4,280 research outputs found
Xeff analysis method optimization to enhance IACTs performances
The seek of high precision analyses in -ray astronomy leads to the
implementation of multivariate combination, benefiting from several
reconstruction methods. Such analysis, called , was developed for the
H.E.S.S. data using three shower reconstruction methods. This paper presents
the improvement granted to this analysis by refining the distribution
calculation of discriminant variables, considering observation conditions, and
adding new variables in the combination. The efficiency of the
analysis is presented using simulations and real data. A comparison with the
standard analysis (model++), for a typical set of sources, shows a significant
gain in sensitivity.Comment: Contribution to the Proceedings of the 34th International Cosmic Ray
Conference (ICRC 2015), The Hague, The Netherland
Dependable Distributed Computing for the International Telecommunication Union Regional Radio Conference RRC06
The International Telecommunication Union (ITU) Regional Radio Conference
(RRC06) established in 2006 a new frequency plan for the introduction of
digital broadcasting in European, African, Arab, CIS countries and Iran. The
preparation of the plan involved complex calculations under short deadline and
required dependable and efficient computing capability. The ITU designed and
deployed in-situ a dedicated PC farm, in parallel to the European Organization
for Nuclear Research (CERN) which provided and supported a system based on the
EGEE Grid. The planning cycle at the RRC06 required a periodic execution in the
order of 200,000 short jobs, using several hundreds of CPU hours, in a period
of less than 12 hours. The nature of the problem required dynamic
workload-balancing and low-latency access to the computing resources. We
present the strategy and key technical choices that delivered a reliable
service to the RRC06
Sagittarius dwarf spheroidal galaxy observed by H.E.S.S
Dwarf spheroidal galaxies are characterized by a large measured mass-to-light
ratio and are not expected to be the site of high-luminosity non-thermal
high-energy gamma-ray emissions. Therefore they are among the most promising
candidates for indirect searches of dark matter particle annihilation signals
in gamma rays. The Sagittarius dwarf spheroidal galaxy has been regularly
observed by the High Energy Stereoscopic System (H.E.S.S.) of Cherenkov
telescopes for more than 90 hours, searching for TeV gamma-ray emission from
annihilation of dark matter particles. In absence of a significant signal, new
constraints on the annihilation crosssection of the dark matter particles
applicable for Majorana Weakly Interacting Massive Particles (WIMPs) are
derived.Comment: In Proceedings of the 33rd International Cosmic Ray Conference
(ICRC2013), Rio de Janeiro (Brazil
Optimization of multivariate analysis for IACT stereoscopic systems
Multivariate methods have been recently introduced and successfully applied
for the discrimination of signal from background in the selection of genuine
very-high energy gamma-ray events with the H.E.S.S. Imaging Atmospheric
Cerenkov Telescope. The complementary performance of three independent
reconstruction methods developed for the H.E.S.S. data analysis, namely Hillas,
model and 3D-model suggests the optimization of their combination through the
application of a resulting efficient multivariate estimator. In this work the
boosted decision tree method is proposed leading to a significant increase in
the signal over background ratio compared to the standard approaches. The
improved sensitivity is also demonstrated through a comparative analysis of a
set of benchmark astrophysical sources.Comment: 10 pages, 8 figures, 3 tables, accepted for publication in
Astroparticle Physic
The promise and pitfalls of β-diversity in ecology and conservation
A key challenge in ecology and conservation is to determine how processes at different scales create variation in community composition (β-diversity). In this issue, Oldén & Halme show that grazers increase β-diversity through multiple processes at different scales. We discuss how β-diversity can elucidate fundamental processes of community assembly, challenges in linking processes to patterns, and unresolved questions across scales
OGSA/Globus Evaluation for Data Intensive Applications
We present an architecture of Globus Toolkit 3 based testbed intended for
evaluation of applicability of the Open Grid Service Architecture (OGSA) for
Data Intensive Applications.Comment: To be published in the proceedings of the XIX International Symposium
on Nuclear Electronics and Computing (NEC'2003), Bulgaria, Varna, 15-20
September, 200
A multivariate analysis approach for the Imaging atmospheric Cerenkov Telescopes System H.E.S.S.
International audienceWe present a multivariate classification approach applied to the analysis of data from the H.E.S.S. Very High Energy (VHE) gamma-ray IACT stereoscopic system. This approach combines three complementary analysis methods already successfully applied in the H.E.S.S. data analysis. The proposed approach, with the combined effective estimator Xeff, is conceived to improve the signal-to-background ratio and therefore particularly relevant to the morphological studies of faint extended sources
An architecture to manage security services for cloud applications
The uptake of virtualization and cloud technologies has pushed novel development and operation models for the software, bringing more agility and automation. Unfortunately, cyber-security paradigms have not evolved at the same pace and are not yet able to effectively tackle the progressive disappearing of a sharp security perimeter. In this paper, we describe a novel cyber-security architecture for cloud-based distributed applications and network services. We propose a security orchestrator that controls pervasive, lightweight, and programmable security hooks embedded in the virtual functions that compose the cloud application, pursuing better visibility and more automation in this domain. Our approach improves existing management practice for service orchestration, by decoupling the management of the business logic from that of security. We also describe the current implementation stage for a programmable monitoring, inspection, and enforcement framework, which represents the ground technology for the realization of the whole architecture
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