The first chapter examines the causal effect of education on individuals' retirement decisions and changes in quality of life after retirement. When estimating the return to education, much of the existing literature assumes implicitly that individuals optimize over their career with a fixed year of retirement ("fixed-retirement-age" assumption). Using the provincial compulsory schooling laws as instruments to estimate the causal effects of educational attainment on individuals' retirement decisions and change in the quality of life after retirement, I find that years of schooling have no significant impact on retirement decisions. Furthermore, among those who are already retired, years of schooling do not have any impact on their age at retirement and the change in the quality of life after retirement. Results in this paper support the "fixed-retirement-age" assumption used in empirical studies based on the classical return to education model where the exogenous assumption on retirement age might not be a bad approximation. The second chapter relates to labour market flows and worker trajectories in Canada during COVID-19. We use the confidential-use files of the Labour Force Survey (LFS) to study the employment dynamics in Canada from the beginning of the COVID-19 pandemic through to mid-summer. Using the longitudinal dimension of this dataset, we measure the size of worker reallocation and document the presence of high labour market churning that persists even after the easing of social-distancing restrictions. As of July of 2020, many of the recent job losers -- especially those who had been temporarily laid-off between February and April -- have regained employment. However, this apparent strong recovery dynamics hides important heterogeneity, and large groups of workers, such as those who were not employed prior to the pandemic, face important difficulties with finding a job. Our results further suggest that gross job losses were higher among women and young workers during the shutdown and that older workers were more likely to leave the labour force when the economy reopened. The third chapter analyzes the gender differences in early career labour market trajectories and wage growth in Canada. Using the Longitudinal Workers File (LWF) linked to the 2006 and 2016 Census, I find that, although some progress has been made on the gender gap on labour market trajectories for young workers in their earlier careers, women faced higher penalties for taking time out of the labour market compared with men. More specifically, regardless of the type of job separation, changed employer or occupation, and reason for separation, women's weekly wage annual growth rate was lower compared with their male counterparts. The results from regression analysis suggest that labour market trajectories affect women's and men's weekly wage annual growth rates differently. Women's weekly wage annual growth rate was more sensitive to temporary job separation compared with men, whereas men's weekly wage annual growth rate was more sensitive to permanent job separation. The Oaxaca-Blinder decomposition shows that the total number of permanent separations and the total number of permanent separations due to parental/maternity leave each explains about one-third of the cross-sectional gender differences in weekly wage annual growth rate observed for young workers in Canada.

We present an analysis of the effects of heating, suction, and compressibility on the stability characteristics of boundary-layer flows within the framework of a complete nonparallel, linear, spatial stability theory. Included in the theory are disturbances due to velocity, Pressure, temperature, density, and transport properties as well as 'variations of the fluid properties with temperature. The method of multiple scales is used to account for the nonparallelism of the mean flow and equations are derived for the evolution of the disturbance amplitude and wave number vector. / Ph. D.

To aid in forest management, various approaches using Geographic Information Systems (GIS) have been used to identify the spatial distributions of relative slope instability. This study presents a systematic evaluation of three common slope instability modeling approaches applied in the Blue Ridge Mountains of Virginia. The modeling approaches include the Qualitative Map Combination, Bivariate Statistical Analysis, and the Shallow Landsliding Stability (SHALSTAB) model. Historically, the qualitative nature of the first model has led to the use of more quantitative statistical models and more deterministic physically-based models such as SHALSTAB. Although numerous studies have been performed utilizing each approach in various regions of the world, only a few comparisons of these approaches have been done in order to assess whether the quantitative and deterministic models result in better identification of instability. The goal of this study is to provide an assessment of relative model behavior and error potential in order to ascertain which model may be the most effective at identifying slope instability in a forest management context. The models are developed using both 10-meter and 30-meter elevation data and outputs are standardized and classified into instability classes (e.g. low instability to high instability). The outputs are compared with cross-tabulation tables based on the area (m²) assigned to each instability class and validated using known locations of debris flows. In addition, an assessment of the effects of varying source data (i.e. 10-meter vs. 30-meter) is performed. Among all models and using either resolution data, the Qualitative Map Combination correctly identifies the most debris flows. In addition, the Qualitative Map Combination is the best model in terms of correctly identifying debris flows while minimizing the classification of high instability in areas not affected by debris flows. The statistical model only performs well when using 10-meter data while SHALSTAB only performs well using 30-meter data. Overall, 30-meter elevation data predicts the location of debris flows better than 10-meter data due to the inclusion of more area into higher instability classes. Of the models, the statistical approach is the least sensitive to variations in source elevation data. / Master of Science

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The purpose of the paper was to evaluate the effects of the restoration efforts in Juktån on the plant species richness and composition, vegetation zonation and soil composition. The restoration involved implementation of a dynamic flow, in addition to hydro-geomorphological alterations. Three sites were inventoried in the bypass reach, representing one reach affected only by flow restoration and two reaches affected both by flow and morphological restoration, along with an upstream reference reach unaffected by regulation. Inventories were conducted along an elevational gradient perpendicular to the water and involved occurring species, plant cover, bare ground and soil composition. The results showed a change in species composition after restoration. Riparian associated species were more common after restoration and the proportions of herbs and graminoids increased. Higher flooding caused a change in zonation, increasing the graminoid, riparian forest and amphibious zones along the riparian habitat. Species richness, as well as soil composition remained largely the same. The effects of the hydro-geomorphological alterations were hard to interpret due to lack of data. The results indicate a positive effect of the new flow on the plant species community in the bypass reach, whilst also highlighting the hydro-geomorphologically altered locations as biodiversity hotspots. Time-delay in ecological response is acknowledged as driving factor for the indifference in species richness and soil composition. The hydrological restoration is concluded to be an effective way of simulating natural flow regimes, improving ecological integrity of riparian communities and structural vegetational patterns in the riparian zone of bypass reaches.

