Thesis (Ph. D.)--University of Oregon, 2002. / Typescript. Includes vita and abstract. Includes bibliographical references (leaves 118-120). Also available for download via the World Wide Web; free to University of Oregon users.

Thesis (M. S.)--Mechanical Engineering, Georgia Institute of Technology, 2010. / Committee Co-Chair: Johnson, Eric; Committee Co-Chair: Lipkin, Harvey; Committee Member: Sadegh, Nader. Part of the SMARTech Electronic Thesis and Dissertation Collection.

Thesis (M. Sc.)--York University, 2001. Graduate Programme in Computer Science. / Typescript. Includes bibliographical references (leaves 92-95). Also available on the Internet. MODE OF ACCESS via web browser by entering the following URL: http://wwwlib.umi.com/cr/yorku/fullcit?pMQ67751.

Usage of simulation models is an essential part in many modern engineering disci- plines. Computer models of complex physical systems can be used to expedite the design of control systems and reduce the number of physical tests. Model valida- tion tries to answer the question if the model is a good enough representation of the physical system. This thesis describes techniques to visualize multi-dimensional validation results and the search for an automated validation process. The work is focused on a simulation model of the Primary Environmental Control System of Gripen E, but can be applied on validation results from other simulation models. The result from the thesis can be divided into three major components, static validation, dynamic validation and model coverage. To present the results from the static validation different multi-dimensional visualization techniques are in- vestigated and evaluated. The visualizations are compared to each other and to properly depict the static validation status of the model, a combination of visual- izations are required. Two methods for validation of the dynamic performance of the model are examined. The first method uses the singular values of an error model estimated from the residual. We show that the singular values of the error model relay important information about the model’s quality but interpreting the result is a considerable challenge. The second method aims to automate a visual inspection procedure where interesting quantities are automatically computed. Coverage is a descriptor of how much of the applicable operating conditions that has been validated. Two coverage metrics, volumetric coverage and nearest neigh- bour coverage, are examined and the strengths and weaknesses of these metrics are presented. The nearest neighbour coverage metric is further developed to account for validation performance, resulting in a total static validation quantity.

Numerical modeling techniques commonly used to compute the response of soil and rock media under earthquake shaking are evaluated by analyzing the observations provided by instrumented borehole arrays. The NIED Kik-Net database in Japan is selected as the main source of borehole array data for this study. The stiffness of the site and the availability of high intensity motions are the primary factors considered towards the selection of appropriate Kik-Net borehole arrays for investigation. Overall, 13 instrumented vertical arrays are investigated using over 750 recorded ground motions characterized by low (less than 0.05 g) to high (greater than 0.3 g) recorded peak ground accelerations at the downhole sensor. Based on data from the selected borehole arrays, site response predictions using 1-D linear elastic (LE) analysis, equivalent linear (EQL) analysis, equivalent linear analysis with frequency-dependent soil properties (EQL-FD), and fully nonlinear analysis (NL) are compared with the borehole observations. Initially, the low intensity motions are used to evaluate common assumptions regarding 1-D site response analysis. First, we identify the borehole wavefield best simulating the actual boundary condition at depth by comparing the theoretical linear-elastic (LE) and observed responses. Then, we identify the best-fit small-strain damping profiles that can incorporate the additional in-situ attenuation mechanisms. Finally, we assess the validity of the one-dimensional modeling assumption. Our analyses indicate that the appropriate boundary condition for analysis of a borehole array depends on the depth of the borehole sensor and that, for most of the considered vertical arrays, the one-dimensional assumption reasonably simulates the actual wave propagation pattern. In the second part of this study, we evaluate the accuracy of the EQL, EQL-FD and NL site response methods by quantifying the misfit (i.e., residual) between the simulations and observations at different levels of shaking. The evaluation of the performance of the theoretical models is made both on a site-by-site basis and in an aggregated manner. Thereafter, the variability in the predicted response from the three site response methods is assessed. Comparisons with the observed responses indicate that the misfit of simulations can be significant at short periods and large strains. Moreover, all models seem to be characterized by the same level of variability irrespectively of the level of shaking. Finally, several procedures that can be used to improve the accuracy of the one-dimensional EQL, EQL-FD and NL site response analyses, are investigated. First, an attempt to take into account the shear strength of the soil materials at large shear strains is made. Additionally, several modifications to the EQL-FD approach are proposed. The proposed modifications are evaluated against recordings from the borehole arrays. Our analyses indicate that the accuracy of the theoretical models can be, partly, increased by incorporating the proposed modifications. / text

published_or_final_version / Electrical and Electronic Engineering / Master / Master of Philosophy

