We present the BIP component framework for component-based construction of real-time systems from heterogeneous components. BIP stands for Behavior, Interaction and Priority, the three main elements for building components. It considers that systems can be obtained by composition of 3-layered components, where the lowest layer represents behavior as a set of transitions with triggers and actions; the intermediate level is the set of the interactions between the transitions of the behavior level, and the upper level is a set of dynamic priority rules. BIP has a rigorous formal semantics, and supports a system construction methodology based on a parameterized composition operator on components. The use of a layered composition operator allows incremental construction. The system construction process can be viewed as a sequence of transformations in a three-dimensional space of Behavior X Interaction X Priority, and provides a basis for the study of property preserving transformations between subclasses of systems such as untimed/timed, asynchronous/synchronous. We also provide a distributed semantics for systems in BIP, using a partial state model, and show the use of an auxiliary predicate called Oracle to preserve observational equivalence with respect to the centralized semantics. We present an implementation of BIP as a tool chain that allows modeling, static analysis and execution of BIP descriptions on a dedicated engine. Three different implementations for the engine have been provided, a centralized enumerative engine, a centralized symbolic engine and a distributed engine. We illustrate the use of the tool chain for two major application domains, Software Componentization, and Modeling mixed hw/sw systems.

Macroalgae are an important part of the coral reef ecosystem that has largely been overlooked. However, in the past few decades their abundances have increased and this has been attributed to combinations of coral mortality opening up space in the reef, decreased grazing and increased nutrient load in reefs. This dissertation illustrates a novel means of investigating the effect of various growth and disturbance factors on the dynamics of macroalgae at three different levels (individual, population and 3-species community). Macroalgae are modular and clonal organisms that have differing morphologies depending on the environment to which they are exposed. These traits were exploited in order to understand the factors that were acting on the dominant and common macroalgae in the Florida Reef Tract: Halimeda tuna, Halimeda opuntia and Dictyota sp. The agent-based model SPREAD (SPatially-explicit REef Algae Dynamics) was developed to incorporate the key morphogenetic characteristics of clonality and morphological plasticity. It revolves around the iteration of macroalgal module production in response to light, temperature, nutrients, and space availability, while fragmentation is the source for mortality or new individuals. These processes build the individual algae then the population. The model was parameterized through laboratory experiments, existing literature and databases and results were compared to independently collected field data from four study sites in the Florida Keys. SPREAD was run using a large range of light, temperature, nutrient and disturbance (fragmentation without survival) levels and yielded six morphological types for Halimeda tuna, and two each for Halimeda opuntia and Dictyota sp. The model morphological types that matched those measured in two inshore patch reefs (Cheeca Patch and Coral Gardens) and two offshore spur and groove reefs (Little Grecian and French Reef), were formed in conditions that were similar to the environmental (light, nutrient and disturbance) conditions in the field sites. There were also differences between species in the important factors that influenced their morphologies, wherein H. opuntia and Dictyota were more affected by disturbance than growth factors, while H. tuna morphology was affected by both. Allowing for fragmentation with survival in the model resulted in significantly higher population abundances (percent cover and density). The highest abundances were achieved under high fragment survival probabilities and a high disturbance level (but not large fragment sizes). Incorporating fragmentation with survival and simulating the variations in light, nutrients and disturbance between the inshore patch reefs and offshore spur and groove reefs in SPREAD led to comparable abundances of Halimeda in the virtual reef sites. Adding competition for space and light and epiphytism by Dictyota on the two Halimeda species suggests that it can regulate the populations of the three macroalgae. However, comparing model abundances to the field, competition may not be a strong regulating force for H. tuna in all the sites and H. opuntia in the patch reefs. H. opuntia in the offshore reefs is possibly competitively regulated. Although SPREAD was not able to capture the patterns in the population abundance of Dictyota, this points to the potential importance of other morphometrics not captured by the model, a variation in growth curves between reef habitats, or the differential contribution of sexual reproduction.