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In dilute polymer solution, polymers are able to change the flow structures and suppress the intensity of turbulence, resulting in a considerable friction drag reduction (DR). Despite the extraordinary progress made in the past few decades, some critical questions remain unanswered. This dissertation will try to address two fundamental questions in dilute polymeric turbulence: (I) interactions between polymers and turbulent motions during the qualitative low-extent to high-extent drag reduction (LDR and HDR) transition in inertia-driven turbulence, (II) roles of the inertia- and elasticity-driven turbulent motions in the dynamics of high elasticity polymeric flows. Many studies in the area of DR turbulence have been focused on the onset of DR and the maximum drag rection (MDR) asymptote. Between these two distinct stages, polymeric turbulent flows can also be classified into the qualitative LDR and HDR stages. Understanding the polymer-turbulence interactions during the drastic LDR-HDR transition is of vital importance for the development of efficient flow control technology. However, knowledge regarding this qualitative transition is still limited. In our DNS (direct numerical simulation) study, differences between the LDR and HDR stages are presented by a number of sharp changes in flow structures and statistics. Drag reduction in the flows is thus governed by two different mechanisms. The first is introduced at the onset of DR, which has been well explained by the indiscriminate suppression of turbulent fluctuations during the coil-stretch transition of polymers. The second mechanism starts at the LDR-HDR transition but its physical origin is not clear. Based on instantaneous observations and indirect statistical evidence, we proposed that polymers, after the LDR-HDR transition, could suppress the lift-up process of the near-wall vortices and modify the turbulent regeneration cycles. However, direct evidence to support this hypothesis is not available without a statistical analysis of the vortex configurations. Therefore, a new vortex tracking algorithm -- VATIP (vortex axis tracking by iterative propagation) -- is developed to analyze statistically the configurations and distribution of vortices. Implementing this method in the polymeric turbulence demonstrates that the lift-up process of streamwise vortices in the buffer layer is restrained at HDR, while the generation of hairpins and other three-dimensional vortices is suppressed. In addition, the characteristic lifting angle of conditional eddies extracted by a conditional sampling method is found to be larger in HDR than in the Newtonian turbulence. These observations all support our hypothesis about the mechanism of LDR-HDR transition. Research on the low elasticity turbulence usually considered the flow motions to be Newtonian-like. Turbulence here is driven by the inertial force (and hence called ``inertia-driven'' turbulence (IDT)) while polymers are responsible for dissipating turbulent kinetic energy. In the high elasticity turbulence, recent studies found a completely different turbulent flow type in which turbulence is driven by the elastic force and polymers could also feed energy to the flow. The behaviors of this ``elasticity-driven'' turbulence (EDT) are of significant interest in this area because of its potential connection to the MDR asymptote. However, EDT is difficult to capture by the traditional pseudo-spectral DNS scheme (SM) as a global artificial diffusion (GAD) term is involved in the polymer constitutive equation to stabilize the simulation. In our study, a new hybrid pseudo-spectral/finite-difference scheme is developed to simulate the polymeric turbulence without requiring a GAD. All of the spatial derivative terms are still discretized by the Fourier-Chebyshev-Fourier pseudo-spectral projection except for the convection term in the constitutive equation which is discretized using a conservative second-order upwind TVD (total variation diminishing) finite difference scheme. The numerical study using the hybrid scheme suggests that turbulent flows can be either driven by the inertial or the elastic forces and respectively result in the IDT and EDT flows. A dynamical flow state is also found in the high elasticity flow regime in which IDT and EDT can be sustained alternatively. / Thesis / Doctor of Philosophy (PhD) / Turbulence is known to consume kinetic energy in a fluid system. To enhance the efficiency of fluid transportation, various techniques are developed. Especially, it was found that a small amount of polymers in turbulent flows can significantly suppress turbulent activity and cause considerable friction drag reduction (DR). Extraordinary progress has been made to study this phenomenon, however, some questions still remain elusive. This dissertation tries to address some fundamental questions that relate to the two typical polymeric turbulent motions: the inertia- (IDT) and elasticity-driven turbulence (EDT). In IDT, mechanisms of transitions between the intermediate stages are investigated from the perspective of vortex dynamics. The different effects of polymers at each stage of the flow lead to different flow behaviors. Particularly, starting from the low- to high-extent DR transition, the lift-up process of vortices is suppressed by polymers. The regeneration cycles of turbulence are thus modified, which results in qualitative changes of flow statistics. Numerical study on EDT is enabled by a newly developed hybrid pseudo-spectral/finite-difference scheme. A systematic investigation of the parameter space indicates that EDT is one self-contain turbulence driven purely by the elastic force. It can also interact with IDT and lead to a dynamical flow state in which EDT and IDT can alternatively occur.