2,437 research outputs found

    Mira science with interferometry: a review

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    Model-predicted and observed properties of the brightness distribution on M-type Mira disks are discussed. Fundamental issues of limb-darkening and diameter definition, of assigning observational data to diameter-type quantities and of interpreting such quantities in terms of model diameters are outlined. The influence of model properties upon interpretation of measured data is clarified. The dependence of the centre-to-limb variation (CLV) of intensity on wavelength, on stellar parameters and on variablity phase and cycle may be used for analyzing the geometrical and physical structure of the Mira atmosphere, for determining fundamental stellar parameters, and for investigating the quality of models. Desirable future observations include simultaneous observations in different spectral features at different phases and cycles, observation of the position of the shock front and observation of the time- and wavelength-dependence of deviations from spherical symmetry.Comment: 9 pages, no figure

    Effects of moderate abundance changes on the atmospheric structure and colours of Mira variables (Research Note)

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    Aims. We study the effects of moderate deviations from solar abundances upon the atmospheric structure and colours of typical Mira variables. Methods. We present two model series of dynamical opacity-sampling models of Mira variables which have (1) 1 solar metallicity 3 and (2) "mild" S-type C/O abundance ratio ([C/O]=0.9) with typical Zr enhancement (solar +1.0). These series are compared to a previously studied solar-abundance series which has similar fundamental parameters (mass, luminosity, period, radius) that are close to those of o Cet. Results. Both series show noticeable effects of abundance upon stratifications and infrared colours but cycle-to-cycle differences mask these effects at most pulsation phases, with the exception of a narrow-water-filter colour near minimum phase.Comment: 4 pages, 3 figures, accepted for A&

    R Package clickstream: Analyzing Clickstream Data with Markov Chains

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    Clickstream analysis is a useful tool for investigating consumer behavior, market research and software testing. I present the clickstream package which provides functionality for reading, clustering, analyzing and writing clickstreams in R. The package allows for a modeling of lists of clickstreams as zero-, first- and higher-order Markov chains. I illustrate the application of clickstream for a list of representative clickstreams from an online store

    From Consumer Preferences Towards Buying Decisions - Conjoint Analysis as Preference Measuring Method in Product Recommender Systems

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    This paper briefly introduces the conjoint analysis as a method to measure consumer preferences. Based on the introduction the conjoint analysis is suggested as preference measuring method in product recommender systems. The challenges and limits in applying the conjoint analysis to product recommender systems are analysed and discussed. In the end we present a set of adaptations to the traditional conjoint analysis which address the mentioned challenges and limits

    Implications of Consumer Information Behaviour to Construct Utility-based Recommender Systems: A Prototypical Study

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    Product recommender systems aim to support consumers in making buying decisions. However, such a support requires considering the consumer behaviour in making buying decisions. In this paper, we deduce design requirements for utility-based recommender systems from the theory of consumer information behaviour and present empirically findings from experiments conducted with a prototypical implementation of the proposed requirements. The empirical examination shows that our recommender system has a high predictive validity

    New High Proper Motion Stars from the Digitized Sky Survey. II. Northern Stars with 0.5<mu<2.0 arcsec/yr at High Galactic Latitudes

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    In a continuation of our systematic search for high proper motion stars in the Digitized Sky Survey, we have completed the analysis of northern sky fields at galactic latitudes above 25 degrees. With the help of our SUPERBLINK software, a powerful automated blink comparator developed by us, we have identified 1146 stars in the magnitude range 8<r<20 with proper motions 0.500<mu<2.000 arcsec/yr. These include 1080 stars previously listed in Luyten's proper motion catalogs (LHS, NLTT), 9 stars not previously listed in the Luyten catalogs but reported elsewhere in the literature (including 1 previously reported by our team), and 57 new objects reported here for the first time. This paper includes a list of positions, proper motions, magnitudes, and finder charts for all the new high proper motion stars. Combined with our previous study of low galactic latitude fields (see Paper I), our survey now covers over 98% of the northern sky. We conclude that the Luyten catalogs were 90% complete in the northern sky for stars with 0.5<mu<2.0 arcsec/yr down to magnitude r=19. We discuss the incompleteness of the old Luyten proper motion survey, and estimate completeness limits for our new survey.Comment: To appear in The Astronomical Journa

    Implementing an automated collection follow up system in a not-for-profit Catholic hospital

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    The purpose of this Applied Management Decision Report is to analyze the computer software available which would allow a hospital to be successful in reducing its investment in accounts receivable. The hospital will have to invest in software in order to help achieve stated accounts receivable reduction goals. This report analyzes three separate software alternatives that would allow the Patient Accounts Department to operate more effectively

    Coordinated AMBER and MIDI observations of the Mira variable RR Aql

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    We have used near- and mid-infrared interferometry to investigate the pulsating atmosphere and the circumstellar environment of the Mira variable RR Aql. Observations were taken with the VLTI/AMBER (near infrared) and the VLTI/MIDI (mid infrared) instruments. We have obtained a total of 15 MIDI epochs between Apr 9, 2004 and Jul 28, 2007 covering 4 pulsation cycles and one AMBER epoch on Sep 9, 2006 at phase 2.82. This work is also part of an ongoing project of joint VLTI and VLBA observations to study the connection between stellar pulsation and the mass loss process. Here we present a comparison of the AMBER visibility data to a simple uniform disk model as well as to predictions by recent self-excited dynamic model atmospheres. The best fitting photospheric angular diameter of the model atmosphere at phase 2.82 is 9.9 +/- 2.4 mas.Comment: 4 pages, 3 figures, to appear in Proc. of Cool Stars 1
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