Atomistic computer simulations were performed using embedded atom method interatomic potentials in α-Fe with impurities and defects. The effects of intergranular carbon on fracture toughness and the mechanisms of fracture were investigated. It was found that as the average grain size changes the dominant energy release mechanism also changes. Because of this the role of the intergranular carbon changes and these mechanisms compete affecting the fracture toughness differently with changing grain size. Grain boundary accommodation mechanisms are seen to be dominant in the fracture of nanocrystalline α-Fe. To supplement this work we investigate grain boundary sliding using the Σ = 5,(310)[001] symmetrical tilt grain boundary. We observe that in this special boundary sliding is governed by grain boundary dislocation activity with Burgers vectors belonging to the DSC lattice. The sliding process was found to occur through the nucleation and glide of partial grain boundary dislocations, with a secondary grain boundary structure playing an important role in the sliding process. Interstitial impurities and vacancies were introduced in the grain boundary to study their role as nucleation sites for the grain boundary dislocations. While vacancies and H interstitials act as preferred nucleation sites, C interstitials do not. / Ph. D.

Microstructural data on the orientation and distribution of minerals can be utilized to better understand the processes controlling mineral crystallization during metamorphism and the extent to which equilibrium versus kinetic factors control the evolution of metamorphic rocks. Four studies in this dissertation address this, finding that: i) garnet crystals crystallize via epitaxial nucleation in which garnet crystallizes by templating on the crystal structure of muscovite; ii) the distribution of grain boundary void space at quartz-quartz and garnet-quartz grain boundaries is a function of the orientation of quartz crystals on either side of the grain boundary. There are more voids, and in some cases larger voids, at grain boundaries in which the a-axis of a neighboring quartz grain is perpendicular to the grain boundary than any other orientation; iii) the chemical potentials of garnet-forming components evolve differently in samples in which garnet growth either significantly or minimally overstepped equilibrium garnet-forming reactions; iv) the southwestern Meguma Terrane, Nova Scotia, experienced peak metamorphic conditions of ~630ºC and 4.0 kbar, likely resulting from regional metamorphism during the Neoacadian orogeny. A case study on the mechanisms controlling garnet crystallization in one Nova Scotian sample reveals that the rate limiting step of garnet crystallization was probably the diffusional transport of Al through the intergranular matrix. Taken together, this work has implications for understanding: i) the properties of grain boundaries in metamorphic rocks and ii) the extent to which equilibrium versus kinetic factors impact metamorphic petrogenesis. / Doctor of Philosophy / A fundamental question in the development of metamorphic rocks, or rocks that form due to changes in pressure and temperature conditions deep in the Earth's mountain belts, is: what controls the crystallization of new minerals? While pressure, temperature, and bulk composition likely play a major role in this, it is also possible that the distribution of reactant minerals and the transport of elements through the rock may also play a role in mineral crystallization. This dissertation explores several projects related to this broad topic. In one example, garnet, an important metamorphic mineral, was found to crystallize by utilizing the atomic structure of another mineral in the rock. This creates a favorable pathway for the crystallization of garnet, which preferentially grows on this 'parent' mineral. Further, the distribution of porosity, or void space, at the interfaces between mineral grains in metamorphic rocks is found to be controlled by the orientation of those minerals. This porosity likely formed when the rocks were exhumed from deep in the Earth towards its surface. Metamorphic rocks can also tell the story of continental plates colliding millions of years ago. In an example from the formation of the Appalachian Mountains ~400 million years ago, a combination of collisional tectonic forces and the heat from magmas in the shallow crust resulted in metamorphic rock, which make up much of southern Nova Scotia today. This work has important implications for understanding: i) porosity in metamorphic rocks and ii) how minerals crystallize during metamorphism.

This dissertation focuses on the process of identity development and the role of boundaries in that process. Toward this end a study was conducted to explore the interaction between Hartman's (1991) boundaries, Marcia's (1966) identity statuses, and Berzonsky's (1989) identity styles. Data for this study was collected via survey from a convenience sample of undergraduate college students (n = 549) between ages 18 and 24 and across 4 courses at a large state institution in rural Southeastern United States. A 2-way ANOVA was used in this study to explore differences in boundary scores for both Marcia's (1966) identity statuses and Berzonsky's (1989) identity styles. No significant main effect was found for identity status, and no interactional effect was found between identity status and identity style, but a significant main effect was found for identity style. Post-hoc analyses for identity style revealed the diffuse/avoidant style as significantly higher in boundary score than the informational style, which in turn was significantly higher in boundary score than the normative style, with higher boundary scores indicating thinner boundaries. A discussion of these results and their implications for counseling practice are provided. / Ph. D.

