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Full-Text Articles in Physical Sciences and Mathematics
Introducing Semantics In Web Personalization: The Role Of Ontologies, Magdalini Eirinaki, Dimitrios Mavroeidis, George Tsatsaronis, Michalis Vazirgiannis
Introducing Semantics In Web Personalization: The Role Of Ontologies, Magdalini Eirinaki, Dimitrios Mavroeidis, George Tsatsaronis, Michalis Vazirgiannis
Faculty Publications
Web personalization is the process of customizing a web site to the needs of each specific user or set of users. Personalization of a web site may be performed by the provision of recommendations to the users, high-lighting/adding links, creation of index pages, etc. The web personalization systems are mainly based on the exploitation of the navigational patterns of the web site’s visitors. When a personalization system relies solely on usage-based results, however, valuable information conceptually related to what is finally recommended may be missed. The exploitation of the web pages’ semantics can considerably improve the results of web usage …
Hydrodynamic Description Of The Adiabatic Piston, Alejandro Garcia, M. M. Mansour
Hydrodynamic Description Of The Adiabatic Piston, Alejandro Garcia, M. M. Mansour
Faculty Publications
A closed macroscopic equation for the motion of the two-dimensional adiabatic piston is derived from standard hydrodynamics. It predicts a damped oscillatory motion of the piston towards a final rest position, which depends on the initial state. In the limit of large piston mass, the solution of this equation is in quantitative agreement with the results obtained from both hard disk molecular dynamics and hydrodynamics. The explicit forms of the basic characteristics of the piston’s dynamics, such as the period of oscillations and the relaxation time, are derived. The limitations of the theory’s validity, in terms of the main system …
Estimating Hydrodynamic Quantities In The Presence Of Microscopic Fluctuations, Alejandro Garcia
Estimating Hydrodynamic Quantities In The Presence Of Microscopic Fluctuations, Alejandro Garcia
Faculty Publications
This paper discusses the evaluation of hydrodynamic variables in the presence of spontaneous fluctuations, such as in molecular simulations of fluid flows. The principal point is that hydrodynamic variables such as fluid velocity and temperature must be defined in terms of mechanical variables such as momentum and energy density). Because these relations are nonlinear and because fluctuations of mechanical variables are correlated, care must be taken to avoid introducing a bias when evaluating means, variances, and correlations of hydrodynamic variables. The unbiased estimates are formulated; some alternative, incorrect approaches are presented as cautionary warnings. The expressions are verified by numerical …
A Deep Kinematic Survey Of Planetary Nebulae In The Andromeda Galaxy Using The Planetary Nebula Spectrograph, H. R. Merrett, M. R. Merrifield, N. G. Douglas, K. Kuijken, Aaron J. Romanowsky, N. R. Napolitano, M. Arnaboldi, M. Capaccioli, K. C. Freeman, O. Gerhard, L. Coccato, D. Carter, N. W. Evans, M. I. Wilkinson, C. Halliday, T. J. Bridges
A Deep Kinematic Survey Of Planetary Nebulae In The Andromeda Galaxy Using The Planetary Nebula Spectrograph, H. R. Merrett, M. R. Merrifield, N. G. Douglas, K. Kuijken, Aaron J. Romanowsky, N. R. Napolitano, M. Arnaboldi, M. Capaccioli, K. C. Freeman, O. Gerhard, L. Coccato, D. Carter, N. W. Evans, M. I. Wilkinson, C. Halliday, T. J. Bridges
Faculty Publications
We present a catalogue of positions, magnitudes and velocities for 3300 emission-line objects found by the Planetary Nebula Spectrograph in a survey of the Andromeda galaxy, M31. Of these objects, 2615 are found likely to be planetary nebulae (PNe) associated with M31. The survey area covers the whole of M31's disc out to a radius of Graphic. Beyond this radius, observations have been made along the major and minor axes, and the Northern Spur and Southern Stream regions. The calibrated data have been checked for internal consistency and compared with other catalogues. With the exception of the very central, high …
Planetary Nebula Velocities In The Disc And Bulge Of M31, C. Halliday, D. Carter, T. J. Bridges, Z. C. Jackson, M. I. Wilkinson, D. P. Quinn, N. W. Evans, N. G. Douglas, H. R. Merrett, Aaron J. Romanowsky, K. Kuijken, M. J. Irwin
Planetary Nebula Velocities In The Disc And Bulge Of M31, C. Halliday, D. Carter, T. J. Bridges, Z. C. Jackson, M. I. Wilkinson, D. P. Quinn, N. W. Evans, N. G. Douglas, H. R. Merrett, Aaron J. Romanowsky, K. Kuijken, M. J. Irwin
Faculty Publications
We present radial velocities for a sample of 723 planetary nebulae in the disc and bulge of M31, measured using the WYFFOS fibre spectrograph on the William Herschel Telescope. Velocities are determined using the [O III] λ5007 emission line. Rotation and velocity dispersion are measured to a radius of 50 arcmin (11.5 kpc), the first stellar rotation curve and velocity dispersion profile for M31 to such a radius. Our kinematics are consistent with rotational support at radii well beyond the bulge effective radius of 1.4 kpc, although our data beyond a radius of 5 kpc are limited. We present tentative …
Wide-Field Kinematics Of Globular Clusters In The Leo I Group, G. Bergond, S. E. Zepf, Aaron J. Romanowsky, R. M. Sharples, K. L. Rhode
Wide-Field Kinematics Of Globular Clusters In The Leo I Group, G. Bergond, S. E. Zepf, Aaron J. Romanowsky, R. M. Sharples, K. L. Rhode
Faculty Publications
We present wide-field spectroscopy of globular clusters around the Leo I group galaxies NGC 3379 and NGC 3384 using the FLAMES multi-fibre instrument at the VLT. We obtain accurate radial velocities for 42 globular clusters (GCs) in total, 30 for GCs around the elliptical NGC 3379, eight around the lenticular NGC 3384, and four which may be associated with either galaxy. These data are notable for their large radial range extending from 0$\farcm$7 to 14$\farcm$5 (2 to 42 kpc) from the centre of NGC 3379, and small velocity uncertainties of about 10 km s-1. We combine our sample of 30 …
The Araucaria Project. An Accurate Distance To Ngc 6822 From Near-Infrared Photometry Of Cepheid Variables, W. Gieren, G. Pietrzyński, K. Nalewajko, I. Soszyński, F. Bresolin, R.-P. Kudritzki, D. Minniti, Aaron J. Romanowsky
The Araucaria Project. An Accurate Distance To Ngc 6822 From Near-Infrared Photometry Of Cepheid Variables, W. Gieren, G. Pietrzyński, K. Nalewajko, I. Soszyński, F. Bresolin, R.-P. Kudritzki, D. Minniti, Aaron J. Romanowsky
Faculty Publications
We have measured near-infrared magnitudes in the J and K bands for 56 Cepheid variables in the Local Group galaxy NGC 6822 with well-determined periods and optical light curves in the V and I bands. Using the template light-curve approach of Soszyński and coworkers, accurate mean magnitudes were obtained from these data, which allowed us to determine with unprecedented accuracy the distance to NGC 6822 from a multiwavelength period-luminosity solution in the VIJK bands. From our data, we obtain a distance to NGC 6822 of (m - M)0 = 23.312 ± 0.021 (random error) mag, with an additional systematic uncertainty …