http://hdl.handle.net/1912/10 Thu, 09 Feb 2012 11:24:36 GMT 2012-02-09T11:24:36Z http://hdl.handle.net/1912/5007 Analytical study of the horizontal ducting of sound by an oceanic front over a slope Lin, Ying-Tsong; Lynch, James F. The horizontal ducting of sound by an oceanic temperature front over a sloping bottom is studied with an idealized wedge model consisting of a lateral interface across the slope. The water outside the frontal interface has higher temperature, hence faster sound speed, and it will produce inshore reflection/refraction of the sound. Combining the offshore refraction caused by the sloping bottom, propagating sound can be ducted along the front. An analytical solution to the sound pressure field in the idealized model is derived, and an example is presented to demonstrate and discuss the ducting effect. Author Posting. © Acoustical Society of America, 2011. This article is posted here by permission of Acoustical Society of America for personal use, not for redistribution. The definitive version was published in Journal of the Acoustical Society of America 131 (2012): EL1-EL7, doi:10.1121/1.3662030. Tue, 13 Dec 2011 00:00:00 GMT http://hdl.handle.net/1912/5007 2011-12-13T00:00:00Z http://hdl.handle.net/1912/4996 Circulation and intrusions northeast of Taiwan : chasing and predicting uncertainty in the cold dome Gawarkiewicz, Glen G.; Jan, Sen; Lermusiaux, Pierre F.J.; McClean, Julie L.; Centurioni, Luca; Taylor, Kevin; Cornuelle, Bruce D.; Duda, Timothy F.; Wang, Joe; Yang, Yiing Jiang; Sanford, Thomas B.; Lien, Ren-Chieh; Lee, Craig M.; Lee, Ming-An; Leslie, Wayne; Haley, Patrick J.; Niiler, Pearn P.; Gopalakrishnan, Ganesh; Velez-Belchi, Pedro; Lee, Dong-Kyu; Kim, Yoo Yin An important element of present oceanographic research is the assessment and quantification of uncertainty. These studies are challenging in the coastal ocean due to the wide variety of physical processes occurring on a broad range of spatial and temporal scales. In order to assess new methods for quantifying and predicting uncertainty, a joint Taiwan-US field program was undertaken in August/September 2009 to compare model forecasts of uncertainties in ocean circulation and acoustic propagation, with high-resolution in situ observations. The geographical setting was the continental shelf and slope northeast of Taiwan, where a feature called the "cold dome" frequently forms. Even though it is hypothesized that Kuroshio subsurface intrusions are the water sources for the cold dome, the dome's dynamics are highly uncertain, involving multiple scales and many interacting ocean features. During the experiment, a combination of near-surface and profiling drifters, broad-scale and high-resolution hydrography, mooring arrays, remote sensing, and regional ocean model forecasts of fields and uncertainties were used to assess mean fields and uncertainties in the region. River runoff from Typhoon Morakot, which hit Taiwan August 7–8, 2009, strongly affected shelf stratification. In addition to the river runoff, a cold cyclonic eddy advected into the region north of the Kuroshio, resulting in a cold dome formation event. Uncertainty forecasts were successfully employed to guide the hydrographic sampling plans. Measurements and forecasts also shed light on the evolution of cold dome waters, including the frequency of eddy shedding to the north-northeast, and interactions with the Kuroshio and tides. For the first time in such a complex region, comparisons between uncertainty forecasts and the model skill at measurement locations validated uncertainty forecasts. To complement the real-time model simulations, historical simulations with another model show that large Kuroshio intrusions were associated with low sea surface height anomalies east of Taiwan, suggesting that there may be some degree of predictability for Kuroshio intrusions. Author Posting. © The Oceanography Society, 2011. This article is posted here by permission of The Oceanography Society for personal use, not for redistribution. The definitive version was published in Oceanography 24 no. 4 (2011): 110–121, doi:10.5670/oceanog.2011.99. Thu, 01 Dec 2011 00:00:00 GMT http://hdl.handle.net/1912/4996 2011-12-01T00:00:00Z http://hdl.handle.net/1912/4987 Chemical data quantify Deepwater Horizon hydrocarbon flow rate and