60 research outputs found
The Konkoly Blazhko Survey: Is light-curve modulation a common property of RRab stars?
A systematic survey to establish the true incidence rate of the Blazhko
modulation among short-period, fundamental-mode, Galactic field RR Lyrae stars
has been accomplished. The Konkoly Blazhko Survey (KBS) was initiated in 2004.
Since then more than 750 nights of observation have been devoted to this
project. A sample of 30 RRab stars was extensively observed, and light-curve
modulation was detected in 14 cases. The 47% occurrence rate of the modulation
is much larger than any previous estimate. The significant increase of the
detected incidence rate is mostly due to the discovery of small-amplitude
modulation. Half of the Blazhko variables in our sample show modulation with so
small amplitude that definitely have been missed in the previous surveys. We
have found that the modulation can be very unstable in some cases, e.g. RY Com
showed regular modulation only during one part of the observations while during
two seasons it had stable light curve with abrupt, small changes in the
pulsation amplitude. This type of light-curve variability is also hard to
detect in other Survey's data. The larger frequency of the light-curve
modulation of RRab stars makes it even more important to find the still lacking
explanation of the Blazhko phenomenon. The validity of the [Fe/H](P,phi_{31})
relation using the mean light curves of Blazhko variables is checked in our
sample. We have found that the formula gives accurate result for
small-modulation-amplitude Blazhko stars, and this is also the case for
large-modulation-amplitude stars if the light curve has complete phase
coverage. However, if the data of large-modulation-amplitude Blazhko stars are
not extended enough (e.g. < 500 data points from < 15 nights), the formula may
give false result due to the distorted shape of the mean light curve used.Comment: Accepted for publication in MNRAS, 14 pages, 7 Figure
The logic of walking: representing design knowledge on pedestrian traffic nets
Specific examples of how 'soft' architectural design knowledge can be formalized and made available to knowledge-based design support systems are scarce in the literature. In this paper such an example is presented in some detail. In a context of design of networks of footpaths, streets, or the like for pedestrian traffic, two particular design concepts are studied: concentration of pedestrians' and 'smoothness of walking lines'. The concepts are put to work in a hypothetical design, and on that background their possible representation in Horn clause logic is outlined, and computational aspects of the representation are discussed.
The logic of plaza space: representing design knowledge on shape and function
This paper concludes a series of three, in which the formalization of 'soft' architectural design knowledge is studied in the context of making it accessible to knowledge-based design systems for support of early sketch design. A wide range of design ideas with the common theme of schematic 'plaza design' is studied, including design from scratch and the reconstruction of existing plazas. Formal conceptual models in Horn clause logic are suggested. The additional evidence thus provided, that 'soft' design knowledge may be accessible to design support systems, is the main contribution of the paper, which is rounded off by a brief discussion of the feasibility and future development of such systems.
The logic of worms: a study in architectural knowledge representation
A schematic but nontrivial site-plan prototype is analyzed, and constituent concepts are created and subsequently represented in formal logic, using Horn clause notation. The purpose of this work is to explore logic programming as a means of representing realistic design knowledge in computer systems for support of architectural sketch design. No such system has been implemented as part of the present study, but results are reported which are encouraging and relevant to further research in that direction. Thus the study seems to show that logical analysis of a specific prototype design can yield a 'microcosmos' of general concepts which are meaningful in their own right but also potentially useful in many other contexts than that of the prototype.
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