Permafrost deformation is expected to increase due to climatic perturbations such as amplified air and soil temperatures, resulting in permafrost thawing and subsequent subsidence. Palsas and peat plateaus are uplifted ice-rich peat mounds that experience permafrost subsidence. This is due to the uppermost layer of permafrost, known as the Active Layer (AL), that seasonally thaws and freezes. Interferometric Synthetic Aperture Radar (InSAR) is an interferometric stacking technique successfully applied over permafrost regions when monitoring ground subsidence. The Small Baseline Subset (SBAS) technique is based on interferograms produced by stacking Synthetic Aperture Radar (SAR) acquisitions with small normal baselines. In this study, seasonal Sentinel-1 SAR C-band data obtained during June, July, August and September (JJAS) was used to generate seasonal Line of Sight (LoS) deformation time series of palsas and peat plateaus in Tavvavuoma (Sweden) by using the SBAS technique. Chersky (Russia) has documented permafrost subsidence and was used as a reference site. Findings include that seasonal stacks with short normal baselines generated more robust results than inter-annual stacks with longer normal baselines and temporal data gaps. No instances of pronounced subsidence were reported during JJAS. Nevertheless, minor subsidence during the early season and negative development trends were identified in the Tavvavuoma 2020 andChersky 2020-2021 stacks, respectively. Increased subsidence during the mid-and late thaw season was detected. The SBAS technique performed better and resulted in less temporal and seasonal decorrelation in areas above the tree line (Tavvavuoma) compared to the lowlands in the forest-tundra (Chersky). The challenge lies in whether surface subsidence of palsas and peat plateaus in sporadic permafrost regions experience irreversible long-term changes or seasonally cyclic changes in the permafrost ground regime. Future studies are recommended to implement annual intervals, including winter images over Tavvavuoma.

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<p dir="ltr">Air-entraining agents (AEA) were introduced in the 1930s to improve concrete's resistance to cyclic freezing-thawing exposure. Over the past 90 years, there has been extensive discussion about how traditional AEAs contribute to durability improvements. However, the issue of strength loss associated with conventional AEA use remains unresolved unless the cement is overdosed. Moreover, the effectiveness of traditional AEAs in entraining air voids has proven inconsistent, as it is influenced by various factors. As a result, the increased costs and carbon footprint associated with AEA use continue to be ongoing concerns for the industry.</p><p dir="ltr">Hollow polymeric microspheres have emerged as a promising solution for enhancing concrete's cyclic freezing-thawing resistance by providing encapsulated air without compromising mechanical performance or durability. In this study, the hydration, fresh properties, hardening performance, and freezing-thawing resistance of air-entrained cement mortar and concrete were investigated using the novel hollow polymeric microspheres and a traditional aqueous AEA, respectively. Additionally, the dynamic modulus of elasticity change and surface spalling damage of concrete beams following cyclic freezing-thawing exposure were evaluated. The air-void system and capillary pore structure of cement mortar and concrete, air-entrained with the traditional AEA and microspheres, respectively, were examined through various characterization methods, including optical microscopy (OM), scanning electron microscopy (SEM), mercury intrusion porosimetry (MIP), and 3D X-ray microscopy (micro-CT, or XCT). The properties of mortar and concrete with varying dosages of AEA and microspheres were assessed, and the mechanisms behind the enhanced freezing-thawing resistance were explored.</p><p dir="ltr">The microspheres used in this study were found to have a 'curing' effect, enhancing the hydration, workability, and mechanical strength of the mortar compared to both plain mortar without air entrainment and mortar air-entrained with the traditional aqueous AEA. Evaluating the mechanical strength changes and mass loss of mortar specimens demonstrated that the freezing-thawing resistance of mortar air-entrained with microspheres was superior to that achieved with aqueous AEA. The small size and compressibility of the microspheres resulted in a fine and well-distributed air void system, offering improved freezing-thawing resistance in the mortar specimens.</p><p dir="ltr">Additionally, due to the potential 'curing' and nucleation effects of the microspheres, the strength of air-entrained concrete with microspheres was slightly higher than that of plain concrete without air entrainment. In contrast, the traditional air-entraining method led to a 7.0% to 8.4% strength loss in concrete with 1% entrained air. Furthermore, concrete air-entrained with microspheres exhibited significantly less surface spalling damage compared to plain concrete, thanks to its well-distributed air void system and enhanced strength. On the other hand, although traditionally air-entrained concrete maintained its dynamic modulus throughout the 300 cycles of freezing-thawing exposure, it still suffered severe surface spalling damage, likely due to its reduced strength.</p><p dir="ltr">This study provides valuable insights into the practical application of polymeric microspheres for enhancing the freezing-thawing resistance of concrete.</p>