A study on the possibilities of place-making by systematically separating the traditional responsibilities of the wall as an architectural element. Walls usually serve several simultaneous structural, enveloping and distributional duties. The project consists in designing a house where four distinct but interacting types of walls are present, each with a well defined duty. Each necessary but deliberately insufficient in itself: one provides the structure; another is a continuous skin for enclosure and partition; still another solely weatherproofs and, finally, one filters the light and grants privacy. The four walls function as layers with the capacity of interplay, while retaining their identity. The places resulting from these boundaries assert their presence and function in view of the character bestowed by the form of their enclosure. The choice of material, assembly, texture and color in unique correspondence to each boundary's usefulness, complete the experience of the inhabitant and architectural form comes about. / Master of Architecture

The major goal of this study was to gain a better understanding of the effects that grain boundaries have on conduction in multilayer ceramic (MLC) capacitors. Electrical measurements were made so that current-voltage curves and impedance plots could be constructed. It was found that the current-voltage curves of new COG and X7R multilayer ceramic capacitors are both ohmic at low voltages and super-ohmic at intermediate voltages. Ohmic behavior prevails at high voltages for both types. Such behavior can be attributed to grain boundaries. Grain boundary resistance was clearly exhibited by X7R-type density blanks and one commercially manufactured type of X7R MLC capacitor, while the NPO density blank and two different values of Z5U multilayer ceramic capacitors, each from a different manufacturer, indicated the possibility of grain boundary resistance. All of the samples that were tested showed possible, if not probable, evidence of grain resistance. Only the Z5U-type density blank showed a resistance contribution from the bulk-electrode interfaces. A model for the grain boundary potential barrier height was developed. It was found that barrier height reduction occurs for small grain sizes due to depletion of the grain, and for increased grain curvature. Dopant effects are also responsible for barrier height reduction. These results, and the related modelling, indicate that grain boundary contributions to titanate-based ceramic resistance can vary widely from sample to sample, since there are so many material dependent variables involved. Such measurements as those described here can help clarify how grain boundaries and other factors contribute to ceramic resistance. / M.S.

This thesis investigates the use of the numerical modeling tools LS-DYNA and USA in modeling general far-field underwater explosions (UNDEX) by modeling a three-dimensional box barge that is subjected to a far-field underwater explosion. Past UNDEX models using these tools have not been validated by experiment and most are limited to very specific problems because of the simplifying assumptions they make. USA is a boundary element code that requires only the structural model of the box barge. LS-DYNA is a dynamic finite element code and requires both the structural model and the surrounding fluid model, which is modeled with acoustic pressure elements. Analysis of the box barge problem results finds that the program USA is a valid tool for modeling the initial shock response of surface ships when cavitation effects are not considered. LS-DYNA models are found to be very dependent on the accuracy of the fluid mesh. The accuracy of the fluid mesh is determined by the ability of the mesh to adequately capture the peak pressure and discontinuity of the shock wave. The peak pressure captured by the model also determines the accuracy of the cavitation region captured in the fluid model. Assumptions made in the formulation of the fluid model causes potential inaccurate fluid-structure interaction and boundary condition problems cause further inaccuracies in the box barge model. These findings provide a base of knowledge for the current capabilities of UNDEX modeling in USA and LS-DYNA from which they can be improved in future work. / Master of Science

Over the last few decades, the production and consumption of craft beer in the United States has witnessed a spectacular increase. According to the Brewer's Association (2020), there were approximately 89 breweries operating in the United States in 1978 compared to 8,386 in 2019. Along with this rapid market expansion, the cultural status of beer also underwent significant changes. Despite the exponential rise in the number of craft breweries as well as the emergence of a craft beer culture, little empirical scholarship on the field of craft beer exists. In this study, I analyze the rapid status shift of craft beer by exploring its social history of changes that occurred both exogenously to the cultural field of craft beer as well as endogenous developments within the field. Further, I examine in detail the emergence and role of a critical discourse surrounding craft beer culture in relation to its involvement in the elevation of status as well as the construction of symbolic and social boundaries. The theoretical foundation for this study draws on insights from work on cultural fields (Bourdieu 1993), art worlds (Becker 1982), cultural and artistic legitimation (Baumann 2001; 2007a; 2007b; 2011), social and symbolic boundaries (Lamont and Molnar 2002), and the production of culture perspective (Peterson and Anand 2004). Data for this project come both from secondary and original sources including All About Beer magazine and semi-structured face-to-face interviews with craft beer industry professionals. My findings suggest that while the status elevation of the field of craft beer has closely followed those of other legitimized fields (e.g., film), unique discursive and institutional dynamics are also salient. Specifically, I find that through critical discourse, the status elevation of craft beer in the United States context was directly related to a.) the establishment of beer travel as a cultural good, b.) the linkage of craft beer to predominantly white, middle-class leisure activities, c.) the association of beer to other high status gastronomic fields, and d.) the historicization of the field craft beer particularly via the mythologization of early pioneers. / Doctor of Philosophy / Over the last few decades, the production and consumption of craft beer in the United States has witnessed a spectacular increase. According to the Brewer's Association (2020), there were approximately 89 breweries operating in the United States in 1978 compared to 8,386 in 2019. Along with this rapid market expansion, the public perception of craft beer also underwent significant changes. Despite the exponential rise in the number of craft breweries, craft beer's changing status, and the blossoming of American craft beer culture, little empirical scholarship on craft beer exists that explores the sociological aspects of the field. Drawing on multiple sociological theoretical frameworks I employ a multi-method research design to analyze both secondary and original data to explore questions surrounding the upward status elevation of craft beer from 2002 to 2017 in the United States context. My main findings suggest that through critical discourse, the status elevation of craft beer in the United States context was directly related to a.) the establishment of beer travel as a cultural good, b.) the linkage of craft beer to predominantly white, middle-class leisure activities, c.) the association of beer to other high status gastronomic fields such as wine, and d.) the historicization of the field craft beer particularly via the mythologization of early pioneers.

