Biofilms are communities of sessile microorganisms attached to a surface and imbeddedin a matrix of extracellular polysaccharide substances. These communities can be foundin diverse aquatic environments, such as in industrial pipes and in humans. By formingmicrocolony structures, which are highly resistant to adverse physical conditions as wellas antimicrobial agents, biofilms are very problematic when associated with e.g.persistent infections. In order to find new ways of controlling biofilm growth, theprocesses involved in biofilm development must be investigated further. The maininterest of this study is the occurrence of void formation inside biofilms. Thisphenomenon has been observed in several studies and has been correlated to cell deathinside the microcolonies. The occurrence of cell death has recently been associated withthe presence of nitric oxide in the biofilm. In this study, the implications of nitric oxideaccumulation on biofilm development were investigated using an individual-basedmodel. Specifically, the role of nitric oxide in void formation was considered. A largenumber of simulations were run using different parameter settings in order to determine ifnitric oxide could account for the occurrence of void formation observed experimentally.The general predictions made by the model system showed agreement to someexperimental data, but not to others. Sloughing, the detachment of chunks of cells fromthe biofilm, was observed in the majority of simulations. In some cases, the model alsopredicted the presence of live cells inside the voids, which has been observedexperimentally.

A well-represented description of convection in weather and climate models is essential since convective clouds strongly influence the climate system. Convective processes interact with radiation, redistribute sensible and latent heat and momentum, and impact hydrological processes through precipitation. Depending on the models’ horizontal resolution, the representation of convection may look very different. However, the convective scales not resolved by the model are traditionally parameterized by an ensemble of non-interacting convective plumes within some area of uniform forcing, representing the “large scale”. A bulk representation of the mass-flux associated with the individual plumes in the defined area provide the statistical effect of moist convection on the atmosphere. Studying the characteristics of the ECMWF ensemble prediction system it is found that the control forecast of the ensemble system is not variable enough in order to yield a sufficient spread using an initial perturbation technique alone. Such insufficient variability may be addressed in the parameterizations of, for instance, cumulus convection where the sub-grid variability in space and time is traditionally neglected. Furthermore, horizontal transport due to gravity waves can act to organize deep convection into larger scale structures which can contribute to an upscale energy cascade. However, horizontal advection and numerical diffusion are the only ways through which adjacent model grid-boxes interact in the models. The impact of flow dependent horizontal diffusion on resolved deep convection is studied, and the organization of convective clusters is found very sensitive to the method of imposing horizontal diffusion. However, using numerical diffusion in order to represent lateral effects is undesirable. To address the above issues, a scheme using cellular automata in order to introduce lateral communication, memory and a stochastic representation of the statistical effects of cumulus convection is implemented in two numerical weather models. The behaviour of the scheme is studied in cases of organized convective squall-lines, and initial model runs show promising improvements. / <p>At the time of the doctoral defense, the following paper was unpublished and had a status as follows: Paper 4: Submitted. </p>

Das Auftreten von Starkregen führt zu steigendem Wasserstand und Wasservolumen in den Fließgewässern und zu Überschwemmungen der Flussauen. Tritt Hochwasser im menschlichen Siedlungsraum auf, entstehen Schäden an privatem und öffentlichem Eigentum sowie im gewerblichen Bereich. Deshalb ist es notwendig Dynamiken der Flächennutzungsänderungen zu untersuchen, da die Flächennutzung die Art der anfälligen Elemente im Falle eines Hochwassers und die Schadenshöhe bestimmt. Als Simulationswerkzeug wird der rasterbasierte zelluläre Automat LuSIM (vgl. STRÖBL et al. 2003) genutzt, der als Erweiterung für ArcView 3.x zur Verfügung steht. Das Untersuchungsgebiet befindet sich in der Elbaue, zum Teil im Stadtgebiet Dresden und zum Teil im Stadtgebiet von Radebeul im Landkreis Meißen. In der vorliegenden Arbeit wird die zukünftige urbane Flächennutzungsentwicklung im Untersuchungsgebiet nach drei Szenarios simuliert. Die Neuentstehung von Wohnbauland ist dabei die treibende Kraft. Die Arbeit leistet damit einen Beitrag zur ex ante-Analyse und Bewertung der Hochwasserrisiken. Der zelluläre Automat verortet neue potentielle Wohnstandorte basierend auf Eignungsregeln und dem Bedarf an neuem Wohnbauland. Die Regeln zur Eignung jeder Rasterzelle als Wohnstandort leite ich aus der Analyse historischer Nutzungsänderungen ab. Den Bedarf an zukünftigem Wohnbauland ermittle ich aus dem vom Bundesamt für Bauwesen und Raumordnung (2006) in seiner Raumordnungsprognose 2020/2050 prognostizierten Neubau von Wohnungen.

