There is a strong desire among automobile manufacturers to reduce the fuel consumption and greenhouse gas emissions of their current vehicles. Reducing the overall weight of a vehicle represents the most practical opportunity to reduce fuel consumption. Replacing the current steel sheet structures with lightweight alternatives, such as aluminum, offers an excellent solution. Much of the attention in North America has been focused on copper-containing Al-Mg-Si aluminum alloys (6xxx series), such as AA6111. These alloys offer an excellent combination of good formability and precipitation-strengthening ability.<p> In this study, the effect of solute concentration on the strength and strain aging behavior of a proprietary Al-Mg-Si-(Cu) alloy was evaluated. The experimental design used was a 26 full factorial design, with the primary factors being the solute concentrations of magnesium, silicon, and copper, as well as the effects of applied strain (cold work), and natural and artificial aging heat treatments (e.g., a simulated paint bake process). The primary investigative techniques employed included tensile testing, microhardness measurements, and optical metallography.<p> The results show that cold work and artificial aging produce the most substantial strengthening in the alloys. The occurrence of natural aging prior to forming and artificial aging reduced strengthening. The highest strength levels in the naturally aged and paint baked condition, which most closely resembles what is found in industry, were achieved at a combination of low magnesium levels (i.e., 0.5 wt.%) and high silicon and copper levels (i.e., 0.9 and 0.3 wt.%, respectively).

The effect on urban rainfall of pollution aerosols is studied both by data analysis and computational simulation. Our study examines data for urban areas undergoing decadal clean-up. We compare the annual precipitation between polluted sites and relatively clean sites through the time range before and during their clean-up periods to see how the air quality may affect the precipitation amount. By comparing the annual precipitation amount between two polluted sites with different elevations we demonstrate the role that elevation may play in rainfall suppression. Based on the data we collected, we built a model to analyze the relationship between air pollution aerosols and precipitation. Finally, we used a model of time dependent condensational aerosol growth to numerically study the relationship of air pollution aerosols and precipitation amount. Based on these results, we found a negative relationship of precipitation amount and air pollution amount; also, the simulation results clearly demonstrated that too many air pollution particles will deplete the water vapor and suppress further growth of condensation nuclei (CN) toward cloud condensation nuclei (CNN). This study supported the theoretical explanation on why air pollution could suppress urban rainfall.

The purpose of this exploratory case study was to describe an expert teacher’s decision-making system during interactive instruction using teacher self-report information, classroom observation data, and physiological recordings. Timed recordings of instructional interaction variables using an adapted Stallings Observation System were combined with simultaneous skin voltage measurements in time series analyses to describe observable and physiological elements of an expert teacher’s decision-making process. The mean and standard deviation of observable decision-action rates on teacher-identified “teaching days” were higher than the rates on “guiding” days. Bivariate time series analysis of decision-action rates and physiological response rates showed a significant positive relationship between the teacher’s decision-action rate and her physiological response rate on one teaching day. The positive relationship between the teacher’s decision-action rate and her physiological response rate was found to be context-dependent and related to the teaching strategy being used. High decision-action rates during direct instruction were associated with high physiological response rates compared to lower decision-action rates and physiological response rates while monitoring independent seatwork during a test. Correlation analysis of physiological response rates with time revealed slight, but statistically significant negative trends for four of the five observation days. Major features of the teacher’s decision-making system included focusing attention on academic instruction with the use of routines for managing students and materials to perform teaching tasks; both proactive and reactive improvisational decisions; and physiological events characteristic of autonomic nervous system activity during instructional sequences of high teacher-student interactivity. Damasio’s Somatic Marker Hypothesis (Damasio, 1999) is offered as an explanation for the generation of specific characteristics of the expert teacher’s instruction, such as the high frequency of decision-actions and automaticity of appropriate decisions.

The effect on urban rainfall of pollution aerosols is studied both by data analysis and computational simulation. Our study examines data for urban areas undergoing decadal clean-up. We compare the annual precipitation between polluted sites and relatively clean sites through the time range before and during their clean-up periods to see how the air quality may affect the precipitation amount. By comparing the annual precipitation amount between two polluted sites with different elevations we demonstrate the role that elevation may play in rainfall suppression. Based on the data we collected, we built a model to analyze the relationship between air pollution aerosols and precipitation. Finally, we used a model of time dependent condensational aerosol growth to numerically study the relationship of air pollution aerosols and precipitation amount. Based on these results, we found a negative relationship of precipitation amount and air pollution amount; also, the simulation results clearly demonstrated that too many air pollution particles will deplete the water vapor and suppress further growth of condensation nuclei (CN) toward cloud condensation nuclei (CNN). This study supported the theoretical explanation on why air pollution could suppress urban rainfall.

Thesis (Ph. D.)--University of Missouri-Columbia, 1998. / Typescript. Vita. Includes bibliographical references (leaf 93). Also available on the Internet.

Includes bibliographical references (p. 29-30).

Thesis (doctoral)--K. Ludwig-Maximilians-Universität zu München, 1913. / Vita.

Thesis (M. Phil.)--University of Hong Kong, 2001. / Includes bibliographical references (leaves 71-74).

Thesis (doctoral)--Friedrich-Wilhelms-Universität zu Berlin, 1914. / Vita. Includes bibliographical references.

Thesis (Ph. D.)--University of Texas at Austin, 2003. / Vita. Includes bibliographical references. Available also from UMI Company.