83,739 research outputs found

    Propulsion Working Group report

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    Existing technology limits and performances, high payoff technologies, propulsion technologies, electric propulsion systems, and advanced bipropellant systems are outlined

    On the infeasibility of entanglement generation in Gaussian quantum systems via classical control

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    This paper uses a system theoretic approach to show that classical linear time invariant controllers cannot generate steady state entanglement in a bipartite Gaussian quantum system which is initialized in a Gaussian state. The paper also shows that the use of classical linear controllers cannot generate entanglement in a finite time from a bipartite system initialized in a separable Gaussian state. The approach reveals connections between system theoretic concepts and the well known physical principle that local operations and classical communications cannot generate entangled states starting from separable states.Comment: 6 pages, 3 figures. To appear in IEEE Transactions on Automatic Control, 201

    Nonlocal Dynamics of Passive Tracer Dispersion with Random Stopping

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    We investigate the nonlocal behavior of passive tracer dispersion with random stopping at various sites in fluids. This kind of dispersion processes is modeled by an integral partial differential equation, i.e., an advection-diffusion equation with a memory term. We have shown the exponential decay of the passive tracer concentration, under suitable conditions for the velocity field and the probability distribution of random stopping time.Comment: 7 page

    Coolant side heat transfer with rotation: User manual for 3D-TEACH with rotation

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    This program solves the governing transport equations in Reynolds average form for the flow of a 3-D, steady state, viscous, heat conducting, multiple species, single phase, Newtonian fluid with combustion. The governing partial differential equations are solved in physical variables in either a Cartesian or cylindrical coordinate system. The effects of rotation on the momentum and enthalpy calculations modeled in Cartesian coordinates are examined. The flow of the fluid should be confined and subsonic with a maximum Mach number no larger than 0.5. This manual describes the operating procedures and input details for executing a 3D-TEACH computation

    Machine learning techniques for fault isolation and sensor placement

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    Fault isolation and sensor placement are vital for monitoring and diagnosis. A sensor conveys information about a system's state that guides troubleshooting if problems arise. We are using machine learning methods to uncover behavioral patterns over snapshots of system simulations that will aid fault isolation and sensor placement, with an eye towards minimality, fault coverage, and noise tolerance

    Real Exchange Rate Behavior Under Floating and Fixed Regimes

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    In this paper we examine the stability of the real exchange rate and the macroeconomic effects of alternative exchange-rate regimes, including currency union, on real exchange-rate behaviour. We focus on the Irish punt in order to exploit its diversity of experience over different nominal exchange rate regimes. We make both temporal and cross-country comparisons of real-exchange-rate stability for the Irish punt with sterling, the US dollar and the German mark. We reach two conclusions on the basis of our results. The first is that for Ireland, as for most other countries, purchasing power parity provides a reasonably good description of actual exchange rate behaviour over the long run. Our second principal conclusion concerns regime effects. Currency union appears to matter. The real exchange rates we analyse are unambiguously less variable under currency union than under alternative exchange-rate systems. Otherwise, however, we find no clear-cut differences in behaviour across regimes.Exchange Rates, purchasing power parity, exchange-rate regimes, currency union

    Preliminary geologic mapping near the Nilosyrtis Mensae, Mars

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    Virtually the entire map area is mantled by an irregular deposit of material that is apparently fine-grained and erodible. It is also extremely young, as there is not a single crater larger than 1 km in the map area that was emplaced atop the mantle. Knobs abound in the study area; many are presumably caused by the mantling of pre-existing topography. In many cases the older knob of the core is exposed. Many such knob cores are surrounded by small scarplets; it is not yet clear whether the scarplets are the eroded edges of mantle beds that at one time draped over the knob core and have been subsequently exposed by erosion, or whether they are eroded versions of lobate debris aprons. Many craters in the study area contain concentric crater fill, which may indicate downslope movement of volatile-rich materials or repeated cycles of aeolian gradation
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