1,482 research outputs found
Optimization of the extraordinary magnetoresistance in semiconductor-metal hybrid structures for magnetic-field sensor applications
Semiconductor-metal hybrid structures can exhibit a very large geometrical
magnetoresistance effect, the so-called extraordinary magnetoresistance (EMR)
effect. In this paper, we analyze this effect by means of a model based on the
finite element method and compare our results with experimental data. In
particular, we investigate the important effect of the contact resistance
between the semiconductor and the metal on the EMR effect. Introducing
a realistic in our model we find
that at room temperature this reduces the EMR by 30% if compared to an analysis
where is not considered.Comment: 4 pages; manuscript for MSS11 conference 2003, Nara, Japa
Strongly Secure and Efficient Data Shuffle On Hardware Enclaves
Mitigating memory-access attacks on the Intel SGX architecture is an
important and open research problem. A natural notion of the mitigation is
cache-miss obliviousness which requires the cache-misses emitted during an
enclave execution are oblivious to sensitive data. This work realizes the
cache-miss obliviousness for the computation of data shuffling. The proposed
approach is to software-engineer the oblivious algorithm of Melbourne shuffle
on the Intel SGX/TSX architecture, where the Transaction Synchronization
eXtension (TSX) is (ab)used to detect the occurrence of cache misses. In the
system building, we propose software techniques to prefetch memory data prior
to the TSX transaction to defend the physical bus-tapping attacks. Our
evaluation based on real implementation shows that our system achieves superior
performance and lower transaction abort rate than the related work in the
existing literature.Comment: Systex'1
Magnetic domain walls in constrained geometries
Magnetic domain walls have been studied in micrometer-sized Fe20Ni80 elements
containing geometrical constrictions by spin-polarized scanning electron
microscopy and numerical simulations. By controlling the constriction
dimensions, the wall width can be tailored and the wall type modified. In
particular, the width of a 180 degree Neel wall can be strongly reduced or
increased by the constriction geometry compared with the wall in unconstrained
systems.Comment: 4 pages, 6 figure
Going Further with Point Pair Features
Point Pair Features is a widely used method to detect 3D objects in point
clouds, however they are prone to fail in presence of sensor noise and
background clutter. We introduce novel sampling and voting schemes that
significantly reduces the influence of clutter and sensor noise. Our
experiments show that with our improvements, PPFs become competitive against
state-of-the-art methods as it outperforms them on several objects from
challenging benchmarks, at a low computational cost.Comment: Corrected post-print of manuscript accepted to the European
Conference on Computer Vision (ECCV) 2016;
https://link.springer.com/chapter/10.1007/978-3-319-46487-9_5
Hydrostatic Expansion and Spin Changes During Type I X-Ray Bursts
We present calculations of the spin-down of a neutron star atmosphere due to
hydrostatic expansion during a Type I X-ray burst. We show that (i) Cumming and
Bildsten overestimated the spin-down of rigidly-rotating atmospheres by a
factor of two, and (ii) general relativity has a small (5-10%) effect on the
angular momentum conservation law. We rescale our results to different neutron
star masses, rotation rates and equations of state, and present some detailed
rotational profiles. Comparing with recent observations of large frequency
shifts in MXB 1658-298 and 4U 1916-053, we find that the spin-down expected if
the atmosphere rotates rigidly is a factor of two to three less than the
observed values. If differential rotation is allowed to persist, we find that
the upper layers of the atmosphere spin down by an amount comparable to the
observed values; however, there is no compelling reason to expect the observed
spin frequency to be that of only the outermost layers. We conclude that
hydrostatic expansion and angular momentum conservation alone cannot account
for the largest frequency shifts observed during Type I bursts.Comment: Submitted to the Astrophysical Journal (13 pages, including 4
figures
An Analysis of Rogue AV Campaigns
Rogue antivirus software has recently received extensive attention, justified by the diffusion and efficacy of its propagation. We present a longitudinal analysis of the rogue antivirus threat ecosystem, focusing on the structure and dynamics of this threat and its economics. To that end, we compiled and mined a large dataset of characteristics of rogue antivirus domains and of the servers that host them. The contributions of this paper are threefold. Firstly, we offer the first, to our knowledge, broad analysis of the infrastructure underpinning the distribution of rogue security software by tracking 6,500 malicious domains. Secondly, we show how to apply attack attribution methodologies to correlate campaigns likely to be associated to the same individuals or groups. By using these techniques, we identify 127 rogue security software campaigns comprising 4,549 domains. Finally, we contextualize our findings by comparing them to a different threat ecosystem, that of browser exploits. We underline the profound difference in the structure of the two threats, and we investigate the root causes of this difference by analyzing the economic balance of the rogue antivirus ecosystem. We track 372,096 victims over a period of 2 months and we take advantage of this information to retrieve monetization insights. While applied to a specific threat type, the methodology and the lessons learned from this work are of general applicability to develop a better understanding of the threat economies
Aharonov-Bohm Effect and Disclinations in an Elastic Medium
In this work we investigate quasiparticles in the background of defects in
solids using the geometric theory of defects. We use the parallel transport
matrix to study the Aharonov-Bohm effect in this background. For quasiparticles
moving in this effective medium we demonstrate an effect similar to the
gravitational Aharonov- Bohm effect. We analyze this effect in an elastic
medium with one and defects.Comment: 6 pages, Revtex
Regge Calculus in Teleparallel Gravity
In the context of the teleparallel equivalent of general relativity, the
Weitzenbock manifold is considered as the limit of a suitable sequence of
discrete lattices composed of an increasing number of smaller an smaller
simplices, where the interior of each simplex (Delaunay lattice) is assumed to
be flat. The link lengths between any pair of vertices serve as independent
variables, so that torsion turns out to be localized in the two dimensional
hypersurfaces (dislocation triangle, or hinge) of the lattice. Assuming that a
vector undergoes a dislocation in relation to its initial position as it is
parallel transported along the perimeter of the dual lattice (Voronoi polygon),
we obtain the discrete analogue of the teleparallel action, as well as the
corresponding simplicial vacuum field equations.Comment: Latex, 10 pages, 2 eps figures, to appear in Class. Quant. Gra
Constraint-preserving boundary treatment for a harmonic formulation of the Einstein equations
We present a set of well-posed constraint-preserving boundary conditions for
a first-order in time, second-order in space, harmonic formulation of the
Einstein equations. The boundary conditions are tested using robust stability,
linear and nonlinear waves, and are found to be both less reflective and
constraint preserving than standard Sommerfeld-type boundary conditions.Comment: 18 pages, 7 figures, accepted in CQ
Invariants and Coherent States for Nonstationary Fermionic Forced Oscillator
The most general form of Hamiltonian that preserves fermionic coherent states
stable in time is found in the form of nonstationary fermion oscillator.
Invariant creation and annihilation operators and related Fock states and
coherent states are built up for the more general system of nonstationary
forced fermion oscillator.Comment: 13 pages, Latex, no figure
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