Supervised and unsupervised segmentation of textured images by efficient multi-level pattern classification

This thesis proposes new, efficient methodologies for supervised and unsupervised image segmentation based on texture information. For the supervised case, a technique for pixel classification based on a multi-level strategy that iteratively refines the resulting segmentation is proposed. This strategy utilizes pattern recognition methods based on prototypes (determined by clustering algorithms) and support vector machines. In order to obtain the best performance, an algorithm for automatic parameter selection and methods to reduce the computational cost associated with the segmentation process are also included. For the unsupervised case, the previous methodology is adapted by means of an initial pattern discovery stage, which allows transforming the original unsupervised problem into a supervised one. Several sets of experiments considering a wide variety of images are carried out in order to validate the developed techniques.Esta tesis propone metodologías nuevas y eficientes para segmentar imágenes a partir de información de textura en entornos supervisados y no supervisados. Para el caso supervisado, se propone una técnica basada en una estrategia de clasificación de píxeles multinivel que refina la segmentación resultante de forma iterativa. Dicha estrategia utiliza métodos de reconocimiento de patrones basados en prototipos (determinados mediante algoritmos de agrupamiento) y máquinas de vectores de soporte. Con el objetivo de obtener el mejor rendimiento, se incluyen además un algoritmo para selección automática de parámetros y métodos para reducir el coste computacional asociado al proceso de segmentación. Para el caso no supervisado, se propone una adaptación de la metodología anterior mediante una etapa inicial de descubrimiento de patrones que permite transformar el problema no supervisado en supervisado. Las técnicas desarrolladas en esta tesis se validan mediante diversos experimentos considerando una gran variedad de imágenes

Spectral Variability in Naturally Weathered Rock Surfaces and Implications for Mars

Rock weathering products are important clues for understanding past environmental conditions on Mars. They can be identified using reflectance spectroscopy because the formation of new minerals and textures on a rock surface will change its spectral signature. Previous studies demonstrate that the spectral signature of coated rock surfaces can vary with viewing geometry (the angle between incident and emitted light); however, these photometric effects have not been extensively characterized for naturally weathered rocks. My goal in this study is to quantify how both weathering and viewing geometry affect visible to near-infrared (VNIR) reflectance spectra of a subset of naturally weathered igneous rocks. Improving our understanding of how weathering changes the spectral signature of terrestrial samples can be applied to Martian rocks to make inferences about their original compositions and the environmental conditions that formed any weathering products present. I compared weathered surface compositions and textures to their unweathered rock interiors using powder X-ray diffraction (XRD), petrographic analysis of thin sections, and scanning electron microscopy (SEM) with energy dispersive spectroscopy (EDS). Differences between the surfaces and interiors are primarily textural with minor compositional variations. Weathering rind mineralogy is made up of majority primary minerals, with small volumes of secondary clays and Fe-oxides. Weathered surfaces show increased microfracturing and porosity in their rinds, especially within 1-2 mm of surfaces and macroscale fractures. I used Western Washington University\u27s hemispheric spectrogoniometer to collect reflectance spectroscopy data from natural and cut rock surfaces at many viewing geometries covering the full scattering hemisphere. Additionally, I convolved lab spectra to Mastcam-Z wavelengths and compared them to Mastcam-Z spectra from olivine-bearing rocks in the South Séítah region within Jezero crater on Mars. Viewing geometry findings indicate that spectra taken outside a lab standard geometry (e.g. i=30, e=0, az=0) allow for accurate mineral identification. Using band depth, magnitude of reflectance, or near-infrared slope to interpret differences between spectral observations is not recommended, however, if the spectra were collected at widely different phase angles. Band depths decrease and near-infrared slopes are more positive (red sloped) with increasing phase angle regardless of a sample\u27s surface weathering or scattering behavior. Absorption band center positions can shift slightly with phase angle due to noise and sample heterogeneity, but changes are small with no correlation to viewing geometry. Minor compositional differences between samples create strong signals in the spectral data; thin, intermittent Fe-oxide coatings on a surface begin to mask the sample\u27s primary mineralogy. Relatively unweathered samples tend to be more forward scattering, while weathered samples tend to be more backscattering. This is likely due to surface roughness and near-surface microporosity differences. Direct applications of these findings include making surface texture inferences based on remote phase angle experiments, especially for the olivine-bearing Séítah rocks

Monitoramento do processo FSW empregando espectrogramas para os sinais das forças e do torque da ferramenta para a liga AA5052-H32

