The classic treatment of diffusion by Einstein and by Chandrasekhar assumed conservative boundary conditions; mobile species were neither created nor destroyed on the sample surface. It is normal to assume that vacancies and host interstitials are created and annihilated on incoherent interfaces or free surfaces; i.e., these are assumed to be perfect sources and sinks. Impurities may also be gained or lost at an interface. It seems that no analytic solutions are available for diffusion with annihilating boundary conditions. In this thesis, the author presents massive data obtained by giga event Monte Carlo simulation of the macro-consequence of atomic level assumptions using VIDSIM, a computer simulation program for the simulation of point defect diffusion and interaction in diamond and zinc-blend structure crystals. The author contrasts these results with the error function complement (ERFC) forms obtained with conservative boundary conditions. An empirical formula is proposed with the help of DF_FIT, a fitting program developed by the author to conduct the statistical analysis and fitting the experimental data to certain functions typical for diffusion processes. Investigations on the redistributions of impurities in an atomiclayer- doped (ALD) host materials such as Si is reported. Asymmetric diffusion of ALD impurities is observed and demonstrated. / Graduation date: 1993

Dose calculation methodology was developed for irradiation treatment of complex-shaped foods. To obtain satisfactory electron beam irradiation of food products, a strict process control is required to ensure that the dose delivered to all parts of the treated product falls within some specified range. The Monte Carlo electron transport simulation and computer tomography (CT) scan technology were used to predict the dose distribution in complex shaped foods, an apple phantom composed of paraffin wax, chloroform, and methyl yellow, and a chicken carcass. The Monte Carlo code used was successfully tested against the experimental data, resulting in less than 5% discrepancy between the simulated and measured data. For 1.35 MeV electron beam simulation of apple phantom, tilting and axial rotation ensures dose distribution of the entire surface of the phantom, even reaching the critical regions of the apple stem and calyx ends. For 1 and 5 MeV X-ray simulations, both depth-dose curves show exponential attenuation after a build-up region. The depth to peak for the former is shorter than that of the latter. For 1.35 MeV electron beam simulation of a chicken carcass, dose adsorption occurred up to 5-7 mm deep, resulting in surface irradiation of the carcass. For 10 MeV electron beam simulation, the doses within the carcass reached a peak of 1.2 times the incident dose with increasing depth. Two-sided X-ray (5 MeV) irradiation significantly improved the dose uniformity ratio, from 2.5 to 1.8. A web-based integrated system was developed for data manipulation and management for irradiation treatment of foods. Based on CT scan, three dimensional geometry modeling was used to provide input data to the general Monte Carlo N-Particle (MCNP) code. A web-based interface provided the on-line capability to formulate input data for MCNP and to visualize output data generated by MCNP. The integrated Matlab and Matlab Web Server programs automatically functions through the steps and procedures for data input and output during simulation. In addition, a database having D10 values (decimal reduction value), food nutrition composition, and qualities was integrated into the dose planning system to support food irradiation treatment.

Thesis (M.A. in Defense Analysis Special Operations/Low Intensity Conflict)--Naval Postgraduate School, June 2004. / Thesis advisor(s): Gordon McCormick, Bard Mansager. Includes bibliographical references (p. 119-120). Also available online.

Thesis (M.S. in Mechanical Engineering)--Naval Postgraduate School, March 2004. / Thesis advisor(s): Young S. Shin. Includes bibliographical references (p. 143-145). Also available online.

Thesis (Ph.D.) -- University of Texas at Arlington, 2007.

Thesis (M.S. in Modeling, Virtual Environments, and Simulation (MOVES))--Naval Postgraduate School, June 2003. / Thesis advisor(s): Richard Harkins, John Hiles. Includes bibliographical references (p. 161-163). Also available online.

Thesis--M. Phil., University of Hong Kong, 1982.

Thesis (M.S. in Modeling, Virtual Environments and Simulation)--Naval Postgraduate School, March 2003. / Thesis advisor(s): Rudolph Darken, Barry Peterson. Includes bibliographical references (p. 61). Also available online.

The purpose of this dissertation was to develop the C⁺⁺ program Emergency Dose to calculate transport of radionuclides through indoor spaces using intermediate fidelity physics that provides improved spatial heterogeneity over well-mixed models such as MELCOR[trademark] and much lower computation times than CFD codes such as FLUENT[trademark]. Modified potential flow theory, which is an original formulation of potential flow theory with additions of turbulent jet and natural convection approximations, calculates spatially heterogeneous velocity fields that well-mixed models cannot predict. Other original contributions of MPFT are: 1) generation of high fidelity boundary conditions relative to well-mixed-CFD coupling methods (conflation), 2) broadening of potential flow applications to arbitrary indoor spaces previously restricted to specific applications such as exhaust hood studies, and 3) great reduction of computation time relative to CFD codes without total loss of heterogeneity. Additionally, the Lagrangian transport module, which is discussed in Sections 1.3 and 2.4, showcases an ensemble-based formulation thought to be original to interior studies. Velocity and concentration transport benchmarks against analogous formulations in COMSOL[trademark] produced favorable results with discrepancies resulting from the tetrahedral meshing used in COMSOL[trademark] outperforming the Cartesian method used by Emergency Dose. A performance comparison of the concentration transport modules against MELCOR[trademark] showed that Emergency Dose held advantages over the well-mixed model especially in scenarios with many interior partitions and varied source positions. A performance comparison of velocity module against FLUENT[trademark] showed that viscous drag provided the largest error between Emergency Dose and CFD velocity calculations, but that Emergency Dose’s turbulent jets well approximated the corresponding CFD jets. Overall, Emergency Dose was found to provide a viable intermediate solution method for concentration transport with relatively low computation times. / text

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