36,206 research outputs found

    Orbiting deep space relay station. Volume 3: Implementation plan

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    An implementation plan for the Orbiting Deep Space Relay Station (ODSRS) is described. A comparison of ODSRS life cycle costs to other configuration options meeting future communication requirements is presented

    Orbiting Deep Space Relay Station (ODSRS). Volume 1: Requirement determination

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    The deep space communications requirements of the post-1985 time frame are described and the orbiting deep space relay station (ODSRS) is presented as an option for meeting these requirements. Under current conditions, the ODSRS is not yet cost competitive with Earth based stations to increase DSN telemetry performance, but has significant advantages over a ground station, and these are sufficient to maintain it as a future option. These advantages include: the ability to track a spacecraft 24 hours per day with ground stations located only in the USA; the ability to operate at higher frequencies that would be attenuated by Earth's atmosphere; and the potential for building very large structures without the constraints of Earth's gravity

    Mariner Mars 1964 telecommunication system

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    Radio, telemetry, and command subsystems of Mariner IV telecommunication syste

    Attracted Diffusion-Limited Aggregation

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    In this paper, we present results of extensive Monte Carlo simulations of diffusion-limited aggregation (DLA) with a seed placed on an attractive plane as a simple model in connection with the electrical double layers. We compute the fractal dimension of the aggregated patterns as a function of the attraction strength \alpha. For the patterns grown in both two and three dimensions, the fractal dimension shows a significant dependence on the attraction strength for small values of \alpha, and approaches to that of the ordinary two-dimensional (2D) DLA in the limit of large \alpha. For non-attracting case with \alpha=1, our results in three dimensions reproduce the patterns of 3D ordinary DLA, while in two dimensions our model leads to formation of a compact cluster with dimension two. For intermediate \alpha, the 3D clusters have quasi-2D structure with a fractal dimension very close to that of the ordinary 2D-DLA. This allows one to control morphology of a growing cluster by tuning a single external parameter \alpha.Comment: 6 pages, 6 figures, to appear in Phys. Rev. E (2012

    Erratum: IRAS observations of irregular galaxies

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    In Infrared Astronomy Satellite (IRAS) observations of irregular galaxies, galactic blue luminosities were based on standard optical definitions. The blue luminosities (L sub B) were derived from the blue absolute magnitude (M sub B) or form the in band flux. However, the L sub B system for spiral galaxies was based on quasi-bolometric (rather than in band) fluxes. The formulation and resulting statements are corrected

    Development of quality assurance methods for epoxy graphite prepreg

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    Quality assurance methods for graphite epoxy/prepregs were developed. Liquid chromatography, differential scanning calorimetry, and gel permeation chromatography were investigated. These methods were applied to a second prepreg system. The resin matrix formulation was correlated with mechanical properties. Dynamic mechanical analysis and fracture toughness methods were investigated. The chromatography and calorimetry techniques were all successfully developed as quality assurance methods for graphite epoxy prepregs. The liquid chromatography method was the most sensitive to changes in resin formulation. The were also successfully applied to the second prepreg system

    Sex Differences in Elite Swimming with Advanced Age Are Less Than Marathon Running

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    The sex difference in marathon performance increases with finishing place and age of the runner but whether this occurs among swimmers is unknown. The purpose was to compare sex differences in swimming velocity across world record place (1st–10th), age group (25–89 years), and event distance. We also compared sex differences between freestyle swimming and marathon running. The world\u27s top 10 swimming times of both sexes for World Championship freestyle stroke, backstroke, breaststroke, and butterfly events and the world\u27s top 10 marathon times in 5-year age groups were obtained. Men were faster than women for freestyle (12.4 ± 4.2%), backstroke (12.8 ± 3.0%), and breaststroke (14.5 ± 3.2%), with the greatest sex differences for butterfly (16.7 ± 5.5%). The sex difference in swimming velocity increased across world record place for freestyle (P \u3c 0.001), breaststroke, and butterfly for all age groups and distances (P  \u3c 0.001) because of a greater relative drop-off between first and 10th place for women. The sex difference in marathon running increased with the world record place and the sex difference for marathon running was greater than for swimming (P \u3c 0.001). The sex difference in swimming increased with world record place and age, but was less than for marathon running. Collectively, these results suggest more depth in women\u27s swimming than marathon running
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