. As no physical prior examples of the Fresnel axicons were available for experimentation until recently, very little literature exists. The logarithmic axicon has the advantage of nearly constant longitudinal intensity distribution and an aspheric design producing superior pre-processed images over the aforementioned elements. Point Spread Functions (PSFs) for each of these axicons have been measured. These PSFs form the basis for the design of digital image restoration filters. The performance of these three optical elements and a number of restoration techniques are demonstrated and compared.
Development of a new velocity measurement technique : the laser bessel velocimetry
(Laurentian University of Sudbury, 2015-07-20) Sakah, Mahmud Ali
The present thesis describes the design, construction and testing of a new velocity measurement optical technique system. The technique has similarities with the laser Doppler velocimetry (LDV) in that it uses scattered light detection, in order to measure one component of the velocity vector of moving flows or solid surfaces. It uses the fringes of a Bessel beam produced by an axicon to generate the measurement volume. This technique, which we call Laser Bessel velocimetry (LBV), is noninvasive and permits continuous velocity measurements of moving particles. The experimental measurement set-up including the laser source, the optical devices, a moving stage with known velocities, a photodetector to capture scattered light and signal processing and data acquisition components, was developed and used to provide a proof of concept of this new technique. The set-up was also tested with a commercial LDV system. Two types of refractive linear axicons have been used to generate a Bessel type beam by illuminating the axicons with blue and red collimated and coherent laser light of dissimilar wavelengths, λ. The linear axicons offer the advantage of simplicity. The software tools for measurements, acquisition and analysis of the data are developed using NI Labview and MATLAB. Results from both theoretical simulation and experimental measurements are presented and compared.
Efficient, robust surface functionalization and stabilization of gold nanorods with quaternary ammonium-containing ionomers as multidentate macromolecular ligands
(2016-04-25) Dong, Zhongmin; Xiang, Peng; Huang, Lingqi; Ye, Zhibin
Surface functionalization of gold nanorods (GNRs) is critical to their applications in various fields. While there are several existing strategies, we report in this article a new general strategy for the surface functionalization of GNRs with quaternary ammonium-containing ionomers as a novel class of multidentate macromolecular surface ligands. A range of tetralkylammoniumcontaining hyperbranched polyethylene- and linear poly(n-butyl acrylate)-based ionomers has been specifically designed and employed in the strategy. Acting as multidentate macromolecular analogues of cetyltrimethylammonium bromide (CTAB), the ionomers have been demonstrated to bind onto the GNR surface by displacing the surface-bound CTAB species via ligand exchange to render CTAB-free ionomer-modified GNRs. By properly designing the enabling ionomers, we have shown that the modified GNRs can be endowed with some desired properties, such as excellent dispersibility in various organic solvents, robust stability under multiple rounds (up to 12 investigated) of high-speed centrifugation in organic solvents, amphiphilicity with dispersibility in both aqueous and organic media, fluorescence, and capability in carrying hydrophobic guest species. This strategy thus provides potential new ways for the construction of novel multifunctional GNR nanocomposites.
Modification of cellulose nanocrystals with quaternary ammonium-containing hyperbranched polyethylene ionomers by ionic assembly
(American Chemical Society, 2016-07-25) Huang, Lingqi; Ye, Zhibin; Berry, Richard
In this article, we demonstrate the first surface modification of cellulose nanocrystals (CNCs) with quaternary ammonium-containing ionomers by ionic binding of their positively charged ammonium ions onto the negatively charged surface of CNCs. A range of hyperbranched polyethylene ionomers (I1–I6) having different ionic content (0.2–2.3 mol %) has been designed and employed for this purpose. The simple dropwise addition and mixing of the aqueous dispersion of CNCs with the ionomer solution in tetrahydrofuran (THF) conveniently renders the ionomer-modified CNCs (mCNC1–mCNC6). The presence of adsorbed ionomers on the modified CNCs is confirmed with spectroscopic and X-ray diffraction evidence and quantified through thermogravimetric analysis. The effects of the ionomer to CNC feed mass ratio and the ionomers of different ionic content on the modification have been examined. A study on the morphology of the modified CNCs by atomic force microscopy discloses the occurrence of side-to-side and/or end-to-end assembly of the CNC rods due to the “cross-linking” or bridging effects of the multidentate ionomers. Because of the hydrophobic hyperbranched polyethylene segments in the adsorbed ionomers, the modified CNCs can be dispersed in nonpolar or low-polarity organic solvents (such as THF, toluene, and chloroform). In particular, the THF dispersions of modified CNCs prepared with ionomers having ionic content ≥0.7 mol % (I3–I6) behave as thixotropic organo-gels at concentrations ≥40 mg mL–1. Further, the modified CNCs better disperse than unmodified CNCs in a hydrophobic ethylene–olefin copolymer (EOC) elastomer matrix and show better thermal stability than a surfactant-modified CNC sample. Tensile testing confirms that the EOC composites, filled with the ionomer-modified CNCs, are significantly reinforced with a tensile modulus nearly doubled that of neat EOC, and they demonstrate better elongation at break relative to those filled with unmodified CNCs or surfactant-modified CNCs.
