A field investigation of diffusion within a submerged plant canopy

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 September 1997Saltwater marshes and wetlands are important buffers at the land-sea interface. Among the most biologically active ecosystems on Earth, natural and man-made wetlands are important interceptors of pollutants and nutrients bound for the coastal ocean. The transport, dilution, and deposition processes occurring within the marsh are key factors in determining this interception, and these are in turn determined largely by tidally driven flows as influenced by marsh vegetation and other physical characteristics. Vegetation type and density are of primary importance in these processes, both for pollutant/nutrient uptake concerns and in determining hydrodynamic characteristics of the marsh. This study examines the effect of vegetation density and ambient flow on diffusivity within a tidal marsh canopy, specifically Spartina alterniflora. Vegetation densities from 0-1.4% stem coverage and flows from 2-12 cm/sec were investigated using Rhodamine WT tracer, with resultant measured diffusivities ranging from approximately 0.5-3.0 cm2/sec. Diffusivity was found to be a strong function of ambient current, but a much weaker function of vegetation density. Presence of vegetation caused transverse and vertical diffusivities to be essentially isotropic over all vegetation densities, as opposed to the order of magnitude difference found in earlier non-vegetated studies. Only slight vegetation coverage was found to be necessary to produce this isotropy, with little additional change as stem density increased

Best Practices for Implementing Agile Methods: A Guide for Department of Defense Software Developers

Traditional plan-driven software development has been widely used in the government because it\u27s considered to be less risky, more consistent, and structured. But there has been a shift from this approach to Agile methods which are more flexible, resulting in fast releases by working in an incremental fashion to adapt to the reality of the changing or unclear requirements. This report describes the Agile software development philosophy, methods, and best practices in launching software design projects using the Agile approach. It is targeted to Defense Department software developers because they face broad challenges in creating enterprise-wide information systems, where Agile methods could be used most effectively. Though not a panacea, agile methods offer a solution to an important class of problems faced by organizations today. Technology and E-Government

Toward Visualization-Specific Heuristic Evaluation

This position paper describes heuristic evaluation as it relates to visualization and visual analytics. We review heuristic evaluation in general, then comment on previous process-based, performance-based, and framework-based efforts to adapt the method to visualization-specific needs. We postulate that the framework-based approach holds the most promise for future progress in development of visualization-specific heuristics, and propose a specific framework as a starting point. We then recommend a method for community involvement and input into the further development of the heuristic framework and more detailed design and evaluation guidelines

A field investigation of diffusion within a submerged plant canopy

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Ocean Engineering, 1997, and Thesis (M. Eng.)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, 1997.Includes bibliographical references (leaves 66-69).by Alvin E. Tarrell.M.Eng.M.S

Toward visualization-specific heuristic evaluation

This position paper describes heuristic evaluation as it relates to visualization and visual analytics. We review heuristic evaluation in general, then comment on previous process-based, performance-based, and framework-based efforts to adapt the method to visualization-specific needs. We postulate that the framework-based approach holds the most promise for future progress in development of visualization-specific heuristics, and propose a specific framework as a starting point. We then recommend a method for community involvement and input into the further development of the heuristic framework and more detailed design and evaluation guidelines