environmental distribution Ryerson, Thomas B.; Camilli, Richard; Kessler, John D.; Kujawinski, Elizabeth B.; Reddy, Christopher M.; Valentine, David L.; Atlas, Elliot; Blake, Donald R.; de Gouw, Joost; Meinardi, Simone; Parrish, David D.; Peischl, Jeff; Seewald, Jeffrey S.; Warneke, Carsten Detailed airborne, surface, and subsurface chemical measurements, primarily obtained in May and June 2010, are used to quantify initial hydrocarbon compositions along different transport pathways – in deep subsurface plumes, in the initial surface slick, and in the atmosphere – during the Deepwater Horizon (DWH) oil spill. Atmospheric measurements are consistent with a limited area of surfacing oil, with implications for leaked hydrocarbon mass transport and oil drop size distributions. The chemical data further suggest relatively little variation in leaking hydrocarbon composition over time. While readily soluble hydrocarbons made up ~25% of the leaking mixture by mass, subsurface chemical data show these compounds made up ~69% of the deep plume mass; only ~31% of deep plume mass was initially transported in the form of trapped oil droplets. Mass flows along individual transport pathways are also derived from atmospheric and subsurface chemical data. Subsurface hydrocarbon composition, dissolved oxygen, and dispersant data are used to provide a new assessment of release of hydrocarbons from the leaking well. We use the chemical measurements to estimate that (7.8±1.9) x106 kg of hydrocarbons leaked on June 10, 2010, directly accounting for roughly three-quarters of the total leaked mass on that day. The average environmental release rate of (10.1 ± 2.0) x106 kg/day derived using atmospheric and subsurface chemical data agrees within uncertainties with the official average leak rate of (10.2 ± 1.0) x106 kg/day derived using physical and optical methods. Author Posting. © The Author(s), 2011. This is the author's version of the work. It is posted here by permission of National Academy of Sciences for personal use, not for redistribution. The definitive version was published in Proceedings of the National Academy of Sciences of the United States of America (2012), doi:10.1073/pnas.1110564109. Fri, 11 Nov 2011 00:00:00 GMT http://hdl.handle.net/1912/4987 2011-11-11T00:00:00Z http://hdl.handle.net/1912/4957 Development of an actively compliant underwater manipulator DiPietro, David M. This thesis describes the design, construction, and evaluation of an actively compliant underwater manipulator for installation on the underwater remotely operated vehicle (ROV) JASON. The goal of this work has been to produce a high fidelity force-controllable manipulator exhibiting no backlash, low stiction/friction, high backdriveability, wide dynamic range, and possessing a large work envelope. By reducing the inherent dynamic nonlineari ties, a wide range of joint compliances can realistically be achieved. This feature is important when implementing various force control schemes, particularly impedance control. In addition, a mechanically "clean" transmission reduces the need for sensors and allows the user to rely on integral motor sensors to provide torque, position, and velocity information. A three axis manipulator rated to full ocean depth was built. Each of the revolute joints is driven by a DC brushless sensorimotor working through a multi-stage cable/pulley transmission. The manipulator mechanism and wiring is fully enclosed by cast aluminum housings filled with mineral oil. Mineral oil functions to pressure compensate and lubricate the system. Exterior surfaces of the manipulator are smooth and continuous, and were designed to act as work surfaces. Joints one and two have a 240° range of motion, while joint three can rotate 380°. The manipulator transmissions are modeled and predictions of manipulator stiffness, dynamic range, payload capacity, and hysteresis are compared with the results of tests conducted on the actual system. Operation of the cable/pulley transmissions are evaluated and suggestions for improvements are given. Submitted in partial fulfillment of the requirements for the degree of Master of Science at the Massachusetts Institute of Technology and the Woods Hole Oceanographic Institution May 1988 Sun, 01 May 1988 00:00:00 GMT http://hdl.handle.net/1912/4957 1988-05-01T00:00:00Z