869 research outputs found

    Selected Characteristics of Savings and Thrift Plans for Private Industry Workers

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    [Excerpt] This issue of Beyond the Numbers looks at the growth in the prevalence and at selected characteristics of employer-provided savings and thrift plans in private industry in the United States. The data for this article come from the National Compensation Survey: Health and Retirement Plan Provisions in Private Industry in the United States, 2012. In some instances, comparisons of 2012 data are made to 2009 data, which came from National Compensation Survey: Health and Retirement Plan Provisions in Private Industry in the United States, 2009

    William C. Evans, Jr. in a Senior Saxophone Recital

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    This is the program for the senior saxophone recital of William C. Evans, Jr., accompanied by Jolene Zook on the piano. The recital was held on December 5, 1994, in the Mabee Fine Arts Center Recital Hall

    Optimizing inequality joins in Datalog with approximated constraint propagation

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    Datalog systems evaluate joins over arithmetic (in)equalities as a naive generate-and-test of Cartesian products. We exploit aggregates in a source-to-source transformation to reduce the size of Cartesian products and to improve performance. Our approach approximates the well-known propagation technique from Constraint Programming. Experimental evaluation shows good run time speed-ups on a range of non-recursive as well as recursive programs. Furthermore, our technique improves upon the previously reported in the literature constraint magic set transformation approach

    Origins of Solar System Dust Beyond Jupiter

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    The measurements of cosmic interplanetary dust by the instruments on board the Pioneer 10 and 11 spacecraft contain the dynamical signature of dust generated by Edgeworth-Kuiper Belt objects, as well as short period Oort Cloud comets and short period Jupiter family comets. While the dust concentration detected between Jupiter and Saturn is mainly due to the cometary components, the dust outside Saturn's orbit is dominated by grains originating from the Edgeworth-Kuiper Belt. In order to sustain a dust concentration that accounts for the Pioneer measurements, short period external Jupiter family comets, on orbits similar to comet 29P/Schwassmann-Wachmann-1, have to produce 8×104:g:s18\times 10^4:{\rm g}:{\rm s}^{-1} of dust grains with sizes between 0.01 and 6:mm6:{\rm mm}. A sustained production rate of 3×105:g:s13\times 10^5:{\rm g}:{\rm s}^{-1} has to be provided by short period Oort cloud comets on 1P/Halley-like orbits. The comets can not, however, account for the dust flux measured outside Saturn's orbit. The measurements there can only be explained by a generation of dust grains in the Edgeworth-Kuiper belt by mutual collisions of the source objects and by impacts of interstellar dust grains onto the objects' surfaces. These processes have to release in total 5×107:g:s15\times 10^7:{\rm g}:{\rm s}^{-1} of dust from the Edgeworth Kuiper belt objects in order to account for the amount of dust found by Pioneer beyond Saturn, making the Edgeworth-Kuiper disk the brightest extended feature of the Solar System when observed from afar

    Silicon on ceramic process. Silicon sheet growth development for the large-area silicon sheet task of the low-cost silicon solar array project

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    The technical and economic feasibility of producing solar-cell-quality sheet silicon was investigated. The sheets were made by coating one surface of carbonized ceramic substrates with a thin layer of large-grain polycrystalline silicon from the melt. Significant progress was made in all areas of the program

    Dip-coating process: Silicon sheet growth development for the large-area silicon sheet task of the low-cost silicon solar array project

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    The objective of this research program is to investigate the technical and economic feasibility of producing solar-cell-quality sheet silicon by coating one surface of carbonized ceramic substrates with a thin layer of large-grain polycrystalline silicon from the melt. The past quarter demonstrated significant progress in several areas. Seeded growth of silicon-on-ceramic (SOC) with an EFG ribbon seed was demonstrated. Different types of mullite were successfully coated with silicon. A new method of deriving minority carrier diffusion length, L sub n from spectral response measurements was evaluated. ECOMOD cost projections were found to be in good agreement with the interim SAMIS method proposed by JPL. On the less positive side, there was a decrease in cell performance which we believe to be due to an unidentified source of impurities

    Optimizing Inequality Joins in Datalog with Approximated Constraint Propagation

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    Achieving Innovation and Affordability Through Standardization of Materials Development and Testing

