208 research outputs found
The perturbed sublimation rim of the dust disk around the post-AGB binary IRAS08544-4431
Context: Post-Asymptotic Giant Branch (AGB) binaries are surrounded by stable
dusty and gaseous disks similar to the ones around young stellar objects.
Whereas significant effort is spent on modeling observations of disks around
young stellar objects, the disks around post-AGB binaries receive significantly
less attention, even though they pose significant constraints on theories of
disk physics and binary evolution. Aims: We want to examine the structure of
and phenomena at play in circumbinary disks around post-AGB stars. We continue
the analysis of our near-infrared interferometric image of the inner rim of the
circumbinary disk around IRAS08544-4431. We want to understand the physics
governing this inner disk rim. Methods: We use a radiative transfer model of a
dusty disk to reproduce simultaneously the photometry as well as the
near-infrared interferometric dataset on IRAS08544-4431. The model assumes
hydrostatic equilibrium and takes dust settling self-consistently into account.
Results: The best-fit radiative transfer model shows excellent agreement with
the spectral energy distribution up to mm wavelengths as well as with the
PIONIER visibility data. It requires a rounded inner rim structure, starting at
a radius of 8.25 au. However, the model does not fully reproduce the detected
over-resolved flux nor the azimuthal flux distribution of the inner rim. While
the asymmetric inner disk rim structure is likely to be the consequence of
disk-binary interactions, the origin of the additional over-resolved flux
remains unclear. Conclusions: As in young stellar objects, the disk inner rim
of IRAS08544-4431 is ruled by dust sublimation physics. Additional observations
are needed to understand the origin of the extended flux and the azimuthal
perturbation at the inner rim of the disk.Comment: Accepted for publication in A&A, 13 figures, 13 page
Exploration of WEB resources in the domain of metal processing technologies
The amount of information contained in the WEB grows in a galloping way, which is caused by the spread of Internet access and lowering the cost of storing and sharing data across the network. The vast amount of data, impossible to be analyzed by human, is the reason why finding and selecting valuable information has become a serious problem. Due to this situation, a highly useful and desired solution would be the development of a system that would allow continuous monitoring of the WEB and finding for the user valuable information from the selected Internet resources. This paper describes the concept of such a system, along with its initial implementation and application to search for information in the field of foundry industry
The recommendation system knowledge representation and reasoning procedures under uncertainty for metal casting
The paper presents an information system dedicated to requirements recommendation and knowledge sharing. It presents methodology of constructing domain knowledge base and application procedure on the example of production technology of Austempered Ductile Iron (ADI). For knowledge representation and reasoning Logic of Plausible Reasoning (LPR) is used. Both equally applicable LPR for formalization the knowledge of foundry technology, as well as the described system solution have the unique character
Sparse aperture masking interferometry survey of transitional discs: Search for substellar-mass companions and asymmetries in their parent discs
This is the author accepted manuscript. The final version is available from EDP Sciences via the DOI in this record.Context. Transitional discs are a class of circumstellar discs around young stars with extensive clearing of dusty material within their
inner regions on 10s of au scales. One of the primary candidates for this kind of clearing is the formation of planet(s) within the disc
that then accrete or clear their immediate area as they migrate through the disc.
Aims. The goal of this survey was to search for asymmetries in the brightness distribution around a selection of transitional disc
targets. We then aimed to determine whether these asymmetries trace dynamically-induced structures in the disc or the gap-opening
planets themselves.
Methods. Our sample included eight transitional discs. Using the Keck/NIRC2 instrument we utilised the Sparse Aperture Masking
(SAM) interferometry technique to search for asymmetries indicative of ongoing planet formation. We searched for close-in companions
using both model fitting and interferometric image reconstruction techniques. Using simulated data, we derived diagnostics that
helped us to distinguish between point sources and extended asymmetric disc emission. In addition, we investigated the degeneracy
between the contrast and separation that appear for marginally resolved companions.
Results. We found FP Tau to contain a previously unseen disc wall, and DM Tau, LkHα330, and TW Hya to contain an asymmetric
signal indicative of point source-like emission. We placed upper limits on the contrast of a companion in RXJ1842.9-3532 and
V2246 Oph. We ruled the asymmetry signal in RXJ1615.3-3255 and V2062 Oph to be false positives. In the cases where our data
indicated a potential companion we computed estimates for the value of McM˙
c and found values in the range of 10−5 − 10−3M2
J
yr−1
.
