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With advanced subsonic transports and military aircraft operating in the transonic regime, it is becoming important to determine the effects of the coupling between aerodynamic loads and elastic forces. Since aeroelastic effects can contribute significantly to the design of these aircraft, there is a strong need in the aerospace industry to predict these aero-structure interactions computationally. To perform static aeroelastic analysis in the transonic regime, high fidelity computational fluid dynamics (CFD) analysis tools must be used in conjunction with high fidelity computational structural dynamics (CSD)analysis tools due to the nonlinear behavior of the aerodynamics in the transonic regime. There is also a need to be able to use a wide variety of CFD and CSD tools to predict these aeroelastic effects in the transonic regime. Because source codes are not always available, it is necessary to couple the CFD and CSD codes without alteration of the source codes. In this study, an aeroelastic coupling procedure is developed which will perform static aeroelastic analysis using any CFD and CSD code with little code integration. The aeroelastic coupling procedure is demonstrated on an F/A-18 Stabilator using NASTD (an in-house McDonnell Douglas CFD code)and NASTRAN. In addition, the Aeroelastic Research Wing (ARW-2) is used for demonstration of the aeroelastic coupling procedure by using ENSAERO (NASA Ames Research Center CFD code) and a finite element wing-box code (developed as a part of this research). The results obtained from the present study are compared with those available from an experimental study conducted at NASA Langley Research Center and a study conducted at NASA Ames Research Center using ENSAERO and modal superposition. The results compare well with experimental data. In addition, parallel computing power is used to investigate parallel static aeroelastic analysis because obtaining an aeroelastic solution using CFD/CSD methods is computationally intensive. A parallel finite element wing-box code is developed and coupled with an existing parallel Euler code to perform static aeroelastic analysis. A typical wing-body configuration is used to investigate the applicability of parallel computing to this analysis. Performance of the parallel aeroelastic analysis is shown to be poor; however with advances being made in the arena of parallel computing, there is definitely a need to continue research in this area. / Ph. D.

Integrated circuits have traveled a long way from being a general purpose microprocessor to an application specific circuit. It has become an integral part of the modern era of technology that we live in. As the applications and their complexities are increasing rapidly every day, so are the sizes of these circuits. With the increase in the design size, the associated testing effort to verify these designs is also increased. The goal of this thesis is to leverage some of the static analysis techniques to reduce the effort of testing and verification at the register transfer level. Studying a design at register transfer level gives exposure to the relational information for the design which is inaccessible at the structural level. In this thesis, we present a way to generate a Data Dependency Graph and a Control Flow Graph out of a register transfer level description of a circuit description. Next, the generated graphs are used to perform relation mining to improve the test generation process in terms of speed, branch coverage and number of test vectors generated. The generated control flow graph gives valuable information about the flow of information through the circuit design. We are using this information to create a framework to improve the branch reachability analysis mainly in terms of the speed. We show the efficiency of our methods by running them through a suite of ITC'99 benchmark circuits. / Master of Science

In this dissertation, I present a set of novel constraint-based thread-modular abstract-interpretation techniques for static analysis of concurrent programs. Specifically, I integrate a lightweight constraint solver into a thread-modular abstract interpreter to reason about inter-thread interference more accurately. Then, I show how to extend the new analyzer from programs running on sequentially consistent memory to programs running on weak memory. Finally, I show how to perform incremental abstract interpretation, with and without the previously mentioned constraint solver, by analyzing only regions of the program impacted by a program modification. I also demonstrate, through experiments, that these new constraint-based static analyzers are significantly more accurate than prior abstract interpretation-based static analyzers, with lower runtime overhead, and that the incremental technique can drastically reduce runtime overhead in the presence of small program modifications. / Ph. D.

This research investigates the possibility of controlling a simple biped having two degrees of freedom only. The biped robot walked on large feet. Having large feet enabled the robot to stand on one leg stably. At any time, the robotà ­s center of gravity remained above the area covered by one of the feet. Two servos actuated the two degrees of freedom tilting the robot to the side or moving the legs forward and backward. The biped moved by alternately tilting and striding. Turns were produced by dragging the feet along the ground. As the feet dragged, the friction generated under the feet created a turning moment that rotated the robot. Thus, the robot was able to step and turn on a flat surface. A control algorithm was developed to attempt trajectory tracking with the biped. Trajectories along a surface can be defined in terms of linear and angular velocities. In this research, it was assumed that a high level controller had transformed a desired trajectory into discrete steps of linear and angular velocities. Motion tests showed how various settings of the servos affected the step length and turning angle of the robot. To produce the desired velocities, a program was created to select the servo commands and set the speed parameters. This program applied knowledge of the expected step length and turning angle and performed feedforward control of the velocities. This investigation identified a trajectory tracking scheme that could be used in an observer feedback scenario to achieve accurate control. / Master of Science