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Development Of A Slab-Based Monte Carlo Proton Dose Algorithm With A Robust Material-Dependent Nuclear Halo Model, John Wesley Chapman Jr
Development Of A Slab-Based Monte Carlo Proton Dose Algorithm With A Robust Material-Dependent Nuclear Halo Model, John Wesley Chapman Jr
LSU Doctoral Dissertations
Pencil beam algorithms (PBAs) are often utilized for dose calculation in proton therapy treatment planning because they are fast and accurate under most conditions. However, as discussed in Chapman et al (2017), the accuracy of a PBA can be limited under certain conditions because of two major assumptions: (1) the central-axis semi-infinite slab approximation; and, (2) the lack of material dependence in the nuclear halo model. To address these limitations, we transported individual protons using a class II condensed history Monte Carlo and added a novel energy loss method that scaled the nuclear halo equation in water to arbitrary geometry. …
Innovative Monte Carlo Methods For Sampling Molecular Conformations, Aliasghar Sepehri
Innovative Monte Carlo Methods For Sampling Molecular Conformations, Aliasghar Sepehri
LSU Doctoral Dissertations
Sampling molecular conformations is an important step in evaluating physical, mechanical, hydrodynamic, and optical properties of flexible molecules especially polymers. One powerful method for this purpose is configurational-bias Monte Carlo in which one random segment of a molecule is chosen, all segments toward one random end are removed, and then regrown segment by segment to produce a new geometry to be accepted/rejected according to probability laws. The advantage of this method is the ability to generate acceptable conformations that are favorable for intra- and intermolecular energies to save computational costs. However, when there are several interdependent energetic terms, trial generation …
Advanced Monte Carlo Methods For The Study Of Nucleation, Troy David Loeffler
Advanced Monte Carlo Methods For The Study Of Nucleation, Troy David Loeffler
LSU Doctoral Dissertations
The process of nucleation is an essential part of understanding and controlling phase changes in a wide array of systems. In the past theories such as Classical Nucleation Theory have been used as a tool to aid experimentalist in the study of phase mechanisms. However, recent studies have shown in detail that theories such as this are not reliable, given that it can mispredict nucleation rates by several orders of magnitude. As a result newer methodologies must be developed into order to improve upon these deficiencies. In this study we use atomistic simulations to examine the non-ideal deviations from classical …
A Monte Carlo Approach To Studying The Hydrogen Storage Capabilities Of Potassium Magnesium Hydride (Kmgh3), Brandon L. Borill
A Monte Carlo Approach To Studying The Hydrogen Storage Capabilities Of Potassium Magnesium Hydride (Kmgh3), Brandon L. Borill
LSU Doctoral Dissertations
Grand Canonical Monte Carlo (GCMC) simulations and the weighted histogram analysis method (WHAM) were employed at selected temperatures and pressures in the study of the hydrogen storage capabilities of KMgH3. A specially tailored addition/removal algorithm was employed to add hydrogen directly at the lattice sites. Agreement between experimental results was obtained through GCMC simulations. WHAM type studies were employed to obtain probability distributions for the purpose of learning the probability of finding hydrogen atoms at specific temperatures and hydrogen pressures. The radial distribution function was employed to study the changes in the structure of KMgH3 for the selected model as …
Modeling And Multiresolution Characterization Of Micro/Nano Surface For Novel Tailored Nanostructures, Rajib Mukherjee
Modeling And Multiresolution Characterization Of Micro/Nano Surface For Novel Tailored Nanostructures, Rajib Mukherjee
LSU Doctoral Dissertations
Nanofabrication is state of the art technology. Various chemical, mechanical, biochemical and semiconductor products have characteristics controlled by the nanostructures of the surface and interphase. Surface microscopic imaging is generally used to capture different surface features. By properly analyzing the surface image, valuable information regarding manufacturing process and product performance can be extracted. While microscopy measurements can offer very accurate qualitative information about surface features, for many applications, it is critical to obtain a quantitative description of the surface morphology. Various statistical features can be used to characterize the surface in quantitative way. Such an analysis can be done by …
Computer Simulation Of Ion-Induced Nucleation In The Presence Of Single Ions And Ion Pairs, Samuel Keasler
Computer Simulation Of Ion-Induced Nucleation In The Presence Of Single Ions And Ion Pairs, Samuel Keasler
LSU Doctoral Dissertations
Atmospheric aerosol particles play an important role in climate and human health. Despite their importance, the mechanisms of their formation are still poorly understood. Ion-induced nucleation may play a role in the process, but details are lacking about how the nucleation rate depends on the size, charge, and number of ions in the cluster. In order to better understand the role that ions might play in new particle formation, we have performed a series of AVUS-HR simulations of the water nucleation in the presence of both single ions and ion pairs. These simulations have shown that the location of the …
Atom-Based Computer Simulation Studies Of Gas-To-Liquid Nucleation In Atmospherically Relevant Systems: Clarifying Discrepancies And Elucidating Mechanisms, Ricky Bendanillo Nellas
Atom-Based Computer Simulation Studies Of Gas-To-Liquid Nucleation In Atmospherically Relevant Systems: Clarifying Discrepancies And Elucidating Mechanisms, Ricky Bendanillo Nellas
LSU Doctoral Dissertations
For over a century, nucleation for all systems was thought simplistically to be a process that advances through the formation of critical clusters with a well-defined composition. Our results show intriguing nucleation mechanisms that challenge the aforementioned notion. We employed the simple TraPPE-UA (transferable potential for phase equilibria – united atom) force field and the AVUS-HR approach (a combination of aggregation-volume-bias Monte Carlo, umbrella sampling, and histogram reweighting), to investigate the homogeneous vapor-to-liquid nucleation of various nucleating systems. We found out that these systems could nucleate through a variety of unique non-ideal mechanisms. Alongside existing experimental investigations, this dissertation presents …