In this work, nonlinear acoustic information is combined with traditional linear acoustic information in order to produce a noise-robust set of features for speech recognition. Classical acoustic modeling techniques for speech recognition have relied on a standard assumption of linear acoustics where signal processing is primarily performed in the signal's frequency domain. While these conventional techniques have demonstrated good performance under controlled conditions, the performance of these systems suffers significant degradations when the acoustic data is contaminated with previously unseen noise. The objective of this thesis was to determine whether nonlinear dynamic invariants are able to boost speech recognition performance when combined with traditional acoustic features. Several sets of experiments are used to evaluate both clean and noisy speech data. The invariants resulted in a maximum relative increase of 11.1% for the clean evaluation set. However, an average relative decrease of 7.6% was observed for the noise-contaminated evaluation sets. The fact that recognition performance decreased with the use of dynamic invariants suggests that additional research is required for robust filtering of phase spaces constructed from noisy time series.

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This thesis is primarily concerned with the development and coding of a Levy-type spectral plate element to analyze the harmonic response of simply supported plates in the mid to high frequency range. The development includes the governing PDE, displacement field, shape function, and dynamic stiffness matrix. A two DOF spectral Love bar element and both a four DOF spectral Euler-Bernoulli and a four DOF spectral Timoshenko beam element are also developed to gain insight into the performance of spectral elements. A cantilever beam example is used to show how incorporating eigenfunctions for the dynamic governing PDE into the displacement field enables spectral beam elements to represent the structural dynamics exactly. A simply supported curved beam example is used to show that spectral beam elements can converge the effects of curved geometry with up to a 50% reduction in the number of elements when compared to conventional FE. The curved beam example is also used to show that the rotatory inertia and shear deformation, from Timoshenko's beam theory, can result in up to a 28% shift in natural frequency over the first three bending modes. Finally, a simply supported Levy-plate model is used to show that the spectral Levy-type plate element converges the dynamic solution with up to three orders of magnitude fewer DOF then the conventional FE plate formulation. A simply-supported plate example problem is used to illustrate how the coefficients of the Fourier series expansion can be used as edge DOF for the spectral Levy-plate element. The Levy-plate element development gives insight to future research developing a general spectral plate element. / Master of Science

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The goal of this thesis is to develop a dynamic stability and control module that can be used in the concept exploration phase of design. The purpose of the module is to determine the hydrodynamic coefficients/derivatives and stability characteristics of a given design. Two tools, GEORGE and CEBAXI and LA_57, were used to model a submarine, calculate its hydrodynamic coefficients, and determine its stability in the horizontal and vertical plane. GEORGE was developed and used heavily at Naval Coastal Systems Laboratory (NSWCPC) in Panama City, FL and the CEBAXI and LA_57 program was developed partially at University of California State at Long Beach and at the Carderock Division of the Naval Surface Warfare Center (NSWCCD) and is in use at NSWCCD in Bethesda, MD. Both programs require the hull offsets and geometry of the control surfaces as input. The hull offsets were determined by assuming an idealistic teardrop shape and a method for sizing control surfaces was developed by using previous designs to determine sizing trends. ModelCenter software was used to integrate the methods to determine the offsets and control surface geometry with the stability programs. A design of experiments was performed to determine the influence of various input variables on the stability indices and response surface models were created. The response surfaces were implemented into a Total Ship Systems Engineering optimization process used in the senior ship design course at Virginia Tech. / Master of Science

In robotic systems, reduction of inertia is a key concern. One way to reduce the system inertia is to replace counterbalance masses with an equilibrator, which is a force element like a spring. Although there has been much research on equilibrated mechanisms, there has not much research on the control of these mechanisms. This thesis explores the PID control of equilibrated systems, and compares the results to the PID control of a common method of equilibration, the mass counterweight. Through modeling, simulating, and testing of the two systems, the equilibrated system response was found to be superior to the mass counterweight in measures of settling time and peak overshoot. / Master of Science