published_or_final_version / Dentistry / Doctoral / Doctor of Philosophy

A study of Molecular Dynamics using computational methods and modeling provides the understanding on the interaction of the atoms, properties, structure, and motion and model phenomenon. There are numerous commercial tools available for simulation, analysis and visualization. However any particular tool does not provide all the functionalities. The main objective of this work is the development of the visualization tool customized for our research needs to view the three dimensional orientation of the atom, process the simulation results offline, able to handle large volume of data, ability to display complete frame, atomic trails, and runtime response to the researchers' query with low processing time. This thesis forms the basis for the development of such an in-house tool for analysis and display of simulation results based on Open GL and MFC. Advantages, limitations, capabilities and future aspects are also discussed. The result is the system capable of processing large amount of simulation result data in 11 minutes and query response and display in less than 1 second. / by Meha Garg. / Thesis (M.S.C.S.)--Florida Atlantic University, 2010. / Includes bibliography. / Electronic reproduction. Boca Raton, Fla., 2010. Mode of access: World Wide Web.

Rainfall is a natural process, which has a high degree of variability in both space and time. Information on the spatial and temporal variability of rainfall plays an important role in the process of surface runoff generation. Hence it is important for a variety of applications in hydrology and water resources management. The spatial variability of rainfall can be substantial even for very small catchments and an important factor in the reliability of rainfall-runoff simulations. Catchments in urban areas usually are small, and the management problems often require the numerical simulation of catchment processes and hence the need to consider the spatial and temporal variability of rainfall. A need exists, therefore, to analyse the sensitivity of rainfall-runoff behaviour of catchment modelling systems (CMS) to imperfect knowledge of rainfall input, in order to judge whether or not they are reliable and robust, especially if they are to be used for operational purposes. Development of a methodology for identification of storm events according to the degree of heterogeneity in space and time and thence development of a detailed spatial and temporal rainfall model within a hydroinformatic environment utilising real-time data has been the focus of this project. The improvement in runoff prediction accuracy and hence the importance of the rainfall input model in runoff prediction is then demonstrated through the application of a CMS for differing variability of real storm events to catchments with differing orders of scale. The study identified both spatial and temporal semi-variograms, which were produced by plotting the semi-variance of gauge records in space and time against distance and time respectively. These semi-variograms were utilised in introducing estimators to measure the degree of heterogeneity of each individual storm events in their space and time scale. Also, the proposed estimators use ground based gauge records of the real storm events and do not rely on delicate meteorological interpretations. As the results of the investigation on the developed semi-variogram approach, real storm events were categorised as being High Spatial-High Temporal (HS-HT); High Spatial-Low Temporal; (HS-LT); Low Spatial-High Temporal (LS-HT); and Low Spatial-Low Temporal variability.A comparatively detailed rainfall distribution model in space and time was developed within the Geographical Information Systems (GIS). The enhanced rainfall representation in both space and time scale is made feasible in the study by the aid of the powerful spatial analytic capability of GIS. The basis of this rainfall model is an extension of the rainfall model developed by Luk and Ball (1998) through a temporal discretisation of the storm event. From this model, improved estimates of the spatially distributed with smaller time steps hyetographs suited for especially the urban catchments could be obtained. The importance of the detailed space-time rainfall model in improving the robustness of runoff prediction of CMS was investigated by comparing error parameters for predictions from CMS using alternate rainfall models, for various degrees of spatiotemporal heterogeneity events. Also it is appropriate to investigate whether the degree of this improvement to be dependent on the variability of the storm event which is assessed by the adopted semi-variogram approach. From the investigations made, it was found that the spline surface rainfall model, which considered the spatial and temporal variability of the rainfall in greater detail than the Thiessen rainfall model resulted in predicted hydrographs that more closely duplicated the recorded hydrograph for the same parameter set. The degree of this improvement in the predicted hydrograph was found to be dependent on the spatial and temporal variability of the storm event as measured by the proposed semi-variogram approach for assessing this feature of a storm event. The analysis is based on forty real events recorded from the Centennial Park Catchment (1.3km2) and the Upper Parramatta River Catchment (110km2) in Sydney, Australia. These two case study catchments were selected to ensure that catchment scale effects were incorporated in the conclusions developed during the study.

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Graduation date: 1997

Contamination of ground water by non-aqueous phase liquids (NAPLs) has received increasing attention. The most common approach to numerical modeling of NAPL movement through the unsaturated zone is the use of the finite difference or finite element methods to solve a set of partial differential equations derived from Darcy's law and the continuity equations (Abriola and Pinder, 1985; Kaluarachchi and Parker, 1989). These methods work well in many settings, but have given little insights as to why certain non-ideal flow phenomena will occur. The network modeling method, which considers flow at the pore-scale, was used in this study to better understand macroscopic flow phenomena in porous media. Pore-scale network models approximate porous medium as a connected network of pores and channels. Two and three-dimensional pore-scale network models were constructed in this study. A uniform statistical distribution was assumed to represent the random arrangement of pore and tube sizes. Both hysteristic scanning curves and intermediate fluid distribution are studied. The simulation results suggested that network models may be used to predict the characteristic curves of three-phase systems. The results also suggested that three-dimensional models are necessary to study the three-phase problems. Two-dimensional models do not provide realistic results as evidenced by their inability to provide scale-invariant representation of flow processes. The network sizes used in this study ranged from 10 x 5 (50) to 156 x 78 (12168) pores for two-dimensional and from 10 x 5 x 5 (250) to 100 x 50 x 5 (25000) pores for three-dimensional domains. The domain size of 100 x 50 x 5 pores was large enough to provide descriptions independent of the domain scale. The one important limitation of network models is the considerable computational requirements. The use of very high speed computers is essential. Except for this limitation, the network model provides an invaluable technique to study fluid transport mechanisms in the vadose zone. / Graduation date: 1996

Ozone is recognized as one of the most dangerous irritants to eyes, throat, lungs and etc .. Chamber studies consistently have demonstrated adverse effects of ozone on human lung function. The results of epidemiological studies, however, have been controversial, partly because there are many factors that affect human lung function. Thus it has been difficult to control confounding in epidemiological studies. Among these factors, retention and ventilation are two of the more important because of their strong influence on ozone's physiologically effective dose. This study used a computer simulation model, utilizing data from the "children's Camp Study", to analyze the effects of retention factors and ventilation on ozone's physiologically effective dose. The results of the simulations indicated appreciable improvement in the estimated exposure to ozone when inhaled ozone exposure (effective dose) was included in the model. These results were consistent with the study's a priori- hypothesis (that incorporating retention and ventilation factors into the model would improve the estimated exposure to ozone) primarily because of the greater precision and reduction in bias associated with the use of heart rate data that were child-and hour-specific. The study identified three simulation data sets for which the ozone dose model yielded a more significant coefficient than did the average ozone concentration model. Using the t-statistic, the three models were seen to follow the expected pattern, with statistically significant differences between the R² values (the coefficient of variation changed from 45.4 to 11.0 when the error term was 0. 01). The results of the analyses support the hypothesis that ventilation and retention factors can be used to increase the precision of ozone exposure measurement and reduce exposure assessment errors significantly, thereby sharpening the power of studies evaluating ozone's acute health effects. / Graduation date: 1992

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