Homogeneous Charge Compression Ignition (HCCI) Engines hold promises of being the next generation of internal combustion engines due to their ability to produce high thermal efficiencies and low emission levels. HCCI combustion is achieved through the auto-ignition of a compressed homogenous fuel-air mixture, thus making it a "fusion" between spark-ignition and compression-ignition engines. The main challenge in developing HCCI engines is the absence of a combustion trigger hence making it difficult to control its combustion timing. The aim of this research project is to model and control a natural gas HCCI engine. Since HCCI depends primarily on temperature and chemical composition of the mixture, Exhaust Gas Recirculation (EGR) is used to control ignition timing. In this research, a thermodynamical, physics-based nonlinear model is developed to capture the main features of the HCCI engine. In addition, the Modified Knock Integral Model (MKIM), used to predict ignition timing, is optimized. To validate the nonlinear model, ignition timing under varying conditions using the MKIM approach is shown to be in accordance with data acquired from a model developed using a sophisticated engine simulation program, GT-Power. Most control strategies are based on a linear model, therefore, the nonlinear model is linearized using the perturbation method. The linear model is validated by comparing its performance with the nonlinear model about a suitable operating point. The control of ignition timing can be defined as a regulation process where the goal is to force the nonlinear model to track a desired ignition timing by controlling the EGR ratio. Parameters from the linear model are used to determine the gains of the LQR controller. The performance of the controller is validated by implementing it on the nonlinear model and observing its ability to track the desired timing with 0.5% error within a certain operating range. To increase the operating range of the controller and reduce steady-state error, an integrator is added to the LQR. Finally, it is shown that the LQR controller is able to successfully reject disturbance, parameter variation, as well as noise.

Modeling of natural phenomena has been of particular interest in the graphics ommunity in recent years. This thesis will explore a method for creating and animating orb webs using a coupled spring-mass system. Using a spring-mass system for creating the orb web is ideal as we can represent each web strand using coupled spring-mass pairs. This allows the orb web simulator to be physically based, i.e., the simulation follows the laws that act on objects in the real world. This in turn simplifies the process of animating the web, as the animation emerges from the simulator without anyone having to set it up explicitly. Since this model is physically based, it would allow for realistic visualization of effects such as observing an orb web under a wind. In the children's book ``Charlotte's Web', the spider creates orb webs with words inscribed on them. Charlotte's web is used as an inspiration, in this thesis, to create webs which no real world spider could possibly create, while keeping the model physically based. This involves modifying the orb web such that the target text shows up on the orb web while keeping the web looking as natural as possible.

In this physically-based tornado simulation, the tornado-scale approach techniques are applied to simulate the tornado formation environment. The three-dimensional Navier-Stokes equations for incompressible viscous fluid flows are used to model the tornado dynamics. The boundary conditions applied in this simulation lead to rotating and uplifting flow movement as found in real tornadoes and tornado research literatures. Moreover, a particle system is incorporated with the model equation solutions to model the irregular tornado shapes. Also, together with appropriate boundary conditions, varied particle control schemes produce tornadoes with different shapes. Furthermore, a modified metaball scheme is used to smooth the density distribution. Texture mapping, antialising, animation and volume rendering are applied to produce realistic visual results. The rendering algorithm is implemented in OpenGL.

In this physically-based tornado simulation, the tornado-scale approach techniques are applied to simulate the tornado formation environment. The three-dimensional Navier-Stokes equations for incompressible viscous fluid flows are used to model the tornado dynamics. The boundary conditions applied in this simulation lead to rotating and uplifting flow movement as found in real tornadoes and tornado research literatures. Moreover, a particle system is incorporated with the model equation solutions to model the irregular tornado shapes. Also, together with appropriate boundary conditions, varied particle control schemes produce tornadoes with different shapes. Furthermore, a modified metaball scheme is used to smooth the density distribution. Texture mapping, antialising, animation and volume rendering are applied to produce realistic visual results. The rendering algorithm is implemented in OpenGL.

