63,453 research outputs found

    A charging model for three-axis stabilized spacecraft

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    A charging model was developed for geosynchronous, three-axis stabilized spacecraft when under the influence of a geomagnetic substorm. The differential charging potentials between the thermally coated or blanketed outer surfaces and metallic structure of a spacecraft were determined when the spacecraft was immersed in a dense plasma cloud of energetic particles. The spacecraft-to-environment interaction was determined by representing the charged particle environment by equivalent current source forcing functions and by representing the spacecraft by its electrically equivalent circuit with respect to the plasma charging phenomenon. The charging model included a sun/earth/spacecraft orbit model that simulated the sum illumination conditions of the spacecraft outer surfaces throughout the orbital flight on a diurnal as well as a seasonal basis. Transient and steady-state numerical results for a three-axis stabilized spacecraft are presented

    Energies of B_s meson excited states - a lattice study

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    This is a follow-up to our earlier work on the energies and radial distributions of heavy-light mesons. The heavy quark is taken to be static (infinitely heavy) and the light quark has a mass about that of the strange quark. We now concentrate on the energies of the excited states with higher angular momentum and with a radial node. A new improvement is the use of hypercubic blocking in the time direction. The calculation is carried out with dynamical fermions on a 16 cubed times 32 lattice with a lattice spacing approximately 0.1 fm generated using a non-perturbatively improved clover action. In nature the closest equivalent of this heavy-light system is the B_s meson, which allows us to compare our lattice calculations to experimental results (where available) or to give a prediction where the excited states, particularly P-wave states, should lie. We pay special attention to the spin-orbit splitting, to see which one of the states (for a given angular momentum L) has the lower energy. An attempt is made to understand these results in terms of the Dirac equation.Comment: 35 pages. v3: Data from two new lattices added. New results in several chapter

    Near-earth thermal environmental criteria study

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    A study was made to determine improved values and definitions to be used for thermal environmental design parameters for a spacecraft in near-earth orbit. An algorithm was used to derive a total earth thermal radiation based on a mathematical relationship. Several albedo and earth thermal radiation grid maps were produced on seven track digital magnetic tape. Each map contained the values obtained during a 24 hour period over the entire earth. The output statistics are summarized, and the data processing program is described

    Galois covers of the open p-adic disc

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    This paper investigates Galois branched covers of the open pp-adic disc and their reductions to characteristic pp. Using the field of norms functor of Fontaine and Wintenberger, we show that the special fiber of a Galois cover is determined by arithmetic and geometric properties of the generic fiber and its characteristic zero specializations. As applications, we derive a criterion for good reduction in the abelian case, and give an arithmetic reformulation of the local Oort Conjecture concerning the liftability of cyclic covers of germs of curves.Comment: 19 pages; substantial organizational and expository changes; this is the final version corresponding to the official publication in Manuscripta Mathematica; abstract update

    T.J. Green to Mr. James Meredith (19 September 1962)

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    https://egrove.olemiss.edu/mercorr_anti/1218/thumbnail.jp
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