In late 2007, a perched lava channel, built up to 45 m above the preexisting surface, developed during the ongoing eruption near Pu'u 'Ō'ō cone on Kīlauea Volcano's east rift zone. The lava channel was segmented into four pools extending over a total of 1.4 km. From late October to mid-December, a cyclic behavior, consisting of steady lava level rise terminated by vigorous spattering and an abrupt drop in lava level, was commonly observed in pool 1. We use geologic observations, video, time-lapse camera images, and seismicity to characterize and understand this cyclic behavior. Spattering episodes occurred at intervals of 40-100 min during peak activity and involved small (5-10-m-high) fountains limited to the margins of the pool. Most spattering episodes had fountains which migrated downchannel. Each spattering episode was associated with a rapid lava level drop of about 1 m, which was concurrent with a conspicuous cigar-shaped tremor burst with peak frequencies of 4-5 Hz. We interpret this cyclic behavior to be gas pistoning, and this is the first documented instance of gas pistoning in lava well away from the deeper conduit. Our observations and data indicate that the gas pistoning was driven by gas accumulation beneath the visco-elastic component of the surface crust, contrary to other studies which attribute similar behavior to the periodic rise of gas slugs. The gas piston events typically had a gas mass of about 2,500 kg (similar to the explosions at Stromboli), with gas accumulation and release rates of about 1.1 and 5.7 kg s-1, respectively. The time-averaged gas output rate of the gas pistoning events accounted for about 1-2% of the total gas output rate of the east rift zone eruption.

Relative motion between residual limb and prosthetic socket is an indication of poor fit. Both the fabrication and fitting processes are highly subjective and a favorable result depends upon the technician's expertise. Although numerous methods exist to measure the relative motion, all have limitations and are not well suited for clinical use. A measurement system using optical sensors has been proposed by students at the Technische Universität Darmstadt and evaluations of a functional model have yielded promising results. In this thesis, the existing functional model is improved and expanded to use an array of sensors. A new microcontroller is selected and incorporated into the system. The software and data communication are optimized for fast, reliable performance and the system is then evaluated on a test rig to determine favorable calibration settings and quantify performance. System frequencies up to 1299 Hz are achieved. It is found that the surface microstructure has a dominant effect over short measurement distances; calibrations performed over longer distances are to be preferred. For the chosen calibration factors, the greatest relative errors over a 40 mm distance are found to be 0.90% ± 0.51% in the X direction and -4.76% ± 1.61% in the Y-direction. A systematic drift is also identified. The final system accommodates up to eight sensors and is controlled from a feature-rich MATLAB GUI. / Master of Science / In lower limb prosthetics, the amount of relative motion between the prosthesis and residual limb is considered an indicator of the quality of fit. As existing methods for measuring this motion are generally difficult to use, a simpler system is desired. The task for this master's thesis is to develop an existing functional model into a measurement system with multiple sensors and validate its performance. The first step is to upgrade the microcontroller responsible for reading the sensor data and transmitting it to the PC. The original codes for both the microcontroller and PC-side Graphical User Interface (GUI) are then examined and optimized for maximum speed. The system is expanded to accommodate multiple sensors and its performance evaluated using a test-rig. Finally, the completed system is prepared for use in a future study by creating the appropriate component housings, wiring, and software functionalities.