Conclusions. We found significant asymmetries in four targets. Of these, three were consistent with companions. We resolved a
previously unseen gap in the disc of FP Tau extending inwards from approximately 10 au.We acknowledge support from a STFC Rutherford Fellowship
and Grant (ST/J004030/1, ST/K003445/1), Marie Sklodowska-Curie CIG
grant (Ref. 618910), and Philip Leverhulme Prize (PLP-2013-110). We additionally
acknowledge support from NASA KPDA grants (JPL-1452321, 1474717,
1485953, 1496788). The authors wish to recognise and acknowledge the very
significant cultural role and reverence that the summit of Mauna Kea has always
had within the indigenous Hawaiian community. We are most fortunate to have
the opportunity to conduct observations from this mountain. Some of the data
presented herein were obtained at the W.M. Keck Observatory, which is operated
as a scientific partnership among the California Institute of Technology, the
University of California and the National Aeronautics and Space Administration.
The Observatory was made possible by the generous financial support of
the W.M. Keck Foundatio
Sparse aperture masking interferometry survey of transitional discs. Search for substellar-mass companions and asymmetries in their parent discs
This is the author accepted manuscript. The final version is available from EDP Sciences via the DOI in this record.Context. Transitional discs are a class of circumstellar discs around young stars with extensive clearing of dusty material within their inner regions on 10s of au scales. One of the primary candidates for this kind of clearing is the formation of planet(s) within the disc that then accrete or clear their immediate area as they migrate through the disc.
Aims. The goal of this survey was to search for asymmetries in the brightness distribution around a selection of transitional disc targets. We then aimed to determine whether these asymmetries trace dynamically-induced structures in the disc or the gap-opening planets themselves.
Methods. Our sample included eight transitional discs. Using the Keck/NIRC2 instrument we utilised the Sparse Aperture Masking (SAM) interferometry technique to search for asymmetries indicative of ongoing planet formation. We searched for close-in companions using both model fitting and interferometric image reconstruction techniques. Using simulated data, we derived diagnostics that helped us to distinguish between point sources and extended asymmetric disc emission. In addition, we investigated the degeneracy between the contrast and separation that appear for marginally resolved companions.
Results. We found FP Tau to contain a previously unseen disc wall, and DM Tau, LkHα330, and TW Hya to contain an asymmetric signal indicative of point source-like emission. We placed upper limits on the contrast of a companion in RXJ 1842.9-3532 and V2246 Oph. We ruled the asymmetry signal in RXJ 1615.3-3255 and V2062 Oph to be false positives. In the cases where our data indicated a potential companion we computed estimates for the value of McṀc and found values in the range of 10−5−10−3 M2J yr−1.
Conclusions. We found significant asymmetries in four targets. Of these, three were consistent with companions. We resolved a previously unseen gap in the disc of FP Tau extending inwards from approximately 10 au.We acknowledge support from a STFC Rutherford Fellowship and Grant (ST/J004030/1, ST/K003445/1), Marie Sklodowska-Curie CIG grant (Ref. 618910), and Philip Leverhulme Prize (PLP-2013-110). We additionally acknowledge support from NASA KPDA grants (JPL-1452321, 1474717, 1485953, 1496788). The authors wish to recognise and acknowledge the very significant cultural role and reverence that the summit of Mauna Kea has always had within the indigenous Hawaiian community. We are most fortunate to have the opportunity to conduct observations from this mountain. Some of the data presented herein were obtained at the W.M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California and the National Aeronautics and Space Administration. The Observatory was made possible by the generous financial support of the W.M. Keck Foundation
OPTIMIZATION OF SIMULATION MODEL PARAMETERS FOR SOLIDIFICATION OF METALS WITH USE OF AGENT-BASED EVOLUTIONARY ALGORITHM
The finite elements method (FEM) is currently widely used for simulation of thermal processes.However, one of still unresolved problems remains proper selection of mathematicalmodel parameters for these processes. As far as modelling of cooling casts in forms is concerned,particular difficulties appear while estimating values of numerous coefficients suchas: heat transport coefficient between metal and form, specific heat, metal and form heatconduction coefficient, metal and form density. Coefficients mentioned above depend not onlyon materials properties but also on temperature. In the paper the idea of optimalizationof simulation method parameters based on adaptive adjustment of curve representing simulationresult and result obtained in physical experiment is presented along with the ideaof evolutionary and agent-based evolutionary optimization system designed to conduct suchoptimizations. Preliminary results obtained with use of ABAQUS system available in ACKCYFRONET and software developed at AGH-UST conclude the paper
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