The TG-43 dosimetry parameters of the AdvantageTM 125I model IAI-125A brachytherapy seed were studied. An investigation using modern MCNP radiation transport code with updated cross-section libraries was performed. Twelve different simulation conditions were studied for a single seed by varying the coating thickness, mass density, photon energy spectrum and cross-section library. The dose rate was found to be 6.3% lower at 1 cm in comparison to published results. New TG-43 dosimetry parameters are proposed. The dose distribution for a brachytherapy eye plaque, model EP917, was investigated, including the effects of collimation from high-Z slots. Dose distributions for 26 slot designs were determined using Monte Carlo methods and compared between the published literature, a clinical treatment planning system, and physical measurements. The dosimetric effect of the composition and mass density of the gold backing was shown to be less than 3%. Slot depth, width, and length changed the central axis (CAX) dose distributions by < 1% per 0.1 mm in design variation. Seed shifts in the slot towards the eye and shifts of the 125I-laden silver rod within the seed had the greatest impact on the CAX dose distribution, changing it by 14%, 9%, 4.3%, and 2.7% at 1, 2, 5, and 10 mm, respectively, from the inner scleral surface. The measured, full plaque slot geometry delivered 2.4% ± 1.1% higher dose along the plaque’s CAX than the geometry provided by the manufacturer and 2.2%±2.3% higher than Plaque SimulatorTM (PS) treatment planning software (version 5.7.6). The D10 for the simulated tumor, inner sclera, and outer sclera for the measured slot plaque to manufacturer provided slot design was 9%, 10%, and 19% higher, respectively. In comparison to the measured plaque design, a theoretical plaque having narrow and deep slots delivered 30%, 37%, and 62% lower D10 doses to the tumor, inner sclera, and outer sclera, respectively. CAX doses at –1, 0, 1, and 2 mm were also lower by a factor of 2.6, 1.72, 1.50, and 1.39, respectively. The study identified substantial sensitivity of the EP917 plaque dose distributions to slot design.

Doctor of Philosophy(PhD) / This thesis describes the exploration and the development of computational means to investigate the behaviour of design objects before they are available for investigation in the physical world. The motivation is to inform the design process about the design object’s performance in order to achieve better – more performance-oriented – design outcomes in the sense of energy efficiency and comfort performance than can be achieved by conventional design techniques. The research is structured into five successive parts. - Concept Development – A review of the objective domains comfort assessment and energy efficiency assessment is conducted and the design process, human design activity and the application of simulation in the architectural domain is discussed in order to identify requirements for the development of computational means for design analysis. Requirements regarding model content, model features and model integration are developed. The main requirements are that a highly integrated, three-dimensional and dynamic representation of physical processes is needed and that a universal and integrated representation is required. - Concept Formulation – Based on the identified requirements, the concept for a model is formulated. In order to achieve a universal and integrated representation of physical processes the concept uses the approach of a constructive language. Space is represented with autonomous spatial elements, called congeneric cells. Interaction between the cells is represented by near- and remote-conjunctions. Physical and geometric self-contained formulations of the model reduce the model input requirements, so that geometric information and simple property specification (material, activity) is sufficient to describe the design object in the model. - Model Development – The concept is formulated in mathematical physical terms based on well known physical laws and building physical models (first-principle approach). Heat and moisture conduction, diffusion of various components and a flow model is formulated as near-conjunction processes. Heat radiation, light and sound are modelled with a radiosity approach as remote-conjunctions. The simulation algorithm, which governs the interaction between the cells in order to represent the behaviour of space, is explained. - Computational Implementation – The concept and the model is tested by implementation of a prototype using C++ and OpenGL on a conventional Pentium 4 notebook. The prototype consists of three parts: user-interface, model translator and simulation engine. The user interface functions as model-input and result-output device. The implementation of the concept and of further model parts is described in detail. - Assessment and Testing – The developed concept and the model, as implemented in the prototype, are tested and assessed against the initially developed requirements. The physical model is assessed in regard to plausibility and accuracy of the representation of the physical phenomena. At the end of the thesis the project is summarized, the achievements of the project’s objectives are discussed critically and issues for future research are suggested. Possible applications of the developed model are listed, and the contributions to the application of computational simulation in the architectural domain, developed in this research, are named. At the current stage the required processing time and high memory requirements prevent implementation of a design assessment system, following the suggested concept, at a useful scale. Also the developed physical models require further refinement and testing. Although the general feasibility of the concept and the model was successfully demonstrated, its implementation in a fully applicable design assessment system based on the universal and integrated representation of physical processes was not achieved at this stage. While detailed description and analysis is given in the body of the thesis, detailed formulations of the work and the developed model are given in the appendix. The body and the appendix together provide a complete picture of the research presented.

