318 research outputs found
Performance of a 1200m long suspended Fabry-Perot cavity
Using one arm of the Michelson interferometer and the power recycling mirror
of the interferometric gravitational wave detector GEO600, we created a
Fabry-Perot cavity with a length of 1200 m. The main purpose of this experiment
was to gather first experience with the main optics, its suspensions and the
corresponding control systems. The residual displacement of a main mirror is
about 150 nm rms. By stabilising the length of the 1200 m long cavity to the
pre-stabilised laser beam we achieved an error point frequency noise of 0.1
mHz/sqrt(Hz) at 100 Hz Fourier frequency. In addition we demonstrated the
reliable performance of all included subsystems by several 10-hour-periods of
continuous stable operation. Thus the full frequency stabilisation scheme for
GEO600 was successfully tested.Comment: Amaldi 4 (Perth 2001) conference proceedings, 10 pages, 8 figure
Ensuring properties of interaction systems
We propose results ensuring properties of a component-based system from properties of its interaction model and of its components. We consider here deadlock-freedom and local progress of subsystems. This is done in the framework of interaction systems, a model for component based modelling described in [9]. An interaction system is the superposition of two models: a behavior model and an interaction model. The behavior model describes the behavior of individual components. The interaction model describes the way the components may interact by introducing connectors that relate actions from different components. We illustrate our concepts and results with examples. © Springer-Verlag Berlin Heidelberg 2007
An approach to modelling and verification of component based systems
We build on a framework for modelling and investigating component-based systems that strictly separates the description of behavior of components from the way they interact. We discuss various properties of system behavior as liveness, local progress, local and global deadlock, and robustness. We present a criterion that ensures liveness and can be tested in polynomial time. © Springer-Verlag Berlin Heidelberg 2007
Flexible energy conversion and storage via high-temperature gas-phase reactions: The piston engine as a polygeneration reactor
Piston engines are typically considered devices converting chemical energy into mechanical power via internal combustion. But more generally, their ability to provide high-pressure and high-temperature conditions for a limited time means they can be used as chemical reactors where reactions are initiated by compression heating and subsequently quenched by gas expansion. Thus, piston engines could be âpolygenerationâ reactors that can flexibly change from power generation to chemical synthesis, and even to chemical-energy storage. This may help mitigating one of the main challenges of future energy systems â accommodating fluctuations in electricity supply and demand. Investments in devices for grid stabilization could be more economical if they have a second use.
This paper presents a systematic approach to polygeneration in piston engines, combining thermodynamics, kinetics, numerical optimization, engineering, and thermo-economics. A focus is on the fuel-rich conversion of methane as a fuel that is considered important for the foreseeable future. Starting from thermodynamic theory and kinetic modeling, promising systems are selected. Mathematical optimization and an array of experimental kinetic investigations are used for model improvement and development. To evaluate technical feasibility, experiments are then performed in both a single-stroke rapid compression machine and a reciprocating engine. In both cases, chemical conversion is initiated by homogeneous-charge compression-ignition. A thermodynamic and thermo-economic assessment of the results is positive. Examples that illustrate how the piston engine can be used in polygeneration processes to convert methane to higher-value chemicals or to take up carbon dioxide are presented. Open issues for future research are addressed
The status of GEO 600
The GEO 600 laser interferometer with 600m armlength is part of a worldwide network of gravitational wave detectors. GEO 600 is unique in having advanced multiple pendulum suspensions with a monolithic last stage and in employing a signal recycled optical design. This paper describes the recent commissioning of the interferometer and its operation in signal recycled mode
A Joint Search for Gravitational Wave Bursts with AURIGA and LIGO
The first simultaneous operation of the AURIGA detector and the LIGO
observatory was an opportunity to explore real data, joint analysis methods
between two very different types of gravitational wave detectors: resonant bars
and interferometers. This paper describes a coincident gravitational wave burst
search, where data from the LIGO interferometers are cross-correlated at the
time of AURIGA candidate events to identify coherent transients. The analysis
pipeline is tuned with two thresholds, on the signal-to-noise ratio of AURIGA
candidate events and on the significance of the cross-correlation test in LIGO.
The false alarm rate is estimated by introducing time shifts between data sets
and the network detection efficiency is measured with simulated signals with
power in the narrower AURIGA band. In the absence of a detection, we discuss
how to set an upper limit on the rate of gravitational waves and to interpret
it according to different source models. Due to the short amount of analyzed
data and to the high rate of non-Gaussian transients in the detectors noise at
the time, the relevance of this study is methodological: this was the first
joint search for gravitational wave bursts among detectors with such different
spectral sensitivity and the first opportunity for the resonant and
interferometric communities to unify languages and techniques in the pursuit of
their common goal.Comment: 18 pages, IOP, 12 EPS figure
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