Hardware injections are simulated gravitational-wave signals added to the Laser Interferometer Gravitational-wave Observatory (LIGO). The detectors’ test masses are physically displaced by an ...actuator in order to simulate the effects of a gravitational wave. The simulated signal initiates a control-system response which mimics that of a true gravitational wave. This provides an end-to-end test of LIGO’s ability to observe gravitational waves. The gravitational-wave analyses used to detect and characterize signals are exercised with hardware injections. By looking for discrepancies between the injected and recovered signals, we are able to characterize the performance of analyses and the coupling of instrumental subsystems to the detectors’ output channels. This paper describes the hardware injection system and the recovery of injected signals representing binary black hole mergers, a stochastic gravitational wave background, spinning neutron stars, and sine-Gaussians.
The purpose of this research was to chemically characterize refuse and extract samples and to evaluate gas generation from the Fresh Kills Landfill on Staten Island, N.Y., and to use this information ...to draw conclusions about the overall rate and extent of decomposition within the landfill. The refuse samples were characterized in terms of moisture content, lignin, cellulose, and various selected chemical species. Analysis of the extract samples included measurements of total organic carbon, volatile acids, pH, and other specific materials. Gas-production factors, such as temperature and moisture content, were also studied. Results indicate that refuse samples ranged from basically undecomposed to well decomposed, based on the wide range of cellulose concentrations and cellulose to lignin ratios. Organic parameters in the refuse were strongly correlated to refuse age. Interrelationships between the liquid parameters are generally consistent with published phases of decomposition. For gas-producing refuse samples, moisture contents were significantly higher than for those samples not producing gas. Temperatures between 30°C and 40°C were preferable for gas production.
This chapter features the USA-based LIGO, the Laser Interferometer Gravitational-Wave Observatory – the first of three case studies covering different worldwide interferometric gravitational wave ...detectors. In addition to describing the basic interferometer operation and its various components, we discuss the technological challenges that have been overcome for its successful operation.IntroductionThe prediction of gravitational waves (GWs), oscillations in the spacetime metric that propagate at the speed of light, is one of the most profound differences between Einstein's general theory of relativity and the Newtonian theory of gravity that it replaced. As discussed in Chapter 1, GWs remained a theoretical prediction for more than 50 years until the first observational evidence for their existence came with the discovery and subsequent observations of the binary pulsar PSR 1913+16, by Russell Hulse and Joseph Taylor (Weisberg and Taylor, 2005). In about 300 million years, the PSR 1913+16 orbit will decrease to the point where the pair coalesces into a single compact object, a process that will produce directly detectable gravitational waves. In the meantime, the direct detection of GWs will require similarly strong sources – extremely large masses moving with large accelerations in strong gravitational fields. The goal of LIGO, the Laser Interferometer Gravitational-Wave Observatory (Abramovici et al., 1992), is just that: to detect and study GWs of astrophysical origin. Achieving this goal will mark the opening of a new window on the Universe, with the promise of new physics and astrophysics. In physics, GW detection could provide information about strong-field gravitation, the untested domain of strongly curved space where Newtonian gravitation is no longer even a poor approximation.
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