Theses

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  • The effect of alkalis from supplementary cementing materials on expansion due to alkali-carbonate reaction
    The effect of alkalis from supplementary cementing materials on expansion due to alkali-carbonate reaction
    While much research has been completed on Alkali-Aggregate Reaction (AAR) over the years, few studies have focused on the lesser known Alkali-Carbonate Reaction (ACR). With the increasing use of supplementary cementing materials (SCM), it is important to determine the effects of SCM on ACR. In this research, the concrete prism test was used to evaluate the reactivity of Pittsburgh aggregate when used with cement and a combination of one or two types of SCM. Several concrete prism mixes were completed using eight (8) different types of SCM including slag, silica fume, metakaolin, and five different types of fly ash. The results from the concrete prism test showed that all of the mixes tested were not effective in reducing the expansion due to ACR to levels below the CSA expansion limit (0.04% at 2 years). However, it was found SCM did help reduce expansion due to ACR on a marginally reactive aggregate. The Concrete Microbar test was completed to evaluate the test's validity on determining ACR aggregates with and without SCM. The results from this experimental program suggest that the microbar test should not be used for the acceptability of an aggregate. SCM with low-alkali contents such as metakaolin and CI-LA fly ash were found to help reduce the detrimental expansion of concrete due to ACR.
    The effect of an enclosure retrofit on a multi-unit residential building: single case study
    The effect of an enclosure retrofit on a multi-unit residential building: single case study
    This case study examines the effect of an enclosure retrofit on a high-rise, multi-unit residential building (MURB). Literature on fan pressurization test methodologies and MURB air leakage rates is reviewed. The enclosure for the case study building was tested using the guarded-zone fan pressurization method. Results of the air leakage testing show significant improvement in the enclosure tightness and compare well to measured data for other MURBs across North America. There is recognition of a need to standardize both testing methods and presentation of data for air leakage in MURBs. The issue of abnormal flow exponent values is discussed and recommendations for future research are made.
    The effect of comorbid anxiety in youth with ADHD: an ERP analysis of attentional control and impulse control
    The effect of comorbid anxiety in youth with ADHD: an ERP analysis of attentional control and impulse control
    Differences in attentional and impulse control may underlie the increased impairment associated with youth with ADHD and comorbid anxiety (ADHD+ANX) compared to youth with ADHD without anxiety; however, findings from studies using behavioural and self-report measures have been mixed. This study addressed this issue by exploring the impact of the addition of anxiety on attentional and impulse control at a neural level, using event-related potentials (ERPs). Youth aged 11 to 17 with ADHD without anxiety (n = 34) and ADHD+ANX (n = 33) completed a Go/No-Go and Selective Auditory Attention task. Results indicated that the addition of anxiety in youth with ADHD was associated with enhanced early attentional processing, as well as stronger activation of impulse control, as exhibited by greater EFP and N2 amplitudes, respectively. Future directions and clinical implications of these results are discussed.
    The effect of copper and manganese on phytoplankton in the Grand River (southern Ontario), Lake Erie and Pacific Ocean ecosystems
    The effect of copper and manganese on phytoplankton in the Grand River (southern Ontario), Lake Erie and Pacific Ocean ecosystems
    With the increased use and loading of metals into the environment, the accumulation of toxic metals by phytoplankton has become a concern. Trace metal interactions with phytoplankton are of particular interest due to the influence of phytoplankton on the biogeochemical cycling of metals in aquatic systems. The study of the accumulation of metals and their toxicity in phytoplantkon is also of interest since phytoplankton lie at the base of many aquatic food webs. Toxic metals therefore have the potential to disrupt food webs and may have important implications onaquatic ecosystems.This study has chosen to focus on the response of phytoplankton to two tracemetals in particular: copper (Cu) and manganese (Mn). Although both Cu and Mn are essential elements for phytoplankton, Cu is of particular interest as a toxicant. Anumber of laboratory studies have suggested that there exists a physiologicalinteraction between Cu and Mn, and that Cu toxicity can be decreased in the presenceof high concentrations of Mn. However, few studies have examined the effects ofthese metals on phytoplankton in their natural environments. The significance of thisstudy is that it is one of the first to examine whether the importance of Cu toxicity andthe interaction between Cu and Mn observed in the laboratory is also observable undernatural conditions.Short-term bioassays were conducted in order to observe the response of phytoplankton from the Grand River (Southern Ontario) and Lake Erie to additions of various concentrations of eu and Mn under natural conditions. Similar long-term bioassay experiments were also conducted in the Pacific Ocean. Experiments in the Grand River and the Pacific Ocean revealed no significant decrease in phytoplankton biomass or in photosynthetic efficiency with the addition of various concentrations of Cu and Mn. In Lake Erie, phytoplankton biomass was only adversely affected following relatively high additions of Cu of 60 nM, and only under certain conditions. These results seem to indicate that under the tested conditions, Cu toxicity may not be of particular concern to the phytoplankton of the Grand River, Lake Erie and Pacific Ocean ecosystems.
