Webster, Donald R.

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Now showing 1 - 9 of 9
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    A Bio-inspired Plume Tracking Algorithm for Mobile Sensing Swarms in Turbulent Flow
    (Georgia Institute of Technology, 2013-05) Chang, Dongsik ; Wu, Wencen ; Webster, Donald R. ; Weissburg, Marc J. ; Zhang, Fumin
    We develop a plume tracking algorithm for a swarm of mobile sensing agents in turbulent flow. Inspired by blue crabs, we propose a stochastic model for plume spikes based on the Poisson counting process, which captures the turbulent characteristic of plumes. We then propose an approach to estimate the parameters of the spike model, and transform the turbulent plume field detected by sensing agents into a smoother scalar field that shares the same source with the plume field. This transformation allows us to design path planning algorithms for mobile sensing agents in the smoother field instead of in the turbulent plume field. Inspired by the source seeking behaviors of fish schools, we design a velocity controller for each mobile agent by decomposing the velocities into two perpendicular parts: the forward velocity incorporates feedback from the estimated spike parameters, and the side velocity keeps the swarm together. The combined velocity is then used to plan the path for each agent in the swarm. Theoretical justifications are provided for convergence of the agent group to the plume source. The algorithms are also demonstrated through simulations.
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    Acquisition of a research and teaching salt water flume at Priest Landing, GA.
    (Georgia Institute of Technology, 2011-12-31) Weissburg, Marc J. ; Webster, Donald R. ; Fritz, Hermann M.
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    The hydrodynamics of benthic predation
    (Georgia Institute of Technology, 2010-08-30) Weissburg, Marc J. ; Webster, Donald R.
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    Integrative graduate education and research traineeship: signals in the sea
    (Georgia Institute of Technology, 2008-08-31) Hay, Mark E. ; Sobecky, Patricia A. ; Webster, Donald R.
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    Cue hierarchy and foraging in calanoid copepods: ecological implications of oceanographic structure
    (Georgia Institute of Technology, 2007-01) Woodson, Clifton Brock ; Webster, Donald R. ; Weissburg, Marc J. ; Yen, Jeannette
    Fine-scale water column structure was mimicked in a laboratory plane jet flume to examine responses of the calanoid copepods Temora longicornis and Acartia tonsa to layers consisting of a velocity gradient, density gradient, phytoplankton exudates and food (phytoplankton). Copepods were exposed to isolated layers and combinations of cues as defined by in situ conditions. Behaviors elicited by the velocity gradient and chemical exudate layers included increased swimming speed and turn frequency consistent with excited area-restricted search behavior, which led to increased proportional residence time in the layers. Both species had significant responses to isolated layers of velocity gradients and chemical exudates, with T. longicornis responding more intensely to chemical cues than velocity gradients and A. tonsa responding equally to both. Combined fluid mechanical and chemical cues elicited species-specific responses. For T. longicornis, chemical presence induced responses that strengthened or cancelled initial reactions to the velocity gradient. These results suggest a cue hierarchy where a velocity gradient acts as an initial cue for narrowing search regions, and chemical cues and food presence determine consequent responses. For A. tonsa, combining velocity gradient and chemical cues had the same effect on copepod behavior as the individual cues, which suggests both cues are equal sources of information but are not closely associated. In both species, physical contact with particles or cells initiated feeding behavior, resulting in lower swimming speeds. Fluid density had a potentially aversive effect, as neither species responded with an area-restricted search response and individuals rarely crossed a strong density gradient. Observed behaviors may lead to aggregation, especially when superimposed on rhythmic movements such as diel vertical migration.
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    The small-scale structure of the fluctuating passive scalar field in a turbulent boundary layer
    (Georgia Institute of Technology, 2003-06-15) Webster, Donald R.
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    A novel apparatus for simulating oceanic turbulence in the laboratory
    (Georgia Institute of Technology, 2003) Webster, Donald R.
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    Quantifying the Relationship Between Remotely-Sensed and Modeled Soil Moist
    (Georgia Institute of Technology, 2002-11-20) Webster, Donald R.
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    Mobilization & fate of inorganic contaminants due to resuspension. . .
    (Georgia Institute of Technology, 1998) Sturm, Terry W. ; Amirtharajah, Appiah ; Webster, Donald R. ; Tiller, C.L.