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The charging of space debris due to the ambient plasma environment in the low earth orbit (LEO) and geostationary earth orbit (GEO) regions of the ionosphere has been investigated using both analytic and particle-in-cell (PIC) mod...
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The charging of space debris due to the ambient plasma environment in the low earth orbit (LEO) and geostationary earth orbit (GEO) regions of the ionosphere has been investigated using both analytic and particle-in-cell (PIC) modeling. The analytic estimates have been obtained using improved Orbit Motion Limited (OML) modeling while the simulation studies have been carried out using the open source simulation code SPIS. In the GEO region account has been taken of charging arising from photoemission effects as well as due to the impact of energetic charged particle beams associated with solar flares. The PIC approach has also been used to study differential charging of debris objects that are composed of patches of conducting and insulated regions. For debris sizes larger than a few microns the orbital perturbations arising from the interaction of the debris charge with the ambient magnetic field and ionospheric electric fields are found to be insignificant in comparison to those arising from gravitational and solar radiation pressure effects and hence may have a negligible influence on orbital calculations. However the debris charge can give rise to nonlinear electrostatic wave excitations in the ambient plasma in the form of precursor solitons that move ahead of the debris. A model calculation delineating the conditions and nature of such excitations has been carried out. A controlled laboratory experiment to test this theoretical concept has also been done and has shown the first ever excitation of precursor solitons in a plasma medium. Detection of such waves in the debris orbital regions using ground-based techniques can provide a novel method of detecting centimeter-sized objects that are otherwise difficult to track using optical methods. The discovery of these precursor excitations also opens up potential new areas of fundamental and applied research in the field of plasmas and space physics.
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One of the prevailing needs of the U.S. Air Force has been to utilize a heterogeneous set of physical links (RF, Optical/Laser and SATCOM), for interconnecting a set of terrestrial, space and highly mobile airborne platforms (sate...
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One of the prevailing needs of the U.S. Air Force has been to utilize a heterogeneous set of physical links (RF, Optical/Laser and SATCOM), for interconnecting a set of terrestrial, space and highly mobile airborne platforms (satellites, aircrafts and Unmanned Aerial Vehicles (UAVs)) to form an Airborne Network (AN). Not only does this complex network involve a large set of heterogeneous resources, but also the operative environment of this network is highly dynamic. Thus, there has been a demand for new models to characterize, manage and quantify network performance under such diverse network operating conditions. The goal of this research project was to undertake an investigation into some of the fundamental issues underlying this operative environment that is essential for successful design, deployment and operation of such a complex network. In this respect, studies were conducted in the following four key interrelated topics: (i) the design of mobility patterns of airborne platforms to provide stable operating conditions, (ii) the design of networks that enable graceful performance degradation, (iii) the information transfer capacity of a dynamic heterogeneous airborne network, and (iv) routing performance in diverse network conditions.
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Work performed during the 3-year grant period includes the following: (a) The design of an efficient, bubble-free, nanoscale motor consisting of a copper-platinum segmented rod that operates as a nanobattery in dilute aqueous brom...
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Work performed during the 3-year grant period includes the following: (a) The design of an efficient, bubble-free, nanoscale motor consisting of a copper-platinum segmented rod that operates as a nanobattery in dilute aqueous bromine or iodine solutions. (b) The fabrication of motors driven by both catalytic polymerization and depolymerization reactions. The former were observed to exhibit chemotaxis when placed in a monomer gradient. Scaling down to sub-nm scale, enhanced mobility for single catalyst molecules was also observed during substrate turnover. (c) The identification of a new mechanism for producing self-generated flows. This involves auto diffusio- osmosis due to the dissolution of a wide variety of minerals. Further, the diffusio-osmotic mechanisms was employed to design proof of principle crack sensing and repair systems, as well as to drive flows in and out of dead-end channels. (d) The design of a polymeric material that is self-powered, operates as a non-mechanical fluid pump in response to molecular level inputs, and 'remembers' the presence of the signal to which it was exposed, even when the signal is fleeting.
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During the last couple of decades or so, the subject of nanoscale science began expanding into a unique field of science that offered the prospect of tailoring the design of materials having chosen properties. Two potentially prom...
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During the last couple of decades or so, the subject of nanoscale science began expanding into a unique field of science that offered the prospect of tailoring the design of materials having chosen properties. Two potentially promising approaches were conceived, one involving a bottom up approach while the other a top down method. In both cases, approaching the desirable nanoscale size regime where the properties of matter began to display nonlinear scalable behavior in which each atom counts, the connection to the area of cluster science began to be realized. Four well established academic groups (Castleman-PSU; Khanna---VCU; Sen---PSU; Weiss---PSU) successfully responded to a call for a MURI proposal with the eventual objective of expanding the concept of employing clusters and related superatoms for the use of building blocks for designing matter of nanoscale dimensions with tailored properties. The four groups, which had a history of closely interacting, fashioned a comprehensive research program to lay out the fundamentals for exploring the bottom up approach to design and produce new building blocks for several classes of systems including metals and alloys, metal compounds, metalloids, zintl ions and covalently bound species. Beyond the above, a major objective was to lay the foundation for producing materials with selected band gaps.
