Optimizing Harris Corner Detection on GPGPUs Using CUDA

ABSTRACT Optimizing Harris Corner Detection on GPGPUs Using CUDA The objective of this thesis is to optimize the Harris corner detection algorithm implementation on NVIDIA GPGPUs using the CUDA software platform and measure the performance benefit. The Harris corner detection algorithm—developed by C. Harris and M. Stephens—discovers well defined corner points within an image. The corner detection implementation has been proven to be computationally intensive, thus realtime performance is difficult with a sequential software implementation. This thesis decomposes the Harris corner detection algorithm into a set of parallel stages, each of which are implemented and optimized on the CUDA platform. The performance results show that by applying strategic CUDA optimizations to the Harris corner detection implementation, realtime performance is feasible. The optimized CUDA implementation of the Harris corner detection algorithm showed significant speedup over several platforms: standard C, MATLAB, and OpenCV. The optimized CUDA implementation of the Harris corner detection algorithm was then applied to a feature matching computer vision system, which showed significant speedup over the other platforms

Geophysical Characterization of the Structural Configuration and Tectonic Evolution along the Northern Margin of the Gulf of Mexico Basin, Northwestern Mississippi

The tectonic history of the Gulf of Mexico Basin in northwestern Mississippi is poorly understood due to a lack of publicly available data and overlying Mesozoic sediments. Using an extensive set of geophysical data including: well data, potential field data, and 2-D seismic data, we define distinct zones of varying structural styles across the region and provide new insight into the tectonic evolution of the northern margin of the Gulf of Mexico. The cratonal region is defined by the extent of Precambrian basement across the region and is characterized by an orthogonal set of normal faults related to Precambrian – Cambrian rifting and subsidence along the southern Paleozoic shelf margin. The, now, foreland basin is composed primarily of Cambrian-Devonian shelf carbonates and Carboniferous clastics deposited along the southern continental margin, coinciding with the southern limit of Precambrian cratonal material. Divisible into two structural domains, the Frontal and Allochthonous Domain, the sub-cropping Ouachita orogenic belt is defined by geophysical data in northwestern Mississippi. The Frontal Domain of the Ouachita zone is restricted to the western study area and is characterized by small, imbricate thrusts branching from a lower detachment within autochthonous sediments and an upper detachment along the base of back thrusted Carboniferous sediments. Large thrust sheets of the Allochthonous Domain are correlatable across the study area and are truncated to the north by large intrusions or basement blocks. The seismically defined limit of the basinal zone corresponds to a linear gravity minima separating Mesozoic rift-related basins to the south from Precambrian and intrusive bodies to the north. Geophysical data of the basinal zone characterize multiple igneous bodies of varying ages. Syn-rift Triassic graben clastics confined to grabens paralleling the basinal zone limit are interpreted to be related to a Mesozoic rift-related transform across Mississippi separating rift basins of the larger region

Signing the blues : toward a theoretical model based on the intertextuality of psycholinguistic metonymy and jazz phraseology for reading the texts of Jack Kerouac and Langston Hughes

That marginalized discourse communities practice differing modes of communication is a claim recently argued; critics have focused on the trope of metonymy as a means of signifying a discriminated-against group's silenced status within the mainstream society. What seems to be ignored in this discussion is how differing media--literature, music, painting--constitute texts that cut across discursive space (the site of these media) in a similar fashion. By positing the intertextuality (i.e., the similarity) of psycholinguistic metonymy and jazz phraseology, this thesis demonstrates how literary texts issuing from marginalized discourse communities can speak their subjectivities' full names. In Langston Hughes' "The Blues I'm Playing," metonymy and jazz serve as methods of analysis which show the subject-object relationship in artistic production. Jack Kerouac's On The Road constitutes a narrative subjectivity that, like jazz music, metonymically disrupts itself as silences speak from the realm of an Other. By accounting for the similarities between metonymy and jazz, this thesis asserts that more accurate readings can be derived from literature issuing from discourse communities which use jazz to signify.Thesis (M.A.)Department of Englis

The Influence of Intracortical Microarchitecture on the Mechanical Fatigue of Bone

Mechanical fatigue is the predominant etiology of stress fracture, a known contributor to atypical femoral fracture, and may also play a critical role in fragility fracture. While these fatigue-related fractures are well-documented in humans, they are poorly understood. Extensive research has attempted to characterize the fatigue behavior of cortical bone; however, owing to the inherent variability in bone tissue, samples that appear identical in macrostructure can exhibit a large degree of scatter in fatigue life. The overarching hypothesis of this thesis is that the variance in fatigue-life data can be attributed to intracortical microarchitecture, including the size, spacing, and density of vascular canals and osteocyte lacunae. A series of studies were conducted that utilized ex vivo mechanical testing, high-resolution imaging, and finite element modeling to establish the relationship between intracortical microarchitecture and the fatigue life of bone in compression. Both porosity and canal diameter demonstrated a strong negative relationship with fatigue life, whereas lacunar density was positively correlated. The reduced fatigue life associated with higher porosity was a result of larger, rather than more abundant canals, indicating that canals act as stress concentrators that may impair the fatigue resistance of bone beyond increasing overall porosity. The stress concentrations caused by vascular canals were quantified as stressed volume (i.e., the volume of material above yield) which was positively correlated to porosity and canal diameter. Furthermore, stressed volume proved to be a strong predictor of fatigue-life variance across multiple loading magnitudes. The findings from this thesis suggest that a majority of the fatigue-life variance of cortical bone in compression is driven by intracortical microarchitecture, and fatigue failure may be predicted by quantifying the stress concentrations associated with vascular canals

