13,934 research outputs found
OFT ascent/descent ancillary data requirements document
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
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
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
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
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
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
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
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,
, 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 and . A Bayesian analysis using a standard
Galactic model and these magnitude limits yields a host star mass , a planet mass of at a projected separation of 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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