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.
Browse
7 results
Search Results
Item AI Empowered Music Education(2024) Shrestha, Snehesh; Aloimonos, Yiannis; Fermüller, Cornelia; Computer Science; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Learning a musical instrument is a complex process involving years of practice and feedback. However, dropout rates in music programs, particularly among violin students, remain high due to socio-economic barriers and the challenge of mastering the instrument. This work explores the feasibility of accelerating learning and leveraging technology in music education, with a focus on bowed string instruments, specifically the violin. My research identifies workflow gaps and challenges for the stakeholders, aiming to address not only the improvement of learning outcomes but also the provision of opportunities for socioeconomically challenged students. Three key areas are emphasized: designing user studies and creating a comprehensive violin dataset, developing tools and deep learning algorithms for accurate performance assessment, and crafting a practice platform for student feedback. Three fundamental perspectives were essential: a) understanding the stakeholders and their specific challenges, b) understanding how the instrument operates and what actions the player must master to control its functions, and c) addressing the technical challenges associated with constructing and implementing detection and feedback systems. The existing datasets were inadequate for analyzing violin playing, primarily due to their lack of diversity of body types and skill levels, as well as the absence of well-synchronized and calibrated video data, along with corresponding ground truth 3D poses and musical events. Our experiment design was ensured that the collected data would be suitable for subsequent tasks downstream. These considerations played a significant role in determining the metrics used to evaluate the accuracy of the data and the success metrics for the subsequent tasks. At the foundation of movement analysis lies 3D human pose estimation. Unfortunately, the current state-of-the-art algorithms face challenges in accurately estimating monocular 3D poses during instrument playing. These challenges arise from factors such as occlusions, partial views, human-object interactions, limited viewing angles, pixel density, and camera sampling rates. To address these issues, we developed a novel 3D pose estimation algorithm based on the insight that the music produced by the violin is a direct result of the corresponding motions. Our algorithm integrates visual observations with audio inputs to generate precise, high-resolution 3D pose estimates that are temporally consistent and conducive to downstream tasks. Providing effective feedback to learners is a nuanced process that requires balancing encouragement with challenge. Without a user-friendly interface and a motivational strategy, feedback runs the risk of being counterproductive. While current systems excel at detecting pitch and temporal misalignments and visually displaying them for analysis, they often overwhelm players. In this dissertation, we introduce two novel feedback systems. The first is a visual-haptic feedback system that overlays simple augmented cues on the user's body, gently guiding them back to the correct posture. The second is a haptic band synchronized with the music, enhancing students' perception of rhythmic timing and bowing intensities. Additionally, we developed an intuitive user interface for real-time feedback during practice sessions and performance reviews. This data can be shared with teachers for deeper insights into students' struggles and track progress. This research aims to empower both students and teachers. By providing students with feedback during individual practice sessions and equipping teachers with tools to monitor and tailor AI interventions according to their preferences, this work serves as a valuable teaching assistant. By addressing tasks that teachers may not prefer or physically perform, such as personalized feedback and progress tracking, this research endeavors to democratize access to high-quality music education and mitigate dropout rates in music programs.Item Capacity Bounds For Multi-User Channels With Feedback, Relaying and Cooperation(2010) Tandon, Ravi; Ulukus, Sennur; Electrical Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Recent developments in communications are driven by the goal of achieving high data rates for wireless communication devices. To achieve this goal, several new phenomena need to be investigated from an information theoretic perspective. In this dissertation, we focus on three of these phenomena: feedback, relaying and cooperation. We study these phenomena for various multi-user channels from an information theoretic point of view. One of the aims of this dissertation is to study the performance limits of simple wireless networks, for various forms of feedback and cooperation. Consider an uplink communication system, where several users wish to transmit independent data to a base-station. If the base-station can send feedback to the users, one can expect to achieve higher data-rates since feedback can enable cooperation among the users. Another way to improve data-rates is to make use of the broadcast nature of the wireless medium, where the users can overhear each other's transmitted signals. This particular phenomenon has garnered much attention lately, where users can help in increasing each other's data-rates by utilizing the overheard information. This overheard information can be interpreted as a generalized form of feedback. To take these several models of feedback and cooperation into account, we study the two-user multiple access channel and the two-user interference channel with generalized feedback. For all these models, we derive