Polycyclopentene crystal-decorated carbon nanotubes by convenient large-scale in situ polymerization and their lotus leaf-like superhydrophobic films.
(2016-12-22) Ye, Zhibin; Xu, Lixin; Huang, Lingqi; Meng, Nan; Shu, Yang; Gu, Zhiyong
In situ Pd-catalyzed cyclopentene polymerization in the presence of multi-walled carbon nanotubes (MWCNTs) is demonstrated to effectively render, on a large scale, polycyclopentene-crystal-decorated MWCNTs. Controlling the catalyst loading and/or time in the polymerization offers a convenient tuning of the polymer content and the morphology of the decorated MWCNTs. Appealingly, films made of the decorated carbon nanotubes through simple vacuum filtration show the characteristic lotus-leaf-like superhydrophobicity with high water contact angle (>150°), low contact angle hysteresis (<10°), and low water adhesion, while being electrically conductive. This is the first demonstration of the direct fabrication of lotus-leaf-like superhydrophobic films with solution-grown polymer-crystal-decorated carbon nanotube.
High-performance iron oxide-graphene oxide nanocomposite adsorbents for arsenic removal
(2017-01-01) Ye, Zhibin; Su, Hui; Hmidi, Nuri
We report the synthesis of a new range of iron oxide-graphene oxide (GO) nanocomposites having different iron oxide content (36–80 wt%) as high-performance adsorbents for arsenic removal. Synthesized by co-precipitation of iron oxide on GO sheets that are prepared by an improved Hummers method, the iron oxide in the nanocomposites is featured primarily in the desirable form of amorphous nanoparticles with an average size of ca. 5 nm. This unique amorphous nanoparticle morphology of the iron oxide beneficially endows the nanocomposites with high surface area (up to 341 m2 g-1 for FeOx-GO-80 having the iron oxide content of 80 wt%) and predominant mesopore structures, and consequently increased adsorption sites and enhanced arsenic adsorption capacity. FeOx-GO-80 shows high maximum arsenic adsorption capacity (qmax) of 147 and 113 mg g−1 for As(III) and As(V), respectively. These values are the highest among all the iron oxide-GO/reduced GO composite adsorbents reported to date and are also comparable to the best values achieved with various sophisticatedly synthesized iron oxide nanostructures. More strikingly, FeOx-GO-80 is also demonstrated to nearly completely (>99.98%) removes arsenic by reducing the concentration from 118 (for As(III)) or 108 (for As(V)) to < 0.02 μg L−1, which is far below the limit of 10 μg L−1 recommended by the World Health Organization (WHO) for drinking water. The excellent adsorption performance, along with their low cost and convenient synthesis, makes this range of adsorbents highly promising for commercial applications in drinking water purification and wastewater treatment.
