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"The use of cameras and computer vision algorithms to provide state estimation for robotic systems has become increasingly popular, particularly for small mobile robots and unmanned aerial vehicles (UAVs). These algorithms extract information from the camera images and perform simultaneous localization and mapping (SLAM) to provide state estimation for path planning, obstacle avoidance, or 3D reconstruction of the environment. High resolution cameras have become inexpensive and are a lightweight and smaller alternative to laser scanners. UAVs often have monocular camera or stereo camera setups since payload and size impose the greatest restrictions on their flight time and maneuverability. This thesis explores ORB-SLAM, a popular Visual SLAM method that is appropriate for UAVs. Visual SLAM is computationally expensive and normally offloaded to computers in research environments. However, large UAVs with greater payload capacity may carry the necessary hardware for performing the algorithms. The inclusion of general-purpose GPUs on many of the newer single board computers allows for the potential of GPU-accelerated computation within a small board profile. For this reason, an NVidia Jetson board containing an NVidia Pascal GPU was used. CUDA, NVidia’s parallel computing platform, was used to accelerate monocular ORB-SLAM, achieving onboard Visual SLAM on a small UAV. Committee members:"

Attracting prey by exploiting a visual sensory bias is a common theme in stationary predators across many taxa, particularly for obligate ambush predators, such as orb-weaving spiders, because they construct complex prey traps. Mimicry of UV-reflecting floral-guides has been suggested as the mechanism behind the tendency for spiders and silk web decorations (stabilimenta) to reflect in the UV, to attract pollinators that they then prey upon. Also, many insects are attracted to UV because it most commonly indicates open sky, or a safe flight path. My study focuses on the prey attraction function of stabilimenta, in Argiope trifasciata in eastern Ontario. Decorated webs were no more likely to contain prey than undecorated webs, but for adult spiders, longer stabilimenta were associated with increased likelihood of prey capture. For both adults and juveniles, larger webs were more likely to contain prey in undecorated webs, but for decorated webs, web size was not a predictor of prey presence. I interpret this as evidence for a trade-off between two alternative prey capture strategies: building a web with a large capture area, or building a small web with a stabilimentum. In further support of this trade-off, smaller webs were more likely to contain a stabilimentum, for both juveniles and adults. My data also suggest that close neighbours compete rather than cooperate with each other. Adult webs were spaced farther apart from each other than juvenile webs, more than would be expected based on web diameter difference. For juveniles, webs with a closer neighbour were more likely to be decorated, implying an increased need for prey attraction in the presence of a nearby competitor. For adults, prey was more likely to be found in webs that were more solitary. My results do not support the hypothesis that visually attractive spiders increased prey capture by aggregating. / Thesis (Master, Biology) -- Queen's University, 2009-09-28 10:57:18.156

The computer programs SnapPea by Weeks and Geo by Casson have proven to be powerful tools in the study of hyperbolic 3-manifolds. Manifolds are special examples of spaces called orbifolds, which are modelled locally on R^n modulo finite groups of symmetries. SnapPea can also be used to study orbifolds but it is restricted to those whose singular set is a link.One goal of this thesis is to lay down the theory for a computer program that can work on a much larger class of 3-orbifolds. The work of Casson is generalized and implemented in a computer program Orb which should provide new insight into hyperbolic 3-orbifolds.The other main focus of this work is the study of 2-handle additions. Given a compact 3-manifold M and an essential simple closed curve α on ∂M, then we define M[α] to be the manifold obtained by gluing a 2-handle to ∂M along α. If α lies on a torus boundary component, we cap off the spherical boundary component created and the result is just Dehn filling.The case when α lies on a boundary surface of genus ≥ 2 is examined and conditions on α guaranteeing that M[α] is hyperbolic are found. This uses a lemma of Scharlemann and Wu, an argument of Lackenby, and a theorem of Marshall and Martin on the density of strip packings. A method for performing 2-handle additions is then described and employed to study two examples in detail.This thesis concludes by illustrating applications of Orb in studying orbifoldsand in the classification of knotted graphs. Hyperbolic invariants are used to distinguish the graphs in Litherland’s table of 90 prime θ-curves and provide access to new topological information including symmetry groups. Then by prescribing cone angles along the edges of knotted graphs, tables of low volume orbifolds are produced.

