Thesis (M. Phil.)--University of Hong Kong, 2010. / Includes bibliographical references (p. 67-[70]). Also available in print.

Thesis (Ph. D.)--University of Missouri-Columbia, 2000. / Typescript. Vita. Includes bibliographical references (leaves 133-147). Also available on the Internet.

The last few decades have witnessed what is commonly known as an "information explosion". The advent of the Internet has enabled the sharing of large amounts of information between users in almost every part of the world. This had led to increased bandwidth and storage requirements. These requirements necessitate the development of new techniques to optimize the utilization of existing bandwidth and to minimize storage requirements. In emerging areas of real-time multimedia applications, researchers have successfully developed new approaches, employing techniques such as transform coding, prediction, vector quantization, etc, to efficiently represent and consequently compress data, especially image data. Recently, multiple transform domain representation techniques have been reported which successfully compress one and multidimensional signals. In this thesis, a novel and efficient codec using multiple transform domain representation in conjunction with split vector quantization is presented, which provides superior coding performance for images. An adaptive scheme that further enhances the representation accuracy of the above codec is also described. Results of simulations of the proposed technique are presented that confirm the improved performance of the codec.

Thesis (Ph. D.)--University of California, Riverside, 2009. / Includes abstract. Title from first page of PDF file (viewed January 27, 2010). Includes bibliographical references (p. 99-105). Issued in print and online. Available via ProQuest Digital Dissertations.

The Blind Image Deconvolution/Deblurring (BID) problem was realised in the early 1960s but it still remains a challenging task for the image processing research community to find an efficient, reliable and most importantly a diversely applicable deblurring scheme. The main challenge arises from little or no prior information about the image or the blurring process as well as the lack of optimal restoration filters to reduce or completely eliminate the blurring effect. Moreover, restoration can be marred by the two common side effects of deblurring; namely the noise amplification and ringing artefacts that arise in the deblurred image due to an unrealizable or imperfect restoration filter. Also, developing a scheme that can process different types of blur, especially for real images, is yet to be realized to a satisfactory level. This research is focused on the development of blind restoration schemes for real life blurred images. The primary objective is to design a BID scheme that is robust in term of Point Spread Function (PSF) estimation, efficient in terms of restoration speed, and effective in terms of restoration quality. A desired scheme will require a deblurring measure to act as a feedback of quality regarding the deblurred image and lead the estimation of the blurring PSF. The blurred image and the estimated PSF can then be passed on to any classical restoration filter for deblurring. The deblurring measures presented in this research include blind non-Gaussianity measures as well as blind Image Quality Measures (IQMs). These measures are blind in the sense that they are able to gauge the quality of an image directly from it without the need to reference a high quality image. The non-Gaussianity measures include spatial and spectral kurtosis measures; while the image quality analysers include the Blind/Reference-less Image Spatial QUality Evaluator (BRISQUE), Natural Image Quality Evaluator (NIQE) index and Reblurring based Peak Signal to Noise Ratio (RPSNR) measure. BRISQUE, NIQE and spectral kurtosis, are introduced for the first time as deblurring measures for BID. RPSNR is a novel full reference yet blind IQM designed and used in this research work. Experiments were conducted on different image datasets and real life blurred images. Optimization of the BID schemes has been achieved using a gradient descent based scheme and a Genetic Algorithm (GA). Quantitative results based on full-reference and non-reference IQMs, present BRISQUE as a robust and computationally efficient blind feedback quality measure. Also, parametric and arbitrarily shaped (non-parametric or generic) PSFs were treated for the blind deconvolution of images. The parametric forms of PSF include uniform Gaussian, motion and out-of-focus blur. The arbitrarily shaped PSFs comprise blurs that have a much more complex blur shape which cannot be easily modelled in the parametric form. A novel scheme for arbitrarily shaped PSF estimation and blind deblurring has been designed, implemented and tested on artificial and real life blurred images. The scheme provides a unified base for the estimation of both parametric and arbitrarily shaped PSFs with the BRISQUE quality measure in conjunction with a GA. Full-reference and non-reference IQMs have been utilised to gauge the quality of deblurred images for the BID schemes. In the real BID case, only non-reference IQMs can be employed due to the unavailability of the reference high quality image. Quantitative results of these images depict the restoration ability of the BID scheme. The significance of the research work lies in the BID scheme‘s ability to handle parametric and arbitrarily shaped PSFs using a single algorithm, for single-shot blurred images, with enhanced optimization through the gradient descent scheme and GA in conjunction with multiple feedback IQMs.

No description available.

