Component-based software engineering has been championed because they can be used to shorten the development cycle of system and therefore lower the costs. This research presents a modeling method that integrates the principle of divide and conquer and the use case concept to help model component-based software effectively. A real-world case is modeled and a system is developed to illustrate the concepts, application, and the advantages of using proposed methodology.

As an intern with URS Corporation, I participated in several remediation and wastewater treatment projects during the year 2004. A groundwater remediation project was selected to present in this record of study for my Doctor of Engineering degree not only because I spent more time on it than any other project, but also because it represents the broadness and depth of a typical URS remediation project. In this report, findings from previous environmental investigations were summarized and used for computer modeling and remediation strategy evaluation. Computer models were used to simulate site conditions and assist in remedy design for the site. Current pump-and-treat systems were evaluated by the model under various scenarios. Recommendations were made for the pump-and-treat system to control the contaminant plume. Various remediation technologies were evaluated and compared for their applicability at the site. A combination of on-site remediation and downgradient plume control was chosen as the site remediation strategy. Treatability studies and additional modeling work are needed for the remediation system design and optimization.

Motion control systems are usually designed to track trajectories and/or regulate about a desired point. Most of the other objectives, like minimizing the tracking time or minimizing the energy expended, are secondary which quantify the above described objectives. The control problem in hard disk drives is tracking and seeking the desired tracks. Recent increase in the storage capacity demands higher accuracy of the read/write head. Dual stage actuators as compared to conventional single actuator increases the accuracy of the read/write head in hard disk drives. A scaled up version of the dual stage actuator is considered as the test bed for this thesis. Friction is present in all electromechanical systems. This thesis deals with modelling of the dual stage actuator test bed. A linear model predicts the behavior of the fine stage. Friction is significant in the coarse stage. Considerable time has been spent to model the coarse stage as a friction based model. Initially, static friction models were considered to model the friction. Dynamic models, which describe friction better when crossing zero velocity were considered. By analyzing several experimental data it was concluded that the friction was dependent on position and velocity as compared to conventional friction models which are dependent on the direction of motion. Static and Coulomb friction were modelled as functions of velocity and position. This model was able to predict the behavior of the coarse stage satisfactorily for various initial conditions. A friction compensation scheme based on the modelled friction is used to linearize the system based on feedback linearization techniques.

Crystals are natural phenomena that exhibit high degrees of order, symmetry, and recursion. They naturally form interesting and inspiring geometric shapes. This thesis provides geometric modeling techniques for creating shapes with crystallike geometry. The tiered extrusion method, along with a face grouping technique, simplifies the creation of complex, intricate faceted shapes. In combination with remeshing, these methods provide the capability to generate geometric shapes exhibiting planar faces, symmetry, and fractal geometry. The techniques have also been implemented in software, as a proof of concept. They are used in an interactive geometric modeling system, in which users can use these techniques to create crystal-like shapes. The crystal-like modeling operations are shown to successfully create beautiful geometric shapes. The methods improve upon traditional modeling capabilities, providing an easier way to create crystal-like geometric shapes.

Experimental and analytical studies have been carried out to better understand production mechanisms of heavy oil under steam injection with propane and petroleum distillate as steam additives. The studies have been conducted for heavy oil from San Ardo field (12oAPI, 2800 cp at 53.3oC), under current reservoir conditions. The experiments consist of injecting pure steam, steam-propane, and steampetroleum distillate into a vertical cell containing a mixture of sand, water and San Ardo oil. The injection cell (68.58 cm long with an ID of 7.376 cm) is placed inside a vacuum jacket, set at the reservoir temperature of 53.3oC. Superheated steam at 230oC is injected at 5.5 ml/min (cold-water equivalent) simultaneously with propane or a petroleum distillate slug. The cell outlet pressure is maintained at 260 psig. Six runs were performed, two runs using pure steam, two steam-propane runs using 5:100 propane:steam mass ratio, and two steam-petroleum distillate runs using 5:100 petroleum distillate:steam mass ratio. We develop a simplified analytical model that describes steam front advancement and oil production for the 1D displacement experiments. The model incorporates heat and material balance, fillup time and Darcy’s law pertaining to the injection cell. The analytical model results are compared against the experimental data to verify the validity of the model. The main results of the study are as follows. First, experimental results indicate that compared to pure steam injection, oil production was accelerated by 30% for 5:100 propane:steam injection and 38% for 5:100 petroleum distillate:steam injection respectively. Second, steam injectivity with steam-propane and steam-petroleum distillate increases to 1.4 and 1.9 times respectively, compared with pure steam injection. Third, steam front advancement and oil production data are in good agreement with results based on the new analytical model. The analytical model indicates that the oil production acceleration observed is due to oil viscosity reduction resulting from the addition of propane and petroleum distillate to the steam. Oil viscosity at the initial temperature with pure steam injection is 2281 cp, which is reduced to 261 cp with steam-propane injection and 227 cp with steam-petroleum distillate injection.

