Purchase of dunes: the first step towards nature restoration along the Flemish coast

In 1997 only 1022ha of the remaining 3800ha of coastal dunes was owned by the Flemish Region. The other 2778ha were mostly private property of real estate development firms, large landowners, individuals and, to a lesser degree, public owned by water collection companies, the Ministry of Defence and a couple of municipalities. The then public owned dunes of the Flemish Region were divided as follows among the different administrations of the Ministry of the Flemish Community: 522ha under competence of the Nature Division, 350ha under that of the Waterways and Coast Division and 150ha under that of the Forestry Division. Most of the areas owned by the Nature Division were already purchased between 1956 and 1990. Lack of personnel, funds and strategic perspective prevented the Flemish Region to pursue an active policy of land purchase along the coast. In 1996 an 'Acquisition Plan for the Coastal Dunes' was drawn up by the Group for Applied Ecology of the University of Antwerp under the supervision of the Nature Division. Parliamentary initiatives, following a political debate organised in the frame of the Life nature project 'ICCI', led to the creation of an 'instrument for the acquisition of coastal dunes' by decision of the Flemish government of 3 February 1998. Since 1998 the 'Instrument for the acquisition of coastal dunes' consists of two members of staff, that were added to the Nature Division, and a special article on the budget of the Flemish government. This budgetary article received an initial annual endowment of EUR 1,735,255 in 1998, EUR 3,222,616 in 1999 and EUR 4,462,083 for each year between 2000 and 2004. That initial endowment has been reduced to EUR 2,546,000 in 2005. A weakness in this financing system is that the possibly annually remaining budget cannot be transferred to the budget of the next year, so that no strategic fund can be built up. The active prospecting by the staff of the Acquisition Instrument has allowed the Nature Division to purchase 480ha of dunes between 1998 and 2004. Nearly all these acquisitions were realised with agreement of the former owner. In execution of the Decree of 21 October 1997 concerning Nature Conservation and the Natural Environment, the right of pre-emption of the Flemish Region has been introduced in most of the legally protected areas of Flanders. In the coastal zone however this right of pre-emption has not led to spectacular results, because of a very strongly fragmented property structure and high ground prices due to land speculation. Although the Acquisition Instrument has obtained very good results, a long way still has to be gone before the goal of public ownership of all remaining coastal dunes will be achieved. Essential improvements of the financial and legal instruments for the purchase of dunes should be the creation of a strategic financial fund, an actualisation of the since long outdated expropriation act and improvement of the right of pre-emption for conservation purposes to be able to fend off land speculation

Apsidal motion in the massive binary HD152218

Massive binary systems are important laboratories in which to probe the properties of massive stars and stellar physics in general. In this context, we analysed optical spectroscopy and photometry of the eccentric short-period early-type binary HD 152218 in the young open cluster NGC 6231. We reconstructed the spectra of the individual stars using a separating code. The individual spectra were then compared with synthetic spectra obtained with the CMFGEN model atmosphere code. We furthermore analysed the light curve of the binary and used it to constrain the orbital inclination and to derive absolute masses of 19.8 +/- 1.5 and 15.0 +/- 1.1 solar masses. Combining radial velocity measurements from over 60 years, we show that the system displays apsidal motion at a rate of (2.04^{+.23}_{-.24}) degree/year. Solving the Clairaut-Radau equation, we used stellar evolution models, obtained with the CLES code, to compute the internal structure constants and to evaluate the theoretically predicted rate of apsidal motion as a function of stellar age and primary mass. In this way, we determine an age of 5.8 +/- 0.6 Myr for HD 152218, which is towards the higher end of, but compatible with, the range of ages of the massive star population of NGC 6231 as determined from isochrone fitting.Comment: Accepted for publication in Astronomy & Astrophysic

Grids of Stellar Models and Frequencies with CLES + LOSC

We present a grid of stellar models, obtained with the CLES evolution code, following the specification of ESTA-Task1, and the corresponfing seismic properties, computed with the LOSC code. We provide a complete description of the corresponding files that will be available on the ESTA web-pages.Comment: 8 pages, accepted for publication in Astrophys. Space Sci. (CoRoT/ESTA Volume

Identifying elastoplastic parameters with Bayes' theorem considering output error, input error and model uncertainty