Orientadores: Alberto Luiz Serpa, Antonio Jose RamirezTese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia MecânicaResumo: Este trabalho procura identificar imperfeções durante um processo de soldagem por fricção (FSW) usando o espectrograma da Transformada de Fourier de Curto Tempo (STFT) dos sinais da forças da ferramenta e do torque da ferramenta. Esta técnica foi considerada também uma fonte de informação sobre a estabilidade da soldagem durante o processo, especialmente levando em consideração as forças transversais e laterais. Considerando a importância das forças da ferramenta e do torque da ferramenta, um experimento foi executado usando duas chapas AA5052-H32 de ligas alumínio em uma soldagem de topo. O experimento considerou a variação dos três parâmetros operacionais: velocidade de rotação, velocidade transversal e profundidade de penetração. As respostas foram analisadas utilizando os espectrogramas dos sinais e uma análise estatística que mostra os parâmetros operacionais de influência sobre as ocorrências de falhas usando a técnica STFT. O espectrograma foi capaz de reconhecer o instante em que as falhas ocorreram em uma janela de 2 segundos a 100 Hz da taxa de amostragem. Os resultados mostram que não só as forças laterais e transversais possuem informações relevantes no espectro, mas também a força axial e o torque podem contribuir para o reconhecimento de imperfeções. No entanto, analisando o espectro de um único sinal, as falhas podem não ser detectadas. Usando os padrão dos espectogramas, um sistema de lógica difusa foi projetado para indicar a maior probabilidade de falhaAbstract: This research aims to detect voids and cavities defects during a friction stir welding process using the Short Time Fourier Transform (STFT) spectrogram of the tool forces and the spindle torque signals. This technique was considered also a source of information on the welding stability during the process, especially taking into account the traverse and lateral forces. Considering the importance of the tool forces and the spindle torque during the process, an experiment was run by welding two aluminum AA5052-H32 plates nearly in parallel position and not overlapped (butt welding). The experiment considered the variation of the three operational parameters: rotation speed, traverse speed, and penetration depth. The responses were analyzed using the spectrograms of the signals and a statistical analysis showing the influence of the operational parameters over the fault occurrences using the STFT. The spectrogram was able to recognize the instant when the discontinuities occurred in a window of 2 seconds at 100 Hz of the sample rate. The results show that not only the lateral and traverse forces have relevant information in the spectrum, but also the axial force and the spindle torque can contribute for the recognition of imperfections. However, analyzing the spectrum of one single signal, faults may be undetected. A fuzzy logic system was designed to show the major fault probability using the spectogram patternDoutoradoMecanica dos Sólidos e Projeto MecanicoDoutor em Engenharia Mecânic

MAGNETIC FABRICS AND PALEOMAGNETISM OF NORTH AMERICAN MUDROCKS: RELICS OF COMPLEX BURIAL HISTORIES

Rock fabrics have long been recognized as a key variable influencing unconventional reservoir properties and yet, petrofabric analysis is rarely incorporated in reservoir characterization in a quantitative and scalable manner. This work introduces anisotropy of magnetic susceptibility (AMS) coupled with hand-held x-ray fluorescence (HHXRF) to define the origin of petrofabrics in the Wolfcamp Formation and examine their relationship with total organic carbon (TOC) and oil saturation indices (OSI). Standard paleomagnetic plugs were drilled from three vertical cores spanning the entire Wolfcamp Formation in the Midland Basin, West Texas. Low temperature magnetic experiments suggest paramagnetic minerals contribute between 93.4-98.6% of the low-field bulk magnetic susceptibility (klf) across all lithotypes. Scanning electron microscopy revealed frequent occurrences of paramagnetic minerals such as chlorite, illite, ferroan dolomite, marcasite and pyrite. Fe-rich clays such as chlorite carry the AMS signal in mudrocks with a minor contribution from ferroan dolomite. Conversely, ferroan dolomite carries the AMS signal in most carbonate facies with a minor influence from Fe-rich clays. The degree of magnetic anisotropy (Pj) and shape factor (T) in mudrocks are compositionally dependent and respond to changes in both clay and framework grain concentration. For carbonate facies, Pj and T vary widely due to changes in depositional facies and the concentration of ferroan dolomite. TOC strongly correlates with Pj and strongly oblate magnetic fabrics. This relationship likely stems from the adsorption of organic matter (OM) to clays during deposition and may indicate that organoclay composites were responsible for delivering OM to the sediment-water interface. Elevated OSI are fabric selective, favoring low Pj and T fabrics suggesting that such fabrics facilitate hydrocarbon migration more so than high Pj and T fabrics. Fuzzy-c means clustering provides a framework to describe AMS and geochemical transitions at the core scale and could serve as a tool to map barriers and pathways to hydrocarbon migration. Finally, Ti/Nb and klf data points to a mafic provenance lithotype and suggests layered-intrusive complexes in the Central Basin Uplift were exposed and eroded during deposition of the Wolfcamp Formation. Mafic source rocks likely increased the supply of micronutrients such as dissolved iron and may have enhanced productivity in the Midland Basin

Characterization of Hematite Coated Bedrock Fault Scarps in the Northern Colorado River Extensional Corridor Near Lake Mead, Nevada