Les dunes de sable sont des formes très présentes en milieu marin. Comprendre l'évolution des dunes est un enjeu important pour prévoir les caractéristiques de l'écoulement, les flux sédimentaires, et les variations de la bathymétrie. Les dunes sous-marines représentent un risque pour les activités humaines, a fortiori avec l'intérêt croissant pour les énergies marines renouvelables, pour la navigation, ou l'industrie offshore. Bien que la connaissance des dunes représente un intérêt scientifique et opérationnel de premier ordre, les processus physiques conduisant leur évolution sont toujours mal compris. En outre, la prévision de leurs caractéristiques géométriques et de leur dynamique basée essentiellement sur des formules empiriques reste peu précise. Dans ce travail de thèse, un modèle numérique est d'abord utilisée pour modéliser les dunes soumises à un écoulement stationnaire. Les simulations reproduisent l'évolution d'un fond faiblement perturbé jusqu'à un champ de dunes en équilibre avec l'écoulement et apportent des connaissances approfondies sur les processus physiques mis en jeu. Ensuite, les résultats d'un ensemble de campagnes de mesures réalisées dans la passe sud du bassin d'Arcachon permettent d'étudier la dynamique des dunes tidales in situ et relier leur asymétrie et leur migration aux résiduels de transport sédimentaire. Enfin, l'application du modèle numérique avec les conditions de forçages extraites des campagnes de mesures permet de reproduire la dynamique des dunes tidales ainsi que la génération de rides d'un ordre de grandeur comparable aux rides surimposées observées in situ. Ces résultats ouvrent des perspectives intéressantes en vue du développement d'un modèle opérationnel de prévision de la dynamique des dunes tidales. / Sand dunes are ubiquitous beforms in nature within subaqueous environments. Understanding dune evolution is important issue to accurately predict the ow circulation, sediment uxes and bathymetric variations in sandy subaqueous environments. Sand dunes may pose a significant risk for offshore activities in coastal environments, especially with the growing development of renewable marine energy, for navigation or the offshore industry. Although sand dunes represent a great scientific and operational interest, their evolution is still poorly understood due to their complex behavior. The aim of the thesis work was to study the physical processes driving the evolution of subaqueous sand dunes and to understand their in situ dynamics within tidal environments. First, a numerical model was employed to simulate sand dunes under stationary current conditions. The simulations reproduced the morphodynamic evolution of a slightly perturbed bed until a steady sand dune field in equilibrium with the ow. The results offered a deeper understanding of the physical processes driving the bed evolution to equilibrium. Second, an array of in situ measurements was carried out into the Arcachon inlet, in southwest France, to study the dynamics of tidal sand dunes. For the first time their asymmetry and migration rates were linked to the sediment uxes residuals on a spring-neap tidal cycle. Finally, the numerical model was adapted both to simulate the dynamics of tidal sand dunes, and generate bedforms of the same order of magnitude as the in situ dune-superimposed ripples starting from a at bed. These results open promising perspectives for the development of a numerical tool capable of predicting the behavior of sand dunes within tidal environments.

