5,131 research outputs found

    Open TURNS: An industrial software for uncertainty quantification in simulation

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    The needs to assess robust performances for complex systems and to answer tighter regulatory processes (security, safety, environmental control, and health impacts, etc.) have led to the emergence of a new industrial simulation challenge: to take uncertainties into account when dealing with complex numerical simulation frameworks. Therefore, a generic methodology has emerged from the joint effort of several industrial companies and academic institutions. EDF R&D, Airbus Group and Phimeca Engineering started a collaboration at the beginning of 2005, joined by IMACS in 2014, for the development of an Open Source software platform dedicated to uncertainty propagation by probabilistic methods, named OpenTURNS for Open source Treatment of Uncertainty, Risk 'N Statistics. OpenTURNS addresses the specific industrial challenges attached to uncertainties, which are transparency, genericity, modularity and multi-accessibility. This paper focuses on OpenTURNS and presents its main features: openTURNS is an open source software under the LGPL license, that presents itself as a C++ library and a Python TUI, and which works under Linux and Windows environment. All the methodological tools are described in the different sections of this paper: uncertainty quantification, uncertainty propagation, sensitivity analysis and metamodeling. A section also explains the generic wrappers way to link openTURNS to any external code. The paper illustrates as much as possible the methodological tools on an educational example that simulates the height of a river and compares it to the height of a dyke that protects industrial facilities. At last, it gives an overview of the main developments planned for the next few years

    Pluri-Canonical Models of Supersymmetric Curves

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    This paper is about pluri-canonical models of supersymmetric (susy) curves. Susy curves are generalisations of Riemann surfaces in the realm of super geometry. Their moduli space is a key object in supersymmetric string theory. We study the pluri-canonical models of a susy curve, and we make some considerations about Hilbert schemes and moduli spaces of susy curves.Comment: To appear in the proceedings of the intensive period "Perspectives in Lie Algebras", held at the CRM Ennio De Giorgi, Pisa, Italy, 201

    Progress in construction of the LHC

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    The Large Hadron Collider (LHC) project, approved by the CERN Council in December 1994, has now fully entered its construction phase, with the detailed technical definition of the major systems, and the adjudication of a number of large procurement contracts. We first recall the main features and characteristics of the LHC, report on the advances in definition of the layout and optics as well as on preparation of the injector complex, and review recent progress in the key technical systems of the main ring: magnets, cryogenics and vacuum, as well as civil construction, which has started following acceptance by authorities in the Host States

    Compton telescope with coded aperture mask: Imaging with the INTEGRAL/IBIS Compton mode

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    Compton telescopes provide a good sensitivity over a wide field of view in the difficult energy range running from a few hundred keV to several MeV. Their angular resolution is, however, poor and strongly energy dependent. We present a novel experimental design associating a coded mask and a Compton detection unit to overcome these pitfalls. It maintains the Compton performance while improving the angular resolution by at least an order of magnitude in the field of view subtended by the mask. This improvement is obtained only at the expense of the efficiency that is reduced by a factor of two. In addition, the background corrections benefit from the coded mask technique, i.e. a simultaneous measurement of the source and background. This design is implemented and tested using the IBIS telescope on board the INTEGRAL satellite to construct images with a 12' resolution over a 29 degrees x 29 degrees field of view in the energy range from 200 keV to a few MeV. The details of the analysis method and the resulting telescope performance, particularly in terms of sensitivity, are presented

    Maximum solutions of normalized Ricci flows on 4-manifolds

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    We consider maximum solution g(t)g(t), t[0,+)t\in [0, +\infty), to the normalized Ricci flow. Among other things, we prove that, if (M,ω)(M, \omega) is a smooth compact symplectic 4-manifold such that b2+(M)>1b_2^+(M)>1 and let g(t),t[0,)g(t),t\in[0,\infty), be a solution to (1.3) on MM whose Ricci curvature satisfies that Ric(g(t))3|\text{Ric}(g(t))|\leq 3 and additionally χ(M)=3τ(M)>0\chi(M)=3 \tau (M)>0, then there exists an mNm\in \mathbb{N}, and a sequence of points {xj,kM}\{x_{j,k}\in M\}, j=1,...,mj=1, ..., m, satisfying that, by passing to a subsequence, (M,g(tk+t),x1,k,...,xm,k)dGH(j=1mNj,g,x1,,...,,xm,),(M, g(t_{k}+t), x_{1,k},..., x_{m,k}) \stackrel{d_{GH}}\longrightarrow (\coprod_{j=1}^m N_j, g_{\infty}, x_{1,\infty}, ...,, x_{m,\infty}), t[0,)t\in [0, \infty), in the mm-pointed Gromov-Hausdorff sense for any sequence tkt_{k}\longrightarrow \infty, where (Nj,g)(N_{j}, g_{\infty}), j=1,...,mj=1,..., m, are complete complex hyperbolic orbifolds of complex dimension 2 with at most finitely many isolated orbifold points. Moreover, the convergence is CC^{\infty} in the non-singular part of 1mNj\coprod_1^m N_{j} and Volg0(M)=j=1mVolg(Nj)\text{Vol}_{g_{0}}(M)=\sum_{j=1}^{m}\text{Vol}_{g_{\infty}}(N_{j}), where χ(M)\chi(M) (resp. τ(M)\tau(M)) is the Euler characteristic (resp. signature) of MM.Comment: 23 page

