1,153 research outputs found
A dag-based algorithm for distributed mutual exclusion
Call number: LD2668 .T4 CMSC 1989 N45Master of ScienceComputing and Information Science
Socio-economic readjustment of farm families displaced by the TVA Land Purchase in the Norris Area
At various times in recent years it has been necessary that families or groups of families be removed from their established communities due to the creation of public parks, the formation of artificial lakes by governmental agencies, the retirement of submarginal artificial land, and other related projects. To a considerable extent in the past the land has been condemned and bought, the people forced to leave, and get reestablished as best they might. To some extent guidance and assistance in relocation has helped to reduce hardship. Nevertheless in many instances the social loss to these residents has been great. Relocation in a new area may be easy or difficult depending upon the type of people, how closely connected their lives are to activities peculiar to the area, the nature of their new environment, distance moved, and other factors. By an analysis of what has happened to families relocated from the Norris Dam Area it is hoped that relocation projects of a similar nature may be more intelligently considered. Only when the probably effect on various elements of the population is known and when the successes or failures in adjustment are studied may similar projects be conducted with the least distress to persons involved
Boosting jet power in black hole spacetimes
The extraction of rotational energy from a spinning black hole via the
Blandford-Znajek mechanism has long been understood as an important component
in models to explain energetic jets from compact astrophysical sources. Here we
show more generally that the kinetic energy of the black hole, both rotational
and translational, can be tapped, thereby producing even more luminous jets
powered by the interaction of the black hole with its surrounding plasma. We
study the resulting Poynting jet that arises from single boosted black holes
and binary black hole systems. In the latter case, we find that increasing the
orbital angular momenta of the system and/or the spins of the individual black
holes results in an enhanced Poynting flux.Comment: 7 pages, 5 figure
Numerical stability of a new conformal-traceless 3+1 formulation of the Einstein equation
There is strong evidence indicating that the particular form used to recast
the Einstein equation as a 3+1 set of evolution equations has a fundamental
impact on the stability properties of numerical evolutions involving black
holes and/or neutron stars. Presently, the longest lived evolutions have been
obtained using a parametrized hyperbolic system developed by Kidder, Scheel and
Teukolsky or a conformal-traceless system introduced by Baumgarte, Shapiro,
Shibata and Nakamura. We present a new conformal-traceless system. While this
new system has some elements in common with the
Baumgarte-Shapiro-Shibata-Nakamura system, it differs in both the type of
conformal transformations and how the non-linear terms involving the extrinsic
curvature are handled. We show results from 3D numerical evolutions of a
single, non-rotating black hole in which we demonstrate that this new system
yields a significant improvement in the life-time of the simulations.Comment: 7 pages, 2 figure
Evidence for simultaneous jets and disk winds in luminous low-mass X-ray binaries
Recent work on jets and disk winds in low-mass X-ray binaries (LMXBs)
suggests that they are to a large extent mutually exclusive, with jets observed
in spectrally hard states and disk winds observed in spectrally soft states. In
this paper we use existing literature on jets and disk winds in the luminous
neutron star (NS) LMXB GX 13+1, in combination with archival Rossi X-ray Timing
Explorer data, to show that this source is likely able to produce jets and disk
winds simultaneously. We find that jets and disk winds occur in the same
location on the source's track in its X-ray color-color diagram. A further
study of literature on other luminous LMXBs reveals that this behavior is more
common, with indications for simultaneous jets and disk winds in the black hole
LMXBs V404 Cyg and GRS 1915+105 and the NS LMXBs Sco X-1 and Cir X-1. For the
three sources for which we have the necessary spectral information, we find
that the simultaneous jets/winds all occur in their spectrally hardest states.
Our findings indicate that in LMXBs with luminosities above a few tens of
percent of the Eddington luminosity, jets and disk winds are not mutually
exclusive, and that the presence of disk winds does not necessarily result in
jet suppression.Comment: Updated to match published version (2016, ApJ, 830, L5
- …