Due to its increasing popularity, hierarchical linear modeling (HLM) has been used along with structural equation modeling (SEM) to analyze data with nested structure. In spite of the extensive research on commonly encountered problems such as violation of normality and missing data treatment within the framework of SEM, these areas have been much less explored in HLM. The present study compared HLM and multilevel SEM through a Monte Carlo study from the perspectives of the influence of nonnormality and performance of multiple imputation based on the expectationmaximization (EM) algorithm under various combinations of sample sizes at two levels. The statistical power, parameter estimates, standard errors, and estimation bias for the main effects and cross-level interaction in a two- level model were compared across the four design factors: analysis method, normality condition, missing data proportion, and sample size. HLM and multilevel SEM appeared to have similar power detecting the main effect, while HLM had better power for the cross- level interaction. Neither seemed to be sensitive to violation of the normality assumption. A higher proportion of missing data resulted in larger standard errors and estimation bias. Sample sizes at both the individual and cluster levels played a role in the statistical power for parameter estimates. The two-way interactions for the four factors were generally nonzero. Overall, both HLM and multilevel SEM were quite robust to violation of normality. SEM appears more useful in more complex path models while HLM is superior in detecting main effects. Multiple imputation based on the EM algorithm performed well in producing stable parameter estimates for up to 30% missing data. Sample size design should take into account the level at which the research is most focused.

A thermodynamics-based constitutive model is derived which predicts the nonlinear strain and magnetization response that magnetic shape memory alloys (MSMAs) exhibit when subjected to mechanical and magnetic loads. The model development is conducted on the basis of an extended thermo-magneto-mechanical framework. A novel free energy function for MSMAs is proposed, from which the constitutive equations are derived in a thermodynamically-consistent manner. The nonlinear and hysteretic nature of the macroscopic material behavior is captured through the evolution of internal state variables which are motivated by the crystallographic and magnetic microstructures of MSMAs. Model predictions are presented for different relevant loading cases and analyzed in detail. Finally, magnetostatic boundary value problems for MSMAs are considered and numerically solved using the finite element method. For these computations the developed constitutive model provides the nonlinear magnetic properties of the MSMA. The knowledge of the magnetic field distribution in the computational domain as a function of the applied field, which results from this magnetostatic analysis, is useful for the proper interpretation of experimental results as well as the design of experiments and applications.

This research evaluates and improves capabilities incorporated in the Water Rights Analysis Package (WRAP) modeling system for tracking salt loads, particularly for applications dealing with natural salt pollution problems that are prevalent in several major river basins in Texas and neighboring states. WRAP is the river/reservoir system simulation model incorporated in the Water Availability Modeling (WAM) System applied by agencies and consulting firms in Texas in planning and water right regulatory activities. A salinity simulation component of WRAP called WRAP-SALT was developed recently at Texas A&M University. WRAP-SALT was based on the premise of complete mixing within the monthly computational time step. However, salt concentrations actually have time variation throughout a reservoir. This thesis research investigates more realistic salinity routing methods. Historical gauged data provide a basis for calibration of routing parameters. The timing of the inflow load to determine outflow concentration is calculated by lag parameters with the monthly time steps. Complete mixing occurs during the lag months. Two options are incorporated into WRAP-SALT for setting the lag parameter. With the first option, the model-user sets a constant that is applied during every month of the simulation. This option requires calibration studies to determine the lag. With the alternative option, a variable lag is computed within the model in each month based on the concept of retention time, which is a representation of the time required for a monthly volume of water and its salt load to flow through a reservoir. When the lag is activated, the accuracy between observed and computed mean monthly salinity concentrations through the reservoir is generally improved. The basin-wide simulation was performed for the Brazos River Basin for conditions with and without salt control dams proposed by the Corps of Engineers. The proposed salt control impoundments improve water quality throughout the basin.

Current understanding of small-scale physical processes, such as mixing, in tropical water bodies is lacking and observations are scarce at best. This study sheds more light on these processes through a combined observational-modeling approach. For this purpose, observations were made in Valle de Bravo's freshwater reservoir, about 100 km west of Mexico City and at an elevation of 1830 m above sea surface. Turbulence kinetic energy dissipation (TKED) rates were estimated by fitting a theoretical Batchelor spectrum to the temperature gradient spectrum. From similarity scaling of dissipation rates, it was found that in the surface layer, winds were the main driving force in generating turbulence during the day, while convective forces were responsible during the night. Bottom boundary layer (BBL) mixing was mainly driven by internal wave (first vertical and first horizontal mode) breaking at the bottom. Lognormality of turbulence dissipation rates is also discussed for surface, intermediate and bottom boundary layers. For our modeling efforts, a state-of-the-art one-dimensional turbulence model was used and forced with the observed surface meteorology to obtain simulated temperature and dissipation rate profiles. The model results were found to be in good agreement with the observations, though minor differences in dissipation rates were found in the vicinity of the thermocline and the BBL.

Accurate constitutive modeling of polymeric fibers presents a difficult and distinct challenge. While significant progress has been made in constructing models applicable for small strains and limited strain-rate and temperature regimes, much less has been made for more general conditions. This is due in part to the complexity of polymeric behavior. In this work, experimental results of uniaxial extension tests on Polyethylene terephthalate (PET) were obtained from Dr. S.Bechtel, were analyzed, and were formulated into a new model which explains the behavior of PET at different temperatures and strains. The biggest impediment in the determining the behavior of polymeric was the difference in the behavior of PET above and below its glass transition temperature. Consequently, well established (from microstructural considerations) constitutive models and concepts for rubber elasticity and plasticity were not directly transferable to modeling PET fibers. In the model, the PET fibers were assumed to be constituted by amorphous and crystallization segments and the response of the material during stretching was the combined response of simultaneous stretching of the amorphous and the crystalline segments. The strengthening mechanism is due to orientation of the amorphous segments during stretching. The model involves a friction element which took account of the plastic behavior below the glass transition temperature. The model was used to predict the response of PET at different temperatures and the results from the model showed good agreement with the experimental data. The results from the research will be further used to increase the overall efficiency of the fiber drawing process.