Spatio-temporal systems with heterogeneity in their structure and behavior have two major problems. The first one is that such systems extend over very large spatial and temporal domains and consume a lot of resources to simulate that they are infeasible to study with current platforms. The second one is that the data available for understanding such systems is limited. This also makes it difficult to get the data for validation of their constituent processes while simultaneously considering their global behavior. For example, the valley fever fungus considered in this dissertation is spread over a large spatial grid in the arid Southwest and typically needs to be simulated over several decades of time to obtain useful information. It is also hard to get the temperature and moisture data at every grid point of the spatial domain over the region of study. In order to address the first problem, we develop a method based on the discrete event system specification which exploits the heterogeneity in the activity of the spatio-temporal system and which has been shown to be effective in solving relatively simple partial differential equation systems. The benefit of addressing the first problem is that it now makes it feasible to address the second problem.We address the second problem by making use of a multilevel methodology based on modeling and simulation and systems theory. This methodology helps us in the construction of models with different resolutions (base and lumped models). This allows us to refine an initially constructed lumped model with detailed physics-based process models and assess whether they improve on the original lumped models. For that assessment, we use the concept of experimental frame to delimit where the improvement is needed. This allows us to work with the available data, improve the component models in their own experimental frame and then move them to the overall frame. In this dissertation, we develop a multilevel methodology and apply it to a valley fever model. Moreover, we study the model's behavior in a particular experimental frame of interest, namely the formation of new sporing sites.

Today, there is little understanding of how local decisions and disturbances impact the global performance of the supply chain. In this research, we attempt to gain insight about such relationship using multi-resolution hybrid models. To this end, a novel hybrid architecture and methodology consisting of simulation (system dynamic and discrete-event) and optimization modules is proposed. The proposed methodology, applicable to general supply chains, is divided into fours stages: plan stability analysis (Stage I), plan optimization (Stages II), schedule optimization (Stage III) and concurrent decision evaluation (Stage IV). Functional and process models of the proposed architecture are specified using formal IDEF tools. A realistic three-echelon conjoined supply chain system characterized by communicative and collaborative (VMI) configurations is analyzed in this research. Comprehensive SD models of each player of the supply chain have been developed. General conditions of the stability (settings of control parameters that produce stable response) are derived using z-transformation techniques (Stage I), and insights into the behavior of the supply chain are gained. Next, a novel method for the integration of the stability analysis with performance analysis (optimization) is presented (Stage II) by employing the derived stability conditions derived as additional constraints within the optimization models. Next, in Stage III, the scheduling at each chain partner using discrete-event simulation (DES) modeling techniques is addressed. In Stage IV, the optimality of the SD control parameters (from Stage II) and DES operational policies (from Stage III) for each member are concurrently evaluated by integrating the SD and DES models. Evaluation in Stage IV is performed to better understand the global consequence of the locally optimal decisions determined at each supply chain member. A generic infrastructure has been developed using High Level Architecture (HLA) to integrate the distributed decision and simulation models. Experiments are conducted to demonstrate the proposed architecture for the analysis of distributed supply chains. The progressions of cost based objective function from Stages I-III are compared with that from the concurrent evaluation in Stage IV. Also the ability of the proposed methodology to capture the effect of dynamic perturbations within the supply chain system is illustrated.

The source system is the real or virtual environment that we are interested in modeling. It is viewed as a source of observable data, in the form of time-indexed trajectories of variables. The data that has been gathered from observing or experimenting with a system is called the system behavior data base. The time indexed trajectories of variables provide an important clue to compose the DEVS (discrete event specification) model. Once event set is derived from the time indexed trajectories of variable, the DEVS model formalism can be extracted from the given event set. The process must not be a simple model generation but a meaningful model structuring of a request. The source data and query designed with SES are converted to XML Meta data by XML converting process. The SES serves as a compact representation for organizing all possible hierarchical composition of system so that it performs an important role to design the structural representation of query and source data to be saved. For the real data application, the model structuring with the US Climate Normals is introduced. Moreover, complex systems are able to be developed at different levels of resolution. When the huge size of source data in US Climate Normals are implemented for the DEVS model, the model complexity is unavoidable. This issue is dealt with the creation of the equivalent lumped model based on the concept of morphism. Two methods to define the resolution level are discussed, fixed and dynamic definition. Aggregation is also discussed as the one of approaches for the model abstraction. Finally, this paper will introduce the process to integrate the DEVSML(DEVS Modeling Language) engine with the DEVS model creation engine for the Web Service Oriented Architecture.