Le but de ce travail de thèse est l’étude de la dynamique de sphères de grande taille dans un écoulement fortement turbulent. Pour ce faire, nous avons développé une nouvelle technique optique permettant de suivre la dynamique à 6 dimensions – position et orientation absolues – de plusieurs particules dans un écoulement complexe. Bien que la taille des particules soit comparable à l’échelle intégrale de l’écoulement, nous trouvons que sa dynamique de rotation et de translation est intermittente. De plus, nous observons que la translation et la rotation sont reliées par la force de Magnus. La répartition statistique de l’accélération n’est pas gaussienne et l’échange d’énergie avec le fluide est gouverné par la théorie mathématique des grandes déviations. Nous trouvons que le diamètre influence fortement la manière dont la particule explore l’écoulement. Nous avons ensuite appliqué le suivi de position et d’orientation à une particule instrumentée. Ce système mesure en permanence l’accélération lagrangienne qu’il subit via un accéléromètre embarqué et émet l’information à travers une électronique radio fréquence. L’orientation absolue est nécessaire pour exprimer les signaux de l’accéléromètre et ceux du suivi optique dans un repère commun; cela nous permet de comparer rigoureusement les mesures issues de ces deux techniques indépendantes. À partir de ces résultats nous avons développé des méthodes pour inférer des propriétés de l’écoulement à partir des signaux d’accélération de la particule instrumentée. / The aim of this dissertation is to gain a better understanding of the Lagrangian dynamics of solid large spheres in a complex turbulent environment. Therefore, a novel measurement technique to optically track the 6–dimensional dynamics – position and absolute orientation – of large spheres advected by a complex flow is developed. Although the sphere’s diameter is comparable to the integral length of the underlying flow, we find intermittency for both the translation and the rotation. Moreover, rotation and translation couple in agreement with a lift force. Apart from the fact that the acceleration statistics are not gaussian, and the exchange of energy between the particle and the carrier flow falls into the mathematical theory of large deviations. Additionally, we find that the particle diameter has a surprisingly strong influence on how a particle samples the flow. The 6D–tracking technique is then applied to an instrumented particle, which embarks a 3D–accelerometer and a radio-transmission system to constantly emit the felt Lagrangian acceleration as it is advected in the flow. Measuring the particle’s absolute orientation is a crucial step here to project the acceleration measured by the particle into the laboratory reference frame and enables us to compare the forces obtained by the two independent measurements. Based thereon methods for interpreting the acceleration signals of the instrumented particle are developed and tested.

This thesis investigates the potential of fractal dimension (FD) as a tool for enhancing airborne magnetic data. More specifically, this thesis investigates the potential of FD-based texture transform images as tools for aiding in the interpretation of airborne magnetic data. A series of different methods of estimating FD are investigated, specifically: • geometric methods (1D and 2D variation methods and 1D line divider method); • stochastic methods (1D and 2D Hurst methods and 1D and 2D semi-variogram methods), and; • spectral methods (1D and 2D wavelet methods and 1D and 2D Gabor methods). All of these methods are able to differentiate between varying theoretical FD in synthetic profiles. Moreover, these methods are able to differentiate between theoretical FDs when applied to entire profiles or in a moving window along the profile. Generally, the accuracy of the estimated FD improves when window size is increased. Similarly, the standard deviation of estimated FD decreases as window size increases. This result implied that the use of moving window FD estimates will require a trade off between the quality of the FD estimates and the need to use small windows to allow better spatial resolution. Application of the FD estimation methods to synthetic datasets containing simple ramps, ridges and point anomalies demonstrates that all of the 2D methods and most of the 1D methods are able to detect and enhance these features in the presence of up to 20% Gaussian noise. In contrast, the 1D Hurst and line divider methods can not clearly detect these features in as little as 10% Gaussian noise. Consequently, it is concluded that the 1D Hurst and line divider methods are inappropriate for enhancing airborne magnetic data. The application of these methods to simple synthetic airborne magnetic datasets highlights the methods’ sensitivity to very small variations in the data. All of the methods responded strongly to field lines some distance from the causative magnetic bodies. This effect was eliminated through the use of a variety of tolerances that essentially required a minimum level of difference between data points in order for FD to be calculated. Whilst this use of tolerances was required for synthetic datasets, its use was not required for noise corrupted versions of the synthetic magnetic data. The results from applying the FD estimation techniques to the synthetic airborne magnetic data suggested that these methods are more effective when applied to data from the pole. Whilst all of the methods were able to enhance the magnetic anomalies both at the pole and in the Southern hemisphere, the responses of the FD estimation techniques were notably simpler for the polar data. With the exception of the 1D Hurst and line divider methods, all of the methods were also able to enhance the synthetic magnetic data in the presence of 10% Gaussian noise. Application of the FD estimation methods to an airborne magnetic dataset from the Merlinleigh Sub-basin in Western Australia demonstrated their ability to enhance subtle structural features in relatively smooth airborne magnetic data. Moreover, the FD-based enhancements were able to enhance some features of this dataset better than any of the conventional enhancements considered (i.e. an analytic signal, vertical and total horizontal derivatives, and automatic gain control). Most of the FD estimation techniques enhanced similar features to each other. However, the 2D methods generally produced clearer results than their associated 1D methods. In contrast to this result, application of the FD-based enhancements to more variable airborne magnetic data from the Tanami region in the Northern Territory demonstrated that these methods are not as well suited to this style of data. The main conclusion from this work is that FD-based enhancement of relatively smooth airborne magnetic data can provide valuable input into an interpretation process. This suggests that these methods are particularly useful for aiding in the interpretation of airborne magnetic data from regions such as sedimentary basins where the distribution of magnetic sources is relatively smooth and simple. / http://proxy.library.adelaide.edu.au/login?url= http://library.adelaide.edu.au/cgi-bin/Pwebrecon.cgi?BBID=1339560 / Thesis (Ph.D.) - University of Adelaide, Australian School of Petroleum, 2008

