High-latitude ecosystems have experienced substantial warming over the past 40 years, which is expected to continue into the foreseeable future. Consequently, an increase in vegetation growth has occurred throughout the circumpolar North as documented through remote sensing and plot-level studies. A major component of this change is shrub expansion (shrubbing) in arctic and subarctic ecotones. However, these changes are highly variable depending on plant species, topographic position, hydrology, soils and other ecosystem properties. Changes in shrub and other vegetation properties are critical to document due to their first-order control on water, energy and carbon balances. This study uses a combination of multi-temporal LiDAR (Light Detection and Ranging) and field surveys to measure temporal changes in shrub vegetation cover over the Wolf Creek Research Basin (WCRB), a 180 km2 long-term watershed research facility located ~15 km south of Whitehorse, Yukon Territory. This work focuses on the smaller Granger Basin, a 7.6 km2 subarctic headwater catchment that straddles WCRB’s subalpine and alpine tundra ecozones with a wide range of elevation, landscape topography, and vegetation. Airborne LiDAR surveys of WCRB were conducted in August 2007 and 2018, providing an ideal opportunity to explore vegetation changes between survey years. Vegetation surveys were conducted throughout Granger Basin in summer 2019 to evaluate shrub properties for comparisons to the LiDAR. Machine learning classification algorithms were used to predict shrub presence/absence in 2018 based on rasterized LiDAR metrics with up to 97% overall independent accuracy compared to field validation points, with the best-performing model applied to the 2007 LiDAR to create binary shrub cover layers to compare between survey years. Results show a 63.3% total increase in detectable shrub cover > 0.45 m in height throughout Granger Basin between 2007 and 2018, with an average yearly expansion of 5.8%. These changes in detectable shrub cover were compared across terrain derivatives created using the LiDAR to quantify the influence of topography on shrub expansion. The terrain comparison results show that shrubs in the study area are located in and are preferentially expanding into lower and flatter areas near stream networks, at lower slope positions and with a higher potential for topographic wetness. The greatest differences in terrain derivative value distributions across the shrub and non-shrub change categories were found in terms of stream distance, elevation, and relative slope position. This expansion of shrubs into higher-resource areas is consistent with previous studies and is supported by established physical processes. As vegetation responses to warming have far-reaching influences on surface energy exchange, nutrient cycling, and the overall water balance, this increase in detectable shrub cover has a wide range of impacts on the future of northern watersheds. Overall, the findings from this research reinforce the documented increase in pan-Arctic shrub vegetation in recent years, quantify the variation in shrub expansion over terrain derivatives at the landscape scale, and demonstrate the feasibility of using LiDAR to compare changes in shrub properties over time. / Thesis / Master of Science (MSc)

The weakest points in concrete pavement systems are the concrete joints. They are man-made cracks that allow for temperature-related expansion and contraction of concrete slabs. Sealants are commonly used in pavement joints to keep debris, deicing chemicals, and moisture out of the joint. When a joint sealant fails, the pavement can quickly deteriorate; however, when a joint sealant functions well, the pavement maintains its intended performance. Joint sealants are subjected to two forms of mechanical loads in the field: 1) as slabs contract or expand, the sealant is subjected to tension or compression, respectively; and 2) heavy vehicles travel over the joint and deflect the ends of the pavement slabs, causing sealants to shear. Sealants may also be exposed to a range of environmental factors, such as moisture and ultraviolet radiation. In this research project, to simulate the joint sealant performance, samples were made by buttering the three different silicone sealants, namely Sealant 1, Sealant 2, and Sealant 3, between 1" x 1" x 3" Portland Cement Concrete dogbone-shape samples and 0.2" x 1" x 3" glass substrate samples were prepared according to VTM 90 and ASTM C1135, respectively. The tests were carried out employing an Instron Tensile Testing Machine and unique fixtures designed at Virginia Tech to impart mechanical loading. In comparison to Sealant 2, the results demonstrated that Sealant 1 can withstand larger stresses. All the concrete samples failed due to adhesive failure, whereas some of the Sealant 1 glass samples failed due to adhesive failure at low peak loads and others failed due to a combination of adhesive and cohesive failure. Glass samples of Sealant 2 on the other hand showed just cohesive failure. In case of Sealant 3, samples of both ASTM C1135 and VTM #90 showed adhesive failure and failed by showing reasonable strength. / Master of Science / Concrete pavements have a number of man-made joints that separate adjacent slabs. The purpose of these joints is to allow relatively free concrete expansion and contraction owing to changes in temperature and moisture. To ensure longevity of concrete, these joints must be sealed with a long-lasting material that can protect the joints from moisture, dust, and de-icing salts. The focus of this study is on silicone sealants, which have used for years as a joint sealant material. Three different silicone-based sealants were used. And two test methods, VTM-90, and ASTM C1135, were used to conduct the tensile testing. VTM-90 provides the test method to determine bond of silicone sealant to concrete mortar while ASTM C1135 gives the procedure for quantitative measure of tensile adhesion properties of structural sealants. ASTM C1135 In comparison to Sealant 2, the test results showed that Sealant 1 can withstand high loads. All the VTM-90 samples of Sealant 1, 2 and 3, failed because of adhesive failure, whereas some of the Sealant 1 ASTM C1135 samples failed because of adhesive failure at low peak loads and others because of a combination of adhesive and cohesive failure. On the other hand, ASTM C1135 samples of Sealant 2 showed only cohesive failures while Sealant 3 samples showed adhesive failure.

