4,579 research outputs found
Security Attributes Based Digital Rights Management
Most real-life systems delegate responsibilities to different authorities. We apply this model to a digital rights management system, to achieve flexible security. In our model a hierarchy of authorities issues certificates that are linked by cryptographic means. This linkage establishes a chain of control, identity-attribute-rights, and allows flexible rights control over content. Typical security objectives, such as identification, authentication, authorization and access control can be realised. Content keys are personalised to detect illegal super distribution. We describe a working prototype, which we develop using standard techniques, such as standard certificates, XML and Java. We present experimental results to evaluate the scalability of the system. A formal analysis demonstrates that our design is able to detect a form of illegal super distribution
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Big Data Assurance Evaluation: An SLA-Based Approach.
The Big Data community has started noticing that there is the need to complete Big Data platforms with assurance techniques proving the correct behavior of Big Data
analytics and management. In this paper, we propose a Big Data assurance solution based on Service-Level Agreements (SLAs), focusing on a platform providing Model-based Big Data Analytics-as-a-Service (MBDAaaS)
Towards a Version of Markov’s Theorem for Ribbon Torus-Links in R 4
In classical knot theory, Markov’s theorem gives a way of describing all braids with isotopic closures as links in R3. We present a version of Markov’s theorem for extended loop braids with closure in B3S1as a first step towards a Markov’s theorem for extended loop braids and ribbon torus-links in R4
A new eclipsing binary system with a pulsating component detected by CoRoT
We report the discovery of CoRoT 102980178 (R.A.= 06:50:12.10, Dec.=
-02:41:21.8, J2000) an Algol-type eclipsing binary system with a pulsating
component (oEA). It was identified using a publicly available 55 day long
monochromatic lightcurve from the CoRoT initial run dataset (exoplanet field).
Eleven consecutive 1.26m deep total primary and the equal number of 0.25m deep
secondary eclipses (at phase 0.50) were observed. The following light elements
for the primary eclipse were derived: HJD_MinI= 2454139.0680 + 5.0548d x E. The
lightcurve modeling leads to a semidetached configuration with the photometric
mass ratio q=0.2 and orbital inclination i=85 deg. The out-of-eclipse
lightcurve shows ellipsoidal variability and positive O'Connell effect as well
as clear 0.01m pulsations with the dominating frequency of 2.75 c/d. The
pulsations disappear during the primary eclipses, which indicates the primary
(more massive) component to be the pulsating star. Careful frequency analysis
reveals the second independent pulsation frequency of 0.21 c/d and numerous
combinations of these frequencies with the binary orbital frequency and its
harmonics. On the basis of the CoRoT lightcurve and ground based multicolor
photometry, we favor classification of the pulsating component as a gamma
Doradus type variable, however, classification as an SPB star cannot be
excluded.Comment: 16 pages, 7 figures, 3 tables, accepted to Communications in
Asteroseismolog
On the group of ring motions of an H-trivial link
In this paper we compute a presentation for the group of ring motions of the split union of a Hopf link with Euclidean components and a Euclidean circle. A key part of this work is the study of a short exact sequence of groups of ring motions of general ring links in R3. This sequence allowed us to build the main result from the previously known case of the ring group with one component, which a particular case of the ring groups studied by Brendle and Hatcher. This work is a first step towards the computation of a presentation for groups of motions of H-trivial links with an arbitrary number of components
Solar particle effects on minor components of the Polar atmosphere
Abstract. Solar activity can influence the Earth's environment, and in particular the ozone layer, by direct modulation of the e.m. radiation or through variability of the incoming cosmic ray flux (solar and galactic particles). In particular, solar energetic particles (SEPs) provide additional external energy to the terrestrial environment; they are able to interact with the minor constituents of the atmospheric layer and produce ionizations, dissociations, dissociative ionizations and excitations. This paper highlights the SEP effects on the chemistry of the upper atmosphere by analysing some SEP events recorded during 2005 in the descending phase of the current solar cycle. It is shown that these events can lead to short- (hours) and medium- (days) term ozone variations through catalytic cycles (e.g. HOx and NOx increases). We focus attention on the relationship between ozone and OH data (retrieved from MLS EOS AURA) for four SEP events: 17 and 20 January, 15 May and 8 September. We confirm that SEP effects are different on the night and day hemispheres at high latitudes.</p
Evolution of angular-momentum-losing exoplanetary systems : Revisiting Darwin stability
We assess the importance of tidal evolution and its interplay with magnetic
braking in the population of hot-Jupiter planetary systems. By minimizing the
total mechanical energy of a given system under the constraint of stellar
angular momentum loss, we rigorously find the conditions for the existence of
dynamical equilibrium states. We estimate their duration, in particular when
the wind torque spinning down the star is almost compensated by the tidal
torque spinning it up. We introduce dimensionless variables to characterize the
tidal evolution of observed hot Jupiter systems and discuss their spin and
orbital states using generalized Darwin diagrams based on our new approach. We
show that their orbital properties are related to the effective temperature of
their host stars. The long-term evolution of planets orbiting F- and G-type
stars is significantly different owing to the combined effect of magnetic
braking and tidal dissipation. The existence of a quasi-stationary state, in
the case of short-period planets, can significantly delay their tidal evolution
that would otherwise bring the planet to fall into its host star. Most of the
planets known to orbit F-type stars are presently found to be near this
stationary state, probably in a configuration not too far from that they had
when their host star settled on the zero-age main sequence. Considering the
importance of angular momentum loss in the early stages of stellar evolution,
our results indicate that it has to be taken into account also to properly test
the migration scenarios of planetary system formation.Comment: 22 pages, 11 figures, accepted for publication in A&
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