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Mémoire (M.Sc.)- Université du Québec à Chicoutimi, 1985. / Document électronique également accessible en format PDF. CaQCU

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Measurements of secular period change probe real-time stellar evolution of classical Cepheids making these measurements powerful constraints for stellar evolution models, especially when coupled with interferometric measurements. In this work, we present stellar evolution models and measured rates of period change for two Galactic Cepheids: Polaris and l Carinae, both important Cepheids for anchoring the Cepheid Leavitt law (period-luminosity relation). The combination of previously-measured parallaxes, interferometric angular diameters and rates of period change allows for predictions of Cepheid mass loss and stellar mass. Using the stellar evolution models, We find that l Car has a mass of about 9 M S™ consistent with stellar pulsation models, but is not undergoing enhanced stellar mass loss. Conversely, the rate of period change for Polaris requires including enhanced mass-loss rates. We discuss what these different results imply for Cepheid evolution and the mass-loss mechanism on the Cepheid instability strip.

The world is increasingly becoming urban. In fact, 80 percent of the US population is already living in cities. With the influx of a huge population in urban areas, the urban infrastructures are bound to be stressed. Furthermore, people from every walk of life live in urban areas in search of better economic opportunities. These diverse people have diverse needs. To make matters worse, governments have a limited budget. And, they are faced with the challenge of providing infrastructure and public services fair to everyone. This thesis attempts to respond to these challenges through two manuscripts. The first manuscript proposes a decision-support tool that responds to these challenges along with the flooding vulnerability due to sea-level-rise. As flooding events are getting more frequent and intense, coastal road network is vulnerable and can significantly affect daily mobility. Therefore, the paper proposes an optimization framework that minimizes the cost of mitigation measures for flooding while also considering social equity. As a result, the results of this optimization function is not only financially optimum but also equitable to all. The second manuscript proposes a novel framework for analyzing equity in terms of access to opportunity, rather than equity of outcomes. We showcase the use of a large-scale, high-fidelity agent-based, activity-based travel demand model to produce travel times to employment centers. This travel time is used as a proxy to access to opportunities. The results are visualized in a GIS heatmap. The model is applied to the Metropolitan Washington DC area. This manuscript contributes to the literature by analyzing the equity of opportunities without considering an individual’s socioeconomic characteristics. / Master of Science / The world is increasingly becoming urban. In fact, 80 percent of the US population is already living in cities. With the influx of a huge population in urban areas, the urban infrastructures are bound to be stressed. Furthermore, people from every walk of life live in urban areas in search of better economic opportunities. These diverse people have diverse needs. To make matters worse, governments have a limited budget. And, they are faced with the challenge of providing infrastructure and public services fair to everyone. This thesis attempts to respond to these challenges through two manuscripts. As flooding events are getting more frequent and of more intensity, coastal road network is vulnerable and can significantly affect day-to-day movements. Decision makers face the challenge of mitigating the flood risk under budget constraints and they need to make their decision fair to everyone. The first manuscript proposes a decision-support tool that not only optimizes the use of a limited budget but also ensures the decision is fair to everyone. The idea of what is fair to everyone is a contentious issue. Recently some people have argued against using socioeconomic characteristics of people in making investment decisions. Therefore, the second manuscript proposes a novel framework that analyzes access to employment centers using a higher fidelity advanced travel demand model without the explicit use of socioeconomic characteristics of individuals.

Thesis--(Licentiate)--Royal Institute of Technology, Stockholm, 2007. / Original thesis t.p. and absdtract on 1 leaf inserted. Includes bibliographical references (p. 107-109).

Primary cilia are non-motile organelles having 9+0 microtubules that project from the basal body of the cell. While the main purpose of motile cilia in mammalian cells is to move fluid or mucus over the cell surface, the purpose of primary cilia has remained elusive for the most part. Primary cilia are shortened in the kidney tubules of Tg737orpk mice, which have polycystic kidney disease due to ciliary defects. The product of the Tg737 gene is polaris, which is directly involved in a microtubule-dependent transport process called intraflagellar transport (IFT). In order to determine the importance of polaris in the development of neuronal cilia, cilium length and numerical density of cilia were quantitatively assessed in six different brain regions on postnatal days 14 and 31 in Tg737orpk mutant and wildtype mice. Our results indicate that the polaris mutation leads to shortening of cilia as well as decreased percentage of ciliated neurons in all brain regions that were quantitatively assessed. Maintainance of cilia was especially affected in the ventromedial nucleus of the hypothalamus. Furthermore, the polaris mutation curtailed cilium length more severely on postnatal day 31 than postnatal day 14. These data suggests that even after ciliogenesis, intraflagellar transport is necessary in order to maintain neuronal cilia. Regional heterogeneity in the effect of this gene mutation on neuronal cilia suggests that the functions of some brain regions might be more compromised than others.

