56 research outputs found
Analysis of LIGO data for gravitational waves from binary neutron stars
We report on a search for gravitational waves from coalescing compact binary
systems in the Milky Way and the Magellanic Clouds. The analysis uses data
taken by two of the three LIGO interferometers during the first LIGO science
run and illustrates a method of setting upper limits on inspiral event rates
using interferometer data. The analysis pipeline is described with particular
attention to data selection and coincidence between the two interferometers. We
establish an observational upper limit of 1.7 \times 10^{2}M_\odot$.Comment: 17 pages, 9 figure
Scientific rationale for Uranus and Neptune <i>in situ</i> explorations
The ice giants Uranus and Neptune are the least understood class of planets in our solar system but the most frequently observed type of exoplanets. Presumed to have a small rocky core, a deep interior comprising ∼70% heavy elements surrounded by a more dilute outer envelope of H2 and He, Uranus and Neptune are fundamentally different from the better-explored gas giants Jupiter and Saturn. Because of the lack of dedicated exploration missions, our knowledge of the composition and atmospheric processes of these distant worlds is primarily derived from remote sensing from Earth-based observatories and space telescopes. As a result, Uranus's and Neptune's physical and atmospheric properties remain poorly constrained and their roles in the evolution of the Solar System not well understood. Exploration of an ice giant system is therefore a high-priority science objective as these systems (including the magnetosphere, satellites, rings, atmosphere, and interior) challenge our understanding of planetary formation and evolution. Here we describe the main scientific goals to be addressed by a future in situ exploration of an ice giant. An atmospheric entry probe targeting the 10-bar level, about 5 scale heights beneath the tropopause, would yield insight into two broad themes: i) the formation history of the ice giants and, in a broader extent, that of the Solar System, and ii) the processes at play in planetary atmospheres. The probe would descend under parachute to measure composition, structure, and dynamics, with data returned to Earth using a Carrier Relay Spacecraft as a relay station. In addition, possible mission concepts and partnerships are presented, and a strawman ice-giant probe payload is described. An ice-giant atmospheric probe could represent a significant ESA contribution to a future NASA ice-giant flagship mission
Decoupling-based reconfigurable control of linear systems after actuator faults
In this paper, we provide the complete solution to the reconfigurable control problem after actuator faults in linear dynamical systems by means of disturbance decoupling approaches. The recovery of the closed-loop internal stability and the exact and approximate recovery of nominal tracking and performance are our main reconfiguration goals. We state necessary and sufficient conditions for the solvability of these problems. The approximate approach broadens the scope of potential applications. A thermofluid process is used to illustrate the exact and approximate methods
Decoupling-based reconfigurable control of linear systems after actuator faults
In this paper, we provide the complete solution to the reconfigurable control problem after actuator faults in linear dynamical systems by means of disturbance decoupling approaches. The recovery of the closed-loop internal stability and the exact and approximate recovery of nominal tracking and performance are our main reconfiguration goals. We state necessary and sufficient conditions for the solvability of these problems. The approximate approach broadens the scope of potential applications. A thermofluid process is used to illustrate the exact and approximate methods
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