Thesis (Ph. D.)--University of California, Riverside, 2009. / Includes abstract. Available via ProQuest Digital Dissertations. Title from first page of PDF file (viewed March 12, 2010). Includes bibliographical references (p. 100-106). Also issued in print.

Thesis (M.S.)--East Carolina University, 2009. / Presented to the faculty of the Department of Physics. Advisor: Michael Dingfelder. Title from PDF t.p. (viewed Apr. 23, 2010). Includes bibliographical references.

Thesis (Ph. D.)--University of Washington, 2001. / Vita. Includes bibliographical references (p. 100-105).

Thesis (Ph.D)--Aerospace Engineering, Georgia Institute of Technology, 2009. / Committee Chair: Dr. Dimitri N. Mavris; Committee Member: Dr. Brian J. German; Committee Member: Dr. Daniel P. Schrage; Committee Member: Dr. Frederic Villeneuve; Committee Member: Dr. Michelle R. Kirby; Committee Member: Ms. Antje Lembcke. Part of the SMARTech Electronic Thesis and Dissertation Collection.

With advances in micro-electronic complexity and fabrication, sophisticated algorithms for source localisation and tracking can now be deployed in cost sensitive appliances for both consumer and commercial markets. As a result, such algorithms are becoming ubiquitous elements of contemporary communication, robotics and surveillance systems. Two of the main requirements of acoustic localisation and tracking algorithms are robustness to acoustic disturbances (to maximise localisation accuracy), and low computational complexity (to minimise power-dissipation and cost of hardware components). The research presented in this thesis covers both advances in robustness and in computational complexity for acoustic source localisation and tracking algorithms. This thesis also presents advances in modelling of sound propagation in indoor environments; a key to the development and evaluation of acoustic localisation and tracking algorithms. As an advance in the field of tracking, this thesis also presents a new method for tracking human speakers in which the problem of the discontinuous nature of human speech is addressed using a new state-space filter based algorithm which incorporates a voice activity detector. The algorithm is shown to achieve superior tracking performance compared to traditional approaches. Furthermore, the algorithm is implemented in a real-time system using a method which yields a low computational complexity. Additionally, a new method is presented for optimising the parameters for the dynamics model used in a state-space filter. The method features an evolution strategy optimisation algorithm to identify the optimum dynamics’ model parameters. Results show that the algorithm is capable of real-time online identification of optimum parameters for different types of dynamics models without access to ground-truth data. Finally, two new localisation algorithms are developed and compared to older well established methods. In this context an analytic analysis of noise and room reverberation is conducted, considering its influence on the performance of localisation algorithms. The algorithms are implemented in a real-time system and are evaluated with respect to robustness and computational complexity. Results show that the new algorithms outperform their older counterparts, both with regards to computational complexity, and robustness to reverberation and background noise. The field of acoustic modelling is advanced in a new method for predicting the energy decay in impulse responses simulated using the image source method. The new method is applied to the problem of designing synthetic rooms with a defined reverberation time, and is compared to several well established methods for reverberation time prediction. This comparison reveals that the new method is the most accurate.

Not available / text

published_or_final_version / abstract / toc / Statistics and Actuarial Science / Master / Master of Philosophy

published_or_final_version / abstract / toc / Statistics and Actuarial Science / Master / Master of Philosophy

No description available.

In the research reported here, a two-dimensional Ising-type model was used to study the tracer diffusion coefficients of oxygen ions in YBa2Cu307-x (YBCO) for various values of oxygen concentration and temperature. The first chapter provides a brief introduction to the problem considered in this thesis. This is followed by a short review of superconductivity, with particular reference to the experimental and theoretical aspects of high-temperature superconductivity and its applications. The structure of YBCO is then presented, with emphasis on its behaviour for various values of oxygen concentration and temperature. The model used in the simulations and the results for tracer diffusion coefficients and related quantities obtained by previous workers concludes the chapter. Results from other theoretical models are also included. In the second chapter a theoretical background for the Monte Carlo simulations employed in the present investigation is discussed. This chapter includes a short account on how these numerical methods evolved. The Monte Carlo approach to numerical evaluation of integrals is described. Then the idea of Markov sampling for obtaining members of the canonical ensemble is presented, and the Metropolis algorithm is described. In particular, convergence and the detailed balance condition are discussed. The consequence of starting from an arbitrary initial state when evaluating an observable of interest, and the effect on the reliability of the values of observables, are analysed. The chapter closes with a discussion of Monte Carlo methods applied to a lattice model in statistical mechanics. In chapter three results for the oxygen distribution produced by the diffusion of oxygen in YBCO are presented. These results were obtained from Monte Carlo simulations of the anti-symmetric nextto- nearest neighbour Ising (ASYNNNI) model. In addition to the uniform equilibrium distributions obtained by previous workers, it is found that this model also possesses nonuniform equilibrium oxygen distributions. The nonuniform distributions show a rich phase structure, and some preliminary results for this structure are presented. Results for the tracer diffusion coefficients in the nonuniform equilibrium distributions are given in the last chapter. Both local and global tracer diffusion coefficients for nonuniform equilibrium configurations are presented. Results obtained for uniform and nonuniform equilibrium configurations are compared. / Thesis (M.Sc.)-University of Natal, Pietermaritzburg, 1998.