    The effect of corrosion on shear behaviour of self-consolidating concrete beams
    The effect of corrosion on shear behaviour of self-consolidating concrete beams
    The objectives of this research are to compare the effect of corrosion on shear behavior in particular, and the overall structural response in both NC and SCC beams in general. Twenty reinforced concrete beams were used, with ten specimens cast using normal concrete (NC), and the other ten were cast using self-consolidating concrete (SCC). The dimensions for each beam were 150mm x 220mm x 1400mm. Using accelerated corrosion through the application of a constant current of one ampere, four stages of corrosion were established at 5%, 10%, and 20% of mass loss. Simply supported beams were loaded with two concentrated loads, and a four-point loading test was applied to the reinforced concrete (RC) beams. If (a) is the distance from the concentrated load to the reaction, and (d) is the distance from the center of the tensile flexural rebars to the top of the concrete beam, then a/d=2.5 was applied to assure the highest probability of shear failure mode. The data collected from load cell, LVDTs, corrosion crack patterns and loading cracks patterns were used to study the effects of multiple stages of corrosion on the shear behaviour of reinforced NC and SCC concrete beams. The corroded rebars were then retrieved and cleaned to compare the calculated mass loss with real mass loss. The results showed high correlation between the calculated mass loss (according to Faraday law) and real mass loss. The accelerated corrosion resulted in a corrosion crack pattern, which was documented and analyzed. In this research, the use of NC and SCC showed minor influences on failure mode, while the different states of corrosion showed a higher degree of influence on failure mode and the structural capacity of beams made from both types of concrete. The apparent changes in failure mode were associated with the increased corrosion stage.
    The effect of different mix proportions on the hygrothermal performance of hempcrete in the Canadian context
    The effect of different mix proportions on the hygrothermal performance of hempcrete in the Canadian context
    Hempcrete is a light composite bio-based envelope plus insulation material with lime as binding agent and hemp as a renewable raw material from agriculture. The main qualities of hempcrete are hygrothermal behavior and low environmental impact. There is currently lack of clear cross-industry standards for hempcrete; however, extensive research, laboratory experiments and literature reviews are ongoing. The primary aim of this study was to understand the impact of different mixes on the performance of hempcrete and to establish hygrothermal behavior of a hempcrete wall in the Canadian context (by measuring dry density and some other hygroscopic parameters for 3 different mixes) as well as to define the required minimum thickness for a code compliant wall (as per OBC requirements) based on the most reliable reference R values. Based on the material values acquired from the tests and references, simulations for 2 types of wall assemblies and series of sensitivity analysis were carried out in WUFI software. Finally, further research on hygrothermal performance of hempcrete wall (using Canada grown hemp) was recommended to carry out by measuring thermal conductivity in various mean temperatures.