This final thesis deals with the software supporting the education through the presenting the physical process. Specifically, it deals with the kinematics on the level of the basic school and secondary school. Next there are described the basics of pedagogy, didactics, simulation and modelling referring to the suggested programme. There is also a suggested system and its graphic user interface based on the gained findings which is later implemented.

<p>Ultra/Luminous infrared galaxies (U/LIRGs) are some of the most amazing systems in the local universe exhibiting extreme star formation triggered by mergers. Since molecular gas is the fuel for star formation, studying the warm, dense gas associated with star formation is important in understanding the processes and timescales controlling star formation in mergers. We have used high resolution (∼2.3”) observations of the local LIRG Arp 299 to map out the physical properties of the molecular gas. The molecular lines 12CO J=3-2, 12CO J=2-1 and 13CO J=2-1 were observed with the Submillimeter Array and the short spacings of the 12CO J=3-2 and J=2-1 observations have been recovered using James Clerk Maxwell Telescope single dish observations. We use the radiative transfer code RADEX to measure the physical properties such as density and temperature of the different regions in this system. The RADEX solutions of the two galaxy nuclei, IC 694 and NGC 3690, show two gas components: a warm moderately dense gas with T_kin ∼ 30-500 K (up to 1000K for NGC3690) and n(H2)~0.3-3×10^3 cm^−3 and a cold dense gas with T_kin~10-30 K and n(H2) > 3 × 10^3 cm^−3. The overlap region is shown to have a well-constrained solution with T_kin ∼ 10-30 K and n(H2)~3-30 × 10^3 cm^−3. We estimate the gas masses and star formation rates of each region in order to derive molecular gas depletion times. The depletion time of each region is found to be about 2 orders of magnitude lower than that of normal spiral galaxies. This can be probably explained by a higher fraction of dense gas in Arp 299 than in normal disk galaxies.</p> / Master of Science (MSc)

<p>In this thesis we present a procedure by which synthetic photometry of a hydrodynamic model of star or star-like object can be calculated in a regime where the photosphere is not radially resolved. In order to properly model the unresolved photosphere, we present a method where pressure and density are integrated outward from the outermost resolved radius of the star and then interpolated in temperature-surface gravity space between a set of MARCS \citep{Gustafsson2008a} stellar atmosphere models. These interpolations are accurate to within 10\% of expected temperature values and are determined by minimizing the difference between the integrated pressure, density and surface gravity and that of the atmosphere model. Using the Monte Carlo Radiative Transfer code \texttt{radmc3d}\citep{Dullemond2012}, we produce blackbody spectra of stars and photometric light curves of equal and unequal mass detached binaries and a contact binary. Stellar blackbody spectra are accurate to better than 1\%. Resultant light curves have less scatter than existing methods, such as \texttt{shellspec}\citep{Budaj2004} and show the expected morphology. Our method allows for imaging directly from hydrodynamic simulations, with minimal user set-up. This procedure is designed with the intent of producing simulated photometry of stellar merger models.</p> / Master of Science (MSc)

Organic photovoltaic (OPV) cells are advanced, newly emerging technologies that are lightweight, mechanically flexible devices with highthroughput processes from low cost material in a variety of colors. Rathnayake et al. of Western Kentucky University have developed a nanostructure-based OPV cell. Presented in this thesis is a model and simulation of a generalized PV powered system that can predict the performance of solar arrays in various environmental conditions. The simulation has been carried out in Matlab/Simulink, and upon entering the cell’s parameters, it provides key electrical characteristics such as the cell’s I-V curve and efficiency information. The total system that is simulated consists of three elements: a universal two-cell solar array that can account for partial shading and manufacturing variation, a current-controlled power converter, and an energy storage device with charging and discharging capabilities.

