We develop a viscoelastic version of the volume of fluid algorithm for tracking deformable interfaces. The code uses the piecewise linear interface calculation method to reconstruct the interface, the continuous surface force formulation to model interfacial tension forces and utilizes the semi-implicit Stokes solver (enabling computations at low Reynolds numbers). The algorithm is primarily designed to simulate the flow of superposed fluids and the drop in a flow problem in 2D shear flows of viscoelastic and/or Newtonian fluids. The code is validated against linear stability theory for the two-layer flow case and against experimental and other documented numerical investigations for the droplet-matrix case. / Ph. D.

No / Pressure variation during the coextrusion of two low density polyethylene melts was investigated. Melt streams were delivered to a die from two separate extruders to converge in a 30 degrees degrees geometry to form a two layer extrudate. Melt flow in the confluent region and die land to the die exit was observed through side windows of a visualisation cell. Stream velocity ratio was varied by control of extruder screw speeds. Layer thickness ratios producing wave type interfacial instability were quantified for each melt coextruded on itself and for the combined melts. Stream pressures and screw speeds were monitored and analysed. Wave type interfacial instability was present during the processing of the melts at specific, repeatable, stream layer ratios. Increased melt elasticity appeared to promote this type of instability. Analysis of process data indicates little correlation between perturbations in extruder screw speeds and stream pressures. The analysis did however show covariance between the individual stream pressure perturbations. Interestingly there was significant correlation even when interfacial instability was not present. We conclude that naturally occurring variation in extruder screw speeds do not perturb stream pressures and, more importantly, natural perturbations in stream pressures do not promote interfacial instability.

Future climate changes will alter disturbance regimes worldwide with important implications for many ecological and social systems. In west central British Columbia, Canada, fire and insect disturbances have shaped the historic character of Douglas-fir (Pseudotsuga menziesii var. glauca Beissn. Franco) dominated forests. However, since AD 1900 fire suppression and other forest management practices have led to denser forests and conifer encroachment into grasslands. Considering climate changes in interior British Columbia are expected to result in warmer and drier conditions, understanding the influence of climate on forest disturbances is crucial for land managers tasked with both mitigating the effects of disturbance and promoting resilience in forest ecosystems. This research focused on developing multi-century, annually-resolved records of fire and western spruce budworm outbreaks to evaluate: the historic climate conditions related to these disturbances; the influence of grassland proximity on disturbance-climate relationships; and, whether western spruce budworm outbreaks were related to fire activity. At the landscape scale, a detailed study in the Churn Creek Protected Area revealed spatially variable stand structure and fire-climate relationships at a low elevation forest-grassland ecotone over the interval AD 1600 to 1900. This finding suggests the site was characterized by fires of mixed-severity dominated by frequent, low-severity, fires related to positive antecedent moisture conditions punctuated by widespread fires of moderate to high severity related to intervals of persistent drought. At the regional scale, the influence of interannual climate variability and large-scale patterns of climate variability (e.g. El Nino Southern Oscillation) was evaluated using new and existing records of fire history and multiple climate pattern reconstructions. Regional fire activity was shown to be significantly related to interannual climate variability, and no consistent patterns between regional fire years and the individual phases or phase combinations of large-scale patterns of climate variability were detected. The findings suggest that the spatial expression of large-scale climate patterns translates into weak and undetectable terrestrial effects related to fire activity in this region. The influence of grassland proximity on disturbance history was investigated using site-level and regional tree-ring reconstructions of western spruce budworm outbreaks and fire activity based on four sites adjacent to grasslands and four sites not adjacent to grasslands between AD 1600 and 1900 (fire) and AD 1600 and 2009 (western spruce budworm). Fires affecting grassland proximal sites were more frequent than fires occurring in forests not adjacent to grasslands, and the character of western spruce budworm outbreaks was generally consistent among all sites. Fire activity was related to both warm, dry and cool, wet conditions in the fire year and/or year(s) preceding the fire depending on proximity to grasslands, suggesting climate conditions associated with both fine fuel growth and drying are key determinants for fire activity. The initiation of western spruce budworm outbreaks was significantly related to drought and this relationship was enhanced at sites adjacent to grasslands. At the site-level and regional scale, no consistent association was found between the initiation of western spruce budworm outbreaks and fire years indicating the historic interaction between these disturbances is weak or non-existent. / Graduate

Several times a year companies publish business reports to openly account for their business activities. This thesis examines the effect of those business reports on stock prices of businesses in the German automotive industry. Different statistical methods such as Event Coincidence Analysis and Superposed Epoch Analysis are used to examine possible negative and positive reactions of stock prices before and after the disclosure of business reports. It shows that there seems to be a stronger influence of a negative business report on the daily abnormal rate of return than of a positive business report. Furthermore the thesis confirms the hypothesis of Roeder that the information from a business report is processed not only on the day of publication but also on the day after.

Several times a year companies publish business reports to openly account for their business activities. This thesis examines the effect of those business reports on stock prices of businesses in the German automotive industry. Different statistical methods such as Event Coincidence Analysis and Superposed Epoch Analysis are used to examine possible negative and positive reactions of stock prices before and after the disclosure of business reports. It shows that there seems to be a stronger influence of a negative business report on the daily abnormal rate of return than of a positive business report. Furthermore the thesis confirms the hypothesis of Roeder that the information from a business report is processed not only on the day of publication but also on the day after.