25,338 research outputs found
Message in a Sealed Bottle: Privacy Preserving Friending in Social Networks
Many proximity-based mobile social networks are developed to facilitate
connections between any two people, or to help a user to find people with
matched profile within a certain distance. A challenging task in these
applications is to protect the privacy the participants' profiles and personal
interests.
In this paper, we design novel mechanisms, when given a preference-profile
submitted by a user, that search a person with matching-profile in
decentralized multi-hop mobile social networks. Our mechanisms are
privacy-preserving: no participants' profile and the submitted
preference-profile are exposed. Our mechanisms establish a secure communication
channel between the initiator and matching users at the time when the matching
user is found. Our rigorous analysis shows that our mechanism is secure,
privacy-preserving, verifiable, and efficient both in communication and
computation. Extensive evaluations using real social network data, and actual
system implementation on smart phones show that our mechanisms are
significantly more efficient then existing solutions.Comment: 13 pages, 7 figure
Lossy Quantum Optical Metrology with Squeezed States
We study the precise phase estimation using squeezed states with photon
losses present. Our exact quantum Fisher information calculation shows
significant quantum enhancement and thus reveals the benchmark for practical
quantum metrology in this noisy scenario. However, we find that the existing
parity measurement scheme [P.M. Anisimov et al, Phys. Rev. Lett. 104, 103602
(2010)] behaves worse than even classical cases given very small losses, unless
we take an appropriate loss dependent phase shift. Using our formulae, the two
optimized aspects including the pre-detection phase shift and the consequent
light intensity of a tradeoff strategy for photon resource arrangement can be
both calculated. Therefore our result makes it possible to experimentally
realize quantum metrology of phase estimation with squeezed states.Comment: Published versio
Fine Structures and Overlying Loops of Confined Solar Flares
Using the H observations from the New Vacuum Solar Telescope at
Fuxian Solar Observatory, we focus on the fine structures of three confined
flares and the issue why all the three flares are confined instead of eruptive.
All the three confined flares take place successively at the same location and
have similar morphologies, so can be termed homologous confined flares. In the
simultaneous images obtained by the Solar Dynamics Observatory, many
large-scale coronal loops above the confined flares are clearly observed in
multi-wavelengths. At the pre-flare stage, two dipoles emerge near the negative
sunspot, and the dipolar patches are connected by small loops appearing as
arch-shaped H fibrils. There exists a reconnection between the small
loops, and thus the H fibrils change their configuration. The
reconnection also occurs between a set of emerging H fibrils and a set
of pre-existing large loops, which are rooted in the negative sunspot, a nearby
positive patch, and some remote positive faculae, forming a typical
three-legged structure. During the flare processes, the overlying loops, some
of which are tracked by activated dark materials, do not break out. These
direct observations may illustrate the physical mechanism of confined flares,
i.e., magnetic reconnection between the emerging loops and the pre-existing
loops triggers flares and the overlying loops prevent the flares from being
eruptive.Comment: 8 pages, 5 figures. Accepted for publication in ApJ
Edge reconstruction of fractional quantum Hall liquids with spin degrees of freedom
We study the interplay of confining potential, electron-electron interaction,
and Zeeman splitting at the edges of fractional quantum Hall liquids, using
numerical diagonalization of finite-size systems. The filling factors studied
include 1/3, 5/2, 2/5, and 2/3. In the absence of Zeeman splitting and an edge,
the first two have spin fully polarized ground states, while the latter two
have singlet ground states. We find that with few exceptions, edge
instabilities of these systems are triggered by softening of edge spin waves
for Abelian fractional quantum Hall liquids (1/3, 2/5 and 2/3 liquids), and are
triggered by softening of edge magnetoplasmon excitations for non-Abelian 5/2
liquid at the smoother confinement side. Phase diagrams are obtained in the
accessible parameter spaces.Comment: 10 pages, 9 figures, 5 table
SilentSense: Silent User Identification via Dynamics of Touch and Movement Behavioral Biometrics
With the increased popularity of smartphones, various security threats and
privacy leakages targeting them are discovered and investigated. In this work,
we present \ourprotocoltight, a framework to authenticate users silently and
transparently by exploiting dynamics mined from the user touch behavior
biometrics and the micro-movement of the device caused by user's screen-touch
actions. We build a "touch-based biometrics" model of the owner by extracting
some principle features, and then verify whether the current user is the owner
or guest/attacker. When using the smartphone, the unique operating dynamics of
the user is detected and learnt by collecting the sensor data and touch events
silently. When users are mobile, the micro-movement of mobile devices caused by
touch is suppressed by that due to the large scale user-movement which will
render the touch-based biometrics ineffective. To address this, we integrate a
movement-based biometrics for each user with previous touch-based biometrics.
We conduct extensive evaluations of our approaches on the Android smartphone,
we show that the user identification accuracy is over 99%
Method for removing interference in chaotic signals based on the Lyapunov exponent
A new method based on the phenomenon of synchronization and the properties of
chaos is proposed to reduce interference in the transferred chaotic signals of
synchronized systems. In this paper, the interference is considered as a series
of small deviations from the original clean trajectory in the phase space. By
means of our special design, these small deviations can be estimated using
positive Lyapunov exponents, and removed from interfered chaotic signals.