The present work consists of three parts. In the first part (chapters III and IV), the dynamics of Lorentz lattice gases (LLG) on graphs is analyzed. We study the fixed scatterer model on finite graphs. A tight bound is established on the size of the orbit for arbitrary graphs, and the model is shown to perform a depth-first search on trees. Rigidity models on trees are also considered, and the size of the resulting orbit is established. In the second part (chapter V), we give a complete description of dynamics for LLG on the one-dimensional integer lattice, with a particular interest in showing that these models are not capable of universal computation. Some statistical properties of these models are also analyzed. In the third part (chapter VI) we attempt to partition a pool of workers into teams that will function as independent TSS lines. Such partitioning may be aimed to make sure that all groups work at approximately the same rate. Alternatively, we may seek to maximize the rate of convergence of the corresponding dynamical systems to their fixed points with optimal production at the fastest rate. The first problem is shown to be NP-hard. For the second problem, a solution for splitting into pairs is given, and it is also shown that this solution is not valid for partitioning into teams composed of more than two workers.

Since the 1970s, Asia has experienced rapid urbanization processes, which are distinct from U.S. society, and the direction of Asian urbanization is more strongly affected by economic globalization. The desakota model, proposed by McGee and Ginsburg in 1991, focuses on how internal domestic and local forces drive the specific rural-urban transformation in Asia. However, the McGee-Ginsburg model does not emphasize the importance of globalization on Asian urbanization. To fill the gap, this study develops a GIS-based CA framework based on the desakota model to not only simulate the unique urbanization processes in Asia but also integrate the influence of globalization into Asian urban dynamics. Three approaches are developed in the CA simulation: 1) physical constraints and land-use classification from remotely sensed images in 1993, 2000, and 2008, are incorporated into micro-scale transformation; 2) population dynamics, shifts of economic activities, and foreign direct investment (FDIs), a representative of the impact of globalization, are applied for multi-scale interconnection; 3) the Monte Carlo mechanism is finally introduced to combine the above two approaches and implement the simulation process. The Taipei metropolitan area, a rapid urbanizing region that highly interacts with the global economy in Asia, is chosen to examine this model. The CA simulation model establishes a strong interaction between FDIs, an indicator representing impacts of globalization, and the dazzling Asian urban model. The combination of multi-scale economic factors and micro-scale land-use transformation also reveals how urban growth of the Taipei metropolis in recent years fits the characterization of the desakota model, and how desakota regions, the growth generators, interact with city cores. As a result, the research not only successfully links the influence of globalization with the desakota model and simulates urban dynamics of Asian cities but also provides scenarios of different FDI inputs for governments to better handle urban growth with global impacts under the deep economic recession since 2007.

Recent advances in the field of educational technology have promoted the re-purposing of entertainment-oriented games and software for educational applications. This thesis extends a project developed at Texas A&M University called Room 309, a re-purposed modification of Valve Software’s Source Development Kit that models classroom scenarios to pre-service teachers. To further explore effectiveness in the area of re-playability, this work incorporates emergent game behaviors and environments using cellular automata, randomness, and influence maps within the existing nonemergent structure. By introducing these qualities game play is expected to become less predictable, thus increasing the effectiveness of Room 309 as a learning tool.