Traditional open interventions have been progressively replaced with minimally invasive techniques. Most notably, direct visual feedback is transitioned into indirect, image-based feedback, leading to the wide use of image-guided interventions (IGIs). One essential process of all IGIs is to align some 3D data with 2D images of patient through a procedure called 3D-2D registration during interventions to provide better guidance and richer information. When the 3D data is unavailable, a realistic 3D patient-speci_c model needs to be constructed from a few 2D images. The dominating methods that use only image intensity have narrow convergence range and are not robust to foreign objects presented in 2D images but not existed in 3D data. Feature-based methods partly addressed these problems, but most of them heavily rely on a set of \best" paired correspondences and requires clean image features. Moreover, the optimization procedures used in both kinds of methods are not e_cient. In this dissertation, two topics have been studied and novel algorithms proposed, namely, contour extraction from X-ray images and feature-based rigid/deformable 3D-2D registration. Inspired by biological and neuropsychological characteristics of primary visual cortex (V1), a contour detector is proposed for simultaneously extracting edges and lines in images. The synergy of V1 neurons is mimicked using phase congruency and tensor voting. Evaluations and comparisons showed that the proposed method outperformed several commonly used methods and the results are consistent with human perception. Moreover, the cumbersome \_ne-tuning" of parameter values is not always necessary in the proposed method. An extensible feature-based 3D-2D registration framework is proposed by rigorously formulating the registration as a probability density estimation problem and solving it via a generalized expectation maximization algorithm. It optimizes the transformation directly and treats correspondences as nuisance parameters. This is signi_cantly di_erent from almost all feature-based method in the literature that _rst single out a set of \best" correspondences and then estimate a transformation associated with it. This property makes the proposed algorithm not rely on paired correspondences and thus inherently robust to outliers. The framework can be adapted as a point-based method with the major advantages of 1) independency on paired correspondences, 2) accurate registration using a single image, and 3) robustness to the initialization and a large amount of outliers. Extended to a contour-based method, it di_ers from other contour-based methods mainly in that 1) it does not rely on correspondences and 2) it incorporates gradient information via a statistical model instead of a weighting function. Tuning into model-based deformable registration and surface reconstruction, our method solves the problem using the maximum penalized likelihood estimation. Unlike almost all other methods that handle the registration and deformation separately and optimized them sequentially, our method optimizes them simultaneously. The framework was evaluated in two example clinical applications and a simulation study for point-based, contour-based and surface reconstruction, respectively. Experiments showed its sub-degree and sub-millimeter registration accuracy and superiority to the state-of-the-art methods. It is expected that our algorithms, when thoroughly validated, can be used as valuable tools for image-guided interventions. / published_or_final_version / Orthopaedics and Traumatology / Doctoral / Doctor of Philosophy

Not available / text

M. Tech. Electrical Engineering. / This dissertation presents vision-based systems for monitoring model breakwater armour structures. These model breakwater armour structures are subjected to wave simulations in model halls. The goal of this research was to produce a system that is able to detect changes in the model breakwater armour structure. These changes are detected autonomously or semi-autonomously depending on the method being used. The proposed systems are intended to replace the current flicker technique method, which is subject to human error. This dissertation reviews common image processing methods for monitoring changes in three dimensions. This review refines the search to two techniques, namely the stereopsis and fiducial methods. Each method approaches the problem differently. The stereo method treats the entire structure as a holistic 2.5D volume and shows changes in this volume. In the fiducial method special fiducial targets are attached to key areas on the breakwater armour units. The targets are tracked to compute displacement vectors.

M. Tech. Electronic Engineering. / Discusses the main objective of this research to develop a robust image-based algorithm to detect and determine the orientation of small helipad using shape descriptors and associated pre-processing techniques.