    The effect of essential oils on the growth of bacteria from municipal wastewater treatment
    The effect of essential oils on the growth of bacteria from municipal wastewater treatment
    Bacterial sensitivity to essential oils has been reported in the case of soil isolated bacteria, food isolated bacteria but there is little evidence available to support the fact that wastewater isolated bacteria show sensitivity to essential oils. Keeping in view this fact the present investigation aims to determine the wastewater isolated bacterial strains sensitivity to six commercially available plant essential oils including clove, cinnamon, oregano, tea tree, fennel, and wintergreen. The essential oils were tested against ten laboratory bacterial strains (Acinetobacter baumanii, Escherichia coli: DH5α, E.coli: AD202, Pseudomonas fluorescens, Pseudomonas poae, Pseudomonas putida, staphylococcus aureus, and Stenotrophomonas maltophilia) (2) and ten wastewater isolated bacterial strains (Acinetobacter baumanii, Acinetobacter bouretii, Aeromonas hydrophila, E.coli, Enterobacter cloaceae, Flavobacterium branchiophilum, Klebsiella pneumoniae, Pseudomonas staurtii, Serratia fonticola, and Staphylococcus muscae) using the Kirby-Bauer disc diffusion assay, and the broth tube macrodilution MIC assay. The disc-diffusion assay showed that three of the oils, clove, cinnamon and oregano, were the most effective at inhibiting the growth of all the known single isolates. The broth tube MIC assay found that the WWTP isolated bacterial strains such as E. coli, Staphylococcus muscae, Enterobacter cloaceae, Acinetobacter baumanii were most sensitive to clove oil at MIC concentration ≤ 0.52 mg/ml, cinnamon oil at MIC concentration ≤ 0.51 mg/ml, and oregano oil MIC concentration ≤ 0.47 mg/ml. Finally, wastewater microbial community samples from activated sludge, returned sludge and anaerobic digesters were reduced by 0% > 94.24%, 46% > 99%, 70% > 97% percent when tested against clove, cinnamon, and oregano oils.
    The effect of face-to-face communication on editorial stance:  a case study of the 2010 Liberal Express tour
    The effect of face-to-face communication on editorial stance: a case study of the 2010 Liberal Express tour
    This Major Research Paper explores the value of face-to-face communication in a digital age by examining the effect of face-to-face communication on media coverage. The author outlines the theoretical components of agenda-setting theory, presentation theory, and invitational rhetoric to illustrate the process by which individuals or groups compete to gain attention and power, and the role that face-to-face communication can play to persuade. This theory is examined with a political case study of the Liberal Party of Canada’s cross-Canada bus tour in July and August of 2010. The author provides a discourse analysis of newspaper editorials published in Ontario, Canada before and after then-Party Leader Michael Ignatieff visited. The author observes that the tone of media coverage is more favourable after face-to-face communication with citizens and journalists took place, suggesting that face-to-face communication is an effective tool for politicians in a digital age.
    The effect of free nitrous acid pretreatment on the anaerobic digestibility of thickened waste activated sludge
    The effect of free nitrous acid pretreatment on the anaerobic digestibility of thickened waste activated sludge
    Sludge pretreatment technologies as an avenue to improve solids handling in a WWTP has gained attention and significant research efforts are being directed towards studying several available techniques. The use of FNA as a chemical pretreatment for the AD has shown the potential to enhance the hydrolysis stage by releasing the internal organic matter of TWAS via its biocidal action. The effect of FNA on improving the biodegradability of TWAS was investigated in this thesis. The effect of the FNA on the TWAS characteristics and the methane production in batch tests was first studied. The optimum FNA dose was determined from the batch tests based on both solubilization and methane yields and then tested in a semi-continuous flow system. As the semi-continuous flow system failed when the optimum FNA dose obtained from the batch study was used, another set of semi-continuous flow experiments were conducted using different FNA doses
    The effect of heat-treating temperatures on induced compressive residual stress and fatigue life in 300m landing gear steel due to shot peening
    The effect of heat-treating temperatures on induced compressive residual stress and fatigue life in 300m landing gear steel due to shot peening
    The main objective of the study is to model the behavior of residual stresses in shot peened 300M landing gear steel affected by heat treatment. It is well known that residual stresses can have a significant influence on the mechanical behavior of major components under stresses. Therefore, information regarding the stability of existing residual stress states is of significant importance. In this experiment, special attention is paid to consequences of the heat treatment processes on compressive residual stresses induced in material by shot peening. The relaxation in residual stress due to addition of thermal energy by heat treatment at different temperatures and times is investigated. An existing model was used to create a stress relaxation equation for 300M high strength steels. Effect of heat treatment on residual stress distribution at subsurface level is also be examined. The current study will focus on the initial compressive residual stress field produced by common aerospace peening conditions and by how much isothermal exposures alter this stress and factors affecting the stress relaxation as well as fatigue life of the affected components.
