4,251 research outputs found
Indefinite Morse 2-functions; broken fibrations and generalizations
A Morse 2-function is a generic smooth map from a smooth manifold to a
surface. In the absence of definite folds (in which case we say that the Morse
2-function is indefinite), these are natural generalizations of broken
(Lefschetz) fibrations. We prove existence and uniqueness results for
indefinite Morse 2-functions mapping to arbitrary compact, oriented surfaces.
"Uniqueness" means there is a set of moves which are sufficient to go between
two homotopic indefinite Morse 2-functions while remaining indefinite
throughout. We extend the existence and uniqueness results to indefinite, Morse
2-functions with connected fibers.Comment: 74 pages, 41 figures; further errors corrected, some exposition
added, other exposition improved, following referee's comment
The Economic Impact of a Radiological Dispersal Device (RDE)
While it will not cause the devastation of a nuclear weapon, the radiological dispersal event (RDE) is particularly dangerous in that it has the potential to cause major economic disruptions. The purpose of this research was to develop a generalized methodology that can be used to assess economic impacts, resulting from a (RDE), occurring in any location and across any industry. Currently, there is no universal approach for measuring the costs or economic impacts on businesses, or a common framework for conducting an economic impact for a RDE. The objective of this research was to aid in the RDE response effort by providing government planners, officials, and key stakeholders with an (pre-RDE) economic assessment tool which can be used to quantify the economic impacts arising from a RDE, thereby facilitating the strategic decision making process. A random study site was selected to use as a practical application for the research methodology. Through the use of an economic input-output model, the research identified that the economic impacts to the study site’s output totaled 529.6 million. Overall, 21,374 jobs were affected due to the economic disruptions resulting from the RDE. The culmination of this effort was the development of a generalized, “off the shelf”, economic impact assessment tool that can be used to estimate the financial impacts of a RDE, or any localized event which disrupts an economy
Open TURNS: An industrial software for uncertainty quantification in simulation
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
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Extending synchrotron-based atomic physics experiments into the hard X-ray region
The high-brightness, hard x-ray beams available from third-generation synchrotron sources are opening new opportunities to study the deepest inner shells of atoms, an area where little work has been done and phenomena not observed in less tightly bound inner-shells are manifested. In addition scattering processes which are weak at lower energies become important, providing another tool to investigate atomic structure as well as an opportunity to study photon/atom interactions beyond photoabsorption. In this contribution the authors discuss some of the issues related to extending synchrotron-based atomic physics experiments into the hard x-ray region from the physical and the experimental point of view. They close with a discussion of a technique, resonant Raman scattering, that may prove invaluable in determining the spectra of the very highly-excited states resulting from the excitation of deep inner shells
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Interpreting X-ray and auger resonant Raman spectra
We discuss resonant Raman Scattering in atoms within the context of conservation of energy, arguing that energy conservation determines the principal features of spectra taken at a resolution comparable to the natural widths of the transitions involved. Example systems applicable to atoms or solids are calculated using the model by Tulkki and Aberg, and the model is discussed in terms of energy conservation. Finally, results for X-ray resonant Raman scattering in Xe and Auger resonant Raman scattering in Ar are presented and the two processes are contrasted
INTEGRAL discovery of a bright highly obscured galactic X-ray binary source IGR J16318-4848
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
South-West extension of the hard X-ray emission from the Coma cluster
We explore the morphology of hard (18-30 keV) X-ray emission from the Coma
cluster of galaxies. We analyze a deep (1.1 Ms) observation of the Coma cluster
with the ISGRI imager on board the \emph{INTEGRAL} satellite. We show that the
source extension in the North-East to South-West (SW) direction ()
significantly exceeds the size of the point spread function of ISGRI, and that
the centroid of the image of the source in the 18-30 keV band is displaced in
the SW direction compared to the centroid in the 1-10 keV band. To test the
nature of the SW extension we fit the data assuming different models of source
morphology. The best fit is achieved with a diffuse source of elliptical shape,
although an acceptable fit can be achieved assuming an additional point source
SW of the cluster core. In the case of an elliptical source, the direction of
extension of the source coincides with the direction toward the subcluster
falling onto the Coma cluster. If the SW excess is due to the presence of a
point source with a hard spectrum, we show that there is no obvious X-ray
counterpart for this additional source, and that the closest X-ray source is
the quasar EXO 1256+281, which is located from the centroid of the
excess. The observed morphology of the hard X-ray emission clarifies the nature
of the hard X-ray "excess" emission from the Coma cluster, which is due to the
presence of an extended hard X-ray source SW of the cluster core.Comment: 7pages, 10 figure
INTEGRAL and Swift/XRT observations of IGR~J16460+0849
IGR J16460+0849 is reported in the 3rd IBIS catalog with the shortest
exposure of about 10 ks among all the detected sources, which makes it the most
interesting target to be investigated with a deeper exposure. We analyze all
available observations carried out by the International Gamma-Ray Astrophysics
Laboratory (INTEGRAL) on the unidentified source IGR J16460+0849. The data
were processed by using the latest version OSA 7.0. In addition we analyze also
all the available Swift/XRT data on this source. We find that IGR J16460+0849
has a detection significance of ~ 4.4 sigma in the 20-100 keV band during the
observational period between March 2003 and September 2004, when it was exposed
by ~ 19 ks. Thereafter the source was not detected anymore, despite an
additional exposure of ~ 271 ks. This suggests a flux variability on a
timescale of years. The spectral analysis shows that the IBIS/ISGRI data are
well presented by a power-law shape, with a photon index obtained as
1.45+-0.86. So far, the source has been detected consistently by IBIS/ISGRI in
the subsequent observations and in the adjacent energy bands. We have analyzed
the Swift/XRT observations on IGR J16460+0849 as well, and found no source
inside the IBIS/ISGRI error circle. The non-detection during the Swift/XRT
observation is consistent with the source having a variable nature.Comment: published in A&
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