7,399 research outputs found
Radiating dipole model of interference induced in spacecraft circuitry by surface discharges
Spacecraft in geosynchronous orbit can be charged electrically to high voltages by interaction with the space plasma. Differential charging of spacecraft surfaces leads to arc and blowoff discharging. The discharges are thought to upset interior, computer-level circuitry. In addition to capacitive or electrostatic effects, significant inductive and less significant radiative effects of these discharges exist and can be modeled in a dipole approximation. Flight measurements suggest source frequencies of 5 to 50 MHz. Laboratory tests indicate source current strengths of several amperes. Electrical and magnetic fields at distances of many centimeters from such sources can be as large as tens of volts per meter and meter squared, respectively. Estimates of field attenuation by spacecraft walls and structures suggest that interior fields may be appreciable if electromagnetic shielding is much thinner than about 0.025 mm (1 mil). Pickup of such fields by wires and cables interconnecting circuit components could be a source of interference signals of several volts amplitude
Circuit transients due to negative bias arcs on a high-voltage solar array in low Earth orbit
Arcing to negatively biased, exposed solar cell interconnects on solar arrays placed in plasma environments was established. Arcing, however, may cause damaging interference with the operation of electrical power systems in spacecraft planned to be driven with high-voltage solar arrays. An analytical model was developed to estimate the effects of netagive bias arcs on solar array power system performance. Solar cell characteristics, plasma interactions, and power system features are modeled by a linear, lumped element transient circuit, and the time domain equations are solved. Numerical results for solar array common mode and load voltage transients are calculated for typical conditions. Acceptable load transients are found for a range of arc current amplitudes and time constants
Storage tests of nitrogen tetroxide and hydrazine in aluminum containers
Nitrogen tetroxide and hydrazine compatibility with aluminum alloy storage tank
Estimate of the Collins function in a chiral invariant approach
We estimate the Collins function at a low energy scale by calculating the
fragmentation of a quark into a pion at the one-loop level in the chiral
invariant model of Manohar and Georgi. We give a useful parametrization of our
results and we briefly discuss different spin and/or azimuthal asymmetries
containing the Collins function and measurable in semi-inclusive DIS and e+ e-
annihilationComment: 5 pages, 4 figures, to appear in Proceedings of 10th International
Workshop on Deep Inelastic Scattering (DIS 2002), Cracow, Poland, 30 Apr-4
May 200
Convective instability and mass transport of diffusion layers in a Hele-Shaw geometry
We consider experimentally the instability and mass transport of a
porous-medium flow in a Hele-Shaw geometry. In an initially stable
configuration, a lighter fluid (water) is located over a heavier fluid
(propylene glycol). The fluids mix via diffusion with some regions of the
resulting mixture being heavier than either pure fluid. Density-driven
convection occurs with downward penetrating dense fingers that transport mass
much more effectively than diffusion alone. We investigate the initial
instability and the quasi steady state. The convective time and velocity
scales, finger width, wave number selection, and normalized mass transport are
determined for 6,000<Ra<90,000. The results have important implications for
determining the time scales and rates of dissolution trapping of carbon dioxide
in brine aquifers proposed as possible geologic repositories for sequestering
carbon dioxide.Comment: 4 page, 3 figure
Dispersion relation formalism for virtual Compton scattering and the generalized polarizabilities of the nucleon
A dispersion relation formalism for the virtual Compton scattering (VCS)
reaction on the proton is presented, which for the first time allows a
dispersive evaluation of 4 generalized polarizabilities at a four-momentum
transfer 0.5 GeV. The dispersive integrals are calculated using
a state-of-the-art pion photo- and electroproduction analysis. The dispersion
formalism provides a new tool to analyze VCS experiments above pion threshold,
thus increasing the sensitivity to the generalized polarizabilities of the
nucleon.Comment: 4 pages, 2 figure
Mabahiss Mons, 25.5°N Red Sea Rift: Tectonics and Volcanism of a Large Submarine Dome Volcano
An Expression of Cultural Change: Invisible Converts to Protestantism Among Highland Guatemala Mayas
This is the published version, also found here: http://www.jstor.org/stable/377368
Low-energy and low-momentum representation of the virtual Compton scattering amplitude
We perform an expansion of the virtual Compton scattering amplitude for low
energies and low momenta and show that this expansion covers the transition
from the regime to be investigated in the scheduled photon electroproduction
experiments to the real Compton scattering regime.
We discuss the relation of the generalized polarizabilities of virtual
Compton scattering to the polarizabilities of real Compton scattering.Comment: 13 pages, LaTeX2e/RevTeX, no figure
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