Stressed volume around vascular canals explains compressive fatigue life variation of secondary osteonal bone but not plexiform bone

The fatigue life of bone illustrates a large degree of scatter that is likely related to underlying differences in composition and microarchitecture. Vascular canals act as stress concentrations, the magnitude and volume of which may depend on the size and spatial distribution of canals. The purpose of this study was to establish the relationship between vascular canal microarchitecture, stressed volume and the fatigue life of both secondary osteonal and plexiform bovine bone. Twenty-one cortical bone samples were prepared from bovine femora and tibiae and imaged using micro-computed tomography (μCT) to quantify canal diameter, canal separation and canal number. Samples were cyclically loaded in zero-compression to a peak magnitude of 95 MPa, and fatigue life was defined as the number of cycles until fracture. Finite element models were created from μCT images and used to quantify the stressed volume, i.e., the volume of bone stressed higher than a yield stress of 108 MPa. Fatigue life ranged from 162-633,437 cycles with the fatigue life of plexiform bone (n = 15) being more than 4.5 times longer than secondary bone (n = 6). The fatigue life of secondary bone was negatively correlated with canal diameter (r2 = 0.73) and canal separation (r2 = 0.56), while the fatigue life of plexiform bone was negatively correlated with canal separation (r2 = 0.41), but positively correlated with canal number (r2 = 0.36). Stressed volume was related to canal microarchitecture in secondary bone only, where canal diameters and canal separation were larger than approximately 50 μm and 200 μm, respectively. Consequently, stressed volume explained 89% of the fatigue life variance in secondary bone but was not related to the fatigue life of plexiform bone. These findings suggest that the volume of the stress concentration surrounding vascular canals is dictated by canal size and spacing and may play an important role in the fatigue failure of osteonal bone. We suspect that a larger stressed volume is more likely to encounter and facilitate the propagation of pre-existing microcracks, thereby leading to a reduction in fatigue life

Experimental validation of finite element predicted bone strain in the human metatarsal

Metatarsal stress fracture is a common injury observed in athletes and military personnel. Mechanical fatigue is believed to play an important role in the etiology of stress fracture, which is highly dependent on the resulting bone strain from the applied load. The purpose of this study was to validate a subject-specific finite element (FE) modeling routine for bone strain prediction in the human metatarsal. Strain gauge measurements were performed on 33 metatarsals from seven human cadaveric feet subject to cantilever bending, and subject-specific FE models were generated from computed tomography images. Material properties for the FE models were assigned using a published density-modulus relationship as well as density-modulus relationships developed from optimization techniques. The optimized relationships were developed with a 'training set' of metatarsals (n=17) and cross-validated with a 'test set' (n=16). The published and optimized density elasticity equations provided FE-predicted strains that were highly correlated with experimental measurements for both the training (r2≥0.95) and test (r2≥0.94) sets; however, the optimized equations reduced the maximum error by 10% to 20% relative to the published equation, and resulted in an X=Y type of relationship between experimental measurements and FE predictions. Using a separate optimized density-modulus equation for trabecular and cortical bone did not improve strain predictions when compared to a single equation that spanned the entire bone density range. We believe that the FE models with optimized material property assignment have a level of accuracy necessary to investigate potential interventions to minimize metatarsal strain in an effort to prevent the occurrence of stress fracture.Natural Sciences and Engineering Research Council - Discovery Gran

Stressed volume estimated by finite element analysis predicts the fatigue life of human cortical bone: The role of vascular canals as stress concentrators

The fatigue life of cortical bone can vary several orders of magnitude, even in identical loading conditions. A portion of this variability is likely related to intracortical microarchitecture and the role of vascular canals as stress concentrators. The size, spatial distribution, and density of canals determine the peak magnitude and volume of stress concentrations. This study utilized a combination of experimental fatigue testing and image-based finite element (FE) analysis to establish the relationship between the stressed volume (i.e., volume of bone above yield stress) associated with vascular canals and the fatigue life of cortical bone. Thirty-six cortical bone samples were prepared from human femora and tibiae from five donors. Samples were allocated to four loading groups, corresponding to stress ranges of 60, 70, 80, and 90 MPa, then cyclically loaded in zero-compression until fracture. Porosity, canal diameter, canal separation, and canal number for each sample was quantified using X-ray microscopy (XRM) after testing. FE models were created from XRM images and used to calculate the stressed volume. Stressed volume was a good predictor of fatigue life, accounting for 67% of the scatter in fatigue-life measurements. An increase in stressed volume was most strongly associated with higher levels of intracortical porosity and larger canal diameters. The findings from this study suggest that a large portion of the fatigue-life variance of cortical bone in zero-compression is driven by intracortical microarchitecture, and that fatigue failure may be predicted by quantifying the stress concentrations associated with vascular canals