Hypervelocity impact microfoil perforations in the LEO space environment (LDEF, MAP AO-023 experiment)

The Microabrasion Foil Experiment comprises arrays of frames, each supporting two layers of closely spaced metallic foils and a back-stop plate. The arrays, deploying aluminum and brass foil ranging from 1.5 to some 30 microns were exposed for 5.78 years on NASA's LDEF at a mean altitude of 458 km. They were deployed on the North, South, East, West, and Space pointing faces; results presented comprise the perforation rates for each location as a function of foil thickness. Initial results refer primarily to aluminum of 5 microns thickness or greater. This penetration distribution, comprising 2,342 perforations in total, shows significantly differing characteristics for each detector face. The anisotropy confirms, incorporating the dynamics of particulate orbital mechanics, the dominance of incorporating extraterrestrial particulates penetrating thicknesses greater than 20 microns in Al foil, yielding fluxes compatible with hyperbolic geocentric velocities. For thinner foils, a disproportionate increase in flux of particles on the East, North, and South faces shows the presence of orbital particulates which exceed the extraterrestrial component perforation rate at 5 micron foil thickness by a factor of approx. 4

Mass and Charge Transport in Hydrated Polymeric Membranes

Mass and charge transport through hydrated polymer membranes has significant importance for many areas of engineering and industry. Multi-scale modeling and simulation techniques were used to study transport in relation to two specific membrane applications: (1) food packaging and (2) additives for polymer electrolytes. Chitosan/chitin films were studied due to their use as a sustainable, biodegradable food packaging film. The effects of hydration on the solvation, diffusivity, solubility, and permeability of oxygen molecules in these films were studied via molecular dynamics and confined random walk simulations. With increasing hydration, the membrane was observed to have a more homogeneous water distribution with the polymer chains being fully solvated. Insight from this work will help guide molecular modeling of chitosan/chitin membranes and experimental synthesis of these membranes, specifically highlighting efforts to chemically tailor chitosan membranes to favor discrete as opposed to continuous aqueous domains to help reduce oxygen permeability. Additives for proton exchange membranes (PEMs) were studied to aid in the developing next-generation membrane materials for fuel cell applications. We calculate and present predictions of our analytical model that describes the fundamental relationship between the nanoscale structure of PEMs and their proton conductivity using a set of structural descriptors, accounting for nanopore size, functionalization and connectivity in order to predict proton conductivities in PEMs. The model reproduces experimentally determined conductivities in two current PEM materials. To extend the model based on structural descriptors of PEMs, we studied polyethylene glycol (PEG), a polymer used in electrochemistry applications due to it hydrophilicity and pH-dependent behavior in aqueous environments. We conducted ab initio molecular dynamics simulations of an excess proton in bulk water and aqueous triethylene glycol (TEG) solution and reactive molecular dynamics simulations of an excess proton in bulk water, aqueous TEG solution, and aqueous PEG solution. We determined differences in protonic defect structures, kinetics, thermodynamics, and hydrogen-bond networks associated with structural diffusion between systems. Driving forces for polymeric membrane design goals include economics, efficiency, energy consumption and sustainable production. Insight from this work hopes to aid in determining key design parameters and reduce time-to-discovery for developing next-generation polymeric membranes

Structural Glass Observation Boxes (Willis Tower Ledge)

The 1,350 foot high Willis Tower (formerly known as Sears Tower) was lookingfor a grand attraction for their Skydeck in 2008. Few structures in the world haveglass floors (both interior and exterior), and almost all are continuously supportedalong their edges with steel supports. In order to create a dramatic, unimpededview of the City of Chicago the Skydeck Owners conceived of a glass platform thatwould protrude out of the building envelope and enable tourists, guests, and longtime residents of the City to walk outside the building and look down the 1,350 footexterior to the sidewalk below and have un-impeded views of the city. Thestructural glass floor system was designed to be supported by glass wall panels onthree sides. In addition, the entire platform was constructed to be movable; intoand out of the building. By allowing the glass observation box to move it could beconstructed on the interior of the building and enable the automated windowwashing system for the rest of the building to continue functioning un-obstructed aswell. Every piece of glass on this structure is designed to carry pedestrian loadsand work with elegant connections that are at once exposed and architecturallysculpted to disappear when the view of the city is observed by the guests on top ofthe highest structural glass floor in the world. In addition to gravity loads, andcoordinating the retraction mechanism, the glass was designed with attention toredundant laminates and supports, according to the buildings high wind loads, andrequiring special permissions by the City of Chicago for construction to begin

Preliminary results from the dust flux monitoring instrument during the encounter of Stardust spacecraft with Wild-2 comet

On January 2, 2004, the Stardust spacecraft successfully encountered the Wild-2 comet. The Dust Flux Monitoring Instrument (DFMI) provided quantitative measurements of dust particle fluxes and particle mass distributions throughout the entire flythrough

The Role of Interpretive Evaluation in Engineering Information Systems Requirements

The requirements for complex systems inevitably change continuously. Any successful software or information systems engineering approach needs to observe this simple fact. This paper argues for the critical importance of formative evaluation activities in any non-sequential, or learning-based RE process. We argue that evaluation with its focus on understanding and interpreting the evaluation results, is distinct from measurement. We also outline how evaluation activities can be performed from an interpretivist perspective, in a way that systematically informs formative evaluation activities during gradual, experimental requirements engineering activities

Questioning Ecosystem Assessment and Restoration Practices in a Major Urban Estuary: Perpetuating Myths of Degradation in Spite of Facts

The Jamaica Bay ecosystem is a dichotomy. It encompasses more than 12,000 acres of coastal estuarine marshes and an ecological diversity rivaling any coastal environment in the world. It is considerably altered, and is affected by a variety of ecological insults directly related to the fact that more than 14 million people live in its vicinity. Environmental protection institutions responded to the challenge of protecting the bay, surrounding wetlands and recreational benefits by addressing the increasing load of contaminants into the ecosystem. Billions of dollars have been spent during the past five decades on restoration attempts, including upgrading wastewater treatment plantsand the closure of three major sanitary landfills. Even with the curtailment of untreated wastewater release and ending periodic dredging and filling programs, all activities that are necessary processes in maintaining an urban harbor, the Jamaica Bay ecosystem has reached a point where many believe it to be unrecoverable, requiring massive infusions of restoration dollars. This categorization has been perpetuated based on questionable data (the “myths”) that, when investigated in rigorous scientific detail, prove to be unsubstantiated. In this paper, the origin of these myths and the scientific investigation that dispel them are discussed