Application is illustrated for the Lorenz attractor, and numerical computing
demonstrates that the method is effective in removing typical external
interference
New Vacuum Solar Telescope observations of a flux rope tracked by a filament activation
One main goal of the New Vacuum Solar Telescope (NVST) which is located at
the \emph{Fuxian Solar Observatory} is to image the Sun at high resolution.
Based on the high spatial and temporal resolution NVST H data and
combined with the simultaneous observations from the \emph{Solar Dynamics
Observatory} for the first time, we investigate a flux rope tracked by a
filament activation. The filament material is initially located at one end of
the flux rope and fills in a section of the rope, and then the filament is
activated due to magnetic field cancellation. The activated filament rises and
flows along helical threads, tracking out the twisted flux rope structure. The
length of the flux rope is about 75 Mm, the average width of its individual
threads is 1.11 Mm, and the estimated twist is 1. The flux rope appears as
a dark structure in H images, a partial dark and partial bright
structure in 304 {\AA}, while as bright structures in 171 {\AA} and 131 {\AA}
images. During this process, the overlying coronal loops are quite steady since
the filament is confined within the flux rope and does not erupt successfully.
It seems that, for the event in this study, the filament is located and
confined within the flux rope threads, instead of being suspended in the dips
of twisted magnetic flux.Comment: 15 pages, 5 figures. Accepted for publication in ApJ
Oscillating light wall above a sunspot light bridge
With the high tempo-spatial \emph{Interface Region Imaging Spectrograph} 1330
{\AA} images, we find that many bright structures are rooted in the light
bridge of NOAA 12192, forming a \emph{light wall}. The light wall is brighter
than the surrounding areas, and the wall top is much brighter than the wall
body. The New Vacuum Solar Telescope H and the \emph{Solar Dynamics
Observatory} 171 {\AA} and 131 {\AA} images are also used to study the light
wall properties. In 1330 {\AA}, 171 {\AA}, and 131 {\AA}, the top of the wall
has a higher emission, while in the H line, the wall top emission is
very low. The wall body corresponds to bright areas in 1330 {\AA} and dark
areas in the other lines. The top of the light wall moves upward and downward
successively, performing oscillations in height. The deprojected mean height,
amplitude, oscillation velocity, and the dominant period are determined to be
3.6 Mm, 0.9 Mm, 15.4 km s, and 3.9 min, respectively. We interpret the
oscillations of the light wall as the leakage of \emph{p}-modes from below the
photosphere. The constant brightness enhancement of the wall top implies the
existence of some kind of atmospheric heating, e.g., via the persistent
small-scale reconnection or the magneto-acoustic waves. In another series of
1330 {\AA} images, we find that the wall top in the upward motion phase is
significantly brighter than in the downward phase. This kind of oscillations
may be powered by the energy released due to intermittent impulsive magnetic
reconnection.Comment: 8 pages, 5 figures; accepted for publication in ApJ
Index Modulation for 5G: Striving to Do More with Less
The fifth generation (5G) wireless communications brag both high spectrum
efficiency and high energy efficiency. To meet the requirements, various new
techniques have been proposed. Among these, the recently-emerging index
modulation has attracted significant interests. By judiciously activating a
subset of certain communication {building blocks, such as} antenna, subcarrier
and time slot, index modulation is claimed to have the potential to meet the
challenging 5G needs. In this article, we will discuss index modulation and its
general and specific representations, enhancements, and potential applications
in various 5G scenarios. The objective is to reveal whether, and how, index
modulation may strive for more performance gains with less medium resource
occupation
Properties of the narrow line Seyfert 1 galaxies revisited
There is growing evidence to suggest that the black hole mass has been
previously underestimated with the H line width for certain active
galactic nuclei (AGN). With the assumption of the flatter rather than isotropic
velocity distribution of gases in the broad-line region of AGN, we investigated
the properties of narrow line Seyfert 1 (NLS1) galaxies, like the black hole
mass and the Eddington ratio, and compared with broad line Seyfert 1 (BLS1)
galaxies. Since gamma-rays detected in a few NLS1s which favor a smaller
viewing angle in NLS1s than BLS1s, with the projection effect we estimated the
relative black hole mass and Eddington ratio for NLS1s and BLS1s. The result
implies that the NLS1s and BLS1s have similar black hole masses and Eddington
ratios, peaked at a larger black hole mass and lower Eddington ratio for the
NLS1s than thought before. Furthermore, with applying the correction factor 6
of average black hole mass as derived from the modelling of both optical and UV
data in radio-loud NLS1s by Calderone et al., to the Xu et al. sample, we find
that the NLS1s and BLS1s also show similar black hole masses and Eddington
ratios, peaked at and 0.12 (Eddington ratio) for the
NLS1s. The relation due to the enhanced black hole masses of
NLS1s is discussed. In addition, there seems to show a linear correlation
between jet power and disk luminosity for the flat spectrum radio-loud NLS1
sample, which implies an accretion dominated rather than black hole spin
dominated jet.Comment: 9 pages, 6 figures, accepted for publication in International Journal
of Astronomy and Astrophysic
- …