Thesis (Ph.D.)--Mathematics, Georgia Institute of Technology, 2008. / Committee Chair: Yang Wang; Committee Member: Christopher Heil; Committee Member: Doron Lubinsky; Committee Member: Guillermo Goldsztein; Committee Member: Steven W. McLaughlin

Thesis (M. Phil.)--University of Hong Kong, 1998. / Includes bibliographical references (leaves 98-103).

Thesis (M.S.)--West Virginia University, 2010. / Title from document title page. Document formatted into pages; contains viii, 75 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 72-75).

No description available.

The overall goal of the thesis was to study available geographic information systems (GIS) and to explore the functionality they provide. The implementation was focused on module for vector data creation and data analysis. As examples were used existing systems like GRASS and ArcGIS. The result of this master thesis was a plug-in integrated into the GIS of DELINFO, spol. s r.o. company. The plug-in can open, modify and save vector data in shapefile format. The plug-in is also able to do some basic analysis of the vector data, such as a region intersection, a union, hit tests and a distance measurement. This thesis could be used as a pattern for vector data operations in GIS.

No description available.

Indirect vector controlled induction motor drives are gaining acceptance because they allow the induction motor to be controlled like a separately excited dc motor, i.e. they achieve decoupling of torque and flux producing currents. But, the effectiveness of these drives is lost as they are highly parameter sensitive. Studies have indicated that the decoupling of the torque and the flux channels is lost when machine parameters change with temperature, saturation, etc. Many schemes have been proposed to overcome these parameter sensitivity effects. But most of these schemes themselves are parameter-dependent and hence inapplicable to high precision control applications. A new parameter compensation scheme which uses air gap power equivalence for sensing parameter changes is developed in this thesis. It is shown that this scheme is independent of key motor parameters and requires no additional transducers for implementation. / M.S.

The feasibility of using a vectorized banded direct solver for the compressible Euler and Navier-Stokes equations is examined for both single-grid and multi-grid strategies. A procedure is developed for comparing the computational effort required for the direct method with that of the vertical line Gauss-Seidel iteration scheme in order to provide a criteria for choosing between the two techniques. The direct method is shown to have a relatively wide range of application on a vector processor with large memory. Indeed, the primary limitation of the direct method at this time is machine memory. Results for both inviscid and viscous test problems over a range of Mach numbers and Reynolds numbers are examined for two dimensions. / Ph. D.

published_or_final_version / Electrical and Electronic Engineering / Master / Master of Philosophy

Promotion of agroforestry practices in sub-Sahara Africa may help sustain subsistent food and wood production by integrating trees and crops on farmlands to replenish soil fertility and improve crop yield. Using rotational woodlot and pigeonpea intercropping systems in semi-arid Tanzania as case studies, my research screened suitable tree species to increase fuelwood supply and examined mechanisms for reducing tree-crop competition. By adopting nutrient use efficiency (the ratio of biomass yield to nutrient uptake) as a criterion, I found that selecting tree species of low wood nutrient concentrations would minimize nutrient exports by 42 – 60 %, thus reducing soil nutrient depletion while concurrently sustaining local fuelwood supply harvested from rotational woodlots. Currently smallholder farmers cannot afford to replenish soil fertility because of high fertilizer costs. However, 5-year tree fallowing raised soil N and P levels for maize culture as high as those from recommended fertilizer applications. Post-fallow maize yield was also increased significantly over natural fallow practices. Apparently there is a trade-off between yields of maize and fuelwood under rotational woodlot culture providing farmers the choice to proportion tree and crop composition based on priority demands. An alternative practice of intercropping pigeonpea with maize may also rapidly replenish soil fertility as well as enhance maize yield when competitive interactions between trees and crops are controlled. Vector analysis revealed that such interactions suppressed biomass yields of maize and pigeonpea by 30 % and 60 %, respectively, due to limited soil nutrients and/or moisture. Optimizing yields of both crops would require prescribed fertilizer addition when intercropped, but dose rates can be lowered by half under the improved fallow system due to alleviating interspecific competition. My findings form the basis of a plea for greater use of rotational woodlot and pigeonpea intercropping systems in semi-arid areas. I conclude that smallholder farm management of rotational agroforestry systems can be significantly improved by refining tree selection criteria and mitigating nutrient competition between trees and crops to maintain food and fuelwood production.