Simulation methods

This thesis describes the development of the hardware-in-the-loop simulation for FAU Autonomous Underwater Vehicles. The development was based on the existing simulation platform. For more efficiency and flexibility, this simulation package was ported to Linux. The hardware-in-the-loop simulation enables developers to connect the vehicle directly to a remote simulator. This kind of simulation is used to test the actual software components embedded in the vehicle system. The simulation package was enhanced by the addition of a 3D viewer. This thesis describes the whole development process, from feasibility study and implementation to qualification phases. This viewer is platform independent and designed to be connected to the simulator. It renders the AUV moving in a virtual environment. This tool can be used during all development steps, from tuning phases to post-mission analysis.

Classical trajectory molecular dynamics methods are used to investigate open ended free standing single wall carbon nanotubes ("SWT"). Total energy calculations performed using classical three-body interatomic potentials with periodic boundary conditions along the tube axis, showed that the minimum strain energy varied as 1/$R\sp2$ relative to an unstrained graphite sheet. We discuss the development of a parallel code to simulate short-ranged empirical potentials such as those of Stillinger and Weber, Tersoff, and Tersoff-Brenner. We then use the Tersoff and Tersoff-Brenner potentials to examine SWT and the tube response to axial stretching and compression. Data collected are used to calculate Young's modulus for the tubes and to develop a simple formula that approximates Young's modulus over a range of tube radii. The investigation of the free standing SWT leads to a suggestion for the possible mechanism responsible for holding the tubes open during the growth process.

Warehousing System is a complex problem, requiring simultaneous consideration of a large number of intricately related issues. In this research author focuses on the computerization opportunities that are unique in maintaining smooth storage and retrieval operations and recouping a controlled inventory status of a warehouse system. The main objective in this research is to define how layout decisions can both depend on warehouse's operations and effect inventory control decisions of a warehouse system. Author had defined, designed and implemented a simulated warehousing system using SIMAN. In particular, author uses simulation modeling as an approach to analyze layout design and operations of a warehouse system. Also, author had developed a database management systems software application using dBase IV. This relational database is used to dynamically forecast inventory level. A case study is used as a test bed to verify and validate the work done.

Underwater systems behavior prediction has become an important success factor in the design and implementation of marine systems. Most marine systems involve cables for mooring, deployment, recovery, or towing; however, estimating the response of these systems is difficult because of their non-linear behavior. Thus, numerical models are used to simulate submerged cabled systems. At FAU, many mission specific cable simulations have been developed, but no single, all encompassing software package exists. This thesis develops a Windows(c) based software package to quickly and easily create FEA models of underwater cabled systems and simulate their response. The model is based on a discrete finite element analysis using linear elements. The software provides fully integrated and interactive Graphical User Interfaces with a 3-dimensional graphical display of the model, and integrates adapted data analysis and visualization tools. The software provides an easy and efficient way to simulate an underwater system involving cables.

In this work, we investigate input-to-state stability (ISS) and other related stability properties for control systems with time-delays. To overcome the complexity caused by the presence of the delays, we adopt a Razumikhin approach. The underlying idea of this approach is to treat the delayed variables as system uncertainties. The advantage of this approach is that one works in the more familiar territory of stability analysis for delay-free systems in the context of ISS instead of carrying out stability analysis on systems of functional differential equations. Our first step is to provide criteria on ISS and input-to-input stability properties based on the Razumikhin approach. We then turn our attention to large-scale interconnected systems. It has been well recognized that the small-gain theory is a powerful tool for stability analysis of interconnected systems. Using the Razumikhin approach, we develop small-gain theorems for interconnected systems consisting of two or more subs ystems with time-delays present either in the interconnection channels or within the subsystems themselves. As an interesting application, we apply our results to an existing model for hematopoesis, a blood cell production process,and improve the previous results derived by linear methods. Another important stability notion in the framework of ISS is the integral ISS (iISS) property. This is a weaker property than ISS, so it supplies to a larger class of systems. As in the case of ISS, we provide Razumikhin criteria on iISS for systems with delays. An example is presented to illustrate that though very useful in practice, the Razumikhin approach only provides sufficient conditions, not equivalent conditions. Finally, we address stability of time-varying systems with delays in the framework of ISS.

When interpreting how an animal "learns" discrimination tasks, strain capabilities must be considered, and it should be shown that they comprehend the task in a manner consistent with the given interpretation. A novel visual-discrimination (VD) task for relative-size-relations was used to examine visual cue use in C57BL/6J mice, which are shown to have biologically good vision and neurologically intact memory for VD tasks. Results suggest C57BL/6J strain may not be fully capable of relative cue-size associations or even object recognition-based on a water maze VD task. This is in contrast to previous studies suggesting this mice strain is quite strong in visual skills and on VD tasks. Additionally, cue size and/or cue-pairings do appear to influence specific directional preferences or stereotyped behaviors as trainings continued, and these strategies shifted during novel probes. Future studies should assess how mice discriminate between objects and test rat's capabilities on this task.