UMD Theses and Dissertations

Permanent URI for this collectionhttp://hdl.handle.net/1903/3

New submissions to the thesis/dissertation collections are added automatically as they are received from the Graduate School. Currently, the Graduate School deposits all theses and dissertations from a given semester after the official graduation date. This means that there may be up to a 4 month delay in the appearance of a given thesis/dissertation in DRUM.

More information is available at Theses and Dissertations at University of Maryland Libraries.

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    Near-field microwave microscopy and multivariate analysis of XRD data
    (2011) Long, Christian; Takeuchi, Ichiro; Physics; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    The combinatorial approach to materials research is based on the synthesis of hundreds or thousands of related materials in a single experiment. The popularity of this approach has created a demand for new tools to rapidly characterize these materials libraries and new techniques to analyze the resulting data. The research presented here is intended to make a contribution towards meeting this demand, and thereby advance the pace of materials research. The first part of the dissertation discusses the development of a materials characterization tool called a near field microwave microscope (NFMM). We focus on one particular NFMM topology, the open ended coaxial resonator. The traditional application of this NFMM topology is the characterization of the dielectric properties of materials at GHz frequencies. With the goal of expanding the capabilities of the NFMM beyond this role, we explore two non-traditional modes of operation. The first mode is scanning ferromagnetic resonance spectroscopy. Using this technique, we map the magnetostatic spin wave modes of a single crystal gallium doped yttrium iron garnet disk. The second mode of operation entails combining near field microscopy with scanning tunneling microscopy (STM). Operating in this mode, we show that the NFMM is capable of obtaining atomic resolution images by coupling microwaves through an atomic scale tunnel junction. The second part of the dissertation discusses the analysis of X-Ray Diffraction (XRD) data from combinatorial libraries. We focus on two techniques that are designed to simultaneously analyze all of the XRD spectra from a given experiment, providing a faster method than the traditional one-at-a-time approach. First, we discuss agglomerative hierarchical cluster analysis, which is used to identify regions of composition space that have similar crystal structures. Second, we discuss non-negative matrix factorization (NMF). NFM is used to decompose many experimental diffraction patterns into a smaller number of constituent patterns; ideally, these constituent patterns represent the unique crystal structures present in the samples. Compared to hierarchical clustering, NMF has the advantage of identifying multi-phase regions within the composition space. These techniques are also applicable to other types of spectral data, such as FTIR, Raman spectroscopy, XPS, and mass spectrometry.
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    HUMAN APPEARANCE MODELING IN VISUAL SURVEILLANCE
    (2007-08-07) Yu, Yang; Chellapa, Rama; Electrical Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    We present an appearance model for establishing correspondence between tracks of people which may be taken at different places, at different times or across different cameras. Illumination insensitive color features, i.e., RGB rank feature and brightness-color feature are used. Path-length feature is added for structural information and invariance to motion and pose. The appearance model is constructed by kernel density estimation. Kullback-Leibler distance measures the similarity between the models. To further exploit the information in video sequence, key frame selection method and online hierarchical clustering algorithm are proposed to construct appearance model from video. Key frame selection use the frames with large information gain to represent the appearance model. Online hierarchical clustering algorithm condense the model into a few clusters in the framework of our appearance model. Experimental results demonstrate the important role of the path-length feature in the appearance model and the effectiveness of the proposed appearance model and matching method.