2,441 research outputs found
Mira science with interferometry: a review
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)
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
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
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
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
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
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
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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