13,840 research outputs found

    OFT ascent/descent ancillary data requirements document

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    Requirements are presented for the ascent/descent (A/D) navigation and attitude-dependent ancillary data products to be generated for the space shuttle orbiter in support of orbital flight test requirements, MPAD guidance and navigation performance assessment, and the mission evaluation team. It was intended that this document serve as the sole requirements control instrument between MPB/MPAD and the A/D ancillary data users. The requirements are primarily functional in nature, but some detail level requirements are also included

    Using Numerical Dynamic Programming to Compare Passive and Active Learning in the Adaptive Management of Nutrients in Shallow Lakes

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    This paper illustrates the use of dual/adaptive control methods to compare passive and active adaptive management decisions in the context of an ecosystem with a threshold effect. Using discrete-time dynamic programming techniques, we model optimal phosphorus loadings under both uncertainty about natural loadings and uncertainty regarding the critical level of phosphorus concentrations beyond which nutrient recycling begins. Active management is modeled by including the anticipated value of information (or learning) in the structure of the problem, and thus the agent can perturb the system (experiment), update beliefs, and learn about the uncertain parameter. Using this formulation, we define and value optimal experimentation both ex ante and ex post. Our simulation results show that experimentation is optimal over a large range of phosphorus concentration and belief space, though ex ante benefits are small. Furthermore, realized benefits may critically depend on the true underlying parameters of the problem.adaptive control, adaptive management, dynamic programming, value of experimentation, value of information, nonpoint source pollution, learning, decisions under uncertainty, Resource /Energy Economics and Policy,

    Observation of the dielectric-waveguide mode of light propagation in p-n junctions

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    Theoretical considerations of the propagation of electromagnetic energy near a p-n junction (1) show that the “sandwich” formed by having a depletion layer bounded by the p and n regions can act as a dielectric waveguide. (1,2

    Total economic contribution of the private, recreation-based aquaculture industry in the West: a summary, The

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    April 2012.Includes bibliographical references (page 8).The private, recreation-based aquaculture industry (often referred to as the aquacultural suppliers of recreational fish, or ASRF industry) provides fish for recreational outlets such as private fishing clubs and dude ranches, public reservoirs and streams, and private backyard ponds. Although most people know about the public stocking agencies such as the United States Fish and Wildlife Service and state-level wild-life agencies, no information about the economic scope or contribution of the ASRF in the Western United States has been documented. In order to address this gap in the literature, between 2007 and 2010, researchers in the Department of Agricultural and Resource Economics at Colorado State University and at UC Davis collected data from ASRF producers, their direct customers (recreational fisheries), and recreational anglers in the Western -- United States This data was compiled and, in conjunction with IMPLAN input-output software, was used to estimate the economic contribution of the ASRF industry in that region. The results of this exercise are summarized here in order to increase exposure to the general public

    Hubble Space Telescope Imaging and Spectroscopy of the Sirius-Like Triple Star System HD 217411

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    We present Hubble Space Telescope imaging and spectroscopy of HD 217411, a G3 V star associated with the extreme ultraviolet excess source (EUV 2RE J2300-07.0). This star is revealed to be a triple system with a G 3V primary (HD 217411 A) separated by ~1.1" from a secondary that is in turn composed of an unresolved K0 V star (HD 217411 Ba) and a hot DA white dwarf (HD 217411 Bb). The hot white dwarf dominates the UV flux of the system. However; it is in turn dominated by the K0 V component beyond 3000 {\AA}. A revised distance of 143 pc is estimated for the system. A low level photometric modulation having a period of 0.61 days has also been observed in this system along with a rotational velocity on the order of 60 km s-1 in the K0 V star. Together both observations point to a possible wind induced spin up of the K0 V star during the AGB phase of the white dwarf. The nature of all three components is discussed as are constraints on the orbits, system age and evolution.Comment: 11 pages, 6 figure

    Exactly solvable model of A + A \to 0 reactions on a heterogeneous catalytic chain

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    We present an exact solution describing equilibrium properties of the catalytically-activated A + A \to 0 reaction taking place on a one-dimensional lattice, where some of the sites possess special "catalytic" properties. The A particles undergo continuous exchanges with the vapor phase; two neighboring adsorbed As react when at least one of them resides on a catalytic site (CS). We consider three situations for the CS distribution: regular, annealed random and quenched random. For all three CS distribution types, we derive exact results for the disorder-averaged pressure and present exact asymptotic expressions for the particles' mean density. The model studied here furnishes another example of a 1D Ising-type system with random multi-site interactions which admits an exact solution.Comment: 7 pages, 3 Figures, appearing in Europhysics Letter

    Non equilibrium thermodynamics and cosmological pancakes formation

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    We investigate the influence of non equilibrium thermodynamics on cosmological structure formation. In this paper, we consider the collapse of planar perturbations usually called "Zel'dovich pancakes". We have developed for that purpose a new two fluids (gas and dark matter) hydrodynamical code, with three different thermodynamical species: electrons, ions and neutral particles (T_e\ne T_i \ne T_n). We describe in details the complex structure of accretion shock waves. We include several relevant processes for a low density, high temperature, collisional plasma such as non-equilibrium chemical reactions, cooling, shock heating, thermal energy equipartition between electrons, ions and neutral particles and electronic conduction. We find two different regions in the pancake structure: a thermal precursor ahead of the compression front and an equipartition wave after the compression front where electrons and ions temperatures differ significantly. This complex structure may have two interesting consequences: pre-heating of unshocked regions in the vicinity of massive X-ray clusters and ions and electrons temperatures differences in the outer regions of X-rays clusters.Comment: 30 pages, including 8 figures, accepted for publication in The Astrophysical Journa

    The Star Blended with the MOA-2008-BLG-310 Source Is Not the Exoplanet Host Star

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    High resolution Hubble Space Telescope (HST) image analysis of the MOA-2008-BLG-310 microlens system indicates that the excess flux at the location of the source found in the discovery paper cannot primarily be due to the lens star because it does not match the lens-source relative proper motion, μrel\mu_{\rm rel}, predicted by the microlens models. This excess flux is most likely to be due to an unrelated star that happens to be located in close proximity to the source star. Two epochs of HST observations indicate proper motion for this blend star that is typical of a random bulge star, but is not consistent with a companion to the source or lens stars if the flux is dominated by only one star, aside from the lens. We consider models in which the excess flux is due to a combination of an unrelated star and the lens star, and this yields 95\% confidence level upper limit on the lens star brightness of IL>22.44I_L > 22.44 and VL>23.62V_L >23.62. A Bayesian analysis using a standard Galactic model and these magnitude limits yields a host star mass Mh=0.210.09+0.21 MM_h = 0.21 ^{+0.21}_{-0.09}~ M_\odot, a planet mass of mp=23.49.9+23.9 Mm_p = 23.4 ^{+23.9}_{-9.9}~M_\oplus at a projected separation of a=1.120.17+0.16,a_\perp = 1.12^{+0.16}_{-0.17},AU. This result illustrates excess flux in a high resolution image of a microlens-source system need not be due to the lens. It is important to check that the lens-source relative proper motion is consistent with the microlensing prediction. The high resolution image analysis techniques developed in this paper can be used to verify the WFIRST exoplanet microlensing survey mass measurements.Comment: Submitted to AJ on March 18, 201
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