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$\alpha$ 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$\alpha$ fibrils. There exists a reconnection between the small loops, and thus the H$\alpha$ fibrils change their configuration. The reconnection also occurs between a set of emerging H$\alpha$ 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$\alpha$ 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$\pi$. The flux rope appears as a dark structure in H$\alpha$ 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$\alpha$ 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$\alpha$ 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$^{-1}$, 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$\beta$ 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 $2.0\times10^{7}M_{\odot}$ and 0.12 (Eddington ratio) for the NLS1s. The $M_{BH}-\sigma$ 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