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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Time series study of urban rainfall suppression during clean-up periods

Geng, Jun 15 May 2009 (has links)
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.
2

Time series study of urban rainfall suppression during clean-up periods

Geng, Jun 10 October 2008 (has links)
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.
3

Information Seeking in a Virtual Learning Environment

Byron, Suzanne M. 08 1900 (has links)
Duplicating a time series study done by Kuhlthau and associates in 1989, this study examines the applicability of the Information Search Process (ISP) Model in the context of a virtual learning environment. This study confirms that students given an information seeking task in a virtual learning environment do exhibit the stages indicated by the ISP Model. The six-phase ISP Model is shown to be valid for describing the different stages of cognitive, affective, and physical tasks individuals progress through when facing a situation where they must search for information to complete an academic task in a virtual learning environment. The findings in this study further indicate there is no relationship between the amount of computer experience subjects possess and demonstrating the patterns of thoughts, feelings, and actions described by the ISP Model. The study demonstrates the ISP Model to be independent of the original physical library environments where the model was developed. An attempt is made to represent the ISP model in a slightly different manner that provides more of the sense of motion and interaction among the components of thoughts, feelings, and action than is currently provided for in the model. The study suggests that the development of non-self-reporting data collection techniques would be useful in complementing and furthering research to enhance and refine the representation of the ISP Model. Additionally, expanding the research to include the examination of group interaction is called for to enhance the ISP Model and develop further applications that could potentially aid educational delivery in all types of learning environments.

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