new outer bounds on their capacity regions. We specialize these results for noiseless feedback, additive noisy feedback and user-cooperation models and show strict improvements over the previously known bounds. Next, we study state-dependent channels with rate-limited state information to the receiver or to the transmitter. This state-dependent channel models a practical situation of fading, where the fade information is partially available to the receiver or to the transmitter. We derive new bounds on the capacity of such channels and obtain capacity results for a special sub-class of such channels. We study the effect of relaying by considering the parallel relay network, also known as the diamond channel. The parallel relay network considered in this dissertation comprises of a cascade of a general broadcast channel to the relays and an orthogonal multiple access channel from the relays to the receiver. We characterize the capacity of the diamond channel, when the broadcast channel is deterministic. We also study the diamond channel with partially separated relays, and obtain capacity results when the broadcast channel is either semi-deterministic or physically degraded. Our results also demonstrate that feedback to the relays can strictly increase the capacity of the diamond channel. In several sensor network applications, distributed lossless compression of sources is of considerable interest. The presence of adversarial nodes makes it important to design compression schemes which serve the dual purpose of reliable source transmission to legitimate nodes while minimizing the information leakage to the adversarial nodes. Taking this constraint into account, we consider information theoretic secrecy, where our aim is to limit the information leakage to the eavesdropper. For this purpose, we study a secure source coding problem with coded side information from a helper to the legitimate user. We derive the rate-equivocation region for this problem. We show that the helper node serves the dual purpose of reducing the source transmission rate and increasing the uncertainty at the adversarial node. Next, we considered two different secure source coding models and provide the corresponding rate-equivocation regions.Item Identifying Plant and Feedback in Human Posture Control(2010) Zhang, Yuanfen; Jeka, John; Neuroscience and Cognitive Science; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Human upright bipedal stance is a classic example of a control system consisting of a plant (i.e., the physical body and its actuators) and feedback (i.e., neural control) operating continuously in a closed loop. Determining the mechanistic basis of behavior in a closed loop control system is problematic because experimental manipulations or deficits due to trauma/injury influence all parts of the loop. Moreover, experimental techniques to open the loop (e.g., isolate the plant) are not viable because bipedal upright stance is not possible without feedback. The goal of the proposed study is to use a technique called closed loop system identification (CLSI) to investigate properties of the plant and feedback separately. Human upright stance has typically been approximated as a single-joint inverted pendulum, simplifying not only the control of a multi-linked body but also how sensory information is processed relative to body dynamics. However, a recent study showed that a single-joint approximation is inadequate. Trunk and leg segments are in-phase at frequencies below 1 Hz of body sway and simultaneously anti-phase at frequencies above 1 Hz during quiet stance. My dissertation studies have investigated the coordination between the leg and trunk segments and how sensory information is processed relative to that coordination. For example, additional sensory information provided through visual or light touch information led to a change of the in-phase pattern but not the anti-phase pattern, indicating that the anti-phase pattern may not be neurally controlled, but more a function of biomechanical properties of a two-segment body. In a subsequent study, I probed whether an internal model of the body processes visual information relative to a single or double-linked body. The results suggested a simple control strategy that processes sensory information relative to a single-joint internal model providing further evidence that the anti-phase pattern is biomechanically driven. These studies suggest potential mechanisms but cannot rule out alternative hypotheses because the source of behavioral changes can be attributed to properties of the plant and/or feedback. Here I adopt the CLSI approach using perturbations to probe separate processes within the postural control loop. Mechanical perturbations introduce sway as an input to the feedback, which in turn generates muscle activity as an output. Visual perturbations elicit muscle activity (a motor command) as an input to the plant, which then triggers body sway as an output. Mappings of muscle activity to body sway and body sway to muscle activity are used to identify properties of the plant and feedback, respectively. The results suggest that feedback compensates for the low-pass properties of the plant, except at higher frequencies. An optimal control model minimizing the amount of muscle activation suggests that the mechanism underlying this lack of compensation may be due to an uncompensated time delay. These techniques have the potential for more precise identification of the source of deficits in the postural control loop, leading to improved rehabilitation techniques and treatment of balance deficits, which currently contributes to 40% of nursing home admissions and costs the US health care system over $20B per year.Item Closed Loop System Identification of Postural Control with Bilateral Vestibular Loss(2009) Amenabar, Katharine Elizabeth; Jeka, John