Polaris the Cepheid has been observed for centuries, presenting surprises and changing our view of Cepheids and stellar astrophysics, in general. Specifically, understanding Polaris helps anchor the Cepheid Leavitt law, but the distance must be measured precisely. The recent debate regarding the distance to Polaris has raised questions about its role in calibrating the Leavitt law and even its evolutionary status. In this work, I present new stellar evolution models of Cepheids to compare with previously measured CNO abundances, period change and angular diameter. Based on the comparison, I show that Polaris cannot be evolving along the first crossing of the Cepheid instability strip and cannot have evolved from a rapidly-rotating main sequence star. As such, Polaris must also be at least 118 pc away and pulsates in the first overtone, disagreeing with the recent results of Turner et al. (2013, ApJ, 762, L8).

McMaster University DOCTOR OF PHILOSOPHY (2022) Hamilton, Ontario (Engineering Physics) TITLE: Development and Evaluation of Polaris CANDU Geometry Modelling and of TRACE_Mac/PARCS_Mac Coupling with RRS for CANDU Analysis AUTHOR: Simon Younan, M.A.Sc. (McMaster University), B.Eng. (McMaster University) SUPERVISOR: Dr. David Novog NUMBER OF PAGES: xiv, 163 / In the field of nuclear safety analysis, as computers have become more powerful, there has been a trend away from low-fidelity models using conservative assumptions, to high-fidelity best-estimate models combined with uncertainty analysis. A number of these tools have been developed in the United States, due to the popularity of light water reactors. These include the SCALE analysis suite developed by ORNL, as well as the PARCS and TRACE tools backed by the USNRC. This work explores adapting the capabilities of these tools to the analysis of CANDU reactors. The Polaris sequence, introduced in SCALE 6.2, was extended in this work to support CANDU geometries and compared to existing SCALE sequences such as TRITON. Emphasis was placed on the Embedded Self-Shielding Method (ESSM), introduced with Polaris. Both Polaris and ESSM were evaluated and found to perform adequately for CANDU geometries. The accuracy of ESSM was found to improve when the precomputed selfshielding factors were updated using a CANDU representation. The PARCS diffusion code and the TRACE system thermalhydraulics code were coupled, using the built-in coupling capability between the two codes. In addition, the Exterior Communications Interface (ECI), used for coupling with TRACE, was utilized. A Python interface to the ECI library was developed in this work and used to couple an RRS model written in Python to the coupled PARCS/TRACE model. A number of code modifications were made to accommodate the required coupling and correct code deficiencies, with the modified versions named PARCS_Mac and TRACE_Mac. The coupled codes were able to simulate multiple transients based on prior studies as well as operational events. The code updates performed in this work may be used for many future studies, particularly for uncertainty propagation through a full set of calculations, from the lattice model to a full coupled system model. / Thesis / Doctor of Philosophy (PhD) / Modern nuclear safety analysis tools offer more accurate predictions for the safety and operation of nuclear reactors, including CANDU reactors. These codes take advantage of modern computer hardware, and also a shift in philosophy from conservative analysis to best estimate plus uncertainty analysis. The goal of this thesis was to adapt a number of modern tools to support CANDU analysis and uncertainty propagation, with a particular emphasis on coupling of multiple interacting models. These tools were then demonstrated, and results analyzed. The simulations performed in this work were successful in producing results comparable to prior studies along with experimental and operational data. This included the simulation of four weeks of reactor operation including “shim mode” operation. Sensitivity and uncertainty analyses were performed over the course of the work to quantify the precision and significance of the results as well as to identify areas of interest for future research.

PWR, fuel assembly, benchmark, burnup, lattice, SCALE, Polaris, validation, reactivity