Spontaneous imbibition plays a very important role in the displacement mechanism of non-wetting fluid in naturally fractured reservoirs. We developed a new 2D two-phase finite element numerical model, as available commercial simulators cannot be used to model small-scale experiments with different boundary conditions as well as complex boundary conditions such as fractures and vugs. Starting with the basic equation of fluid flow, we derived the non-linear diffusion saturation equation. This equation cannot be put in weighted-integral weak variational form and hence Rayleigh-Ritz finite element method (FEM) cannot be applied. Traditionally, the way around it is to use higher order interpolation functions and use Galerkin FEM or reduce the differentiability requirement and use Mixed FEM formulation. Other FEM methods can also be used, but iterative nature of those methods makes them unsuitable for solving large-scale field problems. But if we truncate the non-linear terms and decouple the dependent variables, from the spatial as well as the temporal domains of the primary variable to solve them analytically, the non-linear FEM problem reduces to a simple weighted integral form, which can be put into its corresponding weak form. The advantage of using Rayleigh-Ritz method is that it has immediate effect on the computation time required to solve a particular problem apart from incorporating complex boundary conditions. We compared our numerical models with the analytical solution of this diffusion equation. We validated the FDM numerical model using X-Ray Tomography (CT) experimental data from the single-phase spontaneous imbibition experiment, where two simultaneously varying parameters of weight gain and CT water saturation were used and then went ahead and compared the results of FEM model to that of FDM model. A two-phase field size example was taken and results from a commercial simulator were compared to the FEM model to bring out the limitations of this approach.

The main objective of the project was to develop a model for the motion of granular media under vibration in a tub vibrator. For such a system, it was decided that a discrete element method (DEM) was the most appropriate tool to model bulk velocity and circulation of media. In the first phase of the work, a vibratory finisher was modified to introduce planar vibration into a single layer of particles. The motion of the tub was measured using accelerometers and the corresponding granular media behavior was determined by video recording. A discrete element model, based on Cundall’s approach to contact, was developed to model granular flow in different vibratory beds, and the results were compared with experimental measurements of bulk flow velocity and bed expansion for the tub finisher. The sensitivity of the model predictions to the contact parameters was considered and the parameters were optimized with respect to the experimental results. After optimization, the difference between the model predictions of the bulk flow velocity and the measurements was less than 20% at four locations in media beds of two depths. The average bulk density of the vibrating beds was also predicted to be within 20% of the measured values. In the next phase, a two-dimensional discrete element model was developed to model single-cell circulation in vibratory beds that had both vertical and horizontal components of motion. The model predictions were compared with experimental measurements of the onset and growth of circulation in beds of steel and glass spheres as a function of bed depth, inter-particle and wall friction coefficients, and the amplitude of vibration. While the values from the DEM showed an error of up to 50% in the predicted circulation strength, depending on the type of the media and system conditions, the trends predicted by the model closely matched those in the experiments. Finally, a physical model was developed to describe the relationship between the onset and direction of circulation with the vibration of the container. A similar model was used to describe the experimental results as well as the transition in circulation patterns in terms of the resultant shear forces at the vibrating container walls and the interlocking of media close to the container walls. It was also demonstrated that a two-dimensional DEM could model a granular flow in which the media had three-dimensional contact and freedom of movement, but that was driven by vibrations in a plane. In summary, it was found that the linear optimization procedure for the contact parameters is an efficient way to improve the results from DEM. Additionally, the circulation in a tub-vibrator increased with the depth of the particulate media in the container, and with the magnitude of the wall-particle and particle-particle friction coefficients. The strength of circulation also increased with the amplitude of vibration. A strong correlation existed between the total shear force along the vibrating container walls and the circulation behavior. Bulk circulation increased sharply when increasing bed depth increased the pressure and the shear forces at the walls and between particle layers. It was also concluded that dimensionless bed depth (the ratio of bed depth to particle diameter) was not a proper dimensionless group when discussing the circulation behavior and it should act in conjunction with other parameters.

BACKGROUND: Parents of children with juvenile idiopathic arthritis (JIA) are often forced to make trade-offs between the effectiveness, convenience, safety, and cost of drug treatments for their child. METHODS: A discrete choice experiment was administered to parents of children with JIA to determine their preferences for drug treatments. Multinomial logit regression was used to estimate part-worth utilities and willingness-to-pay. RESULTS: Participation in daily activities was the most important attribute, followed by child reported pain. Child age, gender, years with JIA, and household income had the greatest impact on preferences. Parents’ were willing to pay $2,080 to switch from a drug representing methotrexate to etanercept (95% CI $698, $4,065). CONCLUSIONS: Parents of children with JIA have the highest maximum willingness-to-pay for drug treatments that improve daily functioning and reduce pain. Cost is a significant factor in the decisions that parents make surrounding the best treatment for a child.

