38,423 research outputs found
Frustrated double ionization in two-electron triatomic molecules
Using a semi-classical model, we investigate frustrated double ionization
(FDI) in , a two-electron triatomic molecule, when driven by an
intense, linearly polarized, near-infrared (800 nm) laser field. We compute the
kinetic energy release of the nuclei and find a good agreement between
experiment and our model. We explore the two pathways of FDI and show that,
with increasing field strength, over-the-barrier ionization overtakes tunnel
ionization as the underlying mechanism of FDI. Moreover, we compute the angular
distribution of the ion fragments for FDI and identify a feature that can
potentially be observed experimentally and is a signature of only one of the
two pathways of FDI.Comment: 5 pages, 4 figure
Liquid oxygen cooling of high pressure LOX/hydrocarbon rocket thrust chambers
An experimental program using liquid oxygen (LOX) and RP-1 as the propellants and supercritical LOX as the coolant was conducted at 4.14, 8.27, and 13.79 MN/sq m (600, 1200, and 2000 psia) chamber pressure. The objectives of this program were to evaluate the cooling characteristics of LOX with the LOX/RP-1 propellants, the buildup of the soot on the hot-gas-side chamber wall, and the effect of an internal LOX leak on the structural integrity of the combustor. Five thrust chambers with throat diameters of 6.6 cm (2.5 in.) were tested successfully. The first three were tested at 4.14 MN/sq m (600 psia) chamber pressure over a mixture ratio range of 2.25 to 2.92. One of these three was tested for over 22 cyclic tests after the first through crack from the coolant channel to the combustion zone was observed with no apparent metal burning or distress. The fourth chamber was tested at 8.27 MN/sq m (1200 psia) chamber pressure over a mixture range of 1.93 to 2.98. The fourth and fifth chambers were tested at 13.79 MN/sq m (2000 psia) chamber pressure over a mixture ratio range of 1.79 to 2.68
Black hole binary inspiral and trajectory dominance
Gravitational waves emitted during the inspiral, plunge and merger of a black
hole binary carry linear momentum. This results in an astrophysically important
recoil to the final merged black hole, a ``kick'' that can eject it from the
nucleus of a galaxy. In a previous paper we showed that the puzzling partial
cancellation of an early kick by a late antikick, and the dependence of the
cancellation on black hole spin, can be understood from the phenomenology of
the linear momentum waveforms. Here we connect that phenomenology to its
underlying cause, the spin-dependence of the inspiral trajectories. This
insight suggests that the details of plunge can be understood more broadly with
a focus on inspiral trajectories.Comment: 15 pages, 12 figure
Systematics of black hole binary inspiral kicks and the slowness approximation
During the inspiral and merger of black holes, the interaction of
gravitational wave multipoles carries linear momentum away, thereby providing
an astrophysically important recoil, or "kick" to the system and to the final
black hole remnant. It has been found that linear momentum during the last
stage (quasinormal ringing) of the collapse tends to provide an "antikick" that
in some cases cancels almost all the kick from the earlier (quasicircular
inspiral) emission. We show here that this cancellation is not due to
peculiarities of gravitational waves, black holes, or interacting multipoles,
but simply to the fact that the rotating flux of momentum changes its intensity
slowly. We show furthermore that an understanding of the systematics of the
emission allows good estimates of the net kick for numerical simulations
started at fairly late times, and is useful for understanding qualitatively
what kinds of systems provide large and small net kicks.Comment: 15 pages, 6 figures, 2 table
Gravity gradient attitude control system Patent
Gravity gradient attitude control system with gravity gradiometer and reaction wheels for artificial satellite attitude contro
Evolution of the east rim of the Hellas basin, Mars
The Hellas basin is a dominant feature in the ancient, southern cratered highlands of Mars. The east rim of Hellas is a complex geologic region affected by volcanism, tectonism, and channeling. A detailed study of the area between 27.5-42.4 degrees S and 260-275 degrees W was initiated to analyze the processes forming surface materials and to decipher the evolution of this geologically important highland area. Major units include Hadriaca and Tyrrhena Paterae in the north and Hesperian and Amazonian channeled plains and outflow channels in the south. A brief discussion of the findings is presented
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