Molecular dynamics simulations are use to study the energetics and deformation response of random grain boundaries in polycrystalline Nickel. Computer generated samples of defect-free Ni were created, plastically deformed, and examined as a baseline understanding to the underlying mechanisms of deformation and intergranular fracture in FCC metals. Two types of samples were utilized: a sample with columnar grains consisting of pure <110> tilt boundaries and a thin-film sample with 3D grain orientations modeled after an experimental sample of austenitic steel. The structure and energies of these random boundaries under stress and temperature was analyzed. Heterogeneous displacement maps were made for a side-by-side comparison of the dislocation activity and interactions with the grain boundaries. The dislocation behavior was found to be consistent between the two digital sample types and further comparison with experimental samples was made. The intergranular cracking behavior was also studied and various factors were examined to generate general trends. Crack initiation was observed to typically occur in random high-angle boundaries close to a triple junction where the cracks have high angles with respect to the tensile loading direction. The cracking results from the simulations agree well with current preliminary results of experimentally deformed austenitic steel samples. Furthermore, the behavior and failure of the thin-film sample is compared with its corresponding experimental sample. / Master of Science

Operating within a dense urban context, a public building recognizes the activities that are contained within its boundaries... further tying the place to a larger urban spatial sequence. / Master of Architecture

In this dissertation, simulation techniques are used to understand the role of surfaces and grain boundaries in the deformation response of metallic materials. This research utilizes atomistic scale modeling to study nanoscale deformation phenomena with time and spatial resolution not available in experimental testing. Molecular dynamics techniques are used to understand plastic deformation of grain boundaries and surfaces in metals under different configurations and loading procedures. Stress and strain localization phenomena are investigated at plastically deformed boundaries in axially strain thin film samples. Joint experimental and modelling work showed increased stress states at the intersections of slip planes and grain boundaries. This effect, as well as several other differences related to stress and strain localization are thoroughly examined in digital samples with two different grain boundary relaxation states. It is found that localized stress and strain is exacerbated by initial boundary disorder. Dislocation content in the randomly generated boundaries of these samples was quantified via the dislocation extraction algorithm. Significant numbers of lattice dislocations were present in both deformed and undeformed samples. Trends in dislocation content during straining were identified for individual samples and boundaries but were not consistent across all examples. The various contributions to dislocation content and the implications on material behavior are discussed. The effects of grain boundary hydrogen on the deformation response of a digital Ni polycrystalline thin film sample is reported. H content is found to change the structure of the boundaries and effect dislocation emission. The presence of dispersed hydrogen caused a slight increase in yield strength, followed by an increase in grain boundary dislocation emission and an increase in grain boundary crack formation and growth. An atomistic nano indenter is employed to study the nanoscale contact behavior of the indenter-surface interface during nano-indentation. Several indentation simulations are executed with different interatomic potentials and different indenter orientations. A surface structure is identified that forms consistently regardless of these variables. This structure is found to affect several atomic layers of the sample. The implications of this effect on the onset of plasticity are discussed. Finally, the implementation of an elastic/plastic continuum contact solution for use in mesoscale molecular dynamics simulations of solid spheres is discussed. The contact model improves on previous models for the forces response of colliding spheres by accounting for a plastic regime after the point of yield. The specifics of the model and its implementation are given in detail. Overall, the dissertation presents insights into basic plastic deformation phenomena using a combination of experiment and theory. Despite the limitations of atomistic techniques, current computational power allows meaningful comparison with experiments. / Ph. D. / Certain engineering metals have a remarkable bend-then-break quality. This allows a metal component to withstand damage without totally failing. The process of permanent distortion is called plastic deformation. Metals, in nearly all practical forms, contain defects. During plastic deformation, defects are generated, moved, changed and annihilated. The rates of these actions govern the mechanical behavior of metals. There are several types of defects and several ways in which they can interact, forming a complex interplay during plastic deformation. The focus of this dissertation is on plastic deformation associated with two particular defect types: surfaces and grain boundaries. Because these defects occur on a very small length scale, the details of their behavior can best be observed via simulation. For this reason, Molecular Dynamics was employed as the primary research tool, and other methods were used for validation. This allows fully 3D rendering of our simulated samples with atom-scale resolution, and complete stress/energy information. In each of the 6 manuscripts presented in this dissertation, new insights into the plastic deformation around surfaces or grain boundaries is presented.