Thesis (Ph. D.)--Illinois State University, 1987. / Title from title page screen, viewed August 16, 2005. Dissertation Committee: Wayne A. Riddle (chair), D. Reed Jensen, Steven A. Juliano, Charles F. Thompson, James N. Tone. Includes bibliographical references (leaves 103-118) and abstract. Also available in print.

The Okavango River Basin (ORB) located in southern Africa is a region of highly sensitive and biodiverse ecosystems. It spans Angola, Namibia and Botswana, with the world-famous Okavango Delta located in the latter country. The ecosystems depend on the highly seasonal ORB streamflow, which is also the major source of freshwater for the rural population, most of whom depend on subsistence farming. Climate variability and extremes such as droughts, hot days and extreme rainfall events are not well understood over this region. Also, the relationship between climate and other aspects like vegetation and river discharge are not well understood. To contribute to a better understanding of this relationship, the thesis investigated relationships between rainfall, temperature, Normalized Difference Vegetation Index (NDVI) and river discharge, and their interannual variability and trends. It was found that at monthly and seasonal time scales, NDVI spatial patterns are closely related to those of rainfall than temperature. The NDVI-rainfall and NDVI-temperature relationships differ north of 18.9°S where rainfall is higher than to its south. Correlations between NDVI and rainfall show lags of 1-2-months. Large areas across the region show significant warming trends in all seasons but mainly in October-December (OND), as well as wetting mainly in the north. The warming trend may imply more evaporation and desiccation which may exacerbate extreme event impacts such as severe droughts. Interannual variability of rainfall, NDVI and temperature is pronounced with significant correlations with El Niño-Southern Oscillation (ENSO), the subtropical Indian Ocean Dipole (SIOD) and the Botswana High for rainfall and temperature, and for NDVI with ENSO. The temperature (rainfall) correlations with ENSO and the Botswana were positive (negative), with the SIOD they were negative (positive), and the NDVI-ENSO correlations were negative. On longer time scales, the wet 2006-2013 period was analysed relative to much drier 1999-2005 epoch for OND. The 2006-2013 wetter conditions appear linked to La Niña Modoki conditions, regional circulation differences and warmer sea surface temperature near Angola. Extreme rainfall events over the ORB were analysed. The analysis was performed within a larger region in western central southern Africa (WCSA), given that many rainfall events extend beyond river basin boundaries. Focus was placed on extreme rainfall events accumulated over 1-day (DP1) and 3-days (DP3), during the main rainy season, January-April (JFMA). Due to data sparsity, the Climate Hazards Group Infrared Precipitation with Station data (CHIRPS) were used to identify these events. It was found that contributions of DP1 and DP3 events to JFMA rainfall totals are, on average, ~10% and ~17%, respectively, but in some years their contributions exceed 30%. Most of the events result from tropical-extratropical cloud bands, with tropical lows being also important. Interannual variability in extreme events is substantial and appears linked to ENSO and the Botswana High. Although ENSO influences the extreme events and rainfall totals more generally over southern Africa, by far the neutral JFMA 2017 season experienced the wettest conditions over the world-famous Okavango Delta region. Factors that contributed to these heavy rains included a deeper Angola Low, weaker mid-level Botswana High and anomalous westerly moisture fluxes from the tropical southeast Atlantic during January – early March. The second most intense rainfall event occurred on April 22nd, resulting from a cut-off low. DP1 frequencies show significant increasing trends, and similarly, rain-days and rain totals over many areas. These trends have important implications for agricultural and water management as well as wildlife conservation in the ORB. To contribute to a better understanding of drought over the ORB region, the thesis analysed various drought metrics. These include a Cumulative Drought Intensity (CDI) index, based on the product of maximum dry spell duration and maximum temperature anomaly, and the Standardised Precipitation-Evapotranspiration Index (SPEI). Strong horizontal gradients in frequencies of dry spells and hot days were found to shift south over the ORB from August to November as the tropical rain-belt shifts increasingly south of the equator, the Congo Air Boundary declines and the Botswana High strengthens and shifts south-westwards. By December, the tropical gradient in dry spell frequencies is unnoticeable while that across the Limpopo River and southern ORB region, where the Botswana High is centred, stands out. On seasonal time scales, October-November 2013-2021 is particularly hot and dry over the Okavango Delta region. The thesis provided evidence that this hot and dry epoch is related to a stronger and southward shifted Botswana High and reduced low-level moisture convergence. On interannual time scales, there were strong relationships with the Botswana High, and to lesser extent ENSO. A strong drying-warming trend was found in the early summer, linked to a significant strengthening of the Botswana High. These trends, in conjunction with the Coupled Model Intercomparison Project Phase 6 (CMIP6) projected early summer drying over southern Africa found in the literature, may impact severely on the sensitive ecosystems of the ORB, and on water availability as well as subsistence farming in the region.

