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The assessment of quality attributes of software-intensive systems is a challenging issue. This paper outlines a method aimed at quantitative evaluation of certain quality attributes that are important for embedded systems: timeliness, performance and memory consumption. The paper sketches out the key principles for building a formal model for evaluating(More)
A search for periodic gravitational waves, from sources such as isolated rapidly spinning neutron stars, was carried out using 510 h of data from the fourth LIGO science run (S4). The search was for quasimonochromatic waves in the frequency range from 50 to 1500 Hz, with a linear frequency drift _ f (measured at the solar system barycenter) in the range Àf=(More)
Einstein@Home aggregates the computer power of hundreds of thousands of volunteers from 192 countries to mine large data sets. It has now found a 40.8-hertz isolated pulsar in radio survey data from the Arecibo Observatory taken in February 2007. Additional timing observations indicate that this pulsar is likely a disrupted recycled pulsar. PSR J2007+2722's(More)
Domain-independent models of the design process are an important means for facilitating interdisciplinary communication and for supporting multidisciplinary design. Many so-called domain-independent models are, however, not really domain independent. We state that, to be domain independent, the models must abstract from domain-specific aspects, be based on(More)
We report on an all-sky search with the LIGO detectors for periodic gravitational waves in the frequency range 50 –1000 Hz and with the frequency's time derivative in the range ÿ1 10 ÿ8 Hz s ÿ1 to zero. Data from the fourth LIGO science run (S4) have been used in this search. Three different semicoherent methods of transforming and summing strain power from(More)
In this article we discuss an architecture for mobile agents. We focus on the components in the architecture that provide eecient, reliable, secure transportation of agents and ditto communication between agents and their environment. These components provide the basis for building a wide variety of agents with various levels of intelligence. We further(More)
We searched for an anisotropic background of gravitational waves using data from the LIGO S4 science run and a method that is optimized for point sources. This is appropriate if, for example, the gravitational wave background is dominated by a small number of distinct astrophysical sources. No signal was seen. Upper limit maps were produced assuming two(More)
A stochastic background of gravitational waves is expected to arise from a superposition of a large number of unresolved gravitational-wave sources of astrophysical and cosmological origin. It should carry unique signatures from the earliest epochs in the evolution of the Universe, inaccessible to standard astrophysical observations. Direct measurements of(More)