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This report describes how the education system in the United States compares with education systems in the other Group of Eight (G-8) countries - Canada, France, Germany, Italy, Japan, the Russian Federation, the United Kingdomtha...
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This report describes how the education system in the United States compares with education systems in the other Group of Eight (G-8) countries - Canada, France, Germany, Italy, Japan, the Russian Federation, the United Kingdomthat are among the worlds most economically developed countries and among the United States largest economic partners. Comparative Indicators of Education in the United States and Other G-8 Countries: 2009 draws on the most current information about education from four primary sources: the Indicators of National Education Systems (INES) at the Organization for Economic Cooperation and Development (OECD); the Progress in International Reading Literacy Study (PIRLS); the Program for International Student Assessment (PISA); and the Trends in International Mathematics and Science Study (TIMSS). Begun in 2002, the series is published on a biennial basis.
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The Program for International Student Assessment (PISA), sponsored by the Organization for Economic Cooperation and Development (OECD) and carried out in 32 countries, including the United States, evaluates 15-year-old students' l...
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The Program for International Student Assessment (PISA), sponsored by the Organization for Economic Cooperation and Development (OECD) and carried out in 32 countries, including the United States, evaluates 15-year-old students' literacy in three areas: reading, mathematics, and science. The first PISA survey was conducted in 2000, with additional assessments planned on a 3-year cycle. Each survey focuses on one of the three types of literacy; in PISA 2000, reading literacy was the major focus. Therefore, it is possible to perform a detailed examination of reading literacy within and across countries. This report has two objectives: first, to explore how the demographic and educational characteristics of low-performing students compare to other students within the United States; second,to analyze if the United States differs from the other PISA countries in terms of the characteristics of its low-performing students.
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A most pressing need for the DOE environmental management program is the removal of toxic organic compounds present in groundwater and soil at specific DOE sites. While several remediation procedures have been proposed, they suffe...
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A most pressing need for the DOE environmental management program is the removal of toxic organic compounds present in groundwater and soil at specific DOE sites. While several remediation procedures have been proposed, they suffer from one or more drawbacks. The objective of the present research was to develop new catalytic procedures for the removal of toxic organic compounds from the environment through their deep oxidation to harmless products. In water, metallic palladium was found to catalyze the deep oxidation of a wide variety of toxic organic compounds by dioxygen at 80-90 C in the presence of carbon monoxide or dihydrogen. Several classes of organic compounds were examined: benzene, phenol and substituted phenols, nitro and halo organics, organophosphorus, and organosulfur compounds. In every case, deep oxidation to carbon monoxide, carbon dioxide, and water occurred in high yields, resulting in up to several hundred turnovers over a 24 hour period. For substrates susceptible to hydrogenation, the conversions were generally high with dihydrogen than with carbon monoxide. It is clear from the results obtained that we have discovered an exceptionally versatile catalytic system for the deep oxidation of toxic organic compounds in water. This system possesses several attractive features not found simultaneously in other reported systems. These are (a) the ability to directly utilize dioxygen as the oxidant, (b) the ability to carry out the deep oxidation of a particularly wide range of functional organics, and (c) the ease of recovery of the catalyst by simple filtration.
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A most pressing need for the DOE environmental management program is the removalof toxic organic compounds present in groundwater and soil at specific DOE sites. While several remediation procedures have been proposed, they suffer...
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A most pressing need for the DOE environmental management program is the removalof toxic organic compounds present in groundwater and soil at specific DOE sites. While several remediation procedures have been proposed, they suffer from one or more drawbacks. The objective of the present research was to develop new catalytic procedures for the removal of toxic organic compounds from the environment through their deep oxidation to harmless products. In water, metallic palladium was found to catalyze the deep oxidation of a wide variety of toxic organic compounds by dioxygen at 80-90 C in the presence of carbon monoxide or dihydrogen. Several classes of organic compounds were examined: benzene, phenol and substituted phenols, nitro and halo organics, organophosphorus, and organosulfur compounds. In every case, deep oxidation to carbon monoxide, carbon dioxide, and water occurred in high yields, resulting in up to several hundred turnovers over a 24 hour period. For substrates susceptible to hydrogenation, the conversions were generally high with dihydrogen than with carbon monoxide. It is clear from the results obtained that we have discovered an exceptionally versatile catalytic system for the deep oxidation of toxic organic compounds in water. This system possesses several attractive features not found simultaneously in other reported systems. These are (a) the ability to directly utilize dioxygen as the oxidant, (b) the ability to carry out the deep oxidation of a particularly wide range of functional organics, and (c) the ease of recovery of the catalyst by simple filtration.
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In August 1999, practitioners, researchers, academicians, and administrators from around the country assembled at the The Next Millennium Conference: Ending Domestic Violence to reflect on the historical milestones of the domestic...
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In August 1999, practitioners, researchers, academicians, and administrators from around the country assembled at the The Next Millennium Conference: Ending Domestic Violence to reflect on the historical milestones of the domestic violence movement: celebration of advances made in combating, and re-commitment to eliminating domestic violence.
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