xii, 310 p. A print copy of this thesis is available through the UO Libraries. Search the library catalog for the location and call number. / Nostalgia is the longing for a lost, and often substantially reimagined, time or place. Commonly regarded as a conservative impulse available for exploitation by hegemonic forces, nostalgia can also be a source of social questioning and creative inspiration. This dissertation examines the ways in which nostalgic longing imports images and ideas from memory into present discourse and infuses works of art with complication, contradiction, and ambiguity. In the early 1960s, emboldened by Nikita Khrushchev's cultural Thaw, many Soviet filmmakers engaged both personal and social memory to craft challenging reflections of and responses to their times. These filmmakers reengaged the sundered spirit of the 1920s avant-garde and reimagined the nation's artistic and spiritual heritage; they captured the passing moments of contemporary history in a way that animated the permanent, productive, and sometimes stormy dialogue between the present and the persistent past. Mikhail Kalatozov's I Am Cuba (1964), Andrei Tarkovsky's Andrei Rublev (1966, released 1971), and Marlen Khutsiev's Ilich's Gate (1961, released with changes in 1965 as I Am Twenty ) were planned in the anxious years surrounding Khrushchev's fall, and the films mark a high point of Thaw-era cinematic audacity. Each film is epic in scope; each deploys temporal longing to generate narrative ambiguity and dialogue between historical epochs. The films are haunted by ghosts; they challenge the hegemony of the "now" by insisting on the phantom presence of a thousand "thens"; they refurbish old dreams and question contemporary assumptions. The Thaw permitted the intrusion of private memory into public history, and the past became a zone for exploration rather than justification. Easy answers became harder to come by, but the profusion of questions and suggestions created a brief silver age for Soviet cinema. For us, these films offer an extraordinary glimpse into creative life during one of the great, unsung social transitions of the 20th century and reveal the crucial contribution of individual memory in the artistic quest for formal diversity, spiritual inspiration, and ethical living. / Committee in Charge: Dr. H. Leslie Steeves, Chair; Dr. Biswarup Sen; Dr. Julianne Newton; Dr. Jenifer Presto

Master of Science / Department of Civil Engineering / Kyle Riding / Corrosion of reinforcing steel is one of the most common and serious causes of reinforced concrete deterioration. While corrosion is normally inhibited by a passive layer that develops around the reinforcing steel due to the high pH environment of the surrounding concrete, chlorides will break down this protective layer, leading to reinforcement corrosion. Decreasing the diffusivity of the concrete would slow the ingress of chlorides into concrete, and is one of the most economical ways to increase the concrete service life. Optimized concrete mixtures blending portland cement and supplementary cementing materials (SCMs) have become popular throughout the construction industry as a method of improving both fresh and long-term concrete properties such as workability, strength and porosity. It has been shown that use of Class F fly ash, silica fume and ground granulated blast furnace slag (GGBFS) in binary concrete mixture blends can result in a significant reduction in concrete diffusivity. This study investigates the ability of Class C fly ash and ternary concrete mixture blends to also aid in diffusivity reduction. In order to study the effect of incorporation of SCMs into concrete, mixtures containing Class C and Class F fly ash, silica fume and GGBFS were tested following the ASTM C 1556 procedures to measure the concrete’s apparent chloride diffusivity. Structure life cycles were modeled using the measured apparent chloride diffusivities with two finite-difference based life-cycle analysis software packages. To determine whether a correlation between diffusivity and deterioration due to freezing and thawing exists, samples were also tested for their ability to resist deterioration from freezing and thawing cycles using a modified ASTM C 666 Procedure B test. Results show that the use of Class C fly ash yields some service life improvements as compared to the portland cement control mixtures, while ternary mixture blends performed significantly better than the control mixture and equal to or better than the binary SCM mixtures tested. Freeze-thaw tests showed all mixtures to be equally resistant to deterioration due to freezing and thawing.