We discuss Bayesian inference for the identification of elastoplastic material parameters. In addition to errors in the stress measurements, which are commonly considered, we furthermore consider errors in the strain measurements. Since a difference between the model and the experimental data may still be present if the data is not contaminated by noise, we also incorporate the possible error of the model itself. The three formulations to describe model uncertainty in this contribution are: (1) a random variable which is taken from a normal distribution with constant parameters, (2) a random variable which is taken from a normal distribution with an input-dependent mean, and (3) a Gaussian random process with a stationary covariance function. Our results show that incorporating model uncertainty often, but not always, improves the results. If the error in the strain is considered as well, the results improve even more

Solar-like oscillations in a massive star

Seismology of stars provides insight into the physical mechanisms taking place in their interior, with modes of oscillation probing different layers. Low-amplitude acoustic oscillations excited by turbulent convection were detected four decades ago in the Sun and more recently in low-mass main-sequence stars. Using data gathered by the Convection Rotation and Planetary Transits mission, we report here on the detection of solar-like oscillations in a massive star, V1449 Aql, which is a known large-amplitude (b Cephei) pulsator.Comment: Published in Sience, 19 June 2009, vol. 324, p. 154

A data-driven reduced-order surrogate model for entire elastoplastic simulations applied to representative volume elements.

peer reviewedThis contribution discusses surrogate models that emulate the solution field(s) in the entire simulation domain. The surrogate uses the most characteristic modes of the solution field(s), in combination with neural networks to emulate the coefficients of each mode. This type of surrogate is well known to rapidly emulate flow simulations, but rather new for simulations of elastoplastic solids. The surrogate avoids the iterative process of constructing and solving the linearized governing equations of rate-independent elastoplasticity, as necessary for direct numerical simulations or (hyper-)reduced-order-models. Instead, the new plastic variables are computed only once per increment, resulting in substantial time savings. The surrogate uses a recurrent neural network to treat the path dependency of rate-independent elastoplasticity within the neural network itself. Because only a few of these surrogates have been developed for elastoplastic simulations, their potential and limitations are not yet well studied. The aim of this contribution is to shed more light on their numerical capabilities in the context of elastoplasticity. Although more widely applicable, the investigation focuses on a representative volume element, because these surrogates have the ability to both emulate the macroscale stress-deformation relation (which drives the multiscale simulation), as well as to recover all microstructural quantities within each representative volume element.Multiscale modelling of lightweight metallic materials accounting for variability of geometrical and material properties9. Industry, innovation and infrastructure12. Responsible consumption and productio

Probing the properties of convective cores through g modes: high-order g modes in SPB and gamma Doradus stars

In main sequence stars the periods of high-order gravity modes are sensitive probes of stellar cores and, in particular, of the chemical composition gradient that develops near the outer edge of the convective core. We present an analytical approximation of high-order g modes that takes into account the effect of the mu gradient near the core. We show that in main-sequence models, similarly to the case of white dwarfs, the periods of high-order gravity modes are accurately described by a uniform period spacing superposed to an oscillatory component. The periodicity and amplitude of such component are related, respectively, to the location and sharpness of the mu gradient. We investigate the properties of high-order gravity modes for stellar models in a mass domain between 1 and 10 Msun, and the effects of the stellar mass, evolutionary state, and extra-mixing processes on period spacing features. In particular, we show that for models of a typical SPB star, a chemical mixing that could likely be induced by the slow rotation observed in these stars, is able to significantly change the g-mode spectra of the equilibrium model. Prospects and challenges for the asteroseismology of gamma Doradus and SPB stars are also discussed.Comment: 18 pages, 29 figures, accepted for publication in MNRA

Differential population studies using asteroseismology: Solar-like oscillating giants in CoRoT fields LRc01 and LRa01

Solar-like oscillating giants observed by the space-borne satellites CoRoT and Kepler can be used as key tracers of stellar populations in the Milky Way. When combined with additional photometric/spectroscopic constraints, the pulsation spectra of solar-like oscillating giant stars not only reveal their radii, and hence distances, but also provide well-constrained estimates of their masses, which can be used as proxies for the ages of these evolved stars. In this contribution we provide supplementary material to the comparison we presented in Miglio et al. (2013) between populations of giants observed by CoRoT in the fields designated LRc01 and LRa01