Orb weavers intercept insects using non-hardening bioadhesive droplets, supported by two flagelliform fibers. Droplets contain an adhesive glycoprotein core and aqueous layer that confers hygroscopicity. The first study investigates the durability of these droplets to cycling, or repeatedly adhering, extending, and pulling off. Droplets of four species proved resilient, cycling 40 times. Cycling, coupled with droplet humidity responsiveness, qualifies them as smart materials. However, thread adhesion is complex, relying on an integrated performance of multiple droplets and the flagelliform fibers. As insects struggle, the flagelliform fibers bow and the droplets extend, forming a suspension bridge configuration whose biomechanics sum the adhesion of droplets and dissipate the energy of struggling insects. Given this performance, the second study predicts that the material properties of both thread components have evolved in a complementary way. Comparative phylogenetics of 14 study species revealed that their elastic moduli are correlated, with glycoproteins being six times more elastic than flagelliform fibers. Spider mass affects the amount of each material, but not their properties. Since glycoprotein performance changes with humidity, we hypothesized that orb weavers generate greater adhesion at their foraging humidity. After delimiting low and high humidity species groups (eight and six species, respectively), bridge force was determined as total contributing droplet adhesion at three humidities. Only three spiders generated greater adhesion outside of their foraging humidity. The distribution of force along a suspension bridge differed from a previously reported pattern. We also characterize the sheet configuration, which generates force similar to suspension bridges. / Master of Science / In nature, adhesives are used for a variety of functions. Many animals use adhesives use adhesives when climbing. Examples include toe pads of geckos, tarsal pads of ants, and tube feet of and sea urchins. Here, adhesion is repeatedly generated and released as the animal moves. However, some animals depend on permanent adhesives to anchor to surfaces. Marine mussels and barnacles, whose adult forms are sessile, use adhesives to resist the powerful action of waves and currents. Adhesion also plays a critical role in prey capture, where it prevents prey from escaping. The sticky droplets of a sundew plants and the adhesive capture threads of spider orb webs trap flies. Biologists and engineers study these bioadiehsives in search of inspiration and principles that will guide the development of new materials, including adhesives that function underwater, harden rapidly, or remaining pliable after adhering. This study investigated the material properties of capture threads spun by orb weaving spiders, which rely on non-hardening sticky droplets, supported by two protein fibers to capture insects. Inside each droplet is an adhesive core allows droplets to adhere to an insect and to extend as it struggles to escape. Surrounding this core is an aqueous layer that attracts atmospheric water, causing droplets to track changes in ambient humidity. A study of the cycling (or reusability) of four species' droplets repeatedly adhered a droplet to a surface and extending it to pull-off. These droplets were very resilient, cycling 40 times. Cycling, coupled with droplet humidity responsiveness, qualifies them as smart materials. However, prey capture is more complex, relying on the integration of multiple droplets and their supporting flagelliform fibers. As insects struggle, these fibers bow and the droplets extend, forming a suspension bridge configuration whose biomechanics sum the adhesion of droplets to resist an insect escape. The threads of 14 species were examined to test the hypothesis that material properties of both thread components have evolved in a complementary way to optimize adhesive performance. This revealed that the elasticities of the two capture thread components were correlated, with support fiber elasticity being greater. Capture threads generated the greatest adhesion at humidities during times that a spider feeds, although the distribution of this force across a suspension bridge showed different patterns among the species. The functional integration of a capture thread's components and its ability to respond to environmental humidity gives it exciting biomimicry potential.

