Local versus Global Search in Channel Graphs

Previous studies of search in channel graphs has assumed that the search is global; that is, that the status of any link can be probed by the search algorithm at any time. We consider for the first time local search, for which only links to which an idle path from the source has already been established may be probed. We show that some well known channel graphs may require exponentially more probes, on the average, when search must be local than when it may be global.Comment: i+13 pages, 2 figure

Water Quality Monitoring of the Little Calumet East Branch Watershed

The Little Calumet East Branch (LCEB) is a 10-digit hydrologic unit code (HUC) watershed that ultimately discharges into Lake Michigan. The watershed begins in unincorporated LaPorte County and discharges west through unincorporated Porter County, converges with the West Branch of the Little Calumet River, and finally discharges into Lake Michigan via the Burns Ditch Waterway. A water quality monitoring study was performed in the summer of 2012 as part of the watershed management process led by a not-for-profit organization, Save the Dunes. Save the Dunes’ Great Lakes Innovative Stewardship through Education Network (GLISTEN) liaisons initiated weekly monitoring at eleven LCEB sites for nine weeks during the summer 2012 recreational period. The Indiana Department of Environmental Management (IDEM) conducted monthly monitoring of 48 sites in the LCEB including the sites monitored by the GLISTEN liaisons. Parameters measured for in the watershed included nitrogen, pH, phosphorus, dissolved oxygen, conductivity, water flow, and Escherichia coli

Parallel three-dimensional simulations of quasi-static elastoplastic solids

Hypo-elastoplasticity is a flexible framework for modeling the mechanics of many hard materials under small elastic deformation and large plastic deformation. Under typical loading rates, most laboratory tests of these materials happen in the quasi-static limit, but there are few existing numerical methods tailor-made for this physical regime. In this work, we extend to three dimensions a recent projection method for simulating quasi-static hypo-elastoplastic materials. The method is based on a mathematical correspondence to the incompressible Navier-Stokes equations, where the projection method of Chorin (1968) is an established numerical technique. We develop and utilize a three-dimensional parallel geometric multigrid solver employed to solve a linear system for the quasi-static projection. Our method is tested through simulation of three-dimensional shear band nucleation and growth, a precursor to failure in many materials. As an example system, we employ a physical model of a bulk metallic glass based on the shear transformation zone theory, but the method can be applied to any elastoplasticity model. We consider several examples of three-dimensional shear banding, and examine shear band formation in physically realistic materials with heterogeneous initial conditions under both simple shear deformation and boundary conditions inspired by friction welding.Comment: Final version. Accepted for publication in Computer Physics Communication

How an air academy can train officers to improve American public relations abroad

Thesis (M.S.)--Boston Universit