6,694 research outputs found
Fuzzy local linear approximation-based sequential design
When approximating complex high-fidelity black box simulators with surrogate models, the experimental design is often created sequentially. LOLA-Voronoi, a powerful state of the art method for sequential design combines an Exploitation and Exploration algorithm and adapts the sampling distribution to provide extra samples in non-linear regions. The LOLA algorithm estimates gradients to identify interesting regions, but has a bad complexity which results in long computation time when simulators are high-dimensional. In this paper, a new gradient estimation approach for the LOLA algorithm is proposed based on Fuzzy Logic. Experiments show the new method is a lot faster and results in experimental designs of comparable quality
LIME - a flexible, non-LTE line excitation and radiation transfer method for millimeter and far-infrared wavelengths
We present a new code for solving the molecular and atomic excitation and
radiation transfer problem in a molecular gas and predicting emergent spectra.
This code works in arbitrary three dimensional geometry using unstructured
Delaunay latices for the transport of photons. Various physical models can be
used as input, ranging from analytical descriptions over tabulated models to
SPH simulations. To generate the Delaunay grid we sample the input model
randomly, but weigh the sample probability with the molecular density and other
parameters, and thereby we obtain an average grid point separation that scales
with the local opacity. Our code does photon very efficiently so that the slow
convergence of opaque models becomes traceable. When convergence between the
level populations, the radiation field, and the point separation has been
obtained, the grid is ray-traced to produced images that can readily be
compared to observations. Because of the high dynamic range in scales that can
be resolved using this type of grid, our code is particularly well suited for
modeling of ALMA data. Our code can furthermore deal with overlapping lines of
multiple molecular and atomic species.Comment: 13 pages, 12 figures, Accepted by A&A on 06/08/201
LIME - a flexible, non-LTE line excitation and radiation transfer method for millimeter and far-infrared wavelengths
We present a new code for solving the molecular and atomic excitation and
radiation transfer problem in a molecular gas and predicting emergent spectra.
This code works in arbitrary three dimensional geometry using unstructured
Delaunay latices for the transport of photons. Various physical models can be
used as input, ranging from analytical descriptions over tabulated models to
SPH simulations. To generate the Delaunay grid we sample the input model
randomly, but weigh the sample probability with the molecular density and other
parameters, and thereby we obtain an average grid point separation that scales
with the local opacity. Our code does photon very efficiently so that the slow
convergence of opaque models becomes traceable. When convergence between the
level populations, the radiation field, and the point separation has been
obtained, the grid is ray-traced to produced images that can readily be
compared to observations. Because of the high dynamic range in scales that can
be resolved using this type of grid, our code is particularly well suited for
modeling of ALMA data. Our code can furthermore deal with overlapping lines of
multiple molecular and atomic species.Comment: 13 pages, 12 figures, Accepted by A&A on 06/08/201
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