Modeling of natural phenomena has been of particular interest in the graphics ommunity in recent years. This thesis will explore a method for creating and animating orb webs using a coupled spring-mass system. Using a spring-mass system for creating the orb web is ideal as we can represent each web strand using coupled spring-mass pairs. This allows the orb web simulator to be physically based, i.e., the simulation follows the laws that act on objects in the real world. This in turn simplifies the process of animating the web, as the animation emerges from the simulator without anyone having to set it up explicitly. Since this model is physically based, it would allow for realistic visualization of effects such as observing an orb web under a wind. In the children's book ``Charlotte's Web', the spider creates orb webs with words inscribed on them. Charlotte's web is used as an inspiration, in this thesis, to create webs which no real world spider could possibly create, while keeping the model physically based. This involves modifying the orb web such that the target text shows up on the orb web while keeping the web looking as natural as possible.

Transportation sector has been a major contributing factor to the overall emissions of most pollutants and thus their impacts on the environment. Among all transportation activities, on-road travel accounts for most part of the Greenhouse gas (GHG) emissions and fuel use. It also has a very un-desirable impact on the transportation network conditions increasing the traffic congestion levels. The main aim of transportation planning agencies is to implement the policy changes that will reduce automobile dependency and increase transit and non-motorized modes usage. However, planning agencies can come up with proactive economic, land-use and transportation policies provided they have a model which is sensitive to all the above mentioned factors to predict the vehicle fleet composition and usage of households. Moreover, the type of vehicle that a household gets (vehicle type choice) and the annual mileage (usage) associated with that vehicle is very closely related to the person in the household who uses that vehicle the most (allocation to primary driver). So, it is no longer possible to view all these decisions separately. Instead, we need to model all these decisions- vehicle type choice, usage, and allocation to primary driver simultaneously at a household level. In this study, we estimate and apply a joint household-level model of the number of vehicles owned by the household, the vehicle type choice of each vehicle, the annual mileage on each vehicle, as well as the individual assigned as the primary driver for each vehicle. A version of the proposed model system currently serves as the engine for a household vehicle composition and evolution simulator, which itself has been embedded within the larger SimAGENT (for Simulator of Activities, Greenhouse emissions, Networks, and Travel) activity-based travel and emissions forecasting system for the Southern California Association of Governments (SCAG) planning region. / text

Computers are being employed in a variety of ways by a variety of individuals to create imagery. Much work has been done to accurately model natural phenomena in the context of computer graphics as well as model specific artists' tools and techniques. Focusing on the dynamics of water flow across surfaces, it is the goal of this work to develop a physically inspired texturing tool that allows artists to create interesting staining and wearing effects on surfaces. Weathering or the wearing down of materials by natural forces can create complex and beautiful patterns on a variety of surfaces. In this process lies the very essence of the creative act. To distill the essence of the elements of the water staining process, we employ a computer generated particle system in a phenomenological model. The motion of these particles is controlled by physically based constraints, such as wind, gravity, mass, etc. The way in which each particle interacts with or modifies the look of the surface is further controlled by parameters such as surface roughness, surface color and surface hardness. Each particle can remove or deposit material as it flows across the surface, creating complex patterns.

The traditional approaches to engineering of information systems focus on identifying business requirements and delivering the specific functionality required to automate some activities. Not enough attention is being attached to how the created system will interact with the rest of the business. As a result, there is often a gap between the business requirements and the systems implemented to support them. To bridge this gap, many organizations are developing enterprise architecture to provide a holistic vision of how systems will support their business. Model-driven architecture (MDA) focuses on modelling activities in software development process and shifts the software development process from the writing code to the modelling activities. MDA separates the business level from the technological platform which implements information system. The key feature of the model-driven architecture is its ability to transform automatically the platform-independent model (PIM) into the platform-specific model (PSM). MDA uses modelling languages as programming languages Using interface-based programming is the evolution of the object-oriented programming and design. The interfaces have made the software design more adaptable to the rapid changes of the business environment. While using interfaces, software systems achieve reusability, extensibility and maintainability. The CBD approaches use the interface-based design idea and therefore have advantages such as more effective... [to full text]