Microalgae growing in stressed environments and their antioxidant potential from production of secondary metabolites
(2020-08-12) Gauthier, Miranda Rose
Microalgae are photosynthetic microorganisms found in aquatic environments around the world. There is interest in using microalgae to capture carbon (CO2) from industrial off-gas, but sulphur dioxide often present in these gasses increases growing media acidity making it essential to find microalgal strains able to survive in pH 3.0-4.0. High metal concentration, acidity, solar irradiance, and nutrient limitations can instigate the production of protective secondary metabolites with antioxidant potential. Therefore, the antioxidant potential of novel microalgal isolates bioprospected from acidic mine-impacted water systems, identified as Coccomyxa sp. and Chlamydomonas sp., and a culture collection strain Chlamydomonas reinhardtii were tested using three antioxidant assays. Results showed that low pH conditions (pH 3.0) increased biomass production of Coccomyxa sp. but induced the death of C. reinhardtii. Under both pH 3.0 and uncontrolled pH conditions, the bioprospected strains had higher antioxidant potential than C. reinhardtii, with Coccomyxa sp. having the highest potential.
Recovery and repurposing of low-grade thermal resources in the mining and mineral processing industry
(2020-10-29) McLean, Shannon Heather
A substantial quantity of energy is currently lost as waste heat to the atmosphere in the mining and mineral processing industry. The recovery and application of this waste heat to on-site processes is an opportunity to reduce primary fuel usage, operational cost and environmental impacts. To investigate this, research has been conducted within a nickel smelter’s sulphuric acid plant, where operational data was collected on a process water cooling loop that incorporates cooling tower systems. The cooling towers discharge in excess of 50 MW of heat without any recovery. Collected data was then used to develop a model to quantify the potential for low-grade heat recovery and repurposing within the sulphuric acid manufacturing process. Heat pumps were examined as a method to repurpose this waste heat, and use it to replace electric heaters currently used in the mist precipitators and weak acid stripper. The model allows for an economic and environmental impact comparison between various recovery and application scenarios. Results obtained from the model indicated that the implementation of a heat pump system would provide a reduction in annual operating costs that allows a payback period of 3 years. Furthermore, there would be from less primary energy consumption a reduction in CO2 emissions of about 42% from heat pump operation compared to electric heaters for the system. To further quantify environmental benefits from implementing the proposed recovery strategy, a comparative life-cycle assessment (LCA) model was also constructed and applied to the sulphuric acid plant. The LCA showed a 20% reduction in emissions in the cooling tower and heating system would be achieved from the impact categories of global warming, acidification, eutrophication, and human toxicity potentials. This includes emissions from cooling tower fans and water pumps, as well as the mist precipitator air heating. The concepts and models can be applied to a wide range of energy intensive industrial sectors, to help identify and quantify reductions in consumption and improvements in long-term sustainability performance.
Morphometric changes with age in human trabecular bone structural units (BSU) of the lumbar spine
(2020-11-20) Lamarche, Britney A.
Age-related fractures are common at skeletal sites with high proportions of cancellous bone such as the hip and spine. Research has shown that measures of bone quantity alone are imperfect predictors of fracture risk, so recent efforts have focused on combining them with measures of bone quality. One aspect of quality that has received little attention is the microstructure of the trabeculae themselves, which are composed of a patchwork of bone structural units (BSU), also known as hemiosteons or trabecular packets, bonded together by cement lines. Any changes in the size of the BSU can be expected to affect the mechanical and failure behavior of cancellous bone. The present work quantified morphometric changes in BSU from the vertebra of 8 young and 8 old individuals as a function of age and 3-D architectural parameters. Reductions in the size of BSU and increases in the proportion of cement line were found to occur with ageing, but these changes were more highly correlated to deteriorating cancellous architecture. These relationships, and the mechanical implications of smaller BSU and increased amounts of brittle cement line, require further investigation.
