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.