1,306 research outputs found
A Mean Field Model for the Quadrupolar Phases of UPd
UPd is known to exhibit four antiferroquadrupolar ordered phases at low
temperatures. We report measurements of the magnetisation and magnetostriction
of single crystal UPd, along the principal symmetry directions, in fields
up to 33 T. These results have been combined with recent inelastic neutron and
x-ray resonant scattering measurements to construct a mean field model of
UPd including up to fourth nearest neighbour interactions. In particular we
find that anisotropic quadrupolar interactions must be included in order to
explain the low temperature structures derived from the scattering data.Comment: 9 pages, 6 figures, 3 table
Procédé de retransmission à redondance incrémentale adapté aux paquets IP fragmentés
Le problème traité concerne l'optimisation des performances au niveau de la couche réseau (couche 3 de l'OSI) dans le cadre des transmissions sans fil lorsque l'adaptation à la couche accès radio (couches 1 et 2 de l'OSI) nécessite une fragmentation du paquet de la couche 3. L'originalité du travail réside dans l'intégration et l'adaptation du concept de schéma d'ARQ hybride basé sur la redondance incrémentale à la méthode décrite dans [1] qui prend en compte le fait que les paquets de la couche 3 doivent être fragmentés. Il constitue une approche d'optimisation inter-couches. Le premier résultat important est que les performances obtenues par notre solution sont toujours supérieures aux méthodes conventionnelles de l'état de l'art. De plus, nous démontrons deux résultats analytiques qui sont étayés par des simulations
Improved Fault Analysis on SIMECK Ciphers
The advances of the Internet of Things (IoT) have had a fundamental impact and influence in sharping our rich living experiences. However, since IoT devices are usually resource-constrained, lightweight block ciphers have played a major role in serving as a building block for secure IoT protocols. In CHES 2015, SIMECK, a family of block ciphers, was designed for resource-constrained IoT devices. Since its publication, there have been many analyses on its security. In this paper, under the one bit-flip model, we propose a new efficient fault analysis attack on SIMECK ciphers. Compared to those previously reported attacks, our attack can recover the full master key by injecting faults into only a single round of all SIMECK family members. This property is crucial, as it is infeasible for an attacker to inject faults into different rounds of a SIMECK implementation on IoT devices in the real world. Specifically, our attack is characterized by exercising a deep analysis of differential trail between the correct and faulty immediate ciphertexts. Extensive simulation evaluations are conducted, and the results demonstrate the effectiveness and correctness of our proposed attack
Increases in functional diversity of mountain plant communities is mainly driven by species turnover under climate change
The XMM-LSS Survey: A well controlled X-ray cluster sample over the D1 CFHTLS area
We present the XMM-LSS cluster catalogue corresponding to the CFHTLS D1 area.
The list contains 13 spectroscopically confirmed, X-ray selected galaxy
clusters over 0.8 deg2 to a redshift of unity and so constitutes the highest
density sample of clusters to date. Cluster X-ray bolometric luminosities range
from 0.03 to 5x10^{44} erg/s. In this study, we describe our catalogue
construction procedure: from the detection of X-ray cluster candidates to the
compilation of a spectroscopically confirmed cluster sample with an explicit
selection function. The procedure further provides basic X-ray products such as
cluster temperature, flux and luminosity. We detected slightly more clusters
with a (0.5-2.0 keV) X-ray fluxes of >2x10^{-14} erg/s/cm^{-2} than we expected
based on expectations from deep ROSAT surveys. We also present the
Luminosity-Temperature relation for our 9 brightest objects possessing a
reliable temperature determination. The slope is in good agreement with the
local relation, yet compatible with a luminosity enhancement for the 0.15 < z<
0.35 objects having 1 < T < 2 keV, a population that the XMM-LSS is identifying
systematically for the first time. The present study permits the compilation of
cluster samples from XMM images whose selection biases are understood. This
allows, in addition to studies of large-scale structure, the systematic
investigation of cluster scaling law evolution, especially for low mass X-ray
groups which constitute the bulk of our observed cluster population. All
cluster ancillary data (images, profiles, spectra) are made available in
electronic form via the XMM-LSS cluster database.Comment: 12 pages 5 figures, MNRAS accepted. The paper with full resolution
cluster images is available at
http://vela.astro.ulg.ac.be/themes/spatial/xmm/LSS/rel_pub_e.htm
GRB 050223: A dark GRB in a dusty starburst galaxy
Aims: We aim at detecting and determining the properties of the host galaxy
of the dark GRB 050223.
Methods: We use VLT optical/NIR images coupled to Swift X-ray positioning,
and optical spectra of the host galaxy to measure its properties.
Results: We find a single galaxy within the Swift error box of GRB 050223. It
is located at z = 0.584 and its luminosity is L ~ 0.4 L*. Emission lines in the
galaxy spectrum imply an intrinsic SFR > 7 Msun/yr, and a large extinction A_V
> 2 mag within it. We also detect absorption lines, which reveal an underlying
stellar population with an age between 40 Myr and 1.5 Gyr.
Conclusions: The identification of a host galaxy with atypical properties
using only the X-ray transient suggests that a bias may be present in the
former sample of host galaxies. Dust obscuration together with intrinsic
faintness are the most probable causes for the darkness of this burst.Comment: 4 pages, 2 figures, accepted for publication in Astronomy &
Astrophysic
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