UV/Photocatalyst based photoreactor design for water treatment
(2020-12-15) Yongmei, Jiao
A germicidal ultraviolet (UV-C)/photocatalyst based advanced oxidation process (AOP) has potential to disinfect and mineralize waterborne organic pollutants without generating disinfection by-products. But low efficiency has hindered application of this technology. In this study, I have looked to improve the AOP process through use of enhanced photocatalytic surfaces and reactor design. The intention is that the resulting improvements will help in combating the effects of water eutrophication due to global warming, which is often accompanied by accelerated cyanobacterial (blue-green algae) growth and waterway contamination by their toxins. An acidic anatase titanium dioxide (TiO2) slurry doped with tungsten oxide (WO3) or rutile TiO2 was coated onto stainless steel plates, and annealed at 460, 500, and 540°C in a muffled furnace. The coatings were ~10 µm thick and demonstrated good durability. This method enabled bandgap reduction to the visible light spectrum for all coatings, with the smallest bandgap being 2.48 eV. The higher annealing temperatures resulted in rougher coated surfaces, which had negative effect on photocatalytic activities. Methylene blue (MB) degradation tests under UV-C showed that the coatings annealed in 460°C had the best performance and with a rate constant of 5.59 h-1. An UV-C/TiO2 based photocatalytic reactor with a corrugated configuration was designed to accommodate a larger photocatalytic surface per unit volume. With TiO2 coated corrugated plates, a 70 % MB solution was degraded within the first 10 minutes with the highest photonic efficiency of 2.83 %. A light absorption model was developed and validated with light intensity measurements. A set of corrugated photocatalytic reactors with the same surface area, but different geometries were analyzed and the one with flatter configuration showed better energy absorption capacity. A household scale UV-C/TiO2 reactor was then designed for drinking water treatment. A 3D UV-C absorption model, that agreed well with light intensity measurements, was used to predict light energy absorbed by the photocatalyst coatings and to optimize reactor design. The system degraded a synthesized raw water pollutant (uracil) and the organic matter in lake water by 34.2 % and 33.2 % respectively in 24 minutes, and also concurrently inactivated Escherichia coli.
Optimization of small modular nuclear reactor integration at a remote mine site in Canada
(2020-12-16) Eastick, Jeff
The concept of design envelope energy system optimization was developed and used to investigate the feasibility of small modular reactor (SMR) deployment at a remote off-grid mine in northern Canada. A set of design envelope demands was produced based on engineering estimates to represent the anticipated actual nominal and peak demands of the mine, with a focus on preserving characteristic variability on a per-utility basis. The formulation of design envelope optimization was successful in optimizing a mine’s energy supply system given a design envelope of nominal and peak energy demands to ensure the peak demand could always be satisfied, as demonstrated through optimization of a wind-diesel hybrid system. A SMR was integrated into the optimal mine site energy supply (OMSES) optimization model. However, the SMR was not an economic solution for the mine given the economic circumstances of the project. The high specific capital cost of the SMR was not competitive against an incumbent wind-diesel hybrid system. Therefore, additional opportunities to integrate a SMR more deeply into a mine’s operation were conceptualized and proposed for future work.
Computational modelling of membrane viscosity for immersed boundary simulations of red blood cell dynamics
(2021-01-29) Li, Ping
Although tremendous efforts have been devoted to modelling various membrane properties, few studies considered the membrane viscous effects. Meanwhile, immersed boundary method (IBM) has been a popular choice for simulating the motion of deformable cells in flow for the convenience of incorporating the flow-membrane interaction. Unfortunately, the direct implementation of membrane viscosity in IBM suffers severe numerical instability. In this thesis, three numerical schemes for implementing membrane viscosity in IBM are developed. Furthermore, the effects of membrane viscosity on the capsule dynamics in shear flow have been examined in detail. In Chapter 1, the biomechanical properties of red blood cells (RBCs) are introduced followed with a literature review. Also, the motivations and objectives, the structure of this thesis, and the contributions of the candidate are described. In Chapter 2, a finite-difference approach is proposed for implementing membrane viscosity in IBM. To improve the simulation stability, an artificial elastic element is added in series to the viscous component in the membrane mechanics. The detailed mathematical description and key steps for its implementation in immersed boundary programs are provided. Validation tests show a good agreement with analytical solutions and previous calculations. The accuracy dependence on membrane mesh resolution and simulation time step is also examined. In Chapter 3, two other schemes are proposed based on the convolution integral expression of the Maxwell viscoelastic element. Several carefully designed tests are conducted and the results show that the three schemes have nearly identical performances in accuracy,
Effects of blade angle on the force and work during sharp force trauma of porcine ribs
(2021-09-29) Hogue, Maxime
Forensic anthropologists interpret bony injuries to reconstruct what occurred during a homicide, including estimating the amount of force needed to create sharp-force trauma. Because a qualitative scale —mild, moderate and severe— is currently used for predicting the forces involved, recent studies have focused on providing more quantitative data. A stabbing is a dynamic event where both participants may be moving, so the wounds can be expected to occur over a range of orientations. This study analysed the effects of angle on sharp-force injuries. A pneumatic device that can create consistent overhand stabs was used to analyse the change in force and work at angles of 0°, 45° and 90° relative to the long axis of the ribs. The results indicate that the angle of the blade does affect the force and work required to create bony injuries. Therefore, the blade angle needs to be considered in forensic analyses.
