Simlandscape: serious gaming in participatory spatial

In an attempt to improve support for contemporary spatial planning practice, Simlandscape has been developed. In this document the development of Simlandscape as ¿serious game¿ in digital form is described. In its current state, Simlandscape exists in two methodological forms; as an analogue game and as a planning support system using GIS for research and design. The game focuses on simulation of plan processes and on the resulting transformation of areas involved. Players interact with an analogue area model. The planning support system focuses on design and evaluation of plan scenarios and the data handling and presentation accompanying this process. A major challenge now is to integrate, upgrade and digitize components of the analogous game with the planning support system. Several interesting components (practical and scientific) of this project are identified and are discussed

Time Variability of Quasars: the Structure Function Variance

Significant progress in the description of quasar variability has been recently made by employing SDSS and POSS data. Common to most studies is a fundamental assumption that photometric observations at two epochs for a large number of quasars will reveal the same statistical properties as well-sampled light curves for individual objects. We critically test this assumption using light curves for a sample of $\sim$2,600 spectroscopically confirmed quasars observed about 50 times on average over 8 years by the SDSS stripe 82 survey. We find that the dependence of the mean structure function computed for individual quasars on luminosity, rest-frame wavelength and time is qualitatively and quantitatively similar to the behavior of the structure function derived from two-epoch observations of a much larger sample. We also reproduce the result that the variability properties of radio and X-ray selected subsamples are different. However, the scatter of the variability structure function for fixed values of luminosity, rest-frame wavelength and time is similar to the scatter induced by the variance of these quantities in the analyzed sample. Hence, our results suggest that, although the statistical properties of quasar variability inferred using two-epoch data capture some underlying physics, there is significant additional information that can be extracted from well-sampled light curves for individual objects.Comment: Presented at the "Classification and Discovery in Large Astronomical Surveys" meeting, Ringberg Castle, 14-17 October, 200

Micron-sized forsterite grains in the pre-planetary nebula of IRAS 17150-3224 - Searching for clues on the mysterious evolution of massive AGB stars

We study the grain properties and location of the forsterite crystals in the circumstellar environment of the pre-planetary nebula (PPN) IRAS 17150-3224 in order to learn more about the as yet poorly understood evolutionary phase prior to the PPN. We use the best-fit model for IRAS 17150-3224 of Meixner et al. (2002) and add forsterite to this model. We investigate different spatial distributions and grain sizes of the forsterite crystals in the circumstellar environment. We compare the spectral bands of forsterite in the mid-infrared and at 69 micrometre in radiative transport models to those in ISO-SWS and Herschel/PACS observations. We can reproduce the non-detection of the mid-infrared bands and the detection of the 69 micrometre feature with models where the forsterite is distributed in the whole outflow, in the superwind region, or in the AGB-wind region emitted previous to the superwind, but we cannot discriminate between these three models. To reproduce the observed spectral bands with these three models, the forsterite crystals need to be dominated by a grain size population of 2 micrometre up to 6 micrometre. We hypothesise that the large forsterite crystals were formed after the superwind phase of IRAS 17150-3224, where the star developed an as yet unknown hyperwind with an extremely high mass-loss rate (10^-3 Msol/yr). The high densities of such a hyperwind could be responsible for the efficient grain growth of both amorphous and crystalline dust in the outflow. Several mechanisms are discussed that might explain the lower-limit of 2 micrometre found for the forsterite grains, but none are satisfactory. Among the mechanisms explored is a possible selection effect due to radiation pressure based on photon scattering on micron-sized grains.Comment: Accepted by A&

Simlandscape: serious gaming in participatory spatial planning

In an attempt to improve support for contemporary spatial planning practice, Simlandscape has been developed. In this document the development of Simlandscape as serious game in digital form is described. In its current state, Simlandscape exists in two methodological forms; as an analogue game and as a planning support system using GIS for research and design. The game focuses on simulation of plan processes and on the resulting transformation of areas involved. Players interact with an analogue area model. The planning support system focuses on design and evaluation of plan scenarios and the data handling and presentation accompanying this process. A major challenge now is to integrate, upgrade and digitize components of the analogous game with the planning support system. Several interesting components (practical and scientific) of this project are identified and are discussed

Dusty wind of W Hya. Multi-wavelength modelling of the present-day and recent mass-loss

Low- and intermediate-mass stars go through a period of intense mass-loss at the end of their lives in a phase known as the asymptotic giant branch (AGB). During the AGB a significant fraction of their initial mass is expelled in a stellar wind. This process controls the final stages of their evolution and contributes to the chemical evolution of galaxies. However, the wind-driving mechanism of AGB stars is not yet well understood, especially so for oxygen-rich sources. Characterizing both the present-day mass-loss and wind structure and the evolution of the mass-loss rate of such stars is paramount to advancing our understanding of this processes. We modelled the dust envelope of W Hya using an advanced radiative transfer code. The dust model was analysed in the light of a previously calculated gas-phase wind model and compared to measurements available in the literature, such as infrared spectra, infrared images, and optical scattered light fractions. We find that the dust spectrum of W Hya can partly be explained by a gravitationally bound dust shell that probably is responsible for most of the amorphous Al$_2$O$_3$ emission. The composition of the large ($\sim$\,0.3\,$\mu$m) grains needed to explain the scattered light cannot be constrained, but probably is dominated by silicates. Silicate emission in the thermal infrared was found to originate from beyond 40 AU from the star and we find that they need to have substantial near-infrared opacities to be visible at such large distances. The increase in near-infrared opacity of the dust at these distances roughly coincides with a sudden increase in expansion velocity as deduced from the gas-phase CO lines. Finally, the recent mass loss of W Hya is confirmed to be highly variable and we identify a strong peak in the mass-loss rate that occurred about 3500 years ago and lasted for a few hundred years.Comment: 15 pages, 13 figure

Dutch dwellings

Applying Generative Design (GD) for dwelling is not very common but it opens up the possibility to study whether GD systems can reproduce existing design typologies. Dutch dwellings as an exemplification of a design typology are analysed using the SAR methodology. Building regulations are used as input to a GD system along with the typical requirements for a family house. The results show that not all existing typologies can exactly be reproduced, but the generated designs have a remarkable resemblance with Dutch dwellings. They also demonstrate that Dutch dwelling identity is at least partially encoded in Dutch building regulations. Coding of yet unknown architectural identities requires new GD metaphors to support the architect

The electroclinic effect and modulated phases in smectic liquid crystals

We explore the possibility that the large electroclinic effect observed in ferroelectric liquid crystals arises from the presence of an ordered array of disclination lines and walls. If the spacing of these defects is in the subvisible range, this modulated phase would be similar macroscopically to a smectic A phase. The application of an electric field distorts the array, producing a large polarization, and hence a large electroclinic effect. We show that with suitable elastic parameters and sufficiently large chirality, the modulated phase is favored over the smectic A and helically twisted smectic C* phases. We propose various experimental tests of this scenario.Comment: 9 pages, 7 figures; new version includes dipolar interactions and bend-twist couplin