Theses and Dissertations from UMD
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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 IMPACT OF WEB CONTENT FEEDBACK SYSTEM ON THE EFFECTIVENESS OF HEALTH PROMOTION MESSAGES ON YOUTUBE: A NORMS-BASED INQUIRY(2017) Yang, Bo; Nan, Xiaoli; Communication; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)The widespread use of social media in health communication makes it important to understand how the media’s characteristics impact health communication effectiveness. This dissertation used social norms theory to explain the persuasive impact of web content feedback system—a unique feature of social media—on people’s responses to health promotion messages posted on a social media site YouTube. Three common social media content feedback cues (comments, aggregate ratings, and message view count) were examined. These cues were expected to influence people’s health attitudes and behavioral intentions via the mediation of three types of perceived social norms (descriptive norms, injunctive norms and subjective norms). Two experiments examined the norms-mediated model in three health contexts (smoking, binge drinking, and texting while driving). Experiment 1 examined the influence of proportion of positive comments (large, medium, vs. small) and comment focus (message vs. behavior). As expected, proportion of positive comments was negatively related to people’s perceived social approval of smoking and texting while driving (injunctive norms). However, it had a concave downward relationship with perceived social approval of binge drinking (i.e., injunctive norms). The results also suggested an important impact of comment focus on people’s responses to health promotion messages. Experiment 2 examined the influence of proportion of thumbs-up (large, medium, vs. small) and message view count (high, medium vs. low). It was hypothesized that greater proportion of thumbs-up would lead to less favorable beliefs about problem behaviors. This hypothesis was supported only when the outcome variable was texting while driving intention. View count positively predicted people’s smoking and binge drinking intentions and marginally, positively predicted texting while driving subjective norms. It had a concave downward relationship with binge drinking attitudes. Experiment 2 also found complex joint effects of view count and proportion of thumbs-up. In spite of many findings about the influence of comments, ratings, and view count on norms, attitudes, or intentions, both study 1 and study 2 provided limited support for the hypothesized norms-based mediation. Limitations, theoretical and practical implications, and directions for future research are discussed.Item Design, Development, and Evaluation of a Teleoperated Master-Slave Surgical System for Breast Biopsy under Continuous MRI Guidance(2013) Yang, Bo; Desai, Jaydev P.; Mechanical Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)The goal of this project is to design and develop a teleoperated master-slave surgical system that can potentially assist the physician in performing breast biopsy with a magnetic resonance imaging (MRI) compatible robotic system. MRI provides superior soft-tissue contrast compared to other imaging modalities such as computed tomography or ultrasound and is used for both diagnostic and therapeutic procedures. The strong magnetic field and the limited space inside the MRI bore, however, restrict direct means of breast biopsy while performing real-time imaging. Therefore, current breast biopsy procedures employ a blind targeting approach based on magnetic resonance (MR) images obtained a priori. Due to possible patient involuntary motion or inaccurate insertion through the registration grid, such approach could lead to tool tip positioning errors thereby affecting diagnostic accuracy and leading to a long and painful process, if repeated procedures are required. Hence, it is desired to develop the aforementioned teleoperation system to take advantages of real-time MR imaging and avoid multiple biopsy needle insertions, improving the procedure accuracy as well as reducing the sampling errors. The design, implementation, and evaluation of the teleoperation system is presented in this dissertation. A MRI-compatible slave robot is implemented, which consists of a 1 degree of freedom (DOF) needle driver, a 3-DOF parallel mechanism, and a 2-DOF X-Y stage. This slave robot is actuated with pneumatic cylinders through long transmission lines except the 1-DOF needle driver is actuated with a piezo motor. Pneumatic actuation through long transmission lines is then investigated using proportional pressure valves and controllers based on sliding mode control are presented. A dedicated master robot is also developed, and the kinematic map between the master and the slave robot is established. The two robots are integrated into a teleoperation system and a graphical user interface is developed to provide visual feedback to the physician. MRI experiment shows that the slave robot is MRI-compatible, and the ex vivo test shows over 85%success rate in targeting with the MRI-compatible robotic system. The success in performing in vivo animal experiments further confirm the potential of further developing the proposed robotic system for clinical applications.Item Ultra Small Antenna and Low Power Receiver for Smart Dust Wireless Sensor Networks(2009) Yang, Bo; Goldsman, Neil; Electrical Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Wireless Sensor Networks have the potential for profound impact on our daily lives. Smart Dust Wireless Sensor Networks (SDWSNs) are emerging members of the Wireless Sensor Network family with strict requirements on communication node sizes (1 cubic centimeter) and power consumption (< 2mW during short on-states). In addition, the large number of communication nodes needed in SDWSN require highly integrated solutions. This dissertation develops new design techniques for low-volume antennas and low-power receivers for SDWSN applications. In addition, it devises an antenna and low noise amplifier co-design methodology to increase the level of design integration, reduce receiver noise, and reduce the development cycle. This dissertation first establishes stringent principles for designing SDWSN electrically small antennas (ESAs). Based on these principles, a new ESA, the F-Inverted Compact Antenna (FICA), is designed at 916MHz. This FICA has a significant advantage in that it uses a small-size ground plane. The volume of this FICA (including the ground plane) is only 7% of other state-of-the-art ESAs, while its efficiency (48.53%) and gain (-1.38dBi) are comparable to antennas of much larger dimensions. A physics-based circuit model is developed for this FICA to assist system level design at the earliest stage, including optimization of the antenna performance. An antenna and low noise amplifier (LNA) co-design method is proposed and proven to be valid to design low power LNAs with the very low noise figure of only 1.5dB. To reduce receiver power consumption, this dissertation proposes a novel LNA active device and an input/ouput passive matching network optimization method. With this method, a power efficient high voltage gain cascode LNA was designed in a 0.13um CMOS process with only low quality factor inductors. This LNA has a 3.6dB noise figure, voltage gain of 24dB, input third intercept point (IIP3) of 3dBm, and power consumption of 1.5mW at 1.0V supply voltage. Its figure of merit, using the typical definition, is twice that of the best in the literature. A full low power receiver is developed with a sensitivity of -58dBm, chip area of 1.1mm2, and power consumption of 2.85mW.Item STUDY ON-CHIP METAL-INSULATOR-SEMICONDUCTOR-METAL INTERCONNECTS WITH THE ALTERNATING-DIRECTION-IMPLICIT FINITE-DIFFERENCE TIME-DOMAIN METHOD(2005-04-29) Yang, Bo; Goldsman, Neil; Electrical Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)The Alternating-Direction-Implicit Finite-Difference Time-Domain method is used to analyze the on-chip Metal-Insulator-Semiconductor-Metal interconnects by solving Maxwell's equations in time domain. This method is efficient in solving problems with fine geometries much smaller than the shortest wavelength of interest. The iteration algorithm is evaluated thoroughly with respects to stability, numerical dispersion, grid size, time-step size etc.. The dielectric quasi-TEM mode, the slow wave mode, and the skin-effect mode of the MISM structure are all analyzed. We find that semiconductors can readily operate from the slow wave mode, to the transition region, to the skin effect mode in state of art technology. This thesis shows that the silicon substrate losses and the metal line losses can be modeled with high resolution. Signal dispersion and attenuation over a wide range of doping densities and operating frequencies is discussed. Accurate prediction of interconnect losses is critical for high-frequency design with highly constrained timing requirements.