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This thesis addresses the problem of descriptive complexity presented by systems involving a high number of interacting components. It investigates the evaluation measure of performability and its application to such systems. A new description and simulation language, ICE and it's application to performability modelling is presented. ICE (Interacting ComponEnts) is based upon an earlier description language which was first proposed for defining reliability problems. ICE is declarative in style and has a limited number of keywords. The ethos in the development of the language has been to provide an intuitive formalism with a powerful descriptive space. The full syntax of the language is presented with discussion as to its philosophy. The implementation of a discrete event simulator using an ICE interface is described, with use being made of examples to illustrate the functionality of the code and the semantics of the language. Random numbers are used to provide the required stochastic behaviour within the simulator. The behaviour of an industry standard generator within the simulator and different methods of number allocation are shown. A new generator is proposed that is a development of a fast hardware shift register generator and is demonstrated to possess good statistical properties and operational speed. For the purpose of providing a rigorous description of the language and clarification of its semantics, a computational model is developed using the formalism of extended coloured Petri nets. This model also gives an indication of the language's descriptive power relative to that of a recognised and well developed technique. Some recognised temporal and structural problems of system event modelling are identified. and ICE solutions given. The growing research area of ATM communication networks is introduced and a sophisticated top down model of an ATM switch presented. This model is simulated and interesting results are given. A generic ICE framework for performability modelling is developed and demonstrated. This is considered as a positive contribution to the general field of performability research.

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This paper describes the use of corporate decision and strategy simulations as a decision-support instrument under varying market conditions in the tourism industry. It goes on to illustrate this use of simulations with an experiment which investigates how successful different market segmentation approaches are in destination management. The experiment assumes a competitive environment and various cycle-length conditions with regard to budget and strategic planning. Computer simulations prove to be a useful management tool, allowing customized experiments which provide insight into the functioning of the market and therefore represent an interesting tool for managerial decision support. The main drawback is the initial setup of a customized computer simulation, which is time-consuming and involves defining parameters with great care in order to represent the actual market environment and to avoid excessive complexity in testing cause-effect-relationships. (author's abstract) / Series: Report Series SFB "Adaptive Information Systems and Modelling in Economics and Management Science"

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A discrete event simulation was applied to model the perioperative process in the general surgery service at Toronto General Hospital, aiming at reducing the number of surgical cancellations and improving the perioperative process. This model includes emergency case interruptions with two types of emergency cases with different levels of urgency, and takes into account the availability of three types of post-surgical beds: medical surgical intensive care unit, step-down unit and ward beds in decision making level. The effect of three types of scenarios on the number of surgical cancellations was explored: 1) applying effective scheduling rules based on the utilization of post-surgical beds, 2) sequencing the surgical operations based on the length of surgeries and the variance of surgery durations, 3) increasing the number of post-surgical beds.

A discrete event simulation was applied to model the perioperative process in the general surgery service at Toronto General Hospital, aiming at reducing the number of surgical cancellations and improving the perioperative process. This model includes emergency case interruptions with two types of emergency cases with different levels of urgency, and takes into account the availability of three types of post-surgical beds: medical surgical intensive care unit, step-down unit and ward beds in decision making level. The effect of three types of scenarios on the number of surgical cancellations was explored: 1) applying effective scheduling rules based on the utilization of post-surgical beds, 2) sequencing the surgical operations based on the length of surgeries and the variance of surgery durations, 3) increasing the number of post-surgical beds.

This thesis investigates the causes of the long wait-time for patients in Emergency department (ED) of Victoria General Hospital, and suggests changes for improvements. Two prominent simulation techniques have been used to replicate the ED in a simulation model. These are Discrete-event simulation (DES) and Agent-based modeling (ABM). While DES provides the basic modeling framework ABM has been used to incorporate human behaviour in the ED. The patient flow in the ED has been divided into 3 phases: input, throughput, and output. Model results show that there could be multiple interventions to reduce time taken to be seen by the doctor for the first time (also called WTBS) either in the output phase or in the input phase. The model is able to predict that a reduction in the output phase would cause reduction in the WTBS but it is not equipped to suggest how this reduction can be achieved. To reduce WTBS by making interventions in the input phase this research proposes a strategy called fast-track treatment (FTT). This strategy helps the model to dynamically re-allocate resources if needed to alleviate high WTBS. Results show that FTT can reduce WTBS times by up-to 40%.

Computational simulations of a perturbed vortex ring are performed to recreate and understand the instability seen in impacting water droplet experiments. Three initial conditions are tried to respectively trigger a Widnall instability, a Rayleigh centrifugal instability, and a vortex breakdown instability. Simulations with a perturbed solitary ring result in an instability similar to that seen experimentally. Waviness of the core which would be expected from a Widnall instability is not visible. Adding an opposite-signed secondary vortex ring or an image vortex ring to the initial conditions does not appear to significantly change the instability from what is seen with a solitary ring. This suggests that a Rayleigh centrifugal instability or a vortex breakdown instability are not likely at work, though tests are not conclusive. Elliptical streamlines are visible in the core of the solitary ring at early times, suggesting that an elliptic instability may be the source of the experimental instability.

Physical simulations are in general very computationally intensive and required large and costly computing resources. Most of those simulations are rarely interactive as the link between visualization, interaction, and simulation is too slow. The recent development of parallel Graphic Processing Unit (GPU) on graphic cards has enabled us to develop real-time interactive simulators of complex physical phenomenon. In this thesis, two GPU-based implementations of interactive physical simulations are presented: (1) visualization of the electron probability distribution of a hydrogen atom, (2) visualization and simulation of particle based fluid dynamic model using smoothed particle hydrodynamics. These simulations were developed in the context of the Microscopic and Subatomic Visualization (MASAV) project as a demonstration of the capabilities of the GPU to create realistic interactive physical simulators for scientific education. / Computer Graphics