The main objective of the project was to develop a model for the motion of granular media under vibration in a tub vibrator. For such a system, it was decided that a discrete element method (DEM) was the most appropriate tool to model bulk velocity and circulation of media. In the first phase of the work, a vibratory finisher was modified to introduce planar vibration into a single layer of particles. The motion of the tub was measured using accelerometers and the corresponding granular media behavior was determined by video recording. A discrete element model, based on Cundall’s approach to contact, was developed to model granular flow in different vibratory beds, and the results were compared with experimental measurements of bulk flow velocity and bed expansion for the tub finisher. The sensitivity of the model predictions to the contact parameters was considered and the parameters were optimized with respect to the experimental results. After optimization, the difference between the model predictions of the bulk flow velocity and the measurements was less than 20% at four locations in media beds of two depths. The average bulk density of the vibrating beds was also predicted to be within 20% of the measured values. In the next phase, a two-dimensional discrete element model was developed to model single-cell circulation in vibratory beds that had both vertical and horizontal components of motion. The model predictions were compared with experimental measurements of the onset and growth of circulation in beds of steel and glass spheres as a function of bed depth, inter-particle and wall friction coefficients, and the amplitude of vibration. While the values from the DEM showed an error of up to 50% in the predicted circulation strength, depending on the type of the media and system conditions, the trends predicted by the model closely matched those in the experiments. Finally, a physical model was developed to describe the relationship between the onset and direction of circulation with the vibration of the container. A similar model was used to describe the experimental results as well as the transition in circulation patterns in terms of the resultant shear forces at the vibrating container walls and the interlocking of media close to the container walls. It was also demonstrated that a two-dimensional DEM could model a granular flow in which the media had three-dimensional contact and freedom of movement, but that was driven by vibrations in a plane. In summary, it was found that the linear optimization procedure for the contact parameters is an efficient way to improve the results from DEM. Additionally, the circulation in a tub-vibrator increased with the depth of the particulate media in the container, and with the magnitude of the wall-particle and particle-particle friction coefficients. The strength of circulation also increased with the amplitude of vibration. A strong correlation existed between the total shear force along the vibrating container walls and the circulation behavior. Bulk circulation increased sharply when increasing bed depth increased the pressure and the shear forces at the walls and between particle layers. It was also concluded that dimensionless bed depth (the ratio of bed depth to particle diameter) was not a proper dimensionless group when discussing the circulation behavior and it should act in conjunction with other parameters.

BACKGROUND: Parents of children with juvenile idiopathic arthritis (JIA) are often forced to make trade-offs between the effectiveness, convenience, safety, and cost of drug treatments for their child. METHODS: A discrete choice experiment was administered to parents of children with JIA to determine their preferences for drug treatments. Multinomial logit regression was used to estimate part-worth utilities and willingness-to-pay. RESULTS: Participation in daily activities was the most important attribute, followed by child reported pain. Child age, gender, years with JIA, and household income had the greatest impact on preferences. Parents’ were willing to pay $2,080 to switch from a drug representing methotrexate to etanercept (95% CI $698, $4,065). CONCLUSIONS: Parents of children with JIA have the highest maximum willingness-to-pay for drug treatments that improve daily functioning and reduce pain. Cost is a significant factor in the decisions that parents make surrounding the best treatment for a child.

The development of controls for the execution of concurrent code is non-trivial. This work shows how existing discrete-event system (DES) theory can be successfully applied to this problem. From code without concurrency controls and a specification of desired behaviours, a DES representation of the problem is obtained, and then used to generate concurrency control code. By applying rigorously proven DES theory, the resulting code comes with guarantees not present in similar works. All control schemes generated in DES are nonblocking, yielding code that is free of both livelock and deadlock. Additionally, the generated control scheme is minimally restrictive, meaning only problematic behaviours are prevented. If the specifications cannot be enforced as presented, the largest controllable subset is instead enforced. The result, which requires no further interaction to generate, is the best possible control scheme given the interaction between the specifications and the original code. Existing methods encounter difficulties when faced with multiple specifications that interact to form deadlocks. Modular DES theory is successfully applied, allowing resolution of these conflicts without requiring the user to introduce new specifications. Moreover, the approach is independent of specific programming or specification languages. A Java implementation is given, along with two problems showing the process in action. / Thesis (Master, Computing) -- Queen's University, 2008-09-25 09:03:51.593

Discrete-Event systems (DES) is a framework in which problems are modelled as finite-state automata and a solution in the form of a supervisory control scheme can be automatically synthesized via an exhaustive search through the state space of the system. Various extensions to the standard DES framework have been introduced to allow it to be applied to a greater variety of problems. When the system in question is very large or varies with time, a limited lookahead policy can be adopted, in which control decisions are made on-the-fly by looking at finite-step projections of the behaviour of the system's underlying automata. This work presents a new approach to limited lookahead supervision which incorporates many of the extensions to DES that are already present in the literature, such as event probability and string desirability. When dealing with a limited lookahead technique, the projected system behaviour is represented as a lookahead tree with some depth limit decided on by the user. It can be difficult to strike a balance between the complexities associated with storing and analyzing the trees and the amount of information available to make decisions, both of which increase with depth. This work also presents a set of methods which are designed to aid in accurately estimating the state space of lookahead trees with the intent of simplifying the process of determining a favourable depth to use. Finally, the approaches introduced herein are applied to a simulation of an infectious disease outbreak, primarily to showcase them in action, but also for the possibility of illuminating any useful information for real-world health units. / Thesis (Master, Computing) -- Queen's University, 2012-01-20 19:35:58.007