    Imaging extended sources with coded mask telescopes: Application to the INTEGRAL IBIS/ISGRI instrument

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    Context. In coded mask techniques, reconstructed sky images are pseudo-images: they are maps of the correlation between the image recorded on a detector and an array derived from the coded mask pattern. Aims. The INTEGRAL/IBIS telescope provides images where the flux of each detected source is given by the height of the local peak in the correlation map. As such, it cannot provide an estimate of the flux of an extended source. What is needed is intensity sky images giving the flux per solide angle as typically done at other wavelengths. Methods. In this paper, we present the response of the INTEGRAL IBIS/ISGRI coded mask instrument to extended sources. We develop a general method based on analytical calculations in order to measure the intensity and the associated error of any celestial source and validated with Monte-Carlo simulations. Results. We find that the sensitivity degrades almost linearly with the source extent. Analytical formulae are given as well as an easy-to-use recipe for the INTEGRAL user. We check this method on IBIS/ISGRI data but these results are general and applicable to any coded mask telescope.Comment: 9 pages, 6 figures, Accepted for publication in A&

    SPI Measurements of the Diffuse Galactic Hard X-ray Continuum

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    INTEGRAL Spectrometer SPI data from the first year of the Galactic Centre Deep Exposure has been analysed for the diffuse continuum from the Galactic ridge. A new catalogue of sources from the INTEGRAL Imager IBIS has been used to account for their contribution to the celestial signal. Apparently diffuse emission is detected at a level ~10% of the total source flux. A comparison of the spectrum of diffuse emission with that from an analysis of IBIS data alone shows that they are consistent. The question of the contribution of unresolved sources to this ridge emission is still open.Comment: Proceedings of the 5th INTEGRAL Workshop, Munich 16-20 February 2004. ESA SP-552. Reference to Terrier et al. (2004) updated to include astro-ph versio

    High-energy emission from the stellar wind collisions in gamma-2 Velorum

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    The binary system gamma-2 Velorum (WC8+O7.5) contains the nearest known Wolf-Rayet star to the Sun, at a distance of 25831+41_{-31}^{+41} pc. Its strong radio emission shows evidence for a partially absorbed nonthermal component, which has been interpreted as synchrotron emission from electrons accelerated in the colliding wind region. Inverse Compton cooling of these electrons in the intense UV radiation field from the O-type companion star could produce a significant hard X-ray and gamma-ray emission, whose flux depends on the ratio of the energy densities of magnetic to seed photon fields. The Vela region was observed with the INTEGRAL satellite in 2003, as part of the Core Programme. No signals from gamma-2 Vel are detected in the images obtained with the IBIS/ISGRI coded aperture instrument in the energy ranges 20-40 and 40-80 keV. From the derived 3σ\sigma upper limits, we show that the average magnetic field near the region of stellar wind collision should be relatively high, greater than about 1 G. The high-energy emission of gamma-2 Vel might be detected with the forthcoming GLAST experiment.Comment: 4 pages, 3 figures. To appear in the Proceedings of the 5th INTEGRAL Workshop: "The INTEGRAL Universe", February 16-20, 2004, Munich, German

    Maintaining diversity in an ant community: modeling, extending, and testing the dominance-discovery trade-off

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    Journal ArticleAnt communities often consist of many species with apparently similar niches. We present a mathematical model of the dominance-discovery trade-off, the trade-off between the abilities to find and to control resources, showing that it can in principle facilitate the coexistence of large numbers of species

    INTEGRAL discovery of a bright highly obscured galactic X-ray binary source IGR J16318-4848

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    INTEGRAL regularly scans the Galactic plane to search for new objects and in particular for absorbed sources with the bulk of their emission above 10-20 keV. The first new INTEGRAL source was discovered on 2003 January 29, 0.5 degree from the Galactic plane and was further observed in the X-rays with XMM-Newton. This source, IGR J16318-4848, is intrinsically strongly absorbed by cold matter and displays exceptionally strong fluorescence emission lines. The likely infrared/optical counterpart indicates that IGR J16318-4848 is probably a High Mass X-Ray Binary neutron star or black hole enshrouded in a Compton thick environment. Strongly absorbed sources, not detected in previous surveys, could contribute significantly to the Galactic hard X-ray background between 10 and 200 keV.Comment: 6 pages, 4 figures (fig 1 quality lowered), accepted for publication in A&A letters (INTEGRAL special issue
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