Une nouvelle génération de spectromètres imageurs émerge dans le domaine de l'exploration spatiale par l'ajout d'une dimension supplémentaire de mesure, la dimension angulaire. L'imagerie spectroscopique multi-angulaire est conçue pour fournir une caractérisation plus précise des matériaux planétaires et permet une meilleure séparation des signaux provenant de l'atmosphère et la surface. Le capteur Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) à bord de la sonde Mars Reconnaissance Orbiter est une caméra hyperspectrale qui fonctionne systématiquement dans le mode multi-angulaire depuis l'orbite. Néanmoins, les images multi-angulaires hyperspectrales posent certains problèmes de manipulation, de visualisation et d'analyse en raison de leur taille et de leur complexité. Dans ce cadre, cette thèse propose des algorithmes statistiques et physiques pour analyser les images acquises par l'instrument CRISM de manière efficace et robuste. Premièrement, je propose une chaîne de post-traitement visant à améliorer la qualité radiométrique des données CRISM et à générer des produits améliorés, ces dernières données étant conçues pour permettre une analyse fine de la planète Mars. Deuxièmement, je m'intéresse à la correction atmosphérique des images CRISM en exploitant les capacités multi-angulaires de cet instrument. Un algorithme innovant, à base physique est mis en oeuvre pour compenser les effets atmosphériques afin d'estimer la reflectance de surface. Cette approche est particulièrement utilisée dans cette thèse pour déduire les propriétés photométriques des matériaux qui coexistent dans un site spécifique de Mars, le cratère de Gusev. Troisièmement, j'effectue une comparaison d'une sélection des meilleurs techniques existantes, visant à réaliser une déconvolution spectrale des données acquises par l'instrument CRISM. Ces techniques statistiques se sont avérées utiles lors de l'analyse d'images hyperspectrales de manière non supervisé, c'est a dire, sans aucun a priori sur la scène. Une stratégie originale est proposée pour discriminer les techniques les plus appropriées pour l'exploration de Mars, à partir de données indépendantes provenant d'autres capteurs d'imagerie haute résolution afin de construire une vérité de terrain. / New generation of imaging spectrometers are emerging in the field of space exploration by adding an additional view of measurement, the angular dimension. Multi-angle imaging spectroscopy is conceived to provide a more accurate characterization of planetary materials and a higher success in separating the signals coming from the atmosphere and the surface. The Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) aboard the Mars Reconnaissance Orbiter is a hyperspectral camera that operates systematically in multi-angle mode from space. Nonetheless, multi-angle hyperspectral images are related to problems of manipulation, visualization and analysis because of their size and complexity. In this framework, this PhD thesis proposes robust statistical and physical algorithms to analyze images acquired by the CRISM instrument in an efficient manner. First, I propose a tailor-made data pipeline aimed at improving the radiometric quality of CRISM data and generating advanced products, the latter data being devised to perform fine analysis of the planet Mars. Second, I address the atmospheric correction of CRISM imagery by exploiting the multi-angle capabilities of this instrument. An innovative physically-based algorithm compensating for atmospheric effects is put forward in order to retrieve surface reflectance. This approach is particularly used in this thesis to infer the photometric properties of the materials coexisting in a specific site of Mars, the Gusev crater. Third, I perform an intercomparison of a selection of state-of-the-art techniques aimed at performing spectral unmixing of hyperspectral data acquired by the CRISM instrument. These statistical techniques are proved to be useful when analyzing hyperspectral images in an unsupervised manner, that is, without any a priori on the scene. An original strategy is proposed to discriminate the most suitable techniques for the exploration of Mars based on ground truth data built from independent high resolution imagery.