This master's thesis deals with the challenges of undesirable thermal expansion in lightweight materials. Thermal expansion of parts or components can lead to malfunction or breakdowns of complete systems in demanding environment where a large temperature gradient often exists. This work investigates a class of lightweight materials of which the thermal expansion coefficient can be controlled. Moreover, an additive manufacturing approach to produce these thermal management materials with high fidelity and reliability are critical to reach this goal. To achieve these two major research objectives analytic predictions, simulations, and measurement of thermal expansion coefficient with respect to temperature changes are conducted. Design and optimization of a high precision multi-material manufacturing apparatus has been conducted, leading to significant increase in production quality including reliability, efficiency, and costs. / Master of Science / This master’s thesis deals with the challenges of undesirable thermal expansion in lightweight materials. Under thermal load parts or components usually expand and this can lead to malfunction or breakdowns. To encounter this issue of the undesired expansion this work investigates a class of lightweight materials of which the thermal expansion coefficient can be controlled. Moreover, an additive manufacturing approach to produce these thermal management materials with high fidelity and reliability are critical to reach this goal. To achieve these two major research objectives analytic predictions, simulations, and measurement of thermal expansion coefficient with respect to temperature changes are conducted. Design and optimization of a high precision multi-material manufacturing apparatus has been conducted, leading to significant increase in production quality including reliability, efficiency, and costs.

Mémoire numérisé par la Direction des bibliothèques de l'Université de Montréal.

Structural refinements have been completed using data recorded for a Mg-rich cordierite at 24°C, 375°C, 775°C and 24°C (after heating to 775°C) and for an Fe-rich cordierite at 24°C and 375°C. The mean T-0 bond lengths in both cordierites remain unchanged but the mean octahedral bonds (M-0) lengthen upon heating. The unusually low thermal expansion of the Mg-cordierite is the result of its relatively "rigid" tetrahedral framework and the anisotropic expansion of octahedra isolated from each other. This anisotropic expansion leads to a slight rotation of the six-membered rings, a concomitant collapse of the structure parallel to c, and an expansion parallel to a and b. In the Fe-cordierite, the Fe-octahedron is more flattened, resulting in c being smaller and a and b being larger than the cell dimensions in the Mg-cordierite. Upon heating Fe-cordierite, there is no evidence for a rotation of the rings and a, b and c increase as the M-O bonds expand. A re-examination of the water orientation in the cavities of the Mg-cordierite using neutron and X-ray Δp maps confirms the orientation obtained previously by spectroscopic methods for type I water, i.e., H-O-H near (100) with the H-H vector nearly parallel to e. However, no evidence was found in the Δp maps for type II water. A peak ascribed to the alkali atoms that centers the six-membered ring becomes elongated parallel to a upon heating through 375°C, while the peak ascribed to the oxygen associated with H2O is absent in the Mg-cordierite at 775°C and in the Fe-cordierite at 375°C. After heating the Mg-cordierite to 775°C the peak reappeared in the Δp maps computed from data recorded at 24°C, but it no longer showed an elongation parallel to a as it did before heating. / Master of Science