Active Galactic Nuclei (AGNs) are the most mystic objects in the universe. They are usually very far away from our Galaxy, which means that they are ancient objects. They are also luminous and have unique features in their spectra. Studying AGNs helps understanding the early universe and the evolution of galaxies. This Dissertation aims to research the structure of AGNs and the cooling function in the AGNs environment. I first investigate what optical/ultraviolet spectroscopic features would be produced by Broad-line Region (BLR) clouds crossing our line of sight to the accretion disk, the source of the optical/UV continuum. This research, prompted by recent X-ray observations, suggests that single cloud has little effect on the optical/UV spectrum. However, an ensemble of clouds produces a strong distinctive feature between the Lyman limit and Lyα. The extent of these features indicates the line-of-sight covering factor of clouds and may explain the ubiquitous AGN spectral break around 1100Å. I next study, considering the physical parameters of AGNs, how the gas cooling function changes at high temperature (T > 104 K) over a wide range of density (nH < 1012 cm−3) and metallicity (Z < 30Z⊙). I find that both density and metallicity change the ionization status of the gas. I provide numerical cooling functions by describing the total cooling as a sum of four parts: that due to H&He, the heavy elements, electron-electron bremsstrahlung, and grains. Finally, I also provide a function giving the electron fraction, which can be used to convert the cooling function into a cooling rate. Last, I extend the cooling-function study to the seldom-explored low-temperature range (T < 104 K). For primordial gas, gas lacking elements heavier than B, I find that radiative attachment and Compton recoil are important cooling processes when the gas kinetic temperature is lower than the temperature of the cosmic microwave background. I also find that collisional de-excitation of HD and H2 is not important above 1000K unlike claims of previous studies. For the dust-free solar case, we identify water as the dominant coolant in high density-environments. We also analyze the parameter ranges where metal, metal molecules, or all molecules, dominate the total cooling. We provide the density, above which the metal or metal molecules become the dominant coolants, as a function of temperature and metallicity. For the ISM case, with dust and depleted abundances, we find that dust does not directly cool the gas. Rather, dust modifies he cooling by affecting the chemistral balance. Similar to the high-temperature case, I also provide numerical cooling data.

<p dir="ltr">Understanding the nonlinear rheological properties of food is essential for improving processes involving large-amplitude deformation such as pumping, extrusion, and consumer consumption. The development of mathematical analyses for analyzing these nonlinear responses has witnessed a notable upswing in the past decades. A novel mathematical analysis called "Sequence of Physical Processes" (SPP) was developed by Rogers et al. in 2011. Ever since, SPP has shown tremendous potential in characterizing and predicting the nonlinear rheological behavior of soft materials and polymers, yet more investigations are required to validate the efficacy of the SPP approach in the realm of food materials. Therefore, this thesis focuses on applying SPP method onto a range of food materials. Most importantly, we compared the analysis with the results obtained from the well-established Ewoldt-McKinley method of coupling “Fourier Transform with Chebyshev Decomposition” (FTC). As a result, it is found that SPP can provide a detailed picture of the material’s deformation history within an oscillation cycle. The time-dependent nature of SPP data allows a more accurate capture of important rheological transitions, which leads to a higher correlation with compositional and microstructural changes in comparison to the FTC method. Recognizing the potential of SPP analysis in studying food materials, this research emphasizes the necessity for further exploration across a diverse array of food types. The thesis contributes valuable insights to the evolving landscape of nonlinear rheological understanding, with the potential to improving methodologies in food processing.</p>

Climate modeling and tropical cyclone forecasting are two significant is- sues that are continuously being improved upon for more accurate weather forecasting and preparedness. In this thesis, we have studied three climate models and formulated a new model with a view to determine the outgoing longwave radiation (OLR) budget at the top of the atmosphere (TOA) as ob- served by the National Oceanic and Atmospheric Administration’s (NOAA) satellite based Advanced Very High Resolution Radiometer (AVHRR). In 2006, Karnauskas proposed the African meridional OLR as an Atlantic hur- ricane predictor, the relation was further proven in 2016 by Karnauskas and Li. Here we have considered a similar study for all other tropical cyclone basins.