Theses and Dissertations from UMD
Permanent URI for this communityhttp://hdl.handle.net/1903/2
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 give thesis/dissertation in DRUM
More information is available at Theses and Dissertations at University of Maryland Libraries.
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Item EFFECTS OF AUGMENTED REALITY BASED OBJECT ILLUMINATION ON HUMAN PERFORMANCE(2020) Stone, Matthew; Akin, David L; Aerospace Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Extravehicular Activities (EVAs) in space are generally considered to be high-risk, costly activities, due to the nature of the working environment and the limitations imposed on astronaut mobility and dexterity. Procedures are scheduled out and rehearsed far in advance, with time being considered a precious commodity during missions. Providing artificial task guidance to astronauts could potentially improve their efficiency, enabling for shorter duration EVAs and/or a larger quantity of tasks completed. This research quantitatively measured the effects of virtually illuminating or “cueing” objects of interest on a user’s ability to complete a predefined task, through the use of augmented reality (AR) “active display” symbology. This was achieved through the implementation of a Microsoft HoloLens™ head mounted display. It was demonstrated that, after controlling for a variety of factors, virtual illumination techniques improved task completion speed by approximately 100% and reduced perceived mental workload, with no adverse effects on accuracy.Item Real-Time Pose Based Human Detection and Re-Identification with a Single Camera for Robot Person Following(2017) Welsh, John Bradford; Blankenship, Gilmer; Electrical Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)In this work we address the challenge of following a person with a mobile robot, with a focus on the image processing aspect. We overview different historical approaches for person following and outline the advantages and disadvantages of each. We then show that recent convolutional neural networks trained for human pose detection are suitable for person detection as it relates to the robot following problem. We extend one such pose detection network to spatially embed the identity of individuals in the image, utilizing the pose features already computed. The proposed identity embedding allows the system to robustly track individuals in consecutive frames even in long term occlusion or absence. The final system provides a robust person tracking scheme which is suitable for person following.Item The Neural Dynamics of Amplitude Modulation Processing in the Human Auditory System(2010) Li, Kai Sum; Simon, Jonathan Z; Electrical Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)The neural, auditory amplitude modulation transfer function (MTF) is estimated from 3 - 50 Hz using magnetoencephalography (MEG). All acoustic stimuli are amplitude modulated (AM). Two different dynamical stimulus types are used: exponential sweeps with the AM rate changing from 2 up to 60 Hz, and 89 down to 3 Hz. Several carriers are also employed, including 3 pure-tone carriers (250 Hz, 707 Hz and 2 kHz) and 3 bandlimited pink-noise carriers (1/3, 2 and 5 octaves centered at 707 Hz). Neural response magnitudes, phases, group delays and impulse responses are all estimated. Our results show that the shape of modulation transfer function is flat but with a slightly low pass shape below 10 Hz. The phase of the response is approximately linear in many frequencies. The group delay is around 50 ms at 40 Hz for increasing-frequency sweeps and closer to 100 ms for decreasing-frequency sweeps.Item Characterizing Sensory Re-weighting for Human Postural Control(2006-11-06) Oie, Kelvin S; Jeka, John J; Neuroscience and Cognitive Science; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)In order to survive in the wide range of sensory contexts that comprise our physical world, the nervous system employs adaptive mechanisms that optimize functional behaviors within a given sensory environment. Human bipedal stance control requires that the nervous system obtain relevant information about the environment and the body's relationship with it from multiple sensory systems. How does the nervous system accomplish this when the sensory environment compromises the information available from a given sensory system? In previous theoretical and empirical work, we have provided evidence of nonlinearities that are consistent with an hypothesis of sensory re-weighting: The nervous system adapts to changing sensory contexts by decreasing its dependence, or weighting, on the compromised system and increases its weighting of other inputs. This thesis presents empirical findings that further support the sensory re-weighting hypothesis and further efforts towards characterizing sensory re-weighting by providing empirical results that provide important constraints on any proposed sensory re-weighting scheme. First, postural responses to complex visual motion consisting of the sum of 10 different sinusoidal components, were measured at two different amplitudes. Changes in the gain of body sway to visual motion were consistent with the nonlinearities previously interpreted as evidence for sensory re-weighting. Further, the observed changes in gain did not vary significantly as a function of stimulus frequency. Second, we found evidence indicating a temporal asymmetry in the sensory re-weighting process dependent upon the direction of the change in stimulus motion amplitude: the change in postural response is faster to a rapid increase versus decrease in stimulus amplitude. This temporal asymmetry was interpreted functionally: an increase in visual environmental motion may threaten balance, requiring a rapid down-weighting of vision if a strong dependence upon visual information would increase postural response beyond the stability boundaries of stance. Conversely, if stance is already stable in the face of large visual motion amplitude, a decrease in motion amplitude does not threaten balance and adapting rapidly to the new sensory conditions is not critical to avoid falling.