Numerical studies for membrane viscous effects on red blood cell dynamics in flows
(2022-02-23) Rezghi, Ali
In this thesis, three-dimensional simulations are performed to investigate the effects of membrane viscosity on behaviors of red blood cells (RBCs) in simple shear flow and the migration processes of viscoelastic capsules in tube flow. The lattice Boltzmann method is used as the fluid solver, whereas the immersed boundary method is employed to capture the dynamic interaction between the flow and membrane. The RBC membrane follows the Skalak constitutive law for elasticity, and the resistances to area dilation and bending deformation are also included. In addition, the membrane viscosity is incorporated using the recently developed finite difference scheme. The methodology and computer programs are validated carefully by conducting several benchmark test simulations. The lateral migration of viscoelastic capsules in tube flow is investigated in details with various combinations of viscosity ratio, membrane shear viscosity and capillary number. In general, the migration process starts with an initial transient phase, where the capsule deformation and migration velocity suddenly increase from zero to a maximum value. Following that, the deformation and migration velocity gradually reduce as the capsule moves toward the tube centerline. The capsule also performs continuous rotation during the migration, and the rotation gradually slows down with the capsule migration. The interior-exterior fluid viscosity contrast and the membrane viscosity have similar effects in reducing the capsule deformation and inclination angle to the flow direction; however, a strong membrane viscosity may introduce significant oscillations in the capsule deformation, inclination, and migration velocity. Due to the reduced capsule deformation, the migration velocity and capsule rotation become slower for capsules with higher viscosity contrast and/or membrane viscosity. Moreover, the influence of membrane viscosity on the migration dynamics intensifies at higher capillary number. In addition, tank-treading behaviors of RBC in simple shear flow is scrutinized over a wide range of shear rate and exterior fluid viscosity. Detailed comparisons of the tanktreading frequency, deformation, and inclination angle of the cell with experiments are conducted by considering different combinations of membrane and interior fluid viscosities. According to the results, tank-treading frequency diminishes with both membrane viscosity and internal fluid viscosity, although elevating the interior viscosity alone does not sufficiently retard the tank-treading motion to achieve favorable agreement with experimental results. This stronger impact of membrane viscosity has also been noticed for the cell deformation and inclination angle. In particular, including membrane viscosity is essential to reproduce experimental results for the cell orientation. Furthermore, the results indicate that a reasonable agreement can be obtained in comparison to experiments even without applying the shear-thinning model for membrane viscosity. Hence, more supporting evidence is required to justify necessity and applicability of shear-thinning models for membrane viscosity of RBCs. Suggestions for future research have been proposed as well.