J; Kinesiology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Human upright stance can be characterized as a combination of feedback and plant. Feedback consists of integrated sensory signals, producing estimates of position and velocity of the body segments while plant includes both musculotendon dynamics and body dynamics. Separating plant and feedback is possible mathematically through closed loop system identification. By studying bilateral vestibular loss (BVL) patients it is hoped knowledge regarding human posture and the role of the vestibular system will be gained. Two BVL patients and two age, height and gender matched controls had visual and mechanical perturbations applied simultaneously to determine these properties. Both leg and trunk kinematics and EMG data were collected. Using frequency response functions plant and feedback properties were calculated. Plant and feedback dynamics differ. BVL patients show more variable weighted hip EMG data, supporting the idea that this population can not properly use hip movement with their lack of vestibular system.Item The response-monitoring mechanism: Influence of feedback and temperament(2008-05-06) Martin McDermott, Jennifer; Fox, Nathan A; Human Development; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)The purpose of the current study was to examine behavioral and physiological processes underlying response-monitoring and to document the manner in which these processes are expressed during early childhood. As well, this study examined two factors important in understanding individual differences in monitoring: performance feedback and temperament. A total of seventy-four children (mean age 7.5 years) were tested using a modified flanker paradigm administered in both no-feedback and feedback conditions. Accuracy and reaction time measures of behavioral performance were assessed as well as event-related potentials linked to response execution and feedback presentation. Data were also examined in relation to the temperamental dimensions of shyness and inhibitory control. The results indicate a strong impact of trial-by-trial feedback on both behavioral and physiological measures. Overall, feedback served to increase children's task engagement as evidenced by fewer errors of omission and faster reaction times. Similarly, the physiological measures also varied as a function of feedback such that the error-related Positivity (Pe) and the feedback-related negativity (FRN) were more pronounced on incorrect as compared to correct trials in the feedback condition. Larger FRN responses were also associated with fewer errors of commission. These findings were further moderated by individual differences in temperament. Specifically, feedback was particularly influential in increasing task involvement for children low in inhibitory control and enhancing performance accuracy for children low in shyness Overall these results confirm a strong impact of feedback on task engagement as assessed by children's behavioral performance and physiological reactivity. Findings are presented in the framework of individual differences in cognitive control and variations in children's physiological measures of response-monitoring are discussed. Several avenues for future research are provided which emphasize the need for investigations of response-monitoring in young children and also highlight the importance of exploring the applicability of these assessments across various cognitive and social contexts.Item The Development and Validation of the Group Leader Intervention Scales(2004-06-01) Nuijens, Karen L.; Teglasi-Golubcow, Hedwig; Counseling and Personnel Services; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)The purpose of the study was to develop and validate an instrument for examining therapist interventions in group counseling settings. The Group Leader Intervention Scales (GLIS) is a verbal response mode system designed to code group leader verbalizations on six group process variables (structure, group cohesion, modeling, information, exploration, and feedback), and on eleven subscales that examine various aspects of the main categories. The GLIS was developed though a content analysis of session transcripts from a group intervention for children that used stories and peer group processes to increase social problem-solving. High levels of interrater reliability were established between three raters for the six group process variables, and for nine of the eleven subscales. Initial validity of the new instrument was demonstrated by its ability to distinguish between groups based on treatment response (high or low cognitive treatment response), and based on stage of treatment (early, middle, or late).Item A NOVEL AIRFLOW CONTROL VALVE FOR USE IN MEDICAL APPLICATIONS(2004-05-26) Hitchcock, Kathryn Elizabeth; Hristu-Varsakelis, Dimitrios; Mechanical EngineeringRapid improvements in digital technology over the last two decades have led to artificial ventilators that drastically improve physicians' ability to measure and control aspects of their patients' breathing. However, the mechanical systems paired with the new digital controllers have not advanced in parallel with them. As a result, mechanical ventilators do not respond sufficiently fast to changes in operating conditions and can injure patients by allowing the air volume or pressure in their lungs to become too high. This thesis describes a new air flow control valve that can be incorporated in existing ventilators to correct this condition. The valve's low mass and short stroke result in rapid full-range motion with low actuator force and travel. These qualities also make the valve well-suited for use as a flow-change mechanism in instruments that measure airway resistance, including the Airflow Perturbation Device (APD). We describe a series of experiments that verify the valve's performance in both ventilator and APD applications.