The present study focuses on the activity of the Young Communist League (Komsomol) to promote the communist project during the so-called Thaw period in the Soviet Union (1953-1964). The term ‘communist project’ describes the complex temporal triangle in which the relevance of the present was rooted in its relationship to the heroic past and the bright future. Young people were supposed to emulate the heroism of previous generations while fighting remnants of the undesired past. This was presented as a precondition for achieving the communist future. The structure of this study reflects the chronology of the communist project. It analyzes the rhetoric used by the Young Communist League to promote the communist project and explores the strategies used to mobilize youth for building communism. The first chapter focuses on the organizational structure of the Komsomol and assesses its readiness for this task. Despite attempts to strengthen horizontal communication and control, streamline administration and reorganize its structure, the Komsomol remained hierarchal and bureaucratic. The second chapter explores the promotion of past heroism in rituals, social practices and the use of public space. The third chapter is also concerned with the past; it describes the Komsomol’s fight against ‘remnants of the past’, primarily religion and deviant behaviour such as hooliganism, heavy drinking and laziness. The final chapter focuses on the Komsomol’s attempts during the Thaw to bring about the future: its efforts in the economy, moral, political and cultural education, and the realm of leisure.

Les matériaux cimentaires peuvent se détériorer grandement lorsqu'ils sont soumis à des cycles de gel/dégel avec ou sans sels de déverglaçage. Ceci peut porter atteinte à la durabilité à long terme des bétons/mortiers dans les régions aux hivers froids. Laissant de côté les processus d'endommagement et de rupture mécanique à l'oeuvre dans de tels problèmes, ce mémoire de thèse est consacré aux phénomènes physiques et thermo-mécaniques accompagnant la solidification de l'eau dans des solides poreux cohésifs, avec une attention particulière aux «propriétés matériau» issues de l'hydratation du ciment et de l'évolution de la microstructure. Ce travail reprend la poromécanique des milieux poreux partiellement gelés telle que développée par Olivier Coussy, tout en lui adjoignant une analyse de l'effet de la fin de la surfusion (en volume, hors contribution capillaire) et de la présence de sels dans le liquide saturant l'espace poreux. Nous avons mesuré la température de fin de surfusion en fonction de la concentration en sel. Ceci nous permet ensuite de calculer l'angle de contact entre la glace et les parois des pores dans le cadre classique de la nucléation hétérogène : on trouve que cet angle diminue avec la concentration en sel. Nous montrons que la dilatation instantanée consécutive à la fin de la surfusion dépend de la structure poreuse puisque cette dernière détermine la teneur en glace dans l'espace poreux. À l'aide de la distribution de tailles de pores estimée par porosimétrie par intrusion de mercure, nous estimons le degré de saturation en glace en fonction de la température et de la concentration initiale en sel via la relation de Gibbs-Thomson. Nous avons mesuré la déformation d'échantilllons de pâte de ciment saturées. L'analyse poromécanique montre que la déformation dépend de la concentration initiale en sel et de la structure poreuse des pâtes de ciment. En utilisant la même approche expérimentale sur des pâtes de ciment sèches, nous trouvons que la porosité (avec ou sans vide d'air entraîné) influence significativement le coefficient d'expansion thermique du matériau. En ce qui concerne les pâtes de ciment saturées, les mesures expérimentales et l'approche poromécanique en condition drainée ou non-drainée montrent que le degré de saturation initiale en liquide des vides d'air entraîné a un impact important sur la déformation de l'échantillon avec la température / When subject to freezing/thawing cycles with or without deicing salt, cement-based materials can suffer severe damage, which raises the long term sustainability problem of concrete/mortar in cold regions. Leaving aside the precise fracture mechanics and damage processes in this kind of problem, this PhD deals with the physical and thermomechanical phenomena undergone by cohesive porous solids under freezing, with particular attention to the material properties arising from cement hydration and microstructure development. The present work revisits the poromechanics of freezing porous materials developed by Olivier Coussy. This gives the opportunity to add the effect of the bulk supercooling and of salt in the liquid saturating the porous space.We measured the relation between depressed temperature at the end of bulk supercooling and salt concentration. We then obtained that the contact angle between ice and pore wall by heterogeneous nucleation decreases as salt concentration increases. We showed that the instantaneous dilation at the end of bulk supercooling is related to the pore structure because the latter determines the in-pore ice content. Using the pore size distribution measured by mercury intrusion porosimetry, we estimated the ice saturation degree with temperature and NaCl solution at different concentration through the Gibbs-Thomson equation. We measured the deformation of saturated cement pastes. The poromechanical analyses show that the strains depend on the initial salt concentration and pore structure of our cement pastes. By the same experimental approach on dried cement pastes, we concluded that the porosity (with or without air voids) has significant influence on the thermal expansion coefficient of our cement pastes. We also performed measurements on the deformation of saturated air entrained cement pastes. The results obtained by both experiments and poromechanical analyses under drained and undrained conditions showed that the initial saturation degree in air-voids has significant influence on the deformation curves with temperature

Não consta resumo na publicação. / Abstract not available.