Complex systems in areas such as biology, physics, social science, and technology are extensively modeled as networks due to the rich set of tools available for their study and analysis. In such networks, groups of nodes that correspond to functional units or those that share some common attributes result in densely connected structures called communities. Community formation is an inherent process, and it is not easy to detect these structures because of the complex ways in which components of these systems interact. Detecting communities in complex networks is important because it helps us to understand their internal dynamics better, thereby leading to significant insights into the underlying systems. Overlapping communities are formed when nodes in the network simultaneously belong to more than one community, and it has been shown that most real networks naturally contain such an overlapping community structure. In this thesis, I introduce a new approach to overlapping community detection called IDLE that incorporates ideas from another interesting problem: the identification of influential spreaders. Influential spreaders are nodes that play an important role in the propagation of information or diseases in networks. Research suggests that the main core identified by k-core decomposition techniques are the most influential spreaders. In my approach, I use these k-cores as candidate seeds for local community detection. Following a well-defined seed selection process, IDLE builds and prunes their corresponding local communities. It then augments the resulting local communities and puts them together to obtain the global overlapping community structure of the network. My approach improves on the current local community detection techniques, because they use either random nodes or maximal k-cliques as seeds, and they do not focus explicitly on detecting overlapping nodes in the network. Hence their results can be significantly improved in building ground-truth overlapping communities. The results of my experiments on real and synthetic networks indicate that IDLE results in enhanced overlapping community detection and thereby a better identification of overlapping nodes that could be important or influential components in the underlying system. / Master of Science

With overcrowded schools as a project vehicle, this thesis investigates the expansion and contraction of an existing infrastructure" and the relationship that developed between the two. The proposed intervention, guided by the site, touches on an urban scale by generating a gateway into the city. / Master of Architecture

New ultra-low thermal expansion materials, based on the NZP structure, have been developed and evaluated for future application in ceramic diesel engines which require exceptional thermal shock resistance. Twenty-four cation substitutions, with electron valence ranging from +1 to +5, were used to replace Na⁺ in the NZP skeletal framework. The linear thermal expansion measurements were conducted for ternary systems up to 1000°C. Quarternary & quinternary compounds were processed using combinations of alkali-alkali, alkali-alkaline earth, and alkaline earth alkaline earth instead of Na⁺. These were evaluated for solid solubility. Linear thermal expansion values were obtained for those compositions having single phase composition. Axial thermal expansion measurements were conducted using high temperature XRD for compounds having low linear thermal expansion value from room temperature to 1400°C. Several ultra-low expansion materials (less than 10x10⁻⁷/°C in absolute value) were found, which also had axial thermal expansion anisotropy. ‘ The effects of ionic size and valence of the substitution elements are discussed to explain the linear thermal expansion behavior and thermal expansion anisotropy investigated in these compounds. The effect of crystallinity is discussed, and the unit-cell equilibrium is suggested to interpret the general thermal expansion behavior occurring in crystalline solids. Secondary material properties for the compounds Rb_0.5Cs_0.5Zr₂(PO₄)₃ & Ca_0.5Mg_0.5Zr₄(PO₄)₆ with linear thermal expansion values of -0.3x10⁻⁷/°C & -5x10⁻⁷/°C, respectively, have also been characterized. / Ph. D.

Ce projet visait à comparer deux traitements chirurgicaux d'expansion palatine pour la correction des déficits transverses des maxillaires. Dans une étude prospective, les données de 22 sujets ayant terminé leur traitement orthodontique et ayant eu une expansion palatine assistée chirurgicalement (EPRAC) sont comparées à un groupe contrôle historique traité avec une ostéotomie Le Fort 1. L'expansion et la récidive dentaire et squelettique obtenue avec l'EPRAC ainsi que la récidive ont été mesurées sur des modèles d'étude et des radiographies céphalométriques postéro-antérieures standardisées à cinq moments durant le traitement. Dans le groupe EPRAC, l'expansion dentaire moyenne est 7,48 ± 1,39 mm. La récidive est 2,22 ± 1,69 mm (30%). À la fin de la distraction osseuse, 3,49 ± 1,37 mm d'expansion squelettique ont été obtenus. Lors d'une EPRAC, il faut anticiper la perte du tiers de l'expansion dentaire alors que l'expansion squelettique est stable. La récidive postchirurgicale de l'EPRAC semble similaire aux changements de l'arcade dentaire après une expansion à l'aide d'une ostéotomie maxillaire segmentée (3,06 ±1,31 mm)

Background: The Chinese market is growing fast and rapidly in a high pace. Many foreign companies see the possibilities in this and are expanding their business to China. When operating business in China strategic decisions are taken by the management, sometimes without reflection of what influences the process. This makes the influence on the management strategic decision-making process vital when expanding to China, since it may reflect on the company’s strategic plans.   Purpose: To further explore and extend the research area on how the expansion to China influences the management and their strategic decision-making process.   Research questions: RQ1: Do the expansion to China influence the management strategic decision-making process?   RQ2: How does the expansion to China influence the management strategic decision-making process?   Methodology: Conducted as an abductive qualitative multiple case study, examined with semi-structured interviews with an exploratory purpose.   Conclusion: The empirical investigation showed that the management and their strategic decision-making process are influenced by the expansion to China. The influences are; rationality, decision speed, environment, politics, culture and how management view their strategy through the strategic lenses.