Material damage such as dislocations and microcracks are characteristic of early stages of fatigue. Accumulation of these nascent cracks leads to non-linear elastic response of the material. These non-linearities can be detected from harmonic generation for propagating elastic waves. The long term goal of this study is to investigate the non-linear elastic propagation in parts with complex geometry. Cellular Automata is introduced as a new simulation method, in order to develop new analysis on quadratic non-linearities. An existing linear code was progressively modified to take into account a different constitutive law. Also the boundary conditions need to be reviewed to ensure free stress with the non-linear behavior. The propagation of the longitudinal wave is investigated in detail. Numerical accuracy is validated from comparison with a closed, for both linear and non-linear code. The reflection of the non-linear P-wave gives confirmation for the correct treatment of the boundary condition. Finally the capabilities of the Cellular Automata code are underlined for reflection of Lamb waves for various boundary conditions.

<p>Biofilms are communities of sessile microorganisms attached to a surface and imbeddedin a matrix of extracellular polysaccharide substances. These communities can be foundin diverse aquatic environments, such as in industrial pipes and in humans. By formingmicrocolony structures, which are highly resistant to adverse physical conditions as wellas antimicrobial agents, biofilms are very problematic when associated with e.g.persistent infections. In order to find new ways of controlling biofilm growth, theprocesses involved in biofilm development must be investigated further. The maininterest of this study is the occurrence of void formation inside biofilms. Thisphenomenon has been observed in several studies and has been correlated to cell deathinside the microcolonies. The occurrence of cell death has recently been associated withthe presence of nitric oxide in the biofilm. In this study, the implications of nitric oxideaccumulation on biofilm development were investigated using an individual-basedmodel. Specifically, the role of nitric oxide in void formation was considered. A largenumber of simulations were run using different parameter settings in order to determine ifnitric oxide could account for the occurrence of void formation observed experimentally.The general predictions made by the model system showed agreement to someexperimental data, but not to others. Sloughing, the detachment of chunks of cells fromthe biofilm, was observed in the majority of simulations. In some cases, the model alsopredicted the presence of live cells inside the voids, which has been observedexperimentally.</p>

Thesis (M. S.)--Mechanical Engineering, Georgia Institute of Technology, 2010. / Committee Chair: Dr. Michael Leamy; Committee Member: Dr. Karim Sabra; Committee Member: Dr. Aldo Ferri. Part of the SMARTech Electronic Thesis and Dissertation Collection.

Models based on various types of automata are ubiquitous in modern science. These models allow reasoning about deep theoretical questions and provide a basis for the development of efficient algorithms to solve related computational problems. This work discusses several types of automata used in such models, including cellular automata and mandatory results automata. The first part of this work is dedicated to cellular automata. These automata form an important class of discrete dynamical systems widely used to model physical, biological, and chemical processes. Here we discuss a way to study the dynamics of one-dimensional cellular automata through the theory of two-dimensional picture languages. The connection between cellular automata and picture languages stems from the fact that the set of all space-time diagrams of a cellular automaton defines a picture language. We will discuss a hierarchy of cellular automata based on the complexity of the picture languages that they define. In addition to this, we present a characterization of cellular automata that can be described by finite-state transducers. The second part of this work presents a theory of runtime enforcement based on mech- anism models called Mandatory Results Automata (MRAs). MRAs can monitor and trans- form security-relevant actions and their results. Because previous work could not model general security monitors transforming results, MRAs capture realistic behaviors outside the scope of previous models. MRAs also have a simple but realistic operational seman- tics that makes it straightforward to define concrete MRAs. Moreover, the definitions of policies and enforcement with MRAs are significantly simpler and more expressive than those of previous models. Putting all these features together, we argue that MRAs make good general models of (synchronous) runtime mechanisms, upon which a theory of run- time enforcement can be based. We develop some enforceability theory by characterizing the policies deterministic and nondeterministic MRAs enforce.