    The effect of lack of citizenship on the wages of low-skilled non-permanent resident workers in Canada
    The effect of lack of citizenship on the wages of low-skilled non-permanent resident workers in Canada
    This dissertation explores the effects of lack of citizenship on the wages of low-skilled Non-Permanent Residents (NPRs) in Canada—a category that includes temporary foreign workers, refugee claimants, and people with temporary resident visas on humanitarian grounds. The dissertation uses the 2006 census and quantitative methods (cross-tabulation and regression analysis) to evaluate wage differences between low-skilled workers without citizenship and low-skilled workers with citizenship or permanent resident status. Differences are calculated at the industry sector level and occupation level. The analysis further considers a set of intrinsic characteristics of low-skilled workers (including sex, level of education, official language ability and country of birth) and their occupations (provincial location, rural/urban setting). Empirically, this dissertation confirms that there is a penalty attached to lack of citizenship for low-skilled workers. In absolute terms, low-skilled NPRs earn low wages. In relative terms, these NPRs earn less than both the Canadian-born and immigrants low-skilled workers employed in the same occupations. Among low-skilled NPRs themselves, the Canadian labour market exhibits a hierarchy of wages and labour experiences on the lines of workers' country of birth, province of residence, and rural/urban place of work. Among low–skilled workers born in the same country, wages improve when either citizenship or the rights attached to permanent residence are acquired. From a policy perspective, the dissertation identifies the policy origins and drivers of low wages among low-skilled non-citizens. The thesis makes the case for the relevance of quantitative outcomes analyzed through a critical social lens. From a theoretical perspective too, the dissertation also shows how the state as a biased broker (towards capital) facilitates the implementation of non-citizenship as a means to accessing cheap labour.
    The effect of learning, forgetting,  fatigue, and recovery on the performance of dual-resource constrained (DRC) systems
    The effect of learning, forgetting, fatigue, and recovery on the performance of dual-resource constrained (DRC) systems
    Dual-Resource Constrained (DRC) systems consist of two resources: workers and machines (stations). DRCs have become common in manufacturing and service firms that emphasise flexibility, where workers perform different tasks. Although having a flexible workforce is beneficial, it comes at a cost. When workers alternate between different jobs the productivity of the system is affected. On one hand the system becomes more responsive to changes (internal/external), and on the other hand worker productivity and system throughput deteriorate because of the loss of knowledge and workers’ fatigue. This subjects workers to conflicting phenomena. When workers are performing a task they are learning but also accumulating fatigue, which may result in error or injury. When transferred to another task, or on a break, workers may forget what they have learnt but at the same time recover from fatigue, either fully or partially. In particular, forgetting and fatigue are interesting to be considered as they directly affect the quality of products. This research investigates the effects of workers’ learning-forgetting and fatigue-recovery on DRC systems. First, it modifies a known learning-forgetting model by accounting for fatigue and recovery. Second, it assumes that the quality of a production process may deteriorate and generate defective items that require rework. Third, a human error model is developed that considers human learning-forgetting and fatigue-recovery in producing defective items. Fourth, a comprehensive model is developed that integrates learning, forgetting, fatigue, and recovery into a DRC system with quality consideration. This model is investigated for different transfer and flexibility policies. Numerical results provide insights and guidelines that may help operations managers with decisions on how to improve a system’s performance and throughput, while considering worker welfare. Results indicate that it is important to consider workers capabilities and limitations when designing manufacturing systems. They also suggest that ignoring human restrictions and abilities results in unrealistic production planning and erroneous cost estimation.