Fermentation CO2 biosequestration by microalgae for the production of health beneficial natural compounds
(2022-04-21) Yavari, Nasim
In this work, three different microalgal strains were investigated for effective biosequestration of CO2 generated by beer (yeast) fermentation. They were a culture collection Chlamydomonas reinhardtii and two bioprospected strains, Coccomyxa sp. (P-918) obtained from a polishing pond at an operational smelter (pH 2.8) and Chlamydomonas sp. (M-23) obtained from a low pH abandoned mine site (pH 3). The three strains were investigated for use in beer fermentation CO2 fixation and their production of both lipid and protein. The pH of beer fermentation CO2-enriched Chlamydomonas reinhardtii cultures varied between 4.5 and 7.3 throughout the experiment. For the Chlamydomonas sp., pH varied between 4.6 and 7.1 and for Coccomyxa sp. between 5.3 and 7.4. As expected, during higher fermentation activity (day 1 to 3 for each beer kit), more CO2 was released to the microalgal cultures causing a drop in pH. When the rate of fermentation slowed in day 4, there was an increase in pH. For all three microalgal cultures which were grown only under atmospheric CO2 (controls), the pH increased continuously along with microalgal growth over 16 days of experiment. Chlamydomonas reinhardtii control culture pH was 6.7 at the start of the experiment and reached 8.7 at day 16. For the Chlamydomonas sp. control culture, pH increased steadily from 6.6 to 8.4, and for Coccomyxa sp. from 7 to 8.6. Experimental results indicated that the bioprospected Coccomyxa sp. adapted well to the low pH created by sparging in beer fermentation CO2. Its volumetric biomass productivity was 0.124 gdwL-1 day-1, which was higher than both Chlamydomonas reinhardtii (0.072 gdwL-1day-1) and bioprospected Chlamydomonassp. (0.086 gdwL-1day-1). The Coccomyxa sp. when exposed to fermentation CO2 reached a maximum specific growth rate of 0.167 day−1, which was 29% higher than achieved without sparging in fermentation CO2. Moreover, its carbon fixation rate increased from 122.1 to 227.9 mgCO2 L1day-1 with fermentation CO2. However, lipid synthesis occurred more rapidly and efficiently in Chlamydomonas sp. and Chlamydomonas reinhardtii rather than Coccomyxa sp., reaching 39% and 35% of biomass dry weight after 16 days of beer fermentation CO2 exposure. Whereas the amount of lipid in Coccomyxa sp. was 26% of the biomass dry weight at 16 days. This would indicate that the bioprospected Chlamydomonas sp. was a better candidate for biofuel production as its dry weight lipid content increased from 20% to 39% when exposed fermentation CO2. While the lipid content of Chlamydomonas sp. culture that grew under atmospheric CO2 reached 24% of biomass dry weight at the end of experiment (day 16) from its initial 20%. It was found that protein content with fermentation CO2 was 42.5% of Coccomyxa sp. biomass dry weight. Protein content of Chlamydomonas reinhardtii and Chlamydomonas sp. dry weight were 30.7% and 27.4%, respectively.
Application of laser bessel beams in velocity measurements
(2022-06-24) Sakah, Mahmud
In this thesis we explore the use of Laser Bessel beams in solid surface and fluid velocity measurements. We present a novel simple technique to measure two velocity components of a solid surface, using a Bessel beam Laser Doppler Velocimetry (LDV) system. The experiments examined the intersection of similar two Bessel beams to generate interference fringes at the intersection region. These fringes, along with the Bessel beam fringes can be used in a simple LDV system to measure two velocity components. We also explored the use of single Bessel beams for measurement of fluid flow velocity in a horizontal transparent smooth straight circular pipe using forward scattering Laser Bessel velocimetry (LBV). The measurements were validated using a commercial LDV system. In order to produce an acceptable spatial resolution for fluid flow measurements, we investigated experimentally and numerically the use of Durnin rings (annular slits) with finite width to produce nearly Bessel beams with limited transverse profile extent and depth of field (DOF). One purpose of the work was to develop the suitability of laser Bessel Velocimetry for flow conditions where velocity measurements by alternative instrumentation were not feasible or were subject to optical access limitation. We also demonstrated, a significant advantage in using a single Bessel beam to measure the total velocity of two-dimensional flows.
Effects of bone structural unit (BSU) geometry and material properties on crack growth through idealized trabecular microstructures
(2022-10-18) Rahovich, Pavel
Bones containing large proportions of trabecular bone tissue such as the hip, wrist, and spinal column are highly susceptible to fracture. These fractures occur more frequently in the older populations, putting a large burden on the healthcare system and the society as a whole. Bone fracture prediction methods rely heavily on bone quantity measurements when predicting fracture risks. However, research has shown that only using bone quantity as the main predictor fails to identify a large number of patients with a high risk of bone fracture. Recent studies have shown that with age, the microstructure of the trabeculae changes as the patchwork of bone structural units (BSU), also known as trabecular packets, reduce in size due to the remodeling process. Unfortunately, little is known about the mechanical consequences of these changes on the trabeculae’s ability to resist cracking. Smaller BSU with age may reduce fracture risk due to crack blunting or redirection. Conversely, smaller BSU results in a larger proportion of brittle cement line which could provide more preferential paths for crack growth. The present work used extended finite element method (XFEM) crack modeling techniques, which have recently been applied to simulate crack growth in cortical bone, to model crack propagation through idealized trabeculae in 2D. The material properties for the BSU and cement line, as well as the size of the BSU themselves, were varied through parametric studies. Smaller BSU were found to accelerate crack growth within bone. Other geometric parameters like aspect ratio and angle of crack deflection were also identified as major contributors to the bones ability to resist cracks. Future work should investigate more representative BSU geometries to further clarify the role these structures have on fracture risk.
