49,194 research outputs found

    Forecast Rationality and Monetary Policy Frameworks: Evidence from UK Interest Rate Forecasts

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    This paper explores the heterogeneity and rationality of professional forecasts at both short and long forecast horizons. We employ disaggregated survey data for forecasts of three-month inter-bank rates and ten-year gilt yields for the period 1989-2006. We find evidence of heterogeneity among forecasters. Moreover, forecasts violate both the unbiasedness and orthogonality conditions of the rational expectations hypothesis. The majority of biased forecasts underestimate the future spot rate. The rationality of forecasts varies across maturities and forecast horizons with short horizon and short maturity forecasts exhibiting more rationality. It also varies across sub-periods corresponding to different monetary policy frameworks. We produce evidence indicating that both monetary policy actions and elements of communication policy have information content regarding the rationality of forecasts. Changes in official bank rates and disagreement, as recorded in the minutes of the Monetary Policy Committee, influence the rationality of forecasts. The publication of inflation reports has no effect

    Persistent superfluid flow arising from the He-McKellar-Wilkens effect in molecular dipolar condensates

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    We show that the He-McKellar-Wilkens effect can induce a persistent flow in a Bose-Einstein condensate of polar molecules confined in a toroidal trap, with the dipolar interaction mediated via an electric dipole moment. For Bose-Einstein condensates of atoms with a magnetic dipole moment, we show that although it is theoretically possible to induce persistent flow via the Aharonov-Casher effect, the strength of electric field required is prohibitive. We also outline an experimental geometry tailored specifically for observing the He-McKellar-Wilkens effect in toroidally-trapped condensates.Comment: 5 pages 2 figure

    Computer simulation incorporating a helicopter model for evaluation of aircraft avionics systems

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    A computer program was developed to integrate avionics research in navigation, guidance, controls, and displays with a realistic aircraft model. A user oriented program is described that allows a flexible combination of user supplied models to perform research in any avionics area. A preprocessor technique for selecting various models without significantly changing the memory storage is included. Also included are mathematical models for several avionics error models and for the CH-47 helicopter used in this program

    A Coronal Hole's Effects on CME Shock Morphology in the Inner Heliosphere

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    We use STEREO imagery to study the morphology of a shock driven by a fast coronal mass ejection (CME) launched from the Sun on 2011 March 7. The source region of the CME is located just to the east of a coronal hole. The CME ejecta is deflected away from the hole, in contrast with the shock, which readily expands into the fast outflow from the coronal hole. The result is a CME with ejecta not well centered within the shock surrounding it. The shock shape inferred from the imaging is compared with in situ data at 1 AU, where the shock is observed near Earth by the Wind spacecraft, and at STEREO-A. Shock normals computed from the in situ data are consistent with the shock morphology inferred from imaging.Comment: to appear in The Astrophysical Journa

    Optical and near-infrared spectrophotometric properties of Long Period Variables and other luminous red stars

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    Based on a new and large sample of optical and near-infrared spectra obtained at the Mount Stromlo and Siding Spring Observatories (Lancon & Wood 1998; Lancon & Wood, in preparation), spectrophotometric properties of cool oxygen- and carbon-rich Long Period Variables and supergiants are presented. Temperatures of oxygen-rich stars are assigned by comparison with synthetic spectra computed from up-to-date oxygen-rich model atmosphere grids. The existence of reliable optical and near-infrared temperature indicators is investigated. A narrow relation between the bolometric correction BC(I) and the broad-band colour I-J is obtained for oxygen-rich cool stars. The ability of specific near-infrared indices to separate luminosity classes, atmospheric chemistry or variability subtypes is discussed. Some comments are also given on extinction effects, water band strengths in Long Period Variables and the evaluation of 12CO/13CO ratio in red giants.Comment: 14 pages, 21 figures, Latex, accepted for publication in Astronomy and Astrophysics main journal. Also available at http://www-astro.ulb.ac.be/~ralvarez

    Implications of microwave spectroscopy for the water-vapor content of the Venus atmosphere

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    Brightness temperature spectra of Venus computed to determine amount of water vapor in lower atmospher

    Marginal states of the resistive tearing mode with flow in cylindrical geometry

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    The linear stability of tearing modes in a cylindrical plasma subject to a sub-Alfvénic equilibrium shear flow along the equilibrium magnetic field is considered. The equations in the resistive boundary layer at the rational surface are solved numerically using a Fourier transform combined with a finite-element approach. The behaviour of the growth rate as a function of the flow and the various parameters (including a perpendicular fluid viscosity) is obtained. Marginal stability curves showing the dependence of the familiar matching parameter Δ' with flow and shear are also given

    On-line mass spectrometric monitoring of the polymerization of a phenolic-resin-based material

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    Polymerization of phenolic-resin-based materials requires elevated temperatures. The low thermal conductivity of these materials has led to the use of dielectric heating techniques in lieu of standard convection oven heating to obtain a satisfactory cure. The curing rate and therefore the quality of the cured material depends on the heating rate and maximum temperature attained, parameters which are extremely difficult to measure in dielectric heating units. The dielectric curing of these materials was monitored by using a mass spectrometer to measure the partial pressure of phenol in the gas evolved during polymerization. The resulting plots of phenol partial pressure as a function of time have a characteristic shape, and these may be used to indicate the attainment of complete curing. The validity of the mass spectrometric technique was confirmed by chemical analysis of the polymerized samples
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