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    The successful expansion of development, innovation, and production within the aeronautics industry during the 20th century was facilitated by collaboration of government agencies with the commercial aviation companies. One of the initial products conceived from the collaboration was the ANC-5 Bulletin, first published in 1937. The ANC-5 Bulletin had intended to standardize the requirements of various government agencies in the design of aircraft structure. The national space policy shift in priority for NASA with an emphasis on transferring the travel to low earth orbit to commercial space providers highlights an opportunity and a need for the national and global space industries. The same collaboration and standardization that is documented and maintained by the industry within MIL-HDBK-5 (MMPDS-01) and MIL-HBDK-17 (nonmetallic mechanical properties) can also be exploited to standardize the thermal performance properties, processing methods, test methods, and analytical methods for use in aircraft and spacecraft design and associated propulsion systems. In addition to the definition of thermal performance description and standardization, the standardization for test methods and analysis for extreme environments (high temperature, cryogenics, deep space radiation, etc) would also be highly valuable to the industry. Its subsequent revisions and conversion to MIL-HDBK-5 and then MMPDS-01 established and then expanded to contain standardized mechanical property design values and other related design information for metallic materials used in aircraft, missiles, and space vehicles. It also includes guidance on standardization of composition, processing, and analytical methods for presentation and inclusion into the handbook. This standardization enabled an expansion of the technologies to provide efficiency and reliability to the consumers. It can be established that many individual programs within the government agencies have been overcome with development costs generated from these nonstandard requirements. Without industry standardization and acceptance, the programs are driven to shoulder the costs of determining design requirements, performance criteria, and then material qualification and certification. A significant investment that the industry could make to both reduce individual program development costs and schedules while expanding commercial space flight capabilities would be to invest in standardizing material performance properties for high temperature, cryogenic, and deep space environments for both metallic and nonmetallic materials

    Silicon on Ceramic Process: Silicon Sheet Growth and Device Development for the Large-area Silicon Sheet and Cell Development Tasks of the Low-cost Solar Array Project

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    The technical and economic feasibility of producing solar cell quality sheet silicon was investigated. It was hoped this could be done by coating one surface of carbonized ceramic substrates with a thin layer of large-grain polycrystalline silicon from the melt. Work was directed towards the solution of unique cell processing/design problems encountered with the silicon-ceramic (SOC) material due to its intimate contact with the ceramic substrate. Significant progress was demonstrated in the following areas; (1) the continuous coater succeeded in producing small-area coatings exhibiting unidirectional solidification and substatial grain size; (2) dip coater succeeded in producing thick (more than 500 micron) dendritic layers at coating speeds of 0.2-0.3 cm/sec; and (3) a standard for producing total area SOC solar cells using slotted ceramic substrates was developed

    The Speed and Orientation of the Parsec-Scale Jet in 3C 279

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    We have calculated inverse-Compton Doppler factors for 3C 279 using the collection of VLBI data recently published by us, and the collection of multiwavelength spectra recently published by Hartman et al. From the Doppler factor and superluminal apparent speed, we then calculate the Lorentz factor and angle to the line-of-sight of the parsec-scale relativistic jet. We model the jet components as homogeneous spheres and the VLBI core as an unresolved inhomogeneous conical jet. The conical-jet model can be made to match both the observed X-ray emission and the VLBI properties of the core with a suitable choice of Doppler factor, implying the core makes a significant contribution to the X-ray emission. The parameters of the conical models indicate the jet is particle dominated at the radii that produce significant emission, and is not in equipartition. At the inner radius of the conical jet the magnetic field is of order 0.1 G and the relativistic-particle number density is of order 10 cm^{-3}. When all components are included in the calculation, then on average the core produces about half of the X-rays, with the other half being split between the long-lived component C4 and the brightest inner-jet component. We calculate an average speed and angle to the line-of-sight for the region of the jet interior to 1 mas of v=0.992c (gamma=8) and 4 degrees, and an average speed and angle to the line-of-sight for C4 (at a distance from the core of 3 mas) of v=0.997c (gamma=13) and 2 degrees. These values imply average Doppler factors of delta=12 for the inner jet, and delta=21 for C4
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