Fault mirrors are reflective, thin, typically \u3c1 mm thick, fault slip surfaces in exhumed fault zones that can provide a record of thermal, chemical, and rheological changes to fault materials during deformation. This study investigates a series of hematite coated fault mirrors along bedrock fault scarps in Miocene volcanic rocks near Lake Mead, Nevada. The studied faults are located in a structurally complex area that includes NE-SW trending left-lateral strike-slip faults of the Lake Mead fault system, NW-SE right-lateral strike-slip faults of the Las Vegas Shear Zone, and N-S striking extensional faults of the Northern Colorado River Extensional Corridor.New zircon U-Pb ages from fault scarp host rocks 21-BC-03 and 21-BC-05 are and 13.86 ± 0.27 Ma and 12.90 ± 0.31 Ma (2σ standard error), respectively. New apatite (U-Th)/He dates range from 5.64 ± 0.46 Ma to 12.4 ± 0.36 Ma (2σ standard error) and are interpreted to be partially reset after eruption due to reheating. Inverse thermal history modeling in HeFTy of apatite He dates indicates a thermal history of reheating to ~65 °C which is interpreted as shallow burial around ~11 - 5 Ma followed by cooling to the surface, interpreted as exhumation between ~4.5 - 2 Ma. The zircon U-Pb ages, apatite He dates, and inverse thermal history models indicate the fault host rocks were erupted to the surface and stayed within the upper ~2 km of the crust since the Miocene. Nearly vertical fault scarps that host the fault mirror surfaces exhibit two sets of slickenlines, indicating oblique and strike-slip motion, with different orientations indicating that there have been multiple episodes of deformation along the surfaces. Three of the five studied fault scarps have E-W orientations, and one scarp is NW-SE, and one is NE-SW striking. The studied faults are interpreted to have been active during deformation associated with the Lake Mead Fault System and the Las Vegas Valley Shear Zone at 13 – 9 Ma and record both strike slip and oblique slip events in the complex strain field during this time. Micro-nano scale texture and grain morphology analysis of the hematite fault mirror volumes shows extreme strain localization along the fault mirror surface. Some fault mirrors exhibit multiple domains separated by discrete slip surfaces. Comminution and cataclasis appear to be the dominant deformation mechanisms in the fault mirror volume. Hematite textures and morphologies are consistent with observations from other fault systems that are interpreted to record aseismic to sub-seismic slip rates, and relatively low coseismic temperature rise. Fluid injection veins and post-deformation FeO mineralization in fractures are interpreted as evidence of high fluid pressures during slip and fluid circulation postdeformation. The new geochronologic and microstructural data inform on the processes operating along discrete fault surfaces in the shallow crust since the Miocene in the Lake Mead region

Challenges towards Structural Integrity and Performance Improvement of Welded Structures

Welding is a fabrication process that joint materials, is extensively utilized in almost every field of metal constructions. Heterogeneity in mechanical properties, metallurgical and geometrical defects, post-weld residual stresses and distortion due to non-linear welding processes are prime concerns for performance reduction and failures of welded structures. Consequently, structural integrity analysis and performance improvement of weld joints are important issues that must be considered for structural safety and durability under loading. In this study, an extensive experimental program and analysis were undertaken on the challenges towards structural integrity analysis and performance improvement of different welded joints. Two widely used welding techniques including solid-state “friction- stir- welding (FSW)” and fusion arc “gas tungsten arc welding (GTAW)” were employed on two widely utilized materials, namely aluminum alloys and structural steels. Various destructive and non-destructive techniques were utilized for structural integrity analysis of the welded joints. Furthermore, various “post-weld treatment (PWT)” techniques were employed to improve mechanical performances of weld joints. The work herein is divided into six different sections including: (i) Establishment of an empirical correlation for FSW of aluminum alloys. The developed empirical correlation relates the three critical FSW process parameters and was found to successfully distinguish defective and defect-free weld schedules; (ii) Development of an optimized “adaptive neuro-fuzzy inference system (ANFIS)” model utilizing welding process parameters to predict ultimate tensile strength (UTS) of FSW joints; (iii) Determination of an optimum post-weld heat treatment (PWHT) condition for FS-welded aluminum alloys; (iv) Exploration on the influence of non-destructively evaluated weld-defects and obtain an optimum PWHT condition for GTA-welded aluminum alloys; (v) Investigation on the influence of PWHT and electrolytic-plasma-processing (EPP) on the performance of welded structural steel joints; and finally, (vi) Biaxial fatigue behavior evaluation of welded structural steel joints. The experimental research could be utilized to obtain defect free weld joints, establish weld acceptance/rejection criteria, and for the better design of welded aluminum alloy and steel structures. All attempted research steps mentioned above were carried out successfully. The results obtained within this effort will increase overall understanding of the structural integrity of welded aluminum alloys and steel structures

Wavelet methods for the statistical analysis of image texture

This thesis considers the application of locally stationary wavelet-based stochastic models to the analysis of image texture. In the first part we propose a test of stationarity for spatial data on a regular grid. This test is then incorporated into a segmentation framework in order to determine the number of textures contained within an image, a key feature to many texture segmentation approaches. These novel methods are subsequently applied to various texture analysis problems arising from work with an industrial collaborator. The second part of this thesis considers the modelling of the spectral structure of a non-stationary multivariate image, i.e. an image containing different colour channels. We propose a multivariate locally stationary wavelet-based modelling framework which permits a measure of dependence between pairs of channels. The performance of this modelling approach is then assessed using various colour texture examples encountered by an industrial collaborator