63,737 research outputs found
A charging model for three-axis stabilized spacecraft
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
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
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
This paper investigates Galois branched covers of the open -adic disc and
their reductions to characteristic . 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)
https://egrove.olemiss.edu/mercorr_anti/1218/thumbnail.jp
Cooperative Chiral Order in Copolymers of Chiral and Achiral Units
Polyisocyanates can be synthesized with chiral and achiral pendant groups
distributed randomly along the chains. The overall chiral order, measured by
optical activity, is strongly cooperative and depends sensitively on the
concentration of chiral pendant groups. To explain this cooperative chiral
order theoretically, we map the random copolymer onto the one-dimensional
random-field Ising model. We show that the optical activity as a function of
composition is well-described by the predictions of this theory.Comment: 13 pages, including 3 postscript figures, uses REVTeX 3.0 and
epsf.st
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