An exploration of experimental and numerical approaches to design of a ducted helical air turbine
(2023-01-06) Vipond, Philip
The proposed device is a ducted air turbine with a 2-bladed helical rotor. To attempt to characterize the performance of the device, as well as establish a methodology for further experimentation, a campaign of testing was undertaken. The campaign described in the work culminates in a comparative study between a simulated experiment (undertaken using Computational Fluid Dynamics) and a physical experiment (undertaken with a dynamometer, and a duct system connected to a flow meter and centrifugal air pump). The simulated experiment has been transformed using the similarity laws, and the resulting data has been used to predict the performance of the physical experiment by interpolating to the setpoints observed in the physical experiment. These setpoints are defined (in both the simulated and physical experiments) by experimental input variables: bulk flow velocity of the fluid, and rotational velocity of the rotor. Each successful experiment produces experimental output variables: braking torque applied to the rotor, and pressure drop across the duct section which encloses the rotor. A direct comparison of simulated and physical performance data through the use of nondimensional coefficients demonstrates good agreement between the two experiments, though some discrepancy in torque has been identified. The degree of agreement suggests that this implementation of CFD and the similarity laws would be a good basis for future analysis of turbine performance.
Predicting the breakdown pressure in hard rock material subjected to hydraulic fracturing and quantifying fluid flow within a fracture network
(2023-02-16) Baidoo, Mark
This research is part of the Natural Heat Exchange Engineering Technology for Mines (NHEET) project conducted by Mirarco Mining Innovation. The NHEET project consists of developing a system using natural means to provide economically significant thermal regeneration capacity through a volume of rock fragments for ventilating mine workings. This system can provide heating (during winter) and cooling (during summer) of air on seasonal basis, without using artificial refrigeration. Optimizing the system requires creation of a specific volume of rock fragments having, among other criteria, a pre-determined porosity and fragment size distribution to meet the thermal storage and ventilation requirements of the mine site. This research is part of the NHEET project’s scope of work and investigates an alternative system, which consists of a fractured rock mass with sufficient fracture density and connectivity to admit enough airflow for the NHEET system requirements. This alternative system has the potential of reducing the footprint at surface. Firstly, the hydraulic fracturing (HF) method is investigated for preconditioning the rockmass with the objective of strategically creating additional fractures. Increasing the volumetric fracture intensity and fracture network connectivity within the rock mass can optimize airflow within the fracture network. A numerical predictive model for the breakdown pressure in hard rock subjected to hydraulic fracturing is developed using the lattice spring modeling method for HF simulation. The developed numerical model is calibrated based on the results obtained from a HF field experiment conducted in a northern Ontario mine. Secondly, a laboratory experiment is conducted to quantify fluid flow through a fracture network. In this context, a 3D physical model representing a fractured rock mass is generated using 3D printing technology. The 3D printed model is fixed into an experimental setup for fluid flow measurements. This experiment allowed for establishing the behaviour of the changing pressure to fluid transfer through fracture openings. The flow-pressure measurements are compared to a simple model for the volumetric flow rate in a block of naturally fractured rock with a number of fractures. The numerical model developed, and laboratory results obtained in this thesis provide valuable information for the construction of a NHEET system. The numerical predictive model for the breakdown pressure in hard rock subjected to HF is a tool to evaluate the amount of fluid pressure needed to create additional fractures in the rock mass and facilitate the planning of HF operations. The pressure-flow rate laboratory measurements are key data that can be used to calibrate a subsequent numerical simulation at a larger scale, representative of the NHEET system. Additionally, direct fluid flow measurements in fracture networks are useful to assess the influence of various fracture properties (e.g. intensity, connectivity, aperture) on fluid flow.

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