Modeling of natural phenomena has been of particular interest in the graphics ommunity in recent years. This thesis will explore a method for creating and animating orb webs using a coupled spring-mass system. Using a spring-mass system for creating the orb web is ideal as we can represent each web strand using coupled spring-mass pairs. This allows the orb web simulator to be physically based, i.e., the simulation follows the laws that act on objects in the real world. This in turn simplifies the process of animating the web, as the animation emerges from the simulator without anyone having to set it up explicitly. Since this model is physically based, it would allow for realistic visualization of effects such as observing an orb web under a wind. In the children's book ``Charlotte's Web', the spider creates orb webs with words inscribed on them. Charlotte's web is used as an inspiration, in this thesis, to create webs which no real world spider could possibly create, while keeping the model physically based. This involves modifying the orb web such that the target text shows up on the orb web while keeping the web looking as natural as possible.

Modeling of natural phenomena has been of particular interest in the graphics ommunity in recent years. This thesis will explore a method for creating and animating orb webs using a coupled spring-mass system. Using a spring-mass system for creating the orb web is ideal as we can represent each web strand using coupled spring-mass pairs. This allows the orb web simulator to be physically based, i.e., the simulation follows the laws that act on objects in the real world. This in turn simplifies the process of animating the web, as the animation emerges from the simulator without anyone having to set it up explicitly. Since this model is physically based, it would allow for realistic visualization of effects such as observing an orb web under a wind. In the children's book ``Charlotte's Web', the spider creates orb webs with words inscribed on them. Charlotte's web is used as an inspiration, in this thesis, to create webs which no real world spider could possibly create, while keeping the model physically based. This involves modifying the orb web such that the target text shows up on the orb web while keeping the web looking as natural as possible.

The evolution of technology has led the research into new emerging wearable devices such as the Smart Glasses. This technology provides with new visualization techniques. Augmented Reality is an advanced technology that could significantly ease the execution of much complex operations. Augmented Reality is a combination of both Virtual and Actual Reality, making accessible to the user new tools to safeguard in the transfer of knowledge in several environments and for several processes. This thesis explores the development of an android based image recognition application. The feature point detectors and descriptors are used as they can deal great with the correspondence problems. The selection of best image recognition technique on the smart glasses is chosen based on the time taken to retrieve the results and the amount of power consumed in the process. As the smart glasses are equipped with the limited resources, the selected approach should use low computation on it by making the device operations uninterruptable. The effective and efficient method for detection and recognition of the safety signs from images is selected. The ubiquitous SIFT and SURF feature detectors consume more time and are computationally complex and require very high-level hardware components for processing. The binary descriptors are taken into account as they are light weight and can support low power devices in a much effective style. A comparative analysis is being done on the working of binary descriptors like BRIEF, ORB, AKAZE, FREAK, etc., on the smart glasses based on their performance and the requirements. ORB is the most efficient among the